Influence of Wax Inhibitor Molecular Weight: Part 1. Fractionation and Effect on Crystallization of Polydisperse Waxes

The molecular weight distribution of four wax inhibitors was modified by either stepwise precipitation or ultrasonic disintegration, and the effect of the obtained inhibitor fractions on wax crystallization was studied. Stepwise precipitation yielded narrower molecular weight distributions as measured by size exclusion chromatography (SEC), whereas ultrasonic disintegration reduced the average molecular weight and increase the polydispersity index. The polymer hydrodynamic radius was mapped using nuclear magnetic resonance (NMR), and showed similar trends as SEC measurements. Wax appearance temperature (WAT) and gelation temperature of three model oils and one crude oil were tested using differential scanning calorimetry (DSC) and rheometry. Changes in molecular weight could improve as well as diminish WAT depression. Waxy gelation temperature showed similar trends as WAT measurements, but the influence of inhibitor molecular weight was more pronounced. The largest change in gelation temperature was measured for the lowest molecular weight fractions