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

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 H-2 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 degrees C) on both the Pd/AC and Ru/AC catalysts. At a higher temperature (>= 300 degrees 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 H-2 consumption.