Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-I-25equation [2] to nitrogen isotherm adsorption. Experimental study of kinetic carbon monooxideoxidation and acetone hydrogenation were carried out in a fixed-bed reactor at atmospherepressure.Fig.1 shows experimental and theoretical dependencies between pre-exponential factorand average size of particles. There is a good correspondence between experimental data(solid squares) and theoretical results (solid lines). Fig. 2 represents a plot of ln(E-E 0 ) againstthe D f , E 0 =33±1 kJ/mol. Since this experimental data give rise to a good fit to the linepredicted by the eq.2. Dependence between rate constant and fractal dimension is alsodiscussed.151050-5Ir/Al 2O 3Cu/Al 2O 3Cu/Cr 2O 3Co/Al 2O 3Ni/Al 2O 3Ru/Al 2O 3Pt/Al 2O 3Rh/Al 2O 3Coln(E-E 0 )11,511,010,510,09,59,0NaYSGKSKAl 2O 3KSS4KSS3lnk 0 2,0 2,2 2,4 2,6 2,8 3,0-100 5 10 15 20 25 30d,nm8,5D FFigure 1. Dependence of pre-exponentialfactor on average size of particlesFigure 2. Dependence of activationenergy on fractal dimensionThus, in frame on fractal geometry of active component of catalyst we derive a relation(3) between rate constant and geometrical characteristics of catalyst. Theoretical results are ina good agreement with experiments. Our approach allows to determine activation energy ofactivated complex and disturbance energy of catalyst surface and radius such disturbance. Itprovides getting additional information about heterogeneous catalytic reaction mechanismand allows separating the chemical and structural contribution of catalyst to activation energyof heterogeneous catalytic process. Our approach opens new avenues for understandingstructure sensitivity in heterogeneous catalysis.References1. D. Avnir, The Fractal Approach to Heterogeneous Chemistry,Wiley, New York, 19892. Chung-Kung Lee, Cherng-Shyan Tsay J. Phys. Chem. B 1998, 102, 4123-413074