Effect of guest gas on the mixed tetrahydrofuran hydrate kinetics in a quiescent system

Abstract

Clathrate hydrates are ‘inclusion compounds’ that have the ability to encompass multifold volumes of guest gas molecules, thus being advantageous for gas storage and gas separation applications. CO2 capture in the form of hydrates is an environmentally benign and cost-effective approach. In this work, we examine the kinetics of CO2 hydrate formation at different operating conditions that result in the formation of pure sI hydrate, pure sII hydrates and/or a mixture of sI and sII hydrates. Morphology observations of different hydrates formed are presented with the associated CO2 uptake achieved under different experimental conditions. We report strikingly contrasting morphology of mixed CO2 and mixed CH4 hydrates observed in presence of stoichiometric THF (5.6mol%) under similar pressure diving force and operating conditions. Interesting results observed during mixed CO2 hydrates using Differential Scanning Calorimetry (DSC) are documented. Based on DSC thermograms, we report interesting observations on the effect of guest gas in the mixed THF hydrate formation and dissociation. Moreover, mixed CH4/THF hydrates were found to be more stable in comparison to mixed CO2/THF hydrates. This work highlights that the choice of guest gas plays a significant role in the associated hydrate formation kinetics in presence of THF.