Physicochemical properties of biodiesel produced by transeterification of various esterified waste frying oils

Abstract

This study aims at producing biodiesel from esterified waste frying oils (EWFOs), determine the physicochemical properties of the EWFO derived biodiesel (EWFO - Bs) and compare their properties to ASTM standards. The free fatty acid (FFA) contents of the EWFOs were analysed while parameters of the EWFO-Bs analysed included specific gravity at 20^oC (specific gravity bottle), kinematic viscosity at 25^oC (Oswald viscometer), moisture content (oven drying method), iodine value, saponification value, acid value (by titrimetry), flash point (flash point tester), cloud point and pour point (instrumental methods). The free fatty acid (FFA) contents of only 4 EWFO samples were below 0.5% while others ranged between 0.70% and 2.59%. The trans esterification reactions were maintained at the optimum process conditions of methanol to oil molar ratio of 6:1; at 60˚C; for 40 minutes; at 200rpm and the varying catalyst concentration was calculated on the basis of 100 ml of oil reacting with 0.35 g of catalyst. The highest yield of biodiesel obtained was 83.07%. The results of the kinematic viscosity (18.275±1.095 – 82.124±5.729 mm²/s) and moisture content (0.249±0.057 – 1.333 ±0.049 %) did not conform to the ASTM D6751 standard but the results of the specific gravity, iodine value, saponification value and the flash points of all the biodiesels produced conformed with the ASTM D6751 standard. It is concluded that biodiesel yield was highest if the FFA content of the EWFO is < 0.70.

Key Words: Biofuel, esterified oil, trans esterification, biodegradable, saponification and flash point