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

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.