Selective catalytic reduction of NOx by NH3 on Cu-SAPO-34 catalysts: Influence of silicium content on the activity of calcined and hydrotreated samples

International audienceSAPO-34 zeolites with three different Si contents were prepared by hydrothermal synthesis and then around 0.6 wt% Cu was introduced by impregnation. The structure and morphology of the samples were characterised via XRD and SEM techniques, respectively. The acid properties of the different samples were investigated by NH3-TPD. Cu-SAPO-34, with the lowest Si content, exhibits the best efficiency, between 200 and 550 °C, in NH3-SCR of NO after ageing treatment under H2O vapour at 850 °C for 5 h. For the fast reaction, (NO/NO2), a better efficiency is only observed with respect to the catalyst having low Si content

Influence des propriétés texturales et de la méthode de préparation sur les performances hydrogénantes de catalyseurs Pd/C

Nous nous sommes attachés à étudier l influence des propriétés physicochimiques et texturales du charbon sur les caractéristiques et les performances catalytiques de catalyseurs 5% Pd/C dans des réactions d hydrogénation (cinnamaldéhyde et cyclododécatriène). La première voie de préparation de catalyseurs est l échange cationique H+ Pd2+. Cette technique requiert une fonctionnalisation oxydante (HNO3, NaOCl, H2O2) afin de créer des fonctions d ancrage. Les matériaux ainsi préparés sont très dispersés (dPd = 1,5 nm). Cependant leur stabilité thermique est restreinte du fait de la décomposition des fonctions stabilisantes dès 200C. Une technique alternative est la préparation par déposition-précipitation (DP) qui ne requiert aucun prétraitement oxydant mais un contrôle strict des conditions opératoires est nécessaire pour assurer une reproductibilité parfaite. La préparation de catalyseurs Pd/C à partir de deux lots commerciaux (L3S) selon les techniques précédentes conduit à des matériaux aux caractéristiques et aux performances hydrogénantes identiquesMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

NH3–SCR of NOx on Silicoaluminophosphate Molecular Sieves Based Catalysts: A Comparative Study

International audienceIn this study, copper aluminophosphate catalysts were prepared from home made and commercial zeolites. Various formulations were prepared, and several parameters such as the type of structure, the crystal size, the copper and the silicon content were varied. The catalysts were tested in selective catalytic reduction of NO or NO/NO2 by NH3 after calcination at 550 °C and hydrothermal treatment at 850 °C. The efficiency and stability depended mainly on a good correlation between copper and silicon contents. A higher mean crystal size of the starting zeolite could also be beneficial. Thus, a copper catalyst with a copper content of 1.25 wt%, prepared from a Chabazite zeolite furnished by Clariant (Si content = 3 wt%), was the most efficient catalyst after hydrothermal treatment at 850 °C in NO reduction by NH3

Réduction catalytique sélective de NO par NH3 sur Cu-faujasite : effet de l'acidité et approche mécanistique

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

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

Reduction catalytique sélective de NO par NH3 sur Fe-ZSM-5

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

A new V2O5 –MoO3 –TiO2 –SO42− nanostructured aerogel catalyst for diesel DeNO x technology

International audienceA new V2O5–MoO3–TiO2–SO42− nanostructured aerogel system, containing V and Mo loadings representative of the V2O5–MoO3/TiO2 commercial SCR catalyst, was developed via a one step sol–gel method combined with the supercritical drying approach for the low temperature selective catalytic reduction of NO by NH3, in excess O2. The new V2O5–MoO3–TiO2–SO42− catalyst was analysed via XRD, N2-physisorption, H2-TPR, NH3-TPD, Raman spectroscopy, XPS and DR UV-vis spectroscopy. The elaboration and characterization of TiO2, V2O5–TiO2, MoO3–TiO2, V2O5–MoO3–TiO2, TiO2–SO42−, V2O5–TiO2–SO42− and MoO3–TiO2–SO42− aerogel samples were also reported in this work. The results prove the successful synthesis of nanostructured aerogel materials with good crystallinity of the TiO2 anatase phase, a developed mesoporous texture and a nanometer size as new SCR catalysts. V, Mo and SO42− were found to be highly dispersed on the TiO2 surface, and their presence and the diverse interactions developed between them strongly affect the physicochemical properties and catalytic behaviour of the derived sol–gel powders. Among all the samples investigated, the new V2O5–MoO3–TiO2–SO42− aerogel was found to be the most efficient catalyst for the low temperature NO-SCR: compared to a V2O5–WO3/TiO2 commercial catalyst (EUROCAT), it demonstrates similar SCR activity in the 200–375 °C temperature range, but, at higher temperatures (375–500 °C), it exhibits superior catalytic performance. A complete conversion of NO into N2 (100%) was achieved in the 450–500 °C temperature range over the new V2O5–MoO3–TiO2–SO42− nanostructured aerogel catalyst, when the NH3-SCR reaction was realized using 1000 ppm NO and 1000 ppm NH3, in the presence of 3.5% H2O

Comparison of Vehicle Aged SCR Catalyst on a Particulate Filter (SCRF) with Oven Aged Equivalent

International audienceo meet forthcoming Euro 6 Diesel engines NOx emissions legislation; highly efficient after-treatment systems are required. The use of urea or ammonia SCR is a well-established solution for high NOx abatement for diesel engines. The combination of a Cu-Zeolite SCR catalyst and a diesel particulate filter has been widely investigated in recent years to respond to the European NOx emissions regulations especially for those on light-duty vehicles. The after-treatment systems are preferred to be durable during the entirety of vehicle use. Indeed, the SCRF system must withstand the temperature resulting from the active regeneration of the particulate filter continuously. A 160,000 km vehicle aged SCRF catalyst which has endured more than 91 hours at temperatures superior to 600°C during the regeneration of the particulate filter was compared to an SCRF catalyst aged in the laboratory oven for 16 hours at 800°C with 10% H2O. The vehicle aged SCR has not only been exposed to the hydrothermal ageing generated by the diesel particulate regeneration but also has seen chemical elements from urea decomposition, soot accumulation, engine oil and fuel residues. In this paper, deeper comprehension of the behaviour the SCRF catalyst during vehicle ageing was exposed. It is evident that the loss of NOx activity is not only due to the regeneration of the particulate filter but also to the possible contamination from the urea injection and the elements present in the diesel fuel and engine oil. XRF results demonstrate that the concentrations of poisoning elements coming from the engine oil or fuel are concentrated mainly at the outlet of vehicle aged SCRF catalyst. Also, results reveal that the poisoning elements have affected the SCR activity of the vehicle aged SCRF catalyst. Finally, it was possible to establish a correlation between a 160,000 km vehicle aged SCRF catalyst and an equivalent SCRF aged for 16 hours at 800°C

Fe-ZSM-5 Catalyst Prepared by Ion Exchange from Fe(acac)3: Application into NH3-SCR of NO

International audienceIn this study, the introduction of iron into the ZSM-5 zeolite from a water/acetonitrile solution of iron(III) acetylacetonate was studied, using the exchange process. The water and acetonitrile are both necessary to prepare effective Fe-ZSM-5 catalysts in the selective catalytic reaction of NO by NH3. The role of water is to favour the formation of low charged iron cationic species and the role of acetonitrile is to limit the hydrolysis reaction. Using a water/acetonitrile mixture of 75/25 vol:vol, 92 % of the iron in solution is retained by the zeolite at ambient temperature. The resulting catalyst contains iron species, reducible at lower temperatures, and exhibits a better efficiency in the reaction of nitrogen monoxide reduction by ammonia

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