摘要
采用共沉淀的方法合成了一系列不同CeO_2和ZrO_2质量比的催化剂(wCeO_2-(1-w)ZrO_2)并用于汽油车颗粒物的催化燃烧。采用程序控制以10°C?min^(-1)的升温速率,从室温升到850°C氧化测试催化剂的燃烧活性。同时,对催化剂进行了X射线衍射(XRD)、拉曼(Raman)光谱、氮气-吸脱附比表面(N2-BET)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)分析、储氧能力(OSC)、氢气-程序升温还原(H2-TPR)表征。经过800°C焙烧后,70%CeO_2-30%ZrO_2样品表现出最好的活性性能,其Tm(活性测试燃烧反应中燃烧产物浓度达到最大峰值铈所对应的燃烧温度)从空白样品的719°C降低到625°C。同时,70%Ce O2-30%Zr O2样品也表现出优异的热稳定性能。催化燃烧性能与催化剂的结构、表面组成特性以及氧化还原性能有关。XRD和拉曼光谱表明富铈样品具有典型的立方相结构,富锆样品具有四方相结构。XPS表明不同催化剂的Ce中Ce^(3+)的摩尔比例及表面氧与晶格氧的比例存在明显差异,其导致催化性能不同。同时,70%CeO_2-30%ZrO_2样品具有最大的储氧能力及最优异的还原性能。此外,焙烧温度的升高,70%Ce O2-30%ZrO_2样品在结构、表面组成和氧化还原能力并没有出现明显的下降和破坏,表明70%Ce O2-30%ZrO_2样品具有优良的热稳定性能。
A series of CeO2-ZrO2 mixed oxide catalysts having different mass ratios（w CeO2-（1-w）ZrO2） were prepared using a co-precipitation method and subsequently applied to the combustion of soot in gasoline engine exhaust. The soot combustion activities of the catalysts were assessed via the temperature- programmed oxidation of powder mixtures, applying steps of 10 ℃min^（-1）from room temperature to 850 ℃. These catalysts were also characterized by X-ray diffraction（XRD）, Raman spectroscopy, N2adsorption-desorption, scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS）, oxygen storage capacity（OSC）, and H2temperature-programmed reduction（H2-TPR）. After being calcined at 800 ℃, 70%Ce O2-30%Zr O2 exhibited the highest soot combustion activity, such that the maximum product concentration temperature（Tm） was decreased from 719 to 625 ℃ when employing this catalyst. The 70%CeO2-30%ZrO2 also showed excellent thermal stability, indicating that this could be an appropriate catalyst for soot combustion in gasoline direct injection engines. The differences in the soot combustion activities of the catalysts were closely related to their structures, surface compositions, and redox properties. XRD and Raman data demonstrated that the ceriumrich samples presented a typical cubic phase, while a tetragonal phase was observed in the case of the zirconium-rich samples. XPS showed that the molar fraction of Ce^（3＋）in total Ce and the molar fraction of surfaceadsorbed oxygen to lattice oxygen on the surfaces of various samples differed, and these variations induced their different catalytic activities. The 70%CeO2-30%ZrO2 sample showed the largest OSC value and the most pronounced reduction properties. This same material was also found to have excellent thermal stability with regard to structure, surface composition, and redox properties, as reflected in the minimal degradation of the soot combustion activity of this catalyst with increasing calcination temperature.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2016年第7期1747-1757,共11页
Acta Physico-Chimica Sinica
基金
supported by the National High-Tech Research and Development Program of China(863)(2015AA034603)~~
关键词
铈锆固溶体
碳烟燃烧
汽油缸内直喷
汽油车颗粒物器
氧浓度
Cerium-zirconium mixed oxide
Soot combustion
Gasoline direct injection
Gasoline particulate filter
Oxygen concentration
