Effect of Mo and Re Promoters on the Activity and Stability of a Pt/ZrO2 Water-Gas Shift Catalyst (Part 1)

The activity and stability of Pt catalysts for the water-gas shift (WGS) reaction can be profoundly influenced by the presence of promoters. We present the results on the promotion of a Pt/doped ZrO2 catalyst by Mo and Re. The CO conversion rate of the catalysts is approximately 3-times higher in the presence of the promoters after reduction at temperatures higher than 325 degrees C. The stability of the catalysts against sintering under reaction conditions is significantly enhanced by the promoters as well. The active phase is unstable in the presence of steam, even in presence of hydrogen at temperatures as high as 300 degrees C but is re-formed at higher temperatures in reformate. A detailed FTIR investigation reveals that Pt-Re-Mo alloy is the active phase for the material under investigation. The alloy decomposes reversibly below 300 degrees C, but reforms in reformate above 325 degrees C restoring catalytic activity.