A METHOD FOR TREATING CELLULOSIC MATERIAL

Abstract

The present invention provides a method comprising: (i) contacting a cellulose-comprising input material with an aqueous hydrolyzing solution comprising at least 35% wt. of at least one mineral acid to farm a hydrolyzate comprising a mixture of water-soluble carbohydrates and optionally a solid fraction; (ii) contacting said hydrolyzate with an extractant comprising a first solvent S1, to form a first (preferably solid) residue (preferably comprising precipitated carbohydrates, e.g. mono-, di- and/or oligo-saccharides) and an acid-comprising extract; (iii) separating said acid-comprising extract from said first residue; (iv) modifying said acid-comprising extract to form a second (preferably liquid) residue (preferably comprising dissolved carbohydrates) and an acid-comprising modified extract; (v) fractionating said modified extract into an S1-enriched fraction and an acid-enriched fraction; (vi) reusing said SI-enriched fraction to form said extractant; and (vii) reusing said acid-enriched fraction to form said aqueous hydrolyzing solution; wherein (a) at least 10% wt. of the cellulose is hydrolyzed and said mixture of water-soluble carbohydrates comprises monosaccharides, disaccharides and/or oligosaccharides; (b) SI forms a single phase when mixed with an identical weight of 70% sulfuric acid aqueous solution at 25 C.; (c) S1 comprises at least 65% wt. of said extractant; and (d) said acid-comprising extract comprises at least 60% wt. of the acid and at least 5% wt. of the carbohydrates in said hydrolyzate.

Claims

1. A method comprising (i) contacting a cellulose-comprising input material with an aqueous hydrolyzing solution comprising at least 35% wt. of at least one mineral acid to form a hydrolyzate comprising a mixture of water-soluble carbohydrates and optionally a solid fraction; (ii) contacting said hydrolyzate with an extractant comprising a first solvent S1, to form a first (preferably solid) residue (preferably comprising precipitated carbohydrates, e.g. mono-, di- and/or oligo-saccharides) and an acid-comprising extract; (iii) separating said acid-comprising extract from said first residue; (iv) modifying said acid-comprising extract to form a second (preferably liquid) residue (preferably comprising dissolved carbohydrates) and an acid-comprising modified extract; (v) fractionating said modified extract into an S1-enriched fraction and an acid-enriched fraction; (vi) reusing said S1-enriched fraction to form said extractant; and (vii) reusing said acid-enriched fraction to form said aqueous hydrolyzing solution; wherein (a) at least 10% wt. of the cellulose is hydrolyzed and said mixture of water-soluble carbohydrates comprises monosaccharides, disaccharides and/or oligosaccharides; (b) S1 forms a single phase when mixed with an identical weight of 70% sulfuric acid aqueous solution at 25 C.; (c) S1 comprises at least 65% wt. of said extractant; and (d) said acid-comprising extract comprises at least 60% wt. of the acid and at least 5% wt. of the carbohydrates in said hydrolyzate.

2. A method according to claim 1, wherein the weight ratio of said mineral acid in said aqueous hydrolyzing solution to cellulose in said input material is greater than 0.5.

3. A method according to claim 1, wherein the weight ratio of said mineral acid in said aqueous hydrolyzing solution to cellulose in said input material is less than 20.

4. A method according to claim 1, wherein said aqueous hydrolyzing solution comprises a mixture of sulfuric acid and phosphoric acid.

5. A method according to claim 1, wherein said contacting with an aqueous hydrolyzing solution is conducted, at least partially, at a temperature in a range between 15 C. and 80 C.

6. A method according to claim 1, wherein monosaccharides form less than 85% wt. of the water-soluble carbohydrates in said hydrolyzate.

7. A method according to claim 1, wherein said S1 is selected from the group consisting of alcohols comprising 3 to 6 carbon atoms and mixtures thereof.

8. A method according to claim 1, wherein said S1 is selected from the group consisting of tert-butyl alcohol, tert-amyl alcohol and mixtures thereof.

9. A method according to claim 1, wherein acid content of said first residue is less than 500 Kg per ton of said input material.

10. A method according to claim 1, wherein said acid-comprising extract comprises less than 80% wt. of the carbohydrates in said hydrolyzate.

11. A method according to claim 1, wherein said modifying said acid-comprising extract comprises combining said extract with a second solvent S2.

12. A method according to claim 11, wherein said S2 has solubility in water of less than 6% at 25 C.

13. A method according to claim 11, wherein S2 is selected from the group consisting of saturated and unsaturated C5 to C12 hydrocarbons, dichloromethane, chloroform, halogen-substituted hydrocarbon and fluorine-substituted hydrocarbons.

14. A method according to claim 11, wherein said extractant comprises S2.

15. A method according to claim 11, wherein S2/S1 wt./wt. ratio in said modified extract is less than 2.

16. A method according to claim 11, wherein S2/S1 wt./wt. ratio in said modified extract is greater than 0.01.

17. A method according to claim 11, wherein S2 is a hydrocarbon, S2 is tert-amyl alcohol and S2/S1 wt./wt. ratio in said modified extract is greater than 0.01.

18. A method according to claim 11, wherein S2 is a hydrocarbon, S1 is tert-amyl alcohol and S2/S1 wt./wt. ratio in said modified extract is less than 2.

19. A method according to claim 1, wherein said modifying said acid-comprising extract comprises changing the temperature of said extract.

20. A method according to claim 19, wherein said changing the temperature comprises lowering the temperature of said acid-comprising extract by at least 10 C.

21-54. (canceled)

Description

EXAMPLES

Example 1

Modifying an Acid-Comprising Extract by Means of Adding S2

[0152] Example 1 tested the use of tert-amyl alcohol (TAA) and n-pentane as S1 and S2, respectively, and glucose as the carbohydrate.

[0153] A synthetic acid-comprising extract solution was prepared, containing 4.5% wt. glucose, 24.4% wt. sulfuric acid, 10.5% wt. water and 60.6% wt TAA (Sl/mineral acid wt./wt. ratio of about 2.5). This synthetic extract demonstrates an extract formed on contacting hydrolyzate with an extractant composed of TAA as S1. For simplicity, only glucose is used as co-extracted carbohydrate.

[0154] 24.2 g of the acid-comprising extract was mixed with 6.3 g n-pentane at room temperature (S2/S1 wt./wt. ratio of 0.43). The mixture was then allowed to settle overnight. A heavy, second residue, phase was observed. It was separated, weighed (about 1 gr) and analyzed. This second residue contained 26.6% wt. of the glucose present originally in the extract and 9.8% wt. of the sulfuric acid there.

[0155] These results demonstrate that, on mixing S2 with acid-comprising extract, carbohydrates are preferentially rejected into the second residue.

Examples 2-4

Modifying an Acid-Comprising Extract by Means of Adding S2

[0156] Examples 2-4 tested the use of TAA and n-pentane as S1 and S2, respectively, and maltose as the carbohydrate.

[0157] A simulated hydrolyzate was prepared, composed on 61.8% wt. sulfuric acid, 26.7% wt. water and 11.5% wt. maltose. Three synthetic acid-comprising extract solutions were prepared by adding TAA to said simulated hydrolyzate. Their compositions are summarized in Table 1. Those extracts were modified by mixing with n-pentane at room temperature. After settling, a heavy second residue phase and a light modified extract phase were observed in all three. The phases were separated, weighed and analyzed. Total S2/S1 ratios and relative weights of the phases are summarized in table 1. The results of the analysis and related calculations are presented in Tables 2 and 3.

TABLE-US-00001 TABLE 1 Compositions of simulated extracts, S2/S1 ratios and phase weight ratios Light S2/S1 phase/ Synthetic wt./wt. heavy Exam- extract composition in phase ple (% wt.) S1/acid total wt./wt. # TAA Acid Water Maltose wt./wt. mixture ratio 2 59.8 24.8 10.8 4.6 2.4 0.65 17.0 3 63.3 22.7 9.8 4.2 2.8 0.71 15.8 4 68.9 19.2 8.3 3.6 3.6 1.29 34.4

TABLE-US-00002 TABLE 2 Analysis of the formed phases Exam- Light phase Heavy phase ple composition (% wt.) composition (% wt.) # H2SO4 maltose glucose H2SO4 maltose Glucose 2 20.0 0.43 0.35 26.7 27.1 9.2 3 17.8 0.24 0.21 24.9 33.2 12.2 4 12.9 0.20 0.23 24.1 28.7 13.2

TABLE-US-00003 TABLE 3 Carbohydrates rejection and distribution coefficients Acid Water in in heavy heavy Carbohydrates phase phase in heavy out of out of Example phase out of total total D[1] D[1] D[1] # total (% wt.) (% wt.) (% wt.) H2SO4 maltose glucose 2 73 7.3 19.0 0.75 0.016 0.038 3 83 8.2 18.2 0.72 0.0073 0.017 4 74 5.1 11.6 0.53 0.0069 0.017

[0158] [1] D is the distribution coefficient, calculated as concentration in the light phase divided by that in the heavy phase.

[0159] These results demonstrate the following: (i) Modifying the acid-comprising extracts, by mixing with S2, results in the formation of a relatively small heavy second residue phase and a large light modified extract phase. (ii) The small heavy phase contained 73-83% of the carbohydrates originally present in the extract, but only 5-9% of the sulfuric acid originally present there. Displacement of the carbohydrates preferentially to sulfuric acid is also demonstrated by the distribution coefficients. (iii) A fraction of the water in the acid-comprising extract transfer to the second residue. The fraction of water transferred to the second residue is more than 2 times greater than the fraction of the acid transferred there, which means that the acid/water ratio in the modified extract (the light phase) is greater than that of the extract. (iv) The simulated hydrolyzate contained maltose as the sole carbohydrate. The analysis of the two phases, formed during extract modification, contain both maltose and glucose, indicating some hydrolysis of the maltose. Distribution coefficients of maltose are about twice smaller than those of glucose, confirming that higher molecular weight carbohydrates are more efficiently displaced from the extract. This result demonstrates the importance of the embodiment of adjusting decrystallization conditions to minimize formation of monosaccharides.

[0160] In summary: The results confirm that modifying the extracts rejects from the extract the majority of the co-extracted carbohydrate along with a significant amount of the water, while keeping the majority of the extracted acid in the modified extract. That means that (i) S1 with desired high common miscibility with sulfuric acid solution can be used in order to achieve high yield of mineral acid separation from the hydrolyzate; (ii) the co-extracted carbohydrates can be displaced from the extract by the modification before recovering the acid from the modified extract; (iii) that the recovered modified extract is low in carbohydrates, so that carbohydrate losses in case of acid reconcentration are minimal and (iv) reconcentration may not be required due to displacing water from the extract into said second residue.

Example 5

[0161] It was observed that, when adding pentane to a simulated extract feed of TAA:water and sulphuric acid (typical 64:11:25 wt %) a two phase system developed. after separating the phases a new organic phase appeared in the polar phase upon standing. If one shook the new two phase system vigorously, the phases rapidly separated to the same levels as prior to shaking, indicating that the appearance of an organic phase over the previously separated polar bottom phase was not due to slow phase separation. Furthermore, during two experiments extracting sulphuric acid from a spruce hydrolysate using TAA, and following the process to sugar and lignin with all recycling steps (using pentane as S2) substantial amounts(>50%) of the TAA were lost in the process. It was believed that these phenomena were due to dehydration of the alcohol form alkene by-products.

[0162] The above mentioned dehydration products were identified from mixtures of sulphuric acid and TAA by GC/MS and a method for their quantification by GC-FID has been developed.

[0163] The organic phase that appears from the polar phase after TAA extraction from acid by pentane, was confirmed to consist of least partially of TAA and at least partially alkenes. No such organic phase appeared when phosphoric acid (PA) was used instead of sulphuric acid in otherwise identical experiments.

[0164] Experiments were performed to investigate alkene production rates by mixing aqueous acid solution (typically 70 wt %) with TAA. The reaction was carried out in a rotavapor at atmospheric pressure at different temperatures. Alkene yield was calculated as mass loss. Reactions were 2 h except for the 25 C. experiments which were left for typically 16 hours. The results are shown in Tables 4 to 8 below.

[0165] The experimental conditions changed during the experiments, due to evaporation of solvents and products, especially at 50 and 80 C. 25wt % acid concentration at the start of the experiment changed to 50 wt % at high temperatures. There were some alkanes left in the reaction pot, not distilled off, this leads to an underrepresentation of yield. The analyses done suggest that the amount of alkenes in the stillage is 5 wt % at 25 C. and 1-3% at 50 C. There was some alcohol in the condensed distillate, the TAA concentration in the distillate is 5-6 wt % at 80 C. and 1-2% at 50 C. All experiments are performed as open systems, thus showing a worst case scenario as products are continuously removed.

[0166] The results support the theory that acid catalyzed dehydration of TAA to 2-methyl-1 butene, 2-methyl-2 butene, and the three dimers of these.

TABLE-US-00004 TABLE 4 Yield Acid wt % Proportion (distillate Temperature (H.sub.2SO.sub.4 + H.sub.3PO.sub.4 Water g/100 g C. H.sub.3PO.sub.4) in acid wt % Si alcohol * h) 25 25 0 11 TAA 2.0 25 25 0.25 11 TAA 0.2 25 25 0 11 TAA 1.1 25 25 0 15 TAA 0.0 50 25 0 11 TAA 34.0 50 25 0.25 11 TAA 10.0 50 50 0.6 22 TAA 18.0 50 25 0.6 11 TAA 4.0 50 25 1 11 TAA 0.0 50 50 0.25 22 TAA 6.0 50 25 0 11 TBA 2.1 50 25 0 15 TBA 1.3 50 25 0 11 TAA:DEK 6.9 (1:1) 80 50 0.6 22 TAA 39.0 80 25 0.6 11 TAA 41.0 80 25 1 11 TAA 27.0 80 50 1 22 TAA 41.0 80 50 0.25 22 TAA 28.0 80 25 0 11 TAA:DEK 44.0 (1:2)

TABLE-US-00005 TABLE 5 Influence of solvent system Yield Acid wt % Proportion (distillate Temperature (H.sub.2SO.sub.4 + H.sub.3PO.sub.4 Water g/100 g C. H.sub.3PO.sub.4) in acid wt % Si alcohol * h) 50 25 0 15 TBA 1.27 50 25 0 11 TBA 2.05 50 25 0 11 TAA:DEK 6.94 1:1 50 25 0 11 TAA 34 50 50 0.25 22 TAA 5.8 50 25 0.25 11 TAA 10 50 25 0.6 11 TAA 4 50 50 0.6 22 TAA 18 50 25 1 11 TAA 0

TABLE-US-00006 TABLE 6 Influence of PA Yield Acid wt % Proportion (distillate Temperature (H.sub.2SO.sub.4 + H.sub.3PO.sub.4 Water g/100 g C. H.sub.3PO.sub.4) in acid wt % Si alcohol * h) 50 25 0 11 TAA 34 50 25 0.25 11 TAA 10 50 25 0.6 11 TAA 4 50 25 1 11 TAA 0

TABLE-US-00007 TABLE 7 Influence of temperature Yield Acid wt % Proportion (distillate Temperature (H.sub.2SO.sub.4 + H.sub.3PO.sub.4 Water g/100 g C. H.sub.3PO.sub.4) in acid wt % Si alcohol * h) 25 25 0 11 TAA 2.0 25 25 0 11 TAA 0.4 50 25 0 11 TAA 34.0 50 25 0 11 TAA:DEK 6.4 1:1 80 25 0 11 TAA:DEK 1:1 44.0

TABLE-US-00008 TABLE 8 Influence of water Yield Acid wt % Proportion (distillate Temperature (H.sub.2SO.sub.4 + H.sub.3PO.sub.4 Water g/100 g C. H.sub.3PO.sub.4) in acid wt % Si alcohol * h) 25 25 0 11 TAA 0.4 50 25 0 11 TBA 2.1 25 25 0 15 TAA 0.0 50 25 0 15 TBA 1.3

[0167] Table 8 shows that using 63% acid for hydrolysation (wt. ratio acid/water=1.7, rather than the typical 2.3this seemingly small change changes the moles of water:acid from 2.3 to 3.2)

[0168] As seen in Experiment 5, an increase of water activity to an acid/water ratio of 1.7 reduces alkene yield from TAA at 25 C. from 1.3 g to 0 g, and with TBA at 50 C. from 2.2 g to 1.1 g.

[0169] The results suggest that: [0170] Mixtures of TBA and DEK or TAA and DEK for S1 are preferred. [0171] Inclusion of phosphoric acid in the acid mixture in the range 0.05 to 0.25 parts to total acid is preferred. [0172] Water could be added after acid extraction, this lowers reactivity, and may improve alcohol extractability.

Example 6

Influence of DEK

[0173] 45.1 g of spruce wood chips, with 11 wt % moisture, was added 119.2 g of a 69.8 wt % aqueous sulfuric acid solution. The mixture was stirred for 45 minutes at 45 C. After this decrystallization step, approximately 30 g of hydrolysate was transferred to four centrifugation bottles. The hydrolysate was added 1.5 part of S1 solution, four different S1 solutions were used, DEK:TBA (5:5), DEK:TBA(6:4), DEK:TBA (7:3) and DEK:TBA (8:2). After addition the solution was vigorously shaken and centrifuged. The supernatant was removed and the residue was again extracted with S1 of same amount and composition as the first time, this was repeated for a total of 4 extractions. The carbohydrate/lignin residue was analyzed for residual acid content. Pure TBA typically gives an acid consumption (not extracted) of 70 kg sulphuric acid/ton feed, while DEK gives 250 kg. As can be seen from the table below, 50-30% TBA in DEK most preferably 30% gives good acid extraction and will give lower alkene production and better extraction by S2.

TABLE-US-00009 Acid consumption (kg/ton Si dry feed) DEK:TBA (5:5) 80.6 DEK:TBA (6:4) 81.6 DEK:TBA (7:3) 90.3 DEK:TBA (8:2) 118.6

[0174] FIGS. 1 and 2 show results obtained for pentane extraction of a synthetic feed stream (25% sulphuric acid, 15% water, remainder TBA and DEK) extracted by 1 part pentane per 1 part feed.