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Published December 16, 1999 | public
Journal Article

Ethanol Photocatalysis on TiO_2-Coated Optical Microfiber, Supported Monolayer, and Powdered Catalysts: An in Situ NMR Study

Abstract

In situ solid-state NMR methodologies have been employed to investigate the photocatalytic oxidation of ethanol (C_2H_5OH) over a TiO_2-coated optical microfiber catalyst and two other TiO_2-based catalysts. Adsorption of ethanol on the surface of the TiO_2/optical microfiber catalyst formed a strongly hydrogen-bonded species and a Ti ethoxide species. In situ UV irradiation experiments under ^(13)C magic angle spinning (MAS) conditions reveal the formation of two main reaction intermediates, 1,1-diethoxyethane (CH_3CH(OC_2H_5)_2) and acetic acid, under dry conditions. The catalyst was shown to be highly effective for the degradation of ethanol as complete photooxidation of ethanol was observed to form acetic acid and CO_2. These results were compared to those using a monolayer catalyst supported on porous Vycor glass and powdered TiO_2. Solid-state NMR investigations on TiO_2 powder modeled after temperature-programmed desorption experiments confirm the identities of the hydrogen-bonded and Ti ethoxide species and show that the strongly bound ethoxide species has a number of adsorption sites. Kinetic experiments indicate this latter species reacts much more rapidly. Studies of the effect of surface hydration show that the presence of water decreases the rate of ethanol photodegradation. Water and ethanol compete for the same adsorption sites on the surface of the TiO_2 catalysts.

Additional Information

© 1999 American Chemical Society. Received: July 30, 1999; In Final Form: October 10, 1999. Partial support for this research from the National Science Foundation (CHE 97-33188, CAREER Grant) and from the donors of the Petroleum Research Fund, administered by the American Chemical Society, is gratefully acknowledged. D.R. also thanks the A. P. Sloan Foundation for a research fellowship (1999−2001).

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023