Characterization and Evaluation of Carbon-Supported Noble Metals for the Hydrodeoxygenation of Acetic Acid

The gas-phase catalytic hydrodeoxygenation (HDO) of acetic acid (AA) over carbon-supported noble metals (5% M on Cp97, where M = Pt, Pd, Ru, or Rh) were studied. The temperature-dependent conversion and selectivity were studied at 1 atm from 200 to 400 °C. For Pt, Pd, and Rh, the main pathway from 200 to 300 °C was decarbonylation, and from 350 to 400 °C the main pathways were decarbonylation/decarboxylation and ketonization. For Ru, however, from 200 to 250 °C the main pathway was decarboxylation, and from 300 to 400 °C the main pathway was decarbonylation. The activity trend based on turnover frequency at 200 °C was found to be Ru > Rh ≈ Pt > Pd. The activities of all of the catalysts at 200 °C were found to decrease after reaction at 400 °C and a return to 200 °C. This is attributed to sintering and coking. The reaction orders in AA and H2 measured at 200 °C for all of the catalysts are generally well below ∼0.5, suggesting relatively strong adsorption of both reactants on all of the metal surfaces. Th...