Conversão do glicerol na presença do etanol usando catalisador a base de CoFe2O4/SBA-15

Abstract

Glycerol is the main byproduct for obtaining biodiesel, therefore, the growth of its production has caused an increase in the supply of glycerol, drastically reducing its market value. In order to improve the economic efficiency and ecological standards of biodiesel production, attempts have been made to catalytically convert glycerol into bioproducts with higher added value. In this sense, this work aimed to synthesize and characterize the solid based on cobalt ferrite supported on SBA-15 (CoFe2O4/SBA-15) to act as a catalyst in the reaction of conversion of glycerol in the presence of ethanol. The support was synthesized via hydrothermal method using P123 as organic director and TEOS as silica source. While the synthesis of the catalyst occurred through the impregnation of precursors of Fe3+ and Co2+ (Fe(NO3)3 · 9H2O and Co(NO3)2 · 6H2O) via Pechini's method. Characterizations via X-ray diffraction (DRX) and FTIR spectroscopy confirmed the syntheses of SBA-15 and CoFe2O4/SBA-15. Raman spectroscopy allowed the identification of ferrite with a degree of inversion (δ) of 0.4. The redox property of the catalyst was evaluated via the reduction at temperature program (TPR H2) which showed reduction events above 400°C, referring to the reduction of Co2+ and Fe3+ . The N2 physisorption analysis showed a surface area of 372 m2 /g and a total pore volume of 0.65 cm3 /g for the catalyst, indicating the presence of oxide on the surface and in the mesochannels of the support. Through scanning electron microscopy (SEM) it was confirmed that the support morphology was maintained after the impregnation process. Already from the transmission electron microscopy (TEM) it was observed an average particle size of 6.19 nm for the supported cobalt ferrite. The acid-base properties of the catalyst indicated the presence of weak basic sites via CO2 desorption at programmed temperature (TPD-CO2) and the presence of Lewis acid sites via NO and Pyridine adsorption followed by FTIR analysis. The catalytic tests show a greater conversion efficiency of glycerol in the presence of ethanol as a co-solvent, the reaction containing only glycerol showed a conversion of only 20%, while the reactions carried out in 10% glycerol-10% ethanol and 10% of glycerol-20% ethanol had a conversion greater than 80%. In general, acetaldehyde, propanoic acid, acetol and 1,2- propanediol were obtained as reaction products, in increasing order of selectivity. The reaction performed only with glycerol obtained ethanol as one of the products, while the reaction performed only with ethanol formed exclusively acetaldehyde.