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

Lignin pyrolyses and in situ hydrodeoxygenation over MoO 3 with varying lignin/MoO 3 mass ratios (L/M) at different temperatures were studied in a free-falling reactor. The presence of MoO 3 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 MoO 3 amount. Negative apparent solid yield and over 100% apparent gas yield were obtained in some cases because of the reaction of MoO 3 during lignin pyrolysis. To clarify this phenomenon, detailed TG/MS, XRD, and XPS investigations on spent MoO 3 were carried out. The results indicate that Mo 6+ was partly reduced to Mo 4+ and Mo 5+ during the lignin pyrolysis, mainly caused by the reaction with carbon from lignin rather than hydrogen from carrier gas.