Lignin Catalytic Hydroconversion over CoMos/Al2O3: Experimental Study and Kinetic Modelling

Lignin which represents almost 30 wt% of lignocellulosic biomass is the most relevant and abundant bio-resource to produce aromatic compounds thanks to its original polymeric structure composed by methoxy- and hydroxy-phenylpropane units with ether inter-unit linkages [1,2]. The full valorization of lignin co-produced in pulp industry or ethanol biorefinery would be highly beneficial for carbon economy as well as environmental reasons. However the conversion of lignin is not an easy step due to the complex analysis of the starting material and the numerous products formed. Among the various thermochemical processes already proposed in literature, catalytic hydroconversion appeared very attractive to lead to high liquid yield. We propose here the catalytic hydroconversion, with a CoMo based sulfide catalyst, as a mean to depolymerize lignin and produce aromatic compounds. The originality of this work is the use of a batch reactor opened on the gas-phase, with a continuous feeding of H2, a reflux system to remove continuously light products and water from the reacting mixture and recycle the solvent. This advanced reaction system has been demonstrated to be powerful compared to a traditional batch system previously used [4, 5].