Effect of composition and preparation of supported MoO3 catalysts for anisole hydrodeoxygenation

A series of zirconia supported molybdenum oxide materials with Mo loadings of 7, 12, and 19 wt% were synthesized using incipient wetness impregnation. The as synthesized oxide materials were further modified under H-2/CH4 (80/20%, v/v) at 550 and 700 degrees C. The obtained catalysts were characterized by ICP-OES, XRD, Raman spectroscopy, H-2-TPR, NH3-TPD, XPS, (S) TEM-EDX, BET, CHNS and CO chemisorption. While the Mo species, i.e., MoO3 and Zr(MoO4)(2), in the 7 wt% Mo loaded material were found to be of rather amorphous nature, their crystallinity increased significantly with Mo loading. The anisole hydrodeoxygenation performance of the catalysts was evaluated at gas phase conditions in a fixed bed tubular reactor in plug flow regime. A predominant selectivity towards hydrodeoxygenation and methyl transfer reactions rather than to hydrogenation was observed, irrespective of the Mo loading and further treatment, yet interesting differences in activity were observed. The highest anisole conversion was obtained on the catalyst(s) with 12% Mo loading, while the 7% Mo loaded one(s) exhibited the highest turnover frequency (TOFanisole) of 0.15 s(-1). CO chemisorption, XPS analysis and kinetic measurements indicate that treatment under H-2/CH4 slightly reduced the initial anisole conversion, yet enhanced catalyst stability as well as TOF, probably due to the increased amounts of Mo5+ species. The importance of appropriate tuning of the reduction and/or preparation procedures has been addressed to improve the catalysts' performance during anisole HDO.