Mass Spectrometric Studies of Oxygen Isotope Exchange Reactions with Oxide Surfaces
Year: 2024
Type: dissertation
Abstract: Isotopic exchange reactions with the surface of amorphous silica and crystalline quartz were studied mass spectrometrically. A mixture of approximately 2%18o2 in neon was used as the test gas, and was passed over the surface of the oxides. Measurements were taken as a function of temperature and residence time, for kinetic studies. These studies clearly show a second order rate law for the surfaces examined. The rate constant on amorphous silica was 2.2xl02L/mol/sec. The energy of activation was 35.3 kcal/mol and the frequency factor was l.35xl09L/mol/sec. On the crystalline quartz the rate constant was 2.0xl02L/mol/sec. The energy of activation was 65.2 kcal/mol and the frequency factor was 4.52xl02L/mol/sec. The postulated mechanism for a bimolecular reaction would occur at temperatures above that required for dehydroxylation. This allows chemisorption of a molecule of 18o2 to form a bridged six-membered ring upon which a subsequent collision of a second 18o2 molecule results in an oxygen isotope exchange.
DOI: 10.25777/ksew-vn20
Author: Allen, Gayle J.
Institution: Old Dominion University
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6964968105
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