Paradox of heterogeneous kinetics

The rate constants of the individual steps are strong functions of temperature. With changing temperatures, the rate constants change and the same mechanism step can be rate determining at one tanperature, while it can approach equilibrium at a different tanperature. 

The difficulty of combining molecular rigor with macroscopic accuracy makes it rather difficult to combine a design protocol with microkinetic analysis. However, with better understanding of the surface phenomena, better catalyst formulations and better choices of operational parameters will be possible. As the methodology is already clearly laid out by an 

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An interesting feature of LHHW kinetics is worth noting. Many reactions on surfaces known to be nonideal surprisingly follow the ideal LHHW models, a situation that can only be described as the placebo effect or the paradox of heterogeneous kinetics (Boudart et al., 1967 Boudart, 1986). In the same vein but with less justification, it has also been argued for more than four decades—... 

Another explanation of the paradox of heterogeneous kinetics may be the possibility that the more active sites on a distributed site activity surface (i.e., a nonideal surface) tend to compensate for the less active sites, thus creating the placebo effect. 

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