Characterization and reductive amination of cyclohexanol and cyclohexanone over Cu/ZrO 2 catalysts Komandur V.R. Chary * , Kottapalli Kalyana Seela, Dhachapally Naresh, Pagadala Ramakanth Catalysis Division, Indian Institute of Chemical Technology, Hyderabad 500 007, India Received 6 November 2006; received in revised form 11 March 2007; accepted 8 May 2007 Available online 17 May 2007 Abstract Reductive amination of cyclohexanol/cyclohexanone was studied over copper catalysts supported on zirconia. The effect of copper loading and dispersion was studied on the activity and selectivity of the reaction. A series of zirconia supported copper catalysts with varying copper loadings (1–15 wt%) were prepared by incipient wet impregnation method. The catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). Copper dispersion and metal area were determined by N 2 O decom- position by passivation method. X-ray diffraction patterns indicate the presence of crystalline CuO phase from 4.0 wt% Cu on zirconia. TPR patterns reveal the presence of highly dispersed copper oxide at lower temperatures and bulk CuO at higher temperatures. The acid– base properties of catalysts were investigated by means of a model reaction cyclohexanol dehydrogenation to cyclohexanone and com- pare with the results of TPD of ammonia, which allows to measure the acid–base properties of the support and to investigate the changes in surface acidity or basicity, resulting from the metal impregnation. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Copper catalysts, Zirconia; TPR; Dispersion; Reductive amination 1. Introduction Supported copper catalysts catalyze many industrially important reactions. Copper catalysts are widely employed commercially for the dehydrogenation of higher alcohols–aldehydes and ketones, cyclohexanol–cyclohexa- none [1,2], the synthesis of methanol [3], decomposition of N 2 O–N 2 [4,5], the selective catalytic reduction of nitro- gen oxides by hydrocarbons in an oxygen-rich atmosphere [6], CO oxidation [7], the hydrogenolysis of esters [8] and also for the conversion of CO 2 –CO by catalytic hydroge- nation [9]. The catalytic properties of the active copper phase can be greatly influenced by the nature of the sup- ported oxide and the dispersion of the active component [10]. However, the nature of active species of these cata- lysts is still the subject of extensive investigation by many researchers [10,11]. Zirconium containing materials are very useful as cata- lysts, catalysts supports, or promoters in various reactions of industrial importance [12–15]. Copper supported on zir- conia has in fact been found to be superior to copper sup- ported on other oxides such as ZnO, Al 2 O 3 , SiO 2 and TiO 2 . The advantages of using zirconia as a catalyst support is to be a unique metal oxide which explicitly possesses special chemical properties such as: (i) it interacts strongly with the active phase; (ii) it possesses high thermal stability and is more chemically inert than classical oxides; (iii) it is the only metal oxide which may possess all four chemical properties; namely acidity, basicity, reducing ability and oxidizing ability [16]. The application of zirconia as a cat- alyst support is promising and has been employed in many industrially important reactions such as hydro processing, oxidation of alcohols and synthesis of methanol and higher alcohols [3,17,18]. The extreme hardness and high specific 1566-7367/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2007.05.016 * Corresponding author. Tel.: +91 40 27193162; fax: +91 40 27160921. E-mail address: kvrchary@iict.res.in (K.V.R. Chary). www.elsevier.com/locate/catcom Available online at www.sciencedirect.com Catalysis Communications 9 (2008) 75–81