JP7090471B2 - Manufacturing method of p-xylene - Google Patents

Description

The present invention relates to a method for producing p-xylene.

p-Xylene is an industrially useful substance as a raw material for terephthalic acid, which is an intermediate raw material for polyester fibers and PET resins. As a method for producing p-xylene, for example, a method for producing p-xylene from a raw material containing ethylene (Patent Document 1) and a method for producing p-xylene from biomass (Patent Document 2) are known. Various methods for efficiently producing p-xylene have been studied.

Japanese Unexamined Patent Publication No. 2011-79815 Japanese Unexamined Patent Publication No. 2015-193647

An object of the present invention is to provide a method for producing p-xylene capable of obtaining p-xylene in a high yield using a C4 fraction derived from petroleum as a raw material.

One aspect of the present invention is a separation step of obtaining a first raw material containing isobutene and isobutane from a C4 distillate derived from petroleum, and dehydrogenation in which the first raw material is brought into contact with a dimerization catalyst to produce a C8 component. In the step, the C8 component is brought into contact with a dehydrogenation catalyst in which a carrier metal containing Cr is supported on a carrier in the presence of at least one of isobutene and isobutane, and p-xylene is subjected to a cyclization dehydrogenation reaction of the C8 component. The present invention relates to a method for producing p-xylene, comprising a cyclization step of producing p-xylene.

In the above production method, the C8 component is monomerized to the C4 component by carrying out a cyclization dehydrogenation reaction using a specific dehydrogenation catalyst in the presence of at least one of isobutene and isobutane in the cyclization step. Is suppressed. Therefore, according to the above production method, p-xylene can be obtained in high yield from the C4 distillate derived from petroleum.

In one embodiment, the dehydrogenation step is a step of obtaining a second raw material containing the C8 component and at least one C4 component selected from the group consisting of isobutene and isobutane, and the cyclization step is a step of obtaining the second raw material. It may be a step of bringing the second raw material into contact with the dehydrogenation catalyst.

In one embodiment, the amount of Cr carried by the dehydrogenation catalyst may be 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the carrier.

In one embodiment, the carrier metal may further comprise at least one selected from the group consisting of Mg, Zr and K.

In one embodiment, the amount of Mg supported on the dehydrogenation catalyst may be 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the carrier.

In one embodiment, the amount of Zr supported on the dehydrogenation catalyst may be 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the carrier.

In one embodiment, the amount of K carried on the dehydrogenation catalyst may be 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the carrier.

According to the present invention, there is provided a method for producing p-xylene capable of obtaining p-xylene in a high yield using a C4 fraction derived from petroleum as a raw material.

Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.

The method for producing p-xylene according to the present embodiment is a separation step of obtaining a first raw material containing isobutene and isobutane from a C4 distillate derived from petroleum, and a C8 component by contacting the first raw material with a dehydrogenation catalyst. In the presence of at least one of isobutene and isobutane, the C8 component is brought into contact with a dehydrogenation catalyst in which a carrier metal containing Cr is supported on the carrier, and the C8 component is cyclized and dehydrogenated. It comprises a cyclization step of producing p-xylene.

In addition, in this specification, diisobutylene indicates 2,4,4-trimethyl-1-pentene, 2,4,4-trimethyl-2-pentene or a mixture thereof.

In the production method according to the present embodiment, in the cyclization step, a cyclization dehydrogenation reaction is carried out using a specific dehydrogenation catalyst in the presence of at least one of isobutene and isobutane, whereby the C8 component is converted to the C4 component. It can suppress monomerization. Therefore, according to the above production method, p-xylene can be obtained in high yield from the C4 distillate derived from petroleum.

Hereinafter, each step of the manufacturing method according to the present embodiment will be described in detail.

(Separation process)
The separation step is a step of using a petroleum-derived C4 fraction as a raw material to obtain a first raw material containing isobutylene and isobutane.

In the present specification, the C4 fraction refers to a fraction containing a hydrocarbon having 4 carbon atoms as a main component (for example, 80% by mass or more, preferably 95% by mass or more). Examples of the hydrocarbon having 4 carbon atoms include normal butane and isobutane as C4 alkanes, normal butene (1-butene and 2-butene) and isobutene as C4 alkenes, and butadiene as C4 diene.

The C4 fraction preferably contains C4 alkanes and C4 alkenes. The total content of C4 alkanes and C4 alkenes in the C4 fraction is, for example, 80% by mass or more, preferably 95% by mass or more.

The C4 fraction contains isobutanes (isobutane and isobutene) from the viewpoint of efficiently obtaining the first raw material. The content of the iso-form in the C4 fraction may be, for example, 10% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. The upper limit of the content of the iso-form in the C4 fraction is not particularly limited, and may be, for example, 90% by mass or less, 95% by mass or less, or 100% by mass or less.

Since the C4 fraction is derived from petroleum, it may contain sulfur. The sulfur content may be, for example, 1000 mass ppm or less, and may be 10 mass ppm or less.

The petroleum-derived C4 fraction may contain, for example, a product of fluid catalytic decomposition of a heavy oil fraction, a fraction from crude oil, a product of ethylene crackers, and the like.

The heavy oil distillate used as a raw material for fluid contact decomposition is not particularly limited, and is, for example, from a gas oil removed from a heavy oil indirect desulfurization apparatus, a direct desulfurized oil obtained from a heavy oil direct desulfurization apparatus, a normal pressure residual oil, or a heavy oil removing apparatus. It may be the obtained desulfurized oil or the like.

The catalyst used in the flow catalytic cracking is not particularly limited, and may be a known flow catalytic cracking catalyst. Examples of the catalyst for fluid catalytic cracking include amorphous silica alumina and zeolite.

In the separation step, for example, iso-forms (isobutene and isobutane) are separated from the C4 distillate to obtain a first raw material. Since the first raw material is obtained by separating the iso-form from the C4 fraction, the content of the iso-form in the first raw material is larger than the content of the iso-form in the C4 fraction. The separation method is not particularly limited, and examples thereof include methods such as reactive distillation, adsorption separation, membrane separation, and TBA method. As the separation method, reactive distillation is preferable from the viewpoint of economy. When the ratio of the iso-form in the C4 fraction is sufficiently large, it is not always necessary to perform the separation operation, and the C4 fraction can be used as it is as the first raw material.

By performing reactive distillation of the C4 fraction, the iso-form (isobutene and isobutane) and the normal form (normal butene and normal butane) are separated while converting 1-butene in the C4 fraction to 2-butene. Can be done. By converting 1-butene to 2-butene, the difference in boiling point from the iso-form becomes large, so that the iso-form can be efficiently separated by reactive distillation.

Among the above separation methods, the TBA method is a method in which isobutene is selectively hydrated from the C4 distillate, recovered as tertiary butanol (TBA), and the obtained TBA is dehydrated to obtain isobutene. be.

(Dimerization process)
The dimerization step is a step of bringing a first raw material containing isobutene and isobutane into contact with a dimerization catalyst to obtain a C8 component. The first raw material may be gaseous and subjected to a dimerization reaction. The C8 component represents a hydrocarbon having 8 carbon atoms.

In the dimerization step, the first raw material may further contain a C4 component other than isobutene and isobutane, that is, a hydrocarbon having 4 carbon atoms other than isobutene and isobutane. Examples of the hydrocarbon having 4 carbon atoms other than isobutene and isobutane include normal butene and normal butane.

The total content of isobutene and isobutane in the C4 component in the first raw material may be, for example, 90% by mass or more, preferably 95% by mass or more, and more preferably 98% by mass or more based on the total amount of the C4 component. Is. The upper limit of the total content of isobutene and isobutane in the C4 component in the first raw material is not particularly limited, and may be, for example, 100% by mass or 99% by mass or less.

The content of the iso-form (isobutane and isobutene) in the first raw material may be, for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. The upper limit of the content of the iso-form in the first raw material is not particularly limited, and may be, for example, 98% by mass or less, 99% by mass or less, or 100% by mass or less.

The first raw material may further contain components other than hydrocarbons. The first raw material may contain, for example, sulfur. The sulfur content in the first raw material may be, for example, 1000 mass ppm or less, and preferably 10 mass ppm or less.

In the dimerization step, the dimerization reaction may be carried out by contacting the raw material gas containing the first raw material with the dimerization catalyst. The raw material gas may contain components other than the first raw material, and may further contain, for example, an inert gas as a diluent. Examples of the inert gas include nitrogen and the like. Further, the raw material gas may further contain other gases such as carbon dioxide and hydrogen.

The isobutene concentration in the raw material gas may be, for example, 10% by mass or more, or 50% by mass or more. The upper limit of the isobutylene concentration in the raw material gas is not particularly limited, and may be, for example, 100% by mass or less, or 90% by mass or less.

The dimerization catalyst may be any catalyst that is active in the dimerization reaction of isobutene and isobutane. Examples of the dimerization catalyst include acidic catalysts such as sulfuric acid, zeolite, solid phosphoric acid, ion exchange resin, hydrofluoric acid, and ionic liquid.

In the dimerization step, the reaction conditions of the dimerization reaction are not particularly limited and may be appropriately changed depending on the activity of the catalyst used and the like.

In the dimerization step, the C8 component is produced. The C8 component is a hydrocarbon having 8 carbon atoms produced by reacting two molecules of a hydrocarbon having 4 carbon atoms (isobutene, isobutane, etc.) in the first raw material. The C8 component may contain, for example, a dimer of isobutene, a reaction product of isobutene and isobutane, and the like. The C8 component may be, for example, diisobutylene, 2,2,4-trimethylpentane, 2,5-dimethylhexane, 2,5-dimethylhexene or 2,5-dimethylhexadiene, even a mixture thereof. good.

The dimerization step may be a step of obtaining a second raw material containing a C8 component and at least one C4 component selected from the group consisting of isobutene and isobutane. That is, the second raw material may contain isobutene, isobutane, or a mixture thereof in addition to the C8 component. In the present embodiment, the second raw material may be used as it is as a raw material for the cyclization step described later.

(Cyclation process)
In the cyclization step, the C8 component is brought into contact with a dehydrogenation catalyst carrying a carrier metal containing Cr on the carrier in the presence of at least one of isobutene and isobutane to produce the product of the cyclization dehydrogenation reaction of the C8 component. Is obtained as p-xylene. The C8 component may be gaseous and subjected to a cyclized dehydrogenation reaction.

The C8 component is a hydrocarbon having 8 carbon atoms. The C8 component contains a p-xylene precursor selected from the group consisting of diisobutylene, 2,2,4-trimethylpentane, 2,5-dimethylhexane, 2,5-dimethylhexene and 2,5-dimethylhexadiene. Is desirable. The proportion of the p-xylene precursor in the C8 component is, for example, preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 95% by mass or more.

In the cyclization step, the second raw material obtained in the dimerization step may be used as it is as a raw material in the cyclization step. That is, the second raw material may contain a C8 component and at least one C4 component selected from the group consisting of isobutene and isobutane, and hydrocarbons other than these components (for example, C4 such as normal butene and normal butane). Ingredients) may be further contained.

The total content of isobutene and isobutane in the second raw material may be, for example, 5 parts by mass or more, preferably 10 parts by mass or more, and more preferably 20 parts by mass or more with respect to 100 parts by mass of the C8 component. .. With such a content, the monomerization of the C8 component into the C4 component is more significantly suppressed, and p-xylene can be obtained in a higher yield. The total content of isobutene and isobutane in the second raw material may be, for example, 400 parts by mass or less, preferably 300 parts by mass or less, and more preferably 200 parts by mass or less with respect to 100 parts by mass of the C8 component. Is. With such a content, the monomerization of the C8 component into the C4 component is more significantly suppressed, and p-xylene can be obtained in a higher yield.

In the cyclization step, the cyclization dehydrogenation reaction may be carried out by bringing the raw material gas containing the second raw material into contact with the dehydrogenation catalyst. The raw material gas may contain components other than the second raw material, and may further contain, for example, an inert gas as a diluent. Examples of the inert gas include nitrogen and the like. Further, the raw material gas may further contain other gas such as carbon dioxide.

The dehydrogenation catalyst may be any catalyst containing Cr that is active in the cyclization dehydrogenation reaction.

As the carrier, an inorganic carrier is preferable, and an inorganic oxide carrier is more preferable. Further, the carrier preferably contains at least one element selected from the group consisting of Al, Mg, Si, Zr, Ti and Ce, and at least one element selected from the group consisting of Al, Mg and Si. It is more preferable to include it. Further, as the carrier, an inorganic oxide carrier containing Al is particularly preferably used from the viewpoint of obtaining a highly active catalyst having a good affinity with the supported metal.

A preferred embodiment of the dehydrogenation catalyst is shown below.

The dehydrogenation catalyst of this embodiment is a catalyst in which a carrier containing Al is supported by a supported metal containing Cr.

In the dehydrogenation catalyst of this embodiment, the Al content may be 40% by mass or more, and may be 50% by mass or more, based on the total amount of the dehydrogenation catalyst. Further, the Al content may be 95% by mass or less.

In the dehydrogenation catalyst of this embodiment, the Cr content is preferably 5% by mass or more, more preferably 8% by mass or more, and more preferably 12% by mass or more, based on the total amount of the dehydrogenation catalyst. Is even more preferable. The Cr content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total amount of the dehydrogenation catalyst. When the Cr content is in the above range, the yield of p-xylene tends to improve.

The dehydrogenation catalyst of this embodiment may further contain a metal such as Mg, Zr, K or the like.

When the dehydrogenation catalyst of this embodiment contains Mg, the monomerization of the C8 component into the C4 component is more significantly suppressed, and p-xylene tends to be obtained more efficiently.

When the dehydrogenation catalyst of this embodiment contains Mg, the Mg content is preferably 0.1% by mass or more, more preferably 1% by mass or more, based on the total amount of the dehydrogenation catalyst. It is more preferably 5.5% by mass or more. The Mg content is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3.5% by mass or less, based on the total amount of the dehydrogenation catalyst. When the Mg content is in the above range, the monomerization of the C8 component into the C4 component tends to be more significantly suppressed.

When the dehydrogenation catalyst of this embodiment contains Zr, side reactions that form a skeleton other than p-xylene are suppressed, and the p-xylene selectivity in the cyclized dehydrogenation reaction tends to be improved.

When the dehydrogenation catalyst of this embodiment contains Zr, the content of Zr is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the total amount of the dehydrogenation catalyst. , 0.1% by mass or more is more preferable. The Zr content is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on the total amount of the dehydrogenation catalyst. When the Zr content is in the above range, side reactions that form skeletons other than p-xylene are more significantly suppressed, and the p-xylene selectivity in the cyclized dehydrogenation reaction tends to be further improved.

When the dehydrogenation catalyst of this embodiment contains K, monomerization to the C4 component and side reactions that form a skeleton other than p-xylene are suppressed, and the p-xylene selectivity in the cyclized dehydrogenation reaction. Tends to improve. This effect is more pronounced when combined with Zr. That is, the dehydrogenation catalyst of this embodiment may further contain Zr and K.

When the dehydrogenation catalyst of this embodiment contains K, the content of K is preferably 0.1% by mass or more, more preferably 1% by mass or more, based on the total amount of the dehydrogenation catalyst. It is more preferably 5.5% by mass or more. The K content is preferably 8% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less, based on the total amount of the dehydrogenation catalyst. When the K content is within the above range, monomerization to the C4 component and side reactions that form skeletons other than p-xylene are more significantly suppressed, and the p-xylene selectivity in the cyclized dehydrogenation reaction is increased. Tends to improve.

The contents of Al, Cr, Mg, Zr and K in the dehydrogenation catalyst can be measured by an inductively coupled plasma emission spectrophotometer (ICP-AES) under the following measurement conditions. The dehydrogenation catalyst is used for measurement after being melted in alkali and made into an aqueous solution with dilute hydrochloric acid.
・ Equipment: Hitachi High-Tech Science SPS-3000 type ・ High frequency output: 1.2kW
・ Plasma gas flow rate: 18L / min
・ Auxiliary gas flow rate: 0.4 L / min
・ Nebulizer gas flow rate: 0.4 L / min

The carrier may be, for example, a metal oxide carrier containing Al. The metal oxide carrier may be, for example, alumina (Al ₂ O ₃ ), may be a carrier containing alumina (Al ₂ O ₃ ) and an oxide of a Group 2 metal, and may be an Al and a Group 2 metal. It may be a composite oxide with. The metal oxide carrier may be a carrier containing a composite oxide of Al and a Group 2 metal element, and at least one selected from the group consisting of an oxide of alumina and a Group 2 metal element. Gamma-alumina is preferable from the viewpoint of obtaining a highly active catalyst having good affinity with the supported metal.

A supported metal containing Cr is supported on the dehydrogenation catalyst of this embodiment. The supported metal may be supported on the carrier as an oxide, or may be supported on the carrier as a single metal.

The amount of Cr supported on the carrier is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 7.5 parts by mass or more with respect to 100 parts by mass of the carrier. .. The amount of Cr supported is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less with respect to 100 parts by mass of the carrier. When the amount of Cr carried is in the above range, the yield of p-xylene tends to improve.

The carrier may carry a metal element other than Cr. Examples of other metal elements are the same as those of other metal elements that can be contained in the carrier, and may be Mg, Zr, K, or the like. 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 Cr.

When Mg is supported on the carrier, the amount of Mg supported is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and 1 part by mass or more with respect to 100 parts by mass of the carrier. Is more preferable. The amount of Mg supported is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and further preferably 3 parts by mass or less with respect to 100 parts by mass of the carrier. When the amount of Mg supported is in the above range, the monomerization of the C8 component into the C4 component tends to be more significantly suppressed.

When Zr is supported on the carrier, the amount of Zr supported is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and 0.1 parts by mass with respect to 100 parts by mass of the carrier. It is more preferable that the amount is more than one part. The amount of Zr supported is preferably 1 part by mass or less, more preferably 0.8 parts by mass or less, and further preferably 0.5 parts by mass or less with respect to 100 parts by mass of the carrier. .. When the amount of Zr supported is in the above range, side reactions forming a skeleton other than p-xylene are more significantly suppressed, and the p-xylene selectivity in the cyclized dehydrogenation reaction tends to be further improved.

When K is supported on the carrier, the amount of K supported is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and 1 part by mass or more with respect to 100 parts by mass of the carrier. Is more preferable. The amount of K carried is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and further preferably 3 parts by mass or less with respect to 100 parts by mass of the carrier. When the amount of K carried is within the above range, the monomerization of the C8 component to the C4 component and the side reactions forming a skeleton other than p-xylene are more significantly suppressed, and p-xylene selection in the cyclized dehydrogenation reaction. The rate tends to improve.

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.

An aspect of the method of supporting a metal on a carrier is shown below. First, a solution in which a precursor of the target metal (supporting metal) is dissolved in a solvent (for example, water) is prepared. At this time, the amount of water in the solution is set to correspond to the pore volume of the carrier. The carrier is then impregnated with the solution adjusted to a volume that fills the pores of the carrier. Then, the solvent is removed at a low temperature, and the obtained solid is dried. By calcining the dried solid, the target metal can be supported on the carrier.

In the above-mentioned supporting method, the precursor of the carrier metal may be, for example, a salt or a complex containing a metal element. The salt containing a metal element 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 a metal element may be, for example, an alkoxide complex, an ammine complex, or the like.

The drying conditions can be, for example, a drying temperature of 100 to 250 ° C. and a drying time of 3 hours to 24 hours.

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, 200 to 1000 ° C, or 400 to 650 ° 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 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 phase at the initial stage of the reaction refers to a state in which very few of the supported metals contained in the catalyst are reduced and in an active state, and the activity of the catalyst is low.

Next, the reaction conditions and the like in the cyclization step will be described in detail.

In the cyclization step, the C8 component is reacted with a dehydrogenation catalyst in which a carrier metal containing Cr is supported on the carrier in the presence of at least one of isobutene and isobutane to carry out a cyclization dehydrogenation reaction of the C8 component. This is a step of obtaining p-xylene.

The cyclization step may be carried out, for example, by using a reactor filled with a dehydrogenation catalyst and circulating the C8 component through the reactor. At this time, by circulating at least one of isobutene and isobutane together with the C8 component, the cyclization dehydrogenation reaction can be carried out in the presence of at least one of isobutene and isobutane.

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 type reactor, a radial flow type reactor, a tube type reactor and the like.

The reaction form of the cyclization 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 total flow rate of isobutene and isobutane is preferably 10 equivalents or more, more preferably 25 equivalents or more, relative to 1 equivalent of the C8 component. The total flow rate of isobutene and isobutane is preferably 300 equivalents or less, and more preferably 200 equivalents or less, with respect to 1 equivalent of the C8 component.

The reaction temperature of the cyclization dehydrogenation reaction, that is, the temperature in the reactor may be 300 to 800 ° C., 400 to 700 ° C., or 450 to 650 ° C. from the viewpoint of reaction efficiency. When the reaction temperature is 300 ° C. or higher, the amount of p-xylene produced tends to be higher. 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 cyclization step is carried out in a continuous reaction format in which the second raw material is continuously supplied, the weight space velocity (hereinafter referred to as “WHSV”) may be, for example, 0.1 h ^-1 or more. It may be 0.5h ^-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 (second raw material) 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 20h ^-1 or less, the conversion rate of the C8 component 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.

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

(Example 1)
<Manufacturing of diisobutylene>
The C4 fraction obtained by treating Middle Eastern crude oil with a fluid catalytic cracking apparatus was fractionated by a reactive distillation apparatus to obtain isobutane and isobutene from the top of the column and normal butane and normal butene from the bottom of the column. Isobutane was 76% by mass and isobutene was 24% by mass in the column top gas. This tower top gas was treated with a strongly acidic ion exchange resin, Amberlist 35, at 120 ° C., normal pressure, and WHSV = 50h ^-1 using a fixed-bed flow reactor, and isobutane was 76% by mass. , 23% by mass of diisobutylene and 1% by mass of other products were obtained. Diisobutylene was extracted from this product by distillation.

<Preparation of catalyst A-1>
Cr-supported on 10.0 g of a commercially available γ-alumina carrier using an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O) and Mg (NO ₃ ) _{2.6H 2 O.} Impregnated and supported so that the amount is 5.0 parts by mass with respect to 100 parts by mass of the carrier and the amount of Mg supported is 3.0 parts by mass with respect to 100 parts by mass of the carrier, dried at 110 ° C. overnight, and 4 at 600 ° C. Charging for hours was carried out to obtain catalyst A-1.

<Manufacturing of p-xylene>
Cycling using a fixed-bed flow reactor under the conditions of 500 ° C., normal pressure, WHSV = 1h- ¹ , 0.25 equivalents of isobutene, 0.25 equivalents of isobutane, and 0.5 equivalents of nitrogen with respect to 1 equivalent of diisobutylene. A dehydrogenation reaction was carried out. Catalyst A was used as the catalyst. Reaction products from 1 hour to 2 hours after the start of the reaction were collected and analyzed. The results are shown in Table 1.

(Example 2)
<Preparation of catalyst A-2>
The same as in Example 1 except that the amount of Cr supported was 7.5 parts by mass with respect to 100 parts by mass of the carrier and the amount of Mg supported was 2.0 parts by mass with respect to 100 parts by mass of the carrier. A catalyst was prepared to obtain catalyst A-2.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutene 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutene 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 3)
<Preparation of catalyst A-3>
For 10.0 g of a commercially available γ-alumina carrier, an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O), Mg (NO ₃ ) 2.6H ₂ O, and ZrO _{(NO 3 )} . ) Using _{2.2H 2O} , the amount of Cr supported is 7.5 parts by mass with respect to 100 parts by mass of the carrier, the amount of Mg supported is 2.0 parts by mass with respect to 100 parts by mass of the carrier, and the amount of Zr supported is 100 parts by mass of the carrier. It was impregnated and supported so as to be 0.1 part by mass with respect to parts by mass, dried at 110 ° C. overnight, and baked at 600 ° C. for 4 hours to obtain catalyst A-3.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutene 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutene 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 4)
<Preparation of catalyst A-4>
For 10.0 g of a commercially available γ-alumina carrier, an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O), Mg (NO ₃ ) _{2.6H 2 O} , ZrO (NO ₃ ) Using _{2.2H 2O} and KNO ₃ , the amount of Cr supported is 7.5 parts by mass with respect to 100 parts by mass of the carrier, the amount of Mg supported is 2.0 parts by mass with respect to 100 parts by mass of the carrier, and the amount supported by Zr. Is impregnated and supported so that the amount of K is 0.1 parts by mass with respect to 100 parts by mass of the carrier and 1.5 parts by mass with respect to 100 parts by mass of the carrier, dried at 110 ° C. overnight, and dried at 600 ° C. for 4 hours. It was calcined to obtain catalyst A-4.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutane 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutane 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 5)
<Preparation of catalyst A-5>
For 10.0 g of a commercially available γ-alumina carrier, an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O), Mg (NO ₃ ) _{2.6H 2 O} , and KNO ₃ were used. The Cr-supported amount is 8.0 parts by mass with respect to 100 parts by mass of the carrier, the Zr-supported amount is 0.1 parts by mass with respect to 100 parts by mass of the carrier, and the K-supported amount is 3.0 with respect to 100 parts by mass of the carrier. It was impregnated and supported so as to be a part by mass, dried at 110 ° C. overnight, and baked at 600 ° C. for 4 hours to obtain a catalyst A-5.

<Manufacturing of p-xylene>
Production of p-xylene was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
<Preparation of catalyst A-6>
The catalyst was supported in the same manner as in Example 1 except that the amount of Cr supported was 14 parts by mass with respect to 100 parts by mass of the carrier and the amount of Mg supported was 1.5 parts by mass with respect to 100 parts by mass of the carrier. It was prepared and the catalyst A-6 was obtained.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutane 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutane 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 7)
<Preparation of catalyst A-7>
Cr-supported on 10.0 g of a commercially available γ-alumina carrier using an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O) and ZrO (NO ₃ ) _{2.2H 2 O.} Impregnated and supported so that the amount is 15 parts by mass with respect to 100 parts by mass of the carrier and the amount of Zr supported is 0.1 parts by mass with respect to 100 parts by mass of the carrier, dried at 110 ° C. overnight, and baked at 600 ° C. for 4 hours. A-7 was obtained.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutane 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutane 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 8)
<Preparation of catalyst A-8>
For 10.0 g of a commercially available γ-alumina carrier, an aqueous solution of chromium nitrate (manufactured by Wako Pure Chemical Industries, Ltd., [Cr (NO ₃ ) ₃ ] 9H ₃ O), ZrO (NO ₃ ) _{2.2H 2 O} , and KNO ₃ were used. The amount of Cr supported is 15 parts by mass with respect to 100 parts by mass of the carrier, the amount of Zr supported is 0.1 parts by mass with respect to 100 parts by mass of the carrier, and the amount of K supported is 1.5 parts by mass with respect to 100 parts by mass of the carrier. It was impregnated and supported so as to be, dried at 110 ° C. overnight, and baked at 600 ° C. for 4 hours to obtain a catalyst A-8.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutene 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutene 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Example 9)
<Preparation of catalyst A-9>
Using a chromium nitrate aqueous solution (manufactured by Wako Pure Chemical Industries, [Cr (NO ₃ ) ₃ ] 9H ₃ O) and KNO ₃ with respect to 10.0 g of a commercially available γ-alumina carrier, the amount of Cr carried is 100 parts by mass of the carrier. The catalyst A-8 was supported by impregnation so that the amount of K carried was 1.0 part by mass with respect to 100 parts by mass of the carrier, dried overnight at 110 ° C., and baked at 600 ° C. for 4 hours. Obtained.

<Manufacturing of p-xylene>
Same as Example 1 except that "isobutane 0.25 equivalent, isobutane 0.25 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to isobutane 0.5 equivalent and nitrogen 0.5 equivalent. Then, p-xylene was produced. The results are shown in Table 1.

(Comparative Example 1)
Production of p-xylene was carried out in the same manner as in Example 1 except that "0.25 equivalent of isobutane, 0.25 equivalent of isobutane, 0.5 equivalent of nitrogen" in the cyclization dehydrogenation reaction was changed to 1 equivalent of nitrogen. gone. The results are shown in Table 2.

(Comparative Example 2)
Production of p-xylene was carried out in the same manner as in Example 2 except that "0.25 equivalent of isobutane, 0.25 equivalent of isobutane, 0.5 equivalent of nitrogen" in the cyclization dehydrogenation reaction was changed to 1 equivalent of nitrogen. gone. The results are shown in Table 2.

(Comparative Example 3)
P-xylene was produced in the same manner as in Example 4 except that "isobutane 0.5 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to nitrogen 1 equivalent. The results are shown in Table 2.

(Comparative Example 4)
P-xylene was produced in the same manner as in Example 7 except that "isobutane 0.5 equivalent, nitrogen 0.5 equivalent" in the cyclization dehydrogenation reaction was changed to nitrogen 1 equivalent. The results are shown in Table 2.

(Comparative Example 5)
P-xylene was produced in the same manner as in Example 8 except that “isobutene 0.5 equivalent, nitrogen 0.5 equivalent” in the cyclization dehydrogenation reaction was changed to nitrogen 1 equivalent. The results are shown in Table 2.

In Examples 1 to 9, the p-xylene yield is higher than that of Comparative Example by performing the cyclization step in the presence of at least one of isobutene and isobutane. From this result, it can be seen that in the method for producing p-xylene according to the present invention, p-xylene can be efficiently obtained by performing the cyclization step in the presence of at least one of isobutene and isobutane.

Claims (6)

A separation step to obtain a first raw material containing isobutene and isobutane from a petroleum-derived C4 distillate, and
A dimerization step of bringing the first raw material into contact with a dimerization catalyst to produce a C8 component,
A cyclization step in which the C8 component is brought into contact with a dehydrogenation catalyst in the presence of at least one of isobutene and isobutane to produce p-xylene by the cyclization dehydrogenation reaction of the C8 component.
Equipped with
The dehydrogenation catalyst is a dehydrogenation catalyst in which a carrier containing γ-alumina is supported on a carrier metal containing at least one selected from the group consisting of Cr and Mg, Zr and K.
A method for producing p-xylene. The dimerization step is a step of obtaining a second raw material containing the C8 component and at least one C4 component selected from the group consisting of isobutene and isobutane.
The production method according to claim 1, wherein the cyclization step is a step of bringing the second raw material into contact with the dehydrogenation catalyst. The production method according to claim 1 or 2, wherein the amount of Cr supported on the dehydrogenation catalyst is 3 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the carrier. The production method according to any one of claims 1 to 3 , wherein the amount of Mg supported on the dehydrogenation catalyst is 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the carrier. The production method according to any one of claims 1 to 4 , wherein the amount of Zr supported on the dehydrogenation catalyst is 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the carrier. The production method according to any one of claims 1 to 5 , wherein the amount of K supported in the dehydrogenation catalyst is 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the carrier.