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Essentials of Chemical Reaction Engineering, 2nd Edition by H. Scott Fogler

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10.3.7 Temperature Dependence of the Rate Law

Consider a surface-reaction-limited irreversible isomerization

 B

in which both A and B are adsorbed on the surface, and the rate law is

rA=kPA1+KAPA+KBPB(10-64)

The specific reaction rate, k, will usually follow an Arrhenius temperature dependence and increase exponentially with temperature. However, the adsorption of all species on the surface is exothermic. Consequently, the higher the temperature, the smaller the adsorption equilibrium constant. That is, as the temperature increases, KA and KB decrease resulting in less coverage of the surface by A and B. Therefore, at high temperatures, the denominator of catalytic rate laws approaches 1. That is, at high temperatures (low coverage)

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