Lignin Nanoparticles as Highly Efficient, Recyclable Emulsifiers for Enhanced Oil Recovery

Abstract

Emulsification is one of the important processes in chemical flooding to mobilize the residual oil in wells following secondary recovery. Oil displacement efficiency is enhanced and volumetric sweep efficiency is increased by engineering the interactions of the supporting chemicals used with the geological formations present in the wells. Polymers and surfactants are often applied to enhanced oil recovery (EOR) as emulsification displacement. However, polymers are limited by poor temperature and salt tolerance, while surfactants have a high cost. In this contribution, we report on the use of lignin nanoparticles (LNPs) as Pickering emulsifiers obtained from enzymatic hydrolysis of lignin powders to apply in EOR. The interfacial activity of LNPs prepared this way is greatly improved, which substantially promotes its emulsification ability. We show that kerosene emulsified with different concentrations of LNPs can form stable Pickering emulsions, and the emulsions can be stored for up to 6 months. In addition, due to the pH responsive character of lignin, rapid oil–water separation can be achieved by alkali demulsification. This enables the reuse of lignin suspension under pH control, which provides a new platform for the application of green and low-cost flooding, employing LNPs in EOR.