(735g) Effects of Surface Chemistry on Heterogeneous Methane Hydrate Nucleation

Gas hydrates represent an important class of crystalline solids that have applications in wide ranging fields such as petrochemical industry, environment and energy. Gas hydrates comprise cages formed through hydrogen bonding between water molecules entrapping gas (e.g. methane, ethane) in them. Naturally occurring methane hydrates are estimated to be significant sources of energy. The fact that the solubility of methane in water can increase by few orders of magnitude when transitioning from liquid solution to crystalline solids is remarkable. However, the mechanism(s) through which this transition occurs is not well understood. Recent simulation studies, including microsecond long simulations, have provided valuable insights into developing the molecular picture of homogeneous methane hydrate nucleation. It has also been shown that the probability of observing homogeneous nucleation is considerable lower than heterogeneous nucleation. Therefore, it is important to investigate the effect of surfaces on methane hydrate nucleation. Water behavior is strongly influenced by the surface and therefore, it is expected that hydrate nucleation will also be affected by the presence of surface. In our work, we use microsecond long molecular dynamics simulations to investigate the effects of surface chemistry on hydrate nucleation. Specifically, we have performed simulations of methane-water solutions in the presence of hydrophobic and hydrophilic self-assembled monolayers at hydrate forming conditions (i.e. low temperature and high pressure). We observe methane hydrate nucleation in the presence of both surfaces. Interestingly, aspects of hydrate nucleation such as number of cages observed and location of these cages relative to the surface are affected by the surface chemistry. In our presentation, we will discuss hydrate nucleation near these surfaces and the origins of these effects. Our results will provide insights into using surface chemistry to engineer hydrate nucleation.