Chiang Mai Journal of Science

     The stable of natural diatomite supported by potassium hydroxide (KOH) as catalysts were synthesized for biodiesel production. A heterogeneous base catalyst prepared by impregnating KOH onto diatomite was also used to synthesize biodiesel from palm oil. All samples have been thoroughly characterized by Wavelength Dispersive X-ray Fluorescence (WDXRF), X-ray diffraction (XRD), N2 adsorption/desorption, Scanning electron microscopy (SEM), Energy dispersive spectrometer (EDS), and Temperature-programmed desorption of carbon dioxide (CO₂-TPD). The XRD, XRF, and SEM results confi rm that adding KOH to diatomite results in structural change. The SiO₂ and K₂O phases form in the diatomite structural matrix during impregnation and the total basicity amount of this compound promotes the transesterifi cation process. A maximum fatty acid methyl ester (FAME) content of 84.56% was obtained. The reaction conditions were as follows: molar ratio of oil to methanol 1:9, catalyst loading 5 wt%, reaction time 2 h, and reaction temperature 75 °C. This work provides a possible new method for converting KOH from a homogeneous to a heterogeneous catalyst (Diatomite/KOH) that may show stable reusability, avoiding the separation and pollution problems in the environment.