Fischer-Tropsch to olefins over CoMn-based catalysts: Effect of preparation methods

The effects of preparation methods for CoMn-based catalysts on the precursor phase of Co species, the morphology of Co2C nanostructures as well as the catalytic performance for Fischer-Tropsch to olefins were investigated. Five catalysts prepared by precipitation and impregnation methods were compared in detail. CoMn spinel oxide was found in the calcined catalysts prepared by co-precipitation or sequential precipitation starting from the Co salt. However, Co3O4 and MnO2 were the major phases for the calcined catalysts prepared by sequential precipitation starting from the Mn salt or impregnation methods. During the syngas conversion process, Co2C nanoprisms with exposed facets of (101) and (020) were generated from CoMn spinel phase, and exhibited high CO conversion, low methane selectivity and high olefins selectivity. In contrast, Co2C nanospheres carburized from metallic Co or CoO were observed for the other samples with poorer FTO catalytic performance.