Esterification and transesterification of an acid oil using sulfuric acid as catalyst

J.M. MARCHETTI; A.F. ERRAZU

Buenos Aires, Argentina

Congreso; XXII Congreso Interamericano de Ingeniería Química, V Congreso Argentino de Ingeniería Química; 2006

Acid oils have a great amount of free fatty acid (FFA), varying from 3% to 40% depending on the quality of them. This is a great inconvenient when this raw material is used to produce biodiesel if the conventional homogeneous catalyst (potassium or sodium hydroxide) is employed due to several side reactions that can take place When this technology is employed it is non recommendable that free fatty acid are presented in the raw oil. When a basic homogeneous catalyst is employed (KOH, NaOH), the FFA will be transformed into soap. This will consume not only the catalyst but also the raw material and will decrease the global performance of the entire productive plant. The down streaming separation will be more difficult due to this side undesirable product. Because of this, in this work it is studied the esterification and transesterification reaction of an acid oil using sulfuric acid as catalyst. This catalyst will not produce soap; therefore, non-desirable products will not be produced. The effects of the reaction temperature, the amount of catalyst, the molar ratio alcohol/oil and the amount of FFA in the raw oil have been studied. For this work an ideal acid oils has been made by mixing pure oleic acid with refined sunflower oil. Ethanol has been used and the reaction was carried out on a batch reactor, the temperature was controlled by a thermostatic bath. Samples were taken from the reactor, wash with water in order to stop the reaction and then centrifuged for 20 minutes. From the oil phase drops were taken in order to perform the titration analyses to quantify the FFA that are still in the reaction, and some drops were taken for the GC analyses to know the ester production. The operations conditions are not the optimum ones but are the same as those used for basic homogeneous catalyst. The difference is that using this operational conditions bigger residence time are required for the transesterification reaction, however the FFA has been reduced to an acceptable level. The result obtained in this work allow us to show that the alternative esterification and transesterification of acid oils with sulfuric acid can be used not only to reduce the amount of FFA but also to produce biodiesel.