Realization approach of Pd-only three-way catalysts with high catalytic performance and thermal stability

Abstract

Pd-only three-way catalyst (TWC), Pd supported on washcoating (the mixture of alumina and Ce-Zr solid solution)/cordierite, was prepared and its catalytic performance and the operation window (λ-value) at 450 °C were evaluated with the simulated automotive exhaust feed gas. Surfactants such as Tween-80 and Span-20 were added in the process of preparing the catalyst in order to improve the thermal stability and catalytic performance of Pd-only TWC. The fresh and aged catalysts at 1000 °C for 4 h were characterized by low-temperature N2 adsorption, XRD, XPS, and H2-TPR techniques. The results show that the presence of surfactants in the synthesis slurry could influence the physicochemical properties of the final Pd-only TWC. The FTS catalyst prepared with the mixed surfactant of Tween-80 and Span-20 exhibited excellent three-way catalytic performance. After being aged at 1000 °C for 4 h, the catalytic performances of Pd-only TWCs slightly decreased, but the FTS catalyst still demonstrated higher catalytic performance and better thermal stability compared with the Pd-only catalysts prepared with single surfactant or without any surfactant. And the FTS catalyst has a wider λ value (operation window) than other catalysts, even after being aged at 1000 °C.