Solvo-thermal fractionation of biomass

1. A process comprising:

(a) contacting a biomass and a reactive fluid comprising water and supercritical C 1 -C 5 alcohol to form a reactant mixture at a first temperature and a first pressure;

wherein the C 1 -C 5 alcohol is present at a level of about 40 wt % to about 55 wt % in said reactive fluid;

wherein the first temperature is about 243° C. to about 300° C.;

(b) maintaining the reactant mixture at the first temperature and first pressure for a first time period, wherein a reaction occurs; and

(c) optionally quenching the reaction to form at least one reaction product mixture; wherein a product selected from the group consisting of xylose and cellulose is produced by the process.

2. The process of claim 1 , wherein lignin is produced by the process.

3. The process of claim 1 or 2 , further comprising:

(d) recovering one or more products selected from the group consisting of cellulose, xylose and lignin from the at least one reaction product mixture.

4. The process of claim 2 , further comprising:

(d) filtering the at least one reaction product mixture to produce a first solid and a first reaction product mixture filtrate, wherein the first solid comprises cellulose, and the first reaction product mixture filtrate comprises xylose and lignin.

5. The process of claim 4 , further comprising:

(e) partitioning the first reaction product mixture filtrate into a water soluble fraction and an ethanol soluble fraction, wherein the water soluble fraction comprising xylose and the ethanol soluble fraction comprises lignin.

6. The process of claim 1 or 2 , wherein the biomass is a lignocellulosic biomass.

7. The process of claim 1 , wherein the water is sub-critical water.

8. The process of claim 1 , wherein the water is near-critical water.

9. The process of claim 1 , wherein the C 1 -C 5 alcohol is selected from the group consisting of methanol, ethanol, and butanol.

10. The process of claim 1 , wherein the reactive fluid further comprises supercritical CO 2 .

11. The process of claim 10 , wherein the reactive fluid is about 5 wt % to about 20 wt % CO 2 .

12. The process of claim 1 , wherein the first pressure is about 63.8 bar to about 220 bar.

13. The process of claim 1 , wherein the first time period is about 0.1 min to about 60 min.

14. The process of claim 1 , wherein prior to contacting with the reactive fluid, the biomass is present as a slurry.

15. The process of claim 1 , wherein the process is a batch process, a semi-batch process or a continuous process.

16. A process for fractionating a biomass comprising:

(a) feeding a slurry comprising a biomass in a first fluid comprising water and a C 1 -C 5 alcohol and optionally CO 2 to a reactor, wherein the biomass, first fluid, and optional CO 2 form a reactant mixture;

wherein the C 1 -C 5 alcohol is present at a level of about 40 wt % to about 55 wt % in said first fluid;

(b) maintaining the reactant mixture in the reactor at a first temperature and first pressure for a first time period, wherein the C 1 -C 5 alcohol is supercritical at the first temperature and first pressure, and wherein a reaction occurs;

wherein the first temperature is about 243° C. to about 300° C.;

(c) quenching the reaction, wherein one or more reaction product mixtures comprising one or more fractionated products are produced; and

(d) recovering one or more fractionated products from the one or more reaction product mixtures.

17. A process for fractionating a biomass comprising:

(a) forming a first reactant mixture comprising a biomass, water, and CO 2 at a first temperature and a first pressure;

(b) maintaining the first reactant mixture at the first temperature and the first pressure for a first time period, wherein the CO 2 is supercritical and the water is sub-critical, and wherein a first reaction occurs;

wherein the first temperature is about 243° C. to about 300° C.;

(c) recovering a solid from the first reaction mixture;

(d) contacting the solid with a second fluid comprising a C 1 -C 5 alcohol to form a second reactant mixture at a second temperature and a second pressure;

(e) maintaining the second reactant mixture at the second temperature and the second pressure for a second time period, wherein a second reaction occurs; and

(f) quenching the second reaction to form at least one reaction product mixture.