Kinetic Measurements on CO2 Adsorption and Release Using TBAB·38H2O Hydrates as Adsorbents

Abstract

To avoid large energy input during crystallization from TBAB solutions, the solid TBAB hydrates were directly used for carbon capture in this work. The CO2 adsorption and release process of TBAB·38H2O hydrate were measured by in situ Raman and macroscopic method. Results showed that TBAB·38H2O hydrates converted to nCO2·TBAB·38H2O hydrate with no significant structural change. TBAB·38H2O hydrate had a relatively large CO2 storage capacity where 1 volume of hydrate could store 122 volumes of standard CO2 at 278 K, 2 MPa. Increasing pressure could greatly enhance the kinetics of CO2 adsorption and total CO2 storage. In the CO2 release process, nCO2·TBAB·38H2O hydrate did not release all of the trapped CO2 molecules. Forty to seventy percent of the trapped CO2 could not be released within 600 min. The good stability of 512 cages was suggested to allow nCO2·TBAB·38H2O hydrate to hold a certain amount of CO2 at atmospheric pressure. The slow diffusion of CO2 in hydrate phase was also thought to be the controlling step of CO2 release. Increasing the temperature and the specific surface area of hydrate particles would be helpful to strengthen the CO2 release.