Journal of Porous Materials 12: 183–191, 2005 c  2005 Springer Science + Business Media, Inc. Manufactured in The Netherlands. Nitrous Oxide Reduction with Ammonia and Methane Over Mesoporous Silica Materials Modiﬁed with Transition Metal Oxides L. CHMIELARZ ∗ , P.KU ´ STROWSKI, M. KRUSZEC AND R. DZIEMBAJ Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Krakow, Poland chmielar@chemia.uj.edu.pl P. COOL AND E.F. VANSANT Department of Chemistry, University of Antwerp, Laboratory of Inorganic Chemistry, Universiteitsplein 1, 2610 Wilrijk, Belgium Received October 29, 2004; Revised March 4, 2005 Abstract. Transition metal oxides (Cu, Cr and Fe) were deposited on various mesoporous silicas (MCM-48, SBA-15, MCF and x -MSU) by an impregnation method. Electron microprobe analysis, BET, UV-VIS-DRS and temperature programmed desorption of NH 3 were used for the characterization of the samples. The modiﬁed mesoporous silicas were tested as catalysts of the N 2 O decomposition and the N 2 O reduction using ammonia and methane. The Cu-containing samples presented the highest catalytic activity in the N 2 O decomposition, while the Cr- and Fe-modiﬁed materials were more active in the reduction of nitrous oxide with NH 3 and CH 4 . The type of the silica support strongly inﬂuenced the catalytic performance of the studied materials. Keywords: mesoporous silicas, transition metals, catalysis, N 2 O decomposition, N 2 O reduction, ammonia, methane 1. Introduction Nitrous oxide contributes to the destruction of ozone layer in the stratosphere and is considered as a strong greenhouse gas. The concentration of N 2 O in the at- mosphere increases by about 0.2–0.3% per year and is caused mainly by anthropogenic activities [1, 2]. The major source of the nitrous oxide emission is the chemical industry (e.g. production of nitric acid, adypic acid, caprolactam, glyoxal) [3]. The most promising way for the reduction of the N 2 O emission is its cat- alytic decomposition to nitrogen and oxygen. However, the studied catalysts of this process effectively operate in a relatively high temperature range and are there- fore not acceptable for the industrial applications. The nitrous oxide decomposition proceeds according to a ∗ To whom correspondence should be addressed. redox mechanism [4]. N 2 O molecules oxidise active centres, which have to be reduced in order to start the next catalytic cycle. The reduction of active sites is a rate determining step of this process. It seems to be possible to increase the rate of the N 2 O decomposition by using an additional reagent, which can remove oxy- gen bonded to the active sites. Hydrocarbons [5, 6] and ammonia [7, 8] are main candidates that can be used as reducing agents in this process. Mesoporous silicas, which are characterised by a very high surface area, ordered porous structure and high thermal stability, are very promising supports for catalytic applications. The modiﬁcation of these sil- ica materials with transition metal oxides results in the formation of the redox centres. It is possible to obtain different loading and dispersion of transition metal ox- ides by using various deposition methods (e.g. impreg- nation or grafting) [9–12]. This paper presents the study