Valorization of vitreous China waste to EMT/FAU, FAU and Na-P zeotype materials

International audienceIn this study, Na-X, Na-P, SOD and EMT/FAU zeotype materials have been prepared from vitreous China waste by conventional hydrothermal route and alkaline fusion prior to hydrothermal synthesis. The conventional route has shown its limits in the activation of the waste in the chosen experimental conditions, [NaOH] = 3.5 M and T = 60 °C. The amorphous phase of vitreous China waste plays an important role during the zeolitization process because it easily dissolves into the alkaline solution compared to crystalline phases like quartz and mullite. By the conventional route, Na-X and Na-P1 and SOD zeolites were obtained. The alkaline fusion step using NaOH as mineralizer at 550 °C converted the waste to highly active soluble aluminate and silicate salts. The fused material was mixed with distilled water to have liquid to solid ratio L/S = 5, under vigorous stirring at room temperature for 1 day. The obtained gel with molar composition of 7.0 Na2O: 1.0 Al2O3: 4.8 SiO2: 209.4 H2O was converted by hydrothermal crystallization at 60 °C to nanosized EMT/FAU zeotype and geopolymeric amorphous aluminosilicate material. With the increase of fusion time, there is a decrease of the amount of EMT-type zeolite

Selective catalytic reduction of NO by NH3 on cerium modified faujasite zeolite prepared from aluminum scraps and industrial metasilicate

International audienceThis work was devoted to the study of the selective catalytic reduction of NO by NH 3 on calcined and hydrothermal treated cerium loaded zeolite catalysts. The parent faujasite zeolite Na-F (Si/Al = 1.32 and S BET = 749 m 2 /g) used as support for the preparation of the catalysts was obtained from industrial sodium metasilicate and aluminum scraps. As expected, the NO conversion increased with increasing the percentage of cerium in the structure of the faujasite zeolite. Total NO conversion into N 2 was reached at 400°C at a space velocity of 250,000 h-1. The high conversion is due to the redox shift between Ce 3+ / Ce 4+ and the strong acid sites related to the rare earth present in the framework that is the key in SCR of NO process. Moreover, the highest loaded cerium catalyst retained high almost its activity after thermal hydrotreatment at 850°C. This higher loading is desirable for both activity and stability provided that two stages of preparation are used to put the Ce ions in the sodalite cages

Preparation of LTA, HS and FAU/EMT intergrowth zeolites from aluminum scraps and industrial metasilicate

International audienceNa-LTA zeolite crystals were synthesized via hydrothermal method using aluminum scraps and industrial sodium metasilicate. The obtained hydrogel with molar composition: 3.741 Na2O:Al2O3:1.450 SiO2:175.520 H2O, was aged at room temperature for 14 h and heated at 80 °C for 6 h. The use of aluminum scraps provides well-crystallized cubic Na-LTA zeolites with truncated edges and apexes. When H2O/Al2O3 molar ratio was decreased: 3.741 Na2O:Al2O3:1.450 SiO2:92.50 H2O, there is formation of an intergrowth of FAU/EMT phases contaminated with LTA zeolite after 6 h of crystallization. The prolongation of the crystallization time to 48 h leads to the formation of hydoxysodalite zeolite. On the other hand, with the increase in aging time to 96 h, the crystal sizes of zeolite decrease

Catalytic activity of Cu/η-Al2O3 catalysts prepared from aluminum scraps in the NH3-SCO and in the NH3-SCR of NO

International audienceCopper loaded η-alumina catalysts with different copper contents were prepared by impregnation/evaporation method. The catalysts were characterized by XRD, FTIR, BET, UVvis, H 2-TPR and evaluated, for the first time, in the selective catalytic reduction of NO by NH 3 and in the selective catalytic oxidation of NH 3. The characterization techniques showed that the impregnation/evaporation method permits to obtain highly dispersed copper oxide species on the η-alumina surface when low amount of copper is used (1wt. % and 2 wt.%). The wet impregnation method made it possible to reach a well dispersion of the copper species! on the surface of the alumina for the low copper contents Cu(1)-Al 2 O 3 and Cu(2)-Al 2 O 3. The latter justifies the similar behavior of Cu(1)-Al 2 O 3) and Cu(2)-Al 2 O 3 in the selective catalytic oxidation of NH 3 where these catalysts exhibit a conversion of NH 3 to N 2 of the order of 100% at T> 500°C

Copper loaded hydroxyapatite catalyst for selective catalytic reduction of nitric oxide with ammonia

International audienceCopper loaded hydroxyapatite prepared by ion exchange were characterized by XRD, FTIR, BET, UV-vis, H2-TPR and evaluated in the selective catalytic reduction of NO by NH3 under oxidizing atmosphere. The Cu-Hap catalysts, without the libethenite phase presence, have been found to be active, and selective in the NH3-SCR process. The highly dispersed CuO clusters on Ca-Hap surfaces were responsible for the NO conversion in the low temperature range in the NO-SCR with NH3. The presence of 2.5% of H2O in the feed mixture strongly affects the NO conversion in the whole temperature range

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

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

Selective catalytic reduction of NO by NH3 over copper-hydroxyapatite catalysts: effect of the increase of the specific surface area of the support

International audienceThe influence of the increase of the specific surface area of the support Ca-HAp on the dispersion of copper species and their activity in the NO-SCR by NH3 has been studied. The copper ion exchange does not alter the Ca-HAp structure whatever the copper concentration. The increase of the specific surface area of the support changed the dispersion and the reducibility of copper species. The high NO conversion in the whole temperature range for the catalyst with the lowest specific surface area (35 m2/g) was related to the highly dispersed CuO particles that are easily reduced. Nevertheless, the increase of the specific surface area of the support (76 m2/g), induces an increase of the size of CuO particles that become less active in NO-SCR by NH3. The addition of 2.5 % of H2O to the reaction gas feed strongly affects the NO conversion in the whole temperature range. This deactivation can be related to the change of the nature of copper species rather than to the destruction of the Ca-HAp structure

Selective Catalytic Reduction of Nitrogen Oxide by Ammonia over Copper-Hydroxyapatite Catalysts Prepared in Organic Medium

International audienceCopper loaded hydroxyapatite catalysts have been prepared in organic medium by reaction/evaporation and impregnation methods and have been tested in the selective catalytic reduction of NO by NH3. The catalyst characterizations showed the presence of CuO and Cu2O particles deposited on the surface of the carrier in different environments and sizes. Compared to the catalysts prepared by ion exchange and impregnation in aqueous medium method, the ones prepared in organic medium are less efficient in the selective catalytic reduction of NO by NH3