Effects of zinc on Fe-based catalysts during the synthesis of light olefins from the Fischer-Tropsch process

Fe-based catalysts for the production of light olefins via the Fischer-Tropsch synthesis were modified by adding a Zn promoter using both microwave-hydrothermal and impregnation methods. The physicochemical properties of the resulting catalysts were determined by scanning electron microscopy, the Brunauer-Emmett-Teller method, X-ray diffraction, H₂ temperature-programed reduction and X-ray photoelectron spectroscopy. The results demonstrate that the addition of a Zn promoter improves both the light olefin selectivity over the catalyst and the catalyst stability. The catalysts prepared via the impregnation method, which contain greater quantities of surface ZnO, exhibit severe carbon deposition following activity trials. In contrast, those materials synthesized using the microwave-hydrothermal approach show improved dispersion of Zn and Fe phases and decreased carbon deposition, and so exhibit better CO conversion and stability.