Restructuring diffusion controlled

Some consequences which result from the proposed models of equilibrium surface layers are of special practical importance for rheological and dynamic surface phenomena. For example, the rate of surface tension decrease for the diffusion-controlled adsorption mechanism depends on whether the molecules imdergo reorientation or aggregation processes in the surface layer. This will be explained in detail in Chapter 4. It is shown that the elasticity modulus of surfactant layers is very sensitive to the reorientation of adsorbed molecules. For protein surface layers there are restructuring processes at the surface that determine adsorption/desorption rates and a number of other dynamic and mechanical properties of interfacial layers. 

It seems reasonable to assume that an oxidation-reduction dynamic equilibrium is established on the catalyst surface during the reduction step and that appreciable restructuring of the catalyst surface can take place. Since the kinetics of the process are controlled by pore diffusion, particle size and shape once again play an important role in determining the initial activity of the catalyst. In fact, rate measurements conducted by the authors in the laboratory with prereduced catalysts of various particle sizes show that the initial activity of the larger catalyst particles is considerably lower than that of the smaller particles. Consequently, another corrective factor, EFsp, which takes into account the influence of the catalyst particle size on this inherent self-poisoning effect, must be included in the rate equation for use in converter calculations. Values of EFsp for various catalyst size ranges are reported in Table 6.11. 

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