Synthesis and Mössbauer spectroscopic investigation of copper-manganese ferrite catalysts for water-gas shift reaction and methanol decomposition. (November 2017)

• Record Type: Journal Article
• Authors: Velinov, Nikolay; Petrova, Tanya; Genova, Izabela; Ivanov, Ivan; Tsoncheva, Tanya; Idakiev, Vasko; Kunev, Boris; Mitov, Ivan
• Is Part Of: Materials research bulletin. Volume 95(2017)
• Page Start: 556
• Page End: 562
• Publication Date: 2017-11
• Subjects: A. Oxides -- B. Chemical synthesis -- C. Mössbauer spectroscopy -- D. Catalytic properties; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2017.06.019
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: Mössbauer spectroscopy reveals changes in cation distribution with Cu/Mn variation. Partial reduction of Fe3+ to Fe2+ and formation of magnetite or Mn-substituted magnetite is established after WGSR. Cu0.8Mn0.2Fe2O4 exhibits highest activity and stability in WGSR. more reductive medium during MD leads to further reduction of Mn-substituted magnetite phases to χ-Fe5C2 and Mn-reach oxides. Cu1-xMnxFe2O4 reveal higher catalytic activity in MD compared to CuFe2O4 and MnFe2O4. Abstract: Copper-manganese ferrites with nominal compositions Cu1-х Mnх Fe2 O4, where x = 0; 0.2; 0.4; 0.6; 0.8 and 1 are synthesized by sol-gel auto-combustion method. Formation of ferrites with cubic spinel structure and crystallite size of 11–26 nm was observed. A decrease of iron located in tetrahedral positions with the increase of Mn content in ferrite structure was found. The prepared ferrite materials are tested as catalysts in water-gas shift reaction (WGSR) and methanol decomposition (MD). The samples are arranged according the WGS activity in following order: Cu0.8 Mn0.2 Fe2 O4 > Cu0.5 Mn0.5 Fe2 O4 > CuFe2 O4 > Cu0.2 Mn0.8 Fe2 O4 > MnFe2 O4 . All mixed copper-manganese ferrites exhibit higher catalytic activity in methanol decomposition as compared to single CuFe2 O4 and MnFe2 O4 ones. A significant phase transformation with ferrites under the reduction reaction medium which influences the formation of real catalytic active phase is registered. Formation of magnetite or Mn-substituted magnetite is registered during the WGSR, while iron carbides and Mn-rich oxides are the dominant phases during the MD reaction.