Characterization of cobalt-substituted aluminophosphate molecular sieves /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Aluminophosphate is a molecular sieve with structure similar to that of an aluminosilicate zeolite, but with very low ion-exchange capacity and acidic catalytic activity. Substituting a portion of the aluminum ions by cobalt introduces ion-exchange properties and the ability to produce mildly acidic catalysts. Eight samples of different cobalt loadings were tested in this study. It was found that at most 14% of the framework aluminum could be substituted by cobalt. At this level, the number of acidic sites and the activity toward isopropanol decomposition was much larger than the unsubstituted AIPO₄-5. Above this level, a cobalt-rich impurity phase was formed. In the as synthesized cobalt-substituted AIPO₄-5 samples, about 65-81% of the ion-exchange sites were occupied by proton ions, the rest were occupied by Co⁺⁺ ions. Upon calcination at 450°C, these Co⁺⁺ ions were oxidized to form a grey or black powder of C0₂O₃/C0₃O₄ which promoted the production of acetone in isopropanol decomposition. These impurities were removed by ion-exchange with NH₄CI solution. The results of temperature-programmed desorption of ammonia and catalytic activity tests for decomposing isopropanol, methanol, and hexane showed that the cobalt-substituted aluminophosphate molecular sieves have weak acidic sites, a small amount of medium acidic sites, and essentially no strong acidic sites. Coke was formed and deactivated the catalyst during the reactions. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemical engineering." |
| Physical Description: | xviii, 217 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |