Abstract

In this work, the Helmholtz free energy for fluid - fluid interactions is coupled with the Helmholtz free energy for solid - fluid interactions to calculate the adsorption of non-quantum and quantum fluids under confinement, addressing a fundamental phenomenon with potential applications in the use and storage of renewable energy, such as hydrogen in transport. Specifically, the Helmholtz free energy for fluid - fluid interactions is modeled by using the statistical associating fluid theory for a Mie potential for non-quantum and quantum fluids with a variable range (i.e., SAFT-VR Mie and SAFT-VRQ Mie, respectively) whereas the Helmholtz free energy for solid - fluid interactions is described by a model that considers the square-well potential and the simplify version of the pairwise correlation function. The capability of the model is first tested by modeling the adsorption isotherms of neon at 77 K and helium at 77 K and 298 K on MSC5A, where non-quantum and quantum effects are compared for the case of helium. The validated model is applied to describe the adsorption isotherms of hydrogen on two Metal Organic Frameworks (IRMOF-1, and IRMOF-6) and one activated carbon (JX101). According to the results, at high temperatures, both the SAFT-VR-Mie and SAFT-VRQ-Mie equations display similar outcomes for adsorption isotherms, but at low temperatures, the SAFT-VRQ-Mie improves the results significantly, exhibiting a better agreement with the experimental values. Comparing the adsorption isotherms on MOFs and JX101, it is possible to conclude that MOFs present the highest hydrogen adsorption, where the IRMOF-6 is the best option for hydrogen storage.