PROCESS FOR THE CONVERSION OF CELLULOSE

Abstract

A process for the conversion of a cellulose containing feed comprising the steps of: contacting the cellulose containing feed with a molten salt hydrate and mildly hydrolyzing the cellulose to form a solution of partially hydrolized cellulose, separating one or more components of the partially hydrolyzed cellulose from the solution, converting the separated one or more components of the partially hydrolyzed cellulose in a thermo-catalytic process.

Claims

1. Process for the conversion of ligno-cellulosic biomass comprising the steps of: a) contacting the ligno-cellulosic biomass with a molten salt hydrate and hydrolyzing the cellulose to form a solution of partially hydrolized cellulose, b) separating one or more components of the partially hydrolyzed cellulose from the solution, c) converting the separated one or more components of the partially hydrolyzed cellulose in a thermo-catalytic process.

2. The process of claim 1 wherein preferably the hemicellulose is removed before step a) and lignin preferably is removed after step a).

3. Process according to claim 1 or 2 wherein in the hydrolyzing in step a) the pH of the molten salt hydrate solvent is between −3 and 7, preferably the pH is higher than −2.5, more preferably −2, and for feedstock not containing acetyl groups, in particular cellulose or feedstock from which acetyl groups have been removed or feedstock from which hemicellulose has been removed, the pH is preferably higher than −2 or more preferably higher than −1.5.

4. The process according to anyone of claim 1-3 wherein in step a) the pH is autogenic.

5. The process according to anyone of claims 1-4 wherein in step a) no mineral acid is added.

6. The process according to anyone of claims 1-5 wherein no acid removal step is used.

7. The process according to anyone of claims 1-6 wherein the hydrolyzing step a) forms a liquid solution wherein the amount of glucose is less than 50 wt % relative to the total weight of the partially hydrolysed cellulose, preferably less than 40, 30, 20 or even 10 wt % and wherein the total amount of dissolved cellulose is at least 90%, preferably 93%, more preferably at least 96% relative to the total amount of cellulose in the feedstock.

8. The process according to anyone of claims 1-7 wherein in step a) the temperature is between 90° C. and 120° C. at atmospheric pressure.

9. The process according to anyone of claims 1-8 wherein the reaction time in step a) is between 5-25 minutes.

10. The process according to anyone of claims 7-9 wherein mostly oligomeric cellulose components are separated in step b) for conversion in step c).

11. The process according to anyone of claims 7-9 wherein substantially all components of the partially hydrolysed cellulose are separated in step b) for conversion in step c).

12. The process according to anyone of claims 1-6 wherein the hydrolyzing step a) forms a liquid solution wherein the amount of glucose is more than 20, preferably 30, 40 50 or even 60 wt % relative to the total weight of the partially hydrolysed cellulose and wherein glucose is separated from the solution for conversion in step c).

13. The process according to anyone of claims 1-12 wherein the separation in step b) is done using one or more separation processes chosen from the group of a. precipitation of one or more components of the partially hydrolysed cellulose, b. selective absorption of one or more components of the partially hydrolysed cellulose, c. extraction of the inorganic molten salt hydrate, d. precipitation of the inorganic molten salt hydrate, e. complexation and precipitation of the inorganic molten salt hydrate f. electrodialysis, g. membrane separation.

14. The process according to anyone of claims 1-13 wherein the separation of the partially hydrolysed cellulose in step b) is done by adding an anti-solvent to the solution obtained in step a) to precipitate at least the oligomeric components of the partially hydrolysed cellulose.

15. The process according to anyone of claims 1-13 wherein glucose is separated from the solution obtained in step a) or from the separated partially hydrolysed cellulose obtained in step b) by subsequent precipitation step or by selective adsorption in chromatography, simulated moving bed or moving bed process or by a batch process comprising absorption, filtration and desorption steps.

16. The process according to anyone of claims 1-13 wherein in the separation of the partially hydrolysed cellulose in step b) an adsorbent is used that also is a catalyst for the subsequent conversion in step c).

17. The process according to anyone of claims 1-13 wherein in the inorganic molten salt hydrate is separated from the solution using one or more processes from the group consisting of dioxane precipitation, ammonia complexation and precipitation, membrane separation, adsorption on ion exchange resins, electrodialysis, liquid/liquid extraction with a selective organic solvent.

18. The process according to anyone of claims 1-17 wherein in step c) the thermo-catalytic process is selected from the group of pyrolysis processes, catalytic pyrolysis processes, hydrothermal processes or solvo-thermal processes or combinations thereof.

19. The process according to anyone of claim 18 wherein in step c) the conversion is performed at a temperature between 150° C. and 300° C., preferably between 175° C. and 275° C., 175° C. and 250° C., 175° C. and 225° C. and preferably at atmospheric pressure.

20. The process according to anyone of claims 1-19 wherein the molten salt hydrate is an inorganic molten salt hydrate, preferably chosen from the group of ZnCl.sub.2, CaCl.sub.2, LiCl or mixtures thereof, preferably the inorganic molten salt hydrate substantially consisting of ZnCl.sub.2 hydrate.

21. The process according to anyone of claims 1-20 wherein the ZnCl.sub.2 salt is present in the molten salt hydrate in an amount between 62 and 78, more preferably between 65 and 75 and most preferably between 67.5 and 72.5 wt %.

22. The process according to anyone of claims 1-21 wherein the mass ratio of cellulose containing feed relative to molten salt hydrate is between 1/5 and 1/30 preferably between 1/5 and 1/10.

23. The process according to anyone of claims 1-22 wherein the total amount of water present in step a) and b) is between 20 and 40 wt %, preferably 25 and 35 wt % relative to the total weight of the polysaccharide containing feed and the inorganic molten salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

Hydrolising and Dissolving Step a)

[0026] In the process of the invention the molten salt hydrate is preferably an inorganic molten salt hydrate, preferably chosen from the group of ZnCl.sub.2, CaCl.sub.2, LiCl or mixtures thereof. Most preferred is that the inorganic molten salt hydrate substantially consists of ZnCl.sub.2 hydrate. Reference is made to the above cited prior art documents for description of details concerning the dissolution and hydrolysis in molten salt hydrates.

[0027] Therefore, in the process in step a) the pH is preferably autogenic, meaning that the process is performed with no or substantially no addition of acid and the acidity originates only from the polysaccharide containing feed itself. It is in particular preferred that in step a) no mineral acid is added. Small amount of organic acid would not be such a problem in later process steps but it is also preferred that no organic acid is added as it is not needed in the process and it is less desirable as only partial hydrolysis is desired. The hydrolysed solution may comprise acid originating from hydrolysis of groups on the polysaccharide containing feed, in particular acetic acid originating from acetyl groups. A particular advantage and preferred embodiment of the invention is that in the process no acid removal step is used.

[0028] In the process during the mild hydrolyzing in step a), the pH of the molten salt hydrate solvent is between −3 and 7 and preferably the pH is higher than −2.5, more preferably −2. For feedstock not containing acetyl groups, the pH is preferably higher than −2 or more preferably higher than −1.5. Feedstock not containing acetyl groups can be pure cellulose or feedstock from which acetyl groups have been removed (by e.g. treatment with NaOH). Because acetylgroups are more abundant on hemicellulose, the removal of hemicellulose also results in feedstock in which acetyl groups have been substantially removed.

[0029] On hydrolysing and dissolving cellulose in a molten salt hydrate medium a chemical equilibrium is formed in the solution between the dissolved cellulose, oligomeric cellulose (cellobiose and higher oligomers) and the monomeric glucose which at certain conditions after a certain amount of time will have equilibrium concentrations in the molten salt hydrate solution. It is however not necessary and also not desirable in view of process economy to wait until equilibrium is achieved. Preferably, the total amount of partially hydrolised cellulose in the solution at the start of step b) is at least 80, preferably 85, more preferably at least 90% and most preferably at least 96% relative to the total amount of cellulose in the feedstock. It is preferred that in step a) the total amount of by-products, i.e. cellulose derived products not including glucose and cellulose oligomers, is below 15, 12, 9, 6 and most preferably below 3 wt %.

[0030] In a preferred embodiment, the process of the invention involves mild hydrolysis in mild conditions, in particular a low acidity and preferably low temperatures optionally in combination with a short time, to achieve partial hydrolysis of the cellulose, preferably to oligomeric cellulose with low amounts of glucose, with low impurity levels but also a very high degree of dissolution of the cellulose from the biomass. Herein it is preferred that the mild hydrolyzing step a) forms a liquid solution wherein the amount of glucose is less than 50 wt % relative to the total weight of the partially hydrolysed cellulose, preferably less than 40, 30, 20 or even 10 wt %. This embodiment is particularly advantageous in view of achieving high yield in particular in precipitation step b) and low by-product formation.

[0031] In an alternative embodiment, the process of the invention involves mild hydrolysis to achieve partial hydrolysis of the cellulose with however substantial glucose formation, preferably in an amount of more than 10, 20, 40, 60 or even more than 70 wt %. The amount of glucose is typically limited to 90, 80, 70 or 60 wt % relative to the partially hydrolysed cellulose. In mild conditions small amount of side product like furans are formed. In this embodiment the production of glucose is optimised and glucose is separated for conversion in process step c). This embodiment has the advantage that glucose in step c) can be converted in even better defined mild conditions at higher yield and purity. The oligomeric cellulose can either be recycled or be treated in step c) separately under conditions specifically optimised in yield and purity for the oligomers.

[0032] In general it is possible to perform dissolution and hydrolysis in molten ZnCl.sub.2 hydrates comprising 60-80 wt % of salt at temperatures between 70° C. and 180° C. It was found that best results could be obtained when the ZnCl.sub.2 salt is present in the molten salt hydrate in an amount between 62 and 78, more preferably between 65 and 75 and most preferably between 67.5 and 72.5 wt % relative to the weight of the molten salt hydrate.

[0033] In the hydrolysing step a) the temperature is preferably between 90° C. and 120° C., more preferably between 95° C.-110° C. These temperature ranges apply at atmospheric pressure, but lower temperatures can be used at higher pressures, which is an advantage in view of avoiding side reactions but also means a more expensive process. Therefore atmospheric pressure processes are preferred. At too high temperatures by-products are formed and too low temperatures the reaction proceeds slow and more reaction time is needed. The chosen time can also depend on the morphology of the feedstock. The reaction time is chosen high enough to achieve a high degree of dissolution, preferably at least 80, 90 or even 95 wt % at the given temperature. Preferably, the reaction time in step a) is between 5-25 minutes. Typically a dissolution time of between 10 and 25 minutes is chosen at temperatures between 95° C.-110° C. and between 5 and 15 minutes at temperatures between 100° C.-120° C.

[0034] Furthermore, it is preferred that the mass ratio of cellulose containing feed relative to molten salt hydrate is between 1/5 and 1/30, preferably 1/5 and 1/20 and most preferably between 1/5 and 1/7. Increasing the concentration of saccharides relative to ZnCl.sub.2 solution resulted in an increased oligomers in the reaction product and lower amounts of glucose. For ratios of saccharides to molten salt hydrate higher than 1/12, preferably higher than 1/7, significant amounts of oligomers are formed in the equilibrium.

[0035] It is important that the molten salt hydrate is not diluted with water. Water can be contained in the biomass. Therefore the biomass is preferably dried preferably to a water content below 15, 10, 7, 5, 3 wt %. the process the total amount of water present in step a) is preferably between 20 and 40 wt %, preferably 25 and 35 wt % relative to the total weight of the cellulose containing feed and the inorganic molten salt.

[0036] It is preferred to remove hemicellulose from the biomass, for example by using a more dilute ZnCl.sub.2 solution or a dilute acid such that cellulose is not dissolved; for example hydrolysis of real biomass (e.g. bagasse) with 30% ZnCl.sub.2. However, it is also possible to leave hemicellulose in the biomass and subject the cellulose containing biomass as is, i.e. including the hemicellulose, to the partial hydrolysis step b). The term partial hydrolysing in step b) refers to partial hydrolysation of cellulose and in case in step b) the cellulose is partially hydrolised the hemicellulose will be substantially completely hydrolysed.

[0037] The lignin is preferably removed by filtration after step a) and before step b). Compared to conversion processes of the prior art it is an advantage that lignin is removed before step c) because not only this allows separate optimisation of further lignin processing, but it removes a major cause and source of char and other by product formation during thermo-catalytic conversion.

Separation Step b)

[0038] A particular advantage of the invention is that it is obtained free from mineral acid, and hence can be used in the subsequent conversion step without substantial work-up resulting in an economically attractive high yield process with low amount of by-products. When the cellulose is only partially hydrolised it is also possible to separate a high amount of the cellulosic material from molten salt hydrate solution.

[0039] In the process step b) different options exist. One option is a process wherein substantially all components of the partially hydrolysed cellulose are separated in step b) for subsequent conversion in step c). Another option is a process wherein mostly oligomeric cellulose components are separated in step b) for conversion in step c). In yet another option the glucose is separated from the solution for conversion in step c) or glucose is recycled together with the molten salt hydrate to step a) or b). The choice of the options depend on the chosen type of separation process in step b), the chosen conversion process in step c) and on whether the amount of glucose formed in step a) is sufficient to consider removal of glucose before step c).

[0040] The separation in step b) can be done using one or more processes chosen from the group of [0041] a. precipitation of one or more components of the partially hydrolysed cellulose, [0042] b. selective absorption of one or more components of the partially hydrolysed cellulose, [0043] c. extraction of the inorganic molten salt hydrate, [0044] d. precipitation of the inorganic molten salt hydrate, [0045] e. complexation and precipitation of the inorganic molten salt hydrate [0046] f. electrodialysis, [0047] g. membrane separation.

[0048] In a preferred embodiment of the process the separation of the partially hydrolysed cellulose in step b) is done by adding an anti-solvent to the solution obtained in step a) to precipitate at least the oligomeric cellulose components of the partially hydrolysed cellulose. Suitable an anti-solvents are water, hydrocarbons, ketones (preferably acetone or propanone), ethers (preferably dimethyl or diethyl ether, dioxane and tetrahydrofuran), alkyl esters of organic acids (preferably acetates), alcohols (preferably ethanol, methanol or isopropanol), formamides, aromatic solvents and mixtures thereof. Preferably at least 75%, 80, 85 and most preferably at least 90% of the oligomers are recovered in the precipitate. From economic viewpoint it is most advantageous to use part of the product obtained in step c) as the anti-solvent for precipitation and separation of oligomers in step b). In that way the process does not need addition of expensive anti-solvent but also the need to separate and recover the anti-solvent is reduced, so the process can be done without separation or without complete separation of anti-solvent.

[0049] Disaccharides and higher oligomers precipitate very easily and fast, whereas the monosaccharides precipitate more slowly. It is possible to recover all of oligomers without monosaccharides using small amounts of anti-solvent, which presents the economic advantage that only relatively small amounts of anti-solvent need to be used and to be recovered.

[0050] Mono-saccharides can be left in the solution for recycling and will participate in the equilibrium in hydrolysis and dissolution of the cellulose in the biomass in step a). It is also an advantage that oligomer precipitation can be achieved in a short precipitation time and using a short precipitation time is advantageous not only in terms of process economy but also because it is more selective towards oligomers.

[0051] In another embodiment of the invention the glucose is separated from the solution obtained in step a) or from the separated partially hydrolysed cellulose obtained in step b). This can be done by a separate subsequent precipitation step or by selective adsorption in chromatography, simulated moving bed or moving bed process or by a batch process comprising adsorption, filtration and desorption steps. It is also possible to adsorb both glucose and oligomeric cellulose, for example with carbon black, and separate that from the solution. In a particular embodiment in the separation of the partially hydrolysed cellulose in step b) an adsorbent is used that also is a catalyst for the subsequent conversion in step c).

[0052] Alternatively, the inorganic molten salt hydrate is separated from the solution using one or more processes from the group consisting of dioxane precipitation, ammonia complexation and precipitation, membrane separation, adsorption on ion exchange resins, electrodialysis, liquid/liquid extraction with a selective organic solvent.

[0053] In the alternative embodiment wherein mild hydrolysis is done to achieve partial hydrolysis of the cellulose with however substantial glucose formation in an amount of more than 10, 20, 40, 60 or even more than 70 wt % the glucose is separated in step b) for conversion in process step c). Glucose can (I) be removed selectively with recycle of the oligomeric cellulose to step a) or (II) glucose and oligomeric cellulose are both separated from the solution in step b) either by (IIa) sequential separation or (IIb) by simultaneous separation followed by separation of oligomeric cellulose from the glucose.

Conversion Step c)

[0054] After separation step b) the obtained separated partially hydrolysed cellulose is subjected in step c) to a thermo-catalytic process, preferably selected from the group of pyrolysis processes, catalytic pyrolysis processes, hydrothermal processes or solvo-thermal processes or combinations thereof. These processes result in deoxygenated saccharides which have value as platform chemicals.

[0055] It is a great advantage of the present invention over the prior art thermo-catalytic processes that because of the process steps a) and b) the conversion in step c) can be performed in mild conditions, i.e. at significantly lower temperatures and/or in significantly shorter exposure times at such temperatures. Preferably the temperature during conversion is between 150° C. and 300° C., preferably between 150° C. and 275° C., 175° C. and 250° C., 175° C. and 225° C. and preferably at atmospheric pressure. The exposure times are chosen to achieve acceptable conversion without substantial side product formation. Specific embodiments of the conversion processes are described in the prior art references described above.

[0056] The platform chemicals that are obtained in the catalytic pyrolysis process step c) are depending on the specific process and process conditions used but generally are deoxygenated saccharides, which are also referred to as low oxygen bio-oil. These deoxygenated saccharides can be used as fuels, as fuel additive or as starting material for synthesis of other useful compounds including polymers. The advantage of the process of the invention is that less side products, in particular char are formed compared to conventional processes starting from biomass.

EXAMPLES

[0057] The following is a description of certain embodiments of the invention, given by way of example only.

Production Example 1

[0058] In production example 1, bagasse was hydrolysed and dissolved in Zinc chloride hydrate in mild conditions producing with mostly gluco-oligomers and minimum glucose monomers. Generally a yield of less than 5% of glucose monomers was achieved at a very high dissolution yield. The results show that maximized gluco-oligomers production was achieved when no acid was added to the solution. Comparative experiments with 0.1 wt % HCl or 2 wt % acetic acid (using 70% ZnCl.sub.2 at 80° C.-90° C.) showed a large amount of glucose formation in short time. The effect of the ZnCl.sub.2 concentration and of the hydrolysis/dissolution temperature was measured at ZnCl.sub.2 concentration 70% measured at temperatures 92° C., 100° C. and 110° C. and at ZnCl.sub.2 concentration 65% at temperatures 92° C., 100° C. and 110° C.

[0059] The feedstock was bagasse obtained from Brazil. The bagasse was washed with water at room temperature to remove water soluble component. After the washing the bagasse feedstock comprised hemicellulose, cellulose and lignin had the following composition in weight % on a dry basis as determined by analytical method NREL/TP-510-42618 as established by NREL (USA).

TABLE-US-00001 Xylan Glucan Arabinan Acetate lignin Ashes ASL Total 25.80% 42.59% 1.97% 4.68% 23.40% 0.48% 1.08% 100%
A glucan molecule is a polysaccharide of D-glucose monomers. Xylans are polysaccharides made from units of xylose. Arabinan is a polysaccharide that is mostly a polymer of arabinose. Lignin, a large polyaromatic compound, is the other major component of biomass. Part of lignin which is dissolved under the conditions of NREL analysis is referred as acid soluble lignin (ASL). Acetate is produced during hydrolysis of acetyl groups on the polysaccharides,

[0060] The bagasse was washed with water, milled in a Retsch SM100 knife mill equipped with a 4 mm screen, dried at 40° C. in an air oven to a water level below 6 wt %. Composition of the solvent and ratio bagasse to solvent is specified below in the Table 1. Typically, the solvent was heated to the specified reaction temperature, the required amount of solid material (bagasse) was added into the reactor and kept at that temperature for the reaction time under mild mixing (if other not specified). In a reactor as specified below 1000 gr of ZnCl.sub.2 solution with a salt content as specified in the Tables was placed in the reactor and heated to the specified reaction temperature with mild mixing or as indicated in Table 5 without mixing. The 2 L reactor mentioned in Table 1 and 2 is a jacketed glass reactor with circulating water as heat carrier. The tubular reactor mentioned in Table 3 and 5 is a Swagelok tubular reactor with 15 ml in volume. An amount of 10 gr of the obtained dry milled bagasse was added to the preheated solvent in an amount to give a solid liquid ratio S/L (i.e. solid dry bagasse/liquid molten salt hydrate) as specified in the tables. The counting of the reaction time started after addition of the bagasse. After a certain reaction time as specified in the tables the reaction was stopped by cooling the reaction mixture to room temperature. No influence of the type of reactor was observed in these experiments.

[0061] The resulting reaction product was analysed by filtration of undissolved bagasse over filter 50 micrometer. The obtained solution was brown color viscous liquid. A sample of said solution was analysed using Agilent Infinity HPLC equipped with RID and UV-VIS detectors using a Biorad Aminex HPX-87H Column. The analysis results are given in Tables 1 to 5. In Table 4 and 5 the ration S/L is 1/20, 1/10 which means that per each 1 gr bagasse 20 or 10 gr solution was added, respectively. The total amount of dissolved glucan and xylan was determined based on corresponding sugar (glucose and xylose) analysis in the hydrolyzate liquid obtained after filtration of non-dissolved solids with 50 mkm filter and further treatment under conditions which provides complete hydrolysis of the dissolved carbohydrates. under after complete hydrolysis of

TABLE-US-00002 TABLE 1 70% ZnCl.sub.2, 92° C. ZnCl.sub.2 Acid Temp (C.) S/L ratio Reactor Mixing Filtration 70% No acid 92° C. 1/20 2 L Mild 50 micro reactor mixing filter Xylan Glucan Total Total Xylose dissolved Glucose dissolved Time Xylose oligomers furfural xylan Glucose oligomers AHG HMF glucan 15 min 45.9% N.A. 0.0% N.A. 0.5% N.A. 0.0% N.A. 20 min 48.0% 49.2% 0.0% 97.2% 0.0% 73.5% 0.0% 73.5% 30 min 54.0% 45.4% 0.0% 99.4% 0.8% N.A. 0.0% N.A. 40 min 68.9% N.A. 0.8% N.A. 2.0% 92.8% 0.0% 94.8% 50 min 76.8% N.A. 1.0% N.A. 2.8% N.A. N.A.

TABLE-US-00003 TABLE 2 70% ZnCl.sub.2, 100° C. ZnCl.sub.2 Acid Tem. S/L ratio Reactor Mixing Filtration 70% No acid 100° C. 1/10 2 L Mild 50 micro reactor mixing filter Xylan Glucan Total Total Xylose dissolved Glucose dissolved Time.sup.1 Xylose oligomers furfural xylan Glucose oligomers AHG HMF glucan 5 min 34.2% 40.4% 0.2% 74.8%  0.3% 81.4% 0.0% 0.0% 81.7% 10 min 44.7% 52.6% 0.3% 97.6%  0.9% 89.5% 0.1% 0.0% 90.5% 15 min 64.0% 34.0% 0.7% 98.7%  2.6% 92.2% 0.1% 0.0% 94.9% 20 min 64.7% NA 1.1% NA  5.0% NA 0.3% 0.1% NA 40 min 64.9% 31.7% 2.9% 99.5% 19.4% 77.8% 1.2% 0.2% 98.6%

TABLE-US-00004 TABLE 3 70% ZnCl.sub.2, 110° C. ZnCl.sub.2 Acid Tem. S/L ratio Reactor Mixing Filtration 70% No acid 100° C. 1/10 Tubular Mild 50 micro reactor mixing filter Xylan Glucan Total Total Xylose dissolved Glucose dissolved Time.sup.1 Xylose oligomers furfural xylan Glucose oligomers AHG HMF glucan 10 min 60.1% 37.6%  1.8% 99.5%  8.8% 79.9% 0.6% 0.1% 89.4% 15 min 81.8% NA  3.3% NA 18.2% NA 1.3% 0.1% NA 40 min 61.8% NA 16.9% NA 55.2% NA 4.2% 1.1% NA 60 min 45.5% NA 21.8% NA 48.8% NA 3.7% 1.8% NA

TABLE-US-00005 TABLE 4 65% ZnCl.sub.2, 92° C. ZnCl.sub.2 Acid Tem. S/L ratio Reactor Mixing Filtration 65% No acid 92° C. 1/20, 1/10 Tonado Mild 50 micro reactor mixing filter Xylan Glucan Total Total Xylose dissolved Glucose dissolved Time.sup.1 Xylose oligomers furfural xylan Glucose oligomers AHG HMF glucan 15 min  3.9% N.A.  0.0% N.A.  0.0% N.A.  0.0%  0.0% N.A. 20 min  11.6% 85.6%  0.0% 97.2%  0.0% 63.4%  0.0%  0.0% 63.4% 30 min  27.7% N.A.  0.0% N.A.  0.0% N.A.  0.0%  0.0% N.A. 40 min  49.4% 49.4%  0.0% 98.8%  0.5% 65.0%  0.0%  0.0% 65.5% 50 min 42.87% N.A.  0.0% N.A. 0.00% N.A. 0.00%  0.0% N.A. 60 min 49.18% 49.2% 0.49% 98.9% 0.53% 60.3% 0.00%  0.0% 60.8%

TABLE-US-00006 TABLE 5 65% ZnCl.sub.2, 120° C. ZnCl.sub.2 Acid Tem. S/L ratio Reactor Mixing Filtration 65% No acid 120° C. 1/20, 1/10 Tubular No 50 micro reactor mixing filter Xylan Glucan Total Total Xylose dissolved Glucose dissolved Time.sup.1 Xylose oligomers furfural xylan Glucose oligomers AHG HMF glucan 5 min 72% 25%  0% 97.0%  3.3% 61.5% 0.00% 64.80% 10 min 64% 12%  5% 81.0% 12.1% 30.2% 0.13% 42.43% 15 min 60%  0% 11% 71.0% 21.7% 14.6% 0.44% 36.74% 20 min 64%  0% 16% 80.0% 29.6% 19.6% 0.79% 49.99% 25 min 65%  0% 19% 84.0% 28.8% 19.6% 0.83% 49.23%

Production Example 2

[0062] The influence of added acid on acidity of a ZnCl.sub.2 was determined on different ZnCl.sub.2 concentration levels for different amounts of added acetic acid (AA) and hydrochloric acid (HCL). The pH was determined using a Metrohm 907 Titrando pH meter. The results are summarised in Table 6.

TABLE-US-00007 TABLE 6 pH data ZnCl.sub.2 HCl ZnCl.sub.2 AA wt % (wt %) pH wt % (wt %) pH 60.8 0 0.14 70 0 −1.18 70.9 0 −1.3 70 0.05 −1.43 75.9 0 −1.74 70 0.1 −1.77 59.9 1.44 −2.14 70 0.2 −2.15 69.9 1.44 −3.24 70 0.5 −2.47 74.9 1.44 −3.93 70 1 −2.64 58.9 3 −2.18 70 2 −2.79 68.8 3 −3.38 73.7 3 −4.02

[0063] Based on the production examples above, better results are obtained using 70% ZnCl.sub.2 than when using 65% ZnCl.sub.2. Therefore it is preferred to use at least 65 wt % ZnCl.sub.2. At 65% not sufficiently high percentage dissolution to glucans was obtained even at higher temperatures where side product formation started to take place. In case of using 70% ZnCl.sub.2 as solvent, the temperatures and reaction times could remain relatively low with high yield of dissolved glucans and relatively low yield of glucose and the conditions described in Table 7 are recommended.

TABLE-US-00008 TABLE 7 Total Retention Glucose dissolved Temperature time yield Glucan  92° C. 40 min 2.0% 94.8% 100° C. 10-15 min 0.9-2.6% 90.5-94.9% 110° C. <10 min 8.8% 89.4%

[0064] It was observed that optimum results were obtained in a preferred range between 62 and 78 wt %, more preferably between 65 and 75 wt % and most preferably between 67.5 and 72.5 wt % ZnCl.sub.2 (wt % salt in the molten salt hydrate).

Production Example 3: Separation Step b

[0065] The partially hydrolysed cellulose solution obtained in step a) Production example 1 cellulose hydrolysed in 70% ZnCl.sub.2, without addition of acid at 100° C. produced after 15 minutes only 2.6 wt % glucose and 92.2 wt % of oligomers and hardly any side products with a total amount of 94.9 wt % of initial glucans in bagasse being dissolved.

[0066] The hydrolysate obtained was mixed with 2.33 parts of 2-butanone to 1 part (mass) of hydrolysate. The oligomers precipitated almost completely and a relatively small amount of the already small amount of glucose precipitated. In total 85 wt % of the total amount of the cellulose in solution was precipitated which was 81 wt % of the original amount of cellulose in the biomass feedstock. The filtrate containing ZnCl.sub.2 and residual un-precipitated saccharide could be reused as solvent without purification.

Comparative Example 2—Acidic Cellulose Hydrolysis to Hydrolysate

[0067] Cellulose was mixed to 12 times its weight of a 70% ZnCl.sub.2 solution containing additional 0.4 molal of HCl and kept at 70° C. After 60 minutes a composition of 75% glucose, 20% cellobiose (a glucose dimer) and less than 5% 1,6-anhydroglucose and oligomers was obtained. The resulting hydrolysate was precipitated with 2.33 parts of 2-butanone to 1 part (mass) of hydrolysate. 91% of the cellobiose and 45.6% of the glucose precipitated.

The total amount of cellulosic material obtained in step a) and b) available for subsequent conversion in this comparative example therefore was 52 wt %. The advantage of the invention shows in that example 3 no less than 85 wt % of the total amount of cellulose in solution was recovered for further conversion (as opposed to 52 wt %) and this was achieved in only 15 minutes of hydrolysis (as opposed to 60 minutes).