Understanding the Kinetics of CO₂ Hydrate Formation in Dry Water for Carbon Capture and Storage: X-ray Diffraction and In Situ Raman Studies

Hydrate-based carbon capture and storage (HBCS) is a sustainable and promising approach to combating global warming by utilizing water, which is a ubiquitous resource. Here, we report a comprehensive study of CO₂ hydrate formation in dry water (DW), a water-in-air dispersion confined in silica particles, for improving the kinetics of hydrate growth. Utilizing a combination of a home-built high-pressure reactor, in situ Raman spectroscopy, and powder X-ray diffraction (PXRD), we elucidate the crystal structure, growth dynamics, and morphology of CO₂ hydrates formed in DW, with and without the kinetic hydrate promoter, l-tryptophan. Our analysis reveals that CO₂ forms structure I (sI) hydrate in DW, with hydrate growth occurring both on and beneath the silica shell. This results in a substantial increase in CO₂ uptake─approximately 2.8 times higher than that observed in pure water (∼134 v/v compared to ∼48 v/v). Moreover, incorporation of l-tryptophan in DW formation markedly accelerates the DW-CO₂ hydrate formation process, reducing both the induction time and the time required to achieve 90% gas uptake at 274.65 K. These findings offer crucial insights into the formation of CO₂ hydrate in DW, highlighting its potential to improve the efficiency and scalability of HBCS technologies.