Some features of phase formation in the system magnetite-potassium carbonate

Abstract

The solid-phase interaction in the system Fe3O4–K2CO3 was studied. INORGANIC SYNTHESIS AND INDUSTRIAL INORGANIC CHEMISTRY ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 6, pp. 921–924. © Pleiades Publishing, Ltd., 2011. Original Russian Text © O.I. Akhmerov, V.V. Vlasov, Kh.E. Kharlampidi, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 6, pp. 898–901. The catalysts containing iron and potassium oxides are widely used in dehydrogenation of alkylaromatic and olefin hydrocarbons and in a number of other catalytic processes. The phase composition of promoted iron oxide catalysts is important in view of the development of scientific methods of synthesis, optimization of technological process, targeted selection of additives that stabilize the active phase, and determination of the mechanism of the catalytic process. Study of these catalysts is continuing for many years. However, the nature of the active component of a catalyst and the phase composition of compounds formed in the iron-potassium-oxygen system during the synthesis and operation of the catalyst remain controversial [1–5] The study of phase composition of the iron oxide catalytic systems modeling the process of dehydrogenation of hydrocarbons showed that the active components are alkali metal ferrites, such as potassium monoand polyferrites [1]. A suggestion is made to realize the redox mechanism of the process with the formation of oxide iron compounds in various oxidation states. The main component of the catalyst in the dehydrogenation reaction is magnetite, which is in equilibrium with hematite (α-Fe2O3) [2]. The data of [4] suggest that the activity and stability of the catalyst depend on the ratio of potassium mono to poly ferrite, as well as magnetite. The authors of numerous publications concerning the chemical composition of iron oxide dehydrogenation catalysts emphasize the crucial importance of the influence of the valence state of iron on the activity of the catalyst. It is necessary to search for the optimal Fe(II)/Fe(III) ratio that would ensure, on the one hand, a sufficient conversion of the catalyst and, on the other hand, a high selectivity of the dehydrogenation process [3, 5].