Formation of surface cobalt structures in SiC-supported Fischer–Tropsch catalysts
The formation of surface cobalt structures was investigated for a number of β-SiC-supported Fischer–Tropsch catalysts. Several different supports were used, both pristine and alumina-modified β-SiC. The techniques of temperature-programmed reduction, nitrogen physisorption, thermal gravimetric analysis, heat conductivity and catalytic testing in Fischer–Tropsch synthesis were employed. It was determined that despite highly similar manufacturer specifications, differences in support genesis may lead to different porosities, surface cobalt phase compositions and catalytic activity, even with the use of identical catalyst preparation procedures. The control of the formation of the surface cobalt structure can also be realized by parameters of the catalyst preparation, such as one- or multi-step impregnation from aqueous or ethanol solution and annealing in air or helium flow or without gas flow. These findings open avenues of research for the optimization of the whole catalyst formation route on the basis of identification of the most efficient surface cobalt phase composition and realization of higher thermal conductivity.