Development of high-performance biodegradable and non-toxic demulsifier for dehydration of field crude oil emulsion: Statistical design and process optimization

Abstract

In this paper, a simple high-performance non-toxic, and biodegradable demulsifier was synthesized based on the ester of oleic acid and polyethylene glycol to dehydrate crude oil emulsions. Fourier transform infrared, nuclear magnetic resonance, and thermogravimetric analysis were carried out to characterize the synthesized demulsifier. The standard bottle test was carried out to investigate the demulsification performance using the synthesized demulsifier under varying process variables, including the demulsifier concentration, temperature, settling time, and water content in crude oil emulsion. Central Composite Design (CCD) based on the Response Surface Method (RSM) was employed for statistical design and process optimization to maximize the dehydration performances for finding the optimal process variables. The accuracy of the developed statistical models was evaluated using an analysis of variance. The result indicates that the demulsifier concentration, temperature, settling time, and water content have significantly influenced the response demulsification efficiency (DE). At the optimum condition, a maximum DE of 100% and viscosity reduction of 80% were achieved using a 731 ppm demulsifier concentration in 32 min of settling time with a water content of 40% at 80 °C. A more efficient method to predict DE by direct measuring the emulsion viscosity (VIS) was established in a minimal time without a bottle test. The correlation between DE and VIS was also developed to determine the DE of crude oil emulsion. Further, biodegradability and toxicity tests were performed using standard tests method and found to be biodegradable and non-toxic satisfying the environmental standard limits of percent biodegradability and lethal concentration (LC50).