Microwave assisted transesterification of waste frying oil and concentrate methyl ester content of biodiesel by molecular distillation

In this study, microwave assisted transesterification of waste frying oil was carried out in the presence of sodium methoxide (NaOCH3). Parametric studies were performed to investigate suitable reaction conditions such as catalyst amount (0.5–0.75–1.0–1.5 wt.%), reaction time (3–5–7–9 min), temperature (55–60–65 °C), and oil:methanol ratio (1:4–1:5–1:6). Methyl ester content of biodiesel was determined as 90.04–98.85%. ester content of biodiesel was increased from 90.04% to 97.74% by molecular distillation at 170–200 °C, 10 mbar and 0.12–0.24 mL/min feed flow rate. Optimum distillation conditions were determined as 0.18 mL/min feed flow rate and 170 °C evaporator temperature by using 4 × 3 factorial design.