Fusel oil valorisation via solvent extraction distillation and reactive distillation: experimental characterisation and process simulation using Aspen plus and Aspen HYSYS

Abstract

Fusel oil (FO), a higher alcohol by-product of bioethanol fermentation, is routinely discarded as waste in distilleries across the developing world, despite its considerable potential as a source of value-added chemicals. This study investigates the valorisation of crude FO sourced from aZimbabwean ethanol plant through experimental characterisation and Aspen process simulation. The FO was first dehydrated using gravity separation followed by anhydrous sodium sulphate drying, reducing the water content from 13.8% to 0.76% an overall removal efficiency of approximately 94.4%. GC-MS analysis confirmed isoamyl alcohol as the dominant component at 64.10 wt. % in the dried feed, alongside significant active amyl alcohol (14.04 wt. %) and ethanol (10.55 wt. %). Physical characterisation yielded a density of 0.832 g/mL and a kinematic viscosity of 3.87 mm²/s, both consistent with higher alcohol rich FO literature values. Two valorisation pathways were then simulated. The first, a two-column solvent extraction distillation using n-hexane at a 0.3:1mass ratio in Aspen Plus, achieved an isoamyl alcohol purity of approximately 96.4 wt.% with a recovery yield of 94.8%, operating without decanter vessels by leveraging upstream drying. The second, a reactive distillation esterification process simulated in Aspen HYSYS, achieved an isoamyl alcohol conversion of 97.96% and produced a combined C5 acetate ester product at 96.48 wt. % purity and 82.67% recovery, exceeding the 95 wt. % commercial-grade threshold for flavour and fragrance applications. Both routes demonstrated strong alignment with comparable published studies, validating the technical feasibility of transforming Zimbabwean FO from an industrial waste stream into commercially relevant chemical products within a circular economy framework.