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Title: Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor

Abstract

Here, the thermal decomposition of cyclohexanone (C 6H 10=O) has been studied in a set of flash-pyrolysis microreactors. Decomposition of the ketone was observed when dilute samples of C 6H 10=O were heated to 1200 K in a continuous flow microreactor. Pyrolysis products were detected and identified by tunable VUV photoionization mass spectroscopy and by photoionization appearance thresholds. Complementary product identification was provided by matrix infrared absorption spectroscopy. Pyrolysis pressures were roughly 100 Torr, and contact times with the microreactors were roughly 100 μs. Thermal cracking of cyclohexanone appeared to result from a variety of competing pathways, all of which open roughly simultaneously. Isomerization of cyclohexanone to the enol, cyclohexen-1-ol (C 6H 9OH), is followed by retro-Diels–Alder cleavage to CH 2=CH 2 and CH 2=C(OH)–CH=CH 2. Further isomerization of CH 2=C(OH)–CH=CH 2 to methyl vinyl ketone (CH 3CO–CH=CH 2, MVK) was also observed. Photoionization spectra identified both enols, C 6H 9OH and CH 2=C(OH)–CH=CH 2, and the ionization threshold of C 6H 9OH was measured to be 8.2 ± 0.1 eV. Coupled cluster electronic structure calculations were used to establish the energetics of MVK. The heats of formation of MVK and its enol were calculated to be Δ fH 298(cis-CHmore » 3CO–CH=CH 2) = -26.1 ± 0.5 kcal mol –1 and Δ fH 298(s-cis-1-CH 2=C(OH)–CH=CH 2) = -13.7 ± 0.5 kcal mol –1. The reaction enthalpy Δ rxnH 298(C 6H 10=O → CH 2=CH 2 + s-cis-1-CH 2=C(OH)–CH=CH 2) is 53 ± 1 kcal mol –1 and Δ rxnH 298(C 6H 10=O → CH 2=CH 2 + cis-CH 3CO–CH=CH 2) is 41 ± 1 kcal mol –1. At 1200 K, the products of cyclohexanone pyrolysis were found to be C 6H 9OH, CH 2=C(OH)–CH=CH 2, MVK, CH 2CHCH 2, CO, CH 2=C=O, CH 3, CH 2=C=CH 2, CH 2=CH–CH=CH 2, CH 2=CHCH 2CH 3, CH 2=CH 2, and HC≡CH.« less

Authors:
 [1];  [2];  [1];  [1];  [3];  [3];  [3];  [2];  [4];  [1]
  1. Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry
  2. Univ. of Texas, Austin, TX (United States). Dept. of Chemistry
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  4. Univ. of Colorado, Boulder, CO (United States). Center for Combustion and Environmental Research and Dept. of Mechanical Engineering
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; National Science Foundation (NSF); Robert A. Welch Foundation
OSTI Identifier:
1439183
Grant/Contract Number:  
AC02-05CH11231; CHE-1112466; CBET-1403979; F-1283; FG02-07ER15884
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 119; Journal Issue: 51; Related Information: © 2015 American Chemical Society.; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 47 OTHER INSTRUMENTATION

Citation Formats

Porterfield, Jessica P., Nguyen, Thanh Lam, Baraban, Joshua H., Buckingham, Grant T., Troy, Tyler P., Kostko, Oleg, Ahmed, Musahid, Stanton, John F., Daily, John W., and Ellison, G. Barney. Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor. United States: N. p., 2015. Web. doi:10.1021/acs.jpca.5b10984.
Porterfield, Jessica P., Nguyen, Thanh Lam, Baraban, Joshua H., Buckingham, Grant T., Troy, Tyler P., Kostko, Oleg, Ahmed, Musahid, Stanton, John F., Daily, John W., & Ellison, G. Barney. Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor. United States. doi:10.1021/acs.jpca.5b10984.
Porterfield, Jessica P., Nguyen, Thanh Lam, Baraban, Joshua H., Buckingham, Grant T., Troy, Tyler P., Kostko, Oleg, Ahmed, Musahid, Stanton, John F., Daily, John W., and Ellison, G. Barney. Mon . "Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor". United States. doi:10.1021/acs.jpca.5b10984. https://www.osti.gov/servlets/purl/1439183.
@article{osti_1439183,
title = {Isomerization and Fragmentation of Cyclohexanone in a Heated Micro-Reactor},
author = {Porterfield, Jessica P. and Nguyen, Thanh Lam and Baraban, Joshua H. and Buckingham, Grant T. and Troy, Tyler P. and Kostko, Oleg and Ahmed, Musahid and Stanton, John F. and Daily, John W. and Ellison, G. Barney},
abstractNote = {Here, the thermal decomposition of cyclohexanone (C6H10=O) has been studied in a set of flash-pyrolysis microreactors. Decomposition of the ketone was observed when dilute samples of C6H10=O were heated to 1200 K in a continuous flow microreactor. Pyrolysis products were detected and identified by tunable VUV photoionization mass spectroscopy and by photoionization appearance thresholds. Complementary product identification was provided by matrix infrared absorption spectroscopy. Pyrolysis pressures were roughly 100 Torr, and contact times with the microreactors were roughly 100 μs. Thermal cracking of cyclohexanone appeared to result from a variety of competing pathways, all of which open roughly simultaneously. Isomerization of cyclohexanone to the enol, cyclohexen-1-ol (C6H9OH), is followed by retro-Diels–Alder cleavage to CH2=CH2 and CH2=C(OH)–CH=CH2. Further isomerization of CH2=C(OH)–CH=CH2 to methyl vinyl ketone (CH3CO–CH=CH2, MVK) was also observed. Photoionization spectra identified both enols, C6H9OH and CH2=C(OH)–CH=CH2, and the ionization threshold of C6H9OH was measured to be 8.2 ± 0.1 eV. Coupled cluster electronic structure calculations were used to establish the energetics of MVK. The heats of formation of MVK and its enol were calculated to be ΔfH298(cis-CH3CO–CH=CH2) = -26.1 ± 0.5 kcal mol–1 and ΔfH298(s-cis-1-CH2=C(OH)–CH=CH2) = -13.7 ± 0.5 kcal mol–1. The reaction enthalpy ΔrxnH298(C6H10=O → CH2=CH2 + s-cis-1-CH2=C(OH)–CH=CH2) is 53 ± 1 kcal mol–1 and ΔrxnH298(C6H10=O → CH2=CH2 + cis-CH3CO–CH=CH2) is 41 ± 1 kcal mol–1. At 1200 K, the products of cyclohexanone pyrolysis were found to be C6H9OH, CH2=C(OH)–CH=CH2, MVK, CH2CHCH2, CO, CH2=C=O, CH3, CH2=C=CH2, CH2=CH–CH=CH2, CH2=CHCH2CH3, CH2=CH2, and HC≡CH.},
doi = {10.1021/acs.jpca.5b10984},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 51,
volume = 119,
place = {United States},
year = {2015},
month = {11}
}

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