WO2011050424A1

WO2011050424A1 - Catalytic process for the production of alcohols from biomass-related feedstock

Info

Publication number: WO2011050424A1
Application number: PCT/BE2010/000073
Authority: WO
Inventors: Pierre Auguste Jacobs; Bert F. Sels; Stijn Van De Vyver
Original assignee: Katholieke Universiteit Leuven
Priority date: 2009-10-27
Filing date: 2010-10-26
Publication date: 2011-05-05
Also published as: GB0918821D0

Abstract

The present invention pertains generally to a catalytic technology for converting biomass- related feedstock into useful or value-added chemicals. More specifically, this invention relates to a catalytic process for the production of lower alcohols, and preferably for the production of C4 to C6 polyols from polysaccharides with β-glycoside linkages. A particular aspect of the present invention relates to a single-step catalytic process, using a heterogeneous catalyst, to produce C4 to C6 polyols such as sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose from polysaccharides containing β-glycoside functionalities such as in cellulose, chitin and particular bacterial biopolymers. The heterogeneous catalyst which comprises non-noble transition metal(s) and acid carrier(s) is characterized by thermal pretreatment in a carbon-containing atmosphere in order to obtain increased sugar alcohol yields.

Description

Catalytic process for the production of alcohols

from biomass-related feedstock

BACKGROUND OF THE INVENTION

A. Field of the Invention The present invention pertains generally to a catalytic technology for converting biomass- related feedstock into useful or value-added chemicals. More specifically, this invention relates to a novel catalytic process of increased yields for the production of lower alcohols, and preferably for the production of C to C₆ polyols from polysaccharides with β-glycoside linkages. For instance a particular aspect of the present invention relates to a single-step catalytic process, using a heterogeneous catalyst, to produce C₄ to C₆ polyols such as sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose from polysaccharides containing β-glycoside functionalities such as in cellulose, chitin and particular bacterial biopolymers. In order to obtain increased sugar alcohol yields, present invention uses a heterogeneous catalyst which comprises non-noble transition metal(s) and acid carrier(s) and which is characterized by thermal pretreatment in a carbon-containing atmosphere. Thermal pretreatment in a carbon-containing atmosphere of such heterogeneous catalyst precursor according to the invention results in a catalyst that surprisingly allows the production of high yields of C₄ to C₆ polyols.

Several documents are cited throughout the text of this specification. Each of the documents herein (including any manufacturer's specifications, instructions etc.) are hereby incorporated by reference; however, there is no admission that any document cited in this application is prior art of the present invention.

B. Brief Description of the Art

Cellulose, the world's most abundant renewable resource, is a polysaccharide composed of linear chains of D-glucose molecules bound together by β-glycoside linkages. The catalytic conversion of water-insoluble cellulose is significantly more difficult than of starches because the semicrystalline structure and hydrogen bonding limit the catalyst to access the glycoside ether bonds in the polysaccharide. It is well known that the combination of cellulose hydrolysis with instantaneous hydrogenation on supported metal catalysts yields polyols such as sorbitol, mannitol, glycerol, 1 ,2-propanediol and ethylene glycol.

Chitin can be described as cellulose with one hydroxyl group on each monomer substituted with an acetyl amine group. Chitin is namely a long-chain polymer of a N-acetyl-D-glucos-2- amine, a monosaccharide derivative of glucose which is an amide between glucosamine and acetic acid, and is found in many places throughout the natural world. These units form covalent β-glycoside linkages (similar to the linkages between glucose units forming cellulose). This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength. It is the main component of the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans (e.g. crabs, lobsters and shrimps) and insects, the radulas of mollusks and the beaks of cephalopods, including squid and octopuses.

Bacterial cell wall biopolymers are obtainable from microbial processes such as in bacterial sludge, bioflocs or biogranulation bioreactors. A biopolymer in the bacterial cell wall, in particular the cell wall of gram-positive bacteria, is built from alternating units of GlcNAc and N-acetylmuramic acid (MurNAc), cross-linked with oligopeptides at the lactic acid residue of MurNAc. This layered structure is called peptidoglycan. Such peptidoglycan structure has a glycan backbone made up of alternating molecules of N-acetylglucosamine (G) and N-acetylmuramic acid (M) connected by a β-glycoside bond.

The single-step catalytic conversion of the polysaccharide cellulose to polyhydric alcohols has already been investigated a number of times in recent patent applications and publications, using various heterogeneous catalytic systems.

Fukuoka and Dhepe describe in U.S. Patent 2009/217922, in Patent WO 2007/100052 and in Angewandte Chemie International Edition 45, 5161-5163 (2006) the successful catalytic conversion of cellulose into sugar alcohols by supported precious-metal catalysts. Of all the metals tested, supported Pt and Ru gave the highest yields of hexitols. The reactions are carried out with a 60 mL aqueous suspension of 0.8 wt% microcrystalline cellulose (Merck; Avicel) and a pressure of 5 MPa hydrogen at room temperature in a 100 mL stainless steel autoclave heated to 190 °C. For example, after 24 h reaction 0.21 g 2.5 wt% Pt/y-AI₂0₃ catalyzes the conversion of microcrystalline cellulose to give 25% sorbitol and 6% mannitol in yield. Tests carried out by the Applicants have shown that, by pretreatment of cellulose, the yield for sugar alcohols can be increased. In the document the testing of catalysts, like Pt/HUSY, Pt/Si0₂-Al₂0₃, Ru/HUSY, Pt/HZS , Pt/Η-β, Pt/FSM, Pt/Ti0₂, Pt/Zr0₂, Pd/FSM, Ru/Si0₂, Rh/FSM, Ni/Si0₂-Al₂0₃ Pt/C, Ni/Si0₂-Al₂0₃, Pt/HMOR and Ir/FS was also described. Notably, the catalysts were not further pretreated in any carbon-containing atmosphere prior to reaction. By consequence, the authors reported only poor yields when cheap non-noble metals like Ni were employed. A 60 wt% Ni/Si0₂-Al₂0₃ catalyst for instance afforded a sugar alcohol yield of about 1 %.

In Angewandte Chemie International Edition 46, 7636-7639 (2007) Luo and co-workers describe the catalytic conversion of a 50 mL aqueous suspension of 2 wt% microcrystalline cellulose (Alfa Aesar; relative crystallinity of about 84%) in the presence of a noble metal catalyst, i.e. a 4 wt% Ru supported on carbon, in 50 mL water at a temperature of 245 °C and 6 MPa hydrogen pressure. The catalytic reaction yielded 30% sorbitol, 10% mannitol and 6% erythritol at a cellulose conversion of 86%. The authors also tested organic solvents like ethanol or dioxane. No results were reported using Ni containing catalysts.

Chinese Patent Application No. 101 121643 issued to Zhang et al. describes a catalytic process for preparing hexahydric alcohols from pretreated cellulose. Prior to the catalytic reaction, commercial cellulose (Alfa Aesar, 85% crystallinity) is treated with an aqueous solution of 85 wt% phosphoric acid at 50 °C for 40 min, subsequent recovering with water, filtration, washing and drying. A noble metal, i.e. ruthenium, loaded on multiwall carbon nanotube carriers (mRu/CNT) was used here as a catalyst in the reaction with the pretreated cellulose substrate (having a 33% crystallinity). After 24 h at 190 °C and with a hydrogen pressure of 5 MPa, the reaction of the mRu/CNT catalyst with a 20 mL aqueous suspension of 0.8 wt% pretreated cellulose yielded 74% hexahydric alcohols.

Ji et al. published in Angewandte Chemie International Edition 47, 1-5 (2008) and in Catalysis Today 147, 77-85 (2009) the direct catalytic conversion of cellulose in the presence of nickel-promoted tungsten carbide catalysts. The reaction of a 50 mL aqueous suspension of 1 wt% cellulose (Merck, microcrystalline) is carried out with 2% Ni-30% W₂C/AC at a temperature of 245 °C and a pressure of 6 MPa H₂ for 30 minutes. At 100% cellulose conversion they obtain low C₄ to C₆ polyol yields of 8%, including 4% sorbitol, 2% mannitol and 2% erythritol. W₂C/AC, Pt/Al₂0₃, Pt/AC and Ni/AC were also used as heterogeneous catalysts with low C₄ to C₆ polyols yields. For instance, 3% Ni/AC catalyst yielded only 6% C₄ to C₆ polyols at an incomplete cellulose conversion of 69%. Again, this non-noble metal catalyst was not pretreated in a carbon-containing atmosphere prior to reaction.

Since the catalytic conversion of water-soluble starches proceeds much easier than that of water-insoluble cellulose, a large number of research deals with the hydrolysis and hydrogenation of starches. Jacobs et al. described in Patent EP 0329923 (1989) the single-step catalytic conversion of cornstarches to sorbitol with a Ru on acid ultrastable Y zeolite catalyst. Wright employed a nickel-tungsten oxide-copper catalyst to synthesize sorbitol from invert sugars (see U.S. Patent 3,965,199). Schuster employed a catalyst comprising cobalt, copper and manganese for the catalytic hydrogenation of aqueous saccharose solutions (see U.S. Patent 5,107,018). Capik and Wright employed metallic nickel and finely divided nickel phosphate supported on ieselguhr to synthesize sorbitol from invert sugars (see U.S. Patent 3,670,035). Arena employed nickel composited on carbonaceous pyropolymer spheres for the catalytic hydrogenation of starch (see U.S. Patent 4,380,679). Catalytic conversion of water- insoluble cellulose containing β-glycoside linkages is not conducted in the cited references. Moreover, said non-noble metal catalysts are not thermally pretreated in a carbon-containing atmosphere in order to obtain increased sugar alcohol yields.

In light of the above, it is an object of the present invention to provide a new catalytic process for converting polysaccharides containing β-glycoside bonds such as cellulose towards C₄ to C₆ polyols that have a variety of uses. The known procedures as illustrated above have the disadvantage that they use expensive precious-metal catalysts, like platinum or ruthenium, for the production of such polyols from cellulose, or that the yield towards these alcohols is always low when non-noble metal based catalysts such as nickel are used.

SUMMARY OF THE INVENTION

This invention relates generally to a single-step process for catalytic conversion of polysaccharides containing β-glycoside bonds into useful or value-added chemical products. More particularly, in the catalytic process of present invention the heterogeneous catalyst, which has been thermally pretreated in a carbon-containing atmosphere,converts such polysaccharides like cellulose towards lower C₄ to C₆ polyols such as sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose. The invention further includes the preparation of a heterogeneous catalyst to do so consisting of a non-noble transition metal such as iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other non-noble transition metals, supported on an acidic support thermally pretreated in an atmosphere of organic vapors, gases or other carbon containing sources at elevated temperatures. An embodiment of present invention concerns a process for producing C4 to C6 polyol(s), which process comprises reacting polysaccharide polymers composed of or having monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of catalytic material, which comprises or which consists of non-noble transition metal(s) and acid carrier(s) and which is pretreated at elevated temperatures in an atmosphere of organic vapors, gases or other carbon containing sources or which is pretreated by heating in such carbon-containing atmosphere.

In yet another particular embodiment of this process of present invention the reaction zone is pressurized with hydrogen at a pressure between 1 MPa to 30 MPa, preferably between 3 MPa to 15 MPa, yet preferably between 4 MPa to 8 MPa. In this process the reaction zone is preferably heated, and more preferably this reaction zone is heated after pressurizing. In yet a more particular embodiment of this process the reaction conditions in said reaction zone include a temperature of 120 °C to 270 °C, preferably of 150 °C to 250 °C, yet more preferably a temperature of 180 °C to 230 °C. In yet a more particular embodiment of this process the reaction in said reaction zone is carried out under mixing of the reaction medium.

In a particular embodiment of the above described embodiments of the catalytic process of present invention the polysaccharide polymer in the feedstock is a biopolymer. In a more particular embodiment of this process the polymer in the feedstock comprises polysaccharide polymers containing β-glycoside bonds. For instance in an embodiment of this process the polymer in the feedstock comprises polysaccharide polymers of the group consisting of cellulose, hemicellulose and lignin, or of the group consisting of chitin and chitosan. In yet another particular embodiment of this process the feedstock comprises polysaccharide polymers of the group consisting of bacterial cell wall biopolymersor of the group consisting of fructan and glucan.

In yet another embodiment in the above described processes the non-noble transition metal is of the group consisting of iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other transition metals.

In yet another embodiment in the above described processes the acidic carrier is alumina, silica, titania, zirconia, silica-alumina, silica-magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin.

The above described processes of present invention can be used for production of C₄ to C₆ polyols of the group consisting of sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose.

The processes of present invention can be further embodied in that the initial concentration of the polysaccharide polymers composed of monosaccharides bound together by β-glycoside linkages in the aqueous reaction medium is between 1 to 100 wt, preferably between 2 to 70 wt% and yet preferably between 10 to 70 wt%.

Furthermore the claims set out a particular embodiment of the invention.

GLOSSARY OF TERMS

By the term "single-step process" as used herein is meant a sequence of chemical transformations occurring in a single reactor.

The term "polyols" as used herein is to be understood as meaning a group of alcohols comprising from 4 to 6 carbon atoms and more than one hydroxyl functional group such as in sorbitol, mannitol, xylitol and erythritol and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose. The term "polysaccharide" as used herein refers to those saccharides containing more than one monosaccharide unit, which are predominately linked by β-glycoside bonds. Thus, this term includes disaccharides and oligosaccharides. Feedstock comprising biopolymers composed of monosaccharides bound together by β- glycoside linkages is in the meaning that the feedstock contains at least 50%, preferably 60%, more than preferably 70%, yet more than preferably 80%, yet more preferably more than 90%, and most preferably more than 95% by weight of such biopolymers.

DETAILED DESCRIPTION OF THE INVENTION

An object of this invention is the production of C₄ to C₆ polyols such as sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose from polysaccharides containing β- glycoside linkages such as cellulose, by contacting the polysaccharides in an aqueous medium with hydrogen at elevated temperature and pressure in the presence of a heterogeneous catalyst, in particular such heterogeneous catalyst, that has thermally pretreated in a carbon- containing atmosphere to increase the yields of the C₄ to C₆ polyols production.

A particular aspect of the present invention relates to the heterogeneous catalysis of said polysaccharides in a single-step process, which comprises but is not limited to simultaneous hydrolysis and hydrogenation/dehydrogenation/hydrogenolysis/dehydration reactions. The single-step catalytic process is carried out in one reactor.

In contrast to the supported precious-metal catalysts used in prior art, the present invention relates to a less expensive, but surprisingly efficient heterogeneous catalyst composed of non- noble metals. Existing catalytic processes, such as described in Patent WO 2007/100052, in Chinese Patent CN 101 121643 or in Angewandte Chemie International Edition 46, 7636-7639 (2007) require expensive supported precious-metals, like platinum or ruthenium, in order to obtain high yields of alcohols. However, no catalytic system is described that allows for the production of high yields of C₄ to C₆ polyols with heterogeneous catalysts based on less expensive non-noble transition metals such as iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other non- noble transition metals.

It is, therefore, an object of the present invention to provide a single-step catalytic process for the production of C to C₆ polyols and for the preparation of non-noble catalysts to do so.

A further object of the present invention is to provide a catalytic process for the production of C₄ to C₆ polyols from polysaccharides containing the persistent β-glycoside linkages. Often these polysaccharides such as crystalline or partially crystalline cellulose occur as rigid and water-insoluble compounds, which are used in the single-step catalytic process, or which are pretreated according to the known state-of-the-art practice methods. It includes but is not limited to mechanical ball-milling pretreatments, acid pretreatments or steam pretreatments. The pretreatments are performed by the applicants in order to reduce the crystallinity of the said polysaccharides and to increase its reactivity in the catalytic reaction.

Preferred downstream uses of the C₄ to C₆ polyol reaction products such as, for example, sorbitol and mannitol include but are not limited to foods, pharmaceuticals, cosmetics, textiles and polymers. Aqueous sorbitol solutions are used as humectants, softeners and plasticizers in various types of formulation. Xylitol is used as a sweetener and humectant. Erythritol is used in oral pharmaceutical formulations, confectionery, and food products. Sorbitan is used in the manufacturing of surfactants such as polysorbates. Sorbose is an important intermediate in the actual industrial production process of vitamin C. Examples of medications in which isosorbide is used are isosorbide dimethyl ether, which is useful as a pharmaceutical additive, an industrial solvent, and in personal care products, and isosorbide dinitrate, which is effective as a medication to treat angina pectoris.

The heterogeneous catalyst used in the present invention essentially consists of or comprises (i) a non-noble transition metal such as iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other non- noble transition metals, (ii) a solid support material having acidic functions, preferably alumina, silica, titania, zirconia, silica-alumina, silica-magnesia, silica-titania, all types of carbon materials with acidic functions, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin. While some of the aforementioned are not per se acidic, they can easily be treated by various reported means to introduce the surface acidity. For instance, zeolites can be exchanged with NH4 followed by heat treatment. Zeolites can also be treated with acids to introduce acidity. Carbon materials for instance can be oxidized forming oxygen-containing functional chemical groups such as but not limited to carboxylic acids or phenolic groups. Carbon materials are treated in liquid or gas phase with oxidizing compounds such as SO3 and the like to introduce acidity. Unexpectedly when such combination of catalytic elements and the acidic support is heated in the presence of organic vapors, gases or other carbon containing sources, not necessarily free of O containing compounds such as CO, C0₂ or water, in the temperature region between 400 and 1000 °C, preferably between 600 and 900 °C, the resulting catalyst allows the production of high yields of C₄ to C₆ polyols according to the invention.

The preferred weight percentage of non-noble transition metal loaded on the heterogeneous catalyst prepared according to the invention amounts up to about 15 wt%, preferably from about 0.05 to 5 wt% and most preferably from about 0.1 to 3 wt%.

Examples of carbon containing gases that can be used in the present invention include, but are not limited to methane, carbon monoxide, acetylene, ethylene, benzene, synthesis gas (H₂/CO) and/or mixtures thereof. Catalysts are contacted with the carbon containing gases from 1 s to several hours, preferably from minutes to several hours. Skilled persons will recognize that the implied contacting time depends on various parameters such as flow rates, temperature, linear velocity of flow rates in the reactor, etc.

In another aspect of the invention, the organic gas or compound used for the preparation of the catalyst according to the invention can contain oxygen or oxygen containing compounds such as water, C0₂, CO and the like.

Precursors for the synthesis of the heterogeneous catalyst according to the present invention can be prepared by ion exchange or impregnation, and preferably by impregnation. A porous support material can be purchased or prepared by known methods in the art. A typical precursor for nickel can be nickel nitrate dissolved in water. A typical precursor for cobalt can be cobalt nitrate dissolved in water, for iron can be iron nitrate dissolved in water and for chromium can be chromium nitrate dissolved in water. Reasonably skilled persons in the field will recognize that other salt precursors and combination of salt precursors or other metal oxidation states are useful as well.

In order to exert a good catalytic activity, as claimed in the present invention, the catalyst also requires the presence of a solid support material having sufficient acidic functions. Specific examples of the solid support material exhibiting desirable acidic functionalities can be selected from, but not limited to, alumina, silica, titania, zirconia, silica-alumina, silica- magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin. Examples of zeolites that are suitable for the present invention, are defined in the databases of the International Zeolite Association (IZA) (http://topaz.ethz.ch/IZA-SC/StdAtlas.htm).

The catalytic reactions described in the "Examples" of this application are carried out in batch operation in a conventional stainless steel Parr autoclave with a working volume of approximately 100 mL. The batch reactor is equipped with a temperature control system, a digital manometer, a four-bladed impeller, a gas inlet for nitrogen or hydrogen, and a liquid outlet tube. However, no limitations are implied on whether the catalytic reactions are carried out in batch, semi-continuous or continuous operation. In fact, it is believed by the Applicants that higher yields in C to C₆ polyols can be achieved when carrying out the catalytic process in a continuous mode.

The present catalytic process is essentially carried out in aqueous solvents containing the polysaccharides such as cellulose. Persons skilled in the art will recognize that the feedstock concentration is a key parameter. In a particular embodiment of the invention, the initial substrate concentration of the aqueous suspension varies between 1 and 100 wt%, preferably from 2 to 70 wt% and most preferably from 10 to 70 wt%.

During reaction the reactor content is continuously stirred at a stirring speed ranging from 100 to 800 rotations per minute (rpm) and more preferably from 200 to 700 rpm. In a particular embodiment, it is generally preferred that the catalytic process of this invention is carried out at a reaction temperature ranging from about 120 to about 270 °C, more preferably from about 150 to 250 °C, and most preferred from about 180 to 230 °C. It is to be understood that the catalytic process of the present invention is in no way restricted to commercial microcrystalline cellulose as a feedstock. Also lignocellulosic feedstock in the cell walls of plants, microbial cellulose and other forms of cellulose can be used. Structures and properties of different types of cellulose have been reviewed by KJemm et al. in "Cellulose: Fascinating Biopolymer and Sustainable Raw Material", Angewandte Chemie International Edition 44, 3358-3393 (2005).

Lignocellulosic feedstocks are the fibrous material that constitutes the cell walls of plants and that generally comprises three major components: cellulose, hemicellulose and lignin. Hemicellulose is covalently linked to lignin, which in turn can be cross-linked to other polysaccharides such as cellulose resulting in a matrix of lignocellulosic material. Lignin is a hydrophobic cross-linked aromatic polymer and one of the major constituents of the cell walls of plants representing about one-quarter to one-third of the dry mass of wood. Lignocellulosic materials or feedstock also includes biomaterials from crops or biowaste that comprise cellulose, hemicellulose and/or lignin, e.g., papermaking sludge; wood, and wood-related materials, e.g. saw dust, particle board or leaves; and natural fiber sources, e.g. trees such as poplar trees, grasses such as switchgrass, leaves, grass clippings, rice hulls, bagasse, jute, hemp, flax, bamboo, sisal, abaca, straw, corn cobs, corn stover, wheat straw, rice hulls, and coconut hair. Some of these materials include cellulose and a percentage of lignin, e.g., at least about 0.5 percent by weight to about 60 percent by weight or more lignin. Lignin can be thought of as a tri-dimensional polymer of propyl-phenol that is imbedded in and bound to the hemicellulose. Lignins can have significant structural variation that depends, at least in part, upon its source, e.g., whether it is derived from a softwood or a hardwood. Hemicellulose is a branched heteropolymer with a random, amorphous structure that includes a number of different sugar molecules such as xylose, glucose, mannose, galactose, rhamnose, and arabinose. Xylose is the most common sugar molecule present in hemicellulose. Xylose and arabinose are both pentosans, which are polymeric 5-carbon sugars present in plant material. Cellulose is a linear polymer of glucose, wherein the glucose residues are held together by β- glycosidic bonds. Cellulose can be produced by microbials, e.g. microbial cellulose is a form of cellulose that is produced by bacteria. For instance bacteria from the genera Aerobacter, Acetobacter, Achromobacter, Agrobacterium, Alacaligenes, Azotobacter, Pseudomonas, Rhizobium and Sarcina synthesize cellulose. The Acetobacter, e.g. A. xylinus or A. xylinum, is currently commercially used to produce microbial cellulose. For instance bacterial cellulose is obtainable at cost effective rates from Acetobactor xylinum C2 (Xue Lu et al. Shipin exue 2004 25 (1 1 ) 213-215, rstynowicz Alina et al. PL185337 (2003), Li Fei et al. Zhongguo Zaoshi (2009) 28 (3) 56-61 ).

In another embodiment according to the present invention the catalytic reaction does not require a cellulose feedstock, but can be another polysaccharide with β-glycoside linkages, such as chitin, chitosan, fructan or particular glucan. Chitin is made up of a long-chain polymer of N-acetylglucosamine groups. Chitosan is obtained by removing enough acetyl groups (CH3-CO) for the molecule to be soluble in most diluted acids. Chitosan can be recovered from microbial biomass, in particular fungal biomass, including yeast and filamentous fungi. Suitable microbial biomass can be obtained from Aspergillus niger, Aspergillus terreus, Aspergillus oryzae, Absidia butleri Candida guillermondii, Lactarius vellereus, Mucor rouxii, Penicillium chrysogenum, Penicillium notatum, Saccharomyces cerevisiae; and in particular Candida Guillermondii, Aspergillus niger, or Aspergillus terreus. It is possible to generate biomass solely for the purpose of obtaining chitosan. In case the biomass is a by-product of other production processes chitosan is extractable from the biomass. Fructan is a polymer made up of fructose molecules. Generally, there are 3 types of fructans: inulin, levan and graminan. Glucan is a polysaccharide of D-glucose monomers linked by glycosidic bonds In performing the invention microcrystalline cellulose can be pretreated by various means, including, but not limited to, mechanical ball-milling, acid pretreatments or steam pretreatments all of them with the intention to lower the crystallinity of the said polysaccharides such as cellulose. One such example describes the mechanical ball-milling technology, according to the method of Zhao et al. in Energy & Fuels 20, 807-81 1 (2006). Prior to the catalytic experiments, ball-milling is carried out for 24 h with 25 g of cellulose (Avicel PH-101 , microcrystalline) using zirconia balls in a zirconia bottle. Powder X-ray diffraction patterns of the cellulose samples are recorded at room temperature with a STOE STADI P Combi diffractometer. The diffracted intensity of Cu a radiation (wavelength of 0.154 nm) is measured in a 2Θ range between 0° and 60°. Figure 3 shows X-ray diffraction patterns for cellulose samples unmilled and ball-milled for 24 h. In the untreated cellulose, the major peak at 2Θ = 22.5° can be assigned to the crystalline plane 002. A comparison of the diffraction patterns reveals a decrease in crystallinity of cellulose after ball-milling. Infrared (IR) spectra were recorded under vacuum from Br pellets on a Bruker IFS 66v/S instrument. The spectra in Figure 4 also show the changes in the cellulose structure after ball-milling. In another aspect of the invention, the amount of catalyst to be charged in the reactor depends upon the concentration of the particular polysaccharide, the temperature and hydrogen pressure which are employed in the process. In a particular embodiment of the invention, catalyst concentrations range from 0.1 to 10 wt% based on the initial weight of cellulose.

In still another aspect of the invention, the cellulose conversion essentially runs in presence of hydrogen, with a hydrogen pressure preferably above 1 MPa (measured at room temperature). In the Examples of this application, the applicants typically carried out the catalytic process at hydrogen pressures as high as 6 MPa (measured at room temperature), although there is no intention to place any upper limit on the applied hydrogen pressure.

The optimal reaction time for the catalytic process according to the invention depends on the specific catalyst used, the amount of catalyst loaded in the reactor, the cellulose feed concentration, the hydrogen pressure and the applied reaction temperature. The preferred reaction time in the process condition of the Examples exists within a range from 0.5 to 48 hours, more preferably from 1 to 24 hours and most preferred from 4 to 24 hours.

The method of the present invention enables satisfactory conversion rates of the said polysaccharide and yields towards the formation of C₄ to C₆ polyols to be achieved using water as main solvent compound, without the need to add reagents for promoting or moderating the activity of the heterogeneous catalyst, nor to adapt the reactivity of the polysaccharide. This brings the advantage that the catalytic process is simple to apply and that, of course, there is no essential need to provide these reagents.

Upon completion of the catalytic reaction, the autoclave is immediately cooled to room temperature, brought to atmospheric pressure and opened to enable the reactor content to be discharged. The heterogeneous catalyst and an eventually remaining part of insoluble polysaccharides is removed by centrifugal separation, filtration or decantation. The produced alcohols can be separated from the filtrate by any suitable means, for example, crystallization or solvent extraction.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings forming a part of this disclosure, Fig. 1 is a plot of conversion vs. reaction time for cellulose conversion over a noble metal free Ni-based catalyst prepared according to the invention. Reaction conditions: microcrystalline cellulose 1 g, Ni-based catalyst 0.5 g, water 50 mL, initial H₂ pressure 6 MPa, 210 °C, 24 h, stainless steel Parr reactor ( 100 mL).

Fig. 2 is a plot of the yield in sorbitol, mannitol and erythritol vs. time for cellulose conversion over a noble metal free Ni-based catalyst prepared according to the invention. Reaction conditions: microcrystalline cellulose 1 g, Ni-based catalyst 0.5 g, water 50 mL, initial H₂ pressure 6 MPa, 210 °C, 24 h, stainless steel Parr reactor (100 mL).

Fig. 3 shows X-ray diffraction (XRD) patterns of untreated microcrystalline cellulose and cellulose after 24 h ball-milling pretreatment.

Fig. 4 shows infrared (IR) spectra of untreated microcrystalline cellulose and cellulose after 24 h ball-milling pretreatment.

EXAMPLES

Herein below, the present invention will be described in greater detail on the basis of the Examples 1 to 4 and Comparative Examples 1 and 2.

EXAMPLE I : PREPARATION OF A CATALYST ACCORDING TO THE INVENTION

A typical procedure of preparing a Ni-based catalyst according to the invention will be described below. A 20 wt% Νϊ/γ-Α1₂0₃ precursor was prepared via wet impregnation of 1 g γ- AI2O3 support (Puralox, 155 m²/g) with a 20 mL aqueous solution of Ni(N0₃)₂.6H₂0 (Alfa Aesar), subsequent drying overnight in an oven at 80 °C, calcination in a programmable muffle oven under static air at 600 °C (heating rate 5 °C/min) for 5 h, and then reduction under hydrogen at 600 °C for 1 h. Samples of 0.5 g of such catalyst precursor were then placed in a quartz reactor at 600 °C under methane gas with a flow rate of 80 mL/min for 3.5 h. The resulting catalyst has a nickel weight loading of 3.0 wt% and is denoted as Catalyst A.

EXAMPLE 2: CATALYTIC CELLULOSE CONVERSION There will now be shown and described by way of non-limiting example a catalytic process for producing C₄ to C₆ polyols from a microcrystalline cellulose feedstock. 1 g of untreated commercial cellulose (Sigma-Aldrich; microcrystalline Avicel PH- 101 ), 50 mL distilled water and 0.5 g of the Catalyst A described in Example 1 , were loaded in a 100 mL stainless steel Parr reactor. After closing and purging the reactor, it was pressurized with hydrogen to 6 MPa at room temperature, and heated to 210 °C for 24 h, while continuously stirring the reactor content with stirring vanes at 700 rpm. After cooling the reactor to room temperature, the product mixture was centrifuged, filtered over a 0.45 μπι Teflon (PTFE) filter and the filtrate was analyzed using high-performance liquid chromatography (HPLC, Agilent 1200 Series) and a refractive index detector (RID). A Metacarb 67C column (Varian, 300 x 6.5 mm) was used at 85 °C, with water as mobile phase at a flow rate of 0.5 mL/min. Cellulose feed conversions and product yields were calculated on a weight basis. At a cellulose conversion of 87%, the yield towards C₄ to C₆ polyols was 46%, of which sorbitol comprised 30% and mannitol 5%. Erythritol is produced with 10% yield. This Example thus demonstrates surprisingly high yields of C₄ to C_¾ polyols, when compared to non-noble metal based state- of-the-art catalysis, such as described in the Prior Art documents mentioned above.

EXAMPLE 3: PRETREATMENT OF CELLULOSE

The catalytic reaction is carried out under the same standard conditions as in Example 2, using Catalyst A prepared according to the procedure of Example 1. Prior to the catalytic reaction, the microcrystalline cellulose powder is pretreated with mechanical ball-milling. Figures 3 and 4 show the results of X-ray powder diffraction and the infrared (IR) experiments of the untreated and ball-milled cellulose. 1 g of the ball-milled cellulose sample, 50 mL water and 0.5 g of the catalyst described in Example 1 , were loaded in a 100 mL Pan- reactor. The reaction was carried out for 24 h at 190 °C and a hydrogen pressure of 6 MPa (measured at room temperature). At a cellulose conversion of 92%, C₄ to C₆ polyol yields of 70% were obtained, including yields of 50% sorbitol, 6% mannitol and 13% erythritol.

EXAMPLE 4: DIFFERENT NON-NOBLE TRANSITION METAL

The catalytic reaction is carried out under the same standard conditions as in Example 2. Catalyst B was prepared in the same manner as in Example 1 , except that the non-noble transition metal used was cobalt. At a cellulose conversion of 92%, C₄ to C₆ polyol yields of 32% were obtained, including 19% sorbitol, 3% mannitol and 10% erythritol.

EXAMPLE 5: HIGHER INITIAL CONCENTRATIONS

The catalytic reaction is carried out with Catalyst A prepared according to the procedure of Example 1. As in Example 2, the catalyst is tested under the same standard reaction conditions, except that the initial concentrations of cellulose and the catalyst were 5 times higher. At a cellulose conversion of 81%, C₄ to C₆ polyol yields of 43% were obtained, including 26% sorbitol, 5% mannitol and 9% erythritol.

COMPARATIVE EXAMPLE 1 : EFFECT OF NO PRETREATMENT

The catalytic reaction is carried out under the same standard conditions as in Example 2. The applied catalyst is a typical 3 wt% Ni impregnated on activated carbon (Sigma-Aldrich; Darco), which omitted the pretreatment in the organic gases at elevated temperatures such as described in Example 1. The reaction is carried out with the same amount of nickel in the reactor as in Example 2. A cellulose conversion of 81% is obtained with a C₄ to C₆ polyol yield of only 18%, which is considerably lower than the 46% yield obtained with Catalyst A.

COMPARATIVE EXAMPLE 2: EFFECT OF NON-ACIDIC SUPPORT

The catalytic reaction is carried out under the same standard conditions as in Example 2. Catalyst C was prepared in the same manner as in Example 1 , except that γ-Α1₂0₃ was substituted for a non-acidic support material, namely MgAl₂0₄. A cellulose conversion of 80% is obtained with a C₄ to C₆ polyol yield of 15%, which is considerably lower than the 46% yield obtained with Catalyst A prepared according to Example 1 and used in Example 2. This comparative example demonstrates the necessity of a solid support material with sufficient acidic functionalities.

The Examples here above serve to illustrate a convenient form of execution according to the invention. However, it is to be understood that the invention is in no way limited thereto. Some more embodiments of the invention are set forth hereunder. The present invention concerns a process for producing C₄ to C₆ polyol(s), which comprises reacting polysaccharide polymers composed of monosaccharides bound together by β- glycoside linkages under a hydrogen-containing gas in the presence of pretreated catalytic material. Said catalytic material comprises or consists of non-noble transition metal(s) and acid carrier(s), pretreated at elevated temperatures in an atmosphere of organic vapors, gases or other carbon containing sources or a process for producing C4 to C6 polyol(s). Such acidic carrier can for instance be alumina, silica, titania, zirconia, silica-alumina, silica-magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin. The polyol production process is characterized in that it can be a single-step catalytic process. It distinguishes from polyol producing processes in the art by its high C₄ to C₆ polyol yields. The process further can comprise (a) supplying a polymer feedstock which comprises the polysaccharide polymers containing β-glycoside functionalities, the catalytic material and an aqueous medium to a reaction zone; (b) operating said reaction zone under reaction conditions effective to convert at least a portion of said polysaccharide polymers to said C₄ to C₆ polyol(s). The process further can be characterized in that it comprises reacting polysaccharide polymers composed of monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of pretreated catalytic material and that it is a single-step catalytic process. The process consists of (a) supplying a polymer feedstock which comprises the polysaccharide polymers containing β-glycoside functionalities, the catalytic material and an aqueous medium to a reaction zone; (b) operating said reaction zone under reaction conditions effective to convert at least a portion of said polysaccharide polymers to said C₄ to C₆ polyol(s). Furthermore the reaction of the polysaccharide polymers with the catalytic material can be performed in an aqueous medium under a gaseous phase comprising hydrogen. Pretreatment of the catalysts material can comprise heating of the catalyst material in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C. These carbon sources can contain oxygen or oxygen containing compounds such as water, C0₂, CO or water and the like.

Prior to the above production process, the catalyst material is heated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C and preferably between 600 and 900 °C. The non-noble transition metal/acid carrier or support precursor can be prepared by impregnation of acid carrier or support with a solution of the non-noble transition metal. Typical non-noble transition metal for the catalyst of present invention are metals of the group consisting of iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other transition metals. The acidic carrier for present invention can be one of the following materials: alumina, silica, titania, zirconia, silica-alumina, silica-magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin. In a particular embodiment this catalyst precursor or support precursor is pretreated by calcination. Moreover in a particular embodiment this calcination temperature is in the range of 400 to 800° C. Prior to the process, catalyst material is heated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C, wherein the catalyst precursor is pretreated by the steps 1) drying, 2) calcination and 3) subjecting to a reduction reaction. In a particular embodiment such reduction is carried out under hydrogen at a temperature in the range of 400 to 800° C. In a specific embodiment the catalyst material is being pretreated before the production process by heating in an atmosphere of organic vapors, gases or other carbon containing sources.

The C4 to C6 polyol(s) production process of present invention can be further characterized in that the reaction zone is heated after pressurizing and in a particular embodiment the reaction conditions in said reaction zone include a temperature of 120 °C to 270 °C, preferably of 150 °C to 250 °C, yet more preferably a temperature of 180 °C to 230 °C. Furthermore the reaction in said reaction zone is carried out under mixing of the reaction medium. The feedstock for present invention is typically a polysaccharide polymer composed of monosaccharides bound together by β-glycoside linkages. The concentration of the feedstock in the aqueous reaction medium is between 1 to 100 wt, more preferably between 2 to 70 wt% and yet more preferably between 10 to 70 wt%. The process of present invention can be used for the production of C₄ to C₆ polyols of the group consisting of sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose. In one aspect of the invention, the invention concerns a process for producing C₄ to C₆ polyol(s), which process comprises reacting polysaccharide polymers having monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of catalytic material which comprises non-noble transition metal(s) and acid carrier(s) and which has been thermally pretreated in a carbon-containing atmosphere for instance by heating in an atmosphere of organic vapors, gases or other carbon containing sources. This carbon-containing atmosphere can further contain oxygen or oxygen containing compounds such as water, C02, CO and the like. Furthermore, the above process can be characterized in that the catalytic material consists of non-noble transition metal(s) and acid carrier(s) and the polysaccharide polymers are composed monosaccharides bound together by β-glycoside linkages. More specific to above-described embodiments the process is characterized in that prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C and preferably in the temperature region between 600 and 900 °C.

According to one aspect of the present invention, such process as described above is a single- step catalytic process.

A particular embodiment of present invention is a process for producing C4 to C6 polyol(s), which process comprises reacting polysaccharide polymers having monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of catalytic material, which consists of non-noble transition metal(s) and acid carrier(s), and which has for the catalytic process been pretreated by heating in an atmosphere of organic vapors, gases or other carbon containing sources. These carbon containing sources may further contain oxygen or oxygen containing compounds such as water, C02, CO and the like. Such catalytic process involving the pretreated catalytic material can be a single-step catalytic process. Furthermore such process can in a particular embodiment comprise (a) supplying at least 1) polymer feedstock which comprises the polysaccharide polymers containing β-glycoside functionalities, 2) the catalytic material and 3) an aqueous medium to a reaction zone; furthermore (b) operating said reaction zone under reaction conditions effective to convert at least a portion of said polysaccharide polymers to said C4 to C6 polyol(s). Furthermore the reaction zone can be an aqueous medium under a gaseous phase comprising hydrogen.

Further, prior to the catalytic process in the above-described embodiments, the catalyst material is for instance pretreated by heating in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C. Moreover, in the above-described embodiments on a catalytic process, prior to the catalytic process the catalyst material can be pretreated by calcinations or by calcination and reduction. A particular embodiment of pretreatment for the above described catalytic processes concerns pretreating of the catalyst precursor by the steps 1 ) drying, 2) calcination and 3) subjecting to a reduction reaction or the non-noble transition metal /acid carrier or the non-noble transition metal with support precursor obtained by impregnation of acid carrier or support with a solution of the non-noble transition metal. Such calcination temperature is in the range of 400 to 800° C. Such reduction can be carried out under hydrogen at a temperature in the range of 400 to 800° C.

Another aspect of the present invention is that in the above-described embodiments the reactor is pressurized with hydrogen at a pressure between 1 MPa to 30 MPa; preferably with hydrogen at a pressure between 3 MPa to 15 MPa and more preferably hydrogen at a pressure between 4 MPa to 8 MPa. Such reactor is then heated or heated after pressurizing. Furthermore, the reaction conditions in said reaction zone can include a temperature of 120 °C to 270 °C; preferably a temperature of 150 °C to 250 °C and more preferably a temperature of 180 °C to 230 °C. Moreover, in the process of any one of the previous embodiments the reaction conditions in said reaction zone can be under mixing of the reaction medium.

Further, in the above-described embodiments on a catalytic process, the polysaccharide polymer comprised in the feedstock can be a biopolymer, any polysaccharide polymer containing β-glycoside bonds. In other words the polymer comprised in the feedstock can be any of the following 1 ) a polymer of the group consisting of cellulose, hemicellulose and lignin, 2) any polysaccharide polymers of the group consisting of chitin and chitosan, 3) polysaccharide polymers of the group consisting of bacterial cell wall biopolymers or 4) polysaccharide polymers of the group consisting of fructan and glucan. Another aspect of present invention is an above embodied catalytic processwhereby in the pretreated catalytic material the non-noble transition metal is of the group consisting of iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other transition metals. Yet another aspect of present invention is an above embodied process whereby the acidic carrier is alumina, silica, titania, zirconia, silica- alumina, silica-magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like or various types of zeolites of natural or synthetic origin. According to yet another aspect of the present invention, the above embodied catalytic process is used for the production of C4 to C6 polyols of the group consisting of sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose. Further, the polysaccharide polymers composed of monosaccharides bound together by β- glycoside linkages described in the embodiments, can have an initial concentration of in the aqueous reaction medium between 1 to 100 wt%, preferably between 2 to 70 wt% and yet more preferably between 10 to 70 wt%. Another aspect of present invention is a single-step catalytic production method of C4 to C6 polyol(s), comprising 1 ) pretreating the catalytic material containing non-noble transition metal(s) and acid carrier(s) by heating said catalytic material in an atmosphere of organic vapors, gases or other carbon containing sources and 2) reacting polysaccharide polymers having monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of said pretreated catalytic material. Typically, for such single-step catalytic process with high yield production of C4 to C6 polyol(s), the catalyst material is pretreated in particular by preheating and in particular in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C or narrower. Such method can in a particular embodiment be characterized in that the catalyst material is pretreated by preheating in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 600 and 900 °C.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims can be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Claims

Catalytic process for the production of alcohols from biomass-related feedstock CLAIMS We claim:

1 . A process for producing C₄ to C₆ polyol(s), which process comprises reacting polysaccharide polymers having monosaccharides bound together by β-glycoside linkages under a hydrogen-containing gas in the presence of catalytic material, which comprises non- noble transition metal(s) and acid carrier(s), characterized in that this catalyst has been pretreated by heating in an atmosphere of organic vapors, gases or other carbon containing sources.

2. The process of claim 1 , characterized in that the catalytic material consists of non-noble transition metal(s) and acid carrier(s).

3. The process of any one of the previous claims 1 to 2, characterized in that prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C.

4. The process of any one of the previous claims 1 to 2, characterized in that prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 600 and 900 °C.

5. The process of any one of the claims 1 to 4, characterized in that prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources, which contain oxygen or oxygen containing compounds such as water, C0₂, CO and the like.

6. The process of any one of the claims 1 to 5, characterized in that it is a single-step catalytic process.

7. The process of any one of the previous claims, comprising (a) supplying a polymer feedstock which comprises the polysaccharide polymers containing β-glycoside functionalities, the catalytic material and an aqueous medium to a reaction zone; (b) operating said reaction zone under reaction conditions effective to convert at least a portion of said polysaccharide polymers to said C₄ to C₆ polyol(s).

8. The process of any one of the previous claims 6 to 7, wherein prior to the process, catalyst material is heated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C.

9. The process of any one of the previous claims 6 to 7, wherein prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 600 and 900 °C.

10. The process of any one of the previous claims 6 to 7, wherein prior to the process, catalyst material is preheated in the presence of organic vapors, gases or other carbon containing sources, which contain oxygen or oxygen containing compounds such as water, C0₂, CO and the like.

1 1. The process of any one of the previous claims, wherein said reaction in said reaction zone in (b) is carried out in an aqueous medium under a gaseous phase comprising hydrogen.

12. The process of any one of the claims 1 to 1 1 , whereby the non-noble transition metal/acid carrier or support precursor is prepared by impregnation of acid carrier or support with a solution of the non-noble transition metal.

13. The process of any one of the previous claims 1 to 12, wherein the catalyst precursor is pretreated by calcination.

14. The process of any one of the previous claims 1 to 12, wherein the catalyst precursor is pretreated by calcination and reduction.

15. The process of any one of the previous claims 1 to 12, wherein the catalyst precursor is pretreated by the steps 1 ) drying, 2) calcination and 3) subjecting to a reduction reaction.

16. The process of any one of the claims 13 to 15, wherein the calcination temperature is in the range of 400 to 800° C.

17. The process of any one of the claims 13 to 15, wherein the reduction is carried out under hydrogen at a temperature in the range of 400 to 800° C.

18. The process of any one of the previous claims, wherein said reaction zone in (b) is pressurized with hydrogen at a pressure between 1 MPa to 30 MPa.

19. The process of any one of the previous claims, wherein said reaction zone in (b) is pressurized with hydrogen at a pressure between 3 MPa to 15 MPa.

20. The process of any one of the previous claims, wherein said reaction zone in (b) is pressurized with hydrogen at a pressure between 4 MPa to 8 MPa.

21. The process of any one of the previous claims whereby the reaction zone is heated.

22. The process of any one of the previous claims whereby the reaction zone is heated after pressurizing.

23. The process of any one of the previous claims wherein said reaction conditions in said reaction zone in (b) include a temperature of 120 °C to 270 °C.

24. The process of any one of the previous claims wherein said reaction conditions in said reaction zone in (b) include a temperature of 150 °C to 250 °C.

25. The process of any one of the previous claims wherein said reaction conditions in said reaction zone in (b) include a temperature of 180 °C to 230 °C.

26. The process of any one of the previous claims wherein said reaction in (b) is performed under mixing of the reaction medium.

27. The process of any one of the previous claims wherein said the polysaccharide polymer in the feedstock is a biopolymer.

28. The process of any one of the previous claims wherein said the polymer in the feedstock comprises polysaccharide polymers containing β-glycoside bonds.

29. The process of any one of the previous claims wherein said the polymer in the feedstock comprises polysaccharide polymers of the group consisting of cellulose and hemicellulose.

30. The process of any one of the previous claims wherein said the polymer in the feedstock comprises polysaccharide polymers of the group consisting of chitin and chitosan.

31 . The process of any one of the previous claims wherein said the polymer in the feedstock comprises polysaccharide polymers of the group consisting of bacterial cell wall biopolymers.

32. The process of any one of the previous claims wherein said the polymer in the feedstock comprises polysaccharide polymers of the group consisting of fructan and glucan.

33. The process of any one of the previous claims wherein said the feedstock is lignocellulosic feedstock comprising a polysaccharide polymer of the group consisting of cellulose, hemicellulose and lignin.

34. The process of any one of the previous claims wherein said non-noble transition metal is of the group consisting of iron, cobalt, nickel, chromium, vanadium, molybdenum, and alloys or mixtures of said metals with each other and/or with other transition metals.

35. The process of any one of the previous claims wherein said the acidic carrier is alumina, silica, titania, zirconia, silica-alumina, silica-magnesia, silica-titania, all types of carbon materials, including amorphous carbon, templated carbon, graphite, functionalized amorphous and ordered porous carbon material and the like, and various types of zeolites of natural or synthetic origin.

36. The process of any one of the previous claims for the production of C₄ to C₆ polyols of the group consisting of sorbitol, mannitol, xylitol and erythritol, mixtures thereof and their partially dehydrated and/or dehydrogenated products such as sorbitan, isosorbide and sorbose.

37. The process of any one of the previous claims wherein said the catalyst material has been preheated.

38. The process of any one of the previous claims wherein said the initial concentration of the polysaccharide polymers composed of monosaccharides bound together by β-glycoside linkages in the aqueous reaction medium is between 1 to 100 wt%.

39. The process of any one of the previous claims wherein said the initial concentration of the polysaccharide polymers composed of monosaccharides bound together by β-glycoside linkages in the aqueous reaction medium is between 2 to 70 wt%.

40. The process of any one of the previous claims wherein said the initial concentration of the polysaccharide polymers composed of monosaccharides bound together by β-glycoside linkages in the aqueous reaction medium is between 10 to 70 wt%.

41 . A method of single-step catalytic production of C4 to C6 polyol(s), comprising:

(a) pretreating catalytic material containing non-noble transition metal(s) and acid carrier(s) by heating said catalytic material in an atmosphere of organic vapors, gases or other carbon containing sources; and

(b) reacting polysaccharide polymers having monosaccharides bound together by β- glycoside linkages under a hydrogen-containing gas in the presence of catalytic material.

42. The method of claim 41 , characterized in that the catalyst material is pretreated by preheating in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 400 and 1000 °C.

43. The method of claim 41 , characterized in that the catalyst material is pretreated by preheating in the presence of organic vapors, gases or other carbon containing sources in the temperature region between 600 and 900 °C.