Crystal morphology-based kinetic study of carbon dioxide-hydrogen-tetra-n-butyl ammonium bromide hydrates formation in a static system

Abstract

Hydrate based CO2 separation process is affected by many factors which mainly includes additive concentration, gas-liquid volume ratio and operating conditions. The most of the investigations on the CO2 hydrate-based separation in the previous work were carried out around the kinetics and thermodynamics of the hydrate formation along with the CO2 separation efficiency. However, few studies focus on the morphology of hydrate though the difference of the morphologies directly leads to the difference of the CO2 separation efficiency. In this work, the morphology along with the kinetics of the hydrate-based CO2 separation from CO2/H2 (40%/60%) is carried out in the presence of tetra-n-butyl ammonium bromide (TBAB) of 0.29 mol%. The results indicate, firstly, TBAB hydrate formation and TBAB/gas mixture hydrate formation were two independent processes. Secondly, the different operating conditions resulted in different hydrate morphologies. Thirdly, the consumption of CO2 in low pressure (<2.5 MPa) was controlled by the driving force, while that was controlled by the formed hydrate layer in the gas-liquid interface in the relatively high pressure especially for the initial pressure ≥4.5 MPa.