PL124493B1 - Process for catalytic isomerization in vapour phase of methyl-substituted aromatic hydrocarbons - Google Patents

Description

The present invention relates to a gas-phase catalytic isomerization of methyl-substituted aromatic hydrocarbons in the presence of a catalytic composition containing a crystalline aluminosilicate zeolite. Catalytic rearrangement of alkyl groups in alkylaromatic hydrocarbons, aimed at obtaining one or more chemical or petrochemical products. hitherto carried out in the presence of a variety of catalysts. Acid halides such as aluminum chloride, aluminum bromide and mixtures of boron trifluoride with fluorine have been used to rearrange alkylbenzenes to obtain valuable intermediates in the manufacture of synthetic rubbers, plastics, fibers and dyes. silica catalysts of the cracking contact type, such as aluminosilicate and clays and platinum supported on an aluminosilicate support. Many catalysts have at least one of the desirable characteristics of an isomerization catalyst, but most of the practical disadvantages also suffer from a number of disadvantages. For example, acid halides such as aluminum chloride only partially dissolve in the feed and easily escape from the reaction zone. Furthermore, these catalysts are economical due to their extremely corrosive action and the need to isolate their 7 products. Other heterogeneous catalysts, such as aluminosilicate contacts, platinum on alumina 10 15 20 25 80, etc., are not acidic enough to ensure conversion to a sufficient degree and require that the reaction be carried out at relatively high temperatures, above 424-510 ° C. Under these conditions, coke is rapidly formed, which lowers the yield of the desired product reaction and necessitates frequent regeneration of the catalyst in order to remove coke gas. The effect of this is a reduction in the time spent on isomerization and a high consumption of the catalyst rapidly losing its activity. Heterogeneous catalysts, such as crystalline alumina silicates, synthetic and natural, are sufficiently acidic, but are quickly lost activity due to the formation of coke and are poorly selective, which in the formation of excessive amounts of disproportionation products in isomerization reactions. One of the methods of xylene isomerization is the method called Octafining, widely described in the literature, from sources such as PMPitts, JE Gonnor, L.N. Leun, Ind. Eng. Chem. 47, 770 (1955); MJ. Fowle, R.D. Bent, B.E. Miller, paper presented at the IV World Petroleum Congress in Rome, June 1955; F.G. Ciapetta, W.H. Buck, Pat. St. US AP No. 2 589 189, F.G. Ciapetta, Pat. St. US AP No. 2,550,531 (1951) and Octafining Process, Process Issue, Petroleum Refinery, 1st Vol. 38 (1959), No. 11, Nov., p. 278. The catalyst used in these processes is silica-supported platinum, in a mixture with alumina. An improved catalyst for the isomerization plant Octa 124 493 124 493 3 is described in the United States Patent No. 3,856,872. It is a mixture of zeolite, ZSAjbS, and scavenging as alumina, the catalytic composition containing about 10-65% by weight of zeolite. Reactions in the presence of this catalyst are carried out at high spatial velocities. A certain part of the xylene is lost in the presence of this catalyst, due to the "disproportion of xylenes and their transalkylation to ethylbenzene. Metal from group VIII of the boundary system of elements is included in the catalysis. 10 of the thorium containing ZSM-5 mainly as a hydrogenation component in the presence of hydrogen inhibits the formation of coke and increases the stability of the catalytic composition. U.S. Patent No. 3,856,873 describes a method of carrying out the isomerization of alkylaromatic hydrocarbons in the gas phase without the addition of hydrogen, and in the presence of A catalyst composition containing 65% by weight of zeolite of the ZSM-5 type. The zeolite of ZSM-5 is described in US Patent No. 3,702,886 (October 14, 1972). ZSM-5 in a preferred form for the preparation of the composition. used in the process according to the invention is represented by the formula below illustrating the molar ratios of t1 in this material in the anhydrous state: (0.9 ± 0.2 / M2) n 0: Al 2 O 3: x SiO 2, in which M is a group consisting of a mixture of alkali metal cations, especially sodium and tetraalkylammonium cations with alkyl radicals carbon atoms, preferably 2 to 5 carbon atoms, and x has a value of at least 5. Especially preferred is a zeolite which in the anhydrous state is represented by the formula (0.9 ± 0.2) M2 / nO: Al2O3 = ZSiO2, where Z has a value of at least 30 to 350 or more. Other zeolites constituting a component of the catalyst composition used in the process of the invention are also known. The ZSM-11 zeolite is described in US Patent No. 3,709,979-1. 1973), the scope of which is for reference to the present application. * ° ZSM-11 in the preferred form for the preparation of the catalyst composition used in the process according to the invention is represented by the following formula expressing the molar ratios of the oxides in the anhydrous state: (0.9 ± 0.3) M2 / nOAl2O3- (20 - * - 90) SiO2, in which M 'is a mixture of at least one quaternary cation of an element of group VA of the periodic system and alkali metal cations, especially sodium. Primary cations may be present in the zeolite in such quantity that the proportion of quaternary metal cations is 10-90% of the total amount of cations. This zeolite can therefore be represented by the formula (0.9 ± 0.2) [xXR4 + (l-x) M2 / nO]: Al3O3: (20-h90) SiO2, where R is an alkyl radical of 1-7 carbon or aryl atoms, M is an alkali metal cation, X is an element from the V-A group, especially a metal, and x has a value from 0.1 to 0.9. The ZSM-12 zeolite is described in the patent specification. United States No. 3,823,449 (August 27, 1974), the scope of which is a reference to the present ZSM-35 zeolite is described in the United States Patent No. 4,016,245. Molar ratios of oxides in this zeolite in anhydrous state can be expressed by the formula (0.3- ^ 2.5) RaO: (0 + 0 , 8-20 A303 x SiO 2, w- -4 wherein R is an atom-containing organic cation. of nitrogen, M is an alkali metal cation, and x is greater than 8 and is determined by the X-ray diffraction pattern of the zeolite powder. The ZSM-35 zeolite in a preferred embodiment is represented by the anhydrous mole ratio of the oxides by the formula (0.4-2.5 ) R2O: (O ^ -0.6) M2O: Al2O3: y SiO2, where R is an organic cation containing a nitrogen atom, derived from ethylenediamine, pyrrolidine, butylenediamine or an N-methylpyridinium derivative such as hydroxide, sulfate, nitrate or a halide (e.g., bromide, chloride or iodide), M is an alkali metal atom, especially sodium, and y has a value greater than 8 to about 50. The ZSM-38 zeolite is shown in U.S. Patent No. 4,046,859. Mole ratios of oxides including zeolite in anhydrous state m *% ± rya, express by the formula (0.3 - * - 2.5) R20: (OH-0.8) M2O: Ala03:: xSiO2, in which R is an organic cation containing a nitrogen atom , and x is greater than 8, M is an alkali metal cation and is circular ZSM-38 zeolite in a preferred embodiment is represented by the following formula which describes the anhydrous mole ratio of the oxides. (0.4 - * - 2.5) 1 ^ 0:: (0 - 0.6) M2O: Al2O3: y SiO2, where R is an organic cation containing a nitrogen atom, derived from the 2- (hydroxyalkyl) derivative Tralkylammonium, as alkyl radicals containing methyl, ethyl or combinations thereof, M is an alkali metal atom, especially sodium, and y has a value greater than 8 to about 50. US Patent No. 3,702,886 ZSM zeolite - the formula CR20 M'2 / nO) is given in: (Al2O3) x: (SiO2) Y: (M'2 / nO) z, where the ratio W / X is greater than 0.5 and less than 3 , the ratio Y / X is greater than 20, the ratio Z / X is greater than zero and less than 100, R is a nitrogen-containing cation and n is the value of M 'and M ". R may be ammonium cations and derived from primary amines containing 2-1 * 0 carbon atoms, preferably a tetraalkylammonium cation with alkyl groups containing 2 to 5 carbon atoms. M 'represents a metal from Group IA of the Periodic Table, an ammonium group, a hydrogen atom, or mixtures thereof. M "is a metal atom, preferably from the rare earth group (i.e. atomic number 57 to 71), chromium, vanadium, mo libdenum, indium, boron, mercury, tellurium, silver and platinum group metal, i.e. of platinum, palladium and ruthenium. The primary alkali metal cations of these zeolites can be at least partially replaced by methods such as the ion exchange of hydrogen or a hydrogen precursor with metal ions of group VIII of the periodic table, for example nickel, platinum, iron and / or cobalt Although the zeolites described here have an extremely low alumina content, i.e. a high silica to alumina ratio, they are very active, even if the mole ratio of silica to alumina exceeds 30. This is surprising as the catalytic activity depends in general on the structure of the network of aluminum atoms and the cations associated with them. These catalysts retain their crystallinity for a long period despite contact with steam at high temperature, which causes irreversible damage to the structures y other zeolites, such as types X and A. Moreover, carbon deposits formed on them, if they are formed, can be removed by firing at higher temperatures than usual in order to regenerate their activity. In many environments, zeolites of this class show a very poor coke-forming ability as a result of which the working periods between regenerations performed by firing are very long. An important feature of the crystalline structure of the zeolites described here is the limited access to and exit from 2 lattice voids, determined by the pore size of over 5 -10-1 µm and the size of the windows formed by 10-membered rings composed of oxygen atoms. Of course, these rings are formed by regularly spaced tetraheders constituting an anionic network of crystalline alumina silicate in which oxygen atoms are bound to the atoms of silicon or aluminum at the center of the tetrahedra. To summarize the preferred types of catalysts useful in the method According to the invention, the silica to alumina mole ratio is at least about 12 and their structure is such that access to voids in the lattice is restricted. The silica to alumina ratio can be determined by conventional analysis methods. This ratio is as precisely as possible the ratio in the rigid anionic backbone of the zeolite crystal without taking into account the aluminum contained in the binder, or that found in the zeolite channels in the form of cations or whatever. While catalysts with a silica to alumina molar ratio of at least 12 are useful, it is preferable to employ catalysts having a ratio of at least about 30 in the gas phase. The invention makes it possible to carry out the isomerization in the gas phase in the presence of the catalyst very efficiently. , the crystalline component of which, zeolite, alumino-silicates, as mentioned above, has pores that are smaller than that of the crystalline aluminosilicates used hitherto. The zeolites useful in the process according to the invention readily sorbs n-hexane. They have pores greater than about 5 · 10-1 nm or, if they are elliptical in cross-section, at least equal to the pore size of ZSM-5. In addition, their structure must be such that access to the interior of large molecules is limited. Sometimes, based on the knowledge of the crystal structure, it can be inferred that access is limited. For example, if the crystal windows are formed by 8-membered rings of oxygen atoms, no molecules with a cross section larger than that of n-hexane cannot penetrate the interior, and such zeolite is not desirable. 10-membered windows are preferred, although in some cases excessive pore folding or blockage can reduce the effectiveness of the catalyst. However, it does not appear that the twelve-membered rings are usually the constraints required to obtain favorable degrees of conversion. In designing structures useful for a given purpose, phenomena such as pore blockage and others must be taken into account. Instead, judge from the crystal structure whether the catalyst has the desired effect. restricted access, you can easily determine the "access limitation index" by continuously passing an equimolar mixture of n-hexane and 3-methylpentane over a small (about 1 g or less) sample of the catalyst under atmospheric pressure, following the procedure described below. A sample of the catalyst, in the form of granules or extrudate, is crushed to the size of coarse sand and placed in a glass tube. Before starting the test, a stream of air at 538 ° G is passed through the catalyst for at least 15 minutes. The catalyst is washed with helium and the tsmperture is adjusted to 288-510 ° C to obtain a conversion ratio of 10-60%. A mixture of hydrocarbons, diluted with helium in a helium / hydrocarbon molar ratio of 4: 1, is passed over the catalyst at a space velocity (LHSV) of 1 h-1, i.e. one volume Hydrogen hydrocarbons are passed through the same volume of catalyst for an hour. After this stream has been passed for 20 minutes, a sample of the exiting pipe, most preferably gas chromatography, is taken and analyzed to determine the proportion of the unconverted two hydrocarbons. The "Access Restriction Index" is calculated from the following formula: by the formula jQg ^ (fraction of n-hexane that remained) 25 access limitations =. (share of 3-methylpentane that remained) The access restriction index approximates the ratio of the constant cracking rates of the two hydrocarbons. for the method according to the invention, it is characterized by an access limitation index in the range 1 - 12. Table 1 gives access limitation indexes, abbreviated CI, for some typical catalysts. Table 1 Crystalline aluminosilicates ZSM-5 ZSM-11 ZSM-12 ZSM-35 ZSM -38 Beta ZSM-4 H-Zeolon REY Erionit CI & 3 8.7 2 2 2 0.6 0.5 0.5 0.4 38 1 Of course, the values of the access restriction index characterize zeolites, but they are the result of For a given zeolite, the access limitation index may vary from about 1 to about 12, depending on the temperature used, within the limits of 60 288-510 ° and the degree of conversion of hydrocarbons contained in between 10-60%. The size of the access restriction factor may also be influenced by other factors, such as the size of the zeolite crystals, the presence of possibly occluded impurities, and a binder tightly associated with the zeolite. 124 4 l It is obvious to those skilled in the art that the access restriction factor defined herein is very useful. The effective means of characterizing the zeolites of interest is an approximate measure, influenced by the manner of its determination; in some cases there is a probability of an overlapping effect of variables with extreme values. In all cases, however, the access restriction index for the zeopts of interest will be, at temperatures of 28.51 ° C, a value of about 1-12. and d The described zcofts produced in the presence of organic cations are catalytically inactive, probably because of this, because of the organic cations that come from the solution from which the zeolite is formed. They can be activated by heating, for example to a teinfcetature of 53 ° C in an inert atmosphere of 1 * for 1 hour, followed by ion exchange with ammonium salts, and ironing at 33 ° C in the presence of air. The presence of organic cations in the solution from which the zeolite is formed, does not have to be decisive for the formation of the types of zeolites we are interested in, but it seems to favor the formation of these zeolites. Generally speaking, it is necessary to activate this type of catalyst by the method of taffeta exchange with the use of ammonium salts, 2 * and subsequent calcination at a temperature of about 538 ° in the atmosphere of air, lasting from about 15 minutes to about 24 hours. zeolites can be converted into lago type zeotite catalysts by activating them in various ways and by subjecting them to various treatments, such as ion exchange, steam treatment, alumina extraction and calcination in various combinations. Natural materials that can be modified in this way include ferrierite, brevesterite, stilbit, roofiardite, epistiltut * heukndite and clinoptilolite. The preferred crystalline aluminosilicates are: ZS.M-5, ZSM-11, Z & M-12, ZSM-35 and ZSM-38, and in particular ZSM-5. Catalysts useful in the method According to the invention, 40 can be selected based on the density of the crystal lattice in the dried , the hydrogen farm. These should be zeolites for which the lattice density is generally not less than 1.6 g / cm3. It has been found that the most desirable ec4ites meet all tr * x criteria. The preferred catalysts have an access restriction index of 1-12, have a silica to alumina molar ratio of at least 12, and have a dry density of less than 1.6 g / cm 3. S The dry density for crystals of known structure can be calculated from the number of silicon and aluminum atoms to 10O cubic angstroms, as described by W.W. Meir on page 19 of the article Structure of zeolites. This article is found in the Pfocesdings of the ConferehCe on Mole- 5 $ cular Sieves, London * April 19/6 * 7, edited by the Socicty of Chemical Industry, London 1968. If the crystal structure is unknown, the lattice density can be determined by the classical method. For example, you can immerse the zeolite in dry hydrogen form in an organic solvent that is not absorbed by the crystals. Perhaps the extraordinary persistence of activity and stability of Neoliths of this class is related to the high density of their crystal lattice, not less than about 1.6 "g / cm *. The high density of 65 8 must be associated with a relatively small free space inside the crystals , which may result in a more stable structure. These free spaces are, however, important as the site determining the crystalline activity. Table 2 summarizes the crystal lattice density of typical zeolites. Table 2 Zeolite Ferrierite Mordenite ZSM-5, -11 Dachiardite L ¦ Klinoptilolite Laumontit ZSM-4 Heulandyt P. Offretyt Lewinit Erionit Gmelinite Chabazite A [Y Free space cm3 / cm3 0.28 0.28 0.29 0.32 0.32 0.3 £ 0.34 0.38 0, 39 0.41 0.40 0.40 0.35 0 * 44 0.47 0.5 0.48 Lattice 1 density g / cm3 1 1.76 ^ 1.79 1.72 1.61 1.71 1 , 77 1.65 [1.69 1.57 1.55 1.54 1.51 1.46 1.45 1.3 1.27 [Zeolites from this group have a suitable, distinct crystal structure for the use of catalytic compositions according to none of the present invention. ZSM-5, ZSM-11, ZSM-12, ZSM-35 and ZSM-38 zeolites for use in the process according to the invention are produced by the methods given in the relevant patent descriptions given above in the prior art. This type of zeolites can be produced from materials containing the appropriate ingredients, zeelittl. Such components include sodium aluminate, gKnu oxide, sodium silicate, silica hydrosol, silica gel, silicic acid, sodium hydroxide, and tetrapropylammonium derivatives, such as, for example, esteropropylammonium hydroxide. Of course, each of the components of the reaction mixture from which it} gets *! * Zeoht can be introduced as one or a bunch of reagents, which can be mixed in any order * For example, sodium can be added to the mixture in the form of an aqueous solution of sodium hydroxide or an aqueous solution of silicate soda. Cathioa esteropropylammonium can be introduced as bromide. The reaction mixture can be prepared peptidically or continuously. The size of the crystals and the time of crystallization of the compositions vary depending on the nature of the reaction mixture. Obviously, in the case of grinding of very high mole silica to alumina ratios of 35 to about 300 or more, preferably about 70 to about 00, it may be unnecessary to add an alumina source to the reaction mixture. since the residual amounts of gKnu in the BOSUalyelt reagents can be sufficient. 124 493 9 The known zeolite obtained from the reaction mixture with the composition expressed as molar ratios of oxides or in moles of oxides, given in Table 3 Table 3 OH * / SiO 2 R4N + / ( R4N + + + Na +) HaO / OIT Si03 / Al2O3 [Other metal oxides [(% of total oxides) Wide area 0.07-1.0 0.2-0.95 10-300 50-3000 10 - «- 1.0 Advantageous area 0.1-0.8 0.3-0.9 10-300 70-1000 10-5-0.1 Most favorable area 0.2-0.75 1 0.4-0 , 9 10-300 70-500 10-5-0.01 1 Race the meaning given previously. ii: .r; i. ', -¦ - "- ¦'., 20 This is typically prepared by keeping the reactive mixture at a temperature of about 93-177 ° C during the day; about 4 hours to 120 days, preferably at about 4 ° C. 1 £ 0-177 c hours to 8 days. The gel particles are kept under the conditions indicated until crystals form. The solid product is separated from the reaction mixture by cooling it, draining and washing with water. The product is dried, for example at 110 ° C for 8 to 24 hours. If necessary, milder conditions, such as room temperature and reduced pressure, can be stopped. According to the currently used, known methods, isomerization of aromatic hydrocarbons substituted with methyl radicals in the gas phase is carried out x Sie in the presence of a catalyst composition containing about 10-65% by weight of active zeolite When using such catalyst compositions at a temperature of 315-371 ° C, the following reactions occur: (1) acid-catalyzed conversion of ethylbenzene, ** main not disproportionation to benzene and dimethylbenzene, (2) acid-catalyzed isomerization of xylenes, (3) acid-catalyzed disproportionation of xylenes to toluene and C99 methylbenzenes causing xylene loss, (4) if ** paraffins are present, alkylation of xylenes with cracked paraffins, increasing the loss of xylene, which excludes the use of raw material containing paraffins and (5) acid-catalyzed ethylation of xylenes with radicals derived from the decomposition of ethylbenzene, resulting in the loss of xylenes. The method of catalytic isomerization in the gas phase of methyl-substituted carbon aromatic mono-ring, in which the raw material is contacted in the gaseous phase with hydrogen in the molar degree K hydrogen: hydrocarbons of 1-10, under a pressure of 137-3450 kPa, at a flow rate of 0.5-20 h -1 in the presence of a catalytic composition containing Binding material which is a diluent such as alumina and crystalline aluminosilicate zeolite ** per pile a silica / alumina molar amount of at least 12 and an access restriction index of 1-12 according to the invention is that a catalytic composition is used containing 01-5 wt% zeolite containing cations, mainly hydrogen *, ** 10 hydrogen precursor and / or a metal of Group VIII of the Periodic Table and the process is carried out at a temperature of 427-538 ° C. The invention therefore relates to a method for the isomerization of a urea containing methyl substituted monocyst aromatic hydrocarbons in the gas phase in the presence of an improved catalyst composition. The catalytic composition used in the process of the present invention comprises a crystalline aluminosilicate zeolite having a silica / alumina mole ratio of at least 12 and an access restriction index of 1-12, being 0.1-5% of the preferred composition and diluent. such as residual alumina. The zeolite in this composition may contain, instead of at least some of the primary cations, metal cations of Group VIII of the Periodic Table of Elements, for example nickel, platinum, iron and / or cobalt and / or hydrogen, or also hydrogen precursors. The reactions should be carried out at a temperature of at least 427 ° C. The crystalline aluminosilicate zeolites contained in the catalyst composition useful in the process of the invention are generally: tYP "ZSM-5" zeolites or behaving as SM-5 zeolites and represented; are the general formula reflecting the molar ratios of the oxides in the anhydrous state: for ZSM-5: (0.9 ± 0.2) M2 / nO: Al 2 O 3: x SiO 2, where M is a cation, mainly of metal VIII of the periodic group of the element and / or hydrogen system * n denotes a value of M, and x has a value of at least 5; for ZSM-11: (0.9 ± 0.3) M2 / nO: Al 2 O 3: ySiO 2, where M is a cation, mainly metal of the VIII group of the periodic table of elements and / or hydrogen, n is the value of M, and y has the value 20-90; for ZSM-12: (10 ± 0.4) M2 / nO: Al2O3: (20-200) SiO2, where M is a cation, mainly of the VIII metal of the Group VIII of the Periodic Table of the Elements and / or hydrogen, and n is the valence of M; for ZSM-35 and ZSM-38: (0.3 + 2.5) R * 0: (0-0.8) M2O: Al203 = h8Si02, where R is an organic cation containing nitrogen, for ZSM-35 derived from ethylene diamine, pyrrolidine, butylene or N-methylpyridinium derivative * such as hydroxide, sulphate, nitrate or halide, and for ZSM-38 - derived from 2- (hydroxyalkyl) trialkylamino as alkyl radicals containing methyl radicals, ethyl radicals or combinations thereof, and M is a cation, mainly of a metal of Group VIII of the Periodic Table of the Elements and / or hydrogen and by the formula (R20, M'2 / nO) in (Al2O3) x: (SiO2) y: (M "2 / nO ) 2, in which the ratio w / x- is greater than 0.5 and less than 3, the ratio y / x is greater than 20, the ratio z / x is greater than zero and less than 100, R is a cation containing the atom N is the value of M1 or M '. The catalyst composition used in the process of the invention comprises a crystalline aluminosilicate zeolite for which the silica / alumina molar ratio is at least e12 and the access restriction index is I — 12. ZSM-5, ZSM-11, ZSM-12, ZSM-35 and ZSM-38 zeolite are non-limiting examples of such zeolite. When carrying out the isomerization in the length of the extractor, a suitable zeolite catalyst is used in combination with a carrier or a binding material that acts as diluents, such as a porous inorganic oxide carrier or a clay binder. Non-limiting examples of such binders include alumina, zirconium oxide, silica, magnesium oxide, thorium oxide, titanium dioxide, boron oxide, and combinations thereof, generally used as dried inorganic oxide gels and gel-like deposits. Among the suitable clay-type materials, bentonite and diatomaceous earth can be mentioned. The content of a suitable crystalline aluminosilicate zeolite in the catalytic composition further comprising a binder or ncsor is about 0.1-5%, preferably about 0.5-1.5% by weight. According to the invention, a feedstock containing compounds of formula (C6H6-n) Rn is preferably subjected to the isomerization process in which Rn is a methyl radical and n is an integer of 2-4, most preferably a raw material containing xylene. The conditions for carrying out the isomerization are essential for the process according to the invention. In particular, the course of the process is significantly influenced by temperature, pressure, flow rate, molar ratio of reactants, molar ratio of hydrogen / hydrocarbons and the presence of diluents in the raw material. The isomerization should be carried out at a temperature of 427-538 ° C and a pressure of 137-345 kPa. The space velocity related to the total mass of the catalyst (WHSV) can be about 0.5-20 hours-1, and the hydrogen / hydrocarbon molar ratio should be 1-10. The temperature and pressure within these values vary quite a bit. significantly, depending on the balance conditions and the type of raw material. The conditions under which the maximum yield of the desired isomerization product is maximized are considered to be optimal. The temperature and pressure are selected in such a way as to achieve the highest selectivity and maximum efficiency for the given area of the degree of transformation of the raw material. In carrying out the isomerization according to the invention, (1) a catalyst composition containing at most 5% by weight of active zeolite, possibly with metals such as platinum and nickel, and a thinner such as alumina, optionally with metal, is used. - mi such as platinum or nickel and (2) temperature 427-538 ° G. Under these conditions, ethylbenzene is mainly dealkylated to benzene and ethane, and not disproportionated to benzene and diethylbenzene, and therefore the reaction of ethylbenzene is poorly dependent on the acidity of the catalyst. xylenes while reducing the amount of disproportionate xylenes. Reducing the loss of xylenes is important, since about 75% of the xylene stream is recycled, resulting in a loss of 6-10% by weight. Most of the ethylbenzene is converted to benzene and not to a mixture of benzene and diethylbenzene, thereby giving the product quality of the invention is higher than the quality of products obtained by known methods. One can also expect a reduction in the cost of the catalyst, because in the new catalytic composition it is below 5% of active zeolite, while the currently used catalyst compositions contain over 10 to 65% of active zeolite. The method according to the invention is also characterized by greater flexibility in Reference to raw material * As the conversion of ethylbenzene is little dependent on isomerization, it is possible to treat raw materials with a high content of ethylbenzene, which means that thermal cracking products (containing about 30% by weight of ethylbenzene) as well as conventional reformed products can be used. Moreover, at temperatures above 427 ° C, the dealkylation reaction of radicals containing more than 2 carbon atoms takes place more easily. There will therefore be no alkylation of the aromatic rings with paraffins, possibly from the raw material, which eliminates the loss of xylene via this mechanism. In a new way, it is possible to process paraffins, which cracks into lighter paraffins, which eliminates the need for Udex extraction. Finally, it can be assumed that these fragments from the krafemg combine to form new aromatic rings increasing the amount of aromatic compounds. It would be particularly similar if the active zeolite was diluted with alumina bearing a suitable metal (for example, platinum on alumina) to catalyze the reforming; therefore, it is dried (and demonstrated) to maintain a temperature of at least 427 ° C in the reaction space. and catalytically active zeolite to a content of at most 5% by weight, diluted with a thinner such as alumina. The improved ratio between the hydrogenation activity and the acidity of the active zeolite allows for many easily noticeable benefits, which include: (1 ) the use of very diluted X <5%) active zeolite, which can be treated with steam or a base to regulate the acidity, (2) no coupling between the transformation of ethylbenzene and isomerization of xylene, (3) the possibility of using raw materials containing more than 30% by weight of ethylbenzene (4) reduction of xylene losses by disproportionation, (5) workability raw materials containing paraffin, which eliminates the need to extract them by the Udex method, (6) conversion of ethylbenzene to benzene instead of a mixture of benzene and aromatic hydrocarbons Ci0, (7) formation of aromatic rings from paraffin fragments, (8) lower the degree of conversion of ethylbenzene during a single flow through the catalyst layer and (9) ease of control of the efficiency by changing the content of active zeolite in the catalytic composition. As a raw material for the isomerization carried out according to the method according to the invention, preferably monocircular aromatic hydrocarbons substituted at most less courtesy and at most four methyl radicals. These materials can be illustrated by the formula (G6H6-n) Rn, where is a methyl radical and n is an integer, 2-4. Compounds corresponding to this formula include p-xylene, m-xylene, o-xylene, mesitylene (1, 3,5- trimethylbenzene), durene (1,2,4,5-tetramethylbenzene), hemimelitene (1,2,3-trimethylbenzene), pseudo-124 493 13 cumene (1,2,4-trimethylbenzene), prehnitene (1,2,3,4-tetromethylbenzene) and isodrene (1,2,3,5-tetramethylbenzene). Of these compounds, isomeric xylenes and pseudocumene are particularly preferred for use. Examples illustrating the method of the invention are given below. Example 1 A catalytic composition is prepared containing 0.5% by weight of ZSM-5 zeolite containing 0.1% by weight of platinum, with a SiO2 / Al2O3 molar ratio of 70. and Cl is about 8.3, and 99.5% by weight of alumina. The raw material containing 10.4% by weight of ethylbenzene, 0.1% by weight of n-nonane and 89.5% by weight of xylenes is isomerized. The xylenes are a mixture consisting of 73.3% by weight of m-xylene, 17.8% by weight of o-xylemr. 8 * 9% by weight of p-xylene. The raw material mixed with hydrogen in such an amount that the molar ratio of hydrogen / hydrocarbons is 5 is passed over the catalytic composition at a temperature of 482 ° C under a pressure of 1.47 MPa with a space velocity (WHSV) of 1.5 h-1. After 2 hours, the product is analyzed. The results of the analysis are presented in tab. 4. They show that ethylbenzene was converted to 22.6% and the resulting mixture of xylenes contained 60.16% m-xylene, 20.5% p-xylene and 19.33% o-xylene. Example II. The catalytic compositions of Example I are used in a 22 hour isomerization carried out under substantially the same conditions as in Example I, but using a space velocity (WHSV) of 0.75 h-1. Product analysis shows that ethylbenzene is converted to 36.83% and the mixture of xylenes contains 56.5% m-xylene, 22.89% p-xylene and 20.26% o-xylene. The results of the product analysis are presented in tab. 4.Example III. Catalytic compositions were prepared containing 2.5% by weight of the treated HZSM-5 steam (ZSM-5 with a SiO2 / Al2O3 mole ratio of 70 and about 8.3% of Cl) and 97.5% by weight of the oxide. aluminum containing 0.35% by weight of platinum. The isomerization is carried out essentially under the conditions given in Example 1, with the only difference that the space velocity (WHSV) is J.0 h -1. After 19 hours, the product is subjected to an analysis, the results of which are summarized in the tab. 4. They show that ethylbenzene is converted 70.96% and the mixture of xylenes contains 54.13% m-xylene, 23.30% p-xylene and 22.57% o-xylene. Example IV. Catalytic compositions were prepared containing 1.0% by weight of the treated HZSM-5 steam (ZSM-5 with a SiO2 / Al2O3 mole ratio of 70 and a Cl equal to about 8.3) and 99.0% by weight of aluminum oxide, containing 0.6% by weight of platinum. The isomerizations are generally carried out under the conditions set forth in Example 1, except that the temperature is 454 ° C and the space velocity (WHSV) is 4.4 h -1. The isomerized raw material contains 29.3% by weight of ethylbenzene, 63.2% by weight of xylenes and 7.5% by weight of n-nonane. After 10 hours, the product is analyzed, the results of which are summarized in Table 4. They indicate that ethylbenzene is converted to 42.55% and the mixture of xylenes contains 53.71% m-xylene, 22.83% p-xylene and 23.45% o-xylene. Table 4 Product ingredients c2 c3 c4 cs * c6 Benzene ° 7 * Toluene c8 * Ethylbenzene m-xylene | p-xylene o-xylene c9 * c9 ** c. ** Qi-ia ** c13 + Loss of xylene, wt.% Loss of aromatic hydrocarbons (calculated on the rings), 1 wt. | Example I 0.60 0.01 - - - 1.61 - 0.27 0.01 8.05 53.20 18.14 17.10 0.06 0.53 0.39 0.03 0.02 1, 06 0.11 n 1.09 0.01 - - - 2.66 - 0.44 0.01 6.57 49.96 20.25 18.22 0.05 0.30 0.43 - 0.01 107 0.16 III | IV 2.10 0.59 0.29 0.62 0.18 5.13 0.02 1.05 0.23 3.02 46.79 20.14 19.50 - 0.31 0.01 - 0, 03 3.07 1.97 2.96 1.52 M5 1.84 0.77 8.83 0.03 0.53 0.32 16.83 33.71 14.33 14.72 0.97 0.39 0.76 0.01 0.03 0.44 0.73 1 1 = paraffins ** = aromatic hydrocarbons Example V. In order to compare the new one with known isomerization methods, catalytic compositions were prepared containing 65% by weight of ZSM-5 zeolite (containing 0.8% by weight of nickel) with a SiO2 / Al2O3 molar ratio of 70 and a CI of about 8.3, and 35% by weight of oxide The raw material described in Example 1 is subjected to isomerization. This raw material, mixed with hydrogen in a hydrogen / hydrocarbon molar ratio of 4.1, is passed over the catalytic composition at a temperature of 426 ° C under a pressure of 3.95 MPa at a speed of space (WHSV) 1.0 h-1. The results of the analysis of the product obtained after 20.5 hours are given in tab. 5. Table 5 | Product ingredients | 1 1 C c, c4 c5 c6 * Benzene c7 * Toluene c8 * Ethylbenzene m-xylenl p-xylene J o-xylene c9 * 1 Example V 2 1.62 4.20 0.41 0.03 0.00 4.18 0.01 26.59 0.19 0.00 31.42 9.51 0.00 | 124 493 15 cd of table 4 1 1 c9 ** 1 c "** Cit-ia ** Q3 * Loss of xylene, wt% Losses of aromatic hydrocarbons (calculated on the rings), wt. 1 2 1 19.09 1.76 0.29 0.35 59.07 3.79 * - paraffins ** - aromatic hydrocarbons A comparison of these results with those obtained in the experiments described in Examples 1-4 shows the enormous improvement obtained by using the method according to the invention. The loss of xylene of 59.07% using the catalyst described in Example V was reduced to 0.44-3.07% when carrying out the isomerization according to the invention. The loss of aromatic rings was 3.79% when using the process compared to the known method. % of the catalyst, but only - 0.73 to 1.97% when using the method of the invention. The main products obtained in the presence of the known catalyst were C9 aromatic hydrocarbons and toluene, while the degree of isomerization of xylenes was low compared to the degree of dispersion of the OFCJophtening. Claims 1. Method of catalytic isomerization in the gas phase of methyl-substituted mono-ring aromatic ring the raw material of which, in the gas phase, is brought into contact with hydrogen in a hydrogen / hydrocarbon ratio of 1 to 10 at a pressure of 137 to 3450 kPa at a flow rate of 0.5 to 20 hours. -1 in the presence of a catalytic composition containing a diluent binding material such as alumina, crystalline alumina zeolite with a silica / alumina mole ratio of at least 12 and an access restriction index of 1-12, characterized by the use of catalytic composition of zeolite containing mainly hydrogen cations, a hydrogen precursor and / or a metal of Group VIII of the periodic table, and the process is carried out at a temperature of 427-538 ° G. 2. The method according to claim A process as claimed in claim 1, characterized in that the zeolite is catalytic compositions containing zeolites in which the molar ratios of the oxides in the anhydrous state are given by the formula (R20, M'3 / nO) in: (A ^ Oa ^: (SiO 2) Y (: M "2 / nO) z, where the W / X ratio is greater than 0.5 and less than 3, the Y / X ratio is greater than 20, the Z / X ratio is greater than zero and less than 100, R is a cation containing a nitrogen atom, and n is a value of M 'or M ". 3. The method according to claim 1, characterized in that the catalytic composition containing the zeolite ZSM-5, ZSM-11, ZSM-12 is used, ZSM-35 and / or ZSM-38. * »4. The method according to claim 1, characterized in that the catalyst compositions contain zeolite in an amount of about 0.5-1.5% by weight. The method according to claim 1, characterized in that nickel, platinum, iron and / or cobalt are used as the group VIII metal. 6. The method according to claim 1, characterized in that the raw material containing compounds of formula C * H6-n is isomerized. ) Rn in which R is a methyl radical y and n are an integer 2-4. The method according to claim 33 6, characterized in that the raw material containing xylenes is isomerized. LDD Z-d 2, z. 811/1400/84/3, n. 80 + 20 copies. Price PLN 100 PL

Claims (7)

Claims 1. The method of catalytic isomerization in the gas phase of methyl-substituted single ring aromatic hydrocarbons in which the raw material in the gas phase is brought into contact with hydrogen in the molar ratio of hydrogen / hydrocarbons of 1 to 10 at a pressure of 137-3450 kPa. at a flow rate of 0.5-20 hours. -1 in the presence of a catalytic composition containing a diluent binding material such as alumina, crystalline alumina zeolite with a silica / alumina mole ratio of at least 12 and an access restriction index of 1-12, characterized by the use of catalytic composition of zeolite containing mainly hydrogen cations, a hydrogen precursor and / or a metal of Group VIII of the periodic table, and the process is carried out at a temperature of 427-538 ° G. 2. The method according to claim A process as claimed in claim 1, characterized in that the zeolite is catalytic compositions containing zeolites in which the molar ratios of the oxides in the anhydrous state are given by the formula (R20, M'3 / nO) in: (A ^ Oa ^: (SiO 2) Y (: M "2 / nO) z, where the W / X ratio is greater than 0.5 and less than 3, the Y / X ratio is greater than 20, the Z / X ratio is greater than zero and less than 100, R is a cation containing a nitrogen atom and n is a value of M 'or M ". 3. The method according to claim 1, characterized in that the catalytic composition comprises the zeolite ZSM-5, ZSM-11, ZSM-12, ZSM-35 and / or ZSM-38. 4. * » 4. Way according to zistrz. The method of claim 1, wherein the catalyst composition comprises zeolite in an amount of about 0.5-1.5% by weight. 5. The method according to p. I, characterized in that nickel, platinum, iron and / or cobalt are used as the Group VIII metal. 6. The method according to p. The process according to claim 1, characterized in that the isomerization is carried out on the raw material containing compounds of the formula C * H6-n) Rn in which R is a methyl radical and n is an integer of 2-4. 33 7. The method according to p. The process of claim 6, characterized in that the xylene-containing feedstock is isomerized. LDD Z-d 2, issue 811/1400/84/3, no. 80 + 20 copies. Price PLN 100 PL