Síntese e caracterização de óxido de alumínio e/ou silício através do método sol-gel proteico

Abstract

In order to synthesize nanostructured materials with high porosity from a simple, renewable, efficient, low cost and high catalytic performance methodology, aluminum oxide and / or silicon oxide based solids were synthesized using the sol protein gel using porcine gelatin as an organic precursor and aluminum nitrate and / or tetraethyl orthosilicate as inorganic precursors. The characterization was carried out through X-ray Fluorescence, Thermogravimetry, X-ray Diffraction, Infrared Spectroscopy, Scanning Electron Microscopy, Mercury Porosimetry, Nitrogen Sorption and catalytic tests (ethanol dehydration model reaction). The X-ray Fluorescence proved the efficiency of the synthesis methodology regarding the chemical composition of the oxides. The thermogravimetric results indicated the total release of the organic material at the calcination temperature used and that the hybrid material is more thermally stable than the outer ones. The X-ray diffractograms showed an amorphous material profile characteristic of highly dispersed metal oxides. Infrared spectra showed the presence of a hybrid material and gelatin structure characteristic bands prior to calcination that disappeared into the solid spectrum after calcination indicating the loss of organic matter after heat treatment and also exhibited MO stretching vibration in low wavelengths after the calcination that are related to the metal oxides (SiO2 and Al2O3) formed. The images acquired by Scanning Electron Microscopy suggested that the oxides have a sponge-like morphology. This morphology was confirmed by the technique of Mercury Injection and Nitrogen Sorption in which it was possible to observe that the material has high hierarchical porosity and interesting texture properties, especially for materials containing aluminum oxide and silicon oxide. The results of ethanol dehydration showed higher selectivity to diethyl ether compared to ethylene while acetaldehyde showed no results. From the reaction data, the following order of acid strength was obtained: 2 Si: Al> Si: 2Al> Si: Al> Al, proving that the Si: Al ratio and the specific area influence this sequence.