Ultrasound aided in situ transesterification of crude palm oil adsorbed on spent bleaching clay

Adsorbed crude palm oil on spent bleaching clay (SBC) was in situ transesterified to methyl esters (biodiesel) by the aid of ultrasound and organic co-solvents (petroleum ether (PE) or ethyl methyl ketone (EMK)). The SBC under study was found to contain 24.2–27.0% of crude oil with free fatty acids (FFA) of 3.01% and moisture content of 0.29%. The optimized reaction conditions were as follows: methanol to oil molar ratio of 150:1; catalyst (KOH), 20%; reaction temperature, 60 ± 2 °C; reaction time, 2 h. Using PE as a co-solvent, highest conversion of 75.2% was achieved while 60% was recorded with EMK.