Effect of ceria morphology on the performance of MnOx/CeO2 catalysts in catalytic combustion of N,N-dimethylformamide

Abstract

MnO_x/CeO₂ catalysts were prepared by a deposition–precipitation method, through loading MnO_x into ceria supports with different morphologies (nanorods (NRs), nanocubes (NCs) and nano-octahedrons (NOs)). As for the catalytic combustion of N,N-dimethylformamide (DMF), the ceria morphology has a great impact on the catalytic activity, and loading of MnO_x significantly enhances the catalytic activity as follows: MnO_x/CeO₂-NRs > MnO_x/CeO₂-NCs > MnO_x/CeO₂-NOs > CeO₂-NRs > CeO₂-NCs > CeO₂-NOs. The MnO_x/CeO₂-NR catalyst exhibits the best catalytic performance, in which DMF is completely oxidized at 180 °C, and the CO₂ and N₂ yields are 98% and 99%, respectively. The catalytic performance of MnO_x/CeO₂ catalysts at high reaction temperature under the wet reaction conditions with introduction of 5 vol% water vapor is better than that under the dry reaction conditions, in which water easily desorbs from the catalyst surface and then reacts with the reaction intermediates. The results of nitrogen sorption, XRD, O₂-TPD, XPS and NH₃-TPD characterization indicate that the excellent catalytic performance of the MnO_x/CeO₂-NR catalyst is closely related to its high specific surface area, high concentration of oxygen vacancies and active oxygen species, and more and stronger surface acid sites, which are due to the strong interaction between MnO_x and CeO₂ nanorods.