Enhanced Biodiesel Production Using KOH/NaOH Supported on Walnut and Almond Shell Ash

ABSTRACT Biodiesel's desirable characteristics make it an attractive alternative to conventional diesel fuel. To address this, the present study explores catalysts derived from waste materials. Specifically, novel heterogeneous catalysts were prepared using almond shell ash (ASA) and walnut shell ash (WSA) as supports, with both sodium hydroxide (NaOH) and potassium hydroxide (KOH) as active components. The catalysts were characterized using x‐ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses, revealing similar functional groups and amorphous structures. Transesterification experiments were conducted with waste cooking oil (WCO) at 63°C, a 2:1v/v oil‐to‐methanol ratio, and 8.5 wt.% catalyst concentration. This study examined the influence of catalyst composition and reaction time on biodiesel purity. The findings indicated that both ASA‐ and WSA‐supported catalysts produced biodiesel with a purity of approximately 98% under similar conditions, demonstrating their potential as effective and sustainable catalysts.