Hydrate-based CO2 capture: kinetic improvement via graphene-carried –SO3− and Ag nanoparticles

Abstract

Hydrate-based CO₂ capture and sequestration (CCS) has been viewed as a promising technology to control CO₂ in the atmosphere; achieving rapid formation and high storage capacity of CO₂ hydrates is critical for utilizing this technology. Sodium dodecyl sulfate (SDS) has been confirmed as the most efficient promoter for CH₄ hydrate formation, but the promotion of CO₂ hydrate formation by SDS is very poor. Therefore, developing exclusive and efficient promoters for CO₂ hydrate formation is crucial for achieving hydrate-based CCS. In this study, we used graphene nanosheets as carriers and grafted –SO₃⁻ groups (similar to the hydrophilic group of SDS) and Ag nanoparticles of about 2–5 nm on nano-carriers to prepare a novel promoter (named as Ag@SGO), which could overcome the limitations of SDS and improve its promotion efficiency. When 1 mmol L⁻¹ (0.288 g L⁻¹) SDS was used as the promoter, CO₂ hydrate formation lasted over 1000 min and the gas consumption reached merely 2.90 ± 0.22 mmol mL⁻¹ water at 1000 min, clearly denoting poorer promotion compared with the promotion of CH₄ hydrate formation, in which hydrate formation was completed within several hours with the gas consumption reaching 6–7 mmol mL⁻¹ water. However, when Ag@SGO was applied at 0.25 g L⁻¹, majority of the CO₂ hydrate formation was finished at 200–250 min and the gas consumption reached 7.62 ± 0.16 mmol mL⁻¹ water at 1000 min, which was almost 2.6 times as that with SDS. This indicated that graphene-carried –SO₃⁻ and nano-Ag developed in this study produced particularly efficient promotion of CO₂ hydrate formation and therefore, they exhibit significant potential for the industrial application of hydrate-based CCS.