387130 Increases in Methane/Water Solubility Via the Addition of α-Cyclodextrin and Its Effects on the Microfluidic Synthesis of Methane (sI) and Propane (sII) Hydrates

Monday, November 17, 2014: 4:30 PM
Crystal Ballroom A/F (Hilton Atlanta)
Brian Flowers and Ryan L. Hartman, Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL

Cyclodextrins are a class of compounds composed of cyclic glucose molecules. These have been shown to be an effective medium to facilitate transport and increase solubility of non-polar molecules in aqueous solutions. While much research on cyclodextrins have been focused on the protein and pharmaceutical solubility, little has been performed as to how cyclodextrins affect the solubility of simple hydrocarbons (particularly methane and propane) and the potential impact on clathrate gas hydrates. Gas hydrates impact societal problems related to conventional and non-conventional energy production and storage, in addition to global climate change, which motivates the need for laboratory techniques that discover hydrate science. Most laboratory studies on hydrate formation and dissociation have been carried out in high-pressure batch reactors. Thermal resistances and mass transport limitations introduce challenges when hydrate formation and dissociation rates are of similar time scales. However, the study of clathrate hydrates in microscale laminar flow with online analytics offers that opportunity to add new knowledge on hydrate science.  In the first of this two-part study, microfluidic cells and Raman spectroscopy were used to measure the increase in methane solubility as a function of α-cyclodextrin concentration. Due to the small length scales associated with microflow, static equilibrium conditions could be established in a matter of seconds allowing for the experimental determination of dissolved methane at temperatures from 5oC to 30oC, pressures from 100 psig to 1000 psig, and α- cyclodextrin concentrations from 0 to 4.9 weight percent. The second part of this study then examined the effect of increase methane concentration on gas hydrate formation times in microflow . Through our high-pressure microfluidic synthesis and dissociation of methane (sI) and propane (sII) hydrates, on demand, shows the potential to bridge the knowledge gap between the laboratory study of hydrates and the production systems that encounter them. Comparison of the laboratory-scale knowledge to historical nucleation kinetics calculations has the potential to resolve ambiguity in the experimental techniques available to study hydrate formation. In the present work, we will elucidate the rationale behind the high-pressure on-chip synthesis of hydrates and the recent advances we have made in the field.

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