Cobalt aluminate spinel-derived catalysts for glycerol aqueous phase reforming

Abstract

Catalytic activity at mild (235 °C/3.5 MPa) and severe (260 °C/5.0 MPa) APR conditions was investigated over catalysts based on cobalt aluminate spinel synthetized by coprecipitation. Co/Al ratio was varied and physicochemical characteristics were assessed by N2 adsorption, H2 chemisorption, XRD, H2-TPR, DRS-UV, FTIR, CO2-TPD, NH3-TPD and XPS. Formation of cobalt aluminate produced strong Co-O-Al interaction in the catalyst precursor leading to improved Co dispersion upon activation. Co/Al ratio could be used to tune catalyst characteristics, thus selectivity towards the desired reaction pathway. Overall, Co/Al above the stoichiometric value produced smaller and more stable metallic Co, which allowed best APR performance. For instance, at 235 °C/3.5 MPa glycerol conversion and conversion to gas of 0.625CoAl (88% and 22%) were notably higher than those of bare Co3O4 (23% and 5%). At severe conditions, 0.625CoAl catalyst produced 231 μmolH2/gcat min (60% H2). Statistical analysis of data collected from long-term run was used to investigate reaction mechanism. Long-term run revealed that sintering and oxidation were main mechanisms for catalyst deactivation whereas some leaching of Co nanoparticles, and carbonaceous deposition was also detected.