Promoting catalytic hydrogenolysis degradation of black liquor crude lignin by extended soda-oxygen cooking

Abstract

Soda-oxygen cooking was used in this paper to reduce the silicon content in the black liquor (BL) and activate the robust bonds of BL lignin. The effect of the extended cooking process on the structure modification of lignin dissolved in the BL was investigated. The results showed that the G′ unit with a carbonyl group were produced, and the molecular weight was reduced to half of the initial molecular weight after extended delignification cooking. These changes in structure and size significantly improved catalytic hydrogenolysis conversion into monomeric phenols. Compared with that of conventional soda-oxygen cooking, the yield of oil and total monomeric phenols derived from lignin during the extended cooking process increased by 33.6 % and 17.8 %, respectively.