木质素无卤素水相催化脱甲基反应及其利用

Catalytic Demethylation of Lignin in Halogen-free Aqueous Phase System and its Utilization

木质素脱甲基转化成多酚是其高值利用的重要途径。针对传统脱甲基反应的高卤素含量、高酸强度的缺点,以TiOSO 4为前驱体在活性炭(AC)载体上一步法构筑了布朗斯特酸(B酸)和路易斯酸(L酸)共存的固体酸催化剂,在无卤素水相体系实现模型木质素的脱甲基反应。在300℃反应1 h可以获得48.5%的产物收率,高的酸性位含量显著提高脱甲基反应活性,TiO_(2)的表面团聚会降低单位酸性位的活性,B酸和L酸的协同作用促进了脱甲基反应的进行。真实木质素在该反应体系下同样可以进行脱甲基反应,提高木质素的酚羟基含量。将木质素用于聚氨酯表面改性,结合SiO_(2)气相沉积提高聚氨酯阻燃性;结果表明,更多的酚羟基可以提高木质素在聚氨酯阻燃性能的作用。

The demethylation of lignin into polyphenols is an important way for its high value utilization.In view of the shortcomings of traditional demethylation reactions,such as high halogen content and high acid strength,a solid acid catalyst with the coexistence of Bronsted acid(B acid)and Lewis acid(L acid)was constructed by one-step method on activated carbon(AC)carrier with TiOSO 4 as precursor.The demethylation reaction of model lignin was achieved in halogen-free aqueous phase system.The yield of 48.5%was achieved at 300℃for 1 h.The high content of acid sites significantly improved the activity of the demethylation reaction.The surface agglomeration of TiO_(2)reduced the activity of unit acid sites.The synergistic effect of B acid and L acid promoted the demethylation reaction.Real lignin also underwent demethylation reaction under this reaction and increase the phenolic hydroxyl content of lignin.Lignin was used for surface modification of polyurethane,combined with SiO_(2)vapor deposition to improve the flame retardancy of polyurethane.Results showed that more phenolic hydroxyl groups could improve the flame retardancy of lignin in polyurethane.