Ethanol steam reforming over NiLaZr and NiCuLaZr mixed metal oxide catalysts

Abstract

NiLaZr and NiCuLaZr mixed metal oxide catalysts were prepared by co-precipitation with oxalic acid in alcoholic medium, followed by calcination. XRD analysis of the unreduced catalysts showed the formation of crystalline phases corresponding to the pyrochlore structure La2Zr2O7 and NiO following calcination at 850°C, 900°C and 950°C. TEM microscopy of the amorphous solids obtained by calcination at 700°C showed the formation of nanoparticles 20–30nm in size. TPR analysis showed a shift in the Ni and Cu reduction temperature towards lower values with increasing calcination temperature. All catalysts were active in runs of ethanol steam reforming, leading to the formation of gaseous mixtures containing hydrogen, carbon monoxide, carbon dioxide and methane. Deactivation due to carbon formation was observed at the lowest reaction temperature tested (500°C). XRD, FTIR and thermogravimetric analysis revealed differences in the textural properties of catalysts before and after reforming, which varied in degree according to the catalyst calcination temperature. The NiCuLaZr catalysts showed a lower activity than their NiLaZr analogues, a fact that was ascribed to the formation of a nickel–copper solution, with a lower catalytic activity in the cleavage of CC bonds.