Preparation Of Lanthanum Manganese Perovskite Catalysts And Their Catalytic Performance For Methane Combustion

Methane catalytic combustion technology can make methane react with oxygen at a lower temperature, product CO2, H2O and release of energy, which not only improve the utilization efficiency of methane, but also solve the problem of environmental pollution during the combustion of methane in the traditional manner. LaMnO3+δ perovskite-type catalyst exhibited good activity and stability in the application of catalytic combustion for low concentration methane. In this paper, LaMnO3+δ as research subject, examines the influences of preparation methods, calcination temperature, dosage of citric acid and Ca, Sr doped in A bit on the structure of the catalysts and its catalytic performance for low concentration methane (1vol%).1, Studied the influence of precipitation method, coprecipitation method and citric acid complex to the catalytic performance of LaMnO3+δ perovskite-type catalysts for methane catalytic combustion. The catalyst prepared by citrate method has uniform crystal phase, large specific surface area, high stability of perovskite structure, as well as best catalytic activity for methane catalytic combustion. Citric acid complex method is superior to the precipitation and coprecipitation method when prepared lanthanum manganese perovskite type catalyst.2、LaMnO3+δ perovskite-type catalysts were prepared by citric acid complexation method. Investigate the influence of calcination temperature on the structure and methane catalytic combustion performance of the catalyst. The results showed that the content of Mn4+ in the catalyst increased, the content of non-stoichiometric oxygen reduced relatively with the increase of calcination temperature. The increase of calcination temperature is beneficial to improve the thermal stability of the catalyst. The calcination temperature is not more than 700℃, catalyst no sintering basically, when the calcination temperature is higher than 700℃, the catalyst sintering to some extent. The catalyst gave best catalytic activity for methane catalytic combustion when the calcination temperature is 700℃, so 700℃is the best calcination temperature for lanthanum manganese perovskite-type catalyst prepared by citric acid complex method.3、LaMnO3+δ perovskite-type catalysts were prepared by citric acid complex method. Investigate the influence of the dosage of citric acid on the structure and methane catalytic combustion performance of the catalyst. The results showed that the specific surface area of the catalyst decreased first and then increased, the average crystallite size of the catalyst increased first and then reduced with the increased of the dosage of citric acid. Besides, characteristic diffraction peaks of perovskite crystal phase of the catalyst in weakening when the dosage of citric acid increased. The catalyst prepared by citric acid complex method has an impurity phase La2O3 produce when the dosage of citric acid is more than or equal to 1.5. The catalyst has an uniform crystalline phase, a relatively stable structure and the best activity for methane catalytic combustion when the dosage of citric acid is 1.25, so the best dosage of citric acid is 1.25, when lanthanum manganese perovskite-type catalyst prepared by citric acid complex method.4> Ca, Sr doped lanthanum manganese perovskite-type catalysts were prepared by citric acid complex method, and its calcination temperature is 700℃. When the molar doping amount of Ca, Sr is not more than 0.2, Ca and Sr can be doped into A bit of the lanthanum manganese perovskite-type catalysts, and get a single crystalline phase of La1-xMxMnO3+δ(M=Ca, Sr) perovskite-type catalyst. Ca, Sr doping can improve the activity of the catalysts. When the molar doping amount of Ca is 0.1, the catalyst has the highest catalytic activity for methane catalytic combustion, its T50 and T90 is 467.2℃ and 586.9℃ respectively. However, the molar doping amount of Sr is 0.05, when the doping amount of Sr is 0.05, the La1-xSrxMn03+δ catalyst has the best catalytic activity, its T50 and T90 is 495℃and 640℃ respectively. Ca doping leads to catalyst has a slight sintering, the experimental results show that the best Ca doping amount is 0.1, the Ca doping had no significant influence to the stability of the catalyst. Average crystallite size of the catalysts decreased with the increased of Sr doping amount. Sr doping can enhance the anti-sintering ability of the catalyst, but the increase of Sr doping amount is not conductive to the stability of the perovskite structure of the catalyst.