Effect of Fe/Ir ratio on the surface and catalytic properties in citral hydrogenation on Fe-Ir/TiO2 catalysts

Abstract

The selective hydrogenation in liquid phase of citral on Ir/TiO2 and Fe-Ir/TiO2 catalysts have been studied at 363 K and 8.27 bar. The influence of the reduction temperature and the Fe/Ir atomic ratio on the surface and catalytic properties were investigated. The Fe-Ir/TiO2 catalysts were prepared by impregnating a FeCl3 solution on the pre-reduced Ir/TiO2 monometallic catalyst. In the series of catalysts reduced at low temperatures (473 K), incorporation of iron led to an increase in the activity, reaching a maximum in conversion for an atomic ratio Fe/Ir of 1 and then decreasing for higher Fe-loading. On the contrary, those catalysts reduced at high temperatures (773 K) exhibited a different trend, the catalytic activity decreased continuously upon the incorporation of iron. The results also showed that all the studied Ir/TiO2 and Fe-Ir/TiO2 catalysts display high selectivities towards the unsaturated alcohols during citral hydrogenation. The modification of those iridium sites in the close vicinity of Fe3+ ions is suggested as to explain the observed behavior.