A study on ceria supported platinum catalysts for water gas shift reaction

Abstract

A single stage water gas shift reaction has been carried out at a gas hourly space velocity of 45,515 h−1 over supported Pt catalysts prepared by an incipient wetness impregnation method. CeO2, ZrO2, MgO, MgO−Al2O3 (MgO = 30wt%) and Al2O3 were employed as supports for the target reaction. Pt/CeO2 exhibited the highest CO conversion as well as very high CO2 selectivity due to the easier reducibility of Pt/CeO2 and high oxygen storage capacity of CeO2.To optimize a single stage water gas shift catalyst for compact reformers, Pt/CeO2, Pt/ZrO2, and Pt/Ce(1−x)Zr(x)O2 catalysts have been applied for the target reaction. The CeO2/ZrO2 ratio was systematically varied to optimize Pt/Ce(1−x)Zr(x)O2 catalysts. Pt/CeO2 showed the highest turnover frequency and the lowest activation energy among the catalysts. Pt/CeO2 catalyst also showed stable catalytic performance. Thus, Pt/CeO2 can be a promising catalyst for a single stage water gas shift reaction for compact reformers.In order to enhance low temperature activity of Pt/CeO2, sodium was added on Pt/CeO2 catalyst. Sodium has a beneficial effect on stabilizing only oxidized species of Pt, resulting in the improvement of the activity of Pt/CeO2 catalyst at low temperature. The effect of synthesis method on ceria has also been investigated in water gas shift reaction. A simple simultaneous precipitation/digestion method has been developed successfully to obtain the crystalline cerium (III) carbonate by the controlled reaction. Pt/CeO2 catalyst exhibited relatively stable activity even at a very high gas hourly space velocity if an optimized digestion time of 4 h was used for the synthesis of cerium (III) carbonate.