CO2 reforming of methane over carbon fiber-lanthanum oxide supported bimetallic nickel-cobalt catalysts: Kinetic and mechanistic studies

摘要

With high surface area (1393 m(2)/g) and fibrous structure, carbon fiber (CF) was used to prepare a composite of CF-lanthanum oxide (La2O3), which was applied as support to synthesize nickel-cobalt based bimetallic catalyst. The as -prepared catalysts were utilized in CO2 reforming of methane and it performed well at the metal ratio (nickel to cobalt) of 4:1 with an ideal syngas (H-2/CO reached to 1.1) produced. The characterization results showed that La2O3 uniformly grew on the surface of carbon fiber in wrinkled like. Moreover, nickel-cobalt alloy structures were formed on the surface of 4Ni-1Co/CF-La2O3 catalyst, thus improving the resistance to Ni-sintering, then promoting the stability of syngas production. Except for the promotion effect of cobalt, the role of La2O3 addition was also demonstrated by model calculation. It was found that the lanthanum carbonate (La2O2CO3) formed during CO2 adsorption process. The formation of the intermediate could facilitate to the CO2 dissociation by decreasing the CO2 activation energy, thus promoting the CO2 conversion to produce more CO. Combined with the kinetic experimental results, the reaction mechanism over 4Ni-1Co/CF-La2O3 was proposed with the reactants of CH4 and CO2 dissociated both on the surface of the support and the metal active sites. It was corresponded to the Langmuir-Hinshewood mechanism type. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.