Surface science and kinetic studies of model oxide and oxide- supported-metal catalysts /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Surface science and kinetic studies of model oxide and oxide-supported metal catalysts have been carried out by means of a combined ultrahigh vacuum/elevated pressure reactor system and a plug-flow reactor. The reactions studied include: oxidative coupling of methane over powders and thin-films of MgO and Li/MgO; twostep methane dimerization over ruthenium supported on alumina; ethane hydrogenolysis and carbon monoxide methanation over nickel supported on a silica thin-film; and ethylbenzene dehydrogenation to styrene over pure and potassium-promoted iron oxide thin-films. Similarities in the catalytic properties of the model catalysts and of traditional oxides and supported metal catalysts, indicate that the model catalysts are excellent representatives of the more realistic catalysts. By utilizing surface science techniques in conjunction with kinetic experiments, the active site for methane activation over MgO and Li/MgO in the oxidative coupling reaction was identified as an F-type defect. In addition, the rate limiting step in the reaction mechanism over Li/MgO was found to depend upon the concentration of carbon dioxide at the catalyst surface. In the two-step methane dimerization reaction over Ru supported on Al2O3, the ethane yield was found to depend upon the temperature of the methane decomposition step. The reaction intermediates following methane decomposition were identified as either a methylidyne or vinylidene species. The addition of small amounts of sulfur to the catalyst was found to promote ethane formation. The dependence of ethane hydrogenolysis and carbon monoxide methanation upon particle size was studied over model supported nickel catalysts. The absolute activity and the activation energy for ethane hydrogenolysis were observed to vary with particle size. In addition, the hydrogenolysis rates were found to parallel the concentration of bridge-bound CO for increasing particle size. In contrast, Carbon monoxide methanation reaction rates were independent of particle size. The dehydrogenation of ethylbenzene to styrene over model iron oxide catalysts was found to depend upon the concentration of Fe^+3 ions in the near surface region. The active phase for the potassium-promoted catalyst was KFeO2. The presence of surface carbon was also required for the formation of active sites. |
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| Item Description: | Vita. "Major subject: Chemistry." |
| Physical Description: | xiii, 195 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |