Renewable oil-derived comb polymers as green and shear-resistant wax-crystal modifiers for high-wax crude oils

Abstract

The formation of robust wax-crystal networks in high-wax crude oils during cooling leads to significant increases in viscosity, gelation, and restart stress, posing major challenges for pipeline transportation. Here, we present a renewable, oil-derived comb polymer strategy that integrates green feedstock utilization with controlled wax crystallization. A poly(octadecyl acrylate-co-maleic anhydride) (POM) precursor was synthesized via RAFT polymerization and subsequently grafted with glyceride/fatty acid side chains to yield four polymers: OM-GMS, OM-GMO, OM-ATO, and OM-DIO. Among these, OM-GMS demonstrated the most balanced co-crystallization anchoring and steric disruption. At a fixed comparative dosage of 3000 mg/L, OM-GMS reduced the crystallization rate (e.g., in Model oil I from 1.09 to 0.85 min−1 at 10 °C), increased the apparent crystallization activation energy (from 2.12 to 6.91 kJ mol−1), and lowered the crystallinity index (from 20.45% to 13.45%). In crude oils, OM-GMS substantially reduced viscosity (by 58.45% in Crude oil I at 15 °C), yield stress (by 70.7%), gelation temperature (by 5.64 °C), and thixotropic-loop area (by 43.7%). These results establish a direct link between microscopic wax-crystal regulation and macroscopic cold-flow improvement. Integrated DSC, isothermal crystallization kinetics, XRD, PLM, and rheology reveal a unified mechanism. Oil-derived long side chains anchor into wax crystals. Glyceride/polar groups disrupt ordered packing; and the comb architecture shields modified crystals from rapid network reconstruction after shear. This work positions renewable comb polymers as effective, low-carbon alternatives to conventional petroleum-based flow improvers.