Industrial & Engineering Chemistry Research, Vol.58, No.49, 22178-22192, 2019
Innovative Approach To Enhance the Methane Hydrate Formation at Near-Ambient Temperature and Moderate Pressure for Gas Storage Applications
The solidified natural gas (SNG) technology via hydrates is a promising and potential method for storing natural gas. It offers a compact mode of natural gas storage with high degree of safety. In this work, we present the synergistic effects of tetrahydrofuran (THF), hollow silica (HS), and sodium dodecyl sulfate (SDS) in enhancing the kinetics of mixed methane-THF hydrate formation at 6 MPa and 293.2 K in an unstirred reactor configuration. HS at the low loading of 0.5% w HS/v in 5.56 mol % THF solution used in the current study is an innovative approach to improve the surface contact area resulting in kinetic enhancement at moderate conditions (low driving force). However, the mixture of 0.5% w HS/v in 5.56 mol % THF solution resulted in a long induction time (about 400 min), which is not favorable for the SNG technology. Addition of SDS decreased the induction time and increased the hydrate formation rate under similar experimental conditions. The induction time significantly decreased with the increase in the SDS concentration. Additionally, the presence of SDS played a key role in influencing the temperature profile and the hydrate morphology during mixed hydrate formation. The methane gas uptake was 0.0591 (+/- 0.0007) and 0.0615 (+/- 0.0023) mol of methane/mol of water without and with SDS, respectively. Thermal stimulation with Delta T = 15 K was employed to recover methane from hydrates. A recovery of 96-98% of the stored methane gas from the hydrates formed with and without SDS was demonstrated. Interestingly, the presence of HS was effective in preventing the foam generation during hydrate dissociation in the presence of SDS.