Calcium oxide as a solid base catalyst for transesterification of soybean oil and its application to biodiesel production

• Published in: Fuel (Guildford) Vol. 87; no. 12; pp. 2798 - 2806
• Main Authors: Kouzu, Masato, Kasuno, Takekazu, Tajika, Masahiko, Sugimoto, Yoshikazu, Yamanaka, Shinya, Hidaka, Jusuke
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2008; Elsevier
• Subjects: Applied sciences; Biodiesel; Biomass; Calcium oxide; Cation-exchange resin; Energy; Exact sciences and technology; Free fatty acid; Natural energy; Solid base catalyst; Solid base catalyst; Calcium oxide; Free fatty acid; Biodiesel; Cation-exchange resin; Diesel fuel; Biofuel; Transesterification; Calcium carbonate; Soybean oil; Fatty acid methyl ester; Calcium hydroxide; Catalyst; Methanol
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2007.10.019

In order to study solid base catalyst for biodiesel production with environmental benignity, transesterification of edible soybean oil with refluxing methanol was carried out in the presence of calcium oxide (CaO), -hydroxide (Ca(OH) 2), or -carbonate (CaCO 3). At 1 h of reaction time, yield of FAME was 93% for CaO, 12% for Ca(OH) 2, and 0% for CaCO 3. Under the same reacting condition, sodium hydroxide with the homogeneous catalysis brought about the complete conversion into FAME. Also, CaO was used for the further tests transesterifying waste cooking oil (WCO) with acid value of 5.1 mg-KOH/g. The yield of FAME was above 99% at 2 h of reaction time, but a portion of catalyst changed into calcium soap by reacting with free fatty acids included in WCO at initial stage of the transesterification. Owing to the neutralizing reaction of the catalyst, concentration of calcium in FAME increased from 187 ppm to 3065 ppm. By processing WCO at reflux of methanol in the presence of cation-exchange resin, only the free fatty acids could be converted into FAME. The transesterification of the processed WCO with acid value of 0.3 mg-KOH/g resulted in the production of FAME including calcium of 565 ppm.