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13
of this material is as a catalyst in methanol-to-olefin chemistry, which will be
discussed in Chapter 2. SAPO-34 has a three-dimensional channel system
interconnected by small (8 T-atoms) pores. Pores in SAPO-34 are only 0.38
nm in diameter, allowing diffusion of small molecules such as water,
methanol, and linear hydrocarbons. Branched hydrocarbons and aromatic
species, even benzene, can form inside the cage but are not able to pass
through the small pores.
Figure 1.5. Individual SAPO-34 cage. (a) The distinguishing feature of the
CHA topology is the chabazite cage. It is nearly 1.3 nm tall and has six
pores, each with a diameter of 0.38 nm. (b) The largest molecule able to fit
inside the cage is pyrene, a polycyclic aromatic hydrocarbon.
The defining characteristic of this topology is the chabazite cage. It is
over 1 nm in size and large enough to contain the polycyclic aromatic pyrene
(Figure 1.5). Each cage is connected to six others through the 0.38 nm
Object Description
| Title | Modification of methanol-to-olefin hydrocarbon pool species by oxygenates on acidic zeolites |
| Author | Hayman, Miranda Jeanette |
| Author email | mirandah@usc.edu; mirandahayman@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2011-02-11 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-04-26 |
| Advisor (committee chair) | Haw, James F. |
| Advisor (committee member) |
Flood, Thomas C. Jessen, Kristian |
| Abstract | The mechanism of methanol-to-olefin (MTO) catalysis employs organic reaction centers, both aromatic and olefinic, to generate olefins on acid zeolites. Generally, propene is the favored MTO olefin on most zeolite catalysts, but ethylene is a more desirable olefin due to its prevalence in consumer plastics. Much research has been conducted to alter the MTO product selectivities to favor ethylene. This focus of this dissertation is selective modification of the olefinic reaction centers, converting them into aromatic reaction centers known to be responsible for the majority of ethylene production.; Formaldehyde reactivity was studied on HSAPO-34, and found to react with propene through a Prins reaction to form butadiene, which readily cyclized to aromatic species. Evidence of formaldehyde formation was observed from methanol oxidation on the stainless-steel surface of the reactor tubing. This reaction was then studied in HZSM-5 where olefinic reaction centers dominate the hydrocarbon pool. The olefinic reaction centers were converted to aromatic species, and a significant increase in ethylene selectivity was observed. Other oxygenated species, such as acetaldehyde, were also studied in conjunction with methanol on HZSM-5 and an improvement in ethylene selectivity was noted. The consequence of the increased ethylene selectivity however was an increase in the rate of deactivation due to the accelerated formation of aromatic species. |
| Keyword | MTO; methanol-to-olefins; zeolite; heterogeneous catalysis; hydrocarbon pool; HZSM-5 |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3780 |
| Contributing entity | University of Southern California |
| Rights | Hayman, Miranda Jeanette |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Hayman-4358 |
| Archival file | uscthesesreloadpub_Volume23/etd-Hayman-4358.pdf |
Description
| Title | Page 24 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 13 of this material is as a catalyst in methanol-to-olefin chemistry, which will be discussed in Chapter 2. SAPO-34 has a three-dimensional channel system interconnected by small (8 T-atoms) pores. Pores in SAPO-34 are only 0.38 nm in diameter, allowing diffusion of small molecules such as water, methanol, and linear hydrocarbons. Branched hydrocarbons and aromatic species, even benzene, can form inside the cage but are not able to pass through the small pores. Figure 1.5. Individual SAPO-34 cage. (a) The distinguishing feature of the CHA topology is the chabazite cage. It is nearly 1.3 nm tall and has six pores, each with a diameter of 0.38 nm. (b) The largest molecule able to fit inside the cage is pyrene, a polycyclic aromatic hydrocarbon. The defining characteristic of this topology is the chabazite cage. It is over 1 nm in size and large enough to contain the polycyclic aromatic pyrene (Figure 1.5). Each cage is connected to six others through the 0.38 nm |
