Mocular Simulation Of Adsorption Of Carbon Dioxide In The Pore Structure And Diffusion Of Clay Minerals

In view of the increasingly serious harm caused by the greenhouse effect,it is imperative to control the greenhouse effect,and to find a governance both economic and rapid has high value of research.Clay minerals in shale are naturally occurring and widely distributed,which can be used as a natural adsorbent.Therefore,it is of great significance to study the geological storage of carbon dioxide by the use of clay minerals in shale.At present,domestic and foreign scholars mainly study the adsorption performance of clay minerals by carbon dioxide through experimental methods.However,the experimental method cannot accurately reflect the microscopic adsorption mechanism.So,people gradually favor the molecular simulation methods to study the adsorption performance of clay minerals by carbon dioxide.In this article,through the Materials Studio simulation software,fourclay minerals,kaolinite,montmorillonite,illite and 1:1IMON mixed layer,which are very common in nature,were constructed and optimized.And the pore structure of four clay minerals with pore diameters of 2nm,4nm and 6nm were constructed.Studied on the adsorption properties of carbon dioxide by four clay minerals by using Monte Carlo,molecular mechanics,and molecular dynamics simulation methods,and made a comparison.The simulation results are as follows:(1)The adsorption amount of carbon dioxide in the three pore sizes of the four clay minerals increased first and then decreased with the increase of burial depth.Among them,the adsorption amount of kaolinite reached the maximum at 0.75 km,and the other three clay minerals reached the maximum adsorption capacity at 0.5km.The adsorption of carbon dioxide by four clay minerals increased with the increase of pore size,but the adsorption heat decreased with the increase of pore size.Carbon dioxide forms three main adsorption layers in the pores of four clay minerals.Carbon dioxide forms three main adsorption layers in the pores of the four clay minerals,which are the main adsorption layers close to the wall,and the secondary adsorption layer close to the main adsorption layer away from the wall surface and the free layer in the center of the pores.The order of adsorption amount of carbon dioxide by four clay minerals under the same conditions is: Montmorillonite > 1:1 Imon mixed layer > Ili stone > Kaolinite.The adsorption of carbon dioxide bythe pore configuration of four clay minerals is physical adsorption.(2)In the pore structure of four clay minerals,tetrahedral oxygen adsorbs carbon dioxide more than tetrahedral silicon under the same conditions.The adsorption of carbon dioxide by tetrahedral oxygen and tetrahedral silicon is mainly Van der Waals force in the non-bonding action.The adsorption of tetrahedral oxygen and tetrahedral silicon in carbon dioxide and montmorillonite pore structure are the largest.(3)The self-diffusion coefficient of carbon dioxide increased with the increase of buried depth,and gradually increased with the increase of the pore size of clay minerals.After simulation studies,it can be concluded that the clay minerals in the depth range of 0.5km to 0.75 km is most suitable for geological storage of carbon dioxide.