Evolution of iron states and formation of α-sites upon activation of FeZSM-5 zeolites
Evolution of iron states and formation of α-sites upon activation of FeZSM-5 zeolites
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DOI：
10.1006/jcat.2002.3552
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发表时间：
2002-04-25
影响因子：
7.3
通讯作者：
Panov, GI
中科院分区：
文献类型：
--
作者：
Dubkov, KA;Ovanesyan, NS;Panov, GI
用原位穆斯堡尔谱研究了高温活化对以不同方法引入ZSM-5沸石基质中铁的析出的影响。活化过程(在空气中、真空中或在水蒸气中焙烧)导致铁的强烈还原，生成两种类型的双核Fe2+络合物，其组成的离子占总金属含量的60%以上。还原的Fe2+在O-2存在下稳定，但被一氧化二氮可逆地氧化为Fe3+，生成活性α-氧物种，这给沸石带来了独特的氧化性能。吸附水分子配位饱和后，两种铁络合物具有相同的穆斯堡尔谱，与MMO酶中双核铁位的穆斯堡尔谱相近。对参与氧化还原转变的α-氧原子和Fe原子的数量进行了全面的定量比较，结果表明，α位是两个Fe原子都能产生α-氧的双核络合物。(C)2002年埃尔塞维尔科学公司(美国)。
Mossbauer spectroscopy in situ was used to study the effect of high-temperature activation on the evolution of iron introduced into a ZSM-5 zeolite matrix by various methods. The activation process (calcination in air, in vacuum, or in the presence of water vapor) was shown to cause an intensive reduction of iron, yielding two types of dinuclear Fe2+ complexes, which may comprise ions are more than 60% of the total metal content. Reduced Fe2+ stable in the presence Of O-2 but are reversibly oxidized to Fe3+ by nitrous oxide, generating active alpha-oxygen species, which bring unique oxidation properties to the zeolite. After coordinative saturation by adsorbed water molecules, both iron complexes show identical Mossbauer spectra, which are close to the spectra of dinuclear iron sites in the MMO enzyme. A thorough quantitative comparison between the number of a-oxygen atoms and the number of Fe atoms involved in redox transition shows that alpha-sites are dinuclear complexes in which both Fe atoms are capable of alpha-oxygen generation. (C) 2002 Elsevier Science (USA).