REACTION-RATES IN FRACTAL VS UNIFORM CATALYSTS WITH LINEAR AND NONLINEAR KINETICS

Pore fractal objects are expected to be optimal catalysts, since mater ial is supplied to the narrower pores, which are also shorter through the larger pores where diffusion resistance is smaller. To demonstrate this, diffusion and reaction were simulated on Sierpinski-gasket-type fractal objects and on the corresponding nonfractal uniform-pore stru ctures of the same size, porosity and reactive area. Positive order re actions limited by Knudsen diffusion were shown to exhibit larger rate s in fractal than in uniform-pore objects. Fractal catalysts also exhi bited a new intermediate domain in which the rate depends only weakly on the kinetics parameters. In nonmonotonic kinetics the branching poi nt (bifurcation point) was extremely sensitive to the pore structure.