MgO impregnation to Al2O3 supported Ni catalyst for SYNGAS production using greenhouse gases: Some aspects of chemical state of Ni species

Abstract

Al2O3 was prepared by sol–gel method and stabilized at 700 °C, then impregnated with 5, 15, and 30 wt% MgO to obtain the mixed oxide and stabilized again at 700 °C. The catalytic Ni/Al2O3 and Ni/Al2O3–MgO materials were prepared by impregnation method. The catalytic properties were studied on the dry reforming of methane (DRM) reaction using greenhouse gases (CO2+ CH4) to SYNGAS (Carbon Oxide/Hydrogen: CO/H2) at 700 °C for 70 h. The catalysts characterization includes TPR-H2, X-RD, BET, SEM, TPD-CO2, TPO-MS and TEM techniques. The CH4 and CO2 conversion was more stable in the Ni-base catalysts supported on mixed Al2O3–MgO oxides than in the Ni/Al2O3 sample. The Ni/Al2O3–MgO(5%) catalyst showed a lower presence of C (carbon) as evidenced by TPO-MS, XRD, SEM and TEM characterization. This finding reveals that a low quantity of MgO in the catalyst, delays the carbon development and may be associated with the basic character and a greater dispersion of this oxide on the surface of the alumina. In addition to the Ni–Mg–Al–O spinel formation, which enhanced the strong metal-support interaction (SMSI) effect between the support and the active phase. The Ni sintering of the catalysts after catalytic reaction is likely at the expenses of Ni–Al–O and MgNiO2 phases as was evidenced by XRD technique. The effect of the oxidation state of the active phase on the Ni/Al2O3–MgO (5%) sample had influence on the CO2 transformation, H2/CO ratio, basic sites, and stability in the C species.