Weijie Ji, Shikong Shen, Shuben Li, Hongli Wang

Weijie Ji, Shikong Shen, Shuben Li and Hongli Wang Lanzhou Institute of Chemical Physics, 730000, PR China 

A somewhat slow but controllable impregnation method with the dipping of support into an excess of aqueous solution of (NH4)3[Fe(C204)3].xH20 is adopted to prepare well-dispersed or monolayer-type ferric oxide on various supports. Other methods with the same and other conditions are also used to make a comparison among them. The influences on the adsorption process are investigated and the suitable conditions are determined for the different supported systems. Extensive characterization has been done on the physico-chemical properties of these systems. The catalytic performances for different test reactions are also carri out on the various supported systems with distinctly different dispersions. 

Much attention has been devoted in recent litraatuie to the phenomenon of interaction between oxides (refs. 1-3). The supported oxides in the form of three-dimensional crystallites whose properties are similar to bulk crystals, do not interact strongly with the support. However, when the oxide is dispersed in monolayer on the oxidic supports, the interacdon between them becomes strong and the properties of such monolayer of the oxide differ from those of bulk oxide. Growth of three dimensional crystallites occurs only after a substantial fraction of the surface is covered by the monolayer and this is often the case for the oxides of Cr, Mo, W, V, Re and Ni. Extensive studies have been devoted to these systems. For other systems, however, the slate of dispersion is complicated, depending on the nature of the support, the preparative method and the conditions used in such process. In this paper, we tried to prepare well-dispersed iron oxide supported on various supports by different methods and investigate the physico-chemical properties of these iron oxides. 

The supports employed in this study are 7-AI2O3 (225 m /g), MgO (23 m /g), ZrOa (16 m /g), Ti02 (43 rrfl/g) and ZnO Ti02 (anatase) was prepared by hydrolysis of TiCLi. The other chemicals used are commercial products of analytical grade. Three methods were used to prepare the supported oxides. 

The loadings of Fe were determined by atomic absorption spectroscopy or chemical analysis. BET surface areas were measured by N2 adsorption at 77 K. XRD measurements were operated on a Rigaku/D/MAX-RB X-ray diffractometer with Cu Kot. 

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