Hydrogenolysis of Benzyl Phenyl Ether Using Nickel–Molybdenum Clay Catalysts—A Model for Cleaving Ether Linkages in Lignin

The solvent-free hydrogenolysis (HDL) of benzyl phenyl ether (BPE), a model for the C–O (α-O-4) linkage in lignin, was investigated using NiMo-pillared clay catalysts in their reduced (NiMoPR) and sulfided (NiMoPS) forms. NiMoPS show higher activity and selectivity to give an equimolar mixture of toluene and phenol, demonstrating selective cleavage of the Caliphatic–O of BPE, while non-equimolar amounts were found for NiMoPR. Strong acid sites are dominant in NiMoPS, giving a higher total acidity compared to NiMoPR, which explains the higher selectivity of the sulfided catalyst towards the HDL products and monomeric aromatics. To understand the interaction of BPE on the catalyst surface, we carried out a comprehensive investigation of the 2D potential energy surface (PES) of BPE and the vibrational spectra using neutron scattering and computational studies. The results suggest that BPE is weakly adsorbed on NiMoPS and the pillared clay support (PILC) via a van der Waals or H-bonding interaction, but they are strongly chemisorbed on the NiMoPR due to covalent bonding. Weakly adsorbed BPE allows higher mobility during diffusion to the catalytic site, which promotes the higher activity of NiMoPS for the HDL. This work demonstrates the potential use of clay-supported NiMo catalysts for lignin valorization and the future circular economy.