A new bio-based zwitterionic surfactant with improved interfacial activity by optimizing hydrophilic head

Abstract

AbstractBio-based zwitterionic surfactant attracts increasing attention to its application potential of surfactant flooding for enhanced oil recovery because of its environmental friendliness, renewability, and stable interfacial performance under high salinity and high temperature. However, bio-based zwitterionic surfactants which can be applied at the temperature higher than 100°C are still rare. In this paper, a new surfactant, phenyloleamide ethyl hydroxysulfonyl quaternary ammonium salt (PEHSQA), was obtained from biomaterial methyl oleate through alkylated, amidated, and quaternized reactions. As N, N-dimethyl propanediamine (a common amidated reagent in the synthesis of bio-based zwitterionic surfactants derived from fatty acids and esters) has one more carbon atom than N,N-dimethyl-1,2-ethanediamine, the latter was adopted as the amidated reagent optimizing the hydrophilic head of surfactant to improve the interfacial activity, especially the thermal resistance. The interfacial tension (IFT) between Daqing oil and stratum water could be maintained at 2.13×10−3 mN/m with the aid of 1 g/L PEHSQA. Furthermore, the IFT could be maintained at the level of 10−3 mN/m under the condition of 120 °C, with added NaCl of 20 g/L or Ca2+ of 2500 mg/L respectively. The optimization of reducing carbon number in the hydrophilic head of the bio-based zwitterionic surfactant can make a better balance between hydrophilicity and hydrophobicity offered by long fatty carbon chain, which can improve the interfacial activity especially the thermal resistance effectively.