Characterization of biodiesel from frying oil obtained by hydro-esterification using vermiculite as heterogeneous catalyst

This study aimed to understand the synthesis of biodiesel from the residual frying oil through the hydro-esterification reaction using vermiculite as heterogeneous catalytic. The hydrolysis was carried out in an autoclave reactor at a temperature of 300 °C for 3 h. Then, the esterification was performed under the molar ratio of 6:1 of ethyl alcohol/fatty acid, in the presence of 5% of the catalyst concerning the oil mass. We analyzed the physicochemical and thermal characteristics of both the biodiesel and the frying oil, and the spectrophotometric parameters of absorption in the UV–visible region. We found a reaction yield relative to the mass of the residual frying oil of 66.65%. The thermogravimetric curve for biodiesel showed two stages of decomposition: the first stage with 83.1% of mass loss, indicating conversion to monoacylglycerols, and the second with 14.3% of mass loss, attributed to the presence of traces of diacylglycerides and triacylglycerides not converted into esters of ethyl fatty acids. The absorption spectra in the infrared region confirmed the presence of ethyl fatty acid esters at 1749.7 cm⁻¹ but also verified the presence of a vibrational band corresponding to the OH group stretching at 3600 to 3300 cm⁻¹, confirming the presence of moisture or the partial conversion of the glyceride hydrolysis. Finally, the results show a satisfactory conversion, although more detailed studies are still required.