Infrared spectroscopy to understand the effect of sodium and sulfur on catalytic performance of supported iron catalysts for the Fischer-Tropsch synthesis of lower olefins
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Sodium and sulphur are known to promote the catalytic performance of iron-based catalysts, but their effects are not yet fully understood. In this study, IR spectroscopy was utilized to attempt to shine a light on this effect. Both promoted and unpromoted zirconia-supported iron catalysts were prepared and their catalytic performance compared. As expected, the addition of promoters significantly improved the catalytic activity and selectivity. Zirconia as a support was deemed effective but not superior to the more common α-alumina support. IR spectroscopy results supported by Mössbauer spectra indicated that the promoters do not change the binding energy of CO to the catalyst surface, but instead affect the relative amount of different CO-available binding sites. TPR and Mössbauer spectroscopy also determined that the addition of the promoters improve the rate of reduction.