硅藻土抑制瓦斯爆炸的微观机理分析

Microscopic mechanism analysis of inhibition on methane explosion by diatomite

基于量子化学理论,利用过渡态方法和吸附理论对硅藻土抑制瓦斯爆炸机理进行了分析。以甲烷氧化初始链式反应为切入点,分析了硅藻土中2种主要硅醇(孤立硅醇和连生硅醇)与其关键中间产物(•H,•OH和HCHO)的相互作用。从动力学角度,利用反应能垒和反应速率常数随温度变化(25~1000℃)的相互关系说明了硅藻土与自由基反应对链式反应的影响;从吸附角度,利用吸附能和弱相互作用可视化分析说明了硅藻土对HCHO的物理吸附所属弱相互作用类型及吸附对链式反应的影响。结果表明:①硅藻土中的2种常见结构——孤立硅醇和连生硅醇,在与自由基的反应中表现出不同的性质。其中连生硅醇具备更好的抑制效果,在31℃时,便开始影响链式反应;在122℃时,与对应甲烷氧化链式反应达到相同速率,有效减弱链式反应;在259℃及更高温度时,有效抑制链式反应(为链式反应速率的10倍以上)。②硅藻土由于表面的极性羟基结构,2种模型均能与HCHO形成较为稳定的氢键结构。其中,孤立硅醇具备更高的原子利用率,而连生硅醇则吸附性能更强(两者相差约0.9 kJ/mol)。③连生硅醇在消耗自由基和吸附HCHO方面均具备较好的效果,即天然硅藻土可以通过增加连生硅醇浓度以加强抑制效果。④参考连生硅醇抑制机理,在未来筛选新型抑制剂时,可将表面极性羟基浓度作为评选标准之一。

Based on the theory of quantum chemistry,the mechanism of inhibiting gas explosion by diatomite was investigated in this study.Taking the methane oxidation chain reaction as the starting point,the interaction between the two main silanol(single silanol and vicinal silanol)in diatomite and the key intermediate products(•H,•OH and HCHO)was analyzed.From the kinetic point of view,combined with the relationship between reaction energy barrier and reaction rate constant with temperature(25-1000℃),the effect of diatomite and free radical reaction on chain reaction was explained.From the perspective of adsorption,the weak interaction type of physical adsorption of HCHO by diatomite and the effect of adsorption on chain reaction were explained by using the visual analysis of adsorption energy and weak interaction.The results show that:①two common structures in diatomite,i.e.,single silanol and vicinal silanol,show some different properties in the reaction with free radicals.Among them,the vicinal silanol has a better inhibitory effect.At 31℃,it starts to affect the chain reaction,at 122℃,it reaches the same rate as the corresponding methane oxidation chain reaction,which effectively weakens the chain reaction.At the temperatures of 259℃and higher,the chain reaction is effectively inhibited(more than 10 times the rate of the chain reaction).②Due to the polar hydroxyl structure on the surface of diatomite,both models can form a relatively stable hydrogen bond structure with HCHO.Among them,single silanol has higher atom utilization,while vicinal silanol has stronger adsorption performance(the difference is about 0.9 kJ/mol).③Vicinal silanol has a good effect on both the consumption of free radicals and the adsorption of HCHO.That is to say,natural diatomite can enhance the inhibitory effect by increasing the concentration of vicinal silanol.④With reference to the inhibition mechanism of vicinal silanol,in the future screening of new inhibitors,the concentration of surface polar hydroxyl groups can be used as one of the selection criteria.