麦草碱木素光催化降解光谱分析

Spectral analysis of wheat straw soda lignin with photocatalytic degradation

采用自制的光催化降解反应器,在紫外光照射下,对麦草碱木素进行了光催化降解研究。通过对光照、氧气和光敏剂这3个因素进行不同组合,考察了木素光催化降解途径。通过分析木素紫外吸收光谱和傅立叶红外光谱,探讨了木素在不同反应过程中结构的变化情况以及各因素在木素光催化降解过程中的作用,初步研究了木素发生光催化降解的机理。结果表明:在单纯的光照条件下,木素直接发生降解较少;氧气对木素光催化降解起到了重要的作用,有氧条件下光降解实验表明,木素结构中苯环大量开裂,联接木素单元结构间的醚键打开;自由基、单线态氧对木素光催化降解的贡献很大;三重态的光敏剂虽不能直接与木素反应,但在有氧气通入的条件下,三重态光敏剂与分子氧反应会生成的单线态氧,加速了木素光催化降解。

The photocatalytic degradation of lignin obtained from the black liquor of wheat straw soda-AQ digestion proceeded in a self-made reactor. The three basic factors including light, oxygen and photosensitize were combined with different combining types and the catalytic degradation pathway of alkali lignin was studied. The mechanism of photocatalytic process was studied via the UV- vis and FTIR analysis. And also the structure changes in lignin and the attribution of each pathway were discussed with respect to photocatalytic degradation. The results show that little changes occurred directly in lignin structure when lignin was exposed to the U~ light; the benzene rings in lignin can be open with the help of light and oxygen, and also the ether bonds connected with the lignin units were cracked; the addition of photosensitizer Rose Bengal can do favor to produce singlet oxygen which can accelerate the degradation of,lignin at some extent. It indicated that free radicals and singlet oxygen made great contribution to the photocatalytic degradation of lignin. Triplet photosensitizers can not directly react with ligninions; but under the condition of oxygen access, the reaction of triplet photosensitizers and molecular oxygen generated singlet oxygen, which accelerated the lignin＇s photocatalytic degradation