Deacidification of used cooking oils by solvent extraction under lab scale and in a falling film contactor

Abstract

This work evaluated the pretreatment of used cooking oils (UCOs) via liquid-liquid extraction, both at laboratory and bench scales, under batch and continuous operation. Processed UCOs were collected in Bogotá, Colombia, and physical pretreatment was done by extraction with methanol and ethanol in a batch operation. The selected solvent was further tested in an intensified process using a packed falling film contactor in continuous operation. The effectiveness of the treatment was evaluated with respect to the change in the main targeted properties of UCO, namely acidity index, photometric color index, and content of polar compounds. Additional physicochemical properties of UCO were also tracked during extraction. The most effective pretreatment was achieved by using ethanol as solvent with a water content of 5% wt. This was tested in the continuous contactor using an oil:solvent mass ratio of 1:2, a mass flow of oil of 0.74 kg/h and a packing length of 1.07 m. In a single contact stage, a 51% acidity reduction, a 17% reduction in color index, and a 6.7% reduction in the content of polar compounds were achieved. Preliminary estimations for an industrial process indicate processing costs of 332 US$/t and a carbon footprint of CO2 2.17 kg CO2-eq/kg.