Efficient Metal-Acid Bifunctional Catalysts Derived from NiAl-LDO for the Reductive Catalytic Fractionation of Lignocellulose into Phenolic Monomers
Xiaomeng Yang, Fei Geng, Zhengzeng Yang, Armin Rezayan, Chunbao Xu, Dan Wu, Yongsheng Zhang
Abstract
Reductive catalytic fractionation (RCF) is a promising lignin-first strategy to produce valuable phenolics from lignocellulosic biomass. However, this method encounters the challenges of a low yield of phenolic monomers and the use of expensive noble metal catalysts. In this study, a reduced NiAl layered double oxide (NiAl-LDO) catalyst is reported for the RCF of lignocellulosic biomass with high depolymerization efficiency and phenolic monomer yields. The RCF reaction of pine at 260 °C yielded 27.49 wt % of lignin oil and 21.62 wt % of phenolic monomers, with a delignification degree of 92.62%. In addition, high-performance liquid chromatography analysis showed that the solid carbohydrate pulp fraction retained up to 80.63% cellulose, which can be used as an economical feedstock for the production of other platform chemicals. Further characterization and mechanistic studies including NH 3 -TPD, Py-FTIR, and 2D HSQC NMR revealed that the strong acidic sites derived from Ni 2+ at the metal–support interface play a crucial role in promoting the hydrogenolysis of aryl ether bonds within lignin, thereby significantly improving the yield of phenolic compounds. Understanding the role of the NiAl-LDO catalyst acidity in the RCF reaction is beneficial for the production of phenolic products from biomass based on a lignin-first strategy.