Characterization and performance of over-exchanged Cu-ZSM-5 catalysts prepared by solid-state ion exchange for the selective catalytic reduction of NO by n-decane.

National audienceCu-ZSM-5 catalysts have been prepared by solid-state ion exchange at 500°C using CuCl and NH4- ZSM-5 mixture in presence of nitrogen flux. X-ray diffraction technique indicates that zeolite lattice is slightly modified for high copper loadings. The nature of copper species depends on copper exchange levels. For under exchanged catalyst, copper is mainly present as isolated Cu2+. For higher loadings, Cu+ and dispersed CuO-like species with different sizes and environments were detected besides Cu2+ ions. CuO-like species are located in the zeolite channels such as Cu2+-O-Cu2+ dimers or on the surface of zeolite crystals. Copper oxide clusters are not detectable by XRD technique, which indicates that they are amorphous and/or well dispersed on the external surface of the zeolite. The prepared catalysts show good activity in the selective catalytic reduction of NO by n-decane in oxidizing atmosphere independently of copper exchange level. The increase of copper content has an effect on the operating temperature window by decreasing the temperature of maximum NO conversion and total n-C10H22 oxidation. The presence of 25 ppm of SO2 in the reaction feed has a slight inhibiting effect for all catalysts excepting Cu(136)-Z for which NO conversion was enhanced in the temperature range of 320-425 °C

Hydrothermal treatment of Cu-ZSM-5 deNOx catalysts prepared by solid ion exchange

Edit. A. Ghorbel and S. Miertu

Hydrothermal treatment of Cu-ZSM-5 deNOx catalysts prepared by solid ion exchange

Edit. A. Ghorbel and S. Miertu

Characterization and performance of over-exchanged Cu-ZSM-5 catalysts prepared by solid-state ion exchange for the selective catalytic reduction of NO by n-decane.

National audienceCu-ZSM-5 catalysts have been prepared by solid-state ion exchange at 500°C using CuCl and NH4- ZSM-5 mixture in presence of nitrogen flux. X-ray diffraction technique indicates that zeolite lattice is slightly modified for high copper loadings. The nature of copper species depends on copper exchange levels. For under exchanged catalyst, copper is mainly present as isolated Cu2+. For higher loadings, Cu+ and dispersed CuO-like species with different sizes and environments were detected besides Cu2+ ions. CuO-like species are located in the zeolite channels such as Cu2+-O-Cu2+ dimers or on the surface of zeolite crystals. Copper oxide clusters are not detectable by XRD technique, which indicates that they are amorphous and/or well dispersed on the external surface of the zeolite. The prepared catalysts show good activity in the selective catalytic reduction of NO by n-decane in oxidizing atmosphere independently of copper exchange level. The increase of copper content has an effect on the operating temperature window by decreasing the temperature of maximum NO conversion and total n-C10H22 oxidation. The presence of 25 ppm of SO2 in the reaction feed has a slight inhibiting effect for all catalysts excepting Cu(136)-Z for which NO conversion was enhanced in the temperature range of 320-425 °C

Caractérisation de catalyseurs Cu-ZSM-5 préparés par échange ionique en phase solide pour la réduction catalytique sélective de NO en atmosphère oxydante par n-C10H22

International audienceDes catalyseurs Cu-ZSM-5 ont été préparés par échange ionique en phase solide à 500 °C, à partir d'un mélange de CuCl2.2H2O et NH4-ZSM-5, en présence (dynamique) ou en l'absence (statique) de flux d'azote. Les techniques DRX, BET et RMN ont montré que la structure zéolithique a été légèrement détruite pour des teneurs accrues en cuivre. La nature des espèces de cuivre suite à l'échange solide dépend de la teneur en cuivre et de la méthode d'échange. Le cuivre se trouve majoritairement sous forme de Cu2+ pour les catalyseurs ayant un taux d'échange inférieur à 100 %. Pour des teneurs accrues en cuivre, la formation de particules de CuO de grandes tailles a été détectée par DRX pour les catalyseurs préparés sans flux d'azote. Par contre, la présence d'un flux d'azote induit la formation de particules de CuO bien dispersées sur les surfaces et dans les canaux de la zéolithe, non détectables par DRX. Les catalyseurs préparés présentent une bonne activité dans la réduction catalytique sélective de NO par le n-décane en atmosphère oxydante indépendamment de la méthode d'échange

Catalytic activity of Cu-offretite catalysts prepared by solid state ion exchange in the reduction of NO with NH3

International audienceCu-OFF catalysts with different copper loadings, prepared by solid state ion exchange, were characterized by UV-visible reflectance spectroscopy, H2-TPR, NH3-TPD, 27Al MAS NMR and tested for selective catalytic reduction of NO by ammonia in presence of oxygen. At low Cu content (exchange level < 40 %), TPR profiles show the presence of two peaks of comparable areas, suggesting that Cu2+ remain isolated and are reduced in two successive steps: Cu2+?Cu+ at about 220°C and Cu+?Cu0 at 800–850°C. At higher Cu content, the TPR profiles are modified with a large increase of the low temperature peak with depends of the high temperature peak, thus suggesting the formation of Cu oxide clusters in the lattice of offretite. The actidity of the offretite also decreases upon exchange. The NO reduction activity is proportional to the number of Cu2+ ions up to 40% exchange, then decreases. Isolated Cu2+ ions appear then more active than CuO clusters for the selective reduction of NO by NH3

Selective catalytic reduction of NO by NH3 on Cu (II) ion- exchanged offretite prepared by different methods

International audienceThe influence of the preparation method on the NO–SCR by NH3 activity of Cu-OFF catalysts has been studied on presence of oxygen. The catalysts structure and the nature of copper species have been investigated by XRD, 27Al MAS NMR, UV-visible spectroscopy and H2-TPR. Among the examined preparation methods, the ionic exchange in aqueous solution gives the highest efficient catalyst in NO-SCR. It is shown that Cu cationic species are formed in large extent with this method despite the presence of minor amounts of small oxide clusters

Selective catalytic reduction of NO in oxidizing atmosphere with n-C10H22 over Cu-M-ZSM-5 (M : La, Ce, Sm) catalysts prepared by solid ion exchange

International audienceThe influence of addition of rare earth cations ( La, Ce, Sm) upon the redox and adsorptive properties of Cu-M-ZSM-5 catalysts prepared via solid ion exchange has been studied. The activity in the selective catalytic reduction of NO by n-C10H22 in oxidizing atmosphere of the prepared catalysts has also been evaluated. Among the catalysts prepared, Cu-Sm-ZSM5 exhibits the highest de-NOx efficiency

Selective catalytic reduction of nitric oxide with ammonia on copper (II) ion-exchanged offretite

International audienceCopper K-offretite catalysts prepared by ion exchange were characterized by XRD, H2-TPR and evaluated in the selective catalytic reduction of NO (NO-SCR) by ammonia. Despite several successive exchanges, the quantity of copper introduced remains low and the exchange ratio does not exceed 50%. The NO conversion profiles have a sigmoid curve shape. Full NO conversion in N2 is reached above 340 C at a volume space velocity of 332,000 h 1. N2O formation at low temperature is due to the presence of small oxide particles generated by the successive copper exchanges during the preparation. The presence of K ions ‘‘blocks'' the cancrinite access to copper ions and maintains the deNOx efficiency over the whole range of temperature

Characterization and deNO x activity of copper-hydroxyapatite catalysts prepared by wet impregnation

International audienceCopper loaded hydroxyapatite catalysts have been prepared by wet impregnation and have been tested in the selective catalytic reduction of NO by NH3. The catalyst characterization showed the presence of copper oxide nanoparticles entrapped in the mesoporous matrix thus obstructing the Ca-Hap channel apertures. With increasing copper loading, there is a deposition of copper oxide clusters, on the surface of the carrier, containing Cu2+ and Cu+ ions. Compared to the catalyst prepared by the ion exchange method, Cu(1.12)Hapi.e, which exhibited excellent NO conversion over a broad temperature range, the impregnated catalysts are less efficient in the selective catalytic reduction of NO by NH3