Influence of the Acidic Properties of ZrO 2 Based Mixed Oxides Catalysts in the Selective Reduction of NO x with n -Deca
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Influence of the Acidic Properties of ZrO2 Based Mixed Oxides Catalysts in the Selective Reduction of NOx with n-Decane Reem Kourieh • Laurence Retailleau • Simona Bennici • Anne Giroir-Fendler Aline Auroux
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Received: 10 October 2012 / Accepted: 19 November 2012 / Published online: 8 December 2012 Springer Science+Business Media New York 2012
Abstract The selective catalytic reduction of NOx by decane (C10H22–SCR) has been studied over mixed oxides of zirconia with boria, alumina, gallia, india and tungsta. The samples were prepared by coprecipitation and thoroughly characterized using a combination of different techniques to determine their structural and surface properties. Moreover a WO3-containing sample supported on Al2O3–ZrO2 sample was prepared to verify the influence of the tungsta active phase deposited by impregnation. The surface acidity and basicity of the samples (measured by NH3 and SO2 adsorption microcalorimetry) varied in relation to the kind of co-oxide added to zirconia. In particular, the number of surface acid sites expressed in lmolNH3 g-1 increased in the following order WO3–ZrO2 [ Al2O3–ZrO2 [ Ga2O3–ZrO2 [ In2O3–ZrO2 [ WO3/(Al2O3–ZrO2) [ ZrO2 [ B2O3–ZrO2. Correlations between the catalytic behaviour and the samples surface acidity were found and the results show that a moderate acidity (i.e. for Ga2O3–ZrO2) is one of the key parameter for high N2 selectivity and NOx conversion. Keywords Zirconia based mixed oxides Adsorption microcalorimetry Acidity n-Decane NOx HC–SCR
1 Introduction Nitrogen oxides (NOx) produced by internal combustion engines are still an un-solved issue. NOx oxides are the
R. Kourieh L. Retailleau S. Bennici A. Giroir-Fendler A. Auroux (&) Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON), UMR 5256, CNRS, Universite´ Lyon 1, 2 avenue Albert Einstein, 69626 Villeurbanne, France e-mail: [email protected]
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main cause for a lot of environmental problems; such as ozone formation in the troposphere and production of acidic rains [1]. These oxides are very toxic for human health and they can provoke infections and allergies in the respiratory system [2]. Long exposure of NOx with concentration above 0.05 ppm causes hazardous effects for human health [3]. As a result of the negative impact of NOx, the regulation of its emission is becoming stricter, regardless of the region, including Asia, Europe and USA [4]. The next NOx limits (Euro 6 in Europe) will require the introduction of sophisticated after-treatment techniques from the diesel manufacturers [5]. Among the different technologies existing to reduce NOx emission from diesel engines, the selective catalytic reduction by hydrocarbons [6], HC–SCR, is a highly recommended technology, as it is a practical method to use the unburned hydrocarbons that already exist in the exhaust gas [7]. HC–SCR is more costeffective, simpler to apply, but still higher NOx conversion is required to find a final application [5]. Various studies have been performed using ligh
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