Gas hydrates are encapsulation-type of compound composed of hydrogen bonded water cages with guest gas molecules trapped within these cages. Gas hydrates have been explored for their diverse applications in carbon sequestration, natural gas storage and transport, gas separation and water desalination. In this talk, we aim to provide mechanistic insight into the growth process of xenon hydrate film on mica through in situ microscopic analysis. Xenon was chosen as it has emerged as an attractive hydrate former for studying various aspects of hydrate growth dynamics as it can form hydrate at relatively less severe conditions (1.5 bar and 272 K) than other gases such as CH4 and CO2 which require extremely high pressure. The major objective of this research study was to provide insight into xenon hydrate film formation at the xenon–water interface in the presence of a surface and determine the growth rate response to perturbations in the temperature driving force. Mica (sheet silicate) was chosen as a model silicate surface in our study as silicate minerals are widespread across the whole universe in various forms. To our best knowledge, the growth of xenon hydrate film on mica has not been studied before. The orientation and properties of water molecules near a surface are significantly different from those in the bulk state. The geometric constraint by the solid surfaces and attractive/repulsive interactions between a surface and water molecules alter the orientation of water molecules. Mica (sheet silicate) was chosen as a model silicate surface to study the xenon hydrate film growth on substrate surface. Visual investigation through optical microscopy was used to determine the growth rates of xenon hydrate films on mica at sub-zero temperatures. A convective heat transfer model was applied to investigate the growth kinetics and the film thickness of xenon hydrate films. Under the experimental conditions, xenon hydrate was observed to form at a rapid rate of ~200 µm/sec in comparison to those of other gas hydrates which usually take hours to form. Mass transfer studies were also carried out by examining the net mass flux and aqueous solubility of xenon. Both the growth rate analysis and mass transfer studies demonstrated that the mica surface assisted the growth process of xenon hydrate films when the mass flux of xenon was relatively low at lower degree of sub-cooling. Our findings showed that the mica surface aided the growth process of xenon hydrate.

Insight into the surface induced growth of xenon hydrate film on mica at sub-zero temperatures

ACS Spring Meeting 2021

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