不同锰含量纳米MnO2-Fe2O3-CeO2/Al2O3的制备、表征及其催化还原NO/NO_2性能

减少发动机冷启动极低温度下排气中的NO_x对于生态环境与人类健康至关重要,MnO₂在低温区间对NO_x具有较高催化活性,是一种极具发展前景的纳米催化剂。通过超声波辅助共沉淀法制备不同锰含量MnO₂-Fe₂O₃-CeO₂/Al₂O₃纳米催化材料,探讨表面结构特性与其脱硝活性的内在联系。研究发现:锰含量为15%(质量分数)时具有最大比表面积与最小晶粒,活性物质分布最为均匀,金属氧化物结晶度得到抑制,Mn,Fe和Ce呈现较佳共存态,能够促进化学吸附氧的富集,并通过提高NO催化氧化成NO₂来提高快速SCR反应速率,NO₂转化率在50℃时即达到了88.5%。在改善催化材料构效关系、提高NO预氧化和快速SCR反应性能方面,优化锰含量是一种极其有效的方法。

Preparation,characterization and NO/NO2 catalytic reduction performance of MnO2-Fe2O3-CeO2/Al2O3 nanocatalysts with different manganese contents

Reducing NOx emission in the exhaust gas under the extremely low temperature of engine cold start was important for the ecological environment and human health.MnO₂ has high catalytic activity for NO_x in the low temperature range,which is a promising nanocatalyst.The intrinsic relationship between the surface structural characteristics and denitrification activity of MnO₂-Fe₂O₃-CeO₂/Al₂O₃ nanocatalysts produced by ultrasonic assisted coprecipitation method with different manganese contents was discussed.The results show that when the manganese content is 15%(mass fraction),the nanocatalyst has the largest specific surface area and the smallest grain size.At the same time,the distribution of active substances is the most uniform.Meanwhile,the crystallinity of metal oxides is suppressed,and Mn,Fe and Ce are in the best coexistence state,which can promote the enrichment of chemisorption oxygen.The catalytic oxidation of NO to NO₂ improves the reaction rate of fast SCR,and the NO₂ conversion reaches 88.5%at 50℃.Optimizing manganese content is an extremely effective method to improve the structure-activity relationship of catalytic materials and promote the performance of NO preoxidation and fast SCR reaction.