JPH06116174A - Method for isomerizing xylene - Google Patents

Abstract

PURPOSE:To obtain a catalyst for isomerizing xylene, suppressing loss of xylene, checking formation of >=9C aromatic hydrocarbons, capable of decomposing ethylbenzene. CONSTITUTION:Two kinds of catalysts of catalyst A comprising zeolite containing magnesium oxide and a di- or polyvalent metal cation and a refractory inorganic oxide containing platinum and tin and a catalyst B comprising lithium-containing zeolite and a refractory inorganic oxide carrying platinum and tin are used to isomerize xylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for isomerizing xylene, more specifically, a xylene isomer mixture which does not reach a thermodynamic equilibrium composition (a xylene isomer mixture is orthoxylene, (A mixture of meta-xylene and para-xylene) and a hydrocarbon feedstock mainly composed of ethylbenzene are subjected to a xylene isomerization reaction, and a specific xylene isomer, preferably para-xylene, is isolated from the resulting isomerization reaction mixture, In the xylene isomerization step, which comprises recycling the hydrocarbon mixture of the above to the xylene isomerization reaction, while allowing the xylene isomer mixture in the hydrocarbon to reach a thermodynamic equilibrium composition on a specific catalyst. , Ethylbenzene, which accumulates during the process and reduces the efficiency of the isomerization reaction, is removed from the process on the catalyst. Industrially advantageous isomerization method of xylene, which enables efficient continuous conversion to xylene isomer mixture while suppressing loss of the xylene isomer mixture at the same time. Regarding

[0002]

2. Description of the Related Art The demand for xylenes, especially paraxylene, has increased in proportion to the demand for polyester fibers and films. A typical method for producing para-xylene is a step of separating para-xylene from a hydrocarbon mixture raw material by a crystallization method or an adsorption method for a C8 aromatic hydrocarbon feed material, and a residual hydrocarbon mixture being meta-xylene and / or ortho A step of contacting with a catalyst for isomerization of xylene to para-xylene to convert xylenes in the residual hydrocarbon mixture into a xylene isomer mixture having a thermodynamic composition close to that of the hydrocarbon mixture, and by-product from the isomer mixture After removing the substance, it is recycled to the para-xylene separation step.

In the above-mentioned method for producing paraxylene,
To make the composition of the xylene isomer mixture in the isomerization reaction product as close to the thermodynamic equilibrium composition as possible, to suppress side reactions such as disproportionation and hydrogenolysis accompanied by loss of xylenes, and xylene. It is required to convert ethylbenzene, which is difficult to separate by a normal distillation operation due to its similar boiling point to that of other compounds, into a light component or a heavy component which can be easily separated by distillation. Satisfying these requirements is industrially extremely important for improving the efficiency of the isomerization reaction and reducing the cost of the paraxylene production process.

One of the methods recently proposed to meet the above requirements is a method of hydrodealkylating ethylbenzene to mainly convert it into benzene and ethane, and at the same time, bring the composition of xylenes closer to a thermodynamic equilibrium composition. There is. This process has the advantage of generally higher conversion of ethylbenzene, which reduces the amount of recycle to the para-xylene recovery step and produces useful high quality benzene. In this method, it is sufficient to suppress the loss of xylenes as much as possible and to suppress the production of low-value heavy aromatic hydrocarbons having C9 or higher (hereinafter referred to as C9 + aromatics) as much as possible. It is important for cost reduction.

As a method for isomerizing xylene from this point of view, recently, for example, in JP-A-62-169736 and JP-A-3-146135, xylenes are isomerized and ethylbenzene is mainly converted into benzene and ethane. A method of converting is disclosed.
As a result of repeated studies from the above viewpoints, the present inventors have found that as described in JP-A-2-91031, a pentasil-type aluminosilicate zeolite in which at least 50% of cation sites are occupied by alkaline earth metal cations. The inventors have invented a method for isomerizing xylene using a catalyst composition comprising a refractory inorganic oxide carrying platinum, tin and hydrochloric acid, and further an indium compound. However, these disclosed methods are still unsatisfactory, with a considerable loss of xylene and the formation of large amounts of C9 + aromatics.

[0006]

SUMMARY OF THE INVENTION Therefore, the present inventors have made earnest studies on the above-mentioned object, that is, the development of a catalyst having a sufficient xylene isomerization equilibrium reaching ability and a high ethylbenzene decomposing ability while suppressing the loss of xylene and the production of C9 + aromatics as much as possible. As a result of the repetition, the present invention has been achieved.

[0007]

According to the present invention, a hydrocarbon feedstock mainly composed of xylenes and ethylbenzene is (a) (1) magnesium oxide-supported silica /
Pentasil-type crystalline aluminosilicate zeolite in which alumina (molar ratio) is at least 10 and at least 10% of cation sites are occupied by divalent or higher valent metal ticane, and (2) platinum and tin-supported refractory inorganic oxide And (b) (1) a pentasil-type aluminosilicate zeolite having a silica / alumina (molar ratio) of at least 10 in which at least 50% of the cation sites are occupied by lithium cations, and (2) platinum and The xylene in the hydrocarbon raw material is treated by treating in the presence of a catalyst constituent composed of two catalyst compositions (a) and (b) of a catalyst composition composed of a refractory inorganic oxide carrying tin. A method of isomerizing xylene characterized in that it reaches the thermodynamic equilibrium composition and simultaneously decomposes ethylbenzene. Law is provided.

The hydrocarbon feedstock which can be subjected to the process of the present invention consists mainly of C8 aromatics, ie xylenes and ethylbenzene. Other hydrocarbons may be contained in the amount of the above-mentioned supply source. Examples of other hydrocarbons include paraffins such as nonane, naphthenes such as ethylmethylcyclohexane, and aromatic hydrocarbons other than C8 such as toluene and trimethylbenzene.

One of the hydrocarbon feedstocks is a so-called C8 aromatic hydrocarbon fraction. Industrially, an aromatic hydrocarbon component is converted from a feedstock oil such as a catalytic reforming oil or a pyrolysis oil into a sulfolane method, It is produced by separating by solvent extraction by a method such as the UDEX method or the allosolvan method, and then distilling the extracted separated liquid. This mixture is typically 15-25 parts by weight ethylbenzene, 15-25 para-xylene.
Parts by weight, 30 to 60 parts by weight of metaxylene and 15 to 25 parts by weight of orthoxylene.

Furthermore, in recent years, various attempts have been made to improve the recovery of aromatic hydrocarbons such as benzene, toluene and xylene in the reforming of petroleum naphtha, and the solvent extraction step as described above is used from the naphtha reforming oil. Instead, a method of obtaining a C8 aromatic hydrocarbon mixture containing a non-aromatic hydrocarbon that can be used for the production of xylene by only a distillation treatment has been proposed (Japanese Patent Publication No. 57-47231).

The C8 aromatic hydrocarbon mixture obtained by such a method is also one of the hydrocarbon feedstocks used in the present invention, and it contains a small amount of non-aromatic hydrocarbons.

In the present invention, the above C8 aromatic hydrocarbon mixture, and / or the residue after isolation of a specific xylene isomer, particularly paraxylene, from the mixture and / or the residue is subjected to xylene isomerization. The reaction product after the reaction is used as a hydrocarbon feedstock. The composition of the hydrocarbon feedstock varies depending on the composition and manufacturing method of the C8 aromatic hydrocarbon mixture production material, the method for separating a specific xylene isomer, the performance of the isomerization reaction adopted, etc., and may be rigorously specified. Can not. Aromatic hydrocarbons other than C8 and non-aromatic hydrocarbons contained in a small amount in the feedstock have no effect on the present invention.

The catalyst composition used in the process of the present invention is 2
It is composed of two types of catalyst compositions (a) and (b).
Catalyst composition (a) selectively converts some of the ethylbenzene in the feedstock primarily to benzene and ethane. The catalyst composition (b) allows the xylenes in the feed to reach a thermodynamic equilibrium composition.

In each of the above two catalyst compositions:
A pentasil-type aluminosilicate zeolite with a silica-alumina ratio of at least 10 is used. Among them, ZSM disclosed in Japanese Examined Patent Publication No. 46-10064
Zeolites designated -5 are preferred.

In the zeolite used in the catalyst composition (a) of the present invention, at least 10% of its cation site (acid active site based on alumina which is a constituent of the zeolite) is occupied by a metal cation having a valence of 2 or more. It As the divalent or higher valent metal cation, a magnesium or zinc cation is particularly preferable. At the cation site of the zeolite, only one kind of these metal ions may be present, or two or more kinds thereof may be coexisting. Thus, by using the zeolite in which at least 10% of the cation sites of the zeolite are occupied by the metal cations as described above, the disproportionation reaction of the xylenes in the hydrocarbon feedstock under the condition that ethylbenzene can be sufficiently decomposed. It is possible to significantly reduce the loss caused by the above. Protons are usually present at the remaining cation sites that are not occupied by divalent or higher valent metal cations, but monovalent metal cations such as natriumm occupy part or all of the remaining cation sites. Good.

At least one of such cation sites
As the zeolite in which 0% is occupied by a metal cation having a valence of 2 or more, for example, the ZSM-5 zeolite produced as described in the above-mentioned literature is prepared by a method known per se [eg J. Cat., 46,100-108 (1977), J.Cat., 43,292-303 (19
76) [see]], it can be easily produced by subjecting it to an ion exchange treatment using a divalent or higher valent metal cation.

The zeolite used in the catalyst composition (a) of the present invention is further loaded with magnesium oxide in a weight ratio of 0.01 / 1 to 1/1 with respect to the zeolite. Since the pores of zeolite are narrowed by supporting magnesium oxide, the diffusion of ethylbenzene in the pores of zeolite is not affected, but the diffusion of by-products generated from xylenes due to disproportionation is suppressed. result,
The loss of xylenes and the production of C9 + aromatics are greatly suppressed while maintaining the ethylbenzene decomposition activity.

In the preparation of the zeolite supporting magnesium oxide as described above, any of various known supporting methods can be used. However, after impregnating the homogeneous solution containing the magnesium compound with the zeolite, the solvent is added. A method of removing, drying and firing is particularly preferable. As the magnesium compound, compounds such as magnesium hydroxide, magnesium acetate and magnesium nitrate, which become magnesium oxide by firing, are preferably used, and as the solvent, water, methanol and the like are preferably used.

On the other hand, the zeolite used in the catalyst composition (b) of the present invention has at least 50% of its cation sites occupied by lithium cations. As described above, by using the zeolite in which at least 50% of the cation sites of the zeolite are occupied by lithium cations, it is possible to maintain sufficient capacity for achieving the isomerization equilibrium of xylenes while maintaining the non-uniformity of xylenes in the hydrocarbon feedstock. It is possible to significantly suppress the loss due to the chemical reaction. Protons are usually present at the remaining cation sites not occupied by the lithium cations of the zeolite, but other monovalent metal cations such as sodium or divalent or higher valent metal cations are part or all of the remaining cation sites. May occupy.

At least 5 of such cation sites
A zeolite in which 0% is occupied by lithium cations can be easily produced by subjecting it to an ion exchange treatment using lithium cations according to the method described above.

In the catalyst compositions (a) and (b) of the present invention, as a refractory inorganic oxide used as a carrier in a refractory inorganic oxide carrying platinum and tin used in combination with the above zeolite. Is not particularly limited, and those conventionally used as a catalyst carrier can be used, and examples thereof include silica, alumina, silica-alumina, kaolin, silica-magnesium, zeolite, zirconia, and magnesium. Among them, γ-alumina is preferable from the viewpoint of specific surface area and strength during molding.

The amount of platinum supported on such a carrier is such that the nuclear hydrogenation or ring decomposition reaction of xylenes in the hydrocarbon feedstock or xylene isomer reaction mixture is suppressed as much as possible.
In addition, from the viewpoint of accelerating the decomposition of ethylbenzene as much as possible, it is generally 0.005 to 5.
It is in the range of 0% by weight, preferably 0.1 to 1.0% by weight. It is presumed that the function of platinum supported on the refractory inorganic oxide is that in the catalyst composition (a), the deethylation reaction of ethylbenzenes is remarkably promoted as a concerted effect by the combination with the zeolite, and In the catalyst composition (b), it is presumed that coke formation is suppressed by hydrogenation of the coke precursor.

Further, in addition to platinum, tin is supported on the refractory inorganic oxide used in combination with zeolite in the present invention. The function of tin supported on the carrier moderately suppresses the hydrogen dissociation and adsorption ability of coexisting platinum, and as a result, it significantly reduces the nuclear hydrogenation and ring decomposition reaction of xylenes in the hydrocarbon feedstock, while reducing ethylbenzene. It is considered that the conversion reaction of benzene to benzene and ethane can proceed sufficiently. From the above viewpoint, the amount of tin supported is generally in the range of 0.1 / 1 to 10/1, preferably 0.5 / 1 to 5/1, when converted to the tin / platinum atomic ratio.

In the preparation of the refractory inorganic oxide supporting platinum and tin as described above, any of various known supporting methods can be used, but if the effect of tin as described above is taken into consideration. For example, a simultaneous impregnation-supporting method in which a refractory inorganic oxide is impregnated with a uniform solution containing a platinum compound and a tin compound, and then the solvent is removed and dried is preferable. As the platinum compound, for example, chloroplatinic acid, platinum tetraamine complex, etc., and as the tin compound, soluble salts such as stannous chloride, tin sulfate, tetraalkylammonium chlorostannate are preferably used, and as a solvent for dissolving these soluble salts. Is preferably water, methanol, hydrochloric acid, acetone or the like.

The catalyst composition used in the method of the present invention is a catalyst composition (a) and a catalyst composition in which the zeolite and the refractory inorganic oxide are uniformly mixed and then molded into a catalyst shape such as pellets and tablets. It is obtained by combining (b). The proportion of each catalyst component in molding the catalyst composition (a) and the catalyst composition (b) is 0.05 / 1 to 5 in terms of the weight ratio of refractory inorganic oxide / zeolite.
It is preferably within the range of / 1. Catalyst composition (a)
There is no particular limitation on the method of combining the catalyst composition with the catalyst composition (b), but a method of combining a layer consisting of the catalyst composition (a) and a layer consisting of the catalyst composition (b) alone is particularly preferable. The ratio of the catalyst composition (a) to the catalyst composition (b) is preferably in the range of 0.1 / 1 to 1 / 0.1 in terms of weight ratio.

In the present invention, the particular catalyst composition described above is fed by contacting it with a hydrocarbon feedstock consisting essentially of a mixture of xylene isomers that has not reached thermodynamic equilibrium composition and ethylbenzene. It decomposes some of the ethylbenzene in the feed and allows the xylene isomer mixture to reach a thermodynamic equilibrium composition.

The reaction is preferably carried out in the gas phase in the presence of hydrogen. At this time, the reaction temperature is generally 250 to 5
It is in the range of 00 ° C, preferably 280 to 450 ° C.
The feed rate of the raw material is generally in the range of 1 to 500 / hr, preferably 3 to 50 / hr.
HSV) is suitable.

On the other hand, the partial pressure of hydrogen is not precisely defined and can be changed according to the temperature to be used, WHSV, etc., but is generally selected from the range of 10 kPa to 2500 kPa, preferably 80 to 1500 kPa. The hydrogen supply rate is generally 0.1 / 1 to 15/1, preferably 1/1 to 10/1, in terms of the hydrogen / hydrocarbon feed molar ratio. Is appropriate.

[0029]

According to the method of the present invention described above, (i) when the method of the present invention is used in the paraxylene production process, the loss of xylenes can be significantly reduced, resulting in an improved yield of paraxylene. To do. (Ii) As a result of greatly suppressing the generation of C9 + aromatics, advantages such as improvement in the quality of paraxylene produced can be obtained.

[0030]

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[0031]

Reference Example 1 Zeolite ZSM-5 was synthesized according to the method disclosed in US Pat. No. 3,965,207. In the synthesis, water glass was used as a silica source, aluminum sulfate was used as an alumina source, tri-n-propylamine and n-propyl bromide were used as organic nitrogen cation sources, and methyl ethyl ketone was further added and reacted in an autoclave under predetermined conditions. . The product was filtered, washed thoroughly with water, and then dried overnight in an electric dryer at 100 ° C. As a result of X-ray diffraction, the product was identified as ZSM-5. As a result of chemical analysis, the silica / alumina ratio of the product was 70.

Then, the cation of the obtained zeolite
The site was converted from sodium ion to ammonium ion. That is, 10 ml of a 10% ammonium chloride aqueous solution per 1 g of the zeolite was used and treated for 16 hours under reflux. This operation was repeated twice. After that, it is filtered off,
After washing with water and drying at 100 ° C. for 16 hours, ammonium type zeolite ZSM-5 was obtained.

[0033]

[Reference Example 2] 10 g of magnesium nitrate hexahydrate was added to 100
Dissolved in ml water. To this aqueous solution, 10 g of the ammonium-type zeolite ZSM-5 obtained in Reference Example 1 was added, and the mixture was kept under reflux overnight. This operation was repeated 4 times. Then, it was filtered and washed thoroughly with water. Further dried in an electric dryer at 100 ℃ for 16 hours, magnesium type ZSM-5
A zeolite was obtained. As a result of chemical analysis, the dry powder contained 0.20% magnesium. Therefore, in this product, 34% of the cation sites based on alumina are occupied by magnesium.

[0034]

Reference Example 3 10 g of zinc nitrate hexahydrate was dissolved in 100 ml of water. To this aqueous solution, 10 g of the ammonium-type zeolite ZSM-5 obtained in Reference Example 1 was added, and the mixture was kept under reflux overnight. This operation was repeated 4 times. Then, it was filtered and washed thoroughly with water. 16 in an electric dryer at 100 ° C
After drying for an hour, zinc type ZSM-5 zeolite was obtained.
As a result of chemical analysis, the dry powder contained 1.17% zinc. Therefore, in this product, 76% of the cation sites based on alumina are occupied by zinc.

[0035]

Example 1 (1) Magnesium oxide-supported magnesium type ZSM-5
Preparation of magnesium acetate tetrahydrate (1.44 g) was precisely weighed in a 100 ml eggplant-shaped flask and dissolved in 30 ml of water.
Further, 3.0 g of magnesium-type ZSM-5 obtained in Reference Example 2 was added, and the mixture was kept at 80 ° C. for 8 hours with stirring. Then, using a rotary evaporator, water was distilled off under reduced pressure at 40 ° C. Subsequently, after drying in an electric dryer at 100 ° C for 16 hours, it is kept in an electric muffle furnace at 500 ° C for 8 hours.
Magnesium type ZSM-5 supporting 10.8% by weight of magnesium oxide was prepared by firing for a period of time.

(2) Zinc type ZSM supporting magnesium oxide
Preparation of -5 Magnesium acetate tetrahydrate (2.57 g) was precisely weighed in a 100 ml eggplant-shaped flask and dissolved in 30 ml of water.
Further, 3.0 g of the zinc type ZSM-5 obtained in Reference Example 3 was added, and the mixture was kept at 80 ° C. for 8 hours while stirring. Then, using a rotary evaporator, water was distilled off under reduced pressure at 40 ° C. Then, after drying in an electric dryer at 100 ° C. for 16 hours, it was baked in an electric muffle furnace at 500 ° C. for 8 hours to prepare zinc type ZSM-5 carrying 16.1% by weight of magnesium oxide. did.

[0037]

Example 2 10 g of lithium sulfate was dissolved in 100 ml of water. To this aqueous solution, 10 g of the ammonium-type zeolite ZSM-5 obtained in Reference Example 1 was added, and the mixture was kept under perfusion overnight. This operation was repeated 4 times. Then, it was filtered and washed thoroughly with water. Further, it was dried in an electric dryer at 100 ° C. for 16 hours to obtain a lithium type ZSM-5 zeolite.
As a result of chemical analysis, the dry powder contained 0.32% lithium. Therefore, in this product, 100% of the cation sites based on alumina are occupied by lithium.

[0038]

Example 3 (1) Preparation of Pt—Sn—Alumina 1.00 g of commercially available chloroplatinic acid hexahydrate was dissolved in 50 ml of water. On the other hand, 86.4 mg of stannous chloride dihydrate was added to 5
A 0 ml eggplant-shaped flask was precisely weighed, and this was dissolved in 2 ml of hydrochloric acid and 15 ml of water, and 1.33 ml of the above-mentioned chloroplatinic acid aqueous solution was further added. Γ-in dark red-orange aqueous solution
5 g of alumina gel (ACP-11: manufactured by Catalyst Kasei Co., Ltd.) was added, and the mixture was kept at 50 ° C. for 5 hours while stirring. Then, using a rotary evaporator, water was distilled off under reduced pressure at 40 ° C. Then 0.2% platinum and 0.9% by drying in an electric dryer at 100 ° C. for 16 hours.
Alumina containing tin was prepared. (2) Preparation of Ethylbenzene Decomposition Catalyst To the Pt—Sn-alumina obtained in (1), an equal weight of the magnesium oxide-supporting ZSM-5 zeolite obtained in Example 1 (1) and (2) was added, and the mixture was thoroughly mixed. 10-2 after mixing
It was molded into a size of 0 mesh. This composition is referred to as catalysts A and B.

[0039]

Example 4 Pt—Sn-alumina obtained in Example 3 (1) was added to an equal weight of lithium-type ZS obtained in Example 2.
M-5 zeolite was added and mixed well, and then molded into a size of 10 to 20 mesh. This composition is referred to as catalyst C.

[0040]

COMPARATIVE EXAMPLE 1 To the platinum- and tin-containing alumina obtained in Example 3 (1) was added an equal weight of the ZSM-5 zeolite on which no magnesium oxide was loaded, obtained in Reference Examples 2 and 3, and mixed thoroughly. After that, it was molded into a size of 10 to 20 mesh. This composition is designated as catalyst D and E.

[0041]

Example 5 3.0 of catalyst A obtained in Example 3 (2)
g was charged into a flow-type pressurized fixed bed reactor, and then 3.0 g of the catalyst C obtained in Example 4 was charged in the upper layer. After raising the temperature under a nitrogen stream until reaching 400 ° C,
The metal was reduced by substituting it with a hydrogen stream and maintaining it for 2 hours. Then, the temperature was lowered to 380 ° C. under a hydrogen stream, and after the catalyst layer was stabilized at that temperature, a mixture mainly composed of C8 aromatic hydrocarbon was supplied. The reaction conditions are pressure: 830 kPa (120 PSIA), WHSV of catalyst weight based on catalyst A: 10 / hr, hydrogen / raw material mixture (molar ratio): 2, and reaction temperature so that the decomposition rate of ethylbenzene is around 45%. The product obtained by adjusting the value of 100 to 108 hours after passing oil was analyzed. The results are listed in Table 1.

[0042]

[Table 1]

[0043]

[Equation 1]

[0044]

[Sixth Embodiment] The same operation as in the fourth embodiment is performed in the same manner as the third embodiment
It was carried out using the catalyst B obtained in Example 1 and the catalyst C obtained in Example 4. The results are listed in Table 1.

[0045]

Comparative Example 2 For each of the catalysts D and E obtained in Comparative Example 1, the same operation as in Example 4 was carried out. The results are shown in Table 1.
It was shown to.

[0046]

Comparative Example 3 The same operation as in Example 4 was carried out on the catalyst disclosed in Example 1 of JP-A-2-91031. The results are shown in Table 1.

The results in the table show that the catalyst composition of the present invention can effect the decomposition of ethylbenzene and the isomerization of xylene mixtures with less loss of xylene and formation of C9 + aromatics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Namamame 77 Kitayoshida-cho, Matsuyama-shi, Ehime Prefecture Teijin Limited Matsuyama Office

Claims (14)

[Claims] 1. A hydrocarbon feedstock mainly composed of a xylene isomer mixture and ethylbenzene is subjected to a xylene isomerization reaction, a specific xylene isomer is isolated from the resulting isomerization reaction mixture, and the remaining hydrocarbon mixture is converted to the above-mentioned mixture. In a continuous xylene isomerization process comprising recirculating to a xylene isomerization reaction, the hydrocarbon feedstock comprises (a) (1) magnesium oxide supported silica /
Pentasil-type crystalline aluminosilicate zeolite in which alumina (molar ratio) is at least 10 and at least 10% of cation sites are occupied by divalent or higher valent metal ticane, and (2) platinum and tin-supported refractory inorganic oxide And (b) (1) a pentasil-type aluminosilicate zeolite having a silica / alumina (molar ratio) of at least 10 in which at least 50% of the cation sites are occupied by lithium cations, and (2) platinum and The xylene in the hydrocarbon raw material is treated by treating in the presence of a catalyst constituent composed of two catalyst compositions (a) and (b) of a catalyst composition composed of a refractory inorganic oxide carrying tin. A method of isomerizing xylene characterized in that it reaches the thermodynamic equilibrium composition and simultaneously decomposes ethylbenzene. Law. 2. The zeolite (a) contains 0.01 / 1 to 1 in terms of magnesium oxide / zeolite weight ratio.
The isomerization method according to claim 1, wherein the magnesium oxide of 1/1 is supported. 3. The isomerization method according to claim 1, wherein the crystalline aluminosilicate zeolite (a) is ZSM-5. 4. The isomerization method according to claim 1, wherein the metal cation (a) is magnesium and / or zinc. 5. The isomerization method according to claim 1, wherein the refractory inorganic oxide (a) is γ-alumina. 6. The isomerization method according to claim 1, wherein 0.005 to 5% by weight of platinum is supported on the refractory inorganic oxide (a) based on the weight of the inorganic oxide. 7. The isomerization according to claim 1, wherein the refractory inorganic oxide (a) carries 0.1 / 1 to 10/1 tin in terms of tin / platinum atomic ratio. Method. 8. The isomerization method according to claim 1, wherein the weight ratio of the refractory inorganic oxide / zeolite of (a) is in the range of 0.05 / 1 to 5/1. 9. The isomerization method according to claim 1, wherein the crystalline aluminosilicate zeolite (a) is ZSM-5. 10. The isomerization method according to claim 1, wherein the refractory inorganic oxide (b) is γ-alumina. 11. The isomerization method according to claim 1, wherein 0.005 to 5% by weight of platinum is supported on the refractory inorganic oxide (b) based on the weight of the inorganic oxide. 12. The isomerization according to claim 1, wherein the refractory inorganic oxide (b) carries 0.1 / 1 to 10/1 tin in terms of tin / platinum atomic ratio. Method. 13. The isomerization method according to claim 1, wherein the weight ratio of the refractory inorganic oxide / zeolite of (b) is in the range of 0.05 / 1 to 5/1. 14. A catalyst composition (a) and a catalyst composition (b).
The isomerization method according to claim 1, wherein the weight ratio with is within the range of 0.1 / 1 to 1 / 0.1.