Induced heterogeneity model

Induced heterogeneity model, 30 241, 251 Industrial catalytic cracking, 6 271 Industrial reactions see also specific reactions... 

In the induced-heterogeneity model the chemisorption process is assumed to be an activated process and the clean surface is considered as homogeneous and characterized by chemisorption kinetics with activation energy Eq. 

It is, therefore, possible, by partial desorption followed by readsorption and comparing the values of a, b (and to) with those obtained in the original adsorption, to obtain some information on the correlation of the variation with coverage of — and E should site heterogeneity dominate the kinetics, assuming the simple model (SM) to be applicable. For hydrogen on zinc oxide (89), none of these equations (60), (62), (63) reproduces even the main features of the experimental results, but Eq. (66) derived later from the combined site and induced heterogeneity model (CM) does. First, however, we discuss the effect of variation of —AH with q for the CM model. 

Energy models in these models a constant number of reactive sites is supposed, while the activation energy of adsorption changes with the amount adsorbed. Two models, mathematically equivalent, have been used site heterogeneity and induced heterogeneity. 

Though both chemisorption and desorption kinetics can be explained by a model in which the surface is characterized by a fixed heterogeneity with a uniform energy distribution function, in chemisorption other explanations are possible, like induced heterogeneity or surface reconstruction. 

It is therefore not unreasonable to ascribe the wide observation of the Elovich behaviour in chemisorption to the occurrence of one or the other of the considered models (surface heterogeneity, induced heterogeneity, or surfaee reconstruction), and to ascribe the smaller set of systems following the Elovich behaviour in desorption to a unique model — fixed surface heterogeneity. 

V. Bolis, C. Morterra, B. Fubini, R UgUengo, E. Garrone, Temkin-type model for the description of induced heterogeneity—CO adsorption on group-4 transition-metal dioxides. Langmuir 9(6), 1521-1528 (1993). doi 10.1021/la00030a017... 

E. V. Albano. On the influence of reactant s induced surface transformations in the behavior of a heterogeneously catalyzed dimer-monomer reaction model. J Chem Phys 709 7498-7505, 1998. 

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