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The nanocrystalline, porous, perovskite La1–x K x FeO3 (x = 0–0.4) powders and La0.8K0.2FeO3-coated honeycomb ceramic device were prepared by the citrate-gel process and the citrate-gel assisted dip-coating method at a low calcination temperature of 600̊C for 6 h, respectively. All the perovskite powders can effectively catalyze the soot combustion and among them the La0.8K0.2FeO3 catalyst exhibits the highest catalytic activity for the soot combustion, with a lowest T50 (350 °C) owing to a high specific surface area and large pore sizes. This optimized La0.8K0.2FeO3 catalyst is proved by the bench test for the practical exhaust gas emission and the La0.8K0.2FeO3-coated honeycomb ceramic device has a effective capture of particulate matter from the exhaust emission at a low temperature and starts to efficiently catalyze oxidization reactions of the particulate matter at the temperature around 245 °C (T 20), leads the smoke opacity near zero at the operational temperature of 400 °C.

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The porous xCu/(1 - x)Ce-K-O (x = 0.1-0.4) nanocomposites were prepared by the citrate-gel thermal decomposition and reduction process. The effect of nanosized metallic Cu on their microstructure and catalytic properties was investigated by XRD, SEM, BET, TG analysis. With Cu content increasing, the grain size of metallic Cu is increased from 40 nm to 62 nm, whilst the grain size of CeO2 decreases from 38 nm to 20 nm. While, their specific surface area (S(BET)) and average pore size (P(ave)) show an increasing trend with the Cu content increase in the nanocomposites. The catalytic activity for soot combustion is influenced by the Cu content, with a lowest T20 (216 degrees C) and T50 (357 degrees C) for xCu/(1 - x)Ce-K-O (x = 0.3) nanocomposite catalyst. The catalytic performance for the optimal xCu/(1 - x)Ce-K-O (x = 0.3) nanocomposite coated honeycomb ceramic device was evaluated under the practical diesel exhaust emissions at the temperature range of 200-400 degrees C. This 10 wt.% catalyst-loaded honeycomb ceramic device confirms a high catalytic activity and stability for simultaneous removal of soot and NO(x), largely,due to the porous structure and synergistic effect of nano Cu and nano ceria in the catalyst.

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The nanocrystalline, porous, perovskite La0.8K0.2Fe(1-x)Mn(x)O3 (x = 0-0.5) catalysts were prepared by the citrate-gel process. All the perovskite catalysts can effectively catalyze the soot combustion and among them the La0.8K0.2Fe0.7Mn0.3O3 catalyst exhibits the highest catalytic activity, with a lowest T50 (366 degrees C). This optimized La0.8K0.2Fe0.7Mn0.3O3 catalyst then was coated onto a honeycomb ceramic by the citrate-gel assisted dip-coating method and its catalytic performance was evaluated by the bench test in the practical exhaust emission. It is proved that the La0.8K0.2Fe0.7Mn0.3O3-coated honeycomb ceramic device simultaneously has a effective capture of soot particulates and a good absorption of NO(x) from the exhaust emission at a low temperature and begins to efficiently catalyze oxidization reactions of the soot particulates at around 230 degrees C, and conversion of NO(x) at about 290 degrees C, with a conversion rate of 16.6% at 400 degrees C. This catalytic performance enhancement for simultaneous removal of soot and NO(x) can be largely attributed to the synergistic effect of Fe and Mn, pore structure of a large channel with various small pores connected, and microstructural characteristics of La0.8K0.2Fe0.7Mn0.3O3 catalyst. The catalytic mechanism of capture-oxidation-reduction is rationally proposed.

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