Effects of alkalis on the catalytic performance of CoMn catalysts for Fischer-Tropsch to olefin reactions

[Background] Cobalt carbide(Co2C) has recently been reported to catalyze the Fischer-Tropsch to olefin(FTO) conversion of syngas with high selectivity. However, electronic state and coordination structure of cobalt carbide is limited by its complex reaction. [Purpose] This study aims to clarify the effect of alkalis of CoMn catalysts for FTO and understanding the atomic structure of cobalt carbide nanoparticles in the CoMn catalyst. [Methods] X-ray absorption fine structure(XAFS) experimental on beamline(BL14W1) of XAFS spectroscopy at the Shanghai Synchrotron Radiation Facility(SSRF) is conducted to explore the electronic state and coordination structure of cobalt carbide with the effects of alkalis. [Results] X-ray absorption near-edge structures(XANES) spectra indicts that Na, K acted as electronic donors to cobalt than Li. EXAFS spectra clarified show that the atomic structure of cobalt carbide nanoparticles. [Conclusion] The Na, K promoter had benefited the formation of the cobalt carbide in the evolution of the FTO catalysts.