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, dodecyltrimethylammonium 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.