1. Introduction Noble metal free catalysts for VOC removal: formaldehyde oxidation at low temperature over MnO x -SBA-15 Catalyst preparation Unité de Catalyse et de Chimie du Solide - UMR CNRS 8181 USTL - Bâtiment C3 - 59655 Villeneuve dAscq Cedex - France - +33 (0)3 20 43 49 49 Email : remy.averlant@gmail.com - http://uccs.univ-lille1.fr R. Averlant 1,2, S. Royer 3, J.-M. Giraudon 1, J.-P. Bellat 4, J.-F. Lamonier 1 Effect of impregnation solvent and manganese content (continued) 1 Unité de Catalyse et de Chimie du Solide, CNRS UMR 8181 – Université Lille Nord de France 2 French Environment and Energy Management Agency, 20 avenue du Grésillé BP 90406 49004 Angers Cedex 01 France 3 Institut de Chimie des Milieux et Matériaux de Poitiers, CNRS UMR 7285, – Université de Poitiers 4 Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS UMR 6303 – Université de Bourgogne Effect of impregnation solvent and manganese content Fig 1: X-ray powder diffractograms SampleTheoretical Mn content (MnO 2 wt %) S BET (m²/g)V p (cm 3 /g)D crystal (nm) Initial SBA-15 -637.81.21- 20%Mn- W-C200 18.6393.70.6415.7 40%Mn- W-C200 37.6117.10.1919.5 20%Mn- 2S-C200 15.2484.40.9612.3 40%Mn- 2S-C200 33.7373.60.7213.2 Table 1: Physico-chemical properties Fig 2: Nitrogen physisorption isotherms Initial SBA-15 (D channel = 8 nm) (Preparation, see Roggenbuck et. al.[5] Water impregnation + calcination* « 2 solvents » impregnation [6] +calcination* 20%Mn-W-C200 40%Mn-W-C200 20%Mn-2S-C200 20%Mn-2S-C400 20%Mn-2S-C600 40%Mn-2S-C200 Study of the effect of the manganese content Studies of the effect of the calcination temperature and the manganese content Manganese precursor: Mn(NO 3 ) 2, 4H 2 O * Calcination: 3h, 1°C/min [5] J. Roggenbuck et. al., Chem. Mater., 2006, 18, 4151. [6] M. Imperor-Clerc et. al., J. Am. Chem. Soc., 2000, 122, 11925. Fig 3: TEM images of the samples 40%Mn-W-C200 (left) and 40%Mn-2S-C200 (center and right) Manganese particles inside the SBA-15 channel 40%Mn-W-C20040%Mn-2S-C200 Manganese particles outside the SBA-15 channels Effect of calcination temperature The crystallographic framework remains -MnO 2 Pyrolusite (PDF # 01-081-2261) regardless the impregnation solvent and the manganese content (Fig. 1) Water impregnation : increase in crystal size with manganese content large decrease in the surface area and the pore volume (Table 1) spoiling of the mesoporous character of the material (Fig. 2) 2 solvents impregnation : no significant increase in crystal size less large decrease in specific area and pore volume in comparison with the water impregnation (Table 1) remain of the mesoporous character even with a 40% manganese content (Fig. 2) ° ° ° ° Manganese content increase higher H 2 consumption and catalytic activity Catalytic activity better when manganese is impregnated in water Fig. 4: H 2 –TPR profiles Fig. 5: HCHO conversion vs. temperature ° ° ° 200°C 400°C 600°C « 2 solvents method » 20%Mn ° Fig. 7: HCHO conversion vs. temperature Fig. 6: H 2 – TPR profiles -MnO 2 Pyrolusite Mn 2 O 3 Bixbyite (T = 600°C) with crystal size increase Increase in catalytic activity when calcination temperature decreases (Fig. 6) Calcination temperature increase H 2 consumption decrease and higher contribution of the high-temperature region of H 2 consumption : decrease in manganese oxidation state [7] [7] J. Quiroz Torres et. al., Catal. Today, 17, 2011, 277-280 Conclusion Good catalytic result with the sample 40% Mn-W-C200 (100% HCHO conversion into CO 2 at 120°C) The impregnation method deeply influences manganese particle morphology (particles are as a majority included in the mesoporous channel of SBA-15 with the « 2 solvents » method) These different morphologies lead to different reactivity in HCHO oxidation (Catalytic activity is better when the impregnation is performed in water) Exposure to formaldehyde has been the topic of recent considerations of many governments around the world. This pollutant can be found in industrial air (e.g. wood and furniture industry) and in indoor air. Serious health problems such as nasopharyngeal cancer can be caused by a long-term exposure to an air containing a low concentration of formaldehyde (even less than 1 ppm). Several post- treatment technologies have been studied. Catalytic oxidation seems to be a promising solution. Formaldehyde can be converted selectivity in carbon dioxide and water with a relatively low energy consumption. Even though supported noble metals are the most active (e.g. Pt/TiO 2 [1,2]), the development of low-temperature active and cheap catalysts is still a challenge [3]. Here is presented the use of mesoporous silica SBA-15 supported manganese oxides in low-temperature formaldehyde oxidation. Indeed, manganese oxides are known to be the most effective transition metal oxides for this application. SBA-15 is an ordered mesoporous material with a large surface area (>600m²/g) [4]. A large manganese amount could therefore be impregnated. This study is focused on the influence of the impregnation solvent, the manganese content and the calcination temperature on the morphology of the manganese particles of the final material and also on the catalytic activity in the formaldehyde oxidation. [1] C. Zhang et. al., Catal. Today, 126, 2007, 345. [2] H. Huang et. al., J. Catal., 280, 2011, 60. [3] T. Chen et. al., Micropor. Mesopor. Mater., 122, 2009, 270. [4] D. Zhao et. al., Science, 279, 1998, 548. ° ° This work was supported by the French Environment and Energy Management Agency (ADEME) and the Région Nord – Pas de Calais. We also want to thank ADEME for the financial support of the project CORTEA / ADEME n° 11 81 C0108 « CAT » (http://cortea-cat.univ-lille1.fr).