Kinetics of Gas Hydrate Crystallization and Dissociation in Tailored Confined Media

R.L. Hartman, New York University (Principal Investigator)

C.A. Koh, Colorado School of Mines (Co-Investigator)

Gas clathrate hydrates (‘hydrates’) are crystalline lattices of hydrogen-bonded water molecules that encapsulate small hydrocarbon (gas) molecules, such as methane. They are energy-rich entities, vital to sustain our planet, that form spontaneously from water and small hydrophobic molecules under specific temperature and pressure conditions.  Hydrate formation is a nucleation and growth phenomenon, in which there is a critical crystal size beyond which thermodynamics favors growth over dissolution. While homogeneous nucleation of this critical size is possible in bulk water, it is known that heterogeneous nucleation is a dominant process in natural and synthetic hydrates.  Interestingly, the majority of hydrates in science and nature crystallize in confined media, yet only a handful of investigations to date have studied the influence that porous materials have on their crystallization and with limited understanding from bulk experiments.  Crystallization in confinement itself is an emerging area of science.

The overarching goal of this proposed research program will be to discover fundamental molecular-to-pore based multiscale understanding of hydrate crystallization mechanisms in confinement. Here we define the confinement as crystallization constrained to: i) microscale gas-liquid or gas-liquid solid interfaces and ii) highly-ordered, geometric nano- and micro-scale structured surfaces.  Here we hypothesize that the nature of the nanopores determines the gas hydrates nucleated in nanoconfinement, their resultant molecular structure type and their crystallization and dissociation kinetics.  Our research team will design highly-ordered nanoporous structures in microfluidics with in-situ spectroscopic methods, discover why the nanopore geometry controls the nucleated hydrate characteristics, understand why these characteristics influence the resultant hydrate kinetics, elucidate the role of the nanopore hydrophobicity and salt ions, and finally determine the role confinement has on crystal growth beyond the nanopore exits.  A suite of creative synthesis techniques, including high-pressure microfluidics with in-situ analytical methods, will be used together to study the proposed basic science.  Furthermore, use of machine learning will incorporate the physics/mechanistic pore-scale discoveries from advanced experimentation to build first-principle models and generate design rules.