Supported foam–copper catalysts for methanol selective oxidation A.N. Pestryakov a, * , V.P. Petranovskii b , N. Pfa ¨nder a , A. Knop-Gericke a a Department of Inorganic Chemistry, Fritz Haber Institute, Faradayweg 4-6, Berlin D-14195, Germany b Centro de Ciencias de la Materia Condensada, UNAM, Ensenada 22800, Mexico Received 23 March 2004; accepted 30 September 2004 Abstract Structural, mechanical, gas-dynamic and catalytic properties of copper catalysts supported on foam ceramics have been studied. Due to the three-dimensional open-porous cellular structure the foam catalysts have high gas permeability, mechanical strength, and low density. Catalytic activity and selectivity of the foam catalysts in the process of oxidation of methanol to formaldehyde exceed the characteristics of the conventional crystalline and granulated catalysts of the same composition. Different electronic states (ions, charged clusters, nanoparticles and microcrystals) of copper on the catalyst surface have been studied by the method of UV–Vis spectroscopy. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Copper; Foam catalysts; Methanol oxidation; UV–Vis spectroscopy 1. Introduction Silver and copper catalysts are widely used in the processes of selective oxidation of alcohols to aldehydes and ketones [1–7]. Our previous studies revealed that catalysts based on the foam materials are very promising for usage in the processes of partial oxidation of alcoh- ols to aldehydes [8–14]. Thus, bulk foam silver and foam copper catalysts have physicochemical and catalytic properties exceeding the characteristics of the traditional crystalline and granulated catalysts in alcohol partial oxidation. Foam materials have uniform cellular structure with isotropy of mechanical and gas-dynamic properties. Geometric parameters of the ‘‘elementary cell’’ are pre- selected by the preparation conditions; diameters of voids can be varied within the range of 0.5–5.0 mm. Physical properties of the whole foam block depends on the cell average diameter; porosity and volume den- sity can be altered in the ranges of 80–98% and 0.1– 0.5 g/cm 3 , respectively. However, using the bulk metal catalysts leads to high consumption of the metals. This one can be reduced by applying the supported catalysts based on foam ceram- ics. The aim of the present study is investigation of the mechanical, gas-dynamic and catalytic properties of copper catalysts supported on foam ceramics in the methanol partial oxidation. 2. Experimental The catalyst samples were prepared by supporting copper (10–20 wt%) on the modified foam ceramics from aqueous solution of the copper nitrate (C = 20%) followed by chemical reduction with hydrazine sulfate. For better Cu 2+ adsorption on the support surface the samples were kept in the impregnation solution for 1566-7367/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2004.09.015 * Corresponding author. Present address: Department of Organic Chemistry, Tomsk Technical University, Lenin ave 30, Tomsk 634034, Russian Federation. Fax: +7 3822 520808; +30 8413 4401. E-mail addresses: alex@fhi-berlin.mpg.de, anp@tspace.ru (A.N. Pestryakov). www.elsevier.com/locate/catcom Catalysis Communications 5 (2004) 777–781