全氟三乙胺热解机理的实验与理论研究

doi:10.11949/0438-1157.20220725

摘要/Abstract

摘要：

氟胺类物质是最有希望作为哈龙替代品的含氮化合物之一，全氟三乙胺作为典型的氟胺类物质具有良好的灭火效果。为研究全氟三乙胺热解机理，在管式加热炉内对全氟三乙胺进行热分解，通过GC-MS分析全氟三乙胺在不同温度条件下的热解产物，并用Gaussian软件对其热解反应路径进行理论计算。结果表明：保持停留时间为10 s，全氟三乙胺的初始热解温度为600℃，750℃完全热解，热解产物有C₄F₉N、C₃F₇N、C₂F₆和C₃F₈，热解温度较低时C₄F₉N体积分数最大，热解温度较高时C₃F₇N体积分数最大。在全氟三乙胺热解反应路径计算中，全氟三乙胺分子中的C—C键断裂后存在1条反应路径，可生成实验产物中的C₃F₈；全氟三乙胺分子的C—N键断裂后存在3条反应路径，可生成实验产物中的C₃F₇N、 C₄F₉N和C₂F₆。全氟三乙胺热解后产生的CF₃自由基可与H、OH自由基发生反应，从而产生灭火作用。此外，其热解产物C₄F₉N和C₃F₇N具有CN双键，更容易与燃烧活泼自由基·OH、·H发生化学作用，对研究全氟三乙胺的灭火机理具有十分重要的意义。

关键词: 全氟三乙胺, 热解, 高斯计算, 反应路径, 机理

Abstract:

Fluorine amines are one of the most promising nitrogen-containing compounds as halon substitutes. As a typical fluorine amine, perfluorotriethylamine has good fire-extinguishing effect. In order to reveal the pyrolysis mechanism of (C₂F₅)₃N, its pyrolysis products under different temperature conditions are obtained by using GC-MS, and then the pyrolysis reaction paths are theoretically calculated by using Gaussian. The results show that the initial pyrolysis temperature of (C₂F₅)₃N is about 600℃, and the complete pyrolysis is around 750℃, by keeping the residence time at 10 s. The pyrolysis products are C₄F₉N, C₃F₇N, C₂F₆ and C₃F₈. The volume fraction of C₄F₉N is the largest at a low pyrolysis temperature, while the volume fraction of C₃F₇N is the largest at a high pyrolysis temperature. In the calculation of the pyrolysis reaction path of (C₂F₅)₃N, there is one reaction pathway would generate C₃F₈ after the breaking of C—C bond in the (C₂F₅)₃N molecule. In another pyrolysis reaction path of (C₂F₅)₃N, C₂F₆ and the stable product C₄F₉N would be generated after the breaking of C—N bond. The breaking of C—N bond in (C₂F₅)₃N would produce an unstable product N(C₂F₅)₂, the followed breaking of the C—C bond will generate C₃F₇N. The main pyrolysis products of (C₂F₅)₃N are C₄F₉N and C₃F₇N, the two products have CN double bonds and can more easily interact with the combustion active.

Key words: (C₂F₅)₃N, pyrolysis, Gaussian calculation, reaction path, mechanism

中图分类号:

TQ 569

梁天水, 王新科, 刘德智, 钟委. 全氟三乙胺热解机理的实验与理论研究[J]. 化工学报, 2022, 73(10): 4762-4768.

Tianshui LIANG, Xinke WANG, Dezhi LIU, Wei ZHONG. Experimental and theoretical study on the pyrolysis mechanism of (C₂F₅)₃N[J]. CIESC Journal, 2022, 73(10): 4762-4768.

图/表 8

参考文献 4

5	Zhang M L, Lin Z J. Ab initio studies of the thermal decomposition pathways of 1-bromo-3, 3, 3-trifluoropropene[J]. Journal of Molecular Structure: Theochem, 2009, 899(1/2/3): 98-110.
6	Takahashi F, Katta V R, Linteris G T, et al. A computational study of extinguishment and enhancement of propane cup-burner flames by halon and alternative agents[J]. Fire Safety Journal, 2017, 91: 688-694.
7	Takahashi F, Katta V R, Linteris G T, et al. Combustion inhibition and enhancement of cup-burner flames by CF₃Br, C₂HF₅, C₂HF₃Cl₂, and C₃H₂F₃Br[J]. Proceedings of the Combustion Institute, 2015, 35(3): 2741-2748.
8	Linteris G T, Takahashi F, Katta V R. Cup-burner flame extinguishment by CF₃Br and Br₂ [J]. Combustion and Flame, 2007, 149(1/2): 91-103.
9	余彬彬, 蒋新生, 禹进, 等. 全氟己酮抑制航空煤油燃烧实验及化学动力学研究[J]. 化工学报, 2022, 73(4): 1834-1844.
	Yu B B, Jiang X S, Yu J, et al. Experimental and chemical dynamics study on the inhibition of combustion of aviation kerosene by C₆F₁₂O[J]. CIESC Journal, 2022, 73(4): 1834-1844.
10	Tapscott R E, Sheinson R S, Babushok V I, et al. Alternative fire suppressant chemicals [R]. National Institute of Standards and Technology, 2001.
11	Heinonen E W, Lifke J L, Tapscott R E. Advanced streaming agent development(volume Ⅳ): Tropodegradable halocarbons[R]. New Mexico Engineering Research Inst Albuquerque, 1996.
12	梁天水, 刘德智, 王永锦, 等. 全氟三乙胺和全氟己酮混合气体的灭火效果研究[J]. 化工学报, 2020, 71(7): 3387-3392.
	Liang T S, Liu D Z, Wang Y J, et al. Study on fire extinguishing efficiency of the mixtures of C₆F₁₂O and (C₂F₅)₃N[J]. CIESC Journal, 2020, 71(7): 3387-3392.
13	Sheinson R S, Driscoll D C. Fire suppression mechanisms: agent testing by cup burner[C]//International Conference on CFC and Halon Alternatives. Washington, DC, 1989: 10-11.
14	Takahashi K, Sekiuji Y, Yamamori Y, et al. Kinetic studies on the reactions of CF₃ with O(³P) and H atoms at high temperatures[J]. The Journal of Physical Chemistry A, 1998, 102(43): 8339-8348.
15	Linteris G T, Truett L. Inhibition of premixed methane-air flames by fluoromethanes[J]. Combustion and Flame, 1996, 105(1/2): 15-27.
16	Linteris G T, Burgess D R Jr, Babushok V, et al. Inhibition of premixed methane-air flames by fluoroethanes and fluoropropanes[J]. Combustion and Flame, 1998, 113(1/2): 164-180.
17	Hynes R G, Mackie J C, Masri A R. Inhibition of premixed hydrogen-air flames by 2-H heptafluoropropane[J]. Combustion and Flame, 1998, 113(4): 554-565.
18	Babushok V I, Linteris G T, Meier O C. Combustion properties of halogenated fire suppressants[J]. Combustion and Flame, 2012, 159(12): 3569-3575.
19	Takahashi K, Inomata T, Fukaya H, et al. New halon replacements based on perfluoroalkylamines[M]//ACS Symposium Series. Washington, DC: American Chemical Society, 1997: 139-150.
20	Takahashi K, Sekiuji Y, Inomata T, et al. Inhibition of combustion by bromine-free polyfluorocarbons(Ⅰ): Burning velocities of methane flames containing polyfluoroalkylamines[J]. Combustion Science and Technology, 1994, 102(1/2/3/4/5/6): 213-230.
21	Fukaya H, Ono T, Abe T. New fire suppression mechanism of perfluoroalkylamines[J]. Journal of the Chemical Society, Chemical Communications, 1995(12): 1207.
22	Yamamoto T, Yasuhara A, Shiraishi F, et al. Thermal decomposition of halon alternatives[J]. Chemosphere, 1997, 35(3): 643-654.
23	Lu D Y, Chao M Y, Zhou X M. Theoretical studies on the reactions of 1, 1, 2, 2, 3, 3, 4-heptafluorocyclopentane with hydroxyl and hydrogen free radicals[J]. Chinese Journal of Chemistry, 2014, 32(9): 897-908.
24	梁天水, 王宗莹, 高坤, 等. 基于cup burner的含铁基添加剂超细水雾灭火有效性分析[J]. 化工学报, 2019, 70(3): 1236-1242.
	Liang T S, Wang Z Y, Gao K, et al. Analysis of fire suppression effectiveness of ultra-fine water mist containing iron compounds additives in cup burner[J]. CIESC Journal, 2019, 70(3): 1236-1242.
25	Scott A P, Radom L. Harmonic vibrational frequencies: an evaluation of Hartree-Fock, Møller–Plesset, quadratic configuration interaction, density functional theory, and semiempirical scale factors[J]. The Journal of Physical Chemistry, 1996, 100(41): 16502-16513.
26	Liu Y, Yang G C, Sun S L, et al. Density functional theory investigation on the second-order nonlinear optical properties of chlorobenzyl-o-carborane derivatives[J]. Chinese Journal of Chemistry, 2012, 30(10): 2349-2355.
27	Zhou Y, Liu D J, Fu Y, et al. Accurate prediction of Ir—H bond dissociation enthalpies by density functional theory methods[J]. Chinese Journal of Chemistry, 2014, 32(3): 269-275.
28	Bai Q L, Zhang C H, Cheng C H, et al. Synthesis, photophysical properties and near infrared electroluminescence of 1(4), 8(11), 15(18), 22(25)-tetra-(methoxy-phenoxy)phthalocyanine[J]. Chinese Journal of Chemistry, 2012, 30(3): 689-694.
29	Gottlieb A D, Weishäupl R M. Strongly separated pairs of core electrons in computed ground states of small molecules[J]. Computational and Theoretical Chemistry, 2013, 1007: 82-89.
30	Zhang M H, Li R Z, Yu Y Z. A DFT study on the structure and properties of Cu/Cr₂O₃ catalyst[J]. Chinese Journal of Chemistry, 2012, 30(4): 771-778.
31	Raghavachari K, Trucks G W, Pople J A, et al. Reprint of: a fifth-order perturbation comparison of electron correlation theories[J]. Chemical Physics Letters, 2013, 589: 37-40.
32	Gaensslen M, Gross U, Oberhammer H, et al. Perfluorotriethylamine: an amine with unusual structure and reactivity[J]. Angewandte Chemie International Edition in English, 1992, 31(11): 1467-1468.
33	Cobos C J, Hintzer K, Sölter L, et al. Shock wave and modelling study of the dissociation pathways of (C₂F₅)₃N[J]. Physical Chemistry Chemical Physics: PCCP, 2019, 21(19): 9785-9792.
1	Burkholder J B, Cox R A, Ravishankara A R. Atmospheric degradation of ozone depleting substances, their substitutes, and related species[J]. Chemical Reviews, 2015, 115(10): 3704-3759.
2	Molina M J, Rowland F S. Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone[J]. Nature, 1974, 249(5460): 810-812.
3	Kennedy E M, Li K, Moghtaderi B, et al. A process for disposal of halon 1301 (CBrF³)[J]. Chemical Engineering Communications, 1999, 176(1): 195-200.
4	Wan D, Xu J H, Zhang J B, et al. Historical and projected emissions of major halocarbons in China[J]. Atmospheric Environment, 2009, 43(36): 5822-5829.

实验条件	参数设置
毛细柱固定相	10%SE-54
毛细柱柱长	30 m
毛细柱内径	0.25 mm
进样口温度	280℃
检测器温度	240℃
柱箱升温曲线	50~150℃, 10℃/min
分流比	80∶1
载气类型	氦气
载气流速	1.2 ml/min
离子源温度	240℃

实验条件	参数设置
毛细柱固定相	10%SE-54
毛细柱柱长	30 m
毛细柱内径	0.25 mm
进样口温度	280℃
检测器温度	240℃
柱箱升温曲线	50~150℃, 10℃/min
分流比	80∶1
载气类型	氦气
载气流速	1.2 ml/min
离子源温度	240℃

序号	质荷比（m/z）	气体产物
1	CF⁺（31）；C₂F⁺（43）；CF₂⁺（50）；CF₃⁺（69）；C₂F₅⁺（119）	C₂F₆
2	CF⁺（31）；C₂F⁺（43）；CF₂⁺（50）；C₂F₂⁺（62）；CF₃⁺（69）；C₂F₃⁺（81）；C₃F₃⁺（93）；C₂F₄⁺（100）；C₃F₄⁺（112）；C₂F₅⁺（119）；C₃F₅⁺（131）；C₃F₆⁺（150）	C₃F₈
3	CF⁺（31）；CF₂⁺（50）；CF₃⁺（69）；C₂F₄⁺（100）；C₂F₄N⁺（114）；C₂F₅N⁺（133）；C₃F₆N⁺（164）；C₃F₇N⁺（183）	C₃F₇N
4	CF⁺（31）；CF₂⁺（50）；CF₃⁺（69）；C₂F₄⁺（100）；C₂F₄N⁺（114）；C₂F₅⁺（119）；C₃F₆N⁺（164）；C₄F₈N⁺（214）	C₄F₉N

序号	质荷比（m/z）	气体产物
1	CF⁺（31）；C₂F⁺（43）；CF₂⁺（50）；CF₃⁺（69）；C₂F₅⁺（119）	C₂F₆
2	CF⁺（31）；C₂F⁺（43）；CF₂⁺（50）；C₂F₂⁺（62）；CF₃⁺（69）；C₂F₃⁺（81）；C₃F₃⁺（93）；C₂F₄⁺（100）；C₃F₄⁺（112）；C₂F₅⁺（119）；C₃F₅⁺（131）；C₃F₆⁺（150）	C₃F₈
3	CF⁺（31）；CF₂⁺（50）；CF₃⁺（69）；C₂F₄⁺（100）；C₂F₄N⁺（114）；C₂F₅N⁺（133）；C₃F₆N⁺（164）；C₃F₇N⁺（183）	C₃F₇N
4	CF⁺（31）；CF₂⁺（50）；CF₃⁺（69）；C₂F₄⁺（100）；C₂F₄N⁺（114）；C₂F₅⁺（119）；C₃F₆N⁺（164）；C₄F₈N⁺（214）	C₄F₉N

物种	ΔE/(kcal/mol)	(ΔE+ΔE_ZPVE)/(kcal/mol)
全氟三乙胺：N(C₂F₅)₃	0	0
P1：CF₃—CF N—C₂F₅+C₂F₆	-11.63	-13.28
P2：CF₃—CF N—C₂F₅+C₂F₆	-7.85	-9.52
P3：N(C₂F₅)₂CF₂+CF₃	75.73	72.56
P4：N(C₂F₅)₂+C₂F₅	68.60	65.06
TS1	76.56	73.86
TS2	79.00	76.27