A series of x％Mn/Ce0.7Zr0.3O2 (x=O, 5, 10, 15, 30, 50) metal oxide catalysts were prepared by complexing combustion method with citric acid. The catalysts have been investigated to remove of carbon particulate matter (PM)and nitrogen oxides (NOx) emitted from diesel engines. The samples were characterized by XRD, low temperature adsorption-desorption, H2-TPR, O2-TPD and in situ Diffuse Reflectance IR Fourier-Transform spectroscopy (in situ DRIFTs). The results indicate that the ceria-zirconia solid solutions with different Mn-doping content form the modified solid solution structures. During the catalytic reaction for simultaneous removal of PM and NOx, their catalytic performance is directly related to the oxidizing ability of these solid solution catalysts. Among them, 30％Mn/Ceo.7Zr0.3O2 catalyst has higher activity for simultaneous removal of PM and NOx. The ignition temperature and the most combustion temperature of PM are 298 and 504 ℃, and the most conversion of NO achieves 30.6％. On the basis of the experimental results of in situ DRIFTS, a reaction mechanism is proposed, which can preferably explain the reaction process of simultaneous removal of PM and NOx over 30％Mn/Ce07Zr0.3O2. Based on the results of O2-TPD and in situ DRIFTS, superoxide species (O2-) adsorbed on the surface of 30％ Mr/Ce0.7Zr0.3O2 and nitrate species (NO3-) are active species during the reaction of PM and NOx, and further, the formation of the isocyanate species (-NCO) is confirmed.%采用柠檬酸络合燃烧法制备了一系列x%Mn/Ce0.7Zr0.3O2(x=0,5,10,15,30,50)复合金属氧化物催化剂,对其同时去除柴油机尾气中碳烟颗粒物(PM)和氮氧化物(NOx)反应的催化活性进行了评价,并采用XRD、低温氮吸附一脱附、H2.TPR、O2-TPD和原位漫反射红外光谱(in situ DRIFTS)等技术对催化剂的性能进行了表征.结果表明,不同含量Mn掺杂人铈锆固溶体中均形成了三元固溶体催化剂,在同时去除PM和NOx的催化反应中,固溶体催化剂的催化活性与其氧化能力直接相关.其中30%Mn/Ce0.7Zr0.3O2催化剂具有较好的同时去除PM和NOz的催化活性,催化去除PM的Ti和Ym分别为298和504℃,NO的转化率达到30.6%.结合OrTPD和原位红外结果可知,30%Mn/Ce0.7Zr0.3O2表面吸附的超氧物种(O2-)及其与NO反应生成的硝酸盐物种(NO3-)是同时去除PM和NO反应的主要活性物种,进而指出PM和NO在30%Mn/Ce0.7r0.3O2表面反应过程中形成了异氰酸盐(.NC0)中间物种,在原位红外实验的基础上提出了30%Mn/Ce0.7Zr0.3O2复合氧化物催化剂同时去除PM和NOx的反应机理.
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