JP5499918B2 - Catalyst regeneration method - Google Patents

Description

  The present invention relates to a method for regenerating a catalyst deteriorated by a reaction for producing propylene from ethylene in a gas phase.

  In the hydrocarbon conversion reaction, the catalyst is generally deactivated due to carbonaceous (coke) adhesion. For this reason, it is necessary to regenerate the catalyst by removing the coke. Usually, the adhering carbonaceous matter is burned and removed using a gas containing oxygen to regenerate the catalyst. In Patent Document 1, in the aromatic alkylation reaction, the deactivated zeolite β catalyst is oxidized by adhering coke with a gas containing oxygen to regenerate the catalyst. Moreover, in patent document 2, in order to regenerate | regenerate the catalyst used by the fixed bed gas phase reaction, oxygen-containing gas is distribute | circulated and the carbonaceous substance is removed.

Special table 2007-537028 gazette JP 2001-96173 A

  According to the study of the present inventors, in a method for producing propylene by bringing ethylene into contact with a catalyst having zeolite as an active component, a conventional regeneration method using a gas containing oxygen is used. It was found that, although the activity was recovered when coke adhered to the catalyst was completely removed, the selectivity for propylene after the reaction was low and the amount of paraffin produced was increased when the reaction was carried out using the regenerated catalyst. Since the generation of paraffin was suppressed as the activity decreased due to coke adhesion over time, partial regeneration was performed using diluted oxygen without completely removing the coke. As a result, although the conversion rate was improved by the removal of coke, it was still a low value when compared with the selectivity of propylene obtained when the unused catalyst deteriorated with time. In the method of producing propylene by contacting ethylene, regeneration using a gas containing oxygen has the disadvantage that the selectivity for propylene is reduced, although coke removal occurs effectively.

  As a result of intensive studies in order to solve the above problems, the present inventors have determined that a gas that contains water vapor and does not contain oxygen after deactivation of a catalyst that has been subjected to a reaction for synthesizing propylene in the gas phase using ethylene as a raw material. It was discovered that by removing the coke by leaving it in contact with the catalyst, it is possible to regenerate propylene after regeneration with a higher selectivity compared to a regeneration method in which hydrocarbons are removed with a conventional gas containing oxygen. It came to complete. The propylene selectivity after regeneration is equal to or higher than the propylene selectivity obtained when the unused catalyst deteriorates with time.

That is, the gist of the present invention is to produce propylene by contacting ethylene in a gas phase with a catalyst having a zeolite as an active component, and to treat a catalyst deteriorated by coke adhesion at a concentration of 1% by volume to 100% by volume. And a catalyst regeneration method, wherein the catalyst is activated by contact with a regeneration gas not containing oxygen and removing a part of the coke.
Exist.

According to the present invention, it is possible to achieve a propylene selectivity that is equal to or higher than the propylene selectivity obtained by aging the unused catalyst in the regenerated catalyst.
Therefore, according to the present invention, a constant propylene selectivity can be maintained in repeated reaction-regeneration, and a stable propylene yield can be obtained.

Below, the typical aspect for implementing this invention is demonstrated concretely, However, This invention is not limited to the following forms, unless the summary is exceeded. First, the zeolite catalyst used in the present invention will be described. In the present invention, the zeolite catalyst means a catalyst having zeolite as an active component and capable of producing propylene from ethylene under an appropriate temperature condition.
Zeolite, which is an active component, may be used as it is as a catalyst in the reaction, or may be used in the reaction by granulating and molding using a substance or binder that is inert to the reaction, or by mixing them. Examples of the substance or binder inert to the reaction include alumina or alumina sol, silica, silica gel, quartz, and a mixture thereof.

<Zeolite>
Zeolite refers to a crystalline substance in which TO ₄ units having a tetrahedral structure (T is a central atom) share O atoms three-dimensionally to form open regular micropores. . Specific examples include silicates, phosphates, germanium salts, and arsenates that are described in the Data Collection of the Structure Committee of the International Zeolite Association (IZA). Silicates include, for example, aluminosilicates, gallosilicates, ferrisilicates, titanosilicates, borosilicates, etc., and phosphates include, for example, aluminophosphate (ALPO), beryllophosphate, galloline. Acid salts and the like are included. Furthermore, examples of the aluminophosphate include silicoaluminophosphate (SAPO) in which T atoms are partially substituted with Si, and those containing divalent or trivalent cations such as Ga, Mg, Fe, Co, and Zn. .
Of these, aluminosilicates and silicoaluminophosphates are preferred, and aluminosilicates are more preferred.

<Acid amount>
In the present invention, the acid amount on the outer surface of the zeolite (hereinafter sometimes simply referred to as the outer surface acid amount) represents the total amount of acid sites present on the outer surface of the zeolite.
Specifically, the amount of acid on the outer surface is, after predrying at 500 ° C. for 1 hr under vacuum, contact adsorption with pyridine vapor at 150 ° C., and removing excess pyridine with vacuum exhaust and He flow at 150 ° C. The amount of pyridine desorbed per unit weight of zeolite at 150 to 800 ° C. by the temperature programmed desorption method with a temperature rising rate of 10 ° C./min.

The amount of acid on the outer surface is not particularly limited, but is usually 0.6 mmol / g or less, preferably 0.3 mmol / g or less. When the upper limit is exceeded, a reaction that is not shape-selective occurs on the outer surface, and the selectivity for propylene may decrease. The lower limit is not particularly limited and is preferably as small as possible, but is usually 0.01 mmol / g or more.
The total acid amount of the zeolite in the present invention (hereinafter sometimes simply referred to as the total acid amount) is, as a pretreatment, dried at 500 ° C. for 1 hour under He flow, and then at 100 ° C. with 5 vol% ammonia / helium. Desorption of ammonia per unit weight of zeolite at 100 to 800 ° C. by the temperature-programmed desorption method of the zeolite obtained by contact adsorption and contact with water vapor at 100 ° C. to remove excess ammonia. The amount of separation.

  Although the total acid amount is not particularly limited, it is usually 4.8 mmol / g or less, preferably 2.8 mmol / g or less. Moreover, it is 0.15 mmol / g or more normally, Preferably it is 0.30 mmol / g or more. When the upper limit is exceeded, deactivation due to coke adhesion becomes faster, durability tends to decrease, and the acid strength per acid point may be weakened. Conversion may be reduced.

  The ratio of the acid amount on the outer surface of the zeolite and the total acid amount in the present invention is not particularly limited, but the acid amount on the outer surface of the zeolite is usually 5% or less with respect to the acid amount of the entire zeolite, preferably 4.5%. Or less, more preferably 3.5% or less.

If the ratio of the external surface acid amount to the total acid amount exceeds the above upper limit, the selectivity of propylene may decrease due to side reactions occurring on the outer surface of the zeolite. This is presumably because the reaction on the outer surface is not subject to shape-selective restrictions and a product of C ₄ or higher is produced. In addition, it is considered that propylene produced in the pores of the catalyst reacts with the acid points on the outer surface again to cause side reactions, thereby reducing the propylene selectivity.

<Structure>
The zeolite used in the present invention usually has pores.
The average pore size of the zeolite used in the present invention is not particularly limited, but usually the pore size is less than 0.5 nm.
The term “average pore diameter” as used herein refers to a crystallographic free diameter of the channels determined by International Zeolite Association (IZA).
The average pore diameter of less than 0.5 nm means that the diameter of the pore is less than 0.5 nm when the shape of the pore is a perfect circle diameter, but the minor diameter when the shape of the pore is an ellipse. Is less than 0.5 nm.

  If the pore diameter of the zeolite exceeds the upper limit, by-products other than propylene (butene, pentene, etc.) may increase, and it may not be possible to produce propylene from ethylene in a high yield.

  Although the details of the mechanism of action that propylene can be produced in high yield from ethylene by using zeolite with a small average pore diameter is not clear, ethylene can be activated by the presence of strong acid sites, Further, it is considered that propylene can be selectively generated with a small pore diameter. In other words, if the pore diameter is small, propylene, which is the target product, can come out of the pore, but butene and pentene, which are by-products, are too large in the pores. It is estimated that it has remained at It is considered that the propylene selectivity is improved by such a mechanism.

The lower limit of the average pore diameter of zeolite is not particularly limited, but is usually not less than 0.2 nm and preferably not less than 0.3 nm.
If the average pore diameter is less than the lower limit, it is considered that neither ethylene nor propylene can pass through, the action of ethylene and active sites hardly occurs, and the reaction rate tends to decrease.

  The number of oxygen that constitutes the pores of the zeolite used in the present invention is not particularly limited, but usually, one having a structure containing an oxygen 8-membered or 9-membered ring is preferred.

The structure including an oxygen 8-membered or 9-membered ring means a ring structure in which the pores of the zeolite are composed of 8 or 9 TO ₄ units (T is Si, P, Ge, Al, Ga, etc.).
Specifically, the zeolite composed only of an oxygen 8-membered ring can be represented by a code defined by International Zeolite Association (IZA), for example, AFX, CAS, CHA, DDR, ERI, ESV, GIS, GOO, ITE, JBW, KFI, LEV, LTA, MER, MON, MTF, PAU, PHI, RHO, RTE, RTH, and the like.

Specific examples of the zeolite containing an oxygen 9-membered ring and having only pores of oxygen 9-membered or less include NAT, RSN, STT, and the like when expressed by a code defined by International Zeolite Association (IZA).
The framework density of the zeolite used in the present invention is not particularly limited, but a zeolite having a framework density of 18.0 T / nm ³ or less is preferable, and more preferably 17.0 T / nm ³ or less. Usually, it is 13.0 T / nm ³ or more, preferably 14.0 T / nm ³ or more.

Here, the framework density (unit: T / nm ³ ) means the number of T atoms (among atoms constituting the zeolite skeleton, other than oxygen) present per unit volume (1 nm ³ ) of the zeolite. However, this value is determined by the structure of the zeolite.

  From the viewpoint of the above structure, preferred framework structures of the zeolite used in the present invention are AFX, CHA, ERI, LEV, RHO, and RTH, and more preferred framework structures are CHA.

  Specific examples of the CHA-structured zeolite include silicate and phosphate CHA-type zeolites. As described above, examples of the silicate include aluminosilicate, gallosilicate, ferrisilicate, titanosilicate, borosilicate, and the like, and the phosphate includes an aluminophosphate (ALPO) composed of aluminum and phosphorus. -34), silicoaluminophosphate (SAPO-34) composed of silicon, aluminum and phosphorus. Among these, aluminosilicate and silicoaluminophosphate are preferable, and aluminosilicate (hereinafter also referred to as aluminosilicate) is more preferable.

<Composition>
When the zeolite is a silicate, the SiO ₂ / M ₂ O ₃ (M is a trivalent metal such as aluminum, gallium, iron, boron) molar ratio is not particularly limited, but is usually 5 or more, preferably 10 or more is there. If the SiO ₂ / metal molar ratio is too low, the durability of the catalyst may decrease. The upper limit of the SiO ₂ / metal molar ratio is not particularly limited, but is usually 1000 or less. If the SiO ₂ / metal molar ratio is too high, the catalytic activity may decrease.
When the zeolite is an aluminosilicate, the SiO ₂ / Al ₂ O ₃ molar ratio in the aluminosilicate is not particularly limited, but is usually 5 or more, preferably 10 or more, usually 200 or less, preferably 100 or less. It is. If it is less than the lower limit, deactivation due to coke adhesion may be accelerated, aluminum may easily escape from the skeleton, and the acid strength per acid point may be weakened. If the amount exceeds the upper limit, the acid amount is small, and the ethylene conversion rate may decrease.

  When the zeolite is phosphate, (Al + P) / Si molar ratio of silicoaluminophosphate or (Al + P) / M of metalloaluminophosphate having a divalent metal (where M represents a divalent metal) .) The molar ratio is not particularly limited, but is usually 5 or more, preferably 10 or more, and the upper limit is usually 500 or less. If this value is too low, the durability of the catalyst tends to decrease, and if it is too high, the catalytic activity tends to decrease.

  Zeolite is usually of the proton exchange type, but some of them are alkali metals such as Na and K, alkaline earth metals such as Mg and Ca, Cr, Cu, Ni, Fe, Mo, W, Pt, Re, etc. The transition metal may be exchanged.

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

<Manufacturing method>
The method for producing the zeolite used in the present invention is not particularly limited and can be produced by a known method. In general, it can be prepared by a hydrothermal synthesis method. Moreover, what changed the composition by ion exchange, dealumination treatment, impregnation, etc. after hydrothermal synthesis can also be used.
<Method for reducing the ratio of the external surface acid amount to the total acid amount>
The method for reducing the ratio of the outer surface acid amount to the total acid amount is not particularly limited, but 1) a method for silylating the outer surface of the zeolite, 2) a method for performing steam treatment (steaming) on the zeolite, 3 And a method of treating with a dicarboxylic acid.

<Silylation>
The method of silylating the outer surface of the zeolite is to reduce the amount of acid on the outer surface by silylating the outer surface of the active component zeolite of the catalyst. The method of silylation is not particularly limited, and is carried out by liquid phase silylation using alkoxysilane or gas phase silylation using chlorosilane.

  Silylating agents are quaternary alkoxysilanes such as tetramethoxysilane and tetraethoxysilane; tertiary alkoxysilanes such as trimethoxymethylsilane and triethoxymethylsilane; secondary silanes such as dimethoxydimethylsilane and diethoxydimethylsilane. Alkoxysilanes: primary alkoxysilanes such as methoxytrimethylsilane and ethoxytrimethylsilane. Further, chlorosilanes such as tetrachlorosilane, dimethyldichlorosilane, and trimethylchlorosilane can be used. Of these, tetraethoxysilane is preferable for alkoxysilane, and tetrachlorosilane is preferable for chlorosilane.

  The solvent used in the liquid phase silylation method is not particularly limited, but an organic solvent such as benzene, toluene, hexamethyldisiloxane, or water can be used. In the liquid phase silylation method, the amount ratio (mol / mol) of silylating agent / zeolite in the treatment solution is usually 5 or less, preferably 3 or less. Moreover, it is 0.005 or more normally, Preferably it is 0.1 or more. If this value is too high, there is a problem that pores are blocked due to excessive silylation, and if it is too low, silylation is insufficient and the acid sites on the outer surface cannot be poisoned. The temperature of silylation depends on the type of silylating agent and solvent, but is usually 140 ° C. or lower, preferably 120 ° C. or lower. Moreover, it is 20 degreeC or more normally, Preferably it is 40 degreeC or more. When the treatment temperature is too high, there is a problem that silylation does not occur efficiently due to evaporation of the liquid, and when the temperature is too low, there is a problem that the reaction rate of silylation becomes slow. The treatment time is usually 0.5 hours or more, preferably 2 hours or more, and there is no particular upper limit for the treatment time. If the treatment time is too short, silylation does not occur sufficiently, and acid point poisoning may be insufficient.

The gas phase silylation treatment is performed so that the weight of silica deposited on the zeolite is usually 20% by weight or less, preferably 18% by weight or less. Although there is no particular lower limit, it is usually 0.1% by weight or more, preferably 1% by weight or more. If this value is too high, there is a problem that pores are blocked due to excessive silylation, and if it is too low, silylation is insufficient and the acid sites on the outer surface cannot be poisoned.
The temperature of the gas phase silylation depends on the silylating agent, but is usually 20 ° C. or higher, preferably 100 ° C. or higher. Moreover, it is 500 degrees C or less normally, Preferably it is 400 degrees C or less.
If the treatment temperature is too high, decomposition of the silylating agent and collapse of the skeleton of the zeolite may occur, and if the treatment temperature is too low, the silylation reaction may not proceed.

<Steam treatment>
The method for performing the steaming on the zeolite is not particularly limited, but the steaming temperature is preferably 400 ° C or higher, more preferably 500 ° C or higher. Moreover, 700 degrees C or less is preferable, More preferably, it is 650 degrees C or less. If the temperature is too low, the effect of steaming is small, and if it is too high, the structure of the zeolite may collapse.

Steam can also be diluted with an inert gas such as helium or nitrogen. The steam concentration is not particularly limited, and is usually 3% by volume or more, preferably 5% by volume or more. There is no upper limit, and the treatment with 100% water vapor is possible.
It is also possible to physically mix with a compound containing an alkaline earth metal before steaming the zeolite. Examples of the compound containing an alkaline earth metal include calcium carbonate, calcium hydroxide, and magnesium carbonate, among which calcium carbonate is preferable.

The amount of the compound containing an alkaline earth metal is not particularly limited, but is usually 0.5% by weight or more and 45% by weight or less based on the zeolite. Preferably, it is 3 to 40% by weight.
Further, the steaming may be performed in a state where organic substances are present inside the pores for the purpose of selectively dealumination of the acid amount on the outer surface. Although there is no limitation in particular with an organic substance, the structure directing agent used at the time of a zeolite synthesis | combination and the coke produced | generated by reaction are mentioned. These organic substances are present in the pores of the zeolite in a synthesized state, and the coke is allowed to exist inside the pores by passing the catalyst through the catalyst at a temperature of 200 ° C. or higher. Can do.

<Treatment with dicarboxylic acid>
There is no limitation in particular as a method of processing with dicarboxylic acid. Dicarboxylic acid is thought to reduce the amount of acid by promoting the elimination of the metal in the framework such as aluminum of the zeolite, but the molecular size is large compared to the zeolite pores. It cannot penetrate into the hole, and the acid amount on the outer surface can be selectively reduced.

Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, phthalic acid, isophthalic acid, fumaric acid, tartaric acid, and the like. Of these, oxalic acid is preferred.
The dicarboxylic acid is made into a solution and mixed with the zeolite. The concentration of the dicarboxylic acid in the solution is generally 0.01M to 4M, preferably 1M to 3M. The mixing temperature is 15 ° C to 95 ° C, preferably 50 ° C to 85 ° C. Mixing with zeolite may be carried out twice or more in order to promote dealumination of the zeolite surface.

  Moreover, you may carry out in the state in which organic substance exists in the inside of a pore for the purpose of selectively removing the acid amount of an outer surface. Although there is no limitation in particular with an organic substance, the structure directing agent used at the time of a zeolite synthesis | combination and the coke produced | generated by reaction are mentioned. These organic substances are present in the pores of the zeolite in a synthesized state, and the coke is allowed to exist inside the pores by passing the catalyst through the catalyst at a temperature of 200 ° C. or higher. Can do.

The catalytically active component may be used as it is in the reaction as a catalyst, or may be used in the reaction by granulating / molding using a substance or binder that is inert to the reaction, or by mixing them. Examples of the substance or binder inert to the reaction include alumina or alumina sol, silica, silica gel, quartz, and a mixture thereof.
The present invention is a process for producing propylene by contacting ethylene with a catalyst. Next, the reaction method will be described.

(1) Reaction method <Reaction raw material>
The raw material ethylene is not particularly limited. For example, those produced by catalytic cracking or steam cracking from petroleum sources, those obtained by Fischer-Tropsch synthesis using hydrogen / CO mixed gas obtained by coal gasification as raw materials, ethane dehydration Obtained by elemental or oxidative dehydrogenation Propylene metathesis reaction and homologation reaction, MTO reaction, ethanol dehydration, methane oxidative coupling, etc. Those obtained by various known methods can be arbitrarily used. At this time, a state in which a compound other than ethylene resulting from various production methods is arbitrarily mixed may be used as it is, or purified ethylene may be used, but purified ethylene is preferable.

Incidentally, ethanol is easily dehydrated and converted to ethylene by the acid sites present in the zeolite. Therefore, the reaction described in the present invention can be carried out even if ethanol is directly introduced into the reactor as a raw material.
Moreover, when producing propylene by the method of the present invention, ethylene contained in the reactor outlet gas may be recycled.

  The olefin to be recycled is usually ethylene, but other olefins may be recycled. The olefin used as the raw material is preferably a lower olefin, and the branched olefin may be difficult to enter into the zeolite pores due to its molecular size. Preferred are ethylene and linear butene, and most preferred is ethylene.

<Reactor>
The ethylene of the present invention is preferably contacted with a catalyst in a reactor to produce propylene. Although there is no restriction | limiting in particular in the form of the reactor to be used, Usually, a continuous type fixed bed reactor and a fluidized bed reactor are selected. A fluidized bed reactor is preferred.
In addition, when packing the above-mentioned catalyst into the fluidized bed reactor, in order to keep the temperature distribution of the catalyst layer small, particulates inert to the reaction such as quartz sand, alumina, silica, silica-alumina, etc. are mixed with the catalyst. And may be filled. In this case, there is no particular limitation on the amount of granular material inactive to the reaction such as quartz sand. In addition, it is preferable that this granular material is a particle size comparable as a catalyst from the surface of uniform mixing property with a catalyst.

<Diluent>
In the reactor, in addition to ethylene, helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, paraffins, hydrocarbons such as methane, aromatic compounds, and mixtures thereof, A gas inert to the reaction can be present, but among these, water (water vapor) is preferably present together.

(2) Reaction conditions <Substrate concentration>
There is no particular limitation on the concentration of ethylene in all the feed components fed to the reactor (ie, the substrate concentration), but usually ethylene is preferably 90 mol% or less in the total feed components. More preferably, it is 5 mol% or more and 70 mol% or less. When this substrate concentration is too high, the production of aromatic compounds and paraffins becomes remarkable, and the yield of propylene tends to decrease. If the substrate concentration is too low, the reaction rate becomes slow, so a large amount of catalyst is required, and the reactor tends to be too large.
Therefore, it is preferable to dilute ethylene with a diluent described below as necessary so as to obtain such a substrate concentration.

<Space velocity>
The space velocity mentioned here is the flow rate (weight / hour) of ethylene as a reaction raw material per weight of the catalyst (catalytic active component), and the weight of the catalyst is the amount used for granulation / molding of the catalyst. This is the weight of the catalytically active component that does not contain the active component or binder.

Space velocity, but it is not particularly limited but is preferably between 0.01 hr ^-1 for 500HR ^-1, more preferably between 0.1 hr ^-1 to 100 Hr ^-1. If the space velocity is too high, the amount of ethylene in the reactor outlet gas increases, which is not preferable because the propylene yield decreases. On the other hand, if the space velocity is too low, undesirable by-products such as paraffins are produced, and the propylene yield may be reduced.

<Reaction temperature>
The reaction temperature is not particularly limited as long as ethylene is brought into contact with the catalyst to produce propylene, but is usually about 200 ° C or higher, preferably 300 ° C or higher, and usually 700 ° C or lower, preferably 600 ° C or lower. It is. If the reaction temperature is too low, the reaction rate tends to be low, a large amount of unreacted raw material tends to remain, and the yield of propylene also decreases. On the other hand, if the reaction temperature is too high, the yield of propylene is significantly reduced.

<Reaction pressure>
The reaction pressure is not particularly limited, but is usually 2 MPa (absolute pressure, the same applies hereinafter) or less, preferably 1 MPa or less, and more preferably 0.7 MPa or less. Moreover, it is 1 kPa or more normally, Preferably it is 50 kPa or more. When the reaction pressure is too high, the amount of undesired by-products such as paraffins increases, and the yield of propylene tends to decrease. If the reaction pressure is too low, the reaction rate tends to be slow.

<Conversion rate>
In the present invention, the conversion is not particularly limited, but usually the conversion of ethylene is 20% or more, preferably 40% or more, more preferably 50% or more, and usually 95% or less, preferably 90%. The reaction is preferably performed under the following conditions.
If the conversion is less than the lower limit, there is a large amount of unreacted ethylene, and the propylene yield tends to be low. On the other hand, if the upper limit is exceeded, undesirable by-products such as paraffins increase and the propylene yield tends to decrease.
When the reaction is carried out in a fluidized bed reactor, the catalyst can be operated at a preferable conversion rate by adjusting the residence time of the catalyst in the reactor and the residence time in the regenerator.

(3) Reaction product As the reactor outlet gas (reactor effluent), a mixed gas containing propylene, ethylene, by-products and diluent as reaction products is obtained. The propylene concentration in the mixed gas is usually 1% by weight or more, preferably 2% by weight or more, and usually 95% by weight or less, preferably 80% by weight or less.

The mixed gas usually contains ethylene, but it is preferable that at least a part of the ethylene in the mixed gas is recycled to the reactor and reused as a reaction raw material.
Examples of by-products include olefins having 4 or more carbon atoms and paraffins.
Next, the reproduction method will be described.

(1) Reproduction method
(Regenerator)
In the present invention, the form of the regenerator used is not particularly limited, but a continuous fixed bed regenerator or a fluidized bed regenerator is usually selected. A fluidized bed regenerator is preferable. When regenerating in a fixed bed, it is preferable to regenerate by flowing a regeneration gas while keeping the catalyst in the reactor without removing the catalyst. Alternatively, the catalyst may be once extracted and charged into a regenerator separate from the reactor, and then regenerated by contacting with the regeneration gas. In the case of a fluidized bed, a catalyst regenerator is attached to the reactor, the catalyst extracted from the reactor is continuously sent to the regenerator, and the reaction is performed while the catalyst regenerated in the regenerator is continuously returned to the reactor. It is preferable to carry out.

(Regenerative gas composition)
The concentration of water vapor in all feed components supplied to the regenerator is 1% by volume or more and 100% by volume or less. Preferably they are 5 volume% or more and 95 volume% or less, More preferably, they are 10 volume% or more and 90 volume% or less. If this water vapor concentration is low, the coke removal rate tends to be slow.
The regeneration gas preferably contains no oxygen. The oxygen concentration in the regeneration gas is preferably 0.1% by volume or less, more preferably 0.05% by volume or less. If the oxygen content is high, the selectivity for propylene tends to be low after regeneration.

(Diluent)
As what dilutes water vapor, helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, paraffins, hydrocarbons such as methane, and the like can be used. Of these, helium, argon, nitrogen, carbon dioxide, paraffins, and methane are preferred because of their low reactivity with the catalyst.

(2) Reproduction conditions (Space velocity)
The space velocity mentioned here is the flow rate of water vapor per weight of the catalyst (catalytic active component). Here, the weight of the catalyst is the catalytic activity that does not contain inert components and binders used for granulating and molding the catalyst. The weight of the component.
Although the space velocity is not particularly limited but is preferably between 0.01 hr ^-1 for 500HR ^-1, more preferably between 0.1 hr ^-1 to 100 Hr ^-1. If the space velocity is too large, the amount of regenerated gas circulation increases, which may be disadvantageous in terms of cost.

(Regeneration temperature)
The lower limit of the regeneration temperature is 200 ° C. or higher, and the upper limit of the reaction temperature is usually 700 ° C. or lower, preferably 400 ° C. or higher and 650 ° C. or lower. If the reaction temperature is too low, the regeneration speed is low and the regeneration takes a long time. On the other hand, if the regeneration temperature is too high, the framework of the zeolite may collapse and permanently deteriorate.

(Regeneration pressure)
The upper limit of the reaction pressure is usually 2 MPa (absolute pressure, the same applies hereinafter), preferably 1 MPa or less, and more preferably 0.7 MPa or less. The lower limit of the regeneration pressure is not particularly limited, but is usually 1 kPa or more, preferably 50 kPa or more. When the reaction pressure is increased, the regeneration speed is increased. However, if the reaction pressure is too high, the zeolite skeleton may be collapsed and permanently deteriorated.

(Remaining coke amount after regeneration)
In the present invention, it is preferable to regenerate leaving some hydrocarbons without completely removing hydrocarbons adhering to the zeolite by regeneration. The preferable amount of hydrocarbon adhering to the zeolite after regeneration is 8% by weight to 25% by weight based on the weight of the zeolite. More preferably, it is 10 to 20% by weight. If the coke adhesion after regeneration is too small, the propylene selectivity is lowered after regeneration, and the carbon balance value is also lowered, which is not preferable. On the other hand, too much coke is not preferable because the activity does not return and the reaction substrate is not converted.

(Reproduction degree)
The degree of regeneration is such that when the regenerated catalyst is brought into contact with ethylene at the same temperature, pressure and space velocity as when propylene production reaction (production) is carried out, the ethylene conversion is usually 50 to 90%, preferably Is preferably performed so as to be 60 to 90%. If the ethylene conversion after regeneration is too high, the selectivity for propylene may be lowered. On the other hand, if the ethylene conversion is too low, unreacted ethylene may increase and the propylene yield may decrease.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
<Example 1>
Proton-type aluminosilicate having a CHA structure having SiO ₂ / Al ₂ O ₃ = 16 (molar ratio) was used as a catalyst, and propylene was produced using ethylene as a raw material. This aluminosilicate has a pore diameter of 0.38 nm.
The reaction was continued and regeneration was performed according to the present invention after the ethylene conversion was sufficiently reduced, and the reaction was performed after regeneration.

(reaction)
For the reaction, an atmospheric pressure fixed bed flow reactor was used, and 400 mg of the catalyst was packed in a quartz reaction tube having an inner diameter of 6 mm. Ethylene and nitrogen were supplied to the reactor so that the space velocity of ethylene was 13 mmol / g-cat · h, ethylene 30 vol%, and nitrogen 70 vol%, and the reaction was performed at 400 ° C. and 0.1 MPa. The reaction was completed 5 hours and 40 minutes after the start of the reaction.

  Table 1 shows the reaction results at 0.67 hours, 1.92 hours, and 3.17 hours after the reaction was started under the above reaction conditions. The ethylene conversion was calculated as ((number of moles of supplied ethylene−number of moles of ethylene at the outlet of the reactor) / number of moles of supplied ethylene). Moreover, the selectivity of each product was calculated as carbon mole% of the component excluding ethylene in the reactor outlet gas.

(Regeneration)
Steam and nitrogen were supplied to the catalyst after the reaction, and the space velocity of water vapor was 60 mmol / g-cat · h, water vapor was supplied at 30% by volume, and nitrogen was supplied at 70% by volume. Regeneration was performed at 1 MPa for 20 minutes. The oxygen content in the regeneration gas was 0% by volume. The weight of the catalyst coke after regeneration to the zeolite was 19.0% by weight. Using the regenerated catalyst, the reaction was performed under the same reaction conditions as described above except that the amount of the catalyst was 100 mg, and the reaction results at 0.17 hours from the start of the reaction were confirmed. Table 2 shows the reaction results.

  In the reaction using the catalyst regenerated with steam, the ethylene conversion at the time of 0.17 hours from the start of the reaction was 81.3%, and the propylene selectivity was 47.8%. The propylene selectivity at the time when the unused catalyst deteriorated with time and the ethylene conversion reached 77.8% was 47.2% (Table 1). As a result, it was possible to obtain a high propylene selectivity at the same ethylene conversion rate.

<Comparative Example 1>
(reaction)
The reaction was performed under the same reaction conditions as in Example 1, and the reaction was completed 5 hours and 40 minutes after the start of the reaction.
(Regeneration)
Air was supplied to the reaction tube so that the space velocity was 199 mmol / g-cat · h to the catalyst after the reaction, and regeneration was performed at 500 ° C. and 0.1 MPa for 6 minutes and 20 seconds. The moisture content in the regeneration gas was 0.03% by volume, and the oxygen content was 21%. After the regeneration was completed, the reaction was performed under the above conditions except that the catalyst amount was 100 mg, and the reaction results at 0.17 hours from the start of the reaction were confirmed. Table 3 shows the reaction results.

  In the reaction in which air regeneration was performed, the ethylene conversion rate at the time of 0.17 hours from the start of the reaction was 82.9%, and the propylene selectivity was 29.4%. The propylene selectivity at the time when the unused catalyst deteriorated with time and the ethylene conversion reached 77.8% was 47.2% (Table 1). As for the reaction results, propylene selectivity was low at the same ethylene conversion.

※１ 炭素数４の炭化水素化合物
※２ 炭素数５以上の脂肪族炭化水素化合物
※３ 上記以外の炭化水素化合物

* 1 Hydrocarbon compounds with 4 carbon atoms * 2 Aliphatic hydrocarbon compounds with 5 or more carbon atoms * 3 Hydrocarbon compounds other than the above

※１ 炭素数４の炭化水素化合物
※２ 炭素数５以上の脂肪族炭化水素化合物
※３ 上記以外の炭化水素化合物

* 1 Hydrocarbon compounds with 4 carbon atoms * 2 Aliphatic hydrocarbon compounds with 5 or more carbon atoms * 3 Hydrocarbon compounds other than the above

※１ 炭素数４の炭化水素化合物
※２ 炭素数５以上の脂肪族炭化水素化合物
※３ 上記以外の炭化水素化合物

* 1 Hydrocarbon compounds with 4 carbon atoms * 2 Aliphatic hydrocarbon compounds with 5 or more carbon atoms * 3 Hydrocarbon compounds other than the above

  When the catalyst regeneration method of the present invention is used, in the method for producing propylene from ethylene, the propylene selectivity after catalyst regeneration is improved, and a constant propylene selectivity can be maintained in repeated reaction-regeneration, which is stable. Propylene yield can be obtained.

Claims (5)

  In a method for producing propylene by contacting ethylene in a gas phase with a catalyst having a zeolite as an active ingredient, the catalyst deteriorated by coke adhesion contains water vapor at a concentration of 1 to 100% by volume and does not contain oxygen. A method for regenerating a catalyst, wherein the catalyst is activated by bringing it into contact with a regeneration gas to remove a portion of coke.   The method for regenerating a catalyst according to claim 1, wherein the coke is removed while leaving 8 to 25% by weight of the zeolite.   The method for regenerating a catalyst according to claim 1 or 2, wherein the oxygen concentration in the regeneration gas is 0.1 vol% or less.   4. The method for regenerating a catalyst according to claim 1, wherein the zeolite is a zeolite having a CHA structure.   A method for producing propylene, wherein propylene is produced from ethylene using the zeolite regenerated by the method according to claim 1.