Pre-treatment of waste cooking oils for biodiesel production

Production of waste cooking oil in big cities is a problem for public health in different countries around the world. A feasible solution is employing as raw material for biodiesel production. However, the problem is the high content of free fatty acids, moisture and solid particles presented in the oil. Therefore, this article analyses a process to treat Colombian waste cooking oils, by filtrating with a cellulose filter, drying with silica gel, and esterifying with methanol. For removing of particles it was standardized a process of filtration employing paper filter. With this process the solids remotion was 78.63%. After filtration oil was submitted to adsorption with silica gel. The experimental design was two concentration of adsorbent (0.025 g silica gel/ml oil and 0.11 g silica gel /ml oil) and two temperatures (15° C – 60°C). The best condition was temperature of 15 °C and a relation of 0.11 g silica gel /ml oil. The last step evaluated was esterification which to transform free fatty acid in methyl esters. In this reaction were evaluated two temperatures (40 °C and 60 °C), two concentration of sulfuric acid (1% w/w and 3% w/w) and two alcohol:oil molar relations (4:1 and 6:1). According to experimental results the best conditions were 60°C, 1% w/w sulfuric acid with 4:1 alcohol:oil molar relation during 2 hours. Finally oil obtained had less of 1% of moisture, 0.25% of solids suspended and 1.38 mg KOH/g oil of acid value. These attributes satisfactorily meet with ASTM and ISO standards, so it will be possible to use as raw material for biodiesel production. Copyright © 2018, AIDIC Servizi S.r.l.