MnO_x和CeO_2催化剂在含NO气氛中氧化模拟碳烟的研究

Oxidation of model soot over MnO_x and CeO_2 catalysts in the presence of NO

用沉淀法制备了MnOx和CeO2两种催化剂并用于氧化模拟碳烟.XRD、BET、O2-TPD和NO-TPD表征结果表明,CeO2的比表面积和NOx吸附容量更大,而MnOx则具有更多的氧物种(晶格氧O2-).TPO结果表明,气氛中引入的NO明显促进了碳烟的氧化.在无催化剂、加入CeO2和MnOx3种情况下,模拟碳烟的起燃温度Ti分别降低了38、41和101℃.DRIFTs结果表明,催化剂活性氧物种和反应过程中生成的NO-3是NO促进碳烟燃烧的关键因子.可能的反应路径为:低温富氧条件下气相中的O2吸附在催化剂表面上,丰富的活性氧物种(如O2-、O-2和O-)得到激活和转化,进而将弱吸附NO2和活性NO*2氧化成NO-3;在高温时则释放出活性很强的NO*2和O-,因而能促进碳烟氧化,其中间产物为碳氧复合物C(O).

MnOx and CeO2 were prepared by precipitation method as catalysts for the oxidation of model soot.Characterization measurements of XRD,BET,O2-TPD and NO-TPD demonstrated that CeO2 exhibited greater surface area and NOx adsorption capacity,while more oxygen species（lattice oxygen O2-） were detected in MnOx.TPO test revealed that NO in the feeding gases remarkably promoted soot oxidation.The ignition temperature Ti for soot oxidation decreased by 38 ℃ without addition of any catalyst,and decreased by 41 ℃ and 101 ℃ in the presence of CeO2 and MnOx,respectively.In situ DRIFTs showed that the reactive oxygen species on catalysts and NO-3 formed in the reaction process were the key factors for promoting soot oxidation in the presence of NO.The possible pathways were：gaseous O2 in the O2-rich condition was adsorbed onto the surface of catalysts at low temperature,thus abundant reactive oxygen species（such as O2-,O-2 and O-）were activated and transformed;the weakly adsorptive NO2 and reactive NO＊2 were oxidized into NO-3 ;NO-3 released reactive NO2＊ and O-at high temperture in turn,therefore enhancing soot oxidation with C（O） complex as intermediates.