Water-gas shift reaction over supported Pt-CeOx catalysts

We conducted a comparative study for the water-gas shift (WGS) reaction over ceria-promoted Pt catalysts supported on various supports such as gamma-Al2O3, SiO2, TiO2 (P-25), CeO2, SiO2-Al2O3, yttria-stabilized zirconia (YSZ) and ZrO2 in a rather severe reaction condition such as 6.7 vol.% CO, 6.7 VOL% CO2, and 33.2 vol.% H2O in H-2. Among them, Pt-Ce/TiO2 showed the highest WGS activity especially at low temperatures. The effect of preparation sequences on the catalytic activity was also examined for ceria-promoted Pt supported on TiO2 and Pt-Ce/TiO2 prepared with a single-step co-impregnation method showed the highest water-gas shift activity. The CO chemisorptions, the temperature-programmed reduction (TPR), an inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and a transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX) were conducted to characterize catalysts. The close correlation between the low-temperature water-gas shift activity and the amounts of chemisorbed CO as well as the degree of interaction between Pt and ceria has been observed. This Pt-Ce/TiO2 showed the more stable catalytic activity in the cyclic operation and the start-up/shut-down operation compared with the conventional Pt-Ce/CeO2. (C) 2009 Elsevier B.V. All rights reserved.