【摘要】 柴油机氧化催化剂（DOC）能将尾气中部分NO氧化成NO₂,一定浓度的NO₂有利于柴油机颗粒捕集器（DPF）的连续再生和提高选择性催化还原催化剂（SCR）对NO_x的转化效率。针对DOC的新鲜态Pt/Al₂O₃ 催化剂经过1次程序升温NO催化氧化活性明显提升的现象（活化效应）,采用原位红外漫反射实验（in situ DRIFTS）、氢气程序升温还原、X射线光电子能谱（XPS）和高分辨透射电子显微镜（HR-TEM）分析Pt/Al₂O₃催化剂相关过程的物理化学状态。分析结果表明,新鲜态Pt/Al₂O₃催化剂在300℃以下时载体上积累了大量的硝酸盐和亚硝酸盐物种,导致新鲜态催化剂活性不高;进一步的分析表明经一次程序升温后催化剂中与载体结合强的PtO_x物种的分解是引起活化效应的主要原因;经过3次程序升温反应,催化剂中Pt粒子的大小没有发生明显改变。更多还原

【Abstract】 Part of NO is oxidized to NO₂ when the emission gas goes through diesel oxidation catalysts（DOC）. Proper NO₂/NO_x concentration increases the low-temperature soot oxidation rate of diesel particulate filter（DPF） and the NO_x conversion efficiency of selective catalytic reduction catalyst（SCR）. In order to study the degreening effect of DOC, in-situ diffuse reflectance infrared Fourier transform spectroscopy（In-situ DRFTS）, H₂ temperature-programmed reduction（H₂-TPR）, X-ray photoelectron spectroscopy（XPS）and High-revolution transmission electron microscope（HR-TEM） were used to characterize the Pt/Al₂O₃ catalyst. Results show that a large amount of nitrate and nitrite species are accumulated in the fresh Pt/Al₂O₃ catalysts below 300℃, which causes the low activity of fresh catalysts. The decomposition of PtO_x species that interacts strongly with the substrate is the main cause of degreening effect after one temperature-programmed reaction. The particle size of Pt has no significant change after 3-cycle temperature-programmed reaction.更多还原