Ni/SiO2 and Ni/ZrO2 catalysts for the steam reforming of ethanol

SiO2 and ZrO2 supported Ni catalysts were prepared for use in the steam reforming of ethanol. The catalytic performances, in terms of both H-2 productivity and stability towards coking and sintering, were related to the physico-chemical properties of the catalysts. The samples were prepared either by synthesis of the support by precipitation and subsequent impregnation with the active phase, or by direct synthesis through flame pyrolysis. The latter has been chosen because it leads to nanostructured oxides, often quenched in very disperse or metastable form, characterised by high thermal resistance, important for this high temperature application. Many techniques have been used to assess the physico-chemical properties of the catalysts. The samples showed different textural, structural and morphological properties, as well as different reducibility and thermal resistance, depending on the preparation method and support. Therefore, besides evaluating the effect of catalyst formulation and preparation method on the catalytic performance, the influence of all such properties has been considered. The fundamental parameter governing the final catalyst properties was metal-support interaction. In particular, the stronger the latter parameter, the higher was metal dispersion, leading to small and stable Ni clusters. This influenced both activity and the resistance towards coking. Surface acidity was also taken into account considering the effect of the different nature of acid sites (silanols or Lewis as.) of both support and metal phase on catalyst deactivation. The best results were obtained with a 10 wt% Ni/SiO2 sample, prepared by FP, when tested at 625 degrees C. H-2 productivity of 1.44 mol H-2/min kg(cat) was reached, corresponding to ca. 80% of the maximum value achievable under the selected conditions. This result was accompanied by the lowest CO/CO2 ratio and 100% carbon balance without by-products in the outflowing gas. (c) 2012 Elsevier B.V. All rights reserved.