Study on Interfacial Tension Between Alkanolamide Surfactants of Different Carbon Structure and Daqing Crude Oil

A study was done on the interfacial tension between Daqing crude oil and solutions of alkanolamide surfactants with different carbon chain structures which were made of reproducable plants or animals. These surfactants included plant oil acid diethalkanolamide (POAD), lauric acid diethalkanolamide (LAD), myristic acid diethalkanolamide (MAD), palmic acid diethalkanolamide (PAD) and stearic acid diethalkanolamide (SAD) and their combined systems. The results indicated that the longer the carbon chain, the better the interfacial activity. There is an optimum carbon chain length when the surfactant concentration is low. According to the molecular structure of the alkanolamide surfactant, the mechanism of ultra-low interfacial tension of different systems was discussed. The surfactant with mixed carbon chains promotes tight arrangement of the surfactant molecule at interface. So the interfacial tension characteristics were explained microscopically between different surfactant systems and Daqing crude oil. The effects of sodium chloride on the interfacial tension (between POAD + MAD surfactant with Daqing crude oil) were discussed. The higher the surfactant concentration of the POAD + MAD system, the higher the sodium chloride concentration was needed to reach ultra- low interfacial tension.