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75
in this study also show a mechanistic separation between ethylene and the
other olefins based on 13C-incorporation. Ethylene exhibited increased
amounts of 13C throughout the course of the experiment, indicating
formaldehyde impacted ethylene production more than the other olefins.
Table 3.2. Volatile product selectivities and percent 13C incorporation from a
flow of 13C-formaldehyde in methanol on HSAPO-34
1 min TOSa 11 min TOS 21 min TOS
Methanol
Conversionb 98.4 98.7 93.8
Ethylene to
Propenec 1.6 2.3 2.5
Mol C
Selectivities % 13C Mol C
Selectivities % 13C Mol C
Selectivities % 13C
Methane 0.4% --d 0.4 -- 0.5 --
Ethylene 42.0% 12.3% 53.2% 14.3% 52.5% 16.1%
Propene 40.3% 10.0% 34.9% 12.4% 31.7% 13.9%
Butenes 9.9% 10.6% 7.3% 12.5% 6.3% 14.0%
Butadiene 0.4% -- 0.6% -- 0.9% --
Pentenes 5.6% 9.4% 2.3% 10.8% 2.0% 12.5%
DME 0.2% -- 0.3% -- 2.3% X%
Methanol 1.4% X% 1.1% X% 3.9% X%
a Time on stream. b Mole carbon conversion. c Molar ratio. d 13C percentage
not available as MS signal was too low for accurate measurement.
Guenther9 showed the aromatic pool species were primarily
responsible for ethylene production, and thus formaldehyde must be
incorporated into the aromatic hydrocarbon pool. An acid digestion was
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 86 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 75 in this study also show a mechanistic separation between ethylene and the other olefins based on 13C-incorporation. Ethylene exhibited increased amounts of 13C throughout the course of the experiment, indicating formaldehyde impacted ethylene production more than the other olefins. Table 3.2. Volatile product selectivities and percent 13C incorporation from a flow of 13C-formaldehyde in methanol on HSAPO-34 1 min TOSa 11 min TOS 21 min TOS Methanol Conversionb 98.4 98.7 93.8 Ethylene to Propenec 1.6 2.3 2.5 Mol C Selectivities % 13C Mol C Selectivities % 13C Mol C Selectivities % 13C Methane 0.4% --d 0.4 -- 0.5 -- Ethylene 42.0% 12.3% 53.2% 14.3% 52.5% 16.1% Propene 40.3% 10.0% 34.9% 12.4% 31.7% 13.9% Butenes 9.9% 10.6% 7.3% 12.5% 6.3% 14.0% Butadiene 0.4% -- 0.6% -- 0.9% -- Pentenes 5.6% 9.4% 2.3% 10.8% 2.0% 12.5% DME 0.2% -- 0.3% -- 2.3% X% Methanol 1.4% X% 1.1% X% 3.9% X% a Time on stream. b Mole carbon conversion. c Molar ratio. d 13C percentage not available as MS signal was too low for accurate measurement. Guenther9 showed the aromatic pool species were primarily responsible for ethylene production, and thus formaldehyde must be incorporated into the aromatic hydrocarbon pool. An acid digestion was |
