STRUCTURAL FEATURES OF COPPER FERRITE-CHROMITES
L. M. Plyasova1, V. I. Zaikovskii1,2, G. N. Kustova1, T. P. Minyukova1, I. Yu. Molina1, N. V. Shtertser1,2, T. M. Yurieva1
1Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk National Research State University, Novosibirsk, Russia
Keywords: Cu-Fe-Cr шпинель, распределение катионов в структуре шпинели, структурный переход в шпинели, паровая конверсия СО, Cu-Fe-Cr spinel, distribution of cations in the spinel structure, structural transition in spinel, water gas shift reaction
Abstract
The structural features and the distribution of cations over crystallographic sites of copperchromite, copper ferrite, and mixed chromite-ferrites with the spinel structure obtained by thermal decomposition at 600°C and 900°C of mixed hydroxy compounds of copper, iron, and chromium with the composition Cu
2+/(Fe
3++Cr
3+) = 1/2 and different Fe
3+/Cr
3+ ratios are studied using a set of physicochemical methods. It is shown that the spinel-structure phases formed exist in two modifications: cubic and tetragonal, depending on the Fe
3+/Cr
3 ratio. The crystallographic relationship between the cubic and tetragonally distorted phases of spinel is analyzed. The distribution of cations over crystallographic sites, the character and degree of tetragonal distortion of Cu-Fe-Cr spinel depend on the Fe
3+/Cr
3+ ratio: when Fe
3+/Cr
3+ > 1, the ratio of unit cell parameters c */ а * > 1; when Fe
3+/Cr
3+ < 1, the ratio c */ а * < 1; when Fe
3+/Cr
3+ = 1, the spinel is cubic irrespective of the temperature of thermal treatment. The oxygen coordination of copper ions in the spinel structure has a significant effect on the catalytic properties of the samples in the low-temperature water gas shift reaction.
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