摘要
Abstract
Didodecylmethylcarboxyl betaine (diC12B) is an excellent hydrophobic surfactant suitable for surfactant-polymer flooding free of alkali. However,due to strong lipophilicity,diC12B has poor solubility in water and has a relatively high adsorption at sandstone/water interface. In thispaper,the diC12B molecule is modified by introducing EO groups into long hydrocarbon chains in the diC12B molecule to improve its properties. Thus didodecylpolyoxyethylene (4) ether methyl carboxyl betaine (diC12EO4B) was synthesized by using dodecyl bromide and polyethylene glycol (4) as initial materials,followed by etherification,chloration,and then reacted with methyl amine and lithium chloroacetate. The molecular structure of the product was confirmed by1H NMR and MS spectra. Compared with diC12B,the solubility of diC12EO4B in aqueous solution at 25℃ is improved,reaching 1.5×10?4mol/L,which is three times of that of diC12B,and saturated adsorption at quartz/water interface at 45℃ is only 70% of that of diC12B. diC12EO4B keeps high surface activity of the diC12B, as reflected by its low cmc,1.6×10?5mol/L,high effectiveness in reducing surface tension of water,γcmc=29.3mN/m,high saturated adsorption at air/water interface,6.5×10?10mol/cm2,and small cross section area in monolayer at air/water interface,0.26nm2. diC12EO4B displays a good ability in reducing oil/water interfacial tension (IFT). At 45℃ it can solely reduce C7~C9 alkane/Daqing connate water IFT to 10?3mN/m magnitude,and reduce Daqing crude oil/connate water IFT to 10?2mN/m magnitude. By mixing with lipophilic surfactant diC12B and hydrophilic surfactant C16B, diC12EO4B can reduce Daqing crude oil/connate water IFT to 10?3mN/m magnitude in a wide total surfactant concentration,from 0.625mmol/L to 5mmol/L at 45℃,without adding any alkali and electrolytes.关键词
表面活性剂/甜菜碱/合成/超低界面张力/吸附Key words
surfactant/fatty alcohol ether betaine/synthesis/ultralow interfacial tension/adsorption分类
化学化工
