Abstract
The SiO2/TiO2/Nb2O5 material was set by the sol–gel method and was characterized by several techniques through thermogravimetric, spectroscopic, and textural analyzes. For the two synthesized materials, the specific surface area was 350.0 and 494.0 m2 g−1 (SiTiNb-A and SiTiNb-B, respectively). An enhance of the crystalline order with the temperature increase of the thermal treatment was observed. Through X-ray Photoelectron Spectroscopy analysis, the binding energy values for the Ti 2p and Nb 3d levels showed the insertion of Ti and Nb atoms in the silica matrix. The Electron Dispersive Spectroscopy analyses also confirmed the high dispersion of the metals presented on the materials surface. The Thermogravimetric Analysis showed weight loss for the of 37.6% (SiTiNb-A) and 29.7% (SiTiNb-B). The presence of the crystalline phases TiO2-anatase and monoclinic-Nb2O5 in the materials was confirmed through the data obtained by association of powder X-ray Diffraction and FT-Raman. Values obtained from optical band-gap aimed the dependence of the oxides concentration and the calcination temperature. Finally, the pyridine adsorption studies have indicated the presence of Lewis and Brønsted acid sites.
Highlights
The SiO2/TiO2/Nb2O5 material was set by the sol–gel method and was characterized by several techniques through thermogravimetric, spectroscopic, and textural analyzes
These materials combine the mechanical properties of the silica matrix with the chemical properties of the metal oxides, exhibiting different chemical and physical properties from those observed in the oxide alone, especially because the presence of Brønsted and Lewis acid sites on the oxide m ixture[3,4,11,12,13,14]
The results obtained for the TiO2 and N b2O5 amounts in percentage by mass incorporated in the silica matrix, were 4.8 wt.% of TiO2 and 18.4 wt.% of Nb2O5 for SiTiNb-A material and 9.3 wt.% of TiO2 and 11.6 wt.% of Nb2O5 for SiTiNb-B material
Summary
The SiO2/TiO2/Nb2O5 material was set by the sol–gel method and was characterized by several techniques through thermogravimetric, spectroscopic, and textural analyzes. The characteristics of the sol–gel process are well known: the reactions operate at low temperatures obtaining materials with high thermal stability, high purity, controlled porosity and high uniformity for the distribution of the metal oxides in the silica matrix (MxOy or NxOy) and increasing the number of active sites on the surface. These materials combine the mechanical properties of the silica matrix with the chemical properties of the metal oxides, exhibiting different chemical and physical properties from those observed in the oxide alone, especially because the presence of Brønsted and Lewis acid sites on the oxide m ixture[3,4,11,12,13,14]. The main purpose of this work is to obtain and characterize SiO2/TiO2/Nb2O5 ternary oxides obtained by the sol–gel process as well to study its properties, for further applications
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