Understanding the Chemical Demulsification Mechanism of Oil/Water Emulsion by Polyether Polymers

Abstract

Chemical treatment is widely employed as the primary method to break down highly stable and complex water-in-oil (W/O) emulsions. Developing effective demulsifiers for chemical treatments is crucial yet challenging due to complex emulsions and poorly understood demulsification mechanisms. Here, the molecular dynamics simulations were employed to investigate the demulsification mechanism of polyether polymer (EO 5 PO 5 ) at the molecular level. The results demonstrated that EO 5 PO 5 was rapidly adsorbed to the surface of oil droplets driven by van der Waals (vdW) interactions due to its extensive nonpolar surface (1195 Å 2 , account for 79%). At low concentrations (18.71 g L −1 ), the demulsification mechanism of the EO 5 PO 5 polymer involved displacing asphaltene molecules at the oil−water interface, thereby reducing the stability of the interface film. As the concentration increased (50.78 g L −1 ), EO 5 PO 5 molecules formed a threedimensional network structure between oil droplets, creating oil bridges driven by the shrinkage force of the EO 5 PO 5 molecules. Oil molecules then diffused along these EO 5 PO 5 polymer bridges (with a diffusion coefficient of 2.98 × 10 −5 cm 2 s −1 ), completing the demulsification process. EO 5 PO 5 polymer molecules formed a network structure both inside and on the surface of the final stable oil droplets formed. This research enhances the understanding of polymer behavior in emulsions, guiding the development of more efficient chemical demulsifiers.