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Title: Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK)

Abstract

Due to the high global warming potential (GWP) and increasing environmental concerns, efforts on searching the alternative gases to SF{sub 6}, which is predominantly used as insulating and interrupting medium in high-voltage equipment, have become a hot topic in recent decades. Overcoming the drawbacks of the existing candidate gases, C5- perfluorinated ketone (C5 PFK) was reported as a promising gas with remarkable insulation capacity and the low GWP of approximately 1. Experimental measurements of the dielectric strength of this novel gas and its mixtures have been carried out, but the chemical decomposition pathways and products of C5 PFK during breakdown are still unknown, which are the essential factors in evaluating the electric strength of this gas in high-voltage equipment. Therefore, this paper is devoted to exploring all the possible decomposition pathways and species of C5 PFK by density functional theory (DFT). The structural optimizations, vibrational frequency calculations and energy calculations of the species involved in a considered pathway were carried out with DFT-(U)B3LYP/6-311G(d,p) method. Detailed potential energy surface was then investigated thoroughly by the same method. Lastly, six decomposition pathways of C5 PFK decomposition involving fission reactions and the reactions with a transition states were obtained. Important intermediate products weremore » also determined. Among all the pathways studied, the favorable decomposition reactions of C5 PFK were found, involving C-C bond ruptures producing Ia and Ib in pathway I, followed by subsequent C-C bond ruptures and internal F atom transfers in the decomposition of Ia and Ib presented in pathways II + III and IV + V, respectively. Possible routes were pointed out in pathway III and lead to the decomposition of IIa, which is the main intermediate product found in pathway II of Ia decomposition. We also investigated the decomposition of Ib, which can undergo unimolecular reactions to give the formation of IV a, IV b and products of CF{sub 3} + CF-CF{sub 3} in pathway IV. Although IV a is dominant to a lesser extent due to its relative high energy barrier, its complicated decomposition pathway V was also studied and CF{sub 3}, C = CF{sub 2} as well as C-CF{sub 3} species were found as the ultimate products. To complete the decomposition of C5 PFK, pathway V I of Ic decomposition was fully explored and the final products were obtained. Therefore, the integrate decomposition scheme of C5 PFK was proposed, which contains six pathways and forty-eight species (including all the reactants, products and transition states). This work is hopeful to lay a theoretical basis for the insulating properties of C5 PFK.« less

Authors:
; ; ; ; ;  [1]; ;  [2]
  1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, No. 28 XianNing West Road, Xi’an, Shaanxi Province 710049 (China)
  2. Pinggao Group Co. Ltd., Pingdingshan, Henan Province 467001 (China)
Publication Date:
OSTI Identifier:
22611419
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; APPROXIMATIONS; ATOMS; BREAKDOWN; CAPACITY; DECOMPOSITION; DENSITY; DENSITY FUNCTIONAL METHOD; DIELECTRIC MATERIALS; DIFFUSION BARRIERS; FISSION; GASES; KETONES; MIXTURES; SIMULATION; SULFUR FLUORIDES; SURFACES

Citation Formats

Fu, Yuwei, Wang, Xiaohua, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Li, Xi, Yang, Aijun, Wu, Yi, Rong, Mingzhe, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Han, Guohui, and Lu, Yanhui. Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK). United States: N. p., 2016. Web. doi:10.1063/1.4960988.
Fu, Yuwei, Wang, Xiaohua, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Li, Xi, Yang, Aijun, Wu, Yi, Rong, Mingzhe, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Han, Guohui, & Lu, Yanhui. Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK). United States. doi:10.1063/1.4960988.
Fu, Yuwei, Wang, Xiaohua, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Li, Xi, Yang, Aijun, Wu, Yi, Rong, Mingzhe, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn, Han, Guohui, and Lu, Yanhui. 2016. "Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK)". United States. doi:10.1063/1.4960988.
@article{osti_22611419,
title = {Theoretical study of the decomposition pathways and products of C5- perfluorinated ketone (C5 PFK)},
author = {Fu, Yuwei and Wang, Xiaohua, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn and Li, Xi and Yang, Aijun and Wu, Yi and Rong, Mingzhe, E-mail: xhw@mail.xjtu.edu.cn, E-mail: mzrong@mail.xjtu.edu.cn and Han, Guohui and Lu, Yanhui},
abstractNote = {Due to the high global warming potential (GWP) and increasing environmental concerns, efforts on searching the alternative gases to SF{sub 6}, which is predominantly used as insulating and interrupting medium in high-voltage equipment, have become a hot topic in recent decades. Overcoming the drawbacks of the existing candidate gases, C5- perfluorinated ketone (C5 PFK) was reported as a promising gas with remarkable insulation capacity and the low GWP of approximately 1. Experimental measurements of the dielectric strength of this novel gas and its mixtures have been carried out, but the chemical decomposition pathways and products of C5 PFK during breakdown are still unknown, which are the essential factors in evaluating the electric strength of this gas in high-voltage equipment. Therefore, this paper is devoted to exploring all the possible decomposition pathways and species of C5 PFK by density functional theory (DFT). The structural optimizations, vibrational frequency calculations and energy calculations of the species involved in a considered pathway were carried out with DFT-(U)B3LYP/6-311G(d,p) method. Detailed potential energy surface was then investigated thoroughly by the same method. Lastly, six decomposition pathways of C5 PFK decomposition involving fission reactions and the reactions with a transition states were obtained. Important intermediate products were also determined. Among all the pathways studied, the favorable decomposition reactions of C5 PFK were found, involving C-C bond ruptures producing Ia and Ib in pathway I, followed by subsequent C-C bond ruptures and internal F atom transfers in the decomposition of Ia and Ib presented in pathways II + III and IV + V, respectively. Possible routes were pointed out in pathway III and lead to the decomposition of IIa, which is the main intermediate product found in pathway II of Ia decomposition. We also investigated the decomposition of Ib, which can undergo unimolecular reactions to give the formation of IV a, IV b and products of CF{sub 3} + CF-CF{sub 3} in pathway IV. Although IV a is dominant to a lesser extent due to its relative high energy barrier, its complicated decomposition pathway V was also studied and CF{sub 3}, C = CF{sub 2} as well as C-CF{sub 3} species were found as the ultimate products. To complete the decomposition of C5 PFK, pathway V I of Ic decomposition was fully explored and the final products were obtained. Therefore, the integrate decomposition scheme of C5 PFK was proposed, which contains six pathways and forty-eight species (including all the reactants, products and transition states). This work is hopeful to lay a theoretical basis for the insulating properties of C5 PFK.},
doi = {10.1063/1.4960988},
journal = {AIP Advances},
number = 8,
volume = 6,
place = {United States},
year = 2016,
month = 8
}
  • We present new reaction pathways relevant to low-temperature oxidation in gaseous and condensed phases. The new pathways originate from γ-ketohydroperoxides (KHP), which are well-known products in low-temperature oxidation and are assumed to react only via homolytic O-O dissociation in existing kinetic models. Our ab initio calculations identify new exothermic reactions of KHP forming a cyclic peroxide isomer, which decomposes via novel concerted reactions into carbonyl and carboxylic acid products. Geometries and frequencies of all stationary points are obtained using the M06-2X/MG3S DFT model chemistry, and energies are refined using RCCSD(T)-F12a/cc-pVTZ-F12 single-point calculations. Thermal rate coefficients are computed using variational transition-statemore » theory (VTST) calculations with multidimensional tunneling contributions based on small-curvature tunneling (SCT). These are combined with multistructural partition functions (QMS-T) to obtain direct dynamics multipath (MP-VTST/ SCT) gas-phase rate coefficients. For comparison with liquid-phase measurements, solvent effects are included using continuum dielectric solvation models. The predicted rate coefficients are found to be in excellent agreement with experiment when due consideration is made for acid-catalyzed isomerization. This work provides theoretical confirmation of the 30-year-old hypothesis of Korcek and co-workers that KHPs are precursors to carboxylic acid formation, resolving an open problem in the kinetics of liquid-phase autoxidation. The significance of the new pathways in atmospheric chemistry, low-temperature combustion, and oxidation of biological lipids are discussed.« less
  • The photoinitiated unimolecular decomposition of formaldehyde via the H+HCO radical channel has been examined at energies where the S{sub 0} and T{sub 1} pathways both participate. The barrierless S{sub 0} pathway has a loose transition state (which tightens somewhat with increasing energy), while the T{sub 1} pathway involves a barrier and therefore a tight transition state. The product state distributions which derive from the S{sub 0} and T{sub 1} pathways differ qualitatively, thereby providing a means of discerning the respective S{sub 0} and T{sub 1} contributions. Energies in excess of the H+HCO threshold have been examined throughout the range 1103{<=}E{supmore » {dagger}}{<=}2654 cm{sup -1} by using two complementary experimental techniques; ion imaging and high-n Rydberg time-of-flight spectroscopy. It was found that S{sub 0} dominates at the low end of the energy range. Here, T{sub 1} participation is sporadic, presumably due to poor coupling between zeroth-order S{sub 1} levels and T{sub 1} reactive resonances. These T{sub 1} resonances have small decay widths because they lie below the T{sub 1} barrier. Alternatively, at the high end of the energy range, the T{sub 1} pathway dominates, though a modest S{sub 0} contribution is always present. The transition from S{sub 0} dominance to T{sub 1} dominance occurs over a broad energy range. The most reliable value for the T{sub 1} barrier (1920{+-}210 cm{sup -1}) is given by the recent ab initio calculations of Yamaguchi et al. It lies near the center of the region where the transition from S{sub 0} dominance to T{sub 1} dominance takes place. Thus, the present results are consistent with the best theoretical calculations as well as the earlier study of Chuang et al., which bracketed the T{sub 1} barrier energy between 1020 and 2100 cm-1 above the H+HCO threshold. The main contribution of the present work is an experimental demonstration of the transition from S{sub 0} to T{sub 1} dominance, highlighting the sporadic nature of this competition. (c) 2000 American Institute of Physics.« less
  • Decompositions and polymerizations of perfluorinated compounds gases were demonstrated employing atmospheric pressure plasmas with continuous-wave microwave excitations. The atmospheric pressure plasma was generated at a low gas temperature of 520 K. Spherical-shaped particles of approximately 50-120 nm in diameter were synthesized in CF{sub 4}/He and C{sub 4}F{sub 8}/He plasma on Si substrate with dc voltage biasing, which was set in the plasma downstream region. The gas temperature in plasma was important to generate particles because particles were not generated at a high gas temperature of 850 K. The particles were determined to consist of carbon and fluorine atom composition frommore » an energy dispersive x-ray spectroscopy. Furthermore, the effect of H{sub 2} addition on the CF{sub 4}/He plasma was investigated. The decomposition efficiency of CF{sub 4} was increased with H{sub 2} addition and obtained over 80% without emissions of carbon dioxide.« less