单 位：
南京林业大学江苏省林业资源高效加工利用协同创新中心;中国林业科学研究院林产化学工业研究所江苏省生物质能源与材料重点实验室生物质化学利用国家工程实验室
摘 要：
催化加氢脱氧是实现木质素提质的重要方式。笔者采用流动电催化技术对木质素模型化合物进行加氢脱氧研究。以磷酸为阳极电解液,铂片电极为阳极电极,杂多酸磷钨酸为阴极电解液,石墨棒电极为阴极电极,构建炭载催化剂直接分布在阴极电解液中的流动电催化体系。考察了不同炭载催化剂(Pt/C、Pd/C、Ru/C、Rh/C)、反应时间、温度以及电流密度对底物2-甲氧基-4-丙基苯酚的转化率及产物选择性的影响。结果表明:Pt/C催化剂表现出最佳的催化活性。在温和条件下(温度50℃,反应时间1 h,电流密度175 mA/cm~2),电催化转化率超过92%,主要电催化产物丙基环己烷和4-丙基环己醇的选择性超过87%,其他产物为4-丙基环己酮和2-甲氧基-4-丙基环己醇等,且温度、反应时间和电流密度的增加均可提升电催化底物的转化率和产物选择性。同时,提出了2-甲氧基-4-丙基苯酚的电化学加氢脱氧反应路径。此外,考察了其他木质素单体(愈创木酚、间甲酚、丁香酚)和β-O-4结构木质素模型化合物(2-苯氧基-1-苯乙醇)的电催化加氢脱氧研究。结果表明:该催化体系可有效实现酚类模型化合物中芳环的氢化、甲氧基的脱除、羟基的脱除和芳香醚键的解聚。
译 名：
Electrochemical catalysis of lignin model compounds
作 者：
HAN Shuangmei;ZHAI Qiaolong;WANG Ruizhen;XU Junming;JIANG Jianchun;Jiangsu Province Biomass Energy and Material Laboratory; National Engineering Lab.for Biomass Chemical Utilization, Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry;Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University;
关键词：
lignin;;hydrodeoxygenation;;heteropolyacid;;flow electrocatalysis
摘 要：
Hydrodeoxygenation is an important way to improve the quality of lignin. However, the traditional hydrodeoxygenation of lignin-derived phenolic compounds requires high temperature and high pressure. The high temperature often causes the formation of char or tar and deactivation of catalysts, which limits its reaction to a large extent. In contrast, electrocatalytic hydrogenation(ECH) is a promising approach, and its conditions are mild(atmospheric pressure and temperature <100 ℃). The low temperature avoids the catalyst problems caused by the high temperature. ECH can provide hydrogen or oxygen source through the ionization of solvent water, avoiding the use of hydrogen or oxidant in the reaction process and adjusting the electrode potential or current and other means to control the reaction rate and the selectivity of products. In this study, a new electrocatalytic technology was used to investigate the hydrodeoxygenation of lignin model compounds. Using phosphoric acid as anode electrolyte, platinum plate as anode electrode, heteropolyacid phosphotungstic acid(PW_(12)) as cathode electrolyte, graphite rod as cathode electrode, and sodium borohydride as reductant and hydrogen source, carbon loaded catalysts were directly distributed in the cathode electrolyte in a flow electrocatalytic system. Herein, the effects of different catalysts(Pt/C, Pd/C, Ru/C, Rh/C), reaction time, temperature, and current density on the conversion of 2-methoxy-4-propylphenol and the selectivity of the products were investigated. The results showed that the Pt/C catalyst had the best catalytic activity. Under mild conditions(50 ℃, 1 h, 175 mA/cm~2), the electrocatalytic conversion was achieved more than 92%. The selectivity of the main electrocatalytic products(propylcyclohexane and 4-propylcyclohexanol) was more than 87%. Other obtained products were 4-propylcyclohexanone, 2-met-hoxy-4-propylcyclohexanol, etc. The reaction time, temperature and current density had great effects on the improvement for the conversion of electrocatalytic substrates and selectivity of products. In addition, each type of catalytic hydrogenation intermediates was used as substrates for the electrocatalytic study and the electrochemical hydrodeoxidation reaction path of 2-methoxy-4-propylphenol was proposed. Other lignin monomers(guaiacol, m-cresol, eugenol) and lignin model compound with β-O-4 structure(2-phenoxy-1-phenylethanol) for electrocatalytic hydrodeoxygenation were investigated. The results showed that the catalytic system can effectively realize the hydrogenation of aromatic rings, the removal of methoxyl groups, the elimination of hydroxyl groups and the depolymerization of aromatic ether bonds in the model phenolic compounds. On the basis of previous studies, this study provides a new green and mild hydrodeoxygenation method for electrochemical catalysis of lignin-derived phenolic compounds. Simultaneously, this research can be widely applied for catalytic hydrodeoxygenation of lignin model compounds.
