PRODUCTION THEREOF

FIELD OF THE INVENTION

The present invention relates to novel viscous carbohydrate compositions, to methods for the production thereof, and to methods for processing lignocellulosic materials for producing said novel viscous carbohydrate compositions therefrom as well as to the production of further useful products.

BACKGROUND

The carbohydrates-conversion industry is large and increases rapidly. Thus, nearly 100 million tons of carbohydrates are fermented annually to fuel-grade ethanol and this number is expected to triple in the next decade. Millions of tons of carbohydrates are also fermented every year into food and feed products, such as citric acid and lysine. Fermentation to industrial products is also increasing, such as the production of monomers for the polymer industry, e.g. lactic acid for the production of polylactide. Carbohydrates are an attractive and environmental-friendly substrate since they are obtained from renewable resources, such as sucrose from sugar canes and glucose from corn and wheat starches. Such renewable resources are limited in volume and increased consumption is predicted to increase food costs. There is therefore a strong motivation to generate carbohydrates from renewable non-food resources. It is particularly desired to produce such carbohydrates at costs that are lower than those of the food carbohydrates. Low cost carbohydrates will open the way for much greater production of biofuels and industrial products, such as monomers. Thus, new processes are being developed for the production of alternative fuels such as fatty acid esters and hydrocarbons which can be directly formed by fermentation or produced by conversion of fermentation products. The majority of the future production from carbohydrates will use fermentation, but chemical conversion of carbohydrates also seems attractive.

An abundant and relatively-low cost source of carbohydrates is woody material, such as wood and co-products of wood processing and residues of processing agricultural products, e.g. corn stover and cobs, sugar cane bagasse and empty fruit bunches from palm oil production. There is also the potential of growing for that purpose switch grass and other "energy crops" that generate low-cost rapid growing biomass. Such carbohydrate sources contain as their main components cellulose, hemicellulose and lignin and are also referred to as lignocellulosic material. Such material also contains mineral salts, ashes, and organic compounds, such as tall oils. Cellulose and hemicellulose, which together form 65-80% of the lignocellulosic material, are polysaccharides and their hydrolysis forms carbohydrates suitable for fermentation and chemical conversion to products of interest. Hydrolysis of hemicellulose is relatively easy, but that of cellulose, which typically forms more than one half of the polysaccharides content, is difficult due to its crystalline structure. Presently known methods for converting lignocellulosic material to carbohydrates involve enzymatic- catalyzed and/or acid-catalyzed hydrolysis. In many cases, pre-treatments are involved, e.g. lignin and/or hemicellulose extraction, steam or ammonia explosion, etc. The known technologies are still too expensive and there is a strong need for alternative, lower-cost ones. In addition, carbohydrates cost could be lowered by valorizing co-products such as lignin and tall oils. There is therefore a need for technology that, in addition to using low-cost hydrolysis, generates those co-products at high quality.

Acid hydrolysis of lignocellulosic material was considered and tested as a pre- treatment for enzymatic hydrolysis. Alternatively, acid could be used as the sole hydrolysis catalyst, obviating the need for high-cost enzymes. Most of the efforts focused on sulfuric acid and hydrochloric acid (HCI), with preference for the latter. In fact, HCI-based hydrolysis of lignocellulosic material, using no enzymes, was implemented on an industrial scale. Such hydrolysis forms a hydrolyzate stream containing the carbohydrate products, other soluble components of the lignocellulosic material and HCI. Since the lignin fraction of the material does not hydrolyze and stays essentially insoluble, the process also forms a co-product stream containing the lignin dispersed in or wetted by an aqueous solution of HCI.

Since HCI acts as a catalyst, it is not consumed in the process. It should be separated from the hydrolysis products and co-products and recycled for re-use. Such separation and recycle presents many challenges, some of which are listed in the following. Thus, the recovery yield needs to be high in order to minimize costs related to acid losses, to consumption of a neutralizing base and to disposal of the formed salt. In addition, residual acid content of the product and the co-products should be low in order to enable their optimal use. Acid recovery from the hydrolyzate should be conducted in conditions i.e. mainly temperature, minimizing thermal and HCI-catalyzed carbohydrates degradation. Recovery of HCI from lignin co-product stream is complicated by the need to deal with solids and by the need to form HCI-free lignin. The literature suggests washing HCI off the lignin, but the amount of water required is large, the wash solution is therefore dilute and recycle to hydrolysis requires re-concentration at high cost. Another major challenge is related to the concentration of the separated and recovered acid. For high yield hydrolysis of the cellulosic fraction of the lignocellulosic material, concentrated HCI is required, typically greater than 40%. Thus, the recovered acid is preferably obtained at that high concentration in order to minimize re-concentration costs.

Still another challenge is related to the fact that HCI forms an azeotrope with water. Since HCI is volatile, recovery from HCI solutions by distillation is attractive in a generating gaseous, nearly dry HCI stream. Yet, due to the formation of the azeotrope, such distillation is limited to removing HCI down to azeotropic concentration which is about 20%, depending on the conditions. Further removal of HCI requires co-distillation with water to form a vapor phase wherein HCI concentration is about 20%. Therefore, in order to achieve complete removal of the acid from the carbohydrate, distillation to dryness would be required. Alternatively, addition of water, or steam stripping, dilutes the residual acid to below the azeotropic concentration. As a result, mainly water evaporates, i.e. the residual HCI is obtained in a highly dilute HCI stream, which then entails high re-concentration costs. Furthermore, studies of , such removal have concluded that steam stripping cannot achieve full removal of the acid. K. Schoenemann in his presentation entitled "The New Rheinau Wood Saccharification Process" to the Congress of Food and Agricultural Organization of The United Nations at Stockholm in July 1953 reviewed the concentrated HCI-based processes and the related physical properties data. His conclusion was: "as the boiling line .... demonstrates, it is not possible to distill the hydrogen chloride completely from the sugar solution by a simple distillation, not even by spray-distillation, as it was attempted formerly. Thus, the hydrochloric acid could be removed in a post-evaporation down to 3.5%, calculated on sugars by injecting steam, which acts like alternating diluting and distilling." Such amount of residual HCI in the carbohydrates is industrially unacceptable.

In addition, HCI removal from highly concentrated carbohydrate solutions is complicated by the high viscosity of the formed streams. Some efforts were made in the past to remove the residual acid by spray drying the hydrolyzate. Based on various studies, spray drying cannot achieve complete removal of the acid. Such incomplete removal of the acid decreases recovery yield and requires neutralization in the product or indirectly on an ion-exchanger. In addition, since the feed to the spray drier should be fluid, the amount of water and HCI removed by distillation from the hydrolyzate is limited According to F. Bergius, the developer of the HCI-hydrolysis technology, in his publication " Conversion of wood to carbohydrates and problems in the industrial use of concentrated hydrochloric acid" published in Industrial and Engineering Chemistry (1937), 29, 247-53, 80% of the HCI can be removed by evaporation prior to spray drying. Thus, large amounts of water and HCI should be removed in the spray drier, which increases both the capital and the operating cost of such a process.

In latter developed technologies, a fraction of the acid in the hydrolyzate is distilled out as a gaseous, nearly dry HCI, to reach azeotropic concentration. Optionally, another fraction of the acid is distilled as gas of azeotropic composition. Then, the residual acid is removed by alternative, non-distillative means, such as crystallization, membrane separation and solvent extraction by various solvents. The assignee of the present invention has several patent applications in which an acid-base couple extractant is used for that purpose. Solvent extraction was found to fully remove the residual acid, but at a relatively high equipment cost and with the need for special operations to avoid extractant losses and product contamination by the extractant.

An object of the present invention is to provide a method for high yield recovery of HCI from the products and co-products of HCI hydrolysis of lignocellulosic material. A related object is to recover that acid at high concentration to minimize re-concentration needs. Another object is to produce carbohydrates and co-products of high quality that are essentially free of HCI. Still another object is to form a carbohydrate composition with minimal moisture and HCI contents that is fluid enough for low-cost spray-drier based removal of residual HCI.

SUMMARY OF THE INVENTION

The present invention provides,, according to a first aspect, a viscous fluid comprising between 2%wt and 25%wt water at least 75%wt carbohydrate, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water,, between 0%wt and 25% wt of a second organic solvent and between 10%wt and 55%wt HCI, as calculated by 100 time HCI weight divided by the combined weights of HCI and water, which second organic solvent is characterized by at least one of:

(a2) having a polarity related component of Hoy's cohesion parameter between 0 and 15MPa ^1/2 ;

(b2) having a hydrogen bonding related component of Hoy!s cohesion parameter between 0 and 20 Pa ^1/2 ; and

(c2) having a solubility in water of less than 15%, and forming a heterogeneous azeotrope with water, wherein the weight/weight ratio of said second organic solvent to water is in the range of between 50 and 0.02, and wherein the solubility of water in said organic solvent is less than 20%.

According to an embodiment, the viscous fluid viscosity as measured at 80°C by the Brookfield method is less than 150cP. According to various embodiments, in said viscous fluid the HCI/water weight/weight ratio is in the range between 0.2 and 1.0, the carbohydrate/water weight/weight ratio is in the range between 2 and 20, and the HCI/carbohydrate weight/weight ratio is in the range between 0.02 and 0.15.

According to an embodiment, the second organic solverit/water weight/weight ratio in said viscous fluid is R2, wherein the second organic solvent forms a heterogeneous azeotrope with water and the second organic solvent/water weight/weight ratio in said azeotrope is R22 and wherein R2 is greater than R22 by at least 0%.

According to another embodiment, the second organic solvent forms a heterogeneous azeotrope with water, wherein said second organic solvent has a boiling point at 1 atm in the range between 100°C and 200°C and wherein said heterogeneous azeotrope has a boiling point at 1 atm of less than 100°C.

According to another embodiment, preferably said viscous fluid is maintained under a pressure of less than 400mbar.

According to an embodiment the viscous fluid comprises glucose and at least one carbohydrate selected from the group consisting of mannose, galactose, xylose, arabinose, and fructose, more preferably the viscous fluid comprises at least two carbohydrates selected from the group consisting of mannose, galactose, xylose, arabinose and fructose.

The present invention provides, according to still another embodiment, a viscous fluid consisting essentially of: between 2%wt and 25%wt water, at least 75%wt carbohydrate, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water, between 0%wt and 25%wt of a second organic solvent and between 10%wt and 55%wt HCI, as calculated by 100 time HCI weight divided by the combined weights of HCI and water, which second organic solvent is characterized by at least one of: (a2) having a polarity related component of Hoy's cohesion parameter between 0 and 15MPa ^/2 ; (b2) having a hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20MPa ^/2 ; and (c2) having a solubility in water of less than 15% and forming a heterogeneous azeotrope with water, wherein the weight/weight ratio of said second organic solvent to water is in the range of between 50 and 0.02, and wherein the solubility of water in said organic solvent is less than 20%.

The present invention provides, according to a second aspect a method for the deacidification of a first aqueous solution comprising the steps of (i) providing a first aqueous solution comprising carbohydrates, HCI and water, wherein the weight/weight ratio of carbohydrates to water is in the range of between 0.4 and 3 and wherein the weight/weight ratio of HCI to water is in the range between 0.17 and 0.50;

(ii) contacting said first aqueous solution with a second organic solvent to form a second evaporation feed, which second organic solvent forms a heterogeneous azeotrope with water and is characterized by at least one of (a2) having a polarity related component of Hoy's cohesion parameter between 0 and 15MPa ^{1 2} .

(b2) having a hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20MPa ^{1 2} ; and

(c2) having a solubility in water of less than 15%, and forming a heterogeneous azeotrope with water wherein the weight/weight ratio of said second organic solvent to water is in the range of between 50 and 0.02, and wherein the solubility of water in said organic solvent is less than 20% and

(iii) evaporating water, HCI and a second organic solvent from said second evaporation feed at a temperature below 100°C and at a pressure below l atm, whereupon a second vapor phase and the viscous fluid of the first aspect of the present invention are formed.

According to an embodiment, providing said first aqueous solution comprises hydrolyzing a polysaccharide-comprising material in an HCI-comprising hydrolysis medium, wherein HCI concentration is greater than azeotropic.

According to another embodiment, the weight/weight ratio of said second organic solvent to water in said second evaporation feed is R23, wherein the weight/weight ratio of said second organic solvent to water in said azeotrope is R22 and wherein R23 is greater than R22 by at least 10%.

According to another embodiment, the method further comprises the steps of condensing the vapors in said second vapor phase to form two phases, a second organic solvent-rich one and a first water-rich one, separating said phases, using said second organic solvent-rich phase in step (ii), and using said first water-rich phase for generating said hydrolysis medium.

According to another embodiment, said viscous solution comprises carbohydrate oligomers and the method further comprises the steps of diluting said viscous fluid to form oligomers and an HCI-comprising diluted fluid, and maintaining said HCI- comprising diluted fluid at a temperature and for a residence time sufficient for the hydrolysis of at least 50% of said oligomers.

According to another embodiment, the method further comprises the steps of diluting said viscous fluid to form the HCI-comprising diluted fluid, and separating HCI from said HCI-comprising diluted fluid by means selected from solvent extraction, membrane separation, ion-exchange and combinations thereof to form a de-acidified carbohydrates solution.

According to another embodiment, the method further comprises the steps of diluting said viscous fluid to form the HCI-comprising diluted fluid, neutralizing at least a fraction of said HCI to form a diluted fluid comprising a chloride salt and carbohydrates, and separating said salt from said carbohydrates by means selected from membrane separation and chromatography to form a de-acidified carbohydrates solution.

According to an embodiment, the weight/weight ratio of HCI to carbohydrates in said de-acidified carbohydrate solution is less than 0.03.

The present invention provides, according to a third aspect, a method for the production of a carbohydrate composition comprising

(i) providing a lignocellulosic material feed comprising a polysaccharide and lignin;

(ii) hydrolyzing said polysaccharide in an HCI-comprising hydrolysis medium to form a first aqueous solution comprising carbohydrates, HCI and water, wherein the weight/weight ratio of carbohydrates to water is in the range of between 0.4 and 3 and wherein the weight/weight ratio of HCI to water is in the range between 0.17 and 0.50

(iii) contacting said first aqueous solution with a second organic solvent to form a second evaporation feed, which second organic solvent forms with water a heterogeneous azeotrope and is characterized by at least one of:

(a2) having a polarity related component of Hoy's cohesion parameter between 0 and 15MPa ^1/2

(b2) having a hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20MPa ^1/2 ; and

(c2) having a solubility in water of less than 15%, and forming a heterogeneous azeotrope with water wherein the weight/weight ratio of said second organic solvent to water is in the range of between 50 and 0.02, and wherein the solubility of water in said organic solvent is less than 20%; and (iv) evaporating water, HCI and the second organic solvent from said second evaporation feed at a temperature below 100°C and at a pressure below 1atm, whereupon a second vapor phase and a viscous fluid according to the first aspect of the present invention as defined hereinbefore, are formed.

According to an embodiment of said third aspect, the weight/weight ratio of said second organic solvent to water in said second evaporation feed is R23, wherein the weight/weight ratio of said second organic solvent to water in said azeotrope is R22 and wherein R23 is greater than R22 by at least 10%.

According to another embodiment, the method further comprises the steps of condensing the vapors in said second vapor phase to form two phases, a second organic solvent-rich one and a first water-rich one, separating said phases, using said second organic solvent-rich phase in step (iii) and using said first water-rich phase for generating said hydrolysis medium.

According to another embodiment, said hydrolyzing forms a hydrolyzate, forming said first aqueous solution comprises separating a portion of the HCI from said hydrolyzate to form a first separated HCI stream and an HCI-depleted hydrolyzate and said first separated HCI stream is used for generating said hydrolysis medium.

According to still another embodiment the amount, the purity and the concentration of HCI within said hydrolyzate are W4, P4 and C4, respectively and the amount, the purity and the concentration of HCI in said first separated HCI stream are W5, P5 and C5, respectively, and W5/W4 is greater than 0.1 , P5/P4 is greater than 1.8, and C5/C4 is greater than 1.8.

According to a related embodiment, the method further comprises the steps of separating another portion of HCI from said HCI-depleted hydrolyzate to form a second separated HCI stream, and using said second separated HCI stream for generating said hydrolysis medium.

According to a related embodiment, the amount, the purity and the concentration of HCI in said second separated HCI stream are W7, P7 and C7, respectively, and W7/W4 is greater than 0.1 , P7/P4 is greater than 1.8, and C7/C4 is greater than 0.4.

According to another embodiment of said third aspect, said viscous solution comprises carbohydrate oligomers and the method further comprises the steps of diluting said viscous fluid to form oligomers and an HCI-comprising diluted fluid and maintaining said diluted fluid at a temperature and for a residence time sufficient for the hydrolysis of at least 50% of said oligomers. According to another embodiment, the method of the third aspect further comprises the steps of diluting said viscous fluid to form the HCI-comprising diluted fluid, and separating HCI from said HCI-comprising diluted fluid by means selected from solvent extraction, membrane separation, ion-exchange and combinations thereof to form a de-acidified carbohydrates solution.

According to still another embodiment, the method of the third aspect further comprises the steps of diluting said viscous fluid to form the HCI-comprising diluted fluid, neutralizing at least a fraction of said HCI to form a diluted fluid comprising a chloride salt and carbohydrates, and separating said salt from said carbohydrates by means selected from membrane separation and chromatography to form a de-acidified carbohydrates solution.

According to an embodiment, the weight/weight ratio of HCI to carbohydrates within said de-acidified carbohydrate solution is less than 0.03.

The present invention further provides, according to a fourth aspect, a tetramers composition comprising hetro-oligosaccharides with a degree of polymerization of at least tetramers, which tetramers are composed of glucose and at least one sugar selected from the group consisting of mannose, xylose, galactose, arabinose and fructose, preferably at least two sugars from said list and optionally at least three sugars from said list. According to an embodiment, said composition comprises at least two types of hetro-tetramers, each one of which is composed of glucose and at least one sugar selected from the group consisting of mannose, xylose, galactose, arabinose and fructose, preferably at least two sugars from said list. According to a preferred embodiment, said tetramers composition is essentially HCI free.

According to an embodiment, the sugars in said tetramers form at least 0.5%wt of the sugars in said tetramers composition, preferably at least 1 %wt and more preferably at least 1.5%wt. According to a related embodiment, the rest of the sugars in said tetramers composition are in the forms of monomers, dimers, trimers and oligomers with a degree of oligomerization greater than four. According to a related embodiment, at least a fraction of said dimers, trimers and oligomers with a degree of oligomerization greater than four are hetero-oligosaccharides. According to an embodiment, the sugar concentration in said tetramer composition is greater than 20%wt, preferably greater than 25%, more preferably greater than 30%, and most preferably greater than 35%wt. The term hetro-oligosaccharides, as used herein, means oligosaccharides composed of at least two different sugars. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figure and examples so that it may be more fully understood.

In the drawings:

Figure 1 is a flow diagram of a preferred embodiment of the process of the present invention.

With specific reference now to the figure in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of one of the methods of the invention. In this regard, no attempt is made to show details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the attached figure making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

DETAILED DESCRIPTION

In some embodiments, the term "consisting essentially of refers to a composition whose only active ingredients are the indicated active ingredients, however, other compounds may be included which are involved directly in the technical effect of the indicated active ingredients. In some embodiments, the term "consisting essentially of" refers to a composition whose only active ingredients acting in a particular pathway, are the indicated active ingredients, however, other compounds may be included which are involved in the indicated process, which for example have a mechanism of action related to but not directly to that of the indicated agents. In some embodiments, the term "consisting essentially of" refers to a composition whose only active ingredients are the indicated active ingredients, however, other compounds may be included which are for stabilizing, preserving, etc. the composition, but are not involved directly in the technical effect of the indicated active ingredients. In some embodiments, the term "consisting essentially of" may refer to components which facilitate the release of the active ingredients. In some embodiments, the term "consisting essentially of refers to a composition, which contains the active ingredients and other acceptable solvents, which do not in any way impact the technical effect of the indicated active ingredients.

The present invention provides, according to an aspect, a viscous fluid consisting essentially of: between 2%wt and 25%wt water, at least 75%wt carbohydrate, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water, between 0%wt and 25%wt of a second organic solvent and between 10%wt and 55%wt HCI, as calculated by 100 time HCI weight divided by the combined weights of HCI and water, which second organic solvent is characterized by at least one of: (a2) having a polarity related component of Hoy's cohesion parameter between 0 and 15MPa ^{1 2} ; (b2) having a Hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20MPa ^1/2 ; and (c2) having a solubility in water of less than 15% and forming a heterogeneous azeotrope with water, wherein the weight/weight ratio of said second organic solvent to water is in the range of between 50 and 0.02, and wherein the solubility of water in said organic solvent is less than 20%.

Preferred embodiments of the present invention are described in the following in reference to the flow diagram in Figure 1. In the following, numbers and letters in [X] refer to operations (boxes in the diagram) and numbers and letters in <X> refer to streams (arrows).

According to an embodiment of the method of the present invention, a polysaccharide in a polysaccharide-comprising feed (<ps> in Fig. 1) is hydrolyzed in an HCI-comprising hydrolysis medium (hydrolysis takes place in [(ii)]). Unless specified otherwise, the term acid hereinafter means HCI. According to a preferred embodiment, the polysaccharide-comprising feed is a lignocellulosic material, also referred to herein as a lignocellulosic material feed or lignocellulosic feed. According to an embodiment, HCI concentration in the hydrolysis medium is greater than 30%. The hydrolysis medium is formed, according to an embodiment, by contacting the lignocellulosic feed with a recycled reagent HCI stream <rg6>. According to an embodiment of the invention, within the recycled reagent HCI, the concentration and purity of HCI are C6 and P6, respectively. According to an embodiment, P6 is greater than 80%, preferably greater than 85%, more preferably greater than 90% and most preferably greater than 95%. According to another embodiment, C6 is greater than 30%, preferably greater than 35%, more preferably greater than 38% and most preferably greater than 40%, as calculated by 100 time HCI weight divided by the combined weights of HCI and water.

According to one embodiment, said contacting is carried out in a batch mode, while according to another it is carried out in a continuous mode. According to a preferred embodiment, contacting is conducted in a counter-currently mode, e.g. in a tower reactor into which, according to one embodiment, the lignocellulosic feed is introduced from top and the recycled reagent HCI stream flows in from the bottom. The recycled reagent HCI stream comes in containing essentially no carbohydrates. As the reagent stream flows upwards, carbohydrates from polysaccharides hydrolysis start to build up in it. At the same time, the lignocellulosic material losses its polysaccharides as it moves downwards, counter-currently to the recycled reagent HCI stream.

According to a preferred embodiment, the lignocellulosic material is fed into a series of N reactors - numbered for the purpose of the explanation here - as D _T to D _N (wherein reactors D-, to D _N are not shown in Figure 1 ). The recycled reagent HCI stream is introduced into D _N for a contact of a selected residence time. Then, it is separated and moved to reactor D _N- i for an additional contact of a selected residence time, after which it is moved to D _N-2 , etc. Finally, it is moved into reactor for a contact of a selected time with a fresh lignocellulosic solid material. Thus, the fresh solid material is contacted first with an aqueous HCI solution that was previously contacted N-1 times. At the end of the selected residence time, the aqueous HCI solution is removed from the reactor and the solid material is contacted again with an aqueous HCI solution, this time with one that was previously contacted N-2 times. Finally, the solid material is contacted with a fresh recycled reagent HCI stream at the end of which the residual solid is separated and removed from the reactor. The emptied reactor is then re-filled with fresh lignocellulosic material and goes again through the series of contacts, i.e. starting with contact with an aqueous HCI solution that was previously contacted N-1 times. According to a preferred embodiment, while the aqueous HCI solution moves from one reactor to the other, the solid material stays in the same reactor for N contacts, after which it is removed.

Various polysaccharide-comprising feeds are suitable according to the method of the present invention. The terms saccharide, sugar and carbohydrate in both singular and plural forms are used herein interchangeably. Any polysaccharide is suitable, e.g. polymers of the monomers glucose, xylose, arabinose, mannose, galactose, and their combination. The monomers of interest are typically of either 6 carbon sugars (hexoses) or 5 carbon sugars (pentoses). The terms glucose and dextrose are used here interchangeably. The polymers could be homogenous, i.e. composed of only one type carbohydrate, and or heterogeneous, i.e. comprised of different carbohydrates, e.g. arabinoxylene consisting mainly of xylose and arabinose or glucomannane consisting mainly of glucose and mannose. Various polysaccharides are suitable for the method of the present invention. Of particular interest are cellulose and hemicellulose.

Any polysaccharide-comprising feed is suitable, particularly ones that comprise cellulose, e.g. recycled paper, co-products of the pulp and paper industry, biomass cell walls and the like. Of particular interest are lignocellulosic materials. As used here, the term lignocellulosic material, or lignocellulosic material feed, refers to any material comprising cellulose and lignin. Typically, lignocellulosic material further comprises hemicellulose, additional components such as extractives and mineral compounds. The weight ratios between the various components - mainly the three major ones, i.e. cellulose, hemicellulose and lignin -change according to the source of the lignocellulosic material. The same is true for the content of mineral compounds, also referred to as ashes and for the extractives.

The term extractives, as used herein, means oil-soluble compounds present in various lignocellulosic feeds, e.g. tall oils.

Various lignocellulosic materials are known and are suitable for the present invention. Of particular interest are wood, wood-processing co-products such as wood chips from oriented strand boards production, agricultural residues such as stover and corn cobs, sugar cane bagasse, switch grass and other energy crops, and various combinations of those. Lignocellulosic material could be used as such or after some pre- treatment. Any pre-treatment that does not lead to the hydrolysis of the majority of the cellulose content is suitable.

According to an embodiment, the lignocellulosic material is dried prior to the combining with the recycled reagent HCI stream. Lignocellulosic material could be obtained from various sources at various degrees of moisture. Various methods of drying are suitable. According to an embodiment, drying is to a moisture content of about 10% or lower.

According to another embodiment, the lignocellulosic material is comminuted prior to the combining with the recycled reagent HCI stream.

According to an embodiment, the lignocellulosic material is pre-treated for the removal and/or for the hydrolysis of hemicellulose prior to the combining with the recycled reagent HCI stream. Such removal and/or hydrolysis could be conducted by various means, e.g. elevated temperature treatment with water/steam and/or with dilute HCI solution, enzymatic hydrolysis, and the like. Such treatment extracts hemicellulose into an aqueous phase, hydrolyzes hemicellulose into water soluble sugars and combinations of those, leading to lignocellulosic material wherein cellulose is the main polysaccharide. According to a preferred embodiment, the polysaccharides of the lignocellulosic material are not hydrolyzed, nor extracted prior to the combining with the recycled reagent HCI stream.

According to other embodiments, the lignocellulosic material is pre-treated by at least one of steam explosion, ammonia explosion and delignification. According to the embodiment wherein the lignocellulosic material undergoes pre- hydrolysis or hemicellulose extraction, the hydrolysis in [(ii)] of Fig. 1 is mainly of cellulose. According to the embodiment wherein there is no pre-hydrolysis or extraction of hemicellulose, both hemicellulose and cellulose are hydrolyzed in [(ii)]. HCI acts as a catalyst and is not consumed, except possibly for neutralizing basic components of the lignocellulosic material.

According to an embodiment of the invention, at least 70%wt of the polysaccharides in the feed material hydrolyze into soluble carbohydrates, preferably more than 80%, more preferably more than 90%, and most preferably more than 95%. According to an embodiment, hydrolysis forms soluble carbohydrates. Accordingly, the concentration of the soluble carbohydrates in the medium increases with the progress of the hydrolysis reaction.

As indicated, according to an embodiment, the fresh lignocellulosic material is contacted several times with an HCI solution, which leads to an increased degree of hydrolysis of its polysaccharides content. According to an embodiment, when removed from D _N , essentially all the polysaccharides content of a lignocellulosic material feed is hydrolyzed into soluble carbohydrates, while the lignin content stays essentially insoluble. According to an embodiment, the removed insoluble lignin is in the form of a solid dispersion in an HCI solution or as a wet cake wetted by such solution. That removed composition forms, according to an embodiment, an HCI-comprising lignin stream of the present invention (<lg8> in Fig. 1 ). According to an embodiment of the invention, in said HCI-comprising lignin stream, HCI amount, concentration and purity are W8, C8 and P8, respectively.

As the recycled HCI stream moves through the reactors, its carbohydrates content increases and reaches the maximal value at the end of the contact with the fresh lignocellulosic material. According to an embodiment, after contact with the fresh lignocellulosic material, the aqueous solution is removed from Di (not shown) which is a component of (ii) in Figure 1 , and used to form the first aqueous solution comprising carbohydrates, HCI and water. The removed aqueous solution is also referred to as the hydrolyzate (<hy4> in Fig. 1 ).

According to the method of the present invention, in that first aqueous solution, the carbohydrates to water weight/weight ratio is in the range of between 0.2 and 2.0, preferably between 0.3 and 1 .5, more preferably between 0.4 and 1 .0 and most preferably between 0.5 and 0.9 and the HCI/water weight/weight ratio is in the range of between 0.1 7 and 0.6, preferably between 0.20 and 0.50 and more preferably between 0.25 and 0.40. According to an embodiment, this first aqueous solution is a product of further treating the formed hydrolyzate, as further described in the following.

According to an embodiment of the invention, in the hydrolysis-formed hydrolyzate, HCI amount, concentration and purity are W4, C4 and P4, respectively. Preferably, said hydrolyzate is essentially solids free, meaning containing essentially no insoluble compounds. According to an embodiment, said hydrolyzate comprises solids and those are separated by at least one of filtration and centrifugation. According to another embodiment, the carbohydrate concentration in <hy4> is greater than 15%wt (as calculated by 100CH/(CH+W), wherein CH and W are the weights of the carbohydrates and the water, respectively), preferably greater than 20%wt, more preferably greater than 25%wt, and most preferably greater than 30%wt. While there is no significant consumption of HCI in the hydrolysis process, W4 is in many cases smaller than the amount of HCI in the recycled HCI reagent (W6), since part of the acid is contained in <lg8>. C4 is similar in size to HCI concentration in that reagent (C6), but typically somewhat smaller. As carbohydrates are being added into the solution during the hydrolysis, the purity of HCI in the solution decreases. According to various embodiments, P4 is between 20% and 70%, more preferably between 30% and 60%.

In a preferred embodiment, the hydrolysis and the contacting of the present method are conducted in a continuous mode. In that case, amounts of stream and of components are presented in terms of flow rate, e.g. as the ratio between the flow rate of HCI and that of the initial lignocellulosic material feed in the hydrolysis medium. According to a preferred embodiment, that weight/weight ratio is between 0.2 and 5, preferably between 0.5 and 3.

Unless specified otherwise, the concentration of a component in a medium, e.g. in a gaseous stream, a solution or a suspension, is presented in weight percent (%wt) calculated from the weight, or flow rate, of said component in that medium and the combined weights, flow rates, of that component and the water in that medium. Thus, e.g. in a medium composed of 30Kg water, 20Kg of HCI and 50Kg of carbohydrate, the concentration of HCI according to the presentation here is 40%. In some other cases, as indicated, the concentration is on an "as is" basis, i.e. calculated from the weight, flow rate, of the component in that medium divided by the total weight, flow rate, of the medium.

Unless specified otherwise, the purity of a component in a medium is the purity in a homogeneous phase (liquid and/or gas). In case the medium comprises insolubles, the purity referred to is that in the solution that would form on separation of those insolubles. Unless specified otherwise, the purity is calculated on a water-free, or solvent-free, and weight basis. Thus, HCI purity in a solution composed of 50Kg water, 20Kg of HCI and 20Kg of carbohydrate and 10Kg mineral salt, as presented here, is 40%.

According to an embodiment, the lignocellulosic feed further comprises an organic compound, e.g. tall oil, and a fraction of the organic compound is dissolved and/or dispersed in the formed hydrolyzate. According to a related embodiment, the organic compound-comprising hydrolyzate is brought into contact at a temperature T3 with a third organic solvent (not shown in Fig. 1 ), whereupon said organic compound selectively transfers to said third organic solvent to form an organic compound-depleted hydrolyzate and a first organic compound-carrying solvent. According to an embodiment, the first organic compound-carrying solvent has a commercial value as such. According to another embodiment, the method further comprises a step of recovering said third organic solvent and organic compound from said first organic compound-carrying solvent to form a separated organic compound and a regenerated third organic solvent. Various methods are suitable for such recovering, including distilling the third organic solvent and extracting it into another solvent, wherein the organic compound has limited miscibility. According to an embodiment, said organic compound is a tall oil. According to an embodiment, the separated organic compounds formed according to the present invention differ in composition from present commercial products and are of higher quality. Without wishing to be limited by theory, that could be the results of recovery in an acidic medium and/or of fractionation between the various streams of the process. Thus, the organic compounds extracted from the hydrolyzate can be enriched in components, which at high HCI concentration, typically greater than 30%, dissolve in the aqueous medium, rather than adsorb on the solid lignin product of hydrolysis.

According to a preferred embodiment, said contacting of the hydrolyzate with the third organic solvent is conducted while the hydrolyzate is high in HCI concentration, e.g. while the HCI concentration therein is at least 25%, preferably at least 28% and more preferably at least 32%. According to a related embodiment, said contacting is conducted prior to the following step of separating a portion of the HCI in the hydrolyzate. The inventors have found that the solubility of some of those organic compounds in the hydrolyzate decreases with decreasing HCI concentration. Contacting with the third organic solvent while HCI concentration is still high provides for high yield of recovering organic compounds on one hand and avoids their precipitation in the next steps, which precipitation may form undesired coating of equipment.

The method of the presented invention further comprises a step [C] of separating a portion of the HCI from said hydrolyzate to form a first separated HCI stream < s5> wherein HCI amount, concentration and purity are W5, C5 and P5, respectively, and an HCI-depleted hydrolyzate <dh>. According to a preferred embodiment, said separation involves distilling HCI out of the hydrolyzate and the first separated HCI stream <1 s5> is gaseous. Preferably, a significant fraction of the HCI in the hydrolyzate is distilled out in [C], so that W5/W4 is greater than 0.1 , preferably greater than 0.2, more preferably greater than 0.25 and most preferably greater than 0.3. The first separated HCI stream may contain small amounts of water, e.g. water vapors in a gaseous first separated HCI stream, and possibly also small amounts of some other volatile components of the hydrolyzate. Yet, both C5 and P5 are high, typically greater than 90%, preferably greater than 95% and more preferably greater than 97%. According to an embodiment, P5/P4 is greater than 1.8, preferably greater than 2.0, more preferably greater than 2.2 and most preferably greater than 2.5. According to another embodiment, C5/C4 is greater than 1.8, preferably greater than 2.0, more preferably greater than 2.2 and most preferably greater than 2.5.

According to an embodiment, the method further comprises a step [I] of separating another portion of HCI from the HCI-depleted hydrolyzate to form a second separated HCI stream <2s7> wherein HCI amount, concentration and purity are W7, C7 and P7, respectively, and a further-depleted hydrolyzate, which according to some embodiments, forms a first aqueous solution within the present invention (<as1 > in Fig. 1 ). According to a preferred embodiment, said separation in [I] involves distilling HCI out of the HCI-depleted hydrolyzate and the second separated HCI stream is gaseous. Preferably, a significant fraction of the HCI in the HCI-depleted hydrolyzate is distilled out in [I], so that W7/W4 is greater than 0.1 , preferably greater than 0.2, more preferably greater than 0.3 and most preferably greater than 0.4. Said second separated HCI stream is, according to a preferred embodiment a water-HCI azeotrope so that C7 is about azeotropic. The second separated HCI stream <2s7> is essentially carbohydrate free, but may contain small amounts of volatile components of the hydrolyzate. Yet, P7 is high, typically greater than 90%, preferably greater than 95% and more preferably greater than 97%. According to an embodiment, P7/P4 is greater than 1.8, preferably greater than 2.0, more preferably .greater than 2.2 and most preferably greater than 2.5. According to another embodiment, C7/C4 is greater than 0.4, preferably greater than 0.5, more preferably greater than 0.6 and most preferably greater than 0.7.

As indicated, according to an embodiment, said separating in [I] involves distilling HCI and the second separated HCI stream is of azeotropic concentration. It is important to note that, according to a preferred embodiment, distilling here and optionally other distillation steps in the method of the present invention are conducted at sub- atmospheric pressure in order to maintain low distillation temperature so that undesired degradation of carbohydrates is avoided. The composition of the azeotrope changes with the distillation temperature. As used herein, the term azeotropic composition refers to the composition of the azeotrope at the conditions - including temperature and pressure - of the distillation. In addition, the azeotropic composition is also affected by the presence of other solutes in the solution. Thus, the azeotropic composition of the second separated HCI stream may vary with the concentration of carbohydrates in the distilled solution.

Since the azeotropic distillation in [I] separates both HCI and water, the carbohydrates concentration increases during the distillation. According to an embodiment of the invention, the carbohydrates concentration in <dh> is in the range between 20% and 40% and that concentration in <as1 > is greater than that in <dh> by at least 50%. According to an embodiment, the carbohydrates concentration in <as1 > is greater than 30%wt, preferably greater than 40%wt, more preferably greater than 50%wt and most preferably greater than 55%wt.

In the hydrolyzate <hy4>, HCI/carbohydrates weight/weight ratio is typically about 1 or greater than 1. According to various embodiments, the distillations in [C] and [I] remove together about 50% - 70% of that initial HCI content and about a similar proportion of the initial water content there. In order to approach a full recovery of the acid, the rest of the acid in that stream should be removed. Spray drying is economically unattractive. On a large industrial scale, e.g. about 100 tons of carbohydrates per hour or more, the amounts of water and acid to be distilled would make spray drying of <as1 > highly expensive in both capital and operating cost. The inventors of the present invention have found a way to further remove acid and water from <as1 >.

According to an embodiment of the invention, the hydrolyzate, the depleted hydrolyzate, the further depleted hydrolyzate and or the first aqueous stream (<as1 > in Fig. 1) is contacted ([(iii)] in Fig. 1 ) with a second organic solvent <2os> to form a second evaporation feed <2ef>. According to the method, water, HCI and the second organic solvent are distilled ([(iv)] in Fig. 1) from said second evaporation feed, preferably at a temperature below 100°C and at a pressure below 1 atm, whereupon a second vapor phase (<2vp> in Fig. 1) and a viscous fluid (<vf> in Fig. 1) are formed. According to an embodiment, at least one of the temperature and the pressure vary during the distillation operation, but during at least a fraction of the distillation time, temperature is below 100°C and pressure is below 1 atm.

According to an embodiment, in the hydrolyzate, the depleted hydrolyzate, the further depleted hydrolyzate and or the first aqueous stream, when contacting with the second solvent the carbohydrates to water weight/weight ratio is in the range between

0.4 and 3.0, preferably between 0.7 and 2.8, more preferably between 1.0 and 2.5 and most preferably between 1.5 and 2.2, and the HCI/water weight/weight ratio is in the range between 0.17 and 0.5, preferably between 0.20 and 0.40 and more preferably between 0.25 and 0.35.

The terms "organic solvent" and "solvent" are used herein interchangeably.

The first organic solvent and the second organic solvent of the present invention are characterized by forming with water a heterogeneous binary azeotrope to be distinguished from a homogeneous binary azeotrope. In case two compounds (A and B) form a binary homogeneous azeotrope, at the azeotropic composition there is a single liquid phase with a given A/B ratio and when vapors are distilled out of it, they contain A and B at the same A/B ratio. Therefore, distillation does not change the composition of the liquid phase. The case of a heterogeneous azeotrope is different. According to the present invention, the second organic solvent and water are of limited mutual solubility. Combining them in ratios exceeding the solubility limits forms a binary system with two liquid phases - a solvent-saturated aqueous solution and a water-saturated solvent solution. Vapors distilled from that two-liquid phases binary system have - at determined temperature and pressure - a given solvent/water ratio. While these conditions are maintained and as long as the two phases are present in the liquid system, the solvent/water ratio in the vapor phase stays unchanged. The solvent/water ratio in the vapor phase is such that, on condensing the vapors, two phases are formed,

1. e. the solvent/water ratio in the vapor phase is outside the mutual solubility limit.

According to an embodiment of the present invention, the solubility of the second organic solvent in water, as determined, for example ,by combining, at 25°C, an essentially pure solvent and de-ionized water,, is less than 15%wt, preferably less than 10%wt, more preferably less than 5% and most preferably less than 1 %. According to another embodiment, the solubility of water in the second organic solvent, when similarly determined, is less than 20%wt, preferably less than 15%wt, more preferably less than 10% and most preferably less than 8%. According to another embodiment, in the heterogeneous azeotrope with water, the second organic solvent to water weight/weight ratio is in the range between 50 and 0.02, preferably between 20 and 0.05, more preferably between 10 and 0.1 and most preferably between 5 and 0.2.

Solubility data is presented herein as the concentration of the solute in a saturated solvent solution at 25°C. Thus, e.g. solvent solubility in water of 10%wt means that the concentration of the solvent in its saturated aqueous solution at 25°C is 10%wt.

According to another embodiment, the second organic solvent is characterized by having a polarity related component of Hoy's cohesion parameter of between 0 and 1 5MPa ^1/2 , preferably between 4MPa ^1/2 and 12MPa ^1/2 and more preferably between 6 Pa ^/2 and 10MPa ^1/2 . According to still another embodiment, the second organic solvent is characterized by having a hydrogen bonding related component of Hoy's cohesion parameter of between 0 and 20MPa ^1/2 , preferably between 1 MPa ^1/2 and 15MPa ^1/2 and more preferably between 2MPa ^{1 2} and 14MPa ^1/2 .

The cohesion parameter or solubility parameter, was defined by Hildebrand as the square root of the cohesive energy density:

wherein AE _vap and V are the energy or heat of vaporization and the molar volume of the liquid, respectively. Hansen extended the original Hildebrand parameter to a three- dimensional cohesion parameter. According to this concept, the total solubility parameter δ is separated into three different components, or, partial solubility parameters relating to the specific intermolecular interactions:

wherein S _d , δ _ρ and £ _h are the dispersion, polarity, and Hydrogen bonding components respectively. Hoy proposed a system to estimate total and partial solubility parameters. The unit used for those parameters is MPa ^1/2 . A detailed explanation of that parameter and its components could be found in "CRC Handbook of Solubility Parameters and Other Cohesion Parameters", second edition, pages 122-138. That and other references provide tables with the parameters for many compounds. In addition, methods for calculating those parameters are provided.

According to still another embodiment, the second organic solvent has a boiling point at 1atm in the range between 100°C and 200°C, preferably between 110°C and 190°C, more preferably between 120°C and 180°C and most preferably between 30°C and 160°C.

According to a preferred embodiment, the second organic solvent is selected from the group consisting of C ₅ -C ₈ alcohols, their chlorides and/or combinations thereof, including primary, secondary, tertiary and quaternary ones, including aliphatic and aromatic ones and including linear and branched ones, toluene, xylenes, ethyl benzene, propyl benzene, isopropyl benzene nonane and the like.

As used herein, the terms evaporation and distillation and the terms evaporate and distill are interchangeable.

The viscous fluid formed in [(iv)] comprises at least one carbohydrate, water, HCI and optionally also the second solvent. The viscous fluid is homogeneous according to one embodiment and heterogeneous according to another. According to an embodiment, the viscous fluid is heterogeneous and comprises a continuous phase and a dispersed phase, in which dispersed phase the major component is the second solvent, according to one embodiment, and solid carbohydrate according to another.

The viscous fluid comprises at least 75% carbohydrates, preferably at least 80%, more preferably at least 83% and most preferably at least 86% as calculated by 100CH/(CH+W), wherein CH is the amount of carbohydrates and W is the amount of water. Typically, the majority of the carbohydrates in the viscous fluid are the products of hydrolyzing the polysaccharides of the polysaccharide comprising feed to hydrolysis (<ps>), typically a lignocellulosic material. Alternatively, carbohydrates from other sources are combined with those products of hydrolysis to form the second evaporation feed and end up in the viscous fluid. According to another embodiment, the viscous fluid comprises carbohydrates formed in isomerization of other carbohydrate, e.g. fructose formed from glucose.

According to various embodiments, the carbohydrates in the viscous solution are monomers, dimmers, trimers, higher oligomers, and their combinations. Those monomers, dimmers, trimers, and/or higher oligomers comprise monomers selected from the group consisting of glucose, xylose, mannose, arabinose, galactose, other sugar hexoses, other pentoses and combinations of those. According to a preferred embodiment, glucose is the main carbohydrate therein. The term monomers is used here to describe both non-polymerized carbohydrates and the units out of which oligomers are formed.

The water content of the viscous fluid is between 2%wt and 25%wt, preferably between 3%wt and 20%wt, more preferably between 4%wt and 18%wt and most preferably between 5%wt and 15%wt (calculated "as is"). The HCI concentration of the viscous fluid is between 10%wt and 55%wt, preferably between 15%wt and 50%wt, more preferably between 18%wt and 40%wt and most preferably between 20%wt and 38%wt as calculated by 100HCI/(HCI+W), wherein HCI is the amount of HCI in the viscous fluid and W is the amount of water therein. The second organic solvent content of the viscous fluid is between 0%wt and 25%wt, preferably between 1 %wt and 20%wt, more preferably between 2%wt and 18%wt and most preferably between 3%wt and 15%wt.

According to an embodiment, the HCI/water weight/weight ratio in the viscous fluid is in the range between 0.20 and 1 .0, preferably between 0.3 and 0.9 and more preferably between 0.4 and 0.8. According to another embodiment, the carbohydrate/water weight/weight ratio in the viscous fluid is in the range between 2 and 20, preferably between 3 and 15, more preferably between 4 and 12 and most preferably between 5 and 1 1 . According to still another embodiment, the HCI/carbohydrate weight/weight ratio in the viscous fluid is in the range between 0.02 and 0.15, preferably between 0.03 and 0.12, and more preferably between 0.04 and 0.10.

According to an alternative embodiment the hydrolyzate, the HCI-depleted hydrolyzate, the further depleted hydrolyzate and or the first aqueous stream forms the second evaporation feed as such, i.e. with no addition of the second solvent. Water and HCI are distilled from the second evaporation feed at a temperature below 100°C and at a pressure below 1 atm, whereupon the second vapor phase and the viscous fluid are formed. The viscous fluid of this alternative embodiment comprises carbohydrates, HCI and water according to the above composition, but no solvent. According to a first modification, evaporation starts in the absence of a solvent, and the second organic solvent is added to the composition during evaporation. According to a second modification, evaporation is conducted in the absence of a solvent, and the second organic solvent is added to the formed solution (distillation product) at the end of the evaporation. In both modifications, the viscous fluid comprises the second organic solvent according to the above composition.

The distillation in [(iv)] removes much of the acid and the water left in <as1 > after HCI separation in [C] and [I]. According to an embodiment, the combined acid removal in [C], [I] and [(iv)] is greater than 80% of the initial acid content of the hydrolyzate, preferably greater than 85%, more preferably greater than 90%, and most preferably greater than 95%. According to another embodiment, the combined water removal in [C], [I] and [(iv)] is greater than 80% of the initial water content of the hydrolyzate, preferably greater than 85%, more preferably greater than 90%, and most preferably greater than 95%.

As a result of that water removal, the formed viscous fluid <vf> is highly concentrated in carbohydrates. It was surprisingly found that, according to an embodiment, the viscosity of the viscous fluid, as measure at 80°C by the Brookfield method is less than 150cP, preferably less than 120cP more preferably less than 100cP, and most preferably less than 90cP. It is not clear how such relatively high fluidity was maintained in the highly concentrated <vf>. Without wishing to be limited by theory, a possible explanation to that could be some specific role the solvent plays in <vf> and/or the specific composition of the carbohydrate, e.g. the mix of carbohydrates it is made of and the degree and nature of oligomerization.

According to a preferred embodiment of the invention, the ratio between the amount of first aqueous solution and the amount of the second organic solvent contacted with it in [(iii)] is such that solvent is found in the viscous solution at the end of the distillation. According to a further preferred embodiment, the solvent/water ratio in the viscous fluid is greater than the solvent/water ratio in the water-solvent heterogeneous azeotrope. According to an embodiment of the invention, in the viscous fluid the second organic solvent/water weight/weight ratio is R2, the second organic solvent has heterogeneous azeotrope with water and the second organic solvent/water weight/weight ratio in said azeotrope is R22, and R2 is greater than R22 by at least 10%, preferably by at least 25%, more preferably by at least 40%, and most preferably by at least 50%. According to still another embodiment, the second organic solvent/water weight/weight ratio in said second evaporation feed is R23, the second organic solvent/water weight/weight ratio in said azeotrope is R22, and R23 is greater than R22 by at least 10%, preferably by at least 25%, more preferably by at least 40% and most preferably by at least 50%. According to an embodiment, the second organic solvent used to form the second evaporation feed is not pure, e.g. contains water and/or HCI. According to a related embodiment, the used second organic solvent is recycled from another step in the process, e.g. from condensate of a distillation step. In such case, R23 refers to the ratio between the amounts of solvent on a solutes-free basis and water. As indicated earlier, R22 may depend on the temperature of distillation, on its pressure and on the content of the other components in the evaporation feed, including HCI and carbohydrates. As used hereinbefore, R22 is referred to the second solvent/water weight/weight ratio in the solvent-water binary system. On distillation from the second evaporation feed, there is at least one additional volatile component, co-distilling with water and the solvent, i.e. HCI. Thus, this system could be referred to as a ternary system. In such a system the solvent/water ratio in the vapor phase may differ from that in the binary system. As indicated, that ratio may further depend on the carbohydrates concentration in the second evaporation feed. In such complex systems, R22 refers to the solvent/water ratio in the vapor phase formed on distilling from the second evaporation feed.

According to an embodiment, the method further comprises the steps of condensing the vapors in the second vapor phase (step [O] in Fig. 1 ) to form two phases, a second organic solvent-rich phase (<2osr> in Fig. 1 ) and a first water-rich phase(<1wr> in Fig. 1 ), using the second organic -rich phase in said contacting step [(iii)] and using the first water-rich phase for generating the hydrolysis medium. Any method of condensing is suitable, preferably comprising cooling, pressure increase or both. Typically, the second organic solvent-rich phase also comprises water and HCI and the first water-rich phase also comprises solvent and HCI. Any method of separating the phases is suitable, e.g. decantation and the like. The second organic solvent-rich phase is used in step [(iii)] as is or after some treatment, e.g. removal of dissolved water, HCI or both. The first water-rich phase is used for regenerating the hydrolysis medium as is or after some treatment.

As indicated, the combined HCI removal in [C], [I] and [(iv)] is high, possibly exceeding 95%. Yet, some acid remains and is preferably removed for high recovery as well as for the production of a low-acid product. Thus, according to a preferred embodiment, the viscous fluid is further treated. Such further treatment ([P] in Figure 1 ) comprises, according to various embodiments, oligomers hydrolysis catalyzed by the residual acid, removal of residual acid to form a de-acidified carbohydrates solution, neutralization of the residual acid to form a chloride salt and removing the salt to form the de-acidified carbohydrates solution and various combinations thereof.

According to one embodiment reaching these low HCI concentrations in the de- acidified carbohydrates solution typically represents high yield of acid recovery from the hydrolyzate of the lignocellulosic material. Thus, according to an embodiment of the method, at least 95% of the acid in the hydrolyzate is recovered, more preferably at least 96%, and most preferably at least 98%.

The viscous fluid comprises carbohydrates resulting from the hydrolysis of the polysaccharides. According to an embodiment, the carbohydrates of the viscous fluid are of a low degree of polymerization, e.g. a combination of monosaccharides, disaccharides and oligosaccharides, e.g. trimers and or tetramers, at various ratios depending on the parameters of the hydrolysis reaction, such as HCI concentration, residence time and the like, and on the conditions used for the separation of the first separated HCI stream, the separation of the second separated HCI stream, where applicable,, and for HCI and water and second solvent distillation from the second evaporation feed. Unless otherwise indicated, the term oligosaccharide relates to dimers, trimers, tetramers and other oligomers up to a degree of polymerization of 10. According to an embodiment, essentially all the oligomers in said viscous fluid.are water soluble.

According to an embodiment, the oligosaccharides of the viscous fluid are composed of multiple sugars. According to another embodiment, the oligosaccharides are composed of glucose and at least one sugar selected from the group consisting of mannose, xylose, galactose, arabinose and fructose, optionally at least two such sugars.

According to an embodiment, the viscous fluid of the present invention is further converted into products, preferably selected from the group consisting of biofuels, chemicals, food ingredients and the like. According to a preferred embodiment, said further conversion comprises at least one of final purification, hydrolysis, carbohydrates fraction, dilution, re-concentration, and the like. According to a preferred embodiment, said further conversion comprises oligomers hydrolysis, which hydrolysis uses according to various embodiment, at least one biological catalyst, at least one chemical catalysts or a combination of both. According to an embodiment, said conversion involves fermentation to form fermentation products. According to an embodiment, the viscous fluid is diluted prior to or simultaneously with application of a biological catalyst or of a chemical catalyst, or prior to fermentation. According to an embodiment, the viscous fluid or diluted solution thereof is converted as such. Alternatively, the viscous fluid is first pre-treated. According to an embodiment, pre-treating comprises at least one of adding a component, i.e. a nutrient according to an embodiment, removing a component, i.e. an inhibitor according to an embodiment, oligomers hydrolysis and combinations thereof.

According to an embodiment, oligomers hydrolysis in the . viscous fluid or diluted solution thereof involves chemical catalysis, biological catalysis or a combination of those. According to an embodiment, HCI is used as a chemical catalyst. According to a related embodiment, HCI is added for said catalysis, optionally from a process stream, such as the first separated HCI stream, the second separated HCI stream and from a third separated HCI stream. According to an alternative embodiment, said HCI-catalyzed hydrolysis is conducted prior to the removal of the residual HCI from the viscous fluid.

According to an embodiment, such chemically catalyzed oligomers hydrolysis is conducted at a temperature in the range between 50°C and 130°C. According to another embodiment, the residence time for hydrolysis is between 1 min and 60min.

According to an embodiment, the method further comprises the steps of diluting the viscous fluid to form a diluted fluid that comprises oligomers and HCI,, hereinafter referred to as diluted fluid,, and maintaining said diluted fluid at a temperature and for a residence time Sufficient for the hydrolysis of at least 50% of said oligomers. According to an embodiment, carbohydrates concentration in said diluted fluid is in the range between 1% and 60%, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water, preferably between 2% and 50%, and more preferably between 5% and 40%. According to an embodiment, between 10%wt and 80%wt of the carbohydrates in said diluted fluid are in the form or oligomers, e.g. dimers, timers, tetramers and or higher oligomers, preferably between 20% and 77%, and more preferably between 30% and 70%.

According to an embodiment, the diluting is conducted by mixing with a diluting liquid, preferably water or an aqueous solution. HCI concentration in the diluted fluid depends on its concentration in the viscous fluid and on its concentration in the diluting liquid. According to an embodiment, HCI concentration in the diluted fluid is in the range between 0.2% and 10%, as calculated by 100 times HCI weight divided by the combined weights of the carbohydrate and water, preferably between 0.03% and 8%, and more preferably between 0.5% and 5%.

According to an embodiment, the HCI/carbohydrate w/w ratio in the diluted fluid is similar to that in the viscous fluid. The temperature of maintaining the diluted fluid and the residence time at that temperature are matters of optimization by a person skilled in the art. It is well known that the higher the temperature the greater is the kinetics of hydrolysis of oligomers. At the same time, elevated temperatures and extended residence times increase the degradation of carbohydrates, e.g. to degradation products such as furfural and hydroxyl-methyl-furfural. The optimization is directed to achieving the desired degree of hydrolysis of oligomers with minimal degradation of carbohydrates. According to an embodiment, at least 50% of the oligomers in the diluted fluid are hydrolyzed, preferably at least 80%, more preferably at least 90%, and most preferably at least 95%.

According to an embodiment, the viscous fluid comprises the second solvent and the diluting results in the formation of an organic phase. According to one embodiment, the organic phase is separated prior to the maintaining to form a separated organic phase and a separated diluted fluid. According to another embodiment, the maintaining is conducted in the presence of the organic phase and the latter is separated after the maintaining to form a separated organic phase and a separated maintained diluted fluid. According to an embodiment, the separated organic phase comprises impurities present within the diluted fluid and/or impurities formed during the maintaining. Separating such impurities-comprising organic phase improves the purity of the carbohydrates in the separated maintained diluted fluid.

According to another embodiment the method further comprises the steps of diluting the viscous fluid to form a diluted fluid and separating HCI from the diluted fluid by means selected from solvent extraction, membrane separation, ion-exchange and combinations thereof to form a de-acidified carbohydrates solution. According to an embodiment, the concentration of carbohydrates in the diluted fluid is in the range between 1% and 60%, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water, preferably between 2% and 50%, and more preferably between 5% and 40%. According to an embodiment, HCI concentration in the diluted fluid is in the range between 0.2% and 10%, as calculated by 100 times HCI weight divided by the combined weights of the carbohydrate and water, preferably between 0.03% and 8%, and more preferably between 0.5% and 5%. According to an embodiment, the diluted fluid is maintained at a temperature and for a residence time sufficient for the hydrolysis of at least 50% of the oligomers and the separating of HCI from the diluted fluid is conducted simultaneously with the maintaining, after the maintaining or a combination thereof. According to an embodiment, the separating HCI from the diluted fluid uses solvent extraction, which includes contacting with a selective extractant. According to an embodiment, the selective extractant comprises a water-immiscible amine. According to an embodiment, the contacting with the selective extractant forms the de-acidified carbohydrates solution and an acid-containing extractant. According to an embodiment, the acid-comprising extractant is contacted with a base, e.g. an aqueous solution of a base, whereby a regenerated extractant is formed. According to an embodiment, the regenerated extractant is reused for acid extraction from the diluted fluid.

According to an embodiment, the separating HCI from the diluted fluid involves membrane separation and the membrane separation uses anion-exchange membranes characterized by selective permeation of anions. According to an embodiment, the membrane separation involves electrodialysis in a multi-compartment system, so that a separated de-acidified carbohydrates solution is collected in part of the compartments and an aqueous solution of separated HCI is collected in others.

According to an embodiment, the separating HCI from the diluted fluid involves ion-exchange with an ion-exchanger. According to an embodiment, the ion-exchanger is an anion-exchanger, preferably in a free-base form.

According to an embodiment, the method further comprises the steps of diluting the viscous fluid to form the diluted fluid, neutralizing at least a fraction of the HCI in the diluted fluid to form a diluted fluid comprising a chloride salt and carbohydrates and optionally separating the salt from the carbohydrates by means selected from membrane separation, ion-exchange, chromatography and their combinations to form the de-acidified carbohydrates solution. According to an embodiment, carbohydrate concentration in the diluted fluid is in the range between 1 % and 60%, as calculated by 100 times carbohydrate weight divided by the combined weights of the carbohydrate and water, preferably between 2% and 50%, and more preferably between 5% and 40%. According to an embodiment, HCI concentration in the diluted fluid is in the range between 0.2% and 10%, as calculated by 100 times HCI weight divided by the combined weights of the carbohydrate and water, preferably between 0.03% and 8%, and more preferably between 0.5% and 5%. According to an embodiment, the diluted fluid is maintained at a temperature and for a residence time sufficient for the hydrolysis of at least 50% of the oligomers and the neutralizing is conducted after the maintaining or a combination thereof. According to an embodiment, the diluting and the neutralizing are conducted simultaneously. According to an embodiment, the neutralization and the separating of the salt are conducted simultaneously. The neutralization can be performed with any base. According to a preferred embodiment, neutralizing is performed with a base selected from the group consisting of hydroxides, carbonates or bicarbonates of sodium, potassium, ammonium, calcium, magnesium and combinations thereof.

Any method of selectively separating the chloride salt from the carbohydrate within the diluted solution is suitable for the method of the present invention. According to an embodiment, the separating of the salt involves membrane separation and the membrane separation may use ion-exchange membranes characterized by selective permeation of ions. According to an embodiment, the membrane separation involves electrodialysis (ED) in a multi-compartment system, so that a separated, de-acidified, carbohydrate solution is collected in part of the compartments and an aqueous solution of a separated chloride salt is collected in others.

According to an embodiment, the separating of the salt involves chromatographic separation. According to an embodiment the chromatographic salt separation uses methods similar to the ones used in corn wet milling. According to an embodiment, the chromatographic separation is conducted in a simulated moving bed (SMB) or in a similar system.

According to an embodiment, the chromatographic salt separation is combined with fractionation of the carbohydrates in the diluted fluid.

According to an embodiment, only a fraction of the chloride salt is separated from the dilute fluid. According to another embodiment, no salt is separated and the dilute fluid contains carbohydrates and chloride salt is used as such, e.g. as a precursor for chemical conversion into products such as biofuels and monomers for the polymers industry.

According to the various embodiments, the further steps of separating or neutralizing HCI enable reaching low HCI concentrations in the de-acidified carbohydrates solution. Thus, according to the embodiments of the method, the weight/weight ratio of HCI to carbohydrates in the de-acidified carbohydrate solution is less than 0.03, preferably less than 0.02, and more preferably less than 0.01.

According to an embodiment, oligomers hydrolysis involves enzymatic hydrolysis. According to an embodiment, hydrolysis uses at least one enzyme with cellulose hydrolysis activity, at least one enzyme with hemicellulose hydrolysis activity, at least one enzyme with 1 -4 alpha bond hydrolysis activity, at least one enzyme with 1 - 6 alpha bond hydrolysis activity, at least one enzyme with 1 -4 beta bond hydrolysis activity, at least one enzyme with 1 -6 beta bond hydrolysis activity, and combinations thereof. According to an embodiment, enzymes capable of operating at temperatures greater than 40°C, preferably greater than 50°C and more preferably greater than 60°C are used. According to an embodiment, enzymes capable of operating at a carbohydrates concentration greater than 25%wt, preferably greater than 30%wt, and more preferably greater than 35%wt are used. According to an embodiment, at least one immobilized enzyme is used for oligomers hydrolysis. According to an embodiment, multiple enzymes of the above list are immobilized and used in the converting.

According to an embodiment, carbohydrates within the viscous fluid of the present invention, in the de-acidified carbohydrates solution or within a product of their dilution, are further converted in a simultaneous saccharification and fermentation. As used herein, the term simultaneous saccharification and fermentation means a treatment wherein oligomers hydrolysis and fermentation of the hydrolysis products, optionally combined with fermentation of oligomers, e.g. dimers and trimers,, are conducted simultaneously. According to a preferred embodiment, the hydrolysis and the fermentation are conducted in the same vessel. According to an embodiment, the simultaneous saccharification and fermentation conversion uses at least one enzyme with cellulose hydrolysis activity, at least one enzyme with hemicellulose hydrolysis activity, at least one enzyme with 1 -4 alpha bond hydrolysis activity, at least one enzyme with 1 -6 alpha bond hydrolysis activity, at least one enzyme with 1 -4 beta bond hydrolysis activity, at least one enzyme with 1 -6 beta bond hydrolysis activity, and combinations thereof. According to an embodiment, at least one immobilized enzyme is used in the simultaneous saccharification and fermentation. According to an embodiment, multiple enzymes of the above list are immobilized and used in the converting. According to an embodiment, the fermentation is to form a renewable fuel, such as ethanol, butanol or a fatty acid ester or a precursor of a renewable fuel, such as iso-butanol, and the like. According to another embodiment, the fermentation is to form food or a feed ingredient, such as citric acid, lysine and mono-sodium glutamate, and the like. According to still another embodiment, the fermentation is to form an industrial product, such as, but not limited to, a monomer for the polymers industry, e.g. lactic acid, a chemical for use as such or a precursor of such chemical.

According to the method of the present invention, hydrolysis forms the HCI- comprising lignin stream comprising lignin, HCI and water (<lg8> in Fig. 1 ). According to an embodiment of the invention, within the HCI-comprising lignin stream, HCI amount, concentration and purity are W8, C8 and P8, respectively. According to an embodiment of the invention, a major fraction of the HCI in the HCI reagent stream ends up in the HCI-comprising lignin stream, such that W8/W6 is greater than 30%, preferably greater than 38%, and more preferably greater than 45%. The method of the present invention enables the recovery of essentially all the acid in that stream and obtaining it at a high concentration to minimize re-concentration costs. According to a preferred embodiment, HCI separation from the HCI-comprising lignin stream is done with no or with only a minimal wash with water.

According to an embodiment, the lignocellulosic feed further comprises an organic compound, e.g. tall oil, and the like, and a fraction of the organic compound ends up within the HCI-comprising lignin stream. According to a related embodiment, the HCI-comprising lignin stream is brought into contact with a fourth organic solvent, whereupon the organic compound selectively transfers to the fourth organic solvent to form an organic compound-depleted lignin stream and a second organic compound- carrying solvent. According to an embodiment, the second organic compound-carrying solvent has a commercial value as such. According to another embodiment, the method further comprises a step of recovering the fourth organic solvent and organic compound from the second organic compound-carrying solvent to form a separated organic compound and a regenerated fourth organic solvent. Various methods are suitable for such recovering, including distilling the fourth organic solvent and extracting it into another solvent, wherein the organic compound has limited miscibility. According to an embodiment, the organic compound is a tall oil.

According to an embodiment, a third organic solvent is used to extract organic compounds from the hydrolyzate, a fourth organic compound is used to extract organic compounds form the HCI-comprising lignin stream and the third organic solvent and the fourth organic solvent are of essentially the same composition. According to a related embodiment, the first organic compound-carrying solvent and the second organic compound-carrying solvent are combined to form a combined organic compound- carrying solvent and the organic compound is separated from the combined organic compound carrying solvent.

As used herein, the term of essentially the same composition for two components means that the two are composed of the same compound or isomers with similar properties in case each of those is composed of a single compound, or, in case of mixtures, that at least 50%wt. of the composition of one component is identical to at least 50%wt. of the composition of the other component. That is, by way of example, the case wherein the two components are mixtures of hydrocarbons, e.g. C6 to C9 hydrocarbons and wherein at least 50%wt. of each mixture is the same hydrocarbon, e.g. heptane. According to a preferred embodiment, the third organic solvent, the fourth organic solvent or both are selected from the group consisting of heptanes, octanes and nonanes, and most preferably heptanes.

According to an embodiment, the method comprises a step of forming a second lignin stream from the HCI-comprising lignin stream, which second lignin stream is characterized by a lignin to water weight/weight ratio in the range between 0.1 and 2, preferably between 0.3 and 1.8, more preferably between 0.5 and 1.5, and most preferably between 0.8 and 1.2. The second lignin stream is further characterized by HCI/water weight/weight ratio in the range of between 0.15 and 1 , preferably between 0.2 and 0.8, more preferably between 0.25 and 0.6, and most preferably between 0.3 and 0.5.

According to an embodiment, the forming of the second lignin stream from the HCI-comprising lignin stream comprises separating ([D] in Fig. 1) HCI from the HCI- comprising lignin stream to form a third separated HCI stream <3s9> wherein HCI amount, concentration and purity are W9, C9 and P9, respectively, and forming an HCI- depleted lignin stream <dl>. According to an embodiment, the separating comprises distillation and the third separated HCI stream is gaseous. According to an embodiment, at least a portion of the third separated HCI stream is used to form the recycled reagent HCI, e.g. by combining the third separated HCI stream with at least a portion of the first separated HCI stream.

In a preferred embodiment the HCI streams of about azeotropic concentration, e.g. the second separated HCI stream, are combined with the HCI-comprising lignin stream prior to the separation of the third separated HCI stream, e.g. by distillation.

According to an embodiment, W9/W8 is greater than 0.1 , preferably greater than 0.2, more preferably greater than 0.3, and most preferably greater than 0.4. According to another embodiment, P9/P8 is greater than 1.1 , preferably greater than 1.2, more preferably greater than 1.3, and most preferably greater than 1.4. According to another embodiment, C9/C8 is greater than 1.8, preferably greater than 2.0, more preferably greater than 2.5, and most preferably greater than 3.0.

According to an embodiment, the forming of the second lignin stream further comprises a step ([K] in Fig. 1) of separating HCI from the HCI-depleted lignin stream to form a fourth separated HCI stream <4s10> wherein the HCI amount is W10, and forming a further HCI-depleted lignin stream. According to an embodiment, W10/W8 is greater than 0.1 , preferably greater than 0.2, more preferably greater than 0.3, and most preferably greater than 0.4. According to an embodiment, the further HCI-depleted lignin stream forms the second lignin stream as such or after some modification. According to an embodiment, the separating HCI from the HCI-depleted lignin stream comprises at least one of filtration, press filtration, centrifugation, and the like. According to an embodiment, the filtration, press filtration or centrifugation forms a wet cake of relatively high dry matter content. The inventors have surprisingly found that the separating of residual aqueous HCI solution is markedly improved when conducted on the HCI- depleted lignin stream after separating the third separated HCI stream. According to a preferred embodiment, the dry matter contents of that formed cake is greater than 30%wt, preferably greater than 35%wt, more preferably greater than 38%, and most preferably greater than 40%wt.

According to an embodiment, the lignocellulosic feed further comprises an organic compound, e.g. tall oil, and a fraction of the organic compound ends up in the further HCI-depleted lignin stream and or in the second lignin stream. According to a related embodiment, that further HCI-depleted lignin stream and or the second lignin stream is brought into contact with a fifth organic solvent, whereupon the organic compound selectively transfers to the fifth organic solvent to form an organic compound- depleted lignin stream and a third organic compound-carrying solvent. According to an embodiment, the third organic compound-carrying solvent has a commercial value as such. According to another embodiment, the method further comprises a step of recovering the fifth organic solvent and the organic compound from the third organic compound-carrying solvent to form a separated organic compound and a regenerated fifth organic solvent. Various methods are suitable for such recovering, including distilling the fifth organic solvent and extracting it into another solvent, wherein the organic compound has limited miscibility. According to an embodiment, the organic compound is a tall oil. According to an embodiment, the fifth organic solvent is essentially of the same composition as the third organic solvent, as the fourth organic solvent or both. According to a related embodiment, the third organic compound- carrying solvent is combined with the first organic compound-carrying solvent, with the second organic compound-carrying solvent or with both to form a combination out of which the organic compound and the solvent are separated.

According to an embodiment of the invention, the second lignin stream (<2I> in Fig. 1) is contacted ([(v)] in Fig. 1 ) with a first organic solvent <1 os> to form a first evaporation feed <1 ef>. According to the method, water, HCI and the first organic solvent are distilled ([(vi)] in Fig. 1 ) from the first evaporation feed at a temperature below 100°C and at a pressure below 1 atm, whereupon a first vapor phase (<1vp> in Fig. 1) and a lignin composition ((<lc> in Fig. 1 ) are formed.

The first organic solvent of the present invention forms a heterogeneous azeotrope with water. According to an embodiment of the present invention, the solubility of the first organic solvent in water, as determined by combining an essentially pure solvent and de-ionized water, at 25°C is less than 15%wt, preferably less than 10%wt, more preferably less than 5%, and most preferably less than 1%. According to another embodiment, the solubility of water in the first organic solvent, similarly determined, is less than 20%wt, preferably less than 15%wt, more preferably less than 10%, and most preferably less than 8%. According to another embodiment, in the heterogeneous azeotrope with water, the weight/weight ratio of the first organic solvent to water is in the range between 50 and 0.02, preferably between 20 and 0.05, more preferably between 10 and 1 , and most preferably between 5 and 0.2.

According to another embodiment, the first organic solvent is characterized by having a polarity related component of Hoy's cohesion parameter between 0 and 15, preferably between 4 and 12, and more preferably between 6 and 10. According to still another embodiment, the first organic solvent is characterized by having a hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20, preferably between 1 and 15, and more preferably between 2 and 14.

According to still another embodiment, the first organic solvent has a boiling point at 1 atm in the range between 100°C and 200°C, preferably between 110°C and 190°C, more preferably between 120°C and 180°C, and most preferably between 130°C and 160°C.

According to a preferred embodiment, the first organic solvent is selected from the group consisting of C5-C8 alcohols, C5-C8 chlorides and combinations thereof, including primary, secondary, tertiary and quaternary ones, aliphatic and aromatic ones and linear and branched ones, toluene, xylenes, ethyl benzene, propyl benzene, isopropyl benzene and nonane.

As indicated, the evaporating in [(vi)] forms a lignin composition. The lignin composition of the present invention comprises between 10%wt and 50%wt lignin, preferably between 12%wt and 40%wt, more preferably between 14%wt and 30%wt and most preferably between 15%wt and 25%wt. Unlike carbohydrates in the viscous fluid, lignin concentration is presented herein on an "as is" basis. According to an embodiment, the lignin composition is essentially water free. According to another embodiment, the lignin composition comprises water, but at a concentration of less than 8%wt water, preferably less than 5%wt, more preferably less than 3%wt, and most preferably less than 1 %wt. The lignin composition also comprises between 50%wt and 90%wt of a first solvent, preferably between 60%wt and 88%wt, more preferably between 70%wt and 85%wt and most preferably between 72%wt and 82%wt on an "as is" basis. The lignin composition also comprises, according to some embodiments, HCI, and the HCI concentration is less than 10%wt, preferably less than 8%wt, more preferably less than 6%wt and most preferably less than 4%wt (on an as is basis). According to another embodiment, the lignin composition further comprises at least one carbohydrate and the carbohydrate content is less than 5%wt, preferably less than 4%wt, more preferably less than 3%wt, and most preferably less than 2%wt (on an as is basis).

The majority of the lignin in the composition is insoluble in water, in hydrochloric acid solutions, and in the first solvent. According to one embodiment, the lignin composition comprises insoluble lignin dispersed in a liquid, preferably in a liquid solvent solution, which may contain a few percents of aqueous solution dispersed therein.. According to another embodiment, the lignin composition comprises the wet cake, wherein the lignin is wetted by said liquid solution.

According to an embodiment, the lignin composition further comprises at least one of residual cellulose, a mineral salt and tall oils.

According to a preferred embodiment of the invention, the ratio between the amount of water in the second lignin stream and the amount of the first organic solvent contacted with it in [(v)] is such that the solvent is found in the lignin composition at the end of the distillation. According to a further preferred embodiment, the solvent/water ratio in the lignin composition is greater than the solvent/water ratio in the water-solvent heterogeneous azeotrope. According to an embodiment of the invention, in the lignin composition the first organic solvent to water weight/weight ratio is R1 , the first organic solvent formsa heterogeneous azeotrope with water,, the first organic solvent/water weight/weight ratio in the azeotrope is R12 and R1 is greater than R12 by at least 10%, preferably by at least 25%, more preferably by at least 40% and most preferably by at least 50%. According to still another embodiment, the first organic solvent/water weight/weight ratio in the first evaporation feed is R13, the first organic solvent to water weight/weight ratio in the azeotrope is R12 and R13 is greater than R12 by at least 10%, preferably by at least 25%, more preferably by at least 40% and most preferably by at least 50%. According to an embodiment, the first organic solvent used to form the first evaporation feed is not pure, e.g. containing water and or HCI. According to a related embodiment, the used first organic solvent is recycled from another step in the process, e.g. from a condensate of a distillation step. In such case, R13 refers to the ratio between the solvent on a solutes-free basis and water. As indicated earlier, R12 may depend on the temperature of distillation, on its pressure and on the content of the other components in the evaporation feed, including HCI and carbohydrates. Thus, as in the case of distilling from the second evaporation feed, the solvent/water ratio in the first vapor phase may differ from that in the solvent-water binary system. In that case, R12 as used herein means the solvent/water ratio in the first vapor phase.

According to an embodiment, the method further comprises the steps of condensing the vapors in the first vapor phase (step [Q] in Fig. 1 ) to form two phases, a first organic solvent-rich one (<1 osr> in Fig. 1) and a second water-rich one (<2wr> in Fig. 1 ), using the first organic solvent-rich phase in said contacting step [(v)] and using the second water-rich phase for generating the hydrolysis medium. Any method of condensing is suitable, preferably comprising cooling, pressure increase or both. Typically, the first organic solvent-rich phase also comprises water and HCI and the second water-rich phase also comprises solvent and HCI. Any method of separating the phases is suitable, e.g. decantation, and the like. The first organic solvent-rich phase is used in step [(v)] as is or after some treatment, e.g. removal of dissolved water, HCI or both. The second water-rich phase is used for regenerating the hydrolysis medium as is or after some treatment.

According to a preferred embodiment, the method of the present invention comprises further treating the lignin composition to form a treated lignin composition (step [R] in Fig. 1 ). According to various embodiments, further treating comprises removal of residual HCI from the lignin composition, neutralization of the residual HCI therein, desolventization and additional purification. According to an embodiment, desolventization comprises centrifugation. According to a related embodiment, desolventization comprises contacting the solvent-wetted lignin cake with water whereby water displaces solvent from the solvent wetted cake, followed by centrifugation.

According to an embodiment, HCI concentration within the lignin composition, within the treated lignin composition (<tlc> in Fig. 1 ) or in both is less than 10,000ppm, more preferably less than 5000ppm, and most preferably less than 2000ppm.

According to a preferred embodiment, the first organic solvent is of essentially the same composition as the second organic solvent. According to a related embodiment, the method for the production of carbohydrate comprises (i) providing a lignocellulosic material feed comprising a polysaccharide and lignin; (ii) hydrolyzing the polysaccharide in an HCI-comprising hydrolysis medium to form a first aqueous solution comprising carbohydrates, HCI and water, wherein the weight/weight ratio of carbohydrates to water is in the range between 0.4 and 3 and wherein the weight/weight ratio of HCI to water is in the range between 0.17 and 0.50; and a second lignin stream comprising lignin, HCI and water, wherein the weight/weight ratio of lignin to water is in the range between 0.1 and 2.0 and wherein the weight/weight ratio of HCI to water is in the range between 0.15 and 1 ; (iii) contacting the first aqueous solution with a second organic solvent to form a second evaporation feed, which solvent forms a heterogeneous azeotrope with water and is characterized by at least one of (a) having a polarity related component of Hoy's cohesion parameter between 0 and 5 Pa ^1/2 , (b) having a hydrogen bonding related component of Hoy's cohesion parameter between 0 and 20 MPa ^1/2 , and (c) having a solubility in water smaller than 15%wt, and forming a heterogeneous azeotrope with water, wherein the weight/weight ratio of the second organic solvent to water is in the range between 0.2 and 5, and wherein the solubility of water in the organic solvent is less than 20%; (iv) evaporating water, HCI and the second organic solvent from the second evaporation feed at a temperature below 100°C and at a pressure below 1 atm, whereupon a second vapor phase and a viscous fluid according to the first aspect are formed; (v) diluting the viscous fluid to form a diluted fluid, (vi) treating the diluted fluid by at least one of separating HCI therefrom and neutralizing HCI therein to form a chloride salt, (vii) contacting the second lignin stream with the first organic solvent to form a first evaporation feed, and (viii) evaporating water, HCI and a first organic solvent from the first evaporation feed at a temperature below 100°C and at a pressure below 1 atm, whereupon a first vapor phase and a lignin composition according to the third aspect are formed.

According to a related embodiment, the first vapor phase or its condensate(s) is combined with the second vapor phase or its condensate(s) for further treatment resulting in the formation of a water-rich phase to be used in regenerating the hydrolysis medium and an organic solvent-rich phase to be used in the contacting steps [(iii)] and [(v)].

The method of the present invention further comprises combining (step [S] in Fig. 1) at least portions of multiple HCI-comprising streams to reform the recycled HCI reagent stream. According to a related embodiment, the combining is of at least two HCI-comprising streams selected from the group consisting of the first separated HCI stream, the second separated HCI stream, the third separated HCI stream, the fourth separated HCI stream, the first water-rich phase, and the second water-rich phase. The amount, concentration and purity of HCI in the recycled HCI reagent stream are W6, C6 and P6, respectively. According to an embodiment, W6/W4 is greater than 1 , preferably at least 1.2, more preferably at least 1.5 and most preferably at least 1.8. According to an embodiment, the weight/weight ratio between W6 and that of the initial polysaccharide-comprising feed in forming the hydrolysis medium is between 0.2 and 5, and preferably between 0.5 and 3. According to an embodiment, P6 is greater than 80%, preferably greater than 85%, more preferably greater than 90%, and most preferably greater than 95%. According to another embodiment, C6 is greater than 30%, preferably greater than 35%, more preferably greater than 38%, and most preferably greater than 40%, as calculated by 100 time HCI weight divided by the combined weights of HCI and water. According to a preferred embodiment, formation of the recycled HCI reagent stream does not require water ¹ removal from the HCI- comprising stream. According to another embodiment, water removal from the HCI- comprising stream is limited to less than 0.1 ton of water per one ton of HCI in the recycled HCI reagent stream, preferably less than 0.05 ton, more preferably less than 0.03 ton, and most preferably less than 0.01 ton.

While the invention will now be described in connection with certain preferred embodiments in the following examples so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims. Thus, the following examples which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of formulation procedures as well as of the principles and conceptual aspects of the invention.

Examples

Example 1

Preparation of the first aqueous solution glucose: HCI, water and glucose (CH) were mixed to form HCI/(HCI+water) = 0.248 and CH/(CH+water) = 0.64. The mixture was kept at 40°C for 3 hours, in which time oligomers were formed.

33.6gr of the first aqueous solution were combined in a flask with 8.2gr hexanol to form an evaporation feed. Evaporation was applied at 100-150mbar for about 0.5hr at a temperature that increased from 62°C at the beginning of the distillation to 76°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content there was less than 10%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 1 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) there are presented:

Table 1 : Viscous fluid analysis

The formed viscous fluid had an HCI to carbohydrates weight/weight ratio of about 0.058, which represents HCI removal greater than 95% from a typical hydrolyzate, wherein HCI/carbohydrate weight/weight ratio is greater than 1. Its water/carbohydrate weight/weight ratio is about 10%, representing removal of about 95% of the water in the hydrolyzate, wherein the water/carbohydrate weight/weight ratio is greater than 2. The viscous fluid, as is, before the separation of the solvent, had a viscosity of about 80cP at 80°C, low enough to be fed to a spray drier.

Example 2

Preparation of the first aqueous solution: HCI, water, xylose and glucose (referred to together as carbohydrates, CH) were mixed to form HCI/(HCI+water) = 0.22 and CH/(CH+water) = 0.65. The mixture was kept overnight at 34°C.

33.4gr of that first aqueous solution were combined in a flask with 8.0gr hexanol to form an evaporation feed. Evaporation was applied at 100-150mbar for about 1.5hr at a temperature that increased from 62°C at the beginning of the distillation to 75°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content was less than 10%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 2 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) therein are also presented:

Table 2: Viscous fluid analysis

Acid and water removal in Exp. 2 are slightly lower than those in Exp.1 , and the same is true for the viscosity.

Example 3

32.7gr of the first aqueous solution formed in Example 1 were combined in a flask with 5.9gr hexanol to form an evaporation feed. Evaporation was applied at 100- 150mbar for about 45min at a temperature that increased from 62°C at the beginning of the distillation to 72°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content was less than 10%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 3 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) therein are also presented:

Table 3: Viscous fluid analysis

Example 4

19.3gr of the first aqueous solution formed in Example 1 were combined in a flask with 20.7gr xylenes mixture to form an evaporation feed. Evaporation was applied at 100-150mbar for about 1 hour at a temperature that increased from 65°C at the beginning of the distillation to 69°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content was less than 15%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 4 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) therein are also presented

Table 4: Viscous fluid analysis

Acid and water removal was similar to that for hexanol. The viscosity was also similar.

Example 5

Preparation of the first aqueous solution glucose: HCI, water and carbohydrates mixture (CH) were mixed to form HCI/(HCI+water) = 0.255 and CH/(CH+water) = 0.66. The carbohydrates mixture contained glucose, fructose, xylose, arabinose and galactose at relative weights of 100, 1.25, 11.4, 3 and 4.8, respectively. The mixture was kept at 45°C for 2 hours, in which time oligomers were formed.

32.4gr of that first aqueous solution were combined in a flask with 6.23gr hexanol to form an evaporation feed. Evaporation was applied at 100-150mbar for about 0.5 hour at a temperature that increased from 63°C at the beginning of the distillation to 68°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content was less than 10%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 5 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) therein are also presented:

Table 5: Viscous fluid analysis

The viscosity of the viscous phase here (including the solvent) was lower than that in previous examples, where a single carbohydrate or two carbohydrates were tested. Example 6

Preparation of the first aqueous solution glucose: HCI, water and glucose (CH) were mixed to form HCI/(HCI+water) = 0.285 and CH/(CH+water) = 0.66.

41.8gr of the first aqueous solution were combined in a flask with 10.0gr hexanol to form an evaporation feed. Evaporation was applied at 100-150mbar for about 1.5hr at a temperature that increased from 62°C at the beginning of the distillation to 80°C at its end. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). At the end of the distillation, two phases were observed in the flask - a small amount of a light one and a heavy viscous fluid. The four phases were weighed and analyzed. The viscous fluid was centrifuged for separation of the solvent prior to analysis. The solvent content therein was less than 10%wt. The analysis of the viscous fluid on a solvent-free basis is presented in Table 6 as %wt. In addition, CH/(CH+water) and HCI/(HCI+water) therein are also presented

Table 6: Viscous fluid analysis

Example 7

Preparation of the lignin solution: 18.77gr lignin, 18.14gr HCI and 60.28gr water were mixed. The solution was combined in a flask with 243.2 gr of fresh hexanol. Distillation was applied at atmospheric pressure at about 102-103°C for 3 hours. The distillate was cooled and collected to form an organic solvent-rich light phase (light) and an aqueous phase (heavy). In the feed flask remained a lignin cake in a brown liquid, rich in solvent.

The cake was filtered and analyzed. The DS of the cake was about 38%, the hexanol content was about 60%, and the HCI content, on as is basis, was about 0.7%.

It will be understood by those skilled in the art that various changes in form and details may be made herein without departing from the spirit and scope of the invention as set forth in the appended claims. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed in the scope of the claims. In the claims articles such as "a,", "an" and "the" mean one or more than one unless indicated to the contrary or otherwise evident from the context. Claims or descriptions that include "or" or "and/or" between members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The invention includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The invention also includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process. Furthermore, it is to be understood that the invention provides, in various embodiments, all variations, combinations, and permutations in which one or more limitations, elements, clauses, descriptive terms, etc., from one or more of the listed claims is introduced into another claim dependent on the same base claim unless otherwise indicated or unless it would be evident to one of ordinary skill in the art that a contradiction or inconsistency would arise. Where elements are presented as lists, e.g., in Markush group format or the like, it is to be understood that each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should it be understood that, in general, where the invention, or aspects of the invention, is/are referred to as comprising particular elements, features, etc., certain embodiments of the invention or aspects of the invention consist, or consist essentially of, such elements, features, etc. For purposes of simplicity those embodiments have not in every case been specifically set forth in haec verba herein. Certain claims are presented in dependent form for the sake of convenience, but Applicant reserves the right to rewrite any dependent claim in independent format to include the elements or limitations of the independent claim and any other claim(s) on which such claim depends, and such rewritten claim is to be considered equivalent in all respects to the dependent claim in whatever form it is in (either amended or unamended) prior to being rewritten in independent format.