Effect of metal–support interaction on the selective hydrodeoxygenation of anisole to aromatics over Ni-based catalysts

Abstract

Hydrodeoxygenation (HDO) of anisole has been often investigated in connection with biofuel production by bio-oil upgrading, because this molecule is representative of the methoxyphenyl components generated by flash pyrolysis of lignocellulose biomass. In the present work a series of Ni-containing (20wt% loading) catalysts based on carriers as diverse as SBA-15, Al-SBA-15, γ-Al2O3, microporous carbon, TiO2 and CeO2 were selected in order to investigate the possible influence of metal–support interactions on the selectivity of anisole HDO toward aromatic products. Both, supports and catalysts were extensively characterized by N2 adsorption–desorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR) and ammonium programmed desorption (NH3-TPD). Subsequently, the catalysts were tested for the hydrodeoxygenation of anisole in a continuous flow high pressure reactor. Under low hydrogen pressure (3bars) and moderate temperature (290–310°C) and space velocity (20.4 and 81.6h−1), these catalysts show a very high HDO activity that, for most of them approaches to 100%. Differences in product distribution among the catalysts are attributed not only to variations in the dispersion of the active phase, but also to the influence of the support properties in tuning its reactivity. In particular, acidity of the support is very relevant because strong acid sites may contribute the hydrogenolysis of anisole, while metallic sites will further hydrogenate intermediate compounds to yield cyclohexane. Therefore, the selective production of aromatics, from biomass derived feedstock in a biorefinery scheme can be promoted by an adequate selection of the catalysts characteristics. In this respect, a maximum yield of 64% of benzene was obtained in this study over Ni/C catalysts.