MgO/NiAl2O4 as a new formulation of reforming catalysts: Tuning the surface properties for the enhanced partial oxidation of methane

Abstract

Magnesia modified nickel aluminate spinel catalysts were synthesised and characterised by BET, TEM, XRD, H2-TPR, XPS, CO2-TPD and TGA-MS techniques. The addition of this promoter induced significant changes in the textural, structural and chemical properties of the resulting spinel derived catalysts. Thus, it enhanced the resistance of the deposited Ni particles against sintering, whereas, upon increasing MgO loading, it drastically modified the density and the strength of the surface basic sites. In fact, an apparent weakening of the surface basic sites with the abundance of highly dispersed Mg species was interestingly observed.The changes provoked by MgO addition deeply influenced the catalytic performance of the prepared samples in the partial oxidation of methane reaction at 700°C. In this sense, it was found a good correlation between the measured density of the strong basic sites on the different samples, including the bare NiAl2O4, and their catalytic activity. Hence, the MgO(5 wt.%)/NiAl2O4 sample, with a magnesium loading close to the theoretical monolayer and the lowest strong basic density sites, exhibited the best catalytic performance under both stoichiometric (O/C=1) and non-stoichiometric (O/C=0.75) conditions during a relatively prolonged time on stream.