Synthesis And Properties Of Amphoteric Surfactants With Ethylene Oxide Groups

A series of amphoteric surfactants with ethylene oxide groups were designed and synthesized in this dissertation. In order to provide basis for surfactant molecule design in enhanced oil recovery, the molecular structures which can reduce the crude oil/water interfacial tension to ultralow value were obtained by researching the relationship between molecular structure and interface performance of these kinds of surfactants.First, the series of alkyl polyoxyethylene ether with different carbon chain and different ethylene oxide groups were synthesized by linear chain or branched chain fatty alcohol and ethylene oxide (EO). Then, the9linear chain amphoteric surfactants with ethylene oxide groups{N, N-dimethyl-N-[2-hydroxy-3-linear chain alkyl (ethylene oxide)n] ammonio} acetate (C12(3), C12(7), C14(3), C14(5), C16(3), C16(5), C16(7), C18(5), C18(7)) and the7branched chain amphoteric surfactants with ethylene oxide groups{N, N-dimethyl-N-[2-hydroxy-3-branched chain alkyl (ethylene oxide)n] ammonio} acetate (GC16(3), GC16(5), GC16(7), GC18(5), GC18(9), GC20(5), GC20(9)) were synthesized by alkyl polyoxyethylene ether, epichlorohydrin, dimethylamine and sodium chloroacetate. The structures of the products were confirmed by ESI/MS and the active matter contents of amphoteric surfactants were determined with the phosphotungstic acid method.Second, the surface tension and interfacial tension of amphoteric surfactants were investigated. The branched chain structure surfactants had higher surface activity and interfacial activity than linear chain structure surfactants. The interfacial tensions of branched chain amphoteric surfactants with ethylene oxide groups were mainly studied. When the branched chain surfactants used alone, for Daqing No.2crude oil, the dynamic interfacial tension of GC16(3) and GC20(5) can reach low value (10-2mN/m magnitude), and for Daqing No.4crude oil, the dynamic interfacial tension of GC16(3) and GC20(5) can reach ultralow value (10-3mN/m magnitude). The results showed that the interfacial tension can be affected by the length of carbon chain, the length of EO and crude oil. The system of GC16(3) and sodium chloride, and the system of GC20(5) and sodium chloride had synergistic effect. In addition, the dynamic interfacial tensions of different mass ratio of the GC16(3)/GC18(5) compound system, the GC20(5)/GC18(5) compound system and the GC16(3)/GC20(5) compound system were investigated. For the compound system which can reduce the interfacial tension to ultralow value, the effects of sodium chloride and temperature were studied. The results showed that, for Daqing crude oil/water system, the GC16(3)/GC20(5) system of a certain mass ratio and the GC20(5)/GC18(5) system of a certain mass ratio had a certain salt tolerance and temperature resistance properties.