Characterization of Silicon-Aluminum-Zirconium Oxide Obtained by the Sol-Gel Process

Study of the characteristics and properties of the SiO2/TiO2/Nb2O5 material obtained by the sol–gel process

“…They have been characterized by a flat surface with a rough structure. This characteristic is quite usual for mixed oxides obtained by the sol–gel process 3 , 4 . Note that the particle size distribution is quite heterogeneous, which is characteristic for mixed oxides obtained by the sol–gel process; and the distribution cannot be estimated by SEM analysis.…”

“…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 (M x O y or N x O y ) and increasing the number of active sites on the surface. Besides this, 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 mixture 3 , 4 , 11 – 14 . Hence, the oxides mixture are interesting materials for various applications 3 , 4 : as heterogeneous catalysis 2 , 9 , 15 , 16 , photoanodes for solar cells 6 , photocatalytic activity 7 , optical properties 8 , bioactive glass 10 , preconcentration systems of metallic ions 11 , 17 – 19 , dye remediation or adsorbent in aqueous solution 5 , 20 , adsorption of interest molecules 21 , development of new chemically modified electrodes 22 , 23 , among others.…”

Kinetics of Soybean Oil Hydrolysis on Niobium Catalysts

“…There is a progressive reduction of the bands corresponding to LAS and BAS after the release of pyridine at 423 K. The concentrations of BAS and LAS expressed in milligrams of pyridine adsorbed per gram of sample (mg Py g cat −1 ) were determined by integration of the peaks at 1541 and 1447 cm −1 related to the pyridine adsorbed at the Brønsted and Lewis sites, respectively, of the spectra collected after the release of pyridine at 423 K , , according to the procedure described by Emeis , , . The results are summarized in Tab.…”

“…2, FTIR spectra after pyridine adsorption are compared to the spectra of pyridine-free adsorbed materials on the surface of each material. The spectra of the vibrational modes pf pyridine are usually observed in the wavelength range of 1700-1400 cm -1 [61][62][63].…”

“…This work Literature Ref. ) were determined by integration of the peaks at 1541 and 1447 cm -1 related to the pyridine adsorbed at the Brønsted and Lewis sites, respectively, of the spectra collected after the release of pyridine at 423 K [61,68], according to the procedure described by Emeis [61,63,74]. The results are summarized in Tab.…”