基于Gaussian的甲烷爆炸微观反应计算分析

Calculation and analysis on micro reaction of methane explosion based on Gaussian

为从微观热力学及动力学角度更深入了解甲烷爆炸微观反应机理,应用Gaussian软件DFT理论,B3LYP-D3(BJ)/6-31+G*水平对利用敏感性分析方法得出的甲烷爆炸反应简化机理中各驻点进行结构优化与频率计算,在M06-2X/def2-tzvpp水平上计算单电能,得到反应物、中间体、过渡态、产物的稳定构型及其参数、热力学数据,并计算得到各反应的焓变、吉布斯自由能变及自由能垒。研究结果表明:甲烷爆炸微观反应机理中基元反应1,9无过渡态,其他反应存在过渡态;基元反应1,4等为反应体系提供热量,保证甲烷氧化反应不断进行,反应1放热最多,焓变为-433.7 kJ·mol^(-1);关键自由基OH·的生成是反应3 O_(2)+H·→OH·+O·与反应4 O·+H_(2)→OH·+H·相互协同与促进的结果;反应3 O_(2)+H·→OH·+O·为该甲烷爆炸机理的决速步,自由能垒为312.4 kJ·mol^(-1)。研究结论可为深入研究甲烷爆炸微观反应机理和化学抑爆机理提供借鉴。

In order to further understand the micro reaction mechanism of methane explosion from the perspectives of micro thermodynamics and kinetics,the structure optimization and frequency calculation of each stagnation point in the simplified mechanism of methane explosion reaction proposed by the sensitivity analysis method was conducted by using the Gaussian software DFT theory and B3LYP-D3(BJ)/6-31+G*level.The single electrical energy at M06-2X/def2-tzvpp level was calculated,then the stable configurations and their parameters and the thermodynamic data of reactants,intermediates,transition states and products were obtained,and the enthalpy change,Gibbs free energy change,and free energy barrier of each reaction were calculated.The results showed that there was no transition state in elementary reaction 1 and 9 in the micro reaction mechanism of methane explosion,and there were transition states in other reactions.The elementary reaction 1 and 4 provided heat for the reaction system and ensured the continuous oxidation reaction of methane.The heat release of reaction 1 was the greatest,and the enthalpy change was-433.7 kJ·mol^(-1).The generation of key free radical OH was the result of the interaction and promotion of reaction 3 O_(2)+H·→OH·+O·and reaction 4 O·+H_(2)→OH·+H·.The reaction 3 O_(2)+H·→OH·+O·was the rate-determining step of the mechanism of methane explosion,and the free energy barrier was 312.4 kJ·mol^(-1).The research results provide reference for further study on the micro reaction mechanism and chemical explosion suppression mechanism of methane explosion.