Quadruple-branched jellyfish-like demulsifier used for completely demulsifying water-in-oil emulsion at low temperature and its demulsification mechanism

Abstract

The separation of oil–water emulsions is a pressing and crucial task due to the significant impact on transportation costs and pipeline corrosion. Currently, commercially available demulsifiers mainly utilize ethylene oxide and propylene oxide as raw materials. However, these demulsifiers involve complex and hazardous production processes, exhibit low demulsification efficiency (DE), and require high temperatures exceeding 60 °C. To address these challenges, this study presents a two-step synthesis method for producing a demulsifier (PDB-C6) that resembles a jellyfish. This demulsifier demonstrates a high DE in demulsification processes, operating at lower temperatures and shorter timeframes. Its hydrophilic head can locate water droplets in the emulsions, while the four hydrophobic tails can assist its rapid migration in the oil phase towards the oil–water interface for demulsification. The demulsifying performance was investigated in two W/O emulsions with different oil contents. Bottle tests showed that the DE of PDB-C6 in a 30% oil content W/O emulsion reached 100% with the dosage of 300 mg/L at 40 °C for 2 h, while the dosage of 400 mg/L for 3 h also achieved 100% of DE in a 70% oil content W/O emulsion. In addition, PDB-C6 had excellent demulsification performance in both high salinity and a wide pH range (2–12). Given its low demulsifier amount, low demulsification temperature, short demulsification time and high DE, PDB-C6 shows promise for wide-ranging applications in the petroleum industry. The impacts of PDB-C6 on the oil–water interface were systematically investigated and its possible demulsification mechanism in W/O emulsions was explored in detail. The findings revealed that PDB-C6 had excellent demulsification performance by rapidly migrating to the oil–water interface where it replaced natural surfactant and formed an unstable composite membrane, ultimately reducing the stability of the emulsion and leading to demulsification.