Controlling the wax crystallization behaviors via the ratio of phenyl to aliphatic branches in block copolymer synthesized by RAFT copolymerization

Abstract

The precipitation and deposition of waxes in high waxy crude oil often result in the low throughput and clogging of pipeline. Adding polymers is a practical approach to solve these problems. In this study, poly(styrene‐co‐docosyl maleate)s (PSDMs) were synthesized by reversible addition‐fragmentation chain transfer polymerization. The chemical structure and molecular weight of copolymers were characterized using Fourier infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The ratio of phenyl to aliphatic branches varies from 10:8 to 25:8. The crystallization and morphology of waxes in model oil were investigated by x‐ray diffraction, differential scanning calorimetry, and polarized light microscopy. The cold flow behaviors of crude oil were evaluated by rheological methods. With the increase of the ratio of phenyl to aliphatic branches, the crystallinity, viscosity, and yield stress of crude oil first increase and then decrease. In the presence of PSDM‐2, the crystallinity and enthalpy of phase transition (ΔH) are reduced by 44.2% and 48.9%. Thus, the pour point, viscosity, and yield stress of crude oil are reduced by 6.0°C, 76.8% and 77.4%, respectively. Therefore, well‐defined PSDMs are promising to be remarkable flow improvers for waxy crude oils.