Transesterification of linoleic and oleic sunflower oils to biodiesel using CaO as a solid base catalyst

Abstract

The purpose of this work was to characterize biodiesel (i.e., methyl esters, MEs) produced from linoleic and oleic sunflower oils (LSO and OSO, respectively) by alkali transesterification with methanol using CaO as a heterogeneous catalyst under different reaction conditions. The parameters investigated were the methanol/oil mole ratio (4.5:1, 6:1, 7.5:1, 9:1 and 12:1) and the mass ratio of CaO to oil (2 and 3 %). The physical and chemical properties of the feedstocks and the MEs, such as density at 15 °C, kinematic viscosity at 40 °C, acid value, iodine value, saponification value, cetane index and fatty acid (methyl ester) composition, were determined in order to investigate the effects of the properties of the LSO and OSO and reaction parameters on the product characteristics, yields and purity. The properties of the feedstocks had a decisive effect on the physical and chemical properties of the MEs. The studied reaction conditions did not significantly affect the properties of the MEs. The produced MEs generally met the criteria required for commercial biodiesel; in fact, the only exception was the iodine value of the ME produced from LSO. The product yields only slightly changed with the applied conditions; the highest yield (99.22 %) was obtained for the ME-LSO produced at 6 mol % methanol to oil ratio, while the lowest one (93.20 %) was for ME-OSO produced under the lowest methanol/oil mole ratio (4.5:1). The applied amounts of catalyst had a similar influence on the oil conversion to biodiesel. The yields of the ME-LSOs were, in general, somewhat higher than those obtained for the ME-OSOs under the same conditions, which was attributed to the influence of the respective acid value and viscosity of the feedstock.