Application Of Surfactant Micelles And Mimic Micelles In Natural Gas Hydrate

Natural gas hydrate?NGH?is an ice-like crystalline compound formed by the interaction of water molecules and natural gas molecules at a certain temperature and pressure.Due to its theoretical gas storage multiple of 170?180 v/v,and the storage conditions of natural gas hydrate are milder?-5?15^oC,1?2 MPa?and secure,it has great potential in the field of natural gas storage and transportation.How to make the formation of natural gas hydrate faster and more efficient is the key of natural gas hydrate storage and transportation technology.Adding surfactants as promoters has been considered to be the most effective method to promote hydrate formation.Researchers have conducted deep research on the application of surfactant in hydrate field and achieved a lot of results,but there are still some problems to be solved,for example,the influence of surfactant micelles on hydrate formation has not been fully studied so far.To solve this problem,this paper conducted relevant research,and the specific research contents and research results were as follows:?1?Based on the conclusion that sodium dodecyl sulfate?SDS?under the condition of hydrate formation could not form micelles,three quaternary ammonium surfactants dodecyl trimethyl ammonium bromide?DTAB?,tetradecyl trimethyl ammonium bromide?TTAB?and cetyl trimethyl ammonium bromide?CTAB?were selected to study the surfactant micelles effects on methane hydrate formation.When DTAB without micelles formation was used as the promoter,the gas storage capacity was only about 60 v/v,and the promoting effect was better at low concentration.When using TTAB and CTAB,micelles played an important role in promoting the formation of methane hydrate.The promoting ability of TTAB and CTAB at low concentration was relatively poor,and the promoting effect on nucleation probability and gas storage capacity was significantly improved when the concentration reached the critical micelles concentration?CMC?.Although the solution had good wettability on the surface of the reactor,the hydrate was mainly formed at the bottom of the reactor rather than growing along the reactor sidewall.After the DTAB was fixed on the surface of the polystyrene spheres to form M-micelle-DTAB,the hydrate formed dense blocks at the bottom of the reactor,and the gas storage capacity increased to 92v/v compared with DTAB.?2?SDS was synthesized into polystyrene spheres solution?PSNS?,and two new polystyrene spheres solutions,20%Fe₃O₄/PSNS and 40%Fe₃O₄/PSNS,were synthesized by the immobilization of Fe₃O₄ nanoparticles on the polystyrene spheres.In the experiment to study their effects on the formation and decomposition of methane hydrate,it was found that the gas storage capacity of the hydrate generated by the three polystyrene spheres solutions and the methane recovery rate after decomposition were higher than 100 v/v and 72.5%of SDS.Compared with the three polystyrene spheres solutions,it was found that Fe₃O₄/PSNS not only reduced the reaction equilibrium time of hydrate from 19 h to 9 h with the increase of Fe₃O₄content,but also improved the recovery rate of methane after hydrate decomposition,which were 92.15%and 89.80%respectively when 20%Fe₃O₄/PSNS and40%Fe₃O₄/PSNS as promoters,both higher than 85%of PSNS.