Molecular simulation of energy storage properties of R32, R134A and R1234YF in MOF-5 AND MOF-177

The addition of porous nanomaterials is promising to enhance the thermal energy property of the organic working fluid. In this paper, molecular dynamics (MD) and grand canonical Monte Carlo simulations are employed to investigate the adsorption and energy storage properties of R32, R134a and R1234yf in MOF-5 and MOF-177. The results showed that the working fluid with small molecular size is easier to absorb and desorb in MOF structure. Besides, the MOF with larger specific surface area and pore size can absorb more organic working fluids, which can result in the larger enhancement of energy storage.

Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrogen and their Equimolar Mixture

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through calculation of absolute and excess adsorption isotherms, isosteric heats and the selectivity. Moreover, a molecular picture is provided through z-density profiles at low and high pressure. It is found that an interlayer distance of about twice the van der Waals distance of the adsorbate is recommended to enhance the adsorbing ability. Furthermore, the graphene structures with slit-shaped pores were found to be very capable of adsorbing methane and separating methane from hydrogen in a mixture at reasonable working conditions (300 K and well below 15 atm).

Adsorption And Diffusion of The H2/CO2 /CO /MeOH /EtOH Mixture Into The ZIF-7 Using Molecular simulation

The adsorption and diffusion of synthesis gas components (methanol, ethanol, H2, CO2, and CO molecules) in ZIF-7 by grand canonical Monte Carlo and molecular dynamics simulation were investigated. The initial diffusion coefficient at the beginning of the process depends on the kinetic diameter of the guest molecules. Also, the diffusion coefficient at equilibrium conditions probably depends on the interaction between the guest molecules with the ZIF-7 framework. The radial distribution function results indicate that the distribution of guest molecules in the framework is affected by the interaction between the guest molecules. These results also demonstrate that the Zn atom and the organic linker are favorable sites for CO2, CO, and H2. In contrast, the organic linker is the most favorable adsorption site for methanol and ethanol guest molecules. In addition, the diffusion coefficient of guest molecules in binary mixtures is related to the attraction or repulsion between the guest molecules.