Viscosity Modification of Heavy Crude Oil by Using a Chitosan-Based Cationic Surfactant

Recently, global attraction has shifted toward heavy unconventional crude oil due to the depletion of light oil resources. Generally, heavy crude oils are highly viscous in nature; due to this, their production and transportation are challenging. Asphaltenes and resins content directly affects the viscosity of crude oil. Many viscosity reducing agents affecting asphaltenes dispersion have been developed in the recent past. The current work proposes a novel environmentally friendly chitosan-based cationic surfactant (CBCS), which can interact with polar and nonpolar constituents of crude oil matrix, thereby reducing its viscosity. The CBCS was synthesized by a two-step process. First, chitosan was modified to ortho-carboxymethyl chitosan (O-CMC). In the second step, CBCS was prepared by the reaction between O-CMC and an intermediate, which was obtained by the reaction between 4-(dimethylamino) benzaldehyde and bromodecane. The chemical structures of all synthesized compounds were characterized by infrared (IR) spectroscopy, nuclear magnetic resonance (H-1 NMR and C-13 NMR) spectroscopy, thermo-gravimetry (TG), and X-ray diffraction (XRD). The effect of synthesized surfactant on the viscosity of the sample crude oil was estimated by rheological studies at different temperatures (20, 30, 50, and 70 degrees C). The results indicated that the viscosity of crude oil had been effectively improved as the concentration of surfactant increased from 0 to 600 ppm. The highest percent degree of viscosity reduction (DVR) was measured at 20 degrees C in comparison to 70 degrees C. The main cause of viscosity reduction, asphaltenes dispersion, was investigated by UV-vis spectroscopy analysis and viscosity measurements.