Enhanced activity and stability of MgO-promoted Ni/Al₂O₃ catalyst for dry reforming of methane: Role of MgO

Highly dispersed nickel nanoparticles (NPs) were deposited on Al₂O₃ NPs by atomic layer deposition (ALD). Various amounts of MgO were loaded on Ni/Al₂O₃ catalysts by the incipient wetness (IW) method for dry reforming of methane. Fresh and used catalysts were systematically characterized to reveal the effects of MgO on the catalytic performance. MgO was found to increase the basic amount and basic strength of catalyst surfaces, which provided additional surface oxygen species and assisted the adsorption and activation of CO₂. Although the formation of NiO-MgO solid solution, during the calcination of incipient wetness, did not improve the overall reducibility, the Ni NPs from NiO-MgO solid solution after reduction formed an intimate interaction with MgO, which could inhibit Ni NPs from sintering and provide sufficient metal-support interface for CO₂ activation. The MgO-promoted Ni/Al₂O₃ reached a methane reforming rate of 1780 L_CH4g_Ni⁻¹ h⁻¹ at 850 °C, which is 26% more than that of the pristine Ni/Al₂O₃. The higher CO₂ activity enhanced the oxidation rate of the surface carbon generated from side-reactions, thereby resulting in a higher reforming rate and inhibiting coke formation, especially the detrimental graphitic encapsulating carbon on the active nickel surface.