Acid esterification vs glycerolysis of acid oil soapstock for FFA reduction

Abstract

In this study, the efficiency of esterification vs glycerolysis for the reduction of Free Fatty Acid (FFA) content of acid soapstock oil (128.8 mg KOH g−1) was studied. Further, alkaline transesterification of the pre-treated oil mixed with sunflower oil (to achieve FFA content <2%) was conducted to maximize Fatty Acid Methyl Esters (FAME) production. Homogeneous acid esterification was conducted at 65°C, using 2.0 wt% H2SO4 as catalyst and 9:1 molar ratio of methanol to oil. Glycerolysis was performed at 200°C using a 6:1 molar ratio of glycerol:oil. Both reactions lasted 6 h. Final acid value of the product was around 10 mg KOH g−1 for both processes, showing negligible differences between them. After transesterification of the mixtures it was possible to obtain biodiesel with around 90% FAME content, thus showing potential for the recovery of such waste material. (c) 2018 Taylor & Francis Group, London, UK.