钒基催化剂NH3-SCR低温反应特性研究

利用固定床反应器及原位漫反射傅里叶变换红外光谱仪,通过稳态及瞬态反应,研究了V2O5-WO3/TiO2催化剂低温NH3选择性催化还原(SCR)机理及低温活性的影响因素.结果表明:低温时,V2O5-WO3/TiO2 SCR催化剂首先吸附气态NH3,形成吸附态NH3\NH4+,然后吸附态NH3\NH4+和气态NO反应,生成N2.因而催化剂表面是否具有吸附氨及氨存储量的大小决定了催化剂的低温活性.此外,反应气中NO2和H2O含量、硫化物、催化剂中活性组分的含量及价态分布均会影响SCR催化剂的低温活性.通过以上试验,结合实际应用经验,为如何设计低温V2O5-WO3/TiO2 SCR催化剂提出指导和建议.

Performance of SCR Catalysts Based on V2O5-WO3/TiO2 at Low Temperature

The mechanism of NH3 selective catalytic reduction(SCR)of V2O5-WO3/TiO2 based catalyst and the influencing factors of its activity were studied under low temperature condition through both steady-state and transient reactions by using fixed-bed reactor and in-situ diffuse reflectance infrared Fourier transform spectroscopy.The results show that the V2O5-WO3/TiO2 based SCR catalyst first adsorbs gaseous NH3 to form adsorbed NH3\NH4+at low temperature,and then the adsorbed NH3\NH4+reacts with gaseous NO to generate N2.Therefore,the catalyst activity at low temperature is determined by whether and how many the ammonia is adsorbed on the surface of the catalyst.In addition,the content of NO2,H2O,sulfide and active components in the reaction gas and the distribution of the valence state all affect the activity of the SCR catalyst at low temperature.These results combined with the catalyst application experience provide a guidance on how to design V2O5-WO3/TiO2 based SCR catalyst with a good activity under low temperature.