CA1151133A - Aromatic hydrocarbon producing catalyst, and its preparation - Google Patents

Abstract

PATENT OF INVENTION CATALYST FOR THE PRODUCTION OF AROMATIC HYDROCARBONS AND ITS PREPARATION PROCESS Invention by: Jean René BERNARD Michèle BREYSSE SOCIETE ANONYME DITE: ELF FRANCE Monofunctional paraffin dehydrocyclization catalyst characterized in that it contains -: 0.1 to 1 , 5% of platinum 0.1 to 1.5% of rhenium incorporated in the form of carbonyl a small proportion of sulfur introduced by a sulfur compound reducible or decomposable by hydrogen such as the ratio x of the number of sulfur atoms the number of platinum and rhenium atoms deposited on the catalyst is between 0.05 and 0.6, the support being constituted by a crystalline zeolitic aluminosilicate compensated for more than 90% by alkaline cations, having a pore diameter greater than 6.5 Angstr? ms.

Description

~ 5 ~ 3 The present invention relates to a novel catalyst for hydrocyclization of paraffins C.6 to C.10 and its method of preparation tion. This catalyst is particularly efficient for production light aromatics from petroleum fractions obtained by direct tillation.
The usual methods for carrying out aro-matisation are based on the use of catalysts made up of a noble metal on a support, in particular catalysts containing 0.2 to 0.8% by weight of platinum on a support of alumina chlorinated at 0.5 -

2% weight. It is generally accepted that these working catalysts follow a bifunctional mechanism combining the hydrogenating activity -dehydrogenating of the metal and the isomerizing-cyclizing activity of the sup-acid port A very significant improvement in these catalysts has consisted of adding a second metal to the catalyst, which provides increased stability and the ability to work more low pressure, under conditions or aromatization reactions are favored US Patent 3,415,737 (HE KLUKSDAHL, Chevron Res Co) shows in particular the advantage of using catalysts containing 0.1 to 3% Pt and 0.1 to 3% rhenium. he also claims the presence of 0.05 to 2% sulfur on the cataly-this sulfur being intended to limit the hydrogenolysis activity due rhenium, an activity which leads to rapid deactivation of the cataly-dehydrocyclization sor.
Another type of aromatization catalyst is described in U.S. patents 3,775,502 and 3,819,507 ~ M. OISHI, Sun Res. and Dev. Co). It consists of platinum deposited on X zeolites or exchanged with lithium, sodium or potassium. This catalyst may contain also from 0.1 to 1.2% by weight of rhenium. Although this type of cataly-sor is new, its flavoring activity is comparable to that of previous catalysts. Furthermore, the presence of rhenium in this new type of catalyst does not seem to bring any advantage, since the results obtained with platinum-rhenium-zeolite X are inferior laughing at those of Pt on zeolite X.
Another type of molecular sieve catalyst is described in American patent 4,104,320 (J. Nury, JR Bernard ~ ERAP). he contains from ~ 0.1 to 1.5% by weight of platinum deposited on $ 2 alkali ne, preferably exchanged for potassium or rubidium or cesium. The zeolite L conduit, when loaded with platinum, has a yield ~ Sl ~

and a higher selectivity in aromatics than all the others catalysts described above. Although the operating mechanism of these catalysts has not been fully elucidated, one might think that this catalysis is monofunctional and that it is therefore due to uni-only platinum, the properties of this platinum being modified by the support of zeolite L. The zeolite L usable for these catalysts is compensated by Slcalin cations and therefore platinum, which is in the metallic state under the conditions of catalysis, is strong ~ ent influenced by these alkaline cations since the activity of the ca-talyseur believes when going from lithium to potassium and cesium But if they have remarkable qualities of selectivity and flavoring activity, the catalysts described in the patent cited have a low stability, lower than that of the catalysts mo-bifunctional nometallic based on platinum on chlorinated alumina and therefore, they can only be used under high pressure of hydrogen if we want to obtain reasonable cyble durations In an attempt to stabilize these catalysts, it is possible to use the techniques described in the previous patents, a know the incorporation of rhenium in the catalyst by deposition of acid per rhenic in aqueous solution. This incorporation, whether done in co-impregnation with platinum, or in successive impregnation, does not not lead to an improvement in catalytic stability, and moreover, the activity of these bimetallic catalysts is very clearly inferior higher than that of monometallic catalysts based on zeolite L.
This is in agreement with the observations of the authors of the brief ~
American 3,819,507 who do not observe any beneficial effect of the rheni ~ _ for zeolites X and Y loaded with platinum.
However, we were surprised to find that the poration of rhenium in the form of carbonyl of rhenium Re2 (C0) 10 in the zeolite, preceded or followed by the deposition of platinum by known methods (impregnation, ion exchange of salts or platinum complexes), leads to good activities and stabilities catalytic, after reduction with hydrogen.
The British Revet ~ 2004 764 described a cataly-seur prepared by pyrolysis of rhenium carbonyl on a porous support also containing platinum. This patent shows that the cat-lysers thus prepared are more acti ~ s than the catalysts prepared using perrhenic acid, since they make it possible to obtain ~ lS1 ~ 3. ~

reforming of gasolines an octane number higher than the same reaction temperature. However these catalysts produce more hydrocracking than prepared catalysts res from perrhenic acid, and their advantage is so not really obvious.
On the other hand, the use of carbonyl of rhenium in Pt-Re-zeolite catalysts allows nit an active catalyst, while the use of acid of perrhenic leads to a slightly active catalyst.
However, with these catalysts the selectivity paraffin dehydrocyclization is bad because hydrogenolysis occurs in the proportions recommended for bifunctional supported catalysts in chlorinated alumina, the catalyst obtained is completely poisoned and is practically not active in dehydro-cyclization.
We unexpectedly found that incorporation of sulfur into the catalyst in propor-much weaker than those previously described then leads to good selectivities while obtaining excellent catalytic stability. By example, the sulfur content commonly recommended for the ready-to-use reforming catalysts is about 0.2% by weight, deposited by impregnation with a sulfur compound or presulfurization before catalysis, which - corresponds to a molar ratio x of approximately 2 for contents of 0.3% Pt and 0.3% Re. The x denotes the ratio of the number of sulfur atoms deposited on the cataly-sister to the number of Pt + Re atoms contained in the catalyst.
For such a value, the platinum catalysts rhenium zeolite are not active. Must go down at a molar ratio x of between 0.05 and 0.6 for obtain an active and stable catalyst in dehydrocycliza-tion. For the Pt and Re contents mentioned above X

~ 15 ~ 3 above, this corresponds to a range of 0.005% to 0.06% by weight of sulfur on catalyst, which is notable-less than the 0.2% weight mentioned above.
The invention consists of a new catalyst dehydrocyclization of paraffins containing 0.1 to 1.5 ~ platinum, 0.1 to 1.5 ~ rh ~ nium, sulfur in a form reducible or decomposable by hydrogen so that the molar ratio x is understood between 0.05 and 0.6, the support being constituted by a pore size zeolitic crystalline aluminosilicate - greater than 6.5 Angstroms, ~ - ~~~ --- ~ ~ ~ ~ - ------- ----------- - ----~ lS ~

compensated at more than 90 ~ by alkaline cations.
In another aspect, this invention consists of a new process for the preparation of a catalyst, the steps of which are next, the order in which these steps are performed is ~ onque:
- loading of a non-acidic zeolitic crystalline aluminosilicate pore size greater than 6.5 Angstroms with rhenium, this operation being carried out using rhenium carbonyl Re2 (C0) 10, either by sublimation on the support, or by impregnation generation with an organic solution of Re2 (C0) 10.
- platinum deposition by methods known in the prior art ~
i.e. impregnation with a solution of a platinum compound such as hexachloroplatinic acid 5 platinum chloride tetrammine, dinitritodiamminoplatin or ion exchange by a cationic complex of platinum.
- incorporation of sulfur by impregnating a solution of compound sulfur likely to be reduced or broken down under the conditions catalysis (oxyanion, sulfide, mercaptan, etc.) this operation can be performed at the same time as the previous one. It is also possible to pretreat the catalyst in the reactor dehydrocyclization with a sulfur compound (H2S, dimethyl disul-fure, CS2) before or after reduction by hydro ~ ene.
After carrying out these steps, the catalyst is dried, possibly calcined, then reduced by hydrogen and possibly sulfurized according to the previous recommendations.
The catalysts of the invention have properties exceptional flavoring and excellent stability.
Their support consists of crystalline aluminosilicate zeolitic or molecular sieve. It is essential for dehvdro-

3 ~ cyclization that the molecular sieve serving as support has a weak acidity, or zero acidity or low basicity. This is why the zeolite must have its cation exchange sites compensated for more 90% by alkaline cations, all other cations introducing a certain acidity, either because they are plurivalent and thus create acidic sites, either because they are reducible or decomposable under the conditions of catalysis, reduction or decomposition then corresponding to the formation of protons on the zeolite. It is obvious that the pores of the alkaline zeolite o ~ t an open ~ ure at l ~ Sl ~; ~ 3 less equal to the dimensions of benzene, and among the zeolites used sands, we will mention the faujasites ~ and Y9 the zeolite L, the zeolite omega and zeolite ZSM 4. These zeolites can be used under their ex synthesis form, except the last two which contain alkylammonium cations which must be replaced by alkalis by methods known to those skilled in the art, such as decomposition thermal followed by neutralization with an alkaline base. We can also exchange their synthesis catio ~ s by other alkalis, and the zeolites in question can therefore contain lithium, sodium, potassium, rubidium and / or cesium.
Among these zeolites, the preferred support is the zeolite L qul leads to exceptional yields of aromatics from aliphatic sections This zeolite is synthesized in its form potassium and it can be used as is economically that, but it can also contain sodium and especially rubidium or cesium. The zeolitic support must be shaped to be able be used industrially. This shaping will be done yourself ~
before or after the deposition of platinum, rhenium and sulfur and o ~
will use methods known to those skilled in the art, such as mixture with alumina or clay binders, then extrusion or setting in ~ ball elm by the technique of the drageoir or the "oil drop". A
other usable technique is the shaping of beads or extrudates of a clay such as metakaolin and its conversion into ~ eolite by appropriate techniques. We can also use the zeoli ~ he sou ~
in the form of lozenges, tablets, or in powder form if it is fluidized bed.
Platinum can be deposited by the methods described in prior art. The aqueous route is generally used in particular impregnation and ion exchange. Impregnation can be carried out with any water-soluble platinum compound, such as acid hexachloroplatinic for example Although this compound gives satis-faction it brings some acidity to the catalyst and it's better to use Keller complex or platinum chloride ~
tetrammine or dinitritodiamminoplatin. The latter being not very soluble in water, this impregnation can be carried out hot. It is also possible when using a catio-platinum, to carry out an ion exchange In this case, the . , ~

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support is immersed in the solution containing platinum, then it is removed after a while, washed and dried.
In fact, since the quantities of platinum to be deposited do not represent that a very small fraction of the cations of zeolite and that it has a strong affinity for platinum, all of this metal remains fixed on the support. We can thus deposit the complex of Keller and various other cationic platinum complexes, and dinitritodiamminoplatin, although the latter does or not an ionized compound. It is also possible perform this ion exchange in the presence of an excess a salt of the zeolite cation, for example chlo-potassium rure for zéollthe KL, so distribute the platinum more evenly in the zeolite crystal.
The percentage of platinum to be introduced can vary from 0.1 to 1.5% by weight. For bi- catalysts based on platinum on chlorinated alumina, the percentage of platinum no longer influences the activity dehydrocyclizing rate above 0.3%, because this is the acid function which becomes activity limiting. At on the contrary, the catalysts of the invention do not have that the metallic function, including the dehydro-cycling is very high. Also, this activity believes monotonously with the amount of metal present in the catalyst. In practice, the activity is sensitive from 0.1% Pt. It still grows above 1.5%
Pt, but for these contents, the price of the catalyst becomes too high.
Rhenium can only be deposited using rhenium carbonyl Re2 (CO) 10. Indeed the method aqueous impregnation of perrhenic acid leads to weakly active and not very stable catalysts. The method of the invention therefore consists in mixing the solid catalyst , 'i ls ~

containing or not containing platinum with the carbonyl poar-rhenium, then heat to temperatures between 50 and 200C. This step can be done under air, nitrogen or hydrogen, but preferably done under vacuum ranging from 0.01 to 100 torr to facilitate sublimation mation.
Thus, the rhenium can be distributed in a way homogeneous in the zeolite crystal and, after reduction tion, it will be better dispersed and will thus be able to interaction with platinum.
Another technique consists in impregnating the zeolitic support by a solution of Re2 (CO) 10 in a suitable solvent, such as acetone for example.
The amount of rhenium present in the cat-lyser is between 0.1 and 1.5 ~. This quantity actually needs to be adjusted to the platinum content of catalyst. Indeed, if there is too much rhenium per compared to platinum, the rhenium is then responsible for hydrogenolysis reaction producing mainly methane 2 ~ and ethane at the expense of aromatic production and hydrogen. This hydrogenolysis can be inhibited by sulfur but partially and it's actually better to keep the percentage of rhenium at values not too high compared to those of platinum.
However, the rhenium content should not be too low compared to that of platinum if we wishes to obtain the catalytic stabilization effect.
In fact the proportion of rhenium compared to to the platinum must be adjusted according to the conditions of catalyst work. Indeed, a decrease of pressure increases aromatization, decreases hydrogen lysis and stability. Rhenium is responsible most of the hydrogenolysis and good stability of catalysts. At high operating pressure , .. ,,,. ,, - ~

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(15 to 35 bars for example),] th rhenium level should be lower than that of platinum because the pressure itself sufficiently stabilizes the catalyst, and it is preferable to limit hydrogenolysis. At low operating pressure tion, it may be advantageous to use a catalyst containing more rhenium than platinum, because the cataly-seur must be stabilized by a large amount of rhenium which then no longer has a high hydrogenolysis activity.
Rhenium has strong hydrogen-lysing. If we make a Pt-Re catalyst on zeolite, we realize that this catalyst is very strongly hydro-genolysis and the production of aromatics from ali-phatic is weak. Unlike the phenomena of written in US Patent 3,415,737 for support alumina, this hydrogenolysis decreases little during the time and it is accompanied by deactivation of the function flavoring tion. It is not possible in these conditions, to recover the good selectivity of the cataly-monometallic by a mild start to the cycle which leaves the hydrogenating function of the catalyst deactivate. It is then essential to poison selectively the hydrogenolysis function by sulfur.
This operation is commonly performed on cataly-bifunctional sisters and we cite in the prior art sulfur contents of the order of 0.05% to 2% by weight.
In fact, since sulfur poisons selectively The metallic function of the catalyst is obviously tooth that the sulfur content should be reported to the metal content and we will express this content by the value x Pt - ~ Re in atoms.
The sulfurization of dehydrocyte catalysts Clization of the prior art is done with x = 2 approximately.

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In the case of our invention, such a value is prohibitive, because the catalysts are then total-poisoned and the value of x recommendable is com-taken between 0.1 and 0.6. For such values, the prior art catalysts are actually found too hydrogenating. For example, for a bi-functional containing 0.3% Re and 0.3% Pt on chlorinated alumina, if x = 0.6, the weight percentage of sulfur is 0.05%. For these conditions, such a cat-lyseur is not selective in aromatization.
Sulfur can be water-impregnated in a separate step or at the same time as platinum. We for this, use sulfur oxyanions such as sulfate ions, thiosulfates, sulfites etc. When reduction of the catalyst, this sulfur is reduced at least partially in the form of H2S and poisons selective-the catalyst. You can also use ions sulfides.
Another method is to inject a placed sulfurized on the catalyst in the presence of hydrogen, after reduction of the catalyst. We can use as well hydrogen sulfide, mercaptans, disulfides such as dimethyl disulfide. All of these methods are equivalent and lead to very good catalysts.
When these elements deposit steps are finished, the catalyst is dried. Then it can be calcined in the air between 100 and 600C, but the calcina-tion is not essential. It will then be placed in the reactor and reduced by hydrogen between 300 and 550C.
The catalyst is used for the processes of production of aromatics from petroleum fractions either with a view to producing fuels, or an approach for the production of petrochemical bases (ben-zene, toluene, xylene).

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The operating conditions depend on the type of load and products. In fact, the operating pressure can be between atmospheric pressure and 30 bars, the low pressures favoring the yields in 5 aromatic, accelerating the coking of the catalyst. Of preferably a pressure between 5 and 25 bars.
The temperature is between 420 and 600C, because high temperatures favor good yields 1 () in aromatics. The temperature factor has an influence important on yields. Indeed if we operate by example at 14 bars with a charge of hexane, the cataly-bifunctional sisters of the prior art give an optimum 22% aromatics for temperatures around 525C. Beyond ~, hydrocracking becomes preponderant, and the aromatic yield decreases. However, with the catalysts of the invention, under these conditions, 30% aromatics. If the temperature has risen up to 550C, up to 50% aromatics can be obtained ~ from n hexane at 14 bars.
It is necessary to inject the load on the catalyst with hydrogen, so as to ensure its stability. In ~ ectera preferably 1 to 10 moles of hy-drogen by hydrocarbon. Finally, the load volume injected per apparent volume of catalyst per hour will be from 0.2 to 5 h.
The catalysts of the invention can be used for reforming and aromatization processes and Usable charges are the charges of these processes.
They must be desulphurized and contain 1 ppm of S or less, because the catalyst is sensitive to poisoning.
For the process to be economically interesting they must contain aliphatic or alicy-clicks. The ideal charges are desulfurized gasolines.

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petroleum distillation, the initial point of which tillation is from 50 to 120C and the end point from 70 to 200C.
A 50-80C cup basically contains hydrocarbons with 6 carbon atoms and produces mainly benzene. A 60-100C cut produced a mixture of benzene and toluene. Finally, a cut 80-180 ~ C, produces an excellent reformate yield good octane number, but due to the properties of catalysts this reformate contains significantly more benzene and toluene than conventional reformates and its end point is only slightly increased.
The present invention will be better understood on light the following examples.
lS In these examples, we use an essence of tervalle d ~ - ------ - - - --- - - --- ~ --- ~ -... ... . . . . . .

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60-80C distillation containing 91% C6 hydrocarbons including 1%
benzene and 1.5 ~ of cyclohexane. This charge is desulphurized and the catalysts are reduced by hydrogen to 500C and then tested in a reactor without hydrogen recycling under the following conditions:
S pressure lS bars, molar ratio hydrogen to hydrocarbon: 5, weight load injected per weight of catalyst and per hour 2.5 h l. The temperature is kept constant at 525C over time and we monitors yield trends to assess stability. Like the charge contains 3.5% benzene and C6 naphthenes, we can consider that the dehydrocyclizing activity is zero when the aromatic yield is less than or equal to 4%.

_________ A 0.6% Pt monometallic catalyst deposited by exchange of lS Keller complex on zeolite L in its potassium form (KL) is prepared by impregnation with a solution of Pt (NH3) 4C12 and KCl, washing, drying and calcination in air at 480C.
After reduction with hydrogen ~ we get the results following:

Running time Yield in C - Yield in aromatics ~
(h) (% weight) 1 ~ (% weight) 13.1 37.7 29 7.0 22.9 2,577 2.5 6.9 This example ~ is the excellent initial activity in dehy-drocyclization, but the low stability of the monometal catalysts liques on zeolite.

A commercial catalyst containing 0.3% platinum, 0.3% rhenium, 1.3% chlorine on alumina. After reduction by hydrogen on sulfide with di ~ ethyldisulfide in presence of hydrogen at 370C, so as to inject 0.2% by weight of sulfur on the catalyst, that is x = 2. Then the reaction is carried out in the above conditions.
The results are as follows:

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Tem s de ~ arche Yield in C -C Yield in aromatics h) (% weight) 1 2 (% weight) 24.6 20.1 529 22.1 22.3 77 19.2 22, ~

~ e bifunctional co ~ ercial catalyst is very stable but the aromatic yield is moderately high.

_________ Another sample of the commercial catalyst described in ~ s the previous experiment is sulfurized at o, ~ 6% by weight, that is x = 0.6, all the other operations remaining the same.
lS We then obtain:

Running time Yield in Cl-C2 Yield in aromatics (h) (~ weight) (% weight) 202 ~ 65 15 This example clearly shows that the catalysts of art do not support being weakly sulphurized at x = 0.6, because then the hydrogenolysis in ClC2 becomes very important, the function flavoring is extremely weakened and never returns to level that of Example 2.

_________ A catalyst at 0.6 ~ Pt and 0.3% Re on the zeolite XL es ~
prepared from the catalyst of Example 1 not calcined. This cataly-its is impregnated with a solution of perrhenic acid, then dried and calcined in air at 480C.
The results are as follows:

Te ~ s of walking Efficiency in C - Efficiency in ~ romatic (h) (~ weight) 1 2 (~ weight) 72 9 3.5 ~ 5 ~? 63 These results show that, unlike alumina-supported catalysts, the introduction of rhenium in the form of perrhenic acid is in every way unfavorable to the catalyst: its activity is lower q ~ ue that of monometallic, while aromatization and hydrogenolysis remain weak and unstable. At 72 h, the dehydrocyclizing activity becomes zero.

A catalyst at 0.6 ~ Pt - 0.6% Re on zeoli-the KL is prepared as follows: the support is mixed with the required amount of Re2 (CO) 10, then it is heated under a vacuum of 1 torr at 11O ~ C for 3 h.
After cooling, 60 g of catalyst are impregnated with 66 ml of 0.1 N KCl solution containing the ne-cessation of Pt (NH3) 4C12. The catalyst is then washed, then dried and calcined for 3 h at 480C.
Running time in Cl-C2 Yield in aromati-(h) (% weight) (% weight) 76.7 6 20 28 70.4 5.6 52 64.3 5 Although not selective in flavoring, this cataly lyser becomes active, since it is strongly hydrogenated lysing. This shows compared to the previous example that the use of rhenium carbonyl instead of acid perrhenic introduces strong activity. However, the most of this activity resides in the hydrogen-lysis which is not a desirable reaction.
~ XAMPLE 6 The catalyst of the previous example is im-pregnated with an aqueous solution containing sulphate sodium so as to introduce 0.1 mole of sulfur per Pt + Re (x = 0.1). It is tested after drying:

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Running time Efficiency in C1-C2 Aromatic yield (h ~ (~ weight) (% weight) 56.7 10.7 29 36, ~ 14.6 77 22.5 13.5 The hydrogenolysis decreases clearly while the aromatization is greater than that of the previous example and it remains stable.

__ _ _ _ _ ___ The catalyst of Example 5 is impregnated with a solution aqueous contains t sodium sulfate so that x = l.

Cl-C2 yield h (% by weight) Aromatic yield 12.6 ~ 5.3 24 8.5 4.3 52 6.1 4.6 We see that a sulfur atom introduced by metal atom poisons the catalyst too much since the hydrogenolysis decreases significantly ment compared to 8 11 previous example, as well as flavoring. A
excess sulfur poisons both sromatizing and hydro-genolysis and the best value of x is between O and 1.

_________ A catalyst identical to that of Example 6 is prepared, but it contains 0.6% Pt and 0.3% Re instead of 0.6% Pt and 0.6 ~ Re.
x is always 0.1.

Market indicators Yield in C - Yield in aromatics (h) (~ weight) 1 2 (% weight) 56.2 14, ~
35 29 34.8 21.1 77 18.4 20.5 A lower amount of rhenium decreases slightly 1151:; L3 ~ 3 hydrogenolysis, but significantly increases the yield of aromatics.

_________ A catalyst at 0.6 ~ Pt - O, 3 b Re on zeolite KL is prepared by dry impregnation of Pt (NH3) 2 (N02) 2 dissolved in a 0.1 N solution of KC1 at boiling point. After washing and drying, the catalyst is calcined at 400C, then the carbonyl of - rhenium by the method described above. We finally permeate the catalyst with a solution of Na2SO4 so that x = 0.1.

Running time Yield in C - Yield in aromatics (h) (% weight) (~ weight) 29 28 23.2 __________ The catalyst of the previous example is not treated by Na2SO4, but it is treated in the reactor after reduction by hydrogen, by an equivalent quantity of sulfur (x = 0.1) under form of dimethyl disulfide, at 370C.

Running time Yield in C1-C2 Aromatic yield 25 (h) (% weight) ~ weight) 40.1 25.1 73 32.0 21.0 Sulfurization by dimé ~ hyl disulfide is sensiDlemen ~
equivalent to that obtained with Na2SO4.

EXAMPLES 11 to 15 ____________ ___ A series of catalysts with variable platinum contents 9 rhenium and sulfur are prepared as follows:
35 - Impregnation of the zeolite support KL with Pt (NH3) 2 (N02) 2 dissolved in a 0.1 N solution of KC1 at boiling - Washing -Drying.
- Deposition of rhenium carbonyl by sublimation on the zeoli . .::. , 2 torrs and 110C.
- Impregnation with a solution of Na2SO4 and drying.
The following results are obtained after 77 h of market ;

Examples% Pt Z Re x% Cl C2X Aromatic 11 l 0.67 0.22 18.9 28.2 12 1 0.67 0.47 16.5 27.0 13 0.6 ~, 55 0.6 8.3 10.3 14 l ~, 32 0.35 6.2 10.9 16 0.6 0.55 0.35 19.0 22.6 __________ A catalyst identical to that of Example 11 is prepared using perrhenic acid impregnation instead of sublimation of the rhenium carbonyl. We then obtain:

Running time Yield in Cl-C2 Yield in aromatics (h) (% weight) (% weight) 8.0 16.1 53 4.1 7.9 This example again shows that the use of acid perrhenic is detrimental to the good ~ es catalytic properties of Pt-Re-S- KI system.

__________ A ~ analyzer containing 0.87% Pt - 1% Re on zeoli ~ he KL;
with x = 0.1 is prepared as described in example ll, 2 except that the sublimation step of Re2 (CO) 10 is replaced by a impregnation of a solution of Re2 (CO) 10 in acetone.
The following results are obtained:

Running time Yield in Cl-C2 Yield in aromatics (h) (% weight) (% weight) 3 46.5 16.8 24 30.5 17, ~
72 25.1 16.5 1151 ~

Although this catalyst contains a lot of rhenium and little sulfur, it has an interesting activity and excellent stability which morlter that the catalysts of the invention can be prepared as well by impregnating the carbonyl of rhenium in acetone only by direct sublimation.

__________, A catalyst identical to Example 11 is prepared using sant a support for faujasite NaX instead of zeolite L.

Running time Yield in C - Yield in aromatics (h) (% weight) 1 2 (~ weight) 24 36 24.2 1,577 28.6 23.1 This catalyst, although being inferior to the corresponding catalyst, laying on the basis of zeolite L, however has properties interesting in flavoring, and it is stable.

__________ A preparation identical to that of Example 11 is carried out killed so as to lead to a catalyst containing 0.87% Pt, 1 ~ Re and x = 0.1. After reduction by hydrogen to 500C, this catalyst is tested under the following conditions: pph 2.5 h 1, H2 / HC 5, 500C
instead of 525C and 8 bars instead of 15 bars.
The following results are obtained:

Running time Efficiency in C1- ~ Efficiency in aromatics 30 (h) ~% weight) '(% weight) 24 13.0 38.2 73 9.5 35.0 Although this catalyst contains more rhenium than platinum, it leads to very good yields and selectivities in aro-while maintaining good stability, because it is used at lower pressure than in the previous examples: the strong hydrogenolysis caused by rhenium is inhibited by weak ~ lS ~

pressure, while the yield of aromatics is favored and that the high e ~ rhenium content contributes to improving the satability of the catalyzed.

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1 ~ 51 ~ 3 5 - Catalyst according to claim 1 ct 4, characterized in that the support is preferably a zeolite L exchanged ~ e containing one of the alkali metals selected from the group of sodium, potassium ~ rubidium and cesium.
6 - Catalyst according to ~ claims 1 ~ 4 ~ 5, characterized in that the support is in the form of balls, tablets or pastilles before or after deposition of platinum, rhenium and sulfur ~ .by extrusion, drag ~ ification, coagulation in drops, or any other known method.

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Claims (10)

1 - Monofunctional bi-functional dehydrocyclization catalyst paraffins characterized in that it contains on a support consisting of a zeolitic crystalline aluminosilicate more than 90% offset by alkaline cations, and having a pore diameter greater than 6.5 Angstroms, 0.1 to 1.5% of platinum introduced by impregnation 0.1 to 1.5% of rhenium incorporated as carbonyl sublimated or dissolved in acetone the ratio Rhenium / platinum rate being variable with the pressure used, - a small proportion of sulfur introduced by a compound sulfide reducible or decomposable by hydrogen, such, that the ratio x of the number of sulfur atoms to the number of platinum atoms is between 0.05 and 0.6. 2 - dehydrocyclization catalyst according to claim 1, characterized in that for high pressure uses from 15 bars to 35 bars the rhenium level is lower than that platinum 3 - dehydrocyclization catalyst according to claim 1, characterized in that for low uses pressure the rhenium content is higher than that of platinum to maintain its excellent properties of stability. 4 - Catalyst according to claim 1, characterized in that the support is chosen from the group comprising faujasites X and Y, L zeolite, omega zeolite and zeolite ZSM 4. 19 7 - Process for manufacturing the catalyst according to claim 1, characterized by the following steps taken in a any order:
- the loading of the support by the rhenium is carried out using rhenium carbonyl Re2 (CO) 10, by sublimation tion of the latter in contact with the support in an atmosphere air, nitrogen or hydrogen and preferably under pressure reduced from 0.01 to 100 torr, - the platinum is deposited by methods of impregnation using a solution of a layered platinum selected from the group of hexa-chloroplatinic, platinum chloride tetrammine, dinitrodiamminoplatin, or by ion exchange with a cationic complex of platinum, possibly in presence of an excess of a salt of the zeolite cation, - the incorporation of sulfur is carried out by impregnation-support with a compound solution sulfur selected from the group comprising oxyanions:
sulfates, thiosulfates, sulfites, - the support having received the charges of rhenium, platinum and sulfur is then dried, possibly calcined and necessarily reduced by hydrogen between 300 ° C and 550 ° C before use. 8 - Method of manufacturing the catalyst according to the claims cation 1 and 7 characterized in that the incorporation of sulfur is carried out by pretreatment of the loaded support of rhenium and platinum in the dehydrocyte reactor cleavage with a sulfur compound chosen from the group of hydrogen sulfide, dimethyl disulfide, sulfide carbon, before or after reduction with hydrogen 9 - Process for manufacturing the catalyst according to claim 1 characterized by the following steps taken in a any order:
- the loading of the support by the rhenium is carried out by impregnation with an organic solution of carbony-the rhenium in acetone, - the platinum is deposited by methods of impregnation using a solution of a laid platinum selected from the group of hexa-chloroplatin, platinum chloride tetrammine, dinitrodiamminoplatinel or by ion exchange with a cationic complex of platinum, possibly pre-sence of an excess of a salt of the zeolite cation, - the incorporation of sulfur is carried out by impregnation of the support using a solution of sulfur compound chosen from the group comprising oxyanions: sulfa-tes, thiosulfates, sulfites, - the support having received the charges of rhenium, platinum and sulfur is then dried, possibly calcined and necessarily reduced by hydrogen between 300 ° C
and 550 ° C before use. 10 - Method of manufacturing the catalyst according to the resales dications 1 and 9 characterized in that the incorporation sulfur is carried out by pretreatment of the support charged with rhenium and platinum in the reactor dehydrocyclization with a sulfur compound selected from the hydrogen sulfide group, dimethyl disulfide, carbon sulfide, before or after reduction by hydrogen.