Supercritical ethanolysis for biodiesel production from edible oil waste using ionic liquid [HMim][HSO4] as catalyst

Abstract

Catalytic ethanolysis of waste cooking soybean oil using the ionic liquid [HMim][HSO4], as catalyst, to yield ethyl esters has been investigated. The ionic liquid, labeled as IL, showed stability under high conditions of temperature and pressure. Transesterification temperature was monitored and was maintained constant. The contents of ethyl esters in all samples were determined through GC (by normalization method) and 1H NMR techniques. Highest yield (97.6 %) was obtained after 45min of reaction, at 528K under 9.62MPa in the presence of 0.35mL of IL. The transesterification did not occur with high yielding using the same conditions but in absence of the catalyst. The presence of water in reaction medium, in the range of 1.0–3.0% (v/v) due to ethanol impurity, does not affect the ethyl esters yield. The method proposed in this paper is advantageous over others reported in the literature due to the lower reaction time required and the higher biodiesel yield. The results showed that the biodiesel production by transesterification through supercritical ethanolysis is environmental-friendly and presented promising perspectives.