Hydrogenation of 2,4-dinitro-toluene on Pd/C catalysts: Computational study on the influence of the molecular adsorption modes and of steric hindrance and metal dispersion on the reaction mechanism

A new time-dependent Monte Carlo algorithm was developed to simulate isobar and isotherm three-phase batch hydrogenation of 2,4-dinitro-toluene on Pd/C catalysts. A new reaction mechanism was formulated, involving 9 and 27 toluene derivatives, in solution and adsorbed on the surface, respectively. In fact, three different ways of adsorption were considered for all surface derivatives. Microscopic mechanistic hypotheses were formulated analyzing the mimicked surface populations able to reproduce the experimental catalytic activity-selectivity patterns at different times, temperatures, reagent concentrations, and catalyst particle morphologies. The three different adsorption modes, giving rise to surface species having different steric hindrances, together with the morphology of the particle catalysts, were determinants in reproducing experimental findings. (C) 2002 Elsevier Science (USA).