Formation of sI and sII Clathrate Hydrates via a Particle Fluidization Approach for Marine Decarbonization

Carbon capture and storage (CCS) in subocean environments is a promising solution due to its vast storage potential and accessibility. Herein, the particle fluidization approach is proposed for in situ CO2 hydrate formation in marine environments. We systematically assess the feasibility of clathrate (sI and sII) hydrates for CO2 sequestration in marine environments. Results show that CO2 can compete with promoters to occupy the 51264 cages of sII hydrate, leading to enhanced storage capacity. With sII hydrate synthesized using 1,3-dioxane (5.56 mol %) at 8.5 °C and 3.6 MPa (real marine conditions), a CO2 uptake of 62.18 (±2.23) VgVw–1 (volume of gas at STP/volume of seawater) was achieved, accompanied by an induction time of 7.33 (±0.58) s and a formation rate of 6.562 (±0.491) mmol/(mol·min) (millimoles of gas/mol of seawater per minute). By comparison, sI hydrate exhibits a longer induction time of 2.44 (±0.20) min, a lower formation rate of 0.538 (±0.070) mmol/(mol·min), and a reduced uptake of 47.36 (±1.24) VgVw–1. The milder P–T conditions of sII hydrates make them ideal for various reservoirs, with the northern area of the South China Sea (SCS) potentially storing 19.76–26.05 Gt of CO2. The particle fluidization approach, combined with natural gas hydrate production, offers a transformative and sustainable model for hydrate-based CCS technology.