Controlling and tuning CO2 hydrate nucleation and growth by metal-based ionic liquids

Abstract

The complex kinetic process of CO2 hydrate formation limits its applications of CO2 capture and sequestration et al. In this work, the effects of metal-based ionic liquids with different cations and anions on CO2 hydrate nucleation and growth was studied. The results showed that CO2 hydrate nucleation was promoted by the anions of [NiCl3]-, [MnCl3]-, [FeCl4]-, [C8MIM]+ and [C16MIM]+ ions due to the enhancement of local hydrogen-bonding network to construct crystal nuclei. The induction time of CO2 hydrate nucleation was decreased by 75.0% in the [C16MIM]FeCl4 aqueous solution. However, CO2 hydrate nucleation was inhibited by [C2MIM]+ and [ZnCl3]- anion. The gas storage capacity of CO2 hydrate was increased by mass transfer channels around the metal complex anions which could accelerate the diffusion rate of H2O and CO2 molecules. The co-effect between [C16MIM]+ cations and [FeCl4]- anions on CO2 hydrate growth was the strongest, which increased gas storage capacity by 16.1%. Hence, CO2 hydrate formation can be controlled and tuned by changing cations and anions of metal-based ionic liquids.