Lignin Pyrolysis and in Situ Hydrodeoxygenation over MoO3: Interaction between MoO3 and Lignin

Abstract

Lignin pyrolyses and in situ hydrodeoxygenation over MoO3 with varying lignin/MoO3 mass ratios (L/M) at different temperatures were studied in a free-falling reactor. The presence of MoO3 not only facilitated the depolymerization of lignin to liquid and gas products but also catalyzed the in situ hydrodeoxygenation of the resulting liquid product to phenol, both of which were further intensified with the increases of temperature and the MoO3 amount. Negative apparent solid yield and over 100% apparent gas yield were obtained in some cases because of the reaction of MoO3 during lignin pyrolysis. To clarify this phenomenon, detailed TG/MS, XRD, and XPS investigations on spent MoO3 were carried out. The results indicate that Mo6+ was partly reduced to Mo4+ and Mo5+ during the lignin pyrolysis, mainly caused by the reaction with carbon from lignin rather than hydrogen from carrier gas.