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

Solvated platinum atoms, obtained by metal vapor synthesis (MVS), were conveniently used to prep. ?-iron oxide and ?-alumina supported Pt catalysts contg. small metal nanoparticles of controlled size, ranging 0.5-3.0 nm in diam. (HR-TEM). The ?-Fe2O3-supported Pt system showed higher catalytic activity and selectivity than those of a similarly prepd. ?-Al2O3-supported system in the selective hydrogenation reactions of p- and o-chloronitrobenzene to the corresponding haloanilines, in mild reaction conditions (25 °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/?-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/?-Fe2O3 sample as well as on a sample recovered after the reaction, indicate that the catalytic process did not induce permanent modification in the chem. and/or electronic structure of the catalyst according with the high reusability of the system.