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OP-I-2RELATION BETWEEN THE ACTIVATION ENERGY OFHETEROGENEOUS CATALYTIC REACTIONS AND THE FRACTALDIMENSION OF CATALYSTStrizhak P.E., Gurnyk T.M., Tripolskyi A.I.L.V. Pysarzhevsky Institute of Phisical Chemistry, Ukrainian National Academy ofSciences, Ukraine, E-mail: pstrizhak@hotmail.comIntroductionCharacterization of catalysts in terms of fractal geometry has been found to beuseful in catalytic studies [1]. Particularly, many experiments show an effect of fractalstructure of a catalyst on catalytic reactions. In present study we develop atheoretical approach, which reveals a relation between the fractal dimension ofcatalyst and the activation energy of heterogeneous catalytic processes. The validityof the approach is confirmed by experimental results.TheoryCatalysis at solid surface is associated with active sites. Reactants are adsorbedon the active sites forming activated complex. Formation of activated complexdisturbs surface atoms reorganizing them. As a result, the reorganization of asurface, where active sites are located, may affect chemical reaction rate, namely,the activation energy. In the frame of the fractal approach introducing scalingbetween activation energy and fractal dimension, we derive the following relation:ln( E − E0 ) = ln( πε ) + ln( R / r)(1)aD Fwhere E a is the activation energy of the process on the catalytic surface with fractaldimension D F , E 0 is the activation energy for activated complex on isolated active site,ε is the reorganization energy of the surface per one atom, R is the radius ofdisturbed area of the surface and r is the radius of adsorbed molecule (e.g. N 2 ) usedfor the surface measurement.Results and discussionWe performed an experimental study to verify Eq.1 studying the CO oxidationover various solids with different fractal dimensions [2,3]. According to the theoreticalconsideration, a plot of ln(E-E 0 ) against D F for silica porous materials, whichcharacterized by different surface fractal dimension, is presented in Fig. 1. Thisdependence is linear showing a good agreement between theory and experimental39