Selective Hydrogenation of Crotonaldehyde over Ir-FeOx/SiO2 Catalysts: Enhancement of Reactivity and Stability by Ir-FeOx Interaction

A series of FeOx-promoted Ir/SiO2 catalysts were prepared and tested for gas phase selective hydrogenation of crotonaldehyde. It was found that a catalyst containing Ir nanoparticles contacting with highly dispersed FeOx clusters (3Ir/0.1Fe/SiO2) showed excellent activity and stability, with a 5-fold enhanced steady state crotyl alcohol yield (59.6%) compared to that of the bare Ir/SiO2 (12.4%), while a catalyst promoted with high content of Fe (3Ir/3.5Fe/SiO2) had high initial activity but deactivated rapidly. A catalyst with similar highly dispersed FeOx clusters but prepared by an, inverse 0 impregnation sequence (0.1Fe/3Ir/SiO2) also suffered severe deactivation. Various characterizations revealed that the observed behaviors were closely related to the Ir-FeOx interactions induced by different morphologies of the catalysts. The active sites generated at Ir-FeOx interface were responsible for the better performance. The catalyst deactivation was attributed to the deposit of heavy compound and strong adsorption of CO on the surface, which was induced by the strong Ir-FeOx interaction due to heavy decoration of FeOx on the Ir surface.