Synthesis of a demulsifier with concentrated hydrogen bonding sites and its demulsification mechanism

Abstract

The role of non-covalent interactions in the demulsification process is widely recognized, and the incorporation of flexible chains alongside hydrogen bond donor sites significantly amplifies this effect. In the current work, a demulsifier (DEE-8) has been synthesized that contains two flexible hydrophobic long chains and multiple hydrogen bond sites with relatively clustered heteroatoms. The chemical structure of DEE-8 was characterized using Fourier Transform Infrared Spectroscopy (FT-IR) and Proton Nuclear Magnetic Resonance (¹H NMR) techniques. The demulsification efficacy (DE) was evaluated employing the bottle test methodology. A comprehensive investigation was conducted to assess the effects of various parameters-including concentration, temperature, settling time, pH, and salinity-on the DE of DEE-8. Notably, at a concentration of 250 mg/L, the DE reached 98.6 % within 70 min at a temperature of 40 °C. Furthermore, DEE-8 exhibited outstanding demulsification capabilities across a broad pH range of 4 to 12 and under conditions of elevated salinity. The competitive adsorption between asphaltenes and DEE-8 at the oil-water interface (OWIF) were analyzed through interfacial tension measurements and three-phase contact angle evaluations. In addition, the effect of DEE-8 on the strength of the interfacial film was studied by the droplet coalescence time. Based on previous trials, a possible demulsification mechanism was proposed. The results indicated that the hydrogen bonding sites, such as –OH and amino groups, along with the two hydrophobic long chains present in DEE-8, enhanced the interfacial activity of DEE-8. This enhancement facilitates the spontaneous migration and penetration of DEE-8 into the interfacial membrane, effectively disrupting the interfacial membrane established by asphaltenes. Consequently, this disruption promotes efficient oil-water separation in emulsions.