Solvothermal synthesis and characterization of mixed oxides with perovskite-like structure

Abstract

Solvothermal synthesis was successfully used to prepare LaMeO3 (Me=Mn, Co, Fe) and La1−xSrxMnO3 (x=0.1, 0.3, 0.5), mixed oxides with perovskite-like structure. The prepared materials were examined by X-ray diffraction (XRD), nitrogen adsorption at low temperature (BET), transmission electron microscopy (TEM), decomposition of cyclohexanol (CHOL), temperature programmed reduction with hydrogen (TPRH2), temperature programmed desorption of oxygen (TPDO2) and X-ray photoelectron spectroscopy (XPS). Furthermore, catalytic activity for combustion of 0.6% vol. methane in air (GHSV=40000h−1) was determined.All prepared materials are nanocrystalline and well-crystallized, and they exhibit relatively well-developed specific surface area (9.2–39.2m2/g). The trigonal structure of the Mn-containing samples corresponds to the structure of the high-temperature bulk phase, which cannot be recovered at ambient conditions. Generally, the Mn-containing materials exhibit higher SSA, more basic character of the surface, lower temperature of maximum H2 consumption and higher catalytic activity in lean methane combustion than the corresponding Co- and Fe-based nanocrystals. The highest catalytic activity for lean methane combustion (100% of CH4 conversion at 451°C) is observed for LaMnO3. A partial substitution of La by Sr lowers content of Mn4+ on the surface of the corresponding materials, resulting in lower catalytic activity in lean methane combustion.