JPH0248300B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel catalyst for the dehydrocyclization of C6-C10 paraffins and a method for producing the same. This catalyst has a particularly good effect on the production of light aromatics from petroleum fractions obtained by direct distillation. The traditional method of carrying out the aromatization reaction is to use a catalyst containing a noble metal on a support, more specifically the catalyst is 0.2-0.8% by weight of platinum on a chlorinated alumina support of 0.5-2% by weight. Contained above. These catalysts are generally known to act according to a bifunctional mechanism of hydrogenation-dehydrogenation of the metal and isomerization-cyclization of the acidic support. These catalysts were significantly improved by the addition of a second metal, allowing catalysis at low pressures and increasing stability under conditions favorable to the aromatization reaction. US
Patent 3415737 (HEKLUKSDAHL, Chevron
Res. Co) shows in particular the advantage of using catalysts containing 0.1-3% Pt and 0.1-3% rhenium. The patent further states that on the catalyst 0.05 to 2
claims the presence of % sulfur. This sulfur is intended to limit the hydrocracking activity of rhenium. Note that the above activity rapidly deactivates the dehydrocyclization catalyst. Another type of aromatization catalyst is US Patent 3775502
and 3819507 (M.OISHI, Sun Res.and Dev.Co)
It is described in. The catalyst comprises platinum deposited on zeolite X (ie zeolite exchanged with lithium, sodium or potassium). The catalyst may further contain 0.1-1.2% rhenium. Although this type of catalyst is new, its aromatization activity is comparable to that of the previously mentioned catalysts. The presence of rhenium in the new type of catalyst does not seem to offer any advantage, since the results obtained with platinum-rhenium-zeolite X are inferior to those with zeolite X-Pt. Another type of catalyst supported on a molecular sieve is disclosed in US Patent 4104320 (J. Nury, JRBernard,
ERAP). The catalyst was deposited on an alkali metal zeolite L (preferably exchanged with potassium, rubidium or cesium).
Contains 0.1-1.5% by weight of platinum. When charged with platinum, Zeolite L exhibited greater aromatic selectivity and yield than any of the other catalysts mentioned above. Although the mechanism of action of these catalysts is not fully explained, it appears that the catalysts are monofunctional and therefore rely solely on platinum for catalytic action. The properties of this platinum vary depending on the zeolite L support. Zeolite L useful for these catalysts
are substituted (compensated) by alkali metal cations, so that platinum, which is in the metallic state under catalytic conditions, is strongly influenced by these alkali metal cations. That is, the activity of the catalyst increases as one moves from lithium to potassium and then to cesium. Although the catalyst described in the cited patent has significant aromatization activity and selectivity, its stability is superior to that of bifunctional monometallic catalysts based on platinum on chlorinated alumina. Low and therefore high hydrogen pressures can be used if adequate cycle times are required. In order to attempt to stabilize these catalysts, it is possible to use the techniques described in the aforementioned patents (ie, introducing rhenium into the catalyst by precipitation of an aqueous solution of perrhenic acid). This introduction, whether by co-impregnation or continuous impregnation with platinum, does not improve the catalyst stability, and furthermore the activity of these bimetallic catalysts is lower than that of zeolite L.
The activity is much lower than that of the base monometallic catalyst. This means that platinum-charged zeolite
This is consistent with the views of the authors of US Pat. No. 3,819,507, who found no beneficial effect of rhenium in the case of Y and Y. On the other hand, the inventors have surprisingly found that rhenium in the form of rhenium carbonyl Re ₂ (CO) ₁₀ is present in the zeolite before or after deposition of platinum by known methods (impregnation, ion exchange of platinum complexes or salts). It has been discovered that good catalyst stability and activity can be obtained after reduction with hydrogen. UK patent 2004764 describes a catalyst prepared by pyrolyzing rhenium carbonyl on a porous support containing platinum. According to this patent, the catalyst thus prepared is more active than the catalyst prepared by perrhenic acid, since the reforming of petroleum gives a higher octane number at the same reaction temperature. However, these catalysts produce more hydrogenolysis than catalysts prepared from perrhenic acid, so the advantage is less significant. On the other hand, the use of rhenium carbonyl in a Pt-Re zeolite catalyst yields an active catalyst, but the use of perrhenic acid produces a less active catalyst. However, these catalysts have poor paraffin dehydrocyclization selectivity. The reason for this is that hydrogenolysis occurs at a rate that is favorable for bifunctional catalysts with chlorinated alumina supports, and the resulting catalyst is completely inactivated and virtually inactive with respect to dehydrocyclization. Because there is. The inventors have surprisingly found that when a much lower proportion of sulfur is introduced into the catalyst than mentioned above, good selectivity and excellent catalyst stability can be obtained. For example, the generally desirable sulfur content for ready-to-use reforming catalysts deposited by impregnation with sulfur compounds or presulfided before catalysis is about 0.2% by weight;
This equates to a molar ratio x of approximately 2 for 0.3% Pt and 0.3% Re content. x is Pt contained in the catalyst
It represents the ratio of the number of sulfur atoms deposited on the catalyst to the number of +Re atoms. At these values, the platinum-rhenium-zeolite catalyst is inactive. In order to obtain an active and stable catalyst for dehydrocyclization, the molar ratio x should be reduced to 0.05-0.6. For the above Pt and Re contents, this equates to a range of 0.005 to 0.06% by weight of sulfur, based on the catalyst, which is clearly lower than the 0.2% by weight mentioned above. The present invention is a novel catalyst for paraffin dehydrocyclization, which comprises 0.1-1.5% platinum, 0.1-1.5% platinum, 0.1-1.5% platinum,
1.5% rhenium, molar ratio x such as 0.05-0.6,
It contains sulfur in a form that is reducible or decomposable by hydrogen, and the support is a zeolitic crystalline aluminosilicate with a pore size greater than 6.5 Å that is more than 90% substituted with alkali metal cations. Furthermore, the present invention relates to a novel method for preparing a catalyst comprising the steps described below. The order of the steps is arbitrary: - Charge the non-acidic zeolitic crystalline aluminosilicate with rhenium with a pore size greater than 6.5 Å. The operation involves rhenium carbonyl Re ₂
(CO) ₁₀ is deposited on the carrier by sublimation or by impregnation with an organic solution of Re ₂ (CO) ₁₀ . - Depositing platinum by methods known in the prior art, ie by solutions of platinum compounds such as hexachloroplatinic acid, platinum tetraammine chloride, dinitrodiammine platinum, or by ion exchange with platinum cation complexes. - sulfur compounds (oxyanions, sulfides,
Sulfur is introduced by impregnation with a solution (such as a mercaptan). This operation can be carried out simultaneously with the above-mentioned operation of impregnation. In addition, sulfur compounds (H ₂ S, dimethyl disulfide,
It is also possible to pre-treat the catalyst with CS ₂ ). After carrying out these steps, the catalyst is dried, optionally calcined, and then reduced with hydrogen.
Optionally sulfurized according to the methods described above. The catalyst of the invention has exceptional aromatization properties and excellent stability. The catalyst support is a zeolitic crystalline aluminosilicate or a molecular sieve. For dehydrocyclization, it is important that the molecular sieve serving as a carrier is weakly acidic, non-acidic, or weakly basic. For this reason, the zeolite must have more than 90% of its cation exchange positions replaced with alkali metal cations, all other cations resulting in some acidity. The reason is,
Either because they are multivalent and thus generate acidic sites, or because they are reducible or decomposable under catalytic conditions and the reduction or decomposition generates protons on the zeolite. Evidently, the pores of such alkaline zeolites have an opening at least equal to the size of benzene, and the zeolites that can be used in the present invention include phosiasites X and Y, zeolite L,
Examples include zeolite omega and zeolite ZSM4. These zeolites, with the exception of the last two, can be used in non-synthetic form. The last two contain alkylammonium cations which must be replaced with alkali metal cations by methods known to those skilled in the art (eg, pyrolysis followed by neutralization with an alkali base). Furthermore, these synthetic cations can be exchanged with other alkali metal cations, so that the zeolites can contain lithium, sodium, potassium, rubidium and/or cesium. A preferred support among these zeolites is zeolite L, which provides aromatics in exceptional yields from aliphatic fractions. This zeolite is synthesized in potassium form and can be used economically in that form, but may also contain sodium and especially rubidium or cesium. The zeolite support must be brought into an industrially usable form, and this shaping can be done before or after the platinum, rhenium and sulfur deposition, using methods known to those skilled in the art. For example, after mixing with alumina or clay, it is spheronized by extrusion or drageoir or oildrop techniques. Another technique that can be used is to form or extrude spheres from clay (eg metakaolin) and convert it to zeolite by suitable methods. Zeolites can also be used in the form of pellets, tablets or in powder form if used in a fluidized bed. Platinum can be deposited by methods described in the prior art. Aqueous methods are generally used, especially impregnation and ion exchange. Impregnation can be carried out with any water-soluble platinum compound, such as hexachloroplatinic acid. Although satisfactory results are obtained with this compound, it makes the catalyst somewhat acidic, so preferably Keller complexes or platinum tetraammine chloride or dinitrodiammine platinum are used. Since the latter is not very water soluble, this impregnation is carried out together with heating. If cationic complexes of platinum are used, ion exchange can also be carried out, in which case the support is immersed in a platinum-containing solution and, after a period of time, withdrawn, washed and dried. The amount of platinum to be deposited corresponds to only a very small fraction of the zeolite cations, and since zeolites have a strong affinity for platinum, all the metal remains fixed on the support. The Keller complex and various other cationic complexes of platinum and dinitrodiammine platinum are deposited in this manner. However, dinitrodiammine platinum is not an ionizable compound. It is also possible to carry out this ion exchange in the presence of an excess of a cationic salt of the zeolite (for example potassium chloride in the case of zeolite KL), which results in a more homogeneous distribution of platinum in the zeolite crystals. The percentage of platinum to be introduced ranges from 0.1 to 1.5% by weight. In the case of platinum-based bifunctional catalysts on chlorinated alumina, the percentage of platinum does not affect the dehydrocyclization activity by more than 0.3%, since it is the acid groups that become limiting in activity. However, the catalyst of the present invention has only a metal function, and its dehydrocyclization activity is extremely high. Furthermore, activity increases monotonically with the amount of metal present in the catalyst. In fact, the activity is essentially from 0.1% Pt.
Activity increases above 1.5% Pt, but this amount makes the catalyst too expensive. Rhenium can only be deposited using rhenium carbonyl Re ₂ (CO) ₁₀ . The reason is that the perrhenic acid aqueous impregnation method yields catalysts with poor activity and stability. The process of the invention therefore involves mixing a solid catalyst, which may or may not contain platinum, with rhenium carbonyl powder and then
It involves heating the mixture to a temperature of 50-200°C. This step can be carried out in air, nitrogen or hydrogen, but is preferably carried out under reduced pressure of 0.01 to 100 torr to facilitate sublimation. In this way rhenium can be homogeneously dispersed in the zeolite crystals and more preferably dispersed after reduction and able to interact with platinum. Another method is in a suitable solvent (e.g. acetone)
is to impregnate the zeolite support with a _Re2 (CO) ₁₀ solution. The amount of rhenium present in the catalyst is 0.1
~1.5%. Too much rhenium relative to platinum will cause rhenium to undergo hydrogenolysis reactions (which produce methane and ethane, among other things, and reduce aromatics and hydrogen production), so the amount of rhenium actually affects the catalyst. must be adjusted according to the amount of platinum. This hydrogenolysis is inhibited (but only partially) by sulfur, but in practice it is desirable to keep the percentage of rhenium at a value that is not too high relative to the percentage of platinum. However, in order to achieve a catalyst stabilizing effect, the rhenium content should not be too low compared to the platinum content. In practice, the ratio of rhenium to platinum has to be adjusted according to the operating conditions of the catalyst, since aromatization increases as the pressure decreases, reducing hydrogenolysis and stability. Rhenium performs most of the hydrogenolysis and provides good stability of the catalyst. At high working pressures (for example 15 to 35 bar), the amount of rhenium should be lower than the amount of platinum, since the pressure itself is sufficient to stabilize the catalyst and preferably limit hydrogenolysis. At low working pressures, catalysts with a higher content of rhenium than platinum may be used, since the catalyst should be stabilized by a high content of rhenium, which no longer has a high hydrocracking activity. It's advantageous. Rhenium has remarkable hydrogenolysis properties. When preparing a Pt-Re catalyst on zeolite, this catalyst exhibits significant hydrocracking properties and produces less aromatics from aliphatics. US regarding alumina carrier
Unlike the phenomenon described in patent 3415737, this hydrogenolysis gradually decreases over time and is accompanied by deactivation of the aromatization effect. Under these conditions, good selectivity of single metal catalysts cannot be obtained from the beginning of the cycle, which deactivates the hydrocracking action of the catalyst. Therefore, it is important to selectively deactivate the hydrogenolysis effect with sulfur. This operation is usually carried out over bifunctional catalysts, and in the prior art the sulfur content is approximately 0.05-2% by weight. In reality, sulfur selectively deactivates the function of metals in the catalyst, so the sulfur content must naturally be related to the metal content, and we express this content with the following value: . x=S/Pt+Re (number of atoms) The sulfurization of the dehydrocyclization catalyst in the prior art is x=
It is carried out in approx. In the case of the present invention, the preferable value of x is 0.1 to 0.6, since the catalyst is completely deactivated at such a value. According to this value, the prior art catalyst is in fact highly hydrocracking. For example, for a bifunctional catalyst containing 0.3% Re and 0.3% Pt on chlorinated alumina, if x=0.6, the sulfur is 0.05% by weight. Under these conditions, this type of catalyst is not selective for aromatization. Sulfur can be impregnated together with platinum or in a separate step by an aqueous method. For this purpose, sulfur oxyanions such as sulfate, thiosulfate, sulfite and other ions are used.
During the reduction of the catalyst, this sulfur is at least partially
It is reduced to the H ₂ S form, selectively deactivating the catalyst. Sulfide ions can also be used. Another method consists of introducing a sulfur compound onto the catalyst in the presence of hydrogen after reduction of the catalyst. In this way, hydrogen sulfide, mercaptans, and disulfides such as dimethyl disulfide can be used. All these methods are equivalent and give very good catalysts. At the end of these elemental deposition steps the catalyst is dried. It can then be calcined in air at 100-600°C, although calcination is not essential. It is then placed in a reactor and reduced with hydrogen at 300-550°C. Catalysts are used for fuel production or petrochemical basic raw materials (benzene, toluene, xylene).
Used in aromatic production methods from petroleum fractions. Operating conditions depend on charge and product type. In practice, the operating pressure may be between atmospheric and 30 bar, with lower pressures increasing the aromatic yield and promoting coking of the catalyst. The pressure is preferably 5~
Use 25 bar. Since high temperature increases the aromatic yield, the temperature is
The temperature is 420-600℃. The temperature factor greatly influences the yield, for example at a pressure of 14 bar with n-hexane charge, the bifunctional catalysts of the prior art have a
Gives an aromatic optimum value of 22% at an optimum temperature of 525°C.
If this value is exceeded, hydrogenolysis becomes dominant and the aromatic yield decreases. In contrast, with the catalyst of the invention, 30% aromatics are obtained under the same conditions. If the temperature increases to 550° C., up to 50% aromatics are obtained from n-hexane at 14 bar. A charge is introduced onto the catalyst along with hydrogen to ensure stability. Preference is given to introducing 1 to 10 mol of hydrogen per hydrocarbon. The charge volume introduced per apparent volume of catalyst is 0.2 to 1 hour.
5h ^-1 . The catalyst of the present invention is useful in reforming and aromatization processes, and the charges that can be used are those for this process. Since the catalyst is sensitive to poisoning (deactivation), the charge is desulfurized,
Must have a sulfur content of 1 ppm or less. For the process to be economically advantageous, the charge must contain aliphatic or cycloaliphatic hydrocarbons. The ideal charge is desulfurized petroleum distillate oil,
The starting point of distillation is 50-120°C and the end point is 70-200°C. The 50-80°C fraction mainly contains hydrocarbons of 6 carbon atoms and mainly produces benzene. 60～
The 100°C fraction produces a mixture of benzene and toluene. Finally, the 80-180°C fraction produces reformed products with good octane numbers in excellent yields, but due to the properties of the catalyst, this reformed product contains higher amounts of benzene and toluene than conventional ones. However, the end point of distillation increased only slightly. The invention will be more easily understood from the following examples. The oil used in the following examples contains 91% C6 hydrocarbons, of which 1% is benzene and 1.5%
is the 60-80°C distillation fraction which is cyclohexane. This charge is desulfurized and catalyzed using hydrogen.
Reduction at 500 °C and then without hydrogen recirculation in the reactor under the following conditions: pressure 15 bar, hydrogen:hydrocarbon molar ratio 5, charge weight introduced per catalyst weight and per hour 2.5 Tested as h ^-1 . The temperature was always maintained at 525°C and yield changes were followed to assess stability. Since the charge contained 3.5% benzene and C6 naphthenes, the dehydrocyclization activity can be considered to be zero if the aromatic yield is less than 4%. Example 1 (Comparative Example) Impregnation of a monometallic catalyst containing 0.6% Pt deposited on zeolite L in potassium form (KL) by Keller complex exchange with a solution of Pt(NH ₃ ) ₄ Cl ₂ and KCl, It was prepared by washing, drying and calcination in air at 480°C. After reduction with hydrogen, the following results were obtained. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 13.1 37.7 29 7.0 22.9 77 2.5 6.9 Although this example shows excellent initial dehydrocyclization activity, Monometallic catalysts have low stability. Example 2 (Comparative) A commercially available catalyst containing 0.3% platinum, 0.3% rhenium, 1.3% chlorine was placed in a reactor. After reduction with hydrogen, the catalyst was sulfurized with dimethyl disulfide in the presence of hydrogen at 370° C. in order to introduce 0.2% by weight of sulfur on the catalyst (ie x=2). The reaction was then carried out under the conditions described above. The results were as follows. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 24.6 20.1 29 22.1 22.3 77 19.2 22.8 Commercially available bifunctional catalysts are very stable, but the aromatic yield is It was moderate. Example 3 (Comparative Example) Another sample of the commercial catalyst described in the experiment above was sulfided to 0.06% (ie x=0.6) with no other changes in operation. The results were as follows. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 72 10 29 65 15 77 61 14 As can be seen from this example, the prior art catalyst
A low sulfidation of 0.6 is not acceptable, C1-C2 hydrogenolysis becomes extremely large, and the aromatization effect is extremely low and does not reach the level of Example 2. Example 4 (Comparative Example) A catalyst with 0.6% Pt and 0.3% Re on zeolite KL was prepared from the uncalcined catalyst of Example 1. The catalyst was impregnated with perrhenic acid solution, dried and calcined at 480°C in air. The results were as follows. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 24 17 11 72 9 3.5 As is clear from the results, introduction of rhenium in perrhenic acid form, unlike the alumina supported catalyst is inconvenient for the catalyst from any point of view. That is, the activity is lower than that of single metal catalysts, and aromatization and hydrogenolysis remain low and unstable. Dehydrocyclization activity becomes zero in 72 hours. Example 5 (Comparative Example) A catalyst having 0.6% Pt-0.6% Re on zeolite KL was prepared as follows. The support was mixed with the required amount of Re ₂ (CO) ₁₀ and heated at 110° C. in a vacuum of 1 Torr for 3 hours. After cooling, add 60g of catalyst to the required amount.
It was impregnated with 66 ml of 0.1N-KCl solution containing Pt(NH ₃ ) ₄ Cl ₂ . The catalyst was then washed, dried and heated at 480°C for 3
Calcined for an hour. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 76.7 6 28 70.4 5.6 52 64.3 5 This catalyst is not exceptional for aromatization, but is very hydrocracking So it becomes active. When rhenium carbonyl is used instead of perrhenic acid, stronger activity is obtained compared to the comparative example.
However, most of this activity is hydrogenolysis, which is an undesirable reaction. Example 6 (Invention) The catalyst of the comparative example was impregnated with an aqueous solution containing sodium sulfate, and 0.1 mol of sulfur per Pt+Re was introduced (x=0.1). Tested after drying. Elapsed time C1-C2 yield Aromatic yield (time) (wt%) (wt%) 5 56.7 10.7 29 36.6 14.6 77 22.5 13.5 Hydrogenolysis decreased significantly, while aromatization exceeded the comparative example. , and remains stable. Example 7 (Comparative Example) The catalyst of Example 5 was impregnated with an aqueous solution containing sodium sulfate so that x=1. Elapsed time C1-C2 yield Aromatic yield (time) (wt%) (wt%) 5 12.6 5.3 24 8.5 4.3 52 6.1 4.6 As can be seen from the above results, hydrogenolysis was significantly greater than in the previous example. However, the introduction of one sulfur atom per metal atom significantly inhibits the catalyst, since at the same time the aromatization also decreases significantly. Excess sulfur inhibits two functions: aromatization and hydrogenolysis. Example 8 (Invention) Instead of 0.6% Pt and 0.6% Re, 0.6% Pt and
The catalyst was the same as in Example 6 except that it contained 0.3% Re. x was 0.1. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 56.2 14.9 29 34.8 21.1 77 18.4 20.5 When the amount of rhenium is small, hydrogenolysis is slightly reduced, and aromatic The yield increases considerably. Example 9 (Invention) A catalyst containing 0.6% Pt-0.3% Re on zeolite KL,
Pt( _NH3 ) ₂ dissolved in a 0.1N solution of KCl at boiling point
Prepared by dry impregnation with ( _NO2 ) ₂ . After washing and drying, the catalyst was calcined at 400°C and then rhenium carbonyl was introduced as described above. Finally x=
The catalyst was impregnated with a solution of Na ₂ SO ₄ to a concentration of 0.1. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 48 20 29 28 23.2 77 18 22 Example 10 (Invention) Catalyst of the previous example treated with Na ₂ SO ₄ Instead, after reduction with hydrogen, the reactor was treated with an equal amount of sulfur (x=0.1) in the form of dimethyl disulfide at 370°C. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 25 40.1 25.1 73 32.0 21.0 Sulfurization with dimethyl disulfide is virtually equivalent to that obtained with Na ₂ SO ₄ . Examples 11-15 (Invention) A series of catalysts with varying platinum, rhenium and sulfur contents were prepared as follows. The zeolite KL support was impregnated with Pt(NH ₃ ) ₂ (NO ₂ ) ₂ dissolved in a 0.1N solution of KCl at boiling point, washed and dried. Rhenium carbonyl was deposited on the zeolite by sublimation at a temperature of 110° C. and 2 torr. Impregnated with a solution of Na ₂ SO ₄ and dried. After 77 hours of operation, the following results were obtained.

[Table] Example 16 (Comparative Example) A catalyst similar to Example 11 was prepared except that perrhenic acid impregnation was utilized instead of rhenium carbonyl sublimation. The results were as follows. Elapsed time C1-C2 yield Aromatic yield (time) (wt%) (wt%) 5 8.0 16.1 53 4.1 7.9 In this comparative example, the use of perrhenic acid was
-S-- This shows that it is detrimental to the good catalytic activity of the KL type. Example 17 (Invention) Re ₂ (CO) in acetone instead of ₁₀ sublimation steps
0.87% to Pt-- on zeolite KL as described in Example 11, except that Re ₂ (CO) ₁₀ solution was impregnated.
A catalyst containing 1% Re and x=0.1 was prepared. The following results were obtained. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 3 46.5 16.8 24 30.5 17.2 72 25.1 16.5 This catalyst contains a large amount of rhenium and a small amount of sulfur, but has considerable activity and excellent This shows that the catalyst of the present invention can be prepared either by impregnation of rhenium carbonyl in acetone or by direct sublimation. Example 18 (present invention) Faujasite instead of zeolite L
A catalyst was prepared in the same manner as in Example 11 except that a NaX carrier was used. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 5 42 23 24 36 24.2 77 28.6 23.1 This catalyst is inferior to the corresponding zeolite L-based catalyst, but aromatic It has excellent chemical properties and is stable. Example 19 (Invention) A catalyst containing 0.8% Pt and 1% Re and having x=0.1 was obtained in the same manner as in Example 11. After reduction with hydrogen at 500°C, the catalyst was subjected to the following conditions: pph 2.5h ^-1 ,
H ₂ /HC=5, tested at 500° C. instead of 525° C. and 8 bar instead of 15 bar. The following results were obtained. Elapsed time C1-C2 yield Aromatic yield (hours) (wt%) (wt%) 24 13.0 38.2 73 9.5 35.0 This catalyst has more rhenium content than platinum content, but still maintains good stability. Shows good yield and aromatic selectivity. The reason is that lower pressures are used than in the previous embodiments. The strong hydrogenolysis caused by rhenium is suppressed by low pressure, while the aromatic yield increases,
This is because a higher rhenium content contributes to increasing the stability of the catalyst.

Claims (1)

[Scope of Claims] 1. A monofunctional bimetallic catalyst for the dehydrocyclization of paraffin, on a support consisting of crystalline aluminosilicate zeolite, more than 90% substituted with alkali metal cations, and having a pore size of more than 6.5 Å. a catalyst characterized in that it contains: 0.1-1.5% platinum introduced by impregnation; 0.1-1.5% platinum introduced in the form of carbonyls sublimed or dissolved in acetone. Rhenium (however, the rhenium/platinum ratio varies depending on the working pressure); and the ratio of the number of sulfur atoms to the number of (platinum + rhenium) atoms x
trace amounts of sulfur introduced by sulfur compounds that can be reduced or decomposed by hydrogen, such that 0.05 to 0.6. 2. Catalyst according to claim 1, characterized in that, when used at high pressures of 15 to 35 bar, the amount of rhenium is less than the amount of platinum. 3. Catalyst according to claim 1, characterized in that the rhenium content is greater than the platinum content in order to maintain good stability when used at low pressures. 4. Catalyst according to claim 1, characterized in that the support is selected from the group consisting of Faujasite X, Faujasite Y, Zeolite L, Zeolite Omega and Zeolite ZSM4. 5. The catalyst according to claim 1 or 4, wherein the carrier is exchanged zeolite L containing one kind of alkali metal selected from the group consisting of sodium, potassium, rubidium, and cesium. 6. Catalyst according to claim 1, 4 or 5, characterized in that the support is formed into spheres, tablets or pellets by extrusion, dragage or drop coagulation before or after the deposition of platinum, rhenium and sulfur. . 7. A method for producing a catalyst according to claim 1, characterized in that it comprises the following steps: (a) catalytic sublimation of rhenium carbonyl Re ₂ (CO) ₁₀ onto a support in an atmosphere containing air, nitrogen or hydrogen; (b) by known impregnation methods using solutions of platinum compounds selected from the group consisting of hexachloroplatinic acid, platinum tetraammine chloride, dinitrodiammine platinum, or by cationic complexes of platinum; (c) introduction of sulfur by impregnation of the support with a solution of a sulfide compound selected from the group consisting of oxyanions, sulfates, thiosulfates or sulfites; and ( d) Drying of the support loaded with rhenium, platinum and sulfur. 8. A method according to claim 7, characterized in that step (a) is performed between steps (b) and (c). 9. Process according to claim 7, characterized in that step (a) is carried out under reduced pressure between 0.1 and 100 Torr. 10. Process according to claim 7, characterized in that step (b) is carried out in the presence of an excess of cationic salt of the zeolite. 11. The method according to claim 7, characterized in that the dried carrier is further calcined. 12. Process according to claim 7, characterized in that the support is reduced with hydrogen at a temperature of 300-550<0>C before use. 13. Pretreatment of the rhenium and platinum charged support with a sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl disulfide, carbon disulfide, in a dehydrocyclization reactor, before or after reduction with hydrogen. 13. A method according to claim 12, characterized in that step (c) is carried out by: 14. A process for producing a catalyst according to claim 1, characterized in that it comprises the following steps: (a') charging the support with rhenium by impregnation with an organic solution of rhenium carbonyl in acetone; (b) ) platinum by known impregnation methods using solutions of platinum compounds selected from the group consisting of hexachloroplatinic acid, platinum tetraammine chloride, dinitrodiammine platinum, or by ion exchange with cationic complexes of platinum. (c) introduction of sulfur by impregnation of the support with a solution of a sulfide compound selected from the group consisting of oxyanions, ie sulfates, thiosulfates or sulfites; and (d) deposition of rhenium, platinum and sulfur. Drying of the carrier. 15. A method according to claim 14, characterized in that step (a') is performed between steps (b) and (c). 16. Process according to claim 14, characterized in that step (b) is carried out in the presence of an excess of cationic salt of the zeolite. 17. The method according to claim 14, characterized in that the dried carrier is further calcined. 18. Process according to claim 14, characterized in that the support is reduced with hydrogen at a temperature of 300-550<0>C before use. 19 In a dehydrocyclization reactor, before or after reduction with hydrogen, the rhenium and platinum charged support is pretreated with a sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl disulfide, carbon disulfide. 19. A method according to claim 18, characterized in that step (c) is performed.