基于反应分子动力学的1-丁基-3-甲基咪唑硝酸盐与煤反应机理研究

Research on Reaction Mechanism of[Bmim][NO_(3)]with Bituminous Coal Based on ReaxFF Molecular Dynamics

使用FTT锥形量热仪对烟煤和烟煤-[Bmim][NO_(3)](1-丁基-3-甲基咪唑硝酸盐)混合物进行燃烧性能测试,并结合分子反应动力学方法(ReaxFF)分析1200K,1600K,1800K和2200K四个温度条件下[Bmim][NO_(3)]与煤的化学反应过程。实验结果表明:[Bmim][NO_(3)]的添加会使体系达到热释放速率(HRR)峰值的时间提前,即促进烟煤的氧化燃烧反应。模拟结果表明:当模拟温度为1200K时,仅产生了少量H_(2)O和NO_(2);当模拟温度升高至1600K时,开始产生小分子烷烃、CO和CO_(2),但数目较少且产生时间延后;当模拟温度继续升高至1800K时,开始产生少量的H_(2)等气体无机物,CO与CO_(2)的数目较1600K时增加一倍,且初次出现时间提前约100ps;当模拟温度为2200K时,反应物中的N元素转化为NH_(3)和HCN,CO数目继续增加,CO_(2)数目逐渐降低。总体来看,温度较低时反应过程主要受[NO_(3)]-影响,[NO_(3)]-通过与煤分子中羧基反应使煤分子脱氢形成得电子结构,从而易于发生分解反应;当温度继续升高,[Bmim]+开始显著参与反应过程,[Bmim]+热解产生的自由基与煤分子发生反应,生成大量NH_(3)和HCN,从而会对人体和环境造成危害。

The FTT cone calorimeter was used to test the combustion performance of bituminous coal and the mixture of bituminous coal and[Bmim][NO_(3)](1-methyl-3-butylimidazole nitrate).In addition,combined with the molecular reaction dynamics method(Reactive Force Filed,ReaxFF),the chemical reactions between[Bmim][NO_(3)]and coal under four temperature conditions of 1200K,1600K,1800K,and 2200Kwere also analyzed.Experimental results show that[Bmim][NO_(3)]promotes the combustion of bituminous coal and shortens the time of reaching the peak of heat release rate(HRR).The simulation results show that only a small amount of H_(2)O and NO_(2)are produced at 1200K.When the temperature increases to 1600K,small molecular alkanes,CO,and CO_(2)are gradually formed in the reaction system,but the quantity is very low,and the production time is delayed.When the temperature further increases to 1800K,a small amount of H_(2) and other inorganic gases start to form.The numbers of CO and CO_(2)molecules are double compared to the numbers at 1600K,and the initial appearing time is also 100ps earlier.At 2200K,the N element in the reactants is transformed into NH_(3) and HCN.The amount of CO keeps increasing,but the amount of CO_(2)gradually decreases.In general,the chemical reaction is mainly affected by[NO_(3)]-at lower temperatures.[NO_(3)]-dehydrogenates coal to form an electronic structure,which is prone to decompose.When the temperature gradually increases,[Bmim]+begins to participate in the reaction process.The free radicals produced by[Bmim]+pyrolysis react with coal molecules and lead to a massive formation of NH_(3) and HCN,which are harmful to the environment and human beings.