Catalisadores anfifílicos de NbO2OH suportados em vermiculita aplicados à reação de cetalização e esterificação

Abstract

The use of clays and clays minerals as a support for metal oxides has been frequently performed due to an increase in the quantity of available reactive sites for application in catalysis, oxidation, photocatalysis, etc. Among the oxides, the niobium oxides have arisen as important materials for researchers because of their excellent catalytic and oxidative properties, besides the great abundance of niobium in Brazil. In this scenario, the objective of this present work was to synthesize, by the precipitation-deposition method, niobium oxyhydroxide composites supported in vermiculite with amphiphilic character, with application in the fatty acid esterification and the glycerol ketalization. Glycerol is a polyalcohol obtained as a byproduct of biodiesel production and corresponds to about 10% by weight of all processed oil. Excess glycerol in the market can make it an environmental liability and cause damage to nature. In the case of the two reactions studied would be reduced to the amount of glycerol that is incinerated today due to lack of use. The composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) spectroscopy, Raman spectroscopy, UV-Visible spectroscopy, scanning electron microscopy (SEM) and zeta potential. Tests for the oleic acid esterification indicated the production of methyl oleate, which was expected and confirmed by FTIR, 1H and 13C NMR and quantified by titration analysis, reaching 82% and 97% of conversion. Glycerol ketalization tests indicated the expected formation of solketal, confirmed by FTIR, 1H and 13C NMR, thin layer chromatography and CG-FID, leading to 86% and 92% of conversion of the isolated product. The results demonstrated that niobium oxyhydroxide composites supported on amphiphilic vermiculite are good catalysts for possible industrial reactions involving the glycerol.