FTIR spectroscopy analysis for monitoring biodiesel production by heterogeneous catalyst

Layered double hydroxides, mixed oxides, and pure oxides based on magnesium and calcium were evaluated as catalysts in the methyl transesterification of soybean oil in a batch reactor. The catalysts were prepared by continuous co-precipitation and characterized by specific surface area, thermogravimetric analysis, temperature-programmed desorption of CO2, and X-ray diffraction. The reactions were performed at 65 degrees C, methanol-to-oil molar ratio 9:1, catalyst dosage of 1 wt.%, and reaction time of 240 min. The biodiesel analysis was carried out by Fourier Transform Infrared spectroscopy (FTIR) and Gas Chromatography (GC). Calcium-based catalyst, pure oxide (CaO) and mixed oxide (CaAl), demonstrated higher activity for methyl transesterification than magnesium-based catalyst. Considering both groups of catalysts, the activity for transesterification was: pure oxide > mixed oxide > > LDH. These results were related to the strength of the basic sites. FTIR and GC results were similar, with the advantage of FTIR analysis being simple, fast, and economical.