CaO-MgFe2O4@K2CO3 as a novel and retrievable nanocatalyst for two-step transesterification of used frying oils to biodiesel

In this study, biodiesel was generated from used frying oil (UFO) in the presence of CaO-MgFe2O4 @K2CO3 as a novel and effective nanocatalyst. Structural and morphological properties of CaO, CaO-MgFe2O4, and CaO-MgFe2O4 @K2CO3 nanocatalysts were evaluated by EDX/SEM, BET, FTIR, TEM, DLS, VSM, and XRD analyses. Also, life cycle assessment and reaction mechanism were investigated. The utmost biodiesel yield using CaO and CaO-MgFe2O4 @K2CO3 nanocatalysts was acheived 93.55% and 96.53%, respectively, at a alcohol/oil ratio of 15:1 for CaO and 18:1 for CaO-MgFe2O4 @K2CO3, catalyst percentage of 4%, temperature of 70 degrees C, and reaction time of 5 h, which indicates a significant increase in the biodiesel yield of CaO-MgFe2O4 @K2CO3 compared to CaO. Also, physical features of biodiesel such as density, viscosity, flashpoint, cetane number, pour point and cloudpoint were 882 kg/m3, 4.4 mm2/s, 168 degrees C, 58.82, 3 degrees C and -2 degrees C, respectively, which are within inter-national standards. Moreover, thermodynamic and kinetic behaviors of transesterification were studied and the results showed that the biodiesel generation process using CaO-MgFe2O4 @K2CO3 is endothermic (Delta H degrees= 61.9 kJ/mol) and non-spontaneous (Delta G degrees >0). The activation energy of the transesterification reaction was 64.62 kJ/ mol, showing the significant potential of the catalyst in the transesterification reaction. Besides, the reusability of CaO-MgFe2O4 @K2CO3 nanocatalyst showed that it can be used in 4 reuse cycles with high biodiesel yield (>90%). Life cycle assessment showed that CaO-MgFe2O4 @K2CO3 has less negative impacts on the environment than common catalysts such as KOH and NaOH. Also, collecting UFO and using it in biodiesel generation helps to reduce environmental pollution.

Automated summary

In this study, a novel nanocatalyst CaO-MgFe2O4@K2CO3 was used to generate biodiesel from used frying oil (UFO). The structural and morphological properties of the nanocatalyst were evaluated and the biodiesel yield was significantly increased compared to the traditional catalyst CaO. The physical features of the biodiesel met international standards and the transesterification reaction was found to be endothermic and non-spontaneous. The reusability of the nanocatalyst was demonstrated and its environmental impact was lower than common catalysts.