Momento (Jul 2007)
Simulación numérica de reacciones químicas catalizadas.
Abstract
The kinetics of the 2CO + O2 -> 2CO2 reaction on Pt(100) nanoparticles was studied using the Monte Carlo simulation method. These particles present surfaces with (1×2) and (1×1) structures, which correspond to α and β phases, respectively. The reaction is considered as following a Langmuir-Hinshelwood type mechanism. The CO2 production rate depends on the CO partial pressure and shows two critical points ξ1 and ξ2 in which first and second order kinetic transitions occur. These points define a reactive zone. Outside this interval the CO2 production is zero because the catalyser’s surface is saturated by the adsorption of O (PCO ξ2). In steady state and on any point in the (ξ1,ξ2) interval the surface of the catalyser is partially covered with CO and O particles. In this case, the adsorbates organize themselves in a natural way on the surface without following an evident regularity criterion, and obeying a self-similarity principle, responsible for the fractal structures formation. In this work the fractal dimension D of adsorbate distributions in the reactive zone was determined as a function of the CO partial pressure. The fractal dimension was calculed using the box counting method. It is also shown the effect of both, CO diffusion and desorption on the fractal dimension.
