Abstract: Au/Fe2O3 catalysts were prepared by the coprecipitation method using seven precipitants, K2CO3, Na2CO3, NH4OH, (NH4)2CO3, NaOH, KOH, and urea. These catalysts were used for the low temperature water-gas shift reaction and characterized by N2 adsorption-desorption, X-ray fluorescence spectroscopy, X-ray diffraction, H2 temperature-programmed reduction, and CO temperature-programmed desorption to explore the cause resulting in their significant difference of catalytic activity. The catalysts prepared using K2CO3 or Na2CO3 as the precipitant exhibited higher activity and better stability above 200 ℃. The samples precipitated with NH4OH or (NH4)2CO3 showed moderate activity maximizing at 200 ℃. The samples prepared using the rest three precipitants presented almost no activity below 300 ℃, attaining only 35% of CO conversion above 350 ℃. The type of precipitant exerted significant effect on the coprecipitation of gold and iron ions, and the crystallization behavior of the resulting precipitates during the subsequent calcination step, which further influenced the gold loading, the dispersion of gold particles, and the reduction and CO adsorption-desorption properties of the iron oxide support. The high catalytic activity of Au/Fe2O3 catalysts at low temperature can be attributed to the synergism between higher dispersion of gold particles and easier reduction property of the iron oxide support. The increase in gold loading and dispersion of gold particles and the decrease in the iron oxide crystallites are favorable for improving the catalytic activity of the Au/Fe2O3 catalysts.

Key words: water-gas shift reaction, gold, supported catalyst, iron oxide, precipitant, coprecipitation