Production and purification of biodiesel produced from used frying oil using hydrodynamic cavitation

This work describes the biodiesel production from used frying oil using a hydrodynamic cavitation reactor as well as separation and purification of fatty acid methyl esters (FAME). Under the optimized process conditions, i.e., methanol to oil molar ratio of 4.5:1 and catalyst (KOH) concentration of 0.55 wt%, the conversion achieved was 93.86 mol%. Higher conversion (93.6%) was obtained in only 20 min as compared to 88.5% in 1 h in stirred tank reactor. Due to the completion of transesterification reaction, the amount of intermediate diglycerides and monoglycerides present in the reaction mixture was less. It helps for the complete separation of methyl ester and glycerol layers without hindrance in 1 h. Small amount KOH catalyst used for completion of reaction reduces amount of KOH and soap in ester layer which further helps to form a less stable emulsion during water washing step. The complete separation was observed at 70 °C temperature in just 3 h. Thus, this study indicates that the increased production capacity can be achieved by shortening the time for the separation and purification.