Guaiacol transformation over unsupported molybdenum-based nitride catalysts

Unsupported Mo2N catalysts were prepared by thermal decomposition of ammonium heptamolybdate to form MoO3 followed by nitridation in either flowing ammonia or a N-2/H-2 mixture. The nitridation was achieved at two different space velocities for each reaction mixture. This resulted in Mo2N catalysts with different surface areas as well as different phases present as were determined by X-ray diffraction (XRD). The activity and selectivity of the catalysts were evaluated for hydrodeoxygenation (HDO) of guaiacol in a batch autoclave at 300 degrees C and 5 MPa hydrogen pressure. The catalyst prepared with flowing ammonia and a space velocity of 29 h(-1) displayed the highest activity (guaiacol conversion) and highest phenol/catechol ratio within the products indicative of HDO activity. This highest activity was attributed to the catalyst containing only gamma-Mo2N phase (as measured by XRD) and having the highest N/Mo atomic ratio. An initial attempt to promote this catalyst with Co, similar to that done for hydrodesulfurization and hydrodenitrogenation catalysts was unsuccessful in forming a single phase cobalt molybdenum nitride, however did show modest improvements in the production of deoxygenated compounds, and suggests further studies into this material for HDO catalysis. (C) 2011 Elsevier B.V. All rights reserved.