Page 120 |
Save page Remove page | Previous | 120 of 139 | Next |
|
small (250x250 max)
medium (500x500 max)
Large (1000x1000 max)
Extra Large
large ( > 500x500)
Full Resolution
All (PDF)
|
This page
All
|
109
Table 4.6. Mole carbon product selectivities for Figure 4.6.
6 Methanol:
1 Acetal.a
12 Methanol:
1 Acetal.a
24 Methanol:
1 Acetal.a Methanolb
Methanol
conversionc 96% 96% 95% 99%
Ethylene to
Propened 1.5 1.0 0.6 0.3
Mole Carbon Selectivities
Ethylene 18% 14% 10% 6%
Propene 18% 22% 24% 32%
C4-C6
e 24% 35% 43% 51%
Aromaticsf 36% 26% 18% 10%
MeOH,
DMEg 3% 4% 4% 1%
a Molar ratio of methanol and acetaldehyde. b Methanol conversion at 648 K c
Mole carbon conversion. d Molar ratio e Includes C4 to C6 alkanes and
alkenes. f Includes benzene, toluene, and di- to tetramethylbenzenes. g Sum
of methanol and dimethyl ether product selectivities.
propene ratio also decreased. At the lowest aldehyde concentration, the
ethylene to propene ratio was 0.6, which was still greater than the native
ethylene to propene ratio of 0.3 under conditions of similar methanol
conversion. With the decrease in acetaldehyde concentration, the selectivity
of the C4 to C6 hydrocarbons increased to 43% and the propene selectivity
decreased to 24%. Ethylene selectivity decreased to 10% and the aromatic
content decreased to 18%. These results were as expected: with a lower
amount of aldehyde, the catalyst reverts to its native hydrocarbon pool which
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 120 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 109 Table 4.6. Mole carbon product selectivities for Figure 4.6. 6 Methanol: 1 Acetal.a 12 Methanol: 1 Acetal.a 24 Methanol: 1 Acetal.a Methanolb Methanol conversionc 96% 96% 95% 99% Ethylene to Propened 1.5 1.0 0.6 0.3 Mole Carbon Selectivities Ethylene 18% 14% 10% 6% Propene 18% 22% 24% 32% C4-C6 e 24% 35% 43% 51% Aromaticsf 36% 26% 18% 10% MeOH, DMEg 3% 4% 4% 1% a Molar ratio of methanol and acetaldehyde. b Methanol conversion at 648 K c Mole carbon conversion. d Molar ratio e Includes C4 to C6 alkanes and alkenes. f Includes benzene, toluene, and di- to tetramethylbenzenes. g Sum of methanol and dimethyl ether product selectivities. propene ratio also decreased. At the lowest aldehyde concentration, the ethylene to propene ratio was 0.6, which was still greater than the native ethylene to propene ratio of 0.3 under conditions of similar methanol conversion. With the decrease in acetaldehyde concentration, the selectivity of the C4 to C6 hydrocarbons increased to 43% and the propene selectivity decreased to 24%. Ethylene selectivity decreased to 10% and the aromatic content decreased to 18%. These results were as expected: with a lower amount of aldehyde, the catalyst reverts to its native hydrocarbon pool which |
