Investigation Of Adsorption Properties In Slit Nanopores Based On Liquid Quasicrystal Model

Molecules confined within narrow pores, with the size of a few molecular diameters, can exhibit different physical behaviors from the bulk fluid. To understand the behaviors resulting from the finite-size effect, the liquid molecules distribution in nanopores is of significant scientific interest. The research of molecular adsorption mechanism of the liquid in nanopores can help us choose appropriate adsorbent, expand considerably the range of adsorbent applications, and have an applicable value for adsorbent regeneration. There is much practical significance for understanding the adsorption mechanism and liquid distribution in limit space.Although the study of adsorption phenomenon has a long history, it is still a very active area of research. Classical thermodynamic theory can only study liquid adsorption equilibrium properties approximation. So a lot of researchers are trying to study molecular interaction potential energy from microscopic view. The physical properties of fluid are different from the bulk fluid, after be confined within a few molecules of the diameter of the nanospace. Because there are two walls of the silt pore around. Liquid molecules not only are acted upon by a number of forces from the other molecules, but also are acted upon by forces from the two walls. Under multiple influence, the liquid molecules will show a series of phenomenon that different from the free state, such as adsorption on the pore wall, the layered phenomenon in the pore, the gas-liquid and liquid-liquid transformation phenomenon and so on. But at the moment, the methods are mainly computer simulations which are adopted to study the adsorption mechanism of liquid in the nanopores, such as Molecular dynamics (MD), Monte Carlo simulation(MC), Density functional theory (DFT), the Lattice theory expanded by Donohue, and so on. The key is to determine the microscopic molecular interaction potential accurately. Molecular simulation has high prediction accuracy, but the algorithm is relatively complex. These methods didn’t explicitly point out the distribution of liquid molecular adsorbed on the nanopore wall, and there are mostly the studies of the gas adsorption. A lot of adsorption experiments and molecular simulation have been done, but there is still a lack of theoretical research on adsorption mechanism at the molecular level.Starting from the perspective of the theory research, firstly the quasi crystal model of fluid molecules is proposed from the microscopic view in this article. Using L-J potential function and Stockmayer potential function to represent the interaction of nonpolar and polar molecules, potential expression is established between liquid molecules, and several matter’s heat of vaporization is calculated at boiling point with the theory. The results show that the calculated value are consistent with experimental value and the liquid crystal model has certain rationality. Secondly, using L-J potential function, Stcokmayer potential function and10-4-3potential function, combining with liquid quasicrystal model in silt pore, we calculate the total potential energy of liquid molecules in theory, and discuss the potential field in slit pores. Furthermore, it can explain some experimental phenomena from the micro calculated data. The results show that it relatively consistent with the existing conclusion, and the model itself has certain rationality. Finally, single saturated adsorption and double saturated adsorption model in slit nanopores are proposed in this paper. Two kinds of representative material’s adsorption heat are calculated respectively when there are monolayer adsorption and double adsorption in this article. The results show that there are more consistent with the existing experiment facts and theories. This work provides a new method to investigate the adsorption mechanism, and a theoretical guidance for adsorbent desorption and regeneration.