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-CH4gNi(-1) h(-1) at 850 degrees 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.