Abstract

Catalysts for the selective reduction of nitrobenzene to aniline prepared from poly(4-vinylpyridine) (P(4-VP))-immobilized [Rh(COD)(amine) 2](PF 6) (COD=1,5-cyclooctadiene, amine=4-picoline, 3-picoline, 2-picoline, pyridine, 3,5-lutidine or 2,6-lutidine) complexes in contact with 80% aqueous 2-ethoxyethanol, 1 x 10 -4 mol Rh/0.5 g of polymer, 0.9 atm of CO pressure at 100°C under water-gas shift reaction conditions (WGSR, CO+H 2O CO 2+H 2) are described. Aniline production (milimole/3 h) depends on the nature of the amine and decreases in the following order: 2-picoline (0.65)>4-picoline (0.59)>3-picoline (0.56)>pyridine (0.49)>3,5-lutidine (0.38)>2,6-lutidine (0.34). The immobilized [Rh(COD)(2-picoline) 2] (PF 6) complex was found to be reusable as a catalyst for the title reaction. The Rh/2-picoline complex was immobilized to the pyridine groups of the organic polymer as supported by Fourier transform infrared (FT-IR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), UV/Vis/diffuse reflectance (DR) spectroscopies, and scanning electron microscopy (SEM) studies. (C) 2000 Elsevier Science B.V.