JP7251481B2 - Method for producing ethylene - Google Patents

Description

The present invention relates to a method for producing ethylene. Specifically, in a method of producing ethylene by contacting propylene with a catalyst in a reactor, the step (I) of supplying propylene to the reactor and contacting it with the catalyst to produce ethylene, and regenerating the catalyst It relates to a method for producing ethylene having a step (II) of causing The present invention also relates to a method for producing ethylene by using a catalyst brought into contact with a hydrogen-containing gas in a method for producing ethylene by contacting propylene and a catalyst in a reactor.

Conventionally, a steam cracking method using naphtha as a raw material is known as a main method for producing ethylene. However, the naphtha steam cracking method produces a large amount of olefins other than ethylene such as propylene and butene, and it is difficult to greatly change the production ratio of each olefin. Therefore, techniques for converting olefins other than ethylene to ethylene are being studied. In particular, a method for producing ethylene from propylene, which is a large amount of by-products, is desired.

For example, Patent Document 1 discusses a method of contacting various olefins such as ethylene, propylene and butene with a silicoaluminophosphate to convert them into other olefins.
For example, Non-Patent Document 1 discloses a method for producing ethylene from propylene as a raw material using a phosphorus-modified MFI-type zeolite catalyst.

JP-A-60-166639

Catalysis Today, 303 (2018), 86-92

However, the technique of Patent Document 1 claims that ethylene can be produced with a maximum yield of 8% by reacting a silicoaluminophosphate SAPO-34 catalyst with propylene, but the activity of the catalyst is greatly reduced, and the long-term It is not a production method that can withstand practical use because ethylene cannot be produced stably over a long period of time.
In addition, according to the technique of Non-Patent Document 1, by modifying the MFI-type zeolite catalyst with phosphoric acid, the ethylene selectivity can be increased to about 70 C-mol% at a propylene conversion rate of 36%, but the ethylene selectivity is very low. It was found that even at the concentration (6.5 mol %, diluted with nitrogen), the catalytic activity decreased over time.

An object of the present invention is to provide a method for stably producing ethylene over a long period of time while minimizing the reduction in ethylene yield when producing ethylene from propylene as a raw material.

As a result of intensive studies to solve the above problems, the present inventors have found that in a method for producing ethylene by supplying propylene to a reactor and bringing it into contact with a catalyst, propylene is supplied to a reactor and brought into contact with a catalyst. The inventors have found that ethylene can be stably produced over a long period of time by comprising the step (I) of producing ethylene by allowing the achieved.

That is, the first gist of the present invention is as follows.
(A1) It has a step (I) of supplying propylene to a reactor and bringing it into contact with a catalyst to produce ethylene, and a step (II) of regenerating the catalyst whose conversion rate of propylene has decreased through the step (I). A method for producing ethylene, characterized by:
(A2) The ethylene conversion according to (A1), wherein in the step (II), a gas containing at least one selected from oxygen, hydrogen, and water vapor is used to regenerate the catalyst with a reduced propylene conversion rate. Production method.
(A3) The method for producing ethylene according to (A1) or (A2), wherein in the step (II), the catalyst having a reduced propylene conversion rate is regenerated with a hydrogen-containing gas.
(A4) The method for producing ethylene according to any one of (A1) to (A3), wherein the temperature in step (II) is 300°C or higher and 800°C or lower.
(A5) The amount of coke accumulated in the catalyst that has undergone the step (II) is 0.1% by mass or more and 30% by mass or less with respect to the mass of the catalyst, according to any one of (A1) to (A4). A method for producing ethylene.
(A6) The method for producing ethylene according to any one of (A1) to (A5), wherein the catalyst is zeolite.
(A7) The method for producing ethylene according to (A6), wherein the zeolite has a pore size of less than 0.5 nm.
(A8) The method for producing ethylene according to (A6) or (A7), wherein the zeolite has an oxygen eight-membered ring structure.
(A9) The method for producing ethylene according to any one of (A6) to (A8), wherein the zeolite is an aluminosilicate containing at least aluminum.
(A10) The conversion of ethylene according to any one of (A1) to (A9), wherein the step (II) is performed such that the propylene conversion rate in the step (I) is 5% or more and 80% or less. Production method.

Moreover, the second gist of the present invention is as follows.
(B1) A method for producing ethylene by contacting propylene with a catalyst in a reactor, wherein the catalyst is a catalyst brought into contact with a hydrogen-containing gas.
(B2) The method for producing ethylene according to (B1), wherein the catalyst is a catalyst obtained by contacting a coke-containing catalyst produced by contact with propylene and a hydrogen-containing gas.
(B3) The method for producing ethylene according to (B1) or (B2), wherein the catalyst is in contact with a hydrogen-containing gas at a temperature of 300°C or higher.
(B4) The method for producing ethylene according to any one of (B1) to (B3), wherein the catalyst is in contact with a gas containing hydrogen having an absolute hydrogen partial pressure of 0.001 MPa or more.
(B5) The method for producing ethylene according to any one of (B1) to (B4), wherein the catalyst contains zeolite.
(B6) The method for producing ethylene according to (B5), wherein the zeolite has pores with a pore diameter of less than 0.5 nm.
(B7) The method for producing ethylene according to (B5) or (B6), wherein the zeolite has an oxygen eight-membered ring structure.
(B8) The method for producing ethylene according to any one of (B5) to (B7), wherein the zeolite contains an aluminosilicate containing at least aluminum.
(B9) The method for producing ethylene according to any one of (B1) to (B8), wherein propylene is brought into contact with the catalyst under conditions such that the conversion of propylene is 5% or more and 80% or less.

Moreover, the third gist of the present invention is as follows.
(C1) A method for producing ethylene by contacting a hydrocarbon and a catalyst in a reactor having a raw material inlet and a product gas outlet,
the hydrocarbon contains at least propylene and a hydrocarbon having 4 or more carbon atoms,
A method for producing ethylene, wherein the mass ratio of hydrocarbons having 4 or more carbon atoms to propylene contained in the hydrocarbon is 0.01 or more and 10 or less.
(C2) The method for producing ethylene according to (C1), wherein the hydrocarbon having 4 or more carbon atoms includes butene.
(C3) The method for producing ethylene according to (C2), wherein the proportion of butene contained in the hydrocarbon having 4 or more carbon atoms is 10 mol% or more relative to the total amount of the hydrocarbon having 4 or more carbon atoms.
(C4) The method for producing ethylene according to (C2) or (C3), wherein the butene contains 10 mol% or more of linear butene.
(C5) The method for producing ethylene according to any one of (C1) to (C4), wherein the reaction temperature in the reactor is 300°C or higher and 800°C or lower.
(C6) Any of (C1) to (C5), wherein at least 10% of hydrocarbons having 4 or more carbon atoms contained in the product gas discharged from the product gas outlet of the reactor are circulated to the reactor. The method for producing ethylene according to 1.
(C7) The method for producing ethylene according to any one of (C1) to (C6), wherein the catalyst contains zeolite.
(C8) The method for producing ethylene according to (C7), wherein the zeolite has pores with a pore diameter of 0.8 nm or less.
(C9) The method for producing ethylene according to (C7) or (C8), wherein the zeolite has an oxygen eight-membered ring structure.
(C10) The method for producing ethylene according to any one of (C7) to (C9), wherein the zeolite contains an aluminosilicate containing at least aluminum.
(C11) The method for producing ethylene according to (C10), wherein the zeolite has a SiO ₂ /Al ₂ O ₃ molar ratio of 5 or more and 500 or less.
(C12) The method for producing ethylene according to any one of (C7) to (C11), wherein the structure of the zeolite is CHA under the code specified by the International Zeolite Association (IZA).

Moreover, the fourth gist of the present invention is as follows.
(D1) A method for producing ethylene by contacting a hydrocarbon and a catalyst containing zeolite as an active ingredient in a reactor having a raw material inlet and a product gas outlet,
The hydrocarbon contains at least a hydrocarbon having 4 or more carbon atoms, and
A method for producing ethylene, wherein the zeolite has at least an eight-membered oxygen ring structure, and the ratio of the outer surface acid amount to the total acid amount is 3% or less.
(D2) The method for producing ethylene according to (D1), wherein the zeolite contains an aluminosilicate containing at least aluminum.
(D3) The method for producing ethylene according to (D1) or (D2), wherein the zeolite has a SiO ₂ /Al ₂ O ₃ molar ratio of 5 or more and 500 or less.
(D4) The method for producing ethylene according to any one of (D1) to (D3), wherein the zeolite is silylated.
(D5) The method for producing ethylene according to any one of (D1) to (D4), wherein the structure of the zeolite is CHA under the code specified by the International Zeolite Association (IZA).
(D6) The method for producing ethylene according to any one of (D1) to (D5), wherein at least butene is included as the hydrocarbon having 4 or more carbon atoms.
(D7) The method for producing ethylene according to (D6), wherein the proportion of linear butene contained in the butene is 10 mol% or more.
(D8) The method for producing ethylene according to any one of (D1) to (D7), wherein the reaction temperature in the reactor is 300°C or higher and 800°C or lower.
(D9) Any of (D1) to (D8), wherein at least 10% of hydrocarbons having 3 or more carbon atoms contained in the product gas discharged from the product gas outlet of the reactor are circulated to the reactor. The method for producing ethylene according to 1.

According to the first gist of the present invention, in a method for producing ethylene by supplying propylene to a reactor and bringing it into contact with a catalyst, ethylene is stably produced by minimizing the fluctuation range of ethylene yield. be able to.
Further, according to the second gist of the present invention, in the method for producing ethylene by contacting propylene with a catalyst, the catalyst is brought into contact with a hydrogen-containing gas and the catalyst is reacted with propylene to achieve a high yield. can stably produce ethylene.
Further, according to the third gist of the present invention, in the method for producing ethylene by supplying propylene to a reactor and bringing it into contact with a catalyst, by supplying a predetermined amount of a hydrocarbon having 4 or more carbon atoms together with propylene, It is possible to stably produce ethylene at a high yield by minimizing the fluctuation range of the ethylene/propylene ratio in the product.
Further, according to the fourth gist of the present invention, when producing ethylene from a hydrocarbon having 4 or more carbon atoms as a raw material, it is possible to achieve a high ethylene yield without increasing the by-product amount of branched olefins that are unsuitable for recycling as a raw material. can provide a method of producing ethylene at a

4 is a graph showing changes in ethylene yield with respect to cumulative time obtained in Example A-1 and Comparative Example A-1. 2 is a graph showing changes in propylene conversion with respect to reaction time and the relationship between propylene conversion and ethylene selectivity in Example A-2. 4 is a graph showing changes in ethylene yield versus cumulative reaction time in Example A-3. 4 is a graph showing changes in propylene conversion and ethylene selectivity with respect to reaction time in Example A-4. 2 is a graph showing the ethylene yield results of Example B-1, Comparative Examples B-1 and B-2.

Although typical embodiments for carrying out the present invention will be specifically described below, the present invention is not limited to the following embodiments as long as it does not exceed the gist thereof, and can be carried out in various modifications. can be done.

A first embodiment of the present invention is a method for producing ethylene by supplying propylene to a reactor and bringing it into contact with a catalyst, wherein the step of supplying propylene to the reactor and bringing it into contact with a catalyst to produce ethylene (I ) and a step (II) of regenerating the catalyst whose propylene conversion rate has decreased through the step (I).

<A1. Catalyst>
A catalyst used in the first embodiment of the present invention will be described. The catalyst used in the reaction according to the present embodiment is not particularly limited as long as it is a solid having a Bronsted acid site, and conventionally known catalysts are used, for example, clay minerals such as kaolin, acidic ion Examples include solid acid catalysts such as exchange resins, zeolites, and mesoporous silica-alumina. In the first embodiment, by introducing a step of regenerating the catalyst whose propylene conversion rate has decreased, the amount of coke components accumulated by the conversion of propylene can be reduced, and ethylene can be produced at a stable yield. can.

Among these solid acid catalysts, those having a molecular sieve effect are preferred, and zeolites are more preferred. A known catalyst can be used as the above catalyst, but zeolite, which is a preferred form of the catalyst, will be described in detail below.

Zeolite is a crystalline substance in which ₄ TO units (T is the central atom) with a tetrahedral structure are connected three-dimensionally by sharing O atoms to form regular open micropores. Point. Specifically, silicates, phosphates, germanium salts, arsenates, etc. listed in the data collection of the structure committee of the International Zeolite Association (hereinafter sometimes referred to as "IZA") included.

Here, silicates include, for example, aluminosilicates, gallosilicates, ferrisilicates, titanosilicates, borosilicates, and the like.
Phosphates include, for example, aluminophosphates, gallophosphates, beryllophosphates, and the like.
Germanium salts include, for example, aluminogermanium salts, and arsenates include, for example, aluminum arsenates.
Furthermore, aluminophosphates include, for example, silicoaluminophosphates in which the T atom is partially substituted with Si, and those containing divalent or trivalent cations such as Ga, Mg, Mn, Fe, Co, and Zn. .

The average pore diameter of the zeolite is not particularly limited, and is usually 0.80 nm or less, preferably 0.55 nm or less, more preferably 0.50 nm or less, even more preferably 0.45 nm or less, and particularly preferably 0.40 nm or less, It is usually 0.25 nm or more, preferably 0.30 nm or more, more preferably 0.33 nm or more, and still more preferably 0.35 nm or more.
Here, the average pore diameter indicates the crystallographic free diameter of the channels defined by IZA. The average pore diameter of 0.55 nm or less means that the average diameter of pores (channels) is 0.55 nm or less when the shape of the pores (channels) is perfectly circular. It means that the minor axis is 0.55 nm or less.

By using zeolite, it is possible to produce ethylene at a high yield using propylene as a raw material. That is, if the average pore diameter is within the above range, diffusion of propylene into the zeolite crystals can be promoted and ethylene can be produced more selectively. Furthermore, contact with a hydrogen-containing gas is considered to be more preferable because the quality of the coke components can be modified while appropriately reducing the amount of the coke components accumulated in the catalyst.

From the above viewpoint, in the present embodiment, the zeolite is preferably an oxygen 8-membered ring structure zeolite.

As the oxygen 8-membered ring structure zeolite, the structure code (Framework Type Code) defined by IZA, for example, preferably AEI, AFX, CHA, ERI, KFI, LEV, SAS, SAV, SZR, PAU, RHO, LTA, etc. mentioned.

The zeolite framework density (unit: T/nm ³ ) is not particularly limited, and is usually 20.0 or less, preferably 18.0 or less, more preferably 17.0 or less, and still more preferably 16.0 or less, It is usually 12.0 or higher, preferably 14.0 or higher, more preferably 14.5 or higher.
Here, the framework density (unit: T/nm ³ ) refers to the number of T atoms (atoms other than oxygen atoms constituting the zeolite skeleton) present per unit volume (1 nm ³ ) of the zeolite. This value is determined by the structure of the zeolite.

From these viewpoints, the oxygen 8-membered ring structure zeolite is preferably a zeolite containing d6r in the skeleton defined as a composite building unit by the International Zeolite Association (IZA), more preferably AEI, AFX, CHA, ERI, KFI, LEV, SAV, more preferably AEI, AFX, CHA, or ERI, even more preferably AEI, CHA, or ERI, particularly preferably CHA or ERI, most preferably CHA .

Specific examples of 8-membered oxygen ring structure zeolites include silicates and phosphates. As described above, examples of silicates include aluminosilicates, gallosilicates, ferrisilicates, titanosilicates, and borosilicates, and examples of phosphates include aluminophosphates composed of aluminum and phosphorus, silicon and silicoaluminophosphates composed of aluminum and phosphorus. Among these, aluminosilicates and silicoaluminophosphates are preferred, and aluminosilicates are more preferred.

A proton-exchanged type of zeolite whose ion-exchange sites are protons (H) is usually used. It may be exchanged with transition metals such as metals, Cr, Cu, Ni, Fe, Mo, W, Pt, and Re. In this case, the zeolite may be subjected to an ion exchange treatment, which will be described later.

In addition to these ion exchange sites, metals are supported on alkali metals such as Na and K; alkaline earth metals such as Ca and Sr; and transition metals such as Cr, Cu, Ni, Fe, Mo, W, Pt and Re. good too. Here, the metal loading can usually be carried out by an impregnation method such as equilibrium adsorption method, evaporation to dryness method, pore-filling method and the like.

When the zeolite is a silicate, SiO ₂ /M ₂ O ₃ (where the denominator of said molar ratio represents the total amount of Al ₂ O ₃ , Ga ₂ O ₃ , B ₂ O ₃ and Fe ₂ O ₃ ) mol The ratio is usually 5 or more, preferably 8 or more, more preferably 10 or more, still more preferably 15 or more, and usually less than 100, preferably 80 or less, more preferably 60 or less, and still more preferably 40 or less. be. The above ratio is a value obtained on the assumption that all Si atoms in the zeolite are contained as SiO ₂ and all the M contained in the zeolite are contained as M ₂ O ₃ . When the SiO ₂ /M ₂ O ₃ molar ratio is within the above range, a sufficient amount of acid derived from strong acid sites and weak acid sites can be obtained, and high propylene conversion activity can be obtained. It is also possible to prevent phenomena such as deactivation of the catalyst due to adhesion of coke, detachment of T atoms other than silicon from the skeleton, and a decrease in acid strength per acid site. The SiO ₂ /M ₂ O ₃ molar ratio of the zeolite of the present invention can usually be measured by ICP elemental analysis or fluorescent X-ray analysis. In the fluorescent X-ray analysis, a calibration curve is created between the fluorescent X-ray intensity of the analytical element in the standard sample and the atomic concentration of the analytical element. Atoms, aluminum, gallium, iron atom content can be determined. Since the fluorescent X-ray intensity of boron element is relatively small, it is preferable to measure the content of boron atoms by ICP elemental analysis.

When the zeolite is a phosphate, the (Al+P)/Si molar ratio of a silicoaluminophosphate or the (Al+P)/M of a metalloaluminophosphate having a divalent metal (where M represents a divalent metal ) The molar ratio is usually 5 or more, preferably 10 or more, and usually 500 or less, preferably 100 or less. Incidentally, the divalent metal specifically includes Ga, Mg, Mn, Fe, Co, or Zn. By adjusting the amount to be equal to or higher than the lower limit, deterioration of the durability of the catalyst can be prevented, and by adjusting the amount to be equal to or higher than the upper limit, deterioration of catalytic activity can be prevented.

The total acid content of the zeolite used in the present embodiment (hereinafter referred to as the total acid content) includes the amount of acid sites present in the crystal pores of the zeolite and the amount of acid sites on the outer surface of the zeolite crystal (hereinafter referred to as the outer surface acid amount). The total acid content is not particularly limited, but is usually 0.01 mmol/g or more, preferably 0.1 mmol/g or more, more preferably 0.3 mmol/g or more, and still more preferably 0.5 mmol/g or more. is. Also, it is usually 2.5 mmol/g or less, preferably 1.5 mmol/g or less, more preferably 1.2 mmol/g or less, and still more preferably 0.9 mmol/g or less. By setting the total acid amount within the above range, propylene conversion activity can be ensured, coke formation inside the pores of the zeolite can be suppressed, and ethylene production can be promoted. The total acid content here is calculated from the desorption amount in ammonia temperature programmed desorption (NH ₃ -TPD). Specifically, after drying the zeolite under vacuum at 500° C. for 30 minutes as a pretreatment, the pretreated zeolite is brought into contact with an excess amount of ammonia at 100° C. to cause the zeolite to adsorb ammonia. Excess ammonia is removed from the obtained zeolite by vacuum drying at 100°C or contacting it with water vapor at 100°C. Next, the ammonia-adsorbed zeolite is heated in a helium atmosphere at a temperature elevation rate of 10°C/min, and the amount of ammonia desorbed at 100-600°C is measured by mass spectrometry. Let the amount of ammonia desorbed per zeolite be the total amount of acid. However, the total acid content in the present invention is the sum of the areas of the waveforms having the peak top at 240° C. or higher after separating the TPD profile into waveforms using a Gaussian function. This "240° C." is an index used only for determining the position of the peak top, and does not mean that the area of the portion above 240° C. is obtained. As long as the waveform has a peak top of 240°C or higher, the "waveform area" is the total area including portions other than 240°C. When there are a plurality of waveforms having peak tops at 240° C. or higher, the sum of the respective areas is used. In addition, the total acid amount in the present embodiment does not include the acid amount derived from weak acid sites having a peak top at less than 240°C. This is because it is not easy to distinguish between adsorption derived from weak acid sites and physical adsorption in the TPD profile.

The outer surface acidity of zeolite is not particularly limited, but is usually 8% or less, preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less with respect to the total acidity of zeolite. , most preferably 0%. If the outer surface acidity is too large, the yield of ethylene tends to decrease due to side reactions occurring at the outer surface acid sites. This is presumed to be due to the progress of reactions that produce hydrocarbons other than the target product at the outer surface acid sites. In addition, it is presumed that the further reaction of the ethylene produced in the pores of the zeolite at the outer surface acid sites is also a factor in the decrease in selectivity.
The value of the outer surface acidity of the zeolite used in the present embodiment can be measured by the method described in International Publication No. 2010/128644. Specifically, after drying the zeolite under vacuum at 500° C. for 1 hour as a pretreatment, the pretreated zeolite is brought into contact with pyridine vapor at 150° C. to adsorb pyridine to the zeolite. Amount of pyridine desorbed per zeolite unit weight at 150 to 800°C by a temperature programmed desorption method at a temperature rising rate of 10°C/min from the pyridine-adsorbed zeolite obtained by removing surplus pyridine from the zeolite by flow determined from
Incidentally, the outer surface acidity and the like of the zeolite are not particularly limited, but can be adjusted by silylation treatment, steam treatment, heat treatment, acid treatment, ion exchange treatment, and the like. Methods such as carrying treatment of metal elements can be mentioned. In addition, there is a method of combining a binder with an acid site on the outer surface of the zeolite when molding the zeolite.

<Silylation treatment>
The method of silylating the zeolite is not particularly limited, and a known method can be used as appropriate. Specifically, liquid-phase silylation, gas-phase silylation, and the like can be performed.

The silylation treatment of zeolite usually coats the acid sites on the outer surface of the zeolite and deactivates it, which is thought to reduce the acidity on the outer surface. When the outer surface acid amount is reduced, side reactions occurring on the outer surface of the zeolite are suppressed. Specifically, by the conversion reaction of propylene, lower olefins such as ethylene and butenes generated in the zeolite pores come into contact with the acid sites on the outer surface of the zeolite, resulting in the generation of components other than the target product. It is considered to have a suppressive effect. In addition, in the silylation of the outer surface acid sites, the silyl groups are also bound to the acid sites that constitute the pores of the zeolite, so the pore diameter of the outer surface openings is slightly reduced, and molecular diffusion out of the crystal occurs. is thought to have the effect of suppressing It is believed that this suppresses the production of hydrocarbons having 5 or more carbon atoms, which are larger molecules, and improves the ethylene selectivity.
The silylation treatment will be specifically described below by taking liquid-phase silylation as an example.

The silylating agent is not particularly limited, and usually one that can silylate the outer surface of the zeolite but cannot silylate the inside of the pores of the zeolite is used. Specifically, silicones, chlorosilanes, alkoxysilanes, siloxanes, silazanes and the like can be used. Among these, chlorosilanes are usually used for gas-phase silylation, and alkoxysilanes are usually used for liquid-phase silylation. More preferable silylating agents are highly reactive and relatively easy to handle. , alkoxysilanes.
Specific examples of silicones include dimethylsilicone, diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethylsilicone, phenylethylsilicone, diphenylsilicone, and methyltrifluoropropylsilicone. , ethyltrifluoropropylsilicone, tetrachlorophenylmethylsilicone, tetrachlorophenylethylsilicone, tetrachlorophenylhydrogensilicone, tetrachlorophenylsilicone, methylvinylsilicone and ethylvinylsilicone.

Specific examples of chlorosilanes include tetrachlorosilane, trichlorosilane, trichloromethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, trichloroethylsilane, dichlorodiethylsilane, and chlorotriethylsilane.
Specific examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane, etc.; quaternary alkoxysilane, trimethoxymethylsilane, trimethoxyethylsilane, triethoxymethylsilane, triethoxyethylsilane, etc.; alkoxysilane, dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane, diethoxydiethylsilane, etc.; secondary alkoxysilane, methoxytrimethylsilane, methoxytriethylsilane, ethoxytrimethylsilane, ethoxytriethylsilane, etc.; is used. Secondary or higher class alkoxysilanes are preferred, tertiary or higher class alkoxysilanes are more preferred, and quaternary or higher class alkoxysilanes are even more preferred.

Specific examples of siloxanes include hexamethyldisiloxane, hexaethyldisiloxane, pentamethyldisiloxane, tetramethyldisiloxane and the like, with hexamethyldisiloxane being preferred.
Specific examples of silazanes include hexamethyldisilazane, dipropyltetramethyldisilazane, diphenyltetramethyldisilazane, tetraphenyldimethyldisilazane and the like, with hexamethyldisilazane being preferred.

The amount of the silylating agent to the zeolite is not particularly limited, but is usually 0.001 mol or more, preferably 0.01 mol or more, more preferably 0.1 mol or more, relative to 1 mol of the zeolite. is. Also, it is usually 5 mol or less, preferably 3 mol or less, more preferably 1 mol or less. By setting the amount of the silylating agent within the above range, the silylation coating of the outer surface acid sites efficiently progresses, and it is possible to suppress the decrease in catalytic activity due to excessive silylation coating, which is preferable. The amount of the silylating agent is represented by the number of moles of Si atoms contained in the silylating agent. will be treated as the number of moles of the agent.

When carrying out liquid phase silylation, a solvent can be used, and examples of the solvent include, but are not limited to, hydrocarbons such as hexane, heptane, octane, nonane, decane, cyclopentane, cyclohexane, benzene, toluene, and xylene. or water can be used. Further, when the liquid-phase silylation is performed using an aqueous solvent, an acidic aqueous solution to which an acid such as sulfuric acid or nitric acid is added can be used in order to promote the silylation reaction.

When liquid-phase silylation is performed, the concentration of the silylating agent in the solution in which the liquid-phase silylation reaction is performed is not particularly limited, but is usually 0.01% by mass or more, preferably 0.5% by mass. above, and more preferably at least 1% by mass. Moreover, it is usually 80% by mass or less, preferably 60% by mass or less, and more preferably 40% by mass or less. By setting the concentration of the silylating agent within the above range, it is preferable in that condensation between the silylating agents can be suppressed and the silylation rate can be maintained.

The amount of the solvent for the zeolite in liquid-phase silylation is not particularly limited, but is usually 1 g or more, preferably 3 g or more, more preferably 5 g or more, per 1 g of the zeolite. Also, it is usually 100 g or less, preferably 80 g or less, more preferably 50 g or less. By setting the amount of the solvent within the above range, it is possible to obtain sufficient stirring efficiency of the slurry and to ensure a certain level of productivity, which is preferable.

When liquid-phase silylation is performed, the zeolite subjected to the silylation treatment may be provided with a specific range of moisture. The water contained in the zeolite may be originally contained in the zeolite, or may be adjusted to a specific range by artificially supplying water. Generally, the zeolite used in the present embodiment is obtained by hydrothermal synthesis, calcined, and if necessary, converted to the ammonium type and then calcined to convert to the proton type. Therefore, it is generally assumed that the water content of zeolite before silylation treatment is usually very low, and it may be subjected to silylation treatment as it is, or water is supplied to zeolite so that it has a specific water content, It may be used after adjusting the moisture content (hereinafter sometimes referred to as humidity conditioning treatment).

The water content is not particularly limited, but the weight of the water contained in the zeolite is represented by mass% with respect to the weight of the dry zeolite, and is usually 30% by mass or less, preferably 25% by mass or less, and the lower limit is is 0% by mass in a completely dry state. By setting the water content within the above range, the silylation coating of the outer surface acid sites proceeds efficiently and pore clogging due to excessive silylation can be prevented, which is preferable.

The humidity conditioning treatment method is not particularly limited as long as it can adjust the moisture content to a predetermined level. For example, a method of leaving the zeolite in an atmosphere having an appropriate relative humidity, a method of allowing the zeolite to coexist with water or a saturated aqueous solution of an inorganic salt in a closed container (desiccator, etc.), and a method of leaving the zeolite in a saturated steam atmosphere. Another example is a method of circulating a gas having an appropriate water vapor pressure. In the above method, the humidity conditioning treatment may be performed while mixing or stirring the zeolite in order to perform more uniform humidity conditioning.

The temperature for the silylation treatment is appropriately adjusted depending on the type of silylating agent and solvent used, and is not particularly limited, but is usually 20°C or higher, preferably 40°C or higher, more preferably 60°C or higher. . Also, it is usually 140° C. or lower, preferably 120° C. or lower, and more preferably 100° C. or lower. By setting the silylation treatment temperature within the above range, the silylation coating of the outer surface acid sites proceeds efficiently and the silylation rate can be maintained.

The time required to raise the temperature from the addition of the silylation agent to the silylation temperature is not particularly limited, and the silylation agent may be added at the silylation temperature, but usually 0.01 hour. As mentioned above, it is preferably 0.05 hours or more, more preferably 0.1 hours or more, and there is no particular upper limit for the time required for temperature rise. When the silylation temperature is high, by setting the time required for temperature rise within the above range, the hydrolysis and polymerization reaction of the silylating agent in the solution are suppressed, and the silylation of the zeolite proceeds efficiently. preferable.

The treatment time for silylation depends on the reaction temperature, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1 hour or longer, as long as the catalyst performance is not impaired. There is no upper limit for By setting the treatment time within the above range, the silylation coating of the outer surface acid sites of the zeolite proceeds, and the outer surface acid amount is sufficiently reduced, which is preferable.

<Steam treatment>
The method of water vapor treatment is not particularly limited, but the gas containing water vapor can be brought into contact within a range that does not impair the effects of the present invention. Specific examples include a method of contacting with a reaction atmosphere containing water vapor, water vapor diluted with air or an inert gas, water vapor together with a lower olefin such as ethylene or propylene, or a reaction atmosphere generating water vapor. A reaction that produces water vapor is a reaction in which dehydration occurs to produce water vapor, such as the dehydration reaction of alcohol. Depending on the conditions, the steam may partially exist as liquid water, but it is preferable that the entire zeolite exists in the form of steam in order to impart a uniform steam treatment effect to the zeolite.

By steaming the zeolite, T atoms other than silicon that form the skeleton of the zeolite are eliminated from the skeleton throughout the crystal. This reduction in total acidity suppresses coke formation inside the pores of the zeolite and improves the intracrystalline diffusibility of molecules. For this reason, it is presumed that the reactivity of propylene, which is a reaction raw material, is relatively increased. Excessive steam treatment may cause a decrease in activity due to a decrease in the total acid content, and an excessive increase in the diffusivity of molecules within crystals, resulting in the formation of hydrocarbon molecules with 4 or more carbon atoms such as butene, pentene, and hexene. The amount of production tends to increase.

The steam treatment temperature is not particularly limited, but is usually 400° C. or higher, preferably 500° C. or higher, more preferably 600° C. or higher. Also, it is usually 1000° C. or lower, preferably 900° C. or lower, more preferably 800° C. or lower. By setting the steam treatment temperature within the above range, T atoms other than silicon can be efficiently removed from the skeleton in a short treatment time without causing collapse of the skeleton structure, which is preferable.

Water vapor (steam) used for water vapor treatment can be used after being diluted with air or an inert gas such as helium or nitrogen. The steam concentration at that time is not particularly limited, but is usually 5% by volume or more, preferably 10% by volume or more, more preferably 20% by volume or more, relative to the entire gas used when steaming the zeolite. and more preferably 30% by volume or more, and usually 100% by volume or less, preferably 90% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less. The upper limit is not particularly limited, and 100% by volume of water vapor can be used. By setting the water vapor concentration within the above range, the T atoms can be efficiently removed from the skeleton in a short treatment time, which is preferable.

The pressure of steam treatment (total pressure including diluent gas) is not particularly limited, but is usually 0.05 MPa or higher (absolute pressure, hereinafter the same), preferably 0.075 MPa or higher, more preferably 0.1 MPa or higher. It is usually 2 MPa or less, preferably 1 MPa or less, more preferably 0.5 MPa or less. By setting the pressure of the steam treatment within the above pressure range, the T atoms can be efficiently removed from the skeleton in a short period of time, which is preferable.

Although the partial pressure of water vapor is not particularly limited, it is usually 0.01 MPa or more (absolute pressure, hereinafter the same), preferably 0.03 MPa or more, more preferably 0.05 MPa or more, and usually 2 MPa or less, preferably It is 1 MPa or less, more preferably 0.5 MPa or less, and still more preferably 0.2 MPa or less. By setting the partial pressure of water vapor within the above pressure range, the T atom can be efficiently removed from the skeleton in a short time, which is preferable.

The steam treatment time is not particularly limited, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1 hour or longer. There is no upper limit to the treatment time as long as it does not significantly impair the catalytic activity. The treatment time can be appropriately adjusted depending on the steam treatment temperature and steam concentration.

The steam treatment may be performed in a state in which organic substances are present inside the pores. The presence of the organic matter inside the pores prevents a drastic decrease in the acid sites inside the pores and significantly reduces the acid sites on the outer surface, especially when a strong steam treatment is performed.
Examples of the organic substance include, but are not particularly limited to, a structure-directing agent used during hydrothermal synthesis of zeolite, coke generated by reaction, and the like. These organic substances can be removed through a combustion process such as air calcination after the zeolite after hydrothermal synthesis (hereinafter sometimes referred to as zeolite before calcination) is subjected to steam treatment, or an oxygen-containing gas such as air can be removed. By treating with steam diluted with , the steam treatment can be performed while removing the organic matter.

<Heat treatment>
The heat treatment method is not particularly limited, but specific examples include a method of subjecting the zeolite to a high temperature treatment in at least one atmosphere selected from air and inert gas. This can reduce the total acid content of the zeolite.

The heat treatment temperature is not particularly limited, but is usually 500° C. or higher, preferably 600° C. or higher, more preferably 700° C. or higher, and usually 1200° C. or lower, preferably 1000° C. or lower, more preferably 900° C. or lower. be. Setting the heat treatment temperature within the above range is preferable in that the T atoms can be efficiently removed from the skeleton in a short treatment time without collapsing the skeleton structure.

Helium, nitrogen, air, or the like can be used as the gas species used in the heat treatment.
The heat treatment may also be performed in a state where organic substances are present inside the pores, similarly to the steam treatment. When an inert gas such as helium or nitrogen is used, the organic substance may be carbonized by heat treatment, but it can be removed by firing in air.

The heat treatment may be performed simultaneously with the calcination performed when producing the zeolite, or may be performed separately. The heat treatment is performed at a relatively high temperature for the purpose of removing the T atoms in the skeleton, etc., and is not particularly limited. is usually performed at a higher temperature than calcination.
The heat treatment time is not particularly limited, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1.0 hour or longer. There is no upper limit to the treatment time as long as it does not significantly impair the catalytic activity, and the treatment time can be appropriately adjusted depending on the heat treatment temperature.

<Acid treatment>
The method of acid-treating zeolite used in the present embodiment is not particularly limited, but a specific example is a method using an acidic aqueous solution.
The type of acid used in the acidic aqueous solution is not particularly limited, but inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid; carboxylic acids such as formic acid, acetic acid and propionic acid; oxalic acid and malonic acid. and the like can be used. Sulfuric acid, nitric acid and hydrochloric acid are preferred among these.

The acid concentration of the acidic aqueous solution is not particularly limited, but is usually 0.01 M or more, preferably 0.1 M or more, more preferably 1 M or more, and usually 10 M or less, preferably 8 M or less. and more preferably 6M or less. By setting the acid concentration within the above range, it is possible to efficiently reduce the total acid amount in a short treatment time without causing the collapse of the skeleton structure, which is preferable.

The amount of the acidic aqueous solution relative to the zeolite is not particularly limited, but the total amount of the acidic aqueous solution is usually 3 g or more, preferably 5 g or more, more preferably 10 g or more, and usually 100 g or less, relative to 1 g of zeolite. It is preferably 80 g or less, more preferably 50 g or less. By setting the amount of the acidic aqueous solution within the above range, it is possible to obtain a sufficient stirring efficiency of the slurry and to ensure a certain level of productivity, which is preferable.

The temperature of the acid treatment is not particularly limited, but it is usually room temperature to 100° C. under normal pressure, and can be carried out at 100° C. or higher in a pressure vessel, usually 40° C. or higher, preferably 60° C. or higher. , more preferably 80° C. or higher, and usually 200° C. or lower, preferably 180° C. or lower, more preferably 160° C. or lower. By setting the acid treatment temperature within the above range, it is possible to efficiently reduce the total amount of acid in a short treatment time while suppressing the collapse of the skeleton structure, which is preferable.

The treatment time of the acid treatment is not particularly limited and depends on the concentration of the acid and the reaction temperature, but it is usually 0.01 hour or more, preferably 0.1 hour or more, as long as it does not impair the performance of the catalyst. There is no particular upper limit for the processing time. The treatment time can be appropriately adjusted depending on the concentration of the acid and the reaction temperature.
Acid treatment and silylation treatment can be performed simultaneously by adding a silylating agent to the acidic aqueous solution. The silylating agent used at that time is the same as the silylating agent described above.

<Ion exchange treatment>
The counter cations of zeolites are usually alkali metals such as sodium, alkaline earth metals, ammonium ( _NH4 ) or protons (H). These counter cations are ion-exchangeable and can be used after metal ion exchange as appropriate. Metals to be exchanged include, but are not limited to, alkali metals such as lithium, sodium, potassium, rubidium and cesium, and alkaline earth metals such as calcium, strontium and barium. Preferred are sodium, potassium, calcium and strontium, more preferred are sodium, potassium and calcium, and still more preferred is calcium.

By ion exchange, the acid amount of the zeolite can be adjusted, and furthermore, the cage space volume can be adjusted, so coke accumulation during the reaction can be suppressed. It is also preferable in that thermal/hydrothermal stability is enhanced and deterioration can be suppressed. Although the method of metal ion exchange is not particularly limited, it can be carried out by a known ion exchange method. The cation of the zeolite used in the ion exchange method is not particularly limited, and sodium type, ammonium type, or proton type is usually used.

As metal sources, nitrates, sulfates, acetates, carbonates, chloride salts, bromide salts, iodide salts and the like are usually used, with nitrates, sulfates and chloride salts being preferred, and nitrates being more preferred. is. The solvent to be used is not particularly limited as long as it dissolves the metal source, but water is usually used.

The concentration of the metal source solution is not particularly limited, but is usually 0.1 M or more, preferably 0.5 M or more, more preferably 1 M or more, and the upper limit is usually 10 M or less, preferably 8 M or less. More preferably, it is 6M or less. It is desirable to adjust the concentration according to the solubility of the metal source.

The temperature for ion exchange is from room temperature to about the boiling point of the solvent. The treatment time may be sufficient as long as the ion exchange reaches a sufficient equilibrium, and is usually about 1 to 6 hours. It is also possible to repeat the ion exchange multiple times in order to increase the metal exchange rate.

The atmosphere in which the ion-exchanged zeolite is dried is not particularly limited. The drying temperature is usually from room temperature to about the boiling point of the solvent. The ion-exchanged zeolite is appropriately calcined before use. The firing temperature may be higher than the decomposition temperature of the metal source, usually 200°C to 600°C, preferably 300°C to 500°C. If the sintering temperature is too low, the metal source tends to remain, and if the sintering temperature is too high, structural collapse of the zeolite and sintering of the metal tend to proceed.

In addition to the above, it is also possible to adjust the outer surface acidity by carrying out a metal element support treatment, or by combining a binder with the outer surface acid points of the zeolite when molding the zeolite.

The average primary particle size of the zeolite used in the present embodiment is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more, more preferably 0.05 μm or more, usually 10 μm or less, It is preferably 5 µm or less, more preferably 1 µm or less, even more preferably 0.5 µm or less, and particularly preferably 0.3 µm or less. The above range is preferable because the diffusivity in the zeolite crystal and the catalyst effectiveness factor in the catalytic reaction are sufficiently high, the zeolite crystallinity is sufficient, and the hydrothermal stability is high.
In addition, the average primary particle size in this specification corresponds to the particle size of the primary particles. Therefore, it differs from the particle size of aggregates measured by a light scattering method or the like. The average primary particle diameter is determined by observing particles with a scanning electron microscope (hereinafter abbreviated as "SEM") or a transmission electron microscope (hereinafter abbreviated as "TEM"), and arbitrarily 20 or more particles. It is obtained by measuring and averaging the particle diameters of the primary particles. When the particle is rectangular, the long side and short side of the particle are measured (the depth is not measured), and the average of the sums, that is, (long side + short side) / 2, is calculated. Primary particle size.

(BET specific surface area)
The BET specific surface area of the zeolite used in the present embodiment is not particularly limited, but is usually 300 m ² /g or more, preferably 400 m ² /g or more, more preferably 500 m ² /g or more, and usually 1000 m 2 /g or more. ² /g or less, preferably 800 m ² /g or less, more preferably 750 m ² /g or less. Within the above range, there are sufficiently many active sites on the inner surfaces of the pores, and the catalytic activity is increased, which is preferable. The BET specific surface area can be measured by a measurement method according to JIS8830 (Method for measuring specific surface area of powder (solid) by gas adsorption). Nitrogen is used as the adsorption gas, and the BET specific surface area is determined by the one-point method (relative pressure: p/p0=0.30).

The pore volume of the zeolite used in the present embodiment is not particularly limited, but is usually 0.1 ml/g or more, preferably 0.2 ml/g or more, and usually 3 ml/g or less, preferably 2 ml. / g or less. Within the above range, there are sufficiently many active sites on the inner surfaces of the pores, and the catalytic activity is increased, which is preferable. The pore volume is preferably a value obtained from a nitrogen adsorption isotherm obtained by a relative pressure method.

The zeolite used in this embodiment can generally be prepared by a hydrothermal synthesis method. For example, in the case of silicates, at least one selected from an aluminum source, a gallium source, a boron source, and an iron source, a silicon source, an alkaline aqueous solution, etc. are added to water to form a uniform gel, and the necessary A structure-directing agent is added and stirred to prepare a raw material gel. The raw material gel thus obtained is heated in a closed container and reacted under autogenous pressure to crystallize. Although the reaction temperature at this time is not particularly limited, it is usually held at 100 to 200° C. for crystallization. During crystallization, seed crystals may be added as necessary, and from the standpoint of manufacturability, addition of seed crystals is preferable in that reaction time can be shortened and crystal grains can be made into fine particles. After filtration and washing of the crystallized solid component, the solid component is dried and subsequently calcined to obtain an alkali (earth) metal type zeolite. Although the drying temperature is not limited, it is usually 100 to 200°C. Although the firing temperature is not limited, it is usually 400 to 700°C. After that, ion exchange is performed with an acidic solution or an ammonium salt solution, followed by calcination to obtain an H-type zeolite.

Specifically, CHA-type zeolite can be produced by known methods such as the method described in US Pat. No. 4,544,538. ERI zeolite can be produced by known methods such as the method described in US Pat. No. 7,344,694.

The cation used as the structure-directing agent is accompanied by an anion that does not inhibit the formation of the zeolite of this embodiment. The anion is not particularly limited, but specifically includes halogen ions such as Cl ⁻ , Br ⁻ and I ⁻ , hydroxide ions, acetates, sulfates and carboxylates. Among them, hydroxide ions are particularly preferably used.

As the structure-directing agent, a phosphorus-containing structure-directing agent or a nitrogen-based structure directing agent can also be used. Phosphorus-containing structure-directing agents include, for example, substances such as tetraethylphosphonium hydroxide and tetraethylphosphonium bromide. However, when the structure-directing agent is removed from the synthetic zeolite by calcination, the phosphorus compound may generate harmful substances such as diphosphorus pentoxide, so the nitrogen-based structure-directing agent is preferable.

After hydrothermal synthesis and calcination, the obtained zeolite is preferably subjected to at least one treatment selected from silylation treatment, steam treatment, heat treatment, acid treatment and ion exchange as described above. Among these, it is preferably subjected to at least one treatment selected from silylation treatment, steam treatment, heat treatment, and ion exchange, and more preferably at least one treatment selected from silylation treatment, steam treatment, and ion exchange. More preferably, at least one treatment selected from silylation treatment and steam treatment is performed, and particularly preferably, silylation treatment is performed.

Since zeolite is a catalytically active component, zeolite may be used as it is for the reaction as a zeolite catalyst. may be used.
Substances and binders inert to the reaction include alumina, alumina sol, silica, silica sol, quartz, and mixtures thereof.

The total acid content and outer surface acid content of the zeolite catalyst as a whole can be measured by the same methods as those for the above-described total acid content and outer surface acid content of zeolite. The total acid amount of the zeolite catalyst is not particularly limited, but is usually 0.01 mmol/g or more, preferably 0.1 mmol/g or more, more preferably 0.3 mmol/g or more, and still more preferably 0.5 mmol/g. / g or more. Also, it is usually 2.5 mmol/g or less, preferably 1.5 mmol/g or less, more preferably 1.2 mmol/g or less, and still more preferably 0.9 mmol/g or less. By setting the total acid amount of the zeolite catalyst within the above range, the propylene conversion activity can be secured, coke formation inside the pores of the zeolite can be suppressed, and ethylene production can be promoted.

Although the amount of acid on the outer surface of the zeolite catalyst is not particularly limited, it is usually 8% or less, preferably 5% or less, more preferably 3% or less, and still more preferably 1% with respect to the total acid amount of the catalyst. Below, it is most preferably 0%. If the outer surface acidity is too large, the ethylene selectivity tends to be significantly reduced due to side reactions occurring at the outer surface acid sites.
In addition, in order to adjust the total acid amount and the outer surface acid amount of the zeolite catalyst, it is preferable to use silica, alumina, or the like having no acid sites as a binder. When a binder having acid sites such as alumina is used, the total acidity of the catalyst and the acidity of the outer surface of the catalyst are measured as a total value including the acidity of the zeolite and the acidity of the binder. be. In that case, it is possible to obtain the acid content of the zeolite without the binder-derived acid content by obtaining the acid content derived from the binder by another method and subtracting this value from the acid content of the catalyst. The acid amount of the binder is obtained from the acid amount of the zeolite obtained from the peak intensity of tetracoordinated Al derived from the acid sites of the zeolite in ²⁷ Al-NMR, and the acid amount of the catalyst obtained by the ammonia temperature programmed desorption method. Calculated by subtraction.

The amount of the phosphorus compound contained in the zeolite catalyst is not particularly limited, but is usually 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0.1% by mass. % or less, particularly preferably 0.01 mass % or less. The phosphorus compound here refers to a substance such as phosphorus oxide, and does not mean zeolite itself such as aluminophosphate or gallophosphate.

The average particle size of the zeolite catalyst varies depending on zeolite synthesis conditions, particularly granulation/molding conditions, but the average particle size is usually 0.01 μm to 500 μm, preferably 0.1 to 100 μm. If the average particle size of the zeolite catalyst is too large, the effective coefficient of the catalyst will tend to decrease, and if it is too small, the handleability will be poor. This average particle size can be determined by SEM observation or the like.

<A2. Method for producing ethylene>
A method for producing ethylene includes a step (I) of contacting with a catalyst to produce ethylene, and a step (II) of regenerating the catalyst that has passed through step (I). Each step will be described in detail below.

<A2-1. Step (I)>
As noted above, ethylene can be produced by contacting propylene with a catalyst such as a zeolite.

The production origin of propylene, which is a raw material, is not particularly limited. For example, those obtained by cracking naphtha by steam cracking or catalytic cracking (hereinafter referred to as naphtha cracked product), ethane, propane, n-butane, atmospheric gas oil (AGO), vacuum gas oil (VGO), natural gas liquid (NGL) produced by thermal decomposition (hereinafter referred to as thermal decomposition product), produced by fluidized catalytic cracking (FCC) of vacuum gas oil or residual oil, produced by MTO (Methanol to Olefin) reaction , those produced by the ETO (Ethylene/Ethanol to Olefin) reaction, those produced by the dehydrogenation reaction of alkanes such as propane, and the Fischer process using a hydrogen/carbon monoxide mixed gas obtained by the gasification of coal as a raw material. Examples thereof include those produced by Tropsch synthesis. Of these, the naphtha decomposition product and the thermal decomposition product are preferred, and the naphtha decomposition product is more preferred.

In addition to propylene, the raw material may contain hydrocarbons other than propylene (hereinafter sometimes referred to as "other hydrocarbons"). That is, any raw material may be used as long as it contains propylene. Examples of compounds other than propylene include olefins other than propylene such as ethylene, butene, pentene, and hexene; paraffins such as methane, ethane, propane, butane, pentane, and hexane; alkynes such as acetylene and methylacetylene; , butadiene, pentadiene, and hexadiene; and aromatic hydrocarbons such as benzene, toluene, and xylene. The above olefins, paraffins, alkynes, and dienes may have a linear structure or a cyclic structure, and may contain branched isomers in any ratio. In addition to propylene, it may contain methanol or dimethyl ether, and there is no restriction on the mixing ratio.

Generally, in the production of ethylene from propylene, the target product, ethylene, is easily converted to other olefins such as butene and hexene upon contact with a catalyst. Therefore, it is preferable to use propylene from which ethylene has been separated as a raw material. . The mass ratio of propylene to ethylene contained in the raw material is not particularly limited, but is usually 1 or more, preferably 5 or more, more preferably 10 or more, still more preferably 15 or more, and particularly preferably 30 or more. and the larger the better.
In addition, olefins with a large number of carbon atoms of butene or more can be partially converted to ethylene by contact with the same catalyst, and the ethylene yield can be improved, so they may be contained together with propylene in the raw material. , the butene produced by this reaction can be recycled and used. The mass ratio of propylene to butene contained in the raw material is not particularly limited, but is usually 1 or more, preferably 5 or more, more preferably 10 or more, and usually 1000 or less, preferably 100 or less, more preferably. is 50 or less.

The reactor used for ethylene production is not particularly limited as long as the propylene feedstock is in the gaseous phase in the reaction zone, but fixed bed reactors, moving bed reactors and fluidized bed reactors are selected. Fluidized bed reactors are preferred for production of constant ethylene yields when the propylene conversion is highly variable.
In addition, it can be carried out in any form of batch, semi-continuous or continuous, but is preferably carried out in a continuous mode. A method using a plurality of arranged reactors may also be used.
When filling the fluidized bed reactor with the above-mentioned catalyst, in order to keep the temperature distribution of the catalyst layer small, granules that are inert to the reaction, such as quartz sand, alumina, silica, and silica-alumina, are mixed with the catalyst. can be filled with In this case, there is no particular limitation on the amount of the granular material that is inert to the reaction, such as quartz sand. From the viewpoint of uniform mixing with the catalyst, the particulate matter preferably has a particle size approximately the same as that of the catalyst.
In addition, the reaction substrate (reaction raw material) may be divided and supplied to the reactor for the purpose of dispersing the heat generated by the reaction.

(substrate concentration)
The concentration of propylene in all feed components supplied to the reactor is not particularly limited, but is usually 3 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol% or more, in all feed components. mol % or more, and usually 100 mol % or less, preferably 80 mol % or less, more preferably 60 mol % or less, still more preferably 40 mol % or less. By setting the substrate concentration within the above range, the production of aromatic compounds and paraffins can be suppressed, and the yield of ethylene can be improved. Moreover, since the reaction rate can be maintained, the amount of catalyst can be suppressed, and the size of the reactor can also be suppressed.
Therefore, it is preferable to dilute the reaction substrate with a diluent described below, if necessary, so as to obtain such a preferable substrate concentration.

(diluent)
In the reactor, in addition to raw materials containing propylene, helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, paraffins, hydrocarbons such as methane, aromatic compounds, and their A mixture or the like can be present, but among these, the coexistence of hydrogen, helium, nitrogen, and water (steam) is preferred, and the coexistence of hydrogen is most preferred in terms of increasing the yield of ethylene. . As such a diluent, an impurity contained in the reaction raw material may be used as it is, or a separately prepared diluent may be used by mixing it with the reaction raw material. Further, the diluent may be mixed with the reaction raw materials before entering the reactor, or may be supplied to the reactor separately from the reaction raw materials.

(weight space velocity)
The weight hourly space velocity referred to here is the flow rate (weight/time) of propylene, which is a reaction raw material, per weight of the catalyst (catalytically active component), and the weight of the catalyst here is used for granulating and molding the catalyst. It is the weight of catalytically active components without inert components or binders.

The weight hourly space velocity is not particularly limited, but is usually 0.01 Hr ^-1 or more, preferably 0.1 Hr ^-1 or more, more preferably 0.2 Hr ^-1 or more, further preferably 0.5 Hr ^-1 or more. and is usually 50 Hr ⁻¹ or less, preferably 10 Hr ⁻¹ or less, more preferably 5 Hr ⁻¹ or less, still more preferably 3 Hr ⁻¹ or less. By setting the weight hourly space velocity within the above range, the ratio of unreacted propylene in the reactor outlet gas can be reduced, and by-products such as aromatic compounds and paraffins can be reduced. It is preferable in that the rate can be improved. In addition, it is possible to reduce the amount of catalyst required to obtain a certain amount of production, which is preferable because the size of the reactor can be reduced.

(reaction temperature)
The reaction temperature is not particularly limited as long as it is a temperature at which propylene is brought into contact with the catalyst to produce ethylene. 450° C. or higher, particularly preferably 475° C. or higher, most preferably 500° C. or higher, and usually 800° C. or lower, preferably 700° C. or lower, more preferably 650° C. or lower, further preferably 600° C. or lower. By setting the reaction temperature within the above range, the production of aromatic compounds and paraffins can be suppressed, so that the yield of ethylene in one pass can be improved. In addition, the propylene conversion activity can be maintained at a high level, and when hydrogen is included in the reaction gas together with propylene, the contact effect can be maximized. can do. Furthermore, when the zeolite is a silicate, dealumination from the zeolite skeleton is suppressed, which is preferable in that the catalyst life can be maintained. In addition, the reaction temperature here refers to the temperature at the outlet of the catalyst layer.

(reaction pressure)
Although the reaction pressure (total pressure) is not particularly limited, it is usually 0.01 MPa (absolute pressure, hereinafter the same) or higher, preferably 0.05 MPa or higher, more preferably 0.1 MPa or higher, and still more preferably 0.2 MPa. That is, it is usually 5 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, and still more preferably 0.4 MPa or less. By setting the reaction pressure within the above range, the production of by-products such as aromatic compounds and paraffins can be suppressed, and the yield of ethylene can be improved. Also, the reaction rate can be maintained.

(Propylene partial pressure)
Although the partial pressure of propylene is not particularly limited, it is usually 0.001 MPa or higher (absolute pressure, hereinafter the same), preferably 0.005 MPa or higher, more preferably 0.0075 MPa or higher, further preferably 0.010 MPa or higher, It is particularly preferably 0.015 MPa or more, most preferably 0.020 MPa or more, and usually 1 MPa or less, preferably 0.5 MPa or less, more preferably 0.2 MPa or less, and still more preferably 0.1 MPa or less. By setting the partial pressure of the raw material within the above range, coking can be suppressed and the yield of ethylene can be improved.

(Coke component)
Propylene conversion tends to accumulate some of it on the inner/outer surfaces of the crystals as coke (heavy components such as polyaromatics) that must be removed by regeneration, reducing catalytic activity. Therefore, the coke content (coke content) is usually 30% by mass or less and 20% by mass with respect to the catalyst, which is the active component, in order to obtain moderate catalytic activity and high ethylene selectivity. % or less, more preferably 15% by mass or less, and usually 0.1% by mass or more, preferably 1.0% by mass or more, and 3.0% by mass or more. It is more preferable to keep it at 5.0% by mass or more. If the coke content in the catalyst is at least the above lower limit, molecular diffusion in the catalyst can be suppressed, cracking of olefins having 4 or more carbon atoms into ethylene can be promoted, and ethylene production can be improved. Since the ethylene selectivity can be maintained high, the catalyst preferably maintains a coke content equal to or higher than the above lower limit. On the other hand, when the amount of coke accumulated in the catalyst exceeds the above upper limit, the catalytic activity tends to decrease. Therefore, it is preferable to adjust the regeneration conditions so that the amount of coke accumulated in the catalyst is within the above range by the regeneration method described later.
In this embodiment, the amount of coke accumulated in the catalyst means that the catalyst in which coke has accumulated due to the conversion reaction of propylene is heated to 550 ° C. at a rate of 10 ° C. under an inert gas such as helium (50 cc / min). /min and held for 30 minutes to remove adsorbed water and light boiling hydrocarbon components, then switch to air flow (50 cc/min) and heat up to 600 ° C. at a heating rate of 10 ° C./min. and held for 60 minutes, and the weight loss due to oxidative combustion in the temperature range of 550° C. or higher at this time is calculated.

(Conversion rate)
In the present embodiment, the conversion rate of propylene is not particularly limited, but the conversion rate is usually 5% or higher, preferably 20% or higher, more preferably 30% or higher, and still more preferably 40% or higher. It is 100% or less, preferably 80% or less, more preferably 60% or less, still more preferably 50% or less. In the present embodiment, by adjusting the propylene conversion rate to be within the above range, it is possible to suppress the by-production of butenes, aromatic compounds, and paraffins, and the accumulation of coke in the pores. Ethylene yield can be improved. In addition, the separation efficiency of components such as ethylene and propylene from the product can be enhanced. That is, in the present embodiment, the catalyst is preferably subjected to a regeneration step so that the conversion of propylene is within the range described above.

Normally, coke accumulation progresses with the passage of reaction time, and the propylene conversion rate tends to decrease. Therefore, as described later, when the amount of coke accumulated in the catalyst increases, the catalyst is put into the regeneration process. preferably provided. Moreover, the method of operating within the range of the above conversion rate is not particularly limited.

(yield)
In the present embodiment, the yield of ethylene is not particularly limited, but the yield is usually 5% or more, preferably 20% or more, more preferably 30% or more, still more preferably 40% or more, and usually It is 100% or less, preferably 80% or less, more preferably 60% or less. When the yield of ethylene is within the above range, the ratio of the target product at the reactor outlet is sufficient, which is preferable in that the cost of raw materials and the load of separation and purification can be reduced.
The yield of butenes, which are by-products, is not particularly limited, but is usually 50% or less, preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, and particularly preferably 5%. Below, the less the better. It is preferable that the yield of butenes is within the above range, since the burden of separation and recycling of butene components can be reduced.

The conversion rate is a value calculated by the following formula.
Propylene conversion rate (%)=[[reactor inlet propylene (mol/Hr)−reactor outlet propylene (mol/Hr)]/reactor inlet propylene (mol/Hr)]×100

The selectivity in this specification is a value calculated by the following formulas. In each formula below, the “derived carbon flow rate (mol/Hr)” of hydrocarbons such as ethylene, butene, C5+, paraffin and aromatic compounds means the molar flow rate of carbon atoms constituting each hydrocarbon. Paraffins are the sum of paraffins having 1 to 4 carbon atoms, aromatic compounds are the sum of benzene, toluene and xylene, and C5+ is the sum of hydrocarbons having 5 or more carbon atoms excluding the aromatic compounds.
Ethylene selectivity (%) = [reactor outlet ethylene-derived carbon molar flow rate (mol/Hr) / [reactor outlet total carbon molar flow rate (mol/Hr) - reactor outlet propylene-derived carbon molar flow rate (mol/Hr) ]]×100
・Butene selectivity (%) = [reactor outlet butene-derived carbon molar flow rate (mol/Hr) / [reactor outlet total carbon molar flow rate (mol/Hr) - reactor outlet propylene-derived carbon molar flow rate (mol/Hr) ]]×100
・C5+ selectivity (%) = [reactor outlet C5+ derived carbon molar flow rate (mol/Hr)/[reactor outlet total carbon molar flow rate (mol/Hr) - reactor outlet propylene-derived carbon molar flow rate (mol/Hr) ]]×100
Paraffin selectivity (%) = [reactor outlet paraffin-derived carbon molar flow rate (mol/Hr) / [reactor outlet total carbon molar flow rate (mol/Hr) - reactor outlet propylene-derived carbon molar flow rate (mol/Hr) ]]×100
Aromatic compound selectivity (%) = [reactor outlet aromatic compound-derived carbon molar flow rate (mol/Hr) / [reactor outlet total carbon molar flow rate (mol/Hr) - reactor outlet propylene-derived carbon molar flow rate ( mol/Hr)]]×100
The yield in the present specification is obtained by multiplying the raw material conversion rate and the selectivity of each component produced. Specifically, the ethylene yield and butene yield are respectively represented by the following equations. .
Ethylene yield (%) = Propylene conversion rate (%) x Ethylene selectivity (%)/100
・Butene yield (%) = propylene conversion rate (%) x butene selectivity (%) / 100

(reaction product)
As the reactor outlet gas (reactor effluent), a mixed gas containing ethylene as a reaction product, propylene as a raw material, butenes as by-products, paraffin, an aromatic compound and a diluent is obtained. The concentration of ethylene in the mixed gas is not particularly limited, but is usually 5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, and is usually 95% by mass or less, preferably 90% by mass or less. is.
Depending on the reaction conditions, the reaction product may contain propylene as an unreacted raw material. However, if the selectivity for ethylene is low, that is, if the selectivity for by-products is high, it will lead to loss of raw materials and increase production costs. Therefore, in some cases, it is preferable to operate under conditions in which the ethylene selectivity is high even under conditions in which the propylene conversion rate is low. In this embodiment, if desired, components other than ethylene may be separated and recovered. The residue from which desired components have been separated and recovered contains light paraffins, light olefins, aromatic compounds and the like. At least part of this residue can be mixed with part of the raw material gas described above and used as so-called recycled gas.

(Separation of product)
A mixed gas containing ethylene, which is a reaction product, unreacted raw materials, by-products, and a diluent, as a reactor outlet gas, is introduced into a known separation/purification facility, and is recovered, purified, and purified according to each component. Recycling and disposal may be carried out.

(recycling)
Components other than ethylene (olefins, paraffins, etc.), especially some or all of the hydrocarbons with 3 or more carbon atoms, are recycled by mixing with the reaction raw materials after being separated and purified, or by directly supplying them to the reactor. You may In addition, among the by-products, components that are inert to the reaction can be reused as a diluent.

<A2-2. Step (II)>
By regenerating the catalyst whose propylene conversion rate has decreased through the step (I), ethylene can be stably produced while minimizing the fluctuation range of the ethylene yield. Note that, in the present embodiment, regeneration of the catalyst means to bring the catalyst in a state in which the propylene conversion rate has decreased into a state in which the propylene conversion rate is higher than that before the regeneration treatment.

As propylene is converted, the amount of coke components accumulated on the catalyst increases. The amount of the coke component accumulated in the catalyst when the catalyst with an increased accumulated amount of the coke component is subjected to the step (II) of regenerating the catalyst is usually 0% by mass or more, preferably 0.01% by mass. above, more preferably 0.1% by mass or more, still more preferably 1.0% by mass or more, particularly preferably 3.0% by mass or more, particularly preferably 5.0% by mass or more, and usually 30% by mass or less, It is preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and particularly preferably 10% by mass or less. If the amount of the coke component accumulated in the catalyst is equal to or more than the above lower limit, the catalytic activity is in a state of being lowered, and the catalytic activity can be effectively recovered in the regeneration step, which is preferable. On the other hand, if the amount of coke components accumulated in the catalyst exceeds the above upper limit, the diffusion of the regeneration gas and cracked gas in the catalyst in the regeneration process is hindered, and the regeneration efficiency tends to decrease significantly. It is preferred to contact with the regeneration gas below. In this regeneration step, the amount of coke components accumulated in the catalyst can be moderately reduced while the catalytic activity can be recovered, so that ethylene can be stably produced at a high yield.

There are no particular restrictions on the step (II) of regenerating the catalyst. For example, when producing ethylene from propylene, at the stage when the coke content of the catalyst increases, after stopping the supply of propylene, the gas used for regeneration (hereinafter sometimes referred to as regeneration gas) is supplied into the reactor. By doing so, the catalyst with increased coke content can be brought into contact with the regeneration gas. In addition, the catalyst with an increased coke content is removed from the reactor in step (I) in which propylene is brought into contact with the catalyst, transferred to the reactor in step (II) for regenerating the catalyst, and the gas used for regeneration is supplied to the catalyst. It may be supplied to regenerate the catalyst.

In particular, when the above step (I) is performed using a fixed bed reactor, when the amount of coke accumulated in the catalyst reaches or exceeds the above upper limit, after stopping the supply of propylene, A regeneration gas may be supplied to contact the catalyst. Alternatively, the catalyst may be extracted from the above reactor, charged into a reactor other than the reactor, and then brought into contact with the regeneration gas.

When the step (I) is carried out using a moving bed reactor or a fluidized bed reactor, a device for contacting the regenerated gas with the catalyst is provided separately from the reactor, and the catalyst extracted from the reactor is is continuously sent to the apparatus, the catalyst is brought into contact with the regeneration gas in the apparatus, and then the reaction for producing ethylene is preferably carried out while the catalyst contacted with the regeneration gas is continuously returned to the reactor.

The gas used in step (II) for regenerating the catalyst is not particularly limited, but preferred examples thereof include gases containing at least one selected from oxygen, hydrogen, and water vapor. Specific regeneration methods include combustion regeneration using a regeneration gas containing oxygen, steam reforming regeneration using steam (water) as a regeneration gas, and hydrocracking using hydrogen as a regeneration gas. Among these, the regeneration gas is preferably a gas containing oxygen or hydrogen, and more preferably a gas containing hydrogen.

The method for producing oxygen is not particularly limited, and examples include oxygen cryogenically separated from air in the atmosphere, oxygen produced from hydrogen peroxide, etc., and oxygen recovered from air in the atmosphere is preferred.

The method for producing steam (water) is not particularly limited, and one obtained by evaporating ordinary water can be used. Water obtained by various production methods, such as tap water, desalted water, and plant process water, can be arbitrarily used.

The method for producing the hydrogen contained in the hydrogen-containing gas is not particularly limited, and examples include those obtained by steam reforming of methane and methanol, those obtained by partial oxidation of hydrocarbons, and those obtained by reforming hydrocarbons with carbon dioxide. obtained by gasification of coal, obtained by thermal decomposition of water typified by the IS (Iodine-Sulfur) process, obtained by photoelectrochemical reaction, and obtained by electrolysis of water Any of those obtained by various production methods can be used.

Any mixture of gases other than these may be used, or purified hydrogen may be used.

Gases other than these contained in gases containing oxygen, hydrogen, and water vapor include hydrocarbons such as helium, argon, nitrogen, carbon monoxide, carbon dioxide, paraffins, and methane, if there is no safety problem. It may include such as. Among these, helium, nitrogen, carbon dioxide, paraffins, and methane are preferred because of their low reactivity.

The pressure of the entire regeneration gas (total pressure) is not particularly limited, but the absolute pressure is usually 0.01 MPa (absolute pressure, hereinafter the same) or more, preferably 0.05 MPa or more, more preferably 0.1 MPa. Above, more preferably 0.2 MPa or more, usually 5 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, still more preferably 0.5 MPa or less. By setting the pressure within the above range, the partial pressure of the hydrocarbon component in the treated gas can be kept low while enhancing the regeneration efficiency, so that high catalytic activity can be maintained.

(hydrogen partial pressure)
The gas containing hydrogen in the regeneration gas is not particularly limited, but the hydrogen partial pressure in absolute pressure is usually 0.001 MPa or more, preferably 0.01 MPa or more, and more preferably 0.03 MPa. Above, more preferably 0.05 MPa or more, particularly preferably 0.1 MPa or more, usually 4 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, still more preferably 0.5 MPa or less, particularly preferably 0.1 MPa or less. 3 MPa or less. By setting the hydrogen partial pressure within the above range, the removal and reformation of the coke components accumulated in the catalyst proceed rapidly, so that the catalyst is efficiently brought into a state that provides high propylene conversion activity and high ethylene selectivity. be able to. In addition, equipment and energy for producing high-pressure hydrogen can be reduced.

The space velocity of the regeneration gas is not particularly limited, but is usually 0.001 Hr ^-1 or more, preferably 0.01 Hr ^-1 or more, more preferably 0.1 Hr ^-1 or more, and usually 20 Hr ^-1 or less. , preferably 10 Hr ⁻¹ or less, more preferably 5 Hr ⁻¹ or less. By setting the weight hourly space velocity within the above range, the concentration of hydrocarbon components and water vapor contained in the catalyst can be reduced, so that the propylene conversion activity can be maintained at a high level. Furthermore, since the distribution of coke components accumulated in the catalyst can be made uniform, uneven reactions within the catalyst can be suppressed, and ethylene selectivity can be increased.

Space velocity is the flow rate of regeneration gas per weight of catalyst (catalytically active components). The weight of the catalyst is the weight of the active ingredient (zeolite) that does not contain any inert ingredients or binders used in the granulation/molding of the catalyst.

The concentration of the regeneration gas in the supply gas for the regeneration step (II) is not particularly limited, but is usually 5% by volume or more, preferably 10% by volume or more, more preferably 30% by volume or more, and is usually It is 100% by volume or less, preferably 90% by volume or less, more preferably 80% by volume or less. The regeneration gas concentration is preferably as high as possible, usually 5% by volume or more, preferably 30% by volume or more, more preferably 60% by volume or more, and usually 100% by volume or less. By setting the regeneration gas concentration within the above range, the contact between the catalyst and the regeneration gas becomes sufficient, and the removal and reformation of coke components proceeds rapidly, resulting in high propylene conversion activity and high ethylene selectivity. It can be made efficient in a catalytic state.

The temperature at which the catalyst is brought into contact with the regeneration gas (hereinafter sometimes referred to as "regeneration temperature") is not particularly limited, but is usually 300°C or higher, preferably 400°C or higher, more preferably 500°C. Above, more preferably 525° C. or higher, particularly preferably 550° C. or higher, and usually 800° C. or lower, preferably 700° C. or lower, more preferably 650° C. or lower, still more preferably 600° C. or lower. By setting the degree of regeneration within the above range, the removal of the coke component proceeds rapidly, so that the catalytic activity can be maintained at a high level. Furthermore, since structural collapse of the catalyst is suppressed, it is preferable in that the life of the catalyst can be maintained.

The contact time with the regeneration gas is not particularly limited, but is usually 1 second or longer, preferably 10 seconds or longer, more preferably 1 minute or longer, still more preferably 5 minutes or longer, and usually 5 hours or shorter. It is preferably 2 hours or less, more preferably 1 hour or less. Since the appropriate time varies depending on the concentration of the regeneration gas and the processing temperature, it is preferable to adjust the time as appropriate. When the apparatus to be brought into contact with the regeneration gas is a fluidized bed apparatus, the treatment time mentioned above means the residence time of the catalyst in the apparatus.

A second embodiment of the present invention is a method of producing ethylene by contacting propylene with a catalyst in a reactor, wherein the catalyst is brought into contact with a gas containing hydrogen as the catalyst to produce ethylene. be. Although the present embodiment will be described in detail below, differences from the first embodiment will be described, and the description of the first embodiment can be appropriately referred to for the rest.

<B1. Catalyst>
The catalyst used in the reaction according to the present embodiment is not particularly limited as long as it is a solid having a Bronsted acid site, and conventionally known catalysts are used, for example, clay minerals such as kaolin, acidic ion Examples include solid acid catalysts such as exchange resins, zeolites, and mesoporous silica-alumina. When producing ethylene from propylene, coke components such as aromatic compounds having a skeleton such as benzene, naphthalene, and anthracene are accumulated in the catalyst. , The above aromatic compounds, which are coke components accumulated in the catalyst, are decomposed and the re-reaction proceeds, so that the amount of coke accumulated in the catalyst is moderately reduced, and the quality of the coke components is improved. can be done. As a result, the catalyst is regenerated, and ethylene can be efficiently produced from propylene.

Among these solid acid catalysts, those having a molecular sieve effect are preferred, and zeolites are more preferred. A known catalyst can be used as the above catalyst, but zeolite, which is a preferred form of the catalyst, is described in the description of the first embodiment <A1. Catalyst>.
Non-Patent Document 1 describes that the ethylene selectivity is improved by modifying the MFI-type zeolite catalyst with phosphoric acid. By doing so, ethylene can be obtained in high yield without modifying the catalyst with phosphoric acid or the like. Therefore, in the present embodiment, by setting the amount of the phosphorus compound in the catalyst to be equal to or less than the upper limit value described in the description of the first embodiment, the corrosion of the reactor due to the phosphorus compound is suppressed, and the yield is high. Ethylene can be obtained.

<B2. Method for producing ethylene>
Ethylene can be produced by contacting a feed containing propylene with a zeolite catalyst. This embodiment is a suitable method for ethylene production and linear butene production, and is particularly suitable for ethylene production. Regarding the method for producing ethylene, the description of the first embodiment <A2-1. Production method of ethylene>.

In the present embodiment, the catalyst is preferably brought into contact with a hydrogen-containing gas so as to achieve the conversion rate of propylene described in the description of the first embodiment. Normally, coke accumulation progresses with the passage of reaction time, and the conversion rate of propylene tends to decrease. Therefore, when the amount of coke accumulated in the catalyst increases, the catalyst is brought into contact with hydrogen to is preferably played. In addition, you may use together and use the reproduction|regeneration methods other than the said method.

<B3. Method of Contacting Catalyst with Gas Containing Hydrogen>
In the present embodiment, in the method of producing ethylene by contacting propylene with a catalyst in a reactor, a catalyst contacted with a hydrogen-containing gas is used as the catalyst to achieve high selectivity and high yield of ethylene. can be produced stably.

Incidentally, referring to the well-known Japanese Patent No. 5545114, it is known to regenerate the catalyst by treating it with hydrogen in the reaction of producing propylene from ethylene as a raw material. However, in the present embodiment, in which propylene, which has higher reactivity and adsorptive capacity than ethylene, is used as a raw material, sequential reactions tend to proceed easily, so the coke component produced is a heavier component, and can be easily treated by hydrogen treatment. It is unlikely that the coke component would be removed in the In addition, under conditions where propylene coexists, adsorption of the catalyst and hydrogen is relatively suppressed (adsorption of the catalyst and propylene takes precedence), so it is considered that the effect of contacting with hydrogen cannot be obtained sufficiently. Surprisingly, however, it was found that even in the method of producing ethylene from propylene as in the present embodiment, the catalyst can be regenerated by contacting the catalyst with a hydrogen-containing gas, and ethylene can be produced at a high yield. . The reason for this is not clear, but by contacting the catalyst with a hydrogen-containing gas, the aromatic compounds, etc., which are coke components accumulated in the catalyst, are decomposed, and the re-reaction proceeds, so that they accumulate in the catalyst. It is considered that the quality of the coke component could be improved while moderately reducing the amount of coke produced. As a result, the catalyst was regenerated and ethylene could be produced from propylene at a high yield. it is conceivable that.

In particular, with the conversion of propylene, the content of coke components in the catalyst used increases. is moderately reduced, the quality of the coke component is modified, and as a result, ethylene can be stably produced at a high yield. Therefore, the contact between the catalyst and hydrogen-containing gas is preferably carried out in a state where the catalyst contains coke components, and the amount of coke components accumulated in the catalyst when contacting with hydrogen gas is usually 0% by mass. Above, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1.0% by mass or more, particularly preferably 3.0% by mass or more, particularly preferably 5.0% by mass or more and is usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and particularly preferably 10% by mass or less. If the amount of the coke component accumulated in the catalyst is equal to or higher than the above lower limit, the catalytic activity is in a state of being lowered, and the catalytic activity can be effectively recovered by hydrogen contact, which is preferable. On the other hand, when the amount of coke components accumulated in the catalyst exceeds the above upper limit, the diffusion of hydrogen gas and cracked gas in the catalyst tends to be hindered, and the regeneration efficiency tends to decrease significantly. Contact with gas is preferred.

There is no particular limitation on the method of bringing the catalyst into contact with the hydrogen-containing gas. For example, when producing ethylene from propylene, at a stage when the coke content of the catalyst has increased, a gas containing hydrogen is supplied into the reactor at the same time as propylene, and the catalyst with increased coke is converted into a gas containing hydrogen. can be contacted. Further, by supplying a hydrogen-containing gas into the reactor after stopping the supply of propylene, the catalyst with an increased coke content can be brought into contact with the hydrogen-containing gas. Additionally, the coke-enriched catalyst may be removed from the reactor and contacted with hydrogen.

In particular, when producing ethylene from propylene using a fixed bed reactor, it is preferable to supply propylene and a gas containing hydrogen simultaneously or separately without extracting the catalyst from the reactor for producing ethylene. Used. That is, when the amount of coke accumulated in the catalyst reaches the above upper limit value or more, a gas containing hydrogen is supplied into the reactor at the same time as propylene or after the supply of propylene is stopped, and the amount of coke is reduced. The increased catalyst can be contacted with a gas containing hydrogen.
Moreover, it is preferable to extract the catalyst from the above reactor, fill the catalyst in a reactor other than the reactor, and then bring the catalyst into contact with the hydrogen gas.

When a moving bed reactor or a fluidized bed reactor is used in the production of ethylene from propylene, a device for contacting a hydrogen-containing gas with a catalyst may be provided separately from the reactor. The catalyst extracted from the reactor is continuously sent to the device, the catalyst is brought into contact with hydrogen gas in the device, and then the catalyst that has been contacted with the hydrogen-containing gas is continuously returned to the reactor to perform the ethylene production reaction. preferably.

The time for which the gas containing hydrogen is brought into contact with the catalyst is not particularly limited, and may be appropriately selected in consideration of the amount of coke accumulated in the catalyst.

The method for producing the hydrogen contained in the hydrogen-containing gas of the present invention is not particularly limited, and examples include those obtained by steam reforming of methane and methanol, those obtained by partial oxidation of hydrocarbons, Those obtained by reforming, those obtained by gasification of coal, those obtained by thermal decomposition of water represented by the IS (Iodine-Sulfur) process, those obtained by photoelectrochemical reaction, and water electricity Those obtained by various production methods such as those obtained by decomposition can be arbitrarily used.

Any mixture of gas other than hydrogen may be used, or purified hydrogen may be used.

Gases other than hydrogen may include, for example, helium, argon, nitrogen, oxygen, carbon monoxide, carbon dioxide, paraffins, and hydrocarbons such as methane. Among these, helium, nitrogen, carbon dioxide, paraffins, and methane are preferred because of their low reactivity.

The gas used for treatment with a gas containing hydrogen contains hydrocarbon components (olefins, paraffins, etc.) in addition to hydrogen. You may recycle and use what was partially or wholly removed.

When supplying a gas containing hydrogen together with propylene, the pressure of the entire gas containing hydrogen (total pressure) is not particularly limited, but is usually 0.01 MPa (absolute pressure, hereinafter the same) or more in absolute pressure, It is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.2 MPa or more, and is usually 5 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, further preferably 0.5 MPa or less. be. By setting the pressure within the above range, the partial pressure of the hydrocarbon component in the treated gas can be kept low while increasing the contact efficiency with the hydrogen gas, so that high catalytic activity can be maintained.

When the gas containing hydrogen is supplied to the reactor at the same time as propylene, the pressure of the gas containing hydrogen is not particularly limited, but the hydrogen partial pressure is usually 0.001 MPa or more, preferably 0.001 MPa or more in absolute pressure. 0.01 MPa or more, more preferably 0.03 MPa or more, still more preferably 0.05 MPa or more, particularly preferably 0.1 MPa or more, usually 4 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, More preferably 0.5 MPa or less, particularly preferably 0.3 MPa or less. By setting the hydrogen partial pressure within the above range, the removal and reformation of the coke components accumulated in the catalyst proceed rapidly, so that the catalyst is efficiently brought into a state that provides high propylene conversion activity and high ethylene selectivity. be able to. In addition, equipment and energy for producing high-pressure hydrogen can be reduced.

The space velocity of the hydrogen-containing gas is not particularly limited, but is usually 0.001 Hr ^-1 or more, preferably 0.01 Hr ^-1 or more, more preferably 0.1 Hr ^-1 or more, and usually 20 Hr -1 ^{or more. 1} or less, preferably 10 Hr ⁻¹ or less, more preferably 5 Hr ⁻¹ or less. By setting the weight hourly space velocity within the above range, the concentration of hydrocarbon components contained in the catalyst can be reduced, so that the propylene conversion activity can be maintained at a high level. Furthermore, since the distribution of coke components accumulated in the catalyst can be made uniform, uneven reactions within the catalyst can be suppressed, and ethylene selectivity can be increased. Moreover, when recovering gas containing hydrogen, the separation and purification load can be suppressed. Moreover, since the amount of hydrogen gas used can be suppressed, the manufacturing cost can be reduced.

Space velocity is the flow rate of hydrogen per weight of catalyst (catalytically active component). The weight of the catalyst is the weight of the active ingredient (zeolite) that does not contain any inert ingredients or binders used in the granulation/molding of the catalyst.

The hydrogen concentration in the hydrogen-containing gas is not particularly limited, but is usually 5% by volume or more, preferably 10% by volume or more, more preferably 30% by volume or more, and usually 100% by volume or less, preferably is 90% by volume or less, more preferably 80% by volume or less. When the step of contacting the catalyst with a hydrogen-containing gas is before or after the step of contacting the catalyst with propylene in a reactor to produce ethylene, the hydrogen concentration is preferably particularly high. It is usually 5% by volume or more, preferably 30% by volume or more, more preferably 60% by volume or more, and usually 100% by volume or less. By setting the hydrogen concentration in the above range, the contact between the catalyst and hydrogen molecules becomes sufficient, and the removal and reformation of coke components proceeds rapidly, so that the catalyst provides high propylene conversion activity and high ethylene selectivity. state to be efficient. In addition, the amount of hydrogen gas used can be reduced, and the separation and purification load can be suppressed.

The temperature at which the catalyst is brought into contact with the hydrogen-containing gas (hereinafter sometimes referred to as "hydrogen contact temperature") is not particularly limited, but is usually 300° C. or higher, preferably 400° C. or higher, more preferably 400° C. or higher. is 450° C. or higher, more preferably 500° C. or higher, particularly preferably 525° C. or higher, and usually 800° C. or lower, preferably 700° C. or lower, more preferably 650° C. or lower, further preferably 600° C. or lower. By setting the hydrogen contact temperature within the above range, the removal of the coke component proceeds rapidly, so that the catalytic activity can be maintained at a high level. Furthermore, since structural collapse of the catalyst is suppressed, it is preferable in that the life of the catalyst can be maintained.

The contact time with the hydrogen-containing gas is not particularly limited, but is usually 1 second or longer, preferably 10 seconds or longer, more preferably 1 minute or longer, still more preferably 5 minutes or longer, and usually 5 hours. Thereafter, it is preferably 2 hours or less, more preferably 1 hour or less. Since the appropriate time varies depending on the concentration of hydrogen gas and the treatment temperature, it is preferable to adjust the time as appropriate. When the apparatus for contacting the hydrogen-containing gas is a fluidized bed apparatus, the treatment time means the residence time of the catalyst in the apparatus.

A third embodiment of the present invention is a method for producing ethylene by contacting a hydrocarbon and a catalyst in a reactor, wherein the hydrocarbon contains at least propylene and a hydrocarbon having 4 or more carbon atoms. , the mass ratio of hydrocarbons having 4 or more carbon atoms to propylene contained in the hydrocarbons is 0.01 or more and 10 or less.

<C1. Catalyst>
The catalyst used in this embodiment will be described. The catalyst used in the reaction according to the present embodiment is not particularly limited as long as it can produce ethylene from a hydrocarbon containing propylene and has a Bronsted acid point and is in a solid state. Conventionally known catalysts can be used. Used. Examples thereof include clay minerals such as kaolin, acidic ion exchange resins, zeolite, solid acid catalysts such as mesoporous silica alumina. In the present embodiment, a step of regenerating a catalyst having a reduced conversion rate of propylene and hydrocarbons having 4 or more carbon atoms may be introduced. By introducing the regeneration step, the amount of coke components accumulated by raw material conversion is reduced can be reduced and ethylene can be produced with a stable yield.

Among these solid acid catalysts, those having a molecular sieve effect are preferred, and zeolites are more preferred. A known catalyst can be used as the above catalyst, but zeolite, which is a preferred form of the catalyst, will be described in detail below.

Zeolite is a crystalline substance in which ₄ TO units (T is the central atom) with a tetrahedral structure are connected three-dimensionally by sharing O atoms to form regular open micropores. Point. Specifically, silicates, phosphates, germanium salts, arsenates, etc. listed in the data collection of the structure committee of the International Zeolite Association (hereinafter sometimes referred to as "IZA") included.

Here, silicates include, for example, aluminosilicates, gallosilicates, ferrisilicates, titanosilicates, borosilicates, and the like.
Phosphates include, for example, aluminophosphates, gallophosphates, beryllophosphates, and the like.
Germanium salts include, for example, aluminogermanium salts, and arsenates include, for example, aluminum arsenates.
Furthermore, aluminophosphates include, for example, silicoaluminophosphates in which the T atom is partially substituted with Si, and those containing divalent or trivalent cations such as Ga, Mg, Mn, Fe, Co, and Zn. .

The average pore diameter of the zeolite is not particularly limited, and is usually 0.80 nm or less, preferably 0.55 nm or less, more preferably 0.50 nm or less, even more preferably 0.45 nm or less, and particularly preferably 0.40 nm or less, It is usually 0.25 nm or more, preferably 0.30 nm or more, more preferably 0.33 nm or more, and still more preferably 0.35 nm or more.
Here, the average pore diameter means the crystallographic free diameter of the channels defined by IZA. The average pore diameter of 0.55 nm or less means that the average diameter of pores (channels) is 0.55 nm or less when the shape of the pores (channels) is perfectly circular. It means that the minor axis is 0.55 nm or less.

By using a zeolite having the above average pore diameter, ethylene can be produced at a high yield using propylene as a raw material. That is, if the average pore diameter is within the above range, diffusion of propylene into the zeolite crystals can be promoted and ethylene can be produced more selectively.
From the above viewpoint, in the present invention, the zeolite is preferably an oxygen 8-membered ring structure zeolite.

As the oxygen 8-membered ring structure zeolite, the structure code (Framework Type Code) defined by IZA, for example, preferably AEI, AFX, CHA, ERI, KFI, LEV, SAS, SAV, SZR, PAU, RHO, RTH, LTA , UFI, and the like.

The zeolite framework density (unit: T/nm ³ ) is not particularly limited, and is usually 20.0 or less, preferably 18.0 or less, more preferably 17.0 or less, and still more preferably 16.0 or less, It is usually 12.0 or higher, preferably 14.0 or higher, more preferably 14.5 or higher.
Here, the framework density (unit: T/nm ³ ) refers to the number of T atoms (atoms other than oxygen atoms constituting the zeolite skeleton) present per unit volume (1 nm ³ ) of the zeolite. This value is determined by the structure of the zeolite.

From these viewpoints, the oxygen 8-membered ring structure zeolite is preferably a zeolite containing d6r in the skeleton defined as a composite building unit by the International Zeolite Association (IZA), more preferably AEI, AFX, CHA, ERI, KFI, LEV, SAV, more preferably AEI, AFX, CHA, or ERI, even more preferably AEI, CHA, or ERI, particularly preferably CHA or ERI, most preferably CHA .

Specific examples of 8-membered oxygen ring structure zeolites include silicates and phosphates. As described above, examples of silicates include aluminosilicates, gallosilicates, ferrisilicates, titanosilicates, and borosilicates, and examples of phosphates include aluminophosphates composed of aluminum and phosphorus, silicon and silicoaluminophosphates composed of aluminum and phosphorus. Among these, aluminosilicates and silicoaluminophosphates are preferred, and aluminosilicates are more preferred.

A proton-exchanged type of zeolite whose ion-exchange sites are protons (H) is usually used. It may be exchanged with transition metals such as metals, Cr, Cu, Ni, Fe, Mo, W, Pt, and Re. Such a zeolite can be prepared by subjecting the zeolite to an ion-exchange treatment, which will be described later.

In addition to these ion exchange sites, metals are supported on alkali metals such as Na and K; alkaline earth metals such as Ca and Sr; and transition metals such as Cr, Cu, Ni, Fe, Mo, W, Pt and Re. good too. Here, the metal loading can usually be carried out by an impregnation method such as equilibrium adsorption method, evaporation to dryness method, pore-filling method and the like.

When the zeolite is a silicate, SiO ₂ /M ₂ O ₃ (where the denominator of said molar ratio represents the total amount of Al ₂ O ₃ , Ga ₂ O ₃ , B ₂ O ₃ and Fe ₂ O ₃ ) mol the ratio is usually 5 or more, preferably 8 or more, more preferably 10 or more, still more preferably 15 or more, usually 500 or less, preferably 100 or less, more preferably 80 or less, further preferably 60 or less, Especially preferably, it is 40 or less. The above ratio is a value obtained on the assumption that all Si atoms in the zeolite are contained as SiO ₂ and all the M contained in the zeolite are contained as M ₂ O ₃ . When the SiO ₂ /M ₂ O ₃ molar ratio is within the above range, a sufficient amount of acid derived from strong acid sites and weak acid sites can be obtained, and the propylene conversion activity becomes higher. In addition, the SiO ₂ /M ₂ O ₃ molar ratio tends to be able to suppress the deactivation of the catalyst due to adhesion of coke, the detachment of T atoms other than silicon from the skeleton, and the decrease in acid strength per acid site. It is preferably within the above range. The SiO ₂ /M ₂ O ₃ molar ratio of zeolite is usually determined by ICP elemental analysis or fluorescent X-ray analysis. In the fluorescent X-ray analysis, a calibration curve is created between the fluorescent X-ray intensity of the analytical element in the standard sample and the atomic concentration of the analytical element. Atoms, aluminum, gallium, iron atom content can be determined. Since the fluorescent X-ray intensity of boron element is relatively small, it is preferable to measure the content of boron atoms by ICP elemental analysis.

When the zeolite is a phosphate, the (Al+P)/Si molar ratio of a silicoaluminophosphate or the (Al+P)/M of a metalloaluminophosphate having a divalent metal (where M represents a divalent metal ) The molar ratio is usually 5 or more, preferably 10 or more, and usually 500 or less, preferably 100 or less. Incidentally, the divalent metal specifically includes Ga, Mg, Mn, Fe, Co, or Zn. By setting the content to the lower limit or more, the durability of the catalyst can be improved, and by setting the content to the upper limit or less, the catalytic activity can be kept high.

The total acidity of zeolite (hereinafter referred to as the total acidity) is the sum of the amount of acid sites present in the zeolite crystal pores and the amount of acid sites on the outer surface of the zeolite crystal (hereinafter referred to as the outer surface acidity). is. The total acid content is not particularly limited, but is usually 0.01 mmol/g or more, preferably 0.1 mmol/g or more, more preferably 0.3 mmol/g or more, and still more preferably 0.5 mmol/g or more. is. Also, it is usually 2.5 mmol/g or less, preferably 1.5 mmol/g or less, more preferably 1.2 mmol/g or less, and still more preferably 0.9 mmol/g or less. By setting the total acid amount within the above range, the propylene conversion activity can be maintained at a high level, coke formation inside the pores of the zeolite can be suppressed, and ethylene production can be promoted. The total acid amount here is calculated from the desorption amount of ammonia in ammonia temperature programmed desorption (NH ₃ -TPD). Specifically, after drying the zeolite under vacuum at 500° C. for 30 minutes as a pretreatment, the pretreated zeolite is brought into contact with an excess amount of ammonia at 100° C. to cause the zeolite to adsorb ammonia. Excess ammonia is removed from the obtained zeolite by vacuum drying at 100°C or contacting it with water vapor at 100°C. Next, the ammonia-adsorbed zeolite was heated in a helium atmosphere at a temperature increase rate of 10°C/min, and the amount of ammonia desorbed at 100-600°C was measured by mass spectrometry, and the total amount of ammonia desorbed per zeolite was measured. Let it be the amount of acid. However, the total acid content is obtained by separating the waveform of the TPD profile using a Gaussian function, and determining the total area of the waveform having the peak top at 240° C. or higher. This "240° C." is an index used only for determining the position of the peak top, and does not mean that the area of the portion above 240° C. is obtained. As long as the waveform has a peak top of 240° C. or more, the “area of the waveform” is the total area of the waveform separated from the waveform. When there are a plurality of waveforms having peak tops at 240° C. or higher, the sum of the respective areas is used. Incidentally, the total acid amount in the present invention does not include the acid amount derived from weak acid sites having a peak top at less than 240°C. This is because it is not easy to distinguish between adsorption derived from weak acid sites and physical adsorption in the TPD profile.

The outer surface acidity of zeolite is not particularly limited, but is usually 8% or less, preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less with respect to the total acidity of zeolite. , most preferably 0%. By keeping the outer surface acid amount at or below these upper limits, it is possible to reduce side reactions that generate unintended hydrocarbons and further improve the yield of ethylene.

The value of the outer surface acidity of zeolite is determined by the method described in WO 2010/128644 pamphlet.
Specifically, after drying the zeolite under vacuum at 500° C. for 1 hour as a pretreatment, the pretreated zeolite is brought into contact with pyridine vapor at 150° C. to adsorb pyridine to the zeolite. Amount of pyridine desorbed per zeolite unit weight at 150 to 800°C by a temperature programmed desorption method at a temperature rising rate of 10°C/min from the pyridine-adsorbed zeolite obtained by removing surplus pyridine from the zeolite by flow determined from
Incidentally, the outer surface acidity and the like of the zeolite are not particularly limited, but can be adjusted by silylation treatment, steam treatment, heat treatment, acid treatment, ion exchange treatment, and the like. Moreover, it can also be adjusted by a method such as carrying treatment of a metal element. Furthermore, it can also be adjusted by a method of binding the outer surface acid sites of the zeolite with a binder when molding the zeolite.

When the zeolite contains an aluminosilicate, the SiO ₂ /Al ₂ O ₃ ratio of the crystal surface layer determined by XPS is not particularly limited, but usually the SiO ₂ /Al ₂ ratio of the entire crystal determined by ICP elemental analysis. It is 1.0 times or more, preferably 1.5 times or more, more preferably 2.0 times or more, still more preferably 3.0 times or more, and most preferably 5.0 times or more that of _O3 . Within this range, it is possible to suppress side reactions in the crystal surface layer and promote ethylene production inside the zeolite crystal.

The SiO ₂ /Al ₂ O ₃ ratio of the zeolite crystal surface layer is a numerical value obtained by X-ray photoelectron spectroscopy (XPS). XPS is an analysis method for obtaining information on the crystal surface, and this analysis method can determine SiO ₂ /Al ₂ O ₃ of the crystal surface layer. Although the measuring method is not particularly limited, the contents of Si and Al can usually be calculated from Si2p spectrum and Al2p spectrum, respectively.

The zeolite may be used as it is without any particular treatment. Using a zeolite in which the pore size of the surface openings is appropriately adjusted can minimize the range of fluctuations in the ethylene/propylene ratio in the product, and can stably produce ethylene at a high yield. Among these, in order to adjust the total acidity of zeolite, a method of performing at least one treatment selected from steam treatment, heat treatment, and ion exchange is preferable, and among these, at least one treatment selected from steam treatment and ion exchange is preferable. The method of applying, especially the method of applying steam treatment, may be preferred for the reason that the treatment is simple. On the other hand, in order to adjust the amount of acid on the outer surface, it may be effective to apply at least one treatment selected from silylation treatment and steam treatment. Moreover, in order to adjust the pore size of the openings on the outer surface, it may be effective to perform silylation treatment. In this way, when the above treatments are appropriately combined, the total acid content of the zeolite, the outer surface acid content, and/or the pore size of the outer surface openings can be appropriately adjusted, which may be preferable in some cases.
These processing methods will be described below.

<Silylation treatment>
The method of silylating the zeolite is not particularly limited, and a known method can be used as appropriate. Specifically, liquid-phase silylation, gas-phase silylation, and the like can be performed.

The silylation treatment of zeolite usually coats the acid sites on the outer surface of the zeolite and deactivates it, which is thought to reduce the acidity on the outer surface. When the outer surface acid amount is reduced, side reactions occurring on the outer surface of the zeolite are suppressed. Specifically, due to the conversion reaction of propylene, lower olefins such as ethylene and butene generated in the zeolite pores come into contact with the acid sites on the outer surface of the zeolite, suppressing reactions that generate components other than the target product. It is thought that there is an effect to do. In addition, in the silylation of the outer surface acid sites, the silyl groups are also bound to the acid sites that constitute the pores of the zeolite, so the pore diameter of the outer surface openings is slightly reduced, and molecular diffusion out of the crystal occurs. is thought to have the effect of suppressing It is believed that this suppresses the production of hydrocarbons having 5 or more carbon atoms, which are larger molecules, and improves the ethylene selectivity.
The silylation treatment will be specifically described below by taking liquid-phase silylation as an example.

The silylating agent is not particularly limited, and usually one that can silylate the outer surface of the zeolite but cannot silylate the inside of the pores of the zeolite is used. Specifically, silicones, chlorosilanes, alkoxysilanes, siloxanes, silazanes and the like can be used. Among these, chlorosilanes are usually used for gas-phase silylation, and alkoxysilanes are usually used for liquid-phase silylation. More preferable silylating agents are highly reactive and relatively easy to handle. , alkoxysilanes.
Specific examples of silicones include dimethylsilicone, diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethylsilicone, phenylethylsilicone, diphenylsilicone, and methyltrifluoropropylsilicone. , ethyltrifluoropropylsilicone, tetrachlorophenylmethylsilicone, tetrachlorophenylethylsilicone, tetrachlorophenylhydrogensilicone, tetrachlorophenylsilicone, methylvinylsilicone and ethylvinylsilicone.

Specific examples of chlorosilanes include tetrachlorosilane, trichlorosilane, trichloromethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, trichloroethylsilane, dichlorodiethylsilane, and chlorotriethylsilane.
Specific examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane, etc.; quaternary alkoxysilane, trimethoxymethylsilane, trimethoxyethylsilane, triethoxymethylsilane, triethoxyethylsilane, etc.; alkoxysilane, dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane, diethoxydiethylsilane, etc.; secondary alkoxysilane, methoxytrimethylsilane, methoxytriethylsilane, ethoxytrimethylsilane, ethoxytriethylsilane, etc.; is used. Secondary or higher class alkoxysilanes are preferred, tertiary or higher class alkoxysilanes are more preferred, and quaternary or higher class alkoxysilanes are even more preferred.

Specific examples of siloxanes include hexamethyldisiloxane, hexaethyldisiloxane, pentamethyldisiloxane, tetramethyldisiloxane and the like, with hexamethyldisiloxane being preferred.
Specific examples of silazanes include hexamethyldisilazane, dipropyltetramethyldisilazane, diphenyltetramethyldisilazane, tetraphenyldimethyldisilazane and the like, with hexamethyldisilazane being preferred.

The amount of the silylating agent to the zeolite is not particularly limited, but is usually 0.001 mol or more, preferably 0.01 mol or more, more preferably 0.1 mol or more, relative to 1 mol of the zeolite. is. Also, it is usually 5 mol or less, preferably 3 mol or less, more preferably 1 mol or less. By setting the amount of the silylating agent within the above range, the silylation coating of the outer surface acid sites efficiently progresses, and it is possible to suppress the decrease in catalytic activity due to excessive silylation coating, which is preferable. The amount of the silylating agent is represented by the number of moles of Si atoms contained in the silylating agent. will be treated as the number of moles of the agent.

When carrying out liquid phase silylation, a solvent can be used, and examples of the solvent include, but are not limited to, hydrocarbons such as hexane, heptane, octane, nonane, decane, cyclopentane, cyclohexane, benzene, toluene, and xylene. or water can be used. Further, when the liquid-phase silylation is performed using an aqueous solvent, an acidic aqueous solution to which an acid such as sulfuric acid or nitric acid is added can be used in order to promote the silylation reaction.

When liquid-phase silylation is performed, the concentration of the silylating agent in the solution in which the liquid-phase silylation reaction is performed is not particularly limited, but is usually 0.01% by mass or more, preferably 0.5% by mass. above, and more preferably at least 1% by mass. Moreover, it is usually 80% by mass or less, preferably 60% by mass or less, and more preferably 40% by mass or less. By setting the concentration of the silylating agent within the above range, it is preferable in that condensation between the silylating agents can be suppressed and the silylation rate can be maintained.

The amount of the solvent for the zeolite in liquid-phase silylation is not particularly limited, but is usually 1 g or more, preferably 3 g or more, more preferably 5 g or more, per 1 g of the zeolite. Also, it is usually 100 g or less, preferably 80 g or less, more preferably 50 g or less. By setting the amount of the solvent within the above range, it is possible to obtain sufficient stirring efficiency of the slurry and to ensure a certain level of productivity, which is preferable.

When liquid-phase silylation is performed, the zeolite subjected to the silylation treatment may be provided with a specific range of moisture. The water contained in the zeolite may be originally contained in the zeolite, or may be adjusted to a specific range by artificially supplying water. Usually, the zeolite of the present invention is obtained by calcining the zeolite obtained by hydrothermal synthesis, and if necessary, converting it to the ammonium type and then calcining it to convert it to the proton type. Therefore, it is generally assumed that the water content of zeolite before silylation treatment is usually very low, and it may be subjected to silylation treatment as it is, or water is supplied to zeolite so that it has a specific water content, It may be used after adjusting the moisture content (hereinafter sometimes referred to as humidity conditioning treatment).

The water content is not particularly limited, but the weight of the water contained in the zeolite is represented by mass% with respect to the weight of the dry zeolite, and is usually 30% by mass or less, preferably 25% by mass or less, and the lower limit is is 0% by mass in a completely dry state. By setting the water content within the above range, the silylation coating of the outer surface acid sites proceeds efficiently and pore clogging due to excessive silylation can be prevented, which is preferable.

The humidity conditioning treatment method is not particularly limited as long as it can adjust the moisture content to a predetermined level. For example, a method of leaving the zeolite in an atmosphere having an appropriate relative humidity, a method of allowing the zeolite to coexist with water or a saturated aqueous solution of an inorganic salt in a closed container (desiccator, etc.), and a method of leaving the zeolite in a saturated steam atmosphere. Another example is a method of circulating a gas having an appropriate water vapor pressure. In the above method, the humidity conditioning treatment may be performed while mixing or stirring the zeolite in order to perform more uniform humidity conditioning.

The temperature for the silylation treatment is appropriately adjusted depending on the type of silylating agent and solvent used, and is not particularly limited, but is usually 20°C or higher, preferably 40°C or higher, more preferably 60°C or higher. . Also, it is usually 140° C. or lower, preferably 120° C. or lower, and more preferably 100° C. or lower. By setting the silylation treatment temperature within the above range, the silylation coating of the outer surface acid sites proceeds efficiently and the silylation rate can be maintained.

The time required to raise the temperature from the addition of the silylation agent to the silylation temperature is not particularly limited, and the silylation agent may be added at the silylation temperature, but usually 0.01 hour. As mentioned above, it is preferably 0.05 hours or more, more preferably 0.1 hours or more, and there is no particular upper limit for the time required for temperature rise. When the silylation temperature is high, by setting the time required for temperature rise within the above range, the hydrolysis and polymerization reaction of the silylating agent in the solution are suppressed, and the silylation of the zeolite proceeds efficiently. preferable.

The treatment time for silylation depends on the reaction temperature, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1 hour or longer, as long as the catalyst performance is not impaired. There is no upper limit for By setting the treatment time within the above range, the silylation coating of the outer surface acid sites of the zeolite proceeds, and the outer surface acid amount is sufficiently reduced, which is preferable. Regarding such silylation and steam treatment, which will be described below, the zeolite itself may be treated at the time of powder, or it may be applied to the zeolite catalyst that has been molded with a binder or the like and is in a state to be used as a zeolite catalyst. good.

<Steam treatment>
The method of water vapor treatment is not particularly limited, but the gas containing water vapor can be brought into contact within a range that does not impair the effects of the present invention. Specific examples include a method of contacting with a reaction atmosphere containing water vapor, water vapor diluted with air or an inert gas, water vapor together with a lower olefin such as ethylene or propylene, or a reaction atmosphere generating water vapor. A reaction that produces water vapor is a reaction in which dehydration occurs to produce water vapor, such as the dehydration reaction of alcohol. Depending on the conditions, the steam may partially exist as liquid water, but it is preferable that the entire zeolite exists in the form of steam in order to impart a uniform steam treatment effect to the zeolite.

By steaming the zeolite, T atoms other than silicon that form the skeleton of the zeolite are eliminated from the skeleton throughout the crystal. This reduction in total acidity suppresses coke formation inside the pores of the zeolite and improves the intracrystalline diffusibility of molecules. For this reason, it is presumed that the reactivity of propylene, which is a reaction raw material, is relatively increased. Excessive steam treatment may cause a decrease in activity due to a decrease in the total acid content, and an excessive increase in the diffusivity of molecules within crystals, resulting in the formation of hydrocarbon molecules with 4 or more carbon atoms such as butene, pentene, and hexene. The amount of production tends to increase.

The steam treatment temperature is not particularly limited, but is usually 400° C. or higher, preferably 500° C. or higher, more preferably 600° C. or higher. Also, it is usually 1000° C. or lower, preferably 900° C. or lower, more preferably 800° C. or lower. By setting the steam treatment temperature within the above range, the T atoms other than silicon are efficiently removed from the skeleton in a short treatment time without causing the collapse of the skeleton structure, and the total acid content and the outer surface acid content are reduced. It is preferable in that it can

Water vapor (steam) used for water vapor treatment can be used after being diluted with air or an inert gas such as helium or nitrogen. The steam concentration at that time is not particularly limited, but is usually 5% by volume or more, preferably 10% by volume or more, more preferably 20% by volume or more, relative to the entire gas used when steaming the zeolite. and more preferably 30% by volume or more, and usually 100% by volume or less, preferably 90% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less. The upper limit is not particularly limited, and 100% by volume of water vapor can be used. By setting the water vapor concentration within the above range, the T atoms can be efficiently removed from the skeleton in a short treatment time, and the total acid amount and the outer surface acid amount can be reduced.

The pressure of steam treatment (total pressure including diluent gas) is not particularly limited, but is usually 0.05 MPa or higher (absolute pressure, hereinafter the same), preferably 0.075 MPa or higher, more preferably 0.1 MPa or higher. It is usually 2 MPa or less, preferably 1 MPa or less, more preferably 0.5 MPa or less. By setting the pressure of the steam treatment within the above pressure range, the T atoms can be efficiently removed from the skeleton in a short time, and the total acid amount and the outer surface acid amount can be reduced, which is preferable.

Although the partial pressure of water vapor is not particularly limited, it is usually 0.01 MPa or more (absolute pressure, hereinafter the same), preferably 0.03 MPa or more, more preferably 0.05 MPa or more, and usually 2 MPa or less, preferably It is 1 MPa or less, more preferably 0.5 MPa or less, and still more preferably 0.2 MPa or less. By setting the partial pressure of water vapor within the above pressure range, it is possible to efficiently remove the T atoms from the skeleton in a short period of time, thereby reducing the total acid amount and the outer surface acid amount.

The steam treatment time is not particularly limited, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1 hour or longer. There is no upper limit to the treatment time as long as it does not significantly impair the catalytic activity. The treatment time can be appropriately adjusted depending on the steam treatment temperature and steam concentration.

The steam treatment may be performed in a state in which organic substances are present inside the pores. The presence of the organic matter inside the pores prevents an extreme decrease in the acid sites inside the pores, and can significantly reduce the acid sites on the outer surface, especially when a strong steam treatment is performed.
Examples of the organic substance include, but are not particularly limited to, a structure-directing agent used during hydrothermal synthesis of zeolite, coke generated by reaction, and the like. These organic substances can be removed by subjecting the zeolite after hydrothermal synthesis (hereinafter sometimes referred to as pre-calcined zeolite) to steam treatment, followed by a combustion process such as air calcination, or by removing an oxygen-containing gas such as air. By treating with steam diluted with , the steam treatment can be performed while removing the organic matter.

<Heat treatment>
The heat treatment method is not particularly limited, but specific examples include a method of subjecting the zeolite to a high temperature treatment in at least one atmosphere selected from air and inert gas. This can reduce the total acid content and outer surface acid content of the zeolite.

The heat treatment temperature is not particularly limited, but is usually 500° C. or higher, preferably 600° C. or higher, more preferably 700° C. or higher, and usually 1200° C. or lower, preferably 1000° C. or lower, more preferably 900° C. or lower. be. Setting the heat treatment temperature within the above range is preferable in that the T atoms can be efficiently removed from the skeleton in a short treatment time without collapsing the skeleton structure.

Helium, nitrogen, air, or the like can be used as the gas species used in the heat treatment.
The heat treatment may also be performed in a state where organic substances are present inside the pores, similarly to the steam treatment. When an inert gas such as helium or nitrogen is used, the organic substance may be carbonized by heat treatment, but it can be removed by firing in air.

The heat treatment may be performed simultaneously with the calcination performed when producing the zeolite, or may be performed separately. The heat treatment is performed at a relatively high temperature for the purpose of removing the T atoms in the skeleton, etc., and is not particularly limited. is usually performed at a higher temperature than calcination.
The heat treatment time is not particularly limited, but is usually 0.1 hour or longer, preferably 0.5 hour or longer, and more preferably 1.0 hour or longer. There is no upper limit to the treatment time as long as it does not significantly impair the catalytic activity, and the treatment time can be appropriately adjusted depending on the heat treatment temperature.

<Acid treatment>
The method of acid-treating zeolite is not particularly limited, but a specific example is a method using an acidic aqueous solution.
The type of acid used in the acidic aqueous solution is not particularly limited, but inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid; carboxylic acids such as formic acid, acetic acid and propionic acid; oxalic acid and malonic acid. and the like can be used. Sulfuric acid, nitric acid and hydrochloric acid are preferred among these.

The acid concentration of the acidic aqueous solution is not particularly limited, but is usually 0.01 M or more, preferably 0.1 M or more, more preferably 1 M or more, and usually 10 M or less, preferably 8 M or less. and more preferably 6M or less. By setting the concentration of the acid within the above range, it is possible to efficiently reduce the total acid amount and the outer surface acid amount in a short treatment time without collapsing the skeleton structure, which is preferable.

The amount of the acidic aqueous solution relative to the zeolite is not particularly limited, but the total amount of the acidic aqueous solution is usually 3 g or more, preferably 5 g or more, more preferably 10 g or more, and usually 100 g or less, relative to 1 g of zeolite. It is preferably 80 g or less, more preferably 50 g or less. By setting the amount of the acidic aqueous solution within the above range, it is possible to obtain a sufficient stirring efficiency of the slurry and to ensure a certain level of productivity, which is preferable.

The temperature of the acid treatment is not particularly limited, but it is usually room temperature to 100° C. under normal pressure, and can be carried out at 100° C. or higher in a pressure vessel, usually 40° C. or higher, preferably 60° C. or higher. , more preferably 80° C. or higher, and usually 200° C. or lower, preferably 180° C. or lower, more preferably 160° C. or lower. By setting the acid treatment temperature within the above range, it is possible to efficiently reduce the total acid amount and the outer surface acid amount in a short treatment time while suppressing the collapse of the skeletal structure.

The treatment time of the acid treatment is not particularly limited and depends on the concentration of the acid and the reaction temperature, but it is usually 0.01 hour or more, preferably 0.1 hour or more, as long as it does not impair the performance of the catalyst. There is no particular upper limit for the processing time. The treatment time can be appropriately adjusted depending on the concentration of the acid and the reaction temperature.
Acid treatment and silylation treatment can be performed simultaneously by adding a silylating agent to the acidic aqueous solution. The silylating agent used at that time is the same as the silylating agent described above.

<Ion exchange treatment>
The counter cations of zeolites are usually alkali metals such as sodium, alkaline earth metals, ammonium ( _NH4 ) or protons (H). These counter cations are ion-exchangeable and can be used after metal ion exchange as appropriate. Metals to be exchanged include, but are not limited to, alkali metals such as lithium, sodium, potassium, rubidium and cesium, and alkaline earth metals such as calcium, strontium and barium. Preferred are sodium, potassium, calcium and strontium, more preferred are sodium, potassium and calcium, and still more preferred is calcium.

By ion exchange, the acid amount of the zeolite can be adjusted, and furthermore, the cage space volume can be adjusted, so coke accumulation during the reaction can be suppressed. It is also preferable in that thermal/hydrothermal stability is enhanced and deterioration can be suppressed. Although the method of metal ion exchange is not particularly limited, it can be carried out by a known ion exchange method. The cation of the zeolite used in the ion exchange method is not particularly limited, and sodium type, ammonium type, or proton type is usually used.

As metal sources, nitrates, sulfates, acetates, carbonates, chloride salts, bromide salts, iodide salts and the like are usually used, with nitrates, sulfates and chloride salts being preferred, and nitrates being more preferred. is. The solvent to be used is not particularly limited as long as it dissolves the metal source, but water is usually used.

The concentration of the metal source solution is not particularly limited, but is usually 0.1 M or more, preferably 0.5 M or more, more preferably 1 M or more, and the upper limit is usually 10 M or less, preferably 8 M or less. More preferably, it is 6M or less. It is desirable to adjust the concentration according to the solubility of the metal source.

The temperature for ion exchange is from room temperature to about the boiling point of the solvent. The treatment time may be sufficient as long as the ion exchange reaches a sufficient equilibrium, and is usually about 1 to 6 hours. It is also possible to repeat the ion exchange multiple times in order to increase the metal exchange rate.

The atmosphere in which the ion-exchanged zeolite is dried is not particularly limited. The drying temperature is usually from room temperature to about the boiling point of the solvent. The ion-exchanged zeolite is appropriately calcined before use. The firing temperature may be higher than the decomposition temperature of the metal source, usually 200°C to 600°C, preferably 300°C to 500°C. If the sintering temperature is too low, the metal source tends to remain, and if the sintering temperature is too high, structural collapse of the zeolite and sintering of the metal tend to proceed.

In addition to the above, it is also possible to adjust the outer surface acidity by carrying out a metal element support treatment, or by combining a binder with the outer surface acid points of the zeolite when molding the zeolite.

Although the average primary particle size of zeolite is not particularly limited, it is usually 0.01 μm or more, preferably 0.03 μm or more, more preferably 0.05 μm or more, and usually 10 μm or less, preferably 5 μm or less, or more. It is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less. The above range is preferable because the diffusivity in the zeolite crystal and the catalyst effectiveness factor in the catalytic reaction are sufficiently high, the zeolite crystallinity is sufficient, and the hydrothermal stability is high.
The average primary particle size in the present embodiment corresponds to the particle size of primary particles. Therefore, it differs from the particle size of aggregates measured by a light scattering method or the like. The average primary particle diameter is determined by observing particles with a scanning electron microscope (hereinafter abbreviated as "SEM") or a transmission electron microscope (hereinafter abbreviated as "TEM"), and arbitrarily 20 or more particles. It is obtained by measuring and averaging the particle diameters of the primary particles. When the particle is rectangular, the long side and short side of the particle are measured (the depth is not measured), and the average of the sums, that is, (long side + short side) / 2, is calculated. Primary particle size.

(BET specific surface area)
The BET specific surface area of zeolite is not particularly limited, but is usually 300 m ² /g or more, preferably 400 m ² /g or more, more preferably 500 m ² /g or more, and usually 1000 m ² /g or less, preferably is 800 m ² /g or less, more preferably 750 m ² /g or less. Within the above range, there are sufficiently many active sites on the inner surfaces of the pores, and the catalytic activity is increased, which is preferable. The BET specific surface area can be measured by a measurement method according to JIS8830 (Method for measuring specific surface area of powder (solid) by gas adsorption). Nitrogen is used as the adsorption gas, and the BET specific surface area is determined by the one-point method (relative pressure: p/p0=0.30).

Although the pore volume of zeolite is not particularly limited, it is usually 0.1 ml/g or more, preferably 0.2 ml/g or more, and usually 3 ml/g or less, preferably 2 ml/g or less. Within the above range, there are sufficiently many active sites on the inner surfaces of the pores, and the catalytic activity is increased, which is preferable. The pore volume is preferably a value obtained from a nitrogen adsorption isotherm obtained by a relative pressure method.

Zeolites can generally be prepared by hydrothermal synthesis. For example, in the case of a silicate, at least one selected from an aluminum source, a gallium source, a boron source, and an iron source, a silicon source, an alkaline aqueous solution, etc. are added to water to form a uniform gel. A structure-directing agent is added and stirred to prepare a raw material gel. The raw material gel thus obtained is heated in a closed container and reacted under autogenous pressure to crystallize. Although the reaction temperature at this time is not particularly limited, it is usually held at 100 to 200° C. for crystallization. During crystallization, seed crystals may be added as necessary, and from the standpoint of manufacturability, addition of seed crystals is preferable in that reaction time can be shortened and crystal grains can be made into fine particles. Then, after filtering and washing the crystallized solid component, the solid component is dried and subsequently calcined to obtain an alkali (earth) metal type zeolite. Although the drying temperature is not limited, it is usually 100 to 200°C. Although the firing temperature is not limited, it is usually 400 to 700°C. After that, ion exchange is performed with an acidic solution or an ammonium salt solution, followed by calcination, whereby an H-type zeolite can be obtained.

Specifically, CHA-type zeolite can be produced by known methods such as the method described in US Pat. No. 4,544,538. ERI zeolite can be produced by known methods such as the method described in US Pat. No. 7,344,694.

The cations used as structure-directing agents are accompanied by anions that do not inhibit zeolite formation. The anion is not particularly limited, but specifically includes halogen ions such as Cl ⁻ , Br ⁻ and I ⁻ , hydroxide ions, acetates, sulfates and carboxylates. Among them, hydroxide ions are particularly preferably used.

As the structure-directing agent, a phosphorus-containing structure-directing agent or a nitrogen-based structure directing agent can also be used. Phosphorus-containing structure-directing agents include, for example, substances such as tetraethylphosphonium hydroxide and tetraethylphosphonium bromide. However, when the structure-directing agent is removed from the synthetic zeolite by calcination, the phosphorus compound may generate harmful substances such as diphosphorus pentoxide, so the nitrogen-based structure-directing agent is preferable.

Since zeolite is a catalytically active component, zeolite may be used as it is for the reaction as a zeolite catalyst. may be used.
Substances and binders inert to the reaction include alumina, alumina sol, silica, silica sol, quartz, and mixtures thereof.
Even if the zeolite is not used as a single zeolite, but is molded using a binder, etc., the total acid content and the outer surface acid content should be measured in the same manner as described above. and the preferred range will also be the same value.
Hereinafter, a preferred embodiment in which the zeolite is not used alone as described above but is used after being molded using a binder or the like will be described using the term zeolite catalyst.

The total acid content and outer surface acid content of the zeolite catalyst as a whole can be measured by the same methods as those for the above-described total acid content and outer surface acid content of zeolite. The total acid amount of the zeolite catalyst is not particularly limited, but is usually 0.01 mmol/g or more, preferably 0.1 mmol/g or more, more preferably 0.3 mmol/g or more, and still more preferably 0.5 mmol/g. / g or more. Also, it is usually 2.5 mmol/g or less, preferably 1.5 mmol/g or less, more preferably 1.2 mmol/g or less, and still more preferably 0.9 mmol/g or less. By setting the total acid amount of the zeolite catalyst within the above range, the propylene conversion activity is maintained at a high level, coke formation inside the pores of the zeolite is suppressed, and ethylene production can be further promoted. preferable.

Although the amount of acid on the outer surface of the zeolite catalyst is not particularly limited, it is usually 8% or less, preferably 5% or less, more preferably 3% or less, and still more preferably 1% with respect to the total acid amount of the catalyst. Below, it is most preferably 0%. By making it below the said upper limit, it is easy to suppress a side reaction and to maintain the selectivity of ethylene in a high state.
In addition, in order to adjust the total acid amount and the outer surface acid amount of the zeolite catalyst, it is preferable to use silica, alumina, or the like having no acid sites as a binder. When a binder having acid sites such as alumina is used, the total acidity of the catalyst and the acidity of the outer surface of the catalyst are measured as a total value including the acidity of the zeolite and the acidity of the binder. be. In that case, it is possible to obtain the acid content of the zeolite without the binder-derived acid content by obtaining the acid content derived from the binder by another method and subtracting this value from the acid content of the catalyst. The acid amount of the binder is obtained from the acid amount of the zeolite obtained from the peak intensity of tetracoordinated Al derived from the acid sites of the zeolite in ²⁷ Al-NMR, and the acid amount of the catalyst obtained by the ammonia temperature programmed desorption method. Calculated by subtraction.

The amount of the phosphorus compound that can be contained in the zeolite catalyst is not particularly limited, but is usually 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0.1% by mass. % or less, particularly preferably 0.01 mass % or less. The phosphorus compound here refers to a substance such as phosphorus oxide, and does not mean zeolite itself such as aluminophosphate or gallophosphate.

The average particle size of the zeolite catalyst varies depending on zeolite synthesis conditions, particularly granulation/molding conditions, but the average particle size is usually 0.01 μm to 500 μm, preferably 0.1 to 100 μm. If the average particle size of the zeolite catalyst is too large, the effective coefficient of the catalyst will tend to decrease, and if it is too small, the handleability will be poor. This average particle size can be determined by SEM observation or the like.

<C2. Method for producing ethylene>
The method for producing ethylene of the present embodiment is a method for producing ethylene by bringing a raw material hydrocarbon containing at least propylene and a hydrocarbon having 4 or more carbon atoms into contact with a catalyst. The mass ratio of 4 or more hydrocarbons is in the range of 0.01 to 10. Each step will be described in detail below.

The production origin of propylene, which is a raw material, is not particularly limited. For example, those obtained by cracking naphtha by steam cracking or catalytic cracking (hereinafter referred to as naphtha cracked product), ethane, propane, n-butane, atmospheric gas oil (AGO), vacuum gas oil (VGO), natural gas liquid (NGL) produced by thermal decomposition (hereinafter referred to as thermal decomposition product), produced by fluidized catalytic cracking (FCC) of vacuum gas oil or residual oil, produced by MTO (Methanol to Olefin) reaction , those produced by the ETO (Ethylene/Ethanol to Olefin) reaction, those produced by the dehydrogenation reaction of alkanes such as propane, and the Fischer process using a hydrogen/carbon monoxide mixed gas obtained by the gasification of coal as a raw material. Examples thereof include those produced by Tropsch synthesis. Of these, the above naphtha decomposition products, the above thermal decomposition products, and MTO reaction products are preferred, and naphtha decomposition products are more preferred.

Examples of hydrocarbons having 4 or more carbon atoms include olefins such as butene, pentene and hexene; paraffins such as butane, pentane and hexane; alkynes such as butyne, pentyne and hexyne; dienes such as butadiene, pentadiene and hexadiene; It may contain aromatic hydrocarbons such as benzene, toluene, and xylene. The olefins, paraffins, alkynes, and dienes described above may contain isomers of straight-chain structures, branched structures, and cyclic structures, but straight-chain structures are preferred in terms of reactivity. In terms of reactivity, olefins are preferable, preferably 8 or less carbon atoms (butene, pentene, hexene, heptene, octene), more preferably 6 or less carbon atoms (butene, pentene, hexene), and further C5 or less (butene, pentene) is preferred, and C4 butene is most preferred. Any of the four isomers can be used as butene.

The raw material hydrocarbon may contain hydrocarbons other than propylene and hydrocarbons having 4 or more carbon atoms (hereinafter sometimes referred to as "other hydrocarbons"), such as methane, ethane, It may contain hydrocarbons having 3 or less carbon atoms such as ethylene, acetylene, propane, and methylacetylene. In addition to propylene, it may contain methanol or dimethyl ether, and the mixing ratio is not limited.

Normally, in the production of ethylene from propylene, the target product, ethylene, may be contained in the raw material hydrocarbon, but it is easily converted to other olefins such as butene and hexene by contact with the catalyst. , propylene from which ethylene is separated is preferably used as a raw material. The mass ratio of propylene to ethylene contained in the raw material hydrocarbon is not particularly limited, but is usually 1 or more, preferably 5 or more, more preferably 10 or more, and still more preferably 15 or more, It is particularly preferably 30 or more, and the larger the better. The higher the above ratio, the more the consumption of ethylene, which is the target product, can be suppressed, and the more efficiently ethylene can be produced.

The reactor used for ethylene production is not particularly limited as long as it is a reactor having a raw material inlet and a product gas outlet, and the propylene feedstock is in the gas phase in the reaction zone. Bed reactors and fluidized bed reactors can be chosen. Fluidized bed reactors are preferred for production of constant ethylene yields when the propylene conversion is highly variable.
Further, it can be carried out in any form of batch type, semi-continuous type or continuous type, but it is preferable to carry out in continuous type, and the method may be a method using a single reactor, serial or parallel A method using a plurality of arranged reactors may also be used.
When filling the fluidized bed reactor with the above-mentioned catalyst, in order to keep the temperature distribution of the catalyst layer small, granules that are inert to the reaction, such as quartz sand, alumina, silica, and silica-alumina, are mixed with the catalyst. can be filled with In this case, there is no particular limitation on the amount of the granular material that is inert to the reaction, such as quartz sand. From the viewpoint of uniform mixing with the catalyst, the particulate matter preferably has a particle size approximately the same as that of the catalyst.
In addition, the reaction substrate (reaction raw material) may be divided and supplied to the reactor for the purpose of dispersing the heat generated by the reaction.

(substrate concentration)
The total concentration of propylene and hydrocarbons having 4 or more carbon atoms in all feed components supplied to the reactor is not particularly limited, but is usually 3 mol% or more, preferably 5 mol% or more, more preferably 5 mol% or more, in all feed components. is 10 mol % or more, more preferably 20 mol % or more, and usually 100 mol % or less, preferably 80 mol % or less, more preferably 60 mol % or less, and still more preferably 40 mol % or less. By setting the substrate concentration within the above range, the production of aromatic compounds and paraffins can be suppressed to a lower level, and the yield of ethylene can be improved. In addition, since the reaction rate can be maintained high, the amount of catalyst can be reduced and the size of the reactor can be reduced.
Therefore, it is preferable to dilute the reaction substrate with a diluent described below, if necessary, so as to obtain such a preferable substrate concentration.

(diluent)
In the reactor, in addition to raw materials containing propylene, helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, paraffins, hydrocarbons such as methane, aromatic compounds, and their A mixture or the like can be present, but among these, the coexistence of hydrogen, helium, nitrogen, and water (steam) is preferred, and the coexistence of hydrogen is most preferred in terms of increasing the yield of ethylene. . As such a diluent, an impurity contained in the reaction raw material may be used as it is, or a separately prepared diluent may be used by mixing it with the reaction raw material. Further, the diluent may be mixed with the reaction raw materials before entering the reactor, or may be supplied to the reactor separately from the reaction raw materials.

(weight space velocity)
The weight hourly space velocity referred to in this specification is the total flow rate (weight/time) of propylene and hydrocarbons having 4 or more carbon atoms, which are reaction raw materials, per weight of the catalyst (catalytically active component), where the weight of the catalyst is the weight of catalytically active components that do not contain inert components or binders used for granulating and molding the catalyst.

The weight hourly space velocity is not particularly limited, but is usually 0.01 Hr ^-1 or more, preferably 0.1 Hr ^-1 or more, more preferably 0.2 Hr ^-1 or more, further preferably 0.5 Hr ^-1 or more. and is usually 50 Hr ⁻¹ or less, preferably 10 Hr ⁻¹ or less, more preferably 5 Hr ⁻¹ or less, still more preferably 3 Hr ⁻¹ or less. By setting the weight hourly space velocity within the above range, the ratio of unreacted propylene in the product gas discharged from the product gas outlet of the reactor can be further reduced, and by-products such as aromatic compounds and paraffins can be reduced. It is preferable because it can also reduce the amount of waste and improve the ethylene yield. In addition, the amount of catalyst required to obtain a certain production volume can be suppressed, and the size of the reactor can be suppressed.

(reaction temperature)
The reaction temperature is not particularly limited as long as it is a temperature at which propylene and hydrocarbons having 4 or more carbon atoms come into contact with the catalyst to produce ethylene, but is usually 300° C. or higher, preferably 400° C. or higher, more preferably 400° C. or higher. is 425°C or higher, more preferably 450°C or higher, particularly preferably 475°C or higher, most preferably 500°C or higher, and usually 800°C or lower, preferably 700°C or lower, more preferably 650°C or lower, further preferably 600°C or lower. ℃ or less. By setting the reaction temperature within the above range, the production of aromatic compounds and paraffins can be suppressed, so that the yield of ethylene in one pass can be improved. In addition, the propylene conversion activity can be maintained at a high level, and when hydrogen is contained in the reaction gas together with propylene and hydrocarbons having 4 or more carbon atoms, the contact effect can be maximized. High ethylene yields can be produced over time. Furthermore, when the zeolite is a silicate, dealumination from the zeolite skeleton is suppressed, which is preferable in terms of maintaining the life of the catalyst. The reaction temperature here means the temperature at the outlet of the catalyst layer.

(reaction pressure)
Although the reaction pressure (total pressure) is not particularly limited, it is usually 0.01 MPa (absolute pressure, hereinafter the same) or higher, preferably 0.05 MPa or higher, more preferably 0.1 MPa or higher, and still more preferably 0.2 MPa. That is, it is usually 5 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, further preferably 0.4 MPa or less. By setting the reaction pressure within the above range, the production of by-products such as aromatic compounds and paraffins can be suppressed, and the yield of ethylene can be improved. Also, the reaction rate can be maintained.

(Reactant partial pressure)
Although the partial pressure of propylene and hydrocarbons having 4 or more carbon atoms is not particularly limited, it is usually 0.001 MPa or more (absolute pressure, hereinafter the same), preferably 0.005 MPa or more, more preferably 0.0075 MPa or more, More preferably 0.010 MPa or more, particularly preferably 0.015 MPa or more, most preferably 0.020 MPa or more, usually 1 MPa or less, preferably 0.5 MPa or less, more preferably 0.2 MPa or less, further preferably 0.2 MPa or less. It is 1 MPa or less. By setting the partial pressure of the raw material within the above range, coking can be suppressed and the yield of ethylene can be improved.

(Ratio of hydrocarbon component having 4 or more carbon atoms to propylene)
The mass ratio of hydrocarbons having 4 or more carbon atoms to propylene contained in the raw material hydrocarbons is 0.01 or more and 10 or less. It is preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.5 or more, preferably 5 or less, more preferably 2 or less, and still more preferably 1 or less.
When the mass ratio of hydrocarbons having 4 or more carbon atoms to propylene in the hydrocarbons is within the above range, the conversion efficiency from raw material propylene to ethylene is increased, and the ethylene/propylene ratio at the reactor product gas outlet changes over time. Although the reason why it is possible to reduce is not yet clear, it is presumed as follows. In a high-temperature catalytic reaction subject to thermodynamic equilibrium constraints between olefins, such as in the present invention, propylene is converted to ethylene and hydrocarbons having 4 or more carbon atoms. On the other hand, some of the hydrocarbons with 4 or more carbon atoms are also converted to propylene and ethylene. As the catalyst activity increases, the composition tends to approach the thermodynamic equilibrium composition between olefins. Therefore, the conversion from propylene to hydrocarbons with 4 or more carbon atoms is suppressed, and the conversion from hydrocarbons with 4 or more carbon atoms to propylene is suppressed, so from propylene and hydrocarbons with 4 or more carbon atoms conversion to ethylene tends to be promoted more effectively, so the conversion efficiency to ethylene can be synergistically increased, and ethylene can be produced at a high ethylene/propylene ratio.
Although the catalyst for obtaining the above effect is not limited, zeolite is preferable because the shape selectivity due to the pore size is likely to be effective, and zeolite having an oxygen eight-membered ring structure with a small pore size close to the molecular size of the target product is more preferable. .

(Proportion of butene)
The proportion of butene contained in hydrocarbons having 4 or more carbon atoms is not particularly limited, but is usually 10 mol % in order to efficiently proceed with the conversion of propylene to ethylene due to reaction equilibrium constraints as described above. Above, it is preferably 30 mol % or more, more preferably 50 mol % or more, still more preferably 80 mol % or more, and the upper limit is 100 mol %.

(Proportion of linear butene)
The ratio of linear butenes (1-butene, 2-butene) contained in butene is not particularly limited, but is usually 10 mol% or more, preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably. is 80 mol % or more, and the upper limit is 100 mol %. From the viewpoint of diffusibility into the zeolite pores, a higher proportion of straight-chain butenes is preferable because the yield of ethylene is likely to be improved.

(Coke component)
Through the conversion of propylene and hydrocarbons with 4 or more carbon atoms, some of it accumulates on the inner/outer surfaces of the crystals as coke (heavy components such as polycyclic aromatics) that must be removed by regeneration, reducing catalytic activity. tends to decrease. Therefore, the coke content (coke content) is usually 30% by mass or less and 20% by mass with respect to the catalyst, which is the active component, in order to obtain moderate catalytic activity and high ethylene selectivity. % or less, more preferably 15% by mass or less, and usually the less the more, the more preferably it has the above-mentioned oxygen eight-membered ring structure and is designated by the International Zeolite Association (IZA) as a composite building unit. In zeolites containing defined d6r in the framework (e.g., AEI, AFX, CHA, ERI, KFI, LEV, SAV), the fineness is such that the wide space inside the pores (cage space) is occupied by a certain amount of coke. Since the pore space can be narrowed, high ethylene selectivity may be expressed, and it is usually 0.1% by mass or more, preferably 1.0% by mass or more, and 3.0% by mass or more. It is more preferable to keep it, and more preferably to keep it at 5.0% by mass or more. By making the coke content in the catalyst equal to or higher than the above lower limit, molecular diffusion in the catalyst can be further suppressed, and conversion of hydrocarbons having 4 or more carbon atoms to ethylene can be promoted, It is preferable that the coke content of the catalyst be maintained at the above lower limit value or more, since a high ethylene selectivity can be maintained during ethylene production. On the other hand, when the amount of coke accumulated in the catalyst exceeds the above upper limit, the catalytic activity tends to decrease. Therefore, it is preferable to adjust the regeneration conditions so that the amount of coke accumulated in the catalyst is within the above range by the regeneration method described later.

In the present invention, the amount of coke accumulated in the catalyst means that the catalyst in which coke is accumulated is heated to 550 ° C. at a temperature increase rate of 10 ° C./min under the flow of an inert gas such as helium (50 cc / min), By holding for 30 minutes, adsorbed water and low-boiling hydrocarbon components were removed, followed by switching to air flow (50 cc/min), heating to 600°C at a temperature increase rate of 10°C/min, and holding for 60 minutes. , can be calculated by determining the weight reduction due to oxidative combustion in the temperature range of 550° C. or higher at this time.

(Conversion rate)
In the present invention, the conversion rate of propylene and hydrocarbons having 4 or more carbon atoms is not particularly limited, but the conversion rate is usually 5% or more, preferably 20% or more, more preferably 30% or more, and still more preferably It is 40% or more, and usually 100% or less, preferably 80% or less, more preferably 60% or less, further preferably 50% or less. By adjusting the propylene conversion rate to be within the above range, it is possible to suppress the by-production of butene, aromatic compounds, and paraffins, and the accumulation of coke in the pores, thereby improving the yield of ethylene. It is preferable because it can be In addition, the separation efficiency of components such as ethylene and propylene from the product can be enhanced. That is, in the present invention, it is preferable to regenerate the catalyst so that the conversion of propylene is within the above range.

Normally, coke accumulation progresses with the passage of reaction time, and the conversion rate of propylene and hydrocarbons having 4 or more carbon atoms tends to decrease, so as described later, the stage when the amount of coke accumulated in the catalyst increases. and preferably subjecting the catalyst to a regeneration step. Moreover, the method of operating within the range of the above conversion rate is not particularly limited.

(yield)
In the present invention, the yield of ethylene is not particularly limited, but the yield is usually 5% or more, preferably 10% or more, more preferably 20% or more, still more preferably 30% or more, and usually 100%. % or less, preferably 80% or less, more preferably 60% or less. When the yield of ethylene is within the above range, the ratio of the target product at the reactor outlet is sufficient, which is preferable in terms of reducing the cost of raw materials and the load of separation and purification.

Yield in the present specification is a value calculated by each of the following formulas. In each formula below, the “derived carbon flow rate (mol/Hr)” of hydrocarbons such as ethylene, propylene, butene, C5+, paraffins and aromatic compounds means the molar flow rate of carbon atoms that make up each hydrocarbon. do. Paraffins are the sum of paraffins having 1 to 4 carbon atoms, aromatic compounds are the sum of benzene, toluene and xylene, and C5+ is the sum of hydrocarbons having 5 or more carbon atoms excluding the aromatic compounds.
Ethylene yield (%) = Reactor generated gas outlet ethylene-derived carbon molar flow rate (mol/Hr) / Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100
・Propylene yield (%) = Reactor generated gas outlet propylene-derived carbon molar flow rate (mol/Hr)/Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100
・Butene yield (%) = Reactor generated gas outlet butene-derived carbon molar flow rate (mol/Hr) / Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100
Here, the butene-derived carbon molar flow rate is treated without distinguishing between isomers.
・C5+ yield (%) = Reactor generated gas outlet C5+ derived carbon molar flow rate (mol/Hr)/Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100
· Paraffin yield (%) = Reactor generated gas outlet paraffin-derived carbon molar flow rate (mol/Hr) / Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100
Aromatic compound yield (%) = Reactor generated gas outlet aromatic compound-derived carbon molar flow rate (mol/Hr) / Reactor generated gas outlet total carbon molar flow rate (mol/Hr) x 100

(reaction product gas)
The reactor product gas outlet gas (reactor exhaust gas) is a mixed gas containing ethylene, which is a reaction product, propylene, which is a raw material, hydrocarbons having 4 or more carbon atoms, paraffin, aromatic compounds, and a diluent. can get. The concentration of ethylene in the mixed gas is not particularly limited, but is usually 5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, and is usually 95% by mass or less, preferably 90% by mass or less. is. It is preferable that the ethylene concentration in the mixed gas is within the above range, since the load of separation and purification can be reduced.
Depending on the reaction conditions, the reaction product gas may contain propylene as an unreacted raw material. However, if the selectivity for ethylene is low, that is, if the selectivity for by-products is high, it will lead to loss of raw materials and increase production costs. Therefore, in some cases, it is preferable to operate under conditions in which the ethylene selectivity is high even under conditions in which the propylene conversion rate is low. In the present invention, if desired, components other than ethylene may be separated and recovered. The residue from which desired components have been separated and recovered contains light paraffins, light olefins, aromatic compounds and the like. At least part of this residue can be mixed with part of the raw material gas described above and used as so-called recycled gas.

(Separation of reaction product gas)
A mixed gas containing ethylene, which is a reaction product, unreacted raw materials, by-products, and a diluent, as a reactor outlet gas, is introduced into a known separation/purification facility, and is recovered, purified, and purified according to each component. Recycling and disposal may be carried out.

(recycling)
Components other than ethylene (olefins, paraffins, etc.), especially part or all of hydrocarbons having 4 or more carbon atoms, are recycled by mixing with the reaction raw materials after being separated and purified, or by directly supplying them to the reactor. You may Preferably, at least 10%, more preferably 20% or more, of the hydrocarbons having 4 or more carbon atoms contained in the produced gas discharged from the produced gas outlet of the reactor are circulated to the reactor. , more preferably 30% or more. In addition, among the by-products, components that are inert to the reaction can be reused as a diluent.

(catalyst regeneration)
Through the conversion of propylene and hydrocarbons having 4 or more carbon atoms (also referred to as C4+), by regenerating the catalyst whose conversion rate has decreased, the fluctuation range of ethylene yield is minimized and ethylene is stably produced. can be manufactured. In the present invention, regeneration of the catalyst means to bring the catalyst in a state in which the conversion rate of propylene and C4+ has decreased into a state in which the conversion rate is higher than before the regeneration treatment.

As propylene and hydrocarbons with 4 or more carbon atoms are converted, the amount of coke components accumulated on the catalyst increases. The amount of the coke component accumulated in the catalyst when the catalyst in which the accumulated amount of the coke component has increased is subjected to the step of regenerating the catalyst is usually 0% by mass or more, preferably 0.01% by mass or more, or more. It is preferably 0.1% by mass or more, more preferably 1.0% by mass or more, particularly preferably 3.0% by mass or more, particularly preferably 5.0% by mass or more, and usually 30% by mass or less, preferably 25% by mass. % by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and particularly preferably 10% by mass or less. When the amount of the coke component accumulated in the catalyst to be subjected to the regeneration process is within the above range, diffusion of the regeneration gas and the cracked gas in the catalyst can be ensured in the regeneration process, and the catalytic activity can be effectively recovered. Therefore, it is preferable. In this regeneration step, the amount of coke components accumulated in the catalyst can be moderately reduced while the catalytic activity can be recovered, so that ethylene can be stably produced at a high yield.

There are no particular restrictions on the process of regenerating the catalyst. For example, when producing ethylene from propylene and a hydrocarbon having 4 or more carbon atoms, at the stage when the coke content of the catalyst increases, after stopping the supply of propylene and the hydrocarbon having 4 or more carbon atoms, By supplying the gas used for regeneration (hereinafter sometimes referred to as regeneration gas), the catalyst with an increased coke content can be brought into contact with the regeneration gas. In addition, the catalyst with increased coke content is removed from the reactor in the step of contacting propylene and hydrocarbons having 4 or more carbon atoms with the catalyst, transferred to the reactor in the step of regenerating the catalyst, and used for regeneration of the catalyst. Gas may be supplied to regenerate the catalyst.

In particular, when the above-mentioned conversion step of propylene and hydrocarbons having 4 or more carbon atoms is performed using a fixed bed reactor, when the amount of coke accumulated in the catalyst exceeds the above-mentioned upper limit, the feedstock is supplied is stopped, regeneration gas can be fed into the reactor to contact the catalyst. Alternatively, the catalyst may be extracted from the above reactor, charged into a reactor other than the reactor, and then brought into contact with the regeneration gas.

When a moving bed reactor or a fluidized bed reactor is used to convert propylene and hydrocarbons having 4 or more carbon atoms, a device for contacting the regenerated gas with the catalyst is installed separately from the reactor. Then, the catalyst extracted from the reactor is continuously sent to the device, the catalyst is brought into contact with the regeneration gas in the device, and then the catalyst contacted with the regeneration gas is continuously returned to the reactor to produce ethylene. It is preferable to carry out the reaction of

The gas used in the step of regenerating the catalyst is not particularly limited, but a preferred example is a gas containing at least one selected from oxygen, hydrogen and water vapor. Specific regeneration methods include combustion regeneration using a regeneration gas containing oxygen, steam reforming regeneration using steam (water) as a regeneration gas, and hydrocracking using hydrogen as a regeneration gas. Among these, the regeneration gas is preferably a gas containing oxygen or hydrogen, and more preferably a gas containing hydrogen.

The method for producing oxygen is not particularly limited, and examples include oxygen cryogenically separated from air in the atmosphere, oxygen produced from hydrogen peroxide, etc., and oxygen recovered from air in the atmosphere is preferred. Atmospheric air may be used as it is as the oxygen-containing gas.

The method for producing steam (water) is not particularly limited, and one obtained by evaporating ordinary water can be used. Water obtained by various production methods, such as tap water, desalted water, and plant process water, can be arbitrarily used.

The method for producing the hydrogen contained in the hydrogen-containing gas is not particularly limited, and examples include those obtained by steam reforming of methane and methanol, those obtained by partial oxidation of hydrocarbons, and those obtained by reforming hydrocarbons with carbon dioxide. obtained by gasification of coal, obtained by thermal decomposition of water typified by the IS (Iodine-Sulfur) process, obtained by photoelectrochemical reaction, and obtained by electrolysis of water Any of those obtained by various production methods can be used.

Any mixture of gases other than these may be used, or purified hydrogen may be used.

Gases other than these contained in gases containing oxygen, hydrogen, and water vapor include hydrocarbons such as helium, argon, nitrogen, carbon monoxide, carbon dioxide, paraffins, and methane, if there is no safety problem. It may include such as. Among these, helium, nitrogen, carbon dioxide, paraffins, and methane are preferred because of their low reactivity.

The pressure of the entire regeneration gas (total pressure) is not particularly limited, but the absolute pressure is usually 0.01 MPa (absolute pressure, hereinafter the same) or more, preferably 0.05 MPa or more, more preferably 0.1 MPa. Above, more preferably 0.2 MPa or more, usually 5 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, still more preferably 0.5 MPa or less. By setting the pressure within the above range, the partial pressure of the hydrocarbon component in the treated gas can be kept low while enhancing the regeneration efficiency, so that high catalytic activity can be maintained.

(hydrogen partial pressure)
The gas containing hydrogen in the regeneration gas is not particularly limited, but the hydrogen partial pressure in absolute pressure is usually 0.001 MPa or more, preferably 0.01 MPa or more, and more preferably 0.03 MPa. Above, more preferably 0.05 MPa or more, particularly preferably 0.1 MPa or more, usually 4 MPa or less, preferably 1 MPa or less, more preferably 0.7 MPa or less, still more preferably 0.5 MPa or less, particularly preferably 0.1 MPa or less. 3 MPa or less. By setting the hydrogen partial pressure within the above range, the removal and reformation of the coke components accumulated in the catalyst proceed rapidly, so that the catalyst is efficiently brought into a state that provides high raw material conversion activity and high ethylene selectivity. be able to. In addition, equipment and energy for producing high-pressure hydrogen can be reduced.

The space velocity of the regeneration gas is not particularly limited, but is usually 0.001 Hr ^-1 or more, preferably 0.01 Hr ^-1 or more, more preferably 0.1 Hr ^-1 or more, and usually 20 Hr ^-1 or less. , preferably 10 Hr ⁻¹ or less, more preferably 5 Hr ⁻¹ or less. By setting the weight hourly space velocity within the above range, the concentration of hydrocarbon components and water vapor contained in the catalyst can be reduced, so that the feedstock conversion activity can be maintained at a high level. Furthermore, since the distribution of coke components accumulated in the catalyst can be made uniform, uneven reactions within the catalyst can be suppressed, and ethylene selectivity can be increased.

Space velocity is the flow rate of regeneration gas per weight of catalyst (catalytically active components). The weight of the catalyst is the weight of the active ingredient (zeolite) that does not contain any inert ingredients or binders used in the granulation/molding of the catalyst.

The concentration of the regeneration gas in the supply gas for the regeneration step is not particularly limited, but is usually 5% by volume or more, preferably 10% by volume or more, more preferably 30% by volume or more, and usually 100% by volume. Below, preferably 90% by volume or less, more preferably 80% by volume or less. The regeneration gas concentration is preferably as high as possible, usually 5% by volume or more, preferably 30% by volume or more, more preferably 60% by volume or more, and usually 100% by volume or less. By setting the regeneration gas concentration within the above range, the contact between the catalyst and the regeneration gas becomes sufficient, and the removal and reformation of the coke component proceeds rapidly, resulting in high raw material conversion activity and high ethylene selectivity. It can be made efficient in a catalytic state.

The temperature at which the catalyst is brought into contact with the regeneration gas (hereinafter sometimes referred to as "regeneration temperature") is not particularly limited, but is usually 300°C or higher, preferably 400°C or higher, more preferably 500°C. Above, more preferably 525° C. or higher, particularly preferably 550° C. or higher, and usually 800° C. or lower, preferably 700° C. or lower, more preferably 650° C. or lower, still more preferably 600° C. or lower. By setting the degree of regeneration within the above range, the removal of the coke component proceeds rapidly, so that the catalytic activity can be maintained at a high level. Furthermore, since structural collapse of the catalyst is suppressed, it is preferable in that the life of the catalyst can be maintained.

The contact time with the regeneration gas is not particularly limited, but is usually 1 second or longer, preferably 10 seconds or longer, more preferably 1 minute or longer, still more preferably 5 minutes or longer, and usually 5 hours or shorter. It is preferably 2 hours or less, more preferably 1 hour or less. Since the appropriate time varies depending on the concentration of the regeneration gas and the processing temperature, it is preferable to adjust the time as appropriate. When the apparatus to be brought into contact with the regeneration gas is a fluidized bed apparatus, the treatment time mentioned above means the residence time of the catalyst in the apparatus.

A fourth embodiment of the present invention is a method for producing ethylene by contacting a hydrocarbon and a catalyst containing zeolite as an active ingredient in a reactor, wherein the hydrocarbon has at least 4 or more carbon atoms. It contains hydrocarbons, the zeolite has at least an oxygen eight-membered ring structure, and the ratio of the outer surface acid amount to the total acid amount is 3% or less. Although the present embodiment will be described in detail below, differences from the third embodiment will be described, and the description of the third embodiment can be referred to as appropriate.

<D1. Catalyst>
The catalyst used in this embodiment will be described. The catalyst used in the reaction according to the present embodiment is one that can produce ethylene from hydrocarbons, is a zeolite having at least an oxygen eight-membered ring structure, and has a ratio of the outer surface acid amount to the total acid amount of 3. % or less is not particularly limited. As for the zeolite, the description in the third embodiment can be referred to.

In this embodiment, the zeolite has an outer surface acidity of 3% or less with respect to the total acidity of the zeolite. The ratio of the outer surface acid content to the total acid content of the zeolite is preferably as small as possible, preferably 2% or less, more preferably 1% or less, still more preferably 0.5%, and most preferably 0%. By setting the ratio of the outer surface acid amount to the above range, the linear olefin contained in the hydrocarbon having 4 or more carbon atoms used as the raw material is inside the zeolite crystal where the shape selectivity of the oxygen 8-membered ring pores is expressed. By reacting only with , ethylene (dynamic molecular diameter: 0.39 nm) and propylene (dynamic molecular diameter: 0.45 nm) with small molecular sizes are easily obtained with high selectivity, and isobutene (dynamic molecular diameter: A branched olefin having a large molecular size such as 0.50 nm) is difficult to diffuse through the oxygen 8-membered ring pores, so that by-products can be suppressed. Similarly, since the reaction point is restricted to the inside of the crystal, branched olefins (isobutene, isopentene, etc.) of straight-chain olefins (straight-chain butene, straight-chain pentene, etc.) contained in hydrocarbons having 4 or more carbon atoms as raw materials etc.) can be suppressed. In addition, ethylene and propylene produced inside the crystal can be suppressed from being consumed by side reactions at the outer surface acid sites where the shape selectivity of zeolite does not work, so high ethylene selectivity can be maintained and ethylene can be manufactured.

<D2. Method for producing ethylene>
The method for producing ethylene of the present embodiment is a method for producing ethylene by contacting a hydrocarbon with a catalyst containing zeolite as an active component in a reactor, wherein the hydrocarbon has at least 4 or more carbon atoms. The zeolite contains hydrogen, has at least an 8-membered oxygen ring structure, and the ratio of the outer surface acid amount to the total acid amount is 3% or less. Each step will be described in detail below, but differences from the third embodiment will be described, and the description of the third embodiment can be referred to as appropriate.

The method for producing hydrocarbon feedstocks having 4 or more carbon atoms is not limited, either. ), obtained by FT (Fischer-Tropsch) synthesis using a hydrogen / CO mixed gas obtained by gasification of coal as a raw material, obtained by oligomerization reaction including dimerization reaction of ethylene, carbon number 4 or more Those obtained by dehydrogenation or oxidative dehydrogenation of paraffin, those obtained by MTO reaction, those obtained by dehydration reaction of alcohol, those obtained by hydrogenation reaction of diene compounds having 4 or more carbon atoms, Those obtained by various known methods can be used. At this time, compounds other than olefins having 4 or more carbon atoms resulting from each production method may be used as they are, or may be used after purification.

The raw material hydrocarbon may contain hydrocarbons other than hydrocarbons having 4 or more carbon atoms (hereinafter sometimes referred to as "other hydrocarbons"), such as methane, ethane, ethylene, It may contain hydrocarbons having 3 or less carbon atoms such as acetylene, propane, propylene and methylacetylene. In addition, it may contain methanol or dimethyl ether, and there is no limitation on the mixing ratio thereof.

Generally, in the production of ethylene from hydrocarbons having 4 or more carbon atoms, ethylene, which is the target product, may be contained in the raw material hydrocarbon, but contact with the catalyst causes propylene, butene, hexene, and the like to be decomposed. Ethylene is preferably used as a separate feedstock because it is easily converted to other olefins. The mass ratio of hydrocarbons having 4 or more carbon atoms to ethylene contained in the raw material hydrocarbon is not particularly limited, but is usually 1 or more, preferably 5 or more, more preferably 10 or more, and still more preferably It is 15 or more, particularly preferably 30 or more, and the larger the better. The higher the above ratio, the more the consumption of ethylene, which is the target product, can be suppressed, and the more efficiently ethylene can be produced.

In addition, propylene can be partially converted to ethylene by contact with the same catalyst and can improve the ethylene yield, so it may be contained in the raw material, and the propylene produced by this reaction can be recycled. You can also use The mass ratio of propylene to hydrocarbons having 4 or more carbon atoms contained in the raw material hydrocarbon is not particularly limited, but is usually 0 or more, preferably 0.01 or more, and more preferably 0.1 or more. , more preferably 0.2 or more, and usually 1000 or less, preferably 100 or less, more preferably 10 or less, still more preferably 5 or less.

In this embodiment, the conversion rate is a value calculated by the following formula. In addition, the C4+ component indicates the total amount of hydrocarbons having 4 or more carbon atoms.
Conversion rate (%) of hydrocarbons having 4 or more carbon atoms (C4+ component) = [[Reactor raw material inlet C4+ component (mol/Hr) - Reactor generated gas outlet C4+ component (mol/Hr)]/Reactor raw material Input port C4 + component (mol / Hr)] × 100
Here, the conversion rate is calculated based on the components introduced as hydrocarbons having 4 or more carbon atoms, and the isomers thereof are treated as the same component. For example, when only 1-butene is used as a raw material, the above conversion rate is calculated as follows. At this time, hydrocarbons having 4 or more carbon atoms other than butene are treated as products as "hydrocarbons having 4 or more carbon atoms other than raw materials".
Conversion rate (%) of hydrocarbons having 4 or more carbon atoms (C4+ component) = [[reactor raw material inlet 1-butene (mol/Hr) - reactor product gas outlet butene (isomer mixture) (mol/Hr) ]/reactor raw material inlet 1-butene (mol/Hr)] × 100

The selectivity in this embodiment is a value calculated by the following equations. In the following formulas, the "derived carbon flow rate (mol/Hr)" of hydrocarbons such as ethylene, propylene, hydrocarbons with 4 or more carbon atoms other than raw materials (C4+ other than raw materials), paraffins and aromatic compounds are each It means the molar flow rate of carbon atoms that make up the hydrocarbon. Paraffin is the sum of paraffins with 1 to 4 carbon atoms, aromatic compounds are the sum of benzene, toluene, and xylene, and C4+ other than raw materials is the sum of hydrocarbons with 4 or more carbon atoms excluding raw materials and the above aromatic compounds. is.
Ethylene selectivity (%) = [reactor generated gas outlet ethylene-derived carbon molar flow rate (mol/Hr) / [reactor generated gas outlet total carbon molar flow rate (mol/Hr) - reactor outlet C4 + component-derived carbon Molar flow rate (mol/Hr)]] × 100
Propylene selectivity (%) = [reactor generated gas outlet propylene-derived carbon molar flow rate (mol/Hr) / [reactor generated gas outlet total carbon molar flow rate (mol/Hr) - reactor produced gas outlet C4+ Component-derived carbon molar flow rate (mol/Hr)]] × 100
・ C4+ selectivity (%) other than raw material = [reactor generated gas outlet C4+ derived carbon molar flow rate other than raw material (mol / Hr) / [reactor generated gas outlet total carbon molar flow rate (mol / Hr) - reaction Device-generated gas outlet C4+ component-derived carbon molar flow rate (mol/Hr)]]×100
Paraffin selectivity (%) = [reactor generated gas outlet paraffin-derived carbon molar flow rate (mol/Hr) / [reactor generated gas outlet total carbon molar flow rate (mol/Hr) - reactor produced gas outlet C4+ Component-derived carbon molar flow rate (mol/Hr)]] × 100
Aromatic compound selectivity (%) = [reactor generated gas outlet aromatic compound-derived carbon molar flow rate (mol/Hr) / [reactor generated gas outlet total carbon molar flow rate (mol/Hr) - reactor produced Gas outlet C4+ component-derived carbon molar flow rate (mol/Hr)]] × 100
The yield in the present embodiment is obtained by multiplying the raw material conversion rate and the selectivity of each component produced. Specifically, the ethylene yield and propylene yield are respectively represented by the following equations. .
Ethylene yield (%) = C4+ component conversion rate (%) x ethylene selectivity (%)/100
・Propylene yield (%) = C4+ component conversion rate (%) x propylene selectivity (%)/100

Examples A to D (corresponding to the first to fourth embodiments, respectively) are shown below to describe the present invention more specifically. The examples are not intended to be limiting.

(Example A)
<Catalyst Preparation Example A1>
2.09 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 47.3 g of a 25% by weight aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (manufactured by Seichem, 25% by weight) were sequentially added to 89.6 g of water. Then, after adding 4.27 g of aluminum hydroxide (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide) and mixing, colloidal silica SI-30 (SiO ₂ 30% by weight, Na 0.2% by weight) was added as a silica source. 3% by weight, manufactured by Nikki Shokubai Kasei) (111 g) was added and thoroughly stirred. Further, 10% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 25, average primary particle size: about 200 nm) was added as seed crystals to the added SiO _{2 ,} and the mixture was further stirred. Then, this gel was put into a 1000 ml autoclave and hydrothermally synthesized at 160° C. for 20 hours while stirring at 250 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 22 by XRF analysis. The average primary particle size of zeolite was about 100 nm by SEM (JSM-6010LV).

The CHA-type zeolite obtained by hydrothermal synthesis is calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. and calcined at 500° C. for 6 hours under air flow to obtain a proton-type CHA-type zeolite.

20 ml of toluene as a solvent and 5 ml of tetraethoxysilane as a silylating agent were added to 2.0 g of the proton-type CHA-type zeolite, and the mixture was heated at 70° C. for 4 hours while stirring. After completion of the reaction, a solid-liquid was separated by filtration, and the solid content was dried at 100° C. to obtain a silylated proton-type CHA-type zeolite (catalyst A). This zeolite had a total acid content of 0.66 mmol/g and an outer surface acid content of 0.002 mmol/g. Furthermore, the proton-type CHA-type zeolite that was steam-treated and silylated was further treated at 650 ° C. for 5 hours under normal pressure with 50% steam (steam/air = 50/50 (volume/volume)) flowing. was obtained (catalyst A1).

<Catalyst Preparation Example A2>
0.570 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 13.5 g of a 25% by weight aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (manufactured by Seichem, 25% by weight) were sequentially added to 15.8 g of water. Then, after adding 0.152 g of aluminum hydroxide (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide) and mixing, colloidal silica ST-40 (SiO ₂ 40% by weight, Na 0.1% by weight) was added as a silica source. 4% by weight, manufactured by Nissan Chemical Industries) was added and thoroughly stirred. Further, 5% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 25, average primary particle size: about 200 nm) was added as seed crystals to the added SiO ₂ , and the mixture was further stirred. Then, this gel was put into a 100 ml autoclave and hydrothermally synthesized at 140° C. for 6 days while stirring at 15 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 53 by XRF analysis. The average primary particle size of zeolite was about 300 nm.

The CHA-type zeolite obtained by the above hydrothermal synthesis was calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. After that, it was calcined at 500° C. for 6 hours under air circulation to obtain a proton-type CHA-type zeolite (catalyst A2).

<Example A1>
Using catalyst A1 and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 200 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and nitrogen were fed to the reactor such that the weight hourly space velocity of propylene was 0.12 Hr ⁻¹ and the propylene content was 10% by volume and nitrogen was 90% by volume. The synthesis reaction was run for 3.33 hours. Next, 100% by volume of hydrogen gas was supplied to the reactor at a space velocity of 25 mmol/(Hr g-cat), and treated for 1.00 hours under conditions of 525° C. and 0.1 MPa (absolute pressure) (catalyst regeneration process). Again under the above reaction conditions, the synthesis reaction of ethylene was carried out for 1.58 hours. By repeating this reaction step and regeneration step, the synthesis reaction of ethylene was carried out for a total of 6.50 hours. Reactor outlet gas was analyzed by gas chromatography. Table 1 shows the reaction results of the synthesis reaction of ethylene. Also, FIG. 1 shows the change in ethylene yield with respect to the cumulative reaction time. The amount of coke accumulated in the catalyst after the reaction step was 17% by mass, and the amount of coke accumulated in the catalyst after the regeneration step was 14% by mass.

<Comparative Example A1>
The same operation as in Example A1 was carried out, except that the synthesis reaction of ethylene was carried out for 7.08 hours under the reaction conditions of Example A1 without passing through the catalyst regeneration step. Table 2 shows the reaction results. Also, FIG. 1 shows the change in ethylene yield with respect to the cumulative reaction time.

<Example A2>
Using catalyst A2 and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 90 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and nitrogen were supplied to the reactor such that the weight hourly space velocity of propylene was 5.0 Hr ⁻¹ and the propylene content was 40% by volume and nitrogen was 60% by volume. Synthesis reactions were carried out for 30 minutes. Then, after cooling to room temperature, air gas was supplied to the reactor at a space velocity of 100 mmol/(Hr g-cat) under the condition of 0.1 MPa (absolute pressure), and the temperature was raised to 500 at a rate of 20 ° C./min. C., held for 1 minute, and then allowed to cool (catalyst regeneration step). The synthesis reaction of ethylene was carried out again for 5 minutes under the above reaction conditions. Reactor outlet gas was analyzed by gas chromatography. FIG. 2 shows the change in propylene conversion with respect to reaction time and the relationship between propylene conversion and ethylene selectivity in the ethylene synthesis reaction. The amount of coke accumulated in the catalyst after the reaction step was 18% by mass, and the amount of coke accumulated in the catalyst after the regeneration step was 13% by mass. In FIG. 2, the open circle plots show the results when the ethylene synthesis reaction was performed for 30 minutes, the catalyst was regenerated, and the reaction was performed again for 5 minutes.

<Example A3>
Using Catalyst A and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 200 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and nitrogen were supplied to the reactor such that the weight hourly space velocity of propylene was 1.0 Hr ⁻¹ , propylene was 20% by volume and nitrogen was 80% by volume, and ethylene was added at 550° C. and 0.1 MPa (absolute pressure). The synthesis reaction was carried out for 5 minutes (reaction step). Next, 100% by volume of hydrogen gas was supplied to the reactor at a space velocity of 100 mmol/(Hr g-cat), and treated for 20 minutes under conditions of 550° C. and 0.1 MPa (absolute pressure) (catalyst regeneration step). . By repeating this reaction step and regeneration step, the synthesis reaction of ethylene was carried out for a total of 18 hours. Reactor outlet gas was analyzed by gas chromatography. FIG. 3 shows the change in ethylene yield versus cumulative reaction time.

<Example A4>
Using Catalyst A and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 200 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and nitrogen were supplied to the reactor so that the weight hourly space velocity of propylene was 5.0 Hr ⁻¹ , propylene was 20% by volume, hydrogen was 50% by volume, and nitrogen was 80% by volume. pressure), the synthesis reaction of ethylene was carried out for 3 minutes (reaction step). Next, 100% by volume of hydrogen gas was supplied to the reactor at a space velocity of 500 mmol/(Hr·g-cat), and treated at 650° C. and 0.1 MPa (absolute pressure) for 40 minutes (catalyst regeneration step). . By repeating this reaction step and regeneration step, the synthesis reaction of ethylene was carried out for a total of 6 hours. Reactor outlet gas was analyzed by gas chromatography. Table 3 and FIG. 4 show changes in propylene conversion rate and ethylene selectivity with respect to reaction time in the ethylene synthesis reaction. The amount of coke accumulated in the catalyst after the reaction step was 16% by mass.

In Examples A1 to A4, the catalyst with a reduced ethylene yield in the step (I) of contacting the catalyst with propylene was subjected to the catalyst regeneration step (II), thereby maintaining a high ethylene yield over a long period of time and producing ethylene. was found to be able to produce On the other hand, in Comparative Example A1 that did not undergo the step (II), the ethylene yield could not be maintained and the ethylene yield decreased to 5%. From this, it was found that ethylene can be produced stably and efficiently by including the contacting step (I) with propylene and the catalyst regeneration step (II) in the method for producing ethylene from propylene.

(Example B)
<Catalyst Preparation Example B1>
2.09 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 47.3 g of a 25% by weight aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (manufactured by Seichem, 25% by weight) were sequentially added to 89.6 g of water. Then, after adding 4.27 g of aluminum hydroxide (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide) and mixing, colloidal silica SI-30 (SiO ₂ 30% by weight, Na 0.2% by weight) was added as a silica source. 3% by weight, manufactured by Nikki Shokubai Kasei) (111 g) was added and thoroughly stirred. Further, 10% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 25, average primary particle size: about 200 nm) was added as seed crystals to the added SiO _{2 ,} and the mixture was further stirred. Then, this gel was put into a 1000 ml autoclave and hydrothermally synthesized at 160° C. for 20 hours while stirring at 250 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 22 by XRF analysis. The average primary particle size of zeolite was about 100 nm.

The CHA-type zeolite obtained by hydrothermal synthesis is calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. and calcined at 500° C. for 6 hours under air flow to obtain a proton-type CHA-type zeolite.

20 ml of toluene as a solvent and 5 ml of tetraethoxysilane as a silylating agent were added to 2.0 g of the proton-type CHA-type zeolite, and the mixture was heated at 70° C. for 4 hours while stirring. After completion of the reaction, a solid-liquid was separated by filtration, and the solid content was dried at 100° C. to obtain a silylated proton-type CHA-type zeolite. Furthermore, the proton-type CHA-type zeolite that was steam-treated and silylated was further treated at 650 ° C. for 5 hours under normal pressure with 50% steam (steam/air = 50/50 (volume/volume)) flowing. was obtained (catalyst B1).

<Catalyst Preparation Example B2>
Catalyst B1 is treated at 650° C. for 5 hours under normal pressure with 50% steam (steam/air=50/50 (volume/volume)) flowing to obtain steam-treated and silylated proton-type CHA type. A zeolite was obtained (catalyst B2).

<Example B1>
Using catalyst B1 and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 200 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and hydrogen were supplied to the reactor so that the weight hourly space velocity of propylene was 0.23 Hr ⁻¹ , propylene was 10% by volume and hydrogen was 90% by volume. A synthesis reaction was carried out, and the reactor outlet gas was analyzed by gas chromatography. Table 4 shows the reaction results. The amount of coke accumulated in the catalyst after the reaction was 12% by mass.

<Comparative Example B1>
The same operation as in Example B1 was performed except that nitrogen was used instead of hydrogen, and propylene was 10% by volume and nitrogen was 90% by volume. Table 4 shows the reaction results. The amount of coke accumulated in the catalyst after the reaction was 18% by mass.

<Comparative Example B2>
The same operation as in Example B1 was performed except that a mixed gas of water vapor and nitrogen was used instead of hydrogen, and propylene was 10% by volume, water vapor was 40% by volume, and nitrogen was 50% by volume. The reaction results are shown in Table 4 and FIG.

<Example B2>
Using catalyst B2 and propylene as a raw material, a synthesis reaction of ethylene was carried out. For the reaction, an atmospheric pressure fixed bed flow reactor was used, and a mixture of 200 mg of the above catalyst and 300 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. Propylene and nitrogen were fed to the reactor such that the weight hourly space velocity of propylene was 0.12 Hr ⁻¹ and the propylene content was 10% by volume and nitrogen was 90% by volume. The synthesis reaction was run for 3.33 hours. At this time, the propylene conversion rate was 28.9%, the ethylene selectivity was 55.7%, the butene selectivity was 27.0%, and the ethylene yield was 16.1%. 100% by volume of hydrogen gas was supplied to the reactor at a hydrogen space velocity of 25 mmol/(Hr g-cat) with respect to the catalyst after the above reaction (hereinafter referred to as "catalyst B2A"), The treatment was performed for 1.00 hours under the condition of 0.1 MPa (absolute pressure). Then, using the catalyst brought into contact with hydrogen, the synthesis reaction of ethylene was carried out again under the above reaction conditions. Table 5 shows the reaction results after 0.33 hours.

<Comparative Example B3>
Example B2 except that 100% by volume of nitrogen gas was used for catalyst B2A instead of 100% by volume of hydrogen gas and supplied to the reactor at a nitrogen space velocity of 25 mmol / (Hr g-cat). performed the same operation. Table 5 shows the reaction results.

<Comparative Example B4>
Instead of 100% by volume hydrogen gas, 50% water vapor gas (water vapor/nitrogen = 50/50 (volume/volume)) was added to catalyst B2A at a space velocity of 25 mmol/(Hr g-cat) in the reactor. The same operation as in Example B2 was performed, except that the solution was supplied to . Table 5 shows the reaction results.

From Example B1, by using a gas containing hydrogen as a carrier gas to produce ethylene by bringing propylene into contact with the catalyst, coking deterioration was greatly suppressed, and the catalyst activity was stabilized. It was found that ethylene can be stably produced at a high yield compared to the case of using nitrogen gas and steam/nitrogen gas of Comparative Example B2 as the diluent gas.
Further, in Example B2, by bringing hydrogen gas into contact with the catalyst whose ethylene yield decreased over time due to propylene conversion, Comparative Example B3 using nitrogen gas and Comparative Example using steam / nitrogen gas It was found that the ethylene yield can be recovered to a large extent efficiently without reducing the ethylene selectivity for B4.

(Example C)
<Catalyst Preparation Example C1>
2.09 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 47.3 g of a 25% by weight aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (manufactured by Seichem, 25% by weight) were sequentially added to 89.6 g of water. Then, after adding and mixing 4.27 g of aluminum hydroxide (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide), colloidal silica SI-30 (SiO ₂ 30% by weight, Na 0.2% by weight) was added as a silica source. 3% by weight, manufactured by Nikki Shokubai Kasei) (111 g) was added and thoroughly stirred. Further, 10% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 25, average primary particle size: about 200 nm) was added as seed crystals to the added SiO _{2 ,} and the mixture was further stirred. Then, this gel was put into a 1000 ml autoclave and hydrothermally synthesized at 160° C. for 20 hours while stirring at 250 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 22 by XRF analysis. The average primary particle size of zeolite was about 100 nm.

The CHA-type zeolite obtained by hydrothermal synthesis is calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. and calcined at 500° C. for 6 hours under air flow to obtain a proton-type CHA-type zeolite.
20 ml of toluene as a solvent and 5 ml of tetraethoxysilane as a silylating agent were added to 2.0 g of the proton-type CHA-type zeolite, and the mixture was heated at 70° C. for 4 hours while stirring. After completion of the reaction, a solid-liquid was separated by filtration, and the solid content was dried at 100° C. to obtain a silylated proton-type CHA-type zeolite (catalyst C1). This zeolite had a total acid content of 0.66 mmol/g and an outer surface acid content of 0.002 mmol/g.

<Example C1>
Ethylene synthesis reaction was carried out using propylene and trans-2-butene as raw materials using catalyst C1. For the reaction, a normal pressure fixed bed flow reactor was used, and a mixture of 90 mg of the above catalyst and 400 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. The reactor was filled so that the weight hourly space velocity of propylene was 4.2 Hr ⁻¹ , the weight hourly space velocity of trans-2-butene was 0.8 Hr ⁻¹ , propylene was 35% by volume, trans-2-butene was 5% by volume, and nitrogen was 60% by volume. The synthesis reaction of ethylene was carried out at 500° C. and 0.1 MPa (absolute pressure) for 10-12 minutes. The product gas discharged from the reactor was analyzed by gas chromatography. Table 6 shows the reaction results of the synthesis reaction of ethylene.

<Example C2>
Propylene weight hourly space velocity of 3.5 Hr ⁻¹ , trans-2-butene weight hourly space velocity of 1.5 Hr ⁻¹ , propylene of 30% by volume, and trans-2-butene of 10% by volume were supplied to the reactor, The same operation as in Example C1 was performed. Table 6 shows the reaction results.

<Example C3>
Propylene weight hourly space velocity of 2.1 Hr ⁻¹ , trans-2-butene weight hourly space velocity of 2.9 Hr ⁻¹ , propylene of 20% by volume and trans-2-butene of 20% by volume were supplied to the reactor, The same operation as in Example C1 was performed. Table 6 shows the reaction results.

<Example C4>
Propylene weight hourly space velocity of 1.0 Hr ⁻¹ , trans-2-butene weight hourly space velocity of 4.0 Hr ⁻¹ , 10% by volume of propylene, and 30% by volume of trans-2-butene were supplied to the reactor, except that The same operation as in Example C1 was performed. Table 6 shows the reaction results.

<Comparative Example C1>
The same operation as in Example C1 was performed, except that only propylene was used as a raw material and supplied to the reactor so that the weight hourly space velocity of propylene was 5.0 Hr ⁻¹ and propylene was 40% by volume. Table 6 shows the reaction results.
From these examples, it was found that ethylene can be produced while stably maintaining a high ethylene/propylene ratio by using a raw material containing propylene and a specific amount of butene as a hydrocarbon having 4 or more carbon atoms. These results suggest that the equilibrium composition between ethylene-propylene-butene shifted to the ethylene side by using a raw material containing a specific proportion of butene as a hydrocarbon having 4 or more carbon atoms. be. That is, by using a raw material containing propylene and a hydrocarbon having 4 or more carbon atoms, it is possible to increase the conversion efficiency from propylene to ethylene, alleviate fluctuations in the high ethylene / propylene ratio, and stably produce ethylene. It is thought that it was possible.

According to this embodiment, it is possible to produce ethylene at a high yield from a propylene raw material. In addition, since a high ethylene/propylene ratio can be stably maintained, the complexity of the process and the load of separation/purification can be reduced.

(Example D)
<Physical property measurement>
In the preparation examples below, X-ray diffraction (XRD) patterns of zeolite crystals obtained by synthesis were obtained using X'Pert Pro MPD manufactured by PANalytical. The X-ray source is CuKα (X-ray output: 40 kV, 30 mA) and the read width is 0.016°.
Rayny EDX-700 manufactured by Shimadzu Corporation was used for X-ray fluorescence analysis (XRF).
In composition analysis by the ICP method, a sample solution was prepared by dissolving a sample with hydrofluoric acid. The sample solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). From the measured values of Si and Al obtained, the SiO ₂ /Al ₂ O ₃ ratio of the sample was determined.
The average primary particle size of zeolite was measured using a SEM (scanning electron microscope) JSM-6010LV manufactured by JEOL Ltd.
XPS (X-ray photoelectron spectroscopy) measurement of the zeolite crystal surface was performed under the following conditions using Quantum 2000 manufactured by PHI. X-ray source: monochromatic Al-Kα, output 16 kV-34 W (X-ray generation area 170 μmφ), charge neutralization: electron gun (2 μA), ion gun (1 V) combined, spectroscopic system: pulse energy 187.85 eV @ wide spectrum , 29.35 eV @ narrow spectrum (C1s, Al2p), 11.75 eV @ narrow spectrum (O1s, Si2p), measurement area: irradiation area 300 μm square, take-off angle: 45° (from the surface).
From the measured values of Si and Al obtained, the SiO ₂ /Al ₂ O ₃ ratio of the zeolite crystal surface was obtained.

<Catalyst Preparation Example D1>
2.09 g of sodium hydroxide (manufactured by Kishida Chemical Co., Ltd.) and 47.3 g of a 25% by weight aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (manufactured by Seichem, 25% by weight) were sequentially added to 89.6 g of water. Then, after adding 4.27 g of aluminum hydroxide (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide) and mixing, colloidal silica SI-30 (SiO ₂ 30% by weight, Na 0.2% by weight) was added as a silica source. 3% by weight, manufactured by Nikki Shokubai Kasei) (111 g) was added and sufficiently stirred. Further, 10% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 25, average primary particle size: about 200 nm) was added as seed crystals to the added SiO _{2 ,} and the mixture was further stirred. Then, this gel was put into a 1000 ml autoclave and hydrothermally synthesized at 160° C. for 20 hours while stirring at 250 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 22 by XRF analysis. The average primary particle size of zeolite was about 100 nm.

The CHA-type zeolite obtained by hydrothermal synthesis is calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. and calcined at 500° C. for 6 hours in an air stream to obtain a proton-type CHA-type zeolite (catalyst DA).
20 ml of toluene as a solvent and 5 ml of tetraethoxysilane as a silylating agent were added to 2.0 g of the proton-type CHA-type zeolite, and the mixture was heated at 70° C. for 4 hours while stirring. After completion of the reaction, a solid-liquid was separated by filtration, and the solid content was dried at 100° C. to obtain a silylated proton-type CHA-type zeolite (catalyst D1).

<Catalyst Preparation Example D2>
59.2 g of N,N,N-trimethyl-1-adamantane ammonium hydroxide aqueous solution (manufactured by Seichem, 25% by mass) and 145.6 g of 1M sodium hydroxide aqueous solution were successively dissolved in 371 g of water, followed by aluminum hydroxide. (manufactured by Aldrich, 50 to 57% by weight in terms of aluminum oxide) was added and stirred, and then 42.1 g of fumed silica as a silica source was added and stirred for 2 hours. Furthermore, 10% by weight of CHA-type zeolite (SiO ₂ /Al ₂ O ₃ ratio: 15, average primary particle size: about 100 nm) was added as seed crystals to the SiO ₂ derived from the silica source, and the mixture was further stirred. Then, this gel was put into a 1000 ml autoclave and hydrothermally synthesized at 160° C. for 42 hours while stirring at 150 rpm under autogenous pressure. The product was filtered, washed with water and dried. The XRD pattern of the product confirmed that the obtained product was the CHA phase. The SiO ₂ /Al ₂ O ₃ ratio was 14 by XRF analysis. The average primary particle size of zeolite was about 100 nm.

The CHA-type zeolite obtained by hydrothermal synthesis is calcined at 580°C for 6 hours under air flow, then ion-exchanged twice with a 1 M ammonium nitrate aqueous solution at 80°C for 1 hour, and dried at 100°C. and calcined at 500° C. for 6 hours under air flow to obtain a proton-type CHA-type zeolite (catalyst DB).
10 ml of hexamethyldisiloxane as a solvent and 2.5 ml of tetraethoxysilane as a silylating agent were added to 1.0 g of the proton-type CHA-type zeolite, and the mixture was heated at 100° C. for 6 hours while stirring. After completion of the reaction, a solid-liquid was separated by filtration, and the solid content was dried at 100° C. to obtain a silylated proton-type CHA-type zeolite (catalyst D2). The SiO ₂ /Al ₂ O ₃ ratio of the entire crystal was 14 by ICP analysis, and the SiO ₂ /Al ₂ O ₃ ratio of the crystal surface was 30 by XPS analysis. Also, the average primary particle size was about 100 nm as measured by a scanning electron microscope.

<Example D1>
Ethylene synthesis reaction was carried out using catalyst D1 and trans-2-butene as a raw material. For the reaction, a normal pressure fixed bed flow reactor was used, and a mixture of 90 mg of the above catalyst and 400 mg of quartz sand was filled in a quartz reaction tube with an inner diameter of 6 mm. trans-2-butene and nitrogen were fed to the reactor such that the weight hourly space velocity of trans-2-butene was 5 Hr ⁻¹ and 40% by volume of trans-2-butene and 60% by volume of nitrogen were heated at 500° C., The synthesis reaction of ethylene was carried out for 8-10 minutes at 0.1 MPa (absolute pressure). The product gas discharged from the reactor was analyzed by gas chromatography. Table 7 shows the reaction results of the synthesis reaction of ethylene.

<Example D2>
An ethylene synthesis reaction was carried out for 10 minutes in the same manner as in Example D1, except that catalyst D2 was used. Table 7 shows the reaction results of the synthesis reaction of ethylene.

<Comparative Example D1>
An ethylene synthesis reaction was carried out for 10 minutes in the same manner as in Example 1, except that catalyst DA was used. Table 1 shows the reaction results of the synthesis reaction of ethylene.
As a catalyst, by using zeolite in which the ratio of outer surface acid sites where shape selectivity does not work is reduced to 3% or less, the ethylene selectivity is high, the ethylene yield itself is equal or higher, and isobutene, that is, It can be seen that the ratio of branched olefins, which are difficult to recycle as raw materials, has greatly decreased.

According to the present embodiment, when ethylene is produced using hydrocarbons having 4 or more carbon atoms, particularly butenes and pentenes, as raw materials, side reactions can be suppressed and ethylene can be produced with high ethylene selectivity. Provided is a method for producing ethylene capable of suppressing isomerization to branched olefins. As a result, equipment and energy required for separating and refining straight-chain olefins and branched olefins can be reduced, and the recycling of hydrocarbons having 4 or more carbon atoms can be facilitated.

Claims (5)

A step (I) of supplying propylene to a reactor and contacting it with a catalyst to produce ethylene, and a step (II) of regenerating the catalyst that has undergone step (I) by contacting it with a gas containing hydrogen. and wherein the catalyst comprises a CHA-type zeolite . A method for producing ethylene by contacting propylene and a catalyst in a reactor, comprising:
A method for producing ethylene, wherein the catalyst is a catalyst contacted with a hydrogen-containing gas and contains a CHA-type zeolite . 3. The method for producing ethylene according to claim 2, wherein the catalyst is a catalyst obtained by contacting a catalyst containing coke produced by contact with propylene and a gas containing hydrogen. 4. The method for producing ethylene according to claim 2, wherein the catalyst is a catalyst obtained by contacting the catalyst with a gas containing hydrogen at a temperature of 300[deg.] C. or higher. The method for producing ethylene according to any one of claims 2 to 4, wherein the catalyst is in contact with a gas containing hydrogen at a hydrogen partial pressure absolute pressure of 0.001 MPa or more.

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