Biodiesel de óleo de fritura via hidroesterificação utilizando vermiculita como catalisador heterogêneo.

Abstract

This study aimed to investigate the synthesis of biodiesel from frying oil through the hydroesterification reaction, using as heterogeneous catalytic support – vermiculite. Both the biodiesel obtained and the raw material (frying oil) were characterized by physical-chemical, thermal and absorption spectrophotometry in the UV-Visible region for better understanding. The synthesis of biodiesel by hydroesterification involved two steps: hydrolysis and esterification, whereby the residual frying oil was subjected to the step of hydrolysis in an autoclave reactor at a temperature of 300 ° C for 03 hours. After the hydrolysis, the glycerin was removed and the fatty acids generated were subjected to the esterification step and processed under the following conditions: 6: 1 molar ratio of the ethyl alcohol / fatty acid in the presence of 5% of the catalyst (vermiculite) relative to the mass of the oil. Subsequently, the mixture was subjected to the stirring process and transferred to the autoclave reactor at 200°C for 01 hour. After that, the mixture was decanted for 2 hours and the phases were separated. The dense phase – biodiesel – was characterized according to the standards of the National Agency for Petroleum, Natural Gas and Biofuel. Thus, the reaction yield in relation to the initial mass of the residual frying oil for biodiesel was 66.65%. It is suggested that this yield was compromised by the acidity of the obtained biodiesel (0.61mg KOH/g), contributing to the release of the free fatty acids in the medium. Regarding the thermal study, the thermogravimetric curves showed that biodiesel is more volatile compared to the frying oil and presented two stages of decomposition: the first probably corresponding to the ethyl ester volatilization, with 83.1% of mass loss, indicating the conversion to monoacylglycerides; and the second stage with 14.3% of mass loss, attributed to the presence of diacylglyceride and/or triacylglyceride traces not converted to esters of ethyl fatty acids. The absorption spectra in the infrared region confirmed the presence of the strongly acidic fatty acid esters of 1749.7 cm-1; however, the presence of medium-sized vibrational band, corresponding to OH group stretching, is also present at 3600 to 3300cm-1, corroborating the thermal and physicochemical profile, confirming the presence of moisture and/or total nonconversion of glyceride hydrolysis. Finally, according to the results presented, this study proved to be feasible in terms of conversion, although it requires further investigation, manipulating the reactional conditions.