Influence of wax inhibitor molecular weight: Fractionation and effect on crystallization of polydisperse waxes

Abstract

The influence of wax inhibitor molecular weight on wax crystallization was investigated in three steps: (1) Wax inhibitor fractionation via stepwise precipitation or ultrasonic disintegration, (2) characterization of inhibitor and sub-fractions in terms of molecular weight distribution, hydrodynamic radius, and precipitation from pure solvent, and (3) inhibitor effect on wax appearance temperature (WAT), waxy gelling, and wax crystal morphology. Stepwise precipitation yielded narrower molecular weight distributions, whereas ultrasonic disintegration reduced the average molecular weight and increase the polydispersity index. Changes in inhibitor molecular weight could improve as well as diminish WAT depression. Waxy gelation temperature showed similar trends, but overall effects were more pronounced. It was concluded the wax inhibitor molecular weight is a parameter that can be used to fine-tune additives to a particular waxy oil, but only after an effective PPD type has been identified.