Abstract:

Molecular dynamics simulation was used to study the formation process of methane hydrate in the wet fixed bed filled with two representative metal-organic framework materials (MOF materials) ZIF-8 and ZIF-67. The results showed that compared with ZIF-67, ZIF-8 material with the stronger adsorption capacity of methane gas can eventually induce more methane and water molecules to convert into hydrates, which was conducive to the natural gas storage by using hybrid adsorption-hydration technique. However, the excellent adsorption property of ZIF-8 on methane will also reduced the concentration of methane in solution, weakened the driving force of hydrate formation, and significantly prolonged the growth time of hydrate by promoting the migration of methane molecules in the solution to the surface of ZIF-8 material and aggregating into nano-bubbles. Therefore, when selecting porous materials suitable for the hybrid adsorption-hydration natural gas storage technology, it was necessary to comprehensively consider the natural gas adsorption characteristics of the dry materials themselves and the hydrate formation kinetics of the fixed bed as a whole.

Key words: molecular simulation, hydrate, adsorption, natural gas, kinetics

摘要：

采用分子动力学模拟方法研究了两种代表性金属-有机骨架材料（MOF材料）ZIF-8和ZIF-67在湿材料固定床体系中的甲烷水合物微观动力学形成过程。结果表明：与ZIF-67相比，ZIF-8材料对甲烷分子的吸附能力更强，最终会诱导更多的甲烷和水分子转化为水合物，有助于吸附-水合耦合储存天然气。但是与此同时，在水合物的形成过程中，ZIF-8对甲烷的吸附作用亦会通过促进溶液中的甲烷分子向ZIF-8固体表面运移并聚集成纳米气泡，从而降低溶液中甲烷浓度、削弱水合物形成驱动力、显著延长水合物的生长时间。因此，在选择适用于吸附-水合耦合天然气存储技术的多孔材料时，需从干材料自身的天然气吸附特性及固定床整体的水合物生成动力学两方面进行综合考虑。

关键词: 分子模拟, 水合物, 吸附, 天然气, 动力学