Effect of rare earths on the hydrogenation properties of p-chloronitrobenzene over polymer-anchored platinum catalysts

The effect of rare earths (Sm3+, Pr3+, Ce3+, Nd3+ and La3+), base (inorganic or organic base) and substrate concentration on the hydrogenation properties of p-chloronitrobenzene (p-CNB) over poly-vinylpyrrolidone-anchored platinum (PVP-Pt) has been studied in ethanol at 303 K and normal pressure. The addition of rare earths except Nd3+ and La3+ to catalytic system improves the selectivity of p-chloroaniline (p-CAN) but has lower activity when PVP-Pt alone is used. The hydrogenation rate of p-CNB and selectivity of p-CNB to p-CAN increase significantly for PVP-RE-Pt and PVP-Pt catalysts in the presence of NaOH. PVP-Sm-Pt catalyst exhibits the highest selectivity (95.8%) of p-CAN when the molar ratio of NaOH to substrate is 0.12. In the same reaction condition, PVP-Ce-Pt* catalyst using PVP (90,000) of large molecular weight as support exhibits the highest activity (60.5 mol H-2 mol Pt-1 min(-1)) and selectivity of p-CAN (98.2%). (C) 2002 Elsevier Science B.V. All rights reserved.