麦草碱木质素的微波辅助液化降解

研究了微波辅助条件下液化剂、催化剂、反应温度和反应时间对麦草碱木质素进行液化降解制备生物油收率的影响,并利用红外光谱(FT-IR)、气相色谱质谱联用仪(GC-MS)和核磁共振氢谱(1H-NMR)对产物进行表征。结果表明,微波辅助下以甲醇为液化剂,硫酸铁为催化剂液化降解碱木质素可以显著缩短液化反应时间,在160℃相对较低液化温度下反应5 min,生物油的收率达到55.22%。液化降解后的木质素残渣结构变化少,表明木质素降解产物的重新聚合的几率低,碱木质素反应原料可以回收再利用以提高原料利用率。生物油主要为单酚类物质,其中,S型、G型和H型单体的含量分别为57.72%、25.28%和8.98%。核磁共振氢谱中β-O-4键和C-C键质子峰的存在说明生物油中含有部分的二聚体和低聚体酚类化合物。

Liquefaction of wheat straw alkali lignin under microwave irradiation

The effects of liquefying agent, catalyst, reaction temperature and time on the yield of bio-oil in microwave assisted liquefaction of wheat straw alkali lignin were investigated. And the liquefaction products were characterized by FT-IR, GC-MS and ¹H-NMR. It is found that microwave irradiation greatly shortens liquefaction time with methanol as liquefying agent and ferric sulfate as catalyst, where the yield of bio-oil is up to 55.22% at the relatively low liquefaction temperature of 160 ℃ for 5 min. The structure of residual lignin after liquefaction exhibits very limited variation, indicating that the degraded lignin fragments have lower probability of recondensation, and residual lignin can be reused to improve the utilization rate of lignin. The identified liquefaction products are mainly monophenolic compounds, in which S, G and H type compounds account for 57.72%, 25.28% and 8.98%, respectively. The existence of the signals for β-O-4 and C-C bonds in the ¹H-NMR spectra suggests that the bio-oils include a small amount of dimers and oligomers except for monophenolic compounds.