TUE-CMS

Abstract: Methane hydrates are crystalline compounds of water and methane molecules which form under high pressure and low temperature conditions. Industrially, methane hydrates are important for several reasons. Huge amounts of methane is trapped in hydrates found in permafrost and the deep ocean regions. They also obstruct gas flow in undersea pipelines, leading to economic loss and ecological risks. Finally, these materials have also been suggested as possible storage media for hydrogen and for sequestrating greenhouse gases such as carbon dioxide.

Understanding the dissociation and formation of hydrates is scientifically challenging. We study both dissociation and formation of hydrates through molecular simulations. To understand the dissociation of methane hydrates in confinement (much of the hydrate s occurring in nature is trapped in sediments) we perform Grand Canonical Ensemble Monte Carlo (GCMC) simulations of these compounds in carbon-like slit-shaped pores of width approximately 1-3 nm. The simulations are set up to mimic the experimental pressure-temperature dissociation measurements of methane and propane hydrates in mesoporous silica gel. To study the formation of hydrates we analysed the nucleating methane hydrate trajectories from MD simulations. We identify a new tool namely Voronoi Tessellation Analysis to investigate and quantify the methane-water cooperative rearrangement during nucleation. Results from our dissociation study show that hydrate dissociation condition and mechanism is dependent on the choice of water models and the width of pore size (Gibbs-Thomson effect is observed). Our hydrate formation analysis show that Voronoi Tessellation is a fast and simple tool to study hydrate nucleation (methane-water ordering is captured and quantified).

• A Monte Carlo simulation study of methane clathrate hydrates confined in slit-shaped pores'', Somendra Nath Chakraborty and Lev D Gelb, Journal of Physical Chemistry B, 116, 2183 (2012)
• “Voronoi Tessellation Analysis of Clathrate Hydrate”, Somendra Nath Chakraborty et. al., Journal of Physical Chemistry C (accepted).