Synthesis And Properties Of Long Chain Alkylimidazole Surfactants

A series of N-alkylimidazole intermediates were designed and synthesized in this dissertation. Based on above intermediates,5switchable and5zwitterionic surfactants were further synthesized. All structures of surfactants have not been reported by now. We studied the relationships between molecular structures and emulsifiability, switchable function, interfacial properties of synthesized surfactants. It will provide experimental support for the molecular design of switchable surfactants and zwitterionic surfactants in enhanced oil recovery.The long-chain N-alkylimidazole compounds were synthesized by n-octylbromide, n-decylbromide, n-dodecylbromide, n-tetradecylbromide and n-hexadecylbromide with imidazole, respectively. The optimum reaction conditions were confirmed. The structures were characterized by ESI/MS and1H NMR.N-alkylimidazolium bicarbonates were prepared by N-alkylimidazole and CO2. The surface properties, emulsifiability and switchablity were studied. The efficient surface activity was shown that surface tension could reach to24.1mNm-1when the long carbon chain increased to16. The optimum emulsification conditions were confirmed as3%concentration of surfactant,1:1ratio (v/v) of alkane/water,30min of ultrasonic treatment. The stable switchability was proved by5cycles of conductivity and emulsification-demulsification used CO2/N2as a trigger.On this basis, N-decylimidazole switchable surfactant was applied to emulsion polymerization to study the switching performance. We researched the effect of different concentrations of surfactant and initiator on the particle sizes and ζ-potential of polystyrene. The cycle changes of particle sizes of emulsion show that N-decylimidazole switchable surfactant possesses switchable and controlling function.Then, five N-alkylimidazole zwitterionic surfactants were prepared with N-alkylimidazole and sodium cloroacetate. The active matter contents were determined by phosphotungstic acid as51.87%,46.11%,52.97%,74.18%and63.45%, respectively. The results of surface properties showed that CMCs decreased and γCMCs increased gradually as the length of carbon chain increased, and surface activity gradually increased. At last, the effect of zwitterionic surfactant concentrations on interfacial tension of Daqing No.2and No.4plant crude oil was researched. The results showed that interfacial activity increased as the carbon numbers increased. The DIFTmin can reach to ultralow value (10-3mN/m magnitude) with Daqing No.2and No.4plant crude oil, while DIFTeq to low value (10-2mN/m magnitude) when N-A14ImC and N-A16ImC were used without alkaline.