Synthesis of p-aminophenol from p-nitrophenol over nano-sized nickel catalysts

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on nano-sized nickel catalysts prepared by a chemical reduction method from aqueous solutions. The catalysts were characterized by XRD, EDS, SEM, HRTEM and Mastersizer 2000. Analysis results show that as-prepared catalysts are pure f.c.c. nickel and are prone to aggregation; the average particle size of nickel catalysts is 57 nm and there are high-density defects on particle surfaces. In hydrogenation reactions of p-nitrophenol, the hydrogenation rate is zero-order dependent on nitro aromatics and increases with increasing of hydrogen pressure. Compared with commercial Raney Ni, catalytic properties (activity, selectivity, and stability) of the as-prepared nickel are superior. The reason proposed for higher catalytic activity of nano-sized nickel is a combination effect of the small particle size and high-density surface defects. The partial sintering of nano-sized nickel might lead to the deactivation of the catalytic activity of nano-sized nickel. (C) 2004 Elsevier B.V. All rights reserved.