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Document Type

Dissertation - University Access Only

Award Date

1993

Degree Name

Doctor of Philosophy (PhD)

Department / School

Chemistry

First Advisor

John J. Fitzgerald

Abstract

1H CRAMPS NMR investigations have been used to identify the protons associated with AI-OH groups of alumina materials. Crystalline boehmite shows a 1H NMR peak at 8.8 ppm assigned to AI2OH protons, whereas diaspore depicts a peak at 10.8 ppm due to the AI3OH protons. Gibbsite and bayerite show three 1H NMR peaks at ca. 5.4 ppm, 4.3 ppm and 2.9 ppm, in approximate 3:2:1 ratios, that are assigned to the AI2OH protons. The protons associated with AI2OH groups are involved in stronger 1H- 1H dipolar interactions than the protons associated with the AI3OH groups. A high surface-area pseudo-boehmite material shows three distinguishable 1H NMR peaks at 5.3, 8.2, and 2.3 ppm associated with the protons from physisorbed water, highly coupled AI2OH groups, and terminal AIOH groups, respectively. Upon heat treatment, the AI2OH groups condensed at lower temperatures (350°C) than the AIOH groups (550°C). The interactions of alumina materials with various surfactants adsorbed at the solid/liquid interface in aqueous media are examined. The adsorption of dodecylsulfate ions on alumina materials was found to increase with the increase of surfactant loading concentration (Co) from 1x10-2 to 1x10-3 M. 1H CRAMPS NMR results suggest a competition between the physisorbed water and the surfactant ions for the hydroxyl sites of the alumina material. The surfactant ions are quite mobile in "wet" DDS-alumina solids, while the removal of water leads to increased surfactant rigidity. Initial solid-state NMR and FTIR spectroscopy results for the hydrolysis of AIN at 100°C in aqueous suspensions have shown boehmite to be the major product of the hydrolysis reaction. 27AI MAS NMR results indicate that during the hydrolysis reaction the aluminum atoms increase in coordination number from four (AIN4) to six (AIO6).

Library of Congress Subject Headings

Aluminum oxide -- Structure
Aluminum oxide -- Surfaces
Nuclear magnetic resonance spectroscopy

Format

application/pdf

Publisher

South Dakota State University

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