Date of Award
Doctor of Philosophy
The reaction of hydrogen and neopentane on iridium films resulted in the production of methane as the only product. The reaction has been studied in the temperature range 403 to 473K. The pressures of the reactant gases were varied over the ranges 1-400 millitorr for neopentane and 20-3000 millitorr for hydrogen to yield kinetic orders for each gas. The limiting orders of the reaction with respect to hydrogen were found to be +2.0 and -0.1, and with respect to neopentane were +0.95 and -0.80. The order with respect to the partial pressure of methane was determined to be -0.03 or essentially zero;Flash desorption experiments were conducted by dosing neopentane onto an iridium sample at 468K and indicated that no hydrocarbons could be desorbed from the sample. Deuterium exchange experiments indicated that once neopentane was absorbed onto the iridium film at 468K it did not desorb without first undergoing carbon-carbon bond scission. The deuterolysis products were predominantly perdeuteromethane with smaller amounts of the less deuterated methanes. Results of dosing only neopentane into the reaction cell at 468K indicated that the surface species were highly dissociated and the surface composition was C(,5)H(,0-2);A mechanism involving the reversible, dissociative adsorption of hydrogen and the irreversible, dissociative adsorption of neopentane was proposed. The neopentane dissociates into single carbon atom fragments on the surface and the surface concentrations of these fragments, C*, CH*, CH(,2)* and CH(,3)*, and H* vary depending upon the reaction conditions. At neopentane pressures > 10 millitorr the surface species CH(,3)*, CH(,3)* and H* are predominant, while at neopentane pressures < 2 millitorr, the concentration of the CH* species is also significant.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Nancy Ellen Kinkade
Kinkade, Nancy Ellen, "A mechanistic study of the hydrogenolysis of neopentane on iridium " (1980). Retrospective Theses and Dissertations. 7381.