Industrial eggshell wastes as the heterogeneous catalysts for microwave-assisted biodiesel production

Active biodiesel production catalysts were derived from waste eggshells by simple calcination in air. The physicochemical properties of the activated catalysts were characterized by XRD, N2 sorption, CO2-TPD, TGA–DTG, XRF, and SEM, while the catalytic activity was tested in producing biodiesel via transesterification on palm oil with methanol under microwave conditions. The effect of microwave power, reaction time, methanol-to-oil ratio, and catalyst loading was investigated. The experimental results revealed that the catalysts exhibited a high content of CaO (99.2 wt%) with a high density of strong base sites. The catalytic testing demonstrated a remarkable enhancement for biodiesel production using microwaves compared to conventional heating. The maximum yield of fatty acid methyl esters reached 96.7% under the optimal condition of reaction time of 4 min with 900 W microwave power, methanol-to-oil ratio of 18:1, and catalyst loading of 15%. The results indicated that the CaO catalysts derived from eggshells showed good reusability and had high potential to be used as biodiesel production catalysts under microwave-assisted transesterification of palm oil.