Selective Hydrogenation of CO 2 to Ethanol over Sodium-Modified Rhodium Nanoparticles Embedded in Zeolite Silicalite-1

Catalytic transformation of CO 2 into chemicals in large demand such as ethanol has attracted much research attention under the background of establishing carbon-neutral societies. Supported Rh catalysts are promising candidates for the hydrogenation of CO 2 to ethanol but suffer from low ethanol productivity and poor catalyst stability. Here, we report that zeolite silicalite-1 embedded Na-promoted Rh nanoparticles (Na-Rh@S-1) demonstrate high productivity and stability for CO 2 hydrogenation to ethanol. The ethanol selectivity of 24% was attained at a CO 2 conversion of 10%, and the space-time yield of ethanol reached 72 mmol g Rh –1 h –1, which outperformed most of the Rh-based catalysts reported to date. While a reference catalyst prepared by impregnation underwent deactivation, the Na-Rh@S-1 catalyst was stable for at least for 100 h owing to the confinement effect. The Na + modifier played crucial roles in enhancing the CO 2 conversion and ethanol selectivity by suppressing methane formation. The characterizations suggest that the presence of Na + enables the coexistence of Rh 0 and Rh + and enhances CO 2 adsorption, thus boosting ethanol formation. A comparative study between CO and CO 2 hydrogenation reveals that the Na-Rh@S-1 catalyst is significantly more active and selective toward CO 2 hydrogenation to ethanol.