archives@tulane.edu / A catalyst is a substance that increases the rate of a reaction without itself being consumed. Catalysis is an enabling technology due to its importance in a wide range of industrial applications. Processes responsible for more than 95% of all produced chemical products by volume employ catalysis, more than 85% of the added value in the chemical industry is produced by means of catalysis, and ca. 20% of the world economy depends directly or indirectly on catalysis. Generally, catalysts are classified into three categories: heterogeneous, homogeneous, or bio catalysts. A heterogeneous catalyst is one that is not in the same phase as the reactants while in homogeneous catalysis, the catalyst is in the same phase as the reactants. Heterogeneous catalysis is currently the most dominant catalysis route due to its advantages. A very important feature is that heterogeneous catalysts can be regenerated and reused for several catalytic cycles, which makes their application highly economical.
Zeolites, which are porous crystalline aluminosilicates, offer great potential as heterogeneous catalysts due to their unique structural characteristics. For example, they can be employed in important chemical reactions such as aromatization, alkylation, dehydration, disproportionation, hydroalkylation, hydrocracking, and hydrogenation. To achieve unique selectivities in these processes, knowing the topology of zeolites is essential because it controls the size and shape of molecules that can be admitted in the framework, and their possible pathways. Since the properties of zeolites are associated with their structure, the synthesis of zeolites with improved topologies and compositions and their fundamental understanding has been and continues to be the objective of many researchers. Even though significant improvements in zeolites have been achieved in the last century, there is still space for growth in some areas including the diversification of zeolite chemical compositions to expand their applications as catalyst. The present dissertation attempts to give an understanding of how different parameters can be linked to the activity of heteroatom-containing zeolites in certain oxidation reactions.
Chapter (1) of the dissertation covers the fundamentals of zeolite materials science and their applications in industry. Chapter (2) describes the experimental methods and analytical tools used in this dissertation. Synthesis and detail characterization of Sn, Sn-Al, and Sn-B substituted into MFI zeolites are discussed in chapter (3). We found that Sn-Al- MFI have both Lewis and Brönsted acidities while Sn-B-MFI shows strong Lewis acidity and weak Brönsted acidity. Moreover, the presence of the second element (Al/B) impacts the Sn uptake. In chapter (4), we report the synthesis of Fe-ZSM-5 zeolites made by a novel method called steam-assisted crystallization and their use in benzene hydroxylation to phenol in the presence of hydrogen peroxide as the oxidant. These materials showed a superior catalytic activity for benzene hydroxylation as compared to conventional Fe- ZSM-5 zeolites. Chapter (5) describes the effect of different trivalent elements (Ga, Al, B) on the acidity of Fe-MFI materials and their relation to the catalytic activity methane partial oxidation to oxygenated compounds including formic acid, methanol, and methyl hydroperoxide. We found that acidity plays a crucial role in the activation of hydrogen peroxides and ultimately methane oxidation. Chapter (6) and (7) present conclusions and potential future works, respectively. / 1 / Meysam Shahami
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_90928 |
| Date | January 2019 |
| Contributors | Shahami, Meysam (author), F. Shantz, Daniel (Thesis advisor), School of Science & Engineering Chemical and Biomolecular Engineering (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 153 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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