Optimizing Al/Zn ratios in K₂O/Zn-Aluminate catalysts for enhanced biodiesel production efficiency

In this study, a series of K₂O/Zn-aluminate catalysts with varying Al/Zn ratios (0.5-4) were examined as heterogeneous base catalysts for the esterification of sunflower oil with methanol. The synthesized nanocatalysts were characterized using XRD, FESEM, EDX, and BET techniques. Furthermore, FTIR and H-NMR analyses were conducted to verify the successful transesterification reaction and biodiesel production. The characterization results the successful synthesis of the K₂O/Zn-aluminate catalysts, demonstrating their favorable surface and structural properties for the esterification process. The reactor performance data under the conditions of 70 °C reaction temperature, 3 h reaction time, a methanol-to-oil ratio of 1:16, and a catalyst loading of 1% by weight revealed that the catalyst with an Al/Zn molar ratio of 4 exhibited the highest catalytic activity. This catalyst achieved a biodiesel production yield of 96% and a conversion efficiency of 94.6%. This yield is comparable to that of other synthesized samples. The enhanced catalytic performance can be attributed to the improved structural properties of the K₂O/Zn-4Al₂O₄ samples. Furthermore, reusability tests were conducted to evaluate the practical viability of these catalysts. The K₂O/Zn-4Al₂O₄ catalysts demonstrated the capacity to be recycled for four cycles without a substantial decline in catalytic activity, maintaining a yield that decreased from 96 to 90%. This stability highlights their potential as a sustainable alternative for biodiesel production.