119 / 2023-06-20 22:00:52

Study on the reaction mechanism of cobalt based catalyst catalyzed ventilation air methane combustion

Ventilation gas; Catalytic combustion; Cobalt based catalyst; Transition state; Density functional

In order to ensure the production safety in the process of coal mining, it is necessary to continuously transport surface air to the underground to dilute the underground gas concentration, thus forming the ventilation gas. In China, the amount of CH4 discharged into the atmosphere by ventilation gas is 1.3 times that of gas transported from west to east. With the acceleration of the international community's response to climate change and the continuous promotion of China's "double carbon" strategy, the utilization of ventilation gas has become an increasingly important research topic. Catalytic combustion is an effective technical means for the utilization of ventilation gas. However, the preparation of high activity and low cost catalysts and the study of their catalytic mechanism are the key scientific problems. In this paper, the preparation of cobalt-based catalyst and its catalytic mechanism for ventilation gas combustion were studied. Firstly, cobalt-based catalysts were prepared by hydrothermal synthesis method, coprecipitation method and solid-phase method, and the prepared catalysts were used in the catalytic combustion of ventilation gas. Combined with the activity evaluation, phase analysis and redox analysis of the three catalysts, the experimental results showed that the catalysts prepared by solid-phase method had outstanding performance, and showed good catalytic activity for ventilation gas combustion when the calcination temperature was 400℃ and the calcination time was 4h. Secondly, in order to further study the catalytic performance of cobalt-based catalyst prepared by solid-state method for the combustion of ventilation gas, the effects of changing calcination temperature, grinding time and cobalt acetate/oxalic acid ratio of cobalt-based catalyst were explored. The results show that the catalyst prepared under the conditions of cobalt acetate/oxalic acid ratio of 1:3, grinding time of 10 min and calcination at 400℃ for 4 hours has the highest activity, and its T50 and T90 are 367.1℃ and 436.56℃ respectively. Finally, combined with the quantum chemical calculation method, the molecular structure of the hypothetical transition state is optimized by using density functional theory (DFT), B3LYP basis set and 6-31g(d) method. The optimal structure of the transition state is determined by verifying the frequency and introverted reaction coordinates (IRC) of the hypothetical transition state structure, thus revealing the reaction mechanism of the catalytic combustion of ventilation gas.