Synthesis and demulsification performance of polyether grafted magnetic nano-Fe3O4 for waxy crude oil emulsions

To solve the demulsification problem of waxy crude oil emulsion on offshore oilfields, alkyl phenolic resin polyether and silicon-containing polyether were grafted onto the surface of epoxy functionalized nano-Fe3O4, respectively, and two magnetic nano demulsifiers with high interfacial activity were successfully synthesized (Fe3O4@AP and Fe3O4@SP). The crystal structure, morphology, particle size, functional groups, chemical composition, thermal stability, and magnetic properties of magnetic nanomaterials synthesized at different stages were characterized and analyzed, confirming the successful synthesis of two magnetic nano-Fe3O4 demulsifiers with a particle size of around 10 nm and superparamagnetism. Through bottle tests, it was demonstrated that at 70 °C and within 90 min, the demulsification efficiencies of alkyl phenolic resin polyether and silicon-containing polyether demulsifiers for crude oil emulsions were 80.0% and 82.5%, respectively. In contrast, the demulsification efficiencies of Fe3O4@AP and Fe3O4@SP reached 95.0% each. Interfacial tension tests revealed that the superior demulsification performance of polyether-grafted nano-Fe3O4 is attributed to the rapid diffusion in the continuous phase and the higher interfacial activity of the magnetic nanoparticles.