FR2683742A1 - Catalyst with MFI structure and its use in the aromatisation of hydrocarbons containing 5 to 12 carbon atoms - Google Patents

Abstract

Composite catalyst which contains: - a zeolite of MFI structure containing at least one element chosen from the group consisting of the alkali and alkaline-earth metals and containing in its structural framework at least the elements silicon, aluminium and/or gallium, - a matrix, - at least one noble metal from the platinum group, at least one additional metal chosen from the group consisting of tin, germanium, indium, copper, iron, molybdenum, gallium, thallium, gold, silver, ruthenium, chromium, tungsten and lead, - at least one halogen chosen from the group consisting of fluorine, chlorine, bromine and iodine, - optionally at least one metal chosen from the group consisting of gallium and zinc, - and, optionally, preferably in the matrix, at least one element chosen from the group consisting of the alkali and alkaline-earth metals. The invention also relates to the use of this catalyst in the reactions of aromatisation of hydrocarbons containing from 5 to 12 carbon atoms per molecule.

Description

The present invention relates to a catalyst, referred to as a composite catalyst, which contains
a zeolite of MFI structure containing at least one selected element
in the group consisting of alkali metals and metals
alkaline earth - and hereinafter referred to as "additional alkaline" - and
containing in its framework silicon and at least one element
chosen from the group formed by aluminum and gallium, said
zeolite being hereinafter referred to as "A / MFI",
- a matrix,
at least one noble metal of the platinum family deposited on the
matrix and / or the MFI (preferably on the matrix),
- deposited on the matrix and / or the MFI (preferably the matrix),
minus an additional metal selected from the group consisting of
tin, germanium, indium, lead, gallium and thallium,
Group Ib metals such as copper, gold, silver, metals of the
group VIII such as nickel, ruthenium, iron and metals from
group VI such as chromium, molybdenum, tungsten,
at least one halogen selected from the group consisting of fluorine,
chlorine, bromine and iodine, deposited in the MFI and / or matrix (
preferably in the matrix),
possibly at least one doping element chosen from the group
consisting of gallium and zinc, deposited in the MFI and / or
matrix (preferably in the MFI),
- and possibly at least one element chosen from the group
consisting of alkali metals and alkaline earth metals, and
in the matrix and / or the MFI (preferably in the matice).

 its preparation and its use in the aromatization reactions of hydrocarbons comprising from 2 to 12 carbon atoms per molecule and more particularly from 5 to 12 carbon atoms per molecule.

 Alkali and alkaline earth metals, other than those contained in the zeolite - the latter being called additional alkali (s) - as well as the platinum and additional metals mentioned above, and exception of gallium and zinc (used as a doping element) are hereinafter referred to as "metals".

 The catalysts based on zeolites doped with thallium, or zinc, or platinum, are known to be active and selective in the aromatization of propane and butane. Conventionally, hydrocarbons containing more than 6 carbon atoms per molecule are converted into aromatics by catalytic reforming using platinum-containing acid alumina-type catalysts, to which tin or rhenium may be added, for example. These reforming catalysts are nevertheless very inefficient for the aromatization of hydrocarbons containing less than 6 carbon atoms per molecule. There is therefore a great practical interest in finding efficient catalysts for the aromatization of C5-C12 hydrocarbon-rich cuts.

The aromatization reaction of hydrocarbons containing less than 9 carbon atoms per molecule in the presence of zeolites has already been the subject of patents and publications. Several catalytic systems based on MFI zeolite are claimed, these systems being distinguishable by the additions they contain. Schematically, we can distinguish
(i) gallium doped systems (US-A-4175057), and
(ii) zinc-doped systems (US-A-4288645).

 These systems all suffer from a major defect, namely a high selectivity in methane. To improve the performance of these catalytic systems, several solutions have been proposed including the addition of platinum (Z. Jin, Y. Makino, A. Miyamoto, T. Inui, Chem.Express, 2, p.515, 1987).

 Recently (French patent application 91/10624 of the applicant), it has been discovered that the use of composite catalysts containing an MFI zeolite on the one hand, and on the other hand a generally amorphous support or matrix on which is deposited a noble metal of the platinum family and at least one additional metal such as tin, lead or indium, leads to catalytic performances in aromatization reactions of paraffins of 5 to 9 carbon atoms markedly improved compared to to the systems of the prior art.

 The use of such catalysts in particular makes it possible to limit the reactions which lead to the formation of methane, an undesired product.

 The research work carried out by the Applicant has led it to discover that, surprisingly, the use of a composite catalyst containing an MFI zeolite which contains at least one element selected from the group consisting of alkali metals and alkalinos -terreux, so called "A / MFl", possibly optionally doped with gallium and / or zinc in oxide form and a matrix on which is deposited at least one noble metal of the platinum family (in particular palladium, platinum, nickel, iridium, rhodium), at least one additional metal selected from the group consisting of tin, germanium, lead, indium, lead, gallium and thallium, the metals of the group lb such as copper, I gold, Group VIII metals such as nickel, ruthenium, iron and Group VI metals such as chromium, molybdenum, tungsten, said matrix also containing at least one halogen (preferably chlorine) and optionally at least one alkali metal or alkaline earth metal (preferably lithium or potassium), leads to catalytic performances in aromatization reactions of paraffins containing from 5 to 12 carbon atoms per molecule significantly improved compared to catalysts of the prior art.

 The MFI zeolite contained in the catalyst of the present invention can be prepared by any of the techniques described in the prior art.

Thus the synthesis of said zeolite can be carried out in a conventional medium
OH- in the presence or absence of organic agent and / or alcohol. The document "Synthesis of high silica zeolites, P. Jacobs and J. Martens,
Studies in Surface Science and Catalysis, Vol. 33, 1987 "describes the conventional synthesis of the MFI zeolite.The MFI zeolite used in the present invention may also have been synthesized in less conventional media such as the fluoride medium present (patent
EP-A-172068) or in the absence (French patent application 90/16529) of organic compound. The zeolite used in the present invention contains, in its crystallized framework, silicon and at least one element selected from the group formed by aluminum and gallium.

After the synthesis step, the MFI zeolite is:
- is converted into a hydrogen form, denoted H-MFI, by
virtually complete elimination of organic compounds and / or
alkaline or alkaline-earth cations that it contains
after synthesis. All the techniques described in the prior art
can be used for the transition to the hydrogen form, as
for example the ionic exchanges followed or not calcination or
various chemical treatments. One or more alkalis
additional salts are then introduced via salts
aqueous or organic solutions by all known techniques
of the prior art, to then obtain the A / MFI.

- directly transformed into a form containing one or
several additional alkalis, by possible total elimination of the
organic compounds, this or these additional alkalis then being
brought by the synthesis medium of the zeolite. Content
additional alkali (s) may then be increased
easily from salts of these alkalis or alkaline earths in
aqueous or organic solutions by all known techniques
of the prior art, to then obtain the A / MFI.

 The content of additional alkali (s) deposited on the MFI zeolite is between 0.001 and 5% by weight, preferably between 0.005 and 3% by weight.

All zeolites synthesized in one of the following systems
Si-Al, Si-Al-Ga, Si-Ga, are suitable for the present invention. However, their Si / T ratio where T represents Al and / or Ga, is generally greater than 7, preferably greater than 10 and even more preferably between 13 and 500.

 Zeolite A / MFI, containing at least one alkali metal or alkaline earth metal, used in the present invention, may be optionally subjected as such to a deposit of gallium and / or zinc, or mixed with the other constituents of the catalyst, gallium and / or zinc can then optionally be subsequently introduced into said mixture.

 In the case where the MFI zeolite after synthesis is first converted to its hydrogen form, the optional deposition of gallium and / or zinc may occur prior to the introduction of at least one of the additional alkali metals.

 Many techniques for deposition of gallium and / or zinc can be used in the present invention, among which we can mention the ion exchange through the use of salts in aqueous solution, or impregnation with solutions of said salts.

 The cumulative content of these two metals optionally deposited on the composite catalyst is between 0.01 and 10% by weight, preferably between 0.03 and 4% by weight.

 The matrix comprises at least one refractory oxide, and in particular at least one oxide of a metal selected from the group consisting of magnesium, aluminum, titanium, zirconium, thorium, silicon and boron. In addition, it may also include coal.

 The preferred matrix is alumina, the surface area of which may advantageously be between 10 and 600 m 2 / g and preferably between 150 and 400 m 2 / g.

 The composite catalyst of the present invention can be prepared in two ways, the principle of which is given below, the practical embodiment being known to those skilled in the art.

First way
The MFI zeolite, or the A / MFI zeolite, is mixed with the matrix. This mixture can be produced between two powders, between two previously shaped solids, between a powder and a solid previously shaped. It is also possible to formulate the two solids together by all the techniques described in the prior art: pelletizing, extrusion, coating, drop coagulation, spray drying. During these shaping operations, it is possible, if necessary, to add a shaping additive, selected from the group consisting of silica and alumina. Thus, the zeolite was mixed with the matrix and shaped. After mixing and shaping, the metals are deposited, the halogen is introduced and optionally gallium and / or zinc are introduced. on the set consisting of the matrix and the zeolite, the order of deposit being small. If it is the MFI zeolite which was initially mixed with the matrix,
The subsequent introduction of an element selected from the group consisting of alkaline and alkaline earth is then necessary.

 It is then considered that most of the metals, preferably from 60 to 100% by weight relative to the composite catalyst, are found on the matrix.

Second way
The halogen, the metals and optionally the alkali or alkaline-earth element are firstly deposited on the matrix on the one hand, and possibly gallium and / or zinc on the A / MFI zeolite on the other hand, or optionally the gallium and / or zinc on the MFI prior to the introduction of at least one additional alkali. The order of introduction of the different elements on the matrix is indifferent. Then the A / MFI zeolite, optionally containing thallium and / or zinc, is mixed with the matrix containing the metals and the halogen, and at their shaping, the shaping being obtained under the same conditions as above. In a variant, the zeolite, on which gallium and / or zinc have been deposited, may be mixed with the matrix at any of the halogen introduction and metal deposition steps and on the matrix.

 The preferred method of preparation consists, optionally in depositing gallium and / or zinc on zeolite A / MFI, to deposit the metals and to introduce the halogen on the matrix, then to introduce the zeolite possibly loaded with gallium and / or or zinc in the matrix loaded with metals and halogen by shaping the two powders. The shaping is preferably carried out after micron milling, which can be carried out using the wet milling technique.

 The composite catalyst contains between 1 and 99% (by weight relative to the total mass of the catalyst) zeolite A / MFI, the complement to 100% being constituted by the matrix, metals and halogen. The respective proportion of zeolite and matrix varies over a wide range, as it depends on the one hand on the Si / T ratio of the zeolite, where T is Al and / or Ga, and on the other hand on the content of metals and in halogen of the matrix in the case of the preferred method of preparation.

 The matrix containing the metals and halogen, in the case of the preferred method of preparation, is generally prepared according to the procedures described in the French patent application 91/10624, part of which is reproduced below. These procedures can be used, for example, on the matrix alone, or on the matrix / zeolite mixture, as has been described in the two preparation routes.

 For the impregnation of metals, either a common solution of the metals which it is desired to introduce, or distinct solutions for the noble metal of the platinum family and for the additional metal and optionally the element chosen from the group consisting of by alkali metals and alkaline earths. When several solutions are used, dryings and / or intermediate calcinations can be carried out. It is usually terminated by calcination, for example between 500 and 1000 ° C., preferably in the presence of molecular oxygen, for example by conducting an air sweep.

 The noble metal of the platinum family may be incorporated in the matrix by impregnation of said matrix with a solution, aqueous or not, containing a salt or a noble metal compound. Platinum is generally introduced into the matrix in the form of chloroplatinic acid, but for any noble metal may also be used ammonia compounds or compounds such as for example ammonium chloroplatinate, platinum dichloride dicarbonyl, hexahydroxyplatinic acid , palladium chloride, palladium nitrate.

 The additional metal selected from the group consisting of tin, germanium, lead, indium, lead, gallium and thallium, the Group Ib metals such as copper, gold, silver, Group VIII metals such as nickel, ruthenium and iron and Group VI metals such as chromium, molybdenum, tungsten can be introduced via compounds such as for example chlorides, bromides and tin nitrates, halides, nitrate, acetate and lead carbonate, germanium chloride and oxalate, nitrate and indium chloride.

 The halogen may be introduced from at least one of the platinum family metal halides or at least one of the additional metal halides, in the case where these metals are introduced from halides. A complementary method may consist of impregnation of the matrix with an aqueous solution containing an acid or a halogenated salt. For example, chlorine can be deposited using a hydrochloric acid solution. Another method may consist of a calcination at a temperature generally of between 400 and 900 OC, in the presence of an organic compound containing halogen, such as Cl14, CH2Cl2, CH3Cl,.

 The element selected from the group consisting of alkali and alkaline earth metals, preferably lithium or potassium, can be introduced via compounds such as for example halide, nitrate, carbonate, cyanide. and the oxalate of said element.

A method of preparation, which we detail below, includes for example the following steps
a) introducing onto the matrix at least one element selected from the group consisting of fluorine, chlorine, bromine and iodine,
a ') Possible introduction on the matrix of at least one element selected from the group consisting of alkali and alkaline earth.

 b) Calcination of the product obtained in step a) or a ').

 c) Introduction on the matrix of at least one noble metal of the platinum family.

 d) calcination of the product obtained in step c).

 e) Introduction on the product obtained in step d) of at least one additional metal named above M.

 If no alkali or alkaline earth metal is used, only steps a), c), d) and e) e> of said preparation process are carried out.

 The use in the present invention of at least one noble metal of the platinum family can be exemplified by the use of ammonia compounds.

 In the case of platinum, mention may be made, for example, of hexamines IV platinum salts of formula Pt (NH 3) 6X 4, platinum IV halopentamine salts of formula (PtX (NH 3) 5) X 3, and platinum N tetrahalogenodiamine salts of formula PtX4 (NH3) 2; platinum complexes with halogen-polyketones and halogenated compounds of formula H (Pt (aca) 2X); X being a halogen selected from the group consisting of chlorine, fluorine, bromine; and iodine, and preferably X being chlorine, and aca representing the radical of formula C5H702 derived from acetylacetone.

 The introduction of the noble metal of the platinum family is preferably carried out by impregnation with an aqueous or organic solution of one of the organometallic compounds mentioned above. Among the organic solvents that can be used, mention may be made of paraffinic, naphthenic or aromatic hydrocarbons, and halogenated organic compounds having, for example, from 1 to 12 carbon atoms per molecule. For example, n-heptane, methylcyclohexane, toluene and chloroform may be mentioned.

Solvent mixtures can also be used.

 After introduction of the noble metal of the platinum family, the product obtained is optionally dried and is preferably calcined at a temperature of between 400 and 1000 OC.

 After this calcination, at least one additional metal is introduced, optionally preceded by a reduction with hydrogen at high temperature, for example between 300 and 500 C. The additional metal M can be introduced in the form of at least one organic compound selected from the group consisting of complexes of said metal, in particular polyketone complexes of the metal M and hydrocarbylmetals such as alkyls, cycloalkyls, aryls, alkylaryls and arylalkyls.

 The introduction of the metal M is advantageously carried out using a solution of the organometallic compound of said metal in an organic solvent. It is also possible to use organohalogen compounds of metal M. As compounds of metal M, mention may be made in particular of tetrabutyltin in the case where M is tin, tetraethylplomb in the case where M is lead and triphenylindium in the case where M is indium.

 The impregnating solvent is selected from the group consisting of paraffinic, naphthenic or aromatic hydrocarbons containing from 6 to 12 carbon atoms per molecule and halogenated organic compounds containing from 1 to 12 carbon atoms per molecule. For example, n-heptane, methylcyclohexane and chloroform may be mentioned. It is also possible to use mixtures of the solvents defined above.

 In the case where the method of preparation as described above is not used, it is also possible to envisage introducing at least one additional metal M before the introduction of at least one noble metal of the family of platinum. If the metal M is introduced before the noble metal, the compound of the metal M used is generally selected from the group consisting of the halide, the nitrate, the acetate, the tartrate, the carbonate and the oxalate of the metal M. The introduction is then advantageously carried out in aqueous solution. In this case, before proceeding to the introduction of at least one noble metal, it is calcined in air at a temperature between 400 and 1000 OC.

The composite catalyst based on an MFI and a matrix preferably contains 1) by weight relative to the matrix:
from 0.01 to 2% and preferably from 0.1 to 0.5% of at least one noble metal of the platinum family, deposited in the matrix and / or the zeolite,
deposited in the matrix and / or the zeolite, at least one additional metal, namely from 0.005 to 2%, preferably from 0.01 to 0.5%, of tin in the case where the additional metal is from tin, from 0.005 to 0.7%, preferably from 0.01 to 0.6%, of at least one metal selected from the group consisting of germanium, indium, lead, gallium and thallium, Group Ib metals such as copper, gold, silver, Group VIII metals such as nickel, ruthenium, iron and Group VI metals such as chromium, molybdenum, tungsten; in the case where the catalyst contains at least two additional metals of said group, the total content of additional metals chosen is between 0.02 and 1.20%, preferably between 0.02 and 1.0%, and still more preferably more preferred between 0.03 and 0.80%.

 from 0.1 to 15%, and preferably from 0.2 to 10%, of a halogen element chosen from the group consisting of fluorine, chlorine, bromine and iodine, preferably chlorine, L halogen being incorporated in the matrix and / or the MFI.

 optionally from 0.01 to 4%, preferably from 0.1 to 0.6%, of at least one metal selected from the group consisting of alkalis and alkaline earths, preferably selected from the group consisting of lithium and potassium.

2) between 1 and 99% by weight of MFI zeolite, containing in its framework silicon and at least one element selected from aluminum and gallium, 3) optionally by weight relative to the zeolite
between 0.001 and 5%, and preferably between 0.005 and 3%, of at least one additional alkali selected from the group consisting of alkalis and alkaline earths,
- optionally still between 0.01 and 10% by weight, preferably between 0.03 and 4%, of a doping element selected from the group consisting of gallium and zinc, preferably gallium, this element being introduced into the IFM and / or the matrix.

 In the process according to the invention, at the end of the preparation, the shaped catalyst contains an MFI zeolite, metals, at least one halogen and a matrix, and is calcined in air at a temperature between 450 and 1000 OC. The catalyst thus calcined may advantageously undergo an activation treatment under hydrogen at high temperature, for example between 300 and 500 OC. The hydrogen treatment procedure consists, for example, in a slow rise in temperature under a stream of hydrogen up to the maximum reduction temperature, generally between 300 and 500 ° C. and preferably between 350 and 450 ° C., followed by maintaining at this temperature for a period generally between 1 and 6 hours.

 The catalyst of the present invention described above is used for the aromatization of alkanes containing from 5 to 12 carbon atoms per molecule, in the presence or absence of olefins. This reaction is of particular interest because it can allow, for example, on the one hand to develop light fractions from refining operations by transforming them into products with higher added value (benzene, toluene and xylenes), on the other hand to transform paraffinic charges that may contain olefins into bases for high octane fuel, while in both cases contributing to the production of large quantities of hydrogen essential for hydrotreatment processes for example.

 The feed which contains compounds containing 5 to 12 carbon atoms per molecule is contacted with the catalyst of the present invention at a temperature of between 400 and 700 OC.

 The following examples specify the invention without limiting its scope.

Example I: Preparation of Alumina Containing Platinum, Tin and Chlorine (Catalyst A)

 The alumina used has a specific surface area of 220 m 2 / g and a pore volume of 0.52 cm 3 / g.

 To 100 g of alumina support is added 500 cm3 of an aqueous solution of hydrochloric acid. It is left in contact for 3 hours, filtered, dried 1 hour at 100-1200C.

The dried product containing the chlorine is then impregnated with platinum, adding to the solid 150 cm3 of an aqueous solution of hexachloroplatinic acid. The platinum concentration of this solution is 2.7 g / l. Leave 6 hours in contact, dry for 1 hour at 100-1200C and then calcine 2 hours at 5300C
On the calcined product containing chlorine and platinum, the tin is impregnated: an organic solution of tetrabutyltin is brought into contact with the alumina support at a rate of 100 cm 3 of solution per 100 g of support for 6 hours. The solid obtained is then drained and dried for 1 hour at 100-120 C and then reduced under a stream of dry hydrogen for 2 hours at 4500C.

 The alumina then contains, by weight, 0.40% platinum, 0.3% tin and 1.0% chlorine.

Example 2: MFI zeolite form hydrogen (catalyst B).

A hydrogenated H-MFI zeolite is used which is obtained from the NaMFI form resulting from the synthesis as follows
- ammonium nitrate treatment
calcination at 5500C under air.

 The characteristics of the solid obtained are: an Si / Al ratio equal to 29 and a sodium content equal to 0.014% by weight. Its pore volume measured by nitrogen adsorption at 77K is 0.192 cm3 / g. The mesh size of the crystal lattice is 5339 cubic Angstroms.

Example 3 Preparation of a MFI Zeolite Form Hydrogen Containing Sodium (Catalyst C)

 This zeolite is prepared from a H-MFI zeolite hydrogen form on which the sodium is deposited with an aqueous solution of sodium nitrate. The concentration of this solution is equal to 48.5 g / l. This is brought into contact with the HMFI zeolite for 6 hours. The solid is then drained, dried at a temperature of about 1200C and then calcined at 5500C in air.

 The characteristics of the solid obtained are: an Si / Al ratio equal to 29 and a sodium content equal to 0.25% by weight. Its pore volume measured by nitrogen adsorption at 77K is 0.189 cm3 / g.

Example 4 Preparation of Mixtures (Catalysts E and F)
Preparation of Alumina Containing Platinum and Tin (Catalyst D)

 The alumina used is identical to that used in Example 1.

On 1009 of this alumina is impregnated with platinum, adding to the solid 150 cm3 of an aqueous solution of hexachloroplatinic acid. The platinum concentration of this solution is 2.7 g / l. Leave 6 hours in contact, dry for 1 hour at 100-1200C and then calcine 2 hours at 5300C
On the calcined product containing platinum, impregnation of tin is carried out: an organic solution of tetrabutyltin is brought into contact with the alumina support in a proportion of 100 cm3 of solution per 100 g of support for 6 hours. The solid obtained is then drained and dried for 1 hour at 100-120 ° C. and then reduced under a stream of dry hydrogen for 2 hours at 450 ° C.

 The alumina thus prepared (catalyst D1 then contains, by weight, 0.40% platinum and 0.3% tin.

Preparation of mixtures (catalysts E and F)
Catalysts E and F are prepared by mixing from catalysts A, C and D. These mixtures are produced in the following proportions:
catalyst E = 60 g catalyst A + 40 g catalyst C
catalyst F = 60 g catalyst D + 40 g catalyst C
Each of the constituents of these mixtures is subjected beforehand to submicron milling. After mixing, the catalysts E and F are shaped by pelletization.

Example 5 Catalyst Performance
It is proposed to transform a charge consisting of a hydrocarbon mixture containing from 5 to 6 carbon atoms per molecule. This is done in the presence of one of the catalysts A, B, C, E and F whose preparation has been described above.

These catalysts have been tested for conversion of a C5-C6 filler whose composition is the following (expressed in% by weight):
Paraffins C5 90%
C6 5.4%
NaDthenes C5 3.7%
C6 0.9%
The operating conditions are as follows
- temperature 4600C
- pressure 2.5 bar
- pph 2 h-1
The results of the test are reported in Table 1.

Table 1

<tb><SEP> r <SEP> Selectivities <SEP> (% <SEP> Weight) <SEP> 1
<tb><SEP> Selectivities <SEP> (%
<tb> Catalyst <SEP> Lesson <SEP> II: Hq <SEP> C2Hs <SEP> C3Hs <SEP> butsna <SEP> oMfn <SEP> Aromaüqua
<tb><SEP> I (% <SEP> weight) <SEP> + <SEP> + <SEP> + <SEP> Cs <SEP> + <SEP> C
<tb><SEP> 1
<tb><SEP> C2Hq <SEP> C3Hs <SEP> hutner
<tb> Catalyst <SEP> A <SEP> 53 <SEP> 3 <SEP> 11 <SEP> 20 <SEP> 17 <SEP> 39 <SEP> 10
<tb> (comparative)
<tb> Catalyst <SEP> B <SEP> 89 <SEP> 28 <SEP> 26 <SEP> 15 <SEP> 20 <SEP> 0
<tb> (comparative)
<tb> Catalyst <SEP> C <SEP> 81 <SEP> 25 <SEP> 26 <SEP> 16 <SEP> 21 <SEP> 0 <SEP> 12
<tb> (comparative)
<tb> Catalyst <SEP> E <SEP> 76 <SEP> 8 <SEP> 16 <SEP> 18 <SEP> 12 <SEP> 1 <SEP> 45
<tb> Catalyst <SEP> F <SEP> 72 <SEP> 8 <SEP> 13 <SEP> 19 <SEP> 15 <SEP> 6 <SEP> 39
<tb> (comparative)
<Tb>
It is therefore found that the catalyst E according to the invention leads to conversions and selectivities in aromatic products which are clearly superior to those of the comparative catalysts, in particular of the catalyst
F.

Claims (13)

1 - Composite catalyst containing on the one hand a zeolite of structure MFI containing in its framework silicon and at least one element selected from the group consisting of aluminum and gallium and on the other hand a matrix, said zeolite containing at least one element called additional alkaline selected from the group consisting of alkali metals and alkaline earth metals, the catalyst additionally containing  at least one noble metal of the platinum family, deposited on the matrix  and / or the zeolite,  at least one additional metal deposited on the matrix and / or the  zeolite, said metal being selected from the group consisting of tin,  germanium, indium, lead, gallium, thallium, copper, gold,  Silver, nickel, ruthenium, iron, chromium, molybdenum and  tungsten,  at least one halogenated element deposited on the matrix and / or the zeolite,  selected from the group consisting of fluorine, chlorine, bromine and iodine. 2 - Catalyst according to claim 1 and further comprising a doping element selected from the group consisting of gallium and zinc, the doping element being deposited in the matrix and / or the zeolite. 3 - Composite catalyst according to one of claims 1 and 2 wherein the zeolite content is 1 to 99% by weight relative to the total mass of the catalyst. 4 - Catalyst according to one of claims 1 to 3 wherein the additional alkali content is between 0.001 and 5% by weight relative to the zeolite. 5 - Catalyst according to one of claims 1 to 4 wherein the noble metal content of the platinum family is between 0.01 and 2%, expressed by weight relative to the matrix. 6 - Catalyst according to one of claims 1 to 5 wherein the additional metal content expressed by weight relative to the matrix is between  - 0.005 and 2% when the additional metal is tin  - 0.005 to 0.7% when the additional metal is selected from  Other additional metals 7 - Catalyst according to one of claims 1 to 6 wherein when there is at least two additional metals, the total content of additional metals, by weight relative to the matrix, is between 0, 02 and 1.20%. 8 - Catalyst according to one of claims 1 to 7 wherein the halogen content (expressed by weight relative to the matrix) is between 0.1 and 15%. 9 - Catalyst according to one of claims 1 to 8 wherein the doping element content, expressed by weight relative to the zeolite is between 0.01 and 10%. 10 - Catalyst according to claim 9 wherein the doping element is gallium.  il - Catalyst according to one of claims 9 and 10 wherein the driver element is deposited in the zeolite. 12 - Catalyst according to one of claims 1 to 1 1 wherein the matrix further contains 0.01 to 4% by weight of a metal selected from the group consisting of alkali metals and alkaline earth metals. 13 - Catalyst according to claim 12 wherein said selected metal is lithium or potassium. 14 - Catalyst according to one of claims 1 to 11 wherein the matrix is an alumina. 15 - Use of the catalyst according to one of claims 1 to 14 in a hydrocarbon aromatization process comprising from 5 to 12 carbon atoms per molecule.