Effect of particle size on steam reforming of ethanol over alumina-supported cobalt catalyst

The relation between particle size and catalytic properties of alumina-supported cobalt catalysts were investigated for steam reforming of ethanol, C2H5OH+H2O-->2CO+4H(2), in order to make effective use of ethanol solution produced by fermentation of biomass. The catalysts prepared from various Go-sources were examined for their performances in steady-state reaction, temperature-programmed reaction (TPR) and temperature-programmed desorption (TPD) at atmospheric pressure by use of a conventional flow reactor. The selectivity of the catalysts for the steam reforming of ethanol were determined as follows: Co(Carbonyl, CVD method) > Co(Chloride) > Co (Carbonyl) > Co(Acetate) > Co (Nitrate). The mean crystallite size of Co species on alumina varies depending on Go-sources and forms the reverse line to the selectivity, except for Co (Chloride). The peak of CO, (mainly carbon dioxide) in the TPD spectrum, measured in the presence of water vapor, of ethanol adsorbed on the Co(Nitrate) catalyst shifts clearly to a higher temperature range with decreasing the crystallite size. This fact indicates that the selectivity for the steam reforming increases with the dispersion degree of the metal on alumina. The effect of the crystallite size on the catalytic properties is related to the strength of adsorption of COx and the catalytic activity for methanation of CO.