Conversion of synthesis gas to isobutylene over precipitated zirconia based catalysts /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=740900351&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD Link to ProQuest copy Link to OAKTrust copy |
| Abstract: | Recent amendments to the Clean Air Act have renewed interest in synthesizing isobutylene from coal derived synthesis gas for use in producing methyl tertiary-butyl ether. Previous work on isosynthesis was performed at extreme conditions or at very low conversions. No rate equation to predict carbon monoxide conversion or methods to predict product distribution existed. In this study zirconia catalysts were synthesized by a precipitation, a hydrothermal, and a calcination method. The effects of sodium, titanium, manganese, cerium, and thorium additives were initially investigated. Catalysts prepared by the precipitation method were most active followed by calcination and hydrothermal preparation. The hydrothermal catalysts were more selective to the iso-C4's. Of the initial catalysts, a 796 (wt) cerium zirconia was found to be most active. When hydrogen sulfide was included in the feed a dramatic shift in product selectivity occurred with no loss in catalytic activity. The C2+C3 fraction was reduced by about half while the Cs fraction was increased by a factor of two an a half. This increase was realized in the formation of 3-methyl-l-butene, the second least thermodynamically favored C5 hydrocarbon, which showed an eighteenfold increase. Presulfiding the catalyst resulted in a more pronounced shift to the C5's with a slight reduction in activity. The theory that oxygen vacancies are the catalytic site for isosynthesis was tested by doping zirconia catalysts with various levels of +1, +2, +3, and +5 oxides. The dopants studied included lithium, magnesium, aluminum, dysprosium, and tantalum. Additionally, a zirconia catalyst containing yttrium, barium, and copper in a 1:2:3 ratio was prepared. Catalyst testing showed that oxygen vacancies are required for an active catalyst and that oxygen vacancies also play a vital role in the selectivity of isosynthesis catalysts. Results indicated that the most active single component doped catalyst should introduce the most oxygen vacancies per cation incorporated into the lattice and have an ionic radius close to that of zirconium. Carbon monoxide conversion was successfully modeled with a rate equation dependent on the partial pressures of CO, H2, and C02. The product distribution was modeled by a simple extension of the rate equation. Reproduced |
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| Item Description: | "Major subject: Chemical Engineering." Vita. |
| Physical Description: | xii, 211 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |