FR2520749A1 - PROCESS FOR REFORMING HYDROCARBONS USING A CATALYST - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR REFORMING HYDROCARBONS. THE PROCESS CONSISTS OF CONTACTING THE HYDROCARBONS IN CONTACT WITH A CATALYST BASED ON A ZEOLITE WITH LARGE DIAMETER PORES, CONTAINING AT LEAST ONE GROUP VIII METAL AND AN ALKALINO-EARTH METAL CHOSEN BETWEEN BARIUM, STRONTIUM AND CALCIUM, OF SELECTIVITY OF THE CATALYST BEING GREATER THAN 60. APPLICATION TO DEHYDROCYCLIZATION OF ALKANES.

Description

The present invention relates to a novel catalyst and process

new dehydrocyclization

  of acyclic hydrocarbons, more particularly a

  dehydrocyclization of alkanes containing at least 6 carbon atoms to form the aromatic hydrocarbons

corresponding ticks.

  Catalytic reforming is a well known process in the petroleum industry and relates to the treatment

  naphtha fractions to improve the octane number.

  The main hydrocarbon reactions that occur during the reforming operation include

  the dehydrogenation of cyclohexanes to aromatic hydrocarbons

  the dehydroisomerization of alkylcyclopentanes to aromatic hydrocarbons, and the dehydrocyclization of paraffins to aromatic hydrocarbons.

  hydrocrackers that produce large amounts of hydro-

  light gaseous carbides, for example methane, ethane, propane and butane, must be particularly minimized during reforming, because this reduces the yield of products

  boiling in the boiling range of gasoline.

  Dehydrocyclization is one of the main reactions of the reforming process. The conventional methods for carrying out these dehydrocyclization reactions are based on the use of catalysts comprising a noble metal, supported on a support. The known catalysts of this kind are based on of alumina carrying 0.2 to 0.8% by weight of platinum and, advantageously, a second

auxiliary metal.

  The possibility of using supports other than alumina has also been studied, and it has been proposed to use certain molecular sieves such as

  zeolites X and Y, which have proved suitable for condi-

  reaction and product molecules are small enough to pass through the pores of the zeolite. However, catalysts based on these

  molecular sieves have not been successful in

  dustry. In the conventional method of carrying out the dehydrocyclization mentioned above,

  pass paraffins to be converted on the cat-

  lyser in the presence of hydrogen, at temperatures of the order of 5000 C and at pressures of 0.5 to 3.0 M Pa Part of the paraffins is converted into aromatic hydrocarbons, and the reaction is accompanied by reactions of isomerization and cracking that also convert paraffins to isoparaffins and hydrocarbons more

light.

  The rate of conversion of hydrocarbons into aromatic hydrocarbons varies with the conditions

  reaction and with the nature of the catalyst.

  The catalysts used hitherto have given moderately satisfactory results with heavy paraffins, but less satisfactory results with

  C 6 to C 6 paraffins, especially C 6 paraffins.

  L-type zeolite catalysts are more selective with respect to the dehydrocyclization reaction they can be used to improve the conversion rate to aromatic hydrocarbons without requiring high temperatures, which usually exert a considerable detrimental effect on the catalyst stability; and they produce excellent results with paraffins C 6 to C 8 However, the length of operations and the ability to regenerate are problems,

  and no satisfactory regeneration processes are known.

sants.

  In a process of dehydrocyclization of hydro-

  aliphatic carbides, hydrocarbons are put into

  contact in the presence of hydrogen with a catalyst

  essentially as an L-type zeolite bearing exchangeable cations of which at least 90% are alkali metal ions selected from the group consisting of sodium, lithium, potassium, rubidium and cesium ions and containing at least one metal selected from the group formed from 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 exerting a dehydrogenating effect, so as to convert

  at least part of the aromatic hydrocarbon load

  ticks. A particularly advantageous embodiment

  The reason for this process is the use of a catalytic

  platinum / alkali metal / zeolite type L, due to its excellent activity and excellent selectivity

  towards the conversion of hexanes and heptanes to hydro-

  aromatic carbides but the length of the operation

remains problematic.

  The present invention overcomes the shortcomings of the prior art by using a catalyst comprising

  a large diameter pore zeolite, an alkaline metal

  earth and a Group VIII metal to reform hydrocarbons with extremely high selectivity towards

  the conversion of alkanes into aromatic hydrocarbons.

  The hydrocarbons are contacted with a catalyst comprising a pore zeolite of large diameter, at least one Group VIII metal (advantageously platinum); and an alkaline earth metal selected from the group consisting of barium, strontium and calcium (preferably barium). According to one aspect of the present invention, the operating conditions are adjusted so that the dehydrocyclization selectivity of n-hexane is In another aspect, the catalyst selectivity index is greater than 60%.

  catalyst gives a satisfactory operating length.

  Large diameter pore zeolite is advantageous

  a type L zeolite which contains 0.1 to 5%

  in weight of platinum and 0.1 to 35% by weight of barium.

  carbides are brought into contact with the zeolite of the type treated by exchange with barium at a temperature of 400 to 600 ° C. (in particular from 430 to 5500 ° C.); at a liquid hourly space velocity of 0.3 to 5; at a pressure of from 0 to 3.5 M Pa (advantageously from 0.35 to 2.1 M Pa); and with an H 2 / HC ratio of 1: 1 to 10: 1

(especially 2: 1 to 6: 1).

  In its broadest aspect, the present invention

  involves the use of a catalyst comprising

  a large diameter pore zeolite, an alkaline metal

  and a Group VIII metal in hydrocarbon reforming, particularly in the dehydrocyclization of alkanes, with extremely high selectivity

  towards the conversion of hexanes into aromatic hydrocarbons

  matic. The term "selectivity" used in this

  memory is defined as the percentage of moles of paraf-

  finely converted to aromatic hydrocarbons with respect to moles converted to aromatic hydrocarbons and cracked products, namely x moles of paraffins converted to selectivity = moles aromatic hydrocarbons

  moles of paraffins converted to hydro-

  aromatic carbides and cracked products Isomerisation reactions and the formation of alkylcyclopentanes are not taken into consideration

  in the determination of selectivity.

  The expression "selectivity to n-hexane"

  used in this memo is defined as

  sensing the percentage of moles of n-hexane converted

  in aromatic hydrocarbons with respect to axux moles conver-

  aromatic hydrocarbons and cracked products.

  Selectivity towards paraf-

  aromatic hydrocarbons is a criterion for assessing

  the efficiency of the process in converting paraffins into desired and valuable products, namely aromatic hydrocarbons and hydrogen, as opposed to

  less desirable hydrocracking products.

  A characteristic characteristic of any catalyst

  of dehydrocyclization estson selectivity index

  selectivity is defined as "selectivity to nhexane" when using n-hexane as the

  charge and when operating at 490 ° C under pressure

  of 0.7 M Pa at an hourly space velocity of

  liquid equal to 3 and with a ratio H 2 / AC equal to 3 after 20 hours.

  Highly selective catalysts produce more hydrogen than less selective catalysts because hydrogen is produced when paraffins are converted to aromatic hydrocarbons, and hydrogen is consumed when paraffins are converted into cracked products. Increased selectivity of the process increases the amount of hydrogen produced

  (more aromatization) and reduces the amount of

  gene consumed (less cracking).

  Another advantage of using highly selective catalysts is that the hydrogen produced by; high selectivity catalysts are purer than the hydrogen produced by less selective catalysts This higher purity comes from the fact that more hydrogen is produced, while less low-boiling hydrocarbons are formed (cracked products) The purity of the hydrogen produced in reforming is decisive

  if, as is usually the case in a refining

  the hydrogen produced is used in processes such as hydrotreating and hydrocracking, which require at least some minimal hydrogen partial pressures. If the purity becomes too low, hydrogen can no longer be used for this purpose. end and should be used in a less interesting way, by

example as a fuel gas.

  In the process according to the invention, the hydro-

  carbides constituting the feed advantageously comprise non-aromatic hydrocarbons containing at least

  6 carbon atoms The charge is advantageously almost

  free of sulfur, nitrogen, metals and other

  known poisons for reforming catalysts.

  The dehydrocyclization is carried out in the presence of hydrogen at a pressure adjusted in such a way as to thermodynamically favor the reaction and to limit the reactions

  undesired hydrocracking by kinetic means.

  The gauge pressures used vary favorably

  from 0 to 3.5 M Pa, especially from 0.35 to 2.1 M Pa, the molar ratio of hydrogen to hydrocarbons being advantageously between 1: 1 and 10: 1, especially between

2: 1 and 6: 1.

  In the temperature range of 400 to 6000 C, the dehydrocyclization reaction takes place at an acceptable rate and selectivity. If the working temperature is below 400 ° C, the reaction rate is insufficient and, in

  Consequently, the yield is too low for

  Likewise, the balance of dehydro-

  cyclisation is unfavorable at low temperatures When the working temperature is above 600 ° C,

  side reactions that interfere, such as

  cracking and coking, manifest themselves and significantly reduce the yield by raising the rate of catalyst deactivation.

  not advisable to exceed the temperature of 600 'C.

  The recommended temperature range (430 to 550 ° C) of the dehydrocyclization is that in which the process is optimal with respect to the activity,

  selectivity and stability of the catalyst.

  The hourly space velocity of hydrocarbons

  liquids is advantageously between 0.3 and 10.

  The catalyst according to the invention is a large diameter pore zeolite loaded with one or more dehydrogenating constituents. The expression "large diameter pore zeolite" is defined as representing a zeolite whose effective pore diameter is 0, 6

1.5 nm.

  Among the large diameter pore crystalline zeolites which have proved advantageous for use in the practice of the present invention, an L-type zeolite and synthetic zeolite with faujasite structure, such as zeolite X and zeolite Y, are the most important and have apparent diameters of

  pores in the range of 0.7 to 0.9 nanometers.

  An L-type zeolite composition, expressed by the molar ratios of the oxides, may be represented by the following formula: (O, 09-1.3) M 2 NO: A 1203 (5.2-6.9) SiO 2: in which M denotes a cation, N represents valence

  M and y may be any value from 0 to about 9.

  Zeolite L, its X-ray diffraction pattern, its properties, and a process for its preparation are described in detail in U.S. Patent No. 3,216,789, which is incorporated herein by reference to illustrate the zeolite of which recommends the use in the present invention The actual formula may vary without changing the crystal structure; for example, the molar ratio of silicon to aluminum

(Si / Al) can vary from 1.0 to 3.5.

  The chemical composition of zeolite Y, expressed by the molar ratios of the oxides, may be represented by the formula: (0.7-1.1) Na 2 O: A 1203: SiO 2: y H 20

  where x is a value ranging from more than 3 to about

  6 and y can be a value up to about 9.

  Zeolite Y has a characteristic powder X-ray diffraction pattern, which can be used with the above formula for identification. Zeolite Y is described in more detail in US Pat. No. 3,130,007 which is incorporated herein by reference to illustrate a

  an advantageous zeolite for use in the present invention.

  Zeolite X is a synthetic crystalline zeolitic molecular sieve which can be represented by the formula: (0.7-1.1) M 2 / n O: A 1203: (2.03, O) Si O 2: y H 20 in which M represents a metal, in particular alkali and alkaline earth metals, N is valence

  M and y can have any value up to

  According to the identity of M and the degree of hydration of the crystalline zeolite zeolite X, its X-ray diffraction pattern, its properties and its method of preparation are described in detail in the US Pat. No. 2,882,244 incorporated herein by reference to illustrate a zeolite

  advantageous to use in the present invention.

  The catalyst of choice according to the invention is an L-type zeolite charged with one or more

dehydrogenating components.

  An essential element of the present invention is the presence of an alkaline earth metal in the

  Large diameter pore zeolite This alkaline metal

  earth must be barium, strontium or calcium, advantageously barium The alkaline earth metal may be incorporated into the zeolite by synthesis, impregnation or ion exchange Barium is preferred to other alkaline earth metals because it gives a slightly less acidic catalyst High acidity is undesirable in the catalyst because it promotes cracking, which leads to

a lower selectivity.

  In one embodiment, at least a portion of the alkali metal is exchanged for barium, by

  known techniques for the treatment of zeolites by.

  ion exchange This involves contacting the zeolite with a solution containing Ba ++ ions in

  excess The barium must constitute 0.1 to 35% of the weight of the zeolite.

  Dehydrocyclization catalysts in accordance with

  in the invention are loaded with one or more Group VIII metals, for example nickel, ruthenium, rhodium,

palladium, iridium or platinum.

  The preferred Group VIII metals are iridium, and especially platinum, which are more selective for dehydrocyclization and they are also more stable in the dehydrocyclization reaction conditions than in the dehydrocyclization reaction. other metals

Group VIII.

  The percentage of platinum recommended in the

  catalyst is between 0.1 and 5%.

  Group VIII metals are introduced into

  zeolite with large diameter pores by synthesis, improper

  cation or exchange in an aqueous solution of a suitable salt If it is desired to introduce two metals of the

  Group VIII in the zeolite, it is possible to conduct

  simultaneously or successively.

  By way of example, platinum can be introduced by impregnating the zeolite with an aqueous solution of platinum (II) tetrammine nitrate, platinum (II) tetrammine hydroxide, dinitrodiamino-platinum or platinum chloride. (II) tetrammine In an ion exchange process, platinum can be introduced through the use of platinum cation complexes such as

  that platinum- (II) nitrate tetrammine.

  An inorganic oxide can be used as a support for binding large diameter pore zeolite

  containing the Group VIII metal and the alkali metal

  The support may be a natural inorganic oxide

  The following are examples of inorganic oxide supports which may be used: clays, alumina and silica, supports in which acidic sites are advantageously exchanged for cations which do not confer a strong acidity (such

Na, K, Rb, Cs, Ca, Sr, or Ba).

  The catalyst can be used in any one

  The conventional types of apparatus known in the prior art can be used in the form of pills, pellets, granules, fragmented elements or in various special forms, arranged in a fixed bed in a reaction zone and the feed material can be passed through the catalyst in the liquid, vapor or mixed phase, in upward or downward flow. Alternatively, it can be prepared in a form suitable for use in moving beds or in processes involving fluidized bodies, in which the charge is passed upward through a turbulent catalyst bed

finely divided.

  After the desired metal or metals have been introduced, the catalyst is treated in the air at

  about 2600 C then reduced in hydrogen at temperatures

  ratures of 200 to 7000 C, preferably 400 to 620 'C.

  At this stage, it is ready to be used 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 advantageous to eliminate any residual acidity in the process. zeolite by treating the catalyst with an aqueous solution of a salt or hydroxide of a suitable alkaline or alkaline earth element to neutralize any hydrogen ions formed during ion reduction

metal by hydrogen.

  To obtain optimal selectivity, the temperature must be adjusted so that the reaction rate is appreciable, but the transformation rate is less than 98%, since an excessive temperature

  and that an excess reaction can impair the selectivity.

  The pressure must also be adjusted within a suitable range

  Too high a pressure imposes a thermal limit

  dynamic (equilibrium) to the desired reaction, especially for the aromatization of hexane, and too much pressure

  bass can cause coke formation and a loss of

  vation. Although the main advantage of the present invention lies in the improvement of the selectivity towards the conversion of paraffins (in particular of C 6 -C 6 paraffins) into aromatic hydrocarbons, it has also surprisingly been found that the selectivity towards the transformation of the This reaction, which on conventional chlorine-treated alumina reforming catalysts involves an acid-catalyzed isomerization step, takes place on the catalyst of the present invention with such good selectivity. or better than on

  catalysts based on chlorinated alumina of the former type

  Thus, the present invention can also be used to catalyze the conversion to aromatic hydrocarbons of high alkylnaphthene content fillers.

with a pentagonal core.

  Another advantage of the invention is that the new catalyst is more stable than the zeolitic catalysts of the prior art. The stability of the catalyst or its resistance to deactivation determines its duration.

  useful service Longer service times reduce

  dead time and the cost of regeneration or

  replacement of the catalyst charge.

  In one embodiment of the present invention

  In this invention, a hydrocarbon feed is contacted with a first catalyst which is a conventional reforming catalyst and with a second catalyst which is a dehydrocyclization catalyst comprising a large diameter pore zeolite, an alkaline earth metal and

a Group VIII metal.

  The use of a reforming catalyst comprises

  a carrier of alumina, platinum and rhenium is

  commented in detail in the United States patent of

  No. 3 415 737, which is incorporated herein by reference.

  to illustrate the use of an advantageous conventional reforming catalyst Other catalysts

  Preferred bimetallic compounds include platinum

  tin, platinum-germanium, platinum-lead and platinum-iridium.

  The hydrocarbons can be brought into contact with the two catalysts in series, the hydrocarbons coming first into contact with the first reforming catalyst (conventional) and then with the second catalyst (dehydrocyclization); or the hydrocarbons first come into contact with the second catalyst and then with the first. Similarly, the hydrocarbons can come into contact in parallel, a fraction of the hydrocarbons coming into contact with the first catalyst and another fraction of the hydrocarbons coming into contact. with the second Similarly, hydrocarbons can be brought into contact with both catalysts simultaneously in the

same reactor.

  The invention is illustrated by the examples

  following, given in a non-limitative manner.

Example I

  A straight-run fraction of a light Arabian crude that had been catalytically hydrotreated to remove sulfur, oxygen, and nitrogen was reformed under 0.7 M Pa pressure at an hourly space velocity. liquid equal to 2 and with

  a ratio H 2 / HC equal to 6, by three different catalysts

  The feed contained 80.2% by volume of paraffins,

  16.7% by volume of naphthenes and 3.1% by volume of hydro-

  aromatic carbides, and it contained 21.8% by volume of C 5 components, 52.9% by volume of C 6 components, 21.3% by volume of C 7 components and 3.2% by volume of C 7 components.

volume of components in C 8.

  In the first test, the straight distillation fraction of light crude oil from Arabia was reformed at 4990 C on a commercial platinum-rheniumalumin sulfide catalyst, described in US Pat.

No. 3,415,737.

  In the second test, the distillation fraction

  Direct light crude oil from Arabia was reformed at 4930 C on a platinum-potassium-zeolite type L catalyst formed by (1) impregnation of an L-type zeolite in the potassium form with 0.8% of platinum. using platinum (II) tetrammine nitrate, (2) drying the catalyst, (3) calcining the catalyst at 260 ° C, and

  (4) Catalyst reduction at 480-500 ° C for one hour.

  In the third run, i.e., the process of the present invention, the straight-run distillation fraction of light crude from Arabia was reformed at 4930 C on a platinum-barium-type L zeolite catalyst formed by 1) ion exchange treatment of an L-type zeolite in the potassium form with a sufficient volume of 0.17 M barium nitrate solution for there to be an excess of barium compared to the ion exchange capacity of zeolite, (2) drying the resulting catalyst formed of L-type zeolite treated by exchange with the

  barium; (3) calcination of the catalyst at 590 ° C., (4)

  cation of the catalyst with 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 in hydrogen at 480-500 C

during one hour.

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

TABLE I

499 C

  Pt / Re / 493 C 493 C Charge Alumina Pt / K / L Pt / Ba / L C 1% by weight of the charge 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

C 6 + P + N 81.3 13.4 7.8 9.3

  Benzene 1.5 15.1 40.6 43.8 aromatic 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 83.7 295, 5 364.9 Selectivity, moles% 20 72 87 P at C 6 + -> aruatic This series of tests shows that the use of a platinum-barium-zeolite type L catalyst in

  reforming gives a selectivity towards the transformation

  It is to be noted that this higher selectivity is accompanied by an increase in the production of hydrogen gas which can be used in other processes. also that the

  purity of hydrogen is greater in the test used

  the catalyst Pt / Ba / L, since it is produced

  more hydrogen and less C 1 + C 2.

Example II

  We conducted a second series of tests to

  demonstrate that the present invention would result in

  with other large diameter pore zeolites in addition to the L-type zeolite The selectivity index

was measured for 4 catalysts.

  This second series of tests was conducted using n-hexane as a filler. All the tests of this series were carried out at 4900 C, at a pressure of 0.7 M Pa, at an hourly space velocity.

  of the liquid equal to 3 and with a ratio H 2 / HC equal to 3.

  In the first test, a platinum-potassium zeolite L-type catalyst was used which was prepared by the operations illustrated in the second method of Example I. In the second test, the platinum-barium-zeolite catalyst was used in the second test. type L which had been prepared by the operations illustrated in the third method of Example I, with the difference that the solution of barium nitrate was 0.3 M instead of 0.17 M.

  In the third trial, a catalyst was used

  platinum-sodium-zeolite Y which had been prepared by impregnation of a zeolite Y in the sodium form with Pt (NH 3) 4 (NO 3) 2 to obtain 0.8% of platinum, then drying, calcination of the catalyst at 260 'C and reduction

in the 480-500 hydrogen. In the fourth test, a catalyst was used.

  platinum-barium-zeolite Y which had been prepared by ion exchange treatment of a zeolite Y in the sodium form with 0.3 M barium nitrate at 800 C, drying and calcination at 590 ° C and then impregnation of the zeolite with Pt (NH 3) 4 (NO 3) 2 so that there is 0.8% of platinum, then drying, calcination of the catalyst at 260 ° C and reduction in hydrogen at 480-500 WC The results

  of these tests are reproduced below in Table IM.

TABLE II

  Transformation Index h 20 h selectivity Pt / K / L 70 59 79 Pt / Ba / 1 85 85 92 Pt / Na / Y 82 79 54 Pt / Ba / Y 74 68 66 Thus, in service, the incorporation of barym a a large-pore zeolite such as a Y-type zeolite results in a dramatic improvement in n-hexane selectivity. It should be noted that the stability of the platinum-barium-type L zeolite catalyst is excellent. hours, there was no decrease in the conversion rate when using the platinum-barium-type L zeolite catalyst.

Example III

  We conducted a third series of tests for

  demonstrate the effect of the addition of other ingredients

catalyst.

  This third series of tests was conducted in

  using a feed that had been hydrotreated

  to remove sulfur, oxygen and nitrogen, containing 80.9% by volume of paraffins, 16.8% by volume

  naphthenes and 1.7% by volume of aromatic hydrocarbons.

  The feed also contained 2.6% by volume of C 5 components, 47.6% by volume of C 6 components, and 43.4% by volume of C 5 components.

  volume of C 7 components and 6.3% by volume of

  C 8 All of the tests in this series were conducted at 490 C under a pressure of 0.7 M Pa at a liquid hourly space velocity of 2.0 and

with an H 2 / HC ratio of 6.0.

  In the first test, a platinum-sodium-zeolite Y catalyst was prepared by the indicated operations.

in the third method of Example II.

  In the second test, a platinum-barium-zeolite Y catalyst was prepared by the illustrated operations

  in the fourth method of Example II.

  In the third run, a platinum-rare earth Y-catalyst was prepared by impregnating a commercially available rare earth Y zeolite from Strem Chemicals Inc. to 0.8% platinum, using Pt (NH 3) 4 (NO 3) 2, then the zeolite

  was dried, calcined at 260 ° C. and reduced to 480-500 ° C.

  In the fourth trial, a cat-

  platinum-rare earth-barium-zeolite Y-lyser by ion exchange treating a commercial rare earth Y zeolite of Strem Chemicals Inc with a 0.3 M Ba (NO 3) 2 solution at 80 ° C drying and calcining the zeolite at 590 ° C., impregnating it with Pt (NH 3) 4 (NO 3) 2 so that there is 0.8% platinum and then

  drying the zeolite, calcining it at 260 ° C and reducing

  at 480-500 C The results of these tests are reproduced

  shown in Table III below.

TABLE III

  Pt / Na / Y Pt / Ba / Y Pt / rare earth / Y Activity towards 1 aromatics, after 3 h, moles% of C in charge Pt / Ba / rare earth / Y 36 This series of tests shows that rare earth to the catalyst exerts an effect

selectivity.

Example IV

  s Selectivity, +% after 3 hours (too low,

not measured

  the addition of an unfavorable Arabian naphtha which had been catalytically hydrotreated to remove sulfur, oxygen and nitrogen, was reformulated under 0.7 M Pa at hourly space velocity. of the liquid equal to 3 and with a ratio H 2 / HC equal to 3 to form a C 5 + product having an aromatic content of 82% by weight by two different processes The feedstock was a catalytically hydrotreated Arabian naphtha containing 67 , 9%

  paraffins, 23.7% naphthenes and 8.4% aromatics.

  The results of distillation according to method D 86 were as follows: Initial Eb 95 C, 5% -103.9 C,

  % -106.7 ° C, 30% -120 ° C, 50% -129.4 ° C, 70% -143.9 ° C,

  90% -160.5 C, 95% -169.4 C, final Eb 187.8 C. In the first process, the naphtha of Arabia has

  was reformed at 516 C in a reactor using a catalyst.

  conventional reforming lyser comprising 0.3% Pt,

  0.6% Re, 1.0% Cl (by weight), on alumina.

  It has been pre-sulphurated separately.

  In the second process, Arabian naphtha was reformed at 493 C in the same reactor, the upper half of which contained the same type of catalyst as in the first process and the lower half of which contained a platinum-barium-zeolite catalyst of the L formed by the operations illustrated in Example I. The results of these two tests are reproduced

in Table IV.

TABLE IV

  Pt / Re / 1/2 Pt / Re / alumina alumina 1/2 Pt / Ba / L Deactivation rate 2.0 1.9 Yield in C 5 + liquids,% by volume 68.9 71.0 Hydrogen, m 3 / j 26.9 29.7 It goes without saying that the present invention has been described only for explanatory purposes - but in no way limiting, and that many modifications can be made to it

without leaving his frame.

Claims (8)

  1 Process for the reforming of hydrocarbons,   in that it consists in bringing in the said hydro-   carbides in contact with a catalyst comprising a large diameter pore zeolite comprising: (a) at least one Group VIII metal; and (b) an alkaline earth metal selected from the group consisting of barium, strontium and calcium, the selectivity index of the catalyst being greater than 60%, the selectivity index being defined as the moles of n -hexane converted to aromatic hydrocarbons based on the moles of n-hexane converted to aromatic hydrocarbons and cracked products, for a n-hexane feed over the catalyst at a temperature of 490 ° C, at a gauge pressure of 0.7 M Pa, at a liquid hourly space velocity equal to 3 and with a ratio H 2 / HC equal at 3, after 20 hours.   2 process for reforming hydrocarbons according to claim 1, characterized in that the pore zeolite of large diameter has an apparent diameter of the pores from 0.7 to 0.9 nanometers.   A process for reforming hydrocarbons according to claim 1, characterized in that the contacting takes place at a temperature of 400 to 6000 C at a liquid hourly space velocity of 0.3 to 5; at a gauge pressure of 0 to 0.5 M Pa and with a ratio H 2 / BC of 1: 1 to 10: 1.   4 Process for reforming hydrocarbons,   in that it consists in bringing in the said hydro-   carbides in contact with a catalyst comprising a large diameter pore zeolite, comprising: (a) at least one Group VIII metal; and (b) an alkaline earth metal selected from the group consisting of barium, strontium and calcium, the operating conditions being adjusted so that the dehydrocyclization selectivity of n-hexane is greater than 60%.   Process for converting hydrocarbons, characterized in that it comprises: (a) bringing said hydrocarbons into contact, under reforming conditions and in the presence of hydrogen, with a first catalyst comprising a metal oxide support on which are deposited in an intimate mixture of platinum and rhenium; and (b) contacting said hydrocarbons with a second catalyst comprising a large diameter pore zeolite containing at least one Group VIII metal, and an alkaline earth metal selected from   the group consisting of barium, strontium and calcium.   6 Hydrocarbon transformation process   5, characterized in that the alkaline earth metal is barium and the Group VIII metal is platinum.   7 Process for converting hydrocarbons   claim 6, characterized in that the catalyst   dehydrocyclization contains 0.1 to 35% by weight barium and 0.1 to 5% platinum.   8 Hydrocarbon transformation process   any of claims 1, 4 and 5,   characterized in that said large diameter pore zeolite is selected from the group consisting of zeolite X, zeolite Y, and type L zeolite.   9 Hydrocarbon transformation process   any of claims 3, 4 and 5,   characterized in that the contacting in the step   (b) takes place at a temperature of 430 to 5500 C; at a   gauge pressure of 0.35 to 2.1 M Pa and with a ratio H 2 / HC of 2: 1 to 6: 1.