Hydrodeoxygenation of guaiacol over carbon-supported molybdenum nitride catalysts: Effects of nitriding methods and support properties

Molybdenum nitride catalysts supported on activated carbon materials with different textural and chemical properties were synthesized by nitriding supported Mo oxide precursors with gaseous NH3 or N2/H2 mixtures using a temperature-programmed reaction. The supports and catalysts were characterized by N2 physisorption, XRD, chemical analysis, TPD, FT-IR and XPS. Guaiacol (2-methoxyphenol) hydrodeoxygenation (HDO) activities at 5 MPa and 300 °C were evaluated in a batch autoclave reactor. Molybdenum nitrides prepared using a N2/H2 mixture resulted in more highly dispersed catalysts, and consequently more active catalysts, relative to those prepared using ammonolysis. The HDO activity was also related to pore size distribution and the concentration of oxygen-containing surface groups of the different carbon supports. Increased mesoporosity is argued to have facilitated the access to active sites while increased surface acidity enhanced their catalytic activity through modification of their electronic properties. The highest activity was thus attributed to the highest dispersion of the unsaturated catalyst species and the highest support mesoporosity. Surprisingly, addition of Co did not improve the HDO activity.

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► Activated carbon supported-nitride catalysts favored direct conversion of guaiacol to phenol.
► Catalysts prepared using N2/H2 mixture were more highly dispersed than those prepared via ammonolysis.
► Activity difference related to molybdenum oxynitride dispersion and support porosity.