Calcium Oxide Derived from Egg Shells: A Low Cost Catalyst for Biodiesel Production

Abstract

  The decrease in fossil fuels reserves triggers the need for alternative sources of energy. One renewable energy source that may be considered as a substitute for traditional fossil fuels is biodiesel. Biodiesel is synthesized from waste cooking oil by transesterification with a CaO catalyst derived from egg shells. The chicken egg shells were treated by calcination in a furnace at a temperature of 900 °C for 3 hours with a flow rate of 10 °C/min. The egg shells were completely converted into CaO catalyst, as characterized by XRD. BET analysis revealed that the catalyst is mesoporous with a surface area of 1.1152 m2/g and an average pore diameter of 78.2 nm. CO2-TPD analysis revealed that the CaO catalyst has strong basic active sites with a basic amount of 630 µmol/g. SEM images show that the catalyst’s morphology is more regular, and the size of its particles decreased after calcination. Results showed the percentage of FFA was 0.4%. The effects of catalyst loading, methanol/oil ratio, temperature, and reaction time on the transesterification of waste cooking oil were investigated. The results obtained showed that 2 wt.% of catalyst, 15:1 of methanol/oil molar ratio, and reaction at 65 °C for 5 hours are the optimum parameters, with a biodiesel yield of 80%. This study revealed that CaO derived from chicken egg shells has good catalytic activity in the transesterification of waste cooking oil into FAME.