Turnover rate constant, adsorption

As the adsorption reactions (14,16,...) are fast, the turnover rate constant, fct, of the overall process is almost the same as the rate constant of electron transfer reactions (15,17,...). Again, the concentration increases during the reduction (reaction 12), with the consequence of a positive shift for °(q --QH2). However, °(Ag + i-Agn +i) also increases with n, and the autocalytic transfer continues up to the Ag" exhaustion. 

Table V collects values for the activation energies of isomerization and protonation as deduced by De Gauw and van Santen [138] from kinetic measurements. A comparison of the turnover frequency per proton (TOF) and / iso is made in Table V. One notes that the large differences in measured overall TOFs of different zeolites disappear for the elementary rate constant fciso. This implies that the difference in apparent acidity of the zeolite is due mainly to the difference in adsorption isotherms of the different zeolites. One notes the small variation in activation and protonation energy values, which implies a slight dependence of protonation on the micropore channel size and dimension.

The kinetics of the CO oxidation reaction over all three noble metals exhibit a Langmuir-Hinshelwood type behavior, due to competitive adsorption of CO and oxygen, characterized by the appearance of rate maximum with increasing CO partial pressure. This is a typical behavior which has been described by many investigators for this reaction system [19,20], The catalytic activity, presented as turnover number of CO2 production, was measured by varying either the partial pressures of CO or O2, or temperature, keeping the other parameters constant. 

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