Chemoselective hydrogenation of halonitroaromatics over γ-Fe2O3-supported platinum nanoparticles: The role of the support on their catalytic activity and selectivity

Abstract

Solvated platinum atoms, obtained by metal vapour synthesis (MVS), were conveniently used to prepare γ-iron oxide and γ-alumina supported Pt catalysts containing small metal nanoparticles of controlled size, ranging 0.5–3.0nm in diameter (HR-TEM). The γ-Fe2O3-supported Pt system showed higher catalytic activity and selectivity than those of a similarly prepared γ-Al2O3-supported system in the selective hydrogenation reactions of p- and o-chloronitrobenzene to the corresponding haloanilines, in mild reaction conditions (25°C, 0.1MPa hydrogen pressure) (p-chloronitrobenzene: specific activity (SA)=59.5min−1, Selectivity (Sel.)=99.9%; o-chloronitrobenzene: SA=42.8min−1, Sel.=99.2%). The Pt/γ-Fe2O3 system also showed high catalytic efficiency (Sel.>98%, at 100% of conversion) in the selective hydrogenations of m-chloro-, p- and o-bromo- and p- and o-iodonitrobenzenes. XPS structural studies performed on a pristine Pt/γ-Fe2O3 sample as well as on a sample recovered after the reaction, indicate that the catalytic process did not induce permanent modification in the chemical and/or electronic structure of the catalyst according with the high reusability of the system.