Insight Into The Reaction Mechanism And Catalytic Performance Of Dry Reforming Of Methane To Syngas Over NiO-MgO Catalyst

Dry?CO₂?reforming of methane?DRM?,not only provides a pathway to consume the two major greenhouse gases,but fulfills a requirement of the Fischer-Tropsch synthesis,for producing industrially important syngas with a H₂/CO ratio?1.Due to the small Ni particles and surface basicity,more and more attention has been paid to the reduced NiO-MgO catalyst.This paper focused on the the reaction mechanism and catalytic performance of dry reforming of methane over NiO-MgO catalyst.The interaction mechanisms of dry reforming of methane,especially in the part of CO₂ activation on the reduced NiO-MgO catalyst,have been systematically investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy?DRIFTS?and density functional theory?DFT?calculations.Based on the results,it was indicated that,what more favorable for CO generation was gaseous CO₂ reaction with deposited C intermediates,namely Eley-Rideal?E-R?type mechanism.In addition,the reaction of monodentate carbonate which formed on MgO surface and served as the active species with H species to generate CO had been proved to be another CO₂ activation pathway.H species,which derived from CH₄ decomposition on Ni surface,would overflow from the metal surface to MgO,followed by activation and dissociation of the monodentate carbonate on MgO surface.M-NiMgO?111??M=Ce,Zr,Ce/Zr?,which combined of the unique MgO?111?surface properties and redox promoters,had been prepared via the solvothermal synthesis method.It was the high surface energy of?111?facet in NiO-MgO solid solution that contributed to the prominent reactivity.The Ce/Zr co-doped catalyst with the molar ratios of 0.01:0.01 performed the highest catalytic activity and long-term stability.The amount of carbon deposition of Ce_0.01/Zr_0.01-NiMgO?111?was only 2.3%even after 100 h reaction.According to XRD,TEM and XPS characterization,it was the stronger interaction between NiO and MgO that contributed to the smaller nickel particle size,which would be favorable for anti-sintering.Furthermore,it was observed that more oxygen species on the Ce_0.01/Zr_0.01-NiMgO?111?surface could effectively increase the CO₂ adsorption capacity as well as coking elimination,further resulting in the high activity with excellent coke resistance.