Cerium modification enhances the performance of Pd/USY for formaldehyde catalytic oxidation at room temperature

Abstract

Pd–Ce/USY catalysts were prepared by an impregnation method and then tested for their performance in formaldehyde (HCHO) catalytic oxidation at room temperature after H₂ reduction activation. We observed that Ce doping had a dramatic promotion effect on the Pd/USY catalysts. The Pd–Ce/USY catalyst with a loading of 0.5 wt% Pd and 0.5 wt% Ce exhibited a HCHO conversion of 80% with a WHSV of 300 000 mL g⁻¹ h⁻¹ and a HCHO inlet concentration of 150 ppm at 25 °C. Multiple physicochemical characterization tests were performed to investigate the mechanism of the Ce-promotion effect. The results illustrated that the Pd dispersion was increased due to the interaction between the CeO₂ and Pd nanoparticles over the 0.5Pd–0.5Ce/USY-R catalyst. The increase in Pd dispersion enhanced the number of hydrogen spillover sites during the H₂ reduction activation process, which induced more oxygen vacancies on the surface of the 0.5Pd–0.5Ce/USY-R catalyst. In addition, abundant oxygen vacancies were also formed owing to the increased ratio of Ce³⁺ on the 0.5Pd–0.5Ce/USY-R catalyst, which facilitated the activation of surface OH groups and surface-active oxygen species. Therefore, the HCHO oxidation performance and stability of the 0.5Pd–0.5Ce/USY-R catalyst was improved.