Temperature-dependent N2O decomposition over Fe-ZSM-5:: Identification of sites with different activity
Temperature-dependent N2O decomposition over Fe-ZSM-5:: Identification of sites with different activity
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DOI：
10.1016/j.jcat.2007.03.027
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发表时间：
2007-07-01
影响因子：
7.3
通讯作者：
Brueckner, A.
中科院分区：
文献类型：
--
作者：
Berrier, E.;Ovsitser, O.;Brueckner, A.
在H-2/Ar或473 < T < 973 K的氩气流中预还原后，在温度范围293 < T < 673 K的Fe- zsm -5上，添加0.3 wt%的框架外铁，研究了N2O的分解。N2O对被还原的Fe2+进行了两种不同的再氧化过程：(i)快速过程始于大约500 K，涉及原子氧沉积在分离的Fe2+上，导致EPR光谱检测到的Fe3+O中心点的形成（位点1）；（ii）缓慢过程主要涉及小feexoy簇的再氧化（位点2），其形成在H2/Ar流中不可避免。位点1的数量随着预还原温度的升高而增加，而位点2的数量与t -红无关。在O-2对铁的再氧化过程中，没有检测到O中心点的形成。EPR光谱首次检测到N2O对Fe2+的再氧化与O中心点-形成之间的直接关系，表明Panov等人首先描述的所谓“α -氧”是O中心点-自由基阴离子。基于原位XANES实验，这使得先前讨论的铁基部分（Fe4+=O）极不可能是高活性氧的来源。(C) 2007爱思唯尔公司版权所有。
Decomposition of N2O has been studied in the temperature range 293 < T < 673 K over Fe-ZSM-5 with 0.3 wt% extra-framework Fe after prereduction in H-2/Ar or Ar flow at 473 < T < 973 K. Two different processes of reoxidation of reduced Fe2+ species by N2O were identified: (i) a fast one starting at approximate to 500 K involving deposition of atomic oxygen on isolated Fe2+ species, leading to the formation of Fe3+O center dot- sites detected by EPR spectroscopy (site 1), and (ii) a slow one related mainly to the reoxidation of small FexOy clusters (site 2), the formation of which cannot be avoided in H2/Ar flow. The number of sites I increases with rising prereduction temperature, whereas sites 2 are independent of T-red.. O center dot- formation could not be detected on reoxidation of Fe species by O-2. For the first time, a direct relation between Fe2+ reoxidation by N2O and formation of O center dot- could be detected by EPR spectroscopy, suggesting that the so-called "alpha-oxygen" first described by Panov et al. is an O center dot- radical anion. Based on in situ XANES experiments, this makes it highly unlikely that the previously discussed ferryl moiety (Fe4+=O) is the source of the highly active oxygen. (C) 2007 Elsevier Inc. All rights reserved.