Synthesis of mesoporous bimetallic Ni–Cu catalysts supported over ZrO2 by a homogenous urea coprecipitation method for catalytic steam reforming of ethanol

Abstract

The synthesis of mesoporous Ni–Cu bimetallic oxides supported over ZrO₂ by the homogenous urea co-precipitation technique and its catalytic efficacy towards steam reforming of ethanol has been explored. The amount of NiO was kept constant and that of CuO was varied to obtain bimetallic supported oxides which were characterized using different techniques like N₂ adsorption–desorption measurements, XRD, H₂-TPR, ICP-OES, TGA and SEM analyses. The results were compared with those obtained by alkali coprecipitation. The oxides prepared by urea coprecipitation were found to exhibit a type IV isotherm and a characteristic H2 type hysteresis, while those prepared by alkali precipitation were found to be nonporous. The studies reveal that this facile route of urea-coprecipitation can generate mesoporosity in zirconia based compositions and because of its simplicity, it holds enormous potential as a soft-templating technique for large scale preparation. The surface area increased on introduction of Cu, exhibits maxima at 3% w/w CuO, and subsequently decrease at higher loadings. The reducibility and the metal support interactions were altered in the presence of Cu, which reflected on its improved catalytic activity towards steam reforming of ethanol. The introduction of Cu species enhances the water gas shift reaction and favors acetaldehyde decomposition and reforming over the ethanol dehydrogenation reaction, as indicated by the reduced levels of acetaldehyde in the product stream. On increasing the reforming temperature, H₂ and CO₂ selectivity and ethanol conversion increased significantly. Bimetallic oxides containing 3% w/w CuO were found to be most effective towards ethanol steam reforming, exhibiting complete ethanol conversion and 84% H₂ selectivity at 600 °C, indicating their potential to be used as stable ESR catalysts.