Formulating liquid CO2-in-water emulsion using non-ionic surfactant alkyl polyglucoside for ultra-rapid CO2 hydrate formation

Hydrate-based CO 2 storage (HBCS) in subsea sediments has emerged as a promising climate mitigation method due to its high CO 2 storage capacity and long-term stability. However, practical application encounters significant challenges due to sluggish CO 2 hydrate formation kinetics, primarily resulting from limited liquid CO 2 -water interfacial contact after CO 2 hydrate film formation and blockage. Generating CO 2 microdroplets in continuous aqueous phase forms CO 2 (L) in H 2 O (C/W) emulsion, which enhances CO 2 dispersion and expands the liquid–liquid interfacial area. However, effective methods to synthesize stable C/W emulsion under high pressures and their role in enhancing CO 2 hydrate formation kinetics is less understood and warrant systematic investigation. In this study, we formulate C/W emulsion using an environmentally benign non-ionic surfactant alkyl polyglucoside (APG), and systematically examine the effects of APG concentrations and stirring rates on C/W emulsion stability in a fully-visual reactor. Under optimal 3.0 wt% APG, C/W emulsion forms under 1800 rpm in 13 s and maintains stability for ∼ 7 hrs with average CO 2 micro-droplet size of ∼ 14 μm. The dispersion of liquid CO 2 microdroplets promotes ultra-rapid CO 2 hydrate formation, achieving a CO 2 uptake of 187.8 v CO2 / v H2O (water conversion of 94.8%) with t 90 of 40 min, representing a ten-fold increase compared to the conventional CO 2 (L)–H 2 O mixing system by stirring. Findings of this study will guide effective methods for synthesizing and improving the stability of C/W emulsion under high pressure. Moreover, enhanced CO 2 hydrate formation kinetics enabled by emulsion-based method can be applied in a series of CO 2 hydrate-based applications. The study offers both mechanistic insights and practical guidance for future field-scale HBCS deployment.