Alkali poisoning of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3

[EN] Fe (2 wt%)-Cu (1.5 wt%)-ZSM-5 SCR catalyst contacted 1.5 wt% of Na and 1.8 wt% of K in order to simulate poisoning by species more specifically contained in exhaust gases from exhaust gases of diesel engines and power plants. Poisoning agents do not cause loss of surface area nor pore occlusion. XRD and SEM results showed that alkali metals introduction did not deteriorate the crystallinity and morphology of zeolite crystals. However, a significant loss of surface acidity was observed upon alkali-poisoned catalysts causing a dramatic deactivation of the NH3-SCR of NO reaction. Na-doped catalyst showed higher low-temperature SCR activity, while potassium has a stronger deactivation effect on Fe-Cu-ZSM-5 than sodium beyond 400 degrees C.Jouini, H.; Mejri, I.; Martinez-Ortigosa, J.; Cerrillo, JL.; Petitto, C.; Mhamdi, M.; Blasco Lanzuela, T.... (2022). Alkali poisoning of Fe-Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3. Research on Chemical Intermediates. 48(8):3415-3428. https://doi.org/10.1007/s11164-022-04768-93415342848

A New Way for Silver Alumina Catalyst Preparation

International audienceA new preparation of silver supported alumina catalysts, with highly dispersed and stable silver particles, is reported. The preparation, performed from a mixture of silver oxide and alumina, consists simply of heating this mixture under an oxidizing gas containing awater vapour concentration higher than 5.0 mol% in a temperature range between 903-948 K

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

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

Selective catalytic reduction of nitrogen oxides over a modified silicoaluminophosphate commercial zeolite

International audienceNitrogen oxides (NOx: NO, NO2) are a concern due to their adverse health effects. Diesel engine transport sector is the major emitter of NOx. The regulations have been strengthened and to comply with them, one of the two methods commonly used is the selective catalytic reduction of NOx by NH3 (NH3-SCR), NH3 being supplied by the in-situ hydrolysis of urea. Efficiency and durability of the catalyst for this process are highly required. Durability is evaluated by hydrothermal treatment of the catalysts at temperature above 800°C. In this study, very active catalysts for the NH3-SCR of NOx were prepared by using a silicoaluminophosphate commercial zeolite as copper host structure. Characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature programmed desorption of ammonia (NH3-TPD) showed that this commercial zeolite was hydrothermally stable up to 850°C and, was able to retain some structural properties up to 950°C. After hydrothermal treatment at 850°C, the NOx reduction efficiency into NH3-SCR depends on the copper content. The catalyst with a copper content of 1.25wt.% was the most active. The difference in activity was much more important when using NO than the fast NO/NO2 reaction mixture

Hydrothermal activation of silver supported alumina catalysts prepared by sol-gel method: Application to the selective catalytic reduction (SCR) of NOx by n-decane

International audience2 wt% Ag- and 2 wt% Ag-1.5 wt% Nb mesoporous alumina catalysts were prepared by non-hydrolytic sol-gel process. Silver accessibility is enhanced by calcination at high temperature. By performing calcination in presence of water vapour, silver particles are well dispersed and interact more strongly with the alumina surface and activity in n-decane-SCR of NOx is greatly improved. Moreover, the addition of niobium in the starting material leads to more efficient catalysts and enhances mainly the low temperature activity

Non-hydrolytic Sol-Gel Preparation of Silver Alumina Based Catalysts for the HCSCR of NOx

International audienceThe preparation of Ag/Al2O3 catalysts by nonhydrolytic sol-gel process leads to highly efficient HCdeNOx materials thanks to the silver ability to diffuse toward the surface. The presence of niobium as co-catalyst, with a Nb content comprised between 1 and 3 wt%, enhances the NO reduction efficiency at low temperatures (< 250 °C)

A highly efficient silver niobium alumina catalyst for the selective catalytic reduction of NO by n-decane

International audienceAgNb/Al2O3 prepared by a nonhydrolytic sol-gel process is a highly efficient catalyst for NOx removal through selective catalytic reduction by hydrocarbons (HC-SCR). This result shows that the HC-SCR process remains a challenging method for lean engine DeNOx

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

Effect of acidic components (SO42- and WO3) on the surface acidity, redox ability and NH3-SCR activity of new CeO2-TiO2 nanoporous aerogel catalysts: A comparative study

International audienceSelective catalytic reduction (SCR) of nitrogen oxide (NO) by ammonia (NH 3) was studied in this work over new sulfate (SO 4 2-) or tungsta (WO 3) modified CeO 2-TiO 2 aerogel catalysts. The catalytic systems were elaborated via sol gel method then characterized by: XRD, N 2-Physisorption at 77 K, DRUV-vis, NH 3-TPD and H 2-TPR. It was revealed that the nature of acidic components influences differently the texture, surface oxygen concentration, acidity, reducibility and NH 3-SCR activity of new Ce-based catalysts. Hence, the incorporation of sulfate modifies the nature of Ce species, improves their dispersion through the Ce-SO 4 2interactions and, particularly, generates new strong acid sites which display superior catalytic performance at high temperature NO reduction (NO conversion into N 2 > 90 % between 450 and 500 °C over CeO 2-TiO 2-SO 4 2catalyst). However, the addition of tungsta affects slightly the surface acidity of CeO 2-TiO 2 catalyst but it induces the creation of more reactive surface oxygen and new redox sites at its surface (mainly due to the existence of W-Ce interactions) leading to highly active WO 3-CeO 2-TiO 2 system for the low temperature NH 3-SCR reaction with above 90 % NO conversion into N 2 between 320 and 400 °C