Produção sustentável de Biodiesel: desenvolvimento de catalisadores verdes, transesterificação de óleo de cozinha residual e conversão do Glicerol em Triacetina

Abstract

Several researches emerge in the search for energy alternatives to the use of fossil fuels, due to environmental concerns. Among the possibilities, there is biodiesel that allows the reduction of the use of diesel, contributing to the reduction of environmental impacts, as it is a natural and renewable source. This work proposed a sustainable process for the production of biodiesel from residual cooking oil (OCR), using low-cost and/or residual green catalysts from the ash of banana peels (BPC) and tangerine peels (TPC), in addition to of sodium and potassium silicates (SPS) originating from beach sand. Furthermore, the synthesis conditions for obtaining glycerol derivatives produced in the transesterification reaction were evaluated. The catalysts produced were characterized through the techniques, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermogravimetric analysis (TG/DTG), desorption at programmed temperature of CO2 (TPD-CO2) and analysis by the method deconvolution of the DTG and TPD-CO2 curves. Biodiesel was characterized by 1H and 13C nuclear magnetic resonance spectroscopy (1H and 13C NMR), TG/DTG using the deconvolution method on the DTG curves, density at 20 °C, kinematic viscosity at 40 °C and acidity index. To evaluate the yield of biodiesel synthesis, the parameters time, molar ratio A/O and catalyst concentration were varied. The solid materials BPC and TPC showed similar composition, with the majority presence of potassium carbonates and in the SPS, mainly potassium and sodium silicates were found. The TPD-CO2 analyzes indicated a greater number of basic sites in the SPS and BPC materials, with forces in the moderate to strong range, and weak sites in the TPC. The OCR biodiesels formed with the catalysts TPC, SPS and BPC showed conversions of 91.32%, 93.89% and 90.88%, respectively. Glycerol was mainly converted into glyceryl triacetate (triacetin) with the application of catalysts based on transition metal oxides, the 13C NMR spectra confirmed the synthesis, through the identification of the acetate carbonyl peaks present in the synthesized acetins. The process developed in this work is considered a more environmentally sustainable route for converting residual cooking oil into derivatives with higher added value. In this way, it is an alternative with less environmental impact to the conventional routes for obtaining biodiesel and triacetin.