Iron phosphide nanocatalysts presenting different stoichiometry as catalysts in the HDO of phenol

Iron phosphide catalysts supported on silica with an iron loading of 15 wt% were synthesized and studied in the hydrodeoxygenation (HDO) of phenol. The amount of phosphorus varied in order to obtain iron phosphides with different stoichiometry. Catalysts containing Fe2P, FeP and FeP2 phases were obtained. The textural and structural properties of the prepared catalysts were evaluated by using different experimental techniques such as N2 adsorption-desorption at -196 °C, X-ray diffraction (XRD), Mössbauer spectroscopy, high resolution transmission spectroscopy (HRTEM), infrared spectroscopy (IR) of adsorbed CO at low temperature, X-ray photoelectron microscopy (XPS) and NH3 thermoprogrammed desorption (NH3-TPD). The catalytic activity was studied at 275 °C and at 15 and 5 bar of hydrogen pressure in the hydrodeoxygenation reaction of phenol. Characterization results evidenced that the initial P/Fe ratio employed in the synthesis not only governed the stoichiometry of the iron phosphide, but also the particle size, metallic surface exposure and acidity. The catalysts presenting unique phases were those presenting better activity in the HDO reaction of phenol. Moreover, Fe2P phase presented better results than FeP in terms of HDO conversion.