JPS634813B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing p-xylene,
More specifically, the present invention relates to an industrially advantageous method for producing p-xylene by methylating toluene with a methylating agent in the gas phase. Among various xylenes, p-xylene is an industrially extremely useful compound because it can be derived into terephthalic acid or terephthalic acid dimethyl ester, which is a raw material for polyester. Conventionally, it has been known that p-xylene can be obtained through separation and isomerization from a petrochemical derivative that mainly contains aromatic hydrocarbons having 8 carbon atoms (so-called _C8 fraction). It is manufactured industrially in large quantities. On the other hand, recently, benzene or mono-
Many methods have also been proposed for alkylating alkyl-substituted benzenes with various alkylating agents. For example, US Pat. No. 4,117,026 includes:
Discloses a method for alkylating C1 _{- C4} monoalkylbenzenes with _C2 - _C15 olefins and/or _C3 - _C60 paraffins using catalysts comprising certain specific crystalline aluminosilicate zeolites. has been done. This process also includes the production of xylene and benzene by disproportionation of toluene itself. However, in the above proposed method, p-
The selectivity of p-dialkylbenzene is still not industrially satisfactory. U.S. Pat. No. 4,086,287 also discloses ethylation of toluene or ethylbenzene with an ethylating agent such as ethylene, ethyl alcohol, ethyl halide, diethyl ether, etc. in the presence of certain crystalline aluminosilicate zeolite catalysts.
A method for producing ethyltoluene or diethylbenzene is disclosed. This method is superior to conventional methods in that it produces less orthodi-substituted products and p-ethyltoluene or p-diethylbenzene is produced with relatively high selectivity. Classes, especially p-
Not applicable to xylene production. U.S. Pat. No. 3,965,207 also discloses that the zeolites are prepared at temperatures between about 500°C and about 750°C in the presence of a catalyst comprising certain crystalline aluminosilicate zeolites having a silica/alumina molar ratio of at least about 12. A method for selectively producing p-xylene by methylating toluene is disclosed. On the other hand, U.S. Patent No. 4034053 and U.S. Patent No.
No. 4158024 discloses a method for producing p-xylene by methylating toluene with a methylating agent in the presence of a crystalline aluminosilicate zeolite catalyst modified with magnesium or its oxide. However, although the above-mentioned proposed methods are excellent in that the proportion of p-xylene in the xylene isomer mixture contained in the reaction mixture and the conversion rate of toluene to xylene are relatively high, they are still unsatisfactory industrially. Moderately high p-xylene concentrations and toluene conversions have not been obtained. In the synthesis of p-xylene by methylation of toluene, the p-xylene concentration in xylene and the toluene conversion rate have important industrial meanings, and in particular, it is desirable that the p-xylene concentration is as high as possible. The value of 85% or more, particularly 90% or more, greatly influences the industrial value of the method. As already proposed by the present inventors
144324), when this methylation reaction is carried out using a crystalline aluminosilicate catalyst, and when the reaction is carried out by shortening the contact time and suppressing the toluene conversion to a low value, a relatively high p-xylene concentration is required. A mixture of xylene isomers is obtained as the reaction product. However, as the toluene conversion rate is increased by increasing the contact time, the concentration of p-xylene in the produced xylene isomer mixture tends to gradually decrease. Therefore, it is obvious that it would be extremely advantageous industrially if p-xylene could be produced from toluene with both the toluene conversion rate and the p-xylene concentration industrially high. , development of such a manufacturing method is strongly desired. It is an object of the present invention to provide an industrial method for producing xylene mixtures enriched in p-xylene by methylation of toluene. Another object of the present invention is to provide an industrial method for producing a xylene mixture with high toluene conversion and high p-xylene concentration. Yet another object of the present invention is to provide an industrial method for producing p-xylene with a high conversion rate of methylating agent to xylene. Further objects and advantages of the present invention will become apparent from the following description. According to the present invention, in the method for producing p-xylene by methylating toluene with a methylating agent in the gas phase, (a) the methylation is carried out from a plurality of series-connected fixed catalyst beds separated from each other; (b) The toluene is supplied together with hydrogen gas only to the first-stage fixed catalyst layer, and the subsequent fixed catalyst layer is (c) The methylating agent is passed through the fixed catalyst layer in sequence, and the amount of toluene supplied at that time is such that the total weight hourly space velocity is in the range of 1 to 300 hr ^-1 . If necessary, the methylating agent is supplied to each catalyst layer together with hydrogen gas, and the methylating agent is supplied to each catalyst layer from 0.01/t mol to 1/t mol per 1 mol of toluene supplied to the first stage catalyst layer. mol (where t is the number of methyl groups in the methyl agent), and the total amount of the methylating agent supplied to all catalyst layers is supplied to the first stage catalyst layer. 0.1/mol of toluene
t mol to 2/t mol, where t has the meaning given above, and (d) each fixed catalyst layer comprises a catalyst comprising a crystalline aluminosilicate containing magnesium oxide or lanthanide oxide. A method is provided, characterized in that the method is filled with: In order to facilitate understanding of the principle of the method of the present invention, a simple model experiment will be explained first. That is, (i) an experiment in which toluene was methylated using a certain amount of catalyst and a mixture of toluene and methanol in a certain proportion (experiment a in Example 2); and (ii) the experiment used in experiment a. The same catalyst as 2
The same amount of toluene and 1/2 amount of methanol as in experiment a were supplied to the first catalyst layer of two serially connected catalyst layers that were equally divided from each other, and the first catalyst layer An experiment (experiment b in Example 2) was conducted in which 1/2 of the remaining amount of methanol was introduced into the reaction mixture discharged from the reactor and supplied to the second catalyst layer to perform methylation. The temperature, catalyst contact time, and other conditions in Experiments a and B were kept as similar as possible. As a result, although the amounts of catalyst, toluene, and methanol used were the same in the experiments, the conversion rate of toluene was higher in experiment b than in experiment a. The results showed that the p-xylene concentration was improved. Furthermore, it was found that the excellent effect of improving the conversion rate of consumed methanol to xylene was also brought about. As described above, according to the present invention, the toluene conversion rate can be increased by continuously performing the methylation in a multistage reaction system consisting of a plurality of serially connected catalyst layers separated from each other. Not only is this possible, but the p-xylene concentration in the resulting xylene isomer mixture can be maintained at a high level, and the conversion rate of the methylating agent to xylene can be significantly improved. be. That is, according to the method of the present invention, a xylene isomer mixture with a higher concentration of p-xylene can be obtained at the same toluene conversion rate compared to the conventional method as described above in which the reaction is carried out using a single catalyst layer. Moreover, when trying to obtain a mixture of xylene isomers with the same p-xylene concentration, it is possible to conduct the reaction with a higher toluene conversion and a higher conversion of the methylating agent to xylene. This provides a significant industrial advantage. The present invention will be explained in more detail below. As described above, the present invention basically performs methylation of toluene while supplying a methylating agent to each catalyst layer of a plurality of series-connected fixed catalyst layers that are separated from each other. It is. The catalyst constituting each fixed catalyst layer used in the method of the present invention is made of crystalline aluminosilicate containing magnesium oxide or lanthanide oxide. As the crystalline aluminosilicate (hereinafter sometimes abbreviated as zeolite) that forms the base of the catalyst, any of those conventionally used in toluene methylation can be used, but in general contains a hydrogen ion precursor such as hydrogen ion or ammonium ion, and the silica/alumina molar ratio is at least
10, preferably 15 to 5000, particularly preferably 20 to
3000 is preferred. In other words, so-called high-silica zeolites, which have a high content of silica relative to alumina, are used as the basis of the catalyst. Many such high-silica zeolites have been proposed so far. Zeolites with extremely high silica content, such as those with a silica/alumina ratio of 5000, are also known. Any high silica zeolite can be used in the present invention as long as the silica/alumina ratio is within the specified ranges. The crystalline aluminosilicate-modified catalyst used in the present invention generally has an α value of 1 to 1000, preferably 5 to 800, more preferably 10 to 800, which affects the relative activity of zeolite.
Preferably, it is within the range of 600. The definition and measurement method of such α value are described in Journal of Catalysis, Vol. 4, p. 527 (1965) and Vol. 6, p. 278 (1966). According to this method, measurements were carried out using silica alumina catalyst N631-HN manufactured by JGC Corporation as a standard. In addition, the catalyst modified with crystalline aluminosilicate used in the present invention is suitably one having relatively small pores, and the storage capacity ratio of cyclohexane to n-hexane at 25°C is generally 0.05.
~0.7, preferably 0.1-0.6, more preferably 0.2-0.6 are advantageously used. As used herein, the term "occlusion capacity ratio (weight) of cyclohexane to n-hexane at 25°C" refers to the amount of n-hexane adsorbed per unit weight of zeolite under a constant hydrocarbon pressure. It is defined as the ratio to the amount of adsorption (wt% cyclohexane/wt% n-hexane). The amount of cyclohexane and n-hexane adsorbed is determined by quantitatively weighing the zeolite catalyst, allowing the adsorbed substance to be saturated for 6 hours at 25℃ under a reduced pressure of 120±20mmHg, and then heating it at 25℃ and 120±20mmHg for 2 hours to remove deposits. Exhaust the time,
It was determined based on the weight increase. The storage capacity ratio (weight) of cyclohexane to n-hexane of ZSM-5 zeolite measured by this method is
It was 0.7. Furthermore, the above catalyst generally has a
It is desirable to have an average crystal size within the range of 4 microns, preferably 0.15 to 3.5 microns, more preferably 0.2 to 3 microns. Typical examples of crystalline aluminosilicate or zeolite having the above-mentioned properties that can be used as the base of the catalyst in the present invention include various ZSM-based zeolites developed by Mobil Oil Corporation. and zeta-based zeolite developed by Imperial Chemical Industries Limited, with ZSM-based zeolite being preferred. Examples of ZSM-based zeolites include ZSM-5
(see U.S. Patent No. 3702886), ZSM-11 (see U.S. Patent No. 3709979), ZSM-12 (see U.S. Patent No.
3832449), ZSM-35 (U.S. Patent No. 4046859)
Examples of zeta-based zeolites include Zeta 1 (see German Patent Publication No. 2,548,697) and Zeta 3 (see German Patent Publication No. 2,548,695). TP-1 series zeolite developed by the present inventors as a high-silica zeolite can also be used (see Japanese Patent Application Laid-Open No. 137500/1983). These TP
-1 series zeolite contains thiol, sulfide,
By using organosulfur compounds such as sulfoxides, sulfones or thiophenes,
It can be made by heating a raw material mixture containing silica, alumina, an alkali metal, and water to a temperature and time sufficient to form a crystalline aluminosilicate. The properties and manufacturing method of these TP-1 zeolites are described in the above-mentioned Japanese Patent Application Laid-Open No. 54
It is explained in detail in the -137500 publication. These zeolites can generally be used in a form containing alkali metal ions or alkaline earth metal ions at cation sites. In the present invention, these zeolites are converted to H-type zeolites and used in a form containing mainly hydrogen ions or hydrogen ion precursors at cation sites. Therefore, in this specification, unless otherwise specified, "zeolite" means H-type zeolite. It has been found that the best results are obtained using ZSM-5 zeolite as the catalyst base. Thus, according to the most preferred embodiment of the invention, ZSM-5 is used as the basis for the methylation catalyst. The zeolite as described above is used as a methylation catalyst in the method of the present invention after being modified with magnesium oxide or lanthanide oxide. By modifying zeolite with magnesium oxide or lanthanide oxide (hereinafter sometimes referred to as "modifier A"), the concentration of p-xylene in the resulting xylene isomer mixture, that is, the selectivity of p-xylene, can be significantly increased. can be improved. The above-mentioned lanthanide oxide is an oxide of a lanthanide metal, such as lanthanum oxide, cerium oxide, ytterbium oxide, dysprosium oxide,
Neodymium oxide and the like are included, of which lanthanum oxide and cerium oxide are preferred. Magnesium oxide and lanthanide oxide as modifying components can each be present on the zeolite alone, or two or more kinds can be present in combination. The content of magnesium oxide and lanthanide oxide is not strictly limited and can be varied widely depending on the type of zeolite to be modified, etc., but in general, it is based on the weight of crystalline aluminosilicate. , magnesium oxide is 1
It can be present in a content of ~100% by weight, preferably 2-80% by weight, more preferably 5-50% by weight, and lanthanide oxides from 1-200% by weight, preferably 10-150% by weight, even more preferably is 20-100
It can be present in a content of % by weight. The catalyst according to the invention comprising crystalline aluminosilicate modified with magnesium oxide or lanthanide oxide can be further treated with one or more metals selected from platinum, rhodium and iridium (hereinafter referred to as "modifier"). (sometimes referred to as "B").
This modification can significantly extend the life of the catalyst. During use of the catalyst, at least a portion of the above metals is present on the zeolite in elemental form, but the remaining portion can also be present in the form of metal oxides or other metal compounds. If platinum, rhodium and/or iridium is present, the content in the catalyst is not critical, but is generally between 0.1 and 10% by weight in metal form, based on the weight of the crystalline aluminosilicate, preferably It may be present in the range of 0.1 to 8% by weight, more preferably 0.1 to 5% by weight. Furthermore, according to the invention, the crystalline aluminosilicate modified with both magnesium oxide or lanthanide oxide and platinum, rhodium and/or iridium may furthermore be a metal of group 1 of the periodic table other than platinum, rhodium and iridium, or rhenium, or rhenium. may be modified with an oxide of (hereinafter sometimes referred to as "modifier C"), thereby greatly improving the toluene conversion rate at the initial stage of the reaction of the catalyst made of the aluminosilicate. It was discovered that Such metals of group of the periodic table other than platinum, rhodium and iridium include iron, cobalt, nickel, ruthenium, palladium and osmium. The content of these metals or their oxides in the catalyst is not limited and can vary within a wide range, but is generally from 0.01 to 10% by weight, preferably from 0.01 to 10% by weight, based on the weight of the crystalline aluminosilicate.
It may be present in an amount of 8% by weight, more preferably 0.01-5% by weight. The term "modified" with metals or metal oxides herein refers to those in which metals or metal oxides are ion-exchanged to the cation sites of the zeolite and/or the metals or metal oxides are physically attached to the surface of the zeolite. It means what it carries. Zeolite modified with the above modifier A, or modifiers A and B, or modifiers A, B, and C,
It can be produced by generally known methods for modifying zeolites with metals or metal oxides. For example, zeolites modified with modifier A, i.e. magnesium oxide or lanthanide oxide, are disclosed in the aforementioned U.S. Pat.
It can be produced by the method described in No. 144323. On the other hand, when producing zeolites modified with the aforementioned modifiers A and B or modifiers A, B and C, the modification with modifiers A, B and C can be carried out separately in any order, or Can be done at the same time. It is preferable that the modification with modifiers A and B is carried out simultaneously. For ease of understanding, specific examples of modification methods will be described in detail below. Commercially available zeolites generally have alkali metals or alkaline earth metals such as sodium, potassium or calcium substituted at their cation sites. This alkali or alkaline earth metal is therefore exchanged with hydrogen or ammonium ions. This exchange is preferably performed before modification with a modifier. According to one method, a zeolite in which alkali metals or alkaline earth metals have been substituted on cation sites is immersed in an aqueous solution containing ammonium ions to obtain a product in which most of the cation sites have been replaced with ammonium ions. By firing ammonium ion type zeolite at a temperature of approximately 200 to 600°C, it becomes hydrogen ion type zeolite. According to another method, zeolites in which the cation sites have been replaced with alkali metals or alkaline earth metals are treated with an inorganic or organic acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid or oxalic acid to remove most of the cation sites. can be converted into hydrogen ion form. However, even if ion exchange is carried out by the above method, it is not possible to convert all the cation sites in the zeolite into hydrogen ion type, and generally a small amount of alkali metal or alkaline earth metal ions remain. To modify zeolite with Modifier A (magnesium oxide or lanthanide oxide) and Modifier B (platinum, rhodium or iridium), Modifier A can be modified by calcining under an oxygen atmosphere according to conventional modification methods. (hereinafter referred to as "precursor A") and a compound that can become metal modifier B (hereinafter referred to as "precursor B") by firing in a reducing atmosphere. can be modified simultaneously or separately. That is, for simultaneous modification, the zeolite to be treated is brought into contact with an aqueous or non-aqueous medium in which the desired precursors A and B are dissolved.
For example, when modifying zeolite with modifier A (magnesium oxide) and modifier B (platinum), zeolite is modified with water-soluble precursor A [e.g. Mg(NO ₃ ) _{2.6H 2} O].
and Precursor B (for example, H ₂ PtCl ₆ .6H ₂ O), and then water is evaporated to support Precursor A and Precursor B on the zeolite. Also, to modify separately, U.S. Patent No. 4034053
The zeolite modified with modifier A is immersed in an aqueous or non-aqueous solution containing precursor B, and then the solvent is evaporated. Precursor B is supported on the zeolite. The zeolite on which precursor A and precursor B or modifier A and precursor B are supported is heated at 100 to 700°C, preferably in an oxygen-containing atmosphere such as air.
Heat at a temperature of 200 to 600°C for about 1 hour to about 24 hours. In use, the zeolite modified by the above method is treated under a reducing atmosphere such as hydrogen gas at a temperature of 200-600°C, preferably 250-550°C. This treatment is usually carried out after charging the catalyst into the reactor. Zeolite is treated with modifier A (magnesium oxide or lanthanide oxide) and modifier B (platinum, rhodium,
iridium) and modifier C (iron, cobalt, nickel, ruthenium, osmium, palladium,
For modification with rhenium), a compound containing precursor A, precursor B, and modifier C (hereinafter referred to as "precursor C") is used in the same manner as the method of modifying with modifier A and modifier B described above. The zeolite is immersed in a mixed aqueous or non-aqueous solution of , and then the solvent is evaporated to form precursor A, precursor B, and precursor C.
is supported on zeolite. Alternatively, zeolite modified with Modifier A and Modifier B by the method described above is immersed in an aqueous or non-aqueous solution containing Precursor C, and then the solvent is evaporated and the zeolite modified with Modifier A and Modifier B is immersed. Precursor C is supported and then fired at a temperature of 100 to 700°C, preferably 200 to 600°C, in an atmosphere containing oxygen (for example, air). When used, the zeolite modified by the above method is heated at 100 to 700°C in a reducing atmosphere such as hydrogen gas.
Preferably it is treated at a temperature of 250-550°C. This treatment is usually carried out after charging the catalyst into the reactor. In this way, the zeolite can be modified with Modifier A, Modifier B, and Modifier C. Examples of various Precursors A, Precursors B and Precursors C used to modify zeolites are shown below. It should be understood that these examples are merely illustrative and that any water-soluble or solvent-soluble compound of each modifier may be used equivalently unless otherwise specified. be. Such compounds include halides, oxides, sulfides, oxyalt salts and complexes. (1) Magnesium compounds; magnesium nitrate, magnesium acetate, magnesium chloride (2) Lanthanum compounds; lanthanum nitrate, lanthanum sulfate, lanthanum trichloride (3) Cerium compounds; cerium nitrate, cerium sulfate (4) Dysprodium compounds; dysprosium nitrate , dysprosium sulfate (5) Ytterbium compound; Ytterbium nitrate, Ytterbium sulfate (6) Platinum compound; Hexachloroplatinic acid, Platinum dichloride, 2
Tetraammine chloride platinum complex (7) Rhodium compound; Rhodium trichloride (8) Iridium compound; Iridium tetrachloride (9) Iron compound; Ferrous nitrate, ferric nitrate (10) Cobalt compound; Cobalt nitrate (11) Nickel compound ; Nickel nitrate, nickel sulfate, nickel dichloride (12) Ruthenium compounds; Ruthenium trichloride, ruthenium oxide (13) Osmium compounds; Osmic acid, osmium tetrachloride (14) Palladium compounds; Palladium dichloride, palladium sulfate, palladium nitrate, Tetraamminepalladium dichloride complex (15) Rhenium compound; rhenium oxide, rhenium trichloride The modified zeolite obtained can be in the form of a fine powder or optionally in various desired forms such as pellets or tablets as commonly used. After molding the alkylated modified zeolite into a molded body, the modified zeolite is molded into silica, alumina, silica-alumina, kaolin or silica according to a conventional method.
It is mixed with a synthetic or natural refractory inorganic oxide commonly used as a binder for zeolite catalysts such as magnesia, the mixture is shaped into the desired form, and the shaped body is then calcined. The amount of modified zeolite as active catalyst component in the compact is generally between 1 and 99 (by weight) based on the weight of the compact.
%, preferably from 10 to 90% (by weight). The catalysts prepared as described above are used alone or in combination to constitute a plurality of series-connected fixed catalyst beds separated from each other according to the method of the invention. In this case, one entire reactor filled with a catalyst can be one catalyst layer unit, or if the reactor is divided into several sections and each section is filled with a catalyst, each of the reactors in the reactor can be It is also possible for one catalyst-packed section to be one catalyst layer unit. Regardless of which type of catalyst layer unit is adopted, each catalyst layer unit is connected in series so that the gas supplied to the first stage catalyst layer passes successively through each subsequent catalyst layer. be done. The connection of each catalyst layer is
When the reaction mixture is transferred from one catalyst layer to the next, the generated xylene is not separated and removed from the reaction mixture in the middle, and the reaction mixture discharged from the catalyst layer in the previous stage is left as it is or with the amount of methyl as described below. Just by adding the converting agent, the reaction mixture is supplied to the next stage catalyst layer, and the produced xylene is separated and recovered only for the reaction mixture discharged from the final stage catalyst bed. The desired number of fixed catalyst beds in carrying out the method of the present invention is at least two, and the greater the number, the greater the effect achieved. The number is sufficient, and the number is preferably from 2 to 20, more preferably from 4 to 20. In addition, the shape and size of each catalyst layer are determined by the D/L required for the piston flow of gas passing through the catalyst layer.
[Here, D represents the diameter of the catalyst layer, and L represents the length of the catalyst layer.] It is desirable to design the catalyst layer so that the above-mentioned pellets are contained in each catalyst layer designed in this way. The catalyst, which is shaped into a shape or a tablet, can be packed in a conventional manner. The amount of the catalyst loaded into each catalyst bed depends on the scale of the plant for carrying out the method of the present invention, the size of the reactor, and the weight hourly space velocity (hereinafter abbreviated as WHSV) required for the toluene to be supplied. However, those skilled in the art will be able to easily determine this based on the disclosure of the present invention. In particular, in the present invention, it is preferable that the catalyst loading amount in each catalyst layer does not differ greatly from each other, and very generally speaking, the catalyst loading amount (Wi) in the fixed catalyst layer of the i-th stage is , the following inequality (1) [Here, Wi is the catalyst packing weight of the i-th stage fixed catalyst bed, Wm is the catalyst packing weight of the m-th stage fixed catalyst bed, and n is the total number of catalyst beds used in the method of the present invention. . ] It is preferable to adjust so as to satisfy the following inequality (2). [In the formula, Wi, Wm, m and n have the above meanings. ] can be adjusted to satisfy. In the present invention, the term "catalyst filling weight" refers to the actual weight of the catalytically active components excluding catalytically inactive components such as binders that may constitute a part of the catalyst. Toluene, which is a raw material, is supplied to the first-stage catalyst layer of the plurality of fixed catalyst layers connected as described above, together with hydrogen gas, which serves as a carrier and suppresses deterioration of catalyst activity. The amount of toluene supplied at this time is not limited and can be varied widely depending on the scale of each catalyst bed, the performance of the packed catalyst, reaction conditions, etc., but in general, the amount of toluene supplied in the multistage reaction system according to the present invention is The total WHSV of toluene in
It is advantageous to control the amount of toluene fed so that it falls within the range of ~300 hr ^-1 , preferably 2-200 hr ^-1 , more preferably 2-100 hr ^-1 . “Weight time space velocity” used in the present invention
(WHSV) is the amount (g) of substance fed onto the catalyst per unit time (hr) per unit amount (g) of catalyst.
is defined as Furthermore, the amount of hydrogen gas supplied to the first stage catalyst layer is not strictly limited and can be varied widely depending on the size of the catalyst layer, etc., but in general, the amount of toluene supplied is Suitably, on a quantity basis, it is provided in an amount ranging from 0.5 to 20 mol, preferably from 0.5 to 15 mol, more preferably from 1 to 10 mol, per mol of said toluene. Although toluene is vaporized in advance before being supplied to the first stage catalyst layer, it is possible to mix at least a portion of the hydrogen gas with this vaporized toluene before supplying it to the first stage catalyst layer. Alternatively, part or all of the hydrogen gas may be supplied to the first stage catalyst layer separately from toluene. On the other hand, according to the method of the present invention, the methylating agent used for toluene methylation is distributed to each of a plurality of series of fixed catalyst beds connected as described above. As the methylating agent that can be used to methylate toluene, any methylating agent conventionally used for nuclear methylation of aromatic hydrocarbons can be used, such as methanol, methyl halide, and dimethyl ether. Among them, methanol, dimethyl ether and mixtures thereof, particularly dimethyl ether or a mixture of methanol and dimethyl ether in any ratio are preferred. As mentioned above, one of the objects of the present invention is to increase the conversion rate of the methylating agent to xylene. Theoretically, the ratio of the methylating agent supplied to each catalyst layer is 1/t mole or less, preferably 0.02/t to 1 mole of toluene supplied to the catalyst layer. 0.5/tmol, more preferably 0.0
It is advantageous to control it within the range of 2/t to 0.3/t mol. Here, t is the number of methyl groups in the methylating agent, t=1 for methanol and methyl halide, and t=2 for dimethyl ether. To do this, the amount of toluene in the reaction mixture supplied to each catalyst layer after the second stage is quantitatively measured, and the amount of methylating agent supplied to each catalyst layer is determined according to the measurement result. Ideally, it would be difficult to determine this, but it would be industrially troublesome and the equipment would be complicated, making it impractical. As a result of the research conducted by the present inventors, the amount of methylating agent supplied to each catalyst layer is based on the amount of toluene supplied to the first stage catalyst layer, and per 1 mole of toluene,
Within the range of 0.01/t to 1/t mole, preferably 0.02/t to
0.5/t mol, more preferably within the range of 0.02/t to 0.3/t mol, where t has the above-mentioned meaning, the above-mentioned object of the present invention can be fully achieved. found. In addition, the total amount of methylating agent supplied to all catalyst layers is 1 toluene supplied to the first stage catalyst layer.
0.1/t to 2/t mole per mole, preferably 0.1/t to 1.
5/tmol, more preferably in the range from 0.1/t to 1/tmol, where t has the meaning given above. Therefore, the amount of methylating agent to be supplied to each catalyst layer can be freely selected within the above-mentioned range as long as the total amount falls within the above-mentioned range. However, it is better that the amount of methylating agent supplied to each catalyst layer is not extremely different from each other, and most preferably, the amount of methylating agent supplied to each catalyst layer is approximately the same, or the amount of methylating agent supplied to each catalyst layer is approximately equal to that of the catalyst in the subsequent stage. The methylating agent is provided in increasing amounts as the layers progress. However,
The amount of methylating agent (Qi) supplied to the i-th stage is determined by the following inequality (3). [Here, Qi is toluene 1 supplied to the first stage
represents the number of moles of the methylating agent supplied to the i-th stage per mole, Qm represents the number of moles of the methylating agent supplied to the m-th stage per mole of toluene supplied to the first stage, and t has the same meaning as above. ] It is desirable to satisfy the following, especially the following inequality (4) [In the formula, Qi, Qm and t have the above meanings. ] It is very advantageous to satisfy the following. The above amount of methylating agent can be supplied directly to each catalyst layer after being vaporized, but usually it can be supplied to the first stage catalyst layer separately from toluene and hydrogen gas, but It is appropriate to supply the mixture with toluene, and for the catalyst layers after the second stage, the reaction mixture discharged from the previous stage catalyst layer is added and mixed in advance, and a predetermined amount of water is supplied. Advantageously, it is supplied to the catalyst bed. This achieves uniform mixing of the reaction mixture and methylating agent supplied to the given catalyst bed, and also serves to cool the reaction mixture. Note that the catalytic methylation reaction of toluene is an exothermic reaction, and the reaction mixture discharged from the catalyst layer is at a considerably high temperature. Therefore, when feeding the next catalyst layer, if the reaction mixture has reached a temperature significantly higher than the desired reaction temperature, if necessary,
Hydrogen gas may be added together with the methylating agent to the excessively high temperature reaction mixture to cool the reaction mixture until the temperature drops to the desired reaction temperature described below. Alternatively, the cooling of the excessively high temperature reaction mixture to the desired reaction temperature is performed by cooling the reaction mixture discharged from the final stage catalyst layer, in combination with or alone with the cooling with hydrogen gas, The reaction may be carried out using a recycled gas from which xylene, unreacted toluene, etc. have been removed. As the conditions for the methylation reaction in each catalyst layer, the same conditions as used in the above-mentioned known method can be used. For example, the reaction temperature in each catalyst layer can generally be within the range of 250 to 700°C, preferably within the range of 300 to 600°C, and the pressure may be within the range of 1 atm to 20 atm, preferably 1 to 700°C. It is appropriate to maintain the pressure within the range of 15 atmospheres. Recovery of xylene from the reaction mixture discharged from the final stage catalyst bed can be carried out by a method known per se. For example, the reaction mixture is sufficiently cooled in a cooler and concentrated in a gas-liquid separator. Separate substances and gases. Next, the concentrated oil/water is separated and the oil is fed to a distillation column to remove unreacted toluene,
Xylene can be easily recovered by separating xylene and other side reaction products. Moreover, the catalyst whose activity has deteriorated due to implementation of the method of the present invention can be regenerated and then used again for implementation of the method of the present invention. To regenerate the catalyst, for example, after separating the reactor and removing the combustible gas, the temperature is raised while passing an inert gas such as nitrogen gas, and then air is added to control the temperature of the catalyst bed and supported on the catalyst. Remove carbonaceous material and finally 500-550
This can be easily done by raising the temperature to ℃. According to the method of the present invention described above, as is clear from the examples below, a very high conversion rate of toluene and methylating agent to xylene is achieved, and at the same time, a high conversion rate of p-xylene in the xylene isomer mixture produced is achieved. concentration, ie high p-xylene selectivity. For example, according to the process of the invention, under suitable conditions toluene conversion is at least 10%, typically between 20 and 60%.
%, and the concentration of p-xylene in the xylene isomer mixture produced is much higher than the previously known thermodynamic composition value, e.g. 80% or more, usually
It will be 70-95%. In addition, in the method of the present invention, since each catalyst layer consists of a fixed catalyst layer, the contact time can be changed arbitrarily, and cooling gas is introduced into each catalyst layer to increase the temperature of the main reaction accompanied by heat generation. Control can be performed easily. In this reaction, the reaction between the methylating agent and toluene is rapid, and while it is advantageous to shorten the contact time, shortening the contact time results in a decrease in toluene conversion, which is disadvantageous from an industrial perspective. In order to improve this disadvantage, the catalyst layer is divided into many layers,
As a result of supplying a methylating agent to each layer, it is possible to significantly improve the conversion rate of toluene, but the method of the present invention also requires that the contact time can be changed arbitrarily due to the characteristics of the reaction. . Although a fluidized bed was also investigated, a fixed bed was the most preferable in view of the characteristics of the reaction of the present invention and the controllability of the reaction, and thus the method of the present invention was arrived at. As described above, according to the present invention, since the catalyst is divided into multiple layers, the reaction heat can be easily removed.
This has the industrial advantage that partial overheating can be avoided and, moreover, the regeneration operation of the catalyst can be simplified. To explain the method of the present invention in terms of an industrially used flow, for example, toluene is set at a desired supply rate with a supply pump, separated with a gas-liquid separator, and the gas is pressurized with a circulating gas pressurizer to produce a hydrogen-containing gas. A mixed flow of toluene (hereinafter referred to as "circulating gas") is heated in a heat exchanger and then in a heating furnace. A toluene-containing circulating gas stream heated to a desired temperature is mixed with a methylating agent whose temperature and pressure have been adjusted in advance and is fed in a downward flow to a fixed bed flow reactor. In a fixed bed reactor, the inside of one reactor may be divided into a plurality of catalyst beds, or the reactor may be divided into a plurality of reactors or a plurality of catalyst beds. A thermocouple for measuring the temperature of each catalyst layer is installed to facilitate control of reaction temperature (control of regeneration conditions during regeneration). The flow from the first catalyst layer is
A nozzle for supplying the methylating agent and the circulating gas necessary for cooling is installed in the flow path that supplies the layer to ensure complete mixing of the flow from the first catalyst layer with the methylating agent and cooling gas. It is desirable to do so.
A commonly used distributor at the inlet of the catalyst bed and a collector installed at the outlet can be used. Blow equipment for methylating agent and cooling gas is installed between each reaction layer to supply the desired methylating agent and cooling gas, but the amount of cooling gas is determined according to the indication from the thermocouple installed in the reactor. It can be decided based on the relationship. The stream exiting the series of reaction beds is cooled in a heat exchanger and then passed through a cooler to a gas-liquid separator as a mixed stream of condensate and gas. The gas separated by the gas-liquid separator is pressurized by a ring gas pressurizer and supplied as a flow to be mixed with toluene and cooling gas, and excess gas is taken out of the system. If the desired hydrogen/toluene molar ratio is lower than hydrogen, it is necessary to introduce hydrogen before or after the recycle gas pressurizer. When the methylating agent is an oxygen-containing compound, water may be separated in the gas-liquid separator, and in this case, it is desirable to install equipment for oil-water separation. The oil layer condensed in the gas-liquid separator is supplied to a distillation column to mainly separate toluene and xylenes.
At the top of the distillation column, a gas and a condensate consisting mostly of toluene are separated. The condensate containing mostly toluene may be used as a raw material for methylation as it is, or the low-boiling fraction may be separated and then the fraction containing mostly toluene may be methylated and supplied. The bottom fraction of the distillation column is fed to a xylene separator and can be separated into xylenes and C ⁺ ₉ aromatics. The xylenes are fed to a p-xylene separation device, and finally become more than 99% p-xylene. As a method for separating p-xylene, for example, the so-called p-xylene adsorption method using a molecular sieve or the crystallization method using crystallization of p-xylene can be used for purification by supplying the p-xylene to an optimal supply port. In addition, the p-xylene concentration in the circulating liquid supplied to the process for separating p-xylene is about 20% by weight in a normal method, but it becomes about 80% by weight or more in the method of the present invention, It will be readily appreciated that the equipment efficiency of the process for the separation of xylene is improved in gas width. The method of the present invention will be described in detail below with reference to Examples. Example 1 Zeolite ZSM-5 (hereinafter simply referred to as ZSM-5) was synthesized according to Example 1 of US Pat. No. 3,965,207. After baking ZSM-5 in air at 500℃ for 16 hours, 20g was heated to 80℃ with 200c.c. of 1M-NH ₄ Cl solution.
Ion exchange was performed for 24 hours. Thereafter, it was thoroughly washed with water, dried at 100°C, and further baked in air at 500°C for 16 hours. This H-type ZSM-5 has a crystal diameter within the range of 0.1 to 2 microns, and the molar ratio of SiO ₃ /Al ₂ O ₃ is
65, the α-value was at least 10,000, and the storage capacity ratio (weight) of cyclohexane/n-hexane at 25°C was 0.7. Further, the content of remaining alkali metals and alkaline earth metals was 0.01% by weight. This α value is based on the activity of ZSM-5 at 540°C (a value calculated by measuring the activity at a temperature of 200 to 250°C and assuming the activation energy is 30 Kcal/mol) and the silica alumina catalyst at 540°C. The activity was determined by comparing the activity with that of N631-HN (manufactured by JGC Corporation). Synthesis of Catalyst A 0.5 g of the above H-type ZSM-5 powder was suspended in a solution containing 0.64 g of Mg(NO ₃ ) 2.6H ₂ O in 10 ml _of water.
This was left overnight while being heated at 80°C, and then water was evaporated over 4 hours using an evaporator. Thereafter, firing was performed at 500° C. for 16 hours in an air atmosphere. As a result, catalyst A modified with MgO was obtained. The catalyst contained 20.0% by weight of magnesium or its oxide, based on the weight of ZSM-5 in Form H. The fired product was molded and ground into 10 to 20 mesh pieces for use. The α value of this catalyst was 60, and the storage capacity ratio (weight) of cyclohexane/n-hexane was 0.44. Synthesis of Catalyst B Catalyst B containing 5.0% by weight of magnesium or its oxide was synthesized according to the synthesis method of Catalyst A. Synthesis of Catalyst C 0.5 g of _the above H-type ZSM-5 powder was suspended in a solution of 0.50 g of La(NO ₃ ) 3.6H ₂ O in 10 ml of water.
This was left overnight while being heated at 80°C, and then the moisture was evaporated. Thereafter, it was fired in air at 500°C for 16 hours. As a result, Catalyst C modified with La ₂ O ₃ was obtained. Catalyst C contained 37.6% by weight of lanthanum or its oxide, based on the weight of Form H ZSM-5. The fired product was molded and ground into 10 to 20 mesh pieces for use. Synthesis of Catalyst D Catalyst D containing 20.2% by weight of lanthanum or its oxide was synthesized according to the synthesis method of Catalyst C. Synthesis of Catalyst E Catalyst E containing 39.4% by weight of dysprosium or its oxide was synthesized according to the synthesis method of Catalyst C, except that 0.46 g of Dy(NO ₃ ) ₃ ·5H ₂ O was used. Synthesis of Catalyst F Catalyst F containing 37.1% by weight of cerium or its oxide was synthesized according to the synthesis method of Catalyst C, except that 0.49 g of Ce(NO ₃ ) ₃ ·6H ₂ O was used. Synthesis of Catalyst G Catalyst G containing 40.4% by weight of ytterbium or its oxide was synthesized according to the synthesis method of Catalyst C, except that 0.44 g of Yb(NO ₃ ) 3.4H _{2 O} was used. Synthesis of Catalyst H 0.16 g of _Mg (NO ₃ ) 2.6H ₂ O in 10 ml of water and
Add the above H into a solution containing 6.63 g of H ₂ PtCl _{6 .}
0.5 g of type ZSM-5 powder was suspended. This is 80℃
After leaving it overnight while heating, the water was evaporated. Thereafter, baking was performed at 500° C. for 16 hours in an air atmosphere. Catalyst H was synthesized by molding the calcined product and pulverizing it into 10 to 20 meshes. Synthesis of Catalyst I 0.27 g of La(NO ₃ ) _{3.6H 2} O in 10 ml of water and
Catalyst I was synthesized according to the synthesis method for Catalyst H, except that a solution containing 6.63 mg of H ₂ PtCl ₆ .6H ₂ O was used. Synthesis of Catalyst J 0.16 g of _Mg (NO ₃ ) 2.6H ₂ O in 10 ml of water and
Catalyst J was synthesized according to the synthesis method of Catalyst H, except that a solution containing 6.41 mg of RhCl ₃ .3H ₂ O was used. Synthesis of catalyst K 0.16 g of Mg(NO ₃ ) 2.6H ₂ O _and IrCl ₄ in 10 ml of water
Add 0.5 of the above ZSM-5 powder to a solution containing 4.34 mg of
g was suspended. This was left overnight at room temperature, and then the water was evaporated. After that, heat at 500℃16 in an air atmosphere.
Time firing was performed. Catalyst K was synthesized by molding the calcined product and pulverizing it into 10 to 20 meshes. Synthesis of catalyst L 0.16 g _of Mg(NO ₃ ) 2.6H ₂ O in 10 ml of water,
0.5 g of the above H-type ZSM-5 powder was suspended in a solution containing 6.63 mg of H ₂ PtCl ₆ .6H ₂ O and 2.13 mg of IrCl ₄ . This was left overnight at room temperature, and then the water was evaporated. Thereafter, firing was performed at 500° C. for 16 hours in an air atmosphere. Catalyst L was synthesized by molding the calcined product and pulverizing it into 10 to 20 meshes. Synthesis of catalyst M 0.16 g _of Mg(NO ₃ ) 2.6H ₂ O in 10 ml of water,
_6.63 mg _{of H2PtCl6.6H2O} and _Ni ( _NO3 ) _2.6H2O
Add the above H-type ZSM-5 powder to a solution containing 1.86 mg of
0.5g was suspended. After this was left at 80°C overnight, the water was evaporated. After that, under an air atmosphere
Firing was performed at 500°C for 16 hours. Mold the baked product 10
Catalyst M was synthesized by grinding to ~20 meshes. Example 2 2.0 g of catalyst A was packed into the first stage of a multi-stage fixed bed flow reactor equipped with reaction tubes capable of stacking 10 catalyst layers and supplying raw materials to each catalyst layer.
Toluene was supplied at a rate of 20.0 g/HR and methanol at 3.5 g/HR at 500° C. under normal pressure (experiment a).
Next, 1.0 g each of catalyst A was packed into the first and second stages of the multi-stage fixed bed flow reactor, and
Toluene was added to the first stage at a rate of 20 g/HR and methanol was added to the second stage at a rate of 1.75 g/HR at 500°C.
Methanol was fed to the stage at a rate of 1.75 g/HR (experiment b). The results of experiments a and b are listed in Table 1 below. It can be seen that experiment b was superior to experiment a in terms of toluene conversion, p-xylene selectivity, methanol selectivity, and xylene yield. Here, toluene conversion rate, p-xylene selectivity,
The methanol selectivity and the xylene yield are each defined by the following formulas, and are similarly defined in the following examples. Toluene conversion rate (%) = [Number of moles of toluene converted/Number of moles of toluene fed] x 100 p-xylene selectivity (%) = [Number of moles of p-xylene produced/Number of moles of xylene produced] ×100 Methanol selectivity (%) = [Number of moles of xylene produced/Number of moles of methanol fed] ×100 Xylene yield (%) = [Number of moles of xylene produced/
Number of moles of toluene converted〕×100

[Table] Note) Reaction time: 1 hour Example 3 Catalyst A was packed into the multistage fixed bed flow reactor used in Example 2, and the following experiments a to d were conducted.
The reaction was carried out at 500° C. under normal pressure in all cases. Further, the total methanol/toluene molar ratio in experiments a to d was 1/2 in all cases. Experiment a: The first layer of the reactor was filled with 1.0 g of catalyst,
A mixture with a methanol/toluene molar ratio of 1/2 was supplied with a WHSV value in the range of 10 to 100. Experiment b: 1.0 g of catalyst in the first and second layers of the reactor
A mixture with a methanol/toluene molar ratio of 1/4 with a WHSV value of 10 to 100 is supplied to the first layer, and the same amount of methanol as supplied to the first layer is supplied to the second layer. supplied. Experiment c: 1.0 g of catalyst in the first to fifth layers of the reactor
A mixture with a methanol/toluene molar ratio of 1/10 with a WHSV value in the range of 10 to 100 is supplied to the first layer, and the same amount as that supplied to the first layer is supplied to the second to fifth layers. of methanol was supplied. Experiment d: 1.0 g of catalyst in the 1st to 10th layers of the reactor
, and the first layer is supplied with a mixture of methanol/toluene molar ratio / with a WHSV value in the range of 10 to 100, and the second to tenth layers are supplied with the same amount of methanol as that supplied to the first layer. was supplied. Here, WHSV is the amount (g) of toluene supplied per unit catalyst amount (g) per unit time (hr),
The same applies to the following examples. Tables 2 and 3 below show the concentrations of p-xylene in the xylene of the reaction mixtures of experiments a to d, respectively.
The toluene conversion rate, methanol selectivity, and xylene yield at 80% and 85% are shown.

[Table] Note) Reaction time 1 hour

[Table] Note) Reaction time: 1 hour Table 4 below shows toluene conversion rates for experiments a to d.
The p-xylene selectivity, methanol selectivity, and xylene yield at 16% are shown.

[Table] Note) Reaction time: 1 hour As shown in Tables 2 to 4, p-xylene selectivity can be increased at the same toluene conversion rate by using multiple catalyst layers, and the p-xylene selectivity can be increased at the same toluene conversion rate.
If a xylene selective xylene mixture is obtained, higher toluene conversion and higher methanol selectivity are possible. Example 4 1.0 g each of catalyst B was packed into the first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2,
A mixture of methanol/toluene with a molar ratio of 1/10 is supplied to the first layer and the WHSV value ranges from 10 to 200.
The same amount of methanol as that fed to the first layer was fed to the layers to the fifth layer. The reaction was conducted at 500℃ under normal pressure.
It was carried out at The results are listed in Table 5 below.

[Table] Example 5 The first to fifth layers of the multistage fixed bed flow reactor used in Example 2 were each filled with 1.0 g of catalyst C.
A mixture with methanol/toluene molar ratio of 1/10 was supplied to the first layer with a WHSV value in the range of 100 to 2000, and the same amount of methanol as supplied to the first layer was supplied to the second to fifth layers. . The reaction was carried out at 500℃ under normal pressure.
It was carried out at The results are listed in Table 6 below.

[Table] As shown in Tables 5 and 6,
By increasing WHSV, p-xylene selectivity can be increased, and by decreasing WHSV, toluene conversion rate and methanol selectivity can be increased. Example 6 1.0 g each of catalyst A was packed into the first and second layers of the multistage fixed bed flow reactor used in Example 2,
A mixture with a methanol/toluene molar ratio in the range of 1/20 to 1/1 at 500°C under normal pressure and a WHSV value of 25 was first prepared.
The second layer was each fed the same amount of methanol as was fed to the first layer. The results are listed in Table 7 below.

[Table] Note) Reaction time: 1 hour Example 7 1.0 g each of catalyst A was packed into the 1st to 10th layers of the multi-stage fixed bed flow reactor used in Example 2.
A mixture with a methanol/toluene molar ratio in the range of 1/20 to 1/4 at 500°C under normal pressure and a WHSV value of 25 was first prepared.
The same amount of methanol as that supplied to the first layer was supplied to each of the second to tenth layers. The results are listed in Table 8 below.

[Table] Note) Reaction time: 1 hour As shown in Tables 7 and 8, increasing the methanol/toluene ratio can increase the toluene conversion rate, and decreasing the methanol/toluene ratio can increase the methanol selectivity. . Example 8 1.0 g each of catalyst A was packed into the first and second layers of the multistage fixed bed flow reactor used in Example 2,
Supplying hydrogen to the first layer at a hydrogen/toluene molar ratio of 0 to 8.75 together with a mixture of methanol/toluene molar ratio 1/4 at 500°C under normal pressure and a WHSV value of 23,
The second layer was fed with the same amount of methanol as was fed to the first layer. The results are listed in Table 9 below.

[Table] Note: Reaction time: 1 hour From Table 9 above, it can be seen that p-xylene selectivity, methanol selectivity, and xylene yield can be increased by using hydrogen as a carrier. Example 9 The first and second layers of the multi-stage fixed bed flow reactor used in Example 2 were each filled with 1.0 g of catalyst A,
A mixture with a methanol/toluene molar ratio of 1/4 was supplied to the first layer at 500°C under normal pressure and a WHSV value of 23.
The layer was fed with the same amount of methanol as was fed to the first layer. Furthermore, hydrogen equivalent to three times the mole amount of the fed toluene was divided and supplied to the first layer and the second layer. The results are listed in Table 10 below.

[Table] Note) Reaction time: 1 hour As shown in Table 10, it is preferable to supply hydrogen as a carrier to the first layer as much as possible. Example 10 The first and second layers of the multistage fixed bed flow reactor used in Example 2 were each filled with 1.0 g of catalyst A,
Toluene was supplied to the first layer at 500° C. and a WHSV value of 23 under normal pressure. Furthermore, methanol corresponding to the amount of toluene fed/mole was divided and supplied to the first layer and the second layer. The results are listed in Table 11 below.

[Table] Note) Reaction time: 1 hour Example 11 1.0 g each of catalyst A was packed into the first to third layers of the multi-stage fixed bed flow reactor used in Example 2.
Toluene was supplied to the first layer at 500° C. and a WHSV value of 23 under normal pressure. Furthermore, methanol equivalent to 1/2 mole of the amount of toluene in the methanol/toluene feed was divided and supplied from the first layer to the third layer. The results are listed in Table 12 below.

[Table] Note) Reaction time: 1 hour From Tables 11 and 12, it can be seen that it is preferable to increase the amount of methylating agent supplied to each layer as it approaches the later stages. Example 12 Using the multistage fixed bed flow reactor used in Example 2, 0.8 g of catalyst A was charged in portions, and toluene was added to the first layer at a rate of 9.21 g/HR at 500°C under normal pressure. 0.80g/methanol is supplied to the second layer.
Feed at HR rate. The results are listed in Table 13 below.

[Table] From Table 13, it can be seen that the amount of catalyst packed in each stage is preferably approximately equal. Example 13 1.0 g each of catalyst E was packed into the first to fifth layers of the multistage fixed bed flow reactor used in Example 2,
At 500°C under normal pressure, a mixture with a WHSV value of 775 and a molar ratio of methanol/toluene of 1/10 was supplied to the first layer, and the same amount of methanol as supplied to the first layer was supplied to the second to fifth layers. supplied. The results are shown below.
Listed in Table 14. Example 14 The reaction was carried out according to the method of Example 13, except that catalyst F was used. The results are listed in Table 14 below.

Table 14 shows that by using a catalyst containing lanthanide oxide, the selectivity of p-xylene can be made much higher than the normal thermodynamic equilibrium concentration. Example 15 1.0 g each of catalyst B was packed into the first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2,
At 500℃ under normal pressure, a mixture of methanol/toluene molar ratio = 1/10 with a WHSV value of 68 is supplied to the first layer together with hydrogen of hydrogen/toluene = 10.5, and the second to fifth layers are supplied to the first layer. The same amount of methanol was supplied. The results are listed in Table 15 below.

[Table] Example 16 The reaction was carried out in the same manner as in Example 15, except that catalyst D was used. The results are shown in Section 16 below.
Listed in the table.

[Table] From Tables 15 and 16 above, catalyst B and catalyst D
has a relatively short active life. Example 17 1.0 g each of catalyst H was packed into the first to fifth layers of the multistage fixed bed flow reactor used in Example 2,
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
As a result, the catalyst was 0.5% by weight based on the zeolite.
of platinum and 5.0% by weight of magnesium or its oxide. Next, WHSV at 500℃ under normal pressure
At a value of 68, a mixture of methanol/toluene molar ratio = / was fed together with hydrogen in a hydrogen/toluene molar ratio = 10.5, and the second to fifth layers were fed with the same amount of methanol as was fed to the first layer. The results are listed in Table 17-1 below.

[Table] As can be understood from Table 17-1 above, the life of the catalyst can be further extended by further modifying the catalyst modified with magnesium oxide with platinum. In addition, the material balance for a reaction time of 106 hours is listed in Table 17-2 below.

[Table] As shown in Table 17-1 above, the method of the present invention has a toluene conversion rate of 27.9 per 100 parts by weight of toluene supplied.
parts by weight, p-xylene production is 25.1 parts by weight, and per 100 parts by weight supplied in normal xylene isomerization, p-
10 parts by weight of xylene, toluene transalkylation method, which has a toluene conversion rate of 45 parts by weight per 100 parts by weight of toluene supplied and 11 parts by weight of p-xylene, has higher equipment efficiency for the purpose of synthesizing p-xylene. It should be understood that this is an industrially advantageous method. Example 18 1.0 g each of catalyst I was packed into the first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2,
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours. The catalyst contains 0.5% by weight of platinum and 5.0% by weight of lanthanum or its oxide based on the zeolite. Next, a reaction was carried out under the same conditions as in Example 17. The results are listed in Table 18 below.

[Table] Table 18 shows that the active life of the catalyst can be extended by further modifying the catalyst modified with lanthanum oxide with platinum. Example 19 1.0 g each of catalyst J was packed into the first to fifth layers of the multistage fixed bed flow reactor used in Example 2,
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
As a result, the catalyst was 0.5% by weight based on the zeolite.
of rhodium and 5.0% by weight of magnesium or its oxide. Next, a reaction was carried out under the same conditions as in Example 17. The results are listed in Table 19 below.

[Table] From Table 19, the life of the catalyst can be extended by further modifying the catalyst modified with magnesium oxide with rhodium. Example 20 The first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2 were each filled with 1.0 g of catalyst K.
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
As a result, the catalyst was 0.5% by weight based on the zeolite.
of iridium and 5.0% by weight of magnesium or its oxide. Next, a reaction was carried out under the same conditions as in Example 17. The results are listed in Table 20 below.

[Table] As shown in Table 20, the life of the catalyst can be extended by further modifying the catalyst modified with magnesium oxide with iridium. Example 21 The first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2 were filled with 1.0 g of catalyst L, and reduced in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
As a result, the catalyst was 0.5% by weight based on the zeolite.
of platinum, 0.25% by weight of iridium and 5.0% by weight of magnesium or its oxide. Next, a reaction was carried out under the same conditions as in Example 17. The results are listed in Table 21 below.

[Table] As shown in Table 21, by further modifying the catalyst modified with magnesium oxide with platinum and iridium, the life of the catalyst can be extended, and the toluene conversion at the initial stage of the reaction is greater than when modified with platinum alone. It is possible to increase the rate. Example 22 The first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2 were filled with 1.0 g of catalyst M, and reduced in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
As a result, the catalyst was 0.5% by weight based on the zeolite.
of platinum, 0.08% nickel and 5.0% by weight
Contains magnesium or its oxide. Next, a reaction was carried out under the same conditions as in Example 17. The results are listed in Table 22 below.

[Table] As shown in Table 22, by further modifying the catalyst modified with magnesium oxide with platinum and nickel, the life of the catalyst can be extended, and the toluene conversion rate at the initial stage of the reaction is higher than when modified with platinum. can be made higher. Example 23 Catalyst B was packed at 1.0 g each into the first to seventh layers of the multistage fixed bed flow reactor used in Example 2, and the first layer was charged with a methanol/toluene molar ratio of 1/1.
A mixture of 10 was passed with a WHSV value of 75. The same amount of methanol as that supplied to the first layer was supplied to the second to seventh layers. The reaction was carried out at 450℃ and under normal pressure.
It was carried out at 500℃. The results are listed in Table 23 below.

[Table] Example 24 1.0 g each of catalyst H was packed into the first to fifth layers of the multi-stage fixed bed flow reactor used in Example 2,
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
The catalyst is 0.5% by weight of platinum and zeolite.
Contains 5.0% by weight of magnesium or its oxide. Next, the first reaction was carried out at a reaction pressure of 2 Kg/cm ² G and 500°C.
A mixture of methanol/toluene molar ratio = 1/10 with a toluene standard WHSV value of 68 was supplied to the layer together with hydrogen of a hydrogen/toluene molar ratio = 10.5, and the same amount as that supplied to the first layer was supplied to the second to fifth layers. of methanol was supplied. The results are listed in Table 24 below.

[Table] Example 25 The first and second layers of the multistage fixed bed flow reactor used in Example 2 were each filled with 1.0 g of catalyst F.
Reduction was carried out in a hydrogen atmosphere at 400°C under normal pressure for 2 hours.
The catalyst is 0.5% by weight of platinum and zeolite.
Contains 5.0% by weight of magnesium or its oxide. Next, the first layer was heated to 500℃ under normal pressure with a WHSV value of 34.
Toluene to dimethyl ether/toluene ratio=
It was fed together with 1/8 dimethyl ether and hydrogen at a hydrogen/toluene ratio of 8.8, and the second layer was fed with the same amount of dimethyl ether as the first layer. The results are listed in Table 25 below.

[Table] Here, dimethyl ether selectivity is defined by the following formula. Dimethyl ether selectivity = [moles of xylene produced/moles of dimethyl ether fed] x 100/2 Table 25 shows that dimethyl ether is advantageous as a methylating agent. Example 26 The following experiments a to d were conducted using catalysts A and B. Experiment a: 1.0% of catalyst A was added to each of the first and second layers of the multistage fixed bed flow reactor used in Example 2.
A mixture of methanol/toluene = 1/4 was supplied to the first layer at a WHSV value of 11.5 based on toluene at 500°C under normal pressure, and the same amount as that supplied to the first layer was supplied to the second layer. of methanol was supplied. Experiment b: The first layer of the multistage fixed bed flow reactor used in Example 2 was filled with 1.0 g of catalyst A, and the second layer was filled with 1.0 g of catalyst B, and a reaction was carried out under the same conditions as in experiment a. Experiment c: The first layer of the multistage fixed bed flow reactor used in Example 2 was filled with 1.0 g of catalyst B, and the second layer was filled with 1.0 g of catalyst A, and the reaction was carried out under the same conditions as in experiment a. Experiment d: 1.0% of catalyst B was added to each of the first and second layers of the multistage fixed bed flow reactor used in Example 2.
The reaction was carried out under the same conditions as in experiment a. The results of experiments a to d are listed in Table 26 below.

[Table] As shown in Table 26, the performance of the methylation reaction can be changed by filling each catalyst layer with different types of catalysts. Example 27 The following experiments a to c were conducted using catalysts H, K, and L. Experiment a: 1.0% of catalyst H was added to each of the first and second layers of the multistage fixed bed flow reactor used in Example 2.
gram each. After reduction in a hydrogen atmosphere at 400°C under normal pressure for 2 hours, methanol/toluene = methanol/toluene was added to the first layer at 500°C under normal pressure with a WHSV value of 35.
A 1/4 mixture was fed with hydrogen in a hydrogen/toluene ratio of 10.5, and the second layer was fed with the same amount of methanol as was fed to the first layer. Experiment b: The first layer of the multi-stage fixed bed flow reactor used in Example 2 was filled with 1.0 g of catalyst H, and the second layer was filled with 1.0 g of catalyst K, and the reaction after hydrogen reduction was carried out under the same conditions as in experiment a. carried out. Experiment c: The first layer of the multistage fixed bed flow reactor used in Example 2 was filled with 1.0 g of catalyst H, and the second layer was filled with 1.0 g of catalyst L, and the reaction after hydrogen reduction was carried out under the same conditions as in experiment a. carried out. The results of experiments a, b, and c are listed in Table 27 below. In experiments b and c, the toluene conversion rate at the initial stage of the reaction was superior to that in experiment a.

【table】

Claims (1)

[Claims] 1. A method for producing p-xylene by methylating toluene with a methylating agent in the gas phase, comprising: (a) a plurality of fixed catalysts connected in series separated from each other; (b) The toluene is supplied together with hydrogen gas only to the first fixed catalyst bed, and the subsequent fixation (c) The methylating agent is passed through the fixed catalyst layer in sequence, and the amount of toluene supplied at that time is such that the total weight hourly space velocity is in the range of 1 to 300 hr ^-1 . The methylating agent is supplied to each of the catalyst layers, and the methylating agent is supplied to each of the catalyst layers.
Within the range of 0.01/t mol to 1/t (where t is the number of methyl groups in the methyl agent) per mol of toluene supplied to the first stage catalyst layer, and The total amount of the methylating agent supplied is within the range of 0.1/t mol to 2/t mol (where t has the above meaning) per 1 mol of toluene supplied to the first stage catalyst layer. can be,
and (d) a method characterized in that each fixed catalyst bed is filled with a catalyst made of crystalline aluminosilicate containing magnesium oxide or lanthanide oxide. 2. The method of item 1, wherein the multistage reaction system comprises 2 to 20 fixed catalyst beds. 3. The first toluene is supplied in an amount such that the total weight hourly space velocity is in the range of 2 to 200 hr ^-1 .
Section method. 4 The amount of hydrogen gas supplied to the fixed catalyst bed in the first stage is equal to the amount of toluene supplied to the fixed catalyst bed in the first stage.
The method of paragraph 1, wherein the amount is 0.5 to 20 moles per mole. 5 The amount of the methylating agent supplied to each catalyst layer is the first
per mole of toluene supplied to the stage catalyst layer
2. The method of claim 1, wherein t has the meaning given above. 6 Amount of methylating agent supplied to stage i (Qi)
is the following formula [Here, Qi is toluene 1 supplied to the first stage
represents the number of moles of the methylating agent supplied to the i-th stage per mole, Qm represents the number of moles of the methylating agent supplied to the m-th stage per mole of toluene supplied to the first stage, and t has the same meaning as above. ] The method of the first term that satisfies the following. 7 The total amount of methylating agent supplied to all catalyst layers is
0.1/t per mole of toluene supplied to the first stage
The method of item 1, wherein the amount is within the range of mol to 1.5/t mol. 8. The method of item 1, wherein the methylating agent is methanol or dimethyl ether or a mixture thereof. 9 The crystalline aluminosilicate contains at least 10
The method of claim 1, having a silica/alumina molar ratio of . 10. The method of claim 1, wherein the catalyst contains 1 to 100% by weight magnesium oxide, based on the weight of the aluminosilicate. 11. The method of paragraph 1, wherein the catalyst contains 1 to 200% by weight of lanthanide oxide, based on the weight of the aluminosilicate. 12. The method of paragraph 1, wherein the catalyst has an alpha value within the range of 1 to 1000. 13. The method of clause 1, wherein the catalyst has a storage capacity ratio (by weight) of cyclohexane to n-hexane at 25°C ranging from 0.05 to 0.7. 14. The method of item 1, wherein the catalyst further contains platinum, rhodium or iridium. 15. The process of claim 14, wherein the catalyst contains from 0.1 to 5% by weight of platinum, rhodium and/or iridium, based on the weight of the aluminosilicate. 16 The crystalline aluminosilicate is a zeolite
The method of the first term which is ZSM-5. 17 Catalyst loading amount of i-stage fixed catalyst bed (Wi)
is the following formula [Here, Wi is the catalyst packing weight of the i-th stage fixed catalyst bed, Wm is the catalyst packing weight of the m-th stage fixed catalyst bed, and n is the total number of catalyst beds used in the method of the present invention. . ] The method of paragraph 7 that satisfies the following. 18. The method of item 1, wherein the temperature within each catalyst layer is maintained within the range of 250°C to 700°C. 19. The method of item 1, wherein the pressure within each catalyst layer is maintained within the range of 1 atm to 20 atm.