Schuit Institute of Catalysis, Inorganic Materials Chemistry, Eindhoven University of Technology, P. O. Box 513, 5600 MB Eindhoven, The Netherlands.
Faraday Discuss. 2017 Sep 21;202:141-156. doi: 10.1039/c7fd00039a.
The 'lignin-first' approach has recently gained attention as an alternative whole biomass pretreatment technology with improved yield and selectivity of aromatics compared with traditional upgrading processes using technical lignins. Metal triflates are effective co-catalysts that considerably speed up the removal of lignin fragments from the whole biomass. As their cost is too high in a scaled-up process, we explored here the use of HCl, HSO, HPO and CHCOOH as alternative acid co-catalysts for the tandem reductive fractionation process. HCl and HSO were found to show superior catalytic performance over HPO and CHCOOH in model compound studies that simulate lignin-carbohydrate linkages (phenyl glycoside, glyceryl trioleate) and lignin intralinkages (guaiacylglycerol-β-guaiacyl ether). HCl is a promising alternative to the metal triflates as a co-catalyst in the reductive fraction of woody biomass. Al(OTf) and HCl, respectively, afforded 46 wt% and 44 wt% lignin monomers from oak wood sawdust in tandem catalytic systems with Pd/C at 180 °C in 2 h. The retention of cellulose in the solid residue was similar.
“木质素优先”方法最近受到关注，作为一种替代的全生物质预处理技术，与使用技术木质素的传统升级工艺相比，它可以提高芳烃的产率和选择性。三氟甲磺酸金属盐是有效的共催化剂，可以大大加快从全生物质中去除木质素片段的速度。由于在规模化过程中成本过高，我们在这里探索了使用 HCl、HSO、HPO 和 CHCOOH 作为串联还原分级过程的替代酸共催化剂。在模拟木质素-碳水化合物键（苯糖苷、甘油三油酸酯）和木质素内键（愈创木基甘油-β-愈创木基醚）的模型化合物研究中，发现 HCl 和 HSO 比 HPO 和 CHCOOH 具有更好的催化性能。在木质生物质还原分级中，HCl 是替代三氟甲磺酸金属盐的有前途的共催化剂。在 Pd/C 串联催化体系中，Al(OTf) 和 HCl 分别在 180°C 下反应 2 小时，从栎木屑中得到 46wt%和 44wt%的木质素单体。固体残渣中纤维素的保留率相似。
