Effect of preparation parameters on activity of Au/Fe2O3 catalyst for water-gas shift reaction

The Au/FeO3 catalyst for water-gas shift reaction was prepared by coprecipitation method. Under vigorous stirring, the aqueous solution of HAuCl(4)(.)4H(2)O and Fe(NO3)(3)(.)9H(2)O was firstly mixed, then the aqueous mixture and the aqueous solution of Na(2)CO(3)(.)10H(2)O were simultaneously added dropwise to deionized water at 60degreesC kept through flowing water and at a constant pH value adjusted by diluted Na2CO3. The brown suspension was kept under stirring for desired time. After cooling to room temperature, the resulting precipitate was alternatively centrifuged and washed until no AgCl precipitate was noted on dropping AgNO3 solution into the filtrate. Further, the paste was dried at 120degreesC, then heated to desired temperature at a heating rate of 5 degreesC/min and calcined at the corresponding temperature for desired time. The effect of the preparation parameters was systematcally explored on the WGS reactivity. The results showed that, some preparation parameters, such as gold loading, precipitant, precipitation manner, pH value during precipitation, calcination atmosphere, temperature, etc, can exert much influence on the catalyst activity. The gold introduced by coprecipitation can highly disperse on the surface of Fe2O3 support. Moreover, the nanometer gold particles can depress the crystallization of the support and significantly reduce the reduction temperature of the support toward Fe3O4. The high catalytic activity of Au/Fe2O3 catalyst under low temperature can be attributed to the synergism between nanoscale gold particle and Fe3O4 phase, while the latter still works at high reaction temperature. If the aggregation of the nano-scale gold particles occurs, the catalytic activity decreases.