【作者】 罗晶；

【导师】 童志权；

【作者基本信息】 湘潭大学 ， 环境工程， 2010， 硕士

【摘要】 为了有效脱除烟气中的NOx,本论文研究了Cr-Ce/TiO₂催化剂对NO的催化氧化和催化还原性能,主要开展了以下方面的工作:（1）考察了Cr/Ce摩尔比、活性组分负载量、载体种类、焙烧温度对Cr-Ce/TiO₂催化氧化NO性能的影响。用BET、XRD技术对不同温度焙烧的催化剂进行表征,研究催化剂的微观结构和物相。结果表明,Cr/Ce摩尔比为2/1、Cr₂O₃和CeO₂的总负载量为载体重量的30%、350℃焙烧6 h制备的Cr-Ce/TiO₂催化剂上活性组分以不定态存在,具有最佳的催化氧化活性。空速10,000 h-1、330℃下NO转化率为80.7%。（2）研究了操作条件对催化剂催化氧化NO性能的影响,NO转化率随O2含量的增加而增大;随着NO进口体积分数的升高和空速的增大而下降。（3）对NO催化氧化反应的动力学进行了分析,得到速率方程: r_NO=kY_NO^aY_O2^b=332.62exp（-19968.93/RT）[NO]^0.93[O₂]^0.21（4）通过阶跃应答实验和FTIR分析技术考察了H2O和SO₂对Cr-Ce/TiO₂催化氧化NO性能的影响和催化剂的中毒机理。H2O对催化剂的毒化作用是可逆的。在H2O和SO₂同时存在的情况下进行NO氧化反应时,催化剂表面形成少量硫酸盐和亚硫酸盐,使活性降低,且不可逆。对中毒后的催化剂进行热处理后,活性虽未能达到原有水平,但在很大程度上得到恢复。（5）考察了Cr/Ce摩尔比、活性组分负载量、焙烧温度对Cr-Ce/TiO₂低温SCR活性的影响。结果表明具有最佳催化氧化活性的催化剂同时具有最佳的催化还原活性,空速10,000 h-1、180℃下NO转化率为99.6%。并考察了操作工况对催化剂SCR活性的影响,NO转化率随NH3/NO、O2含量的增加而升高,并逐渐趋于平缓;随着进口NO浓度、空速的升高而降低。SCR反应过程主要遵循Eley-Rideal机理。（6）通过阶跃应答实验和FTIR分析技术考察了H₂O和SO₂对Cr-Ce/TiO₂催化还原NO性能的影响和催化剂的中毒机理。10%（φ）的H₂O对该催化剂的活性影响很小,NO转化率保持在97.7%以上;反应气中存在SO₂的情况下,催化剂被毒化,表面生成（NH₄）₂SO₄、NH₄HSO₄、金属硫酸盐和亚硫酸盐,致使活性降低。该催化剂有望应用于基本不含SO₂的燃气锅炉烟气和不含SO₂的硝酸尾气等NOx工业废气的低温脱硝。更多还原

【Abstract】 In order to remove the nitrogen oxides from flue gas, Cr-Ce/TiO₂ catalysts were studied for the oxidation and reduction of NO in this paper. The following tasks were carried out:（1） The effects of molar ratio, loading of active component and calcination temperature along with the nature of supports on the performance of the catalytic oxidation of NO were examined. The microstructure of the catalysts calcined at different temperature was characterized by XRD and BET. The Cr-Ce/TiO₂ which was calcined at 350 oC with total loading 30% and molar ratio Cr/Ce=2/1 showed perfect dispersity and stability. The high NO conversion of 80.7% was observed over it at 330 oC and space velocity 10,000 h-1.（2） The effects of operating condition on the catalytic oxidation of NO were also investigated. It was found that NO conversion increased with the enhancement of O₂ concentration and decreased with the rise of NO concentration and GHSV.（3） The reaction kinetic equation was expressed as: r_NO=kY_NO^aY_O2^b=332.62exp（-19968.93/RT）[NO]^0.93[O₂]^0.21（4） The effects of H₂O and SO₂ on the catalytic oxidation of NO were studied by step transient response experiments and FTIR. H₂O poisoning is reversible. After NO oxidation reaction in the presence of H₂O and SO₂, a few sulfates and sulfites were formed causing the irreversible deactivation of catalyst. The catalytic activity of deactivated Cr–Ce/TiO₂ could recover mostly after heat treatment.（5） The effects of calcination temperature, molar ratio and loading of active component as well as operating condition on the performance of SCR were examined. The Cr–Ce/TiO₂ catalyst showing high activity for catalytic oxidation of NO also performed high activity for NH3-SCR. The NO conversion of 99.6% was observed at 180℃and space velocity 10,000 h-1. NO conversion increased with the enhancement of O₂ concentration and NH3/NO, and decreased with the rise of NO concentration and GHSV. The reaction of SCR followed Eley-Rideal mechanism.（6） The effects of H₂O and SO₂ on the performance of SCR were studied by step transient response experiments and FTIR. The 10% （φ） H₂O had little negative effect on catalytic activity, and the NO conversion was kept at level of 97.7%. The catalyst was deactivated irreversiblly in the presence of SO₂ due to the generation of excess amount of sulfate salts. The catalyst is expected to be applied to the removal of NOx from exhaust gas without SO₂ at low temperature.更多还原