Study of Eggshell as Precursor of a Heterogeneous Catalyst in One Step Neutralization and Transesterification Reactions of Acid Macauba and Soybean Oil

Biodiesel is an important biofuel used worldwide as a total or partial substitute for fossil diesel. Many studies have been developed to reduce their costs, specially using acid oils as waste oil and inexpensive heterogeneous catalysts. CaO obtained from calcinated waste eggshells has been the object of study of this work to produce biodiesel using neutral soybean oil (<1.0 mg KOH/g) and high-acidity soybean oil (9.5 mg KOH/g) and macauba oil (20.0 mg KOH/g). A preliminary study of transesterification of neutral soybean oil with methanol in a molar ratio of oil:alcohol 1:12 in 3% of CaO-egg reached conversion 95% of FAME after 4 h of reflux. The progress of the reaction was analyzed both quantitatively by 1H NMR, as qualitatively by HPLC. The resultant biodiesel has met the international specifications as the kinematic viscosity and density, with values 4.37 mm2/s and 885.8 kg/m3, respectively. The study of breakthrough of the reaction between the doped acid soybean oil in the presence of methanol in a molar ratio of oil:alcohol 1:18, using 3% (w/w) CaO-egg indicated that the oil triglyceride only begins to be transesterified after all the neutralization of FFA. After 6 h of reflux the FAME conversion was of 96%. Using the same reaction conditions, while using the acid macauba oil, the FAME content was of 94%. The results showed the efficiency of CaO-egg for simultaneous neutralization/transesterification reaction for high-acidity oil, in only one step reaction