Catalysis Today 191 (2012) 112–115 Contents lists available at SciVerse ScienceDirect Catalysis Today j ourna l ho me p ag e: www.elsevier.com/lo cate/cattod A comparative study of TiO 2 -supported and bulk Co–Mn–Al catalysts for N 2 O decomposition K. Karásková a , ˇ Z. Chromˇ cáková a , S. ˇ Studentová a , V. Matˇ ejka b , K. Jirátová d , L. Obalová a,c,∗ a V ˇ SB – Technical University of Ostrava, Faculty of Metallurgy and Materials Engineering, 17. Listopadu 15, 708 33 Ostrava, Czech Republic b V ˇ SB – Technical University of Ostrava, Nanotechnology Centre, 17. Listopadu 15, 708 33 Ostrava, Czech Republic c V ˇ SB – Technical University of Ostrava, Centre for Environmental Technologies, 17. Listopadu 15, 708 33 Ostrava, Czech Republic d Institute of Chemical Process Fundamentals CAS v.v.i., Rozvojová 135, 165 02 Prague, Czech Republic a r t i c l e i n f o Article history: Received 4 October 2011 Received in revised form 7 February 2012 Accepted 8 March 2012 Available online 18 April 2012 Keywords: Nitrous oxide Catalytic decomposition Layered double hydroxides Mixed oxides Titanium dioxide a b s t r a c t A series of Co–Mn–Al/TiO 2 catalysts with different Co + Mn loading (5–24 wt.%) was prepared by impreg- nation of TiO 2 support. Bulk Co–Mn–Al mixed oxides were prepared by different methods. The prepared catalysts were characterized by chemical analysis, surface area measurement, temperature programmed techniques (TPR, TPD) and tested for N 2 O catalytic decomposition. TiO 2 acted only as a catalytic sup- port and did not contribute to the catalytic activity. The N 2 O conversion over TiO 2 -supported Co–Mn–Al catalysts was increasing with Co + Mn loading, and was proportional to the amount of easily reducible components. Comparing the catalysts with identical amount of active components, the highest catalytic activity was achieved on the calcined precursors having carbonates in their molecules (layered double hydroxides Co–Mn–Al-HT-ex and Co–Mn–Al-carb), the lowest one on the calcined Co–Mn–Al nitrates due to the lower surface area, less advantageous porous structure and worse reducibility. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Catalytic decomposition of nitrous oxide is the subject of research of many groups due to its negative impact on the envi- ronment. In the last years, many catalysts were examined [1], especially Fe-zeolites [2,3], Co-spinels [4,5] or calcined layered dou- ble hydroxides [6,7]. Supported systems present the substantial part of catalysts for N 2 O decomposition. Noble metals supported on oxides have been shown to be effective catalysts for N 2 O conver- sion [8]. Catalytic activity varied with both types of the active site and the kind of support. The most popular support is Al 2 O 3 . Other material can be TiO 2 . The TiO 2 –sepiolite matrix appeared to play a key role in the process – facilitates the migration of oxygen species and their final recombination [9]. Reactivity of N 2 O with TiO 2 (1 1 0) is dictated primarily by reactions at oxygen vacancy sites [10,11]. In terms of thermal N 2 O decomposition activity on TiO 2 , the rutile phase has been shown to be more active than the anatase phase [12]. The effect of CeO 2 amount on TiO 2 properties was studied in [13]; higher activity of the prepared catalyst was connected with a new Ti–O–Ce phase, whereas lower catalytic activity with the presence of CeO 2 crystal phase. The influence of Al 3+ dopants on ∗ Corresponding author at: V ˇ SB – Technical University of Ostrava, Faculty of Met- allurgy and Materials Engineering, 17. Listopadu 15, 708 33 Ostrava, Czech Republic. Tel.: +420 596 991 532; fax: +420 597 323 396. E-mail address: lucie.obalova@vsb.cz (L. Obalová). the catalytic activity of TiO 2 for the decomposition of N 2 O has been studied in [14]. Our previous papers dealt with Co–Mn–Al mixed oxide cata- lysts prepared by thermal decomposition of coprecipitated layered double hydroxide precursors [6,7,15]. The catalyst with molar ratio Co:Mn:Al = 4:1:1 and optimal amount of potassium pro- moter showed the highest activity, especially in simulated process stream (presence of O 2 , H 2 O and NO x ) [15]. However, application of pelletized mixed oxides in industry is connected with several problems: (i) troubles accompanying formation of mixed oxides or their precursors into larger pellets; (ii) relatively low mechanical strength; (iii) low utilization of whole pellet volume (composed of relatively expensive active phase) since the catalytic reaction proceeds mainly on the external catalyst surface. From those rea- sons the preparation of a thin active layer of Co–Mn–Al mixed oxide deposited on the porous material would be advantageous and therefore, we focused on the effect of a support on catalytic properties in this paper. TiO 2 as a support was selected for our first experiments due to its hydrophobic properties, which could be useful for N 2 O decomposition in the presence of water vapor. The aim of the presented work was the examination of titania support effect on the properties and catalytic activity of Co–Mn–Al mixed oxides in N 2 O catalytic decomposition. The examination was carried out in a kinetic regime (over catalyst grains) to obtain the most precise reaction characteristics. For comparison, the unsup- ported Co–Mn–Al mixed oxides were also prepared by two different preparation methods. 0920-5861/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cattod.2012.03.046