| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 91 === NOx and CO removal from the combustion exhaust gases has become a serious environmental problem. In order to reduce these pollutants both noble metals and perovskite-type catalysts have been used. Compared to noble metals being expensive and having the sintered problem, perovskite oxides have better thermal stability and are cheaper, therefore it is noticeable in the last years. The aim of this study was to synthesize the perovskite catalyst of La1-xSrxMnO3, and to investigate the influence of Sr content on the characteristics and the activity for CO+NO reaction.
La1-xSrxMnO3 catalysts were prepared by the amorphous citrate method. Dopping Sr can reduce the temperature for synthesizing La1-xSrxMnO3 . The powder synthesized at 700℃ showed only one phase of La1-xSrxMnO3 perovskite for x≦0.15, and the other phases of SrCO3 for x≧0.2. The lattice parameters and specific surface area of La1-xSrxMnO3 increased and the particle sizes, crystalline sizes of La1-xSrxMnO3 decreased with an increase in the fraction of Sr.
The activity of LaMnO3 catalysts can be enhanced by dopping Sr. In this study, the La0.85Sr0.15MnO3 catalyst had the highest activity and with this catalyst, the temperature for complete conversion of CO＋NO could be down to 400℃. The catalyst also gave a higher conversion of CO into CO2 and NO into N2 at 400℃in the condition of CO：NO＝1：2 (volume ratio). The results of temperature programmed test showed that the La1-xSrxMnO3 (x = 0 ~ 0.2) catalysts for the CO+NO reaction was an oxidation-reduction mechanism and the catalysts after catalytic reaction preserved perovskite phase.
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