Insight into MgO promoter with low concentration for the carbon-deposition resistance of Ni-based catalysts in the CO2 reforming of CH4

Abstract

The CO2 reforming of CH4 is studied over MgO-promoted Ni catalysts, which were supported on alumina prepared from hydrotalcite. This presents an improved stability compared with non-promoted catalysts. The introduction of the MgO promoter was achieved through the ‘‘memory effect’’ of the Ni-Al hydrotalcite structure, and ICP-MS confirmed that only 0.42 wt.% of Mg2+ ions were added into the Ni-Mg/Al catalyst. Although no differences in the Ni particle size and basicity strength were observed, the Ni-Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst. A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2 dissociation to form active surface oxygen arising from the formation of the Ni-MgO interface sites. Therefore, the carbon-resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles, which would increase the conversion of carbon residues from CH4 cracking to yield CO on the Ni metal surface.