Effects of MgO on Ni/Al2O3 catalysts for CO2 reforming of methane to syngas

Carbon dioxide reforming of methane (CRM) converts CH4 and CO2 greenhouse gases into syngas over nickel-based catalysts. We performed CRM in a tubular microreactor at 700 °C by using 5.0 wt.% NiO catalyst, supported over mixtures of γ-Al2O3 + x MgO (x = 20, 30, 63, and 70 wt.%). The process of impregnation was used to prepare the catalysts. For characterization, N2-physisorption, XRD, H2-TPR, TGA, and Raman spectroscopy techniques were employed. Among the examined catalysts, 5Ni/Al2O3 + 63%MgO was found the most active, where it showed ≅ 72% CH4 conversion, 73% CO2 conversion, and 0.82 H2/CO mole ratio over 7 h of reaction. The MgO modifier was the primary component, which favorably affected both Ni dispersion and stability, for the good interaction between NiO and γ-alumina. The mono-supported samples displayed the lowest total hydrogen consumption. In TGA, the 5Ni/Al2O3 + 63%MgO exhibited a significant weight decrease (40%), reflecting its activity. Furthermore, the Raman spectroscopy analysis showed that the crystallinity of the carbon over this catalyst was more pronounced than the others.