Applied Catalysis B: Environmental 165 (2015) 158–168 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h omepa ge: www.elsevier.com/locate/apcatb Mesoporous silica supported Rh catalysts for high concentration N 2 O decomposition Marco Piumetti a , Murid Hussain a,b , Debora Fino a , Nunzio Russo a,∗ a Department of Applied Science and Technology, Politecnico di Torino, Corso Duca, degli Abruzzi 24, 10129 Torino, Italy b Department of Chemical Engineering, COMSATS Institute of Information Technology, M.A. Jinnah Building, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan a r t i c l e i n f o Article history: Received 1 September 2014 Received in revised form 29 September 2014 Accepted 3 October 2014 Available online 12 October 2014 Keywords: N2O decomposition Adipic acid plant Rh catalyst Mesoporous silica MCF a b s t r a c t A set of Rh-containing catalysts (Rh-MCM-41, Rh-SBA-15, Rh-KIT-6 and Rh-MCF, nominal Rh con- tent = 1 wt.%) has been prepared by wet impregnation of mesoporous silicas and tested for high concentration N 2 O abatement. The physico-chemical properties of the materials have been investigated by means of complementary techniques. The best performances, in terms of N 2 O decomposition, have been achieved for the Rh-MCF catalyst, due to the better textural properties of the MCF silica. In fact, the MCF-type support exhibits three- dimensional mesoporosity with ultra-large cells (up to 40 nm), which allow a uniform distribution of small RhO x particles (≈1 nm) over the high (internal) surface area of the MCF. Moreover, the Rh active sites are also readily accessible to N 2 O molecules. The most promising catalyst has shown the highest amount of Rh 1+ species, the easiest rhodium reducibility and the greatest abundance of Rh surface sites. These important features reflect the different Rh particle sizes and play a role in catalytic activity. A remarkable relationship between the catalytic activity and the dimension of the RhO x particles has been observed in the 1–2.5 nm size domain, thus confirming the dispersion-sensitivity of N 2 O decompo- sition over RhO x nanoparticles. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Nitrous oxide (N 2 O) is considered a greenhouse gas since it lasts approximately 150 years in the atmosphere, it has 310 and 21 times greater warming potential than CO 2 or CH 4 , respectively, and it con- tributes to the destruction of stratospheric ozone [1–3]. For these reasons, it has recently received a great deal of attention by scien- tists because of its possible environmental effects [1]. Europe has agreed to reduce greenhouse emissions, including N 2 O, to fulfil the Kyoto protocol. N 2 O is produced from both natural and anthropogenic sources. Biological processes, which take place in soils and oceans, are the primary natural sources of N 2 O. The main contributors of the anthropogenic sources include fertilizers, nitric acid, adipic acid, caprolactam and glyoxal production, fossil fuels and biomass com- bustion, as well as sewage treatment [3,4]. Nitric acid and adipic acid production plants are thought to be the largest industrial ∗ Corresponding author. Tel.: +39 011 0904710; fax: +39 011 0904699. E-mail address: nunzio.russo@polito.it (N. Russo). sources of N 2 O emissions. As a whole, there is a higher N 2 O concen- tration in tail gas emissions from adipic acid plants (usually 20–40% v/v) than from nitric acid production (around 300–3500 ppm). It has in fact been reported that around 10% of N 2 O released into the atmosphere each year originates from adipic acid production, and hence great efforts have been made to abate high-concentration N 2 O [5,6]. Catalytic N 2 O decomposition could be a promising alternative solution, as it makes N 2 O abatement possible at the emission source at lower temperatures (300–500 ◦ C) than the conventional thermal abatement technology [3]. Noble metals, metal oxides, mixed oxides, metal or ion exchanged zeolites and supported metal catalysts have been reported in the literature as promising cata- lysts for N 2 O abatement [4–9]. Rhodium or iridium oxides have been found in particular to be more active in the decomposi- tion of N 2 O than other oxides. However, their low surface areas contribute to their main disadvantages as catalysts [4,10]. Meso- porous materials with large controlled accessible surface areas could be attractive candidates for N 2 O decomposition, since the active phase can be highly dispersed over the support [11]. The dis- covery of ordered mesoporous molecular sieves, such as SBA-15 http://dx.doi.org/10.1016/j.apcatb.2014.10.008 0926-3373/© 2014 Elsevier B.V. All rights reserved.