Catalytic Hydrogenation of p-Chloronitrobenzeneto p-Chloroaniline Mediated by γ-Mo2N

摘要

Promoting the production of industrially important aromatic chloroamines over transition-metal nitrides catalysts has emerged as a prominent theme in catalysis. This contribution provides an insight into the reduction mechanism of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN) over the γ-Mo2N(111) surface by means of density functional theory calculations. The adsorption energies of various molecularly adsorbed modes of p-CNB were computed. Our findings display that, p-CNB prefers to be adsorbed over two distinct adsorption sites, namely, Mo-hollow face-centered cubic (fcc) and N-hollow hexagonal close-packed (hcp) sites with adsorption energies of −32.1 and −38.5 kcal/mol, respectively. We establish that the activation of nitro group proceeds through direct pathway along with formation of several reaction intermediates. Most of these intermediaries reside in a significant well-depth in reference to the entrance channel. Central to the constructed mechanism is H-transfer steps from fcc and hcp hollow sites to the NO/–NH groups through modest reaction barriers. Our computed rate constant for the conversionof p-CNB correlates very well with the experimentalfinding (0.018 versus 0.033 s^–1 at ∼500 K).Plotted species profiles via a simplified kinetics model confirmsthe experimentally reported high selectivity toward the formationof p-CAN at relatively low temperatures. It is hopedthat thermokinetics parameters and mechanistic pathways provided hereinwill afford a molecular level understanding for γ-Mo2N-mediated conversion of halogenated nitrobenzenes into their correspondingnitroanilines; a process that entails significant industrial applications.