Effect of the support and promoters in Fischer-Tropsch synthesis using supported Fe catalysts

Abstract

The effect of support and promoters on the catalytic properties of Fe supported in the FTS was studied. Precursors of supported Fe on SiO2 and SBA −15 were synthesized and doped with Cu and K. The precursors were activated in pure H2 and catalytically tested with a mixture of H2:CO = 2:1, T = 543 K and P = 10 bar. The samples were characterized by atomic absorption, N2 adsorption, X-ray diffraction, TEM and TPR. Also, we used the DFT to study the changes of the electronic structure when the Fe, K and Cu are adsorbed on the SBA-15 surface. The incorporation of different ions do not alter the structural and textural properties of the support. In the FTS, all the catalysts supported on SBA-15 presented a low selectivity towards methane and a promising hydrocarbon production in the range of gasoline, showing positive effect of the support for iron catalysts for the FTS reaction. The activity order obtained was: Fe/K-SBA-15 > Fe/Cu-SBA–15 ≈ Fe-SBA–15 > Fe-SiO2, which is the same order for the selectivity towards olefins. The presence of K on the SBA-15 surface increases the activity and selectivity towards olefins; an effect that can be attributed to the electrostatic effect generated by the alkaline ions.