OP-II-3

OP-I-2results. The best fit of the experimental data by Eq.1 gives the valueE 0 = 33 ± 1 kJ/mol. The intercept of the plot gives the value of reorganization energyof the surface per one atom (ε), equal to 8.6 ± 0.5 J/mol. Assuming that activatedcomplex occupies only one atom of the catalyst surface, it may be estimated that200 – 400 surface atoms are disturbed. The value ε = 8.6 J/mol is the averageenergy for all disturbed atoms of surface which participate in the active complexformation. The ratio of R/r, obtained from the slope of the plot, is equal to 15.5 ± 0.5.This value indicates that the radius of surface reorganization is almost 16 timeshigher than the radius of activated complex. The same correlations were found forother catalytic systems.Fig. 1. The dependence of the activationenergy on the fractal dimension of silicaIn contrast to silica, the samples ofzirconia are characterized by constantsurface fractal dimension. According toEq.1, the activation energy should beconstant, which is in a good agreementwith experimental results, which showE a =100±5 kJ/mol.ConclusionsBased on fractal geometry we derive a relation (1) between the activationenergy and the surface fractal dimension of a catalyst. We show that theoreticalresults are in a good agreement with experiments. Our approach allows to determineactivation energy of activated complex and disturbance energy of catalyst surfaceand radius such disturbance. It provides getting additional information aboutheterogeneous catalytic reaction mechanism and allows separating the chemical andstructural contribution of catalyst to activation energy of heterogeneous catalyticprocess. Our approach opens new avenues for understanding structure sensitivity inheterogeneous catalysis.References[1]. Rothschild W.G., Fractals in Chemistry, John Willey & Sons, New York, 1998, p.235[2]. Trypolskyi A.I., Gurnyk T.M., Strizhak P.E. Chem. Phys. Lett. 2008, 460, p.492-494[3]. Strizhak P.E., Gurnyk T.M., Trypolskyi A.I. Trends in Phys. Chem. 2008, 13, p,55-6540