EP2324132A1

EP2324132A1 - Process for the production of sugars from biomass

Info

Publication number: EP2324132A1
Application number: EP09804523A
Authority: EP
Inventors: Daniele Bianchi; Anna Maria Romano
Original assignee: Eni SpA
Current assignee: Eni SpA
Priority date: 2008-08-06
Filing date: 2009-08-03
Publication date: 2011-05-25
Also published as: UA105365C2; EA201100207A1; MX2011001387A; EA018491B1; BRPI0917585A2; ITMI20081477A1; WO2010015404A1; IT1391099B1

Abstract

Process for the production of sugars from biomass including at least one polysaccharide which comprises putting a biomass in contact with an aqueous solution of at least one organic acid selected from alkyl- or aryl- sulfonic acids having from C₇ to C₂₀ carbon atoms, preferably from C₉ to C₁₅ carbon atoms, or from halogenated carboxylic acids, at a temperature ranging from 80°C to 140°C, preferably from 100°C to 125°C. The sugars thus obtained can be advantageously used as carbon sources in fermentation processes for the production of alcohols (e.g., ethanol, butanol). Said alcohols can be advantageously used as automotive biofuels, or as components which can be added to automotive fuels.

Description

PROCESS FOR THE PRODUCTION OF SUGARS FROM BIOMASS

The present invention relates to a process for the production of sugars from biomasses comprising at least one polysaccharide . More specifically, the present invention relates to a process for the production of sugars from biomass including at least one polysaccharide which comprises the treatment of said biomass with an aqueous solution of at least one organic acid, at a temperature not higher than or equal to 140⁰C.

The sugars thus obtained can be advantageously used as carbon sources in fermentation processes for the production of alcohols (e.g., ethanol, butanol) . Said alcohols can be advantageously used as automotive biofuels, or as components which can be added to automotive fuels.

Generally speaking, a biomass is any substance with an organic, vegetable or animal matrix, which can be used for energy purposes, for example as raw material for the production of biofuels or of components which can be added to fuels. Biomass can therefore form a renewable energy source as an alternative to traditional raw materials of a fossil origin, normally used in the production of fuels. For this purpose, lignocellulosic biomass is particularly useful. The production of sugars from biomass, in particular lignocellulosic biomass, is known in the art.

A lignocellulosic biomass is a complex structure comprising three main components: cellulose, hemicellulose and lignin. Their relative quantities vary- according to the type of lignocellulosic biomass used. For example, in the case of plants, said quantities vary according to the species and age of the plant.

Cellulose is the greatest constituent of lignocellulosic biomass and is generally present in quantities ranging from 30% by weight to 60% by weight with respect to the total weight of the lignocellulosic biomass. Cellulose consists of glucose molecules (from about 500 to 10000 units) bound to each other through a β-1,4 glucoside bond. The establishment of hydrogen bonds between the chains causes the formation of crystalline domains which give resistance and elasticity to vegetable fibres. In nature, it can only be found in its pure state in annual plants such as cotton and flax, whereas in ligneous plants it is always accompanied by hemicellulose and lignin.

Hemicellulose which is generally present in a quantity ranging from 10% by weight to 40% by weight with respect to the total weight of the lignocellulosic biomass appears as a mixed polymer, relatively short (from 10 to 200 molecules) and branched, made up of both sugars with six carbon atoms (glucose, mannose, galactose) and sugars with five carbon atoms (xylose, arabinose) . Some important properties of vegetable fibres are due to the presence of hemicellulose, of which the main property is that of favouring the imbibition of said vegetable fibres, when water is present, causing their swelling. Hemicellulose also has adhesive properties and therefore tends to harden or develop a horny consistency, with the consequence that said vegetable fibres become rigid and are imbibed more slowly.

Lignin is generally present in a quantity ranging from 10% by weight to 30% by weight with respect to the total weight of the lignocellulosic biomass. Its main function consists in binding and cementing the various vegetable fibres with each other giving the plant compactness and resistance and also provides protection against insects, pathogen agents, lesions and ultraviolet light. It is mainly used as fuel but is also currently widely used in industry as a disperser, hardener, emulsifying agent, for plastic laminates, cartons and rubber products. It can also be chemically treated to produce aromatic compounds, such as vanillin, syringaldehyde, p-hydroxybenzaldehyde, which can be used in pharmaceutical chemistry, or in the cosmetic and food industry .

In order to optimize the transformation of lignocellulosic biomass into products for energy use, subjecting said biomass to a preliminary treatment is known, so as to separate the lignin and hydrolyze the cellulose and hemicellulose to simple sugars such as, for example, glucose and xylose, which can then be subjected to fermentation processes to produce alcohols .

The process normally used for the above purpose is acid hydrolysis, which can be carried out in the presence of strong acids diluted or concentrated. This process however has various drawbacks mainly due to the fact that in order to hydrolyze both of the polysaccharide components of the biomass, i.e. cellulose and hemicellulose, drastic conditions are required due to the high stability of the cellulose. The severity of the treatment, in particular the high temperatures normally used, leads to the formation of by-products deriving from the dehydration of the sugars and from the partial depolymerization of the lignin. These by-products, in particular furfural, hydroxymethylfurfural and phenolic compounds, act as growth inhibitors of the microorganisms normally used in the subsequent fermentation processes of the sugars to alcohols, causing a significant decrease in the efficiency and productivity of said processes .

Processes comprising a pre- treatment of the lignocellulosic biomass for overcoming the above drawbacks, are also known. American patent US 4,612,286 for example, describes a method for producing alcohol from biomass containing carbohydrates and lignin, which comprises the following steps: (a) grinding the biomass; (b) subjecting said biomass to acid hydrolysis, operating at a temperature, acid concentration and residence time which are sufficient for effecting the hydrolysis of the hemicellulose in the biomass in order to obtain the separation of the pentose and hexose sugars into a hydrolyzed product having a quantity of furfural which is insufficient for substantially inhibiting the growth of the microorganisms in the subsequent fermentation processes of said sugars, whereas the cellulose in said biomass substantially remains non-hydrolyzed. The acid hydrolysis is preferably carried out at a concentration of acid, preferably sulfuric acid, ranging from about 2% by volume to about 10% by volume, at a temperature of about 120⁰C or lower. The method described above is said to have the following advantages : use of minimum quantities of acid, formation of a high concentration of pentoses in the hydrolyzed product, production of alcohols without the need for energy deriving from sources outside the system.

American patent US 5,125,977 describes a two-step pre-hydrolysis process of a biomass including hemicellulose containing xylane, using diluted acid, preferably sulfuric acid, in a quantity ranging from 0.1% by weight to 2.0% by weight. Said process comprises: treating a hemicellulosic material including xylane which can be slowly hydrolyzed and xylane which can be quickly hydrolyzed with a diluted acid, for a time sufficient for hydrolyzing said xylane which can be quickly hydrolyzed to xylose, at a temperature ranging from about 90⁰C to about 180⁰C, removing said xylose and leaving a residue comprising xylane which can be slowly hydrolyzed; treating said residue with a diluted acid, for a time sufficient for hydrolyzing said xylane which can be slowly hydrolyzed to xylose, at a temperature ranging from about 160⁰C to about 220⁰C; separating said xylose obtaining over 90% of hydrolysis of the xylane. The process described above is said to allow a high hydrolysis of the xylane to xylose avoiding the formation of high quantities of furfural and other by-products which are toxic for the yeasts used in the subsequent fermentations and which cannot be converted into ethanol . American patent US 6,228,177 describes a multifunctional process for the hydrolysis and fractionation of a lignocellulosic biomass in order to separate, from said biomass : the hemicellulosic sugars from other components of the biomass including extracts and proteins; a part of solubilized lignin; cellulose,- glucose deriving from cellulose; and insoluble lignin. Said process comprises: (a) introducing solid fresh biomass or partially fractionated lignocellulosic biomass, said biomasses englobing acid or water, into a reactor and heating to a temperature of up to about 185°C-205°C; (b) allowing the reaction to proceed until about 60% by weight of the hemicellulose has been hydrolyzed in the case of water, or until the complete dissolution in the case of acid; (c) adding a diluted acid, operating at a pH lower than about 5, at a temperature of up to about 205⁰C, for a time ranging from about 5 minutes to about 10 minutes, thus hydrolyzing the remaining hemicellulose (40% by weight) in the case of water; (d) cooling the reaction to a temperature of about 140⁰C; (e) introducing into said reactor and removing, simultaneously, a volumetric flow-rate of diluted acid, operating at a temperature of up to about 14O⁰C, in order to eliminate most of the solubilized components of the biomass, in order to obtain an improved yield of hemicellulosic sugar. The diluted acid used in steps (c) and (e) is preferably sulfuric acid. Said acid is preferably used at a concentration of 0.15% by weight in step (c) and at a concentration of 0.007% by weight in step (e) . The process described above is said to allow a high yield to sugars.

American patent US 5,338,366 describes a method for the acid pre-hydrolysis of a biomass, said method being effected in a single step, which allows the hydrolysis of the hemicellulose to obtain sugars with five carbon atoms, comprising the following steps, said steps being carried out automatically, in continuous and in sequence:

(a) mixing the biomass which contains hemicellulose with a mineral acid solution at a concentration sufficient for hydrolyzing said hemicellulose and for forming a slurry having a consistency which ensures adequate wetting of the biomass with said mineral acid; (b) dehydrating the slurry in order to minimize the quantity of vapour required for heating the biomass to the reaction temperature and maintain the desired concentration of sugars in said slurry after pre-hydroIysis; (c) heating the dehydrated slurry to the reaction temperature, at superatmospheric pressure, by means of direct contact with the vapour; and (d) maintaining the biomass in the dehydrated slurry at the reaction temperature and under pressure conditions for a time which is sufficient for hydrolyzing the hemicellulose of the biomass, but avoiding the hydrolysis of the cellulose, so that sugars with five carbon atoms are mainly produced. The mineral acid is preferably selected from sulfuric acid, hydrochloric acid, or nitric acid, and the hydrolysis temperature ranges from about 120⁰C to about 176°C. The process described above is said to be simple and particularly effective in the pre-hydrolysis of hemicellulose . American patent US 5,424,417 describes a process for pre-hydrolyzing a lignocellulosic material in order to separate a higher percentage of hemicellulose and at least 20% of lignin so as to obtain a more purified cellulose, which comprises: introducing the lignocellulosic material into a pre-hydrolysis reactor; pre-hydrolyzing said lignocellulosic material at a temperature ranging from about 90⁰C to about 240⁰C, passing a diluted acid to obtain a pH ranging from about 1.0 to about 5.5 in said reactor and through said lignocellulosic material and removing said diluted acid from the reactor in order to obtain a pre-hydrolyzed product in solution; recovering said pre-hydrolyzed product in solution; and removing the solid material including at least 20% of the lignin present in said lignocellulosic material from said pre-hydrolysis reactor at the temperatures used during the pre-hydrolysis . The diluted acid is preferably sulfuric acid. The process described above is said to be capable of giving a better extraction of both lignin and hemicellulose, simultaneously and in the same reactor, operating however under less severe conditions of pH, temperature and times with respect to conventional pre-hydrolysis processes.

The American patent US 7,198,925 describes a method for the conversion of a lignocellulosic material to glucose comprising the following steps: (a) transporting one or more bales of lignocellulosic material to a pre- treatment reactor; (b) adding vapour and acid to the reactor, operating at a temperature, at a concentration of acid and for a time sufficient for hydrolyzing the hemicellulose to xylose and increasing the disposition of the cellulose for enzymatic digestion with cellulase, in order to obtain a pre- treated lignocellulosic material; (c) depressurizing the pre-treatment reactor; (d) removing the pre-treated lignocellulosic material from the pre-treatment reactor; and (e) hydrolyzing the pre- treated lignocellulosic material with cellulase to obtain glucose. The acid used is preferably selected from sulfuric acid, sulfurous acid, sulfur dioxide, and the hydrolysis temperature ranges from about 140⁰C to about 28O⁰C. The method described above is said to be simpler and less costly with respect to the known methods allowing bales of lignocellulosic material to be treated directly.

The American patent US 4,237,226 describes a process for the pre- treatment of a cellulosic material, which comprises: preparing a slurry of the cellulosic material; adding an acid to said slurry as catalyst; heating said slurry to a reaction temperature which is such that the cellulose structure of the cellulosic material is modified by interaction with the acid to a form which is much more suitable for hydrolysis with respect to the non- treated cellulosic material; maintaining said slurry with the acid at said reaction temperature for a period of time which is sufficient for allowing the modification of most of the cellulosic material to said form, said period of time, however, being brief enough to prevent the formation of significant quantities of glucose from the cellulosic material and/or a significant re- crystallization of the cellulose structure; and cooling said slurry so as to make the reaction between the acid and cellulosic material thus modified, irrelevant. The acid is preferably sulfuric acid and the hydrolysis temperature ranges from about 180⁰C to about 230⁰C. The process described above is said to shorten the hydrolysis times and increase the yield of sugars. The American patent US 5,916,780 describes an improved process for the pre-treatment of a lignocellulosic material which must be converted to ethanol to be used as fuel, which essentially comprises the following steps: (a) selecting a material comprising at least hemicellulose and at least cellulose, said material being characterized by a ratio of arabinan plus xylan/total polysaccharides not containing starch

(AX/NSP) which is greater than 0.39; and (b) reacting the lignocellulosic material under such conditions as to obtain the hydrolysis of a part of the hemicellulose and cellulose, so as to obtain a pre- treated lignocellulosic material more easily accessible to enzymatic digestion with cellulase. Said acid is preferably sulfuric acid and the hydrolysis temperature ranges from about 180⁰C to about 270⁰C. The process described above is said to produce a higher quantity of glucose using less cellulase with respect to the known processes.

The processes described above however can have various drawbacks.

When inorganic acids (e.g. sulfuric acid) are used, for example, at the end of the acid hydrolysis, an aqueous phase is obtained including pentose and hexose sugars deriving from the hydrolysis of hemicellulose having an acid pH: said aqueous phase must therefore be subjected to neutralization by the addition, for example, of calcium oxide, calcium hydroxide, or barium hydroxide, with the consequent formation of salts (e.g. calcium sulfate, calcium sulfate dihydrate (gypsum) , barium sulfate) which precipitate and must therefore be separated from said phase before the same is subjected to the fermentation processes mentioned above. It is consequently impossible to recover and re-use said inorganic acid. Furthermore, the salts produced must be subsequently disposed of by suitable treatment with a consequent increase in the production costs.

Furthermore, if the acid hydrolysis is carried out at high temperatures, for example higher than 140⁰C, reaction by-products can be formed such as, for example, furfural, hydroxymethylfurfural, phenol compounds which, as mentioned above, act as growth inhibitors of the microorganisms normally used in the subsequent fermentation processes of the sugars .

If, on the contrary, the acid hydrolysis is carried out at low temperatures, for example lower than 140⁰C, a poor destructuring of the lignocellulosic biomass can be obtained, said destructuring being necessary for freeing the cellulose fibres from the lignin lattice which is covering them to allow them to be advantageously used in the subsequent enzymatic hydrolysis step. It is in fact difficult for the enzymes normally used (for example, cellulase) in the enzymatic hydrolysis to reach the cellulose fibres covered by lignin.

The Applicant has now found that the production of sugars from biomass, in particular from biomass including at least one polysaccharide, can be advantageously effected by means of a process which comprises the treatment of said biomass with an aqueous solution of at least one organic acid, at a temperature not higher than or equal to 140⁰C.

Numerous advantages are obtained with this process. This process, for example, allows to obtain a high yield of sugars pentose and hexose, deriving from the acid hydrolysis of said biomass, which can be subsequently used as carbon source in fermentation processes for the production of alcohols (e.g., ethanol, butanol) . Said alcohols can be advantageously used as automotive biofuels, or as components which can be added to automotive fuels . Furthermore, the possibility of operating at a temperature which is not high, i.e. at a temperature lower than or equal to 140⁰C, allows to reduce the formation of by-products such as for example, furfural, hydroxymethy1furfural, phenol compounds which, as specified above, act as growth inhibitors of the micro- organisms normally used in the subsequent fermentation processes of the sugars .

Another important advantage lies in the fact that this process allows to recover the organic acid which can therefore be recycled to the above process. This recovery also allows to avoid neutralization and, therefore, the production of salts and their subsequent disposal.

An object of the present invention therefore relates to a process for the production of sugars from biomass including at least one polysaccharide which comprises putting a biomass in contact with an aqueous solution of at least one organic acid selected from alkyl- or aryl-sulfonic acids having from C₇ to C₂o carbon atoms, preferably from C₉ to Ci₅ carbon atoms, or from halogenated carboxylic acids, at a temperature ranging from 80⁰C to 140⁰C, preferably from 100⁰C to 125°C.

For the purpose of the present invention and of the following claims, the definitions of the numerical ranges always comprise the extremes unless otherwise specified. According to one preferred embodiment of the present invention, said polysaccharide can be selected from cellulose, hemicellulose, or mixtures thereof. Hemicellulose, or mixtures of hemicellulose and cellulose, are particularly preferred. According to a further preferred embodiment of the present invention, said biomass is a lignocellulosic biomass. As already mentioned, the lignocellulosic biomass comprises three components: hemicellulose, cellulose and lignin. Said lignocellulosic biomass is preferably selected from:

- products of cultures expressly cultivated for energy use (for example, miscanthus, millet and common cane), including by-products, residues and wastes of said cultures or of their processing;

- products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and by-products of agricultural, of forestation and of silviculture processing; - agri-foodstuffs by-products intended for human feeding or zootechnics;

- residues, not subjected to chemical treatment, from paper industry;

- waste products coming from the separated collection of solid urban waste (e.g., urban waste of a vegetable origin, paper) .

According to one preferred embodiment of the present invention, said biomass can be subjected to a preliminary grinding process before being put in contact with said aqueous solution of at least one organic acid. Said biomass is preferably ground until particles having a diameter ranging from 0.1 mm to 10 mm, more preferably from 0.5 mm to 4 mm, are obtained. Particles having a diameter of less than 1 mm are particularly preferred. According to one preferred embodiment of the present invention, said biomass is present in the reaction mixture in a quantity ranging from 5% by weight to 40% by weight, preferably from 20% by weight to 35% by weight, with respect to the total weight of the reaction mixture. For the purpose of the present invention and of the following claims, the term "reaction mixture" refers to the mixture comprising the biomass and the aqueous solution of at least one organic acid, said reaction mixture being obtained by putting said biomass in contact with said aqueous solution.

According to one preferred embodiment of the present invention, said at least one organic acid is soluble in water and can be extracted with an organic solvent insoluble in water. For the purpose of the present invention and of the following claims, the term "organic acid soluble in water" refers to an organic acid which has a solubility in distilled water, at 25⁰C, of at least 0.5 g/100 ml of distilled water, preferably of at least 2 g/100 ml of distilled water. For the purpose of the present invention and of the following claims, the term "organic acid which can be extracted with an organic solvent insoluble in water" refers to an organic acid which can be extracted with an organic solvent insoluble in water with a yield of at least 80%, preferably of at least 90%, said yield being calculated with respect to the total quantity of organic acid present in the aqueous solution.

For the purpose of the present invention and of the following claims, the term "organic solvent insoluble in water" refers to an organic solvent which has a solubility in distilled water, at 25°C, lower than 4% by volume, preferably lower than 2% by volume.

According to one preferred embodiment of the present invention, said alkyl- or aryl-sulfonic acids can be selected from: dodecyl- sulfonic acid, para-toluene- sulfonic acid, 1-naphthalene-sulfonic acid, 2- naphthalene- sulfonic acid, 1, 5-naphthalene-disulfonic acid, or mixtures thereof. Para-toluene-sulfonic acid, 2- naphthalene-sulfonic acid, 1, 5-naphthalene-disulfonic acid, or mixtures thereof, are particularly preferred.

According to one preferred embodiment of the present invention, said halogenated carboxylic acids can be selected from those having a number of carbon atoms not higher than 20, preferably ranging from 2 to 15, such as, for example, trifluoroacetic acid, dichloroacetic acid, trichloroacetic acid, perfluoro-octanoic acid, or mixtures thereof .

According to one preferred embodiment of the present invention, said at least one organic acid is present in the aqueous solution at a concentration ranging from 0.1% by weight to 5% by weight, preferably from 0.5% by weight to 2% by weight, with respect to the total weight of the aqueous solution. Said organic acid acts as catalyst by acid hydrolysis of said biomass. In particular, when the starting biomass is a lignocellulosic biomass, said organic acid specifically acts as catalyst for the acid hydrolysis of the hemicellulose . It should be noted that the process object of the present invention, when the starting biomass is a lignocellulosic biomass, not only allows the acid hydrolysis of the hemicellulose to be obtained, but also improves the disposition of the cellulose, said cellulose remaining substantially non- hydrolyzed, for the subsequent enzymatic hydrolysis, thanks to an improved destructuring of the starting biomass .

According to one preferred embodiment of the present invention, said biomass is put in contact with said aqueous solution for a time ranging from 20 minutes to 6 hours, preferably from 30 minutes to 3 hours.

Said biomass is put in contact with said aqueous solution in reactors known in the art, such as, for example, autoclaves, or extruders. According to one preferred embodiment of the present invention, said process also comprises obtaining a first solid phase and a first aqueous phase.

According to a further preferred embodiment of the present invention, said first solid phase comprises lignin and cellulose.

According to one preferred embodiment of the present invention, said first aqueous phase comprises at least one sugar having from C₅ to C₆ carbon atoms and said at least one organic acid. Said at least one organic acid is the organic acid which is put in contact with the biomass. Said sugar is preferably xylose. Said xylose derives from the acid hydrolysis of the hemicellulose .

Said phases can be separated by means of techniques known in the art such as, for example, filtration, centrifugation. Said phases are preferably separated by filtration.

According to one preferred embodiment of the present invention, said first aqueous phase is subjected to extraction with an organic solvent insoluble in water. Said organic solvent insoluble in water is preferably selected from: halogenated hydrocarbons such as, for example, methylene chloride, monochlorobenzene, dichlorobenzene, or mixtures thereof; aromatic hydrocarbons such as, for example, toluene, xylene, or mixtures thereof. Methylene chloride, or toluene are particularly preferred.

Said organic solvent insoluble in water is subsequently evaporated, obtaining a second solid phase comprising said at least one organic acid (i.e. the organic acid which is put in contact with the biomass) and a second aqueous phase comprising said sugar having from C₅ to C₆ carbon atoms .

As specified above, the process, object of the present invention, therefore allows to recover the organic acid which is put in contact with the biomass with a high yield, i.e. with a yield of at least 80%, preferably of at least 90%, said yield being calculated with respect to the total quantity of organic acid which is put in contact with the biomass. Said organic acid can therefore be subsequently re-used according to the process object of the present invention.

According to one preferred embodiment of the present invention, said process also comprises re-using said at least one organic acid. Said second aqueous phase comprising at least one sugar having from C₅ to C_s carbon atoms, can be directly- used in fermentation processes for the production of alcohols (e.g., ethanol, butanol) . Said alcohols can be advantageously used as automotive biofuels, or as components which can be added to automotive fuels.

The process object of the present invention also allows to obtain at least one sugar having from C₅ to C₆ carbon atoms, in particular xylose deriving from the acid hydrolysis of hemicellulose, with a high yield. More in particular, said process allows to obtain a yield of xylose higher than or equal to 80%, said yield being calculated with respect to the total quantity of xylose present in the starting biomass.

The process object of the present invention, also allows high yields of cellulose and lignin to be obtained.

Said first solid phase comprising cellulose and lignin, obtained according to the process object of the present invention, can be used directly in an enzymatic hydrolysis process, in order to hydrolyze the cellulose to glucose. The glucose yield obtained operating in accordance with the process of the present invention is higher than or equal to 90%, said yield being calculated with respect to the total quantity of glucose present in the starting biomass. The quantity of sugars contained in the starting biomass so as the quantity of sugars obtained after hydrolysis (acid or enzymatic hydrolysis) , can be determined by means of techniques known in the art such as, for example High Performance Liquid Chromatography (HPLC) .

The enzymatic hydrolysis process can be carried out according to techniques known in the art as described, for example in American patents US 5,628,830, US 5,916,780 e US 6,090,595, using commercial enzymes such as for example, Celluclast 1.5L (Novozymes) , Econase CE (Rohm Enzymes) , Spezyme (Genecor) , Novozym 188 (Novozymes), used individually or mixed with each other.

A third solid phase comprising lignin and a third aqueous phase comprising glucose which derives from the hydrolysis of cellulose, are obtained from the enzymatic hydrolysis of said first solid phase.

Said third solid phase and said third liquid phase can be separated by means of techniques known in the art such as, for example, filtration, centrifugation. Said phases are preferably separated by filtration.

Said third aqueous phase comprising glucose, can be directly used as raw material in fermentation processes for the production of alcohols (e.g., ethanol, butanol) . Said alcohols can be advantageously used as automotive biofuels, or as components which can be added to automotive fuels.

Said third solid phase comprising lignin can be upgraded as fuel, for example as fuel for producing the energy necessary for sustaining the treatment processes of the biomass.

Some illustrative and non- limiting examples are provided for a better understanding of the present invention and for its embodiment. EXAMPLE 1

30 g of conifer wood previously ground (particle diameter < 1 mm) were added to a solution of 1 g of 2- naphthalenesulfonic acid in 100 ml of water. The reaction mixture thus obtained was kept under stirring in an autoclave, at 120⁰C₇ for 1 hour, obtaining a first solid phase and a first aqueous phase.

After cooling the autoclave to room temperature (23°C) , said phases were separated by filtration.

Said first solid phase comprised 22.44 g (dry weight) of destructured biomass having the following composition:

14.7 g (dry weight) of cellulose (66% by weight of cellulose with respect to the total weight of said first solid phase) and 7.5 g (dry weight) of lignin (33% by weight of lignin with respect to the total weight of said first solid phase) . The composition of the starting biomass was the following: 50% by weight of cellulose, 25% by weight of hemicellulose, 25% by weight of lignin, with respect to the total weight of the starting biomass. Said first aqueous phase was subjected to extraction with 300 ml of methylene chloride. The methylene chloride was subsequently evaporated, at reduced pressure, obtaining a second aqueous phase and a second solid phase which were separated by filtration.

Said second solid phase comprised 0.96 g (dry weight) of 2-naphthalene-sulfonic acid (recovery yield of 96% calculated with respect to the total quantity of acid present in the aqueous solution) .

Said second aqueous phase had a pH equal to 6 and included xylose (yield of 90.6%, calculated with respect to the quantity of xylose present in the starting biomass) . EXAMPLE 2

30 g of conifer wood previously ground (particle diameter < 1 mm) were added to a solution of 1 g of para- toluene-sulfonic acid in 100 ml of water. The reaction mixture thus obtained was kept under stirring in an autoclave, at 120⁰C, for 1 hour, obtaining a first solid phase and a first aqueous phase.

After cooling the autoclave to room temperature (23°C) , said phases were separated by filtration. Said first solid phase comprised 22.17 g (dry weight) of destructured biomass having the following composition: 14.4 g (dry weight) of cellulose (65% by weight of cellulose with respect to the total weight of said first solid phase) and 7.5 g (dry weight) of lignin (34% by weight of lignin with respect to the total weight of said first solid phase) . The composition of the starting biomass was the following: 50% by weight of cellulose, 25% by weight of hemicellulose, 25% by weight of lignin, with respect to the total weight of the starting biomass. Said first aqueous phase was subjected to extraction with 300 ml of methylene chloride. The methylene chloride was subsequently evaporated, at reduced pressure, obtaining a second aqueous phase and a second solid phase which were separated by filtration.

Said second solid phase comprised 0.85 g (dry weight) of para- toluene-sulfonic acid (recovery yield of 85% calculated with respect to the total quantity of acid present in the aqueous solution) . Said second aqueous phase had a pH equal to 6 and included xylose (yield of 89%, calculated with respect to the quantity of xylose present in the starting biomass) . EXAMPLE 3

30 g of conifer wood previously ground (particle diameter < 1 mm) were added to a solution of 1 g of 1,5- naphthalene-disulfonic acid in 100 ml of water. The reaction mixture thus obtained was kept under stirring in an autoclave, at 120⁰C, for 1 hour, obtaining a first solid phase and a first aqueous phase. After cooling the autoclave to room temperature (23⁰C) , said phases were separated by filtration.

Said first solid phase comprised 23.25 g (dry weight) of destructured biomass having the following composition: 14.7 g (dry weight) of cellulose (63% by weight of cellulose with respect to the total weight of said first solid phase) and 7.5 g (dry weight) of lignin (32% by weight of lignin with respect to the total weight of said first solid phase) . The composition of the starting biomass was the following: 50% by weight of cellulose, 25% by weight of hemicellulose, 25% by weight of lignin, with respect to the total weight of the starting biomass.

Said first aqueous phase was subjected to extraction with 300 ml of methylene chloride. The methylene chloride was subsequently evaporated, at reduced pressure, obtaining a second aqueous phase and a second solid phase which were separated by filtration.

Said second solid phase comprised 0.90 g (dry weight) of 1, 5-naphthalene-disulfonic acid (recovery yield of 90% calculated with respect to the total quantity of acid present in the aqueous solution) . Said second aqueous phase had a pH equal to 6 and included xylose (yield of 81%, calculated with respect to the quantity of xylose present in the starting biomass) . EXAMPLE 4 5 g (dry weight) of destructured biomass obtained operating as described in Example 1 (containing 3.3 g (dry weight) of cellulose) , were suspended in 100 ml of acetate buffer at pH 5. An aqueous solution of the enzyme Celluclast 1,5L (Novozymes) corresponding to 33 FPU (Filter Paper Units) and the enzyme Novozym 188

(Novozymes) corresponding to 400 BGU (Beta Glucanase

Units) was subsequently added. The suspension thus obtained was kept under stirring, at 45⁰C, for 72 hours.

At the end of the reaction, 1.7 g (dry weight) of insoluble residue were separated, by filtration, comprising lignin (yield of 97% calculated with respect to the quantity of lignin present in the starting biomass) .

The remaining aqueous solution contained glucose (yield of 94% calculated with respect to the quantity of glucose present in the starting biomass) . EXAMPLE 5

5 g (dry weight) of destructured biomass obtained operating as described in Example 2 (containing 3.3 g (dry weight) of cellulose) , were suspended in 100 ml of acetate buffer at pH 5. An aqueous solution of the enzyme Celluclast 1,5L (Novozymes) corresponding to 33 FPU (Filter Paper Units) and the enzyme Novozym 188 (Novozymes) corresponding to 400 BGU (Beta Glucanase Units) was subsequently added. The suspension thus obtained was kept under stirring, at 45°C, for 72 hours.

At the end of the reaction, 1.9 g (dry weight) of insoluble residue were separated, by filtration, comprising lignin (yield of 90% calculated with respect to the quantity of lignin present in the starting biomass) .

The remaining aqueous solution contained glucose (yield of 90% calculated with respect to the quantity of glucose present in the starting biomass) .

Claims

1. A process for the production of sugars from biomass including at least one polysaccharide which comprises putting a biomass in contact with an aqueous solution of at least one organic acid selected from alkyl- or aryl- sulfonic acids having from C₇ to C₂₀ carbon atoms, or from halogenated carboxylic acids, at a temperature ranging from 80 to 140⁰C.

2. The process according to claim 1, wherein said alkyl- or aryl sulfonic acids have from C₉ to Ci₅ carbon atoms .

3. The process according to claim 1 or 2, wherein said temperature ranges from 100⁰C to 125°C.

4. The process according to any of the previous claims, wherein said polysaccharide is selected from cellulose, hemicellulose, or mixtures thereof.

5. The process according to claim 4, wherein said polysaccharide is selected from hemicellulose, or mixtures of hemicellulose and cellulose.

6. The process according to any of the previous claims, wherein said biomass is a lignocellulosic biomass.

7. The process according to claim 6, wherein said lignocellulosic biomass is selected from: - products of cultures expressly cultivated for energy use (for example, miscanthus, millet and common cane) , including by-products, residues and wastes of said cultures or of their processing; - products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and by-products of agricultural, of forestation and of silviculture processing; - agri-foodstuffs by-products intended for human feeding or zootechnics; residues, not subjected to chemical treatment, from paper industry; waste products coming from the separated collection of solid urban waste (e.g., urban waste of a vegetable origin, paper) .

8. The process according to any of the previous claims, wherein said biomass is subjected to a preliminary grinding process before being put in contact with said aqueous solution of at least one organic acid.

9. The process according to claim 8, wherein said biomass is ground until particles having a diameter ranging from 0.1 mm to 10 mm are obtained.

10. The process according to claim 9, wherein said biomass is ground until particles having a diameter ranging from 0.5 mm to 4 mm are obtained.

11. The process according to claim 10, wherein said biomass is ground until particles having a diameter of less than 1 mm are obtained.

12. The process according to any of the previous claims, wherein said biomass is present in the reaction mixture in a quantity ranging from 5% by weight to 40% by weight with respect to the total weight of the reaction mixture.

13. The process according to claim 12, wherein said biomass is present in the reaction mixture in a quantity ranging from 20% by weight to 35% by weight with respect to the total weight of the reaction mixture .

14. The process according to any of the previous claims, wherein said at least one organic acid is soluble in water and can be extracted by means of an organic solvent insoluble in water.

15. The process according to any of the previous claims, wherein said alkyl- or aryl-sulfonic acids are selected from: dodecyl-sulfonic acid, para-toluene- sulfonic acid, 1-naphthalene-sulfonic acid, 2- naphthalene- sulfonic acid, 1, 5 -naphthalene- disulfonic acid, or mixtures thereof.

16. The process according to claim 15, wherein said at least one organic acid is selected from para- toluene-sulfonic acid, 2-naphthalene-sulfonic acid, 1, 5-naphthalene-disulfonic acid, or mixtures thereof .

17. The process according to any of the previous claims, wherein said halogenated carboxylic acids are selected from those having a number of carbon atoms not higher than 20 such as trifluoroacetic acid, dichloroacetic acid, trichloroacetic acid, perfluoro-octanoic acid, or mixtures thereof.

18. The process according to any of the previous claims, wherein said at least one organic acid is present in the aqueous solution at a concentration ranging from 0.1% by weight to 5% by weight with respect to the total weight of the aqueous solution.

19. The process according to claim 18, wherein said at least one organic acid is present in the aqueous solution at a concentration ranging from 0.5% by weight to 2% by weight with respect to the total weight of the aqueous solution.

20. The process according to any of the previous claims, wherein said biomass is put in contact with said aqueous solution for a time ranging from 20 minutes to 6 hours .

21. The process according to claim 20, wherein said biomass is put in contact with said aqueous solution for a time ranging from 30 minutes to 3 hours.

22. The process according to any of the previous claims, wherein said process comprises obtaining a first solid phase and a first aqueous phase.

23. The process according to claim 22, wherein said first solid phase comprises lignin and cellulose.

24. The process according to claim 22 or 23, wherein said first aqueous phase comprises at least one sugar having from C₅ to C₆ carbon atoms and said at least one organic acid.

25. The process according to claim 24, wherein said at least one organic acid is the organic acid which is put in contact with the biomass .

26. The process according to claim 24 or 25, wherein said sugar is xylose.

27. The process according to any of the claims from 22 to 26, wherein said first aqueous phase is subjected to extraction with an organic solvent insoluble in water.

28. The process according to claim 27, wherein said organic solvent insoluble in water is selected from: halogenated hydrocarbons such as methylene chloride, monochlorobenzene, dichlorobenzene, or mixtures thereof; aromatic hydrocarbons such as toluene, xylene, or mixtures thereof.

29. The process according to claim 28, wherein said organic solvent insoluble in water is selected from methylene chloride, or toluene.

30. The process according to any of the claims from 27 to 29, wherein said organic solvent insoluble in water is evaporated, obtaining a second solid phase, comprising said at least one organic acid, and a second aqueous phase comprising said sugar having from C₅ to C₆ carbon atoms.

31. The process according to any of the previous claims, wherein said process comprises re-using said at least one organic acid.

32. The process according to claim 30, wherein said second aqueous phase comprising at least one sugar having from C₅ to C₆ carbon atoms, is directly used in fermentation processes for the production of alcohols .

33. The process according to claim 23, wherein said first solid phase is directly used in an enzymatic hydrolysis process, for the purpose of hydrolyzing cellulose to glucose.

34. The process according to claim 33, wherein, from the enzymatic hydrolysis of said first solid phase, a third solid phase comprising lignin and a third aqueous phase comprising glucose which derives from the hydrolysis of cellulose, are obtained.

35. The process according to claim 34, wherein said third aqueous phase is directly used as raw material in fermentation processes for the production of alcohols.

36. Automotive biofuels obtained by means of the process according to any of the previous claims .

37. Components which can be added to automotive fuels obtained by means of the process according to any of the previous claims .