Pour point depressant: identification of critical wax content and model system to estimate performance in crude oil

Abstract This study investigates the performance as pour point depressant of 15 samples of modified poly(ethylene-co-vinyl acetate) 10 mol% (EVA10), by hydrolysis and esterification, using wax model systems with different wax contents. Moreover, the best additives were also applied to crude oil (pure and with wax added). Pour point, wax appearance temperature and morphology analyses were used. The correlation between copolymer structure and pour point showed that both the hydrophilic and hydrophobic balance and the architecture of the molecule influence the additive performance. For high wax contents, the hydrolyzed EVA10 presented the best performance at an optimal hydrolysis degree (around 5.0 mol%). Increasing the wax concentration hampered the additive’s action, and the most critical concentration of waxes was observed with an increase from 5 to 6 w/v% wax, when the additive was no longer effective for the systems containing more than 11 w/v% wax. Results from the crude oils with wax added showed how significant the n-alkanes are for the pour point relative to iso- and cycloalkanes, and suggest that it is feasible to use model systems spreadsheet to estimate the performance of the additives in crude oils containing similar wax content.