Turnover Frequency or Specific Activity

When the reaction rate is normalized to the surface area of the active component in the catalyst, such as the metal surface area as just mentioned, it is frequently referred to as the specific activity. If this areal rate is further 

The number of times, n, that the overall reaction takes place through the catalytic cycle represents the number of turnovers, and the rate is then [2] 

The turnover frequency, N, based on this value and expressed as s , is  

The number of turnovers a catalyst can produce is the best way to define the life of a catalyst, and in real systems this number can be very large, frequently exceeding 10 [2]. Because TOFs used in industrial processes are frequently near ls , lifetimes of one month to one year can readily be achieved. 

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