Preparation of SrZrAl multiple oxide catalyst for produce biodiesel from acidified palm oil

The strontium oxide (SrO) is considered as an efficient heterogeneous catalyst for biodiesel production. However, the resistance of SrO to high free fatty acids (FFAs) in low-quality raw materials is a great challenge. In this study, the SrZrAl multiple oxide catalysts are prepared and applied in transesterification of the acidified palm oi. The preparation of the SrZrAl catalysts is optimized from the aspects of the preparation method and zirconium content, where the co-precipitation method with Sr, Zr and Al molar ratio of 6:6:1.5 is preferentially determined. The microstructure and surface chemical properties of SrZrAl catalyst are thoroughly characterized by XRD, CO2/NH3-TPD, XPS and SEM-EDS. The GA-PSO-BP algorithm is used to optimize the transesterification parameters, where the FAME yield of 94.4% could be achieved with the addition of oleic acid of 5 wt% under the condition of the methanol to oil molar ratio of 16:1 and catalyst amount of 3.8 wt% at 171 °C in 2.6 h. Excellent reusability of the SrZrAl catalyst is demonstrated by the fact that the FAME yield of 80.3% is still obtained at the fifth reuse cycle. In addition, the FAME yield reaches 83.4% even at a high oleic acid addition of 15 wt%.