Method for vapor phase pulping with alcohol, sulfur dioxide and ammonia

1. A process for fractionating a lignocellulosic material, said process comprising:

(a) providing a liquid solution comprising an aliphatic alcohol, water, sulfur dioxide, and ammonia, wherein said sulfur dioxide is present in a concentration of from 10 wt % to 50 wt % of said liquid solution;

(b) contacting a lignocellulosic material with a vapor phase of said liquid solution in a cooking stage, wherein said vapor phase comprises water vapor, alcohol vapor, ammonia, and sulfur dioxide gas;

(c) delignifying said lignocellulosic material with said vapor phase in said cooking stage at a cooking temperature selected from 115° C. to 160° C., a cooking pressure selected from 1 atm to 20 atm, and a cooking time selected from 5 minutes to 3 hours, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and

(d) removing cellulose from said mixture and washing said cellulose with a washing solution comprising a second amount of said aliphatic alcohol and a second amount of water, to produce a chemical pulp product and a liquid hydrolyzate stream comprising sugars and lignin.

2. The process of claim 1 , wherein said sulfur dioxide is present in a concentration of from 12 wt % to 30 wt % of said liquid solution.

3. The process of claim 1 , wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and any combinations thereof.

4. The process of claim 1 , wherein said vapor phase contains a mass ratio of said alcohol vapor to said water vapor of from 0.5 to 5.

5. The process of claim 1 , wherein said ammonia is present in said liquid solution in a concentration of from 0.01 wt % to 10 wt %.

6. The process of claim 1 , said process further comprising recovering residual aliphatic alcohol mixed with said cellulose and recycling said residual aliphatic alcohol to said cooking stage.

7. The process of claim 1 , said process further comprising bleaching said chemical pulp product to produce paper furnish.

8. The process of claim 1 , said process further comprising reducing said cooking pressure to release flash vapors, and then compressing and recycling said flash vapors to said cooking stage.

9. A process for fractionating a lignocellulosic material, said process comprising:

(a) contacting a lignocellulosic material with a vapor phase comprising an aliphatic alcohol, water, sulfur dioxide, and ammonia in a cooking stage;

(b) cooking said lignocellulosic material with said vapor phase in said cooking stage at a cooking temperature selected from 65° C. to 160° C., a cooking pressure selected from 1 atm to 20 atm, and a cooking time selected from 1 minute to 3 hours, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and

(c) removing cellulose from said mixture and washing said cellulose with a washing solution comprising a second amount of said aliphatic alcohol and a second amount of water, to produce a cellulose product and a liquid hydrolyzate stream comprising sugars and lignin; and

(d) reducing said cooking pressure to release flash vapors, and then compressing and recycling said flash vapors to said first stage,

wherein said sulfur dioxide is in a sulfur dioxide concentration of from 9 wt % to 90 wt % of said vapor phase;

wherein said vapor phase contains a ratio of said aliphatic alcohol to said water of from 0.5 to 5;

wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and any combinations thereof;

wherein said ammonia is present in said vapor phase in an ammonia concentration of from 0.01 wt % to 10 wt %; and

wherein said sulfur dioxide concentration, said ammonia concentration, said cooking temperature, and said cooking time are varied to adjust a yield of said cellulose product relative to a yield of said sugars.

10. The process of claim 9 , wherein said vapor phase comprises from 9 wt % to 50 wt % sulfur dioxide.

11. The process of claim 9 , wherein said aliphatic alcohol is ethanol, butanol, or a combination of ethanol and butanol.

12. A process for fractionating a lignocellulosic material, said process comprising:

(a) contacting a lignocellulosic material with a liquid solution comprising an aliphatic alcohol, water, sulfur dioxide, and ammonia in a cooking stage, wherein said sulfur dioxide is present in a concentration of from 10 wt % and 50 wt % in said liquid solution;

(b) draining said liquid solution from said cooking stage;

(c) injecting a vapor solution comprising steam and said aliphatic alcohol into said cooking stage to reach a cooking temperature selected from 115° C. to 160° C. and a cooking pressure selected from 1 atm to 20 atm;

(d) delignifying said lignocellulosic material in a vapor phase within said cooking stage at said cooking temperature and said cooking pressure, for a cooking time selected from 5 minutes to 3 hours, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and

(e) removing cellulose from said mixture and washing said cellulose with a washing solution comprising a second amount of said aliphatic alcohol and a second amount of water, to produce a chemical pulp product and a liquid hydrolyzate stream comprising sugars and lignin.

13. The process of claim 12 , wherein said liquid solution comprises sulfur dioxide in a concentration of from 12 wt % to 50 wt %.

14. The process of claim 13 , wherein said liquid solution comprises from sulfur dioxide in a concentration of from 12 wt % to 30 wt %.

15. The process of claim 12 , wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and any combinations thereof.

16. The process of claim 12 , wherein said vapor phase contains a mass ratio of said aliphatic alcohol to said steam of from 0.5 to 5.

17. The process of claim 12 , wherein said ammonia is present in said liquid solution in a concentration of from 0.01 wt % to 10 wt %.

18. The process of claim 12 , said process further comprising reducing said cooking pressure to release flash vapors, and then compressing and recycling said flash vapors to said cooking stage.