Tratamento de fase glicerina resultante de processos produtivos de biodiesel por neutralização em diferentes ácidos e adsorção em carvão ativado: ensaios comparativos

Abstract

Since 2004, Brazil has been adding biodiesel to fossil diesel, and by 2025 the mandatory content will be 15%. Legislation and technical tests have enabled the gradual increase of this blend. Biodiesel production generates the glycerin phase (a mixture rich in glycerol) as a byproduct, requiring commercial solutions for its utilization. Glycerol is a compound widely used in various production processes to obtain various derived products, with broad applications and uses throughout society. It can be used as a raw material in numerous industrial sectors, including the production of cosmetics, food, beverages, medicines, paper, and others. This paper presents the results of the treatment of the glycerin phase from production processes to obtain biodiesel and glycerol. Treatments were performed with silica, activated carbon (to remove moisture and adsorb impurities related to phase color), and reactions with HCl, H2SO4, C6H8O7 (citric acid), and C2H2O4 (acetic acid). The results were analyzed by oxidation/reduction volumetry (titration/back titration) with (i) potassium permanganate (KMnO4)/sodium oxalate (Na2C2O4) and (ii) potassium dichromate (K2Cr2O7)/ammoniacal iron (II) sulfate (Fe(NH4)2(SO4)2.6H2O); infrared absorption spectroscopy (FTIR) and thermogravimetric analysis (TGA). The data obtained were statistically treated by T-tests and F-tests. The treatment of the glycerin phase with acid resulted in spontaneous separation with formation of new phases with concentrated glycerol, being verified by (i) and (ii) in proportions, according to the use of acids (% phase with glycerol/acid used in the treatment): for (i) 52.27%/C6H8O7, 57.35%/C2H4O2, 67%/H2SO4 and 70.42%/HCl; and for (ii) 45.64%/C6H8O7, 52%/C2H4O2, 57.45%/H2SO4 and 65.16%/HCl. There was a better yield in the final glycerol content using the HCl treatment of 93.41%, according to data obtained in TGA. According to the results obtained by FTIR, the spectra revealed typical alcohol bands, such as O-H, C-H and C-O, confirming the presence of glycerol; primary and secondary group stretching bands (C-O) identified, characteristic of propane-1,2,3-triol. The results were considered satisfactory.