Quantum Chemical Study of CH3 + O2 Combustion Reaction System: Catalytic Effects of Additional CO2 Molecule
- Univ. of Central Florida, Orlando, FL (United States); South Ural State Univ., Chelyabinsk (Russia); National Research Nuclear Univ. MEPhl, Moscow (Russia)
- Univ. of Central Florida, Orlando, FL (United States)
The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO2 concentrations. In this work, we explore potential energy surfaces of the four elementary reactions in the CH3 + O2 reactive system in the presence of one CO2 molecule. In the case of reaction CH3 + O2 → CH2O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by ~2.2 kcal/mol. Alternatively, covalently bonded CO2 may form a six-membered ring transition state and reduce the activation barrier by ~0.6 kcal/mol. In case of reaction CH3 + O2 → CH3O + O (R2 channel), covalent participation of CO2 lowers the barrier for the rate limiting step by 3.9 kcal/mol. This is expected to accelerate the R2 process, important for the branching step of the radical chain reaction mechanism. For the reaction CH3 + O2 → CHO + H2O (R3 channel) with covalent participation of CO2, the activation barrier is lowered by 0.5 kcal/mol. The reaction CH2O + OH → CHO + H2O (R4 channel) involves hydrogen abstraction from formaldehyde by OH radical. Its barrier is reduced from 7.1 to 0.8 kcal/mol by formation of vdW complex with spectator CO2. These new findings are expected to improve the kinetic reaction mechanism describing combustion processes in supercritical CO2 medium.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of Central Florida, Orlando, FL (United States)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE)
- Grant/Contract Number:
- FE0025260
- OSTI ID:
- 1480256
- Journal Information:
- Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 121, Issue 30; ISSN 1089-5639
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Quantum chemical and master equation study of OH + CH 2 O → H 2 O + CHO reaction rates in supercritical CO 2 environment
|
journal | November 2018 |
Similar Records
Chemical reaction CO+OH • → CO2+H• autocatalyzed by carbon dioxide: Quantum chemical study of the potential energy surfaces
Potential energy surfaces for the reactions of HO2 radical with CH2O and HO2 in CO2 environment