Study On Synthesis And Property Of Sodium Para-dimethyl Hexadecyl Benzene Sulfonates

Most surfactants for enhancing oil recovery are mixtures of different compounds,such as petroleum sulfonates and heavy alkyl benzene sulfonates.They are mainly composed of alkyl benzene sulfonates,their relative molecular mass and alkyl chain length are not a certain value.Due to their complex components and uncertain structure,it is difficult for us to clarify the relationship between structure and performance,which makes researchers to synthesize alkyl benzene sulfonates with definite structures and study the relationship between structure and properties.In this paper,a series of different structures of Sodium Para-dimethyl Hexadecyl Benzene Sulfonates?PHBS?were synthesized by Friedel-Crafts acylation,Grignard reaction,Pd/C hydrogenation,sulfonation,neutralization,purification and recrystallization.According to the position of benzene ring in the alkyl chain,PHBS were named as p-S16-1,p-S16-2,p-S16-3,p-S16-4,p-S16-5,p-S16-6,p-S16-7,p-S16-8,and the synthesized PHBS and intermediates were characterized by high resolution liquid chromatography mass spectrometry?LC-HRMS?,1H-NMR and carbon spectroscopy.The results showed that the purity of PHBS and intermediates were about 95%.The surface tension of different concentrations and different structures of PHBS solution was determined by platinum ring method at 45 ? in the Na Cl solution with the degree of mineralization is 4000 mg/L.When the concentration of PHBS in the solution increases,the surface tension decreases and tends to be stable.With the difference of the bonding position between the benzene ring and the alkyl group,the surface tension at the critical micelle concentration??cmc?is also different.The more closer to the middle position of alkyl chain,the CMC is higher and the ?cmc value is smaller.When the benzene ring moves to the center of the alkyl chain,the saturated adsorption capacity??max?of the PHBS molecule gradually decreases and the limit occupied area per molecule?Am?gradually increases.The interfacial tension of PHBS was measured at 45°C by using a TX-500 C interfacial tension meter.The results showed that the optimum experimental conditions are interfacial tension meter speed is 7000r/min,oil phase?n-alkane?injection volume is 1?l.The experimental results showed that there are two types of dynamic interfacial tension curves,one is that the interfacial tension decreases gradually over time until it reaches a steady value;the other is that the interfacial tension begins to decrease sharply with time until the minimum value,and then the interfacial tension increases until it reaches an equilibrium value.When the benzene ring moves to the center of the alkyl chain,the minimum number of alkanes(n_min)shows a trend of decreasing first and then increasing and finally decreasing.Interfacial tension of PHBS decreases with the increase of the concentration of PHBS in the solution until the minimum value was obtained.After reaching the minimum value,the interfacial tension increases with the increase of PHBS concentration.The interfacial tension of the PHBS with different structures indicates that the general trend of the interfacial tension change of the PHBS decreased gradually as the benzene ring moves to the center of the alkyl chain.