Remarkably enhancing the biodiesel yield from palm oil upon abalone shell-derived CaO catalysts treated by ethanol

•Enhanced biodiesel yield was obtained as CaO catalysts were treated by ethanol.•Abalone shell-derived CaO was synthesized and used for biodiesel.•The CaO catalyst modified by ethanol showed an enhanced activity compared to U-CaO.•The CaO catalyst modified by ethanol presented a higher reusability than U-CaO.•Strong basicity and porous structure of the catalyst led to good performance.

In the present study, a highly efficient CaO-based catalyst was synthesized by using abalone shell as a precursor and ethanol as a modification agent for biodiesel production. The physico/chemical properties of the catalysts, which could be tailored by altering the ethanol-treatment temperature (room temperature, 100 °C and 160 °C), were monitored by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis and Hammett indicator. Once treated with ethanol, the modified CaO (M-CaO) catalyst exhibited an increased catalytic activity mainly due to the high surface area, increased specific basicity and decreased crystalline size compared to the unmodified CaO (U-CaO) catalyst. Particularly, when the ethanol treatment temperature was 100 °C, the maximal yield of fatty acid methyl ester (FAME) for the M-CaO catalyst could reach 96.2% (87.5% for the U-CaO catalyst). Furthermore, the M-CaO catalyst exhibited good reusability, having a superior catalytic activity compared to the U-CaO catalyst after recycling for more than five cycles.