Synthesis of Sulfobetaine‐Type Zwitterionic Gemini Surfactants (EAPMAC) and Their Oilfield Application Properties

Abstract Four sulfobetaine‐type zwitterionic gemini surfactants bis{[( N ‐ethyl ‐N alkylamide‐ethyl‐ N ‐(2‐hydr oxyl‐3‐sodium sulfonic acid) propyl] methylene} ammonium chlorides (EAPMAC‐11, EAPMAC‐13 EAPMAC‐15, and EAPMAC‐17) were synthesized by three steps using triethylene tetramine, fatty‐acid methyl esters, ethyl chloride, N,N′ ‐dimethyl ethylenediamine, and 3‐chloro‐2‐hydroxypropane sulfonic acid sodium as main raw materials. Their chemical structure was confirmed using Fourier transform infrared spectroscopy (FTIR), 1H‐Nuclear Magnetic Resonance ( 1 H NMR), and elemental analysis. The surface activity, critical micelle concentration, and interfacial activity were correlated with the length of the carbon chain. The results show low emulsifying tendency toward crude oil, low interfical tension, high salt tolerance, and excellent long‐term thermal stability. Moreover, high biocidal activities and good protection of metal surfaces against acidic environments are also reflected. These properties suggest that these new gemini surfactants have enormous application potential in oilfield application areas.