Investigation of kinetics of semi-clathrate formation for CO2 capture in the presence of L-methionine amino acid

Abstract

ABSTRACT Gas hydrates cater to several applications including methane/natural gas storage, CO2 capture, gas separation, desalination, etc. Semi-clathrates are a class of inclusion compounds in which a part of guest molecule (typically anion of tertiary butyl ammonium salts) involves in the formation of cage structure along with water and the other remaining part of guest molecule (cation) occupies and stabilizes the gas hydrate structure. This study is the first effort to explore the kinetics of the formation of tertiary butyl ammonium chloride (TBAC) semi clathrate in the presence of CO2 without and with the addition of a kinetic promoter (L-methionine amino acid). Experimental conditions of the study include starting pressure of 3.4 MPa and temperatures in the range of 279.2–283.2 K. Kinetics of TBAB-CO2 and TBAC-CO2 mixed semi-clathrates have been compared and reported along with morphology observations under similar experimental conditions. TBAC-CO2 mixed semi-clathrates showcase significant reduction in induction time in comparison to TBAB-CO2 mixed semi-clathrates. Also, gas uptake (CO2 storage capacity) is observed to be slightly better for TBAC mixed semi-clathrates at lower concentrations (5 wt%). Though l-methionine amino acid aids in the reduction of t90 (time taken for 90% completion of hydrate formation) for TBAB-CO2 system, such an effect was not observed for TBAC-CO2 system. Formed semi-clathrates can be easily dissociated with low-grade waste heat to release the stored CO2 (based on the observed dissociation by thermal stimulation in conducted experiments), making it an excellent contender for Carbon Capture Utilization and Storage (CCUS) Technology.