Mo-Mn/TiO2催化剂的协同脱硝脱汞特性

摘要

采用浸渍法制备Mo-Mn/TiO2催化剂,研究了反应温度、HCl和SO2对其模拟烟气协同脱硝脱汞活性的影响.研究表明,过高的反应温度不利于汞的脱除过程,过低的温度则抑制脱硝反应的顺利进行,但在200℃时可兼具最优的脱硝和脱汞效率;HCl的加入促进汞的高效氧化,却明显降低催化剂对NO的转化;而烟气中SO2的存在对催化剂的脱硝和脱汞过程均起到抑制作用.利用XRD、H2-TPR和XPS等表征手段对硫中毒反应前后的催化剂进行了研究.结果表明,硫酸盐在催化剂表面的不断沉积和活性组分Mn4+及化学吸附氧Oa的消耗乃是致使催化剂失活的主要原因;另外,SO2与NH3和HHg0对催化剂表面活性位点的竞争吸附,也严重抑制催化剂的脱硝和脱汞反应.Mo-Mn/TiO2的脱硝过程是通过Mn价态之间的相互转化来完成的,其中元素Mo和O2是其转化得以实现的助剂;Mo-Mn/TiO2对汞的脱除以催化氧化为主,金属氧化物中的晶格氧将Hg0转化为HgO而被脱除.%Mo/Mn-TiO2 catalysts were prepared by impregnation method,the effects of reaction temperature,HCl and SO2 on denitrification and mercury removal from simulated flue gas being studied.The studies showed that,too high reaction temperature was not conducive to the removal of mercury,and too low temperature inhibited the denitrification reaction,but the best efficiency of denitdfication and mercury removal can be obtained at 200℃.The addition of HC1 can promote the oxidation of mercury,but significantly decrease the rate of NO conversion.The presence of SO2 in the flue gas played an inhibitory role in the process of denitfification and mercury removal.The catalysts,which before and after the reaction of sulfur poisoning,were studied by XRD,H2-TPR and XPS.The results showed that the continuous deposition of sulfate on the catalyst surface and the consumption of active component Mn4+ and chemical oxygen Oa were the main reasons for the deactivation of the catalyst.In addition,the competitive adsorption of SO2 with NH3 and Hg.on the surface active sites of the catalyst also severely inhibited the denitration and mercury removal.The denitration process of Mo-Mn/TiO2 was accomplished by the conversion of Mn valence states,among which both Mo and O2 were the assistant for the conversion.The removal of mercury by Mo-Mn/TiO2 was mainly catalytic oxidation,the lattice oxygen in the metal oxide transforms Hg.into HgO and was removed.