Catalytic precursors based on molybdenum sulphonates and / or carboxylates, process of preparation thereof and use thereof in hydroconversion processes of fossil feedstocks or feedstocks of renewable origin

Abstract

Described is a process for preparing a catalyst precursor based on at least one transition metal belonging to groups 5 to 12, containing organic sulphur, in the form of sulfonate ions, and / or carboxylate ions, comprising the steps of - reacting an organic acid selected from a sulfonic acid, a carboxylic acid (of fossil or renewable origin), and their combination, with a source of said at least one transition metal, optionally in the presence of a reducing agent; - removing the water produced in the aforementioned reaction by azeotropic distillation, or by anhydrification with a drying agent, to obtain at least one carboxylate and / or sulfonate salt of said transition metal, with the condition that when the acid is only a carboxylic acid and the metal is only Mo, said Mo has an average oxidation state that varies from +6 to +4.

Description

[0001]CATALYTIC PRECURSORS BASED ON MOLYBDENUM SULPHONATES AND / OR CARBOXYLATES, PROCESS OF PREPARATION THEREOF AND USE THEREOF IN HYDROCONVERSION PROCESSES OF FOSSIL FEEDSTOCKS OR FEEDSTOCKS OF RENEWABLE ORIGIN DESCRIPTION The present invention relates to catalytic precursors based on at least one transition metal belonging to one of the groups 5 to 12, e.g. Molybdenum, said precursors containing organic sulphur, in particular sulfonate ions, and / or carboxylate ions, preferably containing at leastsulfonate ions, which are apt to be transformed into acatalyst based on sulphides of said transition metal, e.g. MoS2, usable in microdispersed or dispersed form (slurry) inhydroconversion processes, such as those for thehydroconversion of heavy hydrocarbon residues (e.g.distillation oil residues (vacuum residue)), or in thehydroconversion of renewable / biological feedstocks, e.g. vegetable feedstock or animal fats, to obtain lighter and more valuable hydrocarbons (e.g. fuels) having a wider market. More particularly, the present invention relates to oil- soluble precursors based on Molybdenum and on fatty acids, also of renewable origin, and / or on sulfonic acids, which are capable of forming a Molybdenite having the same morphological and structural properties as the catalystsobtained from commercial precursors based on Molybdenum.Furthermore, the present invention relates to theprocess for preparing such precursors, the process forobtaining the corresponding catalysts in the form of sulfides of said at least one transition metal belonging to one of the groups from 5 to 12, e.g. MoS2, and the hydroconversion process employing the aforementioned sulfide-based precursors or catalysts, e.g. MoS2. As is known, many hydroconversion processes for upgrading heavy oils and petroleum residues take place in the presence of a catalyst which is dispersed in said oils / residues (slurry) and which consists of molybdenum disulfide MoS2(molybdenite in lamellae): generally such molybdenum sulfide is produced in situ, inside the hydroconversion reactor, starting from the corresponding Mo- based precursor that does not contain organic sulfur. The precursor of the aforementioned molybdenite is a Molybdenum carboxylate oil-soluble in heavy oils and is fedin liquid form to the hydroconversion reactor wherein itreacts, in the presence of hydrogen, with the organic sulfurthat is present in the heavy hydrocarbons to be treated, orit reacts with an external source of H2S or with a similar sulfidating agent, forming in situ the solid catalyst (MoS2) finely dispersed in the liquid phase. The catalyst precursor currently in use is a molybdenum octoate, namely molybdenum 2-ethylhexanoate (CAS NR 34041-09-03), in 2-ethylhexanoic acid containing 15.5% by weightof Mo. This precursor is industrially prepared from 2-ethylhexanoic acid which is a branched monocarboxylic acid(C8H16O2) derived from petroleum: said acid is reacted withan inorganic molybdenum compound in which the Mo has a +6oxidation state, generally ammonium molybdate (NH4)2MoO4,ammonium heptamolybdate (NH4)6Mo7O24*4H2O or Molybdic acid(H2MoO4), according to the following reaction4RCOOH + H2MoO4 → MoO(RCOO)4 + 3H2Owhere the formula MoO(RCOO)4is indicative, since Mo oxidation state and salt coordination are not fully identified. The use of 2-ethylhexanoic acid as a reagent is industrially advantageous in that its corresponding Mo carboxylate shows a Molybdenum content that is around 15% by weight with respect to the total weight of the precursor and which is higher than the content of Mo in salts obtained from other short-chain carboxylic acids. There are also other processes in the art for preparing the aforementioned precursor using carboxylic acids wherein the source of Mo are Mo anhydrides in which Mo has a +6 oxidation state or compounds in which Mo has a +4 oxidation state. However, as far as the Applicant is aware, there are notdescribed in the prior art Mo-based precursors that alreadycontain the organic sulphur necessary to generate molybdenite in the aim of obtaining a more manageable hydro- conversion process. Currently, in industrial production processes, there is also a particular need to use raw materials of renewable origin in order to increase sustainability of said industrialprocesses, but also in order to give value to by-products ofreaction which are requested to be disposed of in order to confer an economic circularity to said processes. However, replacing a reagent of fossil origin with the same compound of renewable origin is not always possible: for example, in the case of 2-ethyl hexanoic acid the corresponding acid of renewable origin does not exist sinceonly linear carboxylic acids are obtained from renewablesources such as vegetable oils rather and are not obtainedbranched carboxylic acids such as 2-ethyl hexanoic acid. Furthermore, the commercially available carboxylic acids of renewable origin often occur with a purity lower than that of the compounds of fossil origin as they are generally mixtures of carboxylic acids of various length, optionally also in mixture with the corresponding esters, and therefore it is difficult or impossible to separate from each other in the form of pure or high-purity compounds: this could make such compounds of renewable origin unsuitable as reagents to obtain catalytic precursors since the presence of residues / impurities in the catalytic precursor could adversely affect the formation and performance of the MoS2catalyst. It would therefore be desirable to have available new and inexpensive precursors of MoS2catalysts, that are- capable of forming a microdispersed MoS2 molybdenitecatalyst having the same performance as the MoS2 catalystobtained from Mo-based precursors of fossil origin suchas the precursors obtained from 2-ethylhexanoic or ethylbenzoic acid; and / or- obtainable also from non-pure carboxylic acids (i.e.having a purity of less than 99% up to 70-80% as mixtures of carboxylic acids) as they are derived from renewable sources. A first object of the present invention is therefore a process for preparing a catalyst precursor in the form of salt based on at least one transition metal belonging to oneof the groups from 5 to 12, preferably molybdenum, andcontaining organic sulphur, preferably in the form of sulfonate ions, and / or carboxylate ions, more preferablycontaining at least sulfonate ions, capable of generating,in the presence of hydrogen, a catalyst based on sulfides of said at least one transition metal, e.g. MoS2, said preparation process comprising the steps of- reacting an organic acid selected from a sulfonic acid,a carboxylic acid (of fossil or renewable origin), or their combination, with a source of said at least one transition metal, preferably Molybdenum (VI), more preferably with a source consisting of one or more inorganic compounds of Mo (VI), optionally in the presence of a reducing agent, preferably selected from phenol, naphthol, naphthol derivatives, ascorbic acid,diphenylamine and alkylphenol wherein one or more alkyl groups are a C1-C10alkyl group;- removing the water produced in the aforementionedreaction by azeotropic distillation, or by anhydrification with a drying agent, to obtain at least one carboxylate and / or sulfonate salt of said transition metal, preferably carboxylate and / or sulfonate of Mo, with the condition that when the acid is only a carboxylic acid and the metal is only Mo, said Mo has an average oxidation state that varies from +6 to +4 (extremes excluded), preferably an average oxidation state that varies from +6 to +5. By “organic sulphur ” is meant here to identify sulphur covalently bound to one or more atoms other than sulphur such as, for example, e.g. O,H,C. By “average oxidation state” is meant here to identifythe oxidation state of the obtained salt of Mo, evaluated asknown to the person skilled in the art, for example by colorimetry. The use of a reducing agent is advantageous if one wants to develop more water in a prefixed time interval, thus speeding up the salification reaction. Furthermore, the use of a reducing agent is preferred in case the precursor contains only carboxylate ions. In one embodiment, the catalyst precursor that is obtained from the process of the invention is in the form of salt based on at least one transition metal belonging to one of the groups from 5 to 12 and contains sulfonate ions only, or a combination of sulfonate ions and carboxylate ions or carboxylate ions only deriving from carboxylic acids of renewable origin such as pelargonic acid (C9), a mixture of carboxylic acids of renewable origin with a chain length ranging from C5to C11. In one preferred embodiment, the catalyst precursor thatis obtained from the process of the invention is in the formof salt based on at least one transition metal belonging to one of the groups from 5 to 12 and contains at least sulfonate ions. In particular, the process in accordance with the invention advantageously provides for the steps for preparing the above catalyst precursor in the form of salt based on at least one transition metal belonging to one of the groups from 5 to 12, preferably molybdenum, and containing at least sulfonate ions and optionally carboxylate ions, by means of the following steps of (a) reacting a sulfonic acid (RSO3H), or a mixture ofsulfonic acids, with a source of said at least one transition metal belonging to one of the groups from 5 to 12, preferably Molybdenum (VI), more preferably a source consisting of one or more inorganic compounds of Mo (VI), optionally in the presence of a reducing agent, said reducing agent being selected from phenol,naphthol, naphthol derivatives, ascorbicacid, diphenylamine and alkylphenols wherein one or more alkyl groups are a C1-C10alkyl group; (b) optionally reacting one or more compounds of at leastone transition metal belonging to one of the groups from 5 to 12, preferably one or more compounds of Mo, obtained in the previous step (a), with a carboxylic acid, or with a mixture of carboxylic acids, of fossil or renewable origin, to obtain one or more compounds of said at least one transition metal also containing carboxylate ions; (c) removing the water produced in steps (a) and / or (b)by azeotropic distillation or by anhydrification witha drying agent, to obtain at least one sulfonate salt, optionally containing carboxylate ions, of said at least one metal, preferably a sulfonate salt of Mo containing also carboxylate ions. In step (a) of the process in accordance with the presentinvention, or more generally in the reaction step between organic acid and source of said transition metal, if the transition metal is Mo, the source of molybdenum, in particular the source of Mo (VI), can be selected from molybdic acid H2MoO4and its salts, also in the hydrated form, such as for example ammonium heptamolybdate (ammonium molybdate), sodium molybdate, molybdic anhydride. Sources of other transition metals belonging to the groups from 5 to 12 are, for example, oxides or salts of such transition metals including salts of organic acids: mention may be made, for example, of metal ammonium salts, metal carbamates, metal naphthenates and compounds analogous to the aforementioned sources of Molybdenum. The sulfonic acid RSO3H used in step (a) may be an acid in which the R group is -a linear or branched C1-C24 alkyl group;- an aryl group, possibly substituted;- a di-substituted aryl group, e.g. aryldialkyl havinga C1-C6alkyl group; -a trisubstituted aryl group, e.g. aryltrialkylhaving a C1-C6alkyl group. In one embodiment, the sulfonic acid RSO3H is an acid inwhich the substituent R is aryl group, such as for example tolyl (CH3C6H4−), phenyl (C6H5−), xylyl ((CH3)2C6H3−), naphthyl (C10H7−) group, or an alkylbenzyl group having the alkyl chain ranging from C3to C24, for example a group 2,6-di-tert-butyl- 4-methyl. Examples of sulfonic acid RSO3H includep-toluenesulfonicacid, an alkylbenzenesulfonic acid with alkyl chain from C12to C24, e.g. dodecylbenzenesulfonic acid (DBSA), mixture of alkylbenzenesulfonic acids with C20-C24alkyl chain (e.g. commercial product HSA118 from HUNTSMAN), or their combinations. The amounts of sulfonic acid RSO3H depend both on the type of feedstock (i.e. already containing sulfur or not containing sulfur) that will be used as feed in thehydroconversion process and on the valence of the metal,although this is not binding for the purpose of the present invention. In one embodiment, the amounts of sulfonic acid RSO3Hare such as to advantageously obtain a molar ratio (Rmolar) between sulfur and a transition metal belonging to the groupof molybdenum (Mo)- 0.6≤S / Mo<2, in the case where the precursor is intendedfor the hydroconversion of fossil hydrocarbons which generally already contain an amount of sulphur; preferably S / Mo≤1 when p-toluenesulphonic acid is used. -2≤S / Mo≤4, preferably S / Mo comprised between 3 and 4(extremes included), in the event that the catalyst precursor is intended for the hydro-conversion of sulfur-free feedstocks as it is not of petroleum origin,where Mo denotes both Molybdenum and the other transition metals belonging to the same molybdenum group. Step (a), or more generally the reaction step between organic acid and source of said transition metal, is advantageously conducted under stirring. Furthermore, step (a), or more generally the reaction step between organic acid and source of said transition metal, advantageously takes place at a temperature such that at least one reagent is liquid, e.g. at a temperature of 25°C to 125°C, preferably at a temperature of 60-110°C. In one embodiment, step (a), but more generally the step of reacting an organic acid with the source of the transition metal, is conducted in the presence of inert gas, e.g. nitrogen, argon, or under flushing of said inert gas. Step (a), but more generally the step of reacting an organic acid with the source of said transition metal, can be conducted at a pressure that is advantageously comprised between atmospheric pressure and 1 bar(g), preferably with a nitrogen overpressure ranging from 10 to 100 Pa, preferably from 20 to 65 Pa. In a preferred embodiment, step (a) is conducted in the presence of at least one reducing compound as defined above: in this case, the presence of said reducing compound leads to obtaining one or more organic sulphur-containing compounds in which said transition metal has a lower oxidation state than the starting one, for example Mo (V) and / or Mo (IV). As mentioned above, the advantage of using the reducingcompound, e.g. phenol, is mainly in terms of salification rate evaluated as greater amount of water developed in thesame time interval.If the reducing agent is used in step (a), the molarratio (Rmolar) reducing agent / Metal (wherein “metal” can alsobe the total of the moles of the metals used), preferablymolar ratio (Rmolar) reducing agent / Molybdenum, can becomprised between 0.5 and 1.5. An example of alkylphenols is 2,6-di-tert-butyl-4- methylphenol. Examples of naphthol derivatives are 2-naphthol, 7- methoxy 2-naphthol. If step (b) is carried out, it is conducted at a pressuresubstantially similar to that of step (a). If step (b) is carried out, it is conducted at a temperature that varies in the range defined above for step (a), e.g. 60-125°C. In a preferred embodiment, step (b) is conducted after carrying out step (a) by using at least one reducing compound as defined above: in this case there is the formation of one or more transition metal compounds in which the metal is in a lower oxidation state than the starting one, e.g. Mo (V), and which contain both organic sulphur, preferably sulfonate ions, and carboxylate ions. In another preferred embodiment, step (b) is conducted simultaneously with step (a) in the same reaction reactor. The formation of Mo (V) compounds, optionally in mixture with Mo (IV) compounds, can be detected by colorimetric analysis of the mixture that was obtained from the reduction step (a): in fact it is known that the prevalent presence of Mo (VI) imparts a yellow / brown coloration to the solution (mixture) whereas if the solution formed by the reaction described above has a coloration different fromyellow / brown, for example, a blue or dark violet coloration,this is an indication of the prevalent presence of Mo(V). The carboxylic acid used in step (b) of the process of the present invention is a saturated or unsaturated monocarboxylic acid, preferably a saturated one, or it is a mixture of said carboxylic acids, of renewable origin or fossil origin, without thereby departing from the scope of the present invention. Said carboxylic acid may be of renewable origin or fossil origin. Said carboxylic acid can be selected from -a carboxylic acid, of renewable or fossil origin, havinga C5-C11 long chain (e.g. aliphatic chain), e.g.pelargonic acid (C9) of renewable origin, but also of greater length, e.g. C12-C22; -a mixture of carboxylic acids, of renewable or fossilorigin, having a C5-C22 long chain (e.g. aliphatic chain)or a greater chain; -a mixture of carboxylic acids of renewable origin with a chain (e.g. Aliphatic chain) having a C5-C22length, also unsaturated, and also containing one or more corresponding esters of said acids, e.g. IF001M (FAV)marketed by Matrica; -their combinations.In one embodiment, the carboxylic acid is pelargonicacid (C9) of renewable origin, preferably having a purity ofless than 99% w / w: such acid is particularly preferred when no sulfonic acid is used. In another embodiment, the carboxylic acid is a mixture of carboxylic acids of renewable origin with a chain (e.g. Aliphatic) having a length ranging from C5to C11: such acid is particularly preferred when no sulfonic acid is used. In another embodiment, the carboxylic acid is a mixture of carboxylic acids of renewable origin and triglyceride esters, also unsaturated ones, having a TAN equal to 150 mgKOH / g: such a mixture is particularly preferred when no sulfonic acid is used. The determination of the renewable origin of thecarboxylic acid, or of the mixture of carboxylic acids defined above, can be carried out by measuring the so-called “bio-based carbon”, for example according to the methodology of the ASTM D6866 standard (and subsequent updates, i.e. ASTM D6866-16 Method B) which distinguishes between carbon derived from biomass (from plants or animals), and that derived from fossil fuels. Biomass contains a certain amount of carbon-14 which makes it easily distinguishable from other materials, such as fossil fuels, which do not contain carbon- 14. Since the amount of carbon-14 present in the biomass is known, the percentage of carbon derived from renewable resources is easily calculated on the total carbon of the sample. It is understood that other methodologies and measurements may be used in the present invention to determine the biological origin of the compounds / components / reagents / without thereby departing from the scope of the present invention. The amount of carboxylic acid to be used in step (b) depends on the amount of sulfonic acid used in step (a): since the stoichiometric ratio between sulfur and Mo is atleast equal to 2 in order to be able to form MoS2, the molesof carboxylic acid with respect to the Metal are generally greater than 2 and less than 6. In particular, in the case of molybdenum (Mo), the ratio between the total moles of the two types of acid (sulfonicacid and carboxylic acid) and the metal moles must satisfythe following relationship Rmol(total acid / Mo) = (sulfonic acid) / Mo+(Carboxylic Acid / Mo)≤6 and Rmol(total acid / Mo)=(sulfonic acid) / Mo+(Carboxylic Acid / Mo)≥2. In step (a) and / or step (b) any solvent which is not reactive towards the above acids and metal sources may be added, e.g. THF, to make the mixture containing the reagents less viscous, in particular in the case where one or more of said reagents are high molecular weight compounds, or mixtures of numerous compounds that are homologous between them, or are themselves very viscous compounds, without thereby departing from the scope of the present invention. In step (c), the removal of the water produced in steps (a) and / or (b) can be conducted at a temperature comprised between 60°C and 180°C, depending on the type of removal adopted. The azeotropic distillation of step (c) may advantageously be conducted at a temperature comprised between 110°C and 180°C, preferably between 120°C and 165°C, depending on the solvent used. The azeotropic distillation takes place in fact by adding an azeotropic distillation solvent for the removal of water which can be, for example, toluene, dibutylether (DBE), nonane, ethylbenzene. In one embodiment, it is preferable to use DBE as the azeotropic distillation solvent when only carboxylic acids of renewable origin are used in the present process of the invention. The pressure in the azeotropic distillation can advantageously be the same as in the previous reaction steps: in this case it will only be enough to increase the temperature with respect to the previous reaction steps to trigger the azeotropic distillation at the same pressure. The amount of azeotropic distillation solvent that can be added is generally a large excess, e.g. 10 times, with respect to the theoretical amount of water produced in the salification reaction of step (a) and / or (b), and possibly in the reduction reaction, including the water present in the starting reagents, since said theoretical amount of water can be estimated as reported below by way of illustration considering Mo as the only transition metal. In one embodiment, the amount of solvent (by volume) of azeotropic distillation is advantageously greater, e.g. at least 1.5 times, with respect to at least the volume of the apparatus (trap) at the top of the azeotropic distillation column so as to avoid that all the added solvent fills the trap, thus interrupting the distillation of water. In one embodiment, the amount of water that is removed is equal to at least 75% of the total (theoretical) water, preferably 80-90%, which can be estimated according to a probable reduction and salification reaction, such as those reported below by way of illustrative example. In the case of Molybdenum, this water to be removed can be calculated considering the following relationship: where the coefficient 3.5 represents the sum of the two water inputs (1.5+2) deriving from step (a) in the presence of said reducing agent and from step (b), according to inputs estimated as follows:- Water due to the reduction according to the stoichiometryof a possible reaction between the molybdenum source, e.g. ammonium heptamolybdate (heptamolybdate tetrahydrate), reducing agent, e.g. phenol, a carboxylic acid RCOOH (where R is the hydrocarbon chain): 2(NH4)6Mo7O24*4H2O (solid) +7^*-OH+12RCOOH→ 7 O=^=O* + 14MoO2+12RCOONH4+21H2O according to a possible reaction between molybdic acid, a reducing agent, e.g. phenol: 2H2MoO4+^^^-OH → O=^^ =O* + 2MoO2+ 3H2O^ In both cases, the water produced in the reduction reaction is 1.5*moles of Mo: 0.04 moles of Mo*1.5=0.06 moles H2O (corresponding to1.08 ml of water);- Salification water, e.g. with carboxylic acid, which isworth 2*moles of Molybdenum, assuming that thesalification reaction is only the following one: MoO2+4 RCOOH → Mo(RCOO)4+ 2H2O The water produced in the aforementioned salification reaction is0.04 moles of Mo*2=0.08 moles of H2O (corresponding to1.44 ml of water). Another possible salification reaction of the same starting reagent could be 2MoO2+ 4RCOOH → Mo2O2(RCOO)4+ 2H2O which produces 1 mole of water per atom of molybdenum. If step (a) is conducted without a reducing agent and step (b) is not carried out, the total water to be removed in step (c) will be due only to the water present in the starting reagents and to the water generated in the salification of the sulphonic acid used, without thereby departing from the scope of the present invention. At the end of the azeotropic distillation of step (c), a product is obtained that can still contain non-negligible amounts of azeotropic distillation solvent, e.g. around 10%: it is therefore possible to provide a vacuum distillation step (d), e.g. at a pressure of 170-250 mBar, to be carried out after this step (c) in order to remove the solvent still contained in the product so as to obtain a higher concentration of molybdenum (% by weight) in the obtained product. As an alternative to step (d), it is possible to lower the amount of azeotropic solvent in the final product below negligible values already in the course of step (c) by distilling the azeotropic solvent off according to methodologies known to the person skilled in the art, e.g. longer azeotropic distillation times. The anhydrification of step (c) is generally conducted at temperatures lower than those adopted in the alternative azeotropic distillation, in particular at temperatures lower than 100°C, e.g. at 60-70°C. The term “drying agent” here is intended to identify compounds, other than metal salts, which are reactive withrespect to water and capable to eliminate it thanks to theirtransformation into another molecule (dehydrating agent). The drying agent can be selected from those known in the art, e.g. acetic anhydride in case the reducing agent in step (a) is not used: acetic anhydride forms with wateracetic acid which can be advantageously removed, completelyor in large part, in a subsequent optional step (d) by meansof distillation from the product obtained in the preceding steps. In a particularly preferred embodiment of the process in accordance with the invention, the Applicant has found that 2,2-dimethoxy propane (DMP) having a Teb=84°C turns out to be very advantageous as a drying agent when it is used in the step (c) of the present invention. DMP is particularly beneficial in that- it is not reactive towards phenol and itsderivatives; -it reacts with water developing acetone andmethanol which are low-boiling products allowing to operate at temperatures even <80°C: in this way it is not necessary to heat the mixture obtained in step (a) or in step (b); -the acetone and methanol produced are lightweight andeasy to remove from the salt produced at the end of the reaction in step (a) or in step (b) by means of a subsequent distillation step (optional step (d) of distillation of low boilers such as acetone and methanol). It has also been found by the Applicant that it is alsopossible to use, as a drying agent, mixtures between a dryingagent as defined above, e.g. DMP, and a compound that forms an azeotrope with water, e.g. DBE, without thereby departing from the scope of the present invention. In one embodiment, the drying agent is a DMP+DBE mixture, preferably a mixture 50 / 50 by weight, when only carboxylic acids of renewable origin are used as organic acid in the present process of the invention. The amount of chemical drying agent to be used in step (c) can be estimated first by considering the 1:1 stoichiometry of the reaction between water and the selected drying agent, which can be illustrated, by way of example, for the following reaction between water and (CH3)2C(OCH3)2(DMP): (CH3)2C(OCH3)2 + H2O → (CH3)2C=O+ 2 CH3OH calculating the amounts by weight of DMP according to the following relationship DMP(g)= 104*(moles H2O theoretical)=104*(3.5*moles Molybdenum + moles H2O reagents) It is also possible to use higher amounts of DMP thanstoichiometric ones: for example it is possible to work withan excess of DMP ranging from 5% to 40% by weight compared to the stoichiometric amount (by weight). In the event that DMP is used in step (c) as the drying agent, the product obtained at the end of the anhydrification reaction can be subjected to distillation at 60°C in vacuum, e.g. at 150 mbar, to remove methanol and acetone in order to increase the metal, e.g. molybdenum, titre in the product. The solvent for azeotropic distillation, e.g. toluene, or the drying agent may be added already in step (b) and / or step (a), without thereby departing from the scope of the present invention. In one embodiment, the azeotropic distillation solvent or the drying agent is added in step (b): in this case, the reaction of step (b) can be carried out by operating byreflux until a predefined amount of water is produced, for example until the production of at least 75% of water is reached with respect to the total theoretical amount produced in the aforementioned possible reactions. The precursor based on at least one transition metal belonging to one of the groups from 5 to 12, preferably Mo, which is obtained at the end of the process of the present invention comprises organic sulfur, preferably in the formof sulfonate ions, and / or carboxylate ions, more preferablyonly sulfonate ions. Furthermore, said precursor shows, in the case of Molybdenum, a concentration of Mo (hereinafter also referred to as “titre”) which is generally lower than 15% by weight with respect to the total weight of the precursor, preferably ranging from 2.5% by weight of Mo up to 10% by weight of Mo with respect to the total weight of the precursor. The lower concentration of Mo in the present invention with respect to that in the same precursors of the known art can be compensated for in the hydroconversion process by using a higher precursor / feedstock ratio which does not result in a greater increase of cost as the precursor of the present invention is cheaper from the point of view of its production and / or raw materials: in fact it was also possible to use impure mixtures of carboxylates and / or sulfates in the present process while obtaining catalytic performances in line with the commercial catalysts obtained from pure carboxylic acids, e.g. 2-ethylhexanoic acid (see examples). Furthermore, one of the advantages of the preparation process in accordance with the present invention is to avoid feeding a sulfidating compound, e.g. DMDS, or the like, in the hydroconversion reactor, the dosage of which is rather difficult to adjust in the continuous hydroconversion processes, since conventionally the sulfidating compound must be continuously dosed in amounts which are slightlygreater with respect to the amounts of metal (by ppm) addedto the feedstock to be converted.In particular, in the present preparation process in accordance with the invention the molar ratios between the metal, in particular molybdenum, and the sulphonic acid, andoptionally the carboxylic acid, are modulable depending onthe type of feedstock to be hydroconverted, e.g. conventional fossil feedstocks already containing sulphur or vegetablefeedstock not containing sulphur or combinations thereof.A further advantage of the present invention lies, as mentioned above, in the use of carboxylic acids of renewable origin that are not pure compounds and / or are by-products of other supply chains with a clear circular economy advantage. The Applicant has unexpectedly noticed that the impurities normally present in such carboxylic acids of renewable origin do not negatively affect neither the formation of the precursor nor its characteristics, e.g.solubilization in the feedstocks, decomposition temperatureat the operating temperatures of the hydroconversion process, nor the formation of the corresponding catalyst based on transition metal sulphides, e.g. MoS2, and its characteristics, e.g. lamella formation and stacking in a few layers. DESCRIPTION OF THE DRAWINGS Figure 1 illustrates two FT-IR spectra relating respectively to p-dodecylbenzenesulfonic acid and its Molybdenum salified form. A further object of the present invention is therefore a precursor, preferably oil-soluble, of a sulphide-based catalyst of at least one transition metal belonging to oneof the groups from 5 to 12, e.g. MoS2. Said catalyst precursoris in the form of salt of said at least one transition metal and comprises carboxylate ions and / or sulfonate ions, with the condition that when only carboxylate ions are present and the metal is only Mo, said Mo has an average oxidation state that varies from +6 to +4 (excluding +4), preferably ranging from +6 to +5. The presence of sulfonate ions in the precursor can be detected by IR analysis in combination with quantitative elemental analysis of sulfur. The presence of carboxylate ions in the precursor can also be detected by IR analysis, as known to the person skilled in the art. Said precursor preferably contains at least Molybdenum as catalytically active metal. Furthermore, when said precursor comprises only carboxylate ions and the transition metal is only Mo, the Mo contained in the precursor has an average oxidation state that varies from +6 to +4 (excluding +4), preferably an average oxidation state that varies from +6 to +5, without thereby departing from the scope of the present invention. In one embodiment, said precursor comprises carboxylateions derived from pelargonic acid (C9) of renewable origin.In one embodiment, said precursor comprises carboxylate ions derived from one or more carboxylic acids of renewable origin containing a long hydrocarbon chain (e.g. Aliphaticone), e.g. C5-C11 or C5-C22 chain , said precursor possiblybeing in a mixture with the corresponding esters of such C5- C22carboxylic acids. In another embodiment, said precursor comprises carboxylate ions deriving from a mixture (hereinafter also indicated by the abbreviation FAV for the sake of simplicity) of one or more carboxylic acids of renewable origin havinga long hydrocarbon chain (e.g. palmitic, stearic and keto-stearic acid) in a mixture with di- and tri-glycerides offatty acids having a chain with a number of carbon atomsranging from C9 to C18, di- and tri-glycerides of azelaicacid. Said precursor can advantageously be obtained by the process described above in accordance with the present invention. The concentration (hereinafter also referred to as “titre”) of said transition metal, e.g. Mo, in the precursor object of the present invention, or the total concentration of the transition metals, may be less than 15% by weight with respect to the total weight of the precursor, and therefore said concentration may advantageously vary from 2.5% by weight of Mo up to 10% by weight with respect to thetotal weight of the precursor.The titre of the above catalytically active transition metal, e.g. molybdenum, is important to determine the dosage of the precursor in the hydroconversion reactor with respectto the feedstock that is fed.The precursor in accordance with the present invention is advantageously intended to be fed into a hydrocracking / hydroconversion reactor together with the feedstock to be hydroconverted, i.e. heavy hydrocarbonscontaining sulphur or vegetable feedstocks (which do notcontain sulphur), and intended to be transformed, in the presence of hydrogen, into the microdispersed catalyst based on sulphides of one or more transition metals as defined above, e.g. MoS2, which is usable in hydrocracking / hydroconversion reactions. In practice, the precursor in accordance with the presentinvention is brought into contact with the feedstock to betreated (which may already contain sulphur or be devoid ofsulphur, for example, a heavy hydrocarbon residue, or avegetable or animal feedstock, or combinations thereof) andinto contact with hydrogen under appropriate conditions of temperature and pressure, for example at a temperature of 400-440°C and at a pressure of 130-160 atm, so as to obtain an effluent exiting the hydroconversion reactor and containing the conversion products. Examples of hydroconversion processes include those described, for example, in US 8,147,675 B2, ITMI20061512A1 incorporated herein by reference in its entirety. A further object of the present invention is therefore a hydroconversion process of feedstocks, such as for example petroleum distillation residues, to obtain lighter and more valuable hydrocarbons, e.g. naphtha, diesel, or hydroconversion of feedstocks of renewable / biologicalorigin, e.g. vegetable feedstocks, to obtain hydrocarbons ofrenewable origin, said process comprising at least the step of bringing a catalytic precursor as defined above intocontact with said feedstock and with hydrogen, optionally inthe presence of a sulfidating agent, operating at a temperature of 390-450°C and at a pressure of 110-170 atm so as to obtain, at the outlet of the hydroconversion reactor, an effluent comprising said conversion hydrocarbons and said catalyst formed in situ from said catalytic precursor. In this hydroconversion process, it can also be advantageously provided a further step of gas-liquid physical separation, liquid-liquid physical separation of the heavy phase of said effluent containing dispersed catalyst, solids formed during the hydroconversion reaction,the unreacted feedstock and any phosphorus compounds,nitrogen (e.g. nitrogen-containing compounds), metals (alkali, alkaline-earth, transition) from at least one hydrocarbon phase. Such physical separation may comprise at least, or consist of, one or more high-pressure gas-liquid separations, one or more gas-liquid, low-pressure liquid- liquid separations, a fractional distillation at atmospheric pressure, a vacuum distillation, and combinations thereof. In this way, the hydrocarbon phase contained in the effluent can be separated into several hydrocarbon phases, hereinafter also referred to as “cuts”, having different temperature intervals and therefore with different applications in the “fuel” field. The separated heavy phase can instead be advantageously recycled partly to the reactor and partly sent to the battery limits as a purging stream so as to avoid the accumulation of solids in the hydroconversion reactor. As mentioned above, the precursor in accordance with the invention generates in situ, under hydroconversion conditions and optionally in the presence of a sulfidating agent, a dispersed sulfide-based catalyst of one or more transition metals of the groups from 5 to 12. In particular, the catalyst which is formed in situ underthe aforementioned conditions is generally in the form of particles dispersed in a liquid medium, in particular it is in the form of solid particles having an average size ofless than 100 microns, preferably less than 20 microns,finely dispersed in a liquid medium which may be the reaction effluent. It is therefore a further object of the present invention a hydroconversion catalyst comprising sulfides of one ormore transition metals of the groups from 5 to 12, preferably based on Molybdenum, more preferably MoS2, obtainable in situ from a catalyst precursor as defined above, in the presence of H2, possibly in the presence of sulfidating agents, said catalyst preferably being in the form of solid particles having an average size of less than 100 microns, preferably less than 20 microns obtainable from the precursor defined above in accordance with the present invention. Some illustrative but not limiting examples of the present invention follow. EXAMPLES Acronyms HMA = ammonium heptamolybdate;AcMo= molybdic acid; HTOS= p-toluenesulfonic acid; HSA118= mixture of alkylbenzenesulfonic acids with alkyl group R=C20-C24; DBSA= dodecylbenzenesulfonic acid; PHB= 2,6-di-tert-butyl-4-methylphenol; RV= vacuum residue. Reagents- Molybdic acid (H2MoO4) by Alfa Aesar at a minimum titreof 85% in MoO3;- 2,2-dimethoxypropane (DMP) by Sigma Aldrich with a titreequal to 98%;- Commercial ammonium heptamolybdate (HMA);- Commercial 2,6-di-tert-butyl-4-methylphenol (PHB);- HTOS= p-toluenesulfonic acid monohydrate marketed byAldrich;- Phenol marketed by Aldrich;- FAV = complex mixture (heavy tails) formed by di- andtriglycerides of fatty acids having a chain with a number of carbon atoms ranging from C9 to C18, azelaic di- andtriglycerides, long chain fatty acids (palmitic, stearic and keto-stearic acids), marketed by Matrica under thetrade name IF001M, having a TAN equal to 150 mgKOH / g (measured according to ASTM D 664 standard);- Perlargonic acid of renewable origin marketed by Matrica;- HSA 118= mixture of alkylbenzenesulfonic acids with thealkyl group R=C20-C24, marketed by Huntsman;- Commercial Mo Octanoate (Mo OCT);- Commercial Naphthol;- Vacuum residue = bottom residue of a vacuum distillationcolumn deriving from the refinery processing of crude oils of Caucasian origin, having the following characteristics: RV (3C-180319F5) Density @15 °C kg / m 1004.0Viscosity @ 135 °CPoise 142C %weight 84.56H %weight 10.46N %weight 0.50S %weight 4.30Fe ppm 59Mo ppm 9Ni ppm 88V ppm 154Na ppmRCC %weight 17THF-insoluble %weight 0Asphaltenes-C5 %weight 19.45DAO-C5 %weight 80.55IBP-36 °C %weight 0.036-170 °C %weight 0.0170-350 °C %weight 0.0350-450 °C %weight 7.8450-500 °C %weight 8.7500-540 °C %weight 7.4540+ %weight 76.1Characterization methods- X-RAY DIFFRACTION (XRD)It was conducted using a Philips X'PERT vertical diffractometer equipped with proportional pulse detector and graphite curved crystal secondary monochromator. Diffraction patterns were collected using the angular range 7 ≤ 2θ ≤ 70° with steps of 0.03° 2θ and accumulation times of 24 s / step; the radiation used is CuKα (λ = 1.54178 Å). The identification of the crystalline phases was conducted using the search-match method of the X’Pert HighScore software package marketed by PANalytical that uses the ICSD database for qualitative analysis. The XRD characterization of molybdenite took place through the following parameters: 1) lateral dimension - in the crystallographic direction110 - calculated from the reflection present in the XRDpattern of molybdenite (2θ of 63°); 2) dimension along the stacking direction – in thecrystallographic direction 002 - calculated from thereflection present in the XRD pattern of molybdenite; 3) if there is stacking, indication about the number of layers that are present.- FT-IR ANALYSISIt was conducted using a Perkin-Emer FT-IR infrared spectroscope mod. Frontier, in order to verify the formation of sulfonate salt. The sample, whether liquid or dispersion, is analysed by KBr tablet deposition, then by acquiring the relative spectrum. The sample, if in the form of a solid (salt), is first subjected to washing with ethyl ether, the obtained solid / powdery compound is then intimately mixed with KBr powder with a sample ratio: KBr of about 3:100 to obtain, with the aid of a hydraulic press, a tablet, thusacquiring the relative spectrum. The parameters used were: Resolution 4 cm-1, interval 1 cm-1; spectral range 4000-450 cm-1; number of scans: 1; ambient T measurement. The group of signals comprised between 1159 cm-1and 1007 cm-1obtained using p-dodecylbenzenesulfonic acid as a sample were identified as due to the presence of the O- SO2group, at 1410 cm-1of the R-O-SO2group, while the broad signals at 3401 cm-1and 1726 cm-1are attributable to the action / formation of hydrogen bonds due to the OHpresent on the group R-SO3H. In the p-dodecylbenzenesulfonic acid in its salified form with Mo, the aforementioned broad signals disappear, the absorptions comprised between 1247 cm-1and 992 cm-1due to the R-SO3-Mo group are detected, where the signal at 992 cm-1can be referred to the Mo-O bond of the sulfonic group as well as the signal at 751 cm-1. Figure 1 reports the two spectra, where the ordinate %T represents the percentage of transmitted radiation (transmittance).- MOLYBDENUM TITREIt was measured in the product by ICP spectrometry usingthe Perkin Elmer Optima 5300 DV instrument, in analogy to the ASTM D4951 method.- THF-i (THF-insoluble)It measures the amount of insoluble solid residue (in tetrahydrofuran) that is produced in the hydroconversion reaction and consists of sulfides of the metals initiallypresent in the feedstock, of the coke formed in thereaction and of insoluble asphaltene resins. The lowerthe value of THF-i, and the better the performance of the catalyst in avoiding secondary polymerization reactions of free radicals formed during hydroconversion that increase the formation of solids. The effluent is diluted with THF with a 1 / 100 dilution ratio. The product thus obtained is heated to a temperature close to the boiling temperature of the solvent and then a solid / liquid separation is carried out (e.g. filtration, centrifugation and / or combination of the two). The recovered solid (THF-i) is dried for 24 hours to remove the solvent and quantified.- H2SIt was measured by SIM-DIS gas-chromatographic (GC) analysis using an RGA analyzer (Refinery Gas Analyzer) which is a specific chromatographic gas system for refinery gas for C1-C5 and H2S gas analysis with limit of detection 1000 ppm.- DENSITY at 40 °C and 70 °CIt was measured in accordance with ASTM D7042 standard.- KINEMATIC VISCOSITYIt was measured in accordance with ASTM D7042 standard. EXAMPLES Example of preparation A: synthesis including solventaddition and azeotropic distillation (Synthesis SF121222,SF190623, SF090823) In a 250 ml flask, blanketed with nitrogen (overpressure from 20 to 65 Pa) and equipped with magnetic stirrer, thermometer, distiller with Dean Stark trap and heatingmantle the following compounds are added- molybdic acid (AcMo) as a source of Mo (VI),- p-toluenesulfonic acid (HTOS), and- phenol,in the amounts and proportions reported in Table 1. Table 1 Preparation A (Synthesis SF121222) Reagents g MolesMolybdic acid 6.53 0.040HTOS 15.5 0.08Phenol 4.1 0.044FAV 29.5 0.081Toluene 44.5 R molar S / Mo 2 Rmolar Phenol / Mo1.1 Products Total water (theoretical of the three 3.96 inputs) * Mo % (by weight) from net of reaction 6.2 10% by weightof residual toluene *Total water (three inputs) = see calculation reported below. Heating up to 90°C is effected to dissolve the HTOS;subsequently (after 10 minutes) the FAV or the othercarboxylic acid reported in Table 3 and toluene are alsoadded, where provided. The temperature is increased up to reaching 122°C totrigger azeotropic distillation at the nitrogen overpressureused. It should be noted that if dibutyl ether (DBE) was used instead of toluene, the distillation would be triggered at 140°C at the nitrogen overpressure used, observing a rise in temperature up to 165°C. It is proceeded until 80-90% of the calculated water is recovered in the trap to obtain a theoretical salification of 75% of the acid groups and a molar ratio (Salified acid) / Mo=3. After 18 hours, corresponding to the time taken for the recovery of the aforementioned amount of water due to the salification reaction, the product obtained is subjected to vacuum distillation at a pressure of 170-250 mBar to remove the solvent and maintain a molybdenum content of 6-7% by weight. The following procedure was used to calculate the total reaction water. The reaction water has three overall inputs:1. Water belonging to the reagents, e.g. p-toluenesulfonicacid which is monohydrate: in the present example the water coming from HTOS is equal to 1.44 ml of water corresponding to 0.08 moles;2. Water due to the reduction and salification of molybdenumml H2O = 3.5*moles Molybdenum which derives from the stoichiometric calculations indicated below. 2.1 Water due to the reduction according to thestoichiometry of the reaction between ammoniumheptamolybdate, phenol and carboxylic acids: 2(NH4)6Mo7O24*4H2O(solid)+7^*-OH+12RCOOH→ 7 O=^=O* + 14MoO2+12RCOONH4+21H2O ^ ^^ = phenylO=^=O* = or according to the reaction between molybdic acid and carboxylic acids: 2H2MoO4+^^ -OH → O=^^ =O* + 2MoO2+ 3H2O^ In both cases we have that the reduction water is 1.5*molles Mo: 1.50* 0.04 moles of Mo=0.06 moles H2O correspondingto 1.08 ml of water 2. 2 Salification water worth 2*moles of Molybdenum inreaction: MoO2+4 RCOOH → Mo(RCOO)4+ 2H2O 0.04 moles of Mo*2 =0.08 moles of H2O corresponding to 1.44 ml of water In this preparation A, the removal of toluene was carried out without excessively pushing distillation: it wasconsidered as acceptable, for the purposes of the present invention, 10% by weight of toluene remaining in the reaction product to shorten the synthesis times. It is understood that the person skilled in the art can remove greater amounts of toluene from the product and continue with the azeotropic distillation after distilling the preset amount of water in order to eliminate the remaining toluene that was not previously collected in the trap. Example of preparation B: synthesis including addition of drying agent instead of azeotropic distillation (Synthesis SF110723) In a 250 ml flask, blanketed with nitrogen (overpressure from 20 to 65 Pa) and equipped with magnetic stirrer,thermometer, drop condenser and heating mantle, thefollowing compounds are added -molybdic acid (AcMo),- HSA 118,- 2,6-di-tert-butyl-4-methylphenol (PHB), and- 2,2-dimethoxy propane (DMP),in the amounts and proportions reported in Table 2. About 9g of THF are also added to obtain a more fluid product (lower viscosity) but this is not necessary for the purposes of the present precursor preparation process. Table 2 Preparation B (Synthesis SF110723) Reagents g Moles %Molybdic acid 3.59 0.02212,6-Ditert-butyl-4-methylphenol (PHB) 4.90 0.02232,2-dimethoxy propane 11.83 0.114HSA 118 36.21 0.0691THF 9.22Total reagents 65.75R molar S / Mo 3.13R molar PHB / Mo 1.01Net of reaction 62.55R S / Mo 3.48Table 2 does not report the theoretical total waterbecause with the use of the chemical drying agent it is not possible to measure the water produced by the reaction as in the case of the distillation of preparation A. The amount of dimethoxypropane used is however calculated on the theoretical total water whose calculation is carried out in a manner similar to that described in example of preparation A. Heating up to 70°C is effected and subsequently the carboxylic acid reported in Table 3 is also added, where provided. The mixture is kept at this temperature until the solvents reflux is reached, and refluxing (18 hours) is continued until 80-90% of the calculated water is recovered in the trap to obtain a theoretical salification of 75% of the acids and a molar ratio (Salified acid) / Mo=3. In this case, the mixture obtained, after removing the preset amount of water by anhydrification, is then vacuum distilled at 150 mbar and at 60°C to remove methanol and acetone, thereby increasing the concentration of molybdenum (i.e. Mo titre). Example 1 Following the procedures of the previous preparations, five Molybdenum-based precursors were obtained having the characteristics reported in Table 3. All precursors of Table 3 were obtained using preparation A with azeotropic distillation except for precursor 1D (SF110723) obtained by anhydrification with DMP (preparation B). For precursor 1A (SF171022), the procedure of preparation A was followed except that use was made of Naphthol instead of phenol and HMA (ammonium heptamolybdate) instead of molybdic acid, and in amounts such as to obtain the ratios R S / Mo, R acid / Mo and R phenolic group / Mo indicated in Table 3. The catalyst precursors containing only carboxylateions were used in combination with a feedstock of fossilorigin containing high amounts of sulfur (Vacuum residue), which generated, under the reaction conditions, the corresponding catalyst (molybdenite). The precursors containing sulfonate ions, optionally incombination with carboxylate ions, were used with feedstocksof renewable origin, without the addition of sulfidatingagents: molybdenite was also formed even in the absence ofa sulfidating agent. The following table 3 reports thesummary data of the tests. Table 3 1A 1B 1C 1D 1E 1F Precursor (SF171022) (SF121222) (SF190623) (SF110723) (SF090823)(SF031022) MolybdenumHMA AcMo AAcMo sourcecMo AcMo AcMoSulphonic- HTOS HSAHTOS acid118 HSA118 DBSAReducingNaphthoPhenol agentl Phenol - PHB PhenolCarboxylicC FAC9 acidV - - -R S / Mo 0 2 4 3.14 3.30.7R acid / Mo 5.9 1 0 0 0 4R phenolic0.6 2 0 1 1 0.7group / Mo Mo (%by weight)6 6.7 2.8 2.7 3 9.9CATALYST deriving from precursor Feedstock for RV the catalytic RV Animal Animal Animal Animal test fat fat fat fatMolybdenite unreflected unreflected unreflected unreflected unreflected packedLateral - dimensions- 4.8 4.2 4.9 5.6(nm) Lateral - dimensions- 7 6.4 6.3 6.5(nm)Stacking - - - - - -(*) the sulphur considered in this ratio is that provided by sulphonic acid, if used1The lateral mean dimension of molybdenite was calculated by Sherrer's equation applied to the reflection 110 which is partially convolved with one of the whitlockite reflections (Ca, Mg and Fe phosphate presentas a minor phase within the sample, generated by the presence of such impurities in the animal feedstockand not present in the fossil feedstock). The term “unreflected” is used here to indicate in a synthetic way that in the XRD pattern there is no reflectionin the crystallographic direction 002 relative to thestacking direction, precisely because there is no stacking. In fact, without the reflection in the 002 crystallographic direction, stacking is minimal (e.g. the measurement is below the limit of detectability of the XRD instrument or even monolayer). The low lateral dimension nanometric values reported in Table 3 are an index of an irrelevant stacking. Example 2 Two hydroconversion tests were carried out using two of the precursors prepared in Example 1 in accordance with the invention, then comparing the data with those obtained from the same hydrocracking reaction but using as precursor a Mo- octanoate known in the art. The tests were carried out in a microautoclave, described below under typical hydroconversion conditions, using thevacuum residue defined above as the feedstock to behydroconverted. Approximately 10 grams of vacuum residue and the catalyst precursor are introduced into the stirred reactor, made of AISI 316 stainless steel, with a total volume of 44 ml, in the amounts necessary to guarantee 3000 ppm (by weight) of Molybdenum. The reactor is then pressurized with H2and brought to the temperature of 430°C, by means of an electrically heated furnace. The system is kept under stirring by means of a swinging capillary system (1000 rpm), keeping the pressure constant at 160 bar with an automatic system for replenishing the hydrogen consumed. At the end of the test, lasting four hours, the gaseous products are collected in a bag for gas-chromatographic analysis, taking care to first cool the reactor up to room temperature. Subsequently, the residue present in the reactor is sampled for SIM-DIS gas-chromatographic analysis; then, it is entirely recovered and treated with THF, to then be filtered on 0.5μm Teflon filters, in order to separate and quantify the THF-insoluble component (THF-i), consisting of the molybdenite formed, from the sulfides of the metals containedin the feedstock and from a carbonaceous component. The THF-soluble fraction, on the other hand, is treated with excess n-pentane, to separate the C5 asphaltenes from the DAO (Deasphalted oil) phase, which do not dissolve in n-pentane and precipitate. The catalytic data are reported in Table 4. Table 4: Catalytic tests with feed of H2at 160 bar; reaction time =4 hours; T= 430°C Vacuum residue feedstockMo precursor Mo OCT 1A1F (SF171022) (SF031022) Mo inppm 3000 3000 3000reaction H2S % by2.6 3.6 4.2developed weight / feedTHF-i % by 2.1 2.2 2.27weight / feedThe tests carried out on vacuum residue highlight that, under the same conditions, the proposed catalytic systems show the same performances in terms of formation of solids (defined as insoluble portion after treatment with tetrahydrofuran). This aspect confirms what is reported in table 1 where there is evidence of the formation of MoS2. The latter, in the reaction environment, acts by activating the hydrogen molecules present which subsequently stabilise the free radicals formed during thermal cracking. This step makes it possible to avoid consecutive reactions that lead to an increase in the formation of solids. For this reason, the THF-i parameter is particularly suitable for comparing catalytic performances. In addition, further development of H2S beyond the level expected from the sulphur introduced with the precursor is also observed.

Claims

CLAIMS 1. Process for preparing a catalyst precursor in the form of salt based on at least one transition metal belonging to one of the groups from 5 to 12, and containing organic sulphur in the form of sulfonate ions, and / or containing carboxylate ions, said precursor being capable of generating, in the presence of hydrogen, a catalyst based on sulfides of said at least one transition metal, said preparation process comprising the steps of- reacting an organic acid selected from a sulfonic acid,a carboxylic acid (of fossil or renewable origin), or their combination, with a source of said at least one transition metal, preferably Molybdenum (VI), optionally in the presence of a reducing agent, preferably selectedfrom phenol, naphthol, naphthol derivatives, ascorbic acid, diphenylamine and alkylphenol wherein one or more alkyl groups are a C1-C10alkyl group;- removing the water produced in the aforementionedreaction by azeotropic distillation, or byanhydrification with a drying agent, thus obtaining atleast one carboxylate and / or sulfonate salt of said transition metal, with the condition that when the acid is only a carboxylic acid and the metal is only Mo, said Mo has an average oxidation state that varies from +6 to+4 (excluding +4), preferably an average oxidation state that varies from +6 to +5.

2. Process according to claim 1, wherein said steps arethe following steps of (a) reacting a sulfonic acid (RSO3H), or a mixture ofsulfonic acids, with a source of said at least one transition metal belonging to one of the groups from 5 to 12, optionally in the presence of a reducing agent, said reducing agent being selected from phenol, naphthol, naphthol derivatives, ascorbicacid, diphenylamine and alkylphenols wherein one or more alkyl groups are a C1-C10alkyl group; (b) optionally reacting one or more compounds of at leastone transition metal belonging to one of the groups from 5 to 12, obtained in the previous step (a), with a carboxylic acid, or a mixture of carboxylic acids, of fossil or renewable origin, thus obtaining one ormore compounds of said at least one transition metal also containing carboxylate ions; (c) removing the water produced in steps (a) and / or (b)by azeotropic distillation, or by anhydrification with a drying agent, to obtain at least one sulfonate salt, optionally containing carboxylate ions, of said at least one metal, preferably a sulfonate salt ofMo containing carboxylate ions.

3. Process according to claim 1 or 2, wherein thereaction between the organic acid and the source of said atleast one transition metal advantageously takes place at a temperature ranging from 25°C to 125°C, preferably at a temperature of 60-110°C.

4. Process according to any one of the previous claims,wherein said source of at least one transition metal is a source consisting of one or more inorganic compounds of Mo (VI), preferably selected from molybdic acid H2MoO4and its salts also in hydrated form, more preferably selected from ammonium heptamolybdate (ammonium molybdate), sodium molybdate, molybdic anhydride.

5. Process according to any one of the precedingclaims, wherein said sulfonic acid is selected from p-toluenesulfonic acid, an alkylbenzenesulfonic acid with analkyl chain from C12to C24, e.g. dodecylbenzenesulfonic acid (DBSA), mixture of alkylbenzenesulfonic acids with C20-C24alkyl chain, or combinations thereof.

6. Process according to any one of the previous claims,wherein the carboxylic acid is a monocarboxylic acid,saturated or unsaturated, preferably saturated, or a mixtureof said carboxylic acids, of renewable or fossil origin.

7. Process according to claim 6, wherein the carboxylicacid is selected from -pelargonic acid (C9) of renewable origin;- a mixture of carboxylic acids of renewable origin witha chain length ranging from C5to C11; -a mixture of carboxylic acids of renewable origin andtriglyceride esters, including unsaturated ones, having a TAN equal to 150 mgKOH / g.

8. Process according to any one of the preceding claims,wherein the azeotropic distillation is carried out usingtoluene, dibutyl ether (DBE) or mixtures thereof as the azeotropic distillation solvent.

9. Process according to any of the previous claims from1 to 7, wherein the anhydrification is carried out using 2,2-dimethoxy propane (DMP) or DMP mixed with DBE.

10. Catalyst precursor in the form of salt of at least one transition metal belonging to one of the groups from 5 to 12 comprising sulfonate ions and / or carboxylate ions with the condition that when only carboxylate ions are present and the metal is only Mo, said Mo has an average oxidation state that varies from +6 to +4 (excluding +4), preferably from +6 to +5; said catalyst precursor being preferably obtainable fromthe process as defined in any one of the preceding claims 1-9.

11. Catalyst precursor according to claim 10, wherein the carboxylate ions derive from a carboxylic acid selected from -pelargonic acid (C9) of renewable origin;- a mixture of carboxylic acids of renewable origin witha chain length ranging from C5to C11; -a mixture of carboxylic acids of renewable origin andtriglyceride esters, including unsaturated ones, having a TAN equal to 150 mgKOH / g.

12. Catalyst precursor according to claim 10-11, whereinthe transition metal is Mo.

13. Catalyst precursor according to claim 12, whereinMo has a concentration lower than 15% by weight with respectto the overall weight of the precursor, preferably a concentration ranging from 2.5% by weight of Mo up to 10% by weight compared to the total weight of the precursor, said catalyst precursor being preferably obtainable from the process as defined in any of the previous claims 1 to 9.

14. Hydroconversion process of hydrocarbon feedstock forobtaining lighter hydrocarbons, or of feedstocks of renewable / biological origin, e.g. vegetable feedstocks, animal fats, for obtaining hydrocarbons of renewable origin, said process comprising at least the step of -bringing into contact a catalytic precursor as definedabove in claims 10 to 13, with said feedstock and withhydrogen, optionally in the presence of a sulfidating agent, operating at a temperature of 390-450°C and at a pressure of110-170 atm, thus producing an effluent exiting thehydroconversion reactor, said effluent comprising saidconversion hydrocarbons and said catalyst formed in situ from said precursor.

15. Hydroconversion catalyst comprising sulphides of atleast one transition metal belonging to one of the groupsfrom 5 to 12, preferably comprising MoS2, deriving from thein situ contact of a catalytic precursor as defined in theprevious claims with H2, possibly in the presence of sulfidating agents.

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