Influence of thermal treatment on catalytic performance of Pd/(Ce,Zr)Ox–Al2O3 three-way catalysts

CeO2–ZrO2–Al2O3 (CZA) mixed oxides were synthesized using sol–gel and supercritical drying methods, and their physicochemical properties were characterized by BET surface area (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR) and O2-temperature-programmed desorption (O2-TPD) techniques. The catalytic performances of Pd/CZA catalysts with different thermal treatment were also investigated. The results indicate that catalytic activities are affected by thermal treatment of support or catalyst and Pd/CZA catalysts exhibit good thermal stability. H2-TPR results show that the effect of thermal treatment on the dispersion state of PdO is different between catalyst and support after calcination. However, O2-TPD results show that the influence of thermal treatment on the desorption performance of oxygen is similar in both cases. Desorption of surface oxygen is closely related to surface area of the support. During the calcination of the supports or the catalysts at high temperature, the surface oxygen desorption capacity and the mobility of lattice oxygen decrease due to the sintering of supports, which is harmful to the dispersion of active species, corresponding to the decrease of three-way catalytic activities.