Effect of pH on the catalytic properties of precipitated iron for Fischer-Tropsch synthesis
A serial of Fischer-Tropsch synthesis catalysts (Fe-Cu-K-SiO2) was prepared by the coprecipitation method with varied pH of 6～8.The properties of the catalysts, i.e.crystal phase, particle size, pore structure, reducibility and carburization, were studied by XRD, N2adsorption, H2-TPR, and M9ssbauer spectroscopy.The catalysts were evaluated for Fischer-Tropsch synthesis under typical industrial conditions.The results indicate that the increase of pH values increases the particle size and decreases the surface area, which inhibit the reduction and carburization of the catalysts.As a result, a lower CO conversion and a lower selectivity of CH4but a higher selectivity of CO2and C5+products were obtained in Fischer-Tropsch synthesis.By correlating the M9ssbauer characterization with catalytic results, the CO conversion is revealed to be dependent on the Fe5C2phase while CO2selectivity is related to Fe3O4phase over the catalyst.
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