Transesterification of Rice Bran Oil with Methanol Catalyzed by Mg(Al)La Hydrotalcites and Metal/MgAl Oxides

Both MgAl and Mg(Al)La hydrotalcites were synthesized by an alkali-free coprecipitation method and calcined to their corresponding oxides. MgAl oxide was impregnated with different kinds of metals (M = Cs, Sr, Ba, and La). All materials were characterized by the XRD, FT-IR, BET, NH3 TPD, and SEM techniques. The catalytic activity order of the M/MgAl oxides in the transesterification of glyceryl tributyrate (a model triglyceride) with methanol was found to be Cs > Ba approximate to Sr > La. The Mg(Al)La hydrotalcite that was calcined and then rehydrated contains Bronsted base sites, exhibiting hi-her activity than the calcined sample with Lewis base sites. In file preparation of biodiesel from rice bran oil via a two-step catalyzed process, Crude rice bran oil (11.14% FFAs) was first dewaxed/degummed and then esterified using silica-supported heteropolyacid H3PW12O40. FFAs were decreased to 0.98% at 70 degrees C in 4 h. This oil was then transesterified with methanol using the rehydrated Mg(Al)La hydrotalcites. At a temperature of 100 degrees C, a reaction time of 9 h, a methanol/oil molar ratio of 30:1, and a catalyst content of 7.5 wt %, biodiesel with 97% ester content and 78% product yield was obtained.