(414e) Thermal Expansivity of Gas Hydrate Cavity

Shaunak Potdar

Chemical & Natural Gas Engineering, Texas A&M University-Kingsville

Sangyong Lee*

Chemical & Natural Gas Engineering, Texas A&M University-Kingsville

Jae W. Lee

Chemical Engineering Department, The City College of the City University of New York

ABSTRACT

Clathrate hydrates, also known as gas hydrates are crystalline molecular complexes formed from mixtures of water and low molecular gases, with the gas (guest) molecule occupying the interstitial vacancies of the strongly hydrogen bonded cavities composed of water (host) molecules. The ever increasing importance of gas hydrates as an alternate source of energy, coupled with their ability for gas storage and desalination of water, have provided an impetus for phase equilibrium study of gas hydrates. In this work, we determined the equilibrium conditions for various structure II hydrate formers by performing MD simulations using MOLDY® and demonstrated their lattice distortion. Moreover, by calculating the chemical potentials for theoretical empty cavities of the various hydrate formers considered in this study as well as for the hydrate systems, we evaluated the reference chemical potentials and established its linear variance with the guest size. Furthermore, the effect of temperature on unit cell volume was observed, which will be used to determine the variation of lattice parameter and enthalpy change with temperature.

All simulations were executed in the NVT ensemble, employing the Ewald sum technique to calculate the long range electrostatic forces and the Link cell method to evaluate the short range forces, along with the Gaussian thermostat to maintain a desired temperature.