Preparation of Mn, Fe and Co based perovskite catalysts using microemulsions

Mixed metal oxides with perovskite structure were prepared using microemulsions. The perovskite materials had the nominal composition La0.8Sr0.2M1−xRhxO3 (where M=Mn, Co, Fe and x=0, 0.1). X-ray diffraction analysis showed that the perovskite phase was generally obtained at relatively low temperatures, ≤700 °C. When the calcination temperature was kept low, the surface areas were relatively high and the highest surface area (25 m2/g) was observed for La0.8Sr0.2Mn0.9Rh0.1O3 after calcination at 500 °C. Microstructural analysis using TEM and SEM showed particles in the size range of microns consisting of smaller crystallites in the range of 30–50 nm. The materials were tested as catalysts for the selective reduction of NOx with NH3 (NH3-SCR) and the activity varied between samples with different transition metal. However, potassium, which originated from the technical surfactant used in the microemulsion, was detected by XRF analysis in various amounts in the samples and it was therefore not possible to conclude if the differences in catalytic performance were due to the different transition metals or to the potassium in the samples. Characterisation showed that it was possible to incorporate rhodium in the perovskite materials, which generally resulted in enhanced catalytic activities for the reduction of NOx with NH3.