An efficient ruthenium-vanadium catalyst for selective hydrogenation of ortho-chloronitrobenzene Mariusz Pietrowski *, Maria Wojciechowska Adam Mickiewicz University, Faculty of Chemistry, 60-780 Poznan ´, Grunwaldzka 6, Poland 1. Introduction Halogenated anilines are important intermediates in the manufacturing of a large variety of fine and specialty chemicals. The production of herbicides, fungicides, insecticides and animal repellents, pharmaceuticals, dyes and pigments strongly depends on their supply [1]. Platinum and nickel are the metals most widely used for the hydrogenation of halonitroaromatics. Metals with favourable selectivity patterns are ruthenium [2,3] rhodium [4], and iridium [5], but for economic reasons, their use is limited to special applications. Ruthenium was found to be the most selective catalyst [2], however, its activity for haloaromatic amine formation is low [6]. Therefore, attempts have been made at increasing the activity of ruthenium catalysts, while preserving their high selectivity. For a given hydrogenation reaction, the most important to catalyst activity are intrinsic activities of the metals. These activities, however, can be changed significantly by the use of modifiers (inhibitors, mediators, promoters) which control metal dispersion and metal–support interactions. Taking into consideration the great effect of metal–support interactions on the activity and selectivity of supported metal catalysts, we have chosen magnesium fluoride as a support [7,8]. Thanks to high chemical resistance and almost neutral character of the surface, this support has proved to be excellent for ruthenium catalysts [9–12]. The activity of Ru/MgF 2 was several times higher than that of Ru/Al 2 O 3 at the same almost 100% selectivity of ortho-chloronitrobenzene (o-CNB) reduction to ortho- chloroaniline (o-CAN). In order to improve catalytic activity, a solution of ammonium vanadate and ruthenium(III) chloride was used for co-impregna- tion of the support to get ruthenium crystallites separated by vanadium atoms on the support surface. This procedure was expected to increase dispersion of Ru and to facilitate formation of new Ru n+ centres that could be engaged in the reduction of –NO 2 group. The ruthenium catalysts doped with vanadium showed over twice as high activity as that of monometallic ruthenium catalysts, while maintaining the same high selectivity. 2. Experimental 2.1. Preparation of support and catalysts Magnesium fluoride was obtained by adding small portions of MgCO 3 2H 2 O to an aqueous solution of hydrofluoric acid until neutralisation, and acidifying it by introducing a few additional drops of the acid. The precipitate was then aged at room temperature for a few days under stirring, dried at 353 K and calcined at 673 K for 4 h. After the calcination, MgF 2 was ground to Catalysis Today 142 (2009) 211–214 ARTICLE INFO Article history: Available online 26 November 2008 Keywords: Chloronitrobenzene hydrogenation Ruthenium catalyst Magnesium fluoride Chloroaniline Selective hydrogenation MgF 2 ABSTRACT An attempt has been made at obtaining a catalyst for hydrogenation of ortho-chloronitrobenzene (o-CNB) to ortho-chloroaniline (o-CAN) which would be both selective and active. Ruthenium has been used as the active phase since it is the most selective of all metals investigated in the above reaction. Catalyst precursors, RuCl 3 3H 2 O and NH 4 VO 3 , were introduced onto an unconventional support – MgF 2 and reduced in hydrogen flow at 673 K. The catalysts obtained revealed unusually high activity and selectivity in the reaction of hydrogenation of o-CNB to o-CAN, both in the gas- and liquid phase. The structural study of the Ru-V/MgF 2 catalyst has shown that its high activity and selectivity were determined by the strong metal–support interactions and ruthenium–VO x species electron interactions. ß 2008 Elsevier B.V. All rights reserved. * Corresponding author. Fax: +48 61 8658008. E-mail address: mariop@amu.edu.pl (M. Pietrowski). Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod 0920-5861/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2008.09.040