Efficient demulsification of cationic polyacrylate for oil-in-water emulsion: Synergistic effect of adsorption bridging and interfacial film breaking

The development of reverse demulsifier is an urgent need for the increasing amount of produced liquid in oilfield. Synthesis of reverse demulsifier containing multiple characteristics is an effective method. In view of this, this study reports a series of cationic polyacrylates as the reverse demulsifiers, which were prepared by using 3-chloro-1-propanol to modify the copolymer of acrylate and N-[3-(dimethylamino) propyl] methacryamide (DMAPMA). The properties and performance tests showed that the PMD1 prepared by using methyl acrylate (MA) as monomer (mass ratio of MA to DMAPMA was 2:1) has well water solubility, high interfacial activity, and the best demulsification efficiency. For treating the produced liquid from an offshore oilfield, demulsification efficiency of PMD1 was 94.7% with 50 mg/L dosage, which was much higher than that of the reagent in use (15.7%). Furthermore, the demulsification mechanism of PMD1 was studied by oil-water partition coefficient experiment, zeta potential measurement, optical tweezers method, elastic modulus measurement, and coalescence kinetics experiment. Prominent demulsification ability of PMD1 was attributed to the synergistic effect of adsorption bridging via cationic group and oil/water interfacial film breaking by acrylate group. The cationic polyacrylate combines the advantages of polyacrylate and polycation reverse demulsifiers, which display a great application prospect in the petroleum industry .