Feasible and Clean Solid-Phase Synthesis of LiNbO3 by Microwave-Induced Combustion and Its Application as Catalyst for Low-Temperature Aniline Oxidation

Abstract

In this work, a feasible, fast, clean and efficient microwave-induced combustion method for direct synthesis of LiNbO3 in solid phase was developed. X-ray powder diffraction studies showed that quasi-pure Li-Nb-O phases, such as LiNbO3 and Li3NbO4, or mixtures of LiNbO3, Li3NbO4 and LiNb3O8, could be successfully synthesized. The resulting powders were efficiently applied as catalysts under ambient conditions in the oxidation process of aniline using hydrogen peroxide as oxidant. The proposed method was performed in a commercial system using high-pressure quartz vessels, which allowed safe control of the reactions-that usually occurs in less than 1 min. The results showed that the reaction conditions as well as the structural and morphological characteristics of the catalyst influenced the aniline oxidation process. Therefore, the present method for the preparation of LiNbO3 described herein, displayed many advantages when compared to conventional combustion methods, such as the physical characteristics of the obtained compound. Moreover, this new approach is considerably faster, safer and cleaner than other traditional procedures described in literature for LiNbO3 synthesis. This new microwave-induced combustion method is less time-consuming, saves energy, as well as affording the stoichiometric formation of inorganic particles.