One-pot synthesis of Al2O3-La2O2CO3 systems obtained from the metallic precursor by the sol-gel method

Abstract

A series of mixed oxide‑carbonate Al2O3-La2O2CO3 systems with the La/Al molar ratios of 0.05, 0.1, 0.25, 0.5 and 1.0 have been synthesized by the sol–gel technique from aluminum isopropoxide and metallic lanthanum powder. During the synthesis of Al2O3- La2O2CO3 system, metallic lanthanum acts both as a precursor of lanthanum oxide and as secondary pH modifier of the gel solution. The traditional sol-gel method was modified to provide a better control over the final product surface parameters and structure. The obtained systems were amorphous and highly homogenic. The rate of the metal reaction was used as a limiting factor to control the gel formation. The obtained oxide systems are intended as a support for metallic phase catalysts. Calcination in air at 600°C did not produce systems containing only oxides and the lanthanum (dioxy)carbonate phase was still present. This observation can be explained by the multi stage decomposition process of lanthanum acetate forming during the gel synthesis.The systems were characterized by X-ray powder diffraction, low temperature nitrogen adsorption, transmission and scanning electron microscopy (TEM, SEM and SEM/EDS), thermogravimetric analysis (TGA), and FTIR spectra.