Development and characterization of silica supported cobalt oxides for ethanol oxidation using different preparation methods

Cobalt oxide in spinel structure (Co3O4) is an efficient catalyst for ethanol oxidation due to its potential as an oxygen source. To enhance the catalytic performance, Co3O4 is dispersed on silica (SiO2). The degree of dispersion and form of oxides on the support depend on the preparation method. The objective of this work is to compare physicochemical properties and catalytic performance in ethanol oxidation of silica-supported cobalt catalysts from different preparation methods. The catalysts were prepared by incipient wetness impregnation (IP), precipitation with reverse micelle (RM), and precipitation with NH4OH (PN) methods. The forms and dispersion of cobalt species were investigated by X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS). The cobalt species from RM and IP methods were mainly Co3O4, but that from PN method was the mixed phases of Co3O4, CoO and Co2SiO4. The RM method provided the best dispersion of Co3O4, surface Co3+ and lattice O(2)(- )on SiO2. Consequently, the catalyst from RM method provided the highest ethanol conversion and CO2 yield from all temperature ranges.