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95
Figure 4.2. The effect of various aldehydes on MTO catalysis in HZSM-5.
The GC-FID chromatograms are provided from the reaction of a) a solution
of 18 mol methanol to 1 mol 1,3,5-trioxane, and solutions of 6 mol methanol
to 1 mol b) acetaldehyde, c) propanal, and d) butanal on 200 mg of HZSM-5
(Si/Al = 40) mixed with silicon carbide. The reagents were introduced into
the reactor at 648 K with 50 sccm of flowing helium by a syringe pump for 5
minutes at a methanol flow rate of WHSV = 4 hr-1 before sampling for
simultaneous GC-FID and GC-MS analysis. All of the aldehydes are capable
of increasing aromatic production and thus ethylene selectivity. However,
the activity of the aldehyde decreases with the increasing length of the
carbon chain on the aldehyde.
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 106 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 95 Figure 4.2. The effect of various aldehydes on MTO catalysis in HZSM-5. The GC-FID chromatograms are provided from the reaction of a) a solution of 18 mol methanol to 1 mol 1,3,5-trioxane, and solutions of 6 mol methanol to 1 mol b) acetaldehyde, c) propanal, and d) butanal on 200 mg of HZSM-5 (Si/Al = 40) mixed with silicon carbide. The reagents were introduced into the reactor at 648 K with 50 sccm of flowing helium by a syringe pump for 5 minutes at a methanol flow rate of WHSV = 4 hr-1 before sampling for simultaneous GC-FID and GC-MS analysis. All of the aldehydes are capable of increasing aromatic production and thus ethylene selectivity. However, the activity of the aldehyde decreases with the increasing length of the carbon chain on the aldehyde. |
