XRD characterization of interaction between potassium promoter and magnetite

Abstract

Interactions of the potassium promoter with different kinds of iron oxide as the active component of the catalyst for ethylbenzene dehydrogenation were investigated and compared with each other. By means of XRD method, it was found that magnetite in the form of the inverse spinel structure interacted easily with the potassium promoter to form potassium polyferrate in comparison to hematite with the corundum structure. In the Fe3O4-K2O system, the phase of potassium polyferrate could be formed at temperature of similar to 700 degrees C, while for the alpha-Fe2O3 - K2O system, the temperature as high as similar to 850 degrees C was required for the formation of the potassium polyferrate phase. Moreover, incorporation of the potassium promoter into the magnetite (Fe3O4) would be in favor of inhibiting the oxidation of Fe3O4 to alpha-Fe2O3 in the process of calcination in air, as evidenced by the experimental fact that pure Fe3O4 could be converted into alpha- Fe2O3 by calcination in air at a temperature as low as similar to 300 degrees C, whereas for the system of Fe3O4-K2O (10%), a calcination temperature not lower than similar to 700 degrees C was required for realizing this conversion. Thus, it could be suggested that the potassium polyferrate was probable to serve as a storage phase for potassium in the catalyst of ethylbenzene dehydrogenation to styrene.