Atomically dispersed Rh catalysts formed on defective CeO 2 surfaces with hydroformylation activity

Abstract

The electron density of the metal active sites depends on the surface properties of the support. This study aimed to demonstrate that the formation of atomically dispersed Rh on ceria and the corresponding Rh electron density can be tuned depending on ceria concentration. The highly optimized Rh/CeO2-Al2O3 catalyst exhibited the highest activity during propylene hydroformylation, which was similar to that of the commercially available homogeneous catalyst RhCl(PPh3)3. Combined analytical results and theoretical calculations demonstrated that the increased Ce3+ fraction promoted high Rh electron density and attenuated CO adsorption strength, resulting in an increased hydroformylation activity. Additionally, the catalyst achieved separation and high added value by converting olefins to aldehydes through hydroformylation of olefins in a mixed C2-C4 olefin/paraffin gas. This study showed that atomically dispersed metal supported catalysts can be designed as recyclable heterogeneous catalysts by tailoring the local environment and corresponding electron density of the metal to achieve high activity similar to that of the homogeneous catalysts that manipulate ligands around the metal.