Effects of support surface chemistry in hydrodeoxygenation reactions over CoMo/activated carbon sulfided catalysts

The influence of the nature of the surface of activated carbon supports on the activity of CoMo/activated carbon sulfided catalysts for hydrodeoxygenation of model compounds representative of the composition of pyrolysis oils has been studied. For this purpose, an activated carbon support was subjected to oxidative treatments with HNO3 at various temperatures to modify its surface chemistry. Supported sulfided CoMo catalysts on the resulting activated carbons were prepared. These catalysts were tested for hydrodeoxygenation of model compounds, 4-methylacetophenone (4MA), ethyl decanoate (ED) and 2-methoxyphenol (GUA), representative of the oxygenated functions that should be eliminated for improving oil stability. The activities of the various CoMo catalysts for the hydrogenation of the carbonyl group of 4MA were very similar, and the conversion reached 100% in less than 120 min at 280 degrees C and 7 MPa. Introduction of oxygen-containing functional groups to the carbon supports led to higher decarboxylation in the conversion of the carboxyl group of ED and higher phenol/catechol selectivity from 2-methoxyphenol. The surface chemistry of the support determined the precursor/support interaction and, hence, the nature of the sulfided phases present in the catalyst after activation. The different natures of the metal sulfides formed from the oxide precursors that were bound or not to the oxygen groups on the carbon supports could be responsible for the differences in selectivity displayed by these catalysts. Almost no coking reactions were observed. The results suggest that catalytic conversion of oils obtained from biomass pyrolysis can be controlled and modified by appropriate modifications of the surface chemistry of the activated carbon supports.