工业木质素结构表征及催化降解研究

Research on Structural Characterization and Catalytic Depolymerization of Industrial Lignin Samples

以不同的工业木质素为原料对其结构进行表征;并利用碱性硝基苯氧化和还原催化降解方法,探究不同木质素降解制备酚类单体的差异性。结果表明:1)木质素的含量存在较大差异,有机酸木质素A样品中木质素含量最高(96.5 wt%),而有机酸木质素B样品中木质素含量最低(48.7 wt%);2)木质素结构破坏程度不一致,主要体现在碱木质素和有机酸木质素A样品中可清晰地检测到β-O-4 (A)结构的信号峰,而在木质素磺酸钠和有机酸木质素B样品中观测不到相关信号峰;3)木质素分子量相差不大,基本分布在1 997~2 301 g/mol;4)木质素还原催化降解制备酚类单体产率分别为47.5 mg/g(木质素磺酸钠)、27.3 mg/g(碱木质素)、49.3 mg/g(有机酸木质素A)和26.9 mg/g(有机酸木质素B),均优于碱性硝基苯氧化的结果。由此可知,来源不同的木质素,其纯度(木质素含量)和结构特点存在明显差异,导致其催化降解制备酚类单体的产率低于天然木质素。研究结果可为木质素的高值化利用提供理论依据。

The structure of lignin was characterized with different industrial lignin as raw materials.The differences of phenolic monomers prepared by different lignin were studied by using oxidation and reduction catalytic degradation methods of basic nitrobenzene.The results showed that,1)The contents of lignin were significantly different,in which organic acid lignin A sample had the highest lignin content(96.5 wt%),but that in the organic acid lignin B(48.7 wt%)was the opposite.2)The structural destruction degree of lignin was inconsistent,the signal peak ofβ-O-4(A)structure was detected in alkali lignin and organic acid lignin A samples,while no signal peak was observed in sodium lignosulfonate and organic acid lignin B samples.3)There was little difference in the molecular weight of all lignin samples,distributed in 1997-2301 g/mol.4)The yields of aromatic monomers derived from the reductive catalytic depolymerization of lignin were 47.5 mg/g(sodium lignosulfonate),27.3 mg/g(alkali lignin),49.3 mg/g(organic acid lignin A)and 26.9 mg/g(organic acid lignin B),respectively,which were superior to the results of alkaline nitrobenzene oxidation.It can be seen that the purity(lignin content)and structural features of lignin from different sources were different,thus resulting in lower aromatic monomer yields derived from the depolymerization of lignin than that of natural lignin.The results could provide an important theoretical basis for high value utilization of lignin.