SCR催化剂表面NH3和NO吸附实验与机理研究

Experiment and DFT Study of NH3 and NO Adsorption on SCR Catalyst Surface

选择性催化还原（SCR）技术被广泛应用于大型燃煤机组烟气氮氧化物脱除中,脱硝效率达到90%以上。烟气温度下降会导致SCR系统的催化剂受损,在停机之前会停止向SCR系统喷氨,导致此期间的NO_x排放超标。采集并计算了某电厂停炉过程中排放NO的数据,实验发现NO排放量在此过程中仍会有不同幅度的降低。运用密度泛函理论（DFT）基于V_2O_5团簇模型研究了NO和NH_3在催化剂不同吸附位上的吸附机理。研究结果表明：NO不会稳定吸附在催化剂的表面;NH_3既能吸附在钒基表面的Lewis酸性位,又可吸附在Br？nsted酸性位,而且更稳定。由此可知,停机后由于吸附在催化剂表面的NH_3与烟气中的NO反应,使得出口处的NO量降低。

Selective Catalytic Reduction （SCR） technology is widely used in coal-fired power plants for NOx removal, and its denitration efficiency can reach above 90%. However, when the flue gas temperature is low,it can lead to the destruction of SCR catalyst, and the ammonia spray into the SCR system will be stopped before the system is turned down, ,which possibly results in an excessive NO emission in this pe- riod. The data of NO emission during the boiler shutdown period is collected and processed, and the ex- perimental results show a decrease in the NO emission. The adsorption mechanisms of NO and NH3 on different sites of denitrification catalyst have been studied based on the V2O5 cluster model with the density functional theory （DFT） method. Results indicate that NO cannot be stably adsorbed onto the catalyst surface ,whereas the NH3 can be stably adsorbed on both the Lewis and Brφnsted sites of V2Osmodel surface, and the adsorption on the latter site is found to be more stable. It is found that the amount of NO reduction after shutdown is due to the reaction of NO with the adsorbed NH3 on the catalyst surface.