Data Analysis with an Integral Reactor

This rate is clearly incorrect for any value of n other than unity (see Chapter 5.1), and it is also inappropriate for any type of oxygen adsorption other than molecular adsorption on a single site (or perhaps a vacancy pair defined as an active site). Utilization of the SSA requires that t = T2, and the use of these two incorrect equations (7.31 and 7.32) gives 

It is worth noting at this point that a H-W model invoking product desorption as the RDS could also give equation 7.30 for values of n = 1 or 2, provided the fraction of vacant sites is very low and the fraction of sites covered by the two reactants is very high. It may also be possible to propose a more realistic sequence of steps comprised of reversible and irreversible elementary steps (perhaps even including some quasi-equilibrated steps) that could result in a rate expression of the Mars-van Krevelen form. Consequently, the Mars-van Krevelen rate expression should be considered to be only a mathematical fitting equation with no theoretical basis. 

The use of differential reactors to simplify the acquisition of accurate rate data has been mentioned previously. Under integral reactor conditions, analysis of the rate data can be much more complicated, even if a RDS is incorporated into the model, as demonstrated in Illustration 7.7. 

Illustration 7.7 The Reduction of NO by CH4 on IM2O3 - Integral Reactor Operation and Incorporation of Competitive Product Adsorption into a L-H-type Bimolecular Reaction 

The kineties of this reaction over La203 and Sr-promoted La203 have been studied in detail in recent years by Vannice and coworkers [4,44-47]. Most studies were conducted at low conversions under differential reactor conditions however, with O2 in the feed, a simultaneous CH4 combustion reac- 

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