Formation kinetics and microscopic characteristics of synthesized ternary gas mixture hydrates in TBAB aqueous solutions

Tetrabutylammonium bromide (TBAB) is a typical thermodynamic additive that can enhance the hydrate equilibrium temperature . Additionally, semi-clathrate hydrates formed from TBAB solutions exhibit reasonable CO 2 adsorption performance. In this study, TBAB hydrates were synthesized to determine their carbon capture capacity from a ternary gas mixture of CH 4 /CO 2 /N 2 (0.5/0.4/0.1). We measured the effect of temperature, pressure, and TBAB mass fractions (0.05–0.2) on the formation of gas hydrates, which were analyzed using Raman spectroscopy, powder X-ray diffraction (PXRD), and cryo-scanning electron microscopy (Cryo-SEM). With a 0.05 TBAB aqueous solution, the maximum recovery factor of CH 4 was 1.646 at 290.1 K and 7.0 MPa, whereas the maximum CO 2 split ratio was 0.454 at a pressure of 7.0 MPa and temperature of 280.1 K. Furthermore, the cryo-SEM images revealed that the addition of TBAB significantly increased the specific surface area of the hydrate crystals compared with the pure water system. PXRD and Raman spectroscopy showed that the hydrate structure transformed from a SI to a semi-clathrate hydrate. The hydrate samples formed from the 0.05 TBAB solution were found to be type A and B, leading to greater gas consumption. These results are expected to provide support for hydrate gas separation technology.