High-Pressure Methane Adsorption in Porous Lennard-Jones Crystals

Abstract

Decades of research have yet to yield porous adsorbents that meet the U.S. Department of Energy's methane storage targets. To better understand why, we calculated high-pressure methane adsorption in 600 000 randomly generated porous crystals, or "pseudomaterials," using atomistic grand canonical Monte Carlo (GCMC) simulations. These pseudomaterials were periodic configurations of Lennard-Jones spheres whose coordinates in space, along with corresponding well depths and radii, were all chosen at random. GCMC simulations were performed for pressures of 35 and 65 bar at a temperature of 298 K. Methane adsorption was compared for all materials against a range of other properties: average well depths and radii, number density, helium void fraction, and volumetric surface area. The results reveal structure-property relationships that resemble those previously observed for metal-organic frameworks and other porous materials. We contend that our computational methodology can be useful for discovering useful structure-property relationships related to gas adsorption without requiring experimentally accessible structural data.

Idealized Carbon-Based Materials Exhibiting Record Deliverable Capacities for Vehicular Methane Storage

“…al. studied over 600 000 “pseudomaterials”, with a maximum CH 4 uptake at 65 bar nearly reaching 350 V STP /V . Although these two works shed light on ideal adsorbents for a process, they were unable to give target materials for further testing as they worked on concepts or pseudomaterials.…”

Molecular understanding of the impacts of structural characteristics on ethanol adsorption performance for adsorption heat pumps

“…Porous crystal models comprising LJ spheres have been adopted and validated in previous studies. 30,34,35 In this study, the LJ parameters of these spheres were set based on the UFF force field to present different pseudo atom types. Because the van der Waals radius (σ) and the potential well depth (ε) of atoms in the UFF force field were within 1.052-6.549 Å, and 0.0105-4.2 kJ mol −1 , respectively, the ranges of σ and ε were set from 1 to 6 Å and 0.042 to 4.2 kJ mol −1 , respectively.…”

An upper bound to gas storage and delivery via pressure-swing adsorption in porous materials

“…that the structures considered are representative of the set of possible materials. To further explore material space and address sensitivity to the intermolecular potentials: scaling the Lennard-Jones potential well depths of material atoms to model enhanced interactions [9], placing Lennard-Jones spheres in a unit cell randomly to form "pseudo-materials" [11], and generating fictitious potential energy fields via a generative adversarial network trained on zeolite structures [12] all generated model substrates that failed to meet the ARPA-E methane deliverable capacity target.…”