Interaction Between Sodium Para-dimethyl Alkylbenzene Sulfonates And Inorganic Salts

Surfactants are one of the most important chemical products and widely used,such as engine oil used in automobiles,medicines taken when people are sick,detergents used for laundry and housework,drilling mud used in petroleum industry and flotation agent used in mineral processing.In particular,surfactant plays an irreplaceable role in chemical flooding process.Oil recovery is improved by reducing interfacial tension?IFT?.There are many factors affecting the oil-water interfacial tension of surfactant solution,such as types and concentrations of electrolytes,temperature,structure and concentration of surfactant and so on.In this paper,the effects of the types and concentrations of alkali metal salts on IFT were studied,which is characterized by calculating critical micelle concentration?CMC?,the corresponding area of each molecule(A_min)at the interface,saturated adsorption(?_max)and other performance parameters.This paper is mainly composed of the following four parts:In the first part,the importance of surfactants in oil recovery and the factors that affect the oil-water interfacial tension of surfactants are introduced.In the second part,the synthesis of sodium para-dimethyl alkylbenzene sulfonates?PDABS?was synthesized.Five kinds of PDABS?p-S12-5,p-S14-4,p-S14-5,p-S16-5,p-S18-5?with different alkyl chain structures were prepared via Friedel–Crafts acylation,Grignard reaction,hydrogenation reduction,sulfonation and neutralization.In the third part,the effect of the concentration of alkali metal ion on the oil-water interfacial properties of p-S14-4 was studied by the spinning drop tensiometry.Generally speaking,IFT decreases first and then increases with the increase of alkali metal ion concentration,but there are obvious differences between different alkali metal ions.In the presence of alkali metal ions?Na⁺,K⁺and Cs⁺?,the IFT of oil-water first decreases and then increases with the increase of alkali metal ion concentration.The alkali metal ion concentration corresponding to the minimum IFT is called the optimum electrolyte concentration or the optimum salinity.In the range of experimental concentration,IFT decreases with the increase of Li⁺,and there is no minimum IFT,that is,there is no optimum salinity.Not only the different alkali metal ions affect differently the optimum salinity but also the concentration of p-S14-4 in the experimental concentration range for the same alkali metal ion has no effect on the optimum salinity.Besides,the optimum salinity is affected by the electrostatic interaction,water-oil ratio?WOR?,salting-out effect,and the hydrated radius of alkali metal ion,under the synergistic effect of which,the optimum salinity value order under various alkali metal ions is as follows:Li⁺>Na⁺>Cs⁺>K⁺.The influence mechanism of alkali metal ions on the adsorption of p-S14-4 at the oil-water interface is also discussed in detail.In the fourth part,two factors that affect the minimum alkane carbon number(n_min)were studied.One is the effect of the structure of para-dimethyl alkylbenzene sulfonates.The results show that n_min increases with the increase of alkyl chain length.The other is the concentration of sodium chloride.The n_min increases with the increase of sodium chloride concentration.At lower salt concentration,the scanning curve of surfactant solution for alkanes is relatively smooth,and the minimum alkane carbon number is not obvious,and does not change with the change of electrolyte concentration.At higher salt concentration,the scanning curve of surfactant solution for alkanes changes steeply,and there is the obvious minimum alkane carbon number.