Acta Phys. -Chim. Sin. ›› 2000, Vol. 16 ›› Issue (02): 126-132.doi: 10.3866/PKU.WHXB20000207

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XRD Characterization of Interaction between Potassium Promoter and Magnetite

Zhu Yi-Xiang, Chai Yun-Zhou, Liu Zheng-Yang, Huang Su-Mei, Cheng Xiang-Ming   

  1. State Key Laboratory for Physical Chemistry of the Solid Surfaces Department of Chemical Engineering Institute of Physical Chemistry,Xiamen University,Xiamen 361005
  • Received:1999-04-23 Revised:1999-07-26 Published:2000-02-15
  • Contact: Zhu Yi-Xiang

Abstract:

Interactions of the potassium promoter with different kinds of iron oxide as the active component of the catalyst for ethylbenzene dehydrogenation we re 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 ~700℃,while for the α Fe2O3 K2 O system, the temperature as high as ~850℃was required for the formation of the potassium polyferrate phase. Moreover, incorporation of the potassium promoter in to the magnetite(Fe3O4) would be in favor of inhibiting the oxidation of Fe3O4 t o α Fe2O3 in the process of calcination in air, as evidenced by the experimental fact that pure Fe3O4 could be converted into α-Fe2O3 by calcination in air a t a temperature as low as ~300℃,whereas for the system of Fe3O4 K2O (10%),a calcination temperature not lower than ~700℃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. 

Key words: Ethylbezene, Dehydrogenation, Iron oxide, Catalyst, Potassium promoter, Ferrate