DESCRIPTION

BACKGROUND

Ligno-cellulosic biomass may be used to produce a platform of valuable chemicals and biofuels derived from monomeric sugars, such as glucose and xylose. Recovery of monomeric sugars from the insoluble carbohydrates of the ligno-cellulosic biomass (cellulose and hemicellulose) is a multistep process usually comprising a pre- treatment of the ligno-cellulosic biomass to increase the accessibility to the polysaccharides, which must then be cleaved to monosaccharides in a process known as hydrolysis.

Different physical, thermal, biological and chemical pretreatments have been developed so far. Most effective pretreatments involve hydrothermal processes often in the presence of aggressive chemical agents, such as sulfuric acid, which solubilizes a portion of the hemicellulose.

Hydrolysis of pre-treated ligno-cellulosic biomass can be conducted either as mineral acid catalyzed or as enzymatically catalyzed process.

Enzymatic hydrolysis is a selective process involving enzymes as catalyst, wherein very few by-products are formed. However, it is a slow and expensive process and typically only cellulose is hydrolyzed by the enzymes with high yield, even if enzymes have been recently engineered to operate also on hemicellulose.

In acid hydrolysis, both cellulose and hemicellulose chains are cut into monosaccharides. Acid hydrolysis can be catalyzed with either dilute or concentrated acid, usually with sulfuric acid as catalyst. The negative aspects of acid-catalyzed hydrolysis are high acid consumption and corrosion problems in the concentrated acid hydrolysis, and formation of degradation products mainly in the dilute acid hydrolysis. Moreover, the added acid increases significantly the amount of anionic species, which have to be removed before subsequent conversion steps of the monomeric sugars increasing the complexity and the cost of purification step.

In WO2013026849 it is disclosed a process for the hydrolysis of oligosaccharides present in a liquid biomass feed stream derived from pre-treated ligno-cellulosic biomass. The process comprises creating an acidic stream from the liquid biomass feed stream by increasing the number of H ⁺ ions to the liquid biomass feed stream in an amount sufficient so that the pH of the acidic stream is at least 0.5 pH units less than the pH of the liquid biomass feed stream prior to the addition of the H ⁺ ions wherein less than 80% of the total amount of H ⁺ ions added to the feed stream are derived from an acid or acids, and then hydrolyzing the acidic stream by increasing the temperature of the acidic stream to a hydrolysis temperature greater than 80 °C.

In a preferred embodiment, at least a portion of the H ⁺ ions come from decationization using an ion exchange agent and at least a portion of the acidic stream is separated from the ion exchange agent before hydrolyzing the separated portion of the acidic stream.

The application does not recognize any specific advantage enabled by the disclosed hydrolysis process for recovering a purified monomeric sugar stream from the hydrolyzed acidic stream and therefore it does not disclose any purification configuration of the hydrolyzed acidic stream.

As a result of the severity of the pre-treatment and the hydrolysis processes, it is obtained a ligno-cellulosic biomass hydrolyzate which comprises the desirable monomeric sugars, but also unwanted soluble compounds derived both from the ligno-cellulosic biomass and from the process. In particular, a large amount of impurities, including dissociated salts, sugar degradation products, organic acids, soluble phenolic compounds, and other compounds are present in the sugar stream after the hydrolysis.

These soluble compounds result from degradation or solubilization of the feedstock or from the acids and alkali added in the process. As many of these soluble compounds will limit the following conversion of the monosaccharides to the desired chemicals and biofuels, the hydrolyzate must be refined to produce a purified monomeric sugars liquid stream.

The recovery and purification of monomeric sugar streams from the ligno-cellulosic biomass hydrolyzate has been the subject of a significant amount of research. The processes studied include lime addition and chromatographic separation, which may be conducted by ion exchange and by ion exclusion.

In lime addition, lime (calcium hydroxide), which is insoluble, is added to the sugar stream to precipitate impurities.

The limed sugar solution has an alkaline pH and is neutralized with acid, typically phosphoric acid, sulfurous acid, carbonic acid, or a mixture thereof. Optionally, the lime cake is separated from the sugar by filtration. A second option is to filter the lime cake at alkaline pH and carry out a second filtration to remove material that precipitates during the acidification steps. Lime treatment decreases the toxicity of the sugar stream to yeast and other microbes. However, any handling of the lime cake is difficult and costly. In addition, the introduction of calcium into the stream increases the likelihood that calcium scale will deposit on evaporators, distillation columns, and other process equipment. The clean-up and avoidance of scale increases the cost of sugar processing. Furthermore, the introduction of lime makes the recovery of salt and acetic acid more difficult.

It is known in the art that chromatography and adsorption, or a combination thereof, may be used to produce food grade, high value added monomelic sugar streams. An extensive review of the purification and fractionation processes of ligno-cellulosic hydrolyzates may be found in Jari Heinonen, Tuomo Sainio, "Chromatographic Fractionation of Lignocellulosic Hydrolysates", Advances in Chemical Engineering, Volume 42, pag.261.

In the case of bio-fuel or low added-value chemicals, the recovery of monomeric sugar streams must be accomplished in a cost-effective way.

In order to improve the economics of the acid-catalyzed hydrolysis processes, the hydrolysis acid should be recovered and recycled. In the chromatographic fractionation of concentrated acid ligno-cellulosic hydrolyzates, strong cation-exchange resins in acid form are used as an adsorbent. The hydrolyzates formed in the acid hydrolysis process are fractionated into hydrolysis acid fraction, monosaccharide fraction, and by-products fractions. The hydrolysis acid fraction is led through a concentration step back to the hydrolysis. This recycling lowers the chemical consumption (costs) of the process considerably because the need for fresh acid is reduced.

One of the problem related to the chromatographic separation of hydrolyzates from acid hydrolysis process is the presence in the hydrolyzate of anions from the added mineral acid. Moreover other ionic species from the biomass are present in the hydrolyzate, such as cations and anions originated from salts contained in the biomass and dissolved during the pre treatment and hydrolysis steps.

As evidenced for instance in figure 5.10 of the review of Jari Heinonen at al., reproducing the chromatographic diagram of a concentrated acid spruce hydrolyzate, a huge peak comprising charged species is overlapped to the monomeric sugars peak. Thereby, the separation of a monomeric sugars stream from an acid hydrolyzate with high purity and yield may not be accomplished by means of a unique chromatographic step, while the use of many chromatographic steps will increases the cost of the separation process. In ion exchange, the sugar stream is flowed through columns packed with ion exchange resins. The resins are in a cation exchange or anion exchange form, or a combination of the two. In principle, cation- exchange resins remove cations such as sodium or potassium, while anion-exchange resins remove anions such as sulfate and acetate. For example, ion exchange has been investigated by Nilvebrant et al. (App. Biochem. Biotech., 2001 , 91-93:35-49) in which a spruce hydrolyzate was treated to remove inhibitors, such as phenolic compounds, furan aldehydes and aliphatic acids. The separation was carried out using an anion exchanger, a cation exchanger and a resin without charged groups. The investigators found that a treatment at pH 10.0 using an anionic exchanger removed phenolic compounds since at this pH most of the phenolic groups were ionized.

In practice, several factors limit the effectiveness of ion exchange treatment to remove inhibitors. First, the multi-component nature of the streams results in an inefficient removal of some species, at any single set of conditions. Second, the high ionic load demands very frequent and expensive regeneration of the resin. Finally, not all of the inhibitors are ionic, and ion exchange is ineffective in removing nonionic compounds from sugar.

Ion exclusion uses ion exchange resins, but rather than bind target ions in solution, the charge on the resin matches that of the target ions in the solution, thereby excluding them from the resin.

The excluded compounds then elute from the column readily, while uncharged compounds absorb into the resin and elute from the column more slowly. For example, a concentrated solution of sulfuric acid and glucose has hydrogen as the primary cation. A cation-exchange resin in the hydrogen form will exclude the acid, causing it to elute quickly. The glucose, which is uncharged, is not excluded from the resin and absorbs into the resin void, thereby eluting from the column more slowly than the acid. Ion exclusion has been used for example by Wooley et al., (Ind. Eng. Chem. Res., 1998, 37:3699-3709), which teaches the removal of acetic acid and sulfuric acid from biomass sugars by pumping a product stream over a bed of cation exchange resin in the hydrogen form. The positive charge on the resin repels the hydrogen ion in the sulfuric acid, thereby causing the sulfuric acid to elute from the column very quickly. The uncharged sugar molecules are absorbed into the void space of the resin and elute from the column more slowly than the sulfuric acid. Fully associated acetic acid (non-ionic) is a smaller molecule than sugar or sulfuric acid and so elutes from the column more slowly than sulfuric acid or sugar. Also described is a Simulated Moving Bed (SMB) system for producing a glucose stream free of sulfuric acid and acetic acid. The ion exclusion was carried out at a pH of between about 1-2 and, at such low pH values, significant degradation of xylose is likely.

US5560827 and US5628907 disclose a process for separating an ionic component (acid) from a non-ionic component (sugar) using an SMB arrangement, including a plurality of ion exclusion columns arranged in 4 zones. The separations are run at a low pH using a cationic (or cation- exchange) resin in the hydrogen form. The methods incorporate various arrangements to minimize the dispersion and channeling effects. The sugar/ acid solution is loaded onto the column and the acid elutes first while sugar is eluted later using water.

US5407580 discloses a process for separating an ionic component (acid) from a non-ionic component (sugar) using a preparative-scale ion exclusion system. The system includes a floating head distribution plate to prevent evolution of a dilution layer caused by the shrinkage of the resin bed. The columns can be operated over a range of process conditions to produce separate and distinct elution profiles for the acid and sugar. Acceptable conditions for carrying out the process are at a sulphuric acid concentration of 1.0 to 20.0%, a feed volume of 1.0 to 5.0, a flux rate of 0.1 to 2.0 and using a divinylbenzene resin with a percent crosslinking of between 1.0 and 15.

US5968362 discloses a method of separating sugars and acid by ion exclusion chromatography using an anion exchange resin. The sugars elute through the column, and may contain residual acid and heavy metals. The heavy metals, can be removed and the acid neutralized using a lime treatment. The acid adsorbs to the resin and is retained; it is eluted from the resin with water.

US6663780 discloses a method in which product fractions, such as sucrose, betaine and xylose, are separated from molasses that are obtained from a variety of sources, including beet and cane molasses, as well as hydro lyzates produced from biomass. The process involves treating the molasses with sodium carbonate (pH 9) to precipitate calcium followed by removing the resulting precipitate. The filtrate is then subjected to a simulated moving bed (SMB); process which is carried out using at least two SMB systems packed with a strongly acid cation exchange resin. Sucrose is recovered in a first system and betaine is recovered in a second system. The sucrose obtained from the first system may be crystallized and the crystallization run-off applied to the second system. Also, described is a process for recovering xylose from sulphite cooking liquor using two systems. Prior to fractionation in the first system, the sulphite cooking liquor, having a pH of 3.5, is filtered and diluted to a concentration of 47% (w/w). The xylose fractions obtained from the first system are crystallized and, after adjustment to pH 3.6 with MgO, the run-off is fed to the second system. In the second system, a sequential SMB is used to separate xylose from the crystallization run-off.

A disadvantage of the separation technique disclosed in US6663780 is that the inclusion of two SMB systems is costly and adds to the complexity of the process. Moreover, the initial sucrose purification by crystallization in is an expensive technique.

WO9517517 discloses a method of processing municipal solid waste to recover reusable materials and to make ethanol. Cellulosic material is shredded and pre-treated with acid and lime to remove heavy metals, then treated with concentrated acid (sulfuric) to produce sugars. The sugars and the acid are separated on a strong acidic cation ion exchange resin.

US4101338 discloses a method of separating salts and sucrose present in blackstrap molasses obtained from sugar cane by ion exclusion chromatography. Prior to ion exclusion chromatography, the molasses are treated by removing organic non-sugar impurities and colour. Various methods are suggested for removing these impurities, including a preferred method utilizing precipitation with iron salts, such as ferric chloride or ferric sulfate, to form floes. The insoluble floes are then removed from the molasses stream and the soluble iron salts are removed by the addition of lime and phosphoric acid or inorganic phosphate salts, thereby raising the pH to above 7.0. The molasses stream is then applied to the ion exchange column to produce fractions containing sucrose and separated salts. A disadvantage of this process is that, upon addition, of ferric ions, the molasses has a pH that is in the range of 2.0 to 3.0. At such a low pH, degradation of xylose could occur.

US4631 129 teaches a method of purifying sugar from a sulfite pulping spent liquor stream. The process involves two steps, in which, during the first step, the pH of the spent sulfite liquor is adjusted to below 3.5 and the stream is passed through a strongly acidic ion exclusion resin to recover two lignosulfonate-rich raffinate fractions and a product stream containing the sugar and consisting of 7.8%-55% lignosulfonate.

In the second step, the product stream is adjusted to pH 5.5-6.5. The product stream is then filtered, and applied to a second ion exclusion column to further purify the sugar by separating it from the large amount of lignosulfonates in this stream. A problem with this process is that the use of two ion exclusion systems is costly and adds to the complexity of the process. Moreover, the patent does not quantify or address the separation of compounds present during the processing of biomass such as inorganic salts, including sulfate salts, and acetic acid and other organic acids.

US8003352 discloses a process for obtaining a product sugar stream from cellulosic biomass, which comprises the main steps of pretreating the cellulosic biomass at a pH of about 0.4 to about 2.0 by adding one or more than one acid to the cellulosic biomass to produce a pretreated cellulosic biomass; adding one or more than one base to the pretreated cellulosic biomass to adjust the pretreated cellulosic biomass to a pH of about 4.0 to about 6.0, thereby producing a neutralized cellulosic biomass comprising inorganic salt and acetate salt; hydrolyzing the neutralized cellulosic biomass with cellulase enzymes to produce a crude sugar stream; separating insoluble residue from the crude sugar stream to produce a clarified sugar stream; treating the clarified sugar stream using ion exclusion chromatography with a cation exchange resin at about pH 5.0 to about 10.0 to produce one or more than one raffinate stream comprising the inorganic salt and acetate salt and a product sugar stream comprising sugar. The disclosed process adds thereby a large amount of anionic species which must be removed by chromatography, and then use of enzyme, both the steps increasing considerably the cost of the process.

Although the production of a ligno-cellulosic hydrolyzate and the recovery of a purified stream of monomeric sugars from the ligno- cellulosic hydrolyzate has been extensively studied, the processes developed so far are characterized by high costs and complexity.

Thereby there is still the need to develop a cost-effective process to produce a stream of monomeric sugars from a ligno-cellulosic biomass, said stream having a high purity and said process being characterized by a high sugar recovery yield. SUMMARY It is disclosed a process for producing a purified liquid sugar stream comprising water, monomeric sugars and water soluble compounds which are not monomeric sugars from a liquid biomass feed stream derived from a ligno-cellulosic biomass, said liquid biomass feed stream comprising water, oligomeric sugars and soluble salts comprised of disassociated cations and anions. The process comprises the steps of: a. adding to the liquid biomass feed stream an amount of H ⁺ ions sufficient to create an acidic liquid biomass feed stream having a pH which is less than 3, wherein the majority of the H ⁺ ions are derived from a decationization of the liquid biomass feed stream using an ion exchange agent; b. hydro lyzing at least a portion of the oligomeric sugars of the acidic liquid biomass feed stream to monomeric sugars by increasing the temperature of the acidic liquid biomass feed stream; c. raising the pH of the acidic liquid biomass feed stream to create a liquid sugar stream having a pH in the range of 3 to 8, by adding a sufficient amount of a reference base comprised of a reference cation and a reference anion to form a stoichiometric amount of a reference salt comprised of the reference cation and the disassociated anion, wherein the ratio of the total ionic equivalents of cations different from the reference cations to the total ionic equivalents of cations in the liquid sugar stream is less than 0.20; d. separating the liquid sugar stream into at least the purified liquid sugar stream and a second stream by means of a cationic resin wherein the cation of the cationic resin is the same of the reference cation, wherein the purified liquid sugar stream is characterized by a purity ratio of the total amount of monomeric sugars to the total amount of all the compounds on a dry basis, and the purity ratio of the purified liquid sugar stream is greater than 60%. It is also disclosed that the separation process may be further characterized by a recovery ratio which is the ratio of the total amount of monomeric sugars in the purified liquid stream to the total amount of monomeric sugars in the liquid sugars stream, and that the recovery ratio may be greater than 60% . It is further disclosed that the percent of the total amount of H ⁺ ions derived from an acid or acids added to the liquid biomass feed stream may be a value selected from the group consisting of less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, and substantially 0%. It is also disclosed that the acidic liquid biomass feed stream may have a pH which is less than a value selected from the group consisting of 2.5, 2, and 1.5.

It is further disclosed that the pH of the liquid sugar stream may be adjusted to a value which is in a range selected from group consisting of 5 to 8, 5 to 7, and 5.5 to 6.5.

It is also disclosed that the ratio of the total moles of cations different from the reference cations to the total moles of cations in the liquid sugar stream may be less than a value selected from the group consisting of 0.15, 0.10, 0.05 and 0.03. It is further disclosed that the purity ratio of the purified liquid sugar stream may be greater than a value selected from the group consisting of 70%, 80%, 85% and 90%.

It is also disclosed that the recovery ratio of the separation process may be greater than a value selected from the group consisting of 70%, 80%, 85%, 90%, and 95%.

It is further disclosed that at least a portion of the reference salt may be precipitated before separating the liquid sugar stream.

It is also disclosed that the cationic resin may have an ion-exclusion action.

It is further disclosed that the cationic resin may further have a size- exclusion action.

It is also disclosed that the reference cation may be a monovalent cation.

It is further disclosed that the monovalent cation may be Sodium.

It is also disclosed that the reference base may be sodium hydroxide.

It is further disclosed that the ratio of the total ionic equivalents of non- monovalent cations to the total ionic equivalents of cations in the liquid sugar stream may be less than a value selected from the group consisting of 0.05, 0.03, 0.02 and 0.01.

It is also disclosed that the separation of the purified liquid sugar stream may occur in a continuous mode by means of at least a technique selected from the group consisting of Simulated Moving Bed, Improved Simulated Moving Bed, Sequential Simulated Moving Bed.

It is further disclosed that the purified liquid sugar stream may be further subjected to a refining step to remove at least a portion of the soluble compounds which are not monomeric sugars to produce a refined liquid sugar stream, wherein the refined liquid sugar stream has a purity ratio of the refined liquid sugar stream which is greater than a value selected from the group consisting of 90%, 95%, 97%, 98%, 99% and 99.9%.

It is also disclosed that the refining step may be further characterized by a recovery ratio of the refining step which is the ratio of the total amount of monomeric sugars in the refined liquid stream to the total amount of monomeric sugars in the purified liquid sugars stream, and the recovery ratio of the refining step is greater than a value selected from the group consisting of 95%, 97%, 98% and 99%. It is further disclosed that the refining step may comprise contacting the purified liquid sugar stream with at least an refining material selected from the group consisting of a cationic resin, an anionic resin and a carbonaceous material. It is also disclosed that the carbonaceous material may comprise an activated carbon.

It is further disclosed that the refining step may comprise first contacting the purified liquid sugar stream with at least a first refining material selected from the group consisting of a cationic resin, an anionic resin, or a combination thereof, and then further contacting with a second refining material comprising an activated carbon.

It is also disclosed that the monomeric sugars may comprise C5 monomeric sugars, and the percent amount of C5 monomeric sugars on the total amount of monomeric sugars in the refined liquid sugar stream is greater than a value selected from the group consisting of 50%, 60%, 70%, 80%, and 90%.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a graph showing the composition of the different fractions obtained by batch chromatographic separation according to the disclosed process.

Figure 2 is another graph showing the percent amounts on dry basis of the main components obtained by batch chromatographic separation according to the disclosed process.

DETAILED DESCRIPTION It is disclosed a process for producing a purified liquid stream from a liquid biomass feedstream derived from a ligno-cellulosic biomass. The purified liquid stream may be further refined to produce a refined liquid sugar stream. Both the streams are particularly suitable for feeding catalytical and biological conversion processes to produce biofuels and chemicals.

The liquid biomass feedstream comprises water and water soluble oligomeric sugars, which are derived from the solubilization of at least a portion of the hemicellulose and cellulose by means of a pre-treatment of the ligno-cellulosic biomass. Even if any pre-treatment may be used to produce the liquid biomass feedstream, a preferred pre-treatment comprises an hydrothermal process, which solubilizes a portion of the carbohydrates in the feedstock without the use of any chemicals or catalysts. The solid, not solubilized feedstock may then be further pre- treated and used for feeding another conversion process or processes to different chemical end-products. Preferably, the hydrothermal treatment comprises a soaking step of the ligno-cellulosic feedstock to produce a soaked liquid stream comprising soluble sugars, mainly derived from the hemicellulose of the ligno-cellulosic biomass. The ligno-cellulosic biomass is described in WO2013098789, p.5- 16, and the preferred process for producing the liquid biomass feedstream from the ligno- cellulosic biomass is described in details in a following section of the present specification. The water soluble oligomeric sugars may comprise any sugar soluble in water different from monomeric sugars. Thereby, water soluble oligomeric sugars may comprise C5 and C6 oligomeric sugars. C5 sugars are pentose-based sugars, wherein pentose is a monosaccharide with five carbon atoms. Xylose is an example of monomeric pentose sugar. C6 sugars are hexose-based sugars, being the hexose a monosaccharide with six carbon atoms. Glucose is an example of monomeric hexose sugar. In a preferred embodiment the water soluble oligomers comprises mainly xylooligomers, which are derived from the hemicellulose of the ligno-cellulosic biomass. C5 sugars rich-streams represent a low-value stream which may be derived from the ligno- cellulosic biomass. As examples, C5 sugars rich-streams may be produced also as a by-product in the pulp and paper industry. Besides oligomeric sugars, the liquid biomass feed stream comprises soluble salts which are disassociated into anions and cations. These salts, which may be organic and inorganic salts, are the salts of cations including sodium, calcium, potassium, ammonium, magnesium, and others cations contained in the original ligno-cellulosic biomass and solubilized by the pre-treatment of the ligno-cellulosic biomass.

The liquid biomass feed stream may further comprise other soluble compounds, including monomeric sugars such as glucose, xylose, arabinose, galactose, mannose; acetic acid, lactic acid, oxalic acid, among other organic acids, and the salts of these acids. A variety of other compounds may be present in the liquid biomass feed stream, including sugar degradation products such as furfural and hydroxymethyl furfural, and soluble phenolic compounds derived from lignin. Organic extractive compounds, such as soaps and fatty acids, may also be present. Preferably, the liquid biomass feed stream does not comprise anions from added inorganic acids.

In a preferred embodiment, the liquid biomass feedstream is subjected to a removal step of suspended solids before feeding the disclosed process, as suspended solids may obstruct downstream equipments. Removal of suspended solids may include for instance, but is not limited to, the use of a press, a decanter, a centrifuge, a filter, a flocculating agent, a microfilter, a plate and frame filter, a crossflow filter, a pressure filter, a vacuum filter, or a combination thereof.

In an embodiment, the liquid biomass feedstream is subjected to a concentration step, which may be carried out using any technique known to those of skill in the art. For example, concentration may be carried out by subjecting the liquid biomass feedstream to membrane filtration, evaporation, or a combination thereof. Without being limiting, microfiltration (with a pore size of 0.05 to 5 microns) may be carried out to remove particles, followed by ultrafiltration (500-2000 raw cut off) to remove soluble lignin and other large molecules and reverse osmosis to increase the concentration of soluble compounds, followed by evaporation.

Preferably, the liquid biomass feedstream has a dry matter content by weight which is greater than 3%, more preferably greater than 5% even more preferably greater than 10%, even yet more preferably greater than 15%, and most preferably greater than 20%.

The total percent amount of soluble sugars in the liquid biomass feed stream, which include oligomeric sugars and, if present, monomeric sugar, is preferably greater than 30%, 40%, 50%, 60%, 70%, 80% by weight on a dry basis. For instance, if the liquid biomass feed stream has a dry matter content of 10% and the total amount of soluble sugars is 50%, there are 50grams of soluble sugars in lKg of liquid biomass feed stream.

The total percent amount of soluble salts in the liquid biomass feed stream may be 10% to 70% by weight on a dry basis, or 10% to 60%, or 10% to 50%, or 10% to 40%, or 10% to 30%.

The disclosed process for producing a purified liquid sugar stream from a liquid biomass feedstream comprises at least two steps according to the teaching of WO2013026849, which is incorporated herein by reference.

The first step is to create an acidic stream from the liquid biomass feed stream. This is accomplished by increasing the amount of H ⁺ ions to the liquid biomass feed stream to create the acidic stream. After the desired pH is obtained, the next step is hydrolyzing the oligosaccharides in the acidic stream by raising the temperature of the acidic stream to a hydrolysis temperature for the hydrolysis reaction to occur creating a hydro lyzed stream. After hydrolysis, the hydro lyzed stream can be passed to other unit operations for further processing.

The disclosed process takes advantage of the salt content of the liquid biomass feed stream. In order to obtain the required acidity for the hydrolysis step, the content of salts in the feed stream is reduced via cation exchange while at the same time replacing the cations with H ⁺ ions.

While the salts may naturally occur in the biomass, they can also be added as part of the pre-treatment processes or prior to or during the creation of the acidic stream.

The process of reducing the amount of cations of the soluble salts in the liquid biomass feed stream, called decationization, removes the cations by exchanging them with H ⁺ ions. One way the cations in the liquid biomass feed stream can be replaced by H ⁺ ions is by using an ion exchange agent, such as an ion exchange resin. The cations can also be exchanged using a membrane. For example, Dupont's Nafion(R) PFSA Resins can be used as resins in an exchange column or as a membrane through which the solution is passed. These are per- fluorinated resins in the sulfonyl fluoride (-SO2F) form. Preferably, the ion exchange agent is a strong cationic resin, more preferably a sulphonated resin in Hydrogen form, such as for instance Relite EXC14 by Mitsubishi Chemical Corporation, Japan.

An additional step of separating at least a portion of the acidic stream from the ion exchange media before subjecting the separated portion to the hydrolysis temperatures may be needed. Preferably, all the ion exchange media is removed from the acidic stream before hydrolyzing the oligosaccharides in the acidic stream.

It should be recognized that the amount of salts present influences the amount of H ⁺ ions that can be increased (added to the liquid) via ion exchange. The amount of H ⁺ ions also determines the pH of the acidic stream. These salts can be concentrated according to the steps outlined above. Should the feed stream not have sufficient salts with cations, one can add a salt or cations in another manner to the liquid biomass feed stream prior to, and/ or during, and/ or after the creation of the acidic stream , or combination thereof. Preferably, the salts of Magnesium, Calcium, Sodium, Potassium can be used. Preferably salts with a monovalent cation are used as the cation will not reduce the efficiency of the ion exchange media as much as a bivalent ion.

In the disclosed process, the majority of the H ⁺ ions are derived from the decationization of the liquid biomass feed stream by means of the ion exchange agent. Preferably, more than 60%, 70%, 80%, 90% and 95% of the H+ ions come from the decationation step. In a preferred embodiment, 100% of the H ⁺ ions come from the decationization step, thereby no H ⁺ ion comes from added acids such as sulfuric acid and no additional anion is further added to the biomass feedstream.

If the cations in the liquid biomass feed stream are not in a sufficient amount to reach the desired pH value, or if it is desired to remove only a portion of the cations, additional H ⁺ ions may be added to the stream. The amount of H ⁺ ions can be increased via any known means, including the use of acids, electrical current, the addition of hydrogen peroxide, and the use of a membrane; or even in- situ production of the H ⁺ ions. Increasing the amount of H ⁺ ions, or protons, in-situ can be accomplished by adding a compound which does not contain H ⁺ ions capable of disassociating in water, but rather catalyzes a reaction, or the compound itself reacts, with component(s) already present in the liquid biomass feed stream. For example, AlC contains no H ⁺ ions. However, when added to the liquid biomass feed stream, the AlCb will react with the water in the liquid biomass feed stream to form Al(OH)3 and HC1, thus creating the H ⁺ ion. In this manner, the amount of the H ⁺ ions are increased without adding H ⁺ ions to the liquid biomass feed stream. The percent of the total amount of H ⁺ ions derived from an acid or acids added to the liquid biomass feed stream may be of less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, and substantially 0%. In the case of decationization, the pH of the decationized stream becomes lower than the pH of the feedstream. The pH that can be achieved with decationization depends on the initial cation concentration in the feed liquid, the cations added to the stream, the anions present in the stream, the ion resin exchange capacity, specific velocity through the resin and temperature of exposure. Therefore, the decationization should occur at a temperature in the range of 5°C to 120°C, or 5°C to 100°C, , or 5°C to 80°C, , or 5°C to 70°C _o or 5°C to 100°C, , or 5°C to 100°C, and for a time sufficient to reach a pH of the liquid biomass feed stream which is less than 3.0 more preferably less than 2.5, more preferably less than 2.0, more preferably less than 1.5. One of ordinary skill knows that pH has a lower theoretical limit of up to but not including 0, thus each of the above numbers can be expressed as the upper limit of the pH of the acidic stream, with the pH being greater than, but not including, 0.0.

Once the desired pH is reached, the acidic stream is hydrolyzed by increasing the temperature of the acidic stream to a hydrolysis temperature greater than 80 °C, and preferably within the range of 80 °C to 200 °C. Other ranges are 80 °C to 180 °C, 100 °C to 180 °C, 95 °C to 180°C, 120 °C to 180 °C and 120 °C to 170 °C the most preferred. The hydrolysis temperature is maintained for a time sufficient to hydrolyze the components (oligosaccharides) to the degree desired. The hydrolysis time may be from 1 second to 24 hours, or from 30 second to 18 hours, or from 1 minute to 12hours. Hydrolysis temperature and time are preferably selected to significantly reduce the formation of degradation products.

As a result of the decationization and hydrolysis steps, the large amounts of acid or acids used in the hydrolysis step is avoided, allowing the passage from a rather harsh treatment to a totally mild one and the consumption of acid used can be reduced to the amount needed to regenerate the cationic resin (or not used at all). The acid is then recovered in a separate stream and then more easily disposed of. At the same time, the acidic liquid biomass feed stream after hydrolysis is a cleaner liquid, comprising monomeric sugars, low content of salts and low amount of degradation products that could hinder subsequent chemical or biological transformations of the sugars.

Inventors have found that increasing the amount of H ⁺ ions and removing cations at the same time greatly improves, or simplify, the downstream purification step or steps, permitting to recover a purified liquid sugar stream from the liquid biomass feed stream with a high recovery yield.

After hydrolysis, the pH of the acidic liquid biomass feed stream is increased to a value compatible with the following purification step which comprises the use of a cationic resin. Thereby, the pH of the liquid biomass feed stream is preferably raised to a value in the range of 3 to 8, more preferably of 5 to 8, even more preferably of 5 to 7, and most preferably of 5.5 to 6.5. The increase of pH to the desired value is obtained by adding an amount of a reference base comprised of a reference cation and a reference anion. The term "base" is meant to encompass any soluble species that, when added to pure water, gives a solution with a pH that is more than 7. Preferably, the pH adjustment is carried out using a soluble base. By the term "soluble base", it is meant a base that has a solubility in water that is at least 0.1 M at 20° C. This term is meant to exclude salts that are slightly soluble or insoluble. Examples of insoluble bases that are excluded from the definition of soluble base are CaCO3 and, Ca(OH)2. Non-limiting examples of soluble bases include sodium hydroxide, potassium hydroxide, ammonia, and ammonium hydroxide.

In the disclosed process, as a result of the decationization and neutralization steps, in the liquid sugar stream a huge predominance of only one species of cation, namely the reference cation, is obtained, starting from a plurality of cations of different species in the liquid biomass feed stream, which may be monovalent and multivalent. The liquid sugar stream after neutralization comprises water, monomeric sugars from the hydrolysis step and a salt comprised of the reference cation and the anions of the liquid biomass feed stream. This concept can be conveniently expressed by the ratio of the total ionic equivalents of cations different from the reference cations to the total ionic equivalents of cations in the liquid sugar stream, which is less than 0.20, preferably less than 0.15, more preferably less than 0.10, even more preferably less than 0.05 and most preferably less than 0.03. Ionic equivalents are introduced because cations with different valence may affect differently the cationic resin of the following purification step. The equivalent, sometimes termed the molar equivalent, is a unit of electrical charge used in chemistry. It could be converted to Coulombs 'C (SI unit) using Faraday's constant F in 'C/mol', where 1 'eq' = F 'C.

The equivalent of substance A is the amount of substance A (in moles) multiplied by its valence. The equivalent could be also formally defined through the amount of substance which will either react with or supply one mole of hydrogen ions (H ⁺ ) in an acid-base reaction; or react with or supply one mole of electrons in a redox reaction.

Practically, certain amount of univalent ions provides the same amount of ionic equivalents while the same amount of divalent ions provides twice the amount of ionic equivalents. For example, 1 mmol of Na ⁺ is equal 1 mEq, while 1 mmol of Ca ⁺⁺ is equal 2 mEqs. In an embodiment, the soluble reference salt comprised of the reference cation and the dissociated anion of the liquid biomass feed stream may be at least partially precipitated in solid form. Precipitation may be driven by pH change, concentration of the soluble reference salt, temperature as examples. Precipitation is preferably conduced before subsequent purification step in such a way that precipitated compounds do not enter purification equipment.

The liquid sugar stream is then treated by a cationic exchange resin to separate sugars and other nonionic compounds from the salts and other ionic compounds, thereby producing a purified liquid sugar stream comprising the major portion of the monomeric sugars, and at least a second stream, comprising at least the major portion of the salts and other ionic compounds. In the disclosed process, the cation of the cationic exchange resin is the same species of the reference cation of the reference base added to raise the pH of the acidic biomass feed stream, as the presence of the same species of cations in the liquid sugar stream and the cation resin improves the separation yield, the purity of the product streams and the lifetime of the resin, that is the time that the resin can work with high efficiency before being regenerated.

Thereby, the purified liquid sugar stream is characterized by a purity ratio, which the total amount of monomeric sugars to the total amount of all the compounds on a dry basis, and the purity ratio of the purified liquid sugar stream is greater than 60%, preferably greater than 70%, more preferably greater than 80%, even more preferably greater than 85%, and most preferably greater than 90%. The separation process is further characterized by a recovery ratio which is the ratio of the total amount of monomeric sugars in the purified liquid stream to the total amount of monomeric sugars in the liquid sugars stream. The recovery ratio may be greater than 60%, preferably greater than 70%, more preferably greater than 80%, even more preferably greater than 85%, even yet more preferably greater than 90%, and most preferably greater than 95%.

Preferably, the cationic resin is a strong cation resin, for example, which is not to be considered limiting, with a polystyrene backbone and divinylbenzene crosslinking. These resins have sulfonate functional groups and are available commercially in the sodium form, or, less preferably, in the hydrogen, potassium or ammonium form. The resins are preferably of diameter of from about 0.1 to about 1.0 mm. Cationic exchange resins are available from several vendors, including Dow or Mitsubishi. Preferably, the reference cation is a monovalent cation, such as Sodium or Potassium. More preferably, the reference cation is Na and the preferred base is Sodium hydroxide. Thereby, the cationic resin used for separating the liquid sugar stream is a resin in sodium form. In this case, the disclosed process presents the further advantage of removing the major portion of divalent ions from the liquid biomass feed stream in the decationization step. Divalent cations, such as Magnesium and Calcium, are known to poison the monovalent cationic resin very quickly, thereby reducing the separation efficiency of the resin. Thereby the removal of divalent cations occurs without any devoted softening step or equipment. Being the cation of the cationic resin a monovalent cation, the liquid sugar stream may be further characterized by the ratio of the total ionic equivalents of non- monovalent cations to the total ionic equivalents of cations, which may be less than 0.05, preferably less than 0.03, more preferably less than 0.02 and most preferably less than 0.01.

The separation of the liquid sugar stream in the product streams may occur mainly by means of ion-exclusion principle. The ion exclusion system of the present invention may be operated in a temperature range of about 20° C to about 90° C, preferably at a temperature between about 45° C to about 80° C.

The process of ion exclusion separation may involve the use of one, or more than one, column filled with ion exchange resin, as it is evident to one of skill in the art. For the sake of simplicity, the operation of a single column will be illustrative, but the use of more than one column is also considered to be within the scope of the present invention.

The column may be prepared prior to carrying out the separation by converting it into the desired cationic form, which is preferably Sodium form. This may involve washing a volume of the liquid sugar stream through the column. Alternatively, the column may be prepared by washing it with a volume of solution containing cations corresponding to the reference cation of the liquid sugar stream. Once the column is in the appropriate cation-exchange form, the liquid sugar stream is applied onto the column. A desired liquid flow rate is selected as may be readily determined by one of skill in the art, for example, but not limited to, a liquid flow rate corresponding to about 5% to about 70% of the column volume per hour.

As the purified sugar stream is applied, the charged ions in the salts and other charged compounds are excluded from the resin and flow through the column. The sugar and other nonionic compounds are not repelled by the charged resin, and penetrate the pores of the resin. The sugar and other nonionic compounds are thereby retained by the resin and elute the column more slowly than the ionic compounds. After the desired volume of the clarified sugar stream is injected, the feed is switched to water. The ionic compounds flow through the column and are collected in one or more than one by-product stream. This one or more than one by-product stream contains the majority of the reference salt and other ionic compounds, and small amounts of sugar and it is followed by the elution of sugars arising from the processing of the cellulosic biomass and nonionic compounds, which are collected separately from the one or more than one by-product stream. The purified liquid sugar stream contains most of the sugar and a few amount of the salt and other ionic and neutral components.

As a result of the decationization and hydrolysis steps, inventors have found that the separation of the purified liquid sugar stream and the second stream from the liquid sugar stream is greatly improved with respect to the case of acid hydrolysis. It is believed that this is due to the lower content of salts and other charge species in the liquid sugar stream.

Thereby, by the disclosed process it is possible to recover a highly pure sugar stream wasting few amount of sugars of the feed stream.

In a preferred embodiment, the ion exclusion chromatography is carried out by a Simulated Moving Bed (SMB) device. An SMB contains ion exchange resin similar to that in an ion exclusion system described above, and performs the same type of separation of sugars and nonionic compounds in the purified liquid sugar stream and salts and other ionic compounds in the second stream. For a given feed stream, an SMB is usually run at the same pH and temperature as an ion exclusion system. However, an SMB system has distinct locations for feeding of the liquid sugar stream, feeding of dilution water, and withdrawal of purified liquid sugar stream and second stream. For example, which is not to be considered limiting, four flow locations equally spaced apart may be used on one or more than one column. In a preferred embodiment, one column is used. This simplifies the demarcation of zones and allows for a given column to be brought off line, for cleaning or maintenance without overly disturbing the operation. For example, which is not to be considered limiting, from about 4 to about 16 columns may be used. In a more preferred embodiment, about 4 to about 8 columns are used. However, the number of columns may be adjusted as required.

Another difference between an SMB and a single-column ion exclusion system is that the SMB has a recirculation flow that supplements and is co-current with all of the other flow streams. This recirculation flow is carefully chosen, along with the other flows, to provide the optimum separation between the sugar and salt streams. Additionally, an SMB system simulates movement of the resin bed in a direction opposite to that of the liquid flow.

Improved SMB ("ISMB") systems may also be used as described herein. ISMB systems include variable flow rates of feed, dilution water, product, raffinate, or a combination thereof, or sequential periods with one or more streams closed off, with or without re-circulation of the liquid in the columns, or a combination of two or more of these features. The present invention can be practiced with ISMB or SMB operations, or with Sequential Simulated Moving Bed.

A detailed description on how to operate a SMB separation system may be found in Jari Heinonen, Tuomo Sainio, "Chromatographic Fractionation of Lignocellulosic Hydrolysates", Advances in Chemical Engineering, Volume 42, pag.261. In a preferred embodiment, the cationic resin is selected to have also a size-exclusion action, beside a ion-exclusion action. The second stream separated from the liquid sugar stream will then comprise also a portion of non-ionic compounds present in the liquid sugar stream. As size exclusion is known in the art, a person skilled in the art knows how to select the cation resin to operate the separation also on the basis of size exclusion principle. The purified liquid sugar stream may be further subjected to a refining step to further remove compound which are not monomeric sugars from the purified liquid sugar stream. These compounds are both charged species and neutral compounds present in the liquid sugar stream which have been retained purified liquid sugar stream in the ion-exclusion separation step. By means of the refining step, an ultra-pure refined liquid sugar stream may be obtained, having a purity ratio greater than 90%, 95%, 97%, 98%, 99% and 99.9%. The purity ratio of the refined liquid sugar stream is percent ratio of the total amount of monomeric sugars to the total amount of all the compounds on a dry basis in the refined liquid sugar stream.

Moreover, the recovery of the refined liquid sugar stream may occur with great efficiency and very few sugars may be lost in the refining step. The recovery ratio of the refining step, which is the ratio of the total amount of monomeric sugars in the refined liquid stream to the total amount of monomeric sugars in the purified liquid sugars stream entering the refining step, may be greater than 95%, preferably greater than 97%, more preferably greater than 98% and most preferably greater than 99%.

In a preferred embodiment the removal of the compounds different from monomeric sugars is conducted by means of at least an refining material, and removal occurs by adsorbing the compounds on the refining material. The purified liquid sugar stream is contacted with the refining material or materials, preferably in a column configuration, without adding any further dilution liquid as in the case of chromatographic separation. As the purified liquid sugar stream of the disclosed process contains already a limited amount of compounds different from monomeric sugars, regeneration of the refining material may not be needed often, being adsorption mechanism compatible with an industrial process. The refining material may be an ion-exchange resin, thereby the removal occurs by means of ion exchange. The ion exchange resin is preferably a strong anion-exchange resin in OH ^" form, which retains at least a portion of the anions in the purified liquid sugar stream on positively charged functional groups. In the process, anions are exchanged with OH ^" hydroxyl groups. Thereby, the pH of the refined liquid sugar stream is preferably raised to a value in the range of 3 to 12, more preferably of 6 to 12, even more preferably of 6 to 1 1 , and most preferably of 7 to 10. The removal by means of ion exchange should occur at a temperature in the range of 5°C to 120°C, or 5°C to 100°C, or 5°C to 80°C, or 5°C to 70°C _o or 5°C to 60°C, or 20°C to 60°C.

Even if any kind of strong anionic resin may be used, a copolymer styrene-DVB anion exchange resin containing strongly basic ions groups is preferred. An example of such a resin is Relite EXA268 from Mitsubishi Chemicals, Japan. In another embodiment, the ion exchange resin is a strong cation- exchange resin in H ⁺ form, adsorbing at least a portion of the remaining cations in the purified liquid sugar stream. This resin is preferably similar to the resin used in the decationization step.

The refining material may be a carbonaceous material, preferably an activated carbon.

In a preferred embodiment, the refinement of the purified liquid sugar stream comprises two refining material. The purified liquid sugar stream is first contacted with an ion-exchange resin and then with an activated carbon. The two refining materials are placed in separated columns and the purified liquid sugar stream is inserted into the first column containing the ion-exchange resin, which can be an anionic exchange resin or a cationic exchange resin or a mixture of the two, to remove remnant charged species. The purified liquid sugar stream, after first refinement, is extracted from the first column and inserted into the second column containing the activated carbon to remove preferentially non charged species. The stream exiting from the second column is the refined liquid sugar stream.

In a preferred embodiment, the liquid biomass feed stream is a C5 sugars rich-streams derived mainly from the solubilization of the hemicellulose of the ligno-cellulosic biomass and comprises mainly xylooligomers. Thereby, the refined liquid sugar streams comprises mainly xylose and other C5 monomeric sugars, such as arabinose. Preferably, the percent amount of monomeric C5 sugars on the total amount of monomeric sugars in the refined liquid sugar stream is greater 50%, more preferably greater than 60%, even more preferably greater than 70%, even yet more preferably greater than 80%, and most preferably greater than 90%.

The purified liquid sugar stream or the refined liquid sugar stream may be converted by means of a biological or catalytic conversion process to biofuels or chemicals.

In a preferred embodiment, the refined liquid sugar stream is converted to a polyols mixture comprising ethylene glycol by means of a catalytic conversion process comprising a hydrogenation step of the refined liquid sugar stream to produce a hydrogenated mixture comprising water and a mixture of sugar alcohols; and a hydrogenolysis step of the hydrogenated mixture, to produce the polyols mixture.

In the hydrogenation step, the refined liquid sugar stream is contacted with a hydrogenation catalyst and hydrogen at hydrogenating conditions promoting the hydrogenation of the sugars in the liquid sugar stream. Preferred sugar alcohols are xylitol, sorbitol and arabitol, or mixture thereof. Even more preferably, the hydrogenated mixture comprises xylitol and the preferred amount of xylitol in the hydrogenated mixture on a dry basis is greater than 45%, more preferably greater than 70%, even more preferably greater than 80%, yet even more preferably greater than 90%, being greater than 95% the most preferred value.

The hydrogenolysis reaction of the sugar alcohols in the hydrogenated mixture produces a hydrogenolysis mixture comprising water, ethylene glycol, and propylene glycol. It may further comprise glycerol and other polyols, unwanted compounds, comprising acid lactic or formic acid, and unreacted sugar alcohols.

The polyols stream comprising ethylene glycol and propylene glycol may be recovered from the hydrogenolysis mixture by any process known in the art and still to be invented. An ethylene glycol stream and a propylene glycol stream may then be separated from the polyols mixture preferably by means of distillation. The ethylene glycol stream comprises a plurality of diols, wherein ethylene glycol is the main component, as the amount of ethylene glycol, expressed as molar percent with respect to the plurality of diols, is preferably greater than 80%.

In an embodiment, the ethylene glycol stream further comprises at least one diol selected from 1 ,2-Propylene glycol, 1 ,2-Butanediol and 1 ,2- Pentanediol.

The ethylene glycol stream may be used to produce a polyester resin. In a preferred embodiment, at least 85% of the acid moieties of the polyester are derived from terephthalic acid or its dimethyl ester.

In both method, the polyester may be further polymerized to a higher molecular weight by a solid state polymerization, which is particularly useful for container (bottle) application. Preferred pre-treatments of the ligno-cellulosic feedstock

The liquid biomass feed stream is derived from the ligno-cellulosic feedstock by means of a treatment, or pre-treatment, of the ligno- cellulosic feedstock. The pre-treatment of the ligno-cellulosic biomass is used to solubilize and remove carbohydrates, mainly xylans and glucans, from the ligno- cellulosic feedstock, and at the same time the concentrations of harmful inhibitory by-products such as acetic acid, furfural and hydroxymethyl furfural remain substantially low. Pre-treatment techniques which may be used are well known in the art and include physical, chemical, and biological pre-treatment, or any combination thereof. In preferred embodiments the pre-treatment of ligno-cellulosic biomass is carried out as a batch or continuous process.

Physical pre-treatment techniques include various types of milling/ comminution (reduction of particle size), irradiation

Comminution includes dry, wet and vibratory ball milling.

Although not needed or preferred, chemical pre-treatment techniques include acid, dilute acid, base, organic solvent, lime, ammonia, sulfur dioxide, carbon dioxide, pH-controlled hydro thermolysis, wet oxidation and solvent treatment.

If the chemical treatment process is an acid treatment process, it is more preferably, a continuous dilute or mild acid treatment, such as treatment with sulfuric acid, or another organic acid, such as acetic acid, citric acid, tartaric acid, succinic acid, or any mixture thereof. Other acids may also be used. Mild acid treatment means at least in the context of the invention that the treatment pH lies in the range from 1 to 5, preferably 1 to 3.

In a specific embodiment the acid concentration is in the range from 0.1 to 2.0 % wt acid, preferably sulfuric acid. The acid is mixed or contacted with the ligno-cellulosic biomass and the mixture is held at a temperature in the range of around 160-220 °C for a period ranging from minutes to seconds. Specifically the pre-treatment conditions may be the following: 165- 183 °C, 3- 12 minutes, 0.5- 1.4% (w/w) acid concentration, 15-25, preferably around 20% (w/w) total solids concentration. Other contemplated methods are described in U.S. Pat. Nos. 4,880,473, 5,366,558, 5, 188,673, 5,705,369 and 6,228, 177.

Wet oxidation techniques involve the use of oxidizing agents, such as sulfite based oxidizing agents and the like. Examples of solvent treatments include treatment with DMSO (Dimethyl Sulfoxide) and the like. Chemical treatment processes are generally carried out for about 5 to about 10 minutes, but may be carried out for shorter or longer periods of time. In an embodiment both chemical and physical pre-treatment is carried out including, for example, both mild acid treatment and high temperature and pressure treatment. The chemical and physical treatment may be carried out sequentially or simultaneously.

The current strategies of thermal treatment are subjecting the ligno-cellulosic material to temperatures between 1 10-250°C for 1-60 min e.g.:

Hot water extraction

Multistage dilute acid hydrolysis, which removes dissolved material before inhibitory substances are formed Dilute acid hydrolysis at relatively low severity conditions

Alkaline wet oxidation

Steam explosion

Almost any pre-treatment with subsequent detoxification. If a hydrothermal pre-treatment is chosen, the following conditions are preferred:

Pre-treatment temperature: 1 10-250°C, preferably 120-240°C, more preferably 130-230°C, more preferably 140-220°C, more preferably 150-210°C, more preferably 160- 200°C, even more preferably 170-200°C or most preferably 180-200°C.

Pre-treatment time: 1-60 min, preferably 2-55 min, more preferably 3- 50 min, more preferably 4-45 min, more preferably 5-40 min, more preferably 5-35 min, more preferably 5-30 min, more preferably 5-25 min, more preferably 5-20 min and most preferably 5- 15 min.

Dry matter content after pre-treatment is preferably at least 20% (w/w). Other preferable higher limits are contemplated as the amount of biomass to water in the pre-treated ligno-cellulosic feedstock be in the ratio ranges of 1 :4 to 9: 1 ; 1.3.9 to 9: 1 , 1 :3.5 to 9: 1 , 1 :3.25 to 9: 1 , 1 :3 to 9: 1 , 1 :2.9 to 9: 1 , 1 :2 to 9: 1 , 1.15 to 9: 1 , 1 : 1 to 9: 1 , and 1 :0.9 to 9: 1.

A preferred pretreatment of a ligno-cellulosic biomass include a soaking of the ligno-cellulosic biomass feedstock and optionally a steam explosion of at least a part of the soaked ligno-cellulosic biomass feedstock. The soaking occurs in a substance such as water in either vapor form, steam, or liquid form or liquid and steam together, to produce a product. The product is a soaked biomass containing a soaking liquid, with the soaking liquid usually being water in its liquid or vapor form or some mixture. This soaking can be done by any number of techniques that expose a substance to water, which could be steam or liquid or mixture of steam and water, or, more in general, to water at high temperature and high pressure. The temperature should be in one of the following ranges: 145 to 165°C, 120 to 210°C, 140 to 210°C, 150 to 200°C, 155 to 185°C, 160 to 180°C. Although the time could be lengthy, such as up to but less than 24 hours, or less than 16 hours, or less than 12 hours, or less than 9 hours or less than 6 hours; the time of exposure is preferably quite short, ranging from 1 minute to 6 hours, from 1 minute to 4 hours, from 1 minute to 3 hours, from 1 minute to 2.5 hours, more preferably 5 minutes to 1.5 hours, 5 minutes to 1 hour, 15 minutes to 1 hour.

If steam is used, it is preferably saturated, but could be superheated. The soaking step can be batch or continuous, with or without stirring. A low temperature soak prior to the high temperature soak can be used. The temperature of the low temperature soak is in the range of 25 to 90°C. Although the time could be lengthy, such as up to but less than 24 hours, or less than 16 hours, or less than 12 hours, or less than 9 hours or less than 6 hours; the time of exposure is preferably quite short, ranging from 1 minute to 6 hours, from 1 minute to 4 hours, from 1 minute to 3 hours, from 1 minute to 2.5 hours, more preferably 5 minutes to 1.5 hours, 5 minutes to 1 hour, 15 minutes to 1 hour.

Either soaking step could also include the addition of other compounds, e.g. H2SO4, NH3, in order to achieve higher performance later on in the process. The product comprising the soaking liquid, or soaked liquid, is then passed to a separation step where at least a portion of the soaking liquid is separated from the soaked biomass. The liquid will not completely separate so that at least a portion of the soaking liquid is separated, with preferably as much soaking liquid as possible in an economic time frame. The liquid from this separation step is known as the soaked liquid stream comprising the soaking liquid. The soaked liquid will be the liquid used in the soaking, generally water and the soluble species of the feedstock. These water soluble species comprise glucan, xylan, galactan, arabinan, and their monomers and oligomers. The solid biomass is called the first solid stream as it contains most, if not all, of the solids.

The separation of the soaked liquid can again be done by known techniques and likely some which have yet been invented. A preferred piece of equipment is a press, as a press will generate a liquid under high pressure.

The first solid stream may then optionally be steam exploded to create a steam exploded stream, comprising solids. Steam explosion is a well- known technique in the biomass field and any of the systems available today and in the future are believed suitable for this step. The severity of the steam explosion is known in the literature as Ro, and is a function of time and temperature and is expressed as

Ro = texp[(T- 100)/ 14.75] with temperature, T expressed in Celsius and time, t, expressed in minutes.

The formula is also expressed as Log(Ro), namely Log(Ro) = Ln(t) + [(T- 100)/ 14.75].

Log(Ro) is preferably in the ranges of 2.8 to 5.3, 3 to 5.3, 3 to 5.0 and 3 to 4.3.

The steam exploded stream may be optionally washed at least with water and there may be other additives used as well. It is conceivable that another liquid may be used in the future, so water is not believed to be absolutely essential. At this point, water is the preferred liquid. The liquid effluent from the optional wash may be added to the soaked liquid stream. This wash step is not considered essential and is optional.

The washed exploded stream is then processed to remove at least a portion of the liquid in the washed exploded material. This separation step is also optional. The term at least a portion is removed, is to remind one that while removal of as much liquid as possible is desirable (preferably by pressing), it is unlikely that 100% removal is possible. In any event, 100% removal of the water is not desirable since water is needed for the subsequent hydrolysis reaction. The preferred process for this step is again a press, but other known techniques and those not invented yet are believed to be suitable. The liquid products separated from this process may be added to the soaked liquid stream. In an embodiment, the ligno-cellulosic biomass is exposed to a presoaking step before a soaking step in a temperature range of between 10°C and 150°C, 25°C to 150°C even more preferable, with 25°C to 145°C even more preferable, and 25°C to 100°C and 25°C to 90°C also being preferred ranges. The pre-soaking time could be lengthy, such as up to but preferably less than 48 hours, or less than 24 hours, or less than 16 hours, or less than 12 hours, or less than 9 hours or less than 6 hours; the time of exposure is preferably quite short, ranging from 1 minute to 6 hours, from 1 minute to 4 hours, from 1 minute to 3 hours, from 1 minute to 2.5 hours, more preferably 5 minutes to 1.5 hours, 5 minutes to 1 hour, 15 minutes to 1 hour.

The pre-soaking step is done in the presence of a liquid which is the pre-soaked liquid. After soaking, this liquid preferably has removed less than 5% by weight of the total sugars in the raw material, more preferably, less than 2.5% by weight of the total sugars in the raw material being more preferable, with less than 1% by weight of the total sugars in the raw material, being the most preferred.

This pre-soaking step is useful as a modification to the soaking step of a biomass pre-treatment step. In soaking (not pre-soaking) of the biomass pre-treatment steps, the soaked liquid stream which has been separated from the soaked solids will preferably have reduced filter plugging components so that the soaked liquid can be easily purified, preferably by means of at least one technique selected from the group of chromatography, nanofiltration and ultrafiltration. The soaked liquid stream may be subjected to more than one purification step, which may be done before hydrolysis or decationization. The soaked liquid stream will comprise water, sugars which includes monomeric sugars and oligomeric sugars, salts which are dissociated into anions and cations in the soaked liquid stream, optionally phenols, furfural, oils and acetic acid. The soaked liquid stream will in particular contain xylooligomers. In a preferred embodiment, the liquid biomass feed stream is comprised of the soaked liquid stream.

Ideally, the concentration of the total sugars in the soaked liquid stream should be in the range of 0.1 to 300 g/1, with 50 to 290 g/1 being most preferred, and 75 to 280 g/1 even more preferred, with 100 to 250 g/1 most preferred. This concentration can be done by the removal of water. A 50% removal of water increases the concentration of the non-water species by two. While various concentration increases are acceptable, in one embodiment, at least a two fold increase in the concentration of the xyloligomers in the soaked liquid stream is reached. In one embodiment, at least a fourfold increase in the concentration of the xyloligomers in the soaked liquid stream is reached. In one embodiment, at least a six fold increase in the concentration of the xyloligomers in the soaked liquid stream is reached. Many concentration steps may be applied to the soaked liquid stream before or after each process step.

EXPERIMENTAL

Pretreated stream preparation

Wheat straw, pre-treated at the indicated conditions, is the reference ligno-cellulosic feedstock used for validating the invention. Other ligno- cellulosic feedstocks pre-treated at different conditions were also tested.

Wheat straw was introduced into a continuous reactor and subjected to a soaking treatment at a temperature of 158°C for 65 minutes. The soaked mixture was separated in a soaked liquid and a fraction containing the solid soaked raw material by means of a press. The soaked liquid was then subjected to concentration by means of vacuum evaporation.

The dry matter of the soaked liquid after concentration was 12% and the pH was 4.5. The soaked liquid is the liquid biomass feed stream used for validating the disclosed process.

The composition of the liquid biomass feed stream is reported in Table 1.

Decationization of the liquid biomass feed stream The decationization step was performed in a decationization column having a working volume of 60 liters. The column was filled with a strong cationic resin Relite EXC14 supplied by Mitsubishi Chemical Corporation. The resin was subjected to an activation step by means of HC1. Briefly, 60 gr of HC1 per liter of resin is used in form of a solution at 5% concentration, at a temperature of 25°C and at a rate of 3 BV/h. The resin was then washed with abundant water.

After resin activation, the liquid biomass feed stream was inserted at a rate of 4 BV/h at 25°C.

The decationized liquid biomass feedstream extracted from the decationization column is the acidic liquid biomass feed stream of the disclosed process. The pH of the decationized liquid biomass feedstream was 0.87.

The composition of the acidic liquid biomass feed stream is reported in Table 1. Hydrolysis of the acidic stream

The acidic liquid biomass feed stream was hydrolyzed in a 3 liter PFR reactor according to the following procedure. Residence time was 4.5 minutes and temperature was 145°C.

After hydrolysis, the acidic liquid biomass feed stream was concentrated by vacuum evaporation to reach a dry matter content by weight of about 30.7%. The composition of the acidic liquid biomass feed stream after hydrolysis and concentration is reported in Table 1.

Neutralization of the acidic liquid biomass feed stream

The acidic liquid biomass feed stream was cooled at 25°C Sodium hydroxide added and mixed to the acidic liquid biomass feed stream in a sufficient amount to raise the pH to 6.0.

Different bases were also tested.

The neutralized stream is the liquid sugar stream of the disclosed process.

The composition of the liquid sugar stream is reported in Table 1. It is noted that the ratio of the total ionic equivalents of cations different from Sodium to the total ionic equivalents of cations is 6.7% and the ratio of total ionic equivalents of non-monovalent cations to the total ionic equivalents of cations is 0.6%.

Chromatographic separation of the liquid sugar stream The liquid sugar stream was subjected to chromatographic separation to produce the purified liquid sugar stream of the disclosed process, by means of two different procedures, namely in batch configuration and continuous configuration.

_hltt oe _r neu _r a

d _ii o _rg an _c a _cs

d _c om _p oun _s glycerol 0.47% 0.51% 0.52% 0.48% 0.33% 0.35% 0.00%

5-HMF 0.21% 0.23% 0.24% 0.22% 0.04% 0.00% 0.00% furfural 0.27% 0.30% 0.10% 0.09% 0.00% 0.00% 0.00% formic acid 1.52% 1.68% 1.71% 1.59% 0.49% 0.49% 0.00% lactic acid 0.19% 0.20% 0.21% 0.19% 0.03% 0.02% 0.02% acetic acid 3.45% 3.80% 3.22% 2.99% 0.60% 0.32% 0.00% levulinic

0.21% 0.23% 0.24% 0.22% 0.21% 0.11% 0.00% acid

Other

carboxylic 6.96% 7.66% 7.80% 7.25% 0.36% 0.00% 0.00% acid

Table 1 (a). Composition of the streams of the disclosed process, grouped into different categories

nitrite 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% bromide 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% nitrate 0.51% 0.56% 0.57% 0.53% 0.13% 0.00% 0.00% sulfate 1.08% 1.19% 1.21% 1.13% 0.33% 0.00% 0.00% phosphate 0.15% 0.16% 0.16% 0.15% 0.05% 0.00% 0.00% acetyls 0.48% 0.53% 0.54% 0.50% 0.00% 0.00% 0.00%

Organic Nitrogen (liq) 0.42% 0.46% 0.47% 0.43% 0.24% 0.09% 0.05%

Phenolic compounds 0.40% 0.44% 0.45% 0.42% 0.33% 0.12% 0.00% other compounds 14.44% 11.59% 5.47% 5.08% 4.45% 1.56% 1.47%

density (g/L) 1.06 1.06 1.16 1.16 1.05 1.05 1.05

PH 4.50 0.87 0.34 6.00 6.00 9.52 9.52 conductivity (S/cm) 26 34 34 66 2 0.57 0.57 recovery ratio 90.5% 100% 100%

Purity ratio 8.29% 9.12% 54.52% 50.68% 89.69% 95.00% 96.50% total equivalents of

cations different

from Na/Total 6.7%

equivalents of

cations total equivalents of

0.6%

non-monovalent

cations /total equivalents of

cations

Table 1 (b). Composition of the streams of the disclosed process, grouped into different categories

Batch chromatographic separation A first portion of the liquid sugar stream was subjected to a batch chromatographic separation in a 60 liter column filled with UBK530 by Mitsubishi Chemical Corporation, provided in Sodium form, according to the following procedure: 5% of BV (31iter) of the liquid sugar stream at a temperature of 50°C was inserted into the column at a flow rate of 0.5BV/h, followed by inserting of elution water at the same flow rate for a total bed volume of IBV. Different fractions were collected at step of 0.05BV. The resin has a ion exclusion effect, as evidenced by electrical conductivity measurements, and also a size exclusion effect.

In table 2 the composition of the chromatographic fractions the dry matter content, the purity ratio and the recovery ratio are reported.

The first seven fractions are omitted as they contain substantially only water.

The composition of the fractions are also plotted in figure 1 for clarity.

The different combinations of the chromatographic fractions may be considered as the purified liquid sugar stream, being the other fractions considered as residual streams.

For instance, the purified liquid sugar stream obtained combining fractions 13 to 16 has a purity ratio of 95.7% with a recovery ratio of 93.5%. For instance, the purified liquid sugar stream obtained combining fractions 12 to 17 has a purity ratio of 84.7% and the recovery ratio is increased to 98.8%.

Table 2. Composition of the fractions obtained by batch chromatographic separation

Continuous chromatographic separation

A second portion of the liquid sugar stream was subjected to a continuous chromatographic separation. In a ISMB apparatus composed by 4 columns connected in series, each having a diameter of 1 1 cm and a height of 160cm and filled with UBK530 by Mitsubishi Chemical Corporation, provided in Sodium form.

The ISMB was operated in a standard cyclic mode, and the cycle procedure was shifted of one column in consecutive cycles. Each cycle is composed by two steps, namely a feed step and a recycle step.

In feed step, at steady conditions, the liquid sugar stream and elution water were inserted simultaneously for 750s into the third column of the cycle and into the first column of the cycle, respectively, both at the temperature of 50°C. The liquid sugar stream was introduced at a rate of 8.51/h and the elution water at a rate of 25.41/h. At the same time, from the first column of the cycle a product stream was removed at a rate of 14.31/h, which is considered the purified liquid sugar stream, and a by-product stream (comprising mainly compounds different from monomeric sugars) was removed from the third column of the cycle at a rate of 19.61/h. Following the feed step, in the recycle step the feed and the removal of the streams are stopped and the streams already present inside the columns are circulated internally at a rate of 25.41/h for 765 s.

The composition of the purified liquid sugar stream is reported in Table 1. Refining of the purified liquid sugar stream from continuous chromatographic separation

The purified liquid sugar stream produced by continuous chromatographic separation was subjected to refining to produce the refined liquid sugar stream of the disclosed process. The purified liquid sugar stream was inserted into a column having a working volume of 60 liters. The column was filled with a strong anionic resin Relite EXA268 supplied by Mitsubishi Chemical Corporation.

The resin was subjected to an activation step by means of NaOH. Briefly, 60 gr of NaOH per liter of resin is used in form of a solution at 5% concentration, at a temperature of 25°C and at a rate of 3 BV/h. The resin was then washed with abundant water.

After resin activation, the purified liquid sugar stream was inserted at a rate of 4 BV/h at 25°C. The resin has a ion exchange effect, evidenced by pH measurement. The stream removed from the column is a first refined stream and its composition is reported in Table 1.

The first refined stream was subjected to a second refining step by means of granular activated carbon. The first refined stream was inserted into a column having a working volume of 60 liters. The column was filled with steam activated mineral carbon Cecarbon 1240 Plus, supplied by Ceca (Arkema Group). The resin was subjected to a preliminary standard back-washing step . Briefly, 60 gr of NaOH per liter of activated carbon is used in form of a solution at 5% concentration, at a temperature of 25°C and at a rate of 3 BV/h. The activated carbon was then washed with abundant water. After preparation of the activated carbon, the first refined stream was inserted at a rate of 4 BV/h at 25°C.

The composition of the stream removed from the adsorption column is a second refined stream and its composition is reported in Table 1.

Analysis of results

In table 1 the composition of all the streams of the disclosed process are reported. The composition of the streams before entering the separation process are common to the batch and continuous separation. The streams after chromatographic separation are referred to the continuous configuration. The compositional analyses have been performed to identify a long list of compounds, in order to highlight the effect of each process step.

The compounds have been grouped into general categories to simplify the reading of the tables and showing the categories of compounds relevant for the purification process. Sugar compounds are grouped into monomeric sugars (glucose, xylose, arabinose, fructose, mannose, galactose, ribose) and oligomeric sugars (cellobiose, xylobiose, sucrose, gluco-oligomers, xylo- oligomers, arabino-oligomers ). It is noted that dimers are considered as oligomeric sugars in the framework of the present disclosure.

The category "other neutral compounds" includes glycerol, 5-HMF and furfural, which are neutral compounds different from monomeric and oligomeric sugars, which are neutral. These compounds are usually considered important for conversion process of the monomeric sugars to other compounds, following the disclosed purification process, as they may poison the catalyst and reduce efficiency. It is noted that other neutral compounds may be present also in other categories.

The category "organic acids" includes formic acid, lactic acid, acetic acid, levulinic acid and other carboxylic acid. These acids have been identified by measuring the corresponding anions. The other carboxylix acids include Pyruvic acid, D-Galacturonic acid and Glucuronic acid.

The category "cations" include monovalent inorganic cations (sodium, ammonium and potassium) and non-monovalent inorganic cations (magnesium and calcium). These cations are considered for calculating the two relevant rations of the disclosed process, namely the ratio of the total ionic equivalents of cations different from Sodium to the total ionic equivalents of cations and the ratio of the total ionic equivalents of non- monovalent cations to the total ionic equivalents of cations in the liquid sugar stream.

The category "other anions" indicates the following anions not comprised in the "organic acids" category: chloride, nitrite, bromide, nitrate, sulfate and phosphate.

In the table, acetyls organic nitrogen and phenolic compounds are also reported. Phenolic compounds, which are also considered detrimental for catalyst poisoning, include a long list of compounds, namely: Catechin, 4-hydroxybenzaldehyde, vanillic acid, Caffeic acid, Syringic acid, Vanillin, Syringaldehyde, Acetovanillone, p-coumaric acid, Acetosyringone and ferulic acid. The compounds not present in the previous categories are grouped in the generic category "other compounds" and are calculated as the complementary to 100% on the measured compounds.

Compositions are given as percent amount on a dry basis.

In the table, some relevant physico-chemical properties (dry matter, density, pH and conductivity) affected by the steps of the disclosed process are also reported.

The purity ratio of all the streams of the process and the recovery ratio of the chromatographic separation and refining steps are also reported in the table 1. The purity ratio of the starting liquid biomass feedstream is very low, due to the presence of a relevant amount of oligomeric sugars and other not-sugar compounds in the stream as produced by the pre-treatment. The purity ratio is increased at each process step, mainly in the hydrolysis step, due to the increase of monomeric sugars, and in the chromatographic separation, due to the separation of non-monomeric sugars in the residue stream.

It is noted also that the recovery ratio of the separation and refining steps is very high. No monomeric sugars are lost in both the refining steps within the sensitivity of the measurement. It is pointed out that the surprising result of the disclosed process is represented by the high purity of the purified liquid sugar stream obtained with a high recovery ratio, starting from a liquid biomass feedstream which contains a large amount of impurities. According to inventors knowledge, no other process disclosed in the prior art reaches this result. Without being limited by any interpretation, it is believed that this result is due to the combination of the hydrolysis performed by means of decationization to lower the pH of the liquid biomass feedstream and the specific chromatographic separation of the disclosed process. With reference to the batch chromatographic separation, in figure 2 it is represented the percent amounts on dry basis of main components (namely, glucose, xylose, other monomeric sugars and other compounds) in the relevant chromatographic fractions. It is noted that, in the chromatographic diagram, the peak of the other compounds is almost completely separated from the peaks of the monomeric sugars. Moreover, the peak related to other compounds is greatly reduced with respect to a liquid sugar stream produced by means of acid hydrolysis, due to the added inorganic anions. As a further advantage of the disclosed process, the cations are greatly reduced in the decationization step while pH is lowered. Thereby, in the liquid sugar stream there are fewer cations and inorganic anions with respect to a liquid sugar stream obtained by acid hydrolysis.

After neutralization by NaOH addition, more that 93% of cations in the liquid sugar stream are Sodium, and very few non-monovalent cations are present without any specific softening step.

These features greatly improves the lifetime, or durability, of the separation resin.

Thereby, the disclosed process is effective in producing a high purity liquid sugar stream without wasting significant amount of sugars, as needed to improve the economics in industrial production of commodity bio-chemical products, such as ethylene glycol.