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Title: A master equation simulation for the OH + CH 3 OH reaction

A combined (fixed-J) two-dimensional master-equation / semi-classical transition state theory / variational Rice-Ramsperger-Kassel-Marcus (2DME/SCTST/vRRKM) approach has been used to compute reaction rate coefficients of •OH with CH 3OH over a wide range of temperatures (10 - 2500 K) and pressures (10 -1-10 4 Torr) based on a potential energy surface that has been constructed using a modification of the HEAT thermochemical protocol. The calculated results show that the title reaction is nearly pressure-independent when T > 250 K, but depends strongly on pressure at lower temperatures. Also, the preferred mechanism and rate constants are found to be very sensitive to temperature. The reaction pathway CH 3OH + OH → CH 3O + H 2O proceeds exclusively through tunneling at exceedingly low temperatures (T ≤50 K) typical of those established in interstellar environments. In this regime, the rate constant is found to increase with decreasing temperature, which agrees with low-temperature experimental results. The thermodynamically favored reaction pathway CH 3OH + OH → CH 2OH + H 2O becomes dominant at higher temperatures (T ≥ 200 K), such as those found in Earth’s atmosphere as well as combustion environments. By modifying the ab initio barrier heights slightly, experimental rate constants frommore » 200 to 1250 K can be satisfactorily reproduced.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Florida, Gainesville, FL (United States)
  2. Argonne National Laboratory (ANL),Lemont, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; FG02-07ER15884
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 150; Journal Issue: 8; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Argonne National Laboratory (ANL), Lemont, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; astrochemistry; combustion; electronic structure methods; elementary reactions; kinetics; master equation; partition function; thermochemistry
OSTI Identifier:
1503282

Nguyen, Thanh Lam, Ruscic, Branko, and Stanton, John F. A master equation simulation for the • OH + CH 3 OH reaction. United States: N. p., Web. doi:10.1063/1.5081827.
Nguyen, Thanh Lam, Ruscic, Branko, & Stanton, John F. A master equation simulation for the • OH + CH 3 OH reaction. United States. doi:10.1063/1.5081827.
Nguyen, Thanh Lam, Ruscic, Branko, and Stanton, John F. 2019. "A master equation simulation for the • OH + CH 3 OH reaction". United States. doi:10.1063/1.5081827.
@article{osti_1503282,
title = {A master equation simulation for the • OH + CH 3 OH reaction},
author = {Nguyen, Thanh Lam and Ruscic, Branko and Stanton, John F.},
abstractNote = {A combined (fixed-J) two-dimensional master-equation / semi-classical transition state theory / variational Rice-Ramsperger-Kassel-Marcus (2DME/SCTST/vRRKM) approach has been used to compute reaction rate coefficients of •OH with CH3OH over a wide range of temperatures (10 - 2500 K) and pressures (10-1-104 Torr) based on a potential energy surface that has been constructed using a modification of the HEAT thermochemical protocol. The calculated results show that the title reaction is nearly pressure-independent when T > 250 K, but depends strongly on pressure at lower temperatures. Also, the preferred mechanism and rate constants are found to be very sensitive to temperature. The reaction pathway CH3OH + •OH → CH3O• + H2O proceeds exclusively through tunneling at exceedingly low temperatures (T ≤50 K) typical of those established in interstellar environments. In this regime, the rate constant is found to increase with decreasing temperature, which agrees with low-temperature experimental results. The thermodynamically favored reaction pathway CH3OH + •OH → •CH2OH + H2O becomes dominant at higher temperatures (T ≥ 200 K), such as those found in Earth’s atmosphere as well as combustion environments. By modifying the ab initio barrier heights slightly, experimental rate constants from 200 to 1250 K can be satisfactorily reproduced.},
doi = {10.1063/1.5081827},
journal = {Journal of Chemical Physics},
number = 8,
volume = 150,
place = {United States},
year = {2019},
month = {2}
}