AU655334B2

AU655334B2 - MFI structure catalyst and its use in the aromatization of hydrocarbons having 5 to 12 carbon atoms

Info

Publication number: AU655334B2
Application number: AU28357/92A
Authority: AU
Inventors: Fabio Alario; Jean-Marie Deves
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1991-11-15
Filing date: 1992-11-13
Publication date: 1994-12-15
Anticipated expiration: 2012-11-13
Also published as: DE69203211T2; ATE124295T1; JPH05212289A; EP0542613A1; ES2076718T3; TW235927B; MY109061A; AU2835792A; KR930009647A; KR100245782B1; DE69203211D1; EP0542613B1

Abstract

A composite catalyst which contains: - a zeolite of MFI structure containing at least one element chosen from the group consisting of alkali and alkaline-earth metals and containing in its framework at least the elements silicon, aluminium and/or gallium, - a matrix, - at least one noble metal of 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 alkali and alkaline-earth metals. Use of this catalyst in aromatisation reactions of hydrocarbons containing from 2 to 12 carbon atoms per molecule.

Description

-~L

655334

AUSTRALIA

Patents Act 1990 i t Irr i~ i :.i COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): INSTITUT FRANCAIS DU PETROLE Invention Title: MFI STRUCTURE CATALYST AND ITS USE IN THE AROMATIZATION OF HYDROCARBONS HAVING 5 TO 12 CARBON ATOMS The following statement is a full description of this invention, including the best method of performing it known to me/us: d

?I

I:1 i i ii i r i i 1 Irl i tri I ii

Q

it ,t' i t rr r c i "19 The present invention relates to: a catalyst, known as a composite catalyst and which contains: a MFI structure zeolite containing at least one element chosen from within the group constituted by alkali metals and alkaline earth metals, and referred to hereinafter by the term "additional alkali", and containing in its skeleton silicon and at least one element chosen from within the group formed by aluminium and gallium, said zeolite being referred to hereinafter as

"A/MFI",

10 a matrix, at least one precious metal from the platinum group deposited on the matrix and/or the MFI (preferably on the matrix), deposited on the matrix and/or the MFI (preferably the matrix), at least one additional metal chosen from within the group const- 15 ituted by tin, germanium, indium, lead, gallium and thallium, metals of group Ib such as copper, gold and silver, metals of group VIII such as nickel, ruthenium, iron and metals of group VI such as chromium, molybdenum and tungsten, at least one halogen chosen from within the group constituted ii r i I i I _ZI by fluorine, chlorine, bromine and iodine, deposited in the MFI and/or the matrix (preferably in the matrix), optionally at least one doping element chosen from within the group constituted by gallium and zinc, deposited in the MFI and/or the matrix (preferably in the MFI), and optionally at least one element chosen from within the group constituted by alkali metals and alkaline earth metals, and Sdeposited in the matrix and/or the MFI (preferably in the matrix) S1 and its preparation and use in reactions for the aromatization of hydrocarbons having 2 to 12 carbon atoms per molecule and more particularly 5 to 12 carbon atoms per molecule, or 2 to 4 carbon atoms per molecule, as a function of the charge types Sused.

I The alkali metals and alkaline earth metals, other than those contained in the zeolite and which are referred to as additional alkali(s), as well as metals from the platinum group and additional metals designated hereinafter and with the exception of gallium and zinc (used as a doping element) are referred to hereinafter as "metals".

The zeolite-based catalysts doped with gallium, or zinc, or platinum, are known to be active and selective in the aromatization i <4 min~ 1 SIr A ct 3 of propane and butane. Conventionally, hydrocarbons with more than 6 carbon atoms per molecule are transformed into aromatics by catalytic reforming using catalysts of the acid alumina type containing platinum, to which can e.g. be added tin or rhenium.

However, these reforming catalysts do not have good performance characteristics for the aromatization .of..hydrocarbons containing less than 6 carbon atoms per molecule. Thus, there is a considerable practical interest in finding catalysts with good performance characteristics for the aromatization of fractions rich in hydrocarbons of the C 5 to C 12 type.

The aromatization reaction of hydrocarbons containing less than 9 carbon atoms per molecule in the presence of zeolites has already formed the object of patents and publications. Several MFI zeolite-based catalytic systems have been claimed and differ 15 by the additions which they contain. Thus, a distinction can be made between: gallium-doped systems (US-A-4,175,057) and (ii) zinc-doped systems (US-A-4,288,645).

However, these systems suffer from an important deficiency, namely a high methane selectivity. In order to improve the performance characteristics of such catalytic systems a number of solutions have been proposed, including the addition of platinum Jin, Y. Makino, A. Miyamoto, T. Inui, Chem. Express,

I_

4- 2, p.515, 1987).

Recently (French patent application 91/10624 of the present Applicant), it has been discovered that the use of composite catalysts containing a MFI zeolite on the one hand and on the other hand a support or generally amorphous.jnatrix on._which is deposited a precious metal from the platinum group and at least one additional metal such as tin, lead or indium, leads to catalytic performance characteristics in the aromatization reactions of paraffins with 5 to 9 carbon atoms significantly t improved compared with the prior art systems.

:i The use of such catalysts in particular makes it possible to Slimit the reactions leading to the formation of the undesired i methane.

i Ci Research carried out by the Applicant has led to the discovery that, surprisingly, the use of a composite catalyst containing a MFI zeolite, which contains at least one element chosen from "within the group constituted by alkali metals and alkaline earth metals, known as "A/MFI", optionally doped by gallium and/or zinc in oxide form and a matrix on which is deposited at least one precious metal from the platinum group (particularly palladium, platinum, nickel, iridium and rhodium), at least one additional metal chosen from within the group constituted by tin, germanium, lead, indium, gallium and thallium, metals of group i -iaa III ra -i -Y ifr f ?t CI I' C gr r 5 Ib such as copper, gold and silver, metals of group VIII such as nickel, ruthenium and iron and metals of group VI such as chromium, molybdenum and 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 cataljtic performance characteristics in the aromatization reactions of paraffins containing 5 to 12 carbon atoms per molecule which are significantly improved compared with the prior art catalysts.

10 The MFI zeolite contained in the catalyst of the present invention can be prepared by all procedures described in the prior art. Thus, the synthesis of said zeolite can be carried out in a conventional OH-medium in the presence or absence of an organic agent and/or alcohol. The document "Synthesis of high silica zeolites", by 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 e.g. the fluoride medium in the presence (EP- A-17 2,068) or the absence (French patent application 90/16529) of an organic compound. The crystallized skeleton of the zeolite used in the present invention contains silicon and at least one element chosen from within the group formed by aluminium and gallium.

I

I 6 *I -6- Following the synthesis stage, the zeolite MFI is: it.

a.

t as either transformed into a hydrogen form, designated H-MFI, by the almost total elimination of the organic compounds and/or alkali metal or alkaline earth cations which it contains, optionally after synthesis. All procedures described in the prior art can be used for passing into the hydrogen form, such as ion exchanges, which may or may not be followed by calcination or various chemical treatments. One or more additional alkalis are then introduced via salts in aqueous or organic solutions by all prior art procedures, in order to then obtain the A/MFI, or directly transformed into a form containing one or more additional alkalis, by the possible total elimination of the organic compounds, said additional alkali or alkalis then being supplied by the zeolite synthesis medium. The additional alkali content can optionally be easily increased on the basis of salts of said alkali metals or alkaline earth metals in aqueous or organic solutions by all prior art procedures, in order to then obtain the A/MFI.

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

P 1 ii i r" i ii I i-i ii I~ 1 I ,t ii I:rl it t t i rcrr;~ I i: 7 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, in which T represents Al and/or Ga, generally exceeds 7, preferably exceeds 10 and in even more preferred manner is between 13 and 500.

The A/MFI zeolite, containing at least one alkali metal or alkaline earth metal, used in the present invention can either undergo as it is a gallium and/or zinc deposition, or can be mixed with other constituents of the catalyst, the gallium and/or 10 the zinc being optionally introduceable subsequently into the said mixture.

In the case where, after synthesis, the MFI zeolite is firstly transformed into its hydrogen form, the optional deposition of gallium and/or zinc ran take place prior to the introduction 15 of at least one of the additional alkali metals.

Numerous gallium and/or zinc deposition methcis can be used in the present invention and among these reference can be made to ion exchanges through the use of salts in aqueous solution, or impregnations by solutions of said salts. The total 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.

L T- ~C 1 C Ct -8- The matrix comprises at least one refractory oxide and in particular at least one oxide of a metal chosen from within the group constituted by magnesium, aluminium, titanium, zirconium, thorium, 'ilicon and boron. Moreover, it can also comprise charcoal.

The preferred matrix is alumina, whose specific surface can be advantageously between 10 and 600 and preferably between.......

150 and 400 m2/g.

The composite catalyst according to the invention can be prepared according to two methods, whose principles are given below, whilst the practical realization is known to the Expert.

First method.

The MFI or A/MFI zeolite is mixed with the matrix. Mixing can be performed between two powders, two previously shaped solids, or between a powder and a previously shaped solid. It is also 15 possible to jointly shape the two solids by all prior art procedures, namely pelletizing, extrusion, drageification, drop coagulation and drying by atomization. During these shaping operations, it may be necessary to add a shaping additive chosen from within the group constituted by silica and alumina. In this way the zeolite is mixed with the matrix, followed by shaping.

Following mixing and shaping the metals are deposited and introduction takes place of the halogen and optionally gallium and/or zinc to the system constituted by the matrix and the zeolite, i c Cr C 11ir, Ak I i i r I i i j i j i i

I

si i~ ti r

I

r Lt?: 'f .C.4 -9little significance being attached to the deposition order.

If the MFI zeolite was initially mixed with the matrix, it is then necessary to subsequently introduce an element chosen from within the group constituted by alkali metals and alkaline earth metals. It is then considered that most of the metals, preferably 60 to 100% by weight based on the composite catalyst, occur on the matrix.

Second method.

Prior deposition takes place of the halogen, the metals and optionally the alkali metal or alkaline earth metal on the matrix on the one hand and optionally the gallium and/or zinc on the A/MFI zeolite on the other, or optionally the gallium and/or zinc on the MFI prior to the introduction of at least one additional alkali. The introduction order of the different elements 15 to the matrix is unimportant. This is followed by the mixing of the A/MFI zeolite optionally containing gallium and/or zinc with the matrix containing the metals and the halogen, followed by shaping. Shaping is obtained under the same conditions as hereinbefore. In a variant, the zeolite, on which may optionally have been deposited the gallium and/or zinc, can be mixed with the matrix at a random one of the stages of introducing the halogen and depositing the metals on the matrix.

;1 ~1 i: i$ i:S ij; i-d i:l !il

I::W

i I :-i ilS Irr r i i 1: ~1 10 The preferred preparation method consists, optionally of depositing the gallium and/or zinc on the A/MFI zeolite, depositing the metals and introducing the halogen on the matrix, followed by the introduction of the zeolite optionally charged with gallium and/or zinc in the matrix charged with metals and halogen by shaping the two powders. Shaping preferably-takes place following micron grinding, which can be carried out by using the wet grinding method.

The composite catalyst contains between 1 and 99% (by weight 10 based on the total mass of the catalyst) of A/MFI zeolite, the residue up to 100% being constituted by the matrix, the metals and the halogen. The respective zeolite and matrix proportion varies within a wide range, because it is dependent on the one hand on the Si/T ratio of the zeolite, in which T is Al and/or Gi-, and on the other hand the content of metals and halogen of the matrix in the case of the preferred preparation procedure.

The matrix containing the metals and the halogen, in the case of the preferred preparation procedure, is generally prepared in accordance with French patent application 91/10624, whereof part is reproduced hereinafter. These procedures are e.g. usable on the matrix alone or on the matrix/zeolite mixture, as described in the two preparation methods.

r ;1

I

A,

11 For the impregnation of the metals use is either made of a common solution of the metals which it is wished to introduce, or separate solutions for the precious metal from the platinum group and for the additional metal and optionally the element chosen from within the group constituted by alkali metals and alkaline earth metals. When. .seyeal,. solutions- are. used,, it,. is. possible to carry out intermediate drying and/or calcining operations.

Normally the final stage is a calcination, e.g. at between 500 and 1000 C and preferably in the presence of molecular oxygen, 10 e.g. by carrying out air scavenging.

The precious metal from the platinum group can be incorporated into the matrix by impregnating the latter with the aid of an aqueous or non-aqueous solution, containing a salt or a compound of the precious metal. The platinum is generally introduced into the matrix in the form of chloroplatinic acid, but for any precious metal it is also possible to use ammoniated compounds or compounds such as e.g. ammonium chloroplatinate, dicarbonyl platinum dichloride, hexahydroxyplatinic acid, palladium chloride or palladium nitrate.

The additional metal chosen from within the group constituted by tin, germanium, lead, indium, gallium and thallium, metals of group Ib such as copper, gold and silver, metals of group VIII such as nickel, ruthenium and iron and metals of group VI such as chromium, molybdenum and tungsten can be introduced I- 12 by means of compounds such as e.g. tin chlorides, bromides and nitrates, lead carbonate, acetate, nitrate and halides, germanium chloride and oxalate and indium nitrate and chloride.

The halogen can be introduced on the basis of at least one of the halides of metals from the platinum group or at least one of the halides of the additional metals, in the case where these i metals are introduced on the basis of halides. A complementary i Smethod can consist of an impregnation of the matrix by an aqueous 1 solution containing an acid or a halogen salt. For example, 1i 0 chlorine can be deposited using a hydrochloric acid solution.

Another method can consist of a calcination at a temperature generally between 400 and 900C in the presence of an organic compound containing halogen, such as e.g. CC1H 4 2 C1 2

CK

3 Cl, i etc.

Ai The element chosen from within the group constituted by alkali metals and alkaline earth metals, preferably lithium and potass- Sium, can be introduced by means of compounds such as e.g. the i halide, nitrate, carbonate, cyanide and oxalate of said element.

A subsequently indicated preparation process e.g. comprises the following stages: a) introduction onto the matrix of at least one eleient chosen from within the group constituted by fluorine, chlorine, 13 bromine and iodine, Ii

L

t optional introduction onto the matrix of at least one element chosen from within the group constituted by alkali metals and alkaline earth metals, b) calcination of the product obtained in stage a) or c) introduction onto the matrix of at least one precious metal from the platinum group, d) calcination of the product obtained in stage c), e) introduction onto the product obtained in stage d) of at 10 least one additional metal, called M hereinbefore.

If no use is made of alkali metal or alkaline earth metal, only stages d) and e) of the preparation process are performed.

The use in the present invention of at least one precious metal from the platinum group can e.g. take place by using ammoniated compounds.

In the case of platinum, reference can e.g. be made to the salts of platinum IV hexamines of formula Pt(NH 3 6

X

4 the salts of '1k t I 4

I

11

K:

A i fc I 14 platinum IV halogenopentamines of formula (PtX(NH 3 5

)X

3 salts of platinum N tetrahalogenodiamines of formula PtX 4

(NH

3 2 platinum complexes with halogen-polyketones and halogen compounds of formula H(Pt(aca) 2 X being a halogen chosen from within the group formed by chlorine, fluorine, bromine and iodine and X is preferably chlorine and aca represents the residue of formula C5H 7 0 2 derived from acetyl acetone.

The introduction of the precious metal of the platinum group is preferably carried out by impregnation with the aid of an aqueous or organic solution of one of the aforementioned organometallic compounds. Among the usable organic solvents, reference can be made to paraffinic, naphthenic or aromatic hydrocarbons and halogenated organic compounds e.g. having 1 to 12 carbon atoms per molecule. Reference can e.g. be made to n-heptane, methyl cyclohexane, toluene and chloroform. It is also possible to use solvent mixtures.

Following the introduction of the precious metal of the platinum group, the product obtained is optionally dried and then calcined, preferably at a temperature between 400 and 10000C. After said calcination, introduction takes place of at least one additional metal, optionally preceded by a high temperature hydrogen reduction, e.g. at between 300 and 5000C. The additional metal M can be introduced in the form of at least one organic compound chosen from within the group constituted by complexes of said metal, particularly polyketone complexes of the metal M and hydrocarbyl metals such as alkyls, cycloalkyls, aryls, alkylaryls and aryl alkyls of a metallic type.

The introduction of the metal M advantageously takes place with the aid of a solution-of the organometallic compound of said metal in an organic solvent. It is also possible to use organoi halogen compounds of the metal M. As compounds of the metal M, reference can more particularly be made to tetrabutyl tin i in the case where M is tin, tetraethyl lead in the case where M is lead and triphenyl indium in the case where M is indium.

The impregnation solvent is chosen from within the group constit- 1 tuted by paraffinic, napthenic or aromatic hydrocarbons containing 6 to 12 carbon atoms per molecule and halogenated organic compounds containing 1 to 12 carbon atoms per molecule. Reference can e.g be made to n-heptane, methyl cyclohexane and chloroform.

It is also possible to use mixtures of the above solvents.

In the case where use is not made of the preparation process as described hereinbefore, consideration can be given to the introduction of at least one additional metal M prior to the introduction of at least one precious metal from the platinum group. If the metal M is introduced before the precious metal, the compound of metal M used is generally chosen from within the group constituted,by the halide, nitrate, acetate, tartrate,

I

16 carbonate and oxalate of the metal M. The introduction then advantageously takes place in aqueous solution. In this case, prior to introducing at least one precious metal, calcination takes place in air at a temperature between 400 and 1000 0

C.

The composite catalyst based on a MFI and a matrix preferably contains: 1) by weight, based on the matrix: i;" i s ii iri -ii

I

i- '-j 0.01 to 2% and preferably 0.1 to 0.5% of at least one precious metal from the platinum group, deposited in the matrix and/or the zeolite, deposited in the matrix and/or the zeolite, at least one additional metal, namely 0.005 to preferably 0.01 to tin, in the case where the additional metal is tin, 0.005 to preferably 0.01 to 0.6% of at least one metal chosen from within the group constituted by germanium, indium, lead, gallium and thallium, metals of group Ib such as copper, gold or silver, metals of group VIII such as nickel, ruthenium or iron and metals of group VI such as chromium, molybdenum or tungsten, whilst in the case where the catalyst contains at least two additional metals of said group, the total content of the chosen additional metals is between 0.02 and 1.20%, preferably between 0.02 17 and 1.0% and in even more preferred manner between 0.03 and 0.80%, 0.1 to 15%, preferably 0.2 to 10% of a halogen element ichosen from within the group constituted by fluorine, chlorine, bromine and- iodine, and preferably chlorine, the halogen being incorporated into the matrix and/or the MFI, i optionally 0.01 to preferably 0.1 to 0.6% of at least one metal chosen from within the group constituted by alkali metals and alkaline earth metals and preferably chosen I 10 within the group constituted by lithium and potassium, 2) between 1 and 99% by weight of MFI zeolite, containing in its skeleton silicon and at least one element chosen from among aluminium and gallium, 3) optionally by weight, based on the zeolite: 15 between 0.001 and 5% and preferably between 0.005 and 3% -i of at least one additional alkali chosen from within the group constituted by alkali metals and alkaline earth metals, optionally between 0.01 and 10% by weight and preferably between 0.03 and 4% of a doping element chosen from within 18 the group constituted by gallium and zinc, preferably gallium, said element being introduced into the MFI and/or the matrix.

At the end of the preparation, the shaped catalyst contains a MFI zeolite, metals, at least one.-halogen-and-a.matrix-and.

calcination in air is carried out at a temperature between 450 and 1000 0 C. The thus calcined catalyst can undergo an activation treatment under hydrogen at elevated temperature, e.g. between 300 and 5000C. The treatment procedure under hydrogen e.g.

consists of slowly raising the temperature under a hydrogen flow to the maximum reduction temperature, generally between "300 and 500°C anOr preferably between 350 and 450 0 C, followed by the maintaining of said temperature for generally between 1 and 6 hours.

ij The previously described catalyst according to the invention is used for the aromatization of alkanes containing 2 to 12 and e.g. 2 to 4 or 5 to 12 carbon atoms per molecule, in the presence or absence of olefins. This reaction is of particular interest, because it can e.g. make it possible to valorize the light fractions resulting from refining operations by transforming them into higher value products (benzene, toluene and xylenes) and also transform paraffin charges which may contain olefins into bases for high octane number fuels, whilst in both cases contributing to the production of significant quantities -L I CI i A, 4

II

i i -i 1 i r i i i i t ii EI:I~ i 1 ,r ii r it i .x 'Ps 19 of hydrogen, which is e.g. indispensable for hydrofining processes.

The charge containing compounds containing 5 to 12 carbon atoms per molecule is contacted with the catalyst according to the invention at a temperature between 400 and 700 0

C.

The following examples define the invention without limiting its scope.

Example 1: Preparation of alumina containing platinum, tin and chlorine (catalyst A).

10 The alumina used has a specific surface of 220 m2/g and a pore volume of 0.52 cm 3 To lOOg of alumina support are added 500 cm 3 of an aqueous hydrochloric acid solution. Contact is maintained for 3 hours, followed by draining and drying for 1 hour at 100 to 120 0

C.

On the dried chlorine-containing product is then carried out the impregnation of the platinum, adding to the solid 150 cm 3 of an aqueous hexachloroplatinic acid solution. The platinum concentration of this solution is 2.7g/l. Contact is maintained for 6 hours, followed by drying for 1 hour at 100 to 1200C and calcining for 2 hours at 5300C.

i 20 Impregnation of the tin takes place on the calcined product containing chlorine and platinum. An organic tetrabutyl tin solution is contacted with the alumina support at a rate of 100 cm 3 of solution for 100g of support for 6 hours. The solid obtained is then drained and dried for 1 hour at 100 to 120 0

C

and then reduced under a dry hydrogen flow for 2-hours at 450 By weight, the alumina then contains 0.40% platinum, 0.3% tin and 1.0% chlorine.

Example 2 Hydrogen form MFI zeolite (catalyst B).

iI I j i~iC~ C C C Use is made of a hydrogen form H-MFI zeolite obtained from the Na-MFI form resulting from the synthesis by ammonium nitrate treatment and calcination in air at 5500C.

The characteristics of the solid obtained are a Si/Al ratio of 29 and a sodium content of 0.014% by weight. Its pore volume 15 measured by nitrogen adsorption at 77K is 0.192 cm 3 The mesh volume of the crystal lattice is 5339 cubic Angstr6m.

Example 3 Preparation of a hydrogen form MFI zeolite containing sodium (catalyst C).

This zeolite is prepared from a hydrogen form H-MFI zeolite on which the sodium is deposited with the aid of an aqueous sodium nitrate solution. The concentration of this solution i i -clUU 21 is 48.5g/l. The latter is contacted with the H-MFI zeolite for 6 hours. The solid is then drained, dried at a temperature close to 1200C and then calcined in air at 5500C.

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

Example 4 Preparation of the mixtures (catalysts E and F).

Preparation of the alumina containing the platinum and the tin (catalyst D).

The alumina used is identical to that of Example 1.

On 100g of said alumina impregnation of the platinum takes place, adding to the solid 150 cm 3 of an aqueous hexachloroplatinic acid solution. The platinum concentration of this solution is 2.7g/l. Contact is maintained for 6 hours, followed by drying for 1 hour at 100 to 1200C and calcining for 2 hours at 530°C.

On the platinum-containing calcined product impregnation takes place of the tin. An organic tetrabutyl tin solution is contacted with the alumina support at a rate of 100 cm 3 of solution for 100g of support for 6 hours. The solid obtained is then drained and dried for 1 hour at 100 to 1200C and then reduced C S

C

1 .z 22 under a dry hydrogen flow for 2 hours at 450 0 C. The thus prepared alumina (catalyst D) then contains, by weight, 0.40% platinum and 0.3% tin.

Preparation of the mixtures (catalysts E and F).

v The catalysts E and F are prepared by mixing on the basis of catalysts A, C and D. These mixtures are obtained in the following weight proportions: Catalyst E =60 g catalyst A 40g catalyst C Catalyst F 60g catalyst D 40g catalyst C.

c1' 10 Each of the constituents of these mixtures undergoes beforehand submicron grinding. After mixing, the catalysts E and F are V shaped by pelletizing.

Example 5: Performance characteristics of the catalysts on a charge having 5 and 6 carbon atoms per molecule.

15 The aim is to transform a charge constituted by a mixture of hydrocarbons containing 5 to 6 carbon atoms per molecule. For this purpose working takes place in the presence of one of the catalysts A,B,C,E and F, whose preparation has been described hereinbefore. These catalysts were tested in the transformation e _I i S- 23 of a C5-C6 charge, which has the following composition (in by weight): paraffins C 5

C

6 5.4% naphthenes C 5 3.7%

C

6 0.9%.

The operating conditions are as follows: Temperature 460 0

C

i pressure 2.5 bars I! -1 i 10 pph 2 h 1 The test results are given in Table 1.

A' 1 2 4 f r i I: i it a i i 24 Selectivities (wt. Catalyst Conversion CH 4

C

2

H

6

C

3

H

6 butanes (wt.

C

2

H

4

C

3

H

6 butenes

C

5

C

6 aromatics olefins Catalyst A (comparative) 53 3 11 20 17 39 Catalyst B (comparative) 89 28 26 15 Catalyst C (comparative) 81 25 26 16 21 0 12 Catalyst E 76 8 16 18 12 72 8 13 19 15 Catalyst F (comparative) 6 39 Thus, catalyst E according to the invention leads to superior conversion rates and selectivities as regards aromatic products as compared with the comparative catalyst and in particular Catalyst F.

Example 6 Performance characteristics of catalysts on a charge having 3 carbon atoms per molecule.

The five catalysts A,B,C,E and F, whose preparation was described p~ i I~ l- ~r~-n.rmaa. -r: 25 hereinbefore, were tested in connection with propane transformation under the following conditions: temperature pressure pph 475°C atmospheric 1.0 h 1 l.O h The test results are given in Table 2.

Table 2 Selectivities Catalyst Conversion methane ethane moles) ethylene ;y i r i 1 1.1

E

1-3 i i

P"

Catalyst A (comparative) Catalyst B (comparative) Catalyst C (comparative) wt. propylene 22 23 butanes aromatics butenes 48 27 45 27 Catalyst E 8 26 8 23 4 2 34 Catalyst F (comparative) i II Crr~

I

26 Thus, catalyst E according to the invention leads to much better conversion characteristics and selectivities with regards to aromatic products as compared with the comparative catalysts and in particular catalyst F.

c 1

Claims

1. A process for aromatizing C 5 to C 12 hydrocarbons in the presence of a catalyst, characterised in that the catalyst is a composite catalyst containing on the one hand a MFI structure zeolite containing in its skeleton silicon and at least one element chosen from within the group constituted by aluminium and gallium and on the other a matrix, said zeolite containing at least one element referred to as the additional alkali and chosen from within the group constituted by alkali metals and alkaline earth metals, said catalyst also containing: at least one precious metal from the platinum group, deposited on the matrix and/or zeolite, at least one so-called additional metal deposited on the matrix and/or the zeolite, said metal being chosen from within the group constituted by tin, germanium, indium, lead, gallium, thallium, copper, gold, silver, nickel, ruthenium, iron, chromium, molybdenum and tungsten, at least one halogen element deposited on the matrix and/or 20 the zeolite and chosen from within the group constituted by fluorine, chlorine, bromine and iodine.

2. Process according to claim 1 in which the catalyst also contains a doping element chosen from within the group constituted by gallium and zinc, the doping element being deposited in the matrix and/or the zeolite.

3. Process according to either of the claims 1 and 2, wherein the zeolite content represents 1 to 99% by weight, based on the total weight of the catalyst.

4. Process according to any one of the claims 1 to 3, wherein the additional alkali content is between 0.001 N- 28 and 5% by weight, based on the zeolite. Process according to any one of the claims 1 to 4, wherein the content of the precious metal from the platinum group is between 0.01 and 2% by weight based on the matrix.

6. Process according to any one of the claims 1 to wherein the weight content of the additional metal based on the matrix is between 0.005 and 2% when the additional metal is tin and 0.005 and 0.7% when the additional metal is chosen from among the other additional metals. I* 7. Process according to any one of the claims 1 to 6, wherein when at least two additional metals are present, the total weight content of additional metals based on the matrix is between 0.02 and 1.20%. i 15 8. Process according to any one of the claims 1 to 7, wherein the halogen content (by weight based on the matrix) is between 0.1 and D. Process according to any one of the claims 1 to i wherein the doping element content, expressed by weight based on the zeolite, is between 0.01 and Process according to claim 9, wherein the doping -h element is gallium.

11. Process according to either of the claims 9 and wherein the doping element is deposited in the zeolite.

12. Process according to any one of the claims 1 to S11, wherein the matrix also contains 0.01 to 4% by weight of a metal chosen from within the group constituted by alkali metals and alkaline earth metals. j y^ stafflhIleylkeep/specUi28357.921 10.10 0 :ai 29

13. Process according to claim 12, wherein the chosen metal is lithium or potassium.

14. Process according to any one of the claims 1 to 11, wherein the matrix is an alumina. DATED THIS 10TH DAY OF OCTOBER 1994 INSTITUT FRANCAIS DU PETROLE By its Patent Attorneys: GRIFFITH HACK CO Fellows Institute of Patent Attorneys of Australia. I, :1A staff/hlley/keep/speci28357.92_1 10.10 ;v. *444 I s~C I DESCRIPTIVE ABSTRACT H r t The invention relates to a composite catalyst containing: a MFI structure zeolite containing at least one element chosen from within the group constituted by alkali metals and alkaline earth metals and containing in its skeleton at least the elements silicon, aluminium and/or gallium, a matrix, at least one precious metal from the platinum group, at least one additional metal chosen from within the group constituted by tin, germanium, indium, copper, iron, molybd- enum, gallium, thallium, gold, silver, ruthenium, chromium, tungsten and lead, I I I at least one halogen chosen from within the group constitu- ted by fluorine, chlorine, bromine and iodine, optionally at least one metal chosen from within the group constituted by gallium and zinc, and optionally, preferably in the matrix, at least one element chosen from within the group constituted by alkali metals and alkaline earth metals. The invention also relates to the use of this catalyst in reac- tions for the aromatization of hydrocarbons having 2 to 12 carbon "j V :atoms per molecule. i I.j 44* I4 tc €r A*