Catalysis Letters 70 (2000) 51–56 51 Pillared smectite modified with carbon and manganese as catalyst for SCR of NO x with NH 3 . Part II. Temperature-programmed studies L. Chmielarz a , R. Dziembaj a , T. Grzybek b , J. Klinik b , T. Łojewski a , D. Olszewska b and A.W˛ egrzyn a a Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland b Faculty of Fuels and Energy, University of Mining and Metallurgy, Mickiewicza 30, 30-059 Krakow, Poland Received 25 May 2000; accepted 21 September 2000 Temperature-programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of NH 3 than NO was found, butacidic pre-treatment increased NO sorption to comparable values as well as catalytic performance in SCR of NO x . In this case formation of strongly bound NO − 3 species was recognised, which reacted with NH 3 at a temperature 200 ◦ C higher than weaker adsorbed NO. Keywords: SCR of NO x , zirconia pillared smectites, carbon deposits, manganese oxides, TPD, TPSR 1. Introduction As reported in a previous paper [1], a series of zirconia- pillared smectites modified with carbon and manganese was prepared and used as catalysts for SCR of NO with am- monia.The idea to prepare and test such catalysts arose from another previous study on transition metal oxides sup- ported on active carbons [2]. Active carbons promoted with transition metal oxides were found to catalyse NO x reduction at temperatures below 300 ◦ C [3,4], but their low mechanical and thermal stability preclude their commer- cialapplication. Since active carbons have a great num- ber of small micropores, which are inaccessible to react- ing molecules, it seemed promising to apply a support showing easier accessable pore structure. The pillared smectites were chosen because of their large surface area, high mechanical durability and resistance to SO x poison- ing [5]. Our activity studies [1], which were performed in a plug-flow reactor under steady state conditions, showed that zirconia-pillared smectites are active and selective catalysts for the DeNOx process. The highest activity was found for catalysts prepared from acid pre-treated smectites mod- ified with carbon and manganese. The present paperis devoted to an additional characterisation of these catalysts using temperature-programmed methods (NH 3 -TPD, NO- TPD and TPSR) supported by FTIR spectroscopy of pre- adsorbed NO molecules. 2. Experimental 2.1. Samples Smectite obtained by sedimentation from natural ben- tonite from Jelsowy Potok (Slovakia) was used as a raw material for the preparation of the catalysts. A partof it was pre-treated with 20% HCl. The samples were pillared by impregnation with zirconia oligocations and calcined at temperature up to 500 ◦ C. The pillared materials were contacted with water solution ofpolyacryloamide (Gig- tar) and subsequently carbonised at 500 ◦ C. Both carbon- modified and unmodified samples were promoted by ad- sorption methods with Mn cations and calcined. Thus pre- pared catalysts were stable in both pure helium as well as oxygen-containing atmosphere up to 500 ◦ C. The list of the samples with the respective notation is presented in ta ble 1. The surface and bulk composition, structure and texture of the obtained materials were earlier characterised by XP Table 1 List of the samples. Catalysts code Sample preparation M1 Zirconia-pillared smectite M2 Acid-treated zirconia-pillared smectite M1Mn0.7 M1 promoted with Mn cations (0.7 wt%) M1C M1 modified with carbon deposit M2C M2 modified with carbon deposit M1CMn16 M1C promoted with Mn cations (16 wt%) M2CMn14 M2C promoted with Mn cations (14 wt%)  J.C.Baltzer AG, Science Publishers