Síntese do molibado de zinco pelo método Pechini para aplicação como catalisador nas reações de transesterificação e esterificação

Abstract

Environmental issues being widely discussed by society, competent bodies and authorities of different countries, with emphasis on the environmental pollution caused by the emission of polluting gases into the atmosphere by the burning of fossil fuels. Because of this, biodiesel has been widely studied, in search of new catalysts with high catalytic activity that use the most economically and ecologically viable reaction conditions. Thus, the present work proposed to synthesize by the method of polymeric precursors (Pechini) the zinc molybdate (ZnMoO4) to be used in the catalysis for biodiesel production by the reaction processes of transesterification and esterification, as well as in both simultaneous reactions. The catalysts were characterized by X-Ray Diffraction, Infrared and Raman Spectroscopy, Texture Analysis by Nitrogen Adsorption, Density by Helium Picnometry, Scanning Electron Microscopy and acid-base characterization. The catalyst was used in reactions with soybean oil, oleic acid and their mixtures, using molar composition of methanol: grease matter (12:1), 3 % catalyst concentration, temperature and reaction time variation. The reaction products were characterized by gas chromatography, acid index and nuclear magnetic resonance spectroscopy (RMN 1H e 13C). The synthesis of the catalyst by the method of polymeric precursors was reproducible, practical, fast and with low synthesis temperature. The results indicated a single phase, α-ZnMoO4, with a triclinic crystal structure and surface area of 0.366 m2 g -1 . As in the sample transesterification and esterification reactions, the highest conversion into biodiesel was the one that used synthesis conditions of 120 minutes at 160 °C, reaching a value of 100 % in esterification reactions and 5,7 % in transesterification reactions. For these conditions, a completed conversion into 69,54 % methyl esters was found in the simultaneous transesterification and esterification reaction. Thus, the α-ZnMoO4 catalyst has great potential for application in the production of biodiesel, using materials with less acidity control, for acting in esterification reactions and simultaneously in transesterification and esterification (TES). As there are no patents filed as ZnMoO4 for this purpose, this is an innovative material for catalysis in the production of biodiesel.