Applied Catalysis A: General 249 (2003) 303–311 Microstructural characterization of doped-Pd/C catalysts for the selective hydrogenation of 2,4-dinitrotoluene to arylhydroxylamines G. Neri a , G. Rizzo a , C. Milone a , S. Galvagno a,∗ , M.G. Musolino b , G. Capannelli c a Department of Industrial Chemistry and Materials Engineering, University of Messina, Salita Sperone 31, I-98166 Messina, Italy b Department of Mechanics and Materials, University of Reggio Calabria, Reggio Calabria, Italy c Department of Chemistry and Industrial Chemistry, University of Genova, Genova, Italy Received 17 October 2002; received in revised form 10 March 2003; accepted 11 March 2003 Abstract Pd/C catalysts doped with Fe, Sn and Ca for the selective hydrogenation of 2,4-dinitrotoluene (2,4-DNT) have been characterized by CO chemisorption, X-ray diffraction (XRD) and electron microscopy techniques (TEM-EDX). The promoters modify the microstructural and chemisorption properties of the noble metal particles with respect the undoped-Pd/C catalyst depending on the promoter nature and loading. Particles smaller than those observed on the monometallic catalysts were detected on Fe- and Sn-doped catalysts whereas larger particles were observed on the Ca-promoted samples. The promoters are located on the palladium particles, covering them and/or forming alloys with palladium. The role of the promoters in the selective hydrogenation of 2,4-DNT is discussed on the basis of the characterization results. © 2003 Elsevier Science B.V. All rights reserved. Keywords: 2,4-Dinitrotoluene; Selective hydrogenation; Arylhydroxylamines synthesis; TEM-EDX 1. Introduction The reduction of aromatic nitrocompounds on Pd/C catalysts to the corresponding amines is widely per- formed in both laboratory and industrial scale [1,2]. Very few studies are instead reported concerning the selective hydrogenation of arylnitrocompounds to the corresponding arylhydroxylamines which are key intermediates in the manufacture of a wide va- riety of fine chemicals [2,3]. In previous papers, we have reported results on the selective hydrogenation of 2,4-dinitrotoluene (2,4-DNT) [4–6]. It has been observed that high yields to 2,4-hydroxylaminonitro- ∗ Corresponding author. E-mail address: galvagno@ingegneria.unime.it (S. Galvagno). toluene (2,4-HANT) isomers can be obtained carrying out the reaction over Pd/C catalysts under appropriate conditions. To enhance the performance of the monometallic catalyst in terms of activity, selectivity and/or stability the addition of various promoters has been reported. Strätz has investigated the effect of metallic promoters on the activity of Pd/C catalysts in the hydrogenation of 2,4-dinitrotoluene at 308 K and atmospheric pres- sure [3]. He has found that co-precipitated samples of Pd, Pt and Fe displayed an improved activity, due to a synergic effect. Benedetti and co-workers [7] and Pinna et al. [8] have studied the effect of a sec- ond metal component, like Cu, Sn or Fe, on Pd/SiO 2 catalysts. They have found that only the addition of Fe increases the catalytic activity of palladium. 0926-860X/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0926-860X(03)00230-8