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 ex situ 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 ex situ 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.