反应温度对木质生物质醇解产物分布和反应过程的影响

Effects of Reaction Temperature on the Product Distributions and Process of Woody Biomass Alcoholysis

在密闭不锈钢反应釜中以酸化的正辛醇作溶剂,考察了木质生物质在90～210℃范围内的醇解反应过程.结果表明,生物质液化率在130℃达到最大值83%,110℃低温下液化产物中的轻质油产率超过82%,而重质油产率仅有0.11%,随反应温度升高,轻质油产率逐渐降低,重质油产率却逐渐增大,170℃达最大值12%.轻质油主要由乙酸正辛酯、己酸-4-辛酯、5-甲基糠醛、二辛醚和未反应的正辛醇溶剂组成,重质油是含羟基、甲氧基、羰基和醚键等多种含氧官能团的芳烃或酚类化合物.正辛醇溶剂与纤维素/半纤维素浓酸水解所得乙酸发生酯化反应促进了生物质液化,纤维素/半纤维素降解所得醛类与木质素降解所得酚类化合物发生二次缩聚反应,降低了生物质液化率.

The alcoholysis process of woody biomass with acidified n-octanol as solvent was investigated in an airtight stainless steel autoclave at 90～210℃.The results showed that the highest yield of biomass liquefaction of 83% was obtained at 130℃.The yield of light oil was up to 82% at 110℃,however,the yield of heavy oil was only 0.11%.With reaction temperature increasing,the yield of light oil decreased.On the contrary,the yield of heavy oil increased,and the highest yield of 12% was obtained at 170℃.The light oil was mainly composed of acetic-octyl-ester,hexanoic-4-octyl-ester,5-methyl-furfural,octyl-ether,and unreactive n-octanol.The heavy oil derived was composed of aromatic or phenolic compounds containing various oxygen-bearing functional groups,such as hydroxide,methoxyl,carbonyl and aether.The esterification of n-octanol solvent with acetic acid,derived from the concentrated acid hydrolysis of cellulose and hemicellulose,promoted the liquefaction of biomass.Meanwhile,the aldehyde compounds,derived from the depolymerization of cellulose and hemicellulose,were repolymerized with the phenolic compounds,which were derived from the depolymerization of lignin,and decreased the yield of biomass liquefaction.