Microscopic mechanism analysis of inhibition on methane explosion by diatomite

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 (25-1 000 ℃), 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:① two 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). ② Due 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). ③ Vicinal 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. ④ With 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. © 2022 China Coal Society. All rights reserved.