Preferential oxidation of CO in presence of H2. Behavior of PtSn/g-Al2O3 catalysts modified by K or Ba

Abstract

The behavior of catalysts based on Pt/ -Al2O3 is analyzed in the CO oxidation reaction. Experiments were performed in the temperature range between 50°C and 250°C with a feed H2 rich, and a concentration of 1% CO and 0.6% O2 Catalysts studied were: monometallic Pt/ -Al2O3, bimetallic PtSn/ -Al2O3 with a ratio Sn/Pt=1.6 at/at and two catalysts prepared by modification of the last one with K or Ba. The catalyst that showed maximum activity and selectivity levels is the PtSnK/ -Al2O3. The tin addition increases the activity which allows the reaction to occur at lower temperatures due to the decrease in the CO-Pt interaction. The addition of K or Ba produces a subsequent improvement with respect to the CO oxidation temperature, which leads to a selectivity increase. The selectivity of the CO oxidation passes through a maximum value as a function of the temperature. This maximum is explained by the importance acquired by the reverse of water gas shift reaction at temperatures near 200ºC