Nitrobenzene hydrogenation on Pt-Sn catalysts

Hydrogenation of nitrobenzene has been carried out over Pt and Pt-Sn catalysts at 273 K using ethanol as solvent. In the first stage of the reaction the intermediate phenylhydroxylamine is formed, together with aniline. After almost all nitrobenzene is converted, phenylhydroxylamine is hydrogenated further to aniline. Selectivity to phenylhydroxylamine is scarcely influenced by the level of conversion and by the Pt/Sn ratio. Upon addition of tin, catalytic activity increases at low tin content, and then decreases at higher Sn/Pt ratios. It is suggested that at low concentration tin ions act as promoters by activating the oxygen-containing group. At higher tin content, platinum is poisoned and availability of activated hydrogen becomes rate-determining. © 1987.