MXPA97006330A - Zeolita nu-88, procedure for its preparation and its applications cataliti - Google Patents

Abstract

The present invention is concerned with a new zeolite subsequently named herein, zeolite NU-88, its preparation process, any catalyst comprising the zeolite and any catalytic process using the catalyst.

Description

ZEOLITE NU-88, PROCEDURE FOR ITS PREPARATION AND ITS CATALYTIC APPLICATIONS Description of the invention The present invention is concerned with a new zeolite subsequently named herein, zeolite NU-88, its preparation process, any catalyst comprising the zeolite and any catalytic process using the catalyst. Thus, according to the present invention, zeolite NU-88 is characterized by i) a chemical composition expressed in an anhydrous base in terms of molar ratios of oxides, by the formula: wherein m is equal to or less than 10, p is equal to or less than 20, R represents one or more cations of valence n, X is silicon and / or germanium, preferably silicon, and is chosen from the group formed by the following elements: aluminum, iron, gallium, boron, titanium , vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, preferably Y is aluminum and ii) the fact that it has, in a crude synthesis form, a diffraction diagram X comprising the results presented in table 1.

REF: 25388 Table 1: X-ray diffraction table of zeolite NU-88 (crude synthesis) (1) These peaks are not resolved and are part of the same total. (2) These peaks are not resolved and are part of the same total. The invention is also concerned with the zeolite NU-88 in hydrogenated form, designated by H-NU-88, produced by calcination and / or ion exchange as described hereinafter. The zeolite H-NU-88 has an X-ray diffraction diagram comprising the results presented in table 2 Table 2: X-ray diffraction table of zeolite NU-88 (hydrogenated form) Table 2: X-ray diffraction table of zeolite NU-88 (hydrogenated form) (Continued) (1) These peaks are not resolved and are part of the same total. (2) These peaks are not resolved and are part of the same total. These diagrams are obtained with the help of a diffractometer, using the classic method of pulvidifractometry with copper Ka K Cu irradiation. From the position of the diffraction peaks represented by the angle 2T, the reticular equidistances dh? J characteristic of the sample are calculated by means of the Bragg relation. The calculation of the intensity is made based on a scale of relative intensity on which a value of 100 is attributed to the line with the strongest intensity in the diffraction diagram X and then: very weak (tf) means less than 10, weak (f) means less than 20, average (m) means between 20 and 40, strong (F) means between 40 and 60, very strong (TF) means higher than 60. X diffractograms from which data have been obtained (relative intensity spacings) are characterized by large reflections with numerous peaks forming the bases of other peaks of higher intensity. It may happen that certain bases or all the bases are not resolved, which can be produced by weakly crystalline samples or samples within which the crystals are small enough to give a significant extension of the X-rays. This could also be the case when The equipment or conditions applied to obtain the diagram differ from those used herein. It is estimated that the zeolite NU-88 has a new base structure or topology that is characterized by its X-ray diffraction pattern. The zeolite NU-88 under its "crude form of synthesis" possesses the characteristics obtained by diffraction of rays. X, presented in table 1 and is thus distinguished from known zeolites. The object of the invention also comprises any zeolite of the same structural type as that of the zeolite NU-88. Tables 1 and 2 and the diffractograms of figures 1 and 2 are relatively uncommon for zeolitic structures. As a consequence, these data seem to indicate that zeolite NU-88 has a predetermined structure. Within the framework of the definition of the chemical composition given hereinabove, m is generally comprised between 0.1 and 10, preferably between 0.2 and 9 and even more preferably between 0.6 and 8.; It seems that the zeolite NU-88 is generally looser in a very pure form when m is between 0.6 and 8. This definition also covers the zeolite NU-88 in its "crude form of synthesis" as well as the forms obtained by dehydration and / or calcination and / or ion exchange. The expression "in its crude form of synthesis" designates the product obtained by synthesis and by washing with or without drying or dehydration. In its "crude form of synthesis" zeolite NU-88 may comprise a metal cation M, which is an alkali metal, particularly sodium and / or ammonium, may comprise nitrogen-containing organic cations such as those described hereinafter or its products of decomposition or even its precursors. These organic nitrogenous cations are designated herein by the letter Q which also includes the decomposition products and the precursors of the organic nitrogen cations. Thus, the zeolite NU-88, in its "crude form of synthesis" (not calcined), is characterized by: i) a chemical composition expressed in an anhydrous base, in terms of molar ratios of oxides: 100 XO ?: lower or equal to 10 Y2O3: less than or equal to 10 Q: less than or equal to 10 M2O, where X is silicon and / or germanium, Y is chosen from the group consisting of the following elements: aluminum, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, M is at least one alkali metal cation (group IA of the periodic classification of the elements) and / or ammonium, and Q is at least one cation nitrogen organic or a precursor of organic nitrogenous cation or a decomposition product of organic nitrogenous cation. ii) the fact that it presents, in a crude synthesis form, an X-ray diffraction diagram comprising the results presented in Table 1. The compositions indicated hereinabove for the zeolite NU-88 are given in an anhydrous base , either as the zeolite NU-88 in its "crude form of synthesis" and the activated forms of the zeolite NU-88, ie resulting from a calcination and / or an ion exchange, which may contain water. The molar content of H20 of such formulas and comprising the zeolite NU-88 in its "crude form of synthesis", varies according to the conditions in which they have been prepared and preserved after synthesis or activation. The molar amounts of water contained in these forms are usually comprised between 0 and 100% of X02. The calcined forms of the zeolite NU-88 do not contain any nitrogenous organic compounds or in a smaller quantity than the "crude form of synthesis" insofar as the organic substance is largely eliminated, generally by a heat treatment consisting of burn the organic substance in the presence of air, the hydrogen ion (H +) then forms the other cation. Thus, zeolite NU-88 in its hydrogenated form is characterized by: i) a following chemical composition, expressed on an anhydrous basis, in terms of molar ratios of oxides: 100 X02: less than or equal to 10 Y203: less than or equal to to 10 M20, where X is silicon and / or germanium, and is chosen from the group consisting of the following elements: aluminum, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese , and M is at least one alkali metal cation (group 1A of the periodic classification of the elements) and / or ammonium and / or hydrogen, ii) the fact that it has, in a crude synthesis, a diffraction diagram X-ray comprising the results presented in Table 2. Among the forms of zeolite NU-88 obtained by ion exchange, the ammonium form (NH /) is important because it can be easily converted to the hydrogenated form by calcination. The hydrogenated form and the forms containing metals introduced by ion exchange are described hereinafter. In certain cases, the fact of subjecting the zeolite according to the invention to the action of an acid can lead to the partial or total elimination of a base element such as aluminum, as well as the generation of the hydrogenated form. This can be a means to modify the composition of the substance of the zeolite after it has been synthesized. The invention also makes it possible to obtain the zeolite NU-88 in hydrogenated form, called H-NU-88, produced by calcination and by ion exchange as described hereinafter. One of the objects of the invention is thus the zeolite NU-88 at least partly in H + form (as defined hereinabove) or H or metal, the metal is chosen from the group formed by the groups IA, IB, HA, IIB, IIIA, IIIB (including rare earths), VIII, Sn, Pb and Si, preferably at least in part, in H + form or at least partly in metallic form. A zeolite as such has in general an X-ray diffraction diagram comprising the results presented in table 1. The invention is also concerned with a method of preparing the zeolite NU-88, in which an aqueous mixture is reacted comprising at least one source of at least one oxide X02, at least one source of at least one oxide Y2? 3, optionally at least one source of at least one oxide M20 and at least one organic cation Q nitrogenated, or a nitrogenous organic cation precursor or a nitrogen organic cation decomposition product, the mixture generally has the following molar composition: X02 / Y2O3 at least 10, preferably 10 to 60, even more preferably 15 to 50 (R1 / n) OH / X02 from 0.01 to 2, preferably from 0.05 to 1, more preferably from 0.10 to 0.75 H20 / X02 from 1 to 500, preferably from 5 to 250, even more preferably from 25 to 75 Q / X02 from 0.005 to 1, preferably from 0.02. to 1, still more preferably from 0.05 to 0.5 LpZ / X02 from 0 to 5, preferably from 0 to 1, even more preferably from 0 to 0.25, wherein X is silicon and / or germanium, preferably silicon, and it is chosen from the group consisting of the following elements: aluminum, iron, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, gallium, chromium, manganese, preferably Y is aluminum.

R is a valence cation n comprising M (an alkali metal and / or ammonium cation) and / or Q (an organic nitrogen cation or a precursor thereof or a decomposition product thereof). LpZ is a salt, Z is a valence anion p and L an alkali metal or ammonium ion that can be similar to M or a mixture of M and another alkali metal ion or an ammonium ion necessary to balance the anion Z, Z it may comprise an acid radical added, for example, in the form of a salt of L or of an aluminum salt. In certain cases, it may be advantageous to add a salt of LpZ. Thus, a preferred preparation process is wherein the aqueous medium comprises the salt. Mention may be made, by way of example, for Z, strong acid radicals such as bromide, chloride, iodide, sulfate, phosphate or nitrate or weak acid radicals such as organic acid radicals, for example citrate or acetate. Although LpZ is not essential, it can accelerate the crystallization of zeolite NU-88 from the reaction mixture and can also affect the size and shape of the crystals constituting the zeolite NU-88. In any case, the reaction is continued until the crystallization is obtained. Numerous zeolites have been prepared with organic nitrogenous cations and heterocyclic cores have in particular been quite used for the synthesis of the zeolite. Zeolite ZSM-12 has been synthesized by using different heterocyclic forms, for example the structure based on pyrolidinium.

(CH3) and the piperidinium-based structure: it has been described by Rosinski and others in U.S. Patent 4,391,785 (Mobil). The synthesis of zeolite TPZ-12, which is an isomer of structure of zeolite ZSM-12, is described by Teijin in European patent application EP-A-135,658. The structures considered to be suitable for the synthesis of pure TPZ-12 zeolite are those based on bispyrrolidinium and those based on bispiperidinium wherein n is varied from 4 to 6 and and R2: H, methyl, ethyl, propyl or butyl. The synthesis of zeolite ZSM-12 has also been carried out with structures comprising more than one heterocyclic nucleus. The use of the compound of the polymormonium type it is described by Valyocsik in U.S. Patent 4,539,193 (Mobil).

The use of bis (butylpyrrolidinium) -based structures of general formula: it is described by Valyocsik in U.S. Patent 4,941,963 (Mobil). Four structures have been tested by varying n from 4 to 7. The synthesis of the pure zeolite ZSM-11 has been carried out only with n equal to 6 or 7. According to the invention, Q is preferably a cation of bis ( methyl pyrrolidinium), or one of its decomposition products or one of its precursors, of the general formula: with n = 4, 5 or 6, or Q is 1,4-bis (bisquinoclidinium) butane bromide or one of its decomposition products or one of its precursors, of the following chemical formula: for example, Q is 1,6-bis (methylpyrrolidinium) bromide, hexane, 1,5-bis (methylpyrrolidinium) bromide, pentane, 1,4-bis (methylpyrrolidinium) bromide, or Q is bromide of 1,4. -bis (quinoclidinio) butano.

M and / or Q may be added in the form of hydroxides or salts of mineral acids provided that the ratio (R? / ") OH / X02 is respected. Such substances can be used in the form of simple mixtures or they can be preheated together in the reactor, preferably in solution, before adding them to the other reagents necessary for the synthesis of the zeolite NU-88. The cation M used is preferably an alkali metal, in particular sodium, X02 is preferably silica (Si02) and the oxide Y2O3 is preferably alumina (AI2? 3). In the preferred case where X is silicon, the silica source can be any of those currently used in the synthesis of zeolites, for example solid silica powder, silicic acid, colloidal silica or dissolved silica. Among the powdered silicas, the precipitated silicas can be used, in particular those obtained by precipitation from an alkali metal silicate solution, such as the so-called "KS 300" manufactured by AKZO and similar products, aerosol silicas, pyrogenic silicas, for example " CAB-O-SIL "and silica gels in appropriate contents to be used in reinforcing pigments intended for rubber and silicone rubber. Colloidal silicas having different particle sizes can be used, for example of average equivalent diameter between 10 and 15 μm or between 40 and 50 μm such as those marketed under the trademarks "LUDOX", "NALCOAG" and "SYTON". The dissolved silicas which can be employed also comprise soluble, commercially available glass silicates, containing from 0.5 to 6.0, in particular 2.0 to 4.0 moles of SiO2 per mole of alkali metal oxide, "active" alkali metal silicates, such as those defined in British Patent GB-A-1, 193,254, and silicates obtained by the dissolution of silica in an alkali metal hydroxide or a quaternary ammonium hydroxide or even a mixture thereof. In the preferred case where Y is aluminum, the aluminum source is preferably sodium aluminate or an aluminum salt, for example chloride, nitrate or sulfate, an aluminum or alumina alkoxide itself, preferably in hydrated form or hydratable, such as for example colloidal alumina, pseudoboemite, gamma alumina or alpha or beta trihydrate. Mixtures of the sources cited above can also be used. Certain or the set of alumina and silica sources may eventually be added in the form of aluminosilicate. The reaction mixture is generally reacted under an autogenous reaction pressure, optionally gas, for example nitrogen, is added at a temperature between 85 ° C and 200 ° C, preferably between 120 ° C and 180 ° C and Even more preferred at a temperature not higher than 165 ° C, until the formation of zeolite crystals NU-88, these times vary in general between 1 hour and several months, depending on the composition of the reagent and the temperature of service . The reaction can be carried out with stirring, which is preferable insofar as the reaction time is reduced and the purity of the product improved. Germs can advantageously be used in order to reduce the time necessary for the formation of the crystals and / or the total crystallization time. It may also be advantageous to promote the formation of zeolite NU-88. Such germs comprise zeolites, in particular crystals of zeolite NU-88. The crystalline seeds are generally added in a proportion comprised between 0.01 and 10% by weight of silica used in the reaction mixture. At the end of the reaction, the solid phase is recovered in a filter and washed; it is taken immediately for the subsequent stages such as drying, dehydration and calcination and / or ion exchange. If the product of the reaction contains alkali metal ions, they must be removed at least in part, in order to prepare the hydrogenated form of the zeolite NU-88, by means of at least one ion exchange with an acid, in particular a mineral acid such as hydrochloric acid and / or with the aid of the ammonium compound obtained by ion exchange with a solution of an ammonium salt such as ammonium chloride. The ion exchange can be carried out by means of a thick suspension, in one or several taps, in the ion exchange solution. The zeolite is generally calcined before the ion exchange in order to remove any organic substance absorbed to the extent that ion exchange is facilitated. All operating conditions of such ion exchange are known to one skilled in the art. In general, it is possible to (p) replace the cation (s) of the zeolite NU-88 by any ation or all the metal cations, in particular those of the groups LA, IB, HA, IIB, I HA , IIIB (including rare earths) and VIII (including noble metals) of the periodic classification of the elements and, by extension, lead and bismuth. The exchange is usually carried out with a solution containing an appropriate cation salt, in a manner known to the person skilled in the art.

The invention is also concerned with the composition of a catalyst containing zeolite NU-88. Thus, one of the objects of the invention is a catalyst comprising a zeolite NU-88 as described above or prepared according to the preparation process described above. The invention also concerns a catalyst comprising a zeolite NU-88 as such and also comprising at least one bond or at least one support or at least one other zeolite or at least one metal selected from the group consisting of Elements Cu, Ag, Ga, Mg, Ca, Sr, Zn, Cd, B, Al, Sn, Pb, V, P, Sb, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Pt, Pd , Re and Rh. In the catalysts according to the invention, X02 is preferably silica and Y2? 3 is preferably alumina. Such catalysts can be used in a large number of catalytic processes and with a wide range of feed charges. The NU-88 zeolite forms useful in catalysis generally comprise the hydrogenated and ammonium forms prepared according to the methods described hereinabove. However, the catalysts according to the invention comprising zeolite NU-88 can also contain one or more elements, in particular metals or their cations or compounds of these elements, in particular metal oxides. These catalysts can be prepared by ion exchange or by impregnation of the NU-88 zeolite with the element, cation or compound or with an appropriate precursor of the cation or compound. An ion exchange as such or an impregnation as such can be carried out in the zeolite NU-88 at least in part, preferably completely in its "crude synthesis form" calcined or not, in hydrogenated form and / or in the form of ammonium and / or in any other form exchanged (metallic or not). In the case where a form of zeolite NU-88 containing a metal is prepared by ion exchange, it may be desirable to effect a complete exchange of the metal, which means that substantially the set of interchangeable sites is occupied by the metal. Such forms may be particularly useful in the separation processes. In most cases, however, it is preferable not to make more than a partial exchange of the metal, the remaining sites are occupied by another cation, in particular hydrogen or ammonium cations. In certain cases, it may be desirable to introduce two or more metal cations by ion exchange. In the case where the zeolite NU-88 is impregnated with a metal compound to form a catalyst, the metal compound can be added in an appropriate proportion, but a maximum proportion of 20% by weight is generally sufficient for most of the Applications; for certain applications, it is generally not more than 10% by weight and amounts ranging up to 5% are frequently appropriate. The impregnation can be carried out by any appropriate method, known in the framework of the preparation of catalysts. The metal exchange forms or the forms in which a metal compound has been impregnated can be used as is or treated in order to produce an active derivative. The treatments comprise reduction, for example in an atmosphere comprising hydrogen, in order to produce a metal or other reduced forms. These treatments can be carried out at an appropriate stage of the catalyst preparation or can also be carried out in the catalytic reactor. The catalyst compositions comprising the zeolite NU-88 may be associated, if desired, with a mineral matrix which may be either inert or active in the catalytic scheme. The matrix can only be used as a link to hold the zeolite particles together, optionally in the form of particles, for example in the form of a pellet or extrusion product or it can function as an inert diluent, for example to control the activity per unit of catalyst weight. When the mineral matrix or diurent presents by itself a catalytic activity, can thus form an effective part of the zeolite-matrix catalyst composition. Suitable mineral matrices and diluents comprise substances conventionally used as catalyst supports, such as silica, different forms of alumina, clays such as bentonite, montmorillonites, sepiolite, attapulgite, fuller's earth and synthetic porous materials such as silica- alumina, silica-zirconia, silica-torine, silica-glycine or silica-titanium dioxide. Matrix combinations can be devised within the framework of the present invention, in particular combinations of inert matrices and matrices having a catalytic activity. When the zeolite NU-88 is associated with a mineral matrix substance or a plurality of such substances, the proportion of the matrix substance (s) in the total composition is generally raised to about 90% by weight , preferably up to 50% by weight and even more preferably up to 30% by weight.

For certain applications, another zeolite or molecular sieve may be used in conjunction with the zeolite NU-88 to form a catalyst. A combination as such may be employed as such or associated with one or more of the matrix substances described hereinafter. Mention may be made, as a particular example of the application of a composition as such, of its use as a catalyst additive for fluid catalytic pyrolysis, in which zeolite NU-88 is preferably used in a proportion of 0.5 to 5% by weight of total catalyst. For other applications, zeolite NU-88 can be combined with another catalyst such as platinum on alumina. Any suitable method for mixing the NU-88 zeolite with an organic matrix and / or another zeolite, can be applied, in particular that adapted to the final form under which the catalyst is used, for example, as an extrusion product, tablet or granulated. If the NU-88 zeolites are used to form a catalyst together with a metal compound (for example a hydrogenation / dehydrogenation compound or other metal having a catalytic activity) in addition to the mineral matrix, the metal compound can be exchanged or impregnated in the zeolite NU-88 itself, before adding the matrix substance or in the composition of zeolite-matrix. For certain applications, it may be advantageous to add the metal compound to all or a portion of the matrix substance before mixing the latter with the zeolite NU-88. A wide range of hydrocarbon conversion catalysts comprising zeolite NU-88 can be prepared by ion exchange or by impregnation of the zeolite with one or more cations or oxides derived from elements chosen from the following: Cu, Ag, Ga, Mg , Ca, Sr, Zn, Cd, B, Al, Sn, Pb, V, P, Sb, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Pt, Pd, Re and Rh. In the case where the catalysts comprising zeolite NU-88 contain one or more hydrogenation / dehydrogenation compounds, such as Ni, Co, Pt, Pd, Re and Rh metals, these compounds can be introduced by ion exchange or by impregnation It is an appropriate compound of this metal. Catalyst compositions comprising zeolite NU-88 can find application in reactions comprising saturated and unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, oxygenated organic compounds and organic compounds containing nitrogen and / or sulfur, as well as organic compounds containing other functional groups. One of the objects of the invention is also concerned with any catalytic process in such a way that the zeolite NU-88 is comprised in the catalyst. In general, catalyst compositions containing zeolite NU-88 can be used effectively to perform isomerization, transalkylation and dismutation, alkylation and dealkylation reactions, dehydration and hydration, oligomerization and polymerization, cyclization, aromatization, catalytic pyrolysis, hydrogenation and dehydrogenation, oxidation, halogenation, synthesis of amines, hydrodesulphurization and hydrodenitrification, catalytic elimination of nitrogen oxides (either, preferably, by reduction, generally by nitrogen compounds or by hydrocarbons or by decomposition), ether formation, conversion of hydrocarbons and the synthesis of organic compounds in general. The processes mentioned hereinabove can be carried out either in the liquid phase, or in the vapor phase, under conditions chosen to be the most appropriate for each individual reaction. For example, the reactions carried out in the vapor phase can comprise the application of fluid bed, fixed bed or moving bed operations. Treatment thinners may be used if necessary. According to the application procedure, the appropriate diluents can be inert gases (such as nitrogen or helium), hydrocarbons, carbon dioxide, water or hydrogen. The diluent can be inert or it can exert a chemical action. It may be advantageous, in particular if hydrogen is used, to include a metal compound, such as a hydrogenation / dehydrogenation compound, for example one or more of the metals Ni, Co, Pt, Pd, Re or Rh in the catalyst composition. The present invention is also concerned with any hydrocarbon conversion process during which an alkylbenzene or a mixture of alkylbenzenes is contacted under isomerization conditions, in vapor or liquid phase, with a catalyst containing zeolite NU-88. Isomerization reactions for which catalysts containing zeolite NU-88 are particularly useful are those comprising alkanes and substituted aromatic molecules, in particular xylenes.

These reactions can include those that can be carried out in the presence of hydrogen. The catalyst compositions containing zeolite NU-88, which are particularly useful in the isomerization reactions, comprise those in which the zeolite NU-88 is presented in its acid form (H +), in the form obtained after the exchange of cations , in its form containing metals or in combinations of the precipitated forms. The forms in which the metal is a hydrogenation / dehydrogenation compound such as Ni, Co, Pt, Pd, Re or Rh are particularly useful. Particular isomerization reactions in which a catalyst containing zeolite NU-88 can be useful disclosed include the isomerization and hydroisomerization of xylenes or paraffins, in particular normal hydrocarbons of 4 to 10 carbon atoms, or the isomerization of olefins and the catalytic deparaffinity. Isomerization and hydroisomerization of xylene can be carried out in liquid phase or in vapor phase. In liquid phase, the appropriate isomerization conditions comprise a temperature between 0 and 350 ° C, a pressure comprised between 0.1 and 20 MPa (absolute), preferably between 0.5 and 7 MPa (absolute) and in the case of the application of a dynamic regime, a weight of catalyst per weight per hour (PPH) preferably comprised between 1 and 30 h "1 based on the total composition of the catalyst A diluent may optionally be present, preferably in one or several of them, which have a critical temperature higher than the applied isomerization conditions The diluent, if one is used, may comprise from 1 to 90% by weight of the charge The isomerization and hydroisomerization reactions of vapor phase xylene are carried out at a temperature suitably comprised between 100 and 600 ° C, preferably between 200 and 500 ° C, at a pressure comprised between 0.05 and 10 MPa (absolute), preferably between 0.1 and 5 MPa (absolute) and at a value of of the catalyst per weight per hour (PPH) which can reach up to 80 based on the total composition of the catalyst. When the xylene isomerization is carried out in the presence of hydrogen (in the vapor phase), the hydrogenation / dehydrogenation compound used is preferably Pt or Ni. The hydrogenation / de-hydrogenation compound is generally added in a proportion comprised between 0.5 and 2% by total weight of the catalyst. Metals and / or complementary metal oxides may be present in the catalyst composition. In the isomerization of xylene, ethylbenzene may be present in the xylene filler in a proportion which may reach 40% by weight. With catalyst compositions comprising zeolite NU-88, ethylbenzene is generally transalkylated therewith and with xylenes to form heavier and lighter aromatic compounds. Ethylbenzene also generally reacts to form benzene or light gas, in particular at temperatures above 400X. With such xylene charges containing ethylbenzene, when the reaction is carried out in the presence of hydrogen with a catalyst composition comprising zeolite NU-88 and a hydrogenation / dehydrogenation compound, a certain part of the ethylbenzene is transformed by isomerization to xylenes. It may be equally advantageous to carry out the isomerization reactions of xylene in the presence of a hydrocarbon compound, particularly a paraffin or a naphthene, with or without the complementary presence of hydrogen. The hydrocarbon seems to improve the performance of the catalyst insofar as the reactions that entrain the loss of xylenes are suppressed and in particular when the reactions are carried out in the absence of hydrogen, the life of the catalyst is prolonged. The present invention is also concerned with a hydrocarbon conversion process in which one or more aromatic compounds are contacted, alkylated, under transalkylation conditions, in vapor phase or in liquid phase, with a catalyst containing zeolite NU-88. Catalysts containing zeolite NU-88 are particularly useful in transalkylation and / or dismutation reactions, in particular in reactions involving mono-, di-, tri- or tetra-substituted alkyl aromatic molecules, in particular toluene and xylene . The catalyst compositions containing zeolite NU-88 which are particularly useful in the framework of the transalkylation and / or dismutation reactions include the compositions in which the compound NU-88 occurs under its acid form (H +), its form obtained by exchange of cations or other forms containing metals or combinations of these different forms. The acid form and the forms in which the metal is a hydrogenation / dehydrogenation compound such as Ni, Co, Pt, Pd, Re or Rh are particularly effective. Mention may be made, as a particular example of important processes, of the dismutation of toluene and the reaction of toluene with aromatic compounds comprising at least 9 carbon atoms per molecule, for example trimethylbenzenes. The dismutation of toluene can be carried out in the vapor phase, in the presence or in the absence of hydrogen, although it is preferable to operate in the presence of hydrogen insofar as it contributes to suppress the deactivation of the catalyst. The most favorable reaction conditions are the following: temperatures between 250 and 650 ° C, preferably between 300 and 550 ° C; pressures between 0.03 and 10 MPa (absolute), preferably between 0.1 and 5 MPa (absolute); Weight in weight per hour (PPH) up to 50 (based on the total composition of the catalyst). When the dismutation of the toluene is carried out in the presence of hydrogen, the catalyst may optionally contain a hydrogenation / dehydrogenation compound. A hydrogenation compound dehydrogenation such as Pt, Pd or Ni will preferably be used. The hydrogenation / dehydrogenation compound is usually added at a concentration that can reach 5% by weight of the total composition of the catalyst. Metals and / or complementary metal oxides may be present in the catalyst composition, for example up to 5% by weight of the total catalyst composition. The present invention is also concerned with a hydrocarbon conversion process in which an olefinic or aromatic compound is contacted with an appropriate alkylation compound under alkylation, vapor phase or liquid phase conditions, with a catalyst containing zeolite NU-88. Among the alkylation reactions for which catalysts containing zeolite NU-88 are particularly useful, mention may be made of the alkylation of benzene or of aromatic molecules substituted with methanol or an olefin or ether. Among the specific examples of such processes, mention will be made of methylation of toluene, synthesis of ethylbenzene and the formation of ethyltoluene and eumeno. The alkylation catalysts used in the processes according to this embodiment of the invention may comprise other substances, in particular metal oxides which can improve the catalytic performances. Thanks to the use of a catalyst containing zeolite NU-88, hydrocarbons can be produced by carrying out oligomerization, cyclization and / or aromatization reactions in unsaturated compounds such as ethene, propene or butene or in saturated compounds such as propane or butane or in mixtures of hydrocarbons such as light naphtha . For certain reactions, in particular aromatization reactions, it may be useful for the catalyst to contain a metal or a metal oxide, in particular platinum, gallium, zinc or its oxides. Catalysts containing zeolite NU-88 are useful for a wide range of catalytic pyrolysis reactions, among which are the catalytic pyrolysis of olefins, paraffins or aromatics or even their mixtures. The use of the zeolite NU-88 as a catalyst additive of the fluid catalytic pyrolysis is particularly useful for improving the product of the pyrolysis reaction. The zeolite NU-88 can also be used as a component of a catalyst for catalytic dewaxing in the framework of catalytic hydropyrolysis processes. The hydrogenation and / or dehydrogenation processes, for example the dehydrogenation of corresponding alkanes to olefins, are carried out efficiently by contacting the appropriate charge, under suitable conditions, with a catalyst containing zeolite NU-88, particularly when the latter also comprises a hydrogenation and / dehydrogenation compound such as Ni, Co, Pt, Pd, Re or Ru. A catalyst containing zeolite NU-88 is also a catalyst useful for the formation of ethers, in particular by the reaction of two alcohols or by the reaction of an olefin with an alcohol. The invention is illustrated by means of the following examples.

Example 1: Synthesis of zeolite NU-88 with 1,6-bis (methyl-pyrrolidinium) -hexane bromide (HexPyrr) The structure of 1,6-bis (methylpyrrolidinium) bromide hexane (Hex¬ Pyrr) is the following: A reaction mixture of 60 Si02: 2 Al203: 10 Na20: 10 HexPyrr: 3000 H20 molar composition is prepared from: 48.07 g of "CAB-O-SIL" (BDH Ltd) 12.303 g of SoAl 235 solution (Laroche) (composition by weight: 22.10% of Al20, 20.40% of Na20, 57.50% of H20) 7.4 g of sodium hydroxide pellets 57.2 g of HexPyrr (composition in weight percent: 96.50% HexPyrr; 3.50% of H20) 709 g of water.

The mixture is prepared according to the following operating mode: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 200 g) B - solution containing HexPyrr in water (approximately 150 g) C- dispersion of CAB -O-SIL in the remaining water. Solution A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The mixture is brought to a temperature of 160X. This temperature is maintained throughout the reaction. In addition, the mixture is kept stirred with the help of a tilted blade agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of pH. After 13 days at 160 ° C, the temperature of the reaction mixture drops sharply to room temperature and the product is subjected to vacuum. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 4.82 Al203: 0.337 Na20. The dried solid product is analyzed by pulvidifractometry and is identified as the zeolite NU-88. The diagram obtained is in accordance with the results presented in Table 1. The diffractogram is given in Figure 1 [in the ordinates the intensity I (arbitrary unit) and in the abscissa 2T (Cu K alpha)].

Example 2: Synthesis of zeolite NU-88 with a structure of 1, 5-bis (methylpirtolidinium) pentane bromide (PentPyrr). The structure of the 1,5-bis (methylpyrrolidinium) pentane bromide is as follows: A reaction mixture of molar composition 60 Si02: 1.714 Al203: 12 Na20: 10 PentPyrr: 3000 H20 is prepared from 36.05 g of "CAB-O-SIL" (BDH Ltd) 7,908 g of SoAl 235 solution (Laroche) (Composition in percent by weight: 22.10% AI2? 3, 19.80% Na20, 58.10% H20) 7.6 g sodium hydroxide pellets 41.2 g PentPyrr (composition in weight percent: 97.02% PentPyrr; 2.98% of H20) 532 g of distilled water. The mixture is prepared according to the following mode of operation: A- solution containing sodium hydroxide and sodium aluminate in water (approximately 150 g) B-solution containing PentPyrr in water (approximately 100 g) C- dispersion of CAB -O-SIL in the remaining water. Solution A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The mixture is brought to a temperature of 160X. This temperature is maintained throughout the reaction.

In addition, the mixture is kept stirred with the help of a tilted blade agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of pH. After 22 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is subjected to vacuum. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si0: 4.61 AI2O3: 0.32 Na20. The dry solid product is analyzed by pulvidifractometry and is identified as a product consisting primarily of zeolite NU-88, with traces of analdme (< 5%); the diagram obtained is in accordance with the results presented in table 1.

Eiemolo 3: Synthesis of zeolite NU-88 with PentPyrr. A reaction mixture of molar composition 60 Si02: 1.714 Al203: 18 Na20: 10 PentPyrr: 3000 H20 is prepared from 48.07 g of "CAB-O-SIL" (BDH Ltd) 10.587 g of SoAJ 235 soluton (composition in percent in weight: 22.01% of AI2? 3, 19.81% of Na20; 58.18% H2O) 16.5 g of sodium hydroxide pellets 55.3 g of PentPyrr (composition in percent by weight: 97.02% of PentPyrr; 2.98% water) 708 g of distilled water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 200 g) B - solution containing PentPyrr in water (approximately 150 g) C- dispersion of CAB- O-SIL in the remaining water. Solomon A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The temperature of the mixture is brought to 160X. This temperature is maintained throughout the reaction. In addition, the mixture is kept stirred with the help of a tilted blade agitator.

Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of the pH. After 15 days at 160X, the temperature of the reaction mixture is sharply reduced to room temperature and the product is evacuated. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 5.10 Al203: 0.153 Na20. The dry solid product is analyzed by pulvidifractometry and is identified as the zeolite NU-88; The diagram obtained is in accordance with the results presented in Table 1. Transmission electron microscopy analysis has revealed that the dominant morphology is characterized by plate-shaped crystals joined together to form aggregates. These plates have approximately the following dimensions: 100 x 100 x 10 nm.

Example 4: Synthesis of zeolite NU-88 with PentPyrr. The experiment described in example 3 is reproduced, with the axcepdon that a zeolite germ NU-88 is added to the reaction mixture; the weight of the added germ corresponds to 4% by weight of the total amount of silica used during the experiment. A reaction mixture of molar composition 60 SiO2: 1714 AI2O3: 18 Na20: 10 PentPyrr: 3000 H20 is prepared from 36.05 g of "CAB-O-SIL" (BDH Ltd) 7.805 g of SoAl 235 solution (composition in percent by weight: 22.39% of Al203, 20.49% of Na20, 57.12% of H20) 12.3 g of sodium hydroxide tablets 40.8 g of PentPyrr (composition in weight percent: 97.99% organic components, 2.01% H20) 532 g of water 1.44 g of NU-88 (in the form of the product prepared in example 3). The mixture is prepared according to the following mode of operation: A - soludon containing sodium hydroxide and sodium aluminate in water (approximately 150 g) B - solution containing PentPyrr in water (approximately 100 g) C - dispersion of the germ NU-88 in water (approximately 50 g) D - dispersion of CAB-O-SIL in the remaining water. Solomon A is added to dispersion D with stirring; Solution B is added immediately, then dispersion C. The agitation is continued until the gel is obtained homogeneously. The obtained mixture is transferred immediately to a stainless steel autodave of a liter capacity. The temperature of the mix is then brought to 160X. This temperature is maintained throughout the reaction. In addition, the stirring is maintained by means of a stirred paddle agitator.

Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of pH. After 9 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is evacuated. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 7.0 Al203: 1.26 Na20. The dried solid product is analyzed by polvidifractometry and is identified as a product consisting mainly of zeolite NU-88, with a reduced amount of analcime (approximately 5%); the diagram obtained is in accordance with the results presented in table 1. It is evident that the fact of adding the germ of NU-88 to the reaction mixture has reduced the total duradon of the preparation of the zeolite NU-88.

Example 5: Synthesis of zeolite NU-88 with PentPyrr. A reaction mixture of molar composition 60 Si02: 2 AI2O: 18 Na20: 20 HexPyrr: 5000 H20 is prepared from 28.16 g of "CAB-O-SIL" (BDH Ltd) 13.388 g of sodium aluminate solution (composition in percent by weight: 11.90% of AI2O3, 23.07% of Na20, 65.02% of H2O) 7.3 g of sodium hydroxide tablets 68.3 g of HexPyrr (composition in% by weight: 94.75% organic components, 5.25% H20) 689 g of distilled water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 200 g) B - solution containing HexPyrr in water (approximately 150 g) C- dispersion of CAB- O-SIL in the remaining water. Solomon A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The temperature of the mixture is brought to 160X. This temperature is maintained throughout the reaction. In addition, the mixture is kept stirred with the help of a tilted blade agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of the pH. After 11 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is evacuated. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours.

The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 5.4 Al203: 2.64 Na20. The dry solid product is analyzed by polvidifractometry and is identified as a mixture of zeolite NU-88 and analcime; the composition is approximately the following: 85% of NU-88/15% of analcime.

Example 6. Synthesis of zeolite NU-88 with PentPyrr. A reaction mixture of molar composition 60 Si02: 1.50 Al203: 18 Na20: 10 PentPyrr: 3000 H20 is prepared from 45.06 g of "CAB-O-SIL" (BDH Ltd) 15,931 g of sodium aluminate solution (composition in percent by weight: 12.00% of Al203, 24.44% of Na20, 63.56% of H20) 13.0 g of sodium hydroxide tablets 50.4 g of PentPyrr (composition in weight percent: 99.26% organic, 0.74% H20 ) 662 g of water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 200 g) B - solution containing PentPyrr in water (approximately 150 g) C - dispersion of CAB- O-SIL in the remaining water.

Solution A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The temperature of the mixture is immediately brought to 160X. This temperature is maintained throughout the reaction. In addition, the mixture is kept under agitation with the help of a tilted blade agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of pH. After 12 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is subjected to vacuum. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 4.7 Al203: 0.20 Na20. The dried solid product is analyzed by polvidifractometry and is identified as a product constituted by zeolite NU-88; the diagram obtained is in accordance with the results presented in table 1.

Example 7: Synthesis of zeolite NU-88 with HexPyrr. A reaction mixture of molar composition 60 Si02: 2 Al203: 18 Na20: 10 HexPyrr: 3000 H20 is prepared from 36.05 g of "CAB-O-SIL" 15.309 g of sodium aluminate solution (composition in percent in weight: 13.32% of Al203, 24.43% of Na20, 62.26% of H2O) 9.6 g of sodium hydroxide tablets 43.2 g of HexPyrr (composition in weight percent: 95.83% of organic components, 4.17% of H20) 616 g of distilled water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 200 g) B - solution containing HexPyrr in water (approximately 150 g) C - dispersion of CAB- O-SIL in the remaining water. Solomon A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of one liter. The temperature of the mixture is brought to 160X. This temperature is maintained throughout the reaction. In addition, the mixture is kept under agitation with the help of a tilted blade agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of the pH. After 12 days at 160 ° C, the temperature of the reaction mixture drops sharply to room temperature and the product is evacuated. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 6.54 Al203: 3.92 Na20. The dry solid product is analyzed by polvidifractometry and is identified as a product consisting of a mixture of zeolite NU-88 and analcime; the composition is approximately the following: 70% of NU-88/30% of analcime.

Example 8: Synthesis of NU-88 with a structure of 1,4-bis (methylpyrrolidinium) butane bromide (TetraPyrr) The structure of 1,4-bis (methylpyrrolidinium) butane bromide is as follows: A reaction mixture of molar composition; 60 Si02. 1.5 Al203: 15 Na20: 10 TetraPyrr: 3000 H20 is prepared from 24.03 g of "CAB-O-SIL" (BDH Ltd) 9.711 g of sodium aluminate solution (composition in weight percent: 10.52% Al203 21.56% Na20; 67.92% H20) 5.30 g sodium hydroxide pellets 25.81 g TetraPyrr (composition in weight percent: 99.25% TetraPyrr; 0.25% H20) 352.45 g distilled water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 120 g) B - solution containing TetraPyrr in water (approximately 120 g) C- dispersion of CAB- O-SIL in the remaining water. Solomon A is added to dispersion C under agitation; Solution B is added right away. The agitation is continued until the get of a homogeneous gel. The obtained mixture is transferred immediately to a stainless steel autodave of a capacity of 1 liter. The temperature of the mixture is brought to 160X. This temperature is maintained throughout the reaction. In addition, the mixture is maintained in agitation at 45 revolutions per minute in a rotating system. After 10 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is subjected to vacuum. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 4.46 Al203: 2.72 Na20.

The dried solid product is analyzed by polvidifractometry and is identified as a product consisting of a mixture of zeolite NU-88.

Example 9: Synthesis of NU-88 with a bromide structure of 1,4-bis (bisquinuclidinium) butane (TetraBisQ) The structure of the 1,4-bis (bisquinudidinium) butane bromide is as follows: A molar composition reaction mixture; 60 Si02: 1.5 Al203: 10 Na20: 10 TetraBisQ: 3000 H20 is prepared from 3.00 g of "CAB-O-SIL" (BDH Ltd) 1.214 g of sodium aluminate solution (composition in weight percent: 10.52 % of Al203, 21.56% of Na20, 67.92% of H20) 0.33 g of sodium hydroxide pellets 3.85 g of TetraBisQ (composition in weight by weight: 94.8% of TetraBisQ, 5.2% of H20) 43.94 g of distilled water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium aluminate in water (approximately 11 g) B - solution containing Tetra-BisQ in water (approximately 11 g) C- dispersion of CAB-O-SIL in the remaining water.

Solomon A is added to dispersion C under agitation; Solution B is added right away. The agitation is continued until the get of a homogeneous gel. The obtained mixture is transferred immediately to a stainless steel autodave with a capacity of 75 ml. The mixture is brought to a temperature of 180X. This temperature is maintained throughout the reaction. In addition, the mixture is kept stirred at 45 revolunds per minute in a rotating system. After 12 days at 180X, the temperature of the reaction mixture is abruptly lowered to room temperature and the product is subjected to vacuum. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Al and Na in the product is carried out by means of atomic emission spectroscopy; The following molar composition is found: 100 Si02: 3.1 Al203: 0.65 Na20. The dry solid product is analyzed by polvidifractometry and is identified as a product of zeolite NU-88 Example 10: Synthesis of Ga-NU-88 A reaction mixture of composition 60 SiO 2: 2 Ga 203: 18 Na20: 10 HexPyrr: 3000 H20 is prepared from 36.05 g of "CAB-O-SIL" (BDH Ltd) 21,872 g of sodium gallate solution (composition in percent by weight: 17.14% of Ga203; 23.84% Na20; 59.01% H2O) 7.7 g of sodium hydroxide tablets 42.2 g of HexPyrr (composition in per weight: 99.01% organic components, 1.99% H20) 524 g of water. The mixture is prepared according to the following mode of operation: A - solution containing sodium hydroxide and sodium gallate in water (approximately 150 g) B - solution containing HexPyrr in water (approximately 100 g) C - dispersion of CAB- O-SIL in the remaining water. Solution A is added to dispersion C with stirring; Solution B is added right away. The stirring is continued until a homogeneous gel is obtained. The obtained mixture is transferred immediately to a stainless steel autoclave with a capacity of 1 liter. The temperature of the mix is brought to 160X. This temperature is maintained throughout the reaction. In addition, the stirring is maintained by means of a stirred paddle agitator. Samples of the reaction mixture are taken regularly and the development of the reaction is observed by means of pH. After 10 days at 160X, the temperature of the reaction mixture drops sharply to room temperature and the product is evacuated. The substance is filtered right away; the solid product obtained is washed with demineralized water and dried at 110X for several hours. The analysis of Si, Ga and Na in the product is carried out by means of atomic emission spectroscopy. The following molar composition is found: 100 Si02: 5.35 Ga203: 1.07 Na20. The dry solid product is analyzed by polvidifractometry and is identified as Ga-NU-88, the diagram obtained is in accordance with the results presented in table 1.

Example 11: Preparation of H-NU-88 A part of the product of Example 3 is calcined under a nitrogen atmosphere for 24 hours at 550X; this stage is immediately followed by a second calcination in air, also at 550X for 24 hours. Then the substance obtained is contacted for 2 hours at room temperature with an aqueous solution of 1 mole of ammonium chloride, 50 ml of solution per gram of the solid calcined product are used. Then the substance is filtered, washed with permuted water and dried at 110X. This treatment is repeated. The substance is then calcined in air for 24 hours at 550X. The analysis of Si, Al and Na in the product, carried out by means of atomic emission spectroscopy, has given the following molar composition. 100 Si02: 4.05 Al203: < 0.004 NazO Example 12: Preparadon of H-NU-88 A part of the product of example 6 is calcined under a nitrogen atmosphere for 24 hours at 550X; this stage is immediately followed by a second calcination in air at 450X for 24 hours. Then the obtained substance is contacted for 2 hours at room temperature with an aqueous solution of 1 mole of ammonium chloride, 50 ml of solution per gram of the solid calcined product are used. Then the substance is filtered, washed with permuted water and dried at 110X. This treatment is repeated. The substance is then calcined in air for 24 hours at 550X. The calcined product is analyzed in X-ray diffraction. The diffractogram obtained is given in figure 2 [in the 2T abasa (Cu K alpha) and in the ordinate the intensity I (arbitrary unit)]. The X-ray diffraction diagram is in accordance with Table 2. The analysis of Si, Al and Na in the product, carried out by means of atomic emission spectroscopy, has given the following molar composition: 100 Si02: 3.80 Al203: 0.011 Na2O Example 13: Evaluation of the catalytic properties of zeolite H-NU-88 in the catalytic pyrolysis of methylcidhexane. 1.2 g of the H-NU-88 zeolite, prepared in Example 11, are introduced into a tubular fixed bed reactor. The temperature of the reactor is brought to 500X, then cidohexane is introduced into the reactor. The diluent gas used is nitrogen and the molar ratio of N2 / dclohexane admitted to the reactor is 12. The spacial velocity of methylcidhexane, ie the mass of methyloclohexane used per unit mass of zeolite H-NU-88 and per unit time , is such that it allows to obtain a conversion of 60% by weight. The selectivities for the different products obtained are grouped in the table given below. (1) Compounds comprising at least 8 carbon atoms. This example shows that zeolite H-NU-88 is suffciently active to lead to the pyrolysis of methyldclohexane and a selectivity in gas (C1-C4) of 46.7% by weight for a conversion of 60% by weight.

It is noted that with respect to this date, the best method for solidifying the practice to carry out the tied invention is that which is clear from the present description of the invention. Having described the invendón as above, the content contained in the following is redacted as property

Claims (34)

Claims 1. A zeolite characterized in that it comprises: i) a chemical composition expressed on an anhydrous basis, in terms of molar ratios of oxides, by the formula: 100 XO2, m Y2O3, p R ^ nO, where m is equal to or less than to 10, p is equal to or less than 20, R represents one or more cations of valence n, X is silicon / or germanium, is chosen from the group formed by the following elements: aluminum, iron, gallium, boron, titanium , vanadium, drconium, molybdenum, arsenic, antimony, chromium manganese, ii) the fact that it presents, in a crude form of synthesis, an X-ray diffraction diagram comprising the results presented in table 1 below: 1: X-ray diffraction table of zeolite NU-88 (crude synthesis)
1. Table 1 (continued) (1) These peaks are not resolved are part of the same total. (2) These peaks are not resolved are part of the same total.
2. 2. The zeolite according to claim 1, characterized in that m is between 0.6 8.
3. 3. A zeolite characterized in that it comprises: i) a chemical composition expressed on an anhydrous basis, in terms of molar ratios of oxides, by the formula: 100 X02: less than or equal to 10 Y2? 3: less than or equal to 10 M20, in where X is silicon / or germanium, Y is chosen in the group formed by the following elements: aluminum, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium manganese, ii) The fact of which presents, in calcined form, an X-ray diffraction diagram comprising the results presented in Table 2 below: Table 2: X-ray diffraction table of zeolite NU-88 (hydrogenated form) Table 2: (Continued) (1) These peaks are not resolved are part of the same total. (2) These peaks are not resolved are part of the same total.
4. 4. The zeolite according to any of claims 1 or 2, characterized in that it has the chemical composition expressed on an anhydrous basis, in terms of molar ratios of following oxides: 100 X02: less than or equal to 10 Y203: less than or equal to 10 Q : less than or equal to 10 M20, X is silicious / or germanium, is chosen from the group formed by the following elements: aluminum, iron, gallium, boron, titanium, vanadium, drconium, molybdenum, arsenic, antimony, chrome manganese, wherein M is at least one alkali metal cation (group IA of the periodic classification of the elements) / or ammonium, Q is at least one organic nitrogenous cation or a precursor of organic nitrogenous cation or a decomposition product of organic nitrogenous cation.
5. 5. The zeolite according to claim 4, characterized in that: Q is a cation of bis (methyl pyrrolidinium), or one of its decomposition products or one of its precursors, of general formula with n = 4, 5 or 6, or Q is bromide of 1,4-bis (bisquinudidinium) butane or one of its decomposition products or one of its precursors, of the following chemical formula:
6. 6. The zeolite according to any of claims 4 or 5, characterized in that Q is 1, 6-bis (methylpyrrolidinium) bromide, 1,5-bis (methylpyrrolidinium) bromide, pentane bromide, 1,4-bis (methylpyrrolidinium bromide) bromide. ) butane or 1,4-bis (quinudidinium) butane bromide.
7. 7. The zeolite according to any of claims 1 to 6, characterized in that S is silicon Y is aluminum.
8. 8. The zeolite according to any of claims 1, 2, 4, 5, 6 or 7, characterized in that it is at least partly in H + or NH 4 + or metallic form, the metal is chosen from the group formed by the groups IA, IB, HA, IIB, I HA, IIIB (including rare earths), VIII, Sn, Pb Si.
9. 9. A process for the preparation of the zeolite according to any of claims 1 to 8, characterized in that an aqueous mixture comprising at least one source of at least one X02 oxide is reacted, at least one source of at least one oxide Y2? 3, optionally at least one source of at least one M20 oxide and at least one organic nitrogen cation Q or its precursors, the mixture generally has the molar composition following: X02 / Y203 at least 10, (R1 / n) OH / X02 from 0.01 to 2, H20 / X02 from 1 to 500, Q / XO2 from 0.005 to 1, LpZ / X02 from 0 to 5, where X is silicon and / or germanium, and is chosen from the group consisting of the following elements: aluminum, iron, boron, titanium, vanadium, drconium, molybdenum, arsenic, antimony, gallium, chromium, manganese, R is a valence cation n comprising M (an alkali metal and / or ammonium cation) and / or Q (an organic nitrogenous cation or a precursor thereof or a decomposition product thereof). LpZ is a salt, Z is an anion of valenda and L is an alkali metal or ammonium ion that can be similar to M or a mixture of M and another alkali metal ion or an ammonium ion needed to balance the Z anion Z may comprise an added radical, for example in the form of a salt of L or of an aluminum salt.
10. 10. The process according to claim 9, characterized in that Q is a cation of bis (methylpyrrolidinium) or one of its decomposition products or one of its precursors, of general formula with n = 4, 5 or 6, or Q is 1,4-bis (bisquinudidinium) butane bromide or one of its decomposition products or one of its precursors, of the following chemical formula:
11. 11. The process according to any of claims 9 or 10, characterized in that Q is 1, 6-bis (methyl pyrrolidinium) bromide, 1,5-bis (methylpyrrolidinium) bromide, pentane bromide, 1,4-bis (methyl) bromide. pyrrolidinium) butane or 1,4-bis (quinuclidinium) butapo bromide.
12. 12. The process according to any of claims 9 to 11, characterized in that the aqueous medium comprises the salt LpZ.
13. 13. The process according to any of claims 9 to 12, characterized in that it also comprises a calcina on.
14. 14. The preparation process according to any of claims 9 to 13, characterized in that it also comprises a step of exchange of H + or NH 4 +.
15. 15. The method according to any of claims 9 to 14, characterized in that it further comprises a metal exchange step chosen from the group consisting of groups IA, IB, NA, IIB, IDA, IIIB (including rare earths), VIII, Sn, Pb and Si.
16. 16. A catalyst comprising a zeolite according to any one of claims 1 to 9, characterized in that it is prepared according to any of claims 9 to 15.
17. 7 The catalyst according to claim 16, characterized in that it also comprises a bond or a support or other zeolite or a metal chosen from the group formed by the elements Cu, Ag, Ga, Mg, Ca, Sr, Zn, Cd, B, Al , Sn, Pb, V, P, Sb, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Pt, Pd, Re and Rh.
18. 18. A hydrocarbon conversion process, characterized in that it utilizes a catalyst according to any of claims 16 or 17.
19. 19. The hydrocarbon conversion process according to claim 18, characterized in that, during which, an alkylbenzene or a mixture of alkylbenzenes is contacted in isomerized condoms, in vapor or liquid phase, with a catalyst containing zeolite NU- 88
20. 20. The isomerization or hydroisomerization process of xylene according to claim 19.
21. 21. The hydrocarbon conversion process according to claim 18, characterized in that the isomerization and hydroisomerization of normal paraffins comprising from 4 to 10 carbon atoms per molecule is carried out.
22. 22. The hydrocarbon conversion process according to claim 18, characterized in that the isomerization of olefins is carried out.
23. 23. The hydrocarbon conversion process according to claim 18, characterized in that the catalytic deparaffinization is carried out.
24. 24. The hydrocarbon conversion process according to claim 18, characterized in that one or more alkylated aromatic compounds are contacted in transalkylation conidia, in vapor phase or in liquid phase, with a catalyst containing zeolite NU-88.
25. 25. The procedure of transalquiladon and / or dismutation of xylenes according to claim 24.
26. 26. The process of dismutadon and / or transalquiladon of toluene and aromatic compounds according to claim 24, characterized in that they comprise at least 9 carbon atoms per molecule.
27. 27. The hydrocarbon conversion process according to claim 18, characterized in that an olefinic or aromatic compound is contacted with an appropriate alkylation compound in alkylation conditions, in vapor phase or in liquid phase, with a catalyst containing zeolite NU -88.
28. 28. The hydrocarbon conversion process according to claim 18, characterized in that oligomerization, drying and / or aromatization reactions are carried out in unsaturated compounds or saturated compounds or mixtures of hydrocarbons.
29. 29. The hydrocarbon conversion process according to claim 18, characterized in that catalytic pyrolysis reactions are carried out.
30. 30. The hydrocarbon conversion process according to claim 18, characterized in that hydrogenation and / or dehydrogenation reactions are carried out.
31. 31. The use of a confomation catalyst with any of claims 16 or 17, characterized in that it is applied to carry out an ether formation.
32. 32. The use of a catalyst according to any of claims 16 or 17, characterized in that it is applied to carry out the catalytic elimination of the nitrogen oxides.
33. 33. The use of a catalyst according to claim 32, characterized in that it is applied in the elimination which is carried out by reduction.
34. 34. The use according to any of claims 32 or 33, characterized in that the elimination is carried out by reduction by nitrogenous compounds or by hydrocarbons.