Application of ultrasonic vibrations in the preparation of Ce-Zr-La/Al 2O3 and supported Pd three-way-catalyst

Abstract

CeO2-ZrO2-La2O3ZAl 2O3 (CZLA) was prepared by pretreatment with ultrasonic vibrations and Pd threeway-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"', respectively, after calcination at 900 °C. 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 Ce05Zr05O2 phase. However, ø-Al2O3 was observed in n-CZLA after aging at 1150 t 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 PdVn-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. © Editorial office of Acta Physico-Chimica Sinica.