Combined reforming of methane by carbon dioxide and water: Particle size effect of Ni–Mg nanoparticles

•Preparation of NiO/MgO/α-Al2O3 with various Ni loading.•Evaluation of activity, products selectivities and coking of catalyst in CO2-H2O reforming of methane.•Size dependent evaluation of catalyst activities and coke deposition.

The effect of Ni–Mg particle size on product selectivity, catalyst activity and coke formation on Ni/MgO/α-Al2O3 catalyst were studied in simultaneous steam and CO2 reforming of methane to syngas. The Ni–Mg particle sizes in the range of 13.7–29.7 nm were prepared via incipient wetness impregnation method using α-Al2O3 as support. Experimental results for turn over frequency (TOF) show that the intrinsic catalyst performances were dependent on Ni–Mg particle size. However, the products selectivities and H2/CO ration were found to be independent of Ni–Mg particle size. The experimental results reveal that the coke formation rates on the surface of catalysts are increased by increasing Ni–Mg particle size. Nevertheless, the correlated site carbon atom deposition rates (carbon atoms deposited on one site of catalyst) is shown an opposite trend.