Cryogenic efficient phase separation of oil–water emulsions with amphiphilic hyperbranched poly(amido-amine)

Abstract

To improve the extraction efficiency of practical components of crude oil emulsions, n-hexadecanoyl hyperbranched poly(amido-amine) (CHPAMAM), with hyperbranched poly(amido-amine) (HPAMAM) as the structural core and palmitic acid chains as the decorated shell, has been strategically designed and synthesized as an amphiphilic demulsifier for cryogenic efficient oil–water separation. In the presence of highly interfacial active CHPAMAM, stable oil-in-water emulsions can be partitioned entirely into two phases at low temperature, with a clear phase interface accompanied by an extremely thin transition layer. In simulated emulsions and crude oils produced from China's oilfields, with the addition of 80 ppm CHPAMAM, the oil removal ratios can exceed 99.9%, and simultaneously, the water contents in the oil phase are less than 0.01% to reach demulsification equilibrium within 40 min at 30 °C. The demulsification process is monitored in real-time by laser scanning confocal microscopy (LSCM). The demulsification mechanism of CHPAMAM is studied by adsorption kinetics experiments such as interfacial tension, interfacial rheological properties and liquid film stability, and further validated by dissipative particle dynamics simulation. The simulation reproduces the experimental observation, that is, the amphiphilic macromolecule CHPAMAM can destroy the original interfacial active materials (asphaltene–resin aggregates) that stabilize the oil–water miscible phase equilibrium. Amphiphilic macromolecule CHPAMAM with structure optimization as a special additive shows great promise in enhancing demulsification performance at low temperature.