Oxide support wetting

Two or more soHd catalyst components can be mixed to produce a composite that functions as a supported catalyst. The ingredients may be mixed as wet or dry powders and pressed into tablets, roUed into spheres, or pelletized, and then activated. The promoted potassium ferrite catalysts used to dehydrogenate ethylbenzene in the manufacture of styrene or to dehydrogenate butanes in the manufacture of butenes are examples of catalysts manufactured by pelletization and calcination of physically mixed soHd components. In this case a potassium salt, iron oxide, and other ingredients are mixed, extmded, and calcined to produce the iron oxide-supported potassium ferrite catalyst. 

Sc, Al, Th Zr", and Si, have been prepared according to the wetness impregnation method to investigate their effects on thermal stability of ceria. These impregnation methods are. of course, useful to synthesize ceria-based oxides supported on another oxides such as silica and alumina. The most advantage of the method is that highly dispersion is obtained. 

A series of gallium oxide supported catalysts was prepared by incipient wetness impregnation of a 7-AI2O3 (surface area 108 m. g, non porous, reference Oxid C from Degussa) with appropriate amounts of an aqueous solution of Ga(N03)3,9H20. 

Samples of Cu-Ce oxides are prepared by incipient wetness impregnation method. Cerium hydroxide is precipitated by adding cerium nitrate to a concentrated solution of NaOH. The precipitate is thoroughly washed with warm water, filtered and dried at 373 K before its calcination at 673 K for 6 hours in a flow of dry air. Copper nitrate of different amounts is then impregnated, at room temperature, on the oxide support. The samples are dried at 373 K and calcined at 673, 873 or 1073 K for 6 hours in a flow of dry air. Samples are denoted by lCuxCe673, lCuxCe873 and lCuxCel073 where x indicates the atomic ratio of cerium to copper in the solid, and the last number indicates the calcination temperature value of the sample. 

A new catalyst for the selective oxidation of hydrogen sulfide in Claus tail gas to elemental sulfur has been developed. The catalyst consists of highly dispersed iron oxide supported on a silica carrier. During operation the activity of this catalyst decreases due to transformation of iron(III) oxide into a less active component. X-ray diffraction, wet chemical qualitative analysts and Mossbauer spectroscopy reveal the component comprises iron(II) sulfate. Although the transformation of inon(III) oxide into iron(IQ sulfate causes deactivation, the increase in selectivity results in high sulfur yields (up to 94%). 

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