High performance of K-supported Pr2Sn2O7 pyrochlore catalysts for soot oxidation

A highly active catalyst of K-supported Pr2Sn2O7 pyrochlore nanosphere (K/PrSn) was synthesized by impregnation method with K2CO3 as precursors for soot oxidation in this work. The catalysts were systematically characterized by XRD, SEM, FTIR, N2 adsorption–desorption, H2-TPR and soot-TPR techniques. Pure Pr2Sn2O7 exhibits uniform litchis-like spherical clusters morphology, composed of small nanoparticles of ∼ 30 nm in diameter. K species exist on K/PrSn catalysts surface in three forms: highly dispersed K2CO3, highly dispersed KO2 and bulk KO2. The catalyst containing 10 wt% of K (10 K/PrSn) showed the best catalytic performance and high stability in soot combustion under both tight and loose contact conditions. It can be speculated that potassium supporting plays crucial roles in K/PrSn catalyzed soot oxidation: (1) it improves the catalyst-soot contact by forming macroporous structure and/or due to the low-melting point of alkali metal, (2) it increases the surface basicity, which favors soot oxidation through formation of carbonate intermediates, (3) it enhances the reducibility of the catalyst due to the interaction between K and PrSn support, (4) K species itself may participate in the oxidation of soot particulates. Pr2Sn2O7 pyrochlore supported with high dispersion of potassium exhibits a superior reaction performance and good stability, which has the potential to be applied in some real diesel exhaust control processes.