Catalytic mechanism desorption-controlled reactions

Catalysis is the study of materials that can accelerate reactirms and control reaction mechanisms. After a catalytic cycle, namely adsorption of reactants, reactions and desorption of products, the catalyst is restored to its initial state. An ideal catalyst... 

Reactant equilibrium constants Kp and affect the forward kinetic rate constant, and all Ki s affect die adsorption terms in the denominator of the Hougen-Watson rate law via the 0, parameters defined on page 493. However, the forward kinetic rate constant does not appear explicitly in the dimensionless simulations because it is accounted for in Ihe numerator of the Damkohler number, and is chosen independently to initiate the calculations. Hence, simulations performed at larger adsorption/desorption equilibrium constants and the same intrapellet Damkohler number implicitly require that the forward kinetic rate constant must decrease to offset the increase in reactant equilibrium constants. The vacant-site fraction on the internal catalytic surface decreases when adsorption/desorption equilibrium constants increase. The forward rate of reaction for the triple-site reaction-controlled Langmuir-Hinshelwood mechanism described on page 491 is proportional to the third power of the vacant-site fraction. Consequently, larger T, s at lower temperature decrease the rate of reactant consumption and could produce reaction-controlled conditions. This is evident in Table 19-3, because the... 

The slowest of the following processes at the metal interface controls the hydrogen overvoltage and the reaction mechanism (i) electroactive species transport to the electrode interface (ii) discharge reaction (iii) desorption from the metal surface including catalytic desorption, electrochemical desorption, or emission and (iv) gaseous hydrogen... 

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