La0.7Sr0.3Co1-xFexO3催化剂氮氧化物储存及抗硫性能

采用溶胶-凝胶法通过在静态空气中700°C焙烧制备了不同Fe掺杂量的La0.7Sr0.3Co1-xFexO3(x=0,0.2,0.6,1.0)系列钙钛矿催化剂.考察了Fe掺杂量对催化剂的结构、氮氧化物储存、抗硫及再生性能的影响.研究结果表明:在La0.7Sr0.3CoO3钙钛矿B位用Fe部分取代Co,可有效提高SrCO3物相的分散,X射线衍射(XRD)结果显示样品中基本为钙钛矿物相.随着Fe掺杂量的增加,催化剂的NOx储存量(NSC)下降.对预硫化样品进行NOx储存测试,发现La0.7Sr0.3CoO3催化剂由于表面沉积了硫酸盐,同时钙钛矿结构也遭到了部分破坏,使得NOx储存量和NO氧化能力均大幅度下降,NOx储存量下降了64.2%,NO-to-NO2转化率从72.8%降至43.4%.掺杂Fe元素后,催化剂的抗硫性能都有不同程度的提高,特别是Fe掺杂量为60%的样品具有最佳的抗硫性能和可再生性能.与新鲜样品相比较,再生后样品的NOx储存量仅下降16.6%,而NO-to-NO2转化率为69.1%,几乎与新鲜样品相同.

The Performance of the NOx Storage Capacity and Sulfur Tolerance of the La0.7Sr0.3CO1-xFexO3 Catalyst

In this paper,a series of La0.7Sr0.3Co1-xFexO3(x=0,0.2,0.6,and 1.0) catalysts was synthesized by a sol-gel method with calcination at 700 ℃ in static air.The effect of the Fe doping on the structure,the performance of the NOx storage,sulfur tolerance and regeneration of the perovskite catalysts was investigated.Our results showed that the partial substitution of Co with Fe improved the depersion of the SrCO3 phase,and that the perovskite phase became the only species detected from the X-ray diffraction(XRD) patterns.The NOx storage capacity(NSC) of the catalysts dropped following an increase in the proportion of Fe doping.The deposition of sulfate on the surface and the partial structural damage of the La0.7Sr0.3CoO3 catalyst led to a dramatic reduction in the NSC and the NO oxidation capacity after the sulfation treatment:the NSC being reduced by 64.2%,and the conversion of NO-to-NO2 falling to 43.4% from 72.8%.The sulfur tolerance of the perovskite catalyst,however,was improved after doping with Fe at the B sites of the La0.7Sr0.3CoO3 catalyst.Of all of these catalysts,the perovskite with 60% of Fe doping(the Fe60 sample) gave the best performance for sulfur tolerane properties and regeneration ability.The NSC of the Fe60 sample was reduced by only 16.6%,and the NO-to-NO2 conversion reached the value almost similar to that of the fresh sample(i.e.69.1%).