Transesterification of waste edible oils to biodiesel using calcium oxide@magnesium oxide nanocatalyst.

In the present research, application of waste edible oil (WEO) as a suitable and abundant source for biodiesel production using CaO@MgO nanocatalyst derived from waste chicken eggshells was studied. To this end, FT-IR, XRD, SEM, EDX, Map, and TEM analyses were performed to investigate characteristics of the CaO@MgO nanocatalyst. Also, the physical properties of the biodiesel such as flash point, kinematic viscosity, density, distillation point, cloud point, pour point, cetane number, oxidation stability, and acid number were determined according to the international standards. In addition, FT-IR and HNMR analyses were used to determine the biodiesel characteristics. Moreover, the produced catalyst was successively reused for up to 6 cycles and the results showed that the catalytic activity of the catalyst produced was sufficient for biodiesel production from WEO for up to three cycles, beyond which its catalytic activity decreased. The present work further considered the effects of different parameters on biodiesel production using central composite design to determine optimal conditions. According to the results, the highest biodiesel conversion yield (98.37%) was achieved in a reaction time of 7.08 h, reaction temperature of 69.37 °C, methanol-to-oil ratio of 16.7:1, and catalyst concentration of 4.571 wt% which shows the highest biodiesel conversion yield ever achieved from waste edible oil.