Design and synthetize highly active Pd-only three-way catalyst by optimizing the reducibility of CeO2-ZrO2-Al2O3 support

Abstract

A highly active Pd/CeO2-ZrO2-Al2O3(Pd/CZAm) catalyst was successfully fabricated by optimizing the reducibility of CZAm support through a novel precipitation method. Pd/CZAm-a (aged catalyst) could maintain a superior activity, the T90 (temperature for 90% conversion) of CO, NO and HC has decreased by 36 °C, 30 °C and 54 °C comparing with Pd/CZAc-a (reference catalyst). As characterized, the better activity of Pd/CZAm is associated closely with the advanced reducibility of CZAm support. By controlling the individual precipitation process of CZ and Al2O3 via two different precipitants, the CZAm which displays more homogeneous CZ structure, abundant surface and bulk oxygen defects manifested by XRD, Raman, XPS and TEM-EDS results has been successfully prepared without any additives and excess treatment. Then stronger interaction between CZAm and supported Pd species has been manifested by XPS, H2-TPR and CO-IR results, which prevents the sintering and decomposition of PdO species during aging process. Consequently, Pd/CZAm-a could maintain the better dispersion of Pd species and more oxidized PdO with respect to Pd/CZAc-a.