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利用基于3因素3水平的Box-Behnken设计响应曲面实验,研究了添加干冰为辅助介质的水热预处理条件:预处理温度,预处理时间以及辅助介质添加量这3个因素以及这3个因素中两两交互作用对木质素含量的影响,并对水热预处理条件进行了优化。并采用13C固体核磁波谱(NMR)和红外(FT-IR)光谱分析了木质素的结构变化。根据方差分析,辅助介质添加量对木质素含量的影响最为显著,其次是预处理时间,预处理温度的影响最弱。以木质素含量最小为目标,根据二元回归方程预测出最佳的预处理条件为:温度180℃,时间90 min,0.47 g辅助介质添加量,在最优条件下,木质素含量预计为21.2%,脱除率达到31.6%。固体13C NMR和FTIR分析表明,在水热预处理过程中,木质素的致密结构遭到了破坏,木质素高聚体进行了解聚,产生了单体和低聚体。并且确定玉米芯中的木质素主要是紫丁香基型木质素和愈创木基型木质素。
Using the Box-Behnken design response surface experiment based on 3-level-3 level, the conditions of hydrothermal pretreatment with dry ice as auxiliary medium were studied: the pretreatment temperature, the pretreatment time and the amount of auxiliary medium, and the three factors In the interaction between the two on the lignin content, and hydrothermal pretreatment conditions were optimized. The structural changes of lignin were analyzed by 13C solid-state nuclear magnetic resonance (NMR) and infrared (FT-IR) spectroscopy. According to the analysis of variance, the influence of auxiliary medium on lignin content is the most significant, followed by the pretreatment time, and the influence of pretreatment temperature is the weakest. According to the binary regression equation, the optimal pretreatment conditions were as follows: temperature 180 ℃, time 90 min, dosage of auxiliary agent 0.47 g, under optimal conditions, the content of lignin was estimated to be 21.2 %, Removal rate reached 31.6%. Solid 13 C NMR and FTIR analysis showed that during the hydrothermal pretreatment, the dense structure of lignin was destroyed, and the lignin polymer was depolymerized to produce monomers and oligomers. The lignin in the corncob was identified as predominantly lilac-based and guaiacyl-based lignin.