Inhibition of Wax Crystallization and Asphaltene Deposition by Star Poly(Octadecyl Acrylate‐Styrene) (POA‐St) for African Crude Oil

ABSTRACT In the global energy landscape, the development of desert oil in Africa has increased the diversity of world oil supply and helped maintain the balance of the global energy market. However, wax precipitation and asphaltene deposition cause numerous challenges during the recovery and pipeline transportation of African crude oil. Traditional linear polymer additives often have limited wax‐modifying and asphaltene‐dispersing efficiency. In this work, linear poly(octadecyl acrylate‐styrene) (POA‐St) and a series of star POA‐St copolymers with different arm numbers (3, 4, and 6) were synthesized through reversibly additive fragment chain transfer polymerization. The effects of the linear and star POA‐St on the wax precipitating properties, pour point, rheology, and asphaltene stability of African waxy crude oil were studied in detail. The star POA‐St copolymers show superior performance compared with linear polymers in inhibiting wax crystal formation, improving crude oil rheology, and stabilizing asphaltene. Increasing the arm number of star POA‐St greatly improves its performance. Star POA‐St‐6 reduces the wax appearance temperature of the crude oil from 53.7°C to 51.1°C. At 20°C, the addition of the star POA‐St‐6 reduces the pour point of crude oil from 30°C to 21°C, and the viscosity and yield stress decrease by 74% and 55.2%, respectively. In addition, star POA‐St‐6 increases the initial precipitation points of asphaltene from 44.3% to 57.1%, showing a splendid asphaltene inhibiting efficiency. We speculate that the star POA‐St stabilizes asphaltene aggregates among its arms and changes the wax crystal morphology through co‐crystallization and nucleation effects, thereby exhibiting good performance. These findings provide prospective insights and avenues for the structural optimization and innovation of a new type of pour point depressant.