Molybdenum carbides have shown potential as catalysts in upgrading biomass-derived molecules under reducing environments such as hydroprocessing of fast pyrolysis bio-oil or hydrogenation of carbonyls. Particularly, due in part to their oxophilic nature, they exhibit high selectivity for C-O bond activation, which can be translated into excellent H- and C-atom efficiencies. In comparison, precious metal catalysts (e.g., Ru), although highly active, tend to hydrogenate various functionalities indiscriminately including ring saturation and C-C bond cleavage. Furthermore, carbides are relatively tolerant to sulfur and other impurities, while the latter tend to rapidly poison precious metals. On the other hand, there have also been concerns about carbide stability in oxygenate- and water-rich biomass processing conditions: gradual oxidation of these oxophilic carbides into inactive oxide phases. In recent work, we demonstrated good catalytic performance of molybdenum carbides in hydroprocessing real bio-oils. Indeed, over a temperature range of 140 to 400 °C, carbides were able to stabilize and deoxygenate fast pyrolysis bio-oil maintaining their structural integrity during 100-240 h flow reactor runs. Some degree of coking was observed explaining the observed gradual activity loss. Surface carbon deposits were however quite reactive and could thus be removed via high-temperature reductive treatment. In this presentation, detailed characterization results (STEM, Raman, XPS, XRD, N2 sorption, TPR, ICP) will be presented to illustrate the structural robustness of molybdenum carbides (Mo2C, Ni-Mo2C) subjected to fast pyrolysis bio-oil hydroprocessing as well as the impact of high-temperature reductive treatments on catalyst decoking and regeneration.

Durability of molybdenum carbide catalysts in reductive upgrading of fast pyrolysis bio-oil

255th National Meeting (2018)

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