A simple two-step reaction for synthesizing demulsifiers for a high salt crude oil emulsion

Abstract

In this paper, two demulsifiers (PDA-L and GDA-L) were synthesized by grafting lauric acid on polyethylene glycol diglycidyl ether or glycerol triglycidyl ether. The structure of PDA-L and GDA-L were analyzed by FTIR and 1HNMR, and the demulsification performance in water-in-oil emulsion was detailly evaluated by the bottle test. The results showed that PDA-L exhibited higher demulsification efficiency (DE) compared to GDA-L, attributed to its more appropriate amphiphilic characteristics. Judging by the results, when the dosage of PDA-L was 500 mg/L, the DE could achieve 100 % within 4 h at a temperature of 50 °C, and it also had excellent demulsification performance in a wide pH range (4–10) and high salinity. The competitive adsorption behavior of asphaltenes and PDA-L at the oil–water interface was studied by interfacial tension and three-phase contact angle. Moreover, the effect of PDA-L on the interfacial film strength was studied by coalescence time of droplets and viscoelastic modulus. Based on previous tests, a possible demulsification mechanism was proposed. PDA-L features a hydrophilic core and two extended hydrophobic alkyl chains, allowing it to readily move to the oil–water interface. This process facilitates the replacement of asphaltene and the formation of an unstable composite film, thereby promoting demulsification.