Ru-catalyzed hydrogenation of aromatic diamines: The effect of alkali metal salts

Abstract

The influences of added alkali metal nitrates and nitrites on the performances of ruthenium catalysts in the liquid phase ring hydrogenation of 4,4'-methylenedianiline (MDA) and 1,4-phenylenediamine (PDA) have been examined. Sodium nitrate and sodium nitrile were shown to be the most effective promoters in enhancing the catalytic activity and in suppressing the formation of by-products. The effects of various solvents and the added water on the hydrogenation activity have also been investigated. The promoting effects of sodium nitrate and sodium nitrite were considerably enhanced in the presence of small amounts of water. XRD patterns of the Ru/Al2O3 catalyst sample obtained from the reaction performed in the presence of NaNO3 or NaNO2 revealed that the sodium aluminate (NaAlO2) phase appears indicating that the cations of metal salts are interacting with the supporting material. An active species, NaOCH(CH3)(2), was isolated and identified by spectroscopic and elemental analyses. (C) 1998 Elsevier Science B.V. All rights reserved.