Showing papers by "Frank S. Stone published in 1996"
TL;DR: In this paper, the authors show that CO adsorption on the outgassed oxide occurs with rapid formation of carbonite CO22− ions, accompanied by a slow reaction forming reduced oligomeric (CO)n2− anions and carbonate CO32− ions.
Abstract: Microcrystalline La2O3 outgassed at 873 K has a UV absorption edge centred at ca. 250 nm on which absorption ascribable to surface states is superimposed. This latter absorption is diminished by CO2 adsorption, which produces surface carbonate. UV reflectance and IR results with CO are correlated to show that CO adsorption on the outgassed oxide occurs with rapid formation of carbonite CO22– ions, accompanied at room temperature by a slow reaction forming reduced oligomeric (CO)n2– anions and carbonate CO32–. The reaction stages have been resolved by extending the UV and IR measurements to low temperatures. CO22–, identified by UV absorption at 340 nm and IR bands at 1390 and 987 cm–1, is the only process occurring at 90 K. As the temperature is increased, the ketenic dimer anion C2O32– is formed, characterized by a UV band at 300 nm and IR bands at 2075 and 1367 cm–1. The onward disproportionation producing reduced oligomers and carbonates gives a complex IR spectrum in the 1700–1000 cm–1 range. The bands due to the oligomers are readily discriminated by their sensitivity to oxygen. The discussion illustrates that UV and IR spectroscopy afford a powerful combination in defining and understanding the stages involved in the adsorption and reaction of CO on lanthanum oxide. The nature and extent of the reactivity towards CO shows that the basicity of La2O3 is not as great as that of the alkaline-earth-metal oxides.
20 citations
TL;DR: In this article, the reducibility and selectivity of reduced catalysts for the hydrogenation of propanenitrile at 20-30 bar and 473 K and of ethanenitiitrile with 1 bar and 508 K were determined.
Abstract: Fi/MgO catalysts with 5 to 30 mol % Fe have been prepared by impregnation and coprecipitation. Their reducibility has been measured and a comparison made of their Feo surface areas. Catalysts prepared via coprecipitation yielded larger iron areas than those via impregnation. The activity and selectivity of the reduced catalysts for the hydrogenation of propanenitrile at 20–30 bar and 473 K and of ethanenitrile at 1 bar and 508 K have been determined. The most active catalysts are those prepared by coprecipitation and they show high selectivity for primary amines. The activity for ethanenitrile hydrogenation correlates with the iron surface area.
10 citations