Biodiesel production from degraded vegetable oils – experimental study with supercritical methanol

Abstract

© 2016, Scibulcom Ltd. All rights reserved. The problems related to biodiesel production (difficult separation, insolubility of methanol in oil, negative effects of water and unsaturated fatty acids, long reaction time, etc.) have forced researchers to discover new technologies. The latest research has been focused on transesterification methods under supercritical conditions. Considering the fact that the price of oil makes 80% of the total costs of biodiesel production, the research has aimed at finding cheaper raw material. One of the solutions is the use of degraded oils which can not be used in human diet. The aim of this research paper was to investigate the influence of different process parameters in biodiesel production under supercritical conditions on biodiesel yield. The reactions were performed in a batch reactor at different temperatures (270– 350oC), pressures (8.1–12 Mpa), reaction times (7–30 min), molar ratios of oil and methanol (1:12–1:42), number of rotations of the stirrer (0–670 rpm) and different contents of water (0–10 wt.%). Oil produced from a domestic oil rapeseed variety ‘Kata’ was used in the experiment. The oil which oxidised due to inadequate storage cannot be used in human diet. The results of research have shown significant influence of the analysed parameters on biodiesel yield. Maximum yield (93 wt.%) was achieved during the first 15 min of reaction at a temperature of 350°C and pressure of 12 MPa. Increase in reaction time affected negatively the FAME yield.