Flower-like hollow Ni_0.5/xMgO-Al₂O₃ catalysts with excellent stability for dry reforming of methane: The role of Mg addition

Dry reforming of methane (DRM) suffers catalysts deactivation due to severe coking. Ni/MgO-Al2O3 is a promising system for DRM catalysts with high coking resistance, as the addition of MgO in Ni/Al2O3 catalysts can improve the alkalinity of the support and enhance the metal-support interaction. However, so far the activity and stability of Ni/MgO-Al2O3 is still unsatisfactory while the role of Mg addition remains unclear. In this paper, a series Ni-0.5/xMgO-Al2O3 catalysts with flower-like hollow sphere morphology and high surface area were synthesized via a facile hydrothermal method. Appropriate Mg addition promotes the formation of NiAl2O4 while more Mg addition leads to the formation of NixMgyO. Both cases can enhance the MSI of the catalysts without changing the morphology of the catalyst. More Mg addition also leads to stronger CO2 adsorption via improving the alkalinity. Nevertheless, overdose of Mg results in weaker MSI and the blockage of Ni active sites. Ni-0.5/0.5MgO-Al2O3 with moderate Mg addition shows excellent activity (CH4 similar to 75 %, CO2 similar to 85 %) and stability (>100 h) at a high GHSV = 144000 ml/g(cat)h(-1) and 800 degrees C with nearly no coking formation (<0.8 wt%). This work helps reveal the role of MgO addition in Ni/Al2O3 systems and gives new insights into the design of DRM catalysts with high activity and stability.