INVESTIGATION OF THE WATER-GAS SHIFT REACTION USING TEMPERATURE-PROGRAMMED DESORPTION

The water-gas shift reaction has been investigated by the temperature- programmed desorption (TPD) of reaction components over a commercial l ow-temperature catalyst. It has been found that the oxidation state (a nd consequently the activity) of the catalyst is strongly influenced b y the composition of the gaseous mixture. The adsorption capacity of c atalysts decreases in the order: H2O much-greater-than CO2 congruent-t o CO; hydrogen does not adsorb. The existence of two types of sites fo r carbon oxides adsorption has been found experimentally. A further ty pe of storage (inactive) sites for water exists. On the basis of exper imental results, model equations for TPD of H2O, CO2 and CO were deriv ed. Models best fitting the experimental data were based on the assump tion of a non-uniform heterogeneous surface of the catalyst.