Investigation of Tetra-n-Butyl Ammonium Bromide Semiclathrate Hydrate-Based CO₂ Capture by Kinetic and In Situ Raman Spectroscopy Measurement

Abstract

In this work, the formation of tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate for CO2 capture was studied by conducting experiments in a kinetic setup coupled with high-pressure in situ Raman spectroscopy. The impacts of TBAB concentration and operating temperature on CO2 incorporation into TBAB semiclathrate hydrates were investigated from the macroscopic and microscopic perspectives. It was found that the structure transition of TBAB semiclathrates from type A to type B occurred in the presence of CO2 and could be identified by the splitting of the Raman peak at 1447 and 1465 cm–1 (C–C stretching vibration mode in TBA+). CO2 consumption increased substantially upon the occurrence of hydrate structure transition, indicating that a larger amount of CO2 is incorporated into the TBAB semiclathrate of type B. The structure transition of the TBAB semiclathrate occurring at 2.57 mol % TBAB is faster than that at 0.29 and 3.72 mol % TBAB, and CO2 consumption obtained at 2.57 mol % TBAB is greater. When the temperature is reduced from 282.15 to 279.15 K, the structure transition of the TBAB semiclathrate occurs faster, but the amount of CO2 trapped in the hydrate is reduced. Therefore, the TBAB semiclathrate formed at 2.57 mol % TBAB and 282.15 K is a suitable system for CO2 capture using TBAB semiclathrate hydrates.

Raman Spectroscopy Study on the Competition between CH4 and N2 to Form Mixed Gas Hydrate

“…Figure shows a schematic of the experimental apparatus. A detailed description can be found in the literature . A gas chromatograph (GC-2014, Shimadzu Corp., Japan) with an accuracy of 0.1 mol % was employed to determine the CH 4 and N 2 contents in the residual gas and hydrate phase, respectively.…”

“…To compare the relative concentrations of CH 4 and N 2 trapped in the hydrates, eq is used for the calculation, and this is a method widely used in the literature. , I = S C H 4 S N 2 where S CH 4 and S N 2 represent the integral peak area for CH 4 and N 2 molecules trapped in hydrate cages, respectively, and I is the ratio of S CH 4 to S N 2 , representing the relative content of CH 4 and N 2 in hydrate cages. The competition between CH 4 and N 2 to fill the hydrate cages can be evaluated by the change in the I value over time.…”

“…To compare the relative concentrations of CH 4 and N 2 trapped in the hydrates, eq 1 is used for the calculation, and this is a method widely used in the literature. 36…”

Investigation of Tetrahydrofuran-CH4 Hydrate Formation in Unstirred Conditions from a Different Perspective: Application to Solidified Natural Gas Storage

“…A description of this apparatus has been presented in the literature . Additionally, the cavity filling characteristics for THF and CH 4 molecules within THF-CH 4 hydrate was investigated using a high-pressure in situ Raman spectroscopy equipment, as shown in Figure , which has been described in the literature …”

Absorption of CO2 by Tetra-n-Butylammonium Bromide Semiclathrate Hydrate Slurries in a Bubble Column with Temperature Swing

“…26 At TBAB concentrations below 18 wt %, type B exhibits a higher melting point and is thermodynamically stable. Regardless of the TBAB concentration, the structural transition from type A to type B occurs in the CO 2 -TBAB hydrate system, 27 indicating that type B of the CO 2 -TBAB hydrate is thermodynamically more stable. In this study, the CO 2 -TBAB hydrate was assumed to possess a type B structure because it was formed using aqueous solutions with a 9.0 wt % TBAB concentration.…”