FR2857020A1 - Decreasing flow point of hydrocarbon charges obtained from Fischer-Tropsch reaction by use of mixed zeolite catalyst, for obtaining good quality base lubricants - Google Patents

Abstract

Improving the flow point of a Fischer-Tropsch effluent comprises contacting the latter with a catalyst comprising a zeolite of structure TON(Theta-1, ZSM-22, ISI-1, NU-1O and KS-2) and a zeolite ZBM, a hydro-dehydrogenating element and a porous mineral matrix.

Description

The present invention relates to a method for improving the point

  for the flow of hydrocarbon feedstocks from the Fischer-Tropsch process, in particular to convert, in good yield, fillers having high pour points into at least one cup having a low pour point and a high index

  of viscosity for the oil bases, by passing through a catalytic hydrodewaxing catalyst comprising at least one zeolite (molecular sieve) chosen from the group formed by zeolites of structural type TON (Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2) and at least one zeolite ZBM-30 synthesized preferably in the presence of a particular structurant such as triethylenetetramine, at least one porous mineral matrix, at least one hydro-dehydrogenating element, preferably chosen from the elements of Group VIB and Group VIII of the Periodic Table.

  PRIOR ART High quality lubricants are of paramount importance for the proper functioning of modern machines, automobiles, and trucks. However, the amount of paraffins directly from petroleum, untreated, and having the proper properties to constitute good lubricants is very small compared to the increasing demand in this sector.

  The treatment of heavy petroleum fractions with high levels of linear or low branched paraffins is necessary in order to obtain base oils of good quality and with the best possible yields, by an operation which aims to eliminate linear or very poorly branched paraffins. , which will then be used as base oils or as kerosene or jet fuel.

  Indeed, high molecular weight paraffins which are linear or very weakly branched and which are present in oils or in kerosene or jet fuel lead to high pour points and thus to freezing phenomena for low temperature applications. . In order to decrease the pour point values, these linear paraffins which are not or very slightly connected must be completely or partially eliminated.

  This operation can be carried out by extraction with solvents such as propane or methyl ethyl ketone, which is then referred to as propane or methyl ethyl ketone (MEK) dewaxing. However, these techniques are expensive, time consuming and not always easy to implement.

  Another means is the selective cracking of the longer linear paraffinic chains which leads to the formation of lower molecular weight compounds, a portion of which can be removed by distillation.

  Given their selectivity of form zeolites are among the most used catalysts. The idea that prevails in their use is that there are zeolitic structures whose pore openings are such that they allow the entry into their microporosity linear paraffins long or very little branched but excluding branched paraffins, naphthenes and aromatics. This phenomenon thus leads to selective cracking of linear or very poorly branched paraffins.

  Zeolite catalysts having intermediate pore sizes such as ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM35 and ZSM-38 have been described for use in these processes in particular in US Patents 3,894,938; US 4,176,050; US 4,181,598; US 4, 222,855; US 4,229,282 and US 4,247,388.

  Mixtures of large pore zeolites and these intermediate pore zeolites for use in a dewaxing process are described in WO002088279.

  Furthermore, it has been found that processes using these zeolites (ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38) make it possible to obtain oils by cracking. fillers containing amounts of linear or very poorly branched paraffins less than 50% by weight. However, for feeds containing higher amounts of these compounds it has been found that their cracking leads to the formation of large amounts of lower molecular weight products, such as butane, propane, ethane, and methane, which significantly reduces the yield. in sought after products.

  To overcome these drawbacks, the applicant has focused its research efforts on the development of a method for improving the pour point of hydrocarbon feedstocks from the Fischer-Tropsch process using catalysts comprising at least one zeolite (molecular sieve) selected from the group consisting of zeolites of structure type TON (Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2) and at least one zeolite selected from the group formed by zeolites (ZSM-48 , EU-2, EU3 2857020 11 and ZBM-30), at least one hydro-dehydrogenating element, preferably selected from Group VIB and Group VIII elements of the Periodic Table. The Applicant has surprisingly discovered that the use of a catalyst comprising at least one zeolite of structural type TON and at least one zeolite ZBM-30 preferably synthesized with a particular structurant such as triethylene tetramine makes it possible to lower the point of flow of the filler while obtaining a high viscosity index (VI) and maintaining a good yield of desired products.

  The present invention provides a catalytic process for reducing the pour point of feeds from the Fischer-Tropsch process based on such catalysts.

  OBJECT OF THE INVENTION More specifically, the invention relates to a process for improving the pour point of a paraffinic feedstock produced by Fischer-Tropsch synthesis, in which the feedstock to be treated is brought into contact with a catalyst comprising at least one minus one zeolite (molecular sieve) selected from the group formed by the zeolites of structural type TON (Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2) and at least one zeolite ZBM-30 (synthesized preferably with a particular structurant such as triethylenetetramine), at least one hydrodehydrogenating element, preferably selected from Group VIB and Group VIII elements of the Periodic Table, at least one porous mineral matrix, the process is conducted at a temperature between 200 and 450 ° C, a pressure between 0.1 and 25 MPa and a hourly space velocity between 0.05 and 30 h -1, in the presence of hydrogen at a rate of 50 to 2000 normal liters of hydrogen per liter of charge.

  The zeolites included in the catalyst that can be used in the process according to the invention which are of structural type TON are described in the "Atlas of Zeolite Structure Types", WM Meier, DH Oison and Ch. Baerlocher, 4th Revised edition, 1996, Elsevier.

  The synthesis of zeolite ZBM-30 is described in EP-A-46504.

  Unexpectedly, said catalyst exhibits a greater activity and selectivity in dewaxing (improvement of the Fischer-Tropsch charge flow point) than the zeolite catalytic formulas (molecular sieves) known in the prior art. .

  Thus, this method makes it possible to convert a feedstock having a high pour point into a product having a lower pour point, and makes it possible to obtain oil bases having good cold properties and a high viscosity index and gas oils. of good quality.

  The fillers which can be treated according to the process of the invention are advantageously fractions having relatively high pour points whose value is to be reduced.

  Typical fillers which can be advantageously treated according to the invention generally have a pour point above 0 C. The products resulting from the treatment according to the process have pour points of less than 0 ° C. and preferably less than about -10 C.

  The process according to the invention, under the conditions described above, allows, in particular, the production of products with a low pour point with good yields, and with a high viscosity index in the case of the heavier fractions which are processed for the purpose of producing oil bases.

  Detailed description of the invention

  The process according to the invention uses a catalyst which comprises at least one zeolite chosen from the group formed by zeolites of structural type TON and at least one zeolite ZBM-30 synthesized preferably with a particular structurant such as triethylene tetramine, at least one hydro-dehydrogenating element, preferably selected from Group VIB and Group VIII elements of the Periodic Table and at least one porous mineral matrix.

  The TON structural type zeolite in the catalyst composition is selected from the group consisting of Theta-1, ISl1, NU-10, KZ-2 and ZSM-22 zeolites described in "Atlas of Zeolite Structure Types". , WM Meier, DH Oison 2857020 and Ch. Baerlocher, 4th Revised edition, 1996, Elsevier, and US Pat. NU-10.

  The synthesis of zeolite ZBM-30 is described in EP-A-46504.

  Preferably zeolites NU-10 or ZSM-22 are used with ZBM30. Zeolite ZBM-30 is preferably synthesized according to the methods described in patent EP-A-46504 according to the procedure using the structuring agent triethylenetetramine.

  The overall Si / Al ratio of the zeolites used in the composition of the catalysts of the process according to the invention as well as the chemical composition of the samples are determined by X-ray fluorescence and atomic absorption. The Si / Al ratios of the zeolites described above are those obtained at the synthesis according to the procedures described in the various documents cited or obtained after post-synthesis dealumination treatments well known to those skilled in the art, such as and not limited to the hydrothermal treatments followed or not attacks acids or direct acid attacks by solutions of mineral or organic acids.

  The zeolites used in the composition of the catalysts of the process according to the invention can be calcined and exchanged by at least one treatment with a solution of at least one ammonium salt so as to obtain the ammonium form of the zeolites which, once calcined, leads to to the hydrogen form of said zeolites.

  The zeolites used in the composition of the catalyst of the process according to the invention are at least partly, preferably almost completely, in acid form, that is to say in hydrogen (H +) form. The atomic ratio Na / T is generally less than 10% and preferably less than 5% and even more preferably less than 1%.

  On the other hand, the catalyst contains at least one hydrodehydrogenating element, preferably selected from Group VIB and Group VIII (ie metal or compound) elements of the Periodic Table and at least one mineral matrix. porous.

  In the case where the element is at least one Group VIII metal, preferably when it is at least one noble metal and preferably a noble metal selected from the group consisting of platinum and palladium, it can be introduced on zeolites for example by dry impregnation, ion exchange or any other method known to those skilled in the art, or it can be introduced on the matrix.

  According to a first variant, prior to their shaping at least one of the previously described zeolites is subjected to the deposition of at least one Group VIII metal, preferably selected from the group consisting of platinum and palladium. The zeolites thus loaded with metals are mixed. The mixture of these zeolites which are then in the form of powder is made by all the powder mixing techniques known to those skilled in the art.

  Once the mixture of zeolite powders, loaded with metals, made, the mixture is shaped by any technique known to those skilled in the art. It can in particular be mixed with a matrix, generally amorphous, for example with a wet powder of alumina gel. The mixture is then shaped, for example by extrusion through a die.

  The shaping can be carried out with other matrices than alumina, such as, for example, magnesia, amorphous silica-aluminas, natural clays (kaolin, bentonite, sepiolite, attapulgite), silica, titanium, boron oxide, zirconia, aluminum phosphates, titanium phosphates, zirconium phosphates, coal and mixtures thereof. It is preferred to use matrices containing alumina, in all its forms known to those skilled in the art, and even more preferably aluminas, for example gamma-alumina. Other techniques than extrusion, such as pelletizing or coating, can be used.

  It is also advantageous to use mixtures of alumina and silica, mixtures of alumina and silica-alumina.

  The catalysts obtained are shaped in the form of grains of different shapes and sizes. They are generally used in the form of cylindrical or multi-lobed extrusions such as bilobed, trilobed, straight-lobed or twisted, but may optionally be manufactured and used in the form of crushed powders, tablets, rings, beads. , wheels.

  After the shaping step, the product obtained is subjected to a drying step and then to a calcination step.

  In the case where the hydrogenating metal belongs to group VIII, and preferably is platinum and / or palladium, it can also and advantageously be deposited on the support after shaping the zeolites free of metals, by any known method of those skilled in the art and allowing the deposition of the metal on the molecular sieve. In this case the support is obtained in a manner similar to that described above.

  In the rest of the text, the term "support" will be used to denote the mixture of zeolites (free of metals) plus matrix after shaping, drying and calcination, for example as previously obtained.

  To deposit the metal on the zeolites, it is possible to use the competitive cation exchange technique in which the competitor is preferably ammonium nitrate, the competition ratio being at least equal to approximately 20 and advantageously from approximately 30 to 200. In the case of platinum or palladium, a platinum tetramine complex or palladium tetramine complex is usually used: these will then be deposited substantially entirely on the zeolites. This cation exchange technique can also be used to directly deposit the metal on the molecular sieve powder before it is mixed with a matrix.

  The deposition of the metal (or metals) of group VIII is generally followed by a calcination in air or oxygen, usually between 300 and 600 ° C. for 0.5 to 10 hours, preferably between 350 ° C. and 550 ° C. for 1 to 4 hours. It is then possible to carry out a reduction in hydrogen, generally at a temperature of between 300 and 600 ° C. for 1 to 10 hours, preferably between 350 and 550 ° C. for 2 to 5 hours.

  Platinum and / or palladium can also be deposited either directly on the molecular sieves, but on the matrix (for example the aluminum binder) of the support, before or after the shaping step, by implementing a anion exchange 8 2857020 with hexachloroplatinic acid, hexachloropalladic acid and / or palladium chloride in the presence of a competing agent, for example hydrochloric acid. In general after platinum and / or palladium deposition, the catalyst is as previously calcined and then reduced in hydrogen as indicated above.

  The support of the catalytic dewaxing catalyst according to the present invention generally contains the following contents of matrix and zeolites: 5 to 95% by weight, preferably 10 to 90% by weight, more preferably 15 to 85% by weight and very preferably from 20 to 80% by weight of zeolites such that at least one zeolite is selected from the group consisting of zeolites of structural type TON such as Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2 and at least a zeolite is a zeolite ZBM-30, 5 to 95%, preferably 10 to 90%, more preferably 15 to 85% and very preferably 20 to 80% by weight of at least one porous mineral matrix The distribution between the two zeolites of each of the groups defined above is such that the content of zeolite (s) chosen in the group formed by zeolites of structural type TON (Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2) can 1% to 99%, preferably 5 to 95% and even more preferably may vary between 10 and 90% in relative percentages of all zeolites introduced into the catalyst. Likewise, the ZBM-30 zeolite content varies from 1% to 99%, preferably from 5% to 95%, and even more preferably varies between 10% and 90%, in relative percentages, of all the zeolites introduced into the zeolite. catalyst.

  The noble metal content (s) thus optionally introduced, expressed in% by weight relative to the total mass of the catalyst, is generally less than 5%, preferably less than 3%, even more preferably less than 2% and generally less than 1% by weight.

  In the preferred case where the catalyst comprises a Group VIII hydrogenating metal, preferably a noble metal and advantageously platinum and / or palladium, the catalyst is generally reduced in the reactor in the presence of hydrogen and under conditions well known in the art. the skilled person.

  In the case where the hydrogenating metal is not a noble metal, the Group VIB and Group VIII elements optionally introduced into the catalyst according to the invention may be present in whole or in part in the metallic and / or oxide form. and / or sulphide.

  Among the elements of group VIB, molybdenum and tungsten are preferred.

  Group VIB element sources that can be used are well known to those skilled in the art. For example, among the sources of molybdenum and tungsten, it is possible to use oxides and hydroxides, molybdic and tungstic acids and their salts, in particular ammonium salts such as ammonium molybdate, ammonium heptamolybdate, ammonium tungstate, phosphomolybdic acid, phosphotungstic acid and their salts. Oxides and ammonium salts such as ammonium molybdate, ammonium heptamolybdate and ammonium tungstate are preferably used. The dewaxing catalyst according to the present invention may contain a Group VIII non-noble metal and preferably cobalt and nickel. Advantageously, the following combinations of non-noble group VI and VIII elements are used: nickel-molybdenum, cobalt-molybdenum, iron-molybdenum, fertungsten, nickel-tungsten, cobalt-tungsten, the preferred combinations are: nickel- molybdenum, nickel-tungsten. It is also possible to use combinations of three metals, for example nickel-cobalt-molybdenum.

  Group VIII element sources that can be used are well known to those skilled in the art. For example, use will be made of nitrates, sulphates, phosphates, halides for example, chlorides, bromides and fluorides, carboxylates, for example acetates and carbonates.

  When the hydrogenating function is provided by a group VIII non-noble metal or a group VIII non-noble metal combination and a group VIB metal, the composition of the support consisting of at least one matrix and zeolites described in FIG. The invention is the same as that described above and the weight content of the catalyst in at least one element selected from group VIB and non-noble group VIII is between 0.1 and 60%, preferably between 1 and 50% and even more preferably between 2 and 40%.

  Generally, in order to complete the preparation of the catalyst, the wet solid is allowed to stand under a humid atmosphere at a temperature of between 10 and 80 ° C., and then the wet solid obtained is dried at a temperature of between 60 and 150 ° C., and finally, calcine the solid obtained at a temperature of between 150 and 800 ° C., generally between 250 and 600 ° C.

  The catalysts of the process of the present invention may optionally be subjected to a sulphurization treatment making it possible, at least in part, to convert the metal species into sulphide before they come into contact with the charge to be treated. This sulfidation activation treatment is well known to those skilled in the art and can be performed by any method already described in the literature.

  In the case of non-noble metals, a conventional sulfurization method well known to those skilled in the art consists of heating in the presence or under a flow of a hydrogen / hydrogen sulfide mixture or under pure hydrogen sulfide, at a temperature of between 150 and 800 ° C., preferably between 250 ° and 600 ° C., generally in a crossed-bed reaction zone.

  Charges The hydrocarbon feedstocks treated according to the process of the invention are charges produced by Fischer-Tropsch synthesis and advantageously fractions having relatively high pour points whose value is to be reduced.

  In general, at least part of the compounds having a boiling point greater than or equal to 340 ° C. is treated according to the invention.

  In the Fischer-Tropsch process, the synthesis gas (CO + H2) is catalytically converted into oxygenates and essentially linear hydrocarbons in gaseous, liquid or solid form. These products are generally free of heteroatomic impurities such as, for example, sulfur, nitrogen or metals. They also contain practically little or no aromatics, naphthenes and more generally cycles especially in the case of cobalt catalysts. On the other hand, they may have a significant content of oxygenated products which, expressed by weight of oxygen, is generally less than about 5% by weight and also an unsaturated content (olefinic products in general) generally less than 10% by weight. However, these products, mainly made of normal paraffins, can not be used as such, in particular because of their cold-holding properties that are not very compatible with the usual uses of petroleum fractions. For example, the pour point of a linear hydrocarbon containing 20 carbon atoms per molecule (boiling point equal to about 340 ° C, that is often included in the middle distillate cut) is about +37 ° C. which makes its use impossible, the specification being -15 C for diesel. The hydrocarbons resulting from the Fischer-Tropsch process comprising mainly n-paraffins must be converted into more valuable products such as, for example, gas oil, kerosene, which are obtained, for example, after catalytic reactions of hydroisomerization.

  Typical fillers which can be advantageously treated according to the invention generally have a pour point above 0 C. The products resulting from the treatment according to the process have pour points of less than 0 ° C. and preferably less than about 0 ° C. -10 C.

  In the hydrocarbon feedstock coming into contact with the ZBM-30 catalyst (from which the oils and optionally the high quality distillates can be obtained), preferably at least 50% by weight of the feedstock has a temperature of boiling of at least 340 ° C, and even more preferably at least 60% by weight and more preferably at least 80% by weight of the filler has a boiling point of at least 340 ° C, preferably greater than at least 370 C and even more preferably greater than at least 380 C. This does not mean, for example, that the boiling point is 380 C and more, but 380 C or more.

  The load is therefore mainly composed of normal paraffins.

  In general, the feedstocks suitable for the objective oils have an initial boiling point of greater than at least 340 ° C and more preferably greater than at least 370 ° C and more preferably greater than at least 380 ° C.

  The process according to the invention, under the conditions described below, makes it possible, in particular, to produce products with a low pour point with good yields, and with a high viscosity index in the case of the heavier fractions which are treated. for the purpose of producing oil bases.

  Operating Conditions The operating conditions in which the catalytic dewaxing process of the invention is carried out are the following: the reaction temperature is between 200 and 450 ° C. and preferably between 200 and 420 ° C., advantageously between 250 ° C. and 450 ° C. ; the pressure is between 0.1 and 25 MPa and preferably between 1 and 20 MPa; the hourly volume velocity (wh expressed as the volume of feed injected per unit volume of catalyst per hour) is between about 0.05 and about, and preferably between about 0.1 and about 20 h 1 and even more preferably between about 0.1 and about 10 h -1.

  The contact between the feedstock and the catalyst is carried out in the presence of hydrogen. The level of hydrogen used and expressed in liters of hydrogen per liter of filler is between 50 and about 2000 liters of hydrogen per liter of filler and preferably between 100 and 1500 liters of hydrogen per liter of filler.

  Embodiments In a first preferred embodiment, the catalytic dewaxing process according to the invention may be preceded by a hydroisomerization / hydroconversion step in the presence of a catalyst containing at least one noble metal deposited on an amorphous acidic support.

  This hydroisomerization-hydroconversion step is optionally preceded by a hydrorefining step to remove the (oxygenated) heteroatoms, this hydrorefining step being followed by an intermediate separation.

  The hydroisomerization-hydroconversion step takes place in the presence of hydrogen and in the presence of a bifunctional catalyst comprising an amorphous acidic support (preferably an amorphous silica-alumina) and a hydrodehydrogenating metal function provided by at least one noble metal of group VIII.

  The support is said to be amorphous, that is to say devoid of molecular sieves, and in particular of zeolite, as well as the catalyst. The amorphous acidic support is advantageously an amorphous silica-alumina but other supports are usable. When it is a silica-alumina, the catalyst generally does not contain added halogen, other than that which could be introduced for the impregnation, noble metal for example. The silica-alumina may be obtained by any synthetic technique known to those skilled in the art such as coprecipitation, cogelling techniques.

  During the hydroisomerization-hydroconversion step, the molecules of the feedstock to be treated, for example n-paraffins, in the presence of a bifunctional catalyst undergo isomerization and then optionally hydrocracking to lead respectively to the formation of isoparaffins and lighter cracking products such as gas oils and kerosene. The conversion of products having boiling points greater than or equal to the initial boiling point of the feedstock which is at least 340 ° C., or even 370 ° C., or more preferably at least 380 ° C., in point products boiling point below the initial boiling point of the charge generally varies between 5 and 90%, preferably between 5 and 80% but is generally preferably less than 80% and even more preferably less than 60%.

  The characteristics of the hydroisomerization-hydroconversion catalyst are described in greater detail: The preferred support used for the preparation of the hydroisomerization-hydroconversion pretreatment catalyst described in the context of this patent is composed of SiO 2 silica and Al 2 O 3 alumina. The silica content of the support, expressed as a weight percentage, is generally between 1 and 95%, advantageously even between 5 and 95%, and preferably between 10 and 80% and even more preferably between 20 and 70%, and between 22 and 45%. This silica content is perfectly measured using X-ray fluorescence. For this particular type of reaction, the metal function is provided by a noble metal of group VIII of the periodic table of elements and more particularly platinum and / or palladium.

  The noble metal content, expressed in% by weight of metal relative to the catalyst, is between 0.05 to 10 and more preferably between 0.1 and 5.

  The preparation and shaping of the support, and in particular of the silica-alumina, is done by usual methods well known to those skilled in the art. Advantageously, prior to the impregnation of the metal, the support may undergo calcination, for example a heat treatment at 300-750 ° C (600 ° C preferred) for 0.25-10 hours (preferred 2 hours) under 0-30 ° C. % volume of water vapor (for the preferred silica alumina 7.5%).

  The noble metal salt is introduced by one of the usual methods used to deposit the metal (preferably platinum and / or palladium, platinum being still preferred) on the surface of a support. One of the preferred methods is dry impregnation which consists of introducing the metal salt into a volume of solution which is equal to the pore volume of the catalyst mass to be impregnated. Prior to the reduction operation, the catalyst may be calcined, for example, in a dry air treatment at 300-750 ° C (520 ° C preferred) for 0.25-10 hours (2 hours preferred).

  Before use in the hydroisomerization-conversion reaction, the metal contained in the catalyst must be reduced. One of the preferred methods for conducting the reduction of the metal is the treatment in hydrogen at a temperature of between 150 ° C. and 650 ° C. and a total pressure of between 0.1 and 25 MPa. For example, a reduction consists of a plateau at 150 C for 2 hours, then a rise in temperature up to 450 C at the rate of 1 C / min and then a plateau of 2 hours at 450 C; throughout this reduction step, the hydrogen flow rate is 1000 liters hydrogen / liter catalyst. Note also that any ex-situ reduction method is suitable.

  The operating conditions in which the hydroisomerization hydroconversion step is carried out are described below.

  The pressure will be maintained between 2 and 25 MPa and preferably 3 to 20 MPa and preferably 2 to 18 MPa, the space velocity will be between 0.1 h-1 and 10 h-1, preferably between 0.2 and 10h 1 is advantageously between 0.5 and 5.0h-1. The hydrogen content is between 100 and 2000 liters of hydrogen per liter of filler and preferably between 150 and 1500 liters of hydrogen per liter of filler.

  The temperature used in this step is between 200 and 450 ° C. and preferably from 250 ° C. to 450 ° C., advantageously from 300 ° to 450 ° C., and still more advantageously above 340 ° C., for example between 320 ° C.

  In the case where a hydrorefining step precedes the hydroisomerization hydroconversion step, the two hydrorefining and hydroisomerization-conversion steps can be carried out on both types of catalysts in (two or more) different reactors, and or on at least two catalytic beds installed in the same reactor.

  The use of the catalyst described above in the hydroisomerization hydroconversion step has the effect of increasing the isomerization rate of the heavy fraction (340 C +, or even 370 C + and better still 380 C +) and to reduce its point. flow. More generally, it can be seen that the treatment of the hydroisomerization hydroconversion step then makes it possible to obtain better yields of dewaxed oil fraction which will be obtained in the catalytic dewaxing step and to obtain the desired viscometric properties (viscosity and index viscosity VI).

  In an alternative embodiment, the effluent from the hydroisomerisationconversion stage can be entirely treated in the dewaxing process according to the invention. This variant, with passage in the catalytic dewaxing process of all of the effluent of the hydroconversion-hydroisomerization step, is economically advantageous, since a single distillation unit is used at the end of the process. In addition, at the final distillation (after catalytic dewaxing or subsequent treatments) a cold cold gas oil is obtained.

  Alternatively, the effluent from the hydroisomerization hydroconversion step may be separated from at least a portion (and preferably at least a major part) of light gases which include hydrogen and possibly also compounds hydrocarbons having not more than 4 carbon atoms. Hydrogen can be separated beforehand.

  Advantageously, in another variant embodiment, the effluent resulting from the hydroisomerization-hydroconversion stage is distilled so as to separate the light gases and also to separate at least one residue containing compounds with a boiling point greater than minus 340 ° C. It is preferably an atmospheric distillation.

  It can advantageously be distilled to obtain several fractions (gasoline, kerosene, diesel for example), with a boiling point of at most 340 C and a fraction (called residue) with an initial boiling point greater than at least 340 C and better greater than 350 C and preferably at least 370 C or 380 C.

  This fraction (residue) is then treated in the catalytic dewaxing step, that is to say without undergoing distillation under vacuum. But in another variant, it is possible to use vacuum distillation.

  Generally speaking, the term (s) with initial boiling point of at least 150 ° C. and final up to before the residue, that is to say generally up to 30 ° C., are referred to as middle distillates. at 340 ° C., 350 ° C. or preferably below 370 ° C. or at 380 ° C.

  The effluent from the hydroisomerization-hydroconversion stage may undergo, before or after distillation, other treatments such as, for example, an extraction of at least part of the aromatic compounds.

  In general, at least a portion of the effluent from the hydroisomerization-hydroconversion stage, which effluent may have undergone the separations and / or treatments described above, is subjected to the catalytic dewaxing process according to US Pat. invention.

  It should be noted that compounds boiling above at least 340 ° C are still subjected to catalytic dewaxing.

  The effluent leaving the catalytic hydrodewaxing process according to the invention is advantageously sent to the distillation train, which preferably incorporates atmospheric distillation and vacuum distillation, the purpose of which is to separate the point conversion products. boiling point below 340.degree. C. and preferably below 370.degree. C. (and including in particular those formed during the catalytic hydrodewaxing step), and separating the fraction which constitutes the oil base and whose initial point of boiling is greater than at least 340 C and preferably greater than or equal to 370 C.

  Moreover, this vacuum distillation section makes it possible to separate the different grades of oils.

  Preferably, before being distilled, the effluent leaving the catalytic hydrodewaxing stage is, at least in part and preferably, in its entirety, sent on a hydrofinishing catalyst (hydrofinition) in the presence of hydrogen so as to carry out a thorough hydrogenation of aromatic compounds possibly still present which adversely affect the stability of oils and distillates. However, the acidity of the catalyst must be low enough not to lead to the formation of cracking product boiling point below 340 C so as not to degrade the final yields including oils.

  The catalyst used in this hydrofinishing step comprises at least one Group VIII metal and / or at least one Group VIB element of the Periodic Table. The strong metal functions: platinum and / or palladium, or nickel-tungsten, nickel-molydbene combinations will advantageously be used to carry out a thorough hydrogenation of the aromatics.

  These metals are deposited and dispersed on an amorphous or crystalline oxide type support, such as, for example, aluminas, silicas, siliceluminums.

  The hydrofinishing catalyst (HDF) may also contain at least one element of group VII A of the periodic table of elements. Preferably, these catalysts contain fluorine and / or chlorine.

  The weight contents of metals are between 10 and 30% in the case of non-noble metals and less than 2%, preferably between 0.1 and 1.5%, and even more preferably between 0.1. and 1.0% in the case of noble metals.

  The total amount of halogen is between 0.02 and 30% by weight, advantageously between 0.01 and 15%, or even more advantageously between 0.01 and 10%, preferably between 0.01 and 5%.

  Among the catalysts which can be used in this hydrofinishing step, and which give excellent performance, and especially for the production of medicinal oils, are catalysts containing at least one noble metal of group VIII (platinum and VIII). for example) and at least one halogen (chlorine and / or fluorine), the combination of chlorine and fluorine being preferred.

  The operating conditions in which the hydrofinishing step optionally following the catalytic hydrodewaxing process of the invention are carried out are the following: the reaction temperature is between 180 and 400 ° C. and preferably between 210 and 350 ° C., advantageously 230-320 ° C .; the pressure is between 0.1 and 25 MPa and preferably between 1.0 and 20 MPa; the hourly volume velocity (wh expressed as volume of feed injected per unit volume of catalyst per hour) is from about 0.05 to about 100 and preferably from about 0.1 to about 30 hr-1.

  The contact between the feedstock and the catalyst is carried out in the presence of hydrogen. The level of hydrogen used and expressed in liters of hydrogen per liter of filler is between 50 and about 2000 liters of hydrogen per liter of filler and preferably between 100 and 1500 liters of hydrogen per liter of filler.

  Advantageously, the temperature of the hydrofinishing step (HDF) is lower than the temperature of the catalytic hydrodewaxing step (HDPC). The difference THDPC-25 THDF is generally between 20 and 200 C, and preferably between 30 and 100 C.

  The effluent at the outlet of HDF is then sent to the distillation train.

  In the first preferred embodiment of the process according to the invention including a preliminary hydroconversion / hydroisomerization step, the base oils obtained have a pour point of less than -10 C, a VI greater than 95, preferably greater than 110 and even more preferably greater than 120, a viscosity of at least 3.0 cSt at 100 C, an ASTM color of less than 1 and a UV stability such that the ASTM color increase is between 0 and 4 and preferably between 0.5 and 2.5.

  Another advantage of this embodiment of the process according to the invention is that it is possible to achieve very low aromatics contents, less than 2% by weight, preferably less than 1% by weight and better still less than 0%. , 05% weight and even go up to the production of medicinal grade white oils having aromatic contents of less than 0.01% by weight. These oils have UV absorbance values at 275, 295 and 300 nanometers respectively less than 0.8, 0.4 and 0.3 (ASTM D2008 method) and a Saybolt color between 0 and 30.

  In a particularly interesting way, therefore, the process according to the invention also makes it possible to obtain medicinal white oils. Medical white oils are mineral oils obtained by advanced petroleum refining, their quality is subject to various regulations that aim to ensure their safety for pharmaceutical applications, they are devoid of toxicity and are characterized by their density and viscosity. White medicinal oils mainly comprise saturated hydrocarbons, they are chemically inert and their content of aromatic hydrocarbons is low. Particular attention is paid to aromatic compounds and in particular to 6 polycyclic aromatic hydrocarbons (PAHs for the abbreviation of polycyclic aromatic hydrocarbons) which are toxic and present at concentrations of one part per billion by weight of aromatic compounds in the form of polycyclic aromatic hydrocarbons. white oil. The control of the total aromatic content can be carried out by the ASTM D 2008 method, this UV adsorption test at 275, 292 and 300 nanometers makes it possible to control an absorbance less than 0.8, 0.4 and 0.3 respectively. (That is, the white oils have aromatic contents of less than 0.01% by weight). These measurements are carried out with concentrations of 1 g of oil per liter, in a 1 cm tank. The white oils marketed differ in their viscosity but also in their original crude which can be paraffinic or naphthenic, these two parameters will induce differences both in the physicochemical properties of the white oils considered but also in their chemical composition .

  In a second preferred embodiment, the dewaxing process of the present invention is advantageously used in the following sequence of steps: the charge to be treated is separated (D1) into at least a light fraction 3 with a dot of boiling below 380 C, and at least one heavy fraction 4 (residue).

  said light fraction 3 optionally hydrogenated in a hydrotreatment step (HDT) is subjected to a hydroisomerisation (HISM) said heavy fraction 4 is subjected to a hydrocracking step (HCK) in the presence of hydrogen, then is subjected to a distillation (D2) to produce at least one light fraction (13) and at least one heavy fraction (10).

  the hydroisomerization mixture (HISM) is fractionated (D3) together with at least a portion of the light fraction 13 from distillation D2 to obtain middle distillates having excellent cold properties, and / or a high cetane number and / or reduced emission of pollutants, the heavy fraction derived from D2 is subjected to a dewaxing step (DWX) to obtain, after separation of the volatiles formed, an isomerized liquid product that can be used as a lubricating base of high quality, and the process of dewaxing is the method according to the invention.

  This particularly preferred form of linking comprising the method according to the present invention is illustrated schematically in accordance with the diagram of the figurel.

  A liquid stream 1 consisting of a mixture of linear hydrocarbons from a Fischer-Tropsch synthesis process, also comprising unsaturated products (linear olefins), in an amount of up to 10% by weight, more preferably 2 to 5% by weight, and oxygenated (especially alcohols) in an amount of up to 10% by weight, preferably 2 to 7% by weight, is separated in the distillation column D1 into a light fraction 3 with a boiling point below 380 C, preferably between 260 and 360 C and a heavy fraction 4, constituting the residue of the distillation. The distillation in Dl is preferably carried out in one step (flash) and may be followed by a differential sampling of two fractions directly from the Fischer-Tropsch synthesis reactor.

  Preferably, the mass ratio between the two fractions 3 and 4 is in the range of 0.5 to 2.0, even more preferably 0.8 to 1.5.

  Light fraction 3 supplies a hydroisomerization unit (HISM). However, especially in the case where heteroatoms or unsaturated groups, and oxygenated compounds in particular, are present and may be a drawback for the proper functioning of the catalyst of this step, said fraction 3 comes preferentially to feed a hydrogenation unit ( HDT) in which it comes into contact with hydrogen (line 2) in the presence of a suitable catalyst, under conditions such as to minimize or even render absent the hydrocracking reaction.

  The hydrogenation unit (HDT) may be carried out according to the usual techniques and preferably comprises a pressurized reactor containing a fixed bed of catalyst selected to meet the specifications mentioned above. Typical hydrogenation catalysts adapted to the above specifications include a hydrogenating metal such as nickel, platinum or palladium supported on an inert or acidic solid such as alumina, silica, silica-alumina, zeolite or molecular sieve. It is not excluded that during the hydrogenation also occurs a hydroisomerization reaction and a partial hydrocracking, generally limited to a conversion less than 15% by weight of the total feed fraction. The small fraction of volatile compounds (150 C-) and the water possibly formed can be optionally separated by means of a distillation.

  The light fraction, hydrogenated or not, in a second step, is then subjected to a hydroisomerisation step (HISM) by means of line 6, in which it reacts again in the presence of hydrogen, under the usual conditions allowing to obtain a thorough isomerization and a partial rupture of the linear hydrocarbon chains. Suitable conditions for isomerization are amply reported in the state of the art as well as an extensive list of usable catalysts.

  A portion normally less than 50%, preferably between 0 and 25%, of said light fraction may optionally be taken by means of line 7, before the isomerization step and mixed again with said heavy fraction of the line 4 to be sent to hydrocracking.

  In said isomerization step, typically the hydrocarbon mixture is supplemented with hydrogen (line 5) in an amount of between 150 and 1500 normal liters per liter of liquid and passes over a fixed bed of suitable catalyst, preferably based on of noble metal, with a space velocity between 0.1 and 10 h-1 and a temperature between 300 and 450 C and a pressure between 1 and 10 MPa.

  The isomerized mixture is introduced via line 14 into a fractionation column D3 with the light fraction 13 from distillation column D2 of the heavy fraction sent to hydrocracking. At the outlet of column D3 is obtained in accordance with the embodiment a middle distillate, optionally taken at two different levels to separate kerosene (line 17) from diesel (line 18), having excellent cold properties, a high index cetane, preferably greater than 50 and reduced emission of pollutants.

  At the outlet of the distillation column and D3 fractionation are also obtained reduced amounts of low molecular weight products, particularly, by means of the line 15 a relatively insignificant gaseous fraction C1-05, normally by means of line 16, a light hydrocarbon fraction, preferably having a boiling point below 150 C (naphtha).

  According to a particularly advantageous aspect of this embodiment of the present invention, the amount of such volatile fractions is significantly reduced compared with analogous methods of the prior art, preferably less than 20%, more preferably less than 15% by weight relative to the initial feed of line 1.

  The fraction (line 4) of high-boiling hydrocarbons with a low content of oxygenated and unsaturated compounds is added the necessary amount of hydrogen (line 8) and feeds a hydrocracking unit (HCK) produced by a usual techniques. The product obtained feeds, via line 9, a distillation and fractionation device, which operates preferably to obtain a separation of the hydrocarbon mixture essentially in two fractions. A light fraction having a boiling point of less than 380 ° C., preferably less than 350 ° C. and comprising less than 10% by weight of volatile compounds (150 ° C.), consisting of a product having a high concentration of iso -paraffins, which comes across line 13 feed the fractionation step of the isomerized light fraction in HISM. Such a combination of the two streams, originating from the steps performed on the initial feed and under different but complementary conditions, advantageously makes it possible to obtain kerosene and gas oil fractions with the excellent properties mentioned above. In this case, a portion, preferably less than 50% by weight, of the mixture resulting from distillation D2 is introduced via line 19 at the inlet of the isomerization step (HISM) in order to increase further the grade and distribution of the isomerized fractions and regulate the relative amount of diesel and kerosene produced.

  The residual fraction of the distillation D2 consists of a mixture of high-boiling hydrocarbons surprisingly having a reduced wax content, relative to the products obtained with other catalysts of the prior art under conditions like. Such a residue may also be used as such for particular uses, but is preferably fed (line 10) a catalytic dewaxing step or dewaxing (DWX) prior to its use as a lubricating base. According to a preferred embodiment, it is partly recycled in the hydrocracking step (HCK) by means of line 12 in order to regulate the productivity of the process or to vary the degree of isomerization according to the requirements of the production.

  Said dewaxing step (DWX) is conducted according to the process of the present invention in the presence of a catalyst adapted to the desired objective. The partially isomerized mixture is further reacted in the presence of hydrogen and a suitable solid catalyst as described above, under the conditions of the process according to the invention.

  Advantageously, the amounts of linear paraffins being reduced, the dewaxing step according to the method of the present embodiment can be carried out under conditions of contact time and yield of lubricating base particularly favorable.

  At the end of this dewaxing step, the volatiles formed are separated (generally less than 3% by weight), an isomerized liquid product is obtained (line 11), with excellent cold properties and a high viscosity, having an initial boiling point greater than 350 C, preferably greater than 360 C which has an optimum composition for use as a high quality lubricating base.

  The examples which follow illustrate the invention without, however, limiting its scope.

  EXAMPLE 1 Preparation of a Dewaxing Catalyst C1 According to the Invention Catalyst C1 comprises a zeolite ZSM-22 and a zeolite ZBM-30. This catalyst is obtained according to the procedure described below.

  Zeolite ZSM-22 is obtained according to the synthesis method described in the article Applied Catalysis 1989, 48, page 137 and ZBM-30 zeolite is synthesized according to the BASF patent EP-A-46504 with the organic structuring triethylenetetramine.

  ZSM-22 and ZBM-30 crude synthetic zeolites are calcined at 550 ° C. under a stream of dry air for 12 hours. Then the solid ZSM-22 obtained is subjected to 4 successive ionic exchanges in a solution of 10N NH 4 NO 3 at about 100 ° C. for 4 hours for each exchange.

  The zeolite H-ZSM-22 in acid form thus obtained has an Si / Al ratio = 30 and a Na / Al ratio = 0.003. The zeolite H-ZBM-30 (acid form) thus obtained has an Si / Al ratio of 45 and an Na / Al ratio of less than 0.001.

  Then, 30 grams of zeolite H-ZSM-22 in powder form are mixed with 70 grams of zeolite H-ZBM-30. Then the mixture of the two zeolites is kneaded with a type SB3 alumina gel (supplied by Condéa) previously peptized with an aqueous solution containing nitric acid at 68% by weight and kneaded for 15 minutes. The paste (alumina gel + zeolites) kneaded is then extruded through a die diameter 1.4 mm. The extrudates thus obtained are calcined at 500 ° C. for 2 hours under air. The weight content of zeolite ZSM-22 in the support extrudates is 24% and that of the zeolite H-ZBM-30 is 56%, ie an overall zeolite content of 80% by weight.

  Subsequently, the support extrudates are subjected to a dry impregnation step with an aqueous solution of the platinum salt Pt (NH 3) 42 +, 2OH- and then calcined in dry air at 550 ° C. The platinum content of the catalyst Cl thus obtained is 0.48%.

  Example 2: Use of Catalyst C1 for improving the pour point of a feedstock from the Fischer-Tropsch process 2857020 The catalyst C1 whose preparation is described in Example 1 is used to improve the pour point a filler consisting of paraffins from the Fischer-Tropsch synthesis for the purpose of obtaining oils. For this purpose and in the non-exhaustive context of this example, the Fischer-Tropsch paraffins from the paraffin production unit are distilled to obtain a 370 C + cut. The main characteristics of the load thus obtained are the following: starting point 356 C point 5% 370 C point 10% 383 C point 30% 399 C point 50% 424 C point 80% 509 C point 90% 568 C point 95% 631 C flow point + 83 C density (20/4) 0.789 The catalytic test unit comprises a fixed-bed reactor with up-flow of the feed, in which 80 ml of the catalyst is introduced. Cl. The catalyst is then subjected to an atmosphere of pure hydrogen at a pressure of 10 MPa to ensure the reduction of platinum oxide to platinum metal and the charge is finally injected. The total pressure is 10 MPa, the flow rate of hydrogen is 1000 liters of hydrogen gas per liter of feed injected, the hourly space velocity is 1.1 h -1 and the reaction temperature of 340 C. After reaction, the Effluents are fractionated into light products (PI-150 C gasoline), middle distillates (150-370 C) and residue (370+ C).

  In the following table are reported the yields for the various fractions and the characteristics of the oils obtained directly with the feedstock and with the effluents hydroisomerized on the catalyst C1 (in accordance with the invention) and then catalytically dewaxed.

  26 2857020 Conforms Catalyst Cl Gross conversion to 370 C- 58.8 (% wt) Catch distribution Yield PI-370 C 58.8 (wt%): Yield 370 C + (wt%) 41.2 Oil quality (370 C + fraction) Point d Flow (C) -13 VI (Viscosity Index) 147 Viscosity at 100 ° C. (cSt) 5.8 It is very clearly noted that the feed treated with the catalyst (Cl) according to the invention leads to an oil fraction ( 370 C +) whose pour point is significantly lower than that of the feed while maintaining a high viscosity index.

  EXAMPLE 3 Preparation of Pretreatment Catalyst C2 and Hydrodewaxing Catalyst C3 According to the Invention The pretreatment stage catalyst C2 is prepared from a silica-alumina support used in the form of extrudates. It contains 40% by weight of silica SiO2 and 60% by weight of alumina AI203. The silica-alumina before addition of the noble metal has a surface area of 332 m 2 / g and its total pore volume is 0.82 ml / g.

  Catalyst C2 is obtained after impregnation of the noble metal on the support. The platinum salt H2PtCl6 is dissolved in a volume of solution corresponding to the total pore volume to be impregnated. The solid is then calcined for 2 hours in air at 500 ° C. The platinum content is 0.48% by weight. Measured on the catalyst, the BET surface is equal to 310 m 2 / g. The platinum dispersion measured by H2 / 02 titration is 75%.

  The hydrodewaxing catalyst C3 comprises a zeolite ZSM-22 and a zeolite ZBM-30. This catalyst is obtained according to the procedure described below.

  The zeolite ZSM-22 is obtained according to the synthesis method described in the article of Applied Catalysis, l989, 48, page 137 and zeolite ZBM-30 is synthesized according to the patent BASF EP-A-46504 with the organic structuring agent triethylenetetramine.

  ZSM-22 and ZBM-30 crude synthetic zeolites are calcined at 550 ° C. under a stream of dry air for 12 hours. Then the solid ZSM-22 obtained is subjected to 4 successive ionic exchanges in a solution of 10N NH 4 NO 3 at about 100 ° C. for 4 hours for each exchange.

  The zeolite H-ZSM-22 in acid form thus obtained has an Si / Al ratio = 30 and a Na / Al ratio = 0.003. The zeolite H-ZBM-30 (acid form) thus obtained has an Si / Al ratio of 45 and an Na / Al ratio of less than 0.001.

  Then, 30 grams of zeolite H-ZSM-22 in powder form are mixed with 70 grams of zeolite H-ZBM-30. Then the mixture of the two zeolites is kneaded with a type SB3 alumina gel (supplied by Condéa) previously peptized with an aqueous solution containing nitric acid at 68% by weight and kneaded for 15 minutes. The paste (alumina gel + zeolites) kneaded is then extruded through a die diameter of 1.4 mm. The extrudates thus obtained are calcined at 500 ° C. for 2 hours under air. The weight content of zeolite ZSM-22 in the support extrudates is 24% and that of the zeolite H-ZBM-30 is 56%, ie an overall zeolite content of 80% by weight.

  Subsequently, the support extrudates are subjected to a dry impregnation step with an aqueous solution of the platinum salt Pt (NH 3) 42 +, 2OH- and then calcined in dry air at 550 ° C. The platinum content of the catalyst C2 thus obtained is 0.51%.

  Example 4 Use of catalyst C3 for improving the flow point of a pretreated Fischer-Tropsch paraffinic filler on catalyst C2 (converting hydroisomerization) Catalyst (C2), the preparation of which is described in Example 3 is used to petrify a load of paraffins from the Fischer-Tropsch synthesis in order to obtain oils. The paraffinic feed used in this example is the same as that used and described in Example 2.

  The catalytic test unit comprises a fixed-bed reactor with up-flow of the feed, into which 80 ml of catalyst C2 is introduced. The catalyst is then subjected to an atmosphere of pure hydrogen at a pressure of 10 MPa in order to ensure the reduction of the platinum oxide to platinum metal and the charge is finally injected. The total pressure is 10 MPa, the flow rate of hydrogen is 1000 liters of hydrogen gas per liter of feed injected, the hourly volume velocity is 1.0 and the reaction temperature of 350 C. After reaction, the effluents are fractionated in light products (PI-150 C gasoline), middle distillates (150-370 C) and residue (370+ C).

  The residue (370 + C) is then treated, in order to reduce its pour point, in a second upflow reactor, into which 80 ml of C3 catalyst is introduced. The catalyst is then subjected to an atmosphere of pure hydrogen at a pressure of 10 MPa in order to ensure the reduction of the platinum oxide to platinum metal and the charge is finally injected. The total pressure is 10 MPa, the flow rate of hydrogen is 1000 liters of hydrogen gas per liter of feed injected, the hourly volume velocity is 1.0 h -1 and the reaction temperature 330 C. After reaction, the Effluents are fractionated into light products (PI-150 C gasoline), middle distillates (150-370 C) and oil fraction (370+ C).

  The characteristics of the oil obtained are measured.

  In the following table are reported the yields for the various fractions and the characteristics of the oils obtained directly with the feedstock and with the effluents pretreated on the catalyst C2 and then dewaxed on the catalyst C3 according to the invention.

  29 2857020 Hydroisomerized effluent Catalytically hydroisomerized and catalytically dewaxed effluent on C3 Catalyst C2 (pretreatment) C3 Gross conversion to 370 C- 40.5 28.7 (wt%) Catch distribution Yield PI-370 C 40.5 28.7 * (% wt): Yield 370 C + (% weight) 59.5 71.3 * Oil quality (370 C + fraction) Pour point (C) +42 -24 VI (Viscosity index) / 149 Viscosity at 100 C (cSt) I 6.2 Yields of the dewaxing step It is very clearly noted that the completion of a pretreatment step of the charge on the hydroisomerizing-converting catalyst C2 followed by a treatment on the catalyst C3 (according to the invention) makes it possible to reach flow rates significantly lower than those obtained using only the pretreatment catalyst C2 or the catalyst C1 (see the table of Example 2). On the other hand, it can also be seen that the use of a pretreatment step, upstream of the catalyst C3 according to the invention, makes it possible to obtain a yield of 370 C + oil fraction having a pour point of - 24 C with a yield of 42.4% by weight whereas the catalyst C1 (compliant) used alone does not make it possible to obtain an oil fraction with a pour point as low (it is only -13 C) and the yield in this oil fraction is lower 41.2% (see table of Example 2). Finally, the viscosity number and the VI of the oil fraction obtained with the pretreatment step C2 and the catalyst C3 according to the invention are higher than in the absence of a pretreatment stage (see table of the example 2).

2857020

Claims (14)

  A method for improving the pour point of a feedstock from the Fischer-Tropsch process in which the feedstock to be treated is brought into contact with a catalyst comprising at least one zeolite selected from the group formed by the zeolites of structural type TON (Theta-1, ZSM-22, ISI-1, NU-10 and KZ-2) and at least one zeolite ZBM-30, at least one hydro-dehydrogenating element and at least one porous mineral matrix.   2. The method of claim 1 wherein zeolite ZBM-30 is synthesized in the presence of triethylene tetramine.   3. Method according to claims 1 to 2 wherein the hydrodehydrogenating element is selected from Group VIB elements and Group VIII of the Periodic Table.   4. The method of claim 3 wherein the group VIB hydrodehydrogenating element is molybdenum and / or tungsten.   5. Method according to one of claims 3 to 4 wherein the group VIII hydrodehydrogenating element is a noble metal group VIII.   6. The process according to claim 5 wherein the Group VIII hydrodehydrogenating element is platinum and / or palladium.   7. Method according to one of claims 1 to 6 wherein the treated feeds have at least 50% volume of compounds boiling above 340 C.   8. Method according to one of claims 1 to 7 wherein the operating conditions are as follows: the reaction temperature is between 200 and 450 C.   the pressure is between 0.1 and 25 MPa.   the hourly volume velocity (wh expressed as volume of feed injected per unit volume of catalyst per hour) is between about 0.05 and about 30 hr.   9. Process according to one of claims 1 to 8 wherein the feedstock undergoes before its treatment a hydroisomerisationhydroconversion.   10. The method of claim 9 wherein the effluent from the hydroisomerization-conversion step is sent entirely in the dewaxing step.   11. The method according to claim 9, wherein the hydroisomerization-hydroconversion step is preceded by a hydrorefining step.   12. The method of claim 11 wherein the hydrorefining step is followed by an intermediate separation.   13. Method according to one of claims 1 to 12 wherein the effluent at the outlet of the catalytic hydrodewaxing stage is at least partly sent on a hydrofinishing catalyst.   14. Process in which the following steps are carried out: the feedstock to be treated is separated (D1) into at least one light fraction 3 with a boiling point of less than 380 ° C., and at least one heavy fraction 4 (residue).   said light fraction 3, optionally hydrogenated in a hydrotreating step (HDT), is subjected to a hydroisomerization (HISM), said heavy fraction 4 is subjected to a hydrocracking step (HCK) in the presence of hydrogen, and then subjected to a distillation (D2) to produce at least a light fraction (13) and at least one heavy fraction (10).   the hydroisomerization mixture (HISM) is fractionated (D3) together with at least a portion of the light fraction 13 from distillation D2 to obtain middle distillates having excellent cold properties, and / or a high cetane number and / or a reduced emission of pollutants, the heavy fraction resulting from D2 is subjected to a dewaxing step (DWX) to obtain, after separation of the volatile products formed, an isomerized liquid product which can be used as lubricant base of high quality, and the process of dewaxing is the method according to one of claims 1 to 8.