| With the gradual rise of my country's economy,my country's external dependence on energy consumption has also increased.Taking oil and gas as an example,annual imports account for 70% of my country's total oil and gas consumption.At present,my country's energy consumption mode is relatively simple,and the utilization rate of clean energy is low.In addition,the development of conventional energy has entered an advanced stage,and the development of unconventional oil and gas will become an effective means to adjust the energy structure.Unconventional natural gas,dominated by shale gas,has become the main force in the world's new fossil energy supply,and the recoverable reserves of shale gas in my country rank among the top in the world.However,there are still many basic scientific problems in the efficient development of shale gas.Shale is rich in organic nanopores,and shale gas mainly exists in nanopores.Methane is the main component of shale gas,and the mining process of shale gas is mostly accompanied by water environment.Therefore,studying the interaction between water and methane in organic nanopores is an important topic.In this article,we use molecular dynamics simulation to study the interaction between gas and water in organic nanochannels.It is found that water molecules in nanochannels can be spontaneously replaced by methane molecules.This phenomenon is attributed to the fact that the average potential energy of methane molecules in nanochannels is lower than that of water molecules.This is also the fundamental reason why methane molecules in organic nanochannels can replace water molecules.the reason.In addition,the methane molecules entering the nanochannels of different widths also showed a variety of different distribution patterns.This series of studies provides ideas for understanding the interaction between water molecules and methane molecules in organic nanochannels,and provides basic insights in shale gas development.How to desorb the gas molecules contained in the nanopores is very important in the shale gas production process.We used molecular dynamics simulation methods to study the effect of electric fields on the adsorption behavior of methane gas and water molecules in nanochannels by applying electrostatic fields in different directions.It is found that when an electric field parallel to the gap is applied,water molecules outside the nanochannel will enter the channel and form an ice phase,while the methane molecules will change from the accumulation state in the pores to the free state and dissolve in the water outside the pores.This is because under the action of an electric field,the arrangement of water molecules changes,and a highly ordered network of hydrogen bonds is formed between the water molecules in the nanochannel,which occupies the entire nanochannel.In addition,methane is a non-polar molecule,and its state of motion is not affected by electric fields.The highly ordered arrangement of water molecules in the nanochannel causes the methane initially adsorbed in the nanochannel to be squeezed out of the nanochannel to become free molecules and enter the macroscopic water phase.When an electric field perpendicular to the direction of the gap is applied,it is found that all the water molecules in the channel exit the channel,and the methane molecules in the gap continue to exist in the gap and become free molecules.This is because the electric field has different response speeds to the dipoles of the water molecules inside and outside the nanochannel.Compared with the inside of the nanochannel,the dipole of water molecules outside the channel has a short and high response time to the electric field,forming a stable arrangement.The application of the vertical electric field breaks the original hydrogen bond network of water molecules in the channel.The water molecules are in an unstable state.In order to reach a stable state,the water molecules in the channel will exit the channel and form a stable hydrogen bond network with the bulk water. |
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