Rice husk ash as a catalyst precursor for biodiesel production

The transesterification of soybean oil with methanol was carried out in the presence of Li-modified rice husk ash catalyst at atmospheric pressure. The catalyst was prepared using a simple solid-state reaction, mixing, and well grinding 1.00 g RHA with 1.23 g Li2CO3 calcined at 900 °C in air for 4 h. The catalysts were characterized using XRD, SEM, FTIR, TGA-DTA, and the Hammett indicator. The XRD peaks were mainly consistent with Li2SiO3. The catalyst was highly active because its basic strength (H_) exceeded 15.0. The catalyst was also air-insensitive, as only a few CO32− anions formed on the surface of catalyst after exposure to air for 72 h, and no obvious LiOH formed on the catalyst surface. Under the optimal reaction conditions of a methanol/oil molar ratio of 24:1, a 4% catalyst amount, and a reaction temperature of 65 °C for 3 h, this approach achieved 99.5% conversion to biodiesel.

► The catalyst, Li2SiO3 was prepared from rice husk ash silica. ► This is the first attempt to use silica from RHA as a raw material for biodiesel production. ► The catalyst was highly active because its basic strength (H_) exceeded 15.0. ► The catalyst was air-insensitive for transesterification reaction.