Prehydrolysis and digestion of plant material
First Claim
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1. A method for treating annual, vascular plant material containing hemicellulose and lignin which comprises the steps of:
- a. prehydrolyzing said plant material by heating said plant material under pressure in the presence of steam and the vapors of a dilute acid solution having a pH in the range from 1.5 to about 3.5 at a temperature ranging between about 105°
C. and about 135°
C. for between 7 minutes and about 20 minutes to hydrolyze at least a portion of said hemicellulose into pentoses and hexoses and to leave a fibrous material and a liquid, said liquid containing said pentoses and hexoses;
b. separating said liquid from said fibrous material, and recovering the pentoses and hexoses from said liquid;
c. heating said fibrous material under pressure in the presence of white liquor at a temperature ranging between about 105°
C. and about 135°
C. for a time sufficient to digest said fibrous material;
d. separating the digested fibrous material from spent digestion liquor; and
thene. washing the digested fibrous material.
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Abstract
Plant material containing hemicellulose and lignin is prehydrolyzed in the presence of steam and the vapors of a dilute acid solution having a pH of 1.5-3.5 at a temperature of 105° C to 135° C for 7-20 minutes to hydrolyze the hemicellulose into pentoses and hexoses and to leave a fibrous material and a liquid, said liquid containing said pentoses and hexoses. The liquid is separated from the fibrous material, and the pentoses and hexoses are recovered from the liquid. The fibrous material is digested with white liquor at a temperature of 105° C to 135° C.
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Citations
13 Claims
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1. A method for treating annual, vascular plant material containing hemicellulose and lignin which comprises the steps of:
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a. prehydrolyzing said plant material by heating said plant material under pressure in the presence of steam and the vapors of a dilute acid solution having a pH in the range from 1.5 to about 3.5 at a temperature ranging between about 105°
C. and about 135°
C. for between 7 minutes and about 20 minutes to hydrolyze at least a portion of said hemicellulose into pentoses and hexoses and to leave a fibrous material and a liquid, said liquid containing said pentoses and hexoses;b. separating said liquid from said fibrous material, and recovering the pentoses and hexoses from said liquid; c. heating said fibrous material under pressure in the presence of white liquor at a temperature ranging between about 105°
C. and about 135°
C. for a time sufficient to digest said fibrous material;d. separating the digested fibrous material from spent digestion liquor; and
thene. washing the digested fibrous material. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. In a method for prehydrolyzing and digesting annual, vascular plants containing hemicellulose and lignin including the steps of prehydrolyzing said plants in an acidic aqueous medium under pressure in the presence of steam resulting in a fibrous material and a liquid, said liquid containing pentoses and hexoses, and digesting the resulting fibrous material in an aqueous alkaline medium containing sulfide values therein, the improvement comprising:
prehydrolyzing said plants in contact with the vapors of a dilute acid solution having a pH in the range from 1.5 to about 3.5 at a temperature in the range from 105°
C. to about 135°
C. for from about 7 to 20 minutes to convert at least a portion of said hemicellulose to pentoses and hexoses, separating said liquid from said fibrous material prior to digesting said fibrous material and recovering said pentoses and hexoses from said liquid.
Specification