Journal of Catalysis 226 (2004) 171–182 www.elsevier.com/locate/jcat Modification of acid supports by solid-state redox reaction Part II. Acid and catalytic properties A. Hagen a,b,∗ , E. Schneider c , M. Benter a , A. Krogh a , A. Kleinert c , F. Roessner c a Technical University of Denmark, Department of Chemistry/Interdisciplinary Research Center for Catalysis, Building 312, DK-2800 Kongens Lyngby, Denmark b Risoe National Laboratory, Materials Research Department, Building 228, P.O. Box 49, DK-4000 Roskilde, Denmark c Carl v. Ossietzky University Oldenburg, Institute of Pure and Applied Chemistry/Industrial Chemistry 2, D-26111 Oldenburg, Germany Received 12 February 2004; revised 14 April 2004; accepted 21 May 2004 Abstract ZSM-5 and Y zeolites, γ -alumina, and silica modified by solid-state redox reaction with zinc, gallium, manganese, and iron were studied in the conversion of cyclohexane and the nonoxidative conversion of ethane. The catalytic behavior was related to acid properties characterized by temperature-programmed desorption of ammonia (TPAD).  2004 Elsevier Inc. All rights reserved. Keywords: Solid-state redox reaction; Zeolite; TPAD; Ethane; Cyclohexane 1. Introduction Ion-exchanged zeolites are interesting catalysts in a va- riety of reactions such as nonoxidative conversion of alka- nes [1], selective reduction of NO [2,3], or alkylation reac- tions [4]. In this respect, supported cationic iron, zinc, gal- lium, and manganese species were investigated among other promoters. The conventional method for the preparation of modified zeolites is ion exchange in aqueous solution. However, solid- state reactions have attracted attention because they have a number of advantages over the liquid-phase methods: large amounts of liquids can be avoided because dry powders of the precursors are mixed. The preparation time is consid- erably shortened as the treatment usually comprises heating the mixture only instead of refluxing for hours, filtration, and washing. In addition, a higher or even full exchange degree can be obtained with multivalent cations. In solid-state meth- ods, usually metal salts or oxides are thoroughly mixed with acid supports and react under a thermal treatment [5–8]. Exemplary, looking at zinc-containing ZSM-5 zeolites, the solid-state reactions between ZnO and H-ZSM-5 [9] and * Corresponding author. Fax: +45 4677 5758. E-mail address: anke.hagen@risoe.dk (A. Hagen). between Zn and ZSM-5 zeolite [10] have been studied. In both systems, catalysts with the same catalytic activity in the nonoxidative conversion of ethane were obtained as com- pared with Zn-ZSM-5 zeolites prepared by conventional ion exchange. The underlying solid-state reactions leading to the active catalyst are expressed in Eqs. (1) and (2), respectively, (1) ZnO + 2H-zeolite → Zn (2+) -(zeolite) 2 + H 2 O, (2) Zn (0) + 2H-zeolite → Zn (2+) -(zeolite) 2 + H 2 . In a detailed study comprising a number of metals and sup- ports, the solid-state redox reaction was studied recently [11]. The main results were that zinc metal reacted with pro- tons of a number of supports, namely ZSM-5 and Y zeolites, silica (containing silanol groups), and γ -alumina, yielding zinc ions with similar coordination as in Zn-ZSM-5 pre- pared by liquid ion exchange. In addition to zinc, also gal- lium, manganese, and iron underwent the solid-state redox reaction with the supports listed above. The temperatures at which this process occurred were correlating with the melting points of the metals [11]. The supports used in that study covered a wide variety of acid properties: type, num- ber, strength, and distribution. However, these parameters did not have a decisive effect on the solid-state redox reac- tion. On the other hand, it is well known that acid properties may play important roles in catalytic reactions. There have 0021-9517/$ – see front matter  2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcat.2004.05.027