from first principles PP-I-1

PP-I-14Fractal Approach to Acid-Base Heterogeneous CatalysisSrtizhak P.E., Vlasenko N.V., Kochkin Yu.N., Tripolsky A.I., Serebrii T.G., Gurnik T.N.L.V. Pisarzhevsky Institute of Physical Chemistry NAS of Ukraine, Kyiv, Ukrainepstrizhak@hotmail.comThe most important factors determining the catalytic properties of the substances are chemicalnature of active sites and surface morphology. Recently, we have improved the fractalapproach for quantitative description of an effect of the morphology of a catalyst on itscatalytic performance [1]. Previously, the fractal approach has been applied only to thereduction-oxidation reactions, particularly, to catalytic oxidation of various substances [2].However, it is difficult to correspond the obtained correlations to catalytic activity of thesurface active sites. Contrary, for acid-base heterogeneous catalytic reactions activity of solidsis determined by the acidity spectrum that can be determined experimentally [3]. As exampleto apply the fractal approach to acid-base catalysis, we performed a study of the synthesis ofethyl tert-butyl ether from ethanol and isobutene catalyzed by various solid acids:HC 2 H 5 OH + H 2 C=C(CH 3 ) 2 C 2 H 5 -O-C(CH 3 ) 3Our study reveals a relationship between the reaction rate (TOF) and the catalyst fractaldimension for different types of acidic catalysts, e.g. mixed oxides SiO 2 -Al 2 O 3 -ZrO 2 andhydrogen ion-exchange resins [3-4]. Based on thermodynamic analysis of the reaction, kineticstudies, and studies of the mass transfer effects we analyzed the catalytic performance of thesesolids. Our results indicate that catalyst with a more ordered structure, which is characterizedby lower fractal dimension, has the better catalytic performance associated with increasing therate of the adsorption-desorption of reactants and products [4]. The performed analysis alsoallows one to speculate regarding a structure of the surface activated complex.These results show that application of fractal approach to acid-base heterogeneous catalysisopens new avenues for correlations between surface morphology and its catalytic propertiesas well as gives new opportunities for technological design of optimal catalyst for "structuresensitive"reactions.References:[1] A.I.Trypolskyi, T.M.Gurnyk, P.E.Strizhak, Chem. Phys. Lett. 460 (2008) 492.[2] D. Avnir (Ed.) The Fractal Approach to Heterogeneous Chemistry: Surfaces, Colloids, Polymers. -John Wiley & Sons, 1989.[3] N.V.Vlasenko, Yu.N.Kochkin, A.V.Topka, P.E.Strizhak, Appl.Cat. A 362 (2009) 82.[4] N.V.Vlasenko, Yu.N.Kochkin, A.P.Filippov, T.G.Serebriy, P.E. Strizhak, Catal. Commun 12(2011) 1142.130