玉米秸秆木质素的去甲基化改性研究

Study on demethylation modification of corn stalk lignin

以亚硫酸钠为亲核试剂对玉米秸秆木质素进行去甲基化改性,以增加木质素的羟基质量分数和活性。利用FT-IR、DSC、UV测试以及乙酰化滴定等分析方法研究了不同的反应条件对木质素去甲基化改性效果的影响。结果表明,亚硫酸钠在碱性条件下可与玉米秸秆木质素发生去甲基化反应,其最佳反应条件为:反应时间为2 h、反应温度为60℃、m(木质素)∶m(NaOH)∶m(Na2SO3)为10∶1.5∶2。改性后的木质素与原木质素相比,总羟基质量分数可增加30%左右,其中酚羟基质量分数增加20%左右,反应活性明显增强。

Corn stalk lignin is demethylated with sodium sulfite as nucleophile to increase the mass fraction of hydroxyl and activity of lignin.The effects of different reaction conditions on the demethylation of lignin are studied by means of FT-IR,DSC,UV test and acetylation titration.The experimental results show that demethylation reaction can be occurred between corn stalk lignin and sodium sulfite under alkaline conditions,and the optimal reaction conditions for demethylation are as follows:reaction time is 2 h,reaction temperature is at 60℃,and the mass ratio of lignin∶NaOH∶Na2SO3 is 10∶1.5∶2.Compared with the original lignin,total hydroxyl content of the modified lignin can be increased by about 30%,among which the content of phenolic hydroxyl is increased by about 20%,resulting in a significant improvement of reactivity.