Heat treatment effect on nanostructured sol-gel derived lanthania doped with chromium

Abstract

Chromium doped lanthanum oxide synthesized by glycerol-assisted sol-gel route was heat treated at different temperatures up to 860 °C in order to investigate the effect of treatment temperature on the atomic environment in these samples. The addition of Cr2O3 to La2O3 catalyst support and catalytic promoter was considered because chromium is an interesting catalyst dopant.As the temperature rises from 100 to 860 °C, nanostructured La(OH)CO3, La2O2CO3 and La(OH)3 phases are developed in the treated samples. The crystallites size increases with treatment temperature from about 10 nm up to 30 nm, and at the same time a higher surface basicity is obtained, that would imply an enhanced catalytic activity or an improved behavior as catalyst substrate. The La2O2CO3 stable phase against moisture was obtained by relative low temperature synthesis. The tendency to atmospheric CO2 adsorption was evidenced for La(OH)3 phase developed in the samples treated at 650 and 860 °C.The X-ray diffraction (XRD), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses were used to evidence structural changes with influence on sample properties.