Kinetics Derived from Signal Dispersion

The limitation of such a model to first-order reaction rates is not as restricting as it seems. In fact, many reactions might at least be considered as of pseudo -first order, which means that they behave macroscopically like first-order reactions. This is the case for diluted fluids and for non-catalytic gas/solid reactions such as the so-called shrinking core or shrinking particle model. Other examples are electrochemical reactions [106], 

For the above applied oxidation of methane to carbon dioxide on some metal oxide catalysts, also a first-order reaction was assumed [10, pp. 182 and 193], However, in combinatorial catalysis it may be sufficient to have a first rough idea about the underlying kinetics. Without having prior information about the kinetics, the performance of a reactor is provided with a huge uncertainty. This is obvious if one considers the wide variation of reaction rates. Pre-exponential factors of reaction rate constants derived by the transition-state theory vary widely from approximately 10 to 1016 s-1 [10]. This first information might then be used to develop a pilot plant for the up-scaling and for further detailed kinetic examinations. 

Similar to the sample delivery in a reactor operated in differential mode, the sample is injected into the steady laminar carrier flow in the channel which moves at a mean speed u0/c. 

The concentration of methane at room temperature at any channel position is described by the impulse response without reaction [Eq. (3.4)] [the dispersion coefficient for a rectangular channel with channel depth b and aspect ratio s is given in Eq. (3.3)]  

At the reaction temperature, the concentration of methane obeys the following equation (apparent velocity increase kv given in [38] ss)  

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Kinetics Derived from Tracer Signal Dispersion in a Channel Reactor... 

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