John Kawas

Publication Date

12-1982

Advisor(s) - Committee Chair

Robert Farina, Norman Holy and William Lloyd

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

The activity of Catalyst 3-7A toward the oxidation of formaldehyde, hydrogen cyanide, methane, propane, and isobutene was examined at temperatures between 25°C and 400°C. The catalyst consists of palladium(II) and copper (II) salts impregnated on an alumina support. The oxidation measurements were made primarily with gas chromatographs, although form aldehyde and hydrogen cyanide were also examined using the colorimetric fushsin method and Liebig titrations, respectively. Catalyst 3-7A demonstrated appreciable activity toward the oxidation of all gases studied except formaldehyde where there was no evidence of oxidation. The latter result is quite unexpected since aldehydes are more easily oxidized than alkanes. It is suggested that the inactivity of Catalyst 3-7A toward formaldehyde is attributed to the lack of moisture which is required by the catalyst during oxidation.

All oxidation reactions are believed to occur via a Qacker-type process under pseudo-first order conditions with the palladium(II) concentration maintained constant via the presence of copper (II) which oxidizes metallic palladium, the product in the oxidation reaction. The oxidation products in all the gases examined are believed to be carbon dioxide and water except for hydrogen cyanide where an additional product containing nitrogen should be formed but could not be detected with the gas chromatograph. Rate constants (reported in parenthesis) at 400°C for the following gases are hydrogen cyanide (>26.2 sec-1), methane (6.5-6.6 sec-1), propane (>12.8 sec-1), and isobutene (>15.7 sec-1). These results show that hydrogen cyanide is the most active gas to be oxidized by the catalyst excluding carbon monoxide which is the test gas used I our system and has been previously determined to demonstrate the greatest activity with the catalyst. The three alkane gases show an order of oxidation reactivity which lends some support for ruling out an anionic mechanism since tertiary C-H bonds were found to be more reactive than secondary C-H bonds which in turn were shown to be more reactive than primary C-H bonds. A comparison of Catalyst 3-7A with other catalysts reported in the literature which show similar oxidation behavior with gases could not be made due to lack of data regarding their experimental conditions.

Disciplines

Chemistry

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