Sono-enhanced dispersion of CaO over Zr-Doped MCM-41 bifunctional nanocatalyst with various Si/Zr ratios for conversion of waste cooking oil to biodiesel

Abstract In present work, the catalytic properties of MCM-41 were boosted by introducing Zr into its structure with various amounts of Si/Zr molar ratios. Then it was loaded by calcium through conventional impregnation and sono-dispersion. Synthesized nanocatalysts were analysed using EDX, XRD, FTIR, FESEM and BET-BJH techniques. The results of XRD technique revealed the fabrication of MCM-41 and CaO. The FESEM images proved that the surface particle sizes of the synthesized catalysts were in the range of nanoscale and EDX results represented that Ca was more effectively scattered over the support in sonicated samples compared to non-sonicated one. Also, both FESEM and BET-BJH analysis represented a decrease in MCM-41 specific surface area with Si/Zr molar ratio reduction. The catalytic performances of bifunctional samples were evaluated for transesterification and esterification reactions. The constant operational conditions were as follows: 70 °C, MeOH/Oil = 9 and 5 wt% catalyst. Generally, the obtained results demonstrated a remarkable improvement in biodiesel conversion due to an increase of Zr amounts in catalysts and also the sample which was exposed to ultrasound represented better reusability in comparison with the non-sonicated sample. Among the prepared samples, the sonicated Ca/ZM-U (Si/Zr = 10) sample was the best catalyst for biodiesel production with high reusability.