Ca and Zn mixed oxide as a heterogeneous base catalyst for transesterification of palm kernel oil
Transesterification of palm kernel oil with methanol over mixed oxides of Ca and Zn has been investigated batchwise at 60 °C and 1 atm. CaO·ZnO catalysts were prepared via a conventional co-precipitation of the corresponding mixed metal nitrate solution in the presence of a soluble carbonate salt at near neutral conditions. The catalysts were characterized by using techniques of X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). The results indicated that the mixed oxides possess relatively small particle sizes and high surface areas, compared to pure CaO and ZnO. Moreover, the combination of Ca and Zn reduced the calcination temperature required for decomposition of metal carbonate precipitates to active oxides. Influences of Ca/Zn atomic ratio in the mixed oxide catalyst, catalyst amount, methanol/oil molar ratio, reaction time, and water amount on the methyl ester (ME) content were studied. Under the suitable transesterification conditions at 60 °C (catalyst amount = 10 wt.%, methanol/oil molar ratio = 30, reaction time = 1 h), the ME content of >94% can be achieved over CaO·ZnO catalyst with the Ca/Zn ratio of 0.25. The mixed oxide can be also applied to transesterification of palm olein, soybean, and sunflower oils. Furthermore, the effects of different regeneration methods on the reusability of CaO·ZnO catalyst were investigated.
Graphical abstractCa–Zn mixed oxides have been investigated in transesterification of palm kernel oil at 60 °C and 1 atm. The mixed oxides consist of nano clusters of CaO and ZnO, and possess small particle sizes and high surface areas. The combination of Ca and Zn reduces the calcination temperature required for decomposition of CaCO3 to active CaO. Under the suitable conditions, the methyl ester content of >94.2% can be achieved.Figure optionsDownload full-size imageDownload as PowerPoint slide
Journal: Applied Catalysis A: General - Volume 341, Issues 1–2, 15 June 2008, Pages 77–85