Active Acid Catalyst of Sulphated Zinc Oxide for Transesterification of Soybean Oil with Methanol to Biodiesel

Active solid acid catalysts of sulphated zinc oxide (SO42--ZnO and SO42-/ZnO) were prepared and characterized. The solid acid catalysts were investigated for their performance on transesterification of soybean oil with methanol to produce biodiesel. The SO42--ZnO and SO42-/ZnO catalysts were prepared by coprecipitation and impregnation respectively to compare their performance for biodiesel production. The catalysts were characterized by X-ray Diffraction (XRD) and Fourier Transform Infra Red (FT-IR), while the fatty acid methyl ester (FAME) component in biodiesel product was identified by Gas Chromatography - Mass Spectrometer (GC-MS) and FT-IR. The SO42--ZnO catalyst, prepared by coprecipitation, showed better performance for the transesterification process than the SO42-/ZnO catalyst, prepared by wet impregnation. The trend of performance of both catalyst was due to effect of sulfonate incorporation into the zinc oxide structure to form active acid sites. From the catalyst testing on transesterification of soybean oil with methanol at mild conditions (temperature of 65 °C, methanol to oil mole ratio of 6, and 4 wt% of catalyst loading), the SO42--ZnO catalyst exhibited promising FAME yield of 80.19% at 4 h reaction time. Therefore, the SO42--ZnO catalyst showed potential as a catalyst for transesterification of soybean oil to produce biodiesel.