Π–π Conjugated Molecule-Based Self-Assembly of Surfactants for Promoting Methane Hydrate Formation

Abstract

Self-assembled structures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and reactive red-195 dye molecule (RR195) were achieved under the electrostatic interaction between CTAB and RR195 molecules, π–π interaction between RR195 molecules, and hydrophobic force between CTAB molecules. The self-assembled structure was named as CTAB@RR195 and used for the first time to promote methane hydrate formation. CTAB@RR195 appeared as cubic structures at 50–100 nm with −SO3–/–SO4– groups on the surface and therefore could provide a large area of solid/liquid interface during methane hydrate formation. As a result, CTAB@RR195 could not only reduce the methane hydrate growth periods from over 40 h when CTAB was used to 2–3 h but could also improve the methane uptake from 0.054 to 0.072 to about 0.108 mol gas/mol water.