skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

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:
Research Org.:
Univ. of Central Florida, Orlando, FL (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE); Russian Science Foundation
OSTI Identifier:
1353407
Grant/Contract Number:
FE0025260; 14-43-00052
Resource Type:
Journal Article: 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
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Masunov, Artëm E., Wait, Elizabeth E., Atlanov, Arseniy A., and Vasu, Subith S. Quantum Chemical Study of Supercritical Carbon Dioxide Effects on Combustion Kinetics. United States: N. p., 2017. Web. doi:10.1021/acs.jpca.7b02638.
Masunov, Artëm E., Wait, Elizabeth E., Atlanov, Arseniy A., & Vasu, Subith S. Quantum Chemical Study of Supercritical Carbon Dioxide Effects on Combustion Kinetics. United States. doi:10.1021/acs.jpca.7b02638.
Masunov, Artëm E., Wait, Elizabeth E., Atlanov, Arseniy A., and Vasu, Subith S. Wed . "Quantum Chemical Study of Supercritical Carbon Dioxide Effects on Combustion Kinetics". United States. doi:10.1021/acs.jpca.7b02638. https://www.osti.gov/servlets/purl/1353407.
@article{osti_1353407,
title = {Quantum Chemical Study of Supercritical Carbon Dioxide Effects on Combustion Kinetics},
author = {Masunov, Artëm E. and Wait, Elizabeth E. and Atlanov, Arseniy A. and Vasu, Subith S.},
abstractNote = {In oxy-fuel combustion, the pure oxygen (O2), diluted with CO2 is used as oxidant instead air. Hence, the combustion products (CO2 and H2O) are free from pollution by nitrogen oxides. Moreover, high pressures results in the near-liquid density of CO2 at supercritical state (sCO2). Unfortunately, the effects of sCO2 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: H2CO+HO2→HCO+H2O2 (R1), 2HO2→H2O2+O2 (R2), and CO+OH→CO2+H (R3). In the reaction R3, covalent binding of CO2 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 2HO2→H2O2+O2 the intermediates, containing covalent bonds to CO2 were found not to be competitive. However, the spectator CO2 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 H2CO+HO2→HCO+H2O2 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 CO2 environment is likely to have catalytic effect on combustion reactions, which needs to be included in kinetic combustion mechanisms in supercritical CO2.},
doi = {10.1021/acs.jpca.7b02638},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 19,
volume = 121,
place = {United States},
year = {Wed May 03 00:00:00 EDT 2017},
month = {Wed May 03 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 3works
Citation information provided by
Web of Science

Save / Share:
  • Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO 2/H 2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less
  • The supercritical carbon dioxide medium, used to increase efficiency in oxy combustion fossil energy technology, may drastically alter both rates and mechanisms of chemical reactions. Here we investigate potential energy surface of the second most important combustion reaction with quantum chemistry methods. Two types of effects are reported: formation of the covalent intermediates and formation of van der Waals complexes by spectator CO 2 molecule. While spectator molecule alter the activation barrier only slightly, the covalent bonding opens a new reaction pathway. The mechanism includes sequential covalent binding of CO 2 to OH radical and CO molecule, hydrogen transfer frommore » oxygen to carbon atoms, and CH bond dissociation. This reduces the activation barrier by 11 kcal/mol at the rate-determining step and is expected to accelerate the reaction rate. The finding of predicted catalytic effect is expected to play an important role not only in combustion but also in a broad array of chemical processes taking place in supercritical CO 2 medium. Furthermore, tt may open a new venue for controlling reaction rates for chemical manufacturing.« less
  • Solubility data are presented for a mixture of o-hydroxybenzoic acid (o-HBA) and m-HBA in supercritical CO{sub 2} doped with 3.5 mol% methanol. The data were measured at 318 and 328 K and for pressures in the range of 101--201 bar. Some new data for the solubility of pure m-HBA in methanol-doped supercritical CO{sub 2} are also presented. The solubilities of the HBA isomers are enhanced considerably with the addition of methanol to supercritical CO{sub 2}. However, the solubility enhancement is strongly affected by the spatial arrangement of their functional groups (steric effect). There appears to be preferential interaction between themore » solutes and the cosolvent in the quaternary system, and this phenomenon is consistent with thermodynamic modeling of the system.« less
  • No abstract prepared.
  • Excess sorption isotherms of supercritical carbon dioxide in mesoporous CPG-10 silica glasses with nominal pore sizes of 75 (7.5 nm) and 350 (35 nm) were measured gravimetrically at 35 C and 50 C and pressures of 0-200 bar. Formation of broad maxima in the excess sorption was observed at fluid densities below the bulk critical density. Positive values of excess sorption were measured at bulk densities below about 0.65-0.7 g/cm3, whereas zero and negative values were obtained at higher densities, indicating that the interfacial fluid becomes less dense than the corresponding bulk fluid at high fluid densities. A shift ofmore » the excess sorption peak position to higher fluid density is found with increasing pore width. The excess sorption of CO2 normalized to the specific surface area is higher for the 35 nm pore size material, suggesting pore confinement effects. Conversely, the pore volume normalized excess sorption is higher for the 7.5 nm pore size material. Assessment of mean pore density reveals regions of constant pore fluid density, located between the excess sorption peak and the adsorption/depletion transition. Both materials exhibit such regions of constant mean pore fluid density as a function of bulk CO2 density at the lower temperature of 35 C, but not at 50 C. The results of this study suggest that the CO2 storage capacity in quartz-rich reservoirs is higher for sites with low temperature and rock textures characterized by narrow pores with high surface to volume ratios.« less