Influence of calcium content in Ni/CaO/γ-Al2O3 catalysts for CO2-reforming of methane

In order to improve the thermal stability and carbon-deposition resistance of the Ni/gamma-Al2O3 during the reforming of methane with carbon dioxide, the catalyst was modified by adding an alkaline earth (CaO). The catalysts were prepared by successive impregnation of Ni and Ca on alumina, varying the impregnation order. It was found that calcium decreases the sintering resistance of the support and blocks the small pores, especially when it is added above the nickel. It has also been reported that calcium competes with nickel in the interaction with the support, favoring the formation of nickel species being more easily reducible, when it is added first. In catalytic tests, it has been showed that, in low quantities, calcium increases the catalytic conversion, probably due to attraction effects between CaO and CO2, while in high quantities, calcium decreases the catalytic activity, this effect being associated with the increase in electron density of the catalyst. (C) 2003 Elsevier B.V. All rights reserved.