Oxygen-enhanced water gas shift over cena-supported Au-Cu bimetallic catalysts prepared by wet impregnation and deposition—precipitation

摘要

Au-Cu/ceria bimetallic catalysts were prepared incorporating Au by incipient wetness impregnation (IWI) and deposition-precipitation (DP) methods (with loadings of 1 wt.% and 7 wt.% of Au and Cu, respectively). The as-prepared catalysts were characterized by techniques such as BET, XRD, Raman, XPS, H_2-TPR, CO-TPD and Oxygen Storage Capacity (OSC) measurements. The results indicated a good dispersion of gold and copper for copper ceria catalyst and Au—Cu bimetallic catalysts. Addition of Au to CuO/CeO_2 increases highly the capacity to release lattice oxygen to oxidized CO at low temperatures compared to pure CuO/CeO_2. Au/CeO_2 and Au-CuO/CeO_2 catalyst prepared by DP show higher OSC value than counterparts prepared by IWI, either at 120 and 250 ℃. Also, gold-containing catalysts prepared by DP show lower temperature of reduction that the samples prepared by IWI as a consequence of the higher dispersion of gold in the former samples. The presence of gold at different oxidation states was observed by XPS analysis. Preparation method strongly affects to the atom ratio of Au and Au + Cu with respect to surface ceria. The gold incorporation method was a key factor that enhances the redox properties and activity in both WGS and OWGS reactions. The present study shows the gas phase oxygen enhanced the activity of monometallic CuO/ceria and bimetallic Au-Cu/ceria prepared by IWI and DP methods in both WGS and OWGS reactions. AuCC catalyst prepared by DP shows higher hydrogen yield and also higher CO conversion than other prepared by IWI during OWGS reaction.