Sodium Dodecyl Sulfate and Calcium Hydroxide Exhibit a Synergistic Effect in Promoting the Formation of Carbon Dioxide Hydrate

The continuous increase in carbon dioxide (CO 2­ ) emissions has raised serious environmental concerns, highlighting the urgent need for efficient carbon capture, utilization, and storage (CCUS) technologies. Among the available approaches, CO 2­ hydrate-based sequestration has attracted significant attention due to its high gas storage capacity, mild operating conditions, and environmental compatibility. However, its practical application remains hindered by slow formation kinetics, long induction times, and low gas consumption efficiency. In this study, a novel synergistic promotion strategy was proposed to simultaneously enhance both the formation kinetics and gas storage performance of CO 2­ hydrates. Calcium hydroxide (Ca(OH) 2­ ) was introduced as a reactive additive, which reacts with CO 2­ to generate calcium carbonate (CaCO₃) particles in situ. These CaCO₃ particles effectively shorten the hydrate induction period by providing favorable nucleation sites. Meanwhile, sodium dodecyl sulfate (SDS), a typical surfactant, was employed to modify the surface properties of CaCO₃ particles. The adsorption of SDS onto the CaCO₃ surface enhances its hydrophobicity, thereby improving gas–liquid contact and promoting hydrate nucleation and growth. The experimental results demonstrate that the addition of Ca(OH) 2­ or SDS alone significantly reduces the induction time by up to 91.4% and 82.98%, respectively, compared with pure water. However, their effects on hydrate formation rate and gas consumption are limited. In contrast, the combined SDS–Ca(OH) 2­ system exhibits a pronounced synergistic effect. The induction time is reduced by 88.16%, while the hydrate formation rate and gas consumption are significantly enhanced by 739.13% and 276.19%, respectively. This study provides an effective and promising strategy for improving CO 2­ hydrate formation performance, offering strong potential for large-scale applications in carbon capture and storage.