Efficient Metal-Acid Bifunctional Catalysts Derived\nfrom NiAl-LDO for the Reductive Catalytic Fractionation of Lignocellulose\ninto Phenolic Monomers

Reductive\ncatalytic fractionation (RCF) is a promising lignin-first\nstrategy to produce valuable phenolics from lignocellulosic biomass.\nHowever, this method encounters the challenges of a low yield of phenolic\nmonomers and the use of expensive noble metal catalysts. In this study,\na reduced NiAl layered double oxide (NiAl-LDO) catalyst is reported\nfor the RCF of lignocellulosic biomass with high depolymerization\nefficiency and phenolic monomer yields. The RCF reaction of pine at\n260 °C yielded 27.49 wt % of lignin oil and 21.62 wt % of phenolic\nmonomers, with a delignification degree of 92.62%. In addition, high-performance\nliquid chromatography analysis showed that the solid carbohydrate\npulp fraction retained up to 80.63% cellulose, which can be used as\nan economical feedstock for the production of other platform chemicals.\nFurther characterization and mechanistic studies including NH<sub>3</sub>-TPD, Py-FTIR, and 2D HSQC NMR revealed that the strong acidic\nsites derived from Ni<sup>2+</sup> at the metal–support interface\nplay a crucial role in promoting the hydrogenolysis of aryl ether\nbonds within lignin, thereby significantly improving the yield of\nphenolic compounds. Understanding the role of the NiAl-LDO catalyst\nacidity in the RCF reaction is beneficial for the production of phenolic\nproducts from biomass based on a lignin-first strategy.