A comparison between copper and nickel-based catalysts obtained from hydrotalcite-like precursors for WGSR

Abstract

Nickel or copper-based catalysts were obtained from hydrotalcite-like precursors in this work, in order to find catalysts able to work at intermediates temperatures (200–350 °C) in water gas shift reaction (WGSR). Samples based on nickel (or copper), aluminum and zinc were obtained by co-precipitation, characterized by several techniques and evaluated in WGSR. Zinc caused changes in the cell parameters of hydrotalcite-type structure, which determined the structural and textural properties of calcined samples. For all catalysts, zinc oxide was detected. In the case of nickel-based hydrotalcites, aluminum cations were incorporated into nickel oxide lattice, hindering reduction; however, the addition of zinc decreased this effect. For copper-based samples, aluminum entered into copper oxide lattice and the copper reduction decreased with the increase of zinc amount in solids. After calcination, copper catalysts showed lower specific surface areas than nickel ones. Zinc led to the production of smaller and more reducible nickel oxide particles, due to the decrease of their interaction with Al 3+ species; under reduction, they produced small metallic nickel particles, which are supposed to be highly active and selective to carbon dioxide. Copper catalysts were less active to WGSR, as compared to the nickel ones, this can be related to their low specific surface areas. All catalysts were active in the range of 200–350 °C and thus are candidates to be used in a single stage of WGSR at intermediate temperatures.