Hydrodeoxygenation of 2-Methoxyphenol over Ru, Pd, and Mo₂C Catalysts Supported on Carbon

Abstract

The hydrodeoxygenation (HDO) of 2-methoxyphenol (or guaiacol, GUA) over Pd, Ru, and Mo2C catalysts supported on activated carbon (AC) is compared. The activities of the catalysts for hydrogenation versus deoxygenation on a per site basis, measured over a range of temperatures in a liquid phase batch reactor at high H2 pressure (3.4 MPa), are quantified using lumped kinetics. The overall GUA consumption rate decreases in the order Pd > Ru > Mo2C. Hydrogenation of the phenyl ring of GUA occurs at a low temperature (240 °C) on both the Pd/AC and Ru/AC catalysts. At a higher temperature (≥300 °C), the R–OCH3 and R–OH bonds of the hydrogenated products are cleaved yielding cyclohexanol, cyclohexane (Pd and Ru), and benzene (Ru) as major products. On the Mo2C/AC catalyst, HDO of GUA occurs by direct demethoxylation yielding phenol followed by Ar–OH bond cleavage to ultimately yield benzene at high temperatures. The lumped kinetics indicate that the hydrogenation activity of the Pd catalyst (on a per site basis, as determined from CO uptake measurements) is about 6 times higher than the Ru, but Ru is more active for O removal. Although the Mo2C is the least active, it is the most efficient in terms of O-removal with minimal H2 consumption.