Preparation and Evaluation of Modified Ethylene–Vinyl Acetate Copolymer as Pour Point Depressant and Flow Improver for Jianghan Crude Oil

The ethylene–vinyl acetate copolymer (EVA) was modified by alkali-catalyzed alcoholysis. The alcoholized EVA (EVAL) was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR). Moreover, the influence of modified polar groups of EVA on the crystallization process of wax was investigated through differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results showed that EVAL had better performance than EVA in reducing the pour point and the viscosity of crude oil. EVAL could change the wax crystal habit and obviously lower the wax precipitation amount of crude oil. In addition, EVAL with stronger polarity could provide greater electrostatic repulsion force to wax crystals compared with EVA, which made the wax crystals have more difficulty to connect together and form a much looser network structure.