Transesterification of non-edible oils over potassium acetate impregnated CaO solid base catalyst

Abstract

Biodiesel production through transesterification reaction with methanol using calcium oxide (CaO) as a solid base catalyst is restricted due to the need to the high molar ratio of methanol to oil and long reaction time. Therefore, the CaO catalyst was modified by potassium acetate (PA) to prepare PA/CaO solid base catalyst via wet impregnation method. X-ray Diffraction, Scanning Electron Microscopy, Thermal Gravimetric Analysis, Fourier Transform Infra-Red spectroscopy, Hammett indicator (basic strength), and the Inductive Couple Plasma techniques, were applied to characterize the prepared catalyst. The effect of the PA ratio loaded on CaO and calcination temperature were investigated as well. The catalyst activity was tested through transesterifcation reaction of non-edible oils, namely bitter almond oil BAO and waste fish oil WFO, with methanol. Transesterifcation process was optimized through the parameters involving the solid catalyst amount, methanol to oil molar ratio, reaction temperature, and reaction time. The highest methyl ester yield from both BAO (91.22 wt%) and WFO (93.30 wt%) were achieved by employing 2.0 wt% , and 1.0 wt% of PA/CaO catalyst, respectively, 9:1 methanol to oil molar ratio, 60 °C reaction temperature, and 120 min reaction time. The prepared catalyst was retrievable and thermally stable giving a yield up to 75 wt% after a 4th cycle reuse. The fuel properties of the raw oils were significantly enhanced as a result of transesterification, and were in conformity with the ASTM D 6751 limits. Conversion of the non-edible oils to biodiesel using the catalyst was confirmed by 1H NMR spectroscopy which gives yield percent close to those of the practically obtained. Moreover, the FTIR spectroscopy assured the conversion of the non-edible oils into biodiesel. As such, PA/CaO composite may be considered as a promising solid base catalyst for transesterification of non-edible oils with methanol.