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Title: Quantum Chemical Study of Supercritical Carbon Dioxide Effects on Combustion Kinetics

In oxy-fuel combustion, the pure oxygen (O 2), diluted with CO 2 is used as oxidant instead air. Hence, the combustion products (CO 2 and H 2O) are free from pollution by nitrogen oxides. Moreover, high pressures results in the near-liquid density of CO 2 at supercritical state (sCO 2). Unfortunately, the effects of sCO 2 on the combustion kinetics are far from being understood. In order to assist in this understanding, in this work we are using quantum chemistry methods. Here we investigate potential energy surfaces of important combustion reactions in the presence of carbon dioxide melocule. All transition states, reactant and product complexes are reported for three reactions: H 2CO+HO 2→HCO+H 2O 2 (R1), 2HO 2→H 2O 2+O 2 (R2), and CO+OH→CO 2+H (R3). In the reaction R3, covalent binding of CO 2 to OH radical and then CO molecule opens a new pathway, including hydrogen transfer from oxygen to carbon atoms followed by CH bond dissociation. Compared to bimolecular OH+CO mechanism, this pathway reduces the activation barrier by 5 kcal/mol, and is expected to accelerate the reaction. This is the first report of autocatalytic effect in combustion. In case of hydroperoxyl self-reaction 2HO 2→H 2O 2+O 2more » the intermediates, containing covalent bonds to CO 2 were found not to be competitive. However, the spectator CO 2 molecule is able to stabilize the cyclic transition state and lower the barrier by 3 kcal/mol. Formation of covalent intermediates was also discovered in H 2CO+HO 2→HCO+H 2O 2 reaction, but these specie lead to substantially higher activation barriers which makes them unlikely to play role in hydrogen transfer kinetics. The van der Waals complexation with carbon dioxide also stabilized transition state and reduces reaction barrier. Lastly, these results indicate that CO 2 environment is likely to have catalytic effect on combustion reactions, which needs to be included in kinetic combustion mechanisms in supercritical CO 2.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2]
  1. Univ. of Central Florida, Orlando, FL (United States); National Research Nuclear Univ. MEPhl, Moscow (Russia); South Ural State Univ., Chelyabinsk (Russia)
  2. Univ. of Central Florida, Orlando, FL (United States)
  3. Univ. of Central Florida, Orlando, FL (United States); Florida State Univ., Tallahassee, FL (United States)
Publication Date:
Grant/Contract Number:
FE0025260; 14-43-00052
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 121; Journal Issue: 19; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Research Org:
Univ. of Central Florida, Orlando, FL (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE); Russian Science Foundation
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1353407