Molecular optimization of castor oil maleate as demulsifier for water-in-crude oil emulsions

The formation of stable water-in-oil emulsions is a frequent problem in the oil industry. In general, the difficulty of processing, unwanted water co-production, and damage to machinery are the main issues. Chemical demulsifying additives are used to destabilize petroleum emulsions. In this context, new environmentally friendly demulsifying components are being developed, preferably those produced from low-cost sources. This work synthesized five chemical surfactants based on castor oil maleate (MACO). These additives were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR). The demulsification activity was studied through bottle tests on emulsions formulated with two Brazilian oils. A performance scan evaluated different molecular structures and concentrations of the demulsifiers (100 to 5000 ppm) to determine an optimum demulsifier molecular structure. Dynamic interfacial tension measurements were performed to elucidate the demulsification activity at the water-oil interface under the same experimental conditions as the bottle tests. The Ward and Tordai equation was applied according to asymptotic approximations to assess the diffusivity of additives. All results were discussed correlating the demulsifying mechanisms, performance at the interface, and the possibility of applying the additives. All additives showed demulsifying behavior in the form of a water dropper. The demulsifier containing 2.3 mols of maleic anhydride incorporated with 1.0 mol of castor oil showed more significant activity, with a maximum water resolution of 90% for both emulsion systems.

Automated summary

The formation of stable water-in-oil emulsions is a common issue in the oil industry. This study synthesized five chemical surfactants based on castor oil maleate and evaluated their demulsification activity in two Brazilian oil emulsions. The demulsifier containing 2.3 mols of maleic anhydride incorporated with 1.0 mol of castor oil showed the most significant activity.