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.