| Research Abstract |
Porous layer for catalytic application was fabricated using the control of slurry in the system of metal oxide powders and water. We optimized the condition for slurry formation using various catalytic Al_2O_3 powders dispersed in water. Al_2O_3 layer, fabricated through slurry-coat process, was stable and maintained high surface area and good shape of layer, even when it was subjected to high temperatures up to 1100℃. For practical catalyst, solid-state reaction between compositions (alumina, metal oxides) and sintering behavior of powders at 600-1100℃ were examined by x-ray diffraction, electron spin resonance and surface area measurement Manganese-alumina catalyst, which was even subjected to heat treatment at 1000℃ in air, had the NO removal conversion efficiency of 22% at 350-400℃ Structural change and chemical state of alumina-supported manganese catalytic powders were studied for the purpose of the improvement of performance in automotive lean-burn NOx removal treatment for a model lean exhaust with high space velocity of 100,000h^<-1>. CrOx-LaOx-Al^2O_3 system and their sintering behavior of at 500-1100℃ were also studied. The ESR spectra of samples heat-treated at 900-1000℃ suggested the existence of Cr(3+) in an axial crystal field with low symmetry. CrOx-LaOx-Al_2O_3 catalyst, heated at 900℃ in air, showed the removal conversion of 100% for hydrocarbon (C_3H_6), 95% for CO but 7% for NO at 500℃ for high velocity automotive lean-burn exhaust. Present slurry-controlled process and the modification of alumina catalyst were effective to high surface area stabilization, and improved the performance of automotive exhaust treatment with catalysis.
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