FR2520636A1 - L-TYPE ZEOLITIC COMPOSITION CONTAINING PLATINUM AND BARIUM AND ITS APPLICATION TO HYDROCARBON REFORMING - Google Patents

Abstract

THE INVENTION CONCERNS A NEW CATALYST. THE CATALYST OF THE INVENTION CONTAINS AN L-TYPE ZEOLITE, A GROUP VIII METAL AND AN ALKALINO-EARTH METAL. THIS CATALYST CONTAINS AN L-TYPE ZEOLITE, 0.1 TO 5 BY PLATINUM WEIGHT AND 1 TO 20 BY BARYUM WEIGHT. APPLICATION IN PARTICULAR TO THE DEHYDROCYCLIZATION OF ALKANES.

Description

The present invention relates to a novel catalyst and process

  the use of this catalyst in the reforming of hydrocarbons, more particularly in

  dehydrocyclization of acyclic hydrocarbons containing

  containing at least 6 carbon atoms, to form the hydro-

  corresponding aromatic carbides.

  Catalytic reforming is a well-known operation in the petroleum industry, which relates to the processing of naphtha fractions to improve octane by aromatics production. The most important hydrocarbon reactions that take place during

  reforming include the dehydrogenation of cyclo-

  hexanes to aromatic hydrocarbons, dehydro-

  isomerization of alkylcyclopentanes to aromatic hydrocarbons

  and the dehydrocyclization of acyclic hydrocarbons

  aromatic hydrocarbons Several other reactions

  also occur, and include the following: dealkylation of alkylbenzenes, isomerization of paraffins,

  and hydrocracking reactions which produce hydrocarbons

  light gaseous bursts, eg methane, ethane, propane and butane Hydrocracking reactions must be particularly minimized during reforming, because they lower the yield of products boiling in

  the range of gasoline and hydrogen.

  Due to the demand for high octane gasoline for use as a fuel for

  engine, etc., extensive research is currently

  devoted to the development of reform catalysts

  mage and improved catalytic reforming processes.

  For the success of reforming processes, catalysts must have good selectivity, that is they must be able to give high yields of liquid products in the boiling range of gasoline,

  containing high concentrations of aromatic hydrocarbons

  high octane numbers and, consequently, low yields of light gaseous hydrocarbons. Catalysts

  have a good activity so that the weather

  It is also necessary for catalysts to have good stability so that the activity and selectivity characteristics can be maintained for prolonged periods of time in order to obtain a product of guaranteed quality. or they may be sufficiently regenerable to allow frequent regeneration without their

be altered.

  Catalysts comprising platinum, for example

  platinum attached to alumina, are well known and

  naphtha reforming products The most important products of catalytic reforming are the

  benzene and alkylbenzenes These aromatic hydrocarbons

  are very interesting as high-level components

octane number of gasoline.

  Catalan reforming is also an operation

  important for the chemical industry because of the growing demand for aromatic hydrocarbons for use in

  various chemicals such as synthetic fiber

  thesis, insecticides, adhesives, detergents, plastics, synthetic rubbers and pharmaceutical products, high-octane gasoline, perfumes, drying oils, ion exchange resins and various other products Well known to those skilled in the art An example of this application lies in the production of alkylated aromatic hydrocarbons such as ethylbenzene, cumene and dodecylbenzene by the use of mono-olefins suitable for alkylating benzene. example of this application lies in the field of chlorination of benzene to form chlorobenzene which is then used to prepare

  phenol by hydrolysis with sodium hydroxide.

  The main use of phenol is in the production of phenol-formaldehyde resins and plastics. Another way of obtaining phenol is to use cumene as a starting material and involves the oxidation of cumene by air to cumene hydroperoxide which can then be decon 'Put in phenol and acetone by the action of an acid

  The demand for ethylbenzene comes mainly from

  its use for the production of styrene by selective dehydrogenation; styrene is used for the production of styrene-butadiene rubber and polystyrene. Ortho-xylene is normally oxidized to phthalic anhydride by vapor reaction with air in the presence of a pentoxide catalyst. vanadium Phthalic anhydride is used to produce plasticisers, polyesters and resins. The demand for para-xylene is mainly due to

  its use in the production of terephthalic acid

  or dimethyl terephthalate which is in turn reacted with ethylene glycol and polymerized

  to form polyester fibers Benzene is also

  It is in great demand for its use to produce aniline, "nylon", maleic anhydride, solvents and similar petrochemicals. On the other hand, at least in comparison with benzene and C 8 aromatic hydrocarbons. , toluene is not very

  in the petrochemical industry as a chemical product

  elementary molecule for the construction of molecules; as a result, large amounts of toluene are hydrodealkylated to benzene or disproportionated to benzene and xylene Another application of toluene is related to its transalkylation of trimethylbenzene with toluene

to form xylene.

  To meet this demand for such flavoring products, the technique has developed, and the industry has implemented, several other processes allowing

  to obtain them on an industrial scale One of the

  This has involved the construction of a large number of catalytic reforming equipment dedicated to the production of aromatic hydrocarbons for use as

  starting materials for obtaining chemicals.

  As with most catalytic processes, the primary mode of efficiency assessment for catalytic reforming involves the ability of the process to convert the starting materials into desired products for extended periods of time, with a high degree of efficiency. minimum interference

  from side reactions.

  The dehydrogenation of cyclohexane and alkyl

  Benzene and alkylbenzene cyclohexanes is the most thermodynamically advantageous type of catalytic reforming aromatization reaction. This means that the dehydrogenation of cyclohexanes can give a greater ratio of aromatic product to non-aromatic reactant than any of the other two types of aromatization reactions, at a temperature and a

  In addition, the dehydrogenase

  cyclohexane is the fastest of the three reactions

  It follows from these considerations that

  dynamics and kinetics that the selectivity towards the dehydrogenation of cyclohexanes is greater than the selectivity with respect to dehydroisomerisation or

  dehydrocyclization The dehydroisomerization of alkyl-

  cyclopentanes is a little less favored, both thermodynamically and kinetically. Its selectivity, although generally strong, is lower.

  that the selectivity towards the dehydrogenation the dehydro-

  paraffins cyclization is much less advantageous in terms of thermodynamics and kinetics. In conventional reforming, its selectivity is much lower than

  the selectivity towards the other two aromatics reactions

tisation.

  The disadvantage of selectivity of the dehydro-

  paraffins cyclization is particularly great with regard to the aromatization of compounds having a small number of carbon atoms per molecule The selectivity of the dehydrocyclization in a conventional reforming is very low for C 6 hydrocarbons It increases with the number of carbon atoms per molecule, but

  remains significantly lower than the flavor selectivity

  the dehydrogenation or dehydroisomerisation of naphthenes having the same number of carbon atoms per molecule.

  catalytic reforming requires, above all, an improvement

  the dehydrocyclization selectivity that can be achieved while maintaining an activity and

  satisfactory stability of the catalyst.

  In the dehydrocyclization reaction,

  Acyclic hydrocarbons are both cyclized and dehydrogenated.

  generated to produce aromatic hydrocarbons Conventional methods for conducting such reactions

  dehydrocyclization are based on the use of

  lysers comprising a noble metal attached to a support.

  Known catalysts of this kind are based on alumina

  carrying 0.2 to 0.8% by weight of platinum and, advantageously,

a second auxiliary metal.

  A disadvantage of conventional naphtha reforming catalysts is that, in the case of C 6 to C 8 paraffins, they are usually more selective for other reactions (such as hydrocracking) than they are for dehydrocyclization. important advantage

  of the present invention is its strong selection

  towards dehydrocyclization.

  The possibility of using supports other than alumina has also been studied and it has been proposed

  to use some molecular sieves such as zeolites

  X and Y lites, whose pores are large enough for hydrocarbons boiling in the boiling range of gasoline through them However, catalysts fixed on these molecular sieves have not had commercial success.

  In the classical mode of conducting dehydro-

  cyclization mentioned above, hydro-

  acyclic carbides to be converted to the catalyst in advance.

  hydrogen at temperatures of the order of 500.degree.

  and pressures of 0.5 to 3.0 M Pa.

  The carbides are converted to 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 acyclic hydrocarbons to aromatic hydrocarbons varies with

  number of carbon atoms per molecule of reactant

  the conditions of the reaction and the nature of the

  lyst. The catalysts used up to now have given moderately satisfactory results with heavy paraffins, but less satisfactory results have been obtained with C 6 to C 8 paraffins, in particular C 6 paraffins. Catalysts fixed on a zeolite of the following type L are more selective towards the dehydrocyclization reaction; they can be used to improve the conversion rate of aromatic hydrocarbons without requiring higher temperatures than those

  are dictated by thermodynamic considerations.

  that (high temperatures usually exert a

  considerable disadvantageous effect on the stability of the

  lyst); and they give excellent results with C 6 to C 8 paraffins, but catalysts fixed on an L-type zeolite have not imposed themselves in the industry,

  obviously because of insufficient stability.

  In another process for the dehydrocyclization of aliphatic hydrocarbons, hydrocarbons are contacted in the presence of hydrogen with a catalyst

  consisting essentially of an L-type zeolite

  tradable cations of which at least 90% are

  alkali metal ions selected from the group

  comprising lithium, sodium, potassium, rub-

  dium and cesium, and containing at least one metal selected from the group consisting of metals of Group VIII of the Periodic Table of the Elements, tin and germanium, said metal or said metals comprising at least one Group VIII metal of said Periodic Table producing a dehydrogenating effect, so as to convert at least a part

  of the charge in aromatic hydrocarbons.

  A particularly advantageous variant of this process uses a catalyst of the platinum / metal form

  type L alkaline / zeolite, containing cesium or

  dium because of its excellent activity and excel-

  slow selectivity towards the conversion of hexanes and heptanes to aromatic hydrocarbons, but the stability

remains problematic.

  The present invention overcomes the shortcomings of the prior art using a catalyst comprising an L-type zeolite, an alkaline earth metal selected from the group consisting of barium, strontium and calcium.

  and a Group VIII metal, for hydrocarbon reforming

  This catalyst allows a better selectivity towards

  the conversion of acyclic hydrocarbons into hydrocarbons

  These catalysts also offer a satisfactory operating time. The hydrocarbons are brought into contact with a catalyst comprising an L-type zeolite, at least one Group VIII metal (advantageously platinum); and an alkaline earth metal selected in the

  group consisting of barium, strontium and calcium (especially

barium).

  The catalyst advantageously contains: (a) a type L zeolite containing 0.1 to 5% by weight of platinum (advantageously 0.1 to 1.5% by weight of platinum) and 0.1 to% by weight of barium ( preferably 0.1 to 35% by weight of barium, especially 1 to 20% by weight of barium); and (b) an inorganic binder Most zeolite-type L crystals are advantageously greater than 50 nm,

  especially in excess of 100 nm in the form of

  most advantageous, at least 80% of the crystals

  type L zeolite are greater than 100 nm.

  The hydrocarbons are advantageously a silica, alumina, an aminosilicate or a clay. The hydrocarbons are brought into contact with the zeolite treated by exchange with barium at a temperature of 400 to 600 ° C. (in particular 430 to 5500 ° C.); a liquid hourly space velocity (VSHL)

  from 0.1 to 10 (in particular from 0.3 to 5); manometer pressure

  from 0 to 3.5 M Pa (especially from 0.35 to 2.1 M Pa); and

  an H 2 / HC ratio of 1: 1 to 10: 1 (especially 2: 1 to 6: 1).

  In its broadest aspect, the present invention

  This involves a catalyst comprising an L-type zeolite, an alkaline earth metal and a Group VIII metal and its use in hydrocarbon reforming, particularly in the dehydrocyclization of hydrocarbons.

  acyclic with high selectivity.

  The term "selectivity" as used herein is defined as the percentage of

  moles of acyclic hydrocarbons converted to hydrocarbons

  aromatic compounds with respect to the number of moles converted to aromatic hydrocarbons and cracked products, namely x moles of acyclic hydrocarbons converted to Selectivity aromatic hydrocarbons

Moles of acyclic hydrocarbons

  cliques converted into aromatic hydrocarbons and cracked products

  The isomerization of paraffins and the

  conversion of paraffins and alkylcyclopentanes with the same number of carbon atoms per molecule are not taken into account in the determination of selectivity. The expression "selectivity towards nhexane"

  used in this memo is defined as

  sensing the percentage of moles of n-hexane transformed

  in aromatic hydrocarbons with respect to the trans moles

  formed in aromatic hydrocarbons and

c.

  Selectivity towards the transformation of hydro-

  acyclic carbides into aromatic hydrocarbons gives

  a measure of the efficiency with which the

  forms acyclic hydrocarbons into the desired products and

  interesting, namely aromatic and hydro-

  gene, as opposed to the less desirable products of hydrocracking.

  Very selective catalysts produce more

  hydrogen as catalysts of lower selectivity,

  because hydrogen is produced when hydrocarbons

  Acyclic bures are converted into aromatic hydrocarbons

  and hydrogen is consumed when hydrocarbons are

  Acyclic bures are converted into 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 the use of very selective catalysts is that the hydrogen produced by very selective catalysts is purer than that

  which is produced by catalysts of lesser selectivity.

  This greater purity results from the fact that more hydrogen is produced, while it is formed less

  low boiling point hydrocarbons (cracked products)

  The purity of the hydrogen produced in the reforming is critical if, as is usually the case - in an integrated refinery, the hydrogen produced is used in processes such as hydrotreating and hydrocracking, which require less specific partial pressures of hydrogen If purity becomes too low, hydrogen can no longer be used

  for this purpose and should be used in a less

  health, for example as a fuel gas.

  With regard to acyclic hydrocarbons which can be dehydrocyclized by the process of

  invention, it is most often paraffi-

  but these hydrocarbons can usually

  any acyclic hydrocarbon capable of

  In fact, in the context of the present invention it is desired to include the dehydrocyclization of any acyclic hydrocarbon.

  able to undergo a cyclization to produce a hydro-

  aromatic carbide and capable of being vaporised at

  dehydrocyclization eratures used according to the invention.

  More particularly, acyclic hydrocarbons

  include acyclic hydrocarbons containing

  6 or more carbon atoms per molecule, such

  C 6 to C 20 paraffins and C 6 to C 20 olefins.

  Representative examples of suitable acyclic hydrocarbons include (1) paraffins such as

  n-hexane, 2-methylpentane, 3-methylpentane, n-hexane,

  heptane, 2-methylhexane, 3-methylhexane, 3-ethyl-

  pentane, 2,5-dimethylhexane, n-octane, 2-methyl-

  heptane, 3-methylheptane, 4-methylheptane, 3-

  ethylhexane, n-nonane, 2-methyloctane, 3-methyl-

  octane, n-decane and the like; and (2) olefins such as 1-hexene, 2-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene and similar compounds.

  In a preferred embodiment, the hydro-

  Acyclic carbide is a paraffinic hydrocarbon having about 6 to 10 carbon atoms per molecule. It should be noted that the particular acyclic hydrocarbons mentioned above can be individually charged in the process of the invention, in admixture with one or more of the other acyclic hydrocarbons or in admixture with other hydrocarbons such as naphthenes,

  aromatic hydrocarbons, etc. Thus, hydrophilic fractions

  mixed carbon containing significant amounts

  acyclic hydrocarbons that are usually available

  in a conventional refinery are suitable fillers for the process of the invention; mention is made, for example, of high paraffinic direct distillation naphthas, paraffinic raffinates of extraction or adsorption of aromatic hydrocarbons,

  paraffins rich in C 6 to C 9 and

  A particularly preferred embodiment involves a filler which is a paraffin-rich naphtha fraction boiling in the range of about 60 to about 177 ° C. The best results are generally obtained with a paraffin mixture feed. in C 6 to C 10, in particular

paraffins C 6 to C 8.

  The charge is advantageously virtually free of sulfur, nitrogen, metals and other poisons known to

  reforming catalysts This catalyst is particularly

  The feedstock can be made substantially free of sulfur, nitrogen, metals and other known poisons by conventional catalytic hydrotreatment techniques with, in addition, the use of adsorbents which remove the compounds from the feedstock. sulfur. In the case of a charge that does not already have a

  low sulfur content, it is possible to react

  acceptable by catalytic hydrotreatment of the feedstock in a pretreatment zone where the naphtha is contacted with a suitable catalyst which resists

  Sulfur poisoning A catalyst that

  This hydrodesulphurization process is, for example, formed of a support containing alumina and a small proportion of molybdenum oxide, cobalt oxide and / or nickel oxide. Hydrodesulfurization is usually carried out at a temperature of 315 to 4550 ° C. under a pressure of 1.4 to 14 M Pa and at a liquid hourly space velocity of 1 to 5. Sulfur and nitrogen content

  in the naphtha are converted, respectively, into hydro-

  sulphide and ammonia gene, which can be eliminated before

  reforming by suitable conventional operations.

  According to one aspect of the present invention,

  the acyclic hydrocarbon is brought into contact with the cat-

  lyser in a dehydrocyclization zone maintained in

  conditions of dehydrocyclisation This setting into

  tact can be achieved using the catalyst in a fixed bed system, a moving bed system, a fluidized system, or in a batch type operation;

  However, given the danger of attrition losses from cat-

  expensive and because of well-known practical advantages, it is recommended to use either a system

  fixed bed or a dense phase moving bed system.

  It is also envisaged to be able to implement the

  contact in the presence of a physical mixture with

  In a fixed-bed system, the charge containing acyclic hydrocarbons is preheated by any heating device suitable for the desired reaction temperature, and then transferred to an

  dehydrocyclization containing a fixed bed of catalyst.

  Of course, it should be noted that the dehydrocyclization zone may consist of one or more separate reactors between which there are suitable means ensuring the maintenance of the desired transformation temperature at the inlet of each reactor. It is also important to note that the reactants can be brought into contact with the catalyst bed in an ascending, descending or radial flow mode. In addition, the reactants can be in the liquid phase, in the mixed liquid-vapor phase or in the vapor phase when

  come into contact with the catalyst, the best results

  States being obtained in the vapor phase The dehydro-

  cyclisation then advantageously comprises a dehydrocyclization zone containing one or more fixed beds

  or dense phase catalyst beds in a system

  it is, of course, in accordance with the scope of the present invention not to use the catalyst.

  again in all the beds and then use a catalytic-

  classic dual function in the remaining beds.

  The dehydrocyclization zone may consist of one or more separate reactors between which there are suitable means of heating to compensate for the endothermic nature of the dehydrocyclization reaction.

  which takes place in each catalyst bed.

  Although hydrogen is the preferred diluent for use in the dehydrocyclization process of the invention, other diluents which are practically suitable, either individually or in admixture with hydrogen, may be advantageously used in some cases. examples of C 1 to C 5 paraffins such as methane, ethane, propane, butane and pentane; similar diluents, and their mixtures We like hydrogen because

  that it plays the dual role not only of lowering the pressure

  partial removal of the acyclic hydrocarbon, but also to suppress the formation of carbon deficient carbon deposits (usually called coke) on the catalytic composite. Usually hydrogen is used in sufficient quantities to provide a molar ratio of hydrogen to hydrocarbons. from about 1: 1 to about 1, with the best results being in the range of about 2: 1 to about 6: 1 The charged hydrogen in the dehydrocyclization zone is normally contained in a hydrogen-rich gas stream recycled effluent

  coming from this area after a suitable separation step.

gas / liquid.

  The conditions for dehydrocyclization of hydro-

  carbides used in the process of the invention comprise

  manometric pressure of the reactor selected in

  the range from about 0 to about 3.5 M Pa, the pressure

  recommended metric ranging from about 0.35 to about 2.1 M Pa.

  The dehydrocyclization temperature is preferably from about 430 to about 550 ° C. As is well known to those skilled in the art of dehydrocyclization, the initial choice of temperature in this broad range is primarily dependent on the level of dehydrocyclization. desired conversion of acyclic hydrocarbon, taking into account

  characteristics of the feedstock and the catalyst

  narily, the temperature is then slowly raised

  during the operation to compensate for the inevitable deactivation

  table which takes place in order to ensure a relatively

constant for transformation.

  The liquid hourly space velocity (LHSV) used in the dehydrocyclization process of the invention is selected in a range of about 0.1

  at approximately 10:01, a value within the range of

  about 0.3 to about 5 h 1 being recommended.

  A reforming generally results in the production of hydrogen Thus, hydrogen of external origin does not necessarily need to be added to the reforming system, except for a pre-reduction of the catalyst and when the feed is previously introduced In general, once the reforming is in progress, part of the hydrogen produced is recycled to the catalyst. The presence of hydrogen makes it possible to reduce the formation of coke, which tends to poison the catalyst. Hydrogen is advantageously introduced into the reactor. reforming in a proportion ranging from 1 to about 10 moles of hydrogen per mole of filler Hydrogen may be in admixture with light gaseous hydrocarbons. If the catalyst has deactivated after a period of operation in the presence of carbonaceous deposits, these deposits can be removed from the catalyst by passing an oxygen-containing gas, such as diluted air, in contact with the catalyst. a high temperature in sight

  to remove the carbonaceous deposits of the catalyst by

  The regeneration can be carried out in the semi-regenerative mode according to which the reforming operation is interrupted after a longer or shorter period and the regeneration of the catalyst is carried out.

  or according to the regenerating mode in use, in accordance

a portion of the catalyst is regenerated, while the reforming operation is continued on the rest of the catalyst Two types of regeneration in service are known in the prior art, namely the

  cyclic reforming and continuous reforming

  cyclic forming, the catalyst in one of the reactors of a series is regenerated, while the reforming is

  continued in the rest of the installation In the refor-

  In a continuous pattern, a portion of the deactivated catalyst is removed from the plant, regenerated in a separate regeneration system, while reforming is continued in the facility, and the regenerated catalyst is returned to the facility. The catalyst regeneration process depends on whether the operation is conducted in a fixed bed, in a moving bed or in a fluidized bed. The processes and regeneration conditions are well known in the art.

the prior art.

  The catalyst according to the invention is a type L zeolite loaded with a Group VIII metal and

an alkaline earth metal.

  The type L zeolites are synthetic zeolites

  They correspond to a theoretical formula M 9 / n / (Al O 2) 9 (Si O 2) 27-7 in which M is a cation of

valence n.

  The actual formula may vary without modification of the crystalline structure; for example, the molar ratio of silicon to aluminum (Si / Al) may vary from

1.0 to 3.5.

  Although several cations may be present in the zeolite L, it is recommended in one embodiment to synthesize the potassium form of the zeolite, i.e. the form in which the exchangeable cations present are substantially all The reactants used as a result are easy to obtain and are generally soluble in water. The exchangeable cations present in the zeolite can then be advantageously replaced by other exchange-capable cations, as will be shown in follows, thereby giving an isomorphous form of zeolite L. In a process for producing zeolite L, the

  potassium form of a zeolite L is prepared by heating

  a suitable mixture of an aqueous mixture of metal aluminosilicates whose composition, expressed by the molar ratios of the oxides, falls within the following ranges K 20 / (K 20 + Na 2 O) of about 0.33 to 1 (K 2 O + Na 2 O) / Si O 2 from 0.35 to about 0.5 Si O 2 / A 1203 from 10 to about 28

  H 20 / (K 20 + Na 2 O) from about 15 to 41.

  The desired product is then crystallized in a form relatively free of dissimilar structure zeolites

crystals.

  The potassium form of zeolite L may also be prepared by another process together with other zeolite compounds by the use of a reaction mixture whose composition, expressed as

  molar ratios of oxides, falls within the following ranges

  values: K 20 / (K 20 + Na 2 O) from about 0.26 to 1 (K 2 O + Na 2 O) / Si O 2 from about 0.34 to about 0.5 Si O 2 / A 1203 from 15 to 28 approximately

  H 20 / (K 20 + Na 2 O) from 15 to about 51.

  It should be noted that the presence of sodium in the reaction mixture is not critical

for the present invention.

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

  potassium ions The product obtained in the ranges

  has a composition, expressed in moles of oxides, which corresponds to the formula: 0.9-1.3 f- (1-x) K 20, x Na 2 O 7: A 1203: 5.2-6, 9 If O 2: y H 2 O in which "x" can have any value from 0 to about 0.75 and "y" can have any value

from 0 to about 9.

  Representative examples of reactants for the preparation of zeolite L are activated alumina, gamma-alumina, alumina trihydrate and sodium aluminate as the source of alumina. Silica can be obtained from sodium silicate or potassium, silica gels, silicic acid, aqueous

  colloidal silica and reactive amorphous solid silicas.

  The preparation of particular silica sols which can be advantageously used in the process of the present invention is described in U.S. Patent Nos. 2,574,902 and 2,597,872. Representative examples of silicas from the group of solid silicas reactive amorphs, advantageously having a final particle diameter of less than 1 micrometer, are materials such as "fumed" silicas, precipitated

  chemically, and precipitated silica sols

  potassium hydroxide and sodium hydroxide can

  The usual method of preparing zeolite L is to dissolve the potassium or sodium aluminate and an alkali base, i.e. potassium or sodium hydroxide, in the following manner: This solution is mixed with an aqueous solution of sodium silicate or preferably with a mixture of water and a silicate derived at least in part from an aqueous sol of colloidal silica. The resulting reaction mixture is loaded into a container. eg metal or glass The container must be closed to prevent loss of water The reaction mixture is

  then stirred to ensure homogeneity.

  The zeolite can be prepared satisfactorily

  at temperatures of about 90 to 200 ° C, the pressure being atmospheric or having at least one

  which corresponds to the vapor pressure of the water in equi-

  free with the mixing of the reactants at the temperature

  The highest temperature can be used any suitable heating device, for example an oven, a bath of

  sand, an oil bath or an autoclave with a shirt.

  Heating is continued until the zeolite product is

  The crystalline zeolite crystals are then separated by filtration and washed to

  to rid them of the mother liquor of the body reaction-

  The zeolite crystals should be washed before

  distilled water until the outgoing wash water, in equilibrium with the product, has a pH between about 9 and 12 As the zeolite crystals are washed, the exchangeable cation of the zeolite can be partially removed, and it is considered that it is replaced by hydrogen cations. If the washing is interrupted when the pH of the outgoing washing water is between about 10 and 11, the molar ratio (K 2 O + Na 2 O) / A 1203 of the crystalline product is about 1.0 After this, the zeolite crystals can be dried, advantageously

in a ventilation oven.

  Zeolite L has been characterized in the work entitled "Zeolite Molecular Sieves" by Donald W. Breck, John Wiley & Sons, 1974, as before a skeleton comprising 18 tetrahedral unit cages of the cancrinite type joined in columns by hexagonal and crosslinked double nuclei. by simple oxygen bridges to form dodecagonal planar nuclei These dodecaacnal nuclei form

  parallel to the c-axis without defects of the opposite.

  nite and cancrinite, cages of the cancrinite type are arranged symmetrically on both sides of the double hexane unitary cyclic units. There are four types of cation locations: A in the double hexagonal cores, B in the cages of the type cancrinite, C between cages of the cancrinite type and D on the canal wall

  cations of site D appear only cation exchangeable at the same time.

  During dehydration, cations from site D probably migrate from the walls of the channels to a fifth site, or site E, which is located between sites A of the sorption pores.

  hydrocarbons have a diameter of about 0.7 to 0.8 nm.

  A more complete description of these zeolites is given by

  example, in US Pat. No. 3,216,789, which

  more particularly a classic description This patent is

  mentioned here for reference to illustrate an L-type zeolite

  can be used in the present invention.

  Various factors influence the

  X-ray diffraction of a zeolite

  take the temperature, the pressure, the dimensions of

  crystals, impurities and the type of cations present.

  For example, as the crystal dimensions of

  the L-type zeolite become weaker, the diffraction pattern

  As a result, the term "zeolite L" covers all zeolites

  cages of cancrinite with a different pattern of

  X-ray fraction is substantially similar to the X-ray diffraction patterns shown in the

  U.S. Patent No. 3,216,789, supra.

  The dimensions of the crystals also affect the stability of the catalyst For reasons which are not yet fully understood, catalysts, of which at least 80% of the L-type zeolite crystals are greater than 100.0 nm, have a longer duration. only catalysts in which substantially all the L-type zeolite crystals have dimensions of between 20.0 and 50.0 nm. Thus, among the L-type zeolites, those whose crystallites have the largest dimensions

constitute the medium of choice.

  Type L zeolites are usually synthesized

  largely in the form of potassium, that is,

  that in the theoretical formula given above, most of the M cations are potassium cations. The M cations are exchangeable, so that a given L-type zeolite, for example an L-type zeolite in the potassium form, can be used. used to obtain L-type zeolites containing other cations by exposure of L-type zeolite to ion-exchange treatment in an aqueous solution of suitable salts.

  it is difficult to exchange all the original cations

  ginels, for example potassium cations, as some exchangeable zeolite

  in sites with difficult access for reagents.

  Other zeolites which could be used in the present invention are zeolites of the Ln family. The expression "zeolite of the L family" corresponds to any zeolite which consists of cancrinite cages forming a porous structure whose pores are linked by a dodecagonal ring, the zeolite being endowed with dehydrocyclization activity when a Group VIII metal is introduced therein Zeolites representative of a "zeolite of the L family" include the L-type zeolite described in the US Pat. United States of America No. 3,216,789, zeolite AG 1 as described in British Patent No. 1,393,365; zeolite AG 4 as described in British Patent No. 1,394,163; zeolite AG 5 as described in U.S. Patent 3,298,780; and zeolite K, Ba-G. U.S. Patent Nos. 3,216,789, 3,298,780, and 4,018,870, supra, and British Patent Nos. 1,393,365 and 1,394,163 cited above are mentioned in US Pat. A key element of the present invention is the presence of an alkaline earth metal in the L type zeolite. The alkaline earth metal must be barium, strontium or calcium II. This is advantageously barium. The alkaline earth metal can be incorporated into the zeolite by synthesis, impregnation or ion exchange. Barium is preferred to other alkaline earth metals because the resultant catalyst has a great deal of

  activity, high selectivity and high stability.

  In one embodiment, at least a portion of the alkali metal is exchanged for barium by known techniques for treating zeolites by ion exchange. This involves contacting the

  zeolite with a solution containing excess Ba ++ ions.

  Barium should advantageously constitute 0.1 to 35% of the

  weight of the zeolite, especially 1 to 20% of its weight.

  The catalysts according to the invention are charged with one or more Group VIII metals, for example nickel, ruthenium, rhodium, palladium or iridium.

or platinum.

  The preferred metals of Group VIII are iridium, palladium, and especially platinum, which are more selective with respect to dehydrocyclization and also

  more stable under the conditions of the dehydro-

  cyclization than other Group VIII metals.

  The percentage of platinum recommended in the

  lyser is between about 0.1 and 5%, especially between

0.1 and 1.5%.

  The Group VIII metals are introduced into the zeolite L by synthesis, impregnation or exchange in an aqueous solution of a suitable salt. If it is desired to introduce two Group VIII metals into the zeolite,

  can conduct the operation simultaneously or successively.

  For example, platinum can be introduced

  by impregnation of the zeolite with an aqueous solution of platinum (II) tetrammine nitrate, platinum (II) tetrammine hydroxide, dinitrodiamino-platinum or platinum (II) -tetrammine chloride in a process

  ion exchange, platinum can be introduced using

  cationic complexes of platinum such as

  platinum (II) nitrate.

  An inorganic oxide can be used as a support for binding the L-type zeolite containing the metal

  Group VIII and the alkaline earth metal and to increase

  The support may be a natural or synthetically produced inorganic oxide or a mixture of inorganic oxides The catalyst contains

  advantageously 5 to 25% by weight of inorganic oxide.

  Examples of carriers of inorganic oxides that may be used include aluminosilicates (such as clays), alumina, and silica, where acidic sites are preferably exchanged for cations.

  which do not confer a strong acidity.

  A preferred support formed of an inorganic oxide is the product "Ludox" which is a colloidal suspension of silica in water, stabilized with a small amount

an alkaline base.

  When an inorganic oxide is used as the support, two methods are recommended for preparing the catalyst, although other embodiments may be used. In the first preferred embodiment, the L-type zeolite is formed, then ion-exchanged with a solution of barium, separated from the

  solution of barium, it is dried and calcined, it is im-

  platinum, is calcined, then mixed with the inorganic oxide and extruded through a spinneret to form cylindrical pellets.

  advantage of separating the L-type zeolite from

  of barium and platinum consist in using a

  discontinuous centrifuge or a filter

  This embodiment offers the advantage that

  barium and platinum are all fixed on the zeolite

  It has the disadvantage that the L-type zeolite is a type L and not at all on the inorganic oxide.

  small zeolite, which is difficult to separate

  remove barium solution and platinum solution.

  In the second preferred embodiment,

  the L-type zeolite is mixed with the inorganic oxide

  that and the mixture is extruded through a die to form

  cylindrical pellets, which are then treated

  This embodiment has the advantage that the pellets are easy to separate from the solutions of barium and barium solutions, which are separated by ion exchange with a solution of barium, separated from the barium solution, impregnated with platinum and separated from the platinum solution. platinum, but it has the disadvantage that barium and platinum can also be deposited on the inorganic oxide support and could catalyze undesirable reactions Therefore, the choice of the embodiment that is used is based on the alternation between catalyst selectivity and ease of catalyst separation from barium solutions and

platinum.

  In a third possible embodiment, the L-type zeolite is ion-exchanged with a barium solution, dried and calcined, mixed with the inorganic oxide, and the mixture is extruded through the die to form cylindrical pellets, followed by

  pastilles are impregnated with platinum, separated from the

platinum and calcined.

  In the extrusion of type L zeolite, it is possible to

  add various extrusion additives and various porogens.

  Examples of suitable extrusion adjuvants are ethylene glycol and stearic acid. Examples of suitable porogens are sawdust,

  cellulosic and polyethylene fibers.

  After the desired Group VIII metal or metals have been introduced, the catalyst is treated in

  air or in diluted oxygen at a

  at 260 ° C to 500 ° C and then reduced in hydrogen to

  from 200 to 7000 C, preferably from 480 to 620 ° C,

in particular from 530 to 620 ° C.

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

of metal ions.

  In order to obtain the optimum selectivity, the temperature must be adjusted so that the reaction rate is appreciable, but the transformation

  less than 98%, since an excessive temperature

  The pressure must also be adjusted within a suitable range. An excessively high pressure imposes a thermodynamic limit (equilibrium) on the desired reaction, especially for the aromatization of hexane. and too low a pressure can lead to the formation of

coke and a deactivation.

  Although the main advantage of the invention lies in the improvement of the selectivity towards the conversion of acyclic hydrocarbons (in particular of C 6 to C 8 paraffins) into aromatic hydrocarbons, the surprising fact has also been discovered that the selectivity This reaction, which involves, on conventional chlorine-treated alumina reforming catalysts, an acid-catalyzed isomerization step, is performed on the catalyst of the present invention. with a selectivity as good or better than on prior art chloride-treated alumina-based catalysts.

  The invention can also be used to catalyze the trans-

  formation in aromatic hydrocarbons of heavy loads

  content of pentagonal ring alkylnaphthenes.

  The dehydroisomerization of alkylcyclopentanes is advantageously carried out in a temperature range of 427 to 5340 C (in particular from 438 to 510 ° C); at a liquid hourly space velocity of 0.1 to 20 (especially 0.5 to 10); at a pressure ranging from 0 to 3.5 M Pa (in particular from 0 to 2.1 M Pa); and at a ratio H 2 / HC of O

at 20: 1 (especially 1: 1 to 10: 1).

  It has also surprisingly been found that the selectivity for the conversion of toluene to benzene is excellent. The dealkylation of toluene is conveniently conducted at a temperature of 427 to 649 ° C (especially 454 to 593 ° C) at an hourly space velocity. liquid from 0.1 to 20 (in particular from 0.3 to 10), at a pressure of from 0 to 21 M Pa (especially

  1.4 to 14 M Pa); and an H 2 / HC ratio of 0 to 20: 1 (especially

from 1: 1 to 10: 1).

  Another advantage of the present invention is

  the new catalyst is more stable than catalytic

  The stability of the catalyst or its resistance to deactivation determines the stability of the catalyst.

  service life Longer service times

  vice allow a reduction of downtime and lower costs of regeneration or replacement of the catalyst load.

  The invention is further illustrated by the examples

  following plans that develop forms of

  particularly advantageous methods and compositions.

  Although these examples are given to illustrate the

  they do not limit their scope.

EXAMPLE 1

  A straight-run naphtha of a light crude

  from Arabia, who had been exposed to a hydrotreatment

  lytic system to eliminate sulfur, oxygen and nitrogen, was reformed under a pressure of 0.7 M Pa, at a space velocity VSHL equal to 2 and with a ratio H 2 / HC

  equal to 6 by three different catalysts

  contained 80.2% by volume of paraffins, 16.7% by volume of naphthenes and 3.1% by volume of aromatic hydrocarbons, and it contained 21.8% by volume of C 5 components, 52.9% by volume. volume of C 6 components, 21.3% by volume of

  C 7 components and 3.2% by volume of C 8 components.

  In the first test, the straight-run naphtha of light crude from Arabia was reformed at 4990 C using a commercial platinum-rheniumalumin sulfide catalyst.

  prepared in the manner described in the US Pat.

  No. 3,415,737. In the second test, the straight-run naphtha of a light crude from Arabia was reformed at 4930 C using a platinum-potassium-zeolite type L catalyst formed by 1) impregnation of an L-type zeolite in the potassium form having crystal dimensions

  from about 100 to 400 nm containing 0.8% platinum intro-

  duit by impregnation in the form of platinum-nitrate (II) -

  tetrammine, (2) catalyst drying, (3) catalyst calcination at 260 ° C, and (4) catalyst reduction in

  hydrogen at 480-500 ° C for 1 hour.

  In the third run, that is, the process of the present invention, the straight-run naphtha of light crude from Arabia was reformed at 4930 C using a platinum-barium-type L-zeolite catalyst formed by (1) ion exchange treatment of an L-type zeolite in the potassium form having crystal sizes of about 100 to 400 nm with a sufficient volume of 0.17 M barium nitrate solution to enclose an excess barium, compared to the ion exchange capacity of the zeolite; (2) drying the zeolite catalyst from

  type B treated by barium exchange resulting, (3)

  catalyst at 590 ° C, (4) catalyst impregnation

  0.8% platinum using platinum- (II) tetrammine nitrate, (5) catalyst drying, (6) calcination of the catalyst at 260 ° C, and (7) reduction of the catalyst.

  catalyst in hydrogen at 480-500 ° C for 1 hour.

  The results of these three tests are reproduced in Table I.

TABLE I

  Charge 499 C, Pt / Re / 493 C, 493 C, alumina Pt / K / L Pt / Ba / L C 1,% by weight of the filler 2.8 5.5 3.6

C 2 6.6 2.5 1.3

C 3 9.3 3.2 1.5

  i C 4 0.1 5.8 0.9 0.5 n C 4 0.5 6.8 3.8 2.4 i C 5 5.1 13.6 6.7 5.6 n C 5 11 3 9.8 12.6 12.6 P + N at C 6 + 81.3 13.4 7.8 9.3 Benzene 1.5 15.1 40.6 43.8 Aromatic in

C 7 + 0.8 15.8 12.7 15.0

  C 5 + liquids, yield,% by volume 63 69.9 74.4 Hydrogen, m 3 / m 3 89, 7 295.5 364.9 Selectivity, moles

% 20 72 87

  This series of tests shows that the use of a platinum-barium-type L zeolite catalyst in the reforming gives a selectivity towards the conversion of hexanes to benzene significantly higher than that of the benzene. PRIOR ART It will be noted, in connection with this superiority of selectivity, an increased production of gaseous hydrogen,

  that can be used in other processes.

  It should also be noted that the purity of hydrogen is greater for the effect using the Pt / Ba / L catalyst, since more hydrogen and less C 1 are produced.

plus C 2.

EXAMPLE 2

  A second series of tests were conducted using

  reading as a load of n-hexane hydrotreated

  All the tests of this series were carried out at 490 C, under a pressure of 0.7 M Pa, at a space velocity VSHL equal to 3 and with a ratio of

H 2 / HC equal to 3.

  In the first test, a platinum-potassium zeolite type L catalyst was used which was prepared by the operations illustrated in the second method of

Example 1

  In the second test, a platinum-barium-type L zeolite catalyst was used which had been prepared by

  the operations indicated in the third test of Example 1, with the difference that the barium nitrate solution was 0.3 M

  place of 0.17 M The results of these tests

  are reproduced below in Table II.

TABLE II

  Transformation selectivity n-hexane 5 hours 5 hours 20 hours hours Pt / K / L 70 59 76 79 Pt / Ba / L 85 85 89 92 Therefore, in use, the incorporation of barium into an L-type zeolite causes a dramatic improvement in the selectivity towards n-hexane

  It should be noted that the stability of the platinum-

  barium-zeolite type L is excellent After 20 hours, there was no drop in the rate of transformation when

  platinum-barium-zeolite type L catalyst was used

Lisa.

EXAMPLE 3

  A third series of tests were conducted using

  reading different cationic exchanges All the tests of this series were conducted at 490 C under pressure

  0.7 Pa and with a ratio H 2 / HC equal to 6.

  The charge that had been catalytically hydrotreated

  contained 80.9% by volume of paraffins, 16.8% by volume of naphthenes, 1.7% by volume of aromatic hydrocarbons, 0.4% by volume of olefins, and contained 2.6% by volume

  C 5 hydrocarbon volume, 47.6% by volume of hydrocarbon

  in C 6, 43.4% by volume of C 7 and 6.3% hydrocarbons

in volume of C 8 hydrocarbons.

  In the first test, a platinum-barium-type L-zeolite catalyst was used which was prepared by the operations indicated in the second test of Example 2. It was tested at a liquid hourly space velocity of 2, 0. In the second test, a platinum-calcium-zeolite type L catalyst was used which had been prepared by the same operations, with the exception that a 0.3 M calcium nitrate solubil was used.

  at a space velocity VSHL equal to 2.0.

  In the third trial, a catalyst was used

  platinum-strontium-zeolite type L which had been prepared by the same operations, with the difference that a 0.3 M solution of strontium nitrate had been used in the exchange It was tested at a space velocity

VSHL equal to 2.0.

  In the fourth test, a catalyst was used

  platinum-cesium-zeolite type L which had been prepared by the same operations, with the difference

  0.3 M cesium nitrate was used in the exchange.

  It was tested at a VSHL space velocity equal to 2.0.

  In the fifth trial, a catalyst was used

  platinum-barium-type L-zeolite which had been prepared by the same operations as in the first test.

  was tested at a VSHL space velocity of 6.0.

  In the sixth trial, a catalyst was used

  Platinum-potassium-zeolite type L which had been prepared by the operations indicated in the second method of Example 1 It was tested at a space velocity

VSHL equal to 6.0.

  In the seventh test, an L-type platinum-rubidium-zeolite catalyst was used which was prepared by the first test operations, with the exception that a solution of 0.3 M rubidium nitrate was used in the exchange. was tested at a space velocity

VSHL equals 6.0.

  In the eighth test, a platinum-lanthaneolite L-type catalyst was used which was prepared by the operations of the first test, with the exception that a solution of 0.3 M lanthanum nitrate was used in the exchange. was tested at a space velocity

VSHL equal to 6.0.

  In the ninth test, a platinum-magnesium zeolite L catalyst was used which was prepared by the operations of the first test, with the exception that a solution of 0.3 M magnesium nitrate was used in the exchange. was tested at a space velocity

VSHL equal to 6.0.

  In the tenth test, a platinum-lithium-zeolite L-type catalyst was used which was prepared by the operations of the first test, with the exception that a solution of 0.3 M lithium nitrate was used in the first test. exchange It was tested at a space velocity

VSHL equal to 6.0.

  In the eleventh test, a platinum-sodium-zeolite type L catalyst was used which had been prepared

  by the operations of the first test, except that a solution

  0.3 M sodium nitrate was used in the exchange. It was tested at a VSHL space velocity.

  6.0 The results of the eleven trials are all

* on table III.

TABLE III

Paraffin processing

3 hours 20 hours

  Pt / Ba / L Pt / Ca / L Pt / Sr / L PT / Cs / L Pt / Ba / L Pt / K / L Pt / Rb / L Pt / La / L Pt / Mg / L Pt / Li / L Pt / Na / L VSHL

87 87 83

96 93 63

92 83 61

84 73 73

LHSV

73 63 80

66 71

84 74 72

63 55 63

23 <5 23

77 72 70

74 67 72

  Selectivity, Hydrocarbons moles% aromatics, 3 hrs 20 hrs moles% res res in charge

3 hours 20 hours

res res = 2.0

75 76

65 70

69 62 63

66 61

= 6.0

64 59

57

63

48

22 14

61 60

58

  Therefore, in use, incorporation of barium into L-type zeolites causes a dramatic improvement in selectivity over L-type zeolites bearing other cations (over 25% reduction in the amount of cracked products formed in the -

  case of a zeolite L carrying any other cation).

EXAMPLE 4

  In two tests, a platinum-barium-type L-zeolite catalyst prepared by the operations indicated in the second test of Example 2 was used. In the first test, the dimensions of the zeolite L crystallites were about 100. at 200 nm, measured by a transmission electron microscope In the second test, the dimensions of the zeolite L crystallites were approximately 40 nm. The feedstock used in the two tests contained 70.2% by volume of paraffins.

  24.6% by volume of naphthenes, 5.0% by volume of hydro-

  aromatic hydrocarbons and 29.7% by volume of C 5 hydrocarbons, 43.4% by volume of C 6 hydrocarbons, 21.2% by volume

  C 7 hydrocarbon volume, 5.0% by volume of hydrocarbon

  C 8 and 0.6% by volume of C 9 hydrocarbons.

  The theoretical octane number, without additive, of the feed was 71.4 The catalyst of the first test was reduced in hydrogen for 20 hours at 565 C The catalyst of the second test was reduced in hydrogen during 2 hours at 565 C The conditions of the test were as follows: gauge pressure 0.7 M Pa, LHSV 1.5 and H 2 / HC with recycling equal to 6.0

  has been adjusted so that the liquid product C 5 +

  50% by weight of aromatic hydrocarbons, which corresponds to a theoretical octane number without additive equal to 89 The results of the first test are reproduced

in Table IV.

TABLE IV

  Test duration, temperature, OC, hour yield for 50% in liquid products hydrocarbon weight in C 5 +,% in aromatic burs volume

500 459 86.4

1000 464 86.2

2000 469 86.1

2500 471 86.2

  The results of the second test are shown in Table V.

TABLE V

  Test duration, temperature, O C, hour yield for 50% in liquid products hydrocarbon weight in C 5 +,% in aromatic bursts volume

465 87

472 86

400 478 85

  Thus, in use, the large crystal catalyst according to the present invention has an extremely long service life, while the small crystal catalyst disables much

faster.

EXAMPLE 5

  A fifth series of tests were carried out to demonstrate the influence of the reduction temperature. The charge used was the same as in Example 1. The experimental conditions were as follows: 4901 C, pressure pressure 0.7 M Pa, hourly space velocity

  a liquid equal to 2.0, H 2 / HC equal to 6.0.

  The catalyst used in the first two tests was a catalyst of the Pt / Ba / K / L type prepared as in the third method of Example 1, with the exception that the barium exchange was carried out three times with a solution of 1 M barium nitrate; this only gave one

  low rise in barium content.

  The catalyst used in the last two tests was a Pt / K / L catalyst prepared as in the second

method of Example 1.

  Results obtained after 3 hours of service

are reproduced in Table VI.

"- TABLE VI

  Aromatic Conditions, Selectivity, reduction moles% in moles% charge Pt / Ba / K / L 490 C, 1 hour 59 78

Pt / Ba / K / L 620 C, 20 hours

  res 60 89 Pt / K / L 490 C, 1 hour 55 66

Pt / K / L 620 C, 20 hours

  The results show a significant and surprising difference in the influence of the preparation on the two catalysts. The selectivity of the barium-containing catalyst has been significantly improved, while the selectivity of the catalyst does not contain barium.

been very significantly reduced.

EXAMPLE 6

  A charge of methylcyclopentane that had been catalytically hydrotreated to remove sulfur, oxygen, and nitrogen was dehydroisomerized at 493 C,

  at a pressure of 0.7 Pa, at a specific velocity

  hourly time of the liquid equal to 2 and with a ratio H 2 / HC equal to 6 by a dehydro-isomerization catalyst Ce

  catalyst was prepared (1) by ion exchange of potassium

  b-type sium-barium-zeolite with a sufficient volume of 0.17 M barium nitrate solution to contain an excess of barium compared to the ion exchange capacity of the zeolite; (2) drying the resulting catalyst formed from B-type zeolite treated by barium exchange; (3) calcination of the catalyst at 590 C; (4) impregnating the catalyst with 0.8% platinum using platinum (II) tetrammine nitrate; (5) drying the catalyst; (6) calcination of the catalyst at 260 ° C and (7) reduction of

  catalyst in hydrogen at 480-50 dC

  The feed contained 73% by weight of methylcyclo

  pentane The distillation data of the feedstock were as follows: Initial Eb / 64.4 C, 5% / 67.8 C, 10% / 69.4 C,

  % / 70.5 C, 50% / 71.1 C, 70% / 71.7 C, 90% / 73.90 C,

  % / 78.3 C and final Eb / 105.5 C The feed contained% by volume of paraffins, 80% by volume of naphthenes

  and 10% by volume of aromatic hydrocarbons.

  formation was 78% after 3 hours and 32% after hours Selectivity for dehydro-isomerisation

  was 82 mole% after 3 hours and 86% after 20 hours

res.

EXAMPLE 7

  A charge formed from a straight-run distillation fraction of Arabian oil that had been catalytically hydrotreated to remove sulfur, oxygen and

  the nitrogen was dealkylated at 565 C under manometric pressure.

  than 0.7 M Pa, at a space velocity VSHL equal to 4 and

  with a ratio H 2 AC equal to 3 by a catalyst of desalkyl-

  This catalyst was prepared (1) by ion exchange potassium-barium-zeolite type L with a sufficient volume of 0.17 M barium nitrate solution to contain an excess of barium compared to the exchange capacity. ionic zeolite; (2) drying the resulting catalyst formed from B-type zeolite treated by barium exchange; (3) calcination of the catalyst at 590 C; (4) impregnating the catalyst with 0.8% platinum using platinum (II) tetrammine nitrate; (5) drying the catalyst; (6) calcination of the catalyst at 260 ° C; and (7) reduction of the catalyst in hydrogen

at 480-500C.

  The feedstock contained 1% by volume of C 4 hydrocarbons, 22% by volume of C 5 hydrocarbons, 53% by volume of C 6 hydrocarbons, 21% by volume of C 7 hydrocarbons and 3% by volume of C 7 hydrocarbons. volume of C 8 hydrocarbons; 78% by volume of paraffins, 19% by volume of naphthenes and 3% by volume of aromatic hydrocarbons The results of this test

  are reproduced in the table below (all the

  percentages are expressed by weight) The conversion of paraffins to C 6 + was 96.04 mol% and the selectivity

  towards aromatization was 84.02.

TABLE VII

PRODUCT LOAD

  Methane O 7.66 Ethane O 5.66 Propane O 6.49 i C 4 0.08 1.55 n C 4 0.52 6, 49 i C 5 5.88 3.26 n C 5 12.61 2, 81

C 5 + 80.91 70.34

H 2 O 2.91

  Benzene 1,69 51,10 Aromatic C 7 + 1.62 10.92 It goes without saying that the present invention has been described only for explanatory purposes, but in no way limiting,

  many modifications can be made

without departing from its scope.

Claims (17)

  Composition, characterized in that it comprises   takes (a) an L-type zeolite; (b) at least one Group VIII metal; and (c) an alkaline earth metal selected from   group consisting of barium, strontium and calcium.   2 Composition according to claim 1, characterized   characterized in that the alkaline earth metal is barium   and the Group VIII metal is platinum.   3 Composition according to claim 2, characterized   characterized in that it contains 0.1 to 35% by weight, preferably 1 to 20% by weight of barium and 0.1 to 5% by weight of   weight, preferably 0.1 to 1.5% by weight of platinum.   4 Composition according to claim 3, characterized   characterized in that most crystals of said L-type zeolite are greater than 50 nm, preferably greater than 100 nm; especially greater than 100 nm in proportion at least 80%.   5 Hydrocarbon reforming process, applied   in particular the dehydrocyclisation of acyclic hydrocarbons   the dehydroisomerization of alkylcyclopentanes under dehydroisomerization conditions to produce aromatic hydrocarbons, the dealkylation of toluene under dealkylation conditions to produce benzene, characterized in that it comprises   said hydrocarbons in contact with a catalyst   taking: (a) an L-type zeolite; (b) at least one Group VIII metal; and (c) an alkaline earth metal selected from   group consisting of barium, strontium and calcium.   6 Process for the reforming of hydrocarbons,   it consists in bringing in the said hydro-   carbides in contact with a catalyst comprising (a) an L-type zeolite; (b) at least one Group VIII metal; and (c) an alkaline earth metal selected from the group consisting of barium, strontium and calcium, said catalyst being reduced in a hydrogen atmosphere to a temperature of 480 to 620 C.   The process for reforming hydrocarbons according to claim 6, characterized in that the catalyst   is reduced in a hydrogen atmosphere at a temperature of from 530 to 620 C.   8 Next hydrocarbon reforming process   claims 5 and 7, characterized in that the metal   alkaline earth is the barium and metal of Group VIII is platinum.   A process for reforming hydrocarbons according to claim 8 according to claim 5, characterized in that the catalyst contains 1 to 20% by weight of barium and 0.1 to 1.5% by weight of platinum and in that at least 80% of the L-type zeolite crystals are greater than 100.0 nm.   Hydrocarbon Reforming Process Next   claim 9, characterized in that the setting   tact is carried out at a temperature of 400 to 600 C, preferably 430 to 550 C; at a space hourly spacing of the liquid of 0.1 to 10; at a pressure of from 0 to 3.5 M Pa, preferably from 0.35 to 2.1 M Pa and at a pressure of   H 2 / HC ratio of 1: 1 to 10: 1, preferably 2: 1 to 6: 1.   Process for the dehydrocyclization of acyclic hydrocarbons according to Claim 8 dependent on the   claim 5, characterized in that dehydrocyclization   This is carried out in the presence of 1 to 20% by weight of barium and 0.1 to 5% by weight of platinum; at least 80% of the crystals of the L type zeolite are greater than nm; and the contact takes place at a temperature of 430 to   550 C, at a space velocity VSHL of 0.3 to 5, at a pressure of   gauge pressure 0.35 to 2.1 M Pa and H 2 / HC ratio from 2: 1 to 6: 1.   12 Process for the dehydroisomerization of alkyl   cyclopentanes to produce aromatic hydrocarbons   according to claim 5, characterized in that the dehydro-   isomerization is conducted in the presence of 1 to 20% by weight of barium and 0.1 to 1.5% by weight of platinum; at least   % of the crystals of said L-type zeolite are   at 100 nm; and the contact takes place at a temperature of 438-510 ° C, at a space velocity LHSV of 0.5-10, at a pressure of from 0 to 2.1 M Pa and at a ratio of H 2 / HC of 1: 1 to 10: 1.   13 Method of dealkylation of toluene for   producing benzene according to claim 5, characterized   In that the dealkylation is carried out in the presence of 1 to 20% by weight of barium and 0.1 to 1.5% by weight of platinum, at least 80% of the crystals of the type L zeolite are greater than 100. nm and the contact takes place at a temperature of 454 to 593 C, at a space velocity   liquid time of 0.3 to 10, at a manometric pressure of   1.4 to 14 M Pa and H 2 / HC ratio of 1: 1 to 10: 1.   A process for the reforming of hydrocarbons according to claim 8, characterized in that the reforming is carried out in the presence of 1 to 20% by weight of barium and from 0.1 to 1.5% by weight of platinum, at least 80% crystals of said zeolite of the L family are greater than 100 nm and the contact takes place at a temperature of 221 to 288 C, at a pressure of 0.35 to 2.1 M Pa and at an H 2 / HC ratio of 2: 1 to 6: 1.   A process for preparing a reforming catalyst composition, which comprises: (a) ion exchange treating a potassium-containing L-type zeolite with a solution containing barium ions, at least 80% of the crystals of said L-type zeolite being greater than 100 nm; (b) drying said ion exchange treated L-type zeolite; (c) calcining said dried type L zeolite; (d) impregnating said calcined L-type zeolite   with platinum using platinum-nitrate (II) -   tetramine; (e) drying said impregnated L-type zeolite; and (f) calcining said impregnated L-type zeolite and dried.   16 Next hydrocarbon reforming process   claim 7, subject to claim 7,   in that it implies the presence of 0.1 to 35% in   weight of barium and 0.1 to 5% by weight of platinum.   A process for reforming hydrocarbons according to claim 16, characterized in that it involves the presence of 1 to 20% by weight of barium and 0.1 to 1.5% by weight of platinum; and in that said contact takes place   at a temperature of 430 to 5500 C, at a pressure of   from 0.35 to 2.1 M Pa and at an H 2 / HC ratio of 2: 1 to 6: 1.