WO2011038911A1

WO2011038911A1 - Catalysts and process for the liquefaction of lignins

Info

Publication number: WO2011038911A1
Application number: PCT/EP2010/005962
Authority: WO
Inventors: Daniele Delledonne; Daniele Bianchi; Roberto Buzzoni
Original assignee: Eni SpA
Current assignee: Eni SpA
Priority date: 2009-09-29
Filing date: 2010-09-28
Publication date: 2011-04-07
Anticipated expiration: 2012-03-29
Also published as: EP2483330A1; WO2011038911A8; IT1396566B1; ITMI20091669A1

Abstract

The present invention relates to new polymetallic catalysts supported on at least slightly basic materials and a process for the conversion of lignin to hydrocarbons, which uses said catalysts.

Description

CATALYSTS AND PROCESS FOR THE LIQUEFACTION OF LIGNINS

DESCRIPTION

The object of the present invention refers to suitably supported polymetallic catalysts and a process for the conversion of lignin to hydrocarbons, which uses said catalysts .

The reduction in oil reserves on the one hand, and the continuous increase in the consumptions of oil products on the other, require the exploitation of new raw materials and the implementation of new technologies for their production. This is particularly true in the field of fuels for civil uses, which account for over 60% of extracted oil consumptions. Consequently, in order to slow down the consumption of petroleum, new technologies must be developed, in particular for the production of fuels, starting from non-conventional sources, among which so-called renewable sources can be mentioned.

Among renewable sources for the production of bio- fuels, the following can be mentioned:

- cultivations of cereals, such as maize, wheat, barley, from which bioethanol, used as a substitute for gasolines, can be obtained through the fermentation of starches; and - cultivations of vegetable species with a high content of triglycerides or oils, such as rape, soya, sunflower, palm oils, used for producing biodiesel; - recently, with the development of new technologies, products of a lignocellulosic origin have also been added.

The characteristics of the latter are such as to make them extremely interesting as starting materials, with re- spect to cultivations of cereals and oleaginous species:

(i) they are widely available, also as waste products of the crops indicated above, of the wood and food industries,

(ii) they are inexpensive, (iii) they do not compete with cultivated products for human nutrition, even if they at least partly compete with cultivated products for animal nutrition and for the use of cultivated land.

The use of lignocellulosic products for the production of bioethanol, which can be used as such as fuel or mixed in various ratios with traditional gasolines, has not yet reached the commercial phase. All of these technologies in any case relate to the transformation to bioethanol of the sole cellulose fraction of the biomass, which accounts for about 40-50% by weight of the whole lignocellulosic biomass, and possibly the hemicellulose fraction, which ac- counts for 15-30% by weight. Lignin, formally a complex polymer of C₉ methoxy-substituted alkyl phenols, which forms about 15-30% of the original biomass, is excluded.

The commercial implementation of bioethanol processes from cellulose makes it easy to envisage in the foreseeable future, a wide availability of lignin. Lignin is roughly the constituent which holds together the linear fibres of cellulose in vegetable organisms, preserving them from the aggression of foreign agents. Its approximate molecular formula can be schematized as follows : CioH₁₂0_{3 /} with a relatively low oxygen content ( 25 - 30 % ) , which assumes that it can theoretically be converted to hydrocarbons by hydrodeoxygenation (HDO) and hydrogenation .

Currently in the schemes of advanced biorefinery which envisages the use of lignocellulosic raw materials, the lignin separated from the original biomass is often considered a by-product and economically valorized to low-value solid fuel, for the production of utilities such as vapour and electric energy for internal consumptions, Fernando et al. in Energy & Fuels 2006 , 20 , page 1727 . It would natu- rally be desirable to transform lignin into higher value added products, such as for example a further fuel fraction.

The subject has already been faced and substantially three transformation methods of lignin to fuels have been identified:

( 1 ) gasification to produce synthesis gas, CO and H₂, which in turn, after purification, can be converted to a hydrocarbon fraction by means of the Fischer-Tropsch process;

( 2 ) pyrolysis which converts lignin to a liquid product, called bio-oil, chemically unstable, which must be rapidly deoxygenated and/or hydrogenated . Alternatively, it can be converted to synthesis gas via steam reforming;

(3) liquefaction and direct catalytic hydrodeoxygenation of lignin to products which can enter directly into the refin- ing cycle.

Whereas the first two processes are substantially a concatenation of distinct known processes, in a multistep process, in the best of cases at least two, the third process, at least in some embodiments, can be considered a sin- gle-step process. All three technologies, however, have significant technical criticalities .

The liquefaction of lignin was already faced immediately after the second World War, with the main objective of obtaining some chemical products of the group of phe- nols, with a high yield, to be used in the organic synthesis. A great deal of patent literature is in fact focused on the synthesis of phenols or phenol in particular, of which a few examples are provided hereunder.

US 2,870,133 describes the liquefaction of lignin com- ing from the saccharification of wood, in a continuous process, in the presence of calcium hydroxide and iron sulfate as catalyst, at a very high hydrogen pressure, 70 MPa, and at a temperature of 380°C. The lignin is liquefied in a proportion of 50-60%, to a mixture of products containing substantial quantities of phenols. The high hydrogen pres- sure and high concentration of iron sulfate and calcium hydroxide required, represent the major disadvantages.

CA 700209 discloses a liquefaction process of lignins which produces phenols, alkyl phenols and aromatic hydro- carbons in the presence of FeS as catalyst, used in a concentration of up to 5% by weight, possibly promoted with copper salts, at a temperature of 350-450°C and in the presence of hydrogen at 20 MPa. CA 700210 claims an enhanced liquefaction catalyst of lignin. One of the greatest disadvantages of the process is the presumable incorporation of significant quantities of sulfur from the catalyst to the reaction products, a phenomenon which should be avoided due to the strict regulation limits for the sulfur content in fuels .

The use of hydrocracking catalysts in the liquefaction of lignin is found for example in US 4,420,644 which claims a two-step process, the first for the liquefaction of lignin, in the presence of a catalyst consisting of nickel, cobalt, iron and molybdenum oxides or combinations thereof, supported on an alumina or silica carrier, or combinations thereof, the second for the non-catalytic hydrodealkylation of alkyl phenols for the production of phenol and small quantities of benzene as by-product. Considerable quantities of C1-C3 gas are also obtained. US 4,647,704 claims the catalytic hydrocracking of some types of non-basic lignins, with the use of an innovative hydrocracking catalyst which increases the production of phenol compounds. The catalyst is composed of tungsten oxide, possibly co- promoted with a second metallic oxide or metal selected from nickel, cobalt and palladium, deposited on a substrate normally acid or slightly acid, with a good cracking capacity.

Among the preferred carriers are alumina, aluminum phosphate, silica-alumina and silica-aluminum phosphate. Furthermore, it is affirmed that the yield to products of the group of phenols can be further improved if the hydro- cracking is carried out in the presence of water and/or low-boiling alcohols, especially in the presence of a Friedel-Crafts catalyst. Among the main disadvantages of the method is the high consumption of catalyst, used in a proportion of 25% by weight with respect to the lignin and the restriction with respect to the types of lignin which can be used. The improving effects of the presence of water and a low-boiling alcohol in the solvent of the hydrocrack- ing reaction with respect to the increase in yield of products of the group of phenols, is also confirmed in US 4,731,491 in which the catalyst is a mixture of metallic salts, dispersed in water, based on FeCl₂, CuS0 , SnCl₂ and lastly Na₂S, which acts as sulfiding agent in loco. Also in this case, a significant incorporation of sulfur in the re- action products is envisaged.

From the very beginning, research activities relating to the liquefaction of lignin have led to a wide range of discordant results, with respect to the conversion of lig- nin and selectivity of the products, mainly phenols, as they also depend on the type of lignin, a term which in itself infers non-homogenous materials in relation to the biomass of origin and separation method used, in addition to the operating procedures. M.A Ratcliff et al . in Applied Biochewistry and Biotechnology, 1988, 3/7, page 151, for example, observes a low conversion of Organosolv lignin, within the range of 50-70%, with a selectivity, in batch, to phenols, lower than 2%, whereas Raimo R. Alen et al . in Bioresource Technology, 1993, £5, page 189 under completely analogous operating conditions, observes in the best of cases, the complete conversion of Organosolv lignin and production of about 10% of monocyclic aromatic compounds, with a large preponderance of phenols. R.W. Thring et al . in Fuel, 1996, 15, page 795 who use an Organosolv lignin coming from the ALCELL* process, in tetralin as solvent, observes under the best conditions, a conversion of 50% of lignin and the production of about 8% of monocyclic phenols .

The products obtained with these liquefaction methods, however, have an average oxygen content higher than 15%, this makes them unsuitable for being fed to normal refinery processes for the production of fuels.

US 5,959,167 specifically claims the transformation of lignin to reformulated gasoline in a three-step process. In the first step of the process, the lignin is pre-treated in a so-called depolymerization step catalyzed by bases in aqueous/alcohol solution at a temperature higher than the critical temperature of the alcohol, in the presence of a base, NaOH or KOH, in a proportion of 5-7.5% by weight with respect to the aqueous/alcohol solvent. The alcohol, methanol or ethanol, is in turn used in an excess of 3-5 times with respect to the lignin. The treatment temperature ranges from 260-310°C. The recovery of the product involves the neutralization of the base with hydrochloric acid. The subsequent catalytic hydrotreating of the depolymerized product is carried out in two consecutive steps which differ by type of catalyst and operating conditions, producing a mixture of cyclohexanes , alkylated cyclopentanes , alkyl- benzenes of the series C7-C11 and branched paraffins of the series C5-C12, substantially free of benzene. There are numerous disadvantages of this approach, among which the in- corporation of the alcohol in the depolymerized product, up to about 30% by weight, in relation to the alcohol, and above all their oxidation to formic or acetic acid, which consumes the base and stops the reaction, see for example J. E. Miller et al . Fuel (1999), 78, 1363. Furthermore, the disposal of the neutralization salts should be taken in account , which for a large-scale plant can be problematical.

In a subsequent improvement, in order to reduce the consumption of reagents and alcohol, the basic depolymeri- zation step is carried out in water containing 2-3% of NaOH or KOH, but to the detriment of the conversion of lignin which is now reduced to about 65-70%, and temperature, which is increased to about 300°C (US 2008/0050792) or, alternatively, using solid superbases, such as zeolite 13X exchanged with cesium but reducing the conversion of lignin to less than 60% (US 2003/0100807) .

We have now found that by using particular compositions as catalysts, characterized by the presence of an at least slightly basic carrier, it is possible to convert lignins, of any origin, in a single step and with a high yield, into liquid products : these products can then be easily separated into polar products and hydrocarbon products, and the latter can be used as such as fuels or fed in an ordinary refinery process for the production of gasolines or gas oils. The presence of the at least slightly basic carrier in the catalytic composition allows much higher results to be obtained with respect to those obtained using the catalysts of the prior art exclusively having carriers of an acid nature. The hydrocarbon cuts thus obtained prove to have an oxygen content lower than 6% by weight, preferably lower than 4% by weight, which makes them compatible with both direct use or in a mixture as fuel and also with the major- ity of refinery processes. The chemical characteristics of the hydrocarbon fluid thus obtained are also particular, which unexpectedly preferably contains hydrocarbons with a number of carbon atoms within the range of 18 to 30.

A first object of the present invention therefore re- lates to a process for the liquefaction of lignin which comprises treating lignin with hydrogen in the presence of a catalytic composition (A) containing:

a) a metallic component comprising a metal Mel, in oxide form, selected from molybdenum, tungsten and mixtures thereof, and a metal Me2, in oxide form, selected from nickel, cobalt and mixtures thereof,

b) an at least slightly basic carrier.

Said catalytic composition is preferably used in sul- fided form, i.e. in the form obtained by sulfidation with any known means suitable for the purpose: the sulfidation can be effected before the use of the catalyst in the liquefaction process of lignin, in a separate step, or during the same reaction.

The process of the present invention, defined as liq- uefaction of lignin, corresponds to a hydrocrack- ing/hydrodeoxygenation process . At the end of the process a liquid product is obtained containing a hydrocarbon fraction and a polar fraction.

In particular, the use of these catalytic compositions guarantees good selectivities of lignin to liquid products, in the order of 40-50%, of which the hydrocarbon products represent 7-18%. The remaining part mainly consists of al- kyl phenols .

Furthermore, these catalysts avoid undesired cracking reactions, which would produce excessive quantities of C^.- C₃ hydrocarbons .

The metallic component (a) of the catalytic composition used in the process of the present invention preferably contains molybdenum and nickel or molybdenum and co- bait.

The metal Mel is preferably present in a quantity ranging from 2 to 20%, more preferably in a quantity ranging from 6 to 14%, by weight with respect to the total weight of the sum of (a) and (b) , whereas the metal Me2 is preferably in a quantity ranging from 0.5 to 10%, more preferably in a quantity ranging from 2 to 6%, by weight with respect to the total weight of the sum of (a) and (b) .

The weight percentages of the metal Mel and metal Me2 refer to the content of element expressed as metallic ele- ment; in the catalyst, after calcination, said elements are in oxide form and therefore component (a) is composed of at least one oxide of a metal Mel and at least one oxide of a metal Me2. The catalytic composition is preferably used in sulfided form, i.e. in the form obtained by sulfidation with any method known to experts in the field.

With respect to the carrier (b) of the catalytic composition, this must be at least slightly basic, and can therefore be selected from basic carriers and slightly basic carriers.

An expert in the field is well aware that there are various methods for characterizing the basic properties of a carrier or catalyst, which are selected on the basis of the material to be characterized and application in which it will be tested. The definition of basicity is therefore not linked to a particular technique but comprises the different approaches present in the known art: a review on the definitions of acidity and basicity of carriers and solid catalysts, and on the measurement methods, is contained, for example, in J. Berg et al . in Advances in Colloid and Interface Science 2003, 105 , page 151.

Basic carriers and catalysts which can be conveniently used and are known to experts in the field are listed, for example in H. Hattori in Applied Catalysis A General, 2001, 222, Page 247, and K. Tanabe et al . in Applied Ca- talysis A: General, 1999, 181 page 399. In particular, basic carriers which can be used as component (b) of the catalyst of the present invention are:

1. oxides of alkaline earth metals,

2. rare earth oxides,

3. mixed oxides/hydroxides containing alkaline earth metals,

4. silico-aluminates containing, as counter- ions, ions of alkaline and/or alkaline earth metals,

5. zeolites containing ions of alkaline and/or alkaline earth metals,

6. clays

7. ions of supported alkaline metals, preferably supported on alumina, silica, oxides of alkaline earth metals,

8. ions of alkaline metals and hydroxides of alkaline metals supported on alumina,

9. titanium silicates containing, as counter- ions, ions of alkaline or alkaline earth metals.

The oxides of alkaline earth metals of set 1 are preferably selected from the oxides of Mg, Ca, Sr, Ba.

Among rare earth oxides of set 2, Ce oxide is preferred.

The mixed oxides/hydroxides of set 3 containing alkaline earth metals can be selected from hydrotalcites and sepiolites .

Hydrotalcites are hydroxycarbonates of magnesium and aluminium, crystalline materials based on aluminium and magnesium organized in layered structures, having negative ions between the layers, of a net positive charge, which guarantee the electroneutrality of the system: these mate- rials and their preparation are described, for example in V.V. Brei et al . in Microporous and Mesoporous Materials 2008, 113, page 411.

An example of commercial hydrotalcite which can be conveniently used can be selected from the products Pural MG (Condea Sasol) . Sepiolites are natural hydrated magnesium phyllosilicates . An example of sepiolite which can be conveniently used is Sepiolite Tolsa^® 30/60.

Silico-aluminates of set 4 containing, as counter- ions, ions of alkaline or alkaline earth metals, preferably selected from Na, K, Mg, Ca, Sr, Ba, can be either natural or synthesis products. All known silico-aluminates can be used, and in particular materials belonging to the zeolite families can be conveniently used.

For set 5, all zeolites containing alkaline and/or al- kaline earth cations can be used, and in particular zeolites with a FAU structure and MOR structure are preferably adopted. In particular, among zeolites with a FAU structure, zeolite 13X is used and among zeolites with a MOR structure, mordenite is used. The ions of alkaline or alka- line earth metals are preferably selected from Na, K, Mg, Ca, Sr e Ba.

Zeolites containing alkaline or alkaline earth metals can be zeolites deriving directly from synthesis operations or zeolites prepared with any of the methods known to ex- perts in the field, by means of ion exchange, for example by treating the zeolite with aqueous solutions containing the ion to be inserted as counter-ion.

A detailed description of zeolite structures which can be used in the present invention is provided in Ch. Baer- locher, W.M. Meier, D.H. Olson Atlas of Zeolite Framework Types, 5th revised edition, 2001 ELSEVIER, ISBN: 0-444- 50701-9.

Among the clays of set 6 which can be included in the present invention, both cationic and anionic clays, natural and synthetic, can be mentioned. Cationic clays having charge balancing cations selected from ions of alkaline and/or alkaline earth metals, preferably from Na, K, g, Ca, Sr, Ba, fall within the scope of the present invention. Natural or synthetic anionic clays having exchangeable ani- ons such as charge compensators are included in the present invention: this type of material is also described in the state of the art with terms such as hydrotalcite-type (HT) materials or layered double hydroxides (LDH's). Clays, their preparation and some of their uses, above all of catalytic interest, are described for example in A.Vaccari in Catalysis Today, 1998, 41, page 53. In particular, materials which can be classified as "Hydrotalcite-like anionic clays", wherein exchangeable anions, which compensate the charges, are positioned between the positively charged bidimensional layers, are described, for example in P. A. Jacobs et al . in Catalysis Reviews, 2001, 4_3, page 443.

With respect to the carriers of set 7, the ions of supported alkaline metals, preferably on materials such as alumina, silica, oxides of alkaline earth metals are pref- erably selected from Na and K; the alkaline earth metal oxide preferably used is that of magnesium. The ions are supported by means of any of the known techniques, for example using the incipient wetting impregnation technique.

With respect to the carriers of set 8, the alkaline metals are preferably selected from Na and K.

As far as the carriers of set 9 are concerned, titanium silicates refer to mixed oxides in which octahedra of Ti0₆ and tetrahedra of Si0₂ share some oxygen atoms: the negative charges which are generated in the lattice are counterbalanced by cations. icroporous titanium silicates such as ETS-10 and ETS-4 belong to this family of products. For the purposes of the present invention, titanium silicate called ETS-10 is preferably used.

The ions of alkaline and/or alkaline earth metals which balance the charges of these titanium silicates are preferably selected from Na, K and Mg. The titanium silicate ETS-10 is described for example in US 4,853,202, whereas ETS-4 is described in A. Sacco et al . Studies on Surface Science and Catalysis 2004, 154 , page 763.

Additional components can also be present in the catalytic compositions of the present invention. Among these additional components, all materials which experts in the field use in forming operations are preferred, and all compounds normally used by experts in the field as ligands are particularly preferred.

Ligands which can be conveniently used are silica, alumina, silica-alumina, and alumina is preferably used. Preferably the ligand is present in the composition in a weight ratio ranging from 0.2 to 5, even more preferably from 0.5 to 2 with respect to the total weight of the catalytic composition.

The catalytic compositions (A) described above containing :

a) a metallic component comprising a metal Mel, in oxide form, selected from molybdenum, tungsten and mixtures thereof, and a metal Me2, in oxide form, selected from nickel, cobalt and mixtures thereof;

b) an at least slightly basic carrier,

are new and are further objects of the present invention, In particular, these compositions (A) can additionally con- tain a ligand. The sulfided compositions obtained, by means of sulfidation, from the compositions (A) , possibly containing a ligand, are in turn new and are a further object of the present invention.

The compositions of the present invention are prepared by introducing the metallic component (a) into the catalytic composition, preferably by impregnation of the at least slightly basic carrier (b) , or by ion exchange techniques, according to methods well known to experts in the field. Should ion exchange be effected, this procedure must be such as to maintain at least part of the basic functionalities .

With respect to compositions additionally containing a ligand, the introduction of the metallic component can be effected on the basic carrier, and the resulting product subjected to binding, or the basic carrier alone can be first subjected to binding, subsequently introducing the metallic component. It is preferable to operate by means of incipient wetting impregnation of the carrier (b) , or car- rier already in bound form, with a solution of one or more precursor salts of the metallic oxides which are to be obtained: all the impregnation techniques known to experts in the field can be used. It is possible for example to wet the carrier with an aqueous solution containing at least one soluble precursor of at least one oxide of a metal Mel selected from molybdenum and tungsten, and at least one soluble precursor of at least one metal Me2 selected from cobalt and nickel. Precursors which can be conveniently used for the metal Mel are for example ammonium molbydate (CAS 12054-85-2) and ammonium (para) tungstate (CAS 11120-25-5). Precursors which can be conveniently used for the metal Me2 are for example cobalt nitrate hexahydrate (CAS 10026-22-9) and nickel nitrate hexahydrate (CAS 13478-00-7) . The impregnation is then followed by a thermal treatment in an atmosphere suitable for decomposing the precursor salt and obtaining the oxides, or mixed oxides, of the supported metals Mel and Me2. The resulting product can be dried, for example, preferably in air, between room temperature and 200°C, and calcined in an oxidizing atmosphere at a tem- perature ranging from 200 to 600°C. It is also possible to proceed with subsequent impregnations to reach the desired charge level of oxides.

According to a preferred form of the invention, as already specified, the metals deposited on the catalysts are used in their sulfided form rather than in the form of oxides. The transformation of the metallic oxides into the respective sulfides can be effected with any known medium suitable for the purpose, for example H₂S or dimethylsul- fide: the sulfidation can be effected before the use of the catalyst in the liquefaction process of lignin, in a sepa- rate step, or during the same reaction. In the case of sulfidation in a separate step, the sulfidation temperature is preferably that envisaged for the following liquefaction reaction or slightly lower. Using dimethylsulfide (DMDS) , the duration of the sulfidation reaction is preferably at least 5 hours, operating with a stoichiometric excess of DMDS moles per mole of metal deposited on the catalyst ranging from 5 to 10, in the presence of 4-8 MPa of hydrogen.

When the sulfidation is carried out using H₂S, it can be effected at a temperature of at least 400°C, treating the catalyst in a tubular reactor for at least 3 hours with a stream of hydrogen containing about 5% of H₂S.

Sulfidation techniques which can be conveniently used for transforming the catalysts of the present invention into the corresponding sulfides are described for example in "Petroleum Refining", J.H.Gary, G.E. Handwerk, M.Dekker, ed. 1994.

The catalytic materials of the present invention can be regenerated directly in the reactor or, in some reactor variants, the catalytic material can be extracted from the reactor, re-activated, and reintegrated into the reaction. The regeneration can be effected, for example, by combustion of the products deposited on the catalyst (coke) in air or air-nitrogen mixtures between 450 and 550°C. The lignins which can be subjected to the liquefaction process of the present invention, effected in the presence of the catalysts described above, can be of any origin. All lignins deriving from woody biomasses, for example, separated from the cellulose with any of the known processes, can be used.

In particular Organosolv lignins are used, i.e. coming from a separation process from cellulose which envisages the use of an organic solvent, and even more in particular Acetosolv lignin, i.e. that obtained in a separation process of cellulose from lignin which uses acetic acid as solvent. This type of lignin and its attainment and separation is described for example in X. Pan in Journal of Wood Science, 1999, 45, page 319.

The lignins, treated in the presence of the new catalysts described above, are transformed in a single passage, into liquid products, consisting of a mixture of phenols and hydrocarbons, from which the hydrocarbon fraction can be easily separated and recovered. The conversion of the lignin which can be obtained with the process of the present invention is over 70%, and preferably reaches 90%, calculated with respect to the weight of the initial lignin. The hydrocarbon products represent 7-18% by weight and can be conveniently used as fuels, possibly in a mixture with hydrocarbon cuts of an oil origin. These hydrocarbon products are also used in refinery processes, such as hy- drocracking, for the production of distillates.

For the process of the present invention, the lignin can be used as such or dispersed in a solvent. In the lat- ter case, the solvent can be used in a weight ratio solvent/lignin lower than or equal to 20/1, preferably ranging from 10/1 to l/l. The solvent preferably contains at least 40% by weight of a C₁₀ - Ci₂ non-aromatic hydrocarbon. Said hydrocarbon can be linear, branched or cyclic. It can be selected for example from decane, dodecane and cyclic hydrocarbons. Cyclic hydrocarbons are preferably used, such as for example decahydronaphthalene (decalin) , tetrahy- dronaphthalene (tetralin) and dihydronaphthalene . The rest of the solvent can consist of a recycled fluid of the same process, consisting of polar products of the group of phenols and water.

The liquefaction process of the present invention is preferably effected at a pressure ranging from 5 to 25 MPa, even more preferably from 7 to 15 MPa. The operating tem- perature preferably ranges from 300°C to 500°C, even more preferably from 350°C to 450°C.

The catalyst is preferably used in a weight ratio catalyst/lignin ranging from 0.1 to 20%, even more preferably from 1 to 10%.

The process of the present invention can be effected batchwise, in semi-continuous or in continuous, and in different types of reactors, according to what is normally known in the state of the art. The reaction is preferably carried out in continuous. When the process of the present invention is carried out in continuous, it can be effected in one or more catalytic reactors in series, fixed bed, fluidized bed, stirred or recirculated, or containing the catalyst in dispersion.

For use in the present invention, the catalyst can be formed, preferably with a ligand as previously described.

When the reaction is carried out in continuous, the use of one or more fixed bed catalytic reactors in series is particularly preferred.

The recycling of the polar products obtained at the end of the reaction is favourable for the development of a continuous process as the increase in the polarity of the reaction solvent also increases the solubility of the lignin itself.

The hydrogen is fed in excess, preferably in a volu- metric ratio of 1 volume of liquid lignin per 1,000 volumes of gaseous hydrogen measured under normal conditions (0°C, 100 kPa) . The liquid hourly space velocity (LHSV) , i.e. the ratio between the volume of liquid lignin fed and the volume of catalyst, measured in hours^"1, preferably ranges from 0.2 hours^"1 to 6 hours^"1, more preferably from 0.3 - 3 hours .

The resulting liquid mixture is separated from the gaseous phase. The gaseous fraction thus obtained can be subjected to separation, for example by means of a gas separator, to isolate and recover the C1-C4 hydrocarbons and separate carbon monoxide and. dioxide from the hydrogen which is recycled, after the possible addition of make-up hydrogen, to the lignin liquefaction reactor.

The liquid fraction can be easily separated into its polar constituents, mainly phenols, and non-polar components, by the addition to the same mixture of a polar solvent mixed with water. A mixture of water and acetone is preferably used, in a ratio ranging from 0.5 to 1. The water-acetone solution is added in such a quantity as to cause the formation of two phases, an upper substantially hydrocarbon phase, which contains the non-polar products, the second, lower, substantially aqueous-acetone, which contains the more polar products of the reaction. Quantities of water/acetone mixture which can be used, range for example from 0.1 to 0.5 with respect to the reaction mix- ture as such. The liquid/liquid extraction can be effected with any of the methods known to experts in the field, in a series of mixers and decanters. After the addition of the polar solvent and liquid/liquid extraction, the following products are separated: (i) a possible residual solid part

(ii) a hydrocarbon phase

(iii) a polar phase

The reaction products are recovered from the hydrocar- bon phase (ii) , by removal of the solvent, for example by evaporation. The evaporation can be effected by distillation for example, in order to remove the solvent from the hydrocarbon products obtained from the process, having a boiling point higher than about 180-200°C. Figure 3 illus- trates a sim-dist (simulated distillation by means of gas chromatography) typical of the. hydrocarbon fraction thus recovered (in the ordinate BP °C is the boiling point, in the abscissa mass % is the cumulative quantity in weight percentage of distillate, with respect to the total sam- pie) .

According to a particular embodiment of the invention, the polar solvent and reaction water are removed from the polar phase (iii) , and the residue is recycled to the liquefaction reactor to produce other hydrocarbons .

Figure 4 shows a liquefaction scheme of lignin according to the process of the present invention, effected in continuous and using a water/acetone mixture as polar separation solvent. In this scheme, every stream is identified by its composition and by a number. With reference to this figure, acetone (6) and water (4) are added to the product of the liquefaction reaction, i.e. hydrocrack- ing/hydrodeoxygenation (5) , free of gaseous products and excess hydrogen, in the liquid/liquid extractor. Two phases are formed: the almost completely hydrocarbon phase (11) is sent to an evaporator to recover the solvent, which is re- fed to the reaction (2) , a fraction containing dissolved acetone and light hydrocarbons (12) and the heavy hydrocarbon fraction (8) with an oxygen content preferably lower than 4%.

The polar phase (7) is sent to an evaporator-separator which allows the recovery and recycling of the acetone (6) , the separation of the water produced (10) and insoluble residue of the reaction (13) , possibly with the catalyst to be recycled to the reaction after regeneration. In the par- ticular embodiment of Figure 4, the phenol products in substantially aqueous solution are completely recycled to the reaction (9) for hydrocracking/hydrodeoxygenation. The gases produced substantially CO and C0₂ and Ci - C₄ hydrocarbons (3) , are separated from the hydrogen which is recycled to the reaction.

As already previously mentioned, the main characteristics of the hydrocarbon cut obtained by means of the liquefaction process of the present invention, is that of having an oxygen content lower than 4% by weight, preferably lower than 2% by weight, which makes it compatible with most re- finery processes for the production of gasolines and gas oils. The chemical characteristics of the hydrocarbon fluid (8) , which normally consists of hydrocarbons containing from 18 to 30 carbon atoms, are particular.

Figure 1 shows a mass gas chromatograph typical of hydrocarbon mixtures which can be obtained from Acetosolv lignin, with the liquefaction process of the present invention, wherein in the abscissa, the analysis time is indicated in minutes and in the ordinate the relative abundance with respect to the most intense peak which is conventionally equal to 100%. Figure 2 shows a Desorption Chemical Ionization Mass Spectroscopy typical of the hydrocarbon fractions obtained with the liquefaction process of the Acetosolv lignin of the present invention, which indicates the molecular distribution. In Figure 2, in the abscissa the molecular weight is indicated in a.m.u., and in the ordinate the relative abundance with respect to the most intense peak which is conventionally equal to 100%.

The hydrocarbon mixtures obtained from the process of the present invention preferably prevalently contain hydrocarbons having from 18 to 30 carbon atoms, with a prevalence of hydrocarbons having from 22 to 26 carbon atoms; and they have an oxygen content lower than 4%: these mixtures are new and are a further object of the present in- vention. In particular, the hydrocarbon fractions deriving from the liquefaction of Acetosolv lignin are characterized by the Desorption Chemical Ionization Mass Spectroscopy indicated in Figure 2.

The following examples are an illustration of the yields and compositions obtained under the preferred operating conditions of the process and in no way represent a limitation of the invention.

Example 1

Preparation of the catalyst Ni (4%) Mo (10%) /zeolite 13X

50 g of commercial molecular sieve of the type NaX

(sodium aluminium silicate, ZEOLITE 13X, UCC) are granulated in a mortar and the 20-40 mesh fraction is separated. An impregnation is effected on 15 g of the granulated product thus obtained, with a solution consisting of 1.25 g of nickel nitrate hexahydrate and 1.14 g of ammonium molybdate dissolved in 10.5 g of demineralized water. The impregnated solid is left to rest for 90' and is then dried at 140°C. A further two impregnation and drying cycles as described above, are repeated, and the solid is calcined at 500 °C for 4 hours. A catalyst is obtained with a nickel content of 4% with respect to the total weight of the catalyst and a molybdenum content equal to 10% with respect to the total weight of the catalyst.

Example 2

Preparation of the sulfided catalyst Ni (4%) o (10%) / zeolite 13X

1 g of the catalyst prepared in Example 1, 100 g of decalin and 0.5 ml of dimethyl disulfide are charged into a Hastelloy C, 0.5 1 stirred autoclave. The autoclave is pressurized with hydrogen at about 3 Pa and is heated to 330°C for about 4 hours. It' is then cooled and the excess gas is discharged. The resulting sulfided catalyst is preserved immersed in decalin in an inert atmosphere until use .

Example 3

Preparation of the sulfided catalyst Ni (4%) Mo (10%) / ETS-10

63 g of pseudobohemite (V-250, UOP) are added to 105 g of a solution of acetic acid at 1.5%, the mixture is stirred for 10' and 582 g of a solution of acetic acid at 1.5% are then added. The suspension is heated, under stirring, to 60°C and 45 g of ETS-10, having the following ratios between the constituents, from chemical analysis: Na 0.4: Si 1.0: Ti 0.2: K 0.09 (Engelhard), are then added. The mixture is dried, by heating under stirring. The prod- uct, dried at 120°C for 14 hours, is calcined at 500°C for 4 hours. The material thus obtained, ETS-10 bound with alumina, is ground and granulated in the 20-40 mesh fraction. 15 g of the granulated product are impregnated with a solution consisting of 1.25 g of nickel nitrate hexahydrate and 1.1.4 g of ammonium molybdate dissolved in 13 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours.

A catalyst is obtained with a nickel content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst.

The catalyst thus obtained is sulfided as described in Example 2.

Example 4

Preparation of the sulfided catalyst Ni (4¾) Mo (10%) / sepio- lite

50 g of Sepiolite 30-60 Tolsa are separated from the fine part (passing through a 100 mesh sieve) and calcined at 500°C. 15 g of the calcined product are impregnated with a solution consisting of 1.25 g of nickel nitrate hexahy- drate and 1.14 g of ammonium molybdate dissolved in 11 g of water. The material, left to rest for 90' and dried at 150 °C, is impregnated and dried a further two times as de- scribed above. The dried material is calcined at 500°C for 4 hours .

A catalyst is obtained with a nickel content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst. The catalyst thus obtained is sulfided as described in Exam le 2.

Example 5

Preparation of the sulfided catalyst Ni (4%) Mo (10%) /hydrotalcite

50 g of pseudobohemite (V-250, UOP) and 50 g of hydrotalcite Pural MG70 (Condea/Sasol) , are added to 100 g of a solution of acetic acid at 3%, the mixture is stirred for 10' and 900 g of a solution of acetic acid at 3% are then added. The suspension is heated, under stirring, to 60°C for 90 minutes. The mixture is dried, by heating, under stirring. The product, dried at 120°C for 14 hours, is calcined at 500 °C for 4 hours. The material thus obtained, hydrotalcite bound with alumina, is ground and granulated in the 20-40 mesh fraction. 10 g of the granulated product are impregnated with a solution consisting of 0.83 g of nickel nitrate hexahydrate and 0.76 g of ammonium molybdate dissolved in 11 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours.

A catalyst is obtained with a nickel content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst. The catalyst thus obtained is sulfided as described in Example 2.

Example 6 (comparative catalyst ref . 1)

Preparation of the sulfided catalyst Ni (4%) o (10%) /Al₂0₃

100 g of pseudobohemite (V-250, UOP) are added to 100 g of a solution of acetic acid at 3%, the mixture is stirred for 10' and 900 g of a solution of acetic acid at 3% are then added. The suspension is heated, under stirring, to 60°C for 90 minutes. The mixture is dried, by heating, under stirring. The product, dried at 120°C for 14 hours, is calcined at 500 °C for 4 hours. The material thus obtained is ground and granulated in the 20-40 mesh fraction. 15 g of the granulated product are impregnated with a solution consisting of 1.25 g of nickel nitrate hexahydrate and 1.14 g of ammonium molybdate dissolved in 13.8 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours.

The catalyst thus obtained is sulfided as described in Example 2.

Example 7 Preparation of the sulfided catalyst Co (4¾) Mo (10%) /zeolite 13X

50 g of commercial molecular sieve of the type NaX (sodium aluminium silicate, ZEOLITE 13X, UCC) are granu- lated in a mortar and the 20-40 mesh fraction is separated. An impregnation is effected on 15 g of the granulated product thus obtained, with a solution consisting of 1.25 g of cobalt nitrate hexahydrate and 1.14 g of ammonium molybdate dissolved in 10.5 g of demineralized water. The impregnated solid is left to rest for 90' and is then dried at 140°C. A further two impregnation and drying cycles as described above, are repeated, and the solid is calcined at 500°C for 4 hours. A catalyst is obtained with a cobalt content of 4% with respect to the total weight of the catalyst and a mo- lybdenum content equal to 10% with respect to the total weight of the catalyst .

The catalyst thus obtained is sulfided as described in Example 2.

Example 8

Preparation of the sulfided catalyst Co (4%) Mo (10%) / ETS-10

63 g of pseudobohemite (V-250, UOP) are added to 105 g of a solution of acetic acid at 1.5%, the mixture is stirred for 10' and 582 g of a solution of acetic acid at 1.5% are then added. The suspension is heated, under stir- ring, to 60°C and 45 g of ETS-10, having the following ra- tios between the constituents, from chemical analysis: Na 0.4: Si 1.0: Ti 0.2: K 0.09 (Engelhard), are then added. The mixture is dried, by heating under stirring. The product, dried at 120°C for 14 hours, is calcined at 500°C for 4 hours. The material thus obtained, ETS-10 bound with alumina, is ground and granulated in the 20-40 mesh fraction. 15 g of the granulated product are impregnated with a solution consisting of 1.25 g of cobalt nitrate hexahydrate and 1.14 g of ammonium molybdate dissolved in 13 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours.

A catalyst is obtained with a cobalt content of 4% with respect to the total weight of the catalyst, and a mo- lybdenum content equal to 10% with respect to the total weight of the catalyst .

The catalyst thus obtained is sulfided as described in Example 2.

Example 9

Preparation of the sulfided catalyst Co (4%) Mo (10%) / sepio- lite

50 g of Sepiolite 30-60 Tolsa are separated from the fine part (passing through a 100 mesh sieve) and calcined at 500°C. 15 g of the calcined product are impregnated with a solution consisting of 1.25 g of cobalt nitrate hexahy- drate and 1.14 g of ammonium molybdate dissolved in 11 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours .

A catalyst is obtained with a cobalt content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst.

The catalyst thus obtained is sulfided as described in

Example 2.

Example 10

Preparation of the sulfided. catalyst Co (4%) Mo (10%) / - hydrotalcite

50 g of pseudobohemite (V-250, UOP) and 50 g of hydrotalcite Pural MG70 (Condea/Sasol) , are added to 100 g of a solution of acetic acid at 3%, the mixture is stirred for 10' and 900 g of a solution of acetic acid at 3% are then added. The suspension is heated, under stirring, to 60°C for 90 minutes. The mixture is dried, by heating, under stirring. The product, dried at 120°C for 14 hours, is calcined at 500°C for 4 hours. The material thus obtained, hydrotalcite bound with alumina, is ground and granulated in the 20-40 mesh fraction. 10 g of the granulated product are impregnated with a solution consisting of 0.83 g of cobalt nitrate hexahydrate and 0.76 g of ammonium molybdate dissolved in 11 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as described above. The dried material is calcined at 500°C for 4 hours. A catalyst is obtained with a cobalt content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst.

The catalyst thus obtained is sulfided as described in Example 2.

Example 11 (comparative catalyst ref. 2)

Preparation of the sulfided catalyst Co (4%) Mo (10%) /A1₂Q₃

100 g of pseudobohemite (V-250, UOP) are added to 100 g of a solution of acetic acid at 3%, the mixture is stirred for 10' and 900 g of a solution of acetic acid at 3% are then added. The suspension is heated, under stirring, to 60 °C for 90 minutes. The mixture is dried, by heating, under stirring. The product, dried at 120°C for 14 hours, is calcined at 500°C for 4 hours. The material thus obtained is ground and granulated in the 20-40 mesh fraction. 12.5 g of the granulated product are impregnated with a solution consisting of 1.04 g of cobalt nitrate hexahydrate and 0.95 g of ammonium molybdate dissolved in 11.5 g of water. The material, left to rest for 90' and dried at 150°C, is impregnated and dried a further two times as de- scribed above. The dried material is calcined at 500°C for 4 hours. A catalyst is obtained with a cobalt content of 4% with respect to the total weight of the catalyst, and a molybdenum content equal to 10% with respect to the total weight of the catalyst.

The catalyst thus obtained is sulfided as described in Example 2.

Examples 12-24: Liquefaction test 1

The catalysts prepared in Examples 1-11 are used in the following lignin liquefaction tests: the catalysts are all sulfided, except for the catalyst of Example 1, used in Example 13. The lignin used is of the Acetosolv type for examples 12 to 22 of Table 1, whereas it is of the Or- ganosolv and Kraft type in examples 23 and 24. The Aceto- solv lignin is produced, according to X. Pan in Journal of Wood Science, 1999, 45, page 319, cited previously in the text, from a mixture of fir/pine wood. The Organosolv and Kraft lignins are commercial products from the Aldrich catalogue code 371017 (batch 10228TC) and code 471003 (batch 09724CE) , respectively.

The Acetosolv, Organosolv and Kraft lignins used respectively have the following composition:

C% 67. 1 ; H% 5 •3 ; N% 0 .1 , OS- 0.0 ; 0% 27.6 ;

C% 66. 7 ; H% 5 •3 ; N% 0 .2 OS- 0.0 ; 0% 28.9;

C% 52 .2 ; H% 5.7 ; N% 0 .2 , S% 3. 6 ; 0% 20.9; Solids %

17.5%; 10 g of lignin are charged into a stirred 0.5 1 autoclave, already containing 100 g of decalin as solvent, and the catalyst, in the quantities indicated in Table 1. The autoclave is closed and pressurized with about 4 MPa of hy- drogen at room temperature . It is then heated for 4 hours to the temperature selected and indicated in Table 1. At the end, the autoclave is left to cool and the excess gas is measured and analyzed. The mixture is discharged and treated with a 2/1 acetone/water solution. Two phases are formed, an upper hydrocarbon phase which contains the neutral products and a lower phase which contains the polar products. The heavier neutral products are recovered from the hydrocarbon phase by evaporation of the solvent, whereas substantially all the phenols are recovered from the polar phase. The insoluble residue is determined by calcination, by subtracting the catalyst. The weight values of the fractions obtained are illustrated in Table 1. These fractions, excluding the gases and insoluble residue, were examined for the direct determination of the Carbon, Hydro- gen, Nitrogen, Sulfur and Oxygen by difference, and the results obtained are illustrated in Table 2.

It can be clearly seen from the examples described above that with the use of the new catalysts, it is possible to effectively convert the lignin to the to the benefit of the production of liquid products, and the products ob- tained are less oxygenated than the products obtained with the use of the respective reference catalysts. In particular, the reference catalyst prepared in Example 6 (Ref.l) shows, with respect to the catalysts of the present inven- tion containing the same quantity of nickel and molybdenum, a lower conversion of the lignin, which can be obtained from the larger quantity of solid residue. The reference catalyst prepared in Example 11 (Ref.2) shows, with respect to the catalysts of the present invention containing the same quantity of cobalt and molybdenum, a lower deoxygena- tion of the total of the liquid fraction.

The reference catalyst prepared in Example 1 (Ref.3) shows, with respect to the catalyst of Example 2, completely identical to the catalyst of Example 1 except that it has not been sulfided, a lower conversion of the lignin, which can be obtained from the larger quantity of solid residue, and a lower deoxygenation of the total of the liquid fraction.

Example 25 - Liquefaction test 2

The previous liquefaction example 12 is repeated, except that the polar product obtained by mixing the polar products deriving from some of the previous liquefaction tests according to the invention, substantially containing phenols, is used instead of lignin. The catalyst used is the sulfided catalyst of Example 2. The weight values are indicated in table 3. The test demonstrates that the recycling of the polar products to the reaction is technically possible and produces further hydrocarbons as can be seen from the data indicated in the column "% Hydrocarbons" .

Catalyst ^(a| Ex. cat. Polar products

Solid resiHydrocarbons,

soluble in aceGas^(b), % due % %

tone/water %

Ni(4) o(10)/13X 2 0 70 22 1

Reaction conditions: T 390°C, P 4 MPa initial, time 4 hrs

(a) In brackets the weight % of metal

(b) Blend of C1 -C4, CO, CO.

Elemental analysis

C,% H, % N, % S, % O, %

Polar products from 81.61 7.3 0.0 0.0 11.1 liquefaction test

Polar products soluble 83.9 8.0 0.0 0.0 8.1 in acetone water

Hydrocarbons 88.0 8.9 0.0 0.0 1.9

Table 3

Claims

1) A process for the liquefaction of lignin which comprises treating lignin with hydrogen in the presence of a catalytic composition (A) containing:

b) an at least slightly basic carrier.

2) The process according to claim 1, wherein the catalytic composition is used in sulfided form.

3) The process according to claim 1 or 2, wherein in the catalytic composition, the metal Mel is molybdenum and the metal Me2 is nickel or cobalt.

4) The process according to claim 1 or 2, wherein in the catalytic composition, the metal Mel is present in a quantity ranging from 2 to 20% by weight with respect to the total weight of the sum of (a) and (b) .

5) The process according to claim 4, wherein in the cata- lytic composition, the metal Mel is present in a quantity ranging from 6 to 14% by weight with respect to the total weight of the sum of (a) and (b) .

6) The process according to claim 1 or 2, wherein in the catalytic composition, the metal Me2 is present in a quan- tity ranging from 0.5 to 10% by weight with respect to the total weight of the sum of (a) and (b) .

7) The process according to claim 6, wherein in the catalytic composition, the metal Me2 is present in a quantity ranging from 2 to 6% by weight with respect to the total weight of the sum of (a) and (b) .

8) The process according to claim 1 or 2, wherein in the catalytic composition, the carrier (b) is selected from basic carriers and slightly basic carriers.

9) The process according to claim 1 or 2 or 8, wherein the carrier (b) is selected from:

- oxides of alkaline earth metals,

- rare earth oxides ,

- mixed oxides/hydroxides containing alkaline earth metals,

- silico-aluminates containing, as counter-ions, ions of alkaline and/or alkaline earth metals,

zeolites containing ions of alkaline and/or alkaline earth metals,

- clays

- ions of supported alkaline metals, preferably supported on alumina, silica, oxides of alkaline earth metals,

- ions of alkaline metals and hydroxides of alkaline metals supported on alumina,

- titanium silicates containing, as counter- ions, ions of alkaline or alkaline earth metals.

10) The process according to claim 9, wherein the alkaline earth metal oxide used as carrier (b) is selected from magnesium oxide, calcium oxide, strontium oxide and barium oxide .

11) The process according to claim 9, wherein the rare earth oxide used as carrier (b) is cerium oxide.

12) The process according to claim 9, wherein the mixed oxides/hydroxides containing alkaline earth metals are selected from hydrotalcites and sepiolites.

13) The process according to claim 9, wherein in the sili- co-aluminates containing ions of alkaline or alkaline earth metals, the alkaline or alkaline earth metals are selected from Na, K, Mg, Ca, Sr, Ba.

14) The process according to claim 9, wherein the zeolite containing ions of alkaline or alkaline earth metals is se- lected from zeolites having a FAU structure and zeolites having a MOR structure.

15) The process according to claim 14, wherein the zeolite having a FAU structure is 13X zeolite and the zeolite having a MOR structure is mordenite .

16) The process according to claim 9, wherein the clays are selected from anionic clays and cationic clays.

17) The process according to claim 9, wherein the supported alkaline metals, preferably on alumina, silica, oxides of alkaline earth metals, are selected from Na and K. 18) The process according to claim 9, wherein the titanium silicate is ETS-10.

19) The process according to one or more of the previous claims, wherein the catalytic composition contains a binder .

20) The process according to claim 1 or 2, wherein the lignin is Organosolv lignin.

21) The process according to claim 1 or 2 , wherein the lignin is used as such or dispersed in a solvent.

22) The process according to claim 21, wherein the solvent contains at least 40% by weight of a Ci₀-Ci₂ non-aromatic hydrocarbon .

23) The process according to claim 1 or 2 effected at a pressure ranging from 5 to 25 MPa and a temperature ranging from 300°C to 500°C.

24) The process according to claim 23, effected at a pressure ranging from 7 to 15 MPa and a temperature ranging from 350°C to 450°C.

25) The process according to claim 1 or 2 , wherein the catalytic composition is used in a catalyst/lignin weight ratio ranging from 0.1 to 20%.

26) The process according to claim 1 or 2 , wherein a liquid fraction is obtained as product, which is separated into a polar fraction and a non-polar fraction by addition to the liquid fraction of a polar solvent in a mixture with water. 27) The process according to claim 26, wherein a mixture of water and acetone is used, in a ratio between each other ranging from 0.5 to 1.

28) A composition containing:

a) a metallic component comprising a metal Mel, in oxide form, selected from molybdenum, tungsten and mixtures thereof and a metal M2 , in oxide form, selected from nickel, cobalt and mixtures thereof .

b) an at least slightly basic carrier.

29) A composition obtained by sulfidation of the composition of claim 28.

30) The composition according to claim 28 or 29, wherein in the catalytic composition, the carrier (b) is selected from basic carriers and slightly basic carriers.

31) Compositions according to claim 28 or 29 or 30, wherein the carrier (b) is selected from:

- oxides of alkaline-earth metals,

- rare earth oxides,

- mixed oxides/hydroxides containing alkaline earth metals, - silico-aluminates containing, as counter- ions, ions of alkaline and/or alkaline earth metals,

zeolites containing ions of alkaline and/or alkaline earth metals,

- clays

32) The composition according to claim 28 or 29, wherein in the catalytic composition, the metal Mel is molybdenum and the metal M2 is nickel or cobalt.

33) The composition according to claim 28 or 29, wherein in the catalytic composition, the metal Mel is present in a quantity ranging from 2 to 20% by weight with respect to the total weight of the sum of (a) and (b) .

34) The composition according to claim 28 or 29, wherein in the catalytic composition, the metal Me2 is present in a quantity ranging from 0.5 to 10% by weight with respect to the total weight of the sum of (a) and (b) .

35) The composition according to claim 31, wherein the alkaline earth metal oxide used as carrier (b) is selected from magnesium oxide, calcium oxide, strontium oxide and barium oxide.

36) The composition according to claim 31, wherein the rare earth oxide used as carrier (b) is cerium oxide.

37) The composition according to claim 31, wherein the mixed oxides/hydroxides containing alkaline earth metals are selected from hydrotalcites and sepiolites. 38) The composition according to claim 31, wherein, in the silico-aluminates containing ions of alkaline or alkaline earth metals, the alkaline or alkaline earth metals are selected from Na, K, Mg, Ca, Sr, Ba.

39) The composition according to claim 31, wherein the zeolite containing ions of alkaline or alkaline earth metals is selected from zeolites having a FAU structure and zeolites having a MOR structure. _%

40) The composition according to claim 39, wherein the zeolite having a FAU structure is 13X zeolite and the zeolite having a MOR structure is mordenite.

41) The composition according to claim 31, wherein the clays are selected from anionic clays and cationic clays.

42) The process according to claim 31, wherein the sup- ported alkaline metals, preferably on alumina, silica, oxides of alkaline earth metals, are selected from Na and K.

43) The process according to claim 31, wherein the titanium silicate is ETS-10.

44) A process for preparing the compositions according to claim 28, which comprises: treating the slightly basic carrier with a solution of one or more salts precursors of oxides of the metals Mel and Me2, drying the product thus obtained and calcining it.

45) A hydrocarbon mixture prevalently containing hydrocar- bons containing from 18 to 30 carbon atoms, with an oxygen content lower than 4%.

46) The mixtures according to claim 45, which show the Desorption Chemical Ionization Mass Spectroscopy of figure 2.

47) Use of the mixtures obtained according to claim 1 as fuels, components of fuels and precursors of fuels.

48) Use of the mixtures obtained according to claim 45 as fuels, components of fuels and precursors of fuels.