Síntese e caracterização de estanossilicatos mesoporosos para aplicação em esterificação do ácido levulínico

Abstract

In face of problems associated with the use of fossil fuels, many researches have been dedicated to the development of technologies that promote the use of renewable raw materials. Among the solids with catalytic potential, the mesoporous molecular sieves of the MCM41 type have been highlighted due to their properties, such as high surface areas, uniform pore size distribution and high ion exchange capacity. Therefore, the present work studied the development of materials based on silica, such as mesoporous molecular sieves (MCM41), modified with tin via direct synthesis and by the non-hydrothermal method. The insertion of tin in the structure of MCM41 had the objective of generating acidic sites in them, with a view to its application in the conversion of biomass, in order to obtain chemical inputs of high industrial interest. The synthesized samples were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (DRX), Thermogravimetric analysis (TG/dTG), Adsorption and Desorption Isotherms in liquid nitrogen at 77K, Diffuse ultraviolet-visible reflectance spectroscopy (DRS), determination of surface acidity by thermogravimetric analysis , Infrared Region Spectroscopy with Pyridine, Temperature Programmed Ammonia Desorption (TPD), Temperature Programmed Reduction (TPR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Plasma Atomic Emission Optical Spectrometry coupling (ICP OES) and were subjected to catalytic and stability evaluation. The results show that it is possible to incorporate tin in the MCM41 structure, and the modified materials became more active in the investigated reactions. It was observed that the non-hydrothermal method was effective in obtaining materials with a high degree of ordering, high acidity and promising catalytic activities in the esterification reaction of levulinic acid with different alcohols. Chain size had less influence in decreasing the conversion rate than the nature of the alcohol which led to lower conversions to secondary and tertiary alcohols. All materials proved to be stable and reusable under the studied reaction conditions.