Lignin hydroconversion on MoS2-based supported catalyst: Comprehensive analysis of products and reaction scheme
The hydroconversion of a wheat straw soda lignin was studied in a batch reactor, in tetralin solvent, with a NiMoS/Al2O3 catalyst under H2 pressure at 350 °C. Gaseous, solid and liquid products were separated, quantified and detailed analyses were performed in order to describe and to understand the various reactions occurring versus residence time. In those operating conditions, the weakest β-O-4 and α-O-4 ether linkages of the lignin were first cleaved. The lignin was thus progressively converted into smaller hydrogenated and deoxygenated fragments called lignin residues which were extensively characterized by GPC and NMR. In the liquid phase, smaller monomers and dimers were identified by GC × GC/MS and quantified by GC × GC/FID. The evolution of these molecules was investigated as a function of residence time in order to investigate the catalytic transformation scheme of lignin.