Performance Evaluation of (Ethylene-co-Vinyl Acetate) Copolymers as Pour Point Reducing Agents for Petroleum Middle Distillates

Petroleum, as well as its middle distillate fractions (boiling between 150-400°C), shows a tendency to crystalize paraffin molecules whenever temperature is lowered below the cloud point. Paraffin deposition may occur in storage tanks, pipelines, or conduits, this leading to the impairing of fluid pumping, even with filter plugging of diesel engines. Such drawback may be overtaken by the addition of chemical compounds aiming at inhibiting paraffin deposition. Such inhibitors are not universally effective, since they are operational for a certain molecular weight interval only. This work relates the performance evaluation of commercial poly(ethylene-co-vinyl acetate) samples of varied molecular weights resulting from mechanical shear experiments. Samples included one kind of diesel oil and three kinds of base lube oils: light neutral, medium neutral, and heavy neutral or bright stock oils. Results indicated that mechanical shear was effective only for samples containing 10% w/w of vinyl acetate. Additive performance as lube oil pour point reducing agents is a function of the copolymer composition only for samples the molecular weight of which is compatible with the molecular weight of the oil paraffins.