不同Sr引入方式对LaCoO3钙钛矿NOx储存-还原性能的影响

Effect of Sr Introduced by Different Preparation Methods on LaCoO3 Perovskite for NOx Storage-Reduction Reaction

为提高LaCoO3钙钛矿的NOx脱除性能,分别采用柠檬酸络合法、浸渍法和机械混合法制备了添加Sr的LaCoO3钙钛矿系列催化剂,并通过透射电镜(TEM)、X射线粉末衍射(XRD)和红外(FT-IR)技术对催化剂进行了表征,考察了不同制备方法对催化剂的结构和性能的影响。结果表明,加入Sr后催化剂的NOx脱除效率大大提高。柠檬酸络合法得到的样品中部分Sr取代La进入钙钛矿晶格中,表面的SrCO3总量较少;机械混合法得到的样品中SrCO3晶粒较大,NOx储存速率和释放速率都很缓慢;浸渍法得到的样品中SrCO3晶粒小,储存快,与氧化还原中心的协同作用强,NOx脱除效率最高。

In order to improve the NOx removal efficiency of the LaCoO3 perovskite, a series of Sr-introduced LaCoO3 perovskites were prepared by three different methods of citrate acid complex method(CA), incipient impregnation method(IM) and mechanical blending method(MB). The corresponding samples were characterized by TEM, XRD and FT-IR techniques to carefully investigate the influence of different preparation methods on the structure and reactivity of the catalysts. The results show that Sr addition greatly increased the NOx removal efficiency of the catalysts. As for the LSC-CA sample, a portion of the introduced Sr entered into the perovskite lattice so that the amount of surface SrCO3 was less than the nominal value. The SrCO3 grains in the LSC-MB sample had bigger sizes than those in the LSC-CA and LSC-IM samples, resulting in slower NOx trapping and releasing rate. The LSC-IM sample had plenty of surface SrCO3 with small grain size, which could easily trap NOx and cooperate with the oxidation-reduction center. Therefore, among the three samples, the LSC-IM sample achieved the highest NOx removal efficiency.