Abatement of diesel exhaust pollutants: NOx adsorption on Co,Ba,K/CeO2 catalysts
Abatement of diesel exhaust pollutants: NOx adsorption on Co,Ba,K/CeO2 catalysts
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DOI：
10.1016/s0021-9517(03)00285-9
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发表时间：
2003-12
影响因子：
7.3
通讯作者：
V. Milt;C. Querini;E. Miró;M. Ulla
中科院分区：
文献类型：
--
作者：
V. Milt;C. Querini;E. Miró;M. Ulla
Co,Ba，K/ ceo_2体系是一种潜在的候选体系，可用于同时减排烟尘和nox柴油废气。在这项工作中，我们研究了nox与上述固体的相互作用。no2在Ba、K/ ceo2表面被强烈吸附，形成Ba和K硝酸盐，在He气氛下直至490℃均保持稳定。然而，当Co加入体系（Co,Ba，K/ ceo2催化剂）时，Ba硝酸盐在NO+ o2和He气氛下在约370°C时变得不稳定。DRX、FTIR和LRS表征表明，在400℃煅烧的Co、Ba、K/ ceo2催化剂中，钾有利于bacoo2.93钙钛矿的形成。当K （Co，Ba/ ceo2体系）不存在时，检测不到这种钙钛矿结构。Co,Ba，K/ ceo_2经NO+ o2处理后的FTIR光谱表明，表面n结合的硝酸盐（OBa—NO2）形成，其中NO2作为路易斯碱。由于在不含BaCoO2.93的样品中未检测到上述物质，因此建议它们与钙钛矿结构中的Ba原子有关。微量平衡实验结合FTIR和质谱表征表明，Co,Ba，K/ ceo2样品中形成的硝酸盐在还原气氛下可以很容易地分解成n2，这使得该体系非常有兴趣用作nox催化捕集器。另一方面，在He气氛下，硝酸盐的分解只产生气态氮氧化物。另外，当在NO+ o2气氛下处理的Co，Ba，K/ ceo2催化剂与烟尘紧密混合，然后在He中加热至490℃时，烟尘颗粒被表面硝酸盐部分氧化。
The Co,Ba,K/CeO2system is a potential candidate to be used under the simultaneous abatement of soot and NOxin diesel exhausts. In this work, we study the interactions of NOxwith the said solid. NO2is strongly adsorbed on the Ba,K/CeO2surface through the formation of Ba and K nitrate species which are stable under He atmosphere up to 490°C. However, when Co is incorporated to the system (Co,Ba,K/CeO2catalyst), Ba nitrates become unstable at ca. 370°C, under both NO+O2and He atmosphere. DRX, FTIR, and LRS characterization shows that potassium favors the formation of the BaCoO2.93perovskite in the Co,Ba,K/CeO2catalyst calcined at 400°C. This perovskite structure is not detected when K is absent (Co,Ba/CeO2system). FTIR spectra of Co,Ba,K/CeO2treated with NO+O2indicate the formation of surface N-bound nitrate species (OBa--NO2), where NO2acts as a Lewis base. Since the said species are not detected in the samples without BaCoO2.93, it is suggested that they are related to the Ba atoms of the perovskite structure. Microbalance experiments combined with FTIR and mass spectroscopy characterization show that the nitrate species formed in the Co,Ba,K/CeO2sample can be readily decomposed to N2under a reducing atmosphere, making this system very interesting to be used as a NOxcatalytic trap. On the other hand, under He atmosphere the decomposition of nitrates only produces gaseous NOx. In addition, when the Co,Ba,K/CeO2catalyst previously treated under NO+O2atmosphere is intimately mixed with the soot and then heated in He up to 490°C, the soot particulates are partially oxidized by the surface nitrate species.