Biodiesel Production from Soybean Oil Using Calcium Oxide as a Heterogeneous Catalyst

Abstract

Transesterification of soybean oil was carried out with methanol over calcium oxide at methanol re-fluxing temperature, in order to study the application of heterogeneous catalytic process to biodiesel produc-tion. The catalyst samples were prepared by calcination of the precipitated calcium carbonate at 900°C in the prescribed atmosphere, an ambient air or a helium gas flow. Calcium oxide prepared in an ambient air catalyzed the transesterification of soybean oil, but yield of the fatty acid methyl esters was only 10% for 4h. The calcination in a helium gas flow markedly intensified the activity of calcium oxide, as the obtained catalyst sample completed the transesterification for 2h. The obtained oil after completing the transesterification had appropriate properties for diesel fuel oil. The active catalyst prepared in a helium gas flow has a higher base strength (15.0<H_<18.4) than the dull one in an ambient air (9.3<H_<15.0). Addition-ally, the base Quantity was 5times larger for the active catalyst. The dull catalyst could be activated by calcination at 300°C in a helium gas flow. The poisoning species in an ambient air was elucidated through the activity test for a series of the catalyst sample obtained by conditioning the partial pressure of CO₂ and moisture in the calcining atmosphere.