Molecular mechanisms for thermal degradation of CO-loaded aqueous monoethanolamine solution: a first-principles study
Thermal degradation of aqueous monoethanolamine (MEA), a benchmark solvent, in CO 2 capture processes still remains a challenge. Here, we present molecular mechanisms underlying thermal degradation of MEA based on ab initio molecular dynamics simulations coupled with metadynamics sampling. Isocyanat...
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Veröffentlicht in: | Physical chemistry chemical physics : PCCP 2019-10, Vol.21 (39), p.22132-22139 |
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creator | Yoon, Bohak Stowe, Haley M Hwang, Gyeong S |
description | Thermal degradation of aqueous monoethanolamine (MEA), a benchmark solvent, in CO
2
capture processes still remains a challenge. Here, we present molecular mechanisms underlying thermal degradation of MEA based on
ab initio
molecular dynamics simulations coupled with metadynamics sampling. Isocyanate formation
via
dehydration of carbamic acid (MEACOOH) is predicted to be highly probable and more kinetically favorable than the competing cyclization-dehydration reaction to 2-oxazolidinone (OZD), albeit not substantially. Isocyanate may undergo cyclization to form OZD, which is found to be more facile in aqueous MEA solution than reaction with MEA to form urea, although the latter is thermodynamically more favorable than the former. Our simulations also clearly demonstrate that OZD is a long-lived intermediate that plays a key role in MEA thermal degradation to experimentally observed products. Overall, this work highlights the importance of entropic contributions associated with the local structure and dynamics of solvent molecules around the intermediates, which cannot be solely explained by thermodynamics, in predicting the mechanism and kinetics of thermal degradation of CO
2
-loaded aqueous amine solutions.
While isocyanate tends to be an important intermediate, MEA degradation mechanisms and kinetics are largely governed by entropic effects. |
doi_str_mv | 10.1039/c9cp04518j |
format | Article |
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2
capture processes still remains a challenge. Here, we present molecular mechanisms underlying thermal degradation of MEA based on
ab initio
molecular dynamics simulations coupled with metadynamics sampling. Isocyanate formation
via
dehydration of carbamic acid (MEACOOH) is predicted to be highly probable and more kinetically favorable than the competing cyclization-dehydration reaction to 2-oxazolidinone (OZD), albeit not substantially. Isocyanate may undergo cyclization to form OZD, which is found to be more facile in aqueous MEA solution than reaction with MEA to form urea, although the latter is thermodynamically more favorable than the former. Our simulations also clearly demonstrate that OZD is a long-lived intermediate that plays a key role in MEA thermal degradation to experimentally observed products. Overall, this work highlights the importance of entropic contributions associated with the local structure and dynamics of solvent molecules around the intermediates, which cannot be solely explained by thermodynamics, in predicting the mechanism and kinetics of thermal degradation of CO
2
-loaded aqueous amine solutions.
While isocyanate tends to be an important intermediate, MEA degradation mechanisms and kinetics are largely governed by entropic effects.</description><identifier>ISSN: 1463-9076</identifier><identifier>EISSN: 1463-9084</identifier><identifier>DOI: 10.1039/c9cp04518j</identifier><ispartof>Physical chemistry chemical physics : PCCP, 2019-10, Vol.21 (39), p.22132-22139</ispartof><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27924,27925</link.rule.ids></links><search><creatorcontrib>Yoon, Bohak</creatorcontrib><creatorcontrib>Stowe, Haley M</creatorcontrib><creatorcontrib>Hwang, Gyeong S</creatorcontrib><title>Molecular mechanisms for thermal degradation of CO-loaded aqueous monoethanolamine solution: a first-principles study</title><title>Physical chemistry chemical physics : PCCP</title><description>Thermal degradation of aqueous monoethanolamine (MEA), a benchmark solvent, in CO
2
capture processes still remains a challenge. Here, we present molecular mechanisms underlying thermal degradation of MEA based on
ab initio
molecular dynamics simulations coupled with metadynamics sampling. Isocyanate formation
via
dehydration of carbamic acid (MEACOOH) is predicted to be highly probable and more kinetically favorable than the competing cyclization-dehydration reaction to 2-oxazolidinone (OZD), albeit not substantially. Isocyanate may undergo cyclization to form OZD, which is found to be more facile in aqueous MEA solution than reaction with MEA to form urea, although the latter is thermodynamically more favorable than the former. Our simulations also clearly demonstrate that OZD is a long-lived intermediate that plays a key role in MEA thermal degradation to experimentally observed products. Overall, this work highlights the importance of entropic contributions associated with the local structure and dynamics of solvent molecules around the intermediates, which cannot be solely explained by thermodynamics, in predicting the mechanism and kinetics of thermal degradation of CO
2
-loaded aqueous amine solutions.
While isocyanate tends to be an important intermediate, MEA degradation mechanisms and kinetics are largely governed by entropic effects.</description><issn>1463-9076</issn><issn>1463-9084</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2019</creationdate><recordtype>article</recordtype><sourceid/><recordid>eNqFjz1vAjEQRK0okUI-mvSR9g9cYusOwtEiUJqIhh6t7L1gZHsvXrvg3wNSFMpU86R5U4xSL0a_Gd3277a3o-6mZn64URPTzdqm1_Pu9o8_ZvfqQeSgtTZT005U_eJAtgbMEMnuMXmJAgNnKHvKEQM4-s7osHhOwAMsN01gdOQAfypxFYicmMp5ygGjTwTCoV70BSAMPktpxuyT9WMgASnVHZ_U3YBB6Pk3H9XrerVdfjZZ7O4sR8zH3fVL-19_AuNGT-I</recordid><startdate>20191009</startdate><enddate>20191009</enddate><creator>Yoon, Bohak</creator><creator>Stowe, Haley M</creator><creator>Hwang, Gyeong S</creator><scope/></search><sort><creationdate>20191009</creationdate><title>Molecular mechanisms for thermal degradation of CO-loaded aqueous monoethanolamine solution: a first-principles study</title><author>Yoon, Bohak ; Stowe, Haley M ; Hwang, Gyeong S</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-rsc_primary_c9cp04518j3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><creationdate>2019</creationdate><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Yoon, Bohak</creatorcontrib><creatorcontrib>Stowe, Haley M</creatorcontrib><creatorcontrib>Hwang, Gyeong S</creatorcontrib><jtitle>Physical chemistry chemical physics : PCCP</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Yoon, Bohak</au><au>Stowe, Haley M</au><au>Hwang, Gyeong S</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Molecular mechanisms for thermal degradation of CO-loaded aqueous monoethanolamine solution: a first-principles study</atitle><jtitle>Physical chemistry chemical physics : PCCP</jtitle><date>2019-10-09</date><risdate>2019</risdate><volume>21</volume><issue>39</issue><spage>22132</spage><epage>22139</epage><pages>22132-22139</pages><issn>1463-9076</issn><eissn>1463-9084</eissn><abstract>Thermal degradation of aqueous monoethanolamine (MEA), a benchmark solvent, in CO
2
capture processes still remains a challenge. Here, we present molecular mechanisms underlying thermal degradation of MEA based on
ab initio
molecular dynamics simulations coupled with metadynamics sampling. Isocyanate formation
via
dehydration of carbamic acid (MEACOOH) is predicted to be highly probable and more kinetically favorable than the competing cyclization-dehydration reaction to 2-oxazolidinone (OZD), albeit not substantially. Isocyanate may undergo cyclization to form OZD, which is found to be more facile in aqueous MEA solution than reaction with MEA to form urea, although the latter is thermodynamically more favorable than the former. Our simulations also clearly demonstrate that OZD is a long-lived intermediate that plays a key role in MEA thermal degradation to experimentally observed products. Overall, this work highlights the importance of entropic contributions associated with the local structure and dynamics of solvent molecules around the intermediates, which cannot be solely explained by thermodynamics, in predicting the mechanism and kinetics of thermal degradation of CO
2
-loaded aqueous amine solutions.
While isocyanate tends to be an important intermediate, MEA degradation mechanisms and kinetics are largely governed by entropic effects.</abstract><doi>10.1039/c9cp04518j</doi><tpages>8</tpages></addata></record> |
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title | Molecular mechanisms for thermal degradation of CO-loaded aqueous monoethanolamine solution: a first-principles study |
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