Late-Transition-Metal-Modified β‑Mo₂C Catalysts for Enhanced Hydrogenation during Guaiacol Deoxygenation

Molybdenum carbide has been identified as a promising bifunctional catalyst in the deoxygenation of a variety of pyrolysis vapor model compounds. Although high deoxygenation activity has been demonstrated, complementary hydrogenation activity has been limited, especially for lignin-derived, aromatic model compounds. The ability to control the relative site densities of acidic and hydrogenation functionalities represents a catalyst design challenge for these materials with the goal to improve hydrogenation activity under <i>ex situ</i> catalytic fast pyrolysis (CFP) conditions. Here we demonstrate that the addition of Pt and Ni to β-Mo₂C resulted in an increase in the H*-site density with only a minor decrease in the acid-site density. In contrast, the addition of Pd did not significantly alter the H*- or acid-site densities. High conversions (>94%) and high selectivities to 0-oxygen products (>80%) were observed in guaiacol deoxygenation under <i>ex situ</i> CFP conditions (350 °C and 0.44 MPa H₂) for all catalysts. Pt addition resulted in the greatest deoxygenation, and site-time yields to hydrogenated products over the Pt/Mo₂C catalyst were increased to 0.048 s^–1 compared to 0.015–0.019 s^–1 for all other catalysts. The Pt/Mo₂C catalyst demonstrated the highest hydrogenation performance, but modification with Ni also significantly enhanced hydrogenation performance, representing a promising lower-cost alternative