玉米秆超临界解聚工艺研究

在高压反应釜内，进行超临界条件下解聚玉米秆试验，并通过单因素和正交试验对解聚工艺中溶剂种类、反应温度、反应时间、溶剂用量及高压釜内残存空气除去方式等因素进行了探讨，确定了最佳的解聚工艺：5g玉米秆加20mL甲醇，采用N2置换方式除去高压釜内的空气，300℃下反应60min，残渣率降低到26．89％．GC／MS分析甲醇为溶剂的解聚产物，表明产物成分十分复杂，鉴定出97种化合物，其中83种含氧有机化合物为酯、酚、醚、醇、酮和醛等，还检测出少量正构烷烃、烯烃、芳烃、苯硫酚和含氮有机化合物等，反映了解聚产物的高含氧量和低含氮硫量的特性．其中31．39％的苯酚类物质和5．02％的芳烃类物质可能来源于木质素在超临界甲醇中的解聚作用，而34．63％的甲酯类化合物可能是解聚产生的脂肪酸和苯丙酸等与甲醇酯化的结果．由此可以推断出甲醇超临界解聚过程参与了玉米秆的解聚反应．

Research on Depolymerization Process of Cornstalk in Supercritical Conditions

The reaction of cornstalk powders with different solvents was conducted under supercritical conditions in high-pressure autoclave. Effects of solvent species, reaction temperature, reaction time, solvent volume and methods of removing air on depolymerization of cornstalk were investigated by single factor and orthogonal test. The optimum conditions were identified as follows： 5 g cornstalk with 20 mL methanol was conducted at 300℃ for 60 min with substitute mode of nitrogen to remove any trapped air, and the residue rate decreased to 26.89%. The depolymerization product was analyzed with GC/MS. The results showed that its components were quite complex, and 97 organic compounds were identified. There are 83 kinds of oxygen--containing organic compounds which include esters, phenols,aethers, alcohols, ketones, and aldehydes in the depolymerization product. Small amounts of normal alkanes, alkenes, arenes, thiophenol and nitrogen-containing organic compounds were also detected. All these showed the product＇s characteristics of high oxygen content, low nitrogen content and low sulphur content. The content of phenols was 31.39% whereas the content of arenes was 5.02%, indicating that interaction between methanol and lignin in the cornstalk powders probably resulted from lignin depolymerization. The content of methyl esters was 34.63%, probably resulted from the esterification reactions of fatty acids and benzenepropanoic acids with methanol. These facts further indicated that methanol participated in the depolymerization of the cornstalk powders.