CO2 hydrate formation in superabsorbent hydrogels for carbon capture—A comparison of water-confined framework vs non-water framework

• Rapid CO 2 hydrate growth in hydrogels observed within first 100 min. • Highest water conversion rate achieved was 96.6%. • Hydrogels with higher swelling ratios formed more porous hydrate shells. • Hydrogels exhibited superior CO 2 absorption capacity compared to silica gel. This study investigates the kinetics of CO 2 hydrate formation in saturated hydrogel particles—water-confined frameworks—through both experimental and numerical methods, and compares the results with those obtained in silica gels, silicon-based frameworks. Three hydrogel materials with varying swelling ratios were synthesized via radical polymerization. An advanced shrinking core model was developed, incorporating factors of CO 2 solubility, gas diffusion, gas–water reaction, capillary effects, and hydrogel functional groups. Results showed rapid CO 2 hydrate growth within the first 100 min, with CO 2 uptake reaching 78%–82% of the final amount by 600 min. The highest percent water conversion achieved was 96.6%. Simulations indicated a significant decrease in CO 2 diffusion coefficient through the hydrate shell over time, especially in hydrogels with higher methacrylic acid content. Capillary effects diminished as the reaction proceeded, with final water consumption via capillaries accounting for 14.4%–26.7% of the total. Hydrogels with higher swelling ratios and higher agglomeration degree formed more porous hydrate shells, enhancing CO 2 diffusion but resulting in lower overall CO 2 uptake due to their lower water content. Comparisons with hydrophilic porous silica gel revealed that, although hydrogels initially posed greater mass transfer resistance, they ultimately exhibited superior CO 2 absorption capacity and rate.