Abstract:

CeO2-ZrO2-La2O3/Al2O3 (CZLA) was prepared by pretreatment with ultrasonic vibrations and Pd three-way-catalysts (TWCs) were then synthesized. Supports were characterized using Brunauer-Emmett-Teller(BET) and X-ray diffraction (XRD). Pd catalysts were characterized using NO-temperature programmed desorption (NO-TPD), H2-temperature programmed reduction (H2-TPR) and a catalytic activity test. The specific surface area of the uv-CZLA (CZLA with ultrasonic vibration) and the n-CZLA (CZLA without ultrasonic vibration) was 130 and 117 m2·g-1, respectively, after calcination at 900 ℃. The uv-CZLA material had larger pores of 11.4 nm and this made it more thermally stable than the n-CZLA. uv-CZLA supports were calcined at various temperatures and showed only one Ce0.5Zr0.5O2 phase. However, θ-Al2O3 was observed in n-CZLA after aging at 1150 ℃for 5 h. Almost no difference in NO-TPD was found for fresh and aged Pd/uv-CZLA catalysts. Results from the H2-TPR of the Pd/uv-CZLA catalyst showed a higher reductive peak temperature and a far larger reducing peak area than that of Pd/n-CZLA. Results of three-way reactions show that the catalyst prepared using ultrasonic vibration treatment possesses a lower light-off temperature for the removal of all three main pollutants in vehicle emissions and also a better temperature property.

Key words: Pd three-way-catalyst, Catalytic activity, NO-TPD, H2-TPR, Textural property