Method for processing cellulose-containing biomass

Abstract

Described is a method for processing cellulose-containing biomass with sulfuric acid and certain additives, especially for the pretreatment of cellulose-containing biomass prior to saccharification.

Claims

1. A method for processing cellulose-containing biomass, comprising: subjecting a treatment mixture comprising cellulose-containing biomass, water and sulfuric acid to a temperature in the range of from 100? C. to 220? C. at a pressure in the range of from 100 to 4000 kPa, wherein the pressure is selected so that at least a part of the water is in the liquid state, to generate a treated cellulose-containing biomass, wherein said treatment mixture further comprises one or more compounds of formula (I) ##STR00008## wherein in the formula (I) each x group is formula (II), R.sup.1 is selected from the group consisting of hydrogen and methyl, R.sup.2 is selected from the group consisting of branched and non-branched alkyl having 9 to 22 carbon atoms, R is independently selected from the group consisting of hydrogen and methyl ##STR00009## and x is an integer from 3 to 40.

2. The method according to claim 1, wherein a concentration of the sulfuric acid in the treatment mixture is in a range of from 0.1 wt. % to 25 wt. %, based on the total weight of the cellulose-containing biomass present in the treatment mixture.

3. The method according to claim 1, wherein in said treatment mixture an amount of methanesulfonic acid is less than 100 wt. %, based on the weight of the sulfuric acid present in the treatment mixture.

4. The method according to claim 1, wherein in one or more of said compounds of formula (I) R.sup.1 is hydrogen, each R is hydrogen, R.sup.2 is selected from the group consisting of branched and non-branched alkyl having 10 to 18 carbon atoms, and x is an integer from 5 to 30.

5. The method according to claim 1, wherein in one or more of said compounds of formula (I) (a) R.sup.2 is a branched alkyl having 12 to 14 carbon atoms and x is an integer from 7 to 25 or (b) R.sup.2 is a nonbranched alkyl having 12 to 14 carbon atoms and x is an integer from 7 to 25.

6. The method according to claim 1, wherein said cellulose-containing biomass is selected from the group consisting of plant biomass, agricultural wastes, forestry residues, sugar processing residues, paper waste and blends thereof.

7. The method according to claim 1, wherein the temperature in the range of from 100? C. to 220? C. at a pressure in the range of from 100 kPa to 4000 kPa wherein the pressure is selected so that at least a part of the water is in the liquid state is maintained for a duration of not more than 120 minutes.

8. The method according to claim 1, wherein the temperature is in a range of 110? C. to 180? C.

9. The method according to claim 1, wherein the pressure is in a range of from 100 kPa to 1600 kPa.

10. The method according to claim 1, wherein said treatment mixture comprises 3 wt.-% to 75 wt. of cellulose-containing biomass, based on the total weight of said treatment mixture.

11. The method according to claim 1, wherein said treatment mixture is obtained by adding an aqueous treatment solution containing sulfuric acid and one or more compounds of formula (I) to said cellulose-containing biomass.

12. The method according to claim 11, wherein in said aqueous treatment solution: the concentration of sulfuric acid is in the range of from 0.1 wt. % to 5.5 wt. %, and/or the total concentration of compounds of formula (I) is in the range of from 0.01 wt. % to 5 wt. %, in each case based on the total weight of said aqueous treatment solution.

13. The method according to claim 1, wherein in the treatment mixture the total amount of cellulose-containing biomass, water, sulfuric acid and compounds of formula (I) is at least 95 wt. %, based on the total weight of the treatment mixture.

14. The method according to claim 1, further comprising (a) and/or (b): (a) saccharification of the treated cellulose-containing biomass so that glucose and/or other sugars are formed, and optionally fermentation and/or chemical processing of the formed glucose and/or other sugars, and/or (b) further processing of the treated cellulose-containing biomass to obtain dissolving pulp.

15. The method according to claim 1, wherein in one or more of said compounds of formula (I) R.sup.1 is hydrogen, each R is hydrogen, R.sup.2 is selected from the group consisting of branched and non-branched alkyl having 10 to 14 carbon atoms, and x is an integer from 3 to 20.

16. The method according to claim 1, wherein in one or more of said compounds of formula (I), R.sup.2 is a branched alkyl having 10 to 13 carbon atoms and x is an integer from 3 to 20; or R.sup.2 is a non-branched alkyl having 12 to 14 carbon atoms and x is an integer from 8 to 20.

17. The method according to claim 16, wherein in one or more of said compounds of formula (I), R.sup.2 is a branched alkyl having 10 to 13 carbon atoms and x is an integer from 3 to 20.

18. The method according to claim 16, wherein in one or more of said compounds of formula (I), R.sup.2 is a non-branched alkyl having 12 to 14 carbon atoms and x is an integer from 8 to 20.

Description

EXAMPLES

(1) 1. Pretreatment of Cellulose-Containing Biomass:

(2) An autoclave with an anchor stirrer is filled with a treatment mixture consisting of an amount of chopped straw as specified in table 1 below, and an aqueous treatment solution comprising sulfuric acid in the concentration specified in table 1 and optionally either a compound of formula (I) (examples 7-11) or a comparison additive which is not a compound of formula (I) (examples 2-6) as specified in type and concentration in table 1.

(3) In the above-defined treatment mixture, the weight fraction of chopped straw corresponds to 5% of the total weight of the treatment mixture, and the weight fraction of the aqueous treatment solution corresponds to 95% of the total weight of the treatment mixture.

(4) Hereinbelow, the compounds of formula (I) and the comparison additives which are not compounds of formula (I) are commonly referred to as additives. For the chemical structure of said additives, see table 2 hereinbelow. All additives are commonly used surfactants which are commercially available. For comparison example 1 is carried out using an aqueous treatment solution comprising sulfuric acid in the concentration specified in table 1 and no additive.

(5) For preparing the above-defined aqueous treatment solutions, an aqueous solution comprising 96 wt.-% sulfuric acid is diluted with deionized water.

(6) The autoclave is purged three times with nitrogen gas and the treatment mixture is heated to the target temperature specified in table 1 under stirring (50 rpm). The resulting pressure is in the range of 280 kPa to 340 kPa. After reaching the target temperature, the temperature is maintained for the time interval according to table 1. Thereafter heating is turned off, the mixture is allowed to cool to ambient temperature, and then the autoclave is relaxed and is emptied. The obtained mixture comprising treated cellulose-containing biomass is filtered through a frit (pore size 2), and the weight of the liquid phase obtained as filtrate is determined, see table 1. The weight of the treated cellulose-containing biomass (solid phase) obtained as filtration residue is determined, see table 1, and then a sample of the obtained treated cellulose-containing biomass is subjected to enzymatic saccharification as described herein below.

(7) 2. Enzymatic Saccharification of Cellulose-Containing Biomass:

(8) 4.50 g of the treated cellulose-containing biomass obtained as described above are weighed into a 50 mL tube and filled up with deionized water containing 0.1 wt.-% sodium azide to a volume of 30 mL. A pH-value of 5.5 is adjusted by adding 100 mM phosphate buffer. An enzyme formulation comprising one or more enzymes selected from the group consisting of beta-glucosidases, exo-cellobiohydrolases, endo- and exo-glucanases, glucoside hydrolases and xylanases is added in the concentration as specified in table 1. The mixture is incubated in an Eppendorf-Thermomixer at 350 rpm and 53? C. (50? C. internal). At certain intervals specified in table 1, 1 mL samples are taken and diluted 1:1 with water. After centrifugation of the sample the clear supernatant is analyzed by HPLC for the concentrations of glucose and xylose.

(9) The yields as indicated in table 1 are either absolute yields stated in arbitrary units or normalized absolute yields. Thus, the yields in table 1 are not based on a theoretical yield. The yields of glucose obtained after 24 hours and 48 hours of enzymatic saccharification are extrapolated to the quantity of treated cellulose-containing biomass and normalized with respect to the yield after 24 hours of enzymatic saccharification according to example No. 1 (pretreatment using an aqueous treatment solution comprising sulfuric acid and no additive).

(10) Pretreatment and enzymatic saccharification of examples 1-11 was carried out under the same conditions with the exception of the type of additive in the treatment mixture. Surprisingly it has been found that the presence of a compound of formula (I) in the treatment mixture results in a higher yield of glucose after 24 and 48 hours of enzymatic saccharification (examples 7-11), compared to example 1 where no additive is present in the treatment mixture. On the other hand, the presence of a comparison additive (examples 2-6) in the treatment mixture instead of a compound of formula (I) results in a significantly lower increase of the yield of glucose after 24 hours (examples 4 and 5) and 48 hours (examples 3-5) of enzymatic saccharification or even in a decrease of the yield of glucose after 24 hours (examples 2, 3 and 6) and 48 hours (examples 2 and 6) of enzymatic saccharification. This finding indicates a strong influence of the chemical structure as well as the molecule size of such additives. Furthermore, the results show that not all kinds of surfactants have an advantageous effect on the yield of glucose. More specifically some kinds of surfactants even have a detrimental effect.

(11) It is noted that in the above-described examples the concentration of cellulose-containing biomass based on the total weight of the treatment mixture is rather close to the lower limit of the above-defined preferred range of 3 wt.-% to 75 wt.-%. However it is common practice in the technical field of the present invention that the effect of an additive with respect to biomass is initially studied in the presence of a low concentration of biomass. Based on the results gained from the examples described herein, the skilled person based on his knowledge is capable of routinely scaling up the method of the present invention to higher concentrations of cellulose-containing biomass.

(12) TABLE-US-00001 TABLE 1 Example No. 1 2 3 4 5 6 7 8 9 10 11 Pretreatment of chopped straw to give treated cellulose-containing biomass Mass of chopped 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 straw/g Sulfuric acid conc./ 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 wt.-% of aq. treat- ment solution Additive type and / 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% 0.25% conc./wt.-% of aq. Addi- Addi- Addi- Addi- Addi- Addi- Addi- Addi- Addi- Addi- treatment solution tive 1 tive 2 tive 3 tive 4 tive 5 tive 6 tive 7 tive 8 tive 9 tive 10 Temperature/? C. 155 155 155 155 155 155 155 155 155 155 155 Hold time at target 0 0 0 0 0 0 0 0 0 0 0 temperature/min Liquid phase 115.9 115.0 118.4 117.0 117.2 116.8 113.2 119.5 119.6 120.8 118.7 (filtrate)/g Solid phase (fil- 25.3 27.2 24.1 26.3 26.8 27.5 30.0 24.0 26.0 21.9 27.1 tration residue)/g Enzymatic saccharification Used treated cellu- 4.50 4.50 4.50 4.50 4.50 4.50 4.50 4.50 4.50 4.50 4.50 lose-containing biomass/g Enzyme dosage/ 5 5 5 5 5 5 5 5 5 5 5 mg Protein per g dry treated cellu- lose-containing biomass Glucose concen- 7.70 5.93 7.82 7.86 8.37 3.92 9.83 14.15 12.26 15.90 9.04 tration after 24 h/mg/mL Glucose concen- 8.48 7.06 9.18 9.71 9.97 4.25 11.24 15.45 13.92 17.49 11.38 tration after 48 h/mg/mL Calculations factor cellulose- 5.62 6.04 5.36 5.84 5.96 6.11 6.67 5.33 5.78 4.87 6.02 containing bio- mass treated/ used in sacchari- fication Extrapolated yield of glucose from treated cellulose-containing biomass/absolute Glucose after 24 43.27 35.86 41.89 45.96 49.85 23.94 65.56 75.47 70.86 77.38 54.43 h enzymatic sac- charification/mg/ mL Glucose after 48 47.70 42.66 49.17 56.74 59.38 25.97 74.92 82.41 80.40 85.11 68.55 h enzymatic sac- charification/mg/ mL Norm: Glucose 43.27 43.27 43.27 43.27 43.27 43.27 43.27 43.27 43.27 43.27 43.27 after 24 h enzy- matic sacchari- fication (pre- treatment with- out additive) Yield of glucose from treated cellulose-containing biomass/normalized Glucose after 24 1.00 0.83 0.97 1.06 1.15 0.55 1.52 1.74 1.64 1.79 1.26 h enzymatic sac- charification Glucose after 48 1.10 0.99 1.14 1.31 1.37 0.60 1.73 1.90 1.86 1.97 1.58 h enzymatic sac- charification

(13) TABLE-US-00002 TABLE 2 Additive Compound of name formula (I) Chemical structure Additive 1 no Carboxymethylcellulose having 0.5 carboxy units per cellulose unit Additive 2 no Alkyl polyglucoside based on natural plant origin C.sub.8-C.sub.14 fatty alcohols Additive 3 no Hexyl ethoxylate with about 4 ethylene oxide units Additive 4 no Phenyl ethoxylate with about 15 ethylene oxide units Additive 5 no Sodium linear C10-C13 alkylbenzene sulfonate Additive 6 yes Branched C10-alkyl ethoxylate with about 10 ethylene oxide units Additive 7 yes Mixture of C12-C14-alkyl ethoxylates with on average 9.5 ethylene oxide units Additive 8 yes Branched C13-alkyl ethoxylate with about 10 ethylene oxide units Additive 9 yes Branched C13-alkyl ethoxylate with about 20 ethylene oxide units Additive 10 yes Branched C13-alkyl ethoxylate with about 3 ethylene oxide units