Modification of the thermal stability of doped CeO2–ZrO2 mixed oxides with the addition of triethylamine and its application as a Pd-only three-way catalyst

Abstract

In the present paper, triethylamine-assisted (CZS) and reference (CZ)-doped CeO2–ZrO2 mixed oxides were prepared by co-precipitation. The prepared samples were characterized by N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM), powder X-ray diffraction (XRD), Raman spectroscopy, and H2 temperature-programmed reduction (TPR). The results showed an improved thermal stability of CZS in textural properties with surface area of 32 and 12 m2 g−1 after aging at 1000 and 1100 °C for 10 h, respectively. Investigation of the sintering behavior disclosed that the sintering of crystallites during high-temperature thermal aging might be related to the packing mode of the grains, since the looser structure of CZS compared to that of CZ hindered the grain growth at high-temperature calcination. The results of XRD and Raman revealed identical structural properties for both materials which suggested a cubic phase in fresh samples and a mixture of cubic and tetragonal phases after thermal aging at severe high temperatures (1000 and 1100 °C). The TPR results showed reduction peaks with rather low-temperatures, which was 414 °C after thermal aging at 1000 °C and 367, 577 °C at 1100 °C. This suggested a high thermal stability of CZS in reduction property. Consequently, the high thermal stability of the mixed oxide in both textural and reduction properties would contribute to the stability of the catalytic activity of the Pd-only three-way catalyst after high-temperature thermal aging, that is, Pd/CZS-a exhibits conversion temperatures of the pollutants (T50 and T90) 10–20 °C lower than Pd/CZ-a.