Improving the Activity and Selectivity of Ir/SiO2 for the Selective Hydrogenation of Unsaturated Carbonyl Compounds by SnO2 Promotion

Improving catalytic hydrogenation by modifying noble metal catalysts with metal-oxide promoters is promising, but precisely controlling the metal–promoter interface to optimize performance is still challenging. In this study, we created Ir-SnO2/SiO2 nanocatalysts with different Ir/Sn ratios using IrSn alloy precursors through careful calcination and reduction treatments. The SnO2-promoted catalysts showed much better conversion and selectivity than the original Ir/SiO2 catalyst toward the hydrogenation of acetophenone to phenylethanol. The Ir-SnO2/SiO2 catalyst with an Ir/Sn molar ratio of 5/1 (i.e., sample Ir5-(SnO2)1/SiO2) performed the best, achieving a 94% conversion rate and 99% selectivity. Our study found that SnO2 promoters could reduce the surface electron density of the Ir nanoparticles (NPs), enhancing the adsorption of reactants; meanwhile, the new Ir-SnO2 interface is more active for the dissociation of hydrogen compared to Ir alone. The optimal Ir5-(SnO2)1/SiO2 catalyst has demonstrated versatility by effectively catalyzing the hydrogenation of C═O bonds in a wide range of compounds, showing significant potential for various industrial applications in fine chemical synthesis and energy conversion.