Hydrogenation of o-chloronitrobenzene over polymer-stabilized palladium-platinum bimetallic colloidal clusters

Hydrogenation of o-chloronitrobenzene (o-CNB) has been studied in methanol at 303 K and atmospheric pressure over polyvinylpyrrolidone-stabilized palladium-platinum (PVP-Pd/Pt) bimetallic colloidal clusters. The catalytic properties for the hydrogenation of o-CNB to o-chloroaniline to-CAN) are found to depend on the metal composition of the bimetallic clusters. All the bimetallic clusters are more active than both PVP-Pd and PVP-Pt monometallic clusters. The highest activity (1.81 mol H-2/mol M s) is obtained when PVP-Pd/Pt (1/2) is used as catalyst. The best selectivity to o-CAN (77.5%) is achieved in PVP-Pd/Pt (1/3) catalytic system, which is much higher than those of PVP-Pt and PVP-Pd monometallic colloidal clusters. The addition of the metal cations to the system can considerably affect the catalytic properties of the bimetallic clusters. The modification behavior of metal cations also depends both on the composition of PVP-Pd/Pt bimetallic clusters and the nature of metal cations. For the PVP-Pd/Pt (1/3) bimetallic clusters, when introducing Cr3+ and Co2+, the high activity (0.96 and 1.03 mol H-2/mol M s) and the better selectivity (91.5 and 91.4%) compared with those of the neat PVP-Pd/Pt (1/3) catalysts (1.03 mol H-2/mol M s and 77.5%) are obtained, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.