Mössbauer investigation of supported Fe catalysts. III. In situ kinetics and spectroscopy during Fischer-Tropsch synthesis

In situ constant velocity Mössbauer data have been used to measure the rate of carbiding of 10Fe SiO₂ and 10Fe MgO during the Fischer-Tropsch synthesis reaction at 523 °K and 3.3 H₂ CO. Simultaneous spectroscopic and kinetic measurements reveal the remarkable result that the reaction rate follows the extent of bulk carbide formation and, thus, that incorporation of carbon into the iron particles controls the number of active surface sites until carbiding is complete. Conversion, paraffin to olefin ratio, and C₂ C₁ ratio increase with extent of carbiding. Hydrogenation of a fully carbided catalyst at 523 °K is slow and produces only methane.