Insights into the catalytic activity and surface modification of MoO3 during the hydrodeoxygenation of lignin-derived model compounds into aromatic hydrocarbons under low hydrogen pressures

MoO3 is an effective catalyst for the hydrodeoxygenation (H DO) of lignin-derived oxygenates to generate high yields of aromatic hydrocarbons without ring-saturated products. The catalyst is selective for the CO bond cleavage under low H-2 pressures (<= 1 bar) and temperatures ranging from 593 to 623 K. A bond-dissociation energy analysis of relevant phenolic C-O bonds indicates that the bond strengths follow an order of Ph-OH > Ph-OMe > Ph-O-Ph > Ph-O-Me. However, for all model compounds investigated, the MoO3 catalyst preferentially cleaves phenolic Ph-OMe bonds over weaker aliphatic Ph-O-Me bonds. Characterisation studies reveal that the catalyst surface undergoes partial carburisation as evidenced by the presence of oxycarbide- and oxycarbohydride-containing phases (i.e., MoOxCyHz,). The transformation of bulk phases and the surface modification of MoO3 by carbon-H-2 are investigated to understand the rote of surface carbon in the stabilisation and enhanced activity of the partially reduced MoO3 surface.