Characterization of Vanadium and Titanium Oxide Supported SBA-15 Y. Segura,* ,† P. Cool, † P. Kustrowski, ‡ L. Chmielarz, ‡ R. Dziembaj, ‡ and E. F. Vansant † Department of Chemistry, Laboratory of Adsorption and Catalysis, UniVersity of Antwerp (UA), UniVersiteitsplein 1, B-2610 Wilrijk, Belgium, and Faculty of Chemistry, Jagiellonian UniVersity, Ingardena 3, 30-060 Krakow, Poland ReceiVed: February 14, 2005; In Final Form: April 13, 2005 Supported vanadium and titanium oxide catalysts were prepared by adsorption and subsequent calcination of the vanadyl and titanyl acetylacetonate complexes, respectively, on mesoporous SBA-15 by the molecular designed dispersion (MDD) method. Liquid and gas phase depositions at different temperatures were carried out with vanadyl acetylacetonate, and the different results together with those of titanyl acetylacetonate in the liquid phase deposition were discussed. The bonding mechanism, the influence of the metal interaction with the support material, and differences due to the way of deposition and the temperature were investigated by TGA, chemical analysis, FTIR, and Raman spectroscopy. Elevated dissolving temperatures in the liquid phase led to higher final loadings on the SBA-15 without the formation of clusters, even at high loadings. The decomposition of the anchored vanadium and titanium complexes, their thermal stability, and the conversion to the covalently bound VO x and TiO x species on SBA-15 were studied and investigated by in situ transmission IR spectroscopy. In general, the titanium complex is more reactive than the vanadium complex toward the surface of SBA-15 and has a higher thermal stability. The MDD method of the VO(acac) 2 and TiO(acac) 2 enables to create a dispersed surface of supported VO x and TiO x , respectively. The structure configurations of VO x and TiO x oxide catalysts obtained at different metal loadings were studied by Raman spectroscopy. Pore size distributions, XRD, and N 2 sorption confirmed the structural stability of these materials after grafting. VO x /SBA-15 and TiO x /SBA-15 samples, with different metal loadings, were also catalytically tested for the selective catalytic reduction (SCR) of NO with ammonia. 1. Introduction Metal oxide dispersions in mesoporous materials have been of great interest by means of the incorporation of transition metals in the framework of the support material. The first publication related to this domain was the incorporation of Fe 2 O 3 particles in MCM-41. 1 Since then, much more work has been done in the field of transition metal oxides supported on different porous materials. One of the most common methods for the preparation of metal oxide dispersions on mesoporous materials is the impregnation with solutions of precursor salts. 2,3 The materials described in this work are no longer prepared by the conventional methods but are the result of a molecular designed dispersion (MDD) 4 method of active elements on carefully prepared micelle templated structures (MTS) 5 using their acetylacetonate complexes. The interest of using these complexes is the requirement of obtaining a high dispersion of catalytic active sites on support materials. Their bulky acetylacetonate ()acac) ligands are able to isolate the central metal ion on the surface, allowing high dispersions. Following the MDD process, metal acac complexes are reacted with the surface hydroxyls of the support material and converted into the metal oxide form after calcination. Both liquid and gas phase depositions have been performed to deposit metal acac complexes on different supports. 6 A great variety of acac complexes on different supports have already been studied and reported in the literature. 7-10 Materials containing vanadium and titanium oxides are known as excellent catalysts in several redox reactions. Vanadium oxide is a powerful redox catalyst in many industrial processes, and it is used in oxidation reactions for the manufacturing of important chemicals. 11 Titanium oxide, when it is on a silica support, is mainly used as a photocatalyst, acid catalyst, and redox catalyst. TiO 2 is widely used as well for many oxidation reactions of organic molecules requiring a high disperse layer on the support. 12 Catalysts based on V 2 O 5 /TiO 2 are mainly used in the reduction of nitrogen oxides. The selective catalytic reduction (SCR) of NO x with ammonia is important to reduce emissions of NO from waste gases of stationary sources. However, the use of a silica support instead of titania offers advantages because of the higher surface area and higher resistance to sintering. The V 2 O 5 /TiO 2 system has already been studied widely well. 13,14 In this paper, the systems VO x / SBA-15 and TiO x /SBA-15 are fully characterized and studied separately for the SCR reaction. For the SCR reaction, the vanadia content in the catalyst is preferably lower than the amount required for a monolayer coverage, 15,16 but for other types of oxidation reactions, a higher loading is required with a high dispersion. 17-19 Therefore, the importance of tuning and controlling the final loading of metals and their dispersion on the support material by different deposition methods and temperatures is obvious. VO(acac) 2 and TiO(acac) 2 have already been deposited on different supports such as silica, 20 alumina, 21 MCM-48, 22 or zirconia. 23 Recently, the oxidation of bulkier molecules has required the synthesis of a material like SBA-15, which is a * Corresponding author. E-mail: yolanda.segura@ua.ac.be. † University of Antwerp (UA). ‡ Jagiellonian University. 12071 J. Phys. Chem. B 2005, 109, 12071-12079 10.1021/jp0507750 CCC: $30.25 © 2005 American Chemical Society Published on Web 05/27/2005