Abstract
Biodiesel (fatty acid alkyl esters) is a cleaner burning diesel replacement fuel made from natural, renewable sources such as new and used vegetable oils and animal fats. Just like petroleum diesel, biodiesel operates in combustion-ignition engines. The influence of low frequency ultrasound (28 and 40 kHz) versus mechanical stirring on the trans-esterification of neat vegetable oil under base catalyst was studied. The results of investigation of trans-esterification of with short-chain alcohols (C1〜C4) in the presence of ultrasound to give alkyl esters of fatty acids are presented. Reaction conditions that affect the yield include the type and concentration of the catalyst, the ratio of alcohol to vegetable oil, reaction time and ultrasound frequency. Methanol, ethanol and n-propanol give the best yields in isolated bio-diesel product (>90 %), while the other alcohols give small amounts of esters or do not react at all. A set of experiments was carried out to see the effect of alcohol type to triglycerides. Table 1. The influence of alcohol on the transesterification time [table] When the catalyst was added in a ratio of 0.5% and 1.0% to the vegetable oil (wt./wt.) the yield of isolated product was 90-95% and there were no notable differences in the time to complete the reaction. Low frequency ultrasounds can be a valuable tool for the trans-esterification of fatty acids, aiming to prepare the bio-diesel fuel.
