穆斯堡尔谱学
程序升温还原
分析化学(期刊)
化学
催化作用
X射线晶体学
衍射
穆斯堡尔效应
结晶学
相(物质)
物理
生物化学
有机化学
色谱法
光学
作者
Huiliang Zhang,Jianyi Shen,Xinlei Ge
标识
DOI:10.1006/jssc.1995.1255
摘要
The reduction processes of Fe-Mo-O catalysts with different Fe/Mo atomic ratios were studied by means of temperature-programmed reduction (TPR). In particular, the reduction process of a sample with an Fe/Mo ratio of 0.29 was investigated in detail in combination with in situ Mössbauer spectroscopy (MBS) and X-ray diffraction (XRD). Five peaks are observed in the TPR profile of this sample with peak temperatures at 853, 910, 952, 1014, and 1233 K, respectively, indicating that the reduction of the catalyst proceeds via five stages. MBS and XRD showed that the phases in the sample are MoO3 and Fe2(MoO4)3 before TPR. At the first TPR peak (853 K), Fe2(MoO4)3 was completely transformed into β-FeMoO4 and Mo4O11, while MoO3 was not affected. The β-FeMoO4 phase that formed can convert to α-FeMoO4 when the reduced sample is exposed to air at room temperature. The second TPR peak (910 K) corresponds to the reduction of MoO3 to MoO2. At the third TPR peak (952 K), Mo4O11 was reduced to MoO2 and most of the β-FeMoO4 was transformed to Fe2Mo3O8 and Fe3O4. The Mössbauer spectrum of FeMo3O8 can be fitted with two doublets (IS = 0.90 mm/sec, QS = 0.58 mm/sec and IS = 1.03 mm/sec, QS = 1.05 mm/sec). It is interesting to note that at this stage some Fe2+ ions were reoxidized to Fe3+, and Fe3O4 is formed, probably due to the reaction between Mo6+ and Fe2+ in β-FeMoO4. At the fourth TPR peak (1014 K), β-FeMoO4 was completely converted and the Fe-Mo alloy (a singlet in the Mössbauer spectrum with IS = -0.21 mm/sec) was formed, resulting from the reduction of MoO2 and Fe3O4 or Fe2Mo3O8. At the last peak (1233 K), all the metal oxides (MoO2 and Fe3O4 or Fe2Mo3O8) were reduced to metals. The products detected are Fe3Mo alloy and metallic molybdenum.
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