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Cu(Fe)-containing zeolites are promising catalysts for biomimetic functionalization of light hydrocarbons. Catalysts with various copper states have been elaborated and studied in the peroxide oxidation of methane to methanol and formic acid. ICP-AES, UV–vis DR, EPR, NH3-TPD, H2-TPR, and N2 adsorption techniques were used for the characterization of the Cu(II) states, the textural, acidic and redox properties of the catalysts. The prepared zeolites contained the following Cu species: (1) isolated Cu2+ ions, (2) square planar binuclear oxo/hydroxo complexes ([Cu2(OH)2]2+) in the zeolite channels, (3) CuO- and/or Cu(OH)2-like clusters and nanoparticles on the zeolite external surface. UV–vis DR spectroscopy also was used for studying the ability of different Cu-ZSM-5 to form Cu peroxocomplexes with H2O2. Three types of peroxocomplexes were detected. These were terminal Cu–OOH originated from the isolated Cu2+ ions, binuclear Cu(II) with a terminal OOH group and the binuclear Cu(II) with a bridging OO-group formed from the Cu-species with extra lattice oxygen. 1H and 13C NMR analysis revealed the formation of methylhydroperoxide, formaldehyde, and CO2 as side products during peroxide oxidation of methane. Two pathways of methane oxidation with hydrogen peroxide involving both binuclear Cu-species with extra-lattice oxygen and isolated Fe-sites and/or oligomer oxo-clusters of Fe(III) ions were supposed. [ABSTRACT FROM AUTHOR]

The effect of NH4OH/Cu2+ in a copper-acetate solution on the properties of ion-exchanged Cu-ZSM-5 catalysts in the selective catalytic reduction of NO by NH3 (NO-NH3 SCR) has been studied. The temperature programmed desorption of ammonia (NH3-TPR) on Cu-ZSM-5 and the ammonia adsorption-desorption dynamics at 75-300 °C were studied to identify and quantify the nature of acid sites and ammonia desorption heat of Cu-ZSM-5. The Cu-ZSM-5 catalysts containing Cu-structures with extra-lattice oxygen were active in the low-temperature SCR, whereas those with isolated Cu2+ ions were active in the high-temperature SCR. It was shown that Cu-structures with extra-lattice oxygen were generated during the ion exchange of H-ZSM-5 with a water-ammonia solution of copper-acetate where the NH4OH/Cu2+ ratio was in the range of 6-15. Isolated Cu2+ ions were produced in the ion-exchange mode with the ammonia-free solution. [ABSTRACT FROM AUTHOR]

A series of ZSM-5 samples with similar SiO2/Al2O3 ratio was synthesised using different aluminum sources and by including varying amounts of calcium hydroxide during the synthesis. The samples were subsequently ion-exchanged with Cu-ions, and evaluated with respect to deNOx activity in the absence and presence of water. The choice of aluminum source and the presence of calcium hydroxide during the zeolite synthesis affected the lean deNOx activity of Cu-ZSM-5. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction of nitrogen oxides with ammonia as the reducing agent was studied using Fourier transform infrared (FTIR) spectroscopy. The adsorbed species found on a Cu-ZSM-5 powder during exposure to NO, NO2 or NH3 was compared to the adsorbed species identified during SCR conditions. A blocking effect caused by ammonia at 175 °C was investigated by a stepwise increase of the ammonia concentration, and the spectra indicated that the formation of nitrites or nitrates decreased as surface coverage of ammonia increased. No such effect was observed at 350 °C, since the oxidation of ammonia results in very low ammonia coverage. The effect of changes in the NO to NO2 ratio was also studied at 350 °C, and the species identified during SCR reaction indicated that the enhanced activity at equimolecular amounts of NO and NO2 possibly involves gas phase components as well as adsorbed species. [ABSTRACT FROM AUTHOR]

The structural stability at high temperatures of both Cu-exchanged SAPO-34 and CuAPSO-34 with isomorphously substituted copper ions has been investigated. SAPO-34 undergoes an extensive crystallinity loss upon copper ion exchange. The CuAPSO-34 framework showed good hydrothermal stability, as reflected in its surface area and X-ray diffraction pattern after ageing treatments. This catalyst exhibited good activity in N2O decomposition even when the reaction was run in the presence of H2O or after ageing treatment under H2O vapor at 600 °C for 80 h which, conversely, led to a drastic loss of activity of Cu-ZSM-5. [ABSTRACT FROM AUTHOR]

The method of preparation of modified Cu-substituted zeolite DeNOx catalysts washcoated on monolith ceramics has been developed. Non-modified and modified monolith catalysts were tested in DeNOx reaction with propane. It was shown that the catalyst modified by cerium and containing titania together with H-ZSM-5 and Al2O3 in the washcoating layer demonstrates high level of activity, and its resistance during multiple cycles of poisoning by sulfur compounds and water at 400 and 500°C is also high. [ABSTRACT FROM AUTHOR]

NO decomposition was studied at different temperatures on copper-exchanged ZSM-5, AlMCM-41 and NbMCM-41 molecular sieves. Cu-ZSM-5 zeolites presented the highest activity. SO2 poisoning was also performed and Cu–NbMCM-41 was found to be more resistant. IR results of NO and SO2 coadsorption either at room temperature or at 573 K show evidence that sulfate formation occurred at 573 K and partially prevented NO adsorption on Cu2+ in square planar structure in Cu-ZSM-5. Sulfation of Cu–NbMCM-41 was quite low due to niobium incorporated into the lattice. By contrast, niobium present in the extra-lattice position in CuNb-ZSM-5 and CuNb–AlMCM-41 did not protect the catalyst from sulfation. H2-TPR results suggested that sulfates were formed on copper sites. IR spectra after treatment under SO2 + O2 at 673 K indicated that sulfated species were covalently bonded, their structure varying according to the nature of the support. [ABSTRACT FROM AUTHOR]