Flower-like hollow Ni0.5/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-Al 2 O 3 is a promising system for DRM catalysts with high coking resistance, as the addition of MgO in Ni/Al 2 O 3 catalysts can improve the alkalinity of the support and enhance the metal-support interaction. However, so far the activity and stability of Ni/MgO-Al 2 O 3 is still unsatisfactory while the role of Mg addition remains unclear. In this paper, a series Ni 0.5 /xMgO-Al 2 O 3 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 NiAl 2 O 4 while more Mg addition leads to the formation of Ni x Mg y O. Both cases can enhance the MSI of the catalysts without changing the morphology of the catalyst. More Mg addition also leads to stronger CO 2 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-Al 2 O 3 with moderate Mg addition shows excellent activity (CH 4  ∼ 75 %, CO 2  ∼ 85 %) and stability (>100 h) at a high GHSV = 144000 ml/g cat ·h −1 and 800 °C with nearly no coking formation (<0.8 wt%). This work helps reveal the role of MgO addition in Ni/Al 2 O 3 systems and gives new insights into the design of DRM catalysts with high activity and stability.