Promoting effects of thoria on the nickel-manganese mixed oxide catalysts for the aerobic oxidation of benzyl alcohol

Development of Mesopore Structure of Mixed Metal Oxide through Albumin-Templated Coprecipitation and Reconstruction of Layered Double Hydroxide

Mixed metal oxide (MMO) with relatively homogeneous mesopores was successfully obtained by calcination and reconstruction of albumin-templated layered double hydroxide (LDH). The aggregation degree of albumin-template was controlled by adjusting two different synthesis routes, coprecipitation and reconstruction. X-ray diffraction patterns and scanning electron microscopic images indicated that crystal growth of LDH was fairly limited during albumin-templated coprecipitation due to the aggregation. On the hand, crystal growth along the lateral direction was facilitated in albumin-templated reconstruction due to the homogeneous distribution of proteins moiety. Different state of albumin during LDH synthesis influenced the local disorder and porous structure of calcination product, MMO. The N₂ adsorption-desorption isotherms demonstrated that calcination on reconstructed LDH produced MMO with large specific surface area and narrow distribution of mesopores compared with calcination of coprecipitated LDH.

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

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.