Fischer-Tropsch synthesis to α-Olefins with low CO2 selectivity on a Co2C catalyst

A Co2C catalyst with low CO2 selectivity for the Fischer-Tropsch to Olefins (FTO) was derived from a precursor catalyst prepared by a “melting” method. Co-Mn composite oxide, MnCo2O4.5, was identified as the dominant composition in the catalytic material before it was activated. The catalyst showed a weak interaction between Co and Mn with the presence of Na. Therefore, Co could be liberated easily from MnCo2O4.5 with H2 reduction at a usually used condition for Co-based catalyst for the Fischer-Tropsch Synthesis (FTS). A clear carburization of Co0 to Co2C was observed during the initial period of reaction, and this transformation could be achieved within 6 h. Four different crystal facets, (2 1 0), (0 2 0), (1 1 1), and (1 0 1) for Co2C, were identified once Co0 has been successfully carburized during the reaction. A limited amount of Co0 also transformed to Co3O4 during Co2C formation when H2O was produced by the FT reaction. The prepared catalyst demonstrated outstanding performance in terms of product selectivity. Its selectivity to lower olefins (C2-C4) was as high as 60.26 % with an average olefin/paraffin ratio of 26.69. Additional to high olefin selectivity, the CO2 selectivity was as low as 11.49 %, and that of C1 (CO2 + CH4) could be controlled at 16.44 % with optimal Co/Mn ratio and operating conditions. It was also found that transient state Co0 with Mn and Na as promoters demonstrated similar high olefin to paraffin ratios when compared to Co2C.