Study of the mechanism of pyrolysis of n-hexane initiated by 1-nitropropane

doi:10.11949/0438-1157.20230859

Abstract

Abstract:

To investigate the mechanism of 1-nitropropane (1-NP) initiated n-C₆H₁₄ pyrolysis, molecular dynamics (MD) simulations and synchrotron radiation experiments were used to analyze the pyrolysis process of n-C₆H₁₄ before and after the addition of 1-NP. The SVUV-PIMS technique was used to identify and quantify the resulting pyrolysis products of both n-C₆H₁₄ and n-C₆H₁₄ with the addition of 10% 1-NP. The pyrolysis of n-C₆H₁₄ and 1-NP/n-C₆H₁₄ was simulated at different temperatures using ReaxFF MD simulations, which allowed an in-depth investigation of the effects of temperature and 1-NP addition on the pyrolysis rates, heat sink and product distribution. Based on the simulated species evolution and trajectory information, the reaction pathway of 1-NP initiated n-C₆H₁₄ pyrolysis was explored. The results showed that: the addition of 1-NP to n-C₆H₁₄ significantly increased the production of C₂H₄. The production of C₂H₄ from the pyrolysis of n-C₆H₁₄ with 10% 1-NP added at 2103 K is about 2.2 times that of pure n-C₆H₁₄. The addition of 1-NP improves the heat sink of the fuel and reduces the activation energy of the fuel. The primary pathway of pyrolysis of n-C₆H₁₄ initiated by 1-NP is that 1-NP first cleaves to form NO₂ which then reacts with H to form OH. Secondly, the OH abstracts H from n-C₆H₁₄ to form C₆H₁₃. Finally, C₆H₁₃ is further cleaved to form 1-C₃H₇, 1-C₄H₈, 1-C₅H₁₀ and 2-C₆H₁₂.

Key words: nitropropane, n-hexane, pyrolysis, synchrotron radiation, molecular simulation, ReaxFF, reaction kinetics

摘要：

为研究1-硝基丙烷(1-NP)引发正己烷(n-C₆H₁₄)热解的作用机理，结合分子动力学(MD)模拟和同步辐射实验对添加1-NP前后的n-C₆H₁₄热解过程进行了分析。利用SVUV-PIMS技术鉴定并量化了n-C₆H₁₄和添加10% 1-NP的n-C₆H₁₄热解产物；利用ReaxFF MD模拟了不同温度下n-C₆H₁₄和1-NP/n-C₆H₁₄的热解，分析了温度和1-NP对n-C₆H₁₄热解速率、热沉以及产物分布的影响；根据模拟得到的物种演变与轨迹信息，探究了1-NP引发n-C₆H₁₄热解的反应路径。结果表明：向n-C₆H₁₄中添加1-NP后，C₂H₄产量显著增加，在2103 K温度下添加10%1-NP的n-C₆H₁₄热解产生的C₂H₄约为纯n-C₆H₁₄的2.2倍；添加1-NP提高了燃料的热沉，降低了燃料的活化能；1-NP引发n-C₆H₁₄热解的主要通道为：1-NP首先裂解产生NO₂，NO₂再与H反应生成OH，夺取n-C₆H₁₄的H生成C₆H₁₃，最后C₆H₁₃进一步裂解为1-C₃H₇、1-C₄H₈、1-C₅H₁₀和2-C₆H₁₂。

关键词: 硝基丙烷, 正己烷, 热解, 同步辐射, 分子模拟, ReaxFF, 反应动力学

CLC Number:

TK 46⁺1

Ruizhe CHEN, Yongfeng LIU, Chenyang YIN, Long WANG, Lu ZHANG, Jin’ou SONG. Study of the mechanism of pyrolysis of n-hexane initiated by 1-nitropropane[J]. CIESC Journal, 2023, 74(10): 4319-4329.

陈睿哲, 刘永峰, 殷晨阳, 王龙, 张璐, 宋金瓯. 1-硝基丙烷引发正己烷热解的机理研究[J]. 化工学报, 2023, 74(10): 4319-4329.

Figures/Tables 11

Fig.1 SVUV-PIMS experimental platform

Fig.2 Optimised molecular structure

Fig.3 Initial reaction system

Table 1 IEs， TF， TM and XM of pyrolysis products

m/z	化学式	IEs/eV	T_F/K	T_M/K	X_M/10^-4
15	CH₃	9.82	773	1103	9.751
16	CH₄	—	863	1103	35.06
26	C₂H₂	11.37	983	1103	33.90
28	CO	—	773	1103	6.128
28	C₂H₄	10.51	723	1103	620.5
29	C₂H₅	8.31	823	873	0.129
30	NO	9.24	673	1073	7.472
30	CH₂O	10.83	673	1023	3.448
30	C₂H₆	11.50	773	1103	32.86
32	CH₃OH	10.81	773	1023	1.220
39	C₃H₃	8.69	1103	1103	0.122
40	CH₂ $̿$ C $̿$ CH₂	9.69	1023	1103	2.239
40	CH₃C≡CH	10.32	1103	1103	0.729
41	C₃H₅	8.07	1023	1103	19.11
42	C₃H₆	9.74	673	1103	16.45
44	C₃H₈	11.02	903	1103	8.057
46	NO₂	9.80	673	923	2.270
52	C₄H₄	9.52	1103	1103	3.612
54	C₄H₆	9.04	1023	1103	2.966
56	CH₃CH₂CH $̿$ CH₂	9.58	673	1103	7.240
56	CH₃CH $̿$ CHCH₃	9.09	903	1103	0.732
66	C₅H₆	8.54	1103	1103	0.276
68	C₅H₈	8.60	1023	1103	0.134
70	CH₃CH₂CH₂CH $̿$ CH₂	9.51	863	1103	0.783
70	CH₃CH₂CH $̿$ CHCH₃	9.04	943	1103	0.275
78	C₆H₆	9.25	1103	1103	10.66
80	C₆H₈	8.24	1103	1103	0.0935
82	C₆H₁₀	8.54	1103	1103	0.0319
84	C₆H₁₂	8.97	983	1103	1.129

Table 1 IEs， TF， TM and XM of pyrolysis products

m/z	化学式	IEs/eV	T_F/K	T_M/K	X_M/10^-4
15	CH₃	9.82	773	1103	9.751
16	CH₄	—	863	1103	35.06
26	C₂H₂	11.37	983	1103	33.90
28	CO	—	773	1103	6.128
28	C₂H₄	10.51	723	1103	620.5
29	C₂H₅	8.31	823	873	0.129
30	NO	9.24	673	1073	7.472
30	CH₂O	10.83	673	1023	3.448
30	C₂H₆	11.50	773	1103	32.86
32	CH₃OH	10.81	773	1023	1.220
39	C₃H₃	8.69	1103	1103	0.122
40	CH₂ $̿$ C $̿$ CH₂	9.69	1023	1103	2.239
40	CH₃C≡CH	10.32	1103	1103	0.729
41	C₃H₅	8.07	1023	1103	19.11
42	C₃H₆	9.74	673	1103	16.45
44	C₃H₈	11.02	903	1103	8.057
46	NO₂	9.80	673	923	2.270
52	C₄H₄	9.52	1103	1103	3.612
54	C₄H₆	9.04	1023	1103	2.966
56	CH₃CH₂CH $̿$ CH₂	9.58	673	1103	7.240
56	CH₃CH $̿$ CHCH₃	9.09	903	1103	0.732
66	C₅H₆	8.54	1103	1103	0.276
68	C₅H₈	8.60	1023	1103	0.134
70	CH₃CH₂CH₂CH $̿$ CH₂	9.51	863	1103	0.783
70	CH₃CH₂CH $̿$ CHCH₃	9.04	943	1103	0.275
78	C₆H₆	9.25	1103	1103	10.66
80	C₆H₈	8.24	1103	1103	0.0935
82	C₆H₁₀	8.54	1103	1103	0.0319
84	C₆H₁₂	8.97	983	1103	1.129

Fig.4 Mole fraction of major pyrolysis products

Fig.5 Evolution curves of potential energy

Fig.6 Evolutions of the number of molecules of reactants and products

Fig.7 Fitting of first-order reaction kinetics to reaction rate constants and temperatures

Table 2 Arrhenius parameters of the reaction

反应体系	指前因子/s^-1	表观活化能/(kJ·mol^-1)
n-C₆H₁₄	6555.11	290.7
1-NP/n-C₆H₁₄	14.84	139.6

Fig.8 Initial pyrolysis pathways of n-C6H14

Fig.9 Pyrolysis pathways of 1-NP

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