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为了阐明Fe_2O_3-Sb_2O_4复合氧化物催化剂在丙烯氨氧化中的催化性能,我们采用X线衍射、穆斯堡尔谱和XPS对有、无载体的不同锑铁比和焙烧温度的一系列催化剂进行了研究.X线衍射测定表明,这些样品中都有FeSbO_4,并且a-Fe_2O_3或Sb_2O_4的出现与Sb/Fe有关.催化剂的穆斯堡尔谱都有一对由FeSbO_4中顺磁Fe~(3+)引起的双峰;只有在Sb/Fe<1时,才有a-Fe_2O_3的典型六线谱出现.经800℃焙烧的Sb/Fe>1催化剂还都展现出由FeSb_2O_6中Fe~(2+)引起的另一对双峰.根据对富锑催化剂的XPS分析,结合能为709.3电子伏特的肩峰的出现,又进一步证明这种含Fe~(2+)的新活性组分FeSb_2O_6的存在.丙烯转化速度与Fe~(3+)/Fe~(2+)的关系表明,催化剂的催化性能不只取决于一种活性组分.以丙烯腈的生成速度与Fe~(3+)和Fe~(2+)的浓度关系可以得出结沦:FeSbO_4是基本活性组分,而在其上生成含Fe~(2+)新相则可能是使催化剂具有选择氧化作用的原因.
In order to elucidate the catalytic performance of the Fe 2 O 3 -Sb 2 O 4 composite oxide catalyst for the ammoxidation of propylene, a series of catalysts with and without antimony-iron ratio and calcination temperature were carried out by X-ray diffraction, Mossbauer spectroscopy and XPS X-ray diffraction analysis showed that FeSbO_4 was present in these samples, and the presence of a-Fe_2O_3 or Sb_2O_4 was related to Sb / Fe.The Mossbauer spectra of the catalysts showed a pair of transitions consisting of para- The typical six-line spectrum of a-Fe 2 O 3 appeared only when Sb / Fe <1. The Sb / Fe> 1 catalyst calcined at 800 ℃ also showed the Fe 2+ content in FeSb 2 O 6, , Another pair of bimodal peaks.According to the XPS analysis of the antimony-rich catalyst, the presence of a shoulder peak with an energy of 709.3 eV further proves the existence of FeSb_2O_6, a new Fe 2+ -containing active component. The relationship between the conversion rate of propylene and Fe ~ (3 +) / Fe ~ (2+) shows that the catalytic performance of the catalyst depends not only on an active component, but also on the reaction rate of Fe 3+ and Fe ~ (2+), we can conclude that FeSbO_4 is the basic active component, while the new phase containing Fe 2+ may be the catalyst with Select the cause of oxidation.