Research On Catalytic Combustion Of Acrylonitrile Over Supported Perovskite-Type Catalyst

The control of acrylonitrile exhaust emission is becoming more and more important in China. The method of catalytic combustion of acrylonitrile gas is a hotspot of current research. Perovskite has gained attention due to the advantages of wide application, species diversity, redox ability, good thermal stability, low price, etc. It is the main line of the article that using perovskite in acrylonitrile catalytic reaction system, picking out the best components for synthesis of supported perovskite-type catalyst and screening the best supported perovskite-type catalyst.In this paper, A series of LaBO3 perovskites (B-Fe, Co, Mn and Cr) and La2Cu04 has been synthesised by conventional citric acid route. The results of activity test matched the H2-TPR results very well. It shows that La2CuO4 has the best N2 selectivity. Copper could greatly enhance the low temperature N2 selectivity of catalyst. LaFeo.gCuo.2O3 obtained by B-site substitution through copper displayed highest acrylonitrile conversion rate, reaching 93% at 250° C and 100% at 300℃ as well as 80% N2 yield. Subsequently, the copper doping ratio in LaFeO3 perovskite structure was explored to understand influence of copper to acrylonitrile catalytic activity.The in-situ DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) method was carried out to explore acrylonitrile reaction mechanism of catalytic combustion, using LaFeO3 and LaFeo.6Cuo.4O3 as catalyst. The experimental results showed that B-site doped by Cu has great influence on catalytic combustion reaction mechanism of acrylonitrile. Compared with LaFeO3, Cu could effectively prompt anomeric carbon of acrylonitrile to be oxidized in order to produce malonic acid species, resulting in enhancing the catalytic activity. Besides, it could also promote the elimination of nitrate/nitrite species, leading to the enhancement of N2 selectivity.Based on the conclusion above, diverse methods and supports were applied to synthesis supported perovskite-type catalysts. It turned out that modified citric acid complexing impregnation method is superior to the traditional citric acid complexing impregnation method. s-Zr-67%-2 showed the highest catalysis performance through the modification of the citric acid complexing impregnation method. Unfortunately, the strong oxidation ability leads to the low N2 selectivity. However, s-Al-67%-2 has the best N2 yield with optimal loading ratio 67%. Even though under oxygen-rich concentration, LaFeo.8Cuo.2O3 displayed obvious advantages that catalytic activity could maintain above 50% though the activity test under high oxygen concentration. Finally, water and sulfur-resistance stability experiment was carried out over s-Al-67%-2 and LaFeo.8Cu0.2O3 samples. By contrast, it found that s-Al-67%-2 showed better performance than LaFeo.8Cuo.2O3 no matter what in water-resistance and sulfur-resistance stability test.