Iron phosphide nanocatalysts for oxygen removal from biomass derived biofuel. Phenol as a model molecule

Silica-supported catalysts based on iron phosphides with different stoichiometries were synthesised and tested in the hydrodeoxygenation (HDO) reaction of phenol, a model molecule present in bio-oil derived from pyrolysis of biomass. Tests were performed in a fixed bed reactor under hydrogen pressure (1.5 and 3 MPa). The catalysts were characterized by several characterization techniques in order to evaluate structure, textural and acidic properties and correlate them with the catalytic tests. Characterisation results revealed that by increasing the amount of P, phosphorous rich iron phosphide phases were formed. The surface became enriched with P, and this was associated with the presence of surface P-OH groups that provided Brönsted acid sites to activate O-containing compounds as well as surface hydrogen species that minimised deactivation by coke deposition. Samples containing P/Fe ratios 1 and 2 were the most active in the HDO reaction, being cyclohexane and cyclohexene, the most important reaction products. The product distribution was strongly affected by the reaction pressure employed.