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SYNTHESIS OF IRON OXIDE FROM METAL POWDERS

A comparative analysis of various methods for obtaining highly dispersed iron oxides has been carried out. The advantages and disadvantages of traditional and developing methods of synthesis of iron oxides for catalysts, sorbents and ceramic materials are identified. The advantages of the method of mechanochemical synthesis of obtaining highly dispersed iron oxides for catalysts for the medium-temperature conversion of CO in the production of ammonia and the oxidation of methanol to formaldehyde are shown. The methods of X-ray phase, X-ray structural, synchronous thermal analysis and Mössbauer spectroscopy were used to study the process of mechanochemical oxidation of iron and cast iron powders in order to obtain iron oxides. The phase composition and specific surface area of the obtained oxides are investigated. It was found that in the process of mechanical activation of iron-containing powders in the aquatic environment, the system Fe-Fe3O4-FeOOH is formed. Heat treatment at 450 °C for 6 h causes decomposition of FeOOH to α-Fe2O3 and partial oxidation of metallic iron. By the method of differential dissolution, it was established that the cast iron in the presence of water in a roller-ring vibratory mill for 60 min is oxidized to 77.6%, and the iron is oxidized to 88%. Also in the process of dissolving metal powders in oxalic acid solutions using ultrasound FeC2O4 · 2H2O is formed, which under the conditions of thermolysis decomposes to maghemite – γ-Fe2O3 with the release of CO and CO2, and at 400 °C to hematite – α-Fe2O3. The possibility of using the produced iron oxides for obtaining iron-chromium catalysts for the medium-temperature conversion of CO in the production of ammonia and iron-molybdenum catalysts for formaldehyde synthesis is shown. The CO degree conversion is 92.0% at 340 °C, and the productivity by formaldehyde is 13.0 µmol/(g∙s).