水热预处理过程中pH值对玉米秸秆水解特性的影响

Effect of pH Value on Hydrolysis Performance of Corn Stover During Hydrothermal Pretreatment

关键词:  水热预处理  玉米秸秆  水解液  pH值

Key Words:hydrothermal pretreatment  corn stover  hydrolysate  pH value

摘要:本研究采用乙酸或NaOH调节水热预处理的pH值，通过分析玉米秸秆中纤维素、半纤维素和木素降解产物的变化，研究了水热预处理的pH值对玉米秸秆水解特性的影响。结果表明，在水热预处理过程中，乙酸的添加促进了纤维素和半纤维素降解，但木素溶出率略有下降，水解液中木糖、低聚木糖、葡萄糖等糖类物质含量增加，糠醛和5-羟甲基糠醛等物质含量快速提升；当NaOH用量小于3%时，随着NaOH用量增加，纤维素和半纤维素降解减少，NaOH主要消耗于半纤维素中的乙酰基脱除；当NaOH用量为3%时，此时水热预处理终点pH值为5.84，固体物料得率达到最大值为75.15%；继续增加NaOH用量，木素的溶出率开始增加，固体物料得率下降。结果显示pH值可以成为调控水热预处理水解效果的重要手段。

Abstract:In this paper， acetic acid or sodium hydroxide was used to adjust the pH value of hydrothermal pretreatment， and the effect of pH value on the hydrolysis characteristics of corn stover was studied by analyzing the changes of cellulose， hemicellulose and lignin degradation products in hydrolysate. During the hydrothermal pretreatment process， the addition of acetic acid promoted the degradation of cellulose and hemicellulose， but the lignin dissolution rate decreased slightly， the content of xylose， xylooligosaccharide， glucose and other sugars in the hydrolysate increased， and the contents of furfural and 5-hydroxymethylfurfural increased rapidly. On the other hand， when the addition dosage of sodium hydroxide was less than 3%， the degradation of cellulose and hemicellulose decreased with the increase of sodium hydroxide dosage， and sodium hydroxide was mainly consumed in the removal of acetyl group from hemicellulose. When the dosage of sodium hydroxide was 3%， the pH value at the end of hydrothermal pretreatment was 5.84， and the yield of solid material reached the maximum value of 75.15%. With the further increase of NaOH dosage， the dissolution rate of lignin began to increase， and the yield of solid material decreased. The findings indicated that pH could be used as an important means to control the hydrothermal pretreatment process.