Stability, Adsorption and Diffusion of CH4, CO2 and H2 in Clathrate Hydrates

TL;DR

This study uses ab initio methods to analyze how CH4, CO2, and H2 molecules adsorb and diffuse in clathrate hydrates, highlighting the importance of van der Waals interactions for stability.

Contribution

It provides detailed calculations of adsorption energies, capacities, and diffusion barriers for gases in clathrate hydrates using advanced ab initio techniques.

Findings

Van der Waals interactions are crucial for hydrate stability.

Maximum adsorption capacities and sizes are quantified.

Diffusion activation energies are estimated for each gas.

Abstract

We present a study of the adsorption and diffusion of CH4, CO2 and H2 molecules in clathrate hydrates using ab initio van der Waals density functional formalism [Dion et al. Phys. Rev. Lett. 92, 246401 (2004)]. We find that the adsorption energy is dominated by van der Waals interactions and that, without them, gas hydrates would not be stable. We calculate the maximum adsorption capacity as well as the maximum hydrocarbon size that can be adsorbed.The relaxation of the host lattice is essential for a good description of the diffusion activation energies, which are estimated to be of the order of 0.2, 0.4, and 1.0 eV for H2, CO2, and CH4, respectively.