Date of Award

1-1-1981

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Electron spin resonance (esr) was used to study the radical anion species produced as a result of carbon monoxide adsorption onto separate samples of calcium and magnesium oxides. The oxide samples were thermally out gassed at temperatures of 400(DEGREES) to 1000(DEGREES)C prior to exposure to carbon monoxide. Also prior to carbon monoxide adsorption, an esr signal was not observed for either oxide. The adsorption of carbon monoxide was performed at room temperature. Immediately upon carbon monoxide exposure, the magnesium oxide sample turned light red and the calcium oxide sample turned yellow. Esr signals were also immediately observable in the case of both oxides. The rate of radical growth was slow, requiring in excess of one month to reach maximum concentration. On the basis of esr data, the predominant radical species was assigned as the rhodizonate trianion radical. The radical species was observed to be very reactive with oxygen and polar type molecules. The result of small additions of these reagents is believed to cause reorientation of the rhodizonate radical species relative to the surface. At least seven and five such orientations were observed in the cases of calcium and magnesium oxides, respectively.Experiments were performed to determine the general nature of the surface site responsible for the electron reduction of adsorbed molecules. A comparison of nitrobenzene anion radical and rhodizonate trianion radical formation activities, indicated that the same active side is responsible for both processes. The active site was shown not to be a direct function of surface area, micropore size or previous oxidation or reduction steps imposed on oxide samples prior to the thermal degassing of the sample. The active site appears to be very basic in nature and can be easily poisoned before exposure to carbon monoxide.

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