[关键词]
[摘要]
摘 要:采用浸渍法制备了一系列不同煅烧温度(350~650 ℃)的MnOx/ZSM-5催化剂,使用X射线衍射(XRD)、X射线光电子能谱分析(XPS)、H2程序升温还原(H2-TPR)和N2吸附/脱附等技术对催化剂特征进行了测试。结果表明,煅烧温度对于MnOx/ZSM-5催化剂催化NO氧化的活性有显著影响,与350 ℃下煅烧样品相比,550 ℃煅烧后样品最大NO转化率提高7%。较高的煅烧温度有利于Mn2O3的生成,在煅烧温度高于550 ℃后,Mn2O3成为催化剂表面的主要晶相。但提高煅烧温度,会导致催化剂表面分散度和比表面积降低,还原性能和晶格氧含量下降,不利于催化反应的进行。在反应器入口NO体积分数0.1%,体积空速约17 000 h-1的实验条件下,550 ℃煅烧后的催化剂样品表现出最佳的催化NO氧化效率,350 ℃时NO转化率达到46.8%。但MnOx/ZSM-5抗硫性能较差,还需进一步优化制备方式以提高其含SO2 氛围下的适用性。
[Key word]
[Abstract]
Abstract: A series of MnOx /ZSM-5 catalysts were prepared at different calcination temperatures(from 350 ℃ to 650 ℃)by using the immersion method and the XRD (X-ray diffraction),XPS (X-ray photoelectronic spectrum),H2-TPR (H2 temperature program reduction) and N2 adsorption/desorption technology etc.were employed to test the characteristics of the catalysts.It has been found that the calcination temperature will have a notable influence on the activity of NO oxidation catalyzed by MnOx /ZSM-5.Compared with the sample calcinated at 350 ℃,the maximum NO conversion rate of the sample calcinated at 550 ℃ will increase by 7%.A relatively high calcination temperature will be favorable to the formation of Mn2O3 .When the calcination temperature is higher than 550 ℃, Mn2O3 will become the main crystal phase on the surface of the catalysts.However,to enhance the calcination temperature will result in a decline of the surface dissipation degree on the surface of the catalysts and specific surface area and a drop of the reduction performance and oxygen content in the crystal lattice,thus unfavorable to catalytic reactions.Under the test condition of the volumetric fraction of NO at the inlet of the reactor being 0.1% and the volumetric space velocity being around 17 000 h-1 ,the catalyst sample after calcinated at 550 ℃ will exhibit the optimum No catalytic oxidation efficiency.The NO conversion rate of the sample after calcinated at 350 ℃ will reach 46.8%.However, Mn2O3/ZSM-5 will have a relatively poor performance to resist sulfurization and it will be necessary to further optimize the preparation method to improve the adaptability in the atmosphere containing SO2.
[中图分类号]
TK09
[基金项目]
国家科技支撑计划(2015BAA04B02)