Journal of Catalysis 236 (2005) 387–391 www.elsevier.com/locate/jcat Manganese oxide octahedral molecular sieve catalysts for synthesis of 2-aminodiphenylamine Ranjit Kumar a , Luis J. Garces b , Young-Chan Son a , Steven L. Suib a,b,c,∗ , Russell E. Malz Jr. d a Department of Chemistry, U-3060, University of Connecticut, Storrs, CT 06269-3060, USA b Institute of Materials Science, U-3060, University of Connecticut, Storrs, CT 06269-3060, USA c Department of Chemical Engineering, U-3060, University of Connecticut, Storrs, CT 06269-3060, USA d Uniroyal Chemical Company, Inc., Elm Street, Naugatuck, CT 06770, USA Received 24 August 2005; revised 13 October 2005; accepted 15 October 2005 Available online 11 November 2005 Abstract Cryptomelane-type manganese oxides octahedral molecular sieve (K-OMS-2) were used for the acid-catalyzed condensation of phenylhydrox- ylamine with aniline to produce 2-aminodiphenylamine. The H + -exchanged K-OMS-2 was found to be an efficient catalyst for this reaction. The reaction showed high selectivity (∼96%) for the ortho isomer of aminodiphenylamine compared with the para product. The effect of the amount of H + exchange and temperature was investigated.  2005 Elsevier Inc. All rights reserved. Keywords: OMS-2; Aminodiphenylamine; Phenylhydroxylamine 1. Introduction 2-Aminodiphenylamine (ADPA) and its derivatives are com- pounds of great interest because of their numerous uses, includ- ing as precursors for the synthesis of biologically active com- pounds, as lubricant antioxidants, as fluorescent material, in dye formulations, and in polymer synthesis [1–4]. 2-ADPA also has great therapeutic importance [5]. In general, 2-ADPA is synthe- sized by reduction of the corresponding nitro compound; it has also been synthesized by the rhodium-catalyzed rearrangement of 1,2-diphenylhydrazine [6]. Synthesis of 2-ADPA (ortho iso- mer) has been reported in the literature mostly as a byproduct, with 4-ADPA (para isomer) as the major product [7,8]. Earlier researchers have reported that 4-ADPA can be pro- duced by condensation of phenylhydroxylamine (PHA) and aniline in the presence of concentrated HCl or solid acids like H-ZSM-5, H-Y Zeolite, Nafion, Filtrol (acid clay), Dowex resin, and others [7,8]. This reaction yields predominantly the para isomer of aminodiphenylamine. * Corresponding author. E-mail address: suib@uconnvm.uconn.edu (S.L. Suib). Octahedral molecular sieve (OMS) of manganese oxides have been typically used as oxidation catalysts [9–11]. In the present study, OMS was used as a catalyst for an acid-catalyzed condensation reaction of aniline with phenylhydroxylamine (PHA) to produce 2-ADPA. The catalyst used in the reaction is a cryptomelane-type manganese oxide OMS (K-OMS-2), with the composition KMn 8 O 16 ·nH 2 O. K-OMS-2 is a mixed valent manganese oxide with Mn 4+ , Mn 3+ , and some Mn 2+ sites. K-OMS-2 consists of MnO 6 octahedral units, which are edge- and corner-shared to form 4.6 × 4.6 Å tunnels as a re- sult of 2 × 2 arrangements of octahedra. K + ions are present in the tunnels with small amounts of water (Fig. 1). The K + ions in the tunnel can be exchanged with H + through ion-exchange methods. Fig. 1. Structure of OMS-2 catalysts. 0021-9517/$ – see front matter  2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jcat.2005.10.024