Palladium-Incorporated α-MoC Mesoporous Composites for Enhanced Direct Hydrodeoxygenation of Anisole

Hydrodeoxygenation (HDO) is one of the promising catalytic routes for converting biomass derived molecules to high value products. A key step of HDO is the cleavage of an aromatic C-O bond to accomplish the deoxygenation step, however, which is energetically unfavorable. Herein, we report a series of palladium (Pd)-incorporated alpha-phase of molybdenum carbide (alpha-MoC) mesoporous composites for enhanced HDO activity of a biomass model molecule, anisole. The catalysts, x%Pd/alpha-MoC (x% is the molar ratio of Pd/Mo), were investigated by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), Brunauer-Emmett-Teller (BET), Raman, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. Pd is highly dispersed on alpha-MoC when x% <= 1%, but aggregate to form nanoparticles when x% = 5%. The x%Pd/alpha-MoC catalysts (x% <= 1%) show enhanced HDO activity in terms of turnover frequency (TOF) and apparent activation energy barrier (Ea) compared with alpha-MoC and beta-Mo2C catalysts. The TOF of 1%Pd/alpha-MoC catalyst at 160 degrees C is 0.115 h(-1) and the Ea is 48.2 kJ/mol. Moreover, the direct cleavage of aromatic C-O bond is preferred on 1%Pd/alpha-MoC catalyst. The enhanced HDO activity is attributed to superior H-2 dissociation ability by the highly dispersed Pd sites on carbide. This work brings new insights for rational design of the catalyst for selective C-O bond activation.