NaBH4/I2催化加氢还原碱木质素的研究

从麦草碱法制浆黑液中提取木质素,精制后,以苯乙酮为木质素的模型化合物,对催化剂组成及溶剂进行了考察.在此基础上,以NaBH4/I2为催化剂,无水乙醇为溶剂,对木质素进行加氢还原裂解反应研究.考察了温度和时间对木质素催化加氢效果的影响,采用红外光谱(FTIR)、元素分析及凝胶渗透色谱分析(GPC),表征木质素反应前后结构的变化.凝胶渗透色谱分析表明,加氢还原后木质素的分子量明显降低.采用自动电位滴定法测定反应前后木质素中总羟基含量,反应后木质素中总羟基含量为10.19%.得到了NaBH4/I2催化木质素加氢还原反应的最优条件:以1,2-二氯乙烷和乙醇(2∶1,v/v)作溶剂,m(NaBH4)∶m(I2)=1∶1,温度175℃,反应时间15 h.

Hydrogenation and hydrogenolysis of Alkali Lignin Catalyzed by NaBH4/I2

Lignin was obtained from wheat straw alkaline black liquor and refined by organic solvent.Hydrogenolysis of lignin was investigated in the presence of catalysts NaBH4/I2.The acetophenone was employed the model compound of lignin.The reaction conditions were optimized and the optimum conditions were as follow: NaBH4∶ I2=1∶ 1(mass ratio),T= 175 ℃,reaction time of 15 h,1,2-dichloroethane and ethanol(2∶ 1,v/v)as solvent.Functional groups of lignin were characterized by chemical methods before and after reaction,such as element analysis and GPC and FTIR.The results of GPC showed that the molecular weight of lignin become smaller compared with lignin raw material.The contents of total hydroxyl of lignin were determined by automatic potentiometric titration.The contents of total hydroxyl of products were 10.19%.