Fe和Cu分子筛催化剂同时催化NO_(x)还原和N_(2)O分解  

Simultaneous reduction of NO_(x) and decomposition of N_(2)O over Fe and Cu zeolite catalysts

作　　者：司庆宇 樊星[1] 张玮航 苗静文 刘若雯 SI Qing-yu;FAN Xing;ZHANG Wei-hang;MIAO Jing-wen;LIU Ruo-wen(Key Laboratory of Beijing on Regional Air Pollution Control,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学,区域大气复合污染防治北京市重点实验室,北京100124

出　　处：《中国环境科学》2024年第9期4826-4834,共9页China Environmental Science

基　　金：国家自然科学基金资助项目(21707004);北京市自然科学基金资助项目(8152011)。

摘　　要：采用离子交换法制备了Fe-Beta和Cu-SSZ-13催化剂并采用不同混合方式制备了复合催化剂,考察了催化剂同时催化NO_(x)还原和N_(2)O分解的性能.以实现NO_(x)和N_(2)O同时高效去除、拓宽活性温度窗口为目标,优选出了上Fe下Cu分层填充、Fe-Beta和Cu-SSZ-13质量比为4:1的Fe_(0.4)Cu_(0.1)催化剂,进一步考察了进气组成对NO_(x)、N_(2)O和NH_(3)转化率的影响,并采用N_(2)吸脱附、XRD、NH_(3)-TPD、UV-Vis DRS和H_(2)-TPR等手段对催化剂理化特性进行了表征.结果表明,Cu-SSZ-13和Fe-Beta分别具有更优的催化NO_(x)还原和N_(2)O分解性能.采用Fe_(0.4)Cu_(0.1)催化剂、[NH_(3)]/[NO_(x)]为1时考察的温度范围内NH_(3)仅还原NO_(x),而N_(2)O通过分解去除,450℃时NO_(x)和N_(2)O转化率分别为93.4%和100%.高温(>350℃)下NH_(3)被O_(2)氧化导致NO_(x)转化率随温度升高而降低;高温(≥350℃)下N_(2)O分解形成的氧物种可使NO_(x)在进气中无O_(2)条件下实现高效还原.进气中含2%H_(2)O对高温(450℃)下Fe_(0.4)Cu_(0.1)表面NO_(x)的还原和NH_(3)的氧化无显著影响,但对N_(2)O的转化存在一定的可逆抑制作用.Cu-SSZ-13表面存在大量孤立的Cu^(2+)离子,可为NH_(3)-SCR反应提供充足的活性中心.Fe-Beta表面同时存在能够催化NO氧化的孤立Fe^(3+)离子和催化N_(2)O分解的Fe_(x)O_(y)物种.采用上Fe下Cu分层填充的混合方式时Fe-Beta表面NO氧化过程会消耗N_(2)O分解形成的氧物种,从而有利于低温(≤450℃)下N_(2)O的转化.但由于N_(2)O分解的温度范围内NO_(x)转化率本身较高,NO氧化对于脱硝的促进作用不显著.Fe-Beta and Cu-SSZ-13 catalysts were prepared by ion-exchange method,and composite catalysts were prepared using different mixing methods.Performance of the catalysts in catalyzing NO_(x) reduction and N_(2)O decomposition at the same time was investigated.Fe_(0.4)Cu_(0.1)catalyst,which was composed of Fe-Beta in the top layer and Cu-SSZ-13 in the bottom layer with mass ratio of 4:1,performed the best in catalyzing the removal of NO_(x) and N_(2)O simultaneously and broadening the reactive temperature window.Effects of inlet gas composition on the conversion of NO_(x),N_(2)O,and NH_(3) were investigated.Physicochemical characteristics of the catalysts were characterized by N_(2) adsorption-desorption,XRD,NH_(3)-TPD,UV-Vis DRS and H_(2)-TPR techniques.The results showed that Cu-SSZ-13 and Fe-Beta had superior performance in catalyzing NO_(x) reduction and N_(2)O decomposition,respectively.In the tested temperature range,NO_(x) was reduced by NH_(3) while N_(2)O was decomposed over Fe_(0.4)Cu_(0.1)when[NH_(3)]/[NO_(x)]was 1.NO_(x) and N_(2)O conversion reached 93.4%and 100%,respectively at 450℃.Oxidation of NH_(3) by O_(2) at high temperatures (>350℃) leads to decrease in NO_(x) conversion with increasing temperature.And the formation of oxygen species from the decomposition of N_(2)O at high temperatures (≥350℃) explains the efficient NO_(x) reduction without O_(2) in the inlet gas.The presence of 2% H_(2)O in the inlet gas hardly affected the reduction of NO_(x) and oxidation of NH_(3) over Fe_(0.4)Cu_(0.1) at high temperature(450℃),but did show reversible inhibitory effects on the conversion of N_(2)O.Abundant isolated Cu^(2+)ions were detected over Cu-SSZ-13,providing sufficient active centers for the NH_(3)-SCR reaction.Both isolated Fe^(3+)ions and Fe_(x)O_(y) species,which can catalyze NO oxidation and N_(2)O decomposition,respectively,were detected over Fe-Beta.Using the top-Fe-bottom-Cu composite catalyst,NO oxidation occurs over Fe-Beta,which consumes oxygen species formed from N_(2)O decomposit

关 键 词：NO_(x)还原 N_(2)O分解 Fe-Beta Cu-SSZ-13 复合催化剂 

分 类 号：X511[环境科学与工程—环境工程]