FR3097861A1 - PROCESS FOR CONVERTING A COMPOUND OF FURFURALDEHYDE TYPE USING A HETEROGENIC SULPHIDE CATALYST - Google Patents

Abstract

The present invention relates to a process for converting furfuraldehyde-type compounds to a reduced compound via a heterogeneous sulfurized catalyst.

Description

METHOD FOR CONVERSING A COMPOUND OF THE FURFURALDEHYDE TYPE USING A HETEROGENEOUS SULPHIDE CATALYST

Technical field of the invention

The present invention relates to a method for converting compounds of the furfuraldehyde type into a reduced compound by means of a heterogeneous catalyst in the sulphide form.

Prior art

In recent years, there has been a strong resurgence of interest in the incorporation of products of renewable origin in addition to or as a substitute for products of fossil origin in the fuel and chemical sectors. The production of bio-sourced alkylfurans or hydroxyalkylfurans or furan is thus the subject of intense research and development efforts.

5-hydroxymethylfurfural or even 5-chloromethylfurfural or even 5-hydroxymethylfurfural, or even 2,5-diformylfuran are compounds derived from biomass resulting from the dehydration of sugar (C6) which can be recovered in many fields as precursors of active ingredients in pharmacy, agrochemistry or specialty chemistry.

Furfural is another compound derived from biomass resulting from the dehydration of sugar (C5), compounds that can be obtained by dehydration of sugars (C5) which can be valued in many basic intermediates for industry, such as for example furfuryl alcohol, 2-methylfuran, furan.

In particular, 2,5-dimethylfuran and 2-methylfuran are among the alkylfurans arousing great interest. 2,5-dimethylfuran is of great industrial interest because it can be transformed directly into 2,5-furanedicarboxylic acid (FDCA) via an oxidation process or in 2 steps into terephthalic acid (TA) via a first reaction. of Diels-Alder with ethylene giving paraxylene as described in application WO2018/015112 followed by an oxidation reaction well known to those skilled in the art to produce terephthalic acid. FDCA and TA molecules can be used to produce plasticizers, but also polymers from the family of polyesters or polyamides.

Surprisingly, the applicant has demonstrated that contacting a heterogeneous sulfur catalyst comprising at least one group VIB element and/or one group VIIIB element deposited on a solid support with furan compounds allows the selective conversion of furan compounds by hydrogenation and hydrogenolysis reactions to hydroxyalkyl furans, alkylfurans or furans, without hydrogenating the furan ring.

An advantage of the implementation of sulfur catalysts in the process according to the invention is that said catalysts have a lower manufacturing cost compared to catalysts based on noble metals with at least equivalent or better activity and selectivity.

Another advantage of using sulfur catalysts in the process according to the invention is that said catalysts are resistant to the presence of impurities such as sulfur compounds.

Another advantage of the implementation of sulfur catalysts in the process according to the invention is that said catalysts can be regenerated, which contributes to reducing the cost of the process, in particular on an industrial scale.

Definitions and Abbreviations

It is specified that, throughout this description, the expressions "included between ... and ..." "comprising between ... and ..." must be understood as including the terminals mentioned.

In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, ^81st edition, 2000-2001). For example, group VIIIB according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.

By heterogeneous catalyst is meant a catalyst which is insoluble in the reaction medium.

FDCA means 2,5-furanedicarboxylic acid.

By 5-HMF is meant 5-hydroxymethylfurfural.

By 2,5-DMF is meant 2,5-dimethylfuran.

In the present invention, the terms metal or metals, and elements of groups VIB or VIIIB are used in an equivalent manner.

Wt% denotes a percentage by weight.

Halogen (denoted X) denotes an iodine atom (I), a bromine atom (Br), a chlorine atom (Cl) and a fluorine atom (F).

Within the meaning of the present invention, the various embodiments presented can be used alone or in combination with each other, without limitation of combination.

Object of the invention

The present invention relates to a process for converting a feed comprising a furan compound of formula (I) by bringing said feed into contact with a heterogeneous sulfur catalyst comprising at least one element from group VIB and/or one element from group VIIIB deposited on a porous solid support in oxide form or on an amorphous or crystallized carbon support, and hydrogen, said furan compound of formula (I) being represented by the following general formula

in which

R ₁ and R ₂ are independently chosen from an aldehyde function –C(O)H, a carboxylic acid function –COOH, an ester function –COOR ₃ , a hydroxymethyl function –CH ₂ OH, a methyl halide function, a hydrogen, or an ether function –CH ₂ OR ₄ , R ₃ and R ₄ representing a linear or branched alkyl group of 1 to 6 carbons.

An advantage of the process according to the invention is that the sulfur catalysts have at least equivalent or better activity and selectivity with a lower manufacturing cost compared to catalysts based on noble metals.

Another advantage of the process according to the invention is that the sulfur catalysts are resistant to the presence of impurities such as sulfur compounds.

Another advantage of the process according to the invention is that the sulphide catalysts can be regenerated, which contributes to reducing the cost of the process, in particular on an industrial scale.

Preferably, the process is carried out at a temperature comprised between 100 and 300° C., and at a total pressure comprised between 0.5 and 6.0 MPa.

Preferably, the catalyst is introduced in a charge/catalyst(s) mass ratio of between 0.1 and 1000.

Preferably, the compound of formula (I) is mixed with at least one sulfur compound.

Preferably, the sulfur compound is present in a mass ratio relative to the compound of formula (I) of between 0.1 and 1000.

Preferably, the process is carried out in a solvent chosen from aromatic, furanic, thiophenic or benzene solvents, alone or as a mixture.

Preferably, the group VIIIB element or elements are chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum and the group VIB element or elements are selected from chromium, molybdenum and tungsten.

Preferably, the elements of groups VIB and VIIIB are chosen according to the following combinations NiMo, CoMo, FeMo, NiW, NiMoW and NiCoMo.

Preferably, the porous solid support in oxide form is chosen from aluminas, silicas, silica-aluminas or even titanium or magnesium oxides used alone or in a mixture with alumina or silica. -alumina.

Preferably, the amorphous or crystallized carbonaceous solid support is chosen from activated carbons, carbon blacks, carbon nanotubes, mesostructured carbons and carbon fibers.

Preferably, the catalyst has a porous volume of the support which is generally between 0.4 and 5.0 cm ³ /g.

Preferably, the catalyst has a specific surface of the support which is generally between 40 and 1500 m ² /g.

Preferably, the catalyst has an overall sulfurization rate greater than or equal to 50%.

Preferably, the process comprises the preparation of the sulfurized heterogeneous catalyst comprising the following steps:

at least one step of bringing at least said support into contact with at least one solution containing at least one precursor of at least said metal from group VIIIB or a precursor of at least said metal from group VIB,

at least one drying step to obtain at least said metal from group VIIIB and at least said metal from group VIB in oxide form, then,

at least one sulphidation step so that the metals of said active phase are in the sulphided form.

Preferably, the preparation process further comprises a calcination step implemented after step ii) at a temperature between 200°C and 600°C.

Detailed description of the invention

Process implementation

The present invention relates to a process for converting a feed comprising a furan compound of formula (I) by bringing said feed into contact with a heterogeneous sulfur catalyst comprising at least one element from group VIB and/or one element from group VIIIB , hydrogen, and a furan compound of formula (I)

in which

R ₁ and R ₂ are independently chosen from an aldehyde function –C(O)H, a carboxylic acid function –COOH, an ester function –COOR ₃ , a hydroxymethyl function –CH ₂ OH, a methyl halide function, a hydrogen, or an ether function –CH ₂ OR ₄ , R ₃ and R ₄ representing a linear or branched alkyl group of 1 to 6 carbons.

Advantageously, the process is implemented at a temperature of between 100 and 300°C, preferably between 120 and 240°C, more preferably between 140 and 220°C and very preferably between 160 and 200°C.

Advantageously, the process is implemented at a total pressure of between 0.5 and 6.0 MPa, preferably between 1.0 and 5.0 MPa, preferably between 2.0 and 4.0 MPa, preferably between 2.5 and 3.5 MPa and preferably 3.0 MPa.

The process according to the invention can advantageously be carried out discontinuously or continuously. The reaction time can advantageously vary with the reaction conditions and therefore the feed conversion rate.

In particular, the process according to the invention can be carried out in one or more reactors in series of the fixed bed type or of the bubbling bed type. The process can also be carried out in a Grignard reactor, closed or semi-continuous.

The compound of formula (I) can be introduced into the reaction zone alone or in the presence of a solvent.

In a preferred embodiment, the method comprises a preliminary step of sulfurization in situ or ex situ. Preferably, said step is carried out in situ. Said sulfurization step consists in sulfurizing the metal oxides of the catalyst into sulphides.

The catalyst according to the invention is advantageously introduced in a filler/catalyst(s) mass ratio of between 0.1 and 1000, preferably between 0.2 and 500, preferably between 0.3 and 100, preferably between 0, 05 and 50 and more preferably between 1 and 25.

Charged

The feedstock converted in the process according to the present invention comprises at least one furan compound of formula (I)

in which

R ₁ and R ₂ are independently chosen from an aldehyde function –C(O)H, a carboxylic acid function –COOH, an ester function –COOR ₃ , a hydroxymethyl function –CH ₂ OH, a methyl halide function, a hydrogen, or an ether function –CH ₂ OR ₄ , R ₃ and R ₄ representing a linear or branched alkyl group of 1 to 6 carbons.

Advantageously, the R ₁ group is chosen from a hydrogen (H), an aldehyde function –C(O)H, a carboxylic acid function –COOH, a hydroxymethyl function –CH ₂ OH, a methyl halide function –CH ₂ X, . Preferably, R ₁ is chosen from H, –CH ₂ OH, –CH ₂ Cl, and very preferably is a –CH ₂ OH group.

Advantageously, the R ₂ group is chosen from an aldehyde function –C(O)H, a carboxylic acid function –COOH, a hydroxymethyl function –CH ₂ OH, a methyl halide function –CH ₂ X. Preferably, R ₂ is chosen from –C(O)H, –CH ₂ OH, –CH ₂ Cl, and very preferably R ² is a –C(O)H group.

Advantageously, the R ₃ and R ₄ groups are chosen from alkyls, linear or branched, comprising between 1 and 4 carbon atoms, preferably between 1 and 3 carbon atoms, preferably from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl.

In a preferred embodiment, the compound of formula (I) is derived from biomass and in particular from the dehydration of sugars containing 6 or 5 carbon atoms. Preferably, the compound of formula (I) is derived from the dehydration of sugar chosen from fructose, glucose and xylose. Preferably, in this embodiment, the R ₂ group is an aldehyde function –C(O)H.

In a particular embodiment, the filler is a mixture of compounds of formula (I).

In a particular embodiment, the compound of formula (I) as defined above is mixed with at least one sulfur compound. In particular, when the compound of formula (I) is obtained by the transformation of biomass, said sulfur compound may be an impurity or a solvent resulting from one of the upstream preparation steps of said compound of formula (I).

In particular, said sulfur compound is chosen from the family of thiophene compounds, preferably from thiophene, 2-methylthiophene, 3-methylthiophene and 2,5-dimethylthiphene and very preferably thiophene. In particular, said sulfur compound can be DMSO or sulfolane.

In particular, said sulfur compound is present in a mass ratio relative to the compound of formula (I) of between 0.1 and 1000, preferably between 0.5 and 500 and very preferably between 1 and 250.

Generally, the presence of a sulfur compound with the compound of formula (I) is detrimental to the conversion of the latter because the sulfur compound at least partially poisons the catalysts based on noble metals.

An advantage of the present invention is that when the compound of formula (I) is mixed with a sulfur compound, the implementation of heterogeneous sulfur catalysts comprising at least one metal from group VIB and one metal from group VIIIB in a process according to the invention has proved surprisingly robust to the presence of said sulfur compound and exhibits good activity and selectivity for the conversion of the compound of formula (I).

Solvents

In a preferred embodiment of the invention, the process according to the invention is carried out in the presence of a solvent, the furan compound of formula (I) is then introduced into said process in solution in said solvent in a solvent mass ratio / furan compound of formula (I) between 1 and 1000, preferably between 2 and 500 and even more preferably between 5 and 250.

Said solvent advantageously be chosen from aromatic furan, thiophenic or benzene solvents, alone or as a mixture. Advantageously, said solvents make it possible to solubilize the furan compound of formula (I).

The furan solvents are preferably chosen from furan, 2-methylfuran or 2,5-dimethylfuran, alone or as a mixture. Advantageously, said furan solvent is a recycling of the product(s) obtained by the process according to the invention with the filler.

The thiophene solvents are preferably chosen from thiophene, or alkylthiophenes (substituted in position 2 or 3 for methylthiophenes and substituted in positions 2 and 5 for dimethylthiophenes), alone or as a mixture.

The benzene solvents are preferably chosen from solvents comprising one or more benzene rings, preferably from benzene, toluene, xylenes, any other alkylbenzene, and naphthalene and its derivatives. The benzene solvent can also be chosen from phenol or alkyl phenols, such as, for example, cresols or anisole.

Said solvent can also be chosen from polar solvents, preferably from dimethyl sulfoxide (DMSO) or sulfolane.

Catalysts

The catalysts used in the process according to the invention are heterogeneous sulfur catalysts comprising at least one element from group VIB and/or one element from group VIIIB deposited on a porous solid support in oxide form or an amorphous or crystallized carbon support.

Within the meaning of the present invention, by sulfur catalysts is meant a catalyst in which the metal elements of groups VIB and VIIIB are in sulfurized forms. The sulphide form is obtained by a sulphidation step described below, making it possible to transform the metal oxides into sulphides.

An advantage of the implementation of sulfur catalysts in the process according to the invention is that said catalysts have a lower manufacturing cost compared to catalysts based on noble metals with at least equivalent or better activity and selectivity.

Another advantage of using sulfur catalysts in the process according to the invention is that said catalysts are resistant to the presence of impurities such as sulfur compounds (i.e. thiophene or DMSO).

Another advantage of the implementation of sulfur catalysts in the process according to the invention is that said catalysts can be regenerated, which contributes to reducing the cost of the process, in particular on an industrial scale.

Elements of group VIB designates chromium (Cr), molybdenum (Mo), tungsten (W). Preferably, the group VIB element or elements are chosen from chromium, molybdenum and tungsten. Preferably, the element or elements of group VIB are chosen from molybdenum and tungsten.

Group VIIIB elements are iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and hassium (Hs). Preferably, the group VIIIB element or elements are chosen from iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt). Preferably, the group VIIIB element or elements are chosen from iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd) and platinum (Pt). Very preferably, the group VIIIB element or elements are chosen from iron (Fe), cobalt (Co) and nickel (Ni).

Preferably, the elements of groups VIB and VIIIB are chosen according to the following combinations NiMo, CoMo, FeMo, NiW, NiMoW and NiCoMo, and preferably from NiMo and CoMo.

Group VIB and VIIIB metals are deposited on a support and form the active phase of the catalyst.

Said support may be formed of at least one porous solid in oxide form, preferably chosen from aluminas, silicas, silica-aluminas or even titanium or magnesium oxides used alone or in a mixture. with alumina or silica-alumina. Preferably, the support is chosen from silicas, transition aluminas and silica-aluminas. Very preferably, the support essentially consists of a transition alumina or silica. A support essentially consisting of a transition alumina comprises at least 51% by weight, preferably at least 60% by weight, very preferably at least 80% by weight, or even at least 90% by weight of said transition alumina.

By transition alumina is meant for example an alpha phase alumina, a delta phase alumina, a gamma phase alumina.

A support essentially consisting of silica comprises at least 51% by weight, preferably at least 60% by weight, very preferably at least 80% by weight, or even at least 90% by weight of silica. Even more preferably, said support consists solely of a transition alumina or solely of silica.

According to a variant, the amorphous or crystallized carbon supports are chosen from activated carbons, carbon blacks, carbon nanotubes, mesostructured carbons and carbon fibers.

The specific surface is determined in the present invention by the BET method according to the ASTM D3663 standard, as described in the work Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academic Press, 1999 , for example by means of an Autopore III™ model device from the Micromeritics™ brand.

The specific surface of the support is advantageously between 40 and 1500 m²/g, and preferably between 60 and 1400 m²/g.

The specific surface of the porous support in oxide form is advantageously between 40 and 350 m ² /g, preferably between 60 and 300 m ² /g.

According to a variant, the specific surface of the amorphous or crystallized carbon support is advantageously between 200 m²/g and 1500 m²/g, preferably between 400 m²/g and 1450 m²/g, and preferably between 600 m²/g and 1400 m²/g.

The porous volume of the support is advantageously between 0.4 and 5.0 cm ³ /g, and preferably between 0.5 and 4.0 cm ³ /g. The total porous volume is measured by mercury porosimetry according to standard ASTM D4284 with a wetting angle of 140°, as described in the same work.

The porous volume of the porous support in oxide form is advantageously between 0.4 and 1.4 cm ³ /g, preferably between 0.5 and 1.3 cm ³ /g.

According to a variant, the pore volume of the amorphous or crystallized carbon support is generally between 0.4 and 5.0 cm ³ /g, preferably between 0.5 and 4.0 cm ³ /g and preferably between 0. 6 and 3.5 cm ³ /g.

Said porous or carbonaceous supports are advantageously in the form of balls, extrudates, pellets, or irregular and non-spherical agglomerates, the specific shape of which may result from a crushing step. Very advantageously, said support is in the form of beads or extrudates.

Advantageously, the catalyst used in the process according to the invention has an overall sulfurization rate greater than or equal to 50%, preferably greater than or equal to 55%, preferably greater than or equal to 60%, preferably greater than or equal to 65%, preferably greater than or equal to 70 and very preferably greater than or equal to 75%.

Advantageously, the catalyst used in the process according to the invention also comprises phosphorus on the active phase.

Catalyst Preparation Process

Another object of the invention relates to a method for preparing a catalyst used in the method according to the invention comprising:

i) at least one step of bringing at least one support into contact with at least one solution containing at least one precursor of at least one group VIIIB metal and/or one precursor of at least one group VIB metal,

ii) at least one drying step to obtain at least said metal from group VIIIB and/or at least one metal from group VIB in oxide form, then,

iii) at least one sulphurization step so that the metals of said active phase are in the sulphided form.

According to a variant, the method for preparing the catalyst also comprises a calcination step at a temperature of between 200° C. and 600° C. is implemented after step ii).

The catalyst according to the invention can be prepared by means of any technique known to those skilled in the art allowing the contact of the support and the metals of groups VIB and VIIIB during stage i) and in particular by impregnation of the elements of the groups VIIIB and VIB on the selected medium. This impregnation can for example be carried out according to the method known to those skilled in the art under the terminology of dry impregnation, in which just the quantity of desired elements is introduced in the form of precursors soluble in the chosen solvent, for example demineralized water, so as to fill as exactly as possible the pores of the support.

According to a variant, salts of metals from groups VIB and VIIIB which can be used in the preparation process according to the invention are, for example, cobalt nitrate, nickel nitrate, iron nitrate, ammonium heptamolybdate or metatungstate of ammonia. Any other salt known to those skilled in the art having sufficient solubility and decomposing during the activation treatment can also be used.

According to another variant, the catalyst is prepared by depositing said components of group VIB and/or group VIIIB metals and optionally phosphorus on said support, by one or more steps i) of co-impregnations, i.e. to say that said components of the metals of group VIB, group VIIIB and optionally phosphorus are introduced simultaneously into said support. The co-impregnation step(s) is (are) preferably carried out by dry impregnation or by impregnation in excess of solution. When this first mode comprises the implementation of several co-impregnation steps, each co-impregnation step is preferably followed by an intermediate drying step generally at a temperature below 200° C., advantageously between 50 and 180 °C, preferably between 60 and 150°C, very preferably between 75 and 140°C.

According to a preferred embodiment of co-impregnation, the impregnation solution is preferably an aqueous solution. Preferably, the aqueous impregnation solution when it contains cobalt, molybdenum and phosphorus is prepared under pH conditions favoring the formation of heteropolyanions in solution. For example, the pH of such an aqueous solution is between 1 and 5.

According to another variant, the catalyst precursor is prepared by depositing successively and in any order a component of a metal from group VIB, a component from a metal from group VIIIB and optionally phosphorus on said support for the implementation of step i). The deposits can be made by dry impregnation, by excess impregnation or else by precipitation-deposition according to methods well known to those skilled in the art. In this second embodiment, the deposition of the metal components of groups VIB and VIIIB and optionally phosphorus can be carried out by several impregnations with an intermediate drying step between two successive impregnations generally at a temperature below 200° C., advantageously comprised between 50 and 180°C, preferably between 60 and 150°C, very preferably between 75 and 140°C.

Whatever the mode of deposition of the metals and the optional phosphorus implemented, the solvent which enters into the composition of the impregnation solutions is chosen so as to solubilize the metal precursors of the active phase, such as water or a organic solvent (for example an alcohol).

By way of example, among the sources of molybdenum, use may be made of oxides and hydroxides, molybdic acids and their salts, in particular ammonium salts such as ammonium molybdate, ammonium heptamolybdate, phosphomolybdic acid (H ₃ PMo ₁₂ O ₄₀ ), and their salts, and optionally silicomolybdic acid (H ₄ SiMo ₁₂ O ₄₀ ) and its salts. The sources of molybdenum can also be any heteropolycompound of Keggin, lacunary Keggin, substituted Keggin, Dawson, Anderson, Strandberg type, for example. Preferably, molybdenum trioxide and the heteropolycompounds of Keggin, lacunary Keggin, substituted Keggin and Strandberg type are used.

The tungsten precursors which can be used are also well known to those skilled in the art. For example, among the sources of tungsten, use may be made of oxides and hydroxides, tungstic acids and their salts, in particular ammonium salts such as ammonium tungstate, ammonium metatungstate, phosphotungstic acid and their salts, and optionally silicotungstic acid (H ₄ SiW ₁₂ O ₄₀ ) and its salts. The tungsten sources can also be any heteropolycompound of Keggin, lacunary Keggin, substituted Keggin, Dawson type, for example. Preferably, ammonium oxides and salts are used, such as ammonium metatungstate or heteropolyanions of Keggin, lacunary Keggin or substituted Keggin type.

The cobalt precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example. Cobalt nitrate, cobalt hydroxide and cobalt carbonate are preferably used.

The nickel precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates, acetates and nitrates, for example. Nickel nitrate, nickel hydroxide and nickel hydroxycarbonate are preferably used.

The iron precursors which can be used are advantageously chosen from oxides, hydroxides, carbonates, acetates and nitrates, for example. Iron nitrate and iron acetate are preferred.

The phosphorus can also advantageously be introduced alone or as a mixture with at least one of the metals from group VIB and VIIIB. The phosphorus is preferably introduced as a mixture with the precursors of the metals of group VIB and of group VIII, in whole or in part on the shaped alumina support, by dry impregnation of said alumina support using of a solution containing the metal precursors and the phosphorus precursor. The preferred source of phosphorus is orthophosphoric acid H ₃ PO ₄ , but its salts and esters such as ammonium phosphates or mixtures thereof are also suitable. The phosphorus may also be introduced together with the group VIB element(s) in the form of, for example, heteropolyanions of Keggin, lacunary Keggin, substituted Keggin or of the Strandberg type.

The content of elements from group VIIIB of the catalyst according to the invention is preferably between 1.0 and 20% by weight of oxides of elements from group VIIIB, preferably between 2.0 and 16% by weight of oxides of group VIIIB elements and more preferably between 3.0 and 15% by weight of oxides of group VIIIB elements. Preferably, the Group VIIIB element is iron, cobalt or nickel or a mixture of these two elements, and more preferably, the Group VIIIB element consists solely of cobalt or nickel.

The content of group VIB elements is preferably between 1.5 and 60% by weight of oxides of group VIB elements, more preferably between 3.0 and 50% by weight of group VIB element oxides. Preferably the group VIB element is molybdenum or tungsten or a mixture of these two elements, and more preferably the group VIB element consists only of molybdenum or tungsten.

According to one variant, the catalyst also contains phosphorus, the phosphorus content being between 0.3 and 10.0% by weight, expressed as P ₂ O ₅ relative to the total weight of the catalyst.

Step ii) of drying is implemented at a temperature below 200°C, advantageously between 50 and 180°C, preferably between 60 and 150°C, very preferably between 75 and 140°C. Stage ii) is advantageously carried out in a traversed bed using air or any other hot gas. Preferably, when the drying is carried out in a traversed bed, the gas used is either air or an inert gas such as argon or nitrogen. Very preferably, the drying is carried out in a traversed bed in the presence of air.

Preferably, this drying step ii) lasts between 30 minutes and 4 hours, and preferably between 1 hour and 3 hours.

According to a variant, the dried catalyst can be subjected to a subsequent calcination step, for example in air, at a temperature greater than or equal to 200°C. The calcination is generally carried out at a temperature less than or equal to 600°C, and preferably between 200°C and 600°C, and in a particularly preferred manner between 250°C and 500°C. The calcining time is generally between 0.5 hour and 16 hours, preferably between 1 hour and 5 hours. It is generally carried out under air. Calcination transforms the precursors of group VIB and VIII metals into oxides.

Stage iii) of sulfurization makes it possible to obtain the catalyst in sulphide form by the temperature treatment in contact with a decomposable organic sulfur compound and generator of H ₂ S or directly in contact with a gaseous flow of H ₂ S diluted in H ₂ . Preferably, step iii) of sulfurization is carried out in a sulphur-reducing medium, that is to say in the presence of H ₂ S and hydrogen, in order to transform the metal oxides into sulphides such as, for example, MoS ₂ and Co ₉ S ₈ . Sulfurization is carried out by injecting onto the catalyst a stream containing H ₂ S and hydrogen, or else a sulfur compound capable of decomposing into H ₂ S in the presence of the catalyst and hydrogen. Polysulphides such as dimethyldisulphide (DMDS) are H ₂ S precursors commonly used to sulphide catalysts. The temperature is adjusted so that the H ₂ S reacts with the metal oxides to form metal sulphides. Said sulfurization can be implemented in situ or ex situ (inside or outside the reactor) of the reactor of the process according to the invention at temperatures between 200 and 600° C., and more preferably between 300° C. and 500° C. .

To be active, metals must be sulphurized. The sulfur content in the sulfurized catalyst is measured by elemental analysis according to ASTM D5373. A metal is considered to be sulfurized when the overall sulfurization rate defined by the molar ratio between the sulfur (S) present on the catalyst and said metal is at least equal to 50% of the theoretical molar ratio corresponding to the total sulfurization of the metal(s) considered. The overall sulfurization rate is defined by the following equation:

(S/metal) _catalyst ≥ 0.6 x (S/metal) _theoretical

in which:

(S/metal) _catalyst molar ratio between sulfur (S) and metal present on the catalyst

(S/metal) _Theoretical molar ratio between sulfur and metal corresponding to the total sulphidation of the metal to sulphide.

This theoretical molar ratio varies according to the metal considered:

(S/Fe) _theoretical = 1

(S/Co) _theoretical = 8/9

(S/Ni) _theoretical = 2/3

(S/Mo) _theoretical =2/1

(S/W) _theoretical =2/1

When the catalyst comprises several metals, the molar ratio between the S present on the catalyst and all the metals must also be at least equal to 50% of the theoretical molar ratio corresponding to the total sulphidation of each metal to sulphide, the calculation being carried out in proportion to the relative molar fractions of each metal.

For example, for a catalyst comprising molybdenum and nickel with a respective molar fraction of 0.7 and 0.3, the minimum molar ratio (S/ Mo + Ni) is given by the relationship:

(S/Mo+Ni) _catalyst = 0.6 x {(0.7 x 2)+ (0.3 x (2/3)}

Preferably, the overall sulfurization rate of the metals is greater than or equal to 50%, preferably greater than or equal to 55%, preferably greater than or equal to 60%, preferably greater than or equal to 65%, preferably greater than or equal to equal to 70 and very preferably greater than or equal to 75%.

Sulphidation is implemented on metals in oxide form without a prior metal reduction step being carried out. Indeed, the sulfurization of reduced metals is more difficult than the sulfurization of metals in the form of oxides.

Another object according to the invention relates to a method comprising

A step for preparing the sulfurized heterogeneous catalyst comprising at least one element from group VIB and/or one element from group VIIIB deposited on a porous carbon or solid support in oxide form as described above, and

A step of converting a charge comprising a furan compound of formula (I) as described above by bringing said charge into contact with the catalyst prepared in the previous step, and hydrogen.

Examples

Example 1 – Preparation of an oxide catalyst A (comparative)

The support for catalyst A is a transition alumina with a specific surface area of 140 m²/g and a pore volume of 1.0 cm ³ /g. Catalyst A is prepared by dry impregnation of the support with an aqueous solution of ammonium heptamolybdate and cobalt nitrate, the volume of the solution containing the precursors of the metals being strictly equal to the pore volume of the mass of support. The concentration of metal precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of molybdenum, cobalt on the final catalyst. After dry impregnation on the support, the catalyst is left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried in air in an oven at 90° C. for 12 hours then calcined in air at 450° C. for 2 hours.

Catalyst A obtained after calcination has a content of 10.3% by weight of molybdenum (equivalent MoO ₃ ) and 2.8% by weight of cobalt (equivalent CoO).

Example 2 – Preparation of a reduced catalyst B (comparative)

3 grams of catalyst A are reduced beforehand at 200°C under hydrogen for 2 hours with a hydrogen flow rate of 1 L/h/g. Catalyst B is thus obtained.

Example 3 - Preparation of a sulfur catalyst C (according to the invention)

3 grams of catalyst A are treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g to ensure sulfurization oxide phases, and finally, reduced under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst C is thus obtained. The overall sulfurization rate of the measured catalyst is 61%.

Example 4 - Preparation of Catalyst D

The support for catalyst D is a transition alumina with a specific surface area of 70 m²/g and a pore volume of 1.0 cm ³ /g. The support is dry impregnated with an aqueous solution of ammonium heptamolybdate and nickel nitrate, the volume of the solution containing the precursors of the metals being strictly equal to the pore volume of the support mass. The concentration of metal precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of molybdenum, nickel on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried in air in an oven at 90° C. for 12 hours and then calcined in air at 450° C. for 2 hours. After calcination, the impregnated support has a content of 6.0% by weight of molybdenum (equivalent MoO ₃ ) and 10.2% by weight of nickel (equivalent NiO). 3 grams of the impregnated and then calcined support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst D is thus obtained. The overall sulfurization rate of the measured catalyst is 65%.

Example 5 - Preparation of Catalyst E

The support for catalyst E is a transition alumina with a specific surface area of 265 m²/g and a pore volume of 0.8 cm ³ /g. The support is dry impregnated with an aqueous solution of ammonium metatungstate and nickel nitrate, the volume of the solution containing the precursors of the metals being strictly equal to the pore volume of the support mass. The concentration of metal precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of tungsten, nickel on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried in air in an oven at 90° C. for 12 hours and then calcined in air at 450° C. for 2 hours. After calcination, the impregnated support has a content of 16.4% by weight of tungsten (WO ₃ equivalent) and 1.6% by weight of nickel (NiO equivalent). 3 grams of the impregnated and then calcined support are then previously treated at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulphide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst E is thus obtained. The overall sulfurization rate of the measured catalyst is 57%.

Example 6 - Preparation of Catalyst F

The support for catalyst F is a transition alumina with a specific surface area of 85 m²/g and a pore volume of 0.8 cm ³ /g. The support is dry impregnated with an aqueous solution of molybdenum oxide, cobalt hydroxide and phosphoric acid, the volume of the solution being strictly equal to the pore volume of the mass of support. The concentration of the precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of cobalt, molybdenum and phosphorus on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried under air in an oven at 120° C. for 12 hours. After drying, the impregnated support has a content of 5.9% weight of molybdenum (equivalent MoO ₃ ), 1.3% weight of cobalt (equivalent CoO) and 0.7% weight of phosphorus (equivalent P ₂ O ₅ ). 3 grams of the impregnated and then dried support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst F is thus obtained. The overall sulfurization rate of the measured catalyst is 75%.

Example 7 - Preparation of Catalyst G

The support for catalyst G is a silica with a specific surface area of 220 m²/g and a pore volume of 1.1 cm ³ /g. The support is dry impregnated with an aqueous solution of molybdenum oxide, cobalt hydroxide and phosphoric acid, the volume of the solution being strictly equal to the pore volume of the mass of support. The concentration of the precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of cobalt, molybdenum and phosphorus on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried in air in an oven at 120° C. for 12 hours and then calcined in air at 450° C. for 2 hours. After calcination, the impregnated support has a content of 10.1% by weight of molybdenum (equivalent MoO ₃ ), 1.8% weight of cobalt (equivalent CoO) and 1.1% weight of phosphorus (equivalent P ₂ O ₅ ). 3 grams of the impregnated and then calcined support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst G is thus obtained. The overall sulfurization rate of the measured catalyst is 66%.

Example 8 - Preparation of catalyst H

The support for catalyst H is an activated carbon with a specific surface area of 1380 m²/g and a pore volume of 3.3 cm ³ /g. The support is dry impregnated with an aqueous solution of molybdenum oxide, nickel hydroxycarbonate and phosphoric acid, the volume of the solution being strictly equal to the pore volume of the mass of support. The concentration of the precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of nickel, molybdenum and phosphorus on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water, dried in air in an oven at 120° C. for 12 hours and then calcined in air at 450° C. for 2 hours. After calcination, the impregnated support has a content of 46.1% by weight of molybdenum (equivalent MoO ₃ ), 9.6% weight of nickel (equivalent NiO) and 13.0% weight of phosphorus (equivalent P ₂ O ₅ ). 3 grams of the impregnated and then calcined support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst H is thus obtained. The overall sulfurization rate of the measured catalyst is 63%.

Example 9 - Preparation of Catalyst I

The support for catalyst I is a titanium oxide with a specific surface area of 133 m²/g and a pore volume of 0.50 cm ³ /g. The support is dry impregnated with an aqueous solution of molybdenum oxide, nickel hydroxycarbonate and phosphoric acid, the volume of the solution being strictly equal to the pore volume of the mass of support. The concentration of the precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of nickel, molybdenum and phosphorus on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water and dried under air in an oven at 120° C. for 12 hours. After calcination, the impregnated support has a content of 16.0% by weight of molybdenum (equivalent MoO ₃ ), 3.4% weight of nickel (equivalent NiO) and 3.8% weight of phosphorus (equivalent P ₂ O ₅ ). 3 grams of the impregnated and then calcined support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. The catalyst I is thus obtained. The overall sulfurization rate of the measured catalyst is 72%.

Example 10 - Preparation of Catalyst J

The support for catalyst J is a transition alumina with a specific surface area of 265 m²/g and a pore volume of 0.8 cm ³ /g. The support is dry impregnated with an aqueous solution of phosphomolybdic acid, the volume of the solution being strictly equal to the pore volume of the mass of support. The concentration of the precursors in aqueous solution is adjusted so as to obtain the desired weight percentage of molybdenum and phosphorus on the final catalyst. The dry-impregnated support is then left to mature for 1 hour 30 minutes in an enclosure saturated with water and dried under air in an oven at 120° C. for 12 hours. After drying, the impregnated support has a content of 13.6% by weight of molybdenum (equivalent MoO ₃ ), and 0.6% weight of phosphorus (equivalent P ₂ O ₅ ). 3 grams of the impregnated and then calcined support are then treated beforehand at 350° C. for 2 hours with a charge containing 4% by weight of sulfur in the form of DMDS (dimethyldisulfide) in heptane with a charge rate of 1 L/h/g for ensuring the sulfurization of the oxide phases, and finally, reducing under hydrogen for 2 hours at 200° C. with a hydrogen flow rate of 1 L/h/g. Catalyst J is thus obtained. The overall sulfurization rate of the measured catalyst is 77%.

Example 11 - Evaluation of the catalytic performance of catalysts A to J in a process for converting 5-HMF to DMF

A charge containing 1.25% by weight of 5-hydromethylfurfural in 250 mL of thiophene is used for the evaluation of the catalytic performances of the various catalysts. The 5-HMF conversion reaction is carried out in a Grignard reactor under a total pressure of 3.0 MPa, at 180° C., for 130 min, with stirring at 1000 revolutions per minute and in the presence of 3.0 grams of catalyst. Samples are taken at different time intervals and are analyzed by gas chromatography in order to observe the disappearance of the reagents and the formation of the products, and to deduce their respective concentrations.

The catalytic performances of catalysts A, B, C, D, E, F, G, H, I and J are evaluated in terms of conversion of 5-HMF and carbon yield in 2,5-dimethylfuran in the liquid phase after 130 minutes reaction, taking into account the percentage of carbon in the 5-HMF and in the 2,5-dimethylfuran.

The carbon yield in 2,5-dimethylfuran in the liquid phase after 130 minutes of reaction is obtained by the following equation:

Yield _carbon = ( _{2,5-dimethylfuran concentration, 130 min} *% _{carbon, 2,5-dimethylfuran} )/( _5-HMF concentration _{, initial- 5-HMF concentration, 130min} )*% _{carbon, 5-HMF} )*100

in which :

- _{Carbon yield: carbon} yield in 2,5-dimethylfuran in the liquid phase after 130 min

- % _{carbon, 2,5-dimethylfuran} : mass percentage of carbon in 2,5-dimethylfuran

- % _{carbon, 5-HMF} : mass percentage of carbon in the 5-HMF.

The results obtained with catalysts A to J are presented in Table 1 below.

Catalysts Support Sulfurization rate (%) Metals Additive 5-HMF conversion (%) Carbon yield in 2,5-dimethylfuran (%) A (comparative) Transition alumina -- CoMo 10 0 B (comparative) Transition alumina -- CoMo 7 0 C (compliant) Transition alumina 61 CoMo 85 61 D (compliant) Transition alumina 65 NiMo 59 80 E (compliant) Transition alumina 57 NiW 46 49 F (compliant) Transition alumina 75 CoMo Phosphorus 37 51 G (compliant) Silica 66 CoMo Phosphorus 43 12 H (compliant) Charcoal 63 NiMo Phosphorus 82 41 I (compliant) titanium oxide 72 NiMo Phosphorus 92 52 J(compliant) Transition alumina 77 Mo Phosphorus 82 77

Table: Catalytic performances of catalysts A to J for the conversion of 5-HMF to 2,5-dimethylfuran.

The conversion of 5-HMF and the carbon yield in 2-5 dimethylfuran are given after 130 minutes of reaction.

The conversion of 5-HMF remains low with oxide (oxide catalyst) or reduced (catalyst B) catalysts and is not accompanied by the formation of 2,5-dimethylfuran.

The sulfur catalysts C, D, E, F, G, H, I and J make it possible to obtain sufficient catalytic activities for the reaction of conversion of 5-HMF under the conditions of the process and allow the formation of 2,5-dimethylfuran . Catalyst D has the best carbon yield of 2,5-dimethylfuran.

Claims (15)

Process for converting a feedstock comprising a furan compound of formula (I) by bringing said feedstock into contact with a sulfurized heterogeneous catalyst comprising at least one element from group VIB and/or one element from group VIIIB deposited on a solid support porous in oxide form or on an amorphous or crystalline carbon support, and hydrogen, said furan compound of formula (I) being represented by the following general formula:

in which
R ₁ and R ₂ are independently chosen from an aldehyde function –C(O)H, a carboxylic acid function –COOH, an ester function –COOR ₃ , a hydroxymethyl function –CH ₂ OH, a methyl halide function, a hydrogen, or an ether function –CH ₂ OR ₄ , R ₃ and R ₄ representing a linear or branched alkyl group of 1 to 6 carbons. Process according to Claim 1, carried out at a temperature of between 100 and 300°C, and at a total pressure of between 0.5 and 6.0 MPa. Process according to any one of the preceding claims, in which the catalyst is introduced in a charge/catalyst(s) mass ratio of between 1 and 1000. Process according to any one of the preceding claims, in which the compound of formula (I) is mixed with at least one sulfur compound. Process according to Claim 4, in which the sulfur compound is present in a mass ratio relative to the compound of formula (I) of between 0.1 and 1000. Process according to any one of the preceding claims, implemented in a solvent chosen from aromatic, furanic, thiophenic or benzene solvents, alone or as a mixture. Process according to any one of the preceding claims, in which the element or elements of group VIIIB are chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum and the group VIB element or elements are chosen from chromium, molybdenum and tungsten. Process according to any one of the preceding claims, in which the elements of groups VIB and VIIIB are chosen according to the following combinations NiMo, CoMo, FeMo, NiW, NiMoW and NiCoMo. Process according to any one of the preceding claims, in which the porous solid support in oxide form chosen from aluminas, silicas, silica-aluminas or even titanium or magnesium oxides used alone or as a mixture with alumina or silica-alumina. Process according to one of Claims 1 to 8, in which the solid support is chosen from among amorphous or crystallized carbonaceous compounds are chosen from among activated carbons, carbon blacks, carbon nanotubes, mesostructured carbons and carbon fibers. Process according to any one of the preceding claims, in which the catalyst has a pore volume of the support which is generally between 0.4 and 5.0 cm ³ /g. Process according to any one of the preceding claims, in which the catalyst has a specific surface area of the support which is generally between 40 and 1500 m ² /g. Process according to any one of the preceding claims, in which the catalyst has an overall sulfurization rate greater than or equal to 50%. Process according to any one of the preceding claims comprising the preparation of the heterogeneous sulfurized catalyst comprising the following steps:
i) at least one step of bringing at least one support into contact with at least one solution containing at least one precursor of at least one group VIIIB metal and/or one precursor of at least one group VIB metal,
ii) at least one drying step to obtain at least said metal from group VIIIB and/or at least said metal from group VIB in oxide form, then,
iii) at least one sulphurization step so that the metals of said active phase are in the sulphided form. Process according to Claim 14, in which a step of calcining at a temperature of between 200°C and 600°C is carried out after step ii).