Preparation of Ca- and Na-Modified Activated Clay as a Promising Heterogeneous Catalyst for Biodiesel Production via Transesterification

For efficient biodiesel production, an acid-activated clay (AC) modified by calcium hydroxide and sodium hydroxide (CaNa/AC) was prepared as a catalyst. CaNa/AC and Na/AC were characterized by Hammett indicators, CO2-TPD, FT-IR, XRD, and N-2 adsorption techniques. The influence of catalyst dose, reaction temperature, methanol/oil molar ratio, and reaction time on the transesterification of Jatropha oil was studied. Due to the introduction of calcium, CaNa/AC displayed a higher activity and stability, thereby achieving an oil conversion of 97% under the optimal reaction conditions and maintaining over 80% activity after five successive reuses. The reaction was accelerated as the temperature rose, and the apparent activation energy of CaNa/AC was 75.6 kJ center dot mol(-1). The enhanced biodiesel production by CaNa/AC was ascribed to the increase in active sites and higher basic strength. This study presents a facile and practical method for producing biodiesel on large-scale operation.