Adsorption characteristics of reduced Mo and Ni-Mo catalysts in the hydrodeoxygenation of benzofuran

The promotional effect of Ni on the hydrodeoxygenation (HDO) of benzofuran (BF) over reduced Ni-Mo/-gamma-Al2O3 catalysts was studied. The adsorption characteristics of Al2O3 support, mono-metallic Mo, and bi-metallic Ni-Mo catalysts that were pre-reduced were investigated using the feed molecule (BF) and a probe molecule (NO) as adsorbates. NO was used to probe the coordinatively unsaturated sites (CUS). Three adsorption modes for benzofuran over reduced Al2O3 support, Mo, and Ni-Mo catalysts were proposed that involved OH groups, Bronsted acid sites, and CUS, respectively. Benzofuran molecule adsorbed more strongly on B acid sites and CUS than on OH groups and was activated with weakening of the C-O bond. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place. (C) 2008 Elsevier B.V. All rights reserved.