Enhanced Kinetics of CO₂ Hydrate Formation under Static Conditions

Abstract

Trapping CO2 in hydrates is one of the new technologies for CO2 capture and storage. One of the primary obstacles to this option is the low formation rate. This work presents the rapid formation of CO2 hydrates with a small amount of cyclopentane (CP). The formation kinetics was investigated in a 474 cm3 nonstirred batch reactor with 100 and 200 cm3 of water. At volume ratios of CP to water between 0.01 and 0.1, the maximum growth rate is 0.32 mol h−1 at CO2 pressures ranging from 1.9 to 3.4 MPa and at 274 K. CO2 hydrates (sI) and CO2 + CP (sII) binary hydrates coexist at the end of hydrate growth. The mole ratio of CO2 entrapped in the sI hydrates to that in the sII binary hydrates is higher with 100 cm3 of water than with 200 cm3 of water. The same trend is also observed for the total amount of CO2 entrapped in the hydrate phase. The growth rate depends not only on the water volume but also on the pressure. The hydrate growth rate and the water conversion reach a maximum at 3.06 MPa and then decrease as the pressure increases from 1.9 to 3.4 MPa with 100 cm3 of water and 5 cm3 of CP. The water conversion to the hydrates reaches 52% within 2 h. This accelerated formation kinetics can provide a stepping-stone for developing a new hydrate-based CO2 capture and storage technique.