Recyclable and high-efficiency methane hydrate formation promoter based on SDS-coated superparamagnetic nano-Fe3O4

Gas hydrate has been proposed as an effective medium for gas separation, desalination, gas storage and so on, yet the low reaction rate has been hindering the industrialization of hydrate-based technology. Hence various kinds of promoters, especially nano particles, have been introduced and investigated to increase the rate of hydrate formation. However, the recyclability of these promoters has not been given sufficient attention from an environmental friendly and economic point of view. In this study, a recyclable magnetic Fe3O4 nanoparticle coated with SDS (SDS-coated Fe3O4) was synthesized and successfully used for hydrate formation promotion as well as cycle experiments. The results showed that SDS-coated Fe3O4 exhibited more efficient promotion for hydrate formation than bare Fe3O4 in the studied concentration range. Especially, the induction time and reaction time can be significantly reduced to 77.6 +/- 24.1 and 36 +/- 3 min, respectively, and the methane storage capacity can be maintained up to 130 +/- 5.9 v/v with the concentration of 20 g/L SDS-coated Fe3O4. Further comparison of bare Fe3O4 and SDS-coated Fe3O4 during cycle experiments showed that after 5 cycles, the methane storage capacity and reaction time in presence of SDS-coated Fe3O4 can still be maintained as 119.5 +/- 8 v/v and 110 +/- 10 min, which were even better than the performance of bare Fe3O4 just after two cycles. To sum up, SDS-coated Fe3O4 can be recycled and reused many times for the hydrate formation, indicating that the SDS-coated Fe3O4 has a potential to increase the recyclability and its economy for promoters in the hydrate-based technology.