Mitigating seed sedimentation for sustainable sulfur hexafluoride hydrate formation using cyclopentane hydrate seeds

Sulfur hexafluoride (SF 6 ) is a highly potent greenhouse gas with a long atmospheric lifetime, necessitating efficient and low-energy capture strategies. Hydrate-based SF 6 capture has emerged as a promising alternative due to its low operating cost and high uptake capacity compared with conventional technologies. This study investigates a static hydrate-based SF 6 capture process employing cyclopentane (CP) hydrate seeds and evaluates the synergistic effects of CP seeds and sodium dodecyl sulfate (SDS) under varying driving force (DF) conditions. Visual observations revealed an unfavorable seed-drowning phenomenon under 5 K DF, where SF 6 hydrate accumulation on CP seeds induced early sedimentation. Increasing CP seed concentration suppressed sedimentation by reducing the overall density and increasing the seed stability. Higher DF promoted vertical growth and wall adhesion, mitigating sedimentation even at low seed loadings. The optimized condition (0.0556 mol% CP seed and 500 ppm SDS, 10 K DF) achieved high SF 6 uptake (51.009 mmol SF 6 /mol H 2 O) and rapid formation ( t 90 = 0.492 h) without retardation. Compared with agitated or porous media systems, the CP seed process achieved comparable uptake while exhibiting significantly lower energy demand and improved volumetric efficiency. These findings demonstrate the application of CP seeds to static SF 6 hydrate formation while providing mechanistic design criteria for clean and feasible SF 6 capture.