Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Huo, Erguang; Hu, Zheng; Wang, Shukun; Xin, Liyong; Bai, Mengna

doi:10.1016/j.energy.2022.123435

Cited by 21 publications

(4 citation statements)

References 41 publications

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“…Thus, the ReaxFF molecular dynamics simulation studies of working fluids pyrolysis mechanism are reliable. The ReaxFF force field has been currently employed in the pyrolysis, combustion, and oxidation of HCs, 51,53‐57 coal, 58,59 F‐containing working fluids, 22,23,52,60,61 and biomass 62,63 . The total potential energy of the system is,

E_{system} goodbreak= \begin{matrix} lefttrue \\ E_{italicbond} + E_{italicpen} + E_{italicvdWaals} + E_{italicover} + E_{italicunder} + E_{italicval} \\ + E_{italictors} + E_{italicconj} + E_{italicCoulomb} \end{matrix}

in which E bond is the bond energy of a chemical bond, and its expression is:

E_{bond} goodbreak= \begin{matrix} lefttrue \\ - D_{ε}^{σ} ∙ {italicBO}_{italicij}^{σ} ∙ exp (p_{bε, 1} (1 - {({italicBO}_{italicij}^{σ})}^{p_{italicbε, 2}})) - D_{ε}^{π} \\ ∙ {italicBO}_{italicij}^{π} - D_{ε}^{italicππ} ∙ {italicBO}_{italicij}^{italicππ} \end{matrix}

where BO ij represents the bond order that can be calculated by the distance between two atoms.…”

Section: Methodsmentioning

confidence: 99%

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Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Huo

Xin

Wang

2022

Intl J of Energy Research

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Summary Organic Rankine cycle (ORC) is an effective method used to convert renewable energy and waste heat into electricity. The screening of working fluids is crucial to the design of the ORCs, and their thermal stability is a key factor for the selection of ORC working fluids. This review emphasized the thermal stability studies of ORC working fluids. We reviewed the research methods and thermal stability results of hydrocarbon, fluorine‐containing, and siloxane working fluids and analyzed the effects of working fluid pyrolysis on the performance and safety of ORCs. Compared with the previous articles, which only introduced the thermal stability studies of working fluids, this review also focused on the research methods and the status quo of the working fluid pyrolysis mechanism. The feasibility of the density functional theory method and the ReaxFF force field for the study of working fluid pyrolysis mechanism was demonstrated. Finally, the disadvantages of working fluid thermal stability and pyrolysis mechanism studies were analyzed, and the prospects in this field were also discussed.

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E_{system} goodbreak= \begin{matrix} lefttrue \\ E_{italicbond} + E_{italicpen} + E_{italicvdWaals} + E_{italicover} + E_{italicunder} + E_{italicval} \\ + E_{italictors} + E_{italicconj} + E_{italicCoulomb} \end{matrix}

in which E bond is the bond energy of a chemical bond, and its expression is:

E_{bond} goodbreak= \begin{matrix} lefttrue \\ - D_{ε}^{σ} ∙ {italicBO}_{italicij}^{σ} ∙ exp (p_{bε, 1} (1 - {({italicBO}_{italicij}^{σ})}^{p_{italicbε, 2}})) - D_{ε}^{π} \\ ∙ {italicBO}_{italicij}^{π} - D_{ε}^{italicππ} ∙ {italicBO}_{italicij}^{italicππ} \end{matrix}

where BO ij represents the bond order that can be calculated by the distance between two atoms.…”

Section: Methodsmentioning

confidence: 99%

“…22,51 Thus, the ReaxFF molecular dynamics simulation studies of working fluids pyrolysis mechanism are reliable. The ReaxFF force field has been currently employed in the pyrolysis, combustion, and oxidation of HCs, 51,53-57 coal, 58,59 F-containing working fluids, 22,23,52,60,61 and biomass. 62,63 The total potential energy of the system is,…”

Section: Methodsmentioning

confidence: 99%

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Huo

Xin

Wang

2022

Intl J of Energy Research

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“…However, the supercritical ORC has a high heat source temperature, and the working fluid may decompose in the process of circulation (Huo et al, 2017;Huo et al, 2022a;Huo et al, 2022b). The decomposition products of the working fluid may consist of gaseous, liquid, and solid states, which will affect the performance and even the safety of ORC (Huo et al, 2017;Huo et al, 2019a).…”

Section: Introductionmentioning

confidence: 99%

Thermal decomposition of n-hexane in organic Rankine cycle: a study combined ReaxFF reactive molecular dynamic and density functional theory

Liu,

Wang,

Chen

et al. 2023

Front. Energy Res.

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The thermal decomposition mechanism of n-hexane is investigated by using density functional theory and ReaxFF force field. The initial decomposition reactions, the effect of temperature on thermal decomposition and first-order kinetics are analyzed. The results show that the C-C bonds in n-hexane molecule are more easily decomposed than that of C-H bonds, and the breakage of C3-C4 bond is the main initial decomposition reaction. The main decomposition products of n-hexane are H2, CH4, C2H2, C2H4, C2H6, and C3H6. The decomposition rate of n-hexane is accelerated by temperature. The apparent activation energy and pre-exponential factor of n-hexane thermal decomposition are 209.8 kJ mol−1 and 1.1 × 1013 s−1, respectively.

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“…While the highly symmetrical single carbon structure and C–F bond with strong ionic character make CF 4 decomposition require a high temperature ( 22 ), the introduction of the catalyst can significantly promote the C–F bond activation and decrease the decomposition temperature. Takita et al ( 16 ) first proposed that CF 4 could be hydrolyzed over Ce10%-AlPO 4 at 700 °C, well below its pyrolysis of 1,200 °C ( 23 ). El-Bahy et al ( 19 ) found that the introduction of Ga promoted C–F bond activation by increasing Lewis (L) acid sites on γ-Al 2 O 3 surface, achieving a 84% CF 4 decomposition at 630 °C.…”

mentioning

confidence: 99%

Promoting C–F bond activation via proton donor for CF ₄ decomposition

Chen,

Qu,

Luo

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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Tetrafluoromethane (CF 4 ), the simplest perfluorocarbons, is a permanently potent greenhouse gas due to its powerful infrared radiation adsorption capacity. The highly symmetric and robust C–F bond structure makes its activation a great challenge. Herein, we presented an innovated approach that efficiently activates C–F bond utilizing protonated sulfate (–HSO 4 ) modified Al 2 O 3 @ZrO 2 (S-Al 2 O 3 @ZrO 2 ) catalyst, resulting in highly efficient CF 4 decomposition. By combining in situ infrared spectroscopy tests and density function theory simulations, we demonstrate that the introduced –HSO 4 proton donor has a stronger interaction on the C–F bond than the hydroxyl (–OH) proton donor, which can effectively stretch the C–F bond for its activation. Consequently, the obtained S-Al 2 O 3 @ZrO 2 catalyst achieved a stable 100% CF 4 decomposition at a record low temperature of 580 °C with a turnover frequency value of ~8.3 times higher than the Al 2 O 3 @ZrO 2 catalyst without –HSO 4 modification, outperforming the previously reported results. This work paves a new way for achieving efficient C–F bond activation to decompose CF 4 at a low temperature.

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Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Cited by 21 publications

References 41 publications

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Thermal decomposition of n-hexane in organic Rankine cycle: a study combined ReaxFF reactive molecular dynamic and density functional theory

Promoting C–F bond activation via proton donor for CF ₄ decomposition

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Thermal decomposition and interaction mechanism of HFC-227ea/n-hexane as a zeotropic working fluid for organic Rankine cycle

Cited by 21 publications

References 41 publications

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

Thermal decomposition of n-hexane in organic Rankine cycle: a study combined ReaxFF reactive molecular dynamic and density functional theory

Promoting C–F bond activation via proton donor for CF 4 decomposition

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Product

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Promoting C–F bond activation via proton donor for CF ₄ decomposition