摘要
采用改进的溶胶-凝胶法制备一系列MnO_x/SAPO-34催化剂,考察了各制备参数对催化剂的结构及其低温氨选择性催化还原(NH_3-SCR)脱硝性能的影响,并通过X射线衍射、N_2吸附-脱附、透射电镜、X射线光电子能谱、NH_3程序升温脱附等手段对催化剂进行表征.结果表明,当制备参数为n(乙醇)/n(Mn)=15,n(H_2O)/n(Mn)=20,n(柠檬酸)/n(Mn)=1,Mn负载量为15%(质量分数),催化剂焙烧温度为350℃时,制备的高分散15%-MnO_x/SAPO-34-350℃催化剂具有最佳的低温SCR活性,在空速为45000 h^(-1)的条件下,且反应温度在120～240℃范围时均保持90%以上的NO转化率和接近100%的N_2选择性.MnO_x纳米颗粒高度分散在SAPO-34载体表面,平均粒径约为5.46 nm,纳米颗粒的表面效应使得该催化剂具备较大的比表面积,暴露出大量的活性位点和高活性的MnO_2(110)晶面,同时,高Mn^(4+)比例和更多的化学吸附氧以及适宜的表面酸强度和酸量也是15%-MnO_x/SAPO-34-350℃催化剂呈现最佳低温SCR活性的重要原因.
A series of MnOx/SAPO-34 catalysts were prepared by an improved sol-gel method. The effects of preparation parameters on the structure and activities of the catalysts for the low-temperature NH3-SCR of NO were investigated. The catalysts were characterized by X-ray diffraction(XRD), N2 adsorption-desorption, transmission electron microscope(TEM), X-ray photoelectron spectroscopy(XPS) and NH3-temperature programmed desorption(NH3-TPD). The results show that the highly dispersed 15%-MnOx/SAPO-34-350℃ catalyst exhibited the best low-temperature SCR activity on the preparation conditions of ethanol/Mn mole ratio of 15, H2O/Mn mole ratio of 20, citric acid/Mn mole ratio of 1, Mn loading of 15% and calcination temperature of 350 ℃. The catalyst reached more than 90% NO conversion and nearly 100% N2 selectivity in a wide reaction temperature range of 120~240 ℃ at a space velocity of 45000 h-1. MnOx nanoparticles were highly dispersed on the SAPO-34 surface with about 5.46 nm average particle size. Due to the surface effect of the nanoparticles, the catalyst possessed larger specific surface area, abundant active sites and active(110) crystal plane of MnO2, which may contribute to the excellent catalytic performance. Moreover, the higher Mn4+ concentration, more surface chemisorbed oxygen species, and the appropriate surface acid strength and acid sites also played significant roles in the high SCR activity of the catalyst.
作者
凌微
黄碧纯
LING Wei;HUANG Bichun(School of Environment and Energy,South China University of Technology,Guangzhou 510006;The Key Lab of the Ministry of Education for Pollution Control and Ecosystem Restoration in Industry Clusters,South China University of Technology,Guangzhou 510006)
出处
《环境科学学报》
CAS
CSCD
北大核心
2019年第4期1095-1104,共10页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No.51478191)
