玉米秸秆木质素的去甲基化/羟乙基化复合改性研究

Demethylation/Hydroxyethylation Combined Modification of Corn Straw Lignin

利用亚硫酸钠和乙二醛对玉米秸秆木质素进行去甲基化/羟乙基化复合改性,以提高木质素的羟基含量和反应活性。通过FT-IR、TG、DSC以及乙酰化滴定等技术研究了木质素复合改性效果。结果表明:经过去甲基化/羟乙基化复合改性后的玉米秸秆木质素具有优异的活性,其总羟基质量分数较原料木质素提升了88.33%,酚羟基提升了14.70%,反应活性得到明显增强。FT-IR表征发现:复合改性从多方面提升了木质素的羟基含量,对羟基含量的增加有着较为显著的效果。热重和DSC表征发现:复合改性木质素(G-DL)相较于原料木质素降解得更加彻底,其放热峰出现在77℃,放热量达459.82 J/g,反应活性较去甲基化木质素(DL)和原料木质素更高。

The corn straw lignin was modified by demethylation/hydroxyethylation with sodium sulfite and glyoxal,to further improve the hydroxyl content and activity of lignin.The combined modification effect on lignin was characterized by Fourier transform infrared spectroscopic(FT-IR),thermogravimetric,differential scanning calorimetry(DSC)and acetylation titration.The results showed that the corn straw lignin modified by demethylation/hydroxyethylation had excellent activity.The total hydroxyl mass fraction of the modified lignin was 88.33%higher than that of the original lignin,and the phenolic hydroxyl group increased by 14.70%,which indicated that the reaction activity was significantly enhanced.Microscopic characterization by Fourier tansform infrared spectroscopy showed that the hydroxyl content of lignin was increased in many ways by combined modification,which had a significant effect on the increase of hydroxyl content.It was found by thermogravimetric and differential scanning calorimetry(DSC)analysis characterization that compared with the original lignin,the combined modified lignin(G-DL)degraded more thoroughly,with an exothermic peak at 77℃and an exothermic value of 459.82 J/g.The activity of the reaction was higher than that of demethylated lignin(DL)and raw lignin.