Ni supported high surface area CeO2–ZrO2 catalysts for hydrogen production from ethanol steam reforming

Abstract

The catalytic activity of nano-sized x%Ni/Ce_0.74Zr_0.26O₂ (x = 0, 2, 10 and 20wt%) catalysts have been investigated to develop highly active catalysts for ethanol steam reforming (ESR) into hydrogen. The structure and surface properties of the catalysts were tested by XRD, TPR, HRTEM and BET surface areas. The effect of reaction temperature from 200 °C to 600 °C was studied in a flow system at atmospheric pressure with an ethanol/water molar ratio of 1 : 8. Selectivity was calculated for the catalytic products H₂, CO, CO₂ and CH₄, as well as the intermediates C₂H₆, C₂H₄, C₃H₈, CH₃CHO and CH₃COCH₃, at different reaction temperatures. It was found that complete conversion of ethanol with considerable amounts of H₂ was obtained at 400 °C over all catalysts. H₂ was produced at a very low temperature (200 °C) over 10% and 20% Ni loadings, while a maximum H₂ selectivity (75%) is reached at 600 °C over the 2%Ni/Ce_0.74Zr_0.26O₂ catalyst; this is most likely due to the small nickel particle size (2–4 nm) in 2%Ni, which results in enhancement of the metal–support interactions. Thermal decomposition of ethanol in an ethanol/water mixture under the same reaction conditions, but in the absence of catalyst, was also studied. HRTEM of the spent catalyst (8 h ESR) shows the deposition of carbon in the form of carbon nanotubes (CNTs).