Patent Application
20250010277
The invention relates to a hydrocracking catalyst based on zeolite Y and zeolite beta and also the use thereof for the production of naphtha by hydrocracking of petroleum cuts of the vacuum distillate and gas oil type. This type of process is notably used in schemes intended for the conversion of hydrocarbon feedstocks for the production of petrochemical intermediates and gasoline fuels.
Hydrocracking catalysts are generally classified on the basis of the nature of their acid function, in particular catalysts comprising an amorphous acid function of silica-alumina type and catalysts comprising a zeolitic cracking function such as zeolite Y or zeolite beta.
Hydrocracking catalysts are also classified according to the major product obtained when they are used in a hydrocracking process, the two main products being middle distillates and naphtha.
Naphtha or naphtha cut is understood to mean the petroleum fraction having a boiling point lower than the middle distillates cut. The middle distillates cut generally has a cut point between 150° C. and 370° C. to maximize the production of kerosene and gas oil. Nevertheless, in the case of a process targeted specifically at the production of naphtha for example, the lower cut point of the middle distillates cut can be increased in order to increase the yields of naphtha.
For this purpose, the naphtha cut can have boiling points between the boiling point of hydrocarbon compounds having 6 carbon atoms per molecule (or 68° C. boiling point) up to 216° C. and includes the gasoline cut.
There is a high demand for gasoline and naphtha cuts. This is the reason why refiners have been focusing for several years on hydrocracking catalysts that are selective towards the naphtha cut.
It is known to use catalysts based on FAU-type zeolite to produce a naphtha cut.
U.S. Pat. No. 7,611,689 (Shell) describes a FAU-type zeolite Y, a catalyst comprising said zeolite, the preparation thereof and the use thereof in a hydrocracking process. In particular, the FAU zeolite has a lattice parameter of between 24.40 and 24.50 angstroms (Å), a silica to alumina molar ratio (SAR) of between 5 and 10, and an alkali metal content of less than 0.15% by weight. It is demonstrated that such zeolites have a high selectivity towards the naphtha cut and in particular a high selectivity towards the heavy naphtha cut, when they are used in a hydrocracking process.
Other catalysts based on zeolite Y and zeolite beta can also be used.
U.S. Pat. No. 7,510,645 (UOP) describes a hydrocracking catalyst containing a zeolite beta and a zeolite Y, the zeolite Y having a lattice parameter of between 24.38 and 24.50 angstroms (Å), the catalyst being characterized by a Y/beta weight ratio of between 5 and 12. The catalyst has a relatively high proportion of zeolite Y compared to the proportion of zeolite beta. It is demonstrated that these catalysts have improved selectivity and activity compared to conventional commercial catalysts. Also disclosed is a hydrocracking process using said catalysts at high temperature and high pressure to convert a hydrocarbon feedstock into a product having a lower boiling point and lower molecular weight. In particular, the product obtained comprises a large proportion of a component boiling in the temperature range of the naphtha cut (C6-216° C.).
While attempting to develop a new hydrocracking catalyst that is selective towards the naphtha cut, the applicant discovered, surprisingly, that a catalyst comprising at least one hydrogenating-dehydrogenating element chosen from the group formed by the elements of group VIB and the non-noble elements of group VIII of the periodic table, and a support comprising at least one porous mineral matrix, a zeolite Y having an initial lattice parameter a0 of the unit cell of greater than 24.42 A, and a zeolite beta, the catalyst having a weight ratio of said zeolite Y to said zeolite beta strictly greater than 12, makes it possible to obtain an improved selectivity towards the naphtha cut, notably compared to the catalysts of the prior art.
More specifically, the present invention relates to a hydrocracking catalyst that is selective towards the naphtha cut, comprising at least one hydrogenating-dehydrogenating element chosen from the group formed by the elements of group VIB and the non-noble elements of group VIII of the periodic table, taken alone or as a mixture, and a support comprising at least one porous mineral matrix, a zeolite Y having an initial lattice parameter a0 of the unit cell of greater than 24.42 Å, and a zeolite beta, in which the weight ratio of said zeolite Y to said zeolite beta in the catalyst is strictly greater than 12.
The present invention advantageously relates to a hydrocracking catalyst comprising at least one hydrogenating-dehydrogenating element chosen from the group formed by the elements of group VIB and the non-noble elements of group VIII of the periodic table, taken alone or as a mixture, and a support comprising at least one porous mineral matrix, a zeolite Y having an initial lattice parameter a0 of the unit cell of greater than 24.42 Å, and a zeolite beta, in which the weight ratio of said zeolite Y to said zeolite beta in the catalyst is greater than 12.
The present invention advantageously relates to a hydrocracking catalyst comprising at least one hydrogenating-dehydrogenating element chosen from the group formed by the elements of group VIB and the non-noble elements of group VIII of the periodic table, taken alone or as a mixture, and a support comprising at least one porous mineral matrix, a zeolite Y and a zeolite beta, in which the weight ratio of said zeolite Y to said zeolite beta in the catalyst is greater than 12.
This weight ratio is calculated from the dry weights of zeolites, that is to say the weights of the zeolites corrected for their water content determined by measuring the loss on ignition at 1000° C. (dry weight).
Another subject of the present invention is a process for hydrocracking a hydrocarbon feedstock in the presence of said catalyst.
One advantage of the present invention is that of providing a hydrocracking catalyst for obtaining an improved selectivity towards the naphtha cut when said catalyst is used in a hydrocracking process according to the invention, compared to the catalysts from the prior art.
In the present invention, the selectivity of the hydrocracking catalysts for naphtha production is determined during a catalytic test and corresponds to the fraction, as a weight percentage, of the product boiling in the range of the naphtha cut, i.e. between the boiling temperature of hydrocarbon compounds having 6 carbon atoms per molecule (or 68° C. boiling point) up to 216° C., relative to the total weight of product leaving the process.
For the purposes of the present invention, the various embodiments presented may be used alone or in combination with each other, without any limit to the combinations.
For the purposes of the present invention, the various ranges of parameters for a given step, such as the pressure ranges and the temperature ranges, may be used alone or in combination. For example, for the purposes of the present invention, a preferred range of pressure values can be combined with a range of more preferred temperature values.
In the text hereinbelow, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor-in-chief D. R. Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals from columns 8, 9 and 10 according to the new IUPAC classification, and group VIB corresponds to the metals from column 6.
In the text hereinbelow, the expressions “of between . . . and . . . ” and “between . . . and . . . ” are equivalent and mean that the limit values of the interval are included in the described range of values. If such were not the case and if the limit values were not included in the described range, such a clarification will be given by the present invention.
In accordance with the invention, the catalyst comprises at least one hydrogenating-dehydrogenating element chosen from the group formed by the elements of group VIB and the non-noble elements of group VIII of the periodic table, taken alone or as a mixture.
Preferably, the catalyst according to the invention comprises an active phase comprising, preferably consisting of, at least one group VIB metal and at least one group VIII metal.
Preferably, the group VIII elements are chosen from iron, cobalt and nickel, taken alone or as a mixture, and preferably from nickel and cobalt. Preferably, the group VIB elements are chosen from tungsten and molybdenum, taken alone or as a mixture. The following combinations of metals are preferred: nickel-molybdenum, cobalt-molybdenum, nickel-tungsten, cobalt-tungsten, and very preferably: nickel-molybdenum, nickel-tungsten. It is also possible to use combinations of three metals, for instance nickel-cobalt-molybdenum.
The content in the catalyst of group VIII element is advantageously between 0.5% and 8% by weight of oxide relative to the total weight of said catalyst, preferably between 0.5% and 6% by weight of oxide and very preferably between 1.0% and 4% by weight of oxide. The content in the catalyst of group VIB metal is advantageously between 1% and 30% by weight of oxide relative to the total weight of said catalyst, preferably between 2% and 25% by weight of oxide and very preferably between 5% and 20% by weight of oxide, and even more preferably between 5% and 16% by weight of oxide.
Preferably, the catalyst used according to the invention can also contain a promoter element chosen from phosphorus, boron, silicon, and very preferably phosphorus. When the catalyst contains phosphorus, the phosphorus content is advantageously between 0.5% and 10% by weight of P2O5 oxide relative to the total weight of said catalyst, preferably between 1% and 6% by weight of P2O5 oxide and more preferably between 1% and 4% by weight of P2O5 oxide.
The support The catalyst according to the invention comprises a support which comprises and preferably consists of at least one porous mineral matrix, a zeolite Y having an initial lattice parameter a0 of the unit cell of greater than 24.42 Å, and a zeolite beta.
The porous mineral matrix used in the support of the catalyst, also referred to as binder, advantageously consists of at least one refractory oxide, preferably chosen from the group formed by alumina, silica-alumina, clay, titanium oxide, boron oxide and zirconia, taken alone or as a mixture. Preferably, the porous mineral matrix is chosen from alumina and silica-alumina, taken alone or as a mixture. More preferably, the porous mineral matrix is alumina. The alumina can advantageously be in any of its forms known to those skilled in the art. Very preferably, the alumina is gamma alumina, for example boehmite.
Preferably, said support comprises from 14% to 48% by weight of binder, preferably from 15% to 40% by weight, and very preferably between 20% and 40% by weight, relative to the total weight of said support.
According to the invention, the support comprises a zeolite Y having an initial lattice parameter a0 of the unit cell of greater than 24.42 Å.
Preferably, the initial lattice parameter a0 of the unit cell of the zeolite Y used is between 24.42 Å and 24.70 Å, preferably greater than 24.45 Å and less than 24 0.70 Å, preferably greater than 24.50 Å and less than 24.70 Å, preferably between 24.52 Å and 24.70 Å and preferably between 24.52 Å and 24.65 Å, preferably between 24.52 Å and 24.60 Å and very preferably between 24.52 Å and 24.58 Å.
The initial lattice parameter a0 of the unit cell of the zeolite Y given that is the value of the initial lattice parameter a0 of the zeolite Y used in the synthesis of the catalyst according to the invention.
The initial lattice parameter a0 of the unit cell of the zeolite Y is measured by X-ray diffraction according to standard ASTM 03942-80.
Preferably, said support has a total content of zeolite Y of between 50% and 80% by weight relative to the total weight of said support, preferably between 50% and 70% by weight and preferably between 55% and 65% by weight.
Said zeolites are advantageously defined in the classification “Atlas of Zeolite Framework Types”, 6th Revised Edition”, Ch. Baerlocher, L. B. McCusker, D. H. Olson, 6th Edition, Elsevier, 2007, Elsevier.
According to a preferred embodiment of the invention, the zeolite Y having the particular characteristic defined above and that is suitable for the use of the catalyst support used in the process according to the invention is advantageously prepared from a zeolite Y of FAU structural type preferably having an overall Si/Al atomic ratio after synthesis of between 2.3 and 2.8 and advantageously being in NaY form after synthesis. Said zeolite Y of FAU structural type advantageously undergoes a step of one or more ion exchanges before undergoing the dealumination step. The ion exchange(s) make it possible to partially or completely replace the alkaline cations belonging to groups IA and IIA of the periodic table present in the cation position in the crude synthesis zeolite Y of FAU structural type with NH4+ cations, and preferably Na+ cations with NH4+ cations.
Partial or complete exchange of the alkaline cations with NH4+ cations, is understood to mean the exchange of from 80% to 100%, preferably from 85% to 99.5% and more preferably from 88% to 99%, of said alkaline cations with NH4+ cations. At the end of the ion exchange step(s), the remaining amount of alkaline cations, and preferably the remaining amount of Na+ cations, in the zeolite Y, relative to the amount of alkaline cations, preferably Na+ cations, initially present in the zeolite Y, is advantageously between 0% and 20%, preferably between 0.5% and 15%, and preferably between 1.0% and 12%.
Preferably, this step implements a plurality of ion exchanges with a solution containing at least one ammonium salt chosen from chlorate, sulfate, nitrate, phosphate or acetate salts of ammonium, so as to at least partially remove the alkaline cations, and preferably the Na+ cations, present in the zeolite. Preferably, the ammonium salt is ammonium nitrate NH4NO3.
Thus, the remaining content of alkaline cations and preferably of Na+ cations in the zeolite Y at the end of the ion exchange(s) step is preferably such that the alkaline cation/aluminium molar ratio, and preferably the Na/Al molar ratio, is between 0:1 and 0:1, preferably between 0:1 and 0.005:1, and more preferably between 0:1 and 0.008:1.
The desired alkaline cation/aluminium, preferably Na/Al, ratio is obtained by adjusting the NH4+ concentration of the ion exchange solution, the ion exchange temperature and the number of ion exchanges. The NH4+ concentration of the ion exchange solution in the solution advantageously varies between 0.01 and 12 mol·l−1, and preferably between 1.00 and 10 mol·l−1. The temperature of the ion exchange step is advantageously between 20° C. and 100° C., preferably between 60° C. and 95° C., preferably between 60° C. and 90° C., more preferably between 60° C. and 85° C., and more preferably still between 60° C. and 80° C. The number of ion exchanges advantageously varies between 1 and 10, and preferably between 1 and 4.
Said zeolite Y, preferably of FAU structural type, obtained can then undergo a dealumination treatment step. Said dealumination step may advantageously be carried out by any method known to those skilled in the art. Preferably, the dealumination is carried out by a heat treatment optionally in the presence of water vapour (or “steaming”) and/or by one or more acid attacks advantageously carried out by treatment with an aqueous mineral or organic acid solution.
Preferably, the dealumination step implements a heat treatment followed by one or more acid attacks, or just one or more acid attacks.
Preferably, the heat treatment optionally in the presence of steam, to which said zeolite Y is subjected, is carried out at a temperature of between 200° C. and 900° C., preferably between 300° C. and 900° C., more preferably still between 400° C. and 750° C. The duration of said heat treatment is advantageously greater than or equal to 0.5 h, preferably between 0.5 h and 24 h, and very preferably between 1 h and 12 h. In the case where the heat treatment is carried out in the presence of water, the percentage by volume of steam during the heat treatment is advantageously between 5% and 100%, preferably between 20% and 100%, and very preferably between 40% and 100%. Any volume fraction present that is not steam is formed of air. The flow rate of gas formed of steam and possibly air is advantageously between 0.2 l·h−1·g−1 and 10 l·h−1·g−1 of zeolite Y.
The heat treatment enables the extraction of aluminium atoms from the structure of the zeolite Y while keeping the overall Si/Al atomic ratio of the treated zeolite unchanged.
The step of heat treatment in the presence of steam may advantageously be repeated as many times as is necessary to obtain the zeolite Y suitable for implementing the support of the catalyst used in the process according to the invention and having a lattice parameter a0 of the unit cell of greater than 24.42 Å.
The step of heat treatment optionally in the presence of steam is advantageously followed by an acid attack step. Said acid attack makes it possible to partially or completely remove the aluminic debris resulting from the step of heat treatment in the presence of steam which may partially block the porosity of the dealuminated zeolite; the acid attack thus makes it possible to unblock the porosity of the dealuminated zeolite.
The acid attack may advantageously be carried out by suspending the zeolite Y, which has optionally undergone a heat treatment beforehand, in an aqueous solution containing a mineral or organic acid. The mineral acid may be nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or boric acid. The organic acid may be formic acid, acetic acid, oxalic acid, tartaric acid, maleic acid, malonic acid, malic acid, lactic acid, or any other water-soluble organic acid. The mineral or organic acid concentration in the solution advantageously varies between 0.01 and 2.0 mol·l−1, and preferably between 0.5 and 1.0 mol·l−1. The temperature of the acid attack step is advantageously between 20° C. and 100° C., preferably between 60° C. and 95° C., preferably between 60° C. and 90° C. and more preferably between 60° C. and 80° C. The duration of the acid attack is advantageously between 5 minutes and 8 hours, preferably between 30 minutes and 4 hours, and preferably between 1 hour and 2 hours.
On conclusion of the step(s) of heat treatment optionally in the presence of steam and optionally of the acid attack step, the process for modifying said zeolite Y advantageously includes a step of at least partial or complete exchange of the alkaline cations, and preferably the Na+ cations, still present in cation position in the zeolite Y. The ion exchange step is carried out in a similar manner to the ion exchange step described above.
On conclusion of the step(s) of heat treatment optionally in the presence of steam and optionally of the acid attack step and optionally of the step of partial or complete exchange of the alkaline cations and preferably Na+ cations, the process for modifying said zeolite Y may include a calcination step. Said calcination makes it possible to remove the organic species present within the porosity of the zeolite, for example those supplied by the acid attack step or by the step of partial or complete exchange of the alkaline cations. In addition, said calcination step makes it possible to generate the protonated form of the zeolite Y and to impart upon it an acidity for the purposes of the applications thereof.
The calcination may advantageously be carried out in a muffle furnace or in a tubular furnace, under dry air or under inert atmosphere, in swept bed or traversed bed. The calcination temperature is advantageously between 200° C. and 800° C., preferably between 450° C. and 600° C., and preferably between 500° C. and 550° C. The duration of the calcination hold is advantageously between 1 and 20 hours, preferably between 6 and 15 hours, and preferably between 8 and 12 hours.
Thus, said zeolite Y obtained has an initial lattice parameter a0 of the unit cell greater than 24.42 Å.
Said zeolite Y obtained advantageously has a specific surface area measured by nitrogen physisorption according to the BET method of between 550 and 1000 m2/g, preferably between 600 and 900 m2/g, and preferably between 650 and 800 m2/g.
According to the invention, the support also comprises a zeolite beta.
The zeolite beta is generally synthesized from a reaction mixture containing a structuring agent. The use of structuring agents is well known to those skilled in the art: for example, U.S. Pat. No. 3,308,069 describes the use of tetraethylammonium hydroxide, and U.S. Pat. No. 5,139,759 describes the use of the tetraethylammonium cation derived from a tetraethylammonium halide compound. Another standard method for preparing zeolite beta is given in the book “Verified Synthesis of Zeolitic Materials”.
The zeolite beta used in the support according to the invention preferably has an overall SAR atomic ratio of between 10 and 100, preferentially between 20 and 50, and more preferably between 20 and 30. The zeolite beta used in the support according to the invention advantageously has a specific surface area measured by nitrogen physisorption according to the BET method of between 400 and 800 m2/g, preferably between 500 and 750 m2/g, and preferably between 550 and 700 m2/g.
Preferably, the support has a zeolite beta content of between 2% and 6%, preferably between 2% and 5%, and preferably between 3% and 5% by weight relative to the total weight of said support.
Preferably, the support comprises and preferably consists of:
In accordance with the invention, the weight ratio of said zeolite Y to said zeolite beta in the catalyst is strictly greater than 12.
Preferably, the weight ratio of said zeolite Y to said zeolite beta in the catalyst is between 13 and 40, and preferably between 13 and 30, and preferably between 14 and 20, and even more preferably between 14 and 18.
Preferably, the catalyst has a content of zeolite Y of between 26% and 79% by weight relative to the total weight of said catalyst.
Preferably, said catalyst has a content of zeolite beta of between 1% and 6% by weight relative to the total weight of said catalyst.
Preferably, said catalyst has a content of at least one porous mineral matrix of between 7% and 47% by weight relative to the total weight of said catalyst.
The hydrocracking catalyst according to the invention having a Y/beta ratio within these ranges makes it possible to obtain an improved selectivity towards the naphtha cut when said catalyst is used in a hydrocracking process according to the invention, compared to the catalysts from the prior art.
The catalyst is advantageously prepared according to the conventional methods used in the prior art.
In particular, the catalyst is prepared according to a preparation process comprising:
More particularly, the catalyst is prepared according to a preparation process comprising the following steps:
The support may advantageously be shaped by any technique known to those skilled in the art. The shaping may be carried out for example by extrusion, by pelletizing, by the drop coagulation (oil-drop) method, by granulation on a rotating plate or by any other method that is well known to those skilled in the art.
The support is preferably shaped in the form of grains of various shapes and sizes. They are generally used in the form of cylindrical extrudates or polylobal extrudates, such as trilobal, quadrilobal or polylobal extrudates, of straight or twisted form, but can optionally be manufactured and employed in the form of crushed powders, lozenges, rings, beads or wheels. However, it is advantageous for the catalyst to be in the form of extrudates with a diameter of between 0.5 and 5 mm and more particularly between 0.7 and 3 mm and even more particularly between 1.0 and 2.5 mm. The shapes are cylindrical (which may or may not be hollow), twisted cylindrical, multilobal (for example 2, 3, 4 or 5 lobes) or annular. Any other shape may be used.
One of the preferred shaping methods consists in co-kneading said zeolites with the binder, preferably alumina, in the form of a wet gel for a few tens of minutes, preferably between 10 and 40 minutes, then passing the paste thus obtained through a die to form extrudates with a diameter preferably between 0.5 and 5 mm.
According to another of the preferred shaping methods, said zeolites can be introduced during the synthesis of the porous mineral matrix. For example, according to this preferred embodiment of the present invention, said zeolites Y and beta are added during the synthesis of a porous mineral matrix, such as for example a silico-aluminic matrix: in this case, said zeolites can advantageously be added to a mixture composed of an alumina compound in an acid medium with a completely soluble silica compound.
The group VIB and/or VIII elements may optionally be introduced during the shaping step, by adding at least one compound of said element, so as to introduce at least one portion of said element.
The introduction of at least one hydrogenating-dehydrogenating element can advantageously be accompanied by that of at least one promoter element chosen from phosphorus, boron, silicon and preferably phosphorus and optionally by the introduction of a group VIIA and/or VB element. The shaped solid is optionally dried at a temperature of between 60° C. and 250° C. and optionally calcined at a temperature of from 250° C. to 800° C. for a time of between 30 minutes and 6 hours.
The step of introducing at least one hydrogenating-dehydrogenating element is advantageously carried out by a method well known to those skilled in the art, in particular by one or more operations of impregnating the shaped and calcined or dried, and preferably calcined, support with a solution containing the precursors of the group VIB and/or VIII elements, optionally the precursor of at least one promoter element and optionally the precursor of at least one group VIIA and/or group VB element.
Preferably, said step d) is carried out by a method of dry impregnation with a solution containing the precursors of the hydrogenating/dehydrogenating function, that is to say group VIB and/or VIII elements, optionally followed a drying step and preferably without a calcining step.
In the case where the catalyst of the present invention contains a non-noble group VIII metal, the group VIII metals are preferably introduced by one or more operations of impregnation of the shaped and calcined support, after those of group VIB or at the same time as the latter.
The introduction of at least one hydrogenating-dehydrogenating element can then optionally be followed by drying at a temperature of between 60° C. and 250° C. and optionally by a calcination at a temperature of between 250° C. and 800° C.
The sources of molybdenum and tungsten are advantageously chosen from the oxides and hydroxides, molybdic and tungstic acids and salts thereof, in particular the ammonium salts such as ammonium molybdate, ammonium heptamolybdate and ammonium tungstate, phosphomolybdic acid, phosphotungstic acid and salts thereof, silicomolybdic acid, silicotungstic acid and salts thereof. Use is preferably made of the oxides and the ammonium salts, such as ammonium molybdate, ammonium molybdate, ammonium heptamolybdate and ammonium tungstate.
The sources of non-noble group VIII elements that can be used are well known to those skilled in the art. For example, for the non-noble metals, use will be made of nitrates, sulfates, hydroxides, phosphates, halides such as for example chlorides, bromides and fluorides, carboxylates such as for example acetates and carbonates.
The preferred source of phosphorus is orthophosphoric acid H3PO4, but salts and esters thereof such as ammonium phosphates are also suitable. The phosphorus may be introduced, for example, in the form of a mixture of phosphoric acid and a basic organic compound containing nitrogen such as aqueous ammonia, primary and secondary amines, cyclic amines, compounds of the pyridine and quinoline families and compounds of the pyrrole family. Tungstophosphoric or tungstomolybdic acids can be used.
The phosphorus content is adjusted, without this limiting the scope of the invention, so as to form a mixed compound in solution and/or on the support, for example tungsten-phosphorus or molybdenum-tungsten-phosphorus. These mixed compounds can be heteropolyanions. These compounds can be Anderson heteropolyanions, for example.
The source of boron may be boric acid, preferably orthoboric acid H3BO3, ammonium diborate or pentaborate, boron oxide or boric esters. The boron may be introduced, for example, in the form of a mixture of boric acid, aqueous hydrogen peroxide solution and a basic organic compound containing nitrogen such as aqueous ammonia, primary and secondary amines, cyclic amines, compounds of the pyridine and quinoline families and compounds of the pyrrole family. The boron may be introduced, for example, by a solution of boric acid in a water/alcohol mixture.
Many sources of silicon may be used. Thus, use may be made of ethyl orthosilicate Si(OEt)4, siloxanes, polysiloxanes, silicones, silicone emulsions, halide silicates such as ammonium fluorosilicate (NH4)2SiF6 or sodium fluorosilicate Na2SiF6. Silicomolybdic acid and salts thereof, silicotungstic acid and salts thereof may also advantageously be used. Silicon may advantageously be added, for example, by impregnation of ethyl silicate in solution in a water/alcohol mixture. Silicon may be added, for example, by impregnation of a silicon compound of silicone or silicic acid type suspended in water.
The sources of group VB elements that can be used are well known to those skilled in the art. For example, among the sources of niobium, use may be made of oxides, such as diniobium pentoxide Nb2O5, niobic acid Nb2O5·H2O, niobium hydroxides and polyoxoniobates, niobium alkoxides of formula Nb(OR1)3 where R1 is an alkyl radical, niobium oxalate NbO(HC2O4)5, or ammonium niobate. Use is preferably made of niobium oxalate or ammonium niobate.
The sources of group VIIA elements that can be used are well known to those skilled in the art. For example, fluoride anions can be introduced in the form of hydrofluoric acid or salts thereof. These salts are formed with alkali metals, ammonium or an organic compound. In the latter case, the salt is advantageously formed in the reaction mixture by reaction between the organic compound and hydrofluoric acid. It is also possible to use hydrolysable compounds which can release fluoride anions in water, such as ammonium fluorosilicate (NH4)2SiF6, silicon tetrafluoride SiF4 or sodium tetrafluoride Na2SiF6. The fluorine can be introduced, for example, by impregnation of an aqueous solution of hydrofluoric acid or of ammonium fluoride.
The catalyst according to the invention is then advantageously used in a hydrocracking process, in particular for production of naphtha. The catalyst used in a hydrocracking process, such as the process according to the invention, can advantageously be in sulfided form. The group VIB metals and/or non-noble group VIII metals of said catalyst are therefore present in sulfided form.
The catalysts used in the processes according to the present invention are then advantageously subjected beforehand to a sulfidation treatment for converting, at least in part, the metallic species to sulfided form before they are brought into contact with the feedstock to be treated. This activation treatment by sulfidation is well known to those skilled in the art and can be carried out by any method already described in the literature, either in situ, i.e. in the reactor, or ex situ.
A conventional sulfidation method well known to those skilled in the art consists in heating the catalyst in the presence of hydrogen sulfide (pure or for example under a stream of a hydrogen-hydrogen sulfide mixture) at a temperature of between 150° C. and 800° C., preferably between 250° C. and 600° C., generally in a flow-through bed reaction zone.
Another subject of the present invention is a process for hydrocracking at least one hydrocarbon feedstock, preferably in liquid form, of which at least 50% by weight of the compounds have an initial boiling point above 300° C. and a final boiling point below 650° C., at a temperature of between 200° C. and 480° C., at a total pressure of between 1 MPa and 25 MPa, with a ratio of volume of hydrogen per volume of hydrocarbon feedstock of between 80 and 5000 litres per litre and at an hourly space velocity (HSV) defined by the ratio of the volume flow rate of hydrocarbon feedstock, which is preferably liquid, per the volume of catalyst charged into the reactor of between 0.1 and 50 h−1, in the presence of the catalyst according to the invention.
Advantageously, the catalyst according to the invention is used in the hydrocracking process according to the invention after a pretreatment section containing one or more hydrotreating catalysts which may be any catalyst known to those skilled in the art and which makes it possible to reduce the content of certain contaminants in the feedstock (see below) such as nitrogen, sulfur or metals. The operating conditions (HSV, temperature, pressure, hydrogen flow rate, liquid, reaction configuration, etc.) of this pretreatment section can be diverse and varied in accordance with the knowledge of those skilled in the art.
Very varied feedstocks can be treated by the hydrocracking processes according to the invention. The feedstock used in the hydrocracking process according to the invention is a hydrocarbon feedstock of which at least 50% by weight of the compounds have an initial boiling point above 300° C. and a final boiling point below 650° C., preferably of which at least 60% by weight, preferably of which at least 75% by weight and more preferably of which at least 80% by weight of the compounds have an initial boiling point above 300° C. and a final boiling point below 650° C.
The feedstock is advantageously chosen from LCOs (Light Cycle Oil, light gas oils resulting from a catalytic cracking unit), atmospheric distillates, vacuum distillates, for example gas oils resulting from the direct distillation of crude oil or from conversion units, such as FCC, coking or visbreaking units, feedstocks originating from units for the extraction of aromatics from lubricant oil bases or resulting from the solvent dewaxing of lubricant oil bases, distillates originating from processes for the fixed-bed or ebullated-bed desulfurization or hydroconversion of ARs (atmospheric residues) and/or VRs (vacuum residues) and/or deasphalted oils, and deasphalted oil, or paraffins resulting from the Fischer-Tropsch process, taken alone or as a mixture. Mention may be made of feedstocks of renewable origin (such as vegetable oils, animal fats, oil from the hydrothermal conversion or pyrolysis of lignocellulosic biomass) and also plastic pyrolysis oils. The above list is not limiting. Said feedstocks preferably have a boiling point T5 above 300° C., preferably above 340° C., that is to say that 95% of the compounds present in the feedstock have a boiling point above 300° C., and preferably above 340° C.
The nitrogen content of the feedstocks treated in the process according to the invention is advantageously greater than 500 ppm by weight, preferably between 500 and 10 000 ppm by weight, more preferably between 700 and 4000 ppm by weight and more preferably still between 1000 and 4000 ppm by weight. The sulfur content of the feedstocks treated in the process according to the invention is advantageously between 0.01% and 5% by weight, preferably between 0.2% and 4% by weight and more preferably still between 0.5% and 3% by weight.
The feedstock may optionally contain metals. The cumulative content of nickel and vanadium of the feedstocks treated in the processes according to the invention is preferably less than 1 ppm by weight.
The feedstock may optionally contain asphaltenes. The asphaltene content is generally less than 3000 ppm by weight, preferably less than 1000 ppm by weight and even more preferably less than 200 ppm by weight.
Advantageously, when the catalyst according to the invention is used after a hydrotreating section as described above, the content of nitrogen, sulfur, metals or asphaltenes in the liquid injected into the process according to the invention using the catalyst according to the invention is reduced. Preferably, the content of organic nitrogen in the feedstock treated in the hydrocracking process according to the invention is then, after hydrotreating, between 0 and 200 ppm, preferably between 0 and 50 ppm, and even more preferably between 0 and 30 ppm. The sulfur content is preferably less than 1000 ppm and the asphaltene content is preferably less than 200 ppm whilst the content of metals (Ni or V) is less than 1 ppm.
The hydrocracking process according to the invention may comprise a fractionation step between the pretreatment of the feedstock and the hydrocracking reactor(s) using the catalyst according to the invention. In the preferred case where the hydrocracking process is carried out without (gas and liquid) fractionation between the pretreatment and the hydrocracking reactor(s) using the catalyst according to the invention, the nitrogen and the sulfur removed from the liquid after the pretreatment are injected in the form of NH3 and H2S into the reactor(s) containing the catalyst according to the invention.
In accordance with the invention, the process for hydrocracking said hydrocarbon feedstock according to the invention is carried out at a temperature of between 200° C. and 480° C., at a total pressure of between 1 MPa and 25 MPa, with a ratio of volume of hydrogen per volume of hydrocarbon feedstock of between 80 and 5000 litres per litre and at an hourly space velocity (HSV) defined by the ratio of the volume flow rate of hydrocarbon feedstock per the volume of catalyst charged into the reactor of between 0.1 and 50 h−1.
Preferably, the hydrocracking process according to the invention is performed in the presence of hydrogen at a temperature of between 250° C. and 480° C., preferably between 320° C. and 450° C., very preferably between 330° C. and 435° C., under a pressure of between 2 and 25 MPa, and very preferably between 3 and 20 MPa, at a space velocity of between 0.1 and 20 h−1, preferably between 0.1 and 6 h−1, preferably between 0.2 and 3 h−1 and the amount of hydrogen introduced is such that the litre of hydrogen/litee of hydrocarbon volume ratio is between 100 and 2000 l/l.
The process can be carried out in one step or two steps depending on the degree of conversion of the targeted feedstock, with or without recycling of the unconverted fraction. The catalyst according to the invention can be used in a non-limiting manner in one or two steps of the hydrocracking process, alone or in combination with another hydrocracking catalyst.
These operating conditions used in the processes according to the invention generally make it possible to obtain conversions per pass, into products having boiling points below 340° C. and better still below 370° C., of greater than 15 wt % and more preferably still of between 20 and 100 wt %.
The examples illustrate the invention without limiting the scope thereof.
The support for catalyst A is prepared by shaping by kneading-extrusion of 60% by weight of commercial zeolite Y (zeolite CBV712 from Zeolyst) having a lattice parameter of 24.35 Å, an SiO2/Al2O3 molar ratio of 12, a specific surface area measured by nitrogen physisorption according to the BET method of 850 m2/g, 10% by weight of commercial zeolite beta (zeolite CP814e from Zeolyst) having an SiO2/Al2O3 molar ratio of 25, a specific surface area measured by nitrogen physisorption according to the BET method of 670 m2/g, in the presence of commercial boehmite (Pural SB3 from SASOL). The extrudates obtained are dried at 80° C. then calcined at 600° C. in humid air (5% by weight of water per kg of dry air). The calcined support comprises, on a dry basis, 60% by weight of zeolite Y, 10% weight of zeolite beta and 30% weight of alumina, i.e. a Y/Beta weight ratio=6 in the catalyst.
Catalyst A is prepared by dry impregnation of the resulting support using an aqueous solution containing the elements Ni, Mo. This solution is obtained by dissolving the following precursors in water: nickel nitrate and ammonium heptamolybdate. The amount of precursors in solution is adjusted as a function of the targeted concentrations on the final catalyst. After dry impregnation, the catalyst is dried at 120° C. in air.
The weight percentages in the catalyst are respectively: 15.1% by weight of molybdenum (in MoO3 form), 3.3% by weight of nickel (in NiO form) on a dry basis.
The support for catalyst B is prepared by shaping by kneading-extrusion of 60% by weight of zeolite Y having a lattice parameter of 24.42 Å, an SiO2/Al2O3 molar ratio of 5.2, a specific surface area measured by nitrogen physisorption according to the BET method of 800 m2/g, 10% by weight of zeolite beta (zeolite CP814e from Zeolyst) having an SiO2/Al2O3 molar ratio of 25, a specific surface area measured by nitrogen physisorption according to the BET method of 670 m2/g, in the presence of commercial boehmite (Pural SB3). The extrudates obtained are dried at 80° C. then calcined at 600° C. in humid air (5% by weight of water per kg of dry air). The calcined support comprises, on a dry basis, 60% by weight of zeolite Y, 10% weight of zeolite beta and 30% weight of alumina, i.e. a Y/Beta weight ratio=6 in the catalyst.
Catalyst B is prepared by dry impregnation of the resulting support using an aqueous solution containing the elements Ni, Mo. This solution is obtained by dissolving the following precursors in water: nickel nitrate and ammonium heptamolybdate. The amount of precursors in solution is adjusted as a function of the targeted concentrations on the final catalyst. After dry impregnation, the catalyst is dried at 120° C. in air.
The weight percentages in the catalyst are respectively: 15.1% by weight of molybdenum (in MoO3 form), 3.3% by weight of nickel (in NiO form) on a dry basis.
The support for catalyst C is prepared by shaping by kneading-extrusion of 60% by weight of zeolite Y having a lattice parameter of 24.54 Å, an SiO2/Al2O3 molar ratio of 5.2, a specific surface area measured by nitrogen physisorption according to the BET method of 830 m2/g, 10% by weight of commercial zeolite beta CP814e having an SiO2/Al2O3 molar ratio of 25, a specific surface area measured by nitrogen physisorption according to the BET method of 670 m2/g, in the presence of commercial boehmite Pural SB3. The extrudates obtained are dried at 80° C. then calcined at 600° C. in humid air (5% by weight of water per kg of dry air). The calcined support comprises, on a dry basis, 60% by weight of zeolite Y, 10% weight of zeolite beta and 30% weight of alumina, i.e. a Y/Beta weight ratio=6 in the catalyst.
Catalyst C is prepared by dry impregnation of the resulting support using an aqueous solution containing the elements Ni, Mo. This solution is obtained by dissolving the following precursors in water: nickel nitrate and ammonium heptamolybdate. The amount of precursors in solution is adjusted as a function of the targeted concentrations on the final catalyst. After dry impregnation, the catalyst is dried at 120° C. in air.
The weight percentages in the catalyst are respectively: 15.1% by weight of molybdenum (in MoO3 form), 3.3% by weight of nickel (in NiO form).
The support for catalyst D is prepared by shaping by kneading-extrusion of 63% by weight of zeolite Y having a lattice parameter of 24.54 Å, an SiO2/Al2O3 molar ratio of 5.2, a specific surface area measured by nitrogen physisorption according to the BET method of 830 m2/g, 3.5% by weight of zeolite beta CP814 having an SiO2/Al2O3 molar ratio of 25, a specific surface area measured by nitrogen physisorption according to the BET method of 670 m2/g, in the presence of commercial boehmite Pural SB3.
The extrudates obtained are dried at 80° C. then calcined at 600° C. in humid air (5 wt % of water per kg of dry air). The calcined support comprises, on a dry basis, 63% by weight of zeolite Y, 3.5% weight of zeolite beta and 30% weight of alumina, i.e. a Y/Beta weight ratio=18 in the catalyst. After dry impregnation, the catalyst is dried at 120° C. in air.
Catalyst D is prepared by dry impregnation of the resulting support using an aqueous solution containing the elements Ni, Mo. This solution is obtained by dissolving the following precursors in water: nickel nitrate and ammonium heptamolybdate. The amount of precursors in solution is adjusted as a function of the targeted concentrations on the final catalyst.
The weight percentages in the catalyst are respectively: 10% by weight of molybdenum (in MoO3 form), 2.0% by weight of nickel (in NiO form) on a dry basis.
The performance of the catalysts described above is evaluated in hydrocracking of a feedstock comprising a fraction of vacuum distillates and gas oil in one step using an isothermal test pilot unit in downflow configuration.
This test feedstock undergoes hydrotreating (HDT). After this hydrotreating step, the test feedstock has a density at 15° C. of 0.8755 g/ml, a residual nitrogen content of 23 ppm by weight and a residual sulfur content of 16 ppm by weight. The initial point of the simulated distillation for this test feedstock after hydrotreating is 163.3° C. and the final point is 578.7° C. The 50 wt % point of the simulated distillation is at 391.7° C. In order to simulate the partial pressure of hydrogen sulfide and ammonia generated by the HDT step of the process, the test feedstock is additivated respectively with DMDS and aniline so as to obtain 8820 ppm by weight of sulfur and 1900 ppm by weight of nitrogen in the final additivated feedstock.
Each catalyst is evaluated separately and is sulfided prior to the hydrocracking test under an SRGO (straight run gas oil) feedstock, i.e. a feedstock of gas oil derived from the direct distillation of crude oil additivated with 4% by weight of dimethyl sulfide (DMDS) and 2% by weight of aniline. The sulfidation is carried out at an HSV of 2 h−1 (HSV=Hourly Space Velocity), an H2/feedstock volume ratio of 1000 Nl/l, a total pressure of 140 bar (i.e. 14.0 MPa) and a hold temperature of 350° C. for 6 hours.
After sulfidation, the operating conditions are adjusted to those used for the hydrocracking test: HSV of 1.5 h−1, an H2/feedstock volume ratio of 1000 Nl/l, a total pressure of 140 bar (i.e. 14.0 MPa). The temperature of the reactors is adjusted so as to target a net conversion of the 216° C.+ fraction of 65% by weight after 150 hours with feedstock.
The net conversion is defined as the yield of the cut (or fraction) with a boiling point below 216° C. minus the yield of the cut with a boiling point below 216° C. present in the test feedstock.
The performance of the catalysts is compared with that of catalyst B taken as reference and reported in Table 1. The relative activity in degrees Celsius (° C.) is obtained from the difference in temperature between the reference catalyst B and that obtained for the catalyst to be evaluated in order to obtain a net conversion of 65%. The relative yield of the 68-216° C. cut is taken as the difference between the yield of the catalyst to be evaluated and that of the reference catalyst B obtained in both cases at a net conversion of 65 wt % of the 216° C.+ cut. A positive value leads to an improved performance, i.e. higher activity or higher yield.
The results reported in the table above show that the catalyst D according to the invention having the combination of zeolite Y and zeolite beta with a weight ratio of 18 and a lattice parameter of the zeolite Y of 24.54 Å makes it possible to obtain a gain in selectivity towards the naphtha cut compared to the comparative catalysts A, B and C using a zeolite Y with a lower lattice parameter and/or a lower Y/Beta ratio as well.
The comparison of the performance of catalysts C and D clearly shows that the increase in the lattice parameter of the zeolite Y alone is not sufficient to obtain an increased selectivity towards the naphtha cut. This must be coupled with the use of the zeolite beta at a particular ratio compared to the zeolite Y.
It is also observed that catalyst D (relative activity of D=0) has the additional advantage of a converting activity at least equal to catalysts A and B (relative activity of A=−9 and relative activity of B=0) for a lower total zeolite content (catalyst D total zeolite content=63+3.5=66.5% by weight vs catalyst A and B: total zeolite content=60+10=70% by weight).
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2112644 | Nov 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/082852 | 11/22/2022 | WO |
