Sodium Dodecyl Sulfate Preferentially Promotes Enclathration of Methane in Mixed Methane-Tetrahydrofuran Hydrates

Abstract

Summary Methane storage in mixed hydrates is advantageous due to faster kinetics and added stability. However, capacity needs to be improved. Here we study mixed hydrates of methane (CH 4 ) and tetrahydrofuran (THF), in the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter for hydrate formation. We report the co-existence of pure methane (sI) and mixed CH 4 -THF hydrates (sII) in the presence of SDS; however, in the absence of SDS, co-existence of pure THF (sII) and mixed CH 4 -THF hydrates (sII) was observed. Thus the presence of SDS preferentially promotes the enclathration of methane over that of THF. Furthermore, through in situ Raman spectrometry, complemented by high-pressure differential scanning calorimeter, we present temperature-dependent methane occupancy in small and large cages of sI and sII hydrates. Our findings offer new insights for enhancing the methane storage capacity in more stable sII hydrate configuration for large-scale methane storage via solidified natural gas technology.

Ultra-rapid uptake and the highly stable storage of methane as combustible ice

“…Specific details of the spectrometer used may also be found in the literature. 18,46 The in-situ Raman spectroscopy experiments were conducted in fully stirred operation (600 rpm) throughout, at an experimental temperature of 283.15 K and an initial pressure of 7.2…”

“…The eventual selected location of the Raman probe in the present study was consistent with that used in a previous study published by our group and thus representative schematic illustration of the same is already available in the literature. 46 had been reached, the crystallizer was flushed with methane gas through rapid pressurization and depressurization cycles to remove any air present inside the system, following which methane gas injection was carried out slowly up till the desired experimental pressure making sure that the temperature of the system stays close to the desired experimental temperature.…”

“…When methane gas pressurization up to the desired experimental pressure was completed, the system was isolated, i.e. the gas inlet valve was closed (refer schematic available in the literature) 46 and data acquisition was started. Additionally, at this point, both stirring of the system (600 rpm) and Raman signal acquisition were also simultaneously initiated.…”

Ultra-Rapid Uptake and Highly Stable Storage of Methane as Combustible Ice

“…Specific details of the spectrometer used can also be found in the literature. 18,46 The in situ Raman spectroscopy experiments were conducted in fully stirred operation (600 rpm) at an experimental temperature of 283.15 K and initial pressure of 7.2 MPa (similar to the experimental conditions used for the gas uptake experiments). Also, the same as the gas uptake experiments, a solution volume of 32.4 mL comprising target masses of 26.37 g and 6.39 g for water and DIOX, respectively, was loaded into the crystallizer for in situ Raman spectroscopy measurements.…”

Thermodynamic study on gas hydrates: experimental determination of equilibrium data by high-pressure microcalorimetry and modeling up to 100 MPa.

“…Thenceforth, several groups have applied this technique to study the formation and dissociation of distinct phases of gas hydrates through in situ measurements (HESTER et al, 2006;TANG et al, 2018;ZHONG et al, 2016), as well as to investigate timeindependent signatures for several gas molecules trapped in hydrate cavities, the hydration number and the cages occupancy (BOURRY et al, 2009;CHAZALLON et al, 2017;KUMAR et al, 2019;QIN;KUHS, 2013;UCHIDA et al, 2007). Other groups have studied the effect of the equilibrium conditions, such as pressure and temperature, on hydrates structural features (MAGNOTTI et al, 2015;PETUYA et al, 2018).…”