Preventing hydrates cohesion with a bio-inspired vitamin E derivative

Abstract

A solidified natural gas (SNG) technology was investigated to transport natural gas in a hydrate slurry. A Vitamin E derivative (D-alpha tocopherol succinate, Vitamin E-TS), which is naturally derived and readily available, was used to disperse water in the decane phase under the turbulent mixing condition. Compared to other non-ionic or cationic surfactants, Vitamin E-TS induced fast hydrate formation and a high conversion rate with an advantage of maintaining flowability during hydrate formation. For example, when using sorbitan monostearate (Span-60), hydrates grew to form a thick layer at the decane/water interface. Due to the strong cohesion of hydrate in the layer, a high relative torque was observed on mixing and the impeller was stopped. Moreover, dodecyl-trimethylammonium bromide (DTAB) showed increased relative torque in the early stage of hydrate formation. From the experimental results under both steady and dynamic operating conditions, Vitamin E-TS showed the optimal performance in quickly producing hydrate slurries and high conversion while maintaining fluid flowability. Accordingly, a continuous process was proposed to use water and decane as feed to produce the hydrate slurry in the presence of Vitamin E-TS.