Kinetic analysis of CO2 hydrate formation in the aqueous solutions of transition metal chlorides

CO2 hydrate technology can be applied to seawater desalination. However, the kinetics of CO2 hydrate formation were inhibited in the aqueous solution with inorganic salts, and the kinetic mechanism of CO2 hydrate formation for inorganic salts with different metal cations and anions was still unclear. In this work, CO2 hydrate nucleation and growth were studied in aqueous solutions of metal chlorides. Instead of Na+ and K+ ions, CO2 hydrate nucleation was promoted in the presence of Ni2+, Mn2+, Zn2+ and Fe3+ ions due to the co-ordination bonds between transition metal ions and water molecules to enhance the formation of the critical crystal nuclei. The induction time was increased by 61.1% in aqueous solution with 0.32 mol/L NaCl, while it was shortened by 55.6% in FeCl3 aqueous solution at the same concentration of Cl- anions. In the process of CO2 hydrate growth, Cl- ions played a more important role than the metal ions in affecting the stability of CO2 hydrate cages. The gas storage capacity was reduced by 10.3% in the presence of NaCl, and was lower than that of other metal chlorides. Cl- anions were absorbed on the hydrate surface and involved in hydrate cages to inhibit the hydrate growth due to the hydrogen bonds between the Cl- ions and water molecules of the hydrate cages. (c) 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.