JP7083988B2 - Manufacturing method of conjugated diene - Google Patents

Description

The present invention relates to a method for producing a conjugated diene.

Due to recent motorization mainly in Asia, demand for conjugated diene such as butadiene is expected to increase as a raw material for synthetic rubber. Examples of the method for producing a conjugated diene include a method for producing a conjugated diene by a direct dehydrogenation reaction of n-butene using a dehydrogenation catalyst (Patent Document 1), and a method for producing a conjugated diene by an oxidative dehydrogenation reaction of n-butene. A method for producing a diene (Patent Documents 2 to 4) is known.

Japanese Unexamined Patent Publication No. 2014-205135 Japanese Unexamined Patent Publication No. 57-140730 Japanese Patent Application Laid-Open No. 60-1139 Japanese Patent Application Laid-Open No. 2003-220335

As the demand for conjugated diene increases, it is required to develop various methods for producing conjugated diene, which have different characteristics such as required characteristics of manufacturing equipment, operating cost, and reaction efficiency.

As a novel method for producing a conjugated diene, an object of the present invention is to provide a method for producing a conjugated diene, which has less catalytic deterioration and can efficiently obtain a conjugated diene from an olefin.

The present inventors have found that excellent dehydrogenation activity in the dehydrogenation reaction of olefins can be maintained for a long period of time by subjecting a dehydrogenation catalyst having a specific metal element to a specific steaming treatment. It came to be completed.

One aspect of the present invention comprises a steaming step of steaming a dehydrogenation catalyst and a dehydrogenation step of bringing a raw material gas containing an olefin into contact with the dehydrogenation catalyst to obtain a produced gas containing a conjugated diene. The present invention relates to a method for producing a conjugated diene, wherein the elementary catalyst contains Si, a metal element of Group 14 and Pt, and the ratio (mass ratio) of the total amount of steam supplied to the amount of the dehydrogenation catalyst in the steaming step is 12 or more. ..

In one embodiment, the ratio (mass ratio) of the total amount of steam supplied to the amount of dehydrogenation catalyst in the steaming step may be 15 or more.

In one embodiment, the molar ratio of the carbon group 14 metal element to Pt in the dehydrogenation catalyst may be 1 or more and 4 or less.

In one embodiment, the carbon group 14 metal element may contain Sn.

In one embodiment, the dehydrogenation catalyst may be a catalyst in which a carrier containing Si is supported by a carrier metal containing a metal element of Group 14 and Pt.

In one embodiment, the olefin may be an olefin having 4 to 10 carbon atoms.

In one embodiment, the olefin may be butene and the conjugated diene may be butadiene.

According to the present invention, as a new method for producing a conjugated diene, there is provided a production method capable of efficiently obtaining a conjugated diene from an olefin with little catalyst deterioration.

Hereinafter, a preferred embodiment of the present invention will be described.

The production method according to the present embodiment includes a steaming step of steaming a dehydrogenation catalyst and a dehydrogenation step of bringing a raw material gas containing an olefin into contact with the dehydrogenation catalyst to obtain a produced gas containing a conjugated diene. .. In the present embodiment, the dehydrogenation catalyst contains Si, a metal element of Group 14 and Pt, and the ratio (mass ratio) of the total supply amount of steam (water) to the amount of the dehydrogenation catalyst in the steaming step is , 12 or more.

In the production method according to the present embodiment, by steaming the dehydrogenation catalyst, deterioration of the catalyst in the dehydrogenation step is suppressed, and excellent catalytic activity is maintained for a long period of time. Therefore, in the production method according to the present embodiment, the frequency of catalyst replacement or regeneration can be reduced, and conjugated diene can be efficiently obtained from the olefin. The reason why such an effect is produced is not always clear, but it is presumed as follows, for example.

In this embodiment, since the dehydrogenation catalyst contains Si, it is considered that the acid points on the catalyst are reduced and the side reactions caused by the acid points are suppressed as compared with the catalyst using an alumina carrier or the like. Be done. Further, in the present embodiment, the carbon group 14 metal element in the dehydrogenation catalyst and Pt form bimetallic particles, so that aggregation of the Pt particles is suppressed and the group 14 metal element is converted to Pt. It is thought that electron donation will occur. This is considered to improve the dehydrogenation activity. Further, it is considered that the Pt atom is diluted in the bimetallic particles and the C—C bond cleavage reaction due to the action of the Pt atom on one hydrocarbon molecule at multiple points is suppressed. For these reasons, it is considered that a high olefin conversion rate and a high reaction selectivity are realized in this embodiment.

Further, in the present embodiment, by steaming the dehydrogenation catalyst before it is subjected to the dehydrogenation step, the deterioration of the catalyst in the dehydrogenation step is remarkably suppressed. In the conventional production method without a steaming step, an extra oxide of the 14th metal element in the dehydrogenation catalyst is oxidized during the dehydrogenation reaction to form an amorphous oxide of the 14th metal element (for example, SnOx). ) Is formed, and it is considered that the catalytic activity of the dehydrogenation catalyst is lowered by covering the active points of the dehydrogenation catalyst with the oxide. On the other hand, in the production method according to the present embodiment, by performing the steaming step, the excess 14th metal element in the dehydrogenation catalyst is oxidized, and further, the amorphous 14th metal element is formed. It is considered that the oxide is transformed into a crystalline oxide (for example, SnO ₂ ). As a result, it is considered that the formation of amorphous oxide during the dehydrogenation reaction and the deterioration of catalytic activity due to it are suppressed, and high catalytic activity can be maintained for a long period of time.

In the present embodiment, since it is necessary to change the amorphous oxide of the 14th metal element into a crystalline oxide in the steaming step, the total amount of steam supplied with respect to the amount of the dehydrogenating catalyst in the steaming step. The ratio (mass ratio) is 12 or more. If the total amount of steam supplied is small, the steaming step ends when the amorphous oxide of the carbon group 14 is formed, and the initial activity of the dehydrogenation catalyst is lower than that without steaming. As a result, catalyst deterioration is likely to progress. By ensuring a sufficient total amount of steam supply, the initial activity of the dehydrogenation catalyst is restored, and catalyst deterioration is significantly suppressed.

In the present specification, the conversion rate of the olefin, the selectivity of the conjugated diene and the yield of the conjugated diene are defined by the following formulas (1), (2) and (3).
r _C = {1- (m ₁ / m ₀ )} × 100 (1)
r _S = {m ₂ / (m ₀ -m ₁ )} x 100 (2)
r _Y = (m ₂ / m ₀ ) x 100 (3)
In the formula, r _C is the conversion rate (%) of the olefin, m ₀ is the number of moles of the olefin contained in the raw material gas, and m ₁ is the number of moles of the olefin remaining in the produced gas. _S is the selectivity (%) of the conjugated diene, m ₂ is the number of moles of the conjugated diene contained in the produced gas, and r _Y is the yield (%) of the conjugated diene.

In this embodiment, the raw material gas contains an olefin. The carbon number of the olefin may be the same as the carbon number of the desired conjugated diene. That is, the olefin may be a hydrocarbon compound obtained by hydrogenating one of the double bonds present in the conjugated diene assumed as a product. The carbon number of the olefin may be 4 to 10, and may be 4 to 6.

The olefin may be, for example, chain-like or cyclic. The chain olefin may be, for example, butene, pentene, hexene, heptene, octene, nonene and decene. The chain-shaped olefin may be linear or branched. Examples of the linear olefin include n-butene, n-pentene, n-hexene, n-heptene, n-octene, n-nonene, n-decene and the like. Examples of the branched olefin include isopentene, 2-methylpentene, 3-methylpentene, 2,3-dimethylpentene, isoheptene, isooctene, isononene, and isodecene. The raw material gas may contain one type of olefin or may contain two or more types of olefin.

In the raw material gas, the partial pressure of the olefin may be 1.0 MPa or less, 0.1 MPa or less, or 0.01 MPa or less. By reducing the olefin partial pressure of the raw material gas, the conversion rate of the olefin can be further improved.

Further, the partial pressure of the olefin in the raw material gas is preferably 0.001 MPa or more, and more preferably 0.005 MPa or more, from the viewpoint of reducing the reactor size with respect to the raw material flow rate.

The raw material gas may further contain an inert gas such as nitrogen or argon, or may further contain steam.

When the raw material gas contains steam, the content of steam is preferably 1.0 times mol or more, more preferably 1.5 times mol or more with respect to the olefin. By including steam in the raw material gas, the decrease in catalyst activity may be suppressed more remarkably. The content of steam may be, for example, 50 times the molar amount or less, preferably 10 times the molar amount or less with respect to the olefin.

In addition to the above, the raw material gas may further contain other components such as hydrogen, oxygen, carbon monoxide, carbon dioxide, alkanes, and diene.

In the production method according to the present embodiment, the produced gas contains a conjugated diene. Examples of the conjugated diene obtained by the production method according to the present embodiment include butadiene (1,3-butadiene), 1,3-pentadiene, isoprene, 1,3-hexadiene, 1,3-heptadiene, and 1,3-. Examples thereof include octadiene, 1,3-nonadien and 1,3-decadien. The produced gas may contain one kind of conjugated diene, and may contain two or more kinds of conjugated diene.

Among the above, the production method according to the present embodiment can be particularly preferably used in a method using a raw material gas containing butene as an olefin, that is, a method for producing 1,3-butadiene. The butene used in the production of 1,3-butadiene may be 1-butene or 2-butene. Butene may be a mixture of 1-butene and 2-butene. The 2-butene may be one or both of cis-2-butene and trans-2-butene.

Hereinafter, the dehydrogenation catalyst in this embodiment will be described in detail.

The dehydrogenation catalyst is a solid catalyst that catalyzes the dehydrogenation reaction of an olefin, and contains Si, a metal element of the 14th group, and Pt. Here, the group 14 metal element means a metal element belonging to the group 14 of the periodic table in the periodic table of long-periodic elements based on the provisions of the IUPAC (International Union of Pure and Applied Chemistry).

The Group 14 metal element may be, for example, at least one selected from the group consisting of germanium (Ge), tin (Sn) and lead (Pb). Among these, when the Group 14 metal element is Sn, the above-mentioned effect is more remarkable.

In the dehydrogenation catalyst, the Si content may be, for example, 30% by mass or more, preferably 40% by mass or more, based on the total amount of the dehydrogenation catalyst. Further, the Si content may be, for example, 80% by mass or less, preferably 60% by mass or less, based on the total amount of the dehydrogenation catalyst.

In the dehydrogenation catalyst, the content of the metal element of Group 14 may be, for example, 0.1% by mass or more, preferably 0.5% by mass or more, based on the total amount of the dehydrogenation catalyst. The content of the Group 14 metal element may be, for example, 4% by mass or less, and preferably 3% by mass or less.

In the dehydrogenation catalyst, the content of Pt may be, for example, 0.1% by mass or more, preferably 0.5% by mass or more, based on the total amount of the dehydrogenation catalyst. When the Pt content is high, the amount of platinum per catalyst amount is high, and the reactor size can be reduced. Further, the content of Pt may be, for example, 5% by mass or less, and preferably 3% by mass or less. As a result, the Pt particles formed on the catalyst have a size suitable for the dehydrogenation reaction, and the platinum surface area per unit platinum weight increases, so that a more efficient reaction system can be realized.

In the dehydrogenation catalyst, the molar ratio of the Group 14 metal element to Pt (the number of moles of the Group 14 metal element / the number of moles of Pt) is from the viewpoint that side reactions are further suppressed and the production efficiency of the conjugated diene is further improved. Is preferably 1 or more, more preferably 1.3 or more, and even more preferably 1.5 or more. Further, the molar ratio of the 14th metal element to Pt is preferably 4 or less from the viewpoint of preventing excessive coating of Pt particles by the 14th metal element and further improving the production efficiency of the conjugated diene. It is more preferably less than or equal to, and even more preferably 2.5 or less.

The content of each metal element in the dehydrogenation catalyst can be measured by the method described in the following Examples.

In a preferred embodiment, the dehydrogenation catalyst may be a catalyst in which a carrier containing Si is supported with a carbon group 14 metal element and Pt.

In this embodiment, the carrier may be a carrier containing silica (SiO ₂ ).

The content of silica in the carrier may be 90% by mass or more, 95% by mass or more, or 100% by mass based on the total amount of the carrier.

The carrier may further contain other metal elements other than Si. Other metal elements may exist as an oxide or may exist as a composite oxide with Si.

In this embodiment, a carrier metal containing a carbon group 14 element and Pt is supported on the carrier. The supported metal may be supported on the carrier as an oxide or a composite oxide, or may be supported on the carrier as a single metal.

The carrier may further carry a metal element of Group 14 and other metal elements other than Pt. The other metal element may be supported on the carrier as a single metal, may be supported as an oxide, or may be supported as a composite oxide with a group 14 metal element or Pt. ..

The amount of the Group 14 metal element supported on the carrier is preferably 0.1 part by mass or more, and more preferably 0.5 part by mass or more with respect to 100 parts by mass of the carrier. The amount of the Group 14 metal element supported on the carrier may be 4 parts by mass or less and 3 parts by mass or less with respect to 100 parts by mass of the carrier. When the amount of the carbon group 14 metal element is in the above range, the deterioration of the catalyst is further suppressed, and the high activity tends to be maintained for a longer period of time.

The amount of Pt supported on the carrier is preferably 0.1 part by mass or more, and more preferably 0.5 part by mass or more with respect to 100 parts by mass of the carrier. The amount of Pt supported on the carrier may be 5 parts by mass or less and 3 parts by mass or less with respect to 100 parts by mass of the carrier. With such a Pt amount, the Pt particles formed on the catalyst have a suitable size due to the dehydrogenation reaction, and the platinum surface area per unit platinum weight increases, so that a more efficient reaction system can be realized. Further, with such a Pt amount, high activity can be maintained for a longer period of time while suppressing the catalyst cost.

The amount of other metal elements supported on the carrier may be, for example, 10 parts by mass or less, 5 parts by mass or less, or 0 parts by mass with respect to 100 parts by mass of the carrier.

The method of supporting the metal on the carrier is not particularly limited, and examples thereof include an impregnation method, a deposition method, a coprecipitation method, a kneading method, an ion exchange method, and a pore filling method. In this embodiment, a plurality of types of supported metals may be supported on the carrier one by one, and a plurality of types of supported metals may be supported on the carrier at the same time.

An aspect of the method of supporting on a carrier is shown below. First, the carrier is added to the solution in which the precursor of the supported metal is dissolved, and the solution is stirred. Then, the solvent is removed under reduced pressure and the obtained solid is dried. By calcining the dried solid, the supported metal can be supported on the carrier.

In the above-mentioned carrier method, the precursor of the carrier metal may be, for example, a salt or a complex containing the carrier metal. The salt containing the supporting metal may be, for example, an inorganic salt, an organic acid salt, or a hydrate thereof. The inorganic salt may be, for example, a sulfate, a nitrate, a chloride, a phosphate, a carbonate or the like. The organic salt may be, for example, acetate, oxalate or the like. The complex containing the supported metal may be, for example, an alkoxide complex, an ammine complex, or the like.

The solvent for dissolving the precursor of the supported metal may be any solvent which can dissolve the precursor and can be removed under reduced pressure. Examples of the solvent include water, ethanol, acetone and the like.

In the above-mentioned carrying method, the conditions for stirring can be, for example, a stirring temperature of 0 to 60 ° C. and a stirring time of 10 minutes to 24 hours. The conditions for drying can be, for example, a drying temperature of 100 to 250 ° C. and a drying time of 3 hours to 24 hours.

In the above-mentioned carrier method, firing can be performed, for example, in an air atmosphere or an oxygen atmosphere. The firing may be performed in one stage or in multiple stages of two or more stages. The firing temperature may be, for example, a temperature at which the precursor of the carrier metal can be decomposed. The firing temperature may be, for example, 200 to 1000 ° C, or 400 to 800 ° C. When performing multi-step firing, at least one step may be the firing temperature. The firing temperature at the other steps may be, for example, in the same range as described above, and may be 100 to 200 ° C.

The dispersity of Pt in the dehydrogenation catalyst may be, for example, 10% or more, preferably 15% or more. A dehydrogenation catalyst having such a Pt dispersity tends to maintain high activity for a longer period of time. The dispersity of Pt indicates a value measured by a metal dispersity measuring method using CO as an adsorbed species. Specifically, it is measured with the following equipment and measurement conditions.
・ Equipment: Metal dispersion measuring device R-6011 manufactured by Okura RIKEN Co., Ltd.
・ Gas flow rate: 30 mL / min (helium, hydrogen)
・ Sample amount: Approximately 0.1 g (scale to the 4th digit after the decimal point)
-Pretreatment: The temperature is raised to 400 ° C. over 1 hour under a hydrogen stream, and the reduction treatment is performed at 400 ° C. for 60 minutes. Then, the gas is switched from hydrogen to helium, purged at 400 ° C. for 30 minutes, and then cooled to room temperature under a helium stream. After waiting for the detector to stabilize at room temperature, perform a CO pulse.
-Measurement conditions: Under normal pressure helium gas flow, carbon monoxide is pulse-injected at room temperature (27 ° C.) by 0.0929 ^cm3 , and the amount of adsorption is measured. The number of adsorptions is until the adsorption is saturated (minimum 3 times, maximum 15 times).

The dehydrogenation catalyst may be molded by a method such as an extrusion molding method or a tableting molding method.

The dehydrogenation catalyst may contain a molding aid as long as it does not impair the physical properties and catalytic performance of the catalyst from the viewpoint of improving the moldability in the molding process. The molding aid may be, for example, at least one selected from the group consisting of thickeners, surfactants, water retention agents, plasticizers, binder raw materials and the like. The molding step of molding the dehydrogenation catalyst may be performed at an appropriate stage of the manufacturing step of the dehydrogenation catalyst in consideration of the reactivity of the molding aid.

The shape of the molded dehydrogenation catalyst is not particularly limited, and can be appropriately selected depending on the form in which the catalyst is used. For example, the shape of the dehydrogenation catalyst may be a pellet shape, a granule shape, a honeycomb shape, a sponge shape, or the like.

As the dehydrogenation catalyst, a catalyst that has been subjected to a reduction treatment as a pretreatment may be used. The reduction treatment can be performed, for example, by holding the dehydrogenation catalyst at 40 to 600 ° C. in an atmosphere of a reducing gas. The holding time may be, for example, 0.05 to 24 hours. The reducing gas may be, for example, hydrogen, carbon monoxide, or the like.

By using a dehydrogenation catalyst that has undergone a reduction treatment, the initial induction period of the dehydrogenation reaction can be shortened. The induction period at the initial stage of the reaction refers to a state in which very few of the active metals contained in the catalyst are reduced and in an active state, and the activity of the catalyst is low.

Next, the steaming step and the dehydrogenation step in the present embodiment will be described in detail.

The steaming step is a step of steaming the dehydrogenation catalyst. The steaming step may be carried out, for example, by contacting a dehydrogenation catalyst with a gas containing steam (steaming gas).

The steaming step can be carried out, for example, by continuously flowing a gas containing steam through a reactor filled with a dehydrogenation catalyst. As the reactor, for example, various reactors used for a gas phase reaction using a solid catalyst can be used. Examples of such a reactor include a fixed bed adiabatic type reactor, a radial flow type reactor, a tube type reactor and the like.

The steaming gas may be, for example, a mixed gas of steam and an inert gas. Examples of the inert gas include nitrogen, helium, argon and the like. The mixing ratio of the steam and the inert gas is not particularly limited, but for example, the molar ratio of steam to the inert gas is preferably 0.5 or more, and more preferably 1 or more. This can reduce the fuel cost required to heat the inert gas to a predetermined temperature.

The ratio (mass ratio) of the total amount of steam supplied to the amount of the dehydrogenation catalyst is 12 or more, and is preferably 15 or more, more preferably 20 or more, from the viewpoint of suppressing catalyst deterioration more remarkably. The upper limit of the ratio (mass ratio) of the total amount of steam supplied to the amount of the dehydrogenation catalyst is not particularly limited, but may be, for example, 60 or less, or 40 or less.

The dehydrogenation step is a step of bringing a raw material gas into contact with a dehydrogenation catalyst that has undergone a steaming step to carry out a dehydrogenation reaction of an olefin to obtain a produced gas containing a conjugated diene.

The dehydrogenation step may be carried out, for example, by using a reactor filled with a dehydrogenation catalyst and allowing the raw material gas to flow through the reactor. As the reactor, various reactors used for the gas phase reaction using a solid catalyst can be used. Examples of the reactor include a fixed bed adiabatic type reactor, a radial flow type reactor, a tube type reactor and the like.

The reaction form of the dehydrogenation reaction may be, for example, a fixed bed type, a moving bed type or a fluidized bed type. Of these, the fixed floor type is preferable from the viewpoint of equipment cost.

The reaction temperature of the dehydrogenation reaction, that is, the temperature in the reactor may be 300 to 800 ° C., 400 to 700 ° C., or 500 to 650 ° C. from the viewpoint of reaction efficiency. When the reaction temperature is 300 ° C. or higher, the equilibrium conversion rate of the olefin does not become too low, so that the yield of the conjugated diene tends to be further improved. When the reaction temperature is 800 ° C. or lower, the caulking rate does not become too high, so that the high activity of the dehydrogenation catalyst tends to be maintained for a longer period of time.

The reaction pressure, that is, the air pressure in the reactor may be 0.01 to 1 MPa, 0.05 to 0.8 MPa, or 0.1 to 0.5 MPa. If the reaction pressure is within the above range, the dehydrogenation reaction tends to proceed easily, and a more excellent reaction efficiency tends to be obtained.

When the dehydrogenation step is performed in a continuous reaction format in which the raw material gas is continuously supplied, the WHSV may be, for example, 0.1 h ^-1 or more, or 0.5 h ^-1 or more. Further, the WHSV may be 20h ^-1 or less, and may be 10h ^-1 or less. Here, WHSV is the ratio (F / W) of the supply rate (supply amount / hour) F of the raw material gas to the mass W of the dehydrogenation catalyst. When the WHSV is 0.1 h ^-1 or more, the reactor size can be made smaller. When the WHSV is 20 h ^-1 or less, the conversion rate of the olefin can be further increased. The amount of the raw material gas and the catalyst used may be appropriately selected in a more preferable range depending on the reaction conditions, the activity of the catalyst, and the like, and the WHSV is not limited to the above range.

In the dehydrogenation step, the reactor may be further filled with a catalyst other than the above-mentioned dehydrogenation catalyst (hereinafter, also referred to as “first dehydrogenation catalyst”).

For example, in the present embodiment, a solid catalyst (hereinafter, also referred to as “second dehydrogenation catalyst”) that catalyzes the dehydrogenation reaction from alkenes to olefins is further added before the first dehydrogenation catalyst of the reactor. By filling, the raw material gas may be obtained in the reactor. In other words, the dehydrogenation step may be carried out by using a reactor filled with a first dehydrogenation catalyst and a second dehydrogenation catalyst, and flowing a gas containing an alkane through the reactor. .. Further, the dehydrogenation step may be carried out by sequentially distributing a gas containing an alkane to a reactor filled with a second dehydrogenation catalyst and a reactor filled with a first dehydrogenation catalyst. good.

As described above, according to the production method according to the present embodiment, conjugated diene can be efficiently produced from an olefin while suppressing catalyst deterioration. Therefore, according to the production method according to the present embodiment, the frequency of catalyst regeneration can be reduced. For this reason, the production method according to the present embodiment is very useful when industrially producing a conjugated diene.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples.

(Catalyst Preparation Example 1)
To 3.0 g of silica carrier classified into 20-60 mesh (CARIACT Q-15, manufactured by Fuji Silysia Chemical Ltd.), a solution of 0.104 g of SnCl _{2.2H 2 O} in 10 mL of EtOH was added. .. The obtained mixture was stirred at 40 ° C. for 1 hour using a rotary evaporator, and then EtOH was removed under reduced pressure. The resulting solid was dried overnight in an oven at 130 ° C. Next, the dried solid was calcined at 130 ° C. for 30 minutes and 550 ° C. for 3 hours under air flow to obtain a catalyst precursor A-1 in which Sn was supported on a silica carrier. Then, the total amount of the obtained catalyst precursor A-1 and an aqueous solution of 79.6 mg of H ₂ PtCl _6.2 H ₂ O dissolved in 15 mL of water were mixed. The obtained mixture was stirred at 40 ° C. for 1 hour using a rotary evaporator, and then water was removed under reduced pressure while stirring the mixture. The resulting solid was dried overnight in an oven at 130 ° C. Next, the dried solid was reduced to obtain a catalyst A-1. In the reduction treatment, the temperature of the reactor was raised to 550 ° C. while flowing a mixed gas of hydrogen and He (hydrogen: He = 4: 6 (molar ratio)) at 50 mL / min to the dried solid, and the temperature was changed. This was done by holding for 3 hours.

In this example, the content of Pt, the content of Sn, and the content of Si in the obtained catalyst A-1 were measured by fluorescent X-ray analysis (XRF). The fluorescent X-ray analysis method was performed using a measuring device PW2400 (manufactured by PANalytical), and the content was quantified using the standardless quantitative calculation program UniQuant4. The XRF measurement sample was prepared as follows. Weigh 125 mg of a sample (for example, catalyst A-1) and 125 mg of cellulose (binder) in an agate mortar, mix for 15 minutes, place in a 20 mmΦ tablet molder, and pressure mold for 10 minutes under the conditions of 300 kgf · cm ^-2 . did.

As a result of the measurement, in the catalyst A-1, the Pt content was 1% by mass, the Sn content was 1.8% by mass, the Si content was 45% by mass, and the molar ratio of Sn to Pt (Sn / Pt). Was 3.

(Catalyst Preparation Example 2)
A catalyst was prepared in the same manner as in Catalyst Preparation Example 1 except that the amount of SnCl _{2.2H 2O} was changed to 59.0 mg to obtain a catalyst B-1. When the obtained catalyst B-1 was analyzed, the Pt content was 1% by mass, the Sn content was 1% by mass, the Si content was 46% by mass, and the molar ratio of Sn to Pt (Sn / Pt). Was 1.7.

(Example A-1)
<Steaming process>
A tubular reactor was filled with 0.5 g of catalyst A-1 and the reactor was connected to a fixed bed flow reactor. Next, the reactor was heated to 600 ° C. while circulating a mixed gas of hydrogen and He (hydrogen: He = 4: 6 (mol)) at 50 mL / min, and kept at the temperature for 1 hour. Next, a mixed gas of He and water was supplied to the reactor and held for 6 hours to steam the catalyst. Here, the molar ratio of He and water in the mixed gas was adjusted to 4: 3. The rate of supply of the mixed gas to the reactor was adjusted to 87 mL / min. At this time, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 10.7 g, and the ratio of the total supply amount of water (steam) to the catalyst A-1 is. It is 21.4 (g / g).

<Dehydrogenation process>
Subsequently, a mixed gas (raw material gas) of 1-butene, He and water was supplied to the reactor, and the dehydrogenation reaction of 1-butene in the raw material gas was carried out. Here, the molar ratio of 1-butene, He and water in the raw material gas was adjusted to 1: 4: 3. The supply rate of the raw material gas to the reactor was adjusted to 99 mL / min. WHSV was adjusted to 3.8h ^-1 . The pressure of the raw material gas of the reactor was adjusted to atmospheric pressure.

When 20 minutes had passed from the start of the reaction, the product (produced gas) of the dehydrogenation reaction was collected from the tubular reactor. Further, when 360 minutes had passed from the start of the reaction, the product (produced gas) of the dehydrogenation reaction was collected from the tubular reactor. The reaction start time is the time when the supply of the raw material gas is started. The produced gas collected at each time point was analyzed using a gas chromatograph (TCD-GC) equipped with a thermal conductivity detector. As a result of the analysis, it was confirmed that the produced gas contained 1,3-butadiene. Based on the above gas chromatograph, the concentration of 1-butene (unit: mass%), the concentration of 2-butene (unit: mass%) and the concentration of 1,3-butadiene (unit: mass%) in the produced gas collected at each time point. Mass%) was quantified.

From the concentrations of 1-butene, 2-butene and 1,3-butadiene in the produced gas, the raw material conversion rate (butene conversion rate), the selectivity of 1,3-butadiene (butadiene selectivity) and 1,3 -Butadiene yield (butadiene yield) was calculated. The butene conversion rate is defined by the following formula (4), the butadiene selectivity is defined by the following formula (5), and the butadiene yield is defined by the following formula (6).
Rc = (1 _- MP / M ₀ ) x 100 (4)
_RS = M _b / (M _{0 -} MP) x 100 (5)
_RY = M _b / M ₀ × 100 (6)
In the formula, Rc is the butene conversion rate, _RS is the butadiene selectivity, _RY is the butadiene yield, M ₀ is the number of moles of 1 _- butene in the raw material gas, and MP. Is the total number of moles of 1-butene, t-2-butene and _c -2-butene in the produced gas, and Mb is the number of moles of 1,3-butadiene in the produced gas.

As a result of the analysis, the 1-butene conversion rate after 20 minutes was 32.4%, the butadiene selectivity was 90.8%, the butadiene yield was 29.4%, and the 1-butene conversion rate after 360 minutes. 30.6%, butadiene selectivity is 90.8%, butadiene yield is 27.8%, and the ratio of butadiene yield after 360 minutes to butadiene yield after 20 minutes is 0.94. Met.

(Comparative Example a-1)
The same dehydrogenation step as in Example A-1 was carried out using the catalyst A-1 obtained in Catalyst Preparation Example 1 without performing the steaming step. As a result, the 1-butene conversion rate after 20 minutes was 33.4%, the butadiene selectivity was 89.9%, the butadiene yield was 30.0%, and the 1-butene conversion rate after 360 minutes was 33.4%. 23.9%, butadiene selectivity is 88.8%, butadiene yield is 21.2%, and the ratio of butadiene yield after 360 minutes to butadiene yield after 20 minutes is 0.71. there were.

(Comparative Example a-2)
The steaming step and the dehydrogenation step were carried out in the same manner as in Example A-1 except that the steaming time was changed from 6 hours to 0.5 hours, and the produced gas was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 0.89 g, and the total supply of water (steam) to the catalyst A-1. The volume ratio was 1.8 (g / g).

As a result, the 1-butene conversion after 20 minutes was 29.6%, the butadiene selectivity was 90.8%, the butadiene yield was 26.9%, and the 1-butene conversion after 360 minutes was. 23.2%, butadiene selectivity is 89.9%, butadiene yield is 20.9%, and the ratio of butadiene yield after 360 minutes to butadiene yield after 20 minutes is 0.78. there were.

(Comparative Example a-3)
The steaming step and the dehydrogenation step were carried out in the same manner as in Example A-1 except that the steaming time was changed from 6 hours to 3 hours, and the produced gas was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 5.3 g, and the total supply of water (steam) to the catalyst A-1. The volume ratio was 10.7 (g / g).

As a result, the 1-butene conversion rate after 20 minutes was 11.8%, the butadiene selectivity was 83.5%, the butadiene yield was 9.9%, and the 1-butene conversion rate after 360 minutes was high. The ratio of the butadiene yield after 20 minutes to the butadiene yield after 20 minutes is 0.22, which is 4.0%, the butadiene selectivity is 54.7%, and the butadiene yield is 2.2%. there were.

The results of Examples A-1 and Comparative Examples a-1 to a-3 are shown in Table 1.

(Example B-1)
The steaming step and the dehydrogenation step were carried out in the same manner as in Example A-1 except that the catalyst B-1 was used instead of the catalyst A-1, and the produced gas was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 10.7 g, and the total supply of water (steam) to the catalyst B-1. The volume ratio was 21.4 (g / g).

As a result, the 1-butene conversion rate after 20 minutes was 38.8%, the butadiene selectivity was 92.6%, the butadiene yield was 35.9%, and the 1-butene conversion rate after 360 minutes was 36.9%, butadiene selectivity is 92.5%, butadiene yield is 34.1%, and the ratio of butadiene yield after 360 minutes to butadiene yield after 20 minutes is 0.95. there were.

(Comparative Example b-1)
The steaming step and the dehydrogenation step were carried out in the same manner as in Example B-1 except that the steaming time was changed from 6 hours to 0.5 hours, and the produced gas was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 0.89 g, and the total supply of water (steam) to the catalyst B-1. The volume ratio was 1.8 (g / g).

As a result, the 1-butene conversion after 20 minutes was 42.0%, the butadiene selectivity was 91.8%, the butadiene yield was 38.6%, and the 1-butene conversion after 360 minutes was. 34.7%, butadiene selectivity is 92.1%, butadiene yield is 32.0%, and the ratio of butadiene yield after 360 minutes to butadiene yield after 20 minutes is 0.83. there were.

The results of Example B-1 and Comparative Example b-1 are shown in Table 2.

(Reference example 1)
A catalyst c-1 in which Sn and Pt were supported on an MgAl ₂ O ₄ carrier was prepared. In the catalyst c-1, the content of Pt is 1% by mass, the content of Sn is 12.2% by mass, the content of Mg is 14% by mass, the content of Al is 32% by mass, and the catalyst c-1. The Sn / Pt ratio was 20 which is a suitable Sn / Pt ratio when the _{MgAl2O4 carrier} was used. Catalyst c-1 is used instead of catalyst A-1, 2-butene is used instead of 1-butene, _N2 is used instead of He, and the molar ratio of 2-butene, _N2 and water is 1: 5. : 3 was adjusted and WHSV was changed to 1.0h ^-1 , but the steaming step and dehydrogenation step were performed in the same manner as in Example A-1, and 1 hour and 5 hours after the reaction started. The generated gas over time was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 10.7 g, and the total supply of water (steam) to the catalyst c-1. The volume ratio was 21.4 (g / g).

As a result of the analysis, the 1-butene conversion rate after 1 hour was 40.0%, the butadiene selectivity was 89.7%, the butadiene yield was 35.9%, and the 1-butene conversion rate after 5 hours. Is 36.9%, the butadiene selectivity is 91.7%, the butadiene yield is 33.8%, and the ratio of the butadiene yield after 1 hour to the butadiene yield after 5 hours is 0.94. Met.

(Reference example 2)
The steaming step and the dehydrogenation step were carried out in the same manner as in Reference Example 1 except that the steaming time was changed from 6 hours to 0.5 hours, and the produced gas was analyzed. In the steaming step, the weight flow rate of water (steam) is 1.78 g / h, the total supply amount of water (steam) is 0.89 g, and the total supply of water (steam) to the catalyst c-1. The volume ratio was 1.8 (g / g).

As a result of the analysis, the 1-butene conversion rate after 1 hour was 40.8%, the butadiene selectivity was 87.8%, the butadiene yield was 35.8%, and the 1-butene conversion rate after 5 hours. Is 36.2%, the butadiene selectivity is 91.1%, the butadiene yield is 33.0%, and the ratio of the butadiene yield after 1 hour to the butadiene yield after 5 hours is 0.92. Met.

The results of Reference Examples 1 and 2 are shown in Table 3.

As shown in Reference Examples 1 and 2, the effect of suppressing catalyst deterioration by the steaming step was not obtained when the carrier was MgAl ₂ O ₄ .

Claims (6)

A reduction treatment step that reduces the dehydrogenation catalyst, and
A steaming step of steaming the dehydrogenation catalyst that has undergone the reduction treatment step ,
A dehydrogenation step of contacting a raw material gas containing an olefin with the dehydrogenation catalyst that has undergone the steaming step to obtain a produced gas containing a conjugated diene.
Equipped with
The dehydrogenation catalyst contains Si, Sn and Pt and contains
The ratio (mass ratio) of the total amount of steam supplied to the amount of the dehydrogenation catalyst in the steaming step is 12 or more.
A method for producing a conjugated diene. The production method according to claim 1, wherein the ratio (mass ratio) of the total amount of steam supplied to the amount of the dehydrogenation catalyst in the steaming step is 15 or more. The production method according to claim 1 or 2, wherein the molar ratio of Sn to Pt in the dehydrogenation catalyst is 1 or more and 4 or less. The production method according to any one of claims 1 to 3 , wherein the dehydrogenation catalyst is a catalyst in which a carrier metal containing Sn and Pt is supported on a carrier containing Si. The production method according to any one of claims 1 to 4 , wherein the olefin is an olefin having 4 to 10 carbon atoms. The production method according to any one of claims 1 to 5 , wherein the olefin is butene and the conjugated diene is butadiene.