Microwave-assisted catalytic transesterification of soybean oil using KOH/γ-Al2O3

The present study deals with potassium hydroxide (KOH) impregnated alumina catalysts and tested in biodiesel production with different configurations to optimize catalyst preparation conditions and transesterification reaction. To this aim, a series of KOH/γ-Al₂O₃ was synthesized with numerous amounts of KOH loading (15, 20, 25, 30, 35, 40 wt.%), at different calcination times (2, 3, 4 h) and calcination temperature (400, 500, 600 °C). Besides, the transesterification process was also performed under different heating methods, namely, conventional heating and microwave heating. The structure and textural characteristics of the catalysts were elucidated through X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) analysis. The catalyst prepared with 30 wt.% KOH content, calcined at 400 °C for 3 h, was noted as the suitable catalyst, attaining 97.30% FAMEs content (conversion). The corresponding operating conditions were when the process temperature was 65 °C, catalyst loading of 3 wt.%, methanol to oil molar ratio of 12:1, and reaction duration of 35 min using microwave heating system.