Simultaneous esterification and transesterification for biodiesel synthesis by a catalyst consisting of sulfonated single-walled carbon nanohorn dispersed with Fe/Fe2O3 nanoparticles

Abstract The simultaneous esterification of palmitic acid and transesterification of tributyrin is investigated using a solid acid catalyst newly developed. This catalyst consists of porous single-walled carbon nanohorn (SWCNH) dispersed with Fe/Fe 2 O 3 -mixed nanoparticles. The esterfication of palmitic acid is initially catalyzed by this catalyst, and the transesterification of tributyrin can be observed after most of palmitic acid was consumed. Contrary to a general expectation that the addition of a free fatty acid usually has poisonous effect on transesterification of tributyrin, the addition of palmitic acid shows an effect to enhance the yield of methyl butyrate. As one of the reasons, the palmitic acid adsorbed on Fe/Fe 2 O 3 particles placed in the pores of the catalyst may attract tributyrin molecules, and tributyrin concentrated thereon may diffuse to the acidic sites on the catalyst. However, this effect seems to be reduced significantly when the reaction temperature is high.