Recommended experimental conditions for TPR

Transport effects should be avoided in qualitative analysis and kinetic studies [7]. This is accomplished by using small particles (100 pm), the ratio of reactor diameter to particle size dt/dp should be larger than 15, and the ratio of catalyst bed-length to the particle diameter should be larger than 20. It is also well known that the amount of sample influences the TPR profile resolution [8], i.e. multiple 

The larger the sample size the higher the temperature. The explanation is that H2O inhibits reduction. Also, a large shift is observed for large samples in Fig. 

hence the assumption that the gas phase term is constant is not correct. 

On the basis of the results given in Figs. 11.10 and 11.11, three Arrhenius plots can be constructed, as given in Fig 11.12. In view of the wide range of experimental conditions it is concluded that Eqn. (11.19) is followed well, and reliable activation energies can be calculated. 

For the wet series, none of the models tried is correct. We attribute this to an inhibition by water at the beginning of the peak (Fig. 11.14b) followed by a reduction process exhibiting a runaway character due to autocatalysis or thermal effect. 

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