Investigation on the esterification of fatty acids catalyzed by the H3PW12O40 heteropolyacid

• Main Author: Cardoso, Abiney L.
• Publication Date: 2008
• Other Authors: Augusti, Rodinei, Silva, Márcio J. Da
• Format: Article
• Language: eng
• Source: LOCUS Repositório Institucional da UFV
• Download full: https://doi.org/10.1007/s11746-008-1231-0; http://www.locus.ufv.br/handle/123456789/23226
• topic: Catalytic esterification; Heteropolyacids; Free fatty acids; Biodiesel

In this work, the H3PW12O40 heteropolyacid (HPW) was employed as a homogeneous catalyst to promote the efficient esterification (ethanolysis) of a number of saturated and unsaturated fatty acids (myristic, palmitic, stearic, oleic, and linoleic) under mild reaction conditions. HPW showed a similar activity to those observed for p-toluene sulfonic acid (PTSA) and sulfuric acid (H2SO4), the other acidic catalysts we compared them with in this study. In the HPW-catalyzed esterification of stearic acid, the addition of water caused a remarkable decrease in the ethyl stearate yields. On the other hand, the increase in the HPW concentration (up to a maximum value) promoted a proportional improvement in the oleic acid to ethyl oleate conversion. Kinetic measurements using oleic acid as a prototype substrate revealed that the esterification reactions catalyzed by HPW, H2SO4, and PTSA are of first-order in relation to the fatty acid concentration. Finally, the catalytic activity of HPW remained unaltered even after several recovery/reutilization cycles whereas the tungsten content in the final product (biodiesel produced by the HPW-catalyzed esterification of oleic acid) was found to be at an acceptably low level (0.0095 mg of W per g of biodiesel).