DK163803B - CATALYST AND PROCEDURES FOR REFORMING CARBOHYDRIDES - Google Patents

Description

DK 163803 B

The present invention relates to a novel hydrocarbon reforming catalyst comprising a large pore zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one Group VIII metal.

Catalytic reforming is well known in the petroleum industry and refers to the treatment of naphtha fractions to improve the octane number. The more significant hydrocarbon reactions that occur during the reforming process include dehydrogenation of cyclohexanes to aromatic compounds, dehydroisomerization of alkylcyclopentanes to aromatic compounds, and dehydrocyclization of paraffins to aromatic compounds. Hydrocracking reactions, which give high yields of light gaseous hydrocarbons, e.g. methane, ethane, propane and butane, should be particularly minimized during reform as they reduce the yield of products in the gasoline boiling range.

Dehydrocyclization is one of the main reactions 20 of the reforming process. The conventional methods for carrying out these hydrocyclization reactions are based on the use of catalysts which comprise a noble metal on a support. Known catalysts of this kind are based on alumina, which carry 0.2 to 0.8 weight percent platinum and preferably another auxiliary metal.

The possibility of using carriers other than alumina has also been investigated, and it has been proposed to use certain molecular sieves, such as X and 30 Y zeolites, which proved to be suitable, provided that the reactant and product molecules were sufficiently small to pass through the pores of the zeolite. However, catalysts based on these molecular sieves have not had commercial success.

In the conventional process for carrying out the aforementioned dehydrocyclization, paraffins to be converted are passed over the catalyst for 2 hours.

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presence of hydrogen, at temperatures of the order of 500 ° C and pressures of from 0.5 to 3 MPa. Part of the paraffins is converted to aromatic hydrocarbons and the reaction is accompanied by isomerization and cracking reactions which also convert the paraffins to isoparaffins. and lighter hydrocarbons.

The degree of conversion with respect to the conversion of the hydrocarbons to aromatic hydrocarbons varies with the reaction conditions and the nature of the catalyst.

The catalysts used so far have yielded moderately satisfactory results with heavy paraffins, but less satisfactory results with Cg-Cg-pa raffins, especially Cg paraffins. Catalysts based on a type L zeolite are more selective in the dehydrocyclization reaction and can be used to improve the conversion rate to aromatic hydrocarbons without requiring higher temperatures, which usually have a significant adverse effect on the stability of the catalyst, and provide excellent results with Cg-Cg paraffins. However, operating time and: regeneration ability are problems and satisfactory regeneration procedures are not known.

In another known method for dehydrocyclization of 25 aliphatic hydrocarbons, hydrocarbons are contacted in the presence of hydrogen with a catalyst consisting essentially of a type L zeolite with interchangeable cations, of which at least 90% are alkali metal ions selected from sodium ions. lithium, potassium, rubidium and cesium, and containing at least one metal selected from Group VIII metals in the Periodic Table of the Elements, tin and Germanium, said metal or metals including at least one Group VIII metal of the Periodic System of Dehydrogenase-35 such that at least part of the feed material is converted to aromatic hydrocarbons.

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In a particularly advantageous embodiment of this process, a platinum / alkali metal / type L zeolite catalyst is used due to its excellent action and selectivity in converting hexanes 5 and heptanes to aromatic compounds, but the operating time remains a problem.

The deficiencies of the prior art are overcome by the catalyst according to the invention, which is characterized in that it also contains an alkaline earth metal selected from barium, strontium and calcium and that the catalyst selectivity index is greater than 60%.

Suitable embodiments of the catalyst of the invention are set forth in claims 4-9.

The catalyst of the invention can be used to reform hydrocarbons with an extremely high selectivity for the conversion of alkanes to aromatic compounds, and furthermore provides the catalyst with a satisfactory operating time.

The invention therefore also relates to a process for reforming hydrocarbons by contacting the relevant hydrocarbons with a catalyst comprising a large pore zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one group VIII metal, which process is characterized in that the catalyst also contains an alkaline earth metal selected from barium, strontium and calcium, and that the process conditions are selected from a temperature of from 400 to 600 ° C, an LHSV of from 0.3 to 10, a pressure gauge -30 pressures of from 0 to 3.45 MPa and a H2 / HC ratio of from 1: 1 to 10: 1, so that the selectivity for n-hexane dehydrocyclization is greater than 60%.

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The invention further relates to a process for reforming hydrocarbons, in which, under reforming conditions and in the presence of hydrogen, the relevant hydrocarbons are contacted with a first catalyst comprising a metal oxide support in which platinum and rhenium are incorporated in an intimate mixture. is characterized in that the hydrocarbons are then contacted with another catalyst which comprises a 10 large pore zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one group VIII metal and an alkaline earth metal selected from barium, strontium and calcium, where the selectivity index of the second catalyst is greater than 60%.

Suitable embodiments of the methods of the invention as set forth in claims 10 and 11 may be used.

The large pore zeolite is preferably a type L zeolite containing from 0.1 to 5% by weight platinum and from 0.1 to 35% by weight barium. The hydrocarbons are contacted with the barium-exchanged zeolite at a temperature of from 400 ° C to 600 ° C (preferably 430 ° C to 550 ° C), an LHSV of 0.3 to 5, a pressure gauge of 0 to 3.45 MPa (preferably from 0.35 to 2.07 MPa), and an H / HC ratio of from 1: 1 to 10: 1 (preferably from 2: 1 to 6: 1).

Briefly, the present invention involves the use of a catalyst comprising a large-pore zeolite, an alkaline earth metal and a Group VIII metal in hydrocarbon reforming, in particular dehydrocyclization of alkanes, with an extremely high selectivity in converting hexanes to aromatic compounds. .

The term "selectivity" as used in connection with the present invention is defined as the process

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the proportion of moles of paraffin converted to aromatics compared to moles converted to aromatics and cracked products, ie.

100 x moles of paraffins converted to selectivity = ten! aromatics ......

b selectivity moles of paraffins on aromatics and cracked products Isomerization reactions and alkylcyclopentane formation are not taken into account in the determination of selectivity.

The term "n-hexane selectivity" as used in the present invention is defined as the percentage of moles of n-hexane converted to aromatics relative to moles converted to aromatics and cracked products.

The selectivity of conversion of paraffins to aromatics is a measure of the efficiency of the process in converting paraffins to the desired and valuable products, ie. aromatics and hydrogen as opposed to the less desirable hydrocracking products.

An inherent property of any dehydrocyclization catalyst is its selectivity index. The selectivity index is defined as "n-hexane selectivity" when using n-hexane as feedstock 25 and operating at 490 ° C, 0.790 MPa (abs.), An LHSV of 3, and an I / HC ratio of 3 , after 20 hours.

Highly selective catalysts produce more hydrogen than less selective catalysts as hydrogen is formed when paraffins are converted to aromatic compounds and hydrogen is consumed when paraffins are converted into cracked products. By increasing the selectivity of the process, the amount of hydrogen formed (more aromatization) is increased and the amount of hydrogen consumed (less cracking) is reduced.

Another advantage of using highly selective catalysts is that the hydrogen produced by high selective catalysts is purer than that produced by less selective catalysts.

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This greater purity results because more hydrogen is produced while less is produced by low boiling hydrocarbons (cracked products).

The purity of the hydrogen produced by reforming is critical if, as is usually the case in an integrated refinery, the produced hydrogen is utilized in processes such as hydro-treatment and hydro-cracking, which require at least some minimum partial pressure of hydrogen. If the purity becomes too low, the hydrogen can no longer be used for this purpose and must be used in a less valuable way, e.g. such as fuel gas.

In the process of the invention, the hydrocarbon feed mixture preferably comprises non-aromatic hydrocarbons containing at least 6 carbon atoms. The feed material is preferably substantially free of sulfur, nitrogen, metals and other known toxins for reforming catalysts.

The dehydrocyclization is carried out in the presence of the hydrogen at a pressure which is adjusted to favor the reaction thermodynamically and limit undesired hydrocracking reactions by kinetic agents. The nanometer pressures used are preferably from 0 to 3.45 MPa, and more preferably from 0.35 to 2.07 MPa, with the molar ratio of hydrogen to hydrocarbons being preferably from 1: 1 to 10: 1, and more preferably from 2: 1 to 6: 1.

In the temperature range of 400 ° C to 600 ° C, the dehydrocyclization reaction takes place with acceptable rate and selectivity.

If the operating temperature is below 400 ° C, the reaction rate is insufficient and, consequently, the yield is too low for industrial purposes. In addition, dehydrocyclization equilibrium is unfavorable at low temperatures. When the operating temperature is above 600 ° C, disruptive secondary reactions such as hydrocracking and coke formation occur, which substantially diminishes the yield and increases the catalyst activation rate. Therefore, it is not advisable to exceed a temperature of 600 ° C.

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The preferred temperature range (430 ° C to 550 ° C) for dehydrocyclization is the range in which the process is optimal in terms of activity, selectivity and catalyst stability.

The specific volumetric liquid feed rate LHSV for the hydrocarbons is preferably between 0.3 and 10.

The catalyst used in the invention is a large pore zeolite charged with one or more dehydrogenating components. The term "large pore zeolite" is defined as a zeolite having an effective pore diameter of 6 to 15 angstroms.

Among the large-pore crystalline zeolites which have been found to be useful in the practice of the present invention, type L zeolites and synthetic zeolites with faujasite structure such as zeolite X and zeolite Y are the most important, and apparently have pore sizes of the order of 7 to 9 angstroms.

A composition of type L zeolite, expressed as a 20 molar ratio of oxides, may be represented as follows: (0.9-1.1) M2 / nO: Al2O3 (5.2-6.9) SiO2: yH2O wherein M represents a cation , n denotes the valence of M, and y may be any value from 0 to ca. 9. Zeolite L, its X-ray diffraction pattern, its properties and a process for its preparation are described in detail in U.S. Patent No. 3,216,789. By virtue of the reference thereto, U.S. Pat.

3,216,789 herein to show the preferred zeolite of the present invention. The real formula can vary without changing the crystal structure; eg. For example, the molar ratio of silicon to aluminum (Si / Al) may range from 1.0 to 3.5.

The chemical formula of zeolite Y expressed as molar ratio of oxides can be written as: 35 (0.7-1.1) Na 2 O: Al 2 O 3: xSiO 2: yH 2 O in which x is a value greater than 3 and up to approx. 6, and y may be a value up to approx. 9. Zeolite Y has a characteristic X-ray powder diffraction pattern that 8

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together with the above formula can be used for identification. Zeolite Y is described in greater detail in U.S. Patent No. 3,130,007. By reference thereto, U.S. Patent No. 3,130,007 is incorporated herein to show a zeolite useful in the present invention.

Zeolite X is a synthetic crystalline zeolite molecular sieve which can be represented by the formula: (0.7-1.1) M 2 n0: Al 2 Og: (2.0-3.0) SiC> 2 ryl 2 O 10 wherein M represents a metal, in particular alkali and alkaline earth limes, n is the valence of M, and y may have any value up to approx. 8, depending on the identity of M and the degree of hydration of the crystalline zeolite. Zeolite X, its X-ray diffraction pattern, its properties and a process for its preparation are described in detail in U.S. Patent No. 2,882,244. By virtue of the reference thereto, U.S. Pat.

2,882,244 herein to show a zeolite useful in the present invention.

The preferred catalyst of the invention is a type L zeolite charged with one or more dehydrogenating components.

An essential element of the present invention is the presence of an alkaline earth metal in the large pore zeolite. This alkaline earth metal must be either barium, strontium or calcium, preferably barium. The alkaline earth metal can be incorporated into the zeolite by synthesis, impregnation or ion exchange. Barium is preferred over the other alkaline earth metals as it gives a somewhat less acidic catalyst. Strong acidity is undesirable in the catalyst as it promotes cracking, leading to lower selectivity.

According to one embodiment, at least part of the alkali metal is exchanged with barium using 35 known methods of ion exchange in zeolites. This implies contacting the zeolite with a solution containing excess Ba ions. The barium should comprise from 0.1 to 35% by weight of the zeolite.

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The dehydrocyclization catalysts of the invention are charged with one or more Group VIII metals, e.g. nickel, ruthenium, rhodium, palladium, iridium or platinum.

The preferred Group VIII metals are iridium and, in particular, platinum, which are more selective in dehydrocyclization and, moreover, are more stable under the dehydrocyclization reaction conditions than other Group VIII metals.

The preferred percentage of platinum in the catalyst is between 0.1% and 5%.

Group VIII metals are introduced into the large-pore zeolite by synthesis, impregnation or exchange in an aqueous solution of a suitable salt. When it is desired to introduce two Group VIII metals into the zeolite, the operations can be performed simultaneously or consecutively.

For example, platinum can be introduced by impregnating the zeolite with an aqueous solution of tetrammin platinum. (Change trat, tetramminplatin (III hydroxide, dinitrodiamino-platinum 20 or tetramminplatin (II) chloride). In an ion exchange process, platinum can be introduced using cationic platinum complexes such as tetramminplatin (II) nitrate.

An inorganic oxide can also be used as a carrier for bonding the large-pore zeolite containing the Group 25 VIII metal and the alkaline earth metal. The carrier may be a natural or synthetically produced inorganic oxide or a combination of inorganic oxides. Typical inorganic oxide carriers which may be used are clays, alumina and silica, wherein the acidic sites are preferably exchanged with cations which do not confer strong acidity (such as Na, K, Rb, Cs, Ca, Sr or Ba).

The catalyst can be used in any of the conventional types of apparatus known in the art. It can be used in the form of pellets, pellets, granules, crushed fragments or various special forms, placed as a fixed bed in a reaction zone, and the feed material can be passed therethrough in liquid phase, vapor phase or mixed phase.

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see, and in either upward or downward flow. Alternatively, it may be prepared in a suitable form for use in moving beds, or by fluid-solid processes in which the feedstock is passed upwardly through a turbulent bed of comminuted catalyst.

After the desired metal or metals have been introduced, the catalyst is treated in air at approx. 260 ° C and then reduced in hydrogen at temperatures of from 200 ° C to 700 ° C, preferably from 400 ° C to 620 ° C.

At this stage, it is ready for use in the dehydrocyclization process. In some cases, e.g. however, when the metal or metals have been introduced by an ion exchange process, it is preferred to remove any residual acidity in the zeolite by treating the catalyst with an aqueous solution of a salt or hydroxide of an appropriate alkali or alkaline earth metal to neutralize any hydrogen ions formed during the reduction of metal ions with hydrogen.

To achieve optimum selectivity, the temperature must be set so that the reaction rate is noticeable, but the conversion is less than 98% as too high temperature and excessive reaction can adversely affect the selectivity. The pressure must also be set within a suitable range. Too high pressure 25 will set a thermodynamic (equilibrium) limit for the desired reaction, especially for hexane aromatization, and too low pressure may cause coke formation and deactivation.

Although the primary advantage of the present invention lies in the enhancement of the selectivity of converting paraffins (in particular Cg-Cg paraffins) to aromatics, it has also surprisingly been found that the selectivity of thylcyclopentane for benzene is excellent. This reaction, involving conventional reforming catalysts based on chlorinated alumina, involves an acid-catalyzed isomerization step, taking place on the catalyst of the present invention with a selectivity as good as or better than that of the known catalysts.

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is based on chlorinated alumina. Thus, the present invention can also be used to catalyze the conversion of starting materials with a high content of 5-membered alkyl naphthenes to aromatics.

Another advantage of the present invention is that the catalyst of the present invention is more stable than known zeolitic catalysts. The stability of the catalyst, or resistance to deactivation, determines its useful life. Longer 10 operating times result in fewer downtime and less expense for regenerating or replacing the catalyst charge.

The process of claim 3 is briefly described in bringing a hydrocarbon feedstock into contact with a first catalyst which is a conventional reforming catalyst and a second catalyst which is a dehydrocyclization catalyst comprising a large pore zeolite, a alkaline earth metal and a Group VIII metal.

The use of a reforming catalyst comprising an alumina support, platinum and rhenium is fully discussed in U.S. Patent No. 3,415,737, which, by reference thereto, is incorporated herein to demonstrate the use of an advantageous conventional reforming catalyst. Other advantageous bimetal catalysts include platinum tin, platinum germanium, platinum lead and platinum iridium.

The hydrocarbons may be contacted in series with the two catalysts, the hydrocarbons being first contacted with the first (conventional) reforming catalyst and then with the second (dehydrocyclization) catalyst, or the hydrocarbons first being contacted with the second catalyst and then with the first catalyst. The hydrocarbons can also be contacted in parallel with the catalysts, contacting one fraction of the hydrocarbons with the first catalyst and another fraction of the hydrocarbons contacting the second catalyst. The hydrocarbons can also be brought into contact with 12 at the same time

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both catalysts in the same reactor.

The invention is further illustrated by the following examples which describe particularly advantageous embodiments of the process and catalyst of the invention.

Example 1

An Arabic light "straight run" which had been subjected to hydrofining to remove sulfur, oxygen and nitrogen was subjected to reforming at 0.79 MPa (abs.), A 10 LHSV of 2 and an I / HC ratio of 6 at using three different catalysts. The food mixture contained 80.2 vol% paraffins, 16.7 vol% naphthenes and 3.1 vol% aromatics, and contained 21.8 vol% C5, 52.9 vol% Cg, 21.3 vol% Ο, η and 3.2 vol% Cg.

In the first experiment, the Arab lightweight straight run reform under 499UC was subjected to a commercial sulphided platinum-rhenium alumina catalyst disclosed in U.S. Patent No. 3,415,737.

In the second experiment, the Arab light straight run reforming was subjected to 493 ° C using a platinum-potassium-type L zeolite catalyst prepared by: (1) impregnating a potassium-type L zeolite with 0.8% platinum using tetrairminplatin (II) nitrate, (2) drying the catalyst, (3) calcining the catalyst at 260 ° C, and (4) reducing the catalyst at 480 ° C to 500 ° C for 1 hour. .

In the third experiment, the process of the present invention, the Arab lightweight straight run reforming was subjected to 493 ° C using a platinum-barium type L zeolite catalyst prepared by: (1) ion exchange of a potassium -type L zeolite having a sufficient volume of 0.17 molar barium nitrate solution to contain an excess of barium compared with the ion exchange capacity of the zeolite, (2) drying the obtained barium-exchanged type L zeolite catalyst, ( 3) calcination of the catalyst at 590 ° C, (4) im-13

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priming the catalyst with 0.8% platinum using tetrammin platinum (II) nitrate, (5) drying the catalyst, (6) calcining the catalyst at 260 ° C, and (7) reducing the catalyst in hydrogen at 480 ° C to 5 500 ° C for 1 hour.

The results of these three experiments are listed in Table I.

Table I

Food mixture 499 ° C 493 ° C 493 ° C

thing Pt / Re / Pt / K / L Pt / Ba / L

alumina 10 wt% feed bl. 2.8 5.5 3.6 C2 6.6 2.5 1.3 C3 9.3 3.2 1.5 iC4 0.1 5.8 0.9 0.5 NC4 0.5 6.8 3 , 8 2.4 15 iC5 5.1 13.6 6.7 5.6 NC5 11.3 9.8 12.6 12.6

Cg + P + N 81.3 13.4 7.8 9.3

Benzene 1.5 15.1 40.6 43.8 C + Aromatics 0.8 15.8 12.7 15.0 20 C5 + LV% yield 63 69.9 74.4

Hydrogen, SCF / B 470 1660 2050

Selectivity, mole% 20 72 87

Cg + p -> aromatics

This series of experiments shows that the use of a platinum-barium-type L zeolite catalyst in reforming provides a selectivity for converting hexanes to benzene, which selectivity is clearly better than that obtained in the prior art. It is noted that in connection with this enhanced selectivity there is an increase in the production of hydrogen gas which can be used in other methods. In addition, it is noted that the purity of the hydrogen is higher for the Pt / Ba / L test as more hydrogen and less + C

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Example 2

Another test series was performed to show that the present invention will work with large-pore zeolites other than type L zeolite. The selectivity index was measured for four catalysts.

This second series of experiments was performed using n-hexane as feed material. All experiments in this series were performed at 490 ° C, 0.79 MPa (abs ..), an LHSV of 3 and an I / HC ratio of 3.

In the first experiment, a platinum-potassium type L zeolite was used which was prepared by the procedures set out in the second process of Example 1.

In the second experiment, a platinum-barium type L zeolite was used which was prepared by the procedures set out in the third process of Example 1, except that the barium nitrate solution was 0.3 molar instead of 0.17 molar.

In the third experiment, a platinum sodium zeolite Y was prepared which was prepared by impregnating a sodium zeolite Y with PtiNH 4 (NO 2) 2 to obtain 0.8% platinum, then drying, calcination of the catalyst at 260 ° C and reduction in hydrogen at 480 to 500 ° C.

In the fourth experiment, a platinum-barium zeolite Y was prepared which was prepared by ion exchange of a sodium zeolite Y with 0.3 molar barium nitrate at 80 ° C, drying and calcination at 590 ° C, then impregnating the zeolite with Pt (NH 4) 4 (NC 2) 2 to give 0.8% platinum, and then drying, calcination of the catalyst at 260 ° C and reduction in hydrogen at 480 to 500 ° C. The results of these experiments are listed below in Table II.

Table II

Conversion rate Selectivity-5 hours 20 hours index

Pt / K / L 70 59 79 35 Pt / Ba / L 85 85 92

Pt / Na / Y 82 79 54

Pt / Ba / Y 74 68 66

In operation causes the incorporation of barium into 15

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a large-pore zeolite, such as type Y zeolite, thus drastically improves n-hexane selectivity.

It is noted that the stability of platinum-barium type L zeo-small is excellent. After 20 hours, there was no decrease in conversion rate when using platinum-barium type L zeolite catalyst.

Example 3

A third test series was performed to show the effect of adding additional constituents to the catalyst.

This third series of experiments was carried out using a feed mixture which had been subjected to hydrofining to remove sulfur, oxygen and nitrogen, containing 80.9% by volume of paraffins, 16.8% by volume of naphthenes and 1.7% by volume of aromatics. The food mixture additionally contained 2.6 vol% Ccj, 47.6 vol% Cg, 43.4 vol% C η and 6.3 vol% Cg.

All experiments in this range were performed at 490 ° C, 0.79 MPa (abs.), A LHSV of 2.0, and a Hg / HC ratio of 6.0.

In the first experiment, a platinum-20 sodium zeolite Y was prepared by the procedures set forth in the third process of Example 2.

In the second experiment, a platinum-barium zeolite Y was prepared by the procedures set forth in the fourth process of Example 2.

In the third experiment, a platinum rare-earth metal zeolite Y was prepared by impregnating a soul-dent earth metal zeolite Y obtained from Strem Chemicals Inc. to obtain 0.8% Pt using Pt (NHg) 4 (NOg 2) and the zeolite was dried, calcined at 260 ° C and reduced at 480 to 500 ° C.

In the fourth experiment, a platinum-rare-earth barium zeolite Y was prepared by ion exchange of a commercial, from Strem Chemicals Inc. obtained rare-earth metal zeolite Y with a 0.3 molar Ba (NOg) 2 solution at 80 ° C, drying and calcination of the zeolite at 590 ° C, impregnating the zeolite with Pt (NHg) 4 (NOg) 2 to obtain 0.8% Pt, and then drying, calcining the zeolite at 16

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260 ° C and reduction at 480 to 500 ° C. The results of these experiments are listed below in Table III.

Table III

Catalyst activity with respect to

aromatics determined after 3 hours Selectivity, 5 by painting C5 + mol «% at 3 hours of food mixture

Pt / Na / Y "36 46

Pt / Ba / Y 54 68

Pt / Rare 22 (too low for earth metal / Y to be measured) 10 Pt / Ba / Rare 97

earth metal / Y

This series of experiments shows that the addition of rare earth metal to the catalyst has an adverse effect on the selectivity.

Example 4 An arabic naphtha which had been subjected to hydrofining to remove sulfur, oxygen and nitrogen was subjected to reforming at 0.79 MPa (abs.), An LHSV of 3 and a H2 / HC ratio of 3 to obtain a C 2 t product having a content of 82% by weight aromatics by two different processes. The food blend was an Arab naphtha that was subjected to hydrofining and contained 67.9% paraffins, 23.7% naphthenes and 8.4% aromatics. The distillation results of ASTM method D86 were: start -203 ° F, 5% -219, 10% -224, 30% -248, 50% -265, 70% -291, 90% -25,321, 95% -337, end point 370 ° F.

In the first process, the Arabian naphtha was subjected to reforming at 516 ° C in a reactor using a conventional reforming catalyst comprising 0.3 wt% Pt, 0.6 wt% Re and 1.0 wt% Cl on alumina. It was presulfated separately.

In the second process, the Arabian naphtha was subjected to reforming at 493 ° C in the same reactor, wherein the upper half of the reactor contained the same reactor.

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catalyst as in the first process, and the lower half of the reactor contained a platinum-barium type L zeolite catalyst prepared by the procedures set forth in Example 1.

5 The results of these two experiments are listed in Table IV.

Table IV

Pt / Re / Aluminum 1/2 Pt / Re / Aluminum Nitric Oxide 1/2 Pt / Ba / L_ 1 o Deactivation rate 2.0 1.9 C 2+ yield, LV% yield 68.9 71.0

Hydrogen, SCF / D 950 1050 i i

Claims (11)

A hydrocarbon reforming catalyst comprising a large pore zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one group VIII metal, characterized in that it also contains an alkaline earth metal selected among barium, strontium and calcium, and that the catalyst selectivity index is greater than 60%. A process for reforming hydrocarbons by contacting said hydrocarbons with a catalyst comprising a large pore zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one Group VIII metal , characterized in that the catalyst 15 also contains an alkaline earth metal selected from barium, strontium and calcium and that the process conditions are selected from a temperature of from 400 to 600 ° C, an LHSV of from 0.3 to 10, a pressure gauge of from 0 to 3.45 MPa and a H2 / HC ratio of from 1: 1 to 10: 1, so that the selectivity of n-hexane dehydrocyclization is greater than 60%. A process for reforming hydrocarbons, in which, under reforming conditions and in the presence of hydrogen, the relevant hydrocarbons are contacted with a first catalyst comprising a metal oxide support incorporating platinum and rhenium in intimate admixture, characterized by then contacting the hydrocarbons with another catalyst comprising a large pore 30 zeolite having an effective pore diameter of from 6 to 15 angstroms and containing at least one Group VIII metal and an alkaline earth metal selected from barium, strontium and calcium , where the selectivity index of the second catalyst is greater than 60%. DK 163803B Catalyst according to claim 1, characterized in that the alkaline earth metal is barium and the group VIII metal is platinum. The catalyst of claim 4, characterized in that the catalyst contains from 0.1 to 35% by weight of barium and from 0.1 to 5% by weight of platinum. Catalyst according to claim 1, 4 or 5, characterized in that said large pore zeolite has an apparent pore size of from 7 to 9 steam stream. Catalyst according to claim 6, characterized in that said large pore zeolite is selected from zeolite X, zeolite Y and type L zeolite. 8. Catalyst according to claim 7, characterized in that said large-pore zeolite is zeolite Y. Catalyst according to claim 7, characterized in that said large pore zeolite is a type L zeolite. Process according to claim 3, characterized in that said contacting takes place at a temperature of from 400 ° C to 600 ° C, an LHSV of from 0.3 to 5, a pressure gauge of from 0 to 3.45 MPa and a H2 / HC ratio of from 1: 1 to 10: 1. 11. A method according to claim 2 or 3, characterized in that said contacting takes place at a temperature of from 430 ° C to 550 ° C, a pressure gauge of from 0.35 to 2.07 MPa and a K ratio of 2: 1 to 6: 1.