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研究了低于300°C时两种氧化铈对稀燃阶段NOx存储性能的影响,催化剂由2%(w)Pt/Al2O3(PA)与CeO2-X(X=S,I)机械混合制备.X射线衍射(XRD),BET表面积和扫描电子显微镜(SEM)用于表征材料的物理结构.X射线光电子能谱(XPS)和H2程序升温还原(H2-TPR)用于表面Ce3+和活性氧定量.原位漫反射傅里叶变换红外光谱(in-situ DRIFTS)用于分析表面NOx吸附物种.相比于CeO2-I,CeO2-S具有优良的物理化学性能,包括高比表面积、丰富的空隙结构、较高的抗老化能力及表面Ce3+浓度.因而,Pt/Al2O3+CeO2-S表现出优异的NOx存储能力.此外,PA+CeO2-X(X=S,I)上存在Pt与CeO2之间的相互作用,可提高表面氧物种的活性进而促进NO氧化及NOx存储.PA+CeO2-S上的这种相互作用要强于PA+CeO2-I.研究表明,表面Ce3+浓度和活性氧含量对NOx存储起到重要作用.然而经过水热处理后,Pt与老化的氧化铈(ACS,ACI)之间的相互作用降低,并且两种氧化铈NOx存储性能显著下降.另外,与PA+ACS(ACI)相比,PA+PACS(PACI)样品NOx存储能力得到改善,这归因于表面氧物种活性增加能促进硝酸盐的形成.
The effect of two kinds of cerium oxide on NOx storage performance at lean burn stage was studied when the temperature was below 300 ° C. The catalyst was prepared by mechanical mixing of 2% (w) Pt / Al2O3 (PA) with CeO2-X (X = S, I) X-ray diffraction (XRD), BET surface area and scanning electron microscopy (SEM) were used to characterize the physical structure of the material.X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) were used to quantify the surface Ce3 + and reactive oxygen species In-situ DRIFTS was used to analyze surface NOx adsorbed species, which possessed excellent physico-chemical properties, including high specific surface area and abundant voids compared to CeO2-I Structure, high anti-aging ability and surface Ce3 + concentration, Pt / Al2O3 + CeO2-S exhibits excellent NOx storage capacity.In addition, there are Pt and CeO2 present on PA + CeO2-X The interactions between PA + CeO2-I and PA + CeO2-S can enhance the activity of surface oxygen species and promote NO oxidation and NOx storage. The results show that the surface Ce3 + concentration and reactive oxygen species NOx storage plays an important role.However, after hydrothermal treatment, the interaction between Pt and aged cerium oxide (ACS, ACI) decreases, and the two kinds of ceria NOx storage In addition, the NOx storage capacity of the PA + PACS (PACI) samples was improved compared to PA + ACS (ACI) due to the increased surface oxygen species activity that promoted nitrate formation.