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10
HZSM-5 and HSAPO-34, respectively. Both of these zeolites will be
discussed in further detail in the following sections in addition to other
zeolites used in this research.
1.3. ZSM-5
ZSM-5 is a synthetic aluminosilicate with MFI topology (Figure 1.3).
Chemists at Mobil developed this material in the early 1970s,4 naming it
Zeolite Socony Mobil- five. The topology code also takes its designation
from the name (ZSM-five). ZSM-5 is a two-dimensional medium-pore zeolite
with 10 T-atom pores and two sets of channels that run perpendicular to one
another. The channel diameter is approximately 0.55 nm, large enough to
easily accommodate diffusion of molecules as large as 1,2,4,5-
tetramethylbenzene (durene) through the pores, and the channel
intersections are even larger.
Acid site density can vary on ZSM-5, and is controlled by altering the
amount of aluminum available during synthesis. Commercially available from
Zeolyst International, NH4ZSM-5 can be purchased with aluminum contents
ranging from Si/Al = 11.5 to Si/Al = 140. The proton form of the zeolite can
be obtained through simple calcination of the ammonium form in air at 823 K
overnight.
Industrially, ZSM-5 catalysts have many applications as evidenced by
the number of patents (more than 6500) utilizing them since 1976. HZSM-5
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 21 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 10 HZSM-5 and HSAPO-34, respectively. Both of these zeolites will be discussed in further detail in the following sections in addition to other zeolites used in this research. 1.3. ZSM-5 ZSM-5 is a synthetic aluminosilicate with MFI topology (Figure 1.3). Chemists at Mobil developed this material in the early 1970s,4 naming it Zeolite Socony Mobil- five. The topology code also takes its designation from the name (ZSM-five). ZSM-5 is a two-dimensional medium-pore zeolite with 10 T-atom pores and two sets of channels that run perpendicular to one another. The channel diameter is approximately 0.55 nm, large enough to easily accommodate diffusion of molecules as large as 1,2,4,5- tetramethylbenzene (durene) through the pores, and the channel intersections are even larger. Acid site density can vary on ZSM-5, and is controlled by altering the amount of aluminum available during synthesis. Commercially available from Zeolyst International, NH4ZSM-5 can be purchased with aluminum contents ranging from Si/Al = 11.5 to Si/Al = 140. The proton form of the zeolite can be obtained through simple calcination of the ammonium form in air at 823 K overnight. Industrially, ZSM-5 catalysts have many applications as evidenced by the number of patents (more than 6500) utilizing them since 1976. HZSM-5 |
