基于量子化学计算的正己烷热解反应动力学模拟

doi:10.16085/j.issn.1000-6613.2023-1268

摘要/Abstract

摘要：

为研究正己烷（n-C₆H₁₄）的常压热解特性，提出了正己烷热解（NHP）模型，该模型使用基于误差传播的直接关系图（DRGEP）简化方法和色散校正密度泛函理论的B2PLYP/def2-tzvp方法，得到了一个包含33种物种和134个基元反应的简化机理。利用该模型计算了n-C₆H₁₄在不同温度下主要热解产物乙烯（C₂H₄）、丙烯（C₃H₆）和丁炔（C₄H₆）的相对摩尔分数，并对n-C₆H₁₄的热解过程进行了反应路径分析。利用同步辐射真空紫外光电离质谱法（SVUV-PIMS）结合射流搅拌反应器（JSR）在温度为673~1103K、压力为1atm条件下对n-C₆H₁₄进行了热解实验，并与NHP模型进行了对比分析。结果表明：n-C₆H₁₄热解过程中最主要的产物是C₂H₄，促使C₂H₄生成较为重要的两个反应的指前因子分别为6.01×10¹³s^-1和2.18×10¹³s^-1。在673~1023K温度范围内，结合量子化学计算得到的NHP模型对n-C₆H₁₄主要热解产物的相对摩尔分数进行了预测，与JetSurF 2.0模型相比，C₂H₄和C₄H₆的最大误差分别减小了27.9%和47.9%。反应路径分析表明，C₂H₄主要来源于己基的一系列β位断裂。

关键词: 正己烷, 热解, 计算化学, 反应动力学, 同步辐射真空紫外光电离质谱法, 射流搅拌反应器

Abstract:

To study the atmospheric pressure pyrolysis properties of n-hexane (n-C₆H₁₄), an n-hexane pyrolysis (NHP) model was proposed, which used the error propagation-based direct relation graph (DRGEP) simplification method and the B2PLYP/def2-tzvp method employing dispersion-corrected density-functional theory to obtain a model with 33 components and 134 primitive reactions in a simplified mechanism. The model was utilized to calculate the relative mole fractions of the major pyrolysis products of n-C₆H₁₄, ethylene (C₂H₄), propylene (C₃H₆) and butyne (C₄H₆), at different temperatures, and the reaction pathways were analyzed for the pyrolysis process of n-C₆H₁₄. The pyrolysis of n-C₆H₁₄ was tested using synchrotron radiation vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) coupled with a jet-stirred reactor (JSR) at temperatures ranging from 673K to 1103K and pressures up to 1atm, and was analyzed in comparison with the NHP model. The results showed that the finger-forward factors for the two reactions, which were more important for promoting the generation of C₂H₄, were 6.01×10¹³s^-1 and 2.18×10¹³s^-1, respectively. n-C₆H₁₄ was mainly analyzed by the NHP model combined with the NHP model obtained from quantum chemical calculations in the temperature range of 673—1023K. The relative molar fractions of the main n-C₆H₁₄ pyrolysis products were predicted in terms of their relative molar fractions. Compared with the JetSurF 2.0 model, the maximum errors for C₂H₄ and C₄H₆ were reduced by 27.9% and 47.9%, respectively. The reaction path analysis indicated that the most dominant product during the pyrolysis of n-C₆H₁₄ was C₂H₄, which mainly originated from a series of β-breaks of the hexyl group.

Key words: n-hexane, pyrolysis, computational chemistry, reaction kinetics, synchrotron-base vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), jet-stirred reactor (JSR)

中图分类号:

TK401

殷晨阳, 刘永峰, 陈睿哲, 张璐, 宋金瓯, 刘海峰. 基于量子化学计算的正己烷热解反应动力学模拟[J]. 化工进展, 2024, 43(8): 4273-4282.

YIN Chenyang, LIU Yongfeng, CHEN Ruizhe, ZHANG Lu, SONG Jin’ou, LIU Haifeng. Kinetic simulation of n-hexane pyrolysis reaction based on quantitative calculations[J]. Chemical Industry and Engineering Progress, 2024, 43(8): 4273-4282.

图/表 9

图1 同步辐射JSR装置

表1 气体流量参数

温度/K	总流量 /L·min^-1	n-C₆H₁₄流量 /L·min^-1	Ar流量 /L·min^-1
673	0.94973	0.009497	0.94024
723	0.88405	0.008841	0.87521
773	0.82687	0.008269	0.81860
823	0.77664	0.007766	0.76887
863	0.74064	0.007406	0.73523
903	0.70783	0.007078	0.70075
943	0.67781	0.006778	0.67103
983	0.65022	0.006502	0.64372
1023	0.62480	0.006248	0.61855
1063	0.60129	0.006013	0.59528
1103	0.57948	0.005795	0.57369

图2 简化机理与详细机理误差

图3 1023K时热解产物敏感性

图4 723K和1023K时C2H4敏感性

表2 反应动力学参数

编号	反应	A/s^-1	E_a/cal·mol^-1
R39	C₂H₅(+M) $̿$ C₂H₄+H(+M)	6.01×10¹³	193.2
R109	2-C₆H₁₃(+M) $̿$ C₃H₆+n-C₃H₇(+M)	4.47×10¹¹	28016.2
R110	3-C₆H₁₃(+M) $̿$ C₂H₅+1-C₄H₈(+M)	3.55×10¹²	28310.5
R115	n-C₆H₁₄ $̿$ pC₄H₉+C₂H₅	2.18×10¹³	86959.6
R116	n-C₆H₁₄ $̿$ 2n-C₃H₇	2.18×10¹³	87198.5
R122	n-C₆H₁₄+CH₃ $̿$ 3-C₆H₁₃+CH₄	1.57×10⁵	7534.0

表2 反应动力学参数

编号	反应	A/s^-1	E_a/cal·mol^-1
R39	C₂H₅(+M) $̿$ C₂H₄+H(+M)	6.01×10¹³	193.2
R109	2-C₆H₁₃(+M) $̿$ C₃H₆+n-C₃H₇(+M)	4.47×10¹¹	28016.2
R110	3-C₆H₁₃(+M) $̿$ C₂H₅+1-C₄H₈(+M)	3.55×10¹²	28310.5
R115	n-C₆H₁₄ $̿$ pC₄H₉+C₂H₅	2.18×10¹³	86959.6
R116	n-C₆H₁₄ $̿$ 2n-C₃H₇	2.18×10¹³	87198.5
R122	n-C₆H₁₄+CH₃ $̿$ 3-C₆H₁₃+CH₄	1.57×10⁵	7534.0

图5 相对摩尔分数分布

图6 673K时n-C6H14的一级热解路径

图7 943K/1023K时n-C6H14的热解路径及其能垒

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