Fe改性Mn/CeO_(2)催化剂低温下同时脱硝与脱甲苯实验研究

Experimental study of Fe modified Mn/CeO_(2)catalyst for simultaneous removal of NO and toluene at low temperature

本研究采用浸渍法制备了Fe改性的Mn/CeO_(2)催化剂,并测试了催化剂在低温条件下同时脱硝与脱甲苯的性能。结果表明,Fe_(5)Mn/CeO_(2)催化剂表现出最佳的催化性能,甲苯的转化效率在175℃达到90%,NO转化率在95–300℃达到90%。通过BET、SEM、XRD、XPS、H_(2)-TPR、NH_(3)-TPD和O_(2)-TPD等表征手段对催化剂的理化性质进行分析。XPS结果表明,Fe_(5)Mn/CeO_(2)催化剂中Ce^(3+)和Mn^(4+)的含量增加,促进氧空位和不饱和化学键的形成,提供了更多的活性位点,从而有利于在低温下高效脱除NO和甲苯。H_(2)-TPR、NH_(3)-TPD和O_(2)-TPD表征表明,与其他催化剂相比,Fe_(5)Mn/CeO_(2)催化剂具有优异的氧化还原能力、更强的酸性和更好的氧迁移能力。此外,本研究还探究了Fe_(5)Mn/CeO_(2)催化剂上选择性催化还原(NH_(3)-SCR)反应与甲苯催化氧化反应之间的影响。其中,NH_(3)优先吸附活性位点而抑制了甲苯吸附,而NO_(2)的生成促进了甲苯催化氧化反应;甲苯对NH_(3)-SCR反应的抑制作用随着温度的升高而减弱,在100℃时,甲苯对NH_(3)-SCR反应的抑制作用消失。超过225℃后,甲苯作为还原剂与NO发生反应且促进了NO_(2)的生成,从而对NH_(3)-SCR反应有促进作用。

A series of Mn/CeO_(2)catalysts modified with different Fe contents were prepared by impregnation method and tested for their low-temperature performance for simultaneous de-nitrification and toluene removal.It was found that the Fe_(5)Mn/CeO_(2)catalyst showed the best catalytic performance and the conversion efficiency of toluene reached 90%at 175℃and NO conversion reached 90%at 95−300℃.The physical and chemical properties of the catalysts were characterized by BET,SEM,XRD,XPS,H_(2)-TPR,NH_(3)-TPD and O_(2)-TPD.XPS results showed that the increased content of Ce^(3+)and Mn^(4+)in the Fe_(5)Mn/CeO_(2)catalyst promoted the formation of oxygen vacancies and unsaturated chemical bonds,providing more active sites,thus facilitating the efficient removal of NO and toluene at low temperatures.Compared with other catalysts,H_(2)-TPR,NH_(3)-TPD and O_(2)-TPD indicate that Fe_(5)Mn/CeO_(2)catalyst has great redox ability,stronger acidity and better oxygen migration ability.In addition,this paper explores the effects between selective catalytic reduction(NH_(3)-SCR)and catalytic oxidation reaction of toluene over Fe_(5)Mn/CeO_(2)catalyst.NH_(3)preferentially reacts with the active site on the catalyst to inhibit the toluene oxidation process,while NO promotes the toluene removal process.Toluene can promote the NH_(3)-SCR process in a certain temperature range.While NO promotes the formation of NO_(2),NO_(2)effectively promotes the combination of toluene and active sites,which is conducive to the catalytic oxidation of toluene;The inhibition of toluene on the NH_(3)-SCR process weakens with the increase of temperature.At 100℃,the inhibition of toluene on the NH_(3)-SCR process disappears.When the temperature exceeds 225℃,toluene reacts with NO as a reducing agent and promotes the formation of NO_(2),thus promoting the NH_(3)-SCR reaction.