Mechanochemical preparation and characterization of CaO·ZnO used as catalyst for biodiesel synthesis

Abstract

In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO·ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)2 and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 700 °C in air atmosphere. For comparison, the CaO·ZnO mixed oxide was also prepared using usual coprecipitation procedure (CP) followed by calcination at 700 °C of the formed calcium zinc hydroxide hydrate. The BMH, BM and CP catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), particle size distribution measurement and scanning electron microscopy (SEM and SEM-EDS). In addition, specific surface area (BET), solubility in methanol at 60 °C and alkalinity (Hammett indicator method) were also determined. The activity of BMH, BM and CP catalysts for biodiesel synthesis were tested at 60 °C and 1 bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2 wt% of catalyst based on oil weight.