Research On Au/α-Fe₂O₃ Catalyst Promoted By ZrO₂ And Nb₂O₅ For Low Temperature Water Gas Shift Reaction

The water gas shift (WGS) reaction, CO + H₂O←→CO₂ + H₂ is often used in the low working temperature fuel cells to clear out CO from raw gas and produce hydrogen. Au/α-Fe₂O₃ catalyst is very active in the WGS reaction at low temperatures. However, the fast deactivation of gold catalysts under the hydrogen-rich conditions, which often occurs in synthetic and real reformate tests, has prevent them from extensive applications in the fuel cell systems. In this dissertation, the assembly of the acid oxides Nb₂O₅ and ZrO₂ were firstly prepared and used to modify the catalyst of Au/α-Fe₂O₃. Remarkable progresses have been achieved and are summarized as follows:1. Parallel co-precipitation method and ultrasonic technique were firstly used to prepare the novel Au/α-Fe₂O₃-ZrO₂-Nb₂O₅ catalyst. The preparation method improves the dispersion of Nb₂O₅ in Au/α-Fe₂O₃ catalyst and gives insight into the application of unsolvable solid powder catalytic materials.2. The effect of the preparation parameters is systemically investigated on the Au/α-Fe₂O₃-ZrO₂-Nb₂O₅ WGS reaction activities under various conditions such as precipitation manner, pH value, ultrasonic time, promoter content, gold loading, calcination temperature and so on. The best preparation parameters were determined as follows: parallel co-precipitation method, pH=8.0, ultrasonic time 20min, ZrO₂ and Nb₂O₅ content 10%, gold loading 8% and calcination temperature 300℃.3. Catalysts are characterized by means of BET, XRD, HRTEM, H₂-TPR, CO₂-TPD, UV-Vis DRS, XPS and Raman technique. The investigated results show that: (1) ZrO₂ and Nb₂O₅ enriched on the surface of Au/α-Fe₂O₃-ZrO₂-Nb₂O₅ catalyst because of their strong interaction; (2) The enrichment of ZrO₂ and Nb₂O₅ on the surface effectively prevented the gold particles from sintering, thus improving gold dispersion; (3) The incorporation of ZrO₂ and Nb₂O₅ during co-precipitation led to a progressive improvement of the specific surface area and decreased magnetite and gold crystallite sizes. The enhanced activity and stability of Au/α-Fe₂O₃-ZrO₂-Nb₂O₅ catalyst have been shown to be strongly dependent on the...