Doping effect of Al2O3 and CeO2 on Fe2O3 support for gold catalyst in CO oxidation at low-temperature

• The activity and thermal stability of gold catalyst are enhanced by doping.
• Dopant retards the collapse of mesoporous structure of catalysts.
• Dopant restrains the growth of gold particles and the crystallization of support.
• The effect of doping is a synergy effect between Al2O3 and CeO2 exist.

Al2O3/CeO2 doped Fe2O3 support was synthesized by co-precipitation method, based on which gold was loaded by deposition–precipitation. Both the catalytic activity and thermal stability of the gold catalyst were enhanced significantly by Al2O3/CeO2 doping. The catalyst loaded with 1.0% Au and calcined at 180 °C converted CO completely at −8.9 °C, while the sample modified by Al2O3/CeO2 showed a 100% CO conversion at −20.1 °C. Characterization techniques, such as N2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopic (TEM), thermogravimetry–differential scanning calorimeter (TG–DSC) and CO2 temperature programmed desorption (CO2-TPD) were employed to investigate the structure and surface morphology of the catalysts. Al2O3/CeO2 doping retarded the mesoporous structures of the catalysts from collapse during the calcination at high temperature, which thus maintained higher specific surface area and lower pore size. After being calcined at 500 °C, the average diameter of the gold particles in Au/Fe2O3 was 7.0 nm and the sizes of support grains ranged from 50 to 100 nm. However, the average diameter of the gold particles in Au/Al2O3/CeO2/Fe2O3 was only 5.1 nm and the sizes of support grains ranged from 10 to 30 nm. Gold loaded on the Fe2O3 support by the doping of Al2O3/CeO2 have better catalytic activity for CO oxidation.

The TEM of catalysts calcined at 500 °C is shown, comparing with the catalyst without dopant, Al2O3 doping contribute to the effect against sintering. Further, the effect of doping of Al2O3 and CeO2 is better, the size of gold particles and support grains in the corresponding sample is much smaller than the one in the others.Figure optionsDownload as PowerPoint slide