Interesterification of grease trap waste lipids using methyl acetate under supercritical conditions

Abstract

The production of fatty acid methyl esters (FAMEs) and triacetin (TA) from the lipids of the grease trap waste (GTW) using methyl acetate (MA) under pressurized conditions was investigated. The experiments evaluating the effect of temperature (275–350 ºC), residence time (10–30 min), addition of water (2.5–10 wt% in relation to the MA), free fatty acid (FFA) content (25 and 50 wt% in the GTW) in the formation of FAMEs and TA. The results show that an increase in temperature favors the FAME production in the first 10 min of reaction and from 20 min onward the yield increases at 300 °C and decreases at 325 °C. The TA production was higher in 30 min at 300 ºC. The addition of up to 5 wt% water (in MA) showed a similar yield, while higher contents leads to a reduction in the FAME production after 30 min. The use of a feedstock with up to 50 wt% (by mass) of FFAs has little influence on the formation of FAMEs and leads to lower amounts of TA. The reaction with MA (5 wt% of water) provided a sample with 57 % of FAMEs and 1.4 wt% of TA.