The Study Of Liquid Phase Exfoliation,Assembly Of Vermiculites And Application

As a clean and efficient new energy source,natural gas hydrate has attracted great attention from governments and scholars around the world.Most NGH deposits are in sediment layer,and clay minerals,as an important component of the sediment layer,have an important influence on the formation and decomposition of NGH.Many scholars at home and abroad use real clay minerals to carry out experiments to explore the influence of clay minerals on the formation and decomposition of hydrate.However,due to the diverse composition of clay,rich pore structure,large specific surface area,diverse interlayer ions and complex surface structure,the experimental results show that clay may have inhibiting or promoting effect on hydrate formation,or may not.There is no exact structure-activity relationship between clay and hydrate generation or decomposition.Therefore,controlling of clay properties and obtaining clay materials with highly controllable composition and structure is the key to exploring the structure-activity relationship.In this paper,vermiculite,a typical 2:1 type clay,is selected as the research object.By means of ionic intercalation combined with ultrasonic exfoliation,vermiculite particles is successfully exfoliated and vermiculite nano-flakes is obtained.The size screening of vermiculite nano-flakes is realized by gradient centrifugation,and the controllable size of two-dimensional nano-clay materials were obtained.We study the effect of different sizes of vermiculite nano-flakes on the formation of tetrahydrofuran hydrate and ice.The results show that vermiculite nano-flakes can promote the nucleation of hydrate and ice,but the conversion efficiency of hydrate is decreased.In the formation experiment of methane hydrate,the addition of vermiculite nano-flakes also promote the formation of hydrate,and the methane gas conversion rate reached more than 20%.The concentration of vermiculite nano-flakes has little influence on the methane conversion rate.In addition,Raman technique is used to observe the hydrate growth on the surface of vermiculite membranes.The membrane has little effect on the structure of hydrate.Due to the limited capacity of conventional ultrasonic exfoliation,it is difficult to realize large-scale exfoliation.Based on high-speed stirring,we develope a fast and large-scale vermiculite stripping method by utilizing the shear force.This method has the advantages of short intercalation time,rapid stripping process and large volume of one-time stripping.In addition to the hydrate study,we assembled vermiculite nano-flakes with extremely high aspect ratio to form vermiculite membranes with nano-channels.The transparent vermiculite membrane with adjustable structure can be used for molecular interception and screening.The results show that vermiculite membrane has a good interception effect on methylene blue molecules.