GB2153384A - Method of reforming hydrocarbons - Google Patents

Abstract

A method of reforming hydrocarbons and in particular dehydrocyclizing alkenes wherein the hydrocarbons, eg. alkanes, are contacted with a catalyst containing a large-pore zeolite, a Group VIII metal, and an alkaline earth metal selected from barium, strontium and calcium, the process conditions being adjusted so that the selectivity for n-hexane dehydrocyclization is greater than 60%. The catalyst is preferably a type L, X or Y zeolite containing 0.1 to 5% by weight of platinum and 0.1 to 35% by weight of barium.

Description

1

SPECIFICATION

Method of reforming hydrocarbons GB 2 153 384A 1 This invention relates to a method of reforming hydrocarbons and is particularly useful in 5 dehydrocyclizing alkanes preferably containing at least 6 carbon atoms to form the correspond ing aromatic hydrocarbons.

Catalytic reforming is well known in the petroleum industry and refers to the treatment of naphtha fractions to improve the octane rating. The more important hydrocarbon reactions occurring during reforming operation include dehydrogenation of cyclohexanes to aromatics, 10 clehydroisomerization of alkylcyclopentanes to aromatics, and dehydrocyclization of paraffins to aromatics. Hydrocracking reactions which produce high yields of light gaseous hydrocarbons, e.g. methane, ethane, propane and butane, ar to be particularly minimized during reforming as this decreases the yield of gasoline boiling products.

Dehydrocyclization is one of the main reactions in the reforming process. The conventional 15 methods of performing these dehydrocyclization reactions are based on the use of catalysts comprising a noble metal on a carrier. Known catalysts of this kind are based on alumina carrying 0.2% to 0.8% by weight of platinum and preferably a second auxiliary metal.

The possibility of using carriers other than alumina has also been studied and it was proposed to use certain molecular sieves such as X and Y zeolites, which appeared suitable provided that 20 the reactant and product molecules were sufficiently small to pass through the pores of the zeolite.. However, catalysts based upon these molecular sieves have not been commercially successful.

In the conventional method of carrying out the aforementioned clehydrocyclization, paraffins to be converted are passed over the catalyst, in the presence of hydrogen, at temperatures of 25 the order of 500'C and pressures of from 5 to 30 bars. Part of the paraffins are converted into aromatic hydrocarbons, and the reaction is accompanied by isomerization and cracking reactions which also convert the paraffins into isoparaffins and lighter hydrocarbons.

The rate of conversion of the hydrocarbons into aromatic hydrocarbons varies with the reaction conditions and the nature of the catalyst.

The catalysts hitherto used have given moderately satisfactory results with heavy paraffins, but less satisfactory results with C,-C, paraffins, particularly C, paraffins. Catalysts based on a type L zeolite are more selective with regard to the clehydrocyclization reaction; can be used to improve the rate of conversion to aromatic hydrocarbons without requiring higher temperatures, which usually have a considerable adverse effect on the stability of the catalyst; and produce excellent results with C,-C, paraffins. However, run length and regenerability are problems and satisfactory regeneration procedures are not known.

In one method of clehydrocyclizing aliphatic hydrocarbons, hydrocarbons are contacted in the presence of hydrogen with a catalyst consisting essentially of a type L zeolite having exchangeable cations of which at least 90% are alkali metal ions selected from the group consisting of ions of sodium, lithium, potassium, rubidium and cesium and containing at least one metal selected from the group which consists of metals of Group Vill of Mendeleeff's Periodic Table of Elements, tin and germanium, said metal or metals including at least one metal from Group Vill of said Periodic Table having a dehydrogenating effect, so as to convert at least part of the feedstock into aromatic hydrocarbons.

A particularly advantageous embodiment of this method is a pfatinum/alkali metal/type L zeolite catalyst because of its excellent activity and selectivity for converting hexanes and heptanes to aromatics, but run length remains a problem.

The present invention overcomes the deficiencies of the prior art by using a catalyst comprising a large-pore zeolite, an alkaline earth metal and a Group Vill metal to reform hydrocarbons at an extremely high selectivity for converting alkanes to aromatics. The hydrocarbons are contacted with a catalyst comprising a large-pore zeolite, at least one Group VIII metal (preferably platinum); and an alkaline earth metal selected from the group consisting of barium, strontium and calcium (preferably barium). In accordance with the invention, the process conditions are adjusted so that the selectivity for n-hexane clehydrocyclization is greater than 60%. The catalyst gives satisfactory run length.

Preferably the large-pore zeolite is a type L zeolite which contains from 0. 1 % to 5% by weight platinum and 0. 1 % to 35% by weight barium. The hydrocarbons are generally contacted with the barium-exchanged type zeolite at a temperature of from 400C to 600'C (preferably 430'C to 550'C); a pressure of from 1 atmosphere to 500 psig (1 to 34.5 bar), preferably from 50 to 60 300 psig (3.4 to 20.7 bar); and a H2/hydrocarbon ratio of from 1: 1 to 10: 1 (preferably from 2:1 to 6:1). he contacting is preferably effected at a liquid hourly space velocity (LHSV) of from 0.3 to 5.

In its broadest aspect, the present invention involves the use of a catalyst comprising a large pore zeolite, an alkaline earth metal selected from barium, strontium and calcium, and a Group 65 2 GB 2153 384A 2 Vill metal in the reforming of hydrocarbons, in particular, the dehydrocyclzation of alkanes, at an extremely high selectivity for converting hexanes to aromatics.

The term "selectivity" as used in the present invention is defined as the percentage of moles of paraffin converted to aromatics relative to moles converted to aromatics and cracked 5 products, i.e.-Selectivity = X moles of paraffins converted to aromatics moles of paraffins converted to 10 aromatics and cracked products Isomerization reactions and alkylcyclopentane formation are not considered in determining selectivity.

The term -selectivity for n-hexane- 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 for converting paraffins to aromatics is a measure of the efficiency of the process in converting paraffins to the desired and valuable products: aromatics and hydrogen as 20 opposed to the less desirable products of hydrocracking.

Highly selective catalysts produce more hydrogen than less selective catalysts because hydrogen is produced when paraffins are converted to aromatics and hydrogen is consumed when paraffins are converted to cracked products. Increasing the selectivity of the process increases the amount of hydrogen produced (more aromatization) and decreases the amount of hydrogen consumed (less cracking).

Another advantage of using highly selective catalysts is that the hydrogen produced by highly selective catalysts is purer than that produced by less selective catalysts. This higher purity results because more hydrogen is produced, while less low boiling hydrocarbons (cracked products) are produced. The purity of hydrogen produced in reforming is critical if, as is usually 30 the case in an integrated refinery, the hydrogen produced is utilized in processes such as hydrotreating and hydrocracking, which require at least certain minimum partial pressures 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, for example as fuel gas.

In the method according to the invention, the feed hydrocarbons preferably comprise nonaromatic hydrocarbons containing at least 6 carbon atoms. Preferably, the feedstock is substantially free of sulfur, nitrogen, metals and other known poisons for reforming catalysts.

The dehydrocyclization is carried out in the presence of hydrogen at a pressure adjusted so as to favour the reaction thermodynamically and limit undesirable hydrocracking reactions by kinetic means. The pressures used preferably vary from 1 atmosphere to 500 psig (1 to 34.5 40 bar), more preferably from 50 to 300 psig (3.4 to 20.7 bar), the molar ratio of hydrogen to hydrocarbons preferably being from 1: 1 to 10: 1, more preferably from 2:1 to 6: 1.

In the temperature range of from 400'C to 60WC, the dehydrocyclization reaction occurs with acceptable speed and selectivity.

If the operating temperature is below 40WC, the reaction speed is insufficient and conse- 45 quently the yield is too low for industrial purposes. Also, the dehydrocyclization equilibria is unfavourable at low temperatures. When the operating temperature is above 60WC, interfering secondary reactions such as hydrocracking and coking occur, and substantially reduce the yield and increase the catalyst deactivation rate. It is not advisable, therefore, to exceed the temperature of 60WC.

The preferred tempeature range (43WC to 550C) of dehydrocyclizatioin is that in which the process is optimum with regard to activity, selectivity and the stability of the catalyst.

The liquid hourly space velocity (LI-ISV) of the hydrocarbons is preferably between 0.3 and 5.

The catalyst employed in the invention is a large-pore zeolite charged with one or more dehydrogenating constituents. The term -large-pore zeolite- is defined as a zeolite having an effective pore diameter (i.e. a pore diameter as measured) of 6 to 15 Angstroms.

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

A composition of type L zeolite, expressed in terms of mole ratios of oxides, may be represented as follows:

(0.9-1.3)M2InO:A'201(5.2-6.9)S'02:yH20 3 GB 2 153 384A 3 wherein M designates a cation, n represents the valence of M, and y may be any value from 0 to 9. Zeolite L, its X-ray diffraction pattern, its properties, and method for its preparation are described in detail in U.S. Patent No. 3,216,789. U.S. Patent No. 3,216, 789 shows the preferred zeolite of the present invention. The real formula may vary without changing the crystalline structure; for example, the mole ratio of silicon to aluminum (Si/Al) may vary from 5 1.0 to 3.5.

The chemical formula for zeolite Y expressed in terms of mole ratios of oxides may be written as:

(0.7-1.1)Na2O:A'20,:XS'02:yH20 wherein x is a value greater than 3 up to about 6 and y may be a vlaue up to about 9. Zeolite Y has a characteristic X-ray powder diffraction pattern which may be employed with the above formula for identification. Zeolite Y is described in more detail in U.S. Patent No. 3,130,007. 15 U. S. Patent No. 3,130,007 shows a zeolite useful in the present invention.

Zeolite X is a synthetic crystalline zeolitic molecular sieve which may be represented by the formula:

(0. 7-1 1 1)M2/nO:A'203:(210-310)SiO2:yH20 wherein M represents a metal, particularly alkali and alkaline earth metals, n is the valence of M, and y may have any value up to about 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 method for its preparation are described in detail in U.S. Patent No. 2,882,244. U.S. Patent No. 2,882,244 shows a zeolite useful in the present invention.

The preferred catalyst according to the invention is a type L zeolite charged with one or more dehydrogenating constituents.

An essential element of the present invention is the presence of an alkaline earth metal in the large-pore zeolite. That alkaline eath 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 to the other alkaline earths because it results in a somewhat less acidic catalyst. Strong acidity is undesirable in the catalyst because it promotes cracking resulting in lower selectivity.

In one embodiment, at least part of the alkali metal is exchanged with barium, using techniques known for ion exchange of zeolites. This involves contacting the zeolite with a 35 solution containing excess Ba + + ions. The barium should constitute from 0. 1 % to 35% of the weight of the zeolites.

The dehydrocyclization catalysts employed in accordance with the invention are charged with one or more Group Vill metals, e.g. nickel, ruthenium, rhodium, palladium, iridium or platinum, The preferred Group Vill metals are iridium and particularly platinum, which are more selective with regard to dehydrocyclization and are also more stable under the dehydrocycliza tion reaction conditions than other Group Vill metals.

The preferred percentage of platinum in the catalyst is between 0. 1 % and 5%.

Group Vill metals are introduced into the large-pore zeolite by synthesis, impregnation or exchange in an aqueous solution of an appropriate salt. When it is desired to introduce two 45 Group Vill metals into the zeolite, the operation may be carried out simultaneoulsy or sequentially.

By way of example, platinum can be introduced by impregnating the zeolite with an aqueous solution of tetrammineplatinum (11) nitrate, tetrammineplatinum (11) hydroxide, clinitrodiamino platinum or tetrammineplatinum (11) chloride. In an ion exchange process, platinum can be introduced by using cationic platinum complexes such as tetrammineplatinum (11) nitrate.

An inorganic oxide may be used as a carrier to bind the large-pore zeolite containing the Group Vill metal and alkaline earth metal. The carrier can be a natural or a synthetically produced inorganic oxide or combination of inorganic oxides. Typical inoganic oxide supports which can be used include clays, alumina, and silica, in which acidic sites are preferably exchanged cations which do not impart strong acidity (such as Na, K, Rb, Cs, Ca, Sr, or Ba).

The catalyst can be employed in any of the conventional types of equipment known to the art.

It may be employed in the form of pills, pellets, granules, broken fragments, or various special shapes, disposed as a fixed bed within a reaction zone, and the charging stock may be passed therethrough in the liquid, vapor, or mixed phase, and in either upward or downward flow.

Alternatively, it may be prepared in a suitable form for use in moving beds, or in fluidized-solid processes, in which the charging stock is passed upward through a turbulent bed of finely divided catalyst.

After the desired metal or metals have been introduced, the catalyst is treated in air at about 260C and then reduced in hydrogen at temperatures of from 200'C to 700'C, preferably 65 4 GB 2 153 384A 4 400'C to 620C.

At this stage it is ready for use in the dehydrocyclization process. In some cases however, for example when the metal or metals have been introduced by an ion exchange process, it is preferable to eliminate any residual acidity of the zeolite by treating the catalyst with an aqueous solution of a salt or hydroxide of a suitable alkali or alkaline earth element in order to nuetralize any hydrogen ions formed during the reduction of metal ions by hydrogen.

In order to obtain optimum selectivity, temperature should be adjusted so that reaction rate is appreciable, but conversion is less than 98%, as excessive temperature and excess reaction can have an adverse affect on selectivity. Pressure should also be adjusted within a proper range.

Too high a pressure will place a thermodynamic (equilibrium) limit on the desired reaction, 10 especially for hexane aromatization, and too low a pressure may result in coking and deactivation.

Although the primary benefit of this invention is in improving the selectivity for conversion of paraffins (especially C,-C, paraffins) to aromatics, it is also surprisingly found that the selectivity for conversion of methylcyclopentane to benzene is excellent. This reaction, which on conven- 15 tional reforming catalysts based on chlorided alumina involves an acid catalyzed isomerization step, occurs on the catalyst of this invention with selectivity as good as or better than on the chlorided alumina based catalysts of the prior art. Thus, the present invention can also be used to catalyze the conversion of stocks high in 5-membered-ring alkyl naphthenes to aromatics.

Another advantage of this invention is that the catalyst of the present invention is more stable 20 than prior art zeolite catalysts. Stability of the catalyst, or resistance to deactivation, determines its useful run length. Longer run lengths result in less down time and expense in regenerating or replacing the catalyst charge.

In one embodiment of the present invention, a hydrocarbon feed is contacted with a first catalyst which is a conventional reforming catalyst and a second catalyst which is a dehydrocy- 25 clization catalyst comprising a large-pore zeolite, an alkaline earth metal which is barium, strontium or calcium, and a Group Vill metal.

The use of a reforming catalyst comprising an alumina support, platinum, and rhenium is discussed fully in U.S. Patent 3,415,737, which shows the use of an advantageous conven tional reforming catalyst. Other advantageous bimetallic catalysts include platinum-tin, platinumgermanium, platinum-lead and platinum-iridium.

The hydrocarbons can be contacted with the two catalysts in series, with the hydrocarbons first being contacted with the first (conventional) reforming catalyst, and then with the second (dehydrocyclization) catalyst; or with the hydrocarbons first being contacted with the second catalyst, and then with the first catalyst. Also the hydrocarbons can be contacted in parallel with 35 one fraction of the hydrocarbons being contacted with the first catalyst and another fraction of the hydrocarbons being contacted with the second catalyst. Also the hydrocarbons can be contacted with both catalysts simultaneously in the same reactor The following Examples illustrate the invention.

Example 1

An Arabian Light straight run which had been hydrofined to remove sulfur, oxygen and nitrogen was reformed at 100 psig (7 bar), 2 LI-ISV, and 6 H2/hydrocarbon by three different catalysts. The feed contained 80.2v% paraffins, 16.7v% naphthenes, and 3.1^ aromatics, and it contained 211.8v% C, 52.9v% C, 21.3^ C, and 3.2v% C, In the first run, the Arabian Light straight run was reformed at 49WC using a commercial sulfided platinum-rhenium-alumina catalyst disclosed in U.S. Patent No. 3, 415,737.

In the second run, the Arabian Light straight run was reformed at 493'C using a platinum potassium-type L zeolite catalyst formed by: (1) impregnating a potassium- type L zeolite with 0.8% platinum using tetrammineplatinum (11) nitrate; (2) drying the catalyst; (3) calcining the 50 catalyst at 260C; and (4) reducing the catalyst at 48WC to 50WC for 1 hour.

In the third run, the process of the present invention, the Arabian Light straight run was reformed at 493'C using a platinum-barium-type L zeolite catalyst formed by: (1) ion exchanging a potassium-type L zeolite with a sufficient volume of 0. 17 molar barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite; (2) 55 drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 590C; (4) impregnating the catalyst with 0.8% platinum using tetrammineplatinum (11) nitrate; (5) drying the catalyst; (6) calcining the catalyst at 26WC; and (7) reducing the catalyst in hydrogen at 4BO'C to 50WC for 1 hour.

The results of these three runs are shown in Table 1.

GB 2 153 384A 5 TABLE I

499 0 C Pt/Re/ 493 0 C 493 0 C 5 Feed Alumina Pt/K/L Pt/Ba/L C 1 Wt % Fd 2.8 5.5 3.6 C 2 6.6 2.5 1.3 10 9.3 3.2 1.5 i 4 0.1 5.8 0.9 0.5 NC 4 0.5 6.8 3.8 2.4 1C 5 5.1 13.6 6.7 5.6 NC 11.3 9.8 12.6 12.6 15 C 6 P+N 81.3 13.4 7.8 9.3 Benzene 1.5 15.1 40.6 43.8 C 7 + Aromatics.8 15.8 12.7 15.0 C 5 + LV % Yield 63 69.9 74.4 20 Hydrogen, SCF/B 470 1660 2050 Selectivity, Mole % 20 72 87 C 6 + P --> Aromatics 25 This series of runs shows that the use of a platinum-barium-type L zeolite catalyst in reforming gives a selectivity for converting hexanes to benzene markedly superior to that of the prior art. Notice that associated with this superior selectivity is an increase in hydrogen gas production which can be used in other processes. Notice also that the hydrogen purity is higher for the

Pt/Ba/L run since more hydrogen is produced and less C, and C, are produced.

Example 2

A second series of runs were made to show that the present invention would work with other large-pore zeolites in addition to type L zeolite.

This second series of runs was made using n-hexane as feed. All runs in this series were made 35 at 49WC, 100 psig (7 bar), 3 LI-ISV and 3 H, /hydrocarbon.

In the first run, a platinum-potassium-type L zeolite was used which had been prepared by the procedures shown in the second process of Example 1.

In the second run, a platinum-barium-type L zeolite was used which had been prepared by the procedures shown in the third process of Example 1 except that the barium nitrate solution was 40 0. 3 molar instead of 0. 17 molar.

In the third run, a platinum-sodium-zeolite Y was used which had been prepared by impregnating a sodium-zeolite Y with Pt(NHI(N0j, to give 0.8% platinum, then drying, calcining the catalyst at 26WC and reducing in hydrogen at 480-500'C.

In the fourth run, a platinum-barium-zeolite Y was used which had been prepared by ion exchanging a sodium-zeolite Y with 0.3 molar barium nitrate at WC, drying, and calcining at 59WC, then impregnating the zeolite with Pt(NHI(N01 to give 0.8% platinum, then drying, calcining the catalyst at 26WC, and reducing in hydrogen at 480-500'C. The results of these runs are given below in Table It.

TABLE II

Conversion Pt/K/L ' Hrs. 20 Hrs. 55 59 Pt/Ba/L 85 85 Pt/Na/Y 82 79 Pt/Ba/Y 74 68 60 Thus, in operation, the incorporation of barium into a large-pore zeolite, such as type Y zeolite, causes a dramatic improvement in selectivity for n-hexane. Notice that the stability of the platinum-barium-type L zeolite is excellent. After 20 hours, there was no drop in conversion when platinum-barium-type L zeolite catalyst was used.

6 GB 2 153 384A 6 Example 3

A third series of runs was made to show the effect of adding additional ingredients to the catalyst.

This third series of runs was made using a feed, which had been hydrofined to remove sulfur, oxygen and nitrogen, containing 80.9^ paraffins, 1 6.8v% naphthenes, and 1. 7v% aromatics. 5 The feed also contained 2.6v% C,, 47.6v% C,, 43.4v%C7 and 6.3v% C,, All runs in this series were made at 49WC, 100 psig (7 bar), 2.0 LI-ISV and 6.0 H2/hydrocarbon.

In the first run, a platinum-sodium-zeolite Y was prepared by the procedures shown in the third process of Example 2.

In the second run, a platinum-barium-zeolite Y was prepared by the procedures shown in the 10 fourth process of Example 2.

In the third run, a platinum-rare earth-zeolite Y was prepared by impregnating a commercial rare earth zeolite Y obtained from Strem Chemicals Inc. to give 0.8% Pt using Pt(NI-13),(NO,),, then the zeolite was dried, calcined at 260'C and reduced at 480-500'C.

In the fourth run, a platinum-rare earth-barium-zeolite Y as prepared by ion exchanging a 15 commercial Strem Chemicals Inc. rare earth zeolite Y with a 0.3 molar Ba(NO,), solution at WC, drying and calcining the zeolite at 59WC, impregnating the zeolite with Pt(NH3)4(NO,), to give 0.8% Pt, then drying, calcining the zeolite at 26WC, and reducing at 480-500"C. The results of these runs are given below in Table 111.

1 TABLE III

Activity Aromatics @ 3 Hrs, C 5 + Selectivity, 25 Mole % of Feed % @ 3 Hrs Pt/Na/Y 36 46 Pt/Ba/Y 54 68 30 Pt/Rare Earth/Y 22 (Too Low to Measure Pt/Ba/Rare Earth/Y 36 27 35 This series of runs shows that the addition of rare earth to the catalyst has an adverse effect on selectivity.

Example IV

An Arabian Naphtha which had been hydrofined to remove sulfur, oxygen and nitrogen was 40 reformed at 100 psig (7 bar), 3 LHSV, and 3 H2/hydrogen to produce a C, + product having an aromatics content of 82 wt % by two different processes. The feed was a hydrofined Arabian Naphtha containing 67.9% paraffins, 23.7% naphthenes, and 8.4% aromatics. Distillation results by D86 method were: start-204'F (95'C), 5%-219, 10%-224, 30%-248, 50%-264, 70%-291, 90%-321, 95%-337, EP 370F (1 88'C).

In the first process, the Arabian Naphtha was reformed at 51 6'C in a reactor using a conventional reforming catalyst comprising 0.3 Pt, 0.6 Re, 1.0 Cl (wt %) on alumina. It was presulfided separately.

In the second process, the Arabian Naphtha was reformed at 493C in the same reactor wherein the top half of the reactor contained the same type of catalyst as that of the first process and the bottom half of the reactor contains a platinum-barium-type L zeolite catalyst formed by the procedures shown in Example 1.

The results of these two runs are shown in Table IV.

7 GB 2 153 384A 7 TABLE IV

Pt/Re/ 1/2 Pt/Re/Alumina 5 Alumina 1/2 Pt/Ba/L Deactivation Rate 2.0 1.9 c 5 + yield, LV% yield 68.9 71.0 10 Hydrogen, SCF/D 950 1050

Claims (10)

1. A method of reforming a hydrocarbon feed, which comprises contacting the hydrocarbon 15 feed with a catalyst comprising a large-porse zeolite (as hereinbefore defined) containing:

(a) at least one Group Vill metal; and (b) an alkaline earth metal selected from barium, strontium and calcium, wherein the process conditions are adjusted so that the selectivity for n- hexane dehydrocyclization is greater than 60%.

2. A method according to Claim 1, wherein said alkaline earth metal is barium and said Group Vill metal is platinum.

3. A method according to Claim 2, wherein the catalyst contains from 0. 1 % to 35% by weight barium and from 0. 1 % to 5% by weight platinum.

4. A method according to Claim 1, 2 or 3, wherein said large-pore zeolite has an effective 25 pore diameter of from 7 to 9 Angstroms.

5. A method according to any preceding claim, wherein said large-pore zeolite is selected from zeolite X, zeolite Y and type L zeolite.

6. A method accordina to Claim 5, wherein said large-pore zeolite is zeolite Y.

7. A method according to Claim 5, wherein said large-pore zeolite is a type L zeolite. 30

8. A method according to any preceding claim, wherein said contacting occurs at a temperature of from 430 to 550'C; a pressure of from 50 to 300 psig (3.4 to 20.7 bar); and a H2/hydrocarbon ratio of from 2:1 to 6A.

9. A method of reforming a hydrocarbon feed according to any preceding claim, wherein prior to said contacting the feed is contacted at reforming conditions and in the presence of 35 hydrogen with a catalyst comprising a metallic oxide support having disposed therein in intimate admixture platinum and rhenium.

10. A method in accordance with Claim 1 of reforming a hydrocarbon feed, substantially as described in any one of the foregoing Examples.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935. 1985, 4235. Published at The Patent Office. 25 Southampton Buildings, London. WC2A 'I AY, from which copies may be obtained.