A novel lignocellulose pretreatment technology by combining KOH, urea peroxide and organosilane to improve glucose yield

Abstract

Alkali pretreatments are considered as one of the most popular strategies to pretreat lignocellulose due to its high-efficiency, low-cost, high lignine removing and cellulose content. Nevertheless, glucose concentration obtained from lignocellulose by alkali pretrements still can’t meet biorefinery requirements. Thus, a novel strategy to pretreat lignocellulose by combining KOH, UHP (urea peroxide) and organosilane (KOH-UHP-Si pretreatment) was proposed. This novel strategy solved two difficult problems that seriously affected the combined pretreatment of alkali and advanced oxidant, and then the cellulose relative content and glucose yield were increased by about 2.4 times and 9 times compared with the original straw, about 19% and 20% compared with the alkali (KOH) pretreatment, and about 2.2 times and 3.3 times compared with the advanced oxidation (UHP) pretreatment. After optimizing the pretreatment process, cellulose relative content in corn straw reached 81.4%, and the removal rates of lignin and hemicellulose were increased to 97.3% and 88.13%, respectively. In addition, we illustrated the mechanism of KOH-UHP-Si pretreatment, in which KOH plays the major role, the organosilane suspension and UHP play the auxiliary role. When the organosilane reduced mass transfer resistance in the reaction system, KOH and UHP assisted and promote each other mutually. Besides, we also illustrated the mechanism of urea assisting KOH removal of lignin through quantum chemical calculations. Moreover, the substances contained in wastewater produced by the novel technique could be turned into agricultural fertilizers after being processed simply, and there will be zero emission in the whole process. Our results indicate that KOH-UHP-Si pretreatment was a high efficiency low cost and eco-friendly strategy for lignocellulose pretreatment.