GB2116450A - Zeolite catalyst - Google Patents

Abstract

A zeolite catalyst useful for dehydrocyclizing acyclic hydrocarbons contains a type L zeolite, a Group VIII metal, preferably platinum, and an alkaline earth metal, preferably barium. The catalyst preferably contains from 0.1% to 1.5% by weight platinum and from 1% to 20% by weight barium.

Description

SPECIFICATION Zeolite catalyst This invention relates to a new catalyst and a method using that catalyst in reforming hydrocarbons, more particularly dehydrocyclizing acyclic hydrocarbons containing at least 6 carbon atoms, to form the corresponding aromatic hydrocarbons.

Catalytic reforming is well known in the petroleum industry and refers to the treatment of naphtha fractions to improve the octane rating by the production of aromatics. The more important hydrocarbon reactions occurring during reforming operation include dehydrogenation of cyclohexanes to aromatics, dehydroisomerization of alkylcyclopentanes to aromatics, and dehydrocyclization of acyclic hydrocarbons to aromatics. A number of other reactions also occur, including the following: dealkylation of alkylbenzenes, isomerization of paraffins, and hydrocracking reactions which produce light gaseous hydrocarbons, e.g., methane, ethane, propane and butane. Hydrocracking reactions are to be particularly minimized during reforming as they decrease the yield of gasoline boiling products and hydrogen.

Because of the demand for high octane gasoline for use as motor fuels, etc., extensive research is being devoted to the development of improved reforming catalysts and catalytic reforming processes.

Catalysts for successful reforming processes must possess good selectivity, i.e., be able to produce high yields of liquid products in the gasoline boiling range containing large concentrations of high octane number aromatic hydrocarbons and accordingly, low yields of light gaseous hydrocarbons. The catalysts should possess good activity in order that the temperature required to produce a certain quality product need not be too high. It is also also necessary that catalysts either possess good stability in order that the activity and selectivity characteristics can be retained during prolonged periods of operation, or be sufficiently regenerable to allow frequent regeneration without loss of performance.

Catalysts comprising platinum, for example, platinum supported on alumina, are well known and widely used for reforming of naphthas. The most important products of catalytic reforming are benzene and alkylbenzenes. These aromatic hydrocarbons are of great value as high octane number components of gasoline.

Catalytic reforming is also an important process for the chemical industry because of the great and expanding demand for aromatic hydrocarbons for use in the manufacture of various chemical products such as synthetic fibers, insecticides, adhesives, detergents, plastics, synthetic rubbers, pharmaceutical products, high octane gasoline, perfumes, drying oils, ion-exchange resins, and various other products well known to those skilled in the art. One example of this demand is in the manufacture of alkylated aromatics such as ethylbenzene, cumene and dodecylbenzene by using the appropriate mono-olefins to alkylate benzene. Another example of this demand is in the area of chlorination of benzene to give chlorobenzene which is then used to prepare phenol by hydrolysis with sodium hydroxide. The chief use for phenol is in the manufacture of phenol-formaldehyde resins and plastics.Another route to phenol uses cumene as a starting material and involves the oxidation of cumene by air to cumene hydroperoxide which can then be decomposed to phenol and acetone by the action of an appropriate acid. The demand for ethylbenzene is primarily derived from its use to manufacture styrene by selective dehydrogenation; styrene is in turn used to make styrene-butadiene rubber and polystyrene. Ortho-xylene is typically oxidized to phthalic anhydride by reaction in vapor phase with air in the presence of a vanadium pentoxide catalyst. Phthalic an hydroxide is in turn used for production of plasticizers, polyesters and resins. The demand for para-xylene is caused primarily by its use in the manufacture of terephthalic acid or dimethylterephthalate which in turn is reacted with ethylene glycol and polymerized to yield polyester fibers.Substantial demand for benzene also is associated with its use to produce aniline, Nylon, maleic anhydride, solvents and the like petrochemical products. Toluene, on the other hand, is not, at least relative to benzene and the C8 aromatics, in great demand in the petrochemical industry as a basic building block chemical; consequently, substantial quantities of toluene are hydrodealkylated to benzene or disproportionated to benzene and xylene. Another use for toluene is associated with the transalkylation of trimethylbenzene with toluene to yield xylene.

Responsive to this demand for these aromatic products, the art has developed and industry has utilized a number of alternative methods to produce them in commercial quantities. One response has been the construction of a significant number of catalytic reformers dedicated to the production of aromatic hydrocarbons for use as feedstocks for the production of chemicals. As in the case with most catalytic processes, the principal measure of effectiveness for catalytic reforming involves the ability of the process to convert the feedstock to the desired products over extended periods of time with minimum interference of side reactions.

The dehydrogenation of cyclohexane and alkylcyclohexanes to benzene and alkylbenzenes is the most thermodynamically favorable type of aromatization reaction of catalytic reforming. This means that dehydrogenation of cyclohexanes can yield a high ratio of (aromatic product/nonaromatic reactant) than either of the other two types of aromatization reactions at a given reaction temperature and pressure. Moreover, the dehydrogenation of cyclohexanes is the fastest of the three aromatization reactions. As a consequence of these thermodynamic and kinetic considerations, the selectivity for the dehydrogenation of cyclohexanes if higher than the dehydroisomerization of dehydrocyclization.

Dehydroisomerization of alkylcyclopentanes is somewhat less favored, both thermodynamically and kinetically. its selectivity, although generally high, is lower than that for dehydrogenation.

Dehydrocyclization of paraffins is much less favored both thermodynamically and kinetically. In conventional reforming, its selectivity is much lower than that for the other two aromatization reactions.

The selectivity disadvantage of paraffin dehydrocyclization is particularly large for the aromatization of compounds having a small number of carbon atoms per molecule. Dehydrocyclization selectivity in conventional reforming is very low for C6 hydrocarbons. It increases with the number of carbon atoms per molecule, but remains substantially lower than the aromatization selectivity for dehydrogenation or dehydroisomerization of naphthenes having the same number of carbon atoms per molecule. A major improvement in the catalytic reforming process will require, above all else, a drastic improvement in dehydrocyclization selectivity that can be achieved while maintaining adequate catalyst activity and stability.

In the dehydrocyclization reaction, acyclic hydrocarbons are both cyclized and dehydrogenated to produce aromatics. The conventional 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.

A disadvantage of conventional naphtha reforming catalysts is that with C6-C8 paraffins, they are usually more selective for other reactions (such as hydrocracking) than they are for dehydrocyclization.

A major advantage of the catalyst of the present invention is its high selectivity for dehydrocyclization.

The po. sibiiity 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 have pores large enough for hydrocarbons in the gasoline boiling range to pass through. However, catalysts based upon these molecular sieves have not been commercially successful.

In the conventional method of carrying out the aforementioned dehydrocyclization, acyclic hydrocarbons to be converted are passed over the catalyst, in the presence of hydrogen, at temperatures of the order of 5000C and pressure of from 5 to 30 bars. Part of the hydrocarbons are converted into aromatic hydrocarbons, and the reaction is accompanied by isomerization and cracking reactions which also convert the paraffins into isoparaffins and light hydrocarbons.

The rate of conversion of the acyclic hydrocarbons into aromatic hydrocarbons varies with the number of carbon atoms per reactant molecule, 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 C6-C6 paraffins, particularly C8 paraffins. Catalysts based on a type L zeolite are more selective with regard to the dehydrocyclization reaction; can be used to improve the rate of conversion to aromatic hydrocarbons without requiring higher temperatures than those dictated by thermodynamic considerations (higher temperatures usually have a considerable adverse effect on the stability of the catalyst); and product excellent results with C6-C8 paraffins, but catalysts based on type L zeolite have not achieved commercial usage, apparently because of inadequate stability.

In one method of dehydrocyclizing 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 lithium, sodium, potassium, rubidium and cesium and containing at least one metal selected from the group which consists of metals of Group VIII of the Periodic Table of Elements, tin and germanium, said metal or metals including at least one metal from Group VIII 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 platinum/alkali metal/type L zeolite catalyst containing cesium or rubidium because of its excellent activity and selectivity for converting hexanes and heptanes to aromatics, but stability remains a problem.

The present invention overcomes the deficiencies of the prior art by using a catalyst comprising a type L zeolite, an alkaline earth metal selected from the group consisting of barium, strontium and calcium and a Group VIII metal to reform hydrocarbons. This catalyst give superior selectivity for converting acyclic hydrocarbons to aromatics than shown in prior art processes. This catalyst also gives satisfactory run length. The hydrocarbons are contacted with a catalyst comprising a type L 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).

Preferably, the catalyst contains a type L zeolite containing from 0.1% to 5% by weight platinum (preferably from 0.1% to 1.5% by weight platinum) and 0.1% to 40% by weight barium (preferably from 0.1% to 35% by weight barium, more preferably from 1% to 20% by weight barium). The catalyst preferably also contains an inorganic oxide binder. The majority of the type L zeolite crystals are preferably greater than 500 Angstroms, more preferably greater than 1 000 Angstoms. In the most preferred embodiment, at least 80% of the crystals of type L zeolite are greater than 1000 Angstroms.

The inorganic binder is preferably either a silica, alumina, an aluminosilicate or a clay. The hydrocarbons are contacted with the barium-exchanged type zeolite at a temperature of from 4000C to 6000C (preferably 4300C to 5500C); an LHSV of from 0.1 to 10 (preferably from 0.3 to 5); a pressure of from 1 atmosphere to 500 psig (preferably from 50 to 300 psig); and an H2/HC ratio of from 1:1 to 10:1 (preferably from 2:1 to 6:1).

In its broadest aspect, the present invention involves a catalyst comprising a type K zeolite, an alkaline earth metal and a Group VIII metal and its use in the reforming hydrocarbons, in particular, the dehydrocyclization of acyclic hydrocarbons at a high selectivity.

The term "selectivity" as used in the present invention is defined as the percentage of moles of acyclic hydrocarbons converted to atomatics relative to moles converted to aromatics and cracked products, i.e., 100 x moles of acyclic hydrocarbons converted to aromatics Selectivity = Moles of acyclic hydrocarbons converted to aromatics and cracked products Isomerization of paraffins and interconversion of paraffins and alkylcyclopentanes having the same number of carbon atoms per molecule 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 acyclic hydrocarbons to aromatics is a measure of the efficiency of the process in converting acyclic hydrocarbons to the desired and valuable products: aromatics and hydrogen, as opposed to the less desirable products of hydrocracking.

Highly selective catalysts produce more hydrogen than less selective catalysts because hydrogen is produced when acyclic hydrocarbons are converted to aromatics and hydrogen is consumed when acyclic hydrocarbons 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 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.

FEEDSTOCK Regarding the acyclic hydrocarbons that can be dehydrocyclized by the method of the present invention, they are most commonly paraffins but can in general be any acyclic hydrocarbon capable of undergoing ring-closure to produce an aromatic hydrocarbon. That is, it is intended to include within the scope of the present invention, the dehydrocyclization of any acyclic hydrocarbon capable of undergoing ring-closure to produce an aromatic hydrocarbon and capable of being vaporized at the dehydrocyclization temperatures used herein. More particularly, suitable acyclic hydrocarbons include acyclic hydrocarbons containing 6 or more carbon atoms per molecule such as C6-C20 paraffins, and C6-C20 olefins.Specific examples of suitable acyclic hydrocarbons are; (1) paraffins such as n-hexane, 2-methylpentane, 3-methylpentane, n-heptane, 2-methylhexane, 3-methylhexane, 3-ethylpentane, 2,5 di-methylhexane, n-octane, 2-methylheptane, 3-methylheptane, 4-methylheptane, 3-ethylhexane, n nonane, 2-methyloctane, 3-methyloctane, n-decane and the like compounds; and (2) olefins such as 1 hexane, 2-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene and the like compounds.

In a preferred embodiment, the acyclic hydrocarbon is a paraffinic hydrocarbon having about 6 to 10 carbon atoms per molecule. It is to be understood that the specific acyclic hydrocarbons mentioned above can be charged to the present method individually, in admixture with one or more of the other acyclic hydrocarbons, or in admixture with other hydrocarbons such as naphthenes, aromatics and the like. Thus mixed hydrocarbon fractions, containing significant quantities of acyclic hydrocarbons that are commonly available in a typical refinery, are suitable charge-stocks for the instant method; for example, highly paraffinic straight-run naphthas, paraffinic raffinates from atomatic extraction or adsorption.

C6-C8 paraffin-rich streams and the like refinery streams. An especially preferred embodiment involves a charge stock which is a paraffin-rich naphtha fraction boiling in the range of about 1 400F to about 3500 F. Generally, best results are obtained with a charge stock comprising a mixture of C6C,O paraffins, especially C6-C8 paraffins.

Preferably, the feedstock is substantially free of sulfur, nitrogen, metals and other known poisons for reforming catalysts. This catalysts especially sensitive to sulfur. The feedstock can be made substantially free of sulfur, nitrogen, metals, and other known poisons by conventional hydrofining techniques plus sorbers that remove sulfur compounds.

In the case of a feedstock which is not already low in sulfur, acceptable levels can be reacted by hydrofining the feedstock in a pretreatment zone where the naphtha is contacted with a hydrofining catalyst which is resistant to sulfur poisoning. A suitable catalyst for this hydrodesulfurization process is, tor example, an alumina-containing support and a minor proportion of molybdenum oxide, cobalt oxide and/or nickel oxide. Hydrodesulfurization is ordinarily conducted at 31 50C to 455"C, at 200 to 2000 psig, and at a liquid hourly space velocity of 1 to 5. The sulfur and nitrogen contained in the naphtha are converted to hydrogen sulfide and ammonia, respectively, which can be removed prior to reforming by suitable conventional processes.

DEHYDROCYCLIZATION REACTION According to one aspect of the present invention, the acyclic hydrocarbon is contacted with the catalyst in a dehydrocyclization zone maintained at dehydrocyclization conditions. This contacting may be accomplished by using the catalyst in a fixed bed system, a moving bed system, a fluidized system, or in a batch-type operation; however, in view of the danger of attrition losses of the valuable catalyst and of well-known operational advantages, it is preferred to use either a fixed bed system or a dense-phase moving bed system. It is also contemplated that the contacting step can be performed in the presence of a physical mixture with particles of a conventional dual-function catalyst of the prior art.In a fixed bed system, the acyclic hydrocarbon-containing charge stock is preheated by any suitable heating means to the desired reaction temperature and then passed into a dehydrocyclization zone containing a fixed bed of the catalyst. It is, of course, understood that the dehydrocyclization zone may be one or more separate reactors with suitable means therebetween to ensure that the desired conversion temperature is maintained at the entrance to each reactor. It is also important to note that the reactants may be contacted with the catalyst bed in either upward, downward, or radial flow fashion. In addition, the reactants may be in a liquid phase, a mixed liquid-vapor phase, or a vapor phase when they contact the catalyst, with best results obtained in the vapor phase.The dehydrocyclization system then preferably comprises a dehydrocyclization zone containing one or more fixed bed or dense-phase moving beds of the catalyst. In a multiple bed system, it is, of course, within the scope of the present invention to use the present catalyst in less than all of the beds with a conventional dual-function catalyst being used in the remainder of the beds. The dehydrocyclization zone may be one or more separate reactors with suitable heating means therebetween to compensate for the endothermic nature of the dehydrocyclization reaction that takes place in each catalyst bed.

Although hydrogen is the preferred diluent for use in the subject dehydrocyclization method, in some cases other art-recognized diluents may be advantageously utilized, either individually or in admixture with hydrogen, such as C, to C5 paraffins such as methane, ethane, propane, butane, and pentane; the like diluents, and mixtures thereof. Hydrogen is preferred because it serves the dual function of not only lowering the partial pressure of the acyclic hydrocarbon, but also of suppressing the formation of hydrogen-deficient, carbonaceous deposits (commonly called coke) on the catalytic composite. Ordinarily, hydrogen is utilized in amounts sufficient to insure a hydrogen to hydrocarbon mole ratio of about 1:1 to about 10:1 , with best results obtained in the range of about 2 :1 to about 6 :1.

The hydrogen charged to the dehydrocyclization zone will typically be contained in a hydrogen-rich gas stream recycled from the effluent stream from this zone after a suitable gas/liquid separation step.

The hydrocarbon dehydrocyclization conditions used in the present method include a reactor pressure which is selected from the range of about 1 atmosphere to about 500 psig, with the preferred pressure being about 50 psig to about 300 psig. The temperature of the dehydrocyclization is preferably about 4300C to about 5500C. As is well known to those skilled in the dehydrocyciization art, the initial selection of the temperature within this broad range is made primarily as a function of the desired conversion level of the acyclic hydrocarbon considering the characteristics of the charge stock and of the catalyst. Ordinarily, the temperature then is thereafter slowly increased during the run to compensate for the inevitable deactivation that occurs to provide a relatively constant value for conversion.

The liquid hourly space velocity (LHSV) used in the instant dehydrocyclization method is selected from the range of about 0.1 to about 10 hr-l, with a value in the range of about 0.3 to about 5 hF1 being preferred.

Reforming generally results in the production of hydrogen. Thus exogenous hydrogen need not necessarily be added to the reforming system except for pre-reduction of the catalyst and when the feed is first introduced. Generally, once reforming is underway, part of the hydrogen produced is recirculated over the catalyst. The presence of hydrogen serves to reduce the formation of coke which tends to poison the catalyst. Hydrogen is preferably introduced into the reforming reactor at a rate varying from 1 to about 10 moles of hydrogen per mole of feed. The hydrogen can be in admixture with light gaseous hydrocarbons.

If, after a period of operation, the catalyst has become deactivated by the presence of carbonaceous deposits, said deposits can be removed from the catalyst by passing an oxygencontaining gas, such as dilute air, into contact with the catalyst at an elevated temperature in order to burn the carbonaceous deposits from the catalyst. The regeneration can be performed either in the semiregenerative mode in which the reforming operation is interrupted after a more or less long period or time and catalyst regeneration is carried out, or in the onstream regenerative mode, in which a portion of the catalyst is regenerated while the reforming operation is contained over the remainder of the catalyst. Two types of onstream regeneration are known in the prior art, cyclic and continuous reforming.In cyclic reforming, the catalyst in one of a series of reactors is regenerated while reforming is continued in the rest of the plane. In continuous reforming, a portion of deactivated catalyst is removed from the plant, regenerated in a separate regeneration system while reforming is continued in the plant, and the regenerated catalyst is returned to the plant. The method of regenerating the catalyst will depend on whether there is a fixed bed, moving bed, or fluidized bed operation. Regeneration methods and conditions are well known in the art.

THE CATALYST The catalyst according to the invention is a type L zeolite charged with a Group Vlli metal and an alkaline earth metal.

TYPE L ZEOLITE Type L zeolites are synthetic zeolites. A theoreticai formula is Mg/n [(AlO2)9(SiO2)27] in which M is a cation having the valency n.

The real formula may vary without changing the crystalline structure; for example, the mole ratio of silicon to aluminum (Si/AI) may vary from 1.0 to 3.5.

Although there are a number of cations that may be present in zeolite L, in one embodiment, it is preferred to synthesize the potassium form of the zeolite, i.e., the form in which the exchangeable cations present are substantially all potassium ions. The reactants accordingly employed are readily available and generally water soluble. The exchangeable cations present in the zeolite may then conveniently be replaced by other exchangeable cations, as will be shown below, thereby yielding isomorphic form of zeolite L.

In one method of making zeolite L, the potassium form of zeolite L is prepared by suitably heating an aqueous metal aluminosilicate mixture whose composition, expressed in terms of the mole ratios of oxides, falls within the range: K2O/(K2 + Na2O) From about 0.33 to about 1 (K2O + Na2O)/SiO2 From about 0.35 to about 0.5 SiO2/Ai203 From about 10 to about 28 H2O/(K2O + Na2O) From about 1 5 to about 41 The desired product is hereby crystallized out relatively free from zeolites of dissimilar crystal structure.

The potassium form of zeolite L may also be prepared in another method along with other zeolitic compounds by employing a reaction mixture whose composition, expressed in terms of mole ratios of oxides, falls within the following range: K2O(K2O + Na2O) From about 0.26 to 1 (K2O + Na2O)/SiO2 From about 0.34 to about 0.5 SiO2/Al2O3 From about 1 5 to about 28 H2O/(K2Q + Na2O) From about 15 to about 51 It is to be noted that the presence of sodium in the reaction mixture is not critical to the present invention.

When the zeolite is prepared from reaction mixtures containing sodium, sodium ions are generally also included within the product as part of the exchangeable cations together with the potassium ions.

The product obtained from the above ranges has a composition, expressed in terms of moles of oxides, corresponding to the formula: 0.9-1 .3[(1 - x)K20, xNa2OJ :Al203 :5,2-6.9 SiO2 :yH2O wherein "x" may be any value from 0 to about 0.75 and "y" may be any value from 0 to about 9.

In making zeolite K, representative reactants are activated alumina, gamma alumina, alumina trihydrate and sodium aluminate as a source of alumina. Silica may be obtained from sodium or potassium silicate, silica gels, silicic acid, aqueous colioidal silica sols and reactive amorphous solid silicas. The preparation of typical silica sols which are suitable for use in the process of the present invention are described in U.S. patent No. 2,574,902 and U.S. Patent No. 2,597,872. Typical of the group of reactive amorphous solid silicas, preferably having an ultimate particle size of less than 1 micron, are such materials as fume silicas, chemically precipitated and precipitated silica sols.

Potassium and sodium hydroxide may supply the metal cation and assist in controlling pH.

In making zeolite L, the usual method comprises dissolving potassium or sodium aluminate and alkali, viz., potassium or sodium hydroxide, in water. This solution is admixed with a water solution of sodium silicate, or preferably with a water-silicate mixture derived at least in part from an aqueous colloidal silica sol. The resultant reaction mixture is placed in a container made, for example, of metal or glass. The container should be closed to prevent loss of water. The reaction mixture is then stirred to insure homogeneity.

The zeolite may be satisfactorily prepared at temperatures of from about 900C to 2000C the pressure being atmospheric or at least that corresponding to the vapor pressure of water in equilibrium with the mixture of reactants at the higher temperature. Any suitable heating apparatus, e.g., an oven, sand bath, oil bath of jacketed autoclave, may be used. Heating is continued until the desired crystalline zeolite product is formed. The zeolite crystals are then filtered off and washed to separate them from the reactant mother liquor. The zeolite crystals should be washed, preferably with distilled water, until the effluent wash water, in equilibrium with the product, has a pH of between about 9 and 12. As the zeolite crystals are washed, the exchangeable cation of the zeolite may be partially removed and is believed to be replaced by hydrogen cations.If the washing is discontinued when the pH of the effluent wash water is between about 10 and 11 , the (K2O + Na2O)/Al2O3 molar ratio of the crystalline product will be approximately 1.0. Thereafter, the zeolite crystals may be dried, conveniently in a vented oven.

Zeolite L has been characterized in "Zeolite Molecular Sieves" by Donald W. Breck, John Wiley Et Sons,1974, as having a framework comprising 1 8 tetrahedra unit cancrinite-type cages linked by double 6-rings in columns and crosslinked by single oxygen bridges to form planar 12-membered rings.

These 12-membered rings produce wide channels parallel to the c-axis with no stacking faults. Unlike erionite and cancrinite, the cancrinite cages are symmetrically placed across the double 6-ring units.

There are four types of cation locations: A in the double 6-rings, B in the cancrinite-type cages, C between the cancrinite-type cages, and D on the channel wall. The cations in site D appear to be the only exchangeable cations at room temperature. During dehydration, cations in site D probably withdraw from the channel walls to a fifth site, site E, which is located between the A sites. The hydrocarbon sorption pores are approximately 7 to 8 Angstroms in diameter.

A more complete description of these zeolites is given, e.g., in U.S. Patent No. 3,216,789 which, more particularly, gives a conventional description of these zeolites. U.S. Patent No.3,216,789 shows a type L zeolite useful in the present invention.

Various factors have an effect on the X-ray diffraction pattern of a zeolite. Such factors include temperature, pressure, crystal size, impurities, and type of cations present. For instance, as the crystal size of the type K zeolite becomes smaller, the X-ray diffraction pattern becomes broader and less precise. Thus, the term "zeolite L" includes any zeolites made up of cancrinite cages having an X-ray diffraction pattern substantially similar to the X-ray diffraction patterns shown in U.S. Patent No.

3,216,789.

Crystal size also has an effect on the stability of the catalyst. For reasons not yet fully understood, catalysts having at least 80% of the crystals of the type L zeolite larger than 1000 Angstroms give longer run length than catalysts having substantially all of the crystals of the type K zeolite between 200 and 500 Angstroms. Thus, the larger of these crystallite sizes of type L zeolite is the preferred support.

Type L zeolites are conventionally synthesized largely in the potassium form, i.e., in the theoretical formula given previously, most of the M cations are potassium. The M cations are exchangeable, so that a given type K zeolite, e.g., a type L zeolite in the potassium form, can be used to obtain type L zeolites containing other cations, by subjecting the type L zeolite to ion exchange treatment in an aqueous solution of appropriate salts. However, it is difficult to exchange all of the original cations, e.g., potassium, since some exchangeable cations in the zeolite are in sites which are difficult for the reagents to reach.

Other zeolites that could work in this invention are "zeolites of the L family", The term "zeolite of the L family" is defined as any zeolite which is made up of cancrinite cages to give a pore structure, the pores of which are bound by a 12 sided ring wherein the zeolite has dehydrocyclization activity when a Group VIII metal is introduced into the zeolite. Zeolites which are representative of a "zeolite of the L family" include type L zeolite disclosed in U.S. Patent 3,216,789, AG1 as disclosed in British Patent 1,393,365; AG4 as disclosed in British Patent 2,394,163; AG5 as disclosed in U.s. Patent 3,298,780; and K, Ba-G zeolite. U.S. Patents 3,216,789; 3,298,780, and 4,018,870 and British Patents 1,393,365 and 1,304,1 63 shows representative zeolites of the L family.

ALKALINE EARTH METALS An essential element of the present invention is the presence of an alkaline earth metal in the type L zeolite. That alkaline earth metal must be either barium, strontium or calcium. Preferably the alkaline earth metal is 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 the resulting catalyst has high activity, high selectivity and high stability.

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 solution containing excess Ba++ ions. The barium should preferably constitute from 0.10/0 to 35% of the weight of the zeolite, more preferably from 1% to 20% by weight.

GROUP VIII METALS The catalysts according to 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, paliadium and particularly platinum, which are more selective with regard to dehydrocyclization and are also 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%, more preferably from 0.1% to 1.5%.

Group VIII metals are introduced into the L zeolite by synthesis, impregnation or exchange in an aqueous solution of an appropriate salt. When it is desired to introduce two Group VIII metals into the zeolite, the operation may be carried out simultaneously or sequentially.

By way of example, platinum can be introduced by impregnating the zeolite with an aqueous solution of tetrammineplatinum (Il) nitrate, tetrammineplatinum (II) hydroxide, dinitrodiamino-piatinuni ortetrammineplatinum (II) chioride. In an ion exchange process, platinum can be introduced by using cationic platinum complexes such as tetrammineplatinum (II) nitrate.

CATALYST PELLETS An inorganic oxide can be used as a carrier to bind the type Zeolite containing the Group VIII metal and alkaline earth metal and give the catalyst additional strength. The carrier can be a natural or a synthetically produced inorganic oxide or combination of inorganic oxides. Preferred loadings of inorganic oxide are from 5% to 25% by weight of the catalyst. Typical inorganic oxide supports which can be used include aluminosilicates (such as clays), alumina, and silica, in which acidic sites are preferably exchanged by cations which do not impart strong acidity.

One preferred inorganic oxide support is "Ludox", which is a colloidal suspension of silica in water, stabilised with a small amount of alkali.

When an inorganic oxide is used as a carrier, there are two preferred methods in which the catalyst can be made, although other embodiments could be used.

In the first preferred embodiment, the type L zeolite is made, then the type L zeolite is ion exchanged with a barium solution, separated from the barium solution, dried and calcined, impregnated with platinum, calcined, and then mixed with the inorganic oxide and extruded through a die to form cylindrical pellets. Advantageous methods of separating the type L zeolite from the barium and platinum solutions are by a batch centrifuge or a pressed filter. This embodiment has the advantage that all the barium and platinum are incorporated on the type L zeolite and none are incorporated on the inorganic oxide. It has the disadvantage that the type L zeolite is of small size, which is hard to separate from the barium solution and the platinum solution.

In the second preferred embodiment, the type L zeolite is mixed with the inorganic oxide and extruded through the die to form cylindrical pellets, then these pellets are ion exchanged with a barium solution, separated from the barium solution, impregnated with platinum, separated from the platinum solution, and calcined. This embodiment has the advantage that the pellets are easy to separate from the barrium and platinum solutions, but it has the disadvantage that barium and platinum may be also deposited on the inorganic oxide carrier which could catalyze undesirable reactions. Thus, the choice of which embodiment is used depends on the trade-off between catalyst selectivity and ease of separation of the catalyst from the barrium and platinum solutions.

In a third possible embodiment, the type L zeolite is ion exchanged with a barium solution, dried and calcined, mixed with the inorganic oxide and extruded through the die to form cylindrical pellets, then these pellets are impregnated with platinum, separated from the platinum solution, and calcined.

In the extrusion of type L zeolite, various extrusion aids and pore formers can be added. Examples of suitable extrusion aids are ethylene glycol and stearic acid. Examples of suitable pore formers are wood flour, cellulose and polyethylene fibers.

After the desired Group VIII metal or metals have been introduced, the catalyst is treated in air or diluted O2 at about 2600C to 5000C and then reduced in hydrogen at temperatures of from 2000C to 7000C, preferably 4800C to 6200C, more preferably 5300C to 6200C.

At this stage the catalyst 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 neutralize 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, 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 acyclic hydrocarbons (especially C8-C8 paraffins) to aromatics, it is also surprisingly found that the selectivity for conversion of methylcyciopentane to benzene is excellent. This reaction, which on conventional 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.

Preferably, the dehydroisomerization of alkylcyclopentanes is carried out at a temperature of from 8000F to 10000F (more preferably, from 8200F to 9500F); an LHSV of from 0.1 to 20 (more preferably, from 0.5 to 10); a pressure of from 0 to 500 psig (more preferably, from 1 atmosphere to 300 psig); and an H2/HC ratio of from 0 to 20:1 (more preferably, from 1:1 to 10:1).

It is also surprisingly found that the selectivity for conversion of toluene to benzene is also excellent Preferably, the dealkylation of toiuene is carried out at a temperature of rom 8000F to 1 2000F (more preferably, from 8500F to 1 1000F); an LHSV of from 0.1 to 20 (more preferably, from 0.3 to 10); a pressure of from 0 to 3000 psig (more preferably, from 200 to 2000 psig); and H2/HC ratio of from 0 to 20:1 (more preferably, from 1:1 to 10:1).

Another advantage of this invention is that the catalyst of the present invention is more stable than prior art zeolitic 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.

EXAMPLES The invention will be further illustrated by the following examples which set forth a particular advantageous method and composition embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

EXAMPLE I An Arabian Light straight run naphtha which has been hydrofined to remove sulfur, oxygen and nitrogen was reformed at 100 psig, 1 LHSV, and 6 h2/HC by three different catalysts. The feed contained 80.2v% paraffins, 1 6.7v% naphthenes, and 3.1 v% aromatics, and it contained 21.8v% C5, 52.9v% C6, 21 .3v% Cv, and 3.2v% C8 In the first run, the Arabian Light straight run naphtha was reformed at 4990C using a commercial sulfided platinum-rhenium-alumina catalyst prepared as disclosed in U.S. Patent No. 3,415,737.

In the second run, the Arabian Light straight run naphtha was reformed at 4930C using a platinum-potassium-type L zeolite catalyst formed by: (1) impregnating a potassium-type L zeolite having crystal sizes of from about 1000 to 4000 Angstroms containing 0.8% platinum impregnated as tetrammineplatinum (II) nitrate; (2) drying the catalyst; (3) calcining the catalyst at 2600 C; and (4) reducing the catalyst in hydrogen at 4809C to 5000C for 1 hour.

In the third run, the prowess of the present invention, the Arabian Light straight run naphtha was reformed at 493 OC using a platinum-barium-type Zeolite catalyst formed by: (1) ion exchanging a potassium-type L zeolite having crystal sizes of from about 1000 to 4000 Angstroms 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) drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 5900 C; (4) impregnating the catalyst with 0.8% platinum using tetrammineplatinum (II) nitrate; (5) drying the catalyst; (6) calcining the catalyst at 2600C; and (7) reducing the catalyst in hydrogen at 4800C to 5000C for 1 hour.

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

TABLE I 4990C Pt/Re/ 4930C 4930C Feed Alumina Pt/K/L Pt/Ba/l C1Wt%Fd 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 iQ 5.1 13.6 6.7 5.6 NC5 11.3 9.8 12.6 12.6 C6+P + N 81.3 13.4 7.8 9.3 Benzene 1.5 15.1 40.6 43.8 C, + Aromatics .8 1 5.8 12.7 15.0 C8 + LV% Yield 63 69.9 74.4 Hydrogen, SCF/B 470 1660 2050 Selectivity, Mole % 20 72 87 C6 + PArnmatics This series of runs shows that the use df 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 increased production of hydrogen gas, 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 plus C2 are produced.

EXAMPLE II A second series of runs was made usiing hydrofined n-hexane as feed. All runs in this series were made at 4900C, 100 psig, 3 LHSV and 3 H2/HC.

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

In the second run, a platinum-barium-type L zeolite was used which has been prepared by the procedures shown in the third run of Example I except that the barium nitrate solution was 0.3 molar instead of 0.17 molar. The results of these runs are given below in Table II.

TABLE II Selectivity for Conversion N-hexane 5 Hrs 20 Hrs 5 Hrs 20 Hrs Pt/K/L 70 59 76 79 Pt/Ba/L 85 85 89 92 Thus, in operation, the incorporation of barium into type L 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 was used.

EXAMPLE III A third series of runs was made using different cation exchanges. All runs in this series were made at 4900 C, 100 psig and 6 H2/HC. The feed which was hydrofined, contained 80.9v% paraffins, 1 6.8v% naphthenes, 1 .7v% aromatics, 0.4v% olefins and it contained 2.6v% C5, 47.6v% CG, 43.4v% C7 and 6.3v% C8 hydrocarbons.

In the first run, a platinum-barium-type L zeolite was used which had been prepared by the procedures shown in the second run of Example II. It was tested at an LHSV of 2.0.

In the second run, a platinum-calcium-type L zeolite was used which had been prepared by the same procedures except that a 0.3 molar calcium nitrate solution was used. It was tested at an LHSV of 2.0.

In the third run, a platinum-strontium-type L zeolite was used which had been prepared by the same procedures except that a 0.3 molar strontium nitrate solution was used in the exchange. It was tested at an LHSV of 2.0.

In the fourth run, a platinum-cesium-type L zeolite was used which had been prepared by the same procedures except that a 0.3 molar cesium nitrate solution was used in the exchange. It was tested at an LHSV of 2.0.

In the fifth run, a platinum-barium-type L zeolite was used which had been prepared by the same procedures as the first run. It was tested at an LHSV of 6.0.

In the sixth run, a platinum-potassium-type L zeolite was used which had been prepared by the procedures shown in the second process of Example I. It was tested at an LHSV of 6.0.

In the seventh run, a platinum-rubidium-type L zeolite was used which had been prepared by the procedures of the first run except that a 0.3 molar rubidium nitrate solution was used in the exchange. It was tested at 6.0 LHSV.

In the eighth run, a platinum-lanthanum-type L zeolite was used which had been prepared by the procedures of the first run except that a 0.3 molar lanthanum nitrate solution was used in the exchange.

It was tested at 6.0 LHSV.

In the ninth run, a platinum-magnesium type L zeolite was used which had been prepared by the procedures of the first run except that a 0.3 molar magnesium nitrate solution was used in the exchange. It was tested at 6.0 LHSV.

In the tenth run, a platinum-lithium type L zeolite was used which had been prepared by the procedures of the first run except that a 0.3 molar lithium nitrate solution was used in the exchange. It was tested at 6.0 LHSV.

In the eleventh run, a platinum-sodium type L zeolite was used which had been prepared by the procedures of the first run except that a 0.3 molar sodium nitrate solution was used in the exchange. It was tested at 6.0 LHSV. The results of all eleven runs are shown in Table Ill.

TABLE Ill Selectivity Aromatics Paraffin Conversion Mole % Mole % Feed 3 hrs 20 hrs 3 hrs 20 hrs 3 hrs 20 hrs 2.0 LHSV Pt/Ba/L 87 87 83 85 75 76 Pt/Ca/L 96 93 63 70 65 70 Pt/Sr/L 92 83 61 69 62 63 Pt/Cs/L 84 73 73 75 66 61 6.0 LHSV Pt/Ba/L 73 63 80 83 64 59 Pt/K/L 75 66 71 75 60 57 Pt/Rb/L 84 74 72 77 65 63 Pt/La/L 63 55 63 58 50 48 Pt/Mg/L 23 < 5 23 - 22 14 Pt/Li/L 77 72 70 74 61 60 Pt/Na/L 74 67 72 75 60 Thus, in operation, the incorporation of barium into type L zeolites causes a dramatic improvement in selectivity over type L zeolites having other cations (more than 25% reduction in the amount of cracked products produced for L zeolite having any other cation).

EXAMPLE IV A platinum-barium-type L zeolite was used in two runs which had been prepared by the procedures shown in the second run of Example II. In the first run, the L zeolite crystallite size was about 1000 to 2000 Angstroms by transmission electron microscopy. In the second run, the L zeolite crystallite size was about 400 Angstroms. The feed of both runs contained 70.2v% paraffins, 24.6v% naphthenes, 5.0v% aromatics, and 29.7v% C5,s, 43.4v% C6s, 21 .2v% C7'S, 5.0v% C8,s, 0.6v% C9,s.

Research octane clear of the feed was 71.4. The catalyst of the first run was reduced in hydrogen for 20 hours at 10500 F. The catalyst of the second run was reduced in hydrogen for 2 hours at 10500 F. The run conditions were 1000 psig, 1.5 LHSV, and 6.0 H2/HC recycle. The temperature was controlled to give 50 wt % aromatics in the C5 + liquid product, which corresponds to 89 research octane clear. The results of the first run are shown in Table IV.

TABLE IV For 50 wt % Aromatics C5 + Yield Run Time, Hrs Temperature OF LV % 500 858 86.4 1000 868 86.2 2000 876 86.1 2500 880 86.2 The results of the second run are shown in Table V.

TABLE V For 50 wt % Aromatics C5+ Yield Run Time, Hrs. Temperature OF LV % 100 870 87 200 881 86 400 893 85 Thus, in operation, the large crystal size catalyst of the present invention gives exceptionally long run life, whereas the small crystal size catalyst deactivates much faster.

EXAMPLE V A fifth series of runs was made to show the effects of reduction temperature. The feed used was the same as in Example i. Run conditions were 4900C, 100 psig, 2.0 LHSV, 6.0 H2/HC.

The catalyst used in the first two runs was Pt/Ba/K/L made in the third process of Example I, except that the barium exchange was done three times with a 1 molar barium nitrate solution; this gave only a small increase in barium content.

The catalyst in the last two runs was a Pt/K/L made as in the second process of Example I.

Results obtained after 3 hours of operation are shown in Table VI.

TABLE VI Reduction Aromatics Selectivity Conditions Mole % Feed Mole % Pt/Ba/K/L 4900C, 1 Hr 59 78 Pt/Ba/K/L 6200C, 20 Hrs 60 89 Pt/K/L 4900C, 1 Hr 55 66 Pt/K/L 6200 C, 20 Hrs 23 23 The results show a large and surprising difference in the effect-of preparation on the two catalysts.

The selectivity of the barium-containing catalyst was substantially improved, while the selectivity of the catalyst without barium was very substantially decreased.

EXAMPLE VI A methylcyclopentane feed which had been hydrofined to remove sulfur, oxygen and nitrogen was dehydroisomerized at 9200 F, 100 psig, 2 LHSV and 6 H2/HC by a dehydroisomerization catalyst. This catalyst was prepared by (1) ion exchanging a potassium-barium-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) drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 5800 C; (4) impregnating the catalyst with 0.8% platinum using tetrammineplatinum (II) nitrate; (5) drying the catalyst; (6) calcining the catalyst at 2600C and (7) reducing the catalyst in hydrogen at 4800C to 50000C.

The feed contained 73 wt % methylcyclopentane. The distillation data for the feed was start/1 480F, 5%/1 540F, 10%/1 570F, 30%1 590F, 50%/1 600F, 70%/1 61 0F, 90%/1 650F, 95%/173 F and end point/2220F. The feed contained 10 vol % paraffins, 80 vol % naphthenes, and 10 vol % aromatics. The conversion was 78% after three hours and 32% after twenty hours. The selectivity for dehydroisomerization was 82 mole % after three hours and 86% after twenty hours.

EXAMPLE Vll An Arabian straight run feed which had been hydrofined to remove sulfur, oxygen and nitrogen was dealkylated at 10500F, 100 psig, 4 LHSV, and 3 H2/HC by a dealkylation catalyst. This catalyst was prepared by (1) ion exchanging a potassium-barium-type L 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) drying the resulting barium-exchanged type L zeolite catalyst; (3) calcining the catalyst at 5909C; (4) impregnating the catalyst with 0.8% platinum using tetrammineplatinum (II) nitrate; (5) drying the catalyst; (6) calcining the catalyst at 2600C; and (7) reducing the catalyst in hydrogen at 4800C to 5000C.

The feed contained 1 vol % C4, 22 vol % C5, 53 vol. % C6, 21 vol % C, and 3 vol % C8; 78 vol % paraffins, 1 9 vol % naphthenes, and 3 vol % aromatics. The results of this run is given in the table below (all percentages given in weight %). The conversion of C6 + paraffins was 96.04 mole %, and the selectivity for aromatization was 84.02.

TABLE VII Feed Product Methane 0 7.66 Ethane 0 5.66 Propane 0 6.49 iC4 .08 1.55 nC4 .52 6.49 iCg 5.88 3.26 nC5 12.61 2.81 C5+ 80.91 70.34 H2 0 2.91 Benzene 1.69 51.10 C,+ Aromatics 1.62 10.92 While the present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitutions which may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

Claims (24)

1. A zeolite catalyst comprising: (a) a zeolite of the L family (as hereinbefore defined); (b) at least one Group VIII metal; and (c) an alkaline earth metal selected from barium, strontium and calcium.

2. A catalyst as claimed in Claim 1, wherein the zeolite is a type L zeolite.

3. A catalyst as claimed in Claim 2, wherein said alkaline earth metal is barium and said Group VIII metal is platinum.

4. A catalyst as claimed in Claim 3, wherein the catalyst contains from 0.1% to 35% by weight barium and from 0.1% to 5% by weight platinum.

5. A catalyst as claimed in Claim 4, wherein the catalyst contains from 1 to 20% by weight barium and from 0.1% to 1.5% by weight platinum.

6. A catalyst as claimed in Claim 2, 3, 4 or 5, wherein the majority of the crystals of said type L zeolite are larger than 500 Angstroms.

7. A catalyst as claimed in Claim 6, wherein the majority of the crystals of said type L zeolite are larger than 1000 angstroms.

8. A catalyst as claimed in Claim 7, wherein at least 80% of the crystals of said type L zeolite are larger than 100 Angstroms.

9. A catalyst as claimed in any preceding claim and further comprising an inorganic binder.

10. A catalyst as claimed in Claim 9, wherein the inorganic oxide binder is a silica, alumina or aluminosilicate.

11. A zeolite catalyst in accordance with Claim 2, substantially as described in any one of the foregoing Examples.

12. A method of reforming a hydrogen feed comprising contacting said hydrocarbon feed with a catalyst as claimed in any one of Claims 1 to 10.

13. A method according to Claim 12, wherein said contacting occurs at a temperature of from 400 to 6000C: an LHSV of from 0.1 to 10; a pressure of from 1 atmosphere to 500 psig; and an H2/HC ratiooffrom 1:1 to 10:1.

14. A method according to Claim 1 3, wherein said contacting occurs at a temperature of from 430 to 5000 C; an LHSV of from 0.5 to 5; a pressure of 500 to 300 psig; and an H2/HC ratio of from 2:1 to 6:1.

15. A method of dehydrocyclizing acyclic hydrocarbons under dehydrocyclization conditions with a catalyst as claimed in any one of Claims 1 to 10.

1 6. A method according to Claim 1 5, wherein said contacting occurs at a temperature of from 430 to 5500C; and LHSV of from 0.3 to 5; a pressure of from 50 to 300 psig; and an H2/HC ratio of from 2:1 to 6:1.

17. A method of dehydroisomerization of alkylcyclopentanes under dehydroisomerization conditions to produce aromatics by contacting said alkylcyclopentanes with a catalyst as claimed in any one of Claims 1 to 10.

18. A method according to Claim 1 7, wherein said contacting occurs at a temperature of from 438 to 51 00C; an LHSV of from 0.5 to 10; a pressure of from 1 atmosphere to 300 psig; and an H2/HC ratio of from 1:1 to 10:1.

19. A method of dealkylation of toluene under dealkylation conditions to produce benzene by contacting said toluene with a catalyst as claimed in any one of Claims 1 to 10.

20. A method according to Claim 19, wherein said contacting occurs at a temperature of from 454 to 5930C; an LHSV of from 0.3 to 10; a pressure of from 200 to 2000 psig; and an H2/HC ratio of from 1:1 to 10:1.

21. A method of forming a catalyst as claimed in Claim 2, which comprises: (a) ion exchanging a type L zeolite containing potassium with a solution containing barium ions; (b) drying said ion exchanged type L zeolite; (c) calcining said dried type L zeolite; (d) impregnating said calcined type L zeolite with platinum using tetrammineplatinum (II) nitrate; (e) drying said impregnated type L zeolite; and (f) calcining said dried impregnated type L zeolite.

22. A method of reforming a hydrocarbon feed according to Claim 12, wherein prior to use said catalyst is reduced in a hydrogen atmosphere at a temperature of from 480 to 6200 C.

23. A method according to Claim 22, wherein said catalyst is reduced in a hydrogen atmosphere at a temperature of from 530 to 6200 C.

24. A method of reforming a hydrocarbon feed in accordance with Claim 12, substantially as described in any one of the foregoing Examples.