基于量子化学计算的正己烷热解反应动力学模拟

Kinetic simulation of n-hexane pyrolysis reaction based on quantitative calculations

为研究正己烷(n-C_(6)H_(14))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-C_(6)H_(14)在不同温度下主要热解产物乙烯(C_(2)H_(4))、丙烯(C3H6)和丁炔(C4H6)的相对摩尔分数,并对n-C_(6)H_(14)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-C_(6)H_(14)进行了热解实验,并与NHP模型进行了对比分析。结果表明:n-C_(6)H_(14)热解过程中最主要的产物是C_(2)H_(4),促使C_(2)H_(4)生成较为重要的两个反应的指前因子分别为6.01×10^(13)s^(-1)和2.18×10^(13)s^(-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-C_(6)H_(14)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,C_(2)H_(4)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,C_(2)H_(4)主要来源于己基的一系列β位断裂。

To study the atmospheric pressure pyrolysis properties of n-hexane(n-C_(6)H_(14)),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-C_(6)H_(14),ethylene(C_(2)H_(4)),propylene(C3H6)and butyne(C4H6),at different temperatures,and the reaction pathways were analyzed for the pyrolysis process of n-C_(6)H_(14).The pyrolysis of n-C_(6)H_(14)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 Industry and Engineering Progress,2024,43(8):4273-4282.finger-forward factors for the two reactions,which were more important for promoting the generation of C_(2)H_(4),were 6.01×10^(13)s^(-1)and 2.18×10^(13)s^(-1),respectively.n-C_(6)H_(14)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-C_(6)H_(14)pyrolysis products were predicted in terms of their relative molar fractions.Compared with the JetSurF 2.0 model,the maximum errors for C_(2)H_(4)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-C_(6)H_(14)was C_(2)H_(4),which mainly originated from a series ofβ-breaks of the hexyl group.