MXPA98001051A - Zeolite catalyst selectively and its use in the conversion of aromati compounds - Google Patents

Abstract

A catalyst selectively comprises a synthetic porous crystalline material, having the structure of ZSM-5 and a composition involving the molar ratio: X2O3: (n) YO2, wherein X is a trivalent element, such as aluminum, boron, iron and / or gallium, preferably aluminum, Y is a tetravalent element such as silicon and / or germanium, preferably silicon, and n is greater than about 12, and wherein the crystals have a size greater than at least about 0.5 microns and a surface ratio of YO2 / X2O3 of the crystal. The crystals have a diffusion surface cover modifying a refractory material such as silica or coke. The catalyst is used in a wide variety of selective hydrocarbon conversion processes, particularly in the selective disproportionation of toluene to para-xile

Description

ZEOLITE CATALYST SELECTIVELY AND ITS USE IN THE CONVERSION OF AROM TICOS COMPOUNDS This invention relates to a zeolite catalyst selectively and its use in the conversion of aromatic compounds, particularly the selective production of para-dialkylaromatic compounds. The term "selective form" describes unexpected catalytic selectivity in zeolite. The principles behind the catalysts selectively have been extensively reviewed, for example, by N.Y. Chen, W.E. Garwood and F.G. Dwyer, "Shape Selective Catalyst in Industrial Applications." 36 Marcel Dekker, Inc. (1989). Within a zeolite pore, hydrocarbon conversion reactions such as isomerization, disproportionation, alkylation and transalkylation of aromatics are guided by the constraints imposed by the size of the channel. The selectivity of the reactant occurs when a portion of the feed stack is also considerable to penetrate the pores of the zeolite to the reagent; while the selectivity of the product occurs when part of the products can not remain in the zeolite channels. The distribution of products can also be altered by the transition of the state of REF .: 26841 selectivity in which certain reactions can not occur because the transition of the reaction state is also considerable to form within the pores or cells of the zeolite. Another type of selectivity results from the configuration constraints in the diffusion, where the dimension of the molecules approximates that of the pore system of the zeolite. A small change in the dimensions of the molecule or pore of the zeolite can result in a wide diffusion of changes leading to different distributions of the product. This type of catalyst is selectively shown, for example, in the disproportionation of the selective alkyl-substituted benzene to para-dialkyl-substituted benzene. A representative para-dialkyl-substituted benzene is para-xylene, which is a costly chemical feedstock for the production of polyesters. The production of para-xylene is typically carried out by the methylation of toluene or by the disproportionation of toluene in a catalyst under conversion conditions. Examples include the reaction of toluene with methanol, as described by Chen et al., Amer. Chem. Soc. 101, 6783 (1979), and the disproportion of toluene, as described by Pines in "The Chemestry of Catalytic Hydrocarbon Conversions," Academ. Press, N.Y., 1981, p. 72. Such methods typically result in the production of a mixture of the three xylene isomers, ie, para-xylene, ortho-xylene, and meta-xylene. Depending on the degree of selectivity of the paraxylene catalyst, (para-selectivity) and the reaction conditions, different percentages of para-xylene are obtained. The product, i.e. the amount of xylene produced as a part of the feeder stack, is also affected by the catalyst and the reaction conditions. Another well-known method for producing paraxylene is by the isomerization of an aromatic feeder cell C, which contains a high proportion of other xylene isomers, particularly meta-xylene. Commercially, suitable C aromatic feeder batteries normally contain significant amounts of ethylbenzene, in which separation by physical methods is difficult and, therefore, an important object of most. The isomerization procedures of xylene is to convert ethylbenzene to more removable species quickly without excess xylene losses. Several methods are known in the art to increase the para-selectivity of the zeolite catalysts. This modification typically involves the diffusion characteristics of the zeolite so that the ratio at which the products of the reaction not required may be diffuse inside and outside the pores of the zeolite is reduced compared to the diffusion rate of the zeolite. desired product. For example, US Patent No. 4,117,026 describes a selectivity process in which the absorption rate of the zeolite is increased by placing a layer of coke on the surface of the zeolite. It is also known that by increasing the para-selectivity of a zeolite by depositing or placing on the zeolite an oxide of a metal, such as an alkaline earth metal (US Patent No. 4,288,647), a Group of metals IIIB, eg gallium, indium and / or thallium (US Patent No. 4,276,437), a group of metals IV, for example titanium and / or zirconium (US Patent No. 4,302,620) and a group of metals IVB, for example tin and / or germanium (American Patent No. 4,278,827). An alternative selection process described in, for example, U.S. Patents 5,173,461, 4,950,835, 4927,979, 4,465,886, 477,583, 4,379,761, 4,145,315, 4,127,616, 4,100,215, 4,090,981, 4,060,568 and 3,698,157 are contacted or mixed with the zeolite. a selective agent that contains a silicon compound. Such known methods include both, ex-situ and in-situ selection. In the ex-situ selection the zeolite is pre-treated with the silicon-containing selectivity agent to the outside of the reactor used by the selective aromatic conversion process in a desired manner. In the in-situ selectivity the zeolite is charged into the aromatic conversion reactor and, during a reaction initiation phase, it is contacted or mixed with a mixture of the The selectivity agent containing silicon and an organic carrier, such as toluene. A combination of both in-situ and ex-situ silicon selectivities can be used. In any event, the selective procedure results in the placement of a silica cover on the surface of the - * - 5 zeolite which modifies the diffusion characteristics of the zeolite. Traditionally, the ex-situ pre-selectivity of the zeolites has involved an individual application of the selectivity agent. However, the Patent US Pat. No. 5,476,823 describes a process for modifying the selectivity form of a zeolite by exposing it to at least two of the ex-situ selectivity sequences, each of which includes the steps upon contacting or mixing the zeolite with a selective agent containing silicon in an organic carrier and subsequently calcining the zeolite. Inexplicably, it has not been found that certain abundant forms of ZSM-5 crystals, which have a high aluminum content and an unusual distribution thereof, with the proportions of SiO2 / AlO? mass essentially after them as those on the surface, with a greater response to selectivity than conventional ZSM-5 crystals. Such abundant crystal forms of ZSM-5 are described in International Patent Application No. PCT / US96 / 09878 which describes a synthetic porous crystalline material having the structure of ZSM-5 and a composition involving the molar ratio X203: (n) Y02, wherein X is a trivalent element, such as aluminum, boron, iron and / or gallium, preferably aluminum; Y is a tetravalent element such as silicon and / or germanium, preferably silicon: and n is greater than about 12, and wherein the crystals have a larger dimension of at least about 0.5 microns and a surface ratio of YO; / X_0; which is not more than 20% than the proportion of the mass YO: / X0? of the crystal. It is appreciated that, through ZSM-5, the structure of aluminum that can be partially or completely replaced by other trivalent elements, such as boron, iron and / or gallium, and the silicon structure can be synthesized normally as an aluminosilicate. partially or totally replaced by other trivalent elements such as germanium. Accordingly, the invention lies in one aspect in a catalyst selectively comprising a synthetic porous crystalline material having the structure of ZSM-5 and a composition involving the molar ratio: X > 03: (n) Y02, wherein X is a trivalent element, such as aluminum, boron, iron and / or gallium, preferably aluminum; Y is a tetravalent element such as silicon and / or germanium, preferably silicon; and n is greater than about 12, and wherein the crystals have a larger dimension of at least about 0.5 microns and a proportion of surface in Y? 2 / X: 03 which is not greater than * less than the mass ratio YO: / X203 of the crystal; the catalyst having a diffusion surface cover modifying a refractory material.

Preferably, the crystals have a larger dimension of at least about 1 micron. Preferably, the ratio of the surface YO2 / X2O;) is not greater than 20% of the proportion of mass YO2 / X2O3 of the crystal. Preferably, n is less than about 100 and more preferably is from 25 to about an approximate 40. Preferably, the surface coating is selected from the group consisting of coke, a metal oxide, an oxide of a non-metal and a ceramics of a non-oxide and more preferably comprises silica. In a further aspect, the invention lies in a hcarbon conversion process using the catalyst of one aspect of the invention. The present invention provides a catalyst selectively in which a particular form of a large crystal ZSM-5 is provided with a diffusion surface cover modifying a refractory material as well as to accentuate its selectivity in the hcarbon conversion processes, such as disproportionation of toluene. As used herein, the term "refractory material" is meant to suggest a material which is viable to oppose the conditions experienced in a desired hydrocarbon conversion process within the significant change in chemical or physical composition. The particular shape of the large crystals ZSM-5 used in the catalyst of the invention is described in International Application No. PCT / US96 / 09878 and has a composition that involves the molar ratio: X203: (n) Y02, wherein x is a trivalent element, such as aluminum, boron, iron and / or gallium, preferably silicon; Y is a tetravalent element such as silicon and / or germanium, preferably silicon; and n is greater than about 12, preferably less than 100 and more preferably 25-40, and wherein the catalysts have a surface ratio of YO2 / X2O3 which is not more than 20% less, and preferably not more than 10% less , that the proportion of the mass YO2 / XO. In contrast, the abundant conventional crystal forms of ZSM-5 are rich in aluminum and have a surface ratio of SiO: / Al "0. which is significantly lower (> 20% less) than the proportion of the mass SIO2 / AI2O3.

The term "abundant crystal" ZSM-5 is used herein to suggest that the crystals have a larger dimension, and preferably at least two dimensions, of at least about 0.5 microns, preferably at least 1 micron and more preferably from 1 to the approximate shape of 10 microns measured by standard SEM techniques. The size of the ZSM-5 crystal can also be reduced from the absorption measurements, again by measuring the absorption ratio of 2,3-dimethylbutane at 120 ° C and 60 torr (8 kPa) of hydrogen pressure. The relationship between the size of the crystal measured in microns, d, and the diffusion time measured in minutes, t o.n the time required for the understanding of 30% of the hydrocarbon capacity, is: d = 0.704 x t 0.3%.

Before the application of the modifying diffusion surface cover, the large crystal ZSM-5 according to the invention preferably has an absorption time d, t 0.3 of at least 5 minutes, preferably of at least 10 minutes and more preferably of at least 15 minutes.

The new large crystal of ZSM-5 of the invention is produced from a reaction containing sources of an alkali or alkaline earth metal (M), oxide, a trivalent metal oxide X203, a tetravalent metal oxide YO :, water , and an amino acid or salt thereof (AA) that has the formula: wherein Ri is NH2, NHR3 where R3 is a cyclic or adamantine alkyl group, is a carboxylic acid group or a salt thereof, R2 is H, alkyl, aryl, alkaryl, NH2 or NHR3 where R3 is an alkyl group cyclic or adamantine; A is H or a metal and z is a form O to 15, preferably 1-7; provided that at least one of R: and R is NH2 or NHR3. Examples of suitable amino acids are 6-aminohexanoic acid, N-2-adamantylglycine, N-cyclohexylglycine, lysine, and glutamic acid (and its monosodium salt). Glutamic acid and its monosodium salt are particularly preferred.

The reaction mixture has a composition expressed in terms of mole ratios of oxides, as follows: Preferred Employee Y02 / X2? 3 20-80 20-40 H20 / Y0: 10-90 20-60 AA / YO2 0.05-0.5 0.1-0.2 H / YO2 0.1-0.8 0.3-0.4 The method of the synthesis of the invention works with or without the addition of nuclear seeds. In a preferred embodiment, the reaction mixture contains non-nuclear seeds. The preferred aluminum source is NaA102, while the preferred silicon source is SiO sol (30% SiO2 in H20), which is commercially obtained by Catalog No. SX0140-1 from EM Sciences, Inc. Crystallization is carried out under the conditions either with stirring or static at a temperature of 80 to 225 ° C, preferably 120 to 180 ° C, for 24 hours for 60 days. The resulting crystals ZSM-5 are separated from the liquor or main aqueous solution and recovered and the zeolite is converted to the hydrogen form. Because the large crystals ZSM-5 used in the catalyst of the invention can be synthesized with a relatively low molar ratio of silica / alumina (which is with a relatively high aluminum content), the resulting large crystal, such as ZSM- 5, is typically measured by the alpha values, which compare the catalytic decomposition activity of the catalyst (ratio of the normal conversion of hexane per volume of catalyst per unit time) with the activity of a decomposition catalyst of a silicon standard alumina. The alpha test is described in U.S. Patent No. 3,354,078; in the Journal of Catalystis, Vol. 4, p. 527 (1965); vol 6, p. 278 (1966); and vol. 61, p. 395 (1980). The experimental conditions of the tests used here include a constant temperature of 538 ° C and a variable flow rate as described in 90 detail in the Journal of Catalysis, Vol. 61, p. 395. In the form of hydrogen and before the application of the modifying diffusion surface cover, the large crystals ZSM-5 used in the catalyst of the invention preferably have an alpha value in excess of 300 and - * - - 'preferably in excess of 800.

Surprisingly it has been found that this new form of ZSM-5 has a response usually to selectivity by the application of a modifying diffusion surface covering of a refractory material. This response can take the form of a rapid surface modification or improve the properties of the catalyst or both. The refractory cover is conveniently coke or an oxide of a metal or a non-metal, such as silicon, boron and / or titanium. Alternatively, the refractory cover could comprise a non-oxide ceramic, such as boron nitride. In a preferred embodiment, the cover of the modifying diffusion surface is silica and is applied as an organosilicon compound by ex-situ pre-selectivity and / or in-situ selectivity. A convenient ex-situ pre-selectivity process is described in US Patent No. 5,476,823 and involves contacting or mixing the zeolite with the organosilice compound in an organic carrier, calcining the zeolite and then repeating the contact or mixing of the Once the calcining sequence is repeated one or more times, using the large zeolite crystal of the invention, the number of sequences necessary to reach a given para-selectivity is reduced when compared to conventional forms of ZSM-5. An alternative method of ex-situ selectivity may be used in place of, or more preferably, additional to that published in U.S. Patent No. 5,476,823 described in U.S. Patent No. 5,365,003 and involving agglomeration of a mixture of zeolite, an organisilicon compound and optionally sand in a soft muslin and then calcining the resulting binders. A convenient in situ selectivity method is described in US Patent No. 5,498,814 and involves contacting or mixing the zeolite with a mixture of toluene, hydrogen and an organosilicon compound at a temperature of 350-540 ° C, a pressure atmospheric pressure of -5000 psig (100-35000 kPa) and a hydrogen / hydrocarbon mole ratio of 0.1-20 until the desired para-selectivity is reached. Again, using the large crystal zeolite of the invention, the time or p required to achieve a given para-selectivity is reduced compared to conventional forms of ZSM-5. The silicon selectivity agents used include silicones and siloxanes which can be characterized by the general formula: 25 n wherein Ri is hydrogen, halogen, hydroxyl, alkyl, halogenated alkyl, aryl, halogenated aryl, aralkyl, halogenated aralkyl, alkaryl or halogenated alkaryl. The hydrocarbon substituents generally contain from 1 to 10 carbon atoms, preferably methyl or ethyl groups. R2 is independently selected from the same group as Ri, and n is an agent of at least 2 and generally in the range of 3 to 100. The molecular weight of the silicon compound employed is generally between about 80 to the approximate 20,000 form and preferably within of the approximate range of 150 to 10,000. Representative silicon compounds include dimethyl silicon, diethyl silicon, phenylmethyl silicon, dimethylhydrogen silicon, ethylhydrogen silicon, phenylhydrogen silicon, methylethyl silicon, phenylethyl silicon, diphenyl silicon, methyltrifluoropropyl silicon, ethyltrifluoropropyl silicon, polydimethyl silicon, tetrachlorophenylmethyl silicon, tetrachlorophenylethyl silicon, tetrachlorophenylhydrogen silicon , tetrachlorophenyl phenyl silicon, methylvinyl silicon and ethylvinyl silicon. Silicon compounds do not need to be linear, but they can be cyclic, for example, hexamethyl, cyclotrisiloxane, octamethyl cyclotetrasiloxane, hexaphenyl cyclotrisiloxane and octaphenyl cyclotetrasiloxane. Mixtures of these compounds can also be used, as silicones with other functional groups. Other silicon compounds, including silanes and alkoxy silanes, such as tetramethoxy silane, can also be used. These silicon-containing selectivity agents employed include silanes characterized by the general formula: R2 I F -Si -R3 i wherein Ri, R2 R3 and R4 are independently selected from the group consisting of hydrogen, hydroxyl, halogen, alkyl, halogenated alkyl, alkoxy, aryl, halogenated aryl, aralkyl, halogenated aralkyl, alkaryl, and halogenated alkaryl groups. Mixtures of these compounds can also be used. Preferred silicon-containing selectivity agents include dimethylphenylmethyl polysiloxanes (e.g., Dow-550) and phenylmethyl polysiloxane (e.g., Dow-700). Dow-550 and Dow-710 are obtained from Dow Chemical Co. Preferably the kinetic diameter of the silicon-containing selectivity agent is greater than the pore diameter of zeolite, in order to prevent the selectivity agent from entering the pore and any concomitant reduction in the internal activity of the catalyst. After or each of the applications of the silicon-containing selectivity agent, the zeolite is calcined at 350-550 ° C for 1-24 hours to convert the organosilicon compound to silica. In an alternative embodiment, the cover of the modifying diffusion surface comprises coke and is produced by the pre-bake ex-situ or in-situ of the zeolite. Precooking is conveniently effected by passing an aromatic hydrocarbon, such as toluene, over the zeolite at a relatively high temperature of 500 ° C-650 ° C as well as to deposit at least about 1% by weight, preferably 1-30% by weight. weight of the same coke. The catalyst of the invention may include bonds or matrix of material resistant to temperatures and other conditions employed in the organic conversion process. Such materials include active and inactive materials and natural or synthetic zeolites as well as inorganic materials such as clays, silica and / or metal oxides such as alumina. Subsequently it may exist either naturally or in the form of gelatinous precipitates or gels, which include mixtures of metal or silica oxides. The use of a material tends to be active by changing the conversion and / or selectivity of the catalyst in certain organic conversion processes. Suitable inactive materials serve as diluents for the control of the amount of conversion in a given process so that the products can be obtained economically and orderly without the use of other means for controlling the reaction rate. These materials can be incorporated as clays of natural forms, for example, bentonite and kaolin, to improve the strong pressure of the catalyst under commercial operating conditions. Said materials, ie, clay, oxides, etc., function as bonds for the catalyst. It is desirable to provide a catalyst that has good strong pressure, due to its commercial use, it is convenient to prevent the catalyst break or break into dust-like materials. This clay and / or oxide bond have been commonly employed for the sole purpose of improving the strong pressure of the catalyst. Natural clays, which can be composed of the new crystals, include the montmorillonite and kaolin family, in which the families include the subentonites, and the kaolins commonly known as Dixie, McNamme, Georgia and Florida clays or others. in which the main constituent of the mineral is haloisite, kaolinite, diclite, nacrite, or anauxite. Such clays can be used in the raw state as original mines or initially subjected to calcination, acid treatment or chemical modification. In addition to the aforementioned materials, the ZSM-5 can be composed of a porous matrix material such as silica-alumina, silica-magnesia, silica-zirconia, silica-topa, silica-berilia, silica-titania, as well as ternary compositions such as silica-alumina. -tOi '. a, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia ..

The relative proportions of the finely divided ZSM-5 material and the abundant organic oxide matrix have a ZSM-5 content within the range of 1 to about 90% by weight and more usually in the range of 2 to the approximate form of 80% by weight of the compound. It is appreciated that, through the bond or matrix and the modifying diffusion refractory cover can be formed from the same material, such as silica, there are separate components of the catalyst normally formed by different steps in the catalyst production process. For example, the ZSM-5 can be compounded with the bond or matrix and the resulting composite provided with a cover of a refractory material. Alternatively, the refractory cover can be applied to the ZSM-5 crystals before they are subsequently compounded with the bond or matrix. A hydrogenation / dehydrogenation function can be introduced into the catalyst of the invention, such as the addition of a metal compound such as platinum. While platinum is the preferred metal, other metals from Groups IB to VIII of the Periodic Table can be used, such as palladium, nickel, copper, cobalt, molybdenum, rhodium, ruthenium, silver, gold, mercury, osmium, iron , zinc, cadmium, and mixtures thereof. The metal can be added by cation exchange, in amounts of from about 0.001% to about 2%, typically about 0.5%. for example, a modified platinum catalyst can be prepared by contacting or mixing the catalyst with an aqueous solution of tetramine of platinum nitrate (II) or tetramine of platinum (II) chloride. The catalyst can then be filtered, washed with water and calcined at temperatures of 250 ° C to the approximate 500 ° C shape. The catalyst of the invention is employed in a wide variety of hydrocarbon conversion processes of selective forms, including as non-limiting examples, thermal decomposition of selective hydrocarbon, for example n-paraffins to reducing points of hydrocarbons with reaction conditions including a temperature of 300 ° C to a shape of about 700 ° C, a pressure of about 0.1 atmospheres (1 bar) to about 30 atmospheres (10 to 3000 kPa) and a space velocity per hour by weight of about 0.1 hr ~ "a approximately 20 hr "1; converting the paraffins or olefins to aromatics, for example, benzene, toluene and xylene, with reaction conditions including a temperature of from about 100 ° C to about 700 ° C, a pressure of from about 0.1 atmospheres to about 60 atmospheres (10 to 6000) kPa), a space velocity per hour by weight of from about 0.5 to about 400 and a hydrogen / hydrocarbon mole ratio of from about 0 to about 20; isomerizing alkylaromatics such as xylenes, to a para-isomer rich product with reaction conditions including a temperature of about 250 ° C to about 540 ° C, a pressure of about 0 to about 1000 psig (100 to 7000 kPa) ), a space velocity per hour by weight of from about 0.1 to about 250 and a ratio of moles of hydrogen / hydrocarbon from about 0 to about 20; disproportionation of aromatic alkyl, such as toluene and ethylbenzene, with reaction conditions including a temperature of 100 ° C to an approximate 600 ° C, a pressure of about 0 to about 2000 psig (100 to 14,000 kPa), ratio of hydrogen / hydrocarbon moles from 0 to about 10 and a space velocity per hour by weight from 0.1 to about 100; alkylated aromatic hydrocarbons; for example benzene and alkylbenzenes in the presence of an alkylating agent, for example, olefins, formaldehydes, alkyl aldehydes and alcohols, with reaction conditions including a temperature from about 250 ° C to about 500 ° C. an atmospheric pressure of 200 atmospheres (100 to 20,000 kPa), a space velocity per hour by weight of 2 to an approximate form of 2000 and a ratio of moles of aromatic / alkylated hydrocarbon agent of about 1/1 to an approximate form of 20 /1; and dealkylating alkylaromatics, such as the conversion of ethylbenzene to benzene and C2- light gas, with reaction conditions including a temperature of about 200 ° C to about 540 ° C, a pressure of 0 to about 1000 kPa (100 to 7000) kPa), a space velocity per hour by weight of from about 0.1 to an approximate form of 200 and a hydrogen / hydrocarbon mole ratio of from about 0.5 to an approximate form of 20. In a preferred embodiment, wherein the catalyst of the invention is used in the disproportionation of toluene, the conditions for the process preferably include a temperature of 350-540 ° C, a pressure of 15-800 psig (200-5600 kPa), a ratio of moles of hydrogen to hydrocarbon of 0.1-10 , and a WHSV of 1-10. In another preferred embodiment, wherein the catalyst of the invention is used in the isomerization of xylene, the conditions for the processes preferably include a temperature of 350-500 ° C, a pressure of 50-400 psig (400-3000 kPa), a ratio of moles of hydrogen to hydrocarbon of 1-10, and a WHSV of 3-50. In order to more fully illustrate the nature of the invention and the manner of practicing it, the following examples are presented. In the examples, references are made to the diffusion rates of the characteristics of the porous crystalline materials in particular for 2,2-dimethylbutane. The proportion of the diffusion characteristic is defined as D / r2xl0, where D is the diffusion coefficient (cm2 / sec) and r is the radius of the crystal (cm). the required diffusion parameters can be derived from the absorption measurements provided, the hypothesis is made in the sheet model of the plane that describes the diffusion process. Also, for a given charge in the sorbate Q, the value Q / Q, where Q4 is the equilibrium sorbate charge and is directly proportional to (Dt / r2) 1 where t is the time (sec) required to reach the load of the sorbate Q. The graphic solutions for the model of the sheet of the plane are given by J. Crank in "The Mathematics of Diffusion", Oxford University Press, Ely, London, 1967. The proportion of the diffusion characteristic is measured at a temperature of 120 ° C and a pressure 2, 2-dimethylbutane of 60 torr (8 kPa).

Example 1 They were dissolved in 8.0 parts of H20, 1.0 parts of Al2 (S04) 3.xH20. To this solution was added 1.98 parts of 50% of a sodium hydroxide solution. Dissolving 1. 12 parts of a sodium mono salt was obtained a solution of glutamic acid (MSG) in 2.71 parts of H20 that were added to the previous solution. To this mixture was added 4. 03 parts of Ultrasil of precipitated silica. The suspension was mixed perfectly and then 0.1 parts of ZSM-5 seeds were added to the mixture (solid bases) suspended in 2.28 parts of H20 and the final suspension was mixed for 30 minutes. The composition of the reaction mixture in proportions of mole was: Na + / Si02--0.50 Si02 / Al203 = 36.0 OH / Si02 = 0.50 R / SÍO2 = 0.10 H20 / Si02 = 12.0 The mixture was crystallized in a stainless steel reactor , with stirring at 100 rpm, at 156 ° C for 60 hours. The crystalline product was isolated by filtration and calcined for 16 hours at 538 ° C. An X-ray analysis of the product showed a crystalline material ZSM-5. The molar ratio of the silica / alumina mass of the material was 29.6.

Example 2 The calcined product of Example 1 was contacted or mixed with a 10% solution of NH4C1, It will give the three, 1 hour of contact or mixed at 85 ° c. with aqi ation. Er > -tonces was calcined by 3 o'clock at 5330 c # ^^ converted to the hydrogen form. The material was observed to have an alpha value of 1454. The Microscope for Meticulous Examination (SEM) showed the presence of crystals of 1-3 microns.

Example 3 A sample of the calcined product of Example 1 was mixed with VN3SP Ultrasil silica and Ludok HS-40 silica to give a composite mixture of 65% ZSM-5 / 17.5% SiO2 Ultrasil / 17.5% Ludox SiOg in a 100 % of solid bases. Deionized water (DI) and 3% NaOH (in 100% solids bases) were added to give an extrudable mixture which was extruded to 1/16 inch (l.ßmm) in diameter. The extrudable was dried at 120 ° C, exchanged with an NHN03 IN solution, washed with DI deionized water, dried again at 120 ° C and calcined at 540 ° C for 3 hours. The ammonium removed, washed, dried and calcined was repeated to give a catalyst with an alpha value of 1017 and a sodium content of 70 ppm. The catalyst, there identified as Catalyst A, exhibited a characteristic diffusion ratio of 2,2-dimethylbutane of 27 sec "1 as a measure at 120 ° C and 60 torr (8 kPa) of hydrocarbon pressure.

Example 4 Catalyst A of Example 3 was selective to silicon ex-situ by impregnation at room temperature with Dow 550 in n-decane so that the components were in a weight ratio 1, part of catalyst: 1: 1 part of n-decane: 0.080 parts of Dow 550. After impregnation, the solvent was sectioned by evaporation and the catalyst calcined at 540 ° C mainly in nitrogen for 2 hours, and then in air for 6 hours to give Catalyst B. the same selectivity procedure was repeated for seconds and third cycles to give Catalysts C and D, respectively, with small samples before removing them after each cycle for catalytic evaluation. The characteristic diffusion ratios for 2,2-dimethylbutane measured at 120 ° C and 60 torr (8 kPa) of hydrocarbon pressure for the selective catalysts were as follows: Catalyst B (Selectivity lx) = 7.5 sec "1 Catalyst C (selectivity 2x) = 2.3 sec" 1 Catalyst D (selectivity 3x) = 1.6 sec "1 The catalytic evaluation of each of the selective samples was carried out by mixing 2 grams of the sample with inert sand and loading the mixture into a 0.375 inch (9.5 mm) diameter reactor tube. The reactor was heated in hydrogen and in a hydrogen / toluene feeder 2: 1 was introduced at 3 WHSV, 270 psig (1960 kPa). The temperature was adjusted to carry out the toluene conversion of about 30% by weight and the p-xylene selectivity was measured (by weight of the product C0). The results are shown in Table 1 below.

By means of comparison, a series of four prior art catalysts were produced from ZSM-5 having a crystal size of less than 0.5. The catalysts were subjected to one (Catalyst E), two (Catalyst f), three (Catalyst G), and four (Catalyst H) of the selectivity cycles described above and were tested in the same way as the BD Catalysts of the invention . The results are also given in Table I.

Table I Catalyst No. of Temperature% Conversion Selections ° C of Tolueno p-xi ler.o Invention B 1 390 30 37.4 C 2 395 30 79.4 D 3 395 30 89.3 Prior art E 1 395 30 24.9 F 2 410 30 30.9 G 3 416 30 63.0 H 4 428 30 86.4 From Table I it will be seen that by using the catalyst the large crystal ZSM-5 of the invention, a conversion of toluene of 30% and a p-xylene selectivity of about 90% at a temperature of 395 ° C is reached only after the 3 steps of selection of silicon ex-situ (Catalyst D). In contrast, using the catalysts of the prior art ZSM-5, 4 selection steps and a temperature of 428 ° C are required to achieve the same conversion of toluene and selectivity levels of p-xylene (Catalyst H).

Example 5 A sample of the calcined product ZSM-5 of Example 1 was mixed with silicon VN3SP Ultrasil and ground for 5 minutes. To this mixture was added 14 weight% of 550 Dow resin solids (a polysiloxane) dissolved in 23% dibasic ester, followed by silicon H5-40 Ludox, then 50% NaOH (to give 3% NaOH in 100% of solid base) dissolved in enough water to give an extrudable fine muslin. The proportions of ZSM-5, Ultrasil and Ludox were used as such to give 65% Si02 ZSM-5 / 17.5%, Si02 ex Ultrasil / 17.5%, Si02 ex Ludox at 199% base solids. The resulting mixture was extruded to 1/16 inch (1.6 mm) in diameter. The extrudates were dried at 120 ° C and subjected to 4 cycles of the ammonium exchange / calcination sequence described in Example 3 to give a catalyst with an alpha value of 1089, a sodium content of 2200 ppm and a characteristic ratio 2-dimethylbutane diffusion of 4.3 sec "1 measured at 120EC and 60 torr (0 kPa) of hydrocarbon pressure." The resulting catalyst, identified as Catalyst I, was subjected to catalytic tests as in Example 4 and the Results are given in Table 2.

Example 6 A sample of Catalyst I of Example 5 was ammonium / calcinated exchange to reduce its sodium levels to less than 700 ppm and then subjected to a simple ex-situ silicon selectivity procedure as described in Example 4 The resulting catalyst, identified as Catalyst J, and the samples of Catalyst A (example 3) and Catalyst F (catalyst of the prior art of Example 4) were subjected to catalytic tests as in Example 4. The results are listed in the Table 2 Table 2 Catalyst A I j F No. of 0 1 2 selectivity O ex-situ Temp. ° C 400 410 401 396 Pressure (psig) 272 272 274 275 H2: HC 2 2 2 2 Conv. Tolueno, 30 29. 9 29. 3 30 4% weight Produc. Xylene 16.1 16. 1 14. 3 15. 8 i Weight Selectivity 24 31. 9 86. 0 51. 9 p-xylene,% weight Selectivity 1.0 1.0 2.4 1.5 < ethylbenzene,% weight Benzene / xylene 1.1 1.1 1.25 1.11 (molar) C, "0.5 0.4 0.89 0.58 C, * 0.6 0.7 0.72 0.79 It will be seen in Table 2 that the coextrusion of the ZSM-5 of the Example with the organosilicon compound Dow 550 resulted from a base catalyst, Catalyst I, which was more selective for the production of p-xylene than the base catalyst coextruded with silica. Catalyst A. Additionally, an individual selection cycle of co-extruded base catalyst with Dow 550 results in an 86% increase in p-xylene selectivity (Catalyst J), compared to a p-xylene selectivity of only 37.4% after first selection cycle for the catalyst co-extruded with silica (see Catalyst B in Table 1). In contrast, when the catalyst was produced from ZSM-5 with a crystal size of 0.2-0.5, micron, 2 cycles of ex-situ selection resulted in a p-selectivity of only 52% (Catalyst F in Table 2).

Example 7 A sample of the calcined ZSM-5 product of Example 1 was mixed with LaRoche Versal 300 alumina in proportion to give 65:35 ZSM-5: A1203 in a 100% solids base, and ground for 10-15 minutes. Sufficient DI deionized water was then added for a period of 10 minutes to give a fine extrudable muslin. The resulting mixture was extruded to 1/16 inch (1.6 mm) in diameter. The resulting extrudate was dried at 120 ° C and calcined in liquid nitrogen at 540 ° C for 3 hours. The calcined extrudate was then removed with an IN solution of NH4N0, washed with deionized water, dried at 120 ° C and calcined in an air flow at 540 ° C for 3 hours to give a catalyst with an alpha value of 661, a content sodium of < 50 ppm and a diffusion characteristic ratio for 2,2-dimethylbutane of 110 sec "1 measured at 120 ° C and 60 torr (8 kPa) of hydrogen pressure.

Example 8 The catalyst of Example 7 was selectively calcined using a simulated commercial calcination-selection method. 0.4 grams of the catalyst was mixed with inert sand and loaded into a 0.375"(9.5 mm) diameter stainless steel tube reactor.The samples were dried in hydrogen overnight at 300 ° C and 235 psig (1720 kPa) , where after the temperature of the catalyst bed was increased to 565 ° C and the flows of toluene (1.67 hr "1), H2 (0.5 H2: C1) were established from the calcining process. After 1.3 days in system, the calcination procedure was stopped and the catalyst was separated from the hydrogen at 470 ° C overnight to remove any reactive species from the catalyst. After hydrogen was removed, the reactor pressure was increased to 270 psig (1960 kPa), the reactor temperature was adjusted to 400 ° C and the toluene and hydrogen fluxes were established for the reactor at 3 hr "1 WHSV and 1 H2 / HC The reactor effluent was continuously monitored and the temperature adjusted to approximately 30% of the toluene conversion A summary of this catalytic information is shown in Table 3.

Table 3 Calcining time, days 1.30 WHSV, hr-1 3 H2: HC 1 Temp. ° C 385 Pres. (Psig) 261 Conv. Toluene % weight 29.9 Produc. Xylene% weight 15.6 Sel. P-sileno. % weight 68.8 Sel., Ethylbenzene% weight 1.80 Benzene / Xylene (molar) 1.10 C5- 0.46 C9 + 0.94 Example 9 The coke selectivity catalyst previously of Example 8 was further selective coke at 565 ° C for an additional 0.42 days. Therefore at the end of the calcined period in this example, the main catalyst of Example 8 was coke selectivity for a total of 1.72 days. After the procedures for calcination and separation of hydrogen comprised in Example 8, the reactor pressure was increased to 270 psi and the reactor temperature was adjusted to 400 ° C, in preparation for the catalytic evaluation. After a second coke selectivity treatment, the toluene and hydrogen fluxes were established to the reactor at 3 hr-1 MHSV, 270 psig and 1 H2 / HC. As before, the reactor effluent was continuously monitored and the reactor temperature adjusted to approximately 30% of the toluene conversion. A summary of the catalytic information is shown in Table 4.

Table 4 Calcination time, days 1.72 WHSV, hr-1 3 H2: HC 1 Temp. ° C 396 Pres. (Psig) 276 Conv. Toluene % weight 29.9 Produc. Xylene% weight 14.8 Sel. P-sileno. % weight 83.3 Sel., Ethylbenzene% weight 2.21 Benzene / Xylene (molar) 1.13 C5- 0.61 C9 + 0.91 Example 10 The coke-selective catalyst previously of Example 9 was in addition to coke selectivity at 565 ° C for an additional 0.47 days. Therefore at the end of the coke selectivity period in this example, the main catalyst of Example 7 was coke selectivity for a total of 2.19 days. After the procedures for calcination and separation of hydrogen comprised in Example 8, the reactor pressure was increased to 270 psig and the reactor temperature adjusted to 400 ° C in the preparation for catalytic evaluation. After a second treatment of calcination selectivity, the toluene and hydrogen fluxes were established to the reactor at 3 hr-1 MHSV, 270 psig and 1 H2 / HC. As before, the reactor effluent was continuously monitored and the reactor temperature adjusted to approximately 30% of the toluene conversion. A summary of the catalytic information is shown in Table 5.

Table 5 Calcining time, days 2.19 2.19 WHSV, hr-1 3 3 H2: HC 2 1.5 Temp. ° C 416 415 Pres. (Psig) 271 276 Conv. Toluene % weight 30.6 30.0 Produc. Xylene% weight 12.7 12.8 Sel. P-sileno. % weight 92.7 92.5 Sel., Ethylbenzene% weight 3.5 3.31 Benzene / Xylene (molar) 1.58 1.50 C5- 1.80 1.55 C9 + 0.97 0.94 Following the third calcining treatment, the catalyst was highly selective for the formation of p-xylene, giving approximately 93% selectivity of p-xylene at 416 ° C and 30% conversion of toluene, although slightly reduced in the xylene product compared with the catalyst of Example 9.

It is noted that in relation to this date, the best method known by the Applicant to carry out the aforementioned invention, is that which is clear from the manufacture of the objects to which it relates. Having described the invention as above, the content of the following is claimed as property.

Claims (18)

1. A catalyst selectively comprising a synthetic porous crystalline material having the structure of ZSM-5 and a composition involving the molar ratio: X203: (n) Y02 / characterized in that X is a trivalent element, such as aluminum, boron, iron and / or gallium, preferably aluminum; Y is a tetravalent element such as silicon and / or germanium, preferably silicon; and n is greater than 12, and wherein the crystals have a larger dimension of at least about 0.5 microns and a ratio of surface YO2 / X2O3 which is not more than 20% less than the mass ratio Y02 / X203 of the crystal; the catalyst having a surface coating modifying the diffusion of a refractory material.

2. The catalyst according to claim 1, characterized in that the ratio of the surface Y02 / X2? 3 is not greater than 10% less than proportion of the mass YO2 / X2O3 of the crystal.

3. The catalyst according to claim 1, characterized in that? it is selected from the group consisting of aluminum, boron, iron and / or gallium, and Y is selected from the group consisting of silicon and / or germanium.

4. The catalyst according to claim 1, characterized in that X is aluminum and Y is silicon.

5. The catalyst according to claim 1, characterized in that n is less than about 100.

6. The catalyst according to claim 1, characterized in that n is from 25 to approximately 40.

7. The catalyst according to claim 1, characterized in that the catalyst has a larger dimension of at least about 1 micron.

8. The catalyst according to claim 1, characterized in that the cover of the modified diffusion surface is selected from the group consisting of coke, a metal oxide, a non-metal oxide and a non-oxide ceramic.

9. The catalyst according to claim 1, characterized in that the cover of the modifying diffusion surface comprises silica.

10. The catalyst according to claim 9, characterized in that the silica cover is produced by the steps by (a) treating the zeolite with an organosilicon compound and (b) converting the organosilicon compound to silica.

11. The catalyst according to claim 11, characterized in that step (a) is carried out during the mixing of the zeolite with particles of a binder or matrix.

12. The catalyst according to claim 10, characterized in that steps (a) and (b) are repeated at least once.

13. The catalyst according to claim 1, characterized in that the cover of the modifying diffusion surface comprises coke.

14. A process for the conversion of hydrocarbon in selective form characterized in that it comprises a reaction system comprising a hydrocarbon to be converted, under conditions of conversion with the catalyst of claim 1.

15. The process according to claim 14, characterized in that the hydrocarbon conversion of the selective form is selected from a group consisting of selective hydrocarbon, isomerization of alkylaromatics, disproportionation of alkylaromatics, alkylation of aromatics, dealkylation of alkylaromatics and conversion of paraffins and olefins to aromatics.

16. The process according to claim 15 characterized in that the feeder stack comprises toluene and the conversion of the selective disproportionation of toluene to para-xylene.

17. The process according to claim 16, characterized in that it is carried out at a temperature of about 100 ° C to about 600 ° C, a pressure of about 0 to about 2000 psig (100 to 14000 kPa), a ratio of hydrogen / hydrocarbon mole from 0 to an approximate shape of 10 and a space velocity per hour by weight from 0.1 to an approximate shape of 100.

18. The process according to claim 16, characterized in that the conversion is carried out at a temperature of 350-540 ° C, a pressure of 15-800 psig (200-5600 kPa), a ratio of moles of hydrogen to hydrocarbon of 0.1- 10, and a space velocity per hour by weight of about 1-10.