低共熔溶剂(DES)分级分离木质纤维素组分新技术

Fractionation of lignocellulose with deep eutectic solvent(DES)

采用低共熔溶剂(DES)预处理木质纤维素,以提高残渣纤维素的酶解糖化效率。以稻壳为原料,从6种DES(乳酸-甘氨酸、草酸-氯化胆碱、甲酸-氯化胆碱、乙酸-氯化胆碱、甘油-氯化胆碱、乳酸-氯化胆碱)中,筛选脱木素效果最好的两种DES,即甲酸-氯化胆碱和乳酸-氯化胆碱;然后,利用上述2种DES预处理稻壳、玉米芯、樟木、杉木、800 k Gy玉米芯等5种生物质原料,评价DES预处理生物质分离"三素"效果,结果表明甲酸-氯化胆碱预处理玉米芯分离"三素"效果最好;最后,优化了甲酸-氯化胆碱预处理玉米芯分离"三素"工艺参数,最佳参数为:时间120 min,温度115℃,投料量10%(质量分数)。在优化条件下,残渣纤维素含量74. 31%,木质素脱除率81. 49%,木质素纯度77. 07%,半纤维素完全水解。XRD分析表明,残渣纤维素为Ⅰ型纤维素,结晶度48. 57%;残渣纤维素酶解糖化效率为98. 56%。

Owing to the shortage of fossil fuels and serious environmental problems associated with their use,clean renewable biobased energy has attracted great interest in recent years. A key issue is how to efficiently utilize lignocellolusic biomass,an abundant renewable feedstock in nature. In this work,a deep eutectic solvent（DES） was used to fractionate lignocellulose to improve the saccharification efficiency of residual cellulose. Using rice husk as the raw material,two types of DES（formic acid-choline chloride and lactic acid-choline chloride） with good fractionation efficiency were identified by screening six types of DES（lactic acid-glycine,oxalic acid-choline chloride,and glycerin-choline chloride were found to be less effective）. Then,five different biomass materials（rice husk,corncob,camphorwood,cedar wood and 800 k Gy-corncob） were treated with the two types of DES; formic acidcholine chloride（FaCh） was found to have the highest efficacy. Finally,the key parameters—temperature,time and solid loading—were optimized by single-factor experimental design. The optimal conditions were found to be：reaction time of 120 min,temperature of 115 ℃,and a solid loading of 10%. Under the optimum conditions,the cellulose content in the residual solid was 74. 31%,the lignin removal ratio reached 81. 49%,and the purity of lignin obtained by anti-phase precipitation was 77. 07%. Furthermore,the cellulose was enzymatically hydrolyzed and the maximum saccharification yield was 98. 56%. The probable reason for such a high yield is the fact that the cellulose surface becomes more accessible to the enzyme after DES treatment.