Studies on the Synthesis and Application Properties of a Betaine Surfactant with a Benzene Ring Structure

Two novel betaine surfactants with distinct hydrophilic headgroups were synthesized, including carboxybetaine surfactant (DCB) and sulfobetaine surfactant (DSB). Their properties of reducing the interfacial tension (IFT) of Xinjiang crude oil/water were studied under alkaline-free conditions, as were their thermal stability, wettability, and emulsification properties. The chemical structures of the target products were characterized and analyzed by using 1H-NMR and 13C-NMR. The experimental results indicate that the introduction of a benzene ring to the hydrophobic group can improve the solubility and high-temperature resistance of the betaine surfactant. Thermogravimetric analysis showed that the degradation temperature of the synthesized betaine was above 190 °C. As the concentration of the betaine solution increased, DSB (0.0750 mmol/L) showed a lower critical micelle concentration (CMC) than DCB (0.1852 mmol/L). The wetting ability of DCB was significantly higher than that of DSB, and their contact angles on paraffin film decreased to 28.36° and 35.26°. In addition, both DCB and DSB can reduce the IFT of Xinjiang crude oil/water to ultra-low levels (10−3 mN/m) in the absence of alkali. The appropriate ion concentration has a synergistic effect on the surfactant to reduce the interfacial tension of oil/water and the effect of the three ions on the interfacial tension was as follows: Na+ < Ca2+ < Mg2+.