Dynamic interfacial tensions of p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine solutions

Abstract

Abstract The dynamic interfacial tensions (IFT) of four p -( n -lauryl)-benzyl polyoxyethylene ether carboxybetaine C 12 BE x CB ( x =0, 1, 2, 3) have been investigated by a spinning drop interfacial tensiometer. The influence factors such as ethylene oxide group, surfactant concentration, organic base, electrolyte concentration and type are explored between C 12 BE x CB solutions and two oils including n -alkane model oil and Shengli crude oil. It is found that the n min (the minimum alkane carbon number) and IFT min increase with increase in the ethylene oxide group for n -alkane model oil systems. For Shengli crude oil, the C 12 BE x CB surfactants used alone cannot reduce the IFT to ultralow value. In order to meet the demand, the organic base, monoethanolamine (MEA), is applied together with C 12 BE x CB to form organic base/surfactant system. The results show that there exists a synergistic effect between organic alkaline MEA and C 12 BE x CB surfactant. At optimum MEA concentration (0.10 wt%) and optimum ethylene oxide group number ( x =0, 1), the IFT value becomes lower than 10 −2 mN/m. All these results show that the interfacial surfactant concentration and the surfactant molecular size are two most important factors in dominating ultralow IFT. Moreover, it is found that electrolyte concentration and type have little effects on IFT and the C 12 BE x CB surfactants exhibit good salinity resistance.