甲醇降解碱木质素

采用超临界甲醇法将碱木质素降解为小分子芳香族化合物,考察了反应温度、反应时间和溶剂中水含量对降解反应的影响。碱木质素被降解为约21种单环芳香族化合物,其中7～11种为主要组分,多为以愈创木基结构为主的芳香族衍生物。产物中非酚型组分较稳定,不易发生进一步反应,且随着反应时间的延长,其所占比例不断增大,而酚型组分稳定性较差,易发生进一步反应。碱木质素降解反应速率的突变发生在250～280℃,温度越高,反应速率越大。水的存在有利于醚键的断裂和酚型组分的生成。在水体积分数为50%的甲醇-水共溶剂体系中,2-甲氧基-4-乙基苯酚的选择性最好,其在产物中的质量分数达48.6%。碱木质素的醚键在反应中全部断裂,四氢呋喃不溶物中主要是以缩合结构为主的木质素残片和再聚合产物。

Degradation of Alkali Lignin in Methanol

Alkali lignin was degradation to small molecular weight aromatic compounds using super-critical methanol as solution.The effects of temperature,reaction time and water content on degradation of alkali lignin were investigated.It was found that about 21 species of compounds were obtained.7-11 species of them were preferred and were guaiacyl-based aromatic derivatives.The non-phenol type compounds were too stable to further react,and the fraction of the non-phenol type compounds increased with the increase of reaction time,while the phenol type compounds were so active that could react continuously.The degradation rate of alkali lignin increased sharply under 250-280 ℃ and the higher the temperature was,the faster the reaction occurred.The water in the solvent was favor to the breaking of ether bonds and the formation of phenol type compounds.In the methanol-water co-solvent with volume fraction of water 50%,the selectivity of 2-methoxy-4-ethylphenol was the best and its mass fraction was about 48.6% in the products.The ether bonds were all broken in the degradation and the insoluble species in tetrahydrofuran was mainly composed of lignin fragment and polymer.