Application of Mössbauer spectroscopy in industrial heterogeneous catalysis: effect of oxidant on FePO₄ material phase transformations in direct methanol synthesis from methane

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• 作者：Venkata D. B. C. Dasireddy ; Faiza B. Khan ; Darko Hanzel…
• 关键词：Methane ; Direct methanol synthesis ; Mössbauer spectroscopy ; Iron phosphate catalyst ; Nitrous oxide reactant ; Reduction ; Oxidation ; XRD
• 刊名：Hyperfine Interactions
• 出版年：2017
• 出版时间：November 2017
• 年：2017
• 卷：238
• 期：1
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Nuclear Physics, Heavy Ions, Hadrons; Atomic, Molecular, Optical and Plasma Physics; Condensed Matter Physics; Surfaces and Interfaces, Thin Films;
• 出版者：Springer International Publishing
• ISSN：1572-9540
• 卷排序：238

文摘

The effect of the FePO₄ material phase transformation in the direct selective oxidation of methane to methanol was studied using various oxidants, i.e. O₂, H₂O and N₂O. The phases of the heterogeneous catalyst applied, before and after the reactions, were characterized by M¨ossbauer spectroscopy. The main reaction products were methanol, carbon monoxide and carbon dioxide, whereas formaldehyde was produced in rather minute amounts. The Mössbauer spectra showed the change of the initial catalyst material, FePO₄ (tridymite-like phase (tdm)), to the reduced metal form, iron(II) pyrophosphate, Fe₂P₂O₇, and thereafter, the material phase change was governed by the oxidation with individual oxidizing species.Mössbauer spectroscopy measurements applied along with X-ray diffraction (XRD) studies on fresh, reduced and spent catalytic materials demonstrated a transformation of the catalyst to a mixture of phases which depended on operating process conditions. Generally, activity was low and should be a subject of further material optimization and engineering, while the selectivity towards methanol at low temperatures applied was adequate. The proceeding redox mechanism should thus play a key role in catalytic material design, while the advantage of iron-based heterogeneous catalysts primarily lies in them being comparably inexpensive and comprising non-critical raw materials only.