Formation characteristics of CH4 hydrate in SDS and CT AB solutions
In order to explore micro promotion mechanisms of different accelerators in the process of methane hy-drate formation,the kinetic hydrate promoter sodium dodecyl sulfate(SDS)and thermodynamic hydrate promoter cetyltrimethylammonium bromide(CTAB)were selected as additives,and their effects on the methane hydrate formation rate were studied by molecular dynamics method.By analyzing the potential energy changes,mean square displacements,radial distribution functions,molecular cluster growth rates,the results show that the solu-tions with mass fractions of 0.9％SDS,1.2％SDS,1.2％CTAB and 1.6％CTAB could promote hydrate for-mation.The SDS solution with the mass fraction of 1.2％has the fastest hydrate growth rate,and the SDS pro-motion effect is better than CTAB.By analyzing the distribution of methane density of molecular clouds,it is found that the head group of the negative SDS adsorbs a large number of methane molecules,and the water mole-cules are squeezed to the center.The nitrogen-containing head group of CTAB is oriented towards the homoge-neous solution and contained in the unstable hydrate cage,forming a semi-cage hydrate.By contrast,the gas content of hydrate in CTAB solution is higher.
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