(265g) Cobalt Species Transformation of Carbon Nanotubes Supported Cobalt Catalyst and the Effect On Fischer-Tropsch Synthesis

Currently, the world’s fuel production is based predominantly on crude oil. With the decline of crude oil reserve, identifying other alternative energy sources is of great importance. The processes of Gas-to-liquid (GTL), biomass-to-liquid (BTL) and coal-to-liquid (CTL) attracted much attention in past decades for producing transportation fuels. Fischer–Tropsch synthesis (FTS) is known as the key process for producing hydrocarbons from syngas (CO and H₂) derived from coal, natural gas, or biomass. Many efforts have been paid to improve FTS activity and C₅₊ selectivity, mainly on Co- or Fe- supported on oxides catalysts. Due to the higher activity of supported Co catalyst for FTS, much attention has been paid on the preparation, characterization and FTS performance of Co- catalyst. However, to our best knowledge, few paper reported the decomposition of Co precursor and Co species transformation on CNTs supported Co catalyst.

In this paper, the effect of calcination condition on the cobalt species and Fischer-Tropsch synthesis (FTS) was studied. It was found that higher calcination temperature resulted in decreased FTS activities because CNTs was consumed by oxidation in air at temperature higher than 230 °C. Cobalt species could be transformed from Co₃O₄ to metallic Co in Ar by autoreduction at temperature over 500 °C. The autoreduction route might be from Co₃O₄ to CoO to Co or from Co₃O₄ to Co₂C to Co. Reduction at temperature higher than 500 °C also resulted in decreased FTS activities as a result of CNTs methanation in hydrogen.