Solvo-thermal hydrolysis of xylose

1. A process for producing furfural from xylose comprising:

(a) mixing xylose/XOS with sub-critical or near-critical water to form a mixture

at a first temperature and a first pressure;

wherein the first temperature is about 200° C. to about 374° C.; and

wherein the first pressure is about 100 bar to about 350 bar;

(b) maintaining the mixture at the first temperature and the first pressure for a first time period;

wherein the first time period is about 0.5 s to about 180 s; and

(c) rapidly cooling the mixture to a second temperature and a second pressure; wherein furfural is produced by the process;

wherein the second temperature is about −30° C. to about 60° C.; and

wherein the second pressure is about 1 atm to about 75 atm.

2. The process of claim 1 , wherein the furfural is recovered by removing the water from the mixture to cause precipitation of furfural.

3. The process of claim 1 , wherein the aqueous xylose solution is mixed with the sub-critical or near-critical water in a mixing ratio, and the first temperature is adjusted by changing the mixing ratio and/or by changing the temperature of the sub-critical or near-critical water.

4. The process of claim 1 , wherein the mixture is cooled by adding a coolant.

5. The process of claim 1 , wherein the xylose is converted at a conversion level and furfural is produced in a yield and a selectivity, wherein the yield and the selectivity of furfural production increase with increasing xylose conversion levels.

6. The process of claim 5 , wherein the xylose/XOS conversion level is at least about 60%.

7. The process of claim 1 , wherein the mixture further comprises CO 2 .

8. The process of claim 7 , wherein at the first temperature and the first pressure the mixture is present as a two-phase system comprising an aqueous phase and a CO 2 -rich phase.

9. The process of claim 7 , wherein the mixture comprises about 1 mol % to about 50 mol % CO 2 .

10. The process of claim 7 , wherein the CO 2 is added to the aqueous xylose solution prior to mixing the aqueous xylose solution with the sub-critical or near-critical water.

11. A process for producing furfural from xylose comprising:

(a) mixing xylose/XOS, CO 2 , and sub-critical or near-critical water to form a mixture at a first temperature and a first pressure, wherein at the first temperature and the first pressure the mixture is present as a two-phase system comprising an aqueous phase and a CO 2 -rich phase;

(b) maintaining the mixture at the first temperature and the first pressure for a first time period;

wherein the first temperature is about 200° C. to about 374° C. the first pressure is about 100 bar to about 350 bar and the first time period is about 0.5 s to about 180 s.

(c) rapidly cooling the mixture to a second temperature and a second pressure;

(d) separating the CO 2 -rich phase from the aqueous phase; and

wherein the second temperature is about 31° C. to about 60° C. and the second pressure is about 70 bar to about 100 bar

(e) cooling the CO 2 -rich phase to a third temperature and a third pressure;

wherein furfural is produced by the process wherein the third temperature is about −10° C. to about 50° C. and the third pressure is about 1 atm to about 70 atm.

12. The process of claim 11 , wherein the mixture comprises about 1 mol % to about 50 mol % CO 2 .

13. The process of claim 1 or 11 , wherein the xylose/XOS is added to the process as an aqueous slurry.