EFFECTS OF THE HETEROGENEOUS SURFACE GEOMETRY ON THE SELECTIVITY BEHAVIOR OF A MULTISTEP REACTION

Monte-Carlo simulations of a three-step catalytic (TSC) reaction over fractal surfaces were performed to examine the morphological effects on catalyst selectivity. The effects of the varying probability of reaction steps, rate constant, and cluster size on the macroscopic average selectivity and normalized selectivity distribution (NSD) were scrutinized. Because of the screening effects, the macroscopic average selectivity of a fractal catalyst behaves differently from that of a smooth surface. To further investigate the effect of the surface geometry on selectivity, NSD were analyzed with multifractal scaling techniques. The increased cluster size is found to decrease the position sensitivity of NSD. A large ratio of dimerization to isomerization increases the position distinction of NSD among active sites when the adsorption probability equals one. At small p(1), i.e., an adsorption probability much less than 1, the ratio of dimerization to isomerization caused no effect on the NSD.