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

Solvated platinum atoms, obtained by metal vapour synthesis (MVS), were conveniently used to prepare gamma-iron oxide and gamma-alumina supported Pt catalysts containing small metal nanoparticles of controlled size, ranging 0.5-3.0 nm in diameter (HR-TEM). The gamma-Fe2O3-supported Pt system showed higher catalytic activity and selectivity than those of a similarly prepared gamma-Al2O3-supported system in the selective hydrogenation reactions of p- and o-chloronitrobenzene to the corresponding haloanilines, in mild reaction conditions (25 degrees C, 0.1 MPa hydrogen pressure) (p-chloronitrobenzene: specific activity (SA) = 59.5 min(-1), Selectivity (Sel.) = 99.9%; o-chloronitrobenzene: SA = 42.8 min(-1), Sel. = 99.2%). The Pt/gamma-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/gamma-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.