Sulfonated poly(divinylbenzene) and poly(styrene-divinylbenzene) as catalysts for esterification of fatty acids

Commercial ion-exchange resins (Amberlyst 35 and Amberlyst 36) and a resin synthetized in the laboratory, sulfonated poly(divinylbenzene) were evaluated as catalysts in the esterification of fatty acids (palmitic and oleic) with alcohols (methanol, ethanol and butanol). The study was developed in order to obtain a high rate of fatty acid conversion. The esterification reactions with fatty acids and methanol presented satisfactory conversion to methyl esters achieving a final conversion over 90% in both palmitic and oleic acid. A sample of waste vegetable oils with a high acid content from the residue of the palm oil and soybean oil refining industry were evaluated in the esterification with methanol. The best results were achieved with the new sulfonic resin, poly(divinylbenzene), which was synthesized in the laboratory and has proved efficient for the reaction in the study. Maximum biodiesel production was achieved from a fatty acid residue of the soybean oil refining industry and methanol (93%) which showed conversions very close to those obtained from their respective fatty acids.