Most abundant surface intermediate approximation

The Most Abundant Surface Intermediate (MASI) Approximation Catalytic transformations may include the formation of many intermediates on the catalyst surface, which are difficult to identify. In these cases, it is impossible to formulate a kinetic model based on all elementary steps. Often, one of the intermediates adsorbs much more strongly in comparison to the other surface species, thus occupying nearly all active sites. This intermediate is called the most abundant surface intermediate masi [24]. For a simple monomolecular reaction, Aj A2, the situation can be illustrated with the following scheme ... 

The Most Abundant Reaction Intermediate (MARI) approximation is a further development of the quasi-equilibrium approximation. Often one of the intermediates adsorbs so strongly in comparison to the other participants that it completely dominates the surface. This intermediate is called the MARI. In this case Eq. (156) reduces to... 

In modeling reactions, in general, and catalytic reactions, in particular, the kineticist must draw on as many tools at his disposal as possible. Some of the most important concepts that are routinely used to derive, simplify and evaluate complicated rate expressions are 1) Transition-state theory 2) The steady-state approximation 3) Bond-order conservation calculations for surface species 4) A rate determining step 5) A most abundant reaction intermediate and 6) Criteria to evaluate parameters in derived rate expressions. Let us examine these topics prior to their utilization in deriving and evaluating reaction models and rate equations. 

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