Catalytic Hydrodeoxygenation of Guaiacol on Rh-Based and Sulfided CoMo and NiMo Catalysts

This study investigates the hydrodeoxygenation (HDO) of guaiacol (GUA), a lignin model compound, using two types of catalysts: mono- and bimetallic Rh-based catalysts and classical sulfided CoMo and NiMo catalysts. The former exhibited greater reactivity than the latter. However, substituting some of the Rh ions with another noble metal (i.e., Pd or Pt) produced no positive effect. This study also proposed the mechanisms of GUA HDO for both types of catalysts. The first step of Rh-based catalysts was hydrogenation of GUA's benzene ring, followed by demethoxylation and dehydroxylation. As for the sulfided CoMo and NiMo catalysts, GUA HDO began with demethylation, demethoxylation, and deoxygenation, followed by benzene ring saturation. A better understanding of HDO surface chemistry may lead to more efficient catalysts for target products.