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A series of Co-Mn-Al mixed oxide catalysts with different Cs contents (0.5-4.6 wt%) was prepared by calcination of Co-Mn-Al hydrotalcite (Co:Mn:Al = 4:1:1), followed by impregnation by cesium salt (CsNO, CsCO) using the pore filling method. Chemical analysis, N sorption, temperature programmed reduction (TPR)-H, temperature programmed desorption (TPD)-CO and TPD-NH and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. All prepared catalysts were tested for NO catalytic decomposition in inert gas and in the presence of oxygen, water vapor and nitric oxide. The influence of Cs salts used for catalyst preparation and cesium content on catalyst activity were studied. A significant increase in catalytic activity with increasing amount of cesium promoter was observed without respect to the Cs precursor. The strong promotional effect of cesium is electronic in nature and is discussed in term of changes in surface composition and catalyst reducibility. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZnS nanoparticles deposited on montmorillonite forming ZnS-MMT nanocomposite. [•] Catalyst for photocatalytic decomposition of N2O. [•] Better catalytic performance in fluidized bed than fixed bed. [•] Presence of water vapor inhibited N2O decomposition by photocatalysis. [•] Presence of water vapor improved N2O photolysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] N2O conversion decreased in order Cs>Rb>K>Na=Co4MnAlO x >Li. [•] Alkali metals modified electronic properties and acid–base function of surface. [•] Promotional effect of alkali metals is connected with their ionization potential. [•] Charge transfer and a decrease in binding energies was caused by alkali metals. [•] Good stability of K-promoted Co–Mn–Al mixed oxide catalyst in real waste gas [Copyright &y& Elsevier]

Abstract: TiO2 and Ag-TiO2 (0.05, 0.25 and 1wt% of Ag) thin films were prepared by the sol–gel method. The prepared films were characterized using SEM-EDAX, XRD, Raman spectroscopy, atomic force microscopy and UV–Vis spectrometry. Photocatalytic decomposition of N2O was performed in an annular batch reactor illuminated with an 8W Hg lamp (254nm wavelength). The photoreactivity of Ag-TiO2 increases with the Ag amount to 0.25wt% Ag. Further increase of Ag loading to 1wt% Ag did not change N2O conversion. The Ag particles deposited on the TiO2 surface can act as electron–hole separation centers. The presence of water vapor and oxygen in the reaction mixture slightly improved N2O conversion. [Copyright &y& Elsevier]

Volatile organic compounds (VOCs) are mostly toxic and carcinogenic substances. The technologies for cleaning of exhaust gases containing the constant concentrations of VOCs are commercially available. However, if concentration fluctuations occur in the range of several orders of magnitude, it can cause problems for a subsequent gas cleaning e.g. by thermal or catalytic oxidation. The balancing of VOC concentrations in flue gases can be a great simplification of a subsequent reduction of VOC emissions from sources with time-variable concentrations. Paint shops belong to the important sources of VOCs and are an example of periodic processes with time-variable concentrations of VOCs. One of the main aims was to experimentally determine the conditions, such as the minimal mean residence time, to balance out the fluctuations of inlet VOC concentrations at the laboratory model. After that, the verification of obtained results was applied for a real exhaust gas from a paint shop. [ABSTRACT FROM AUTHOR]

Abstract: Paper deals with design of pilot reactor for low temperature N2O decomposition in off-gases from HNO3 production. Pseudo-homogeneous one-dimensional model of an ideal plug flow reactor was used for modeling of N2O decomposition in a laboratory fixed bed reactor filled with grains or pellets of a Co–Mn–Al mixed oxide catalyst. Increase in inlet pressure up to 0.6MPa did not influence the effective diffusion coefficient, but improved the achieved N2O conversion. Based on the laboratory data of N2O decomposition over Co–Mn–Al mixed oxide pellets, catalyst bed of 3400kg was estimated for target 90% N2O conversion (30000m3 h−1 of exhaust gases from HNO3 plant containing 0.1molar% N2O, 0.01molar% NO, 0.01molar% NO2, 3molar% H2O, 5molar% O2) at 420°C and 600kPa inlet pressure. [Copyright &y& Elsevier]

Abstract: A series of Co–Mn–Al mixed oxides was prepared by a thermal treatment of coprecipitated layered double hydroxide precursors modified with different amount of potassium (0–3wt.%) and tested in N2O catalytic decomposition. Chemical analysis, XRD, XPS, surface area measurements, SEM, and contact potential difference measurements were used for bulk and surface characterization of the catalysts. The Co–Mn–Al mixed oxide with 1.1–1.8wt.%K exhibited the highest conversion of N2O and minimum value of the catalyst surface work function. Direct correlation between the work function values and the activity of the catalysts demonstrates that N2O decomposition over K-promoted Co–Mn–Al mixed oxides proceeds via the cationic redox mechanism and controlled modification of surface electronic properties provides the essential factor for catalyst optimization. [Copyright &y& Elsevier]

Abstract: The present work deals with adsorption/desorption process of NO on activated carbon. The goal of the experiments was to determine under which conditions is the activated carbon bed able to damp down the concentration fluctuations of NO in the gas entering the bed. It was found out that the residence time necessary to balance out the input concentration fluctuations of NO increases along with the average concentration of NO. The minimum mean residence time of 3–9min was found as necessary to level the average NO concentration ranging from 357 to 1428ppm. The decisive parameters for the extent of attenuation are discussed in the terms of linear driving force model for fixed-bed adsorber dynamics. [Copyright &y& Elsevier]

Abstract: Catalytic decomposition of N2O over calcined Co–Mn–Al layered double hydroxide (LDH) modified with slight amount of alkali (Li, Na, K), rare earth (La, Ce), or noble metals (Pd, Pt) was studied. Two methods of promoter addition were applied: impregnation of LDH-related Co–Mn–Al mixed oxide by a promoter-containing solution and incorporation of the promoter during coprecipitation of the LDH precursor. The method of preparation affected the reducibility of the obtained mixed oxide catalysts but its effect on the surface area (with the exception of a cerium-contained sample) and N2O conversion was less evident. The modification of the Co–Mn–Al mixed oxide with K or Na increased N2O conversion, while no effect or a decrease in the N2O conversion was observed over the other examined catalysts. Alkali metals act as electron promoters; therefore, the differences in catalytic activity may be related to changes of oxygen-transition metal bond strength. The Co–Mn–Al mixed oxides with 1.8wt% K exhibited a high catalytic activity even under the simultaneous presence of O2, H2O and NOx. The laboratory stability test revealed maintenance of the beneficial effect for 360h. [Copyright &y& Elsevier]

Abstract: A series of catalysts was prepared by thermal treatment (500°C) of the coprecipitated Co–Mn–Al layered double hydroxide (Co:Mn:Al molar ratio of 4:1:1) doped with various amount of potassium (0–3wt%). Obtained spinel-like mixed oxides were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurements, temperature-programmed H2 reduction, and temperature-programmed CO2 and NH3 desorption. The prepared catalysts were tested for N2O decomposition to determine the effect of K addition on the catalytic activity in the presence of O2, NO x and H2O. An optimum K content of ca. 0.9–1.6wt% was found to achieve a high catalytic activity in the presence of O2 and H2O, while the non-modified Co–Mn–Al mixed oxide was the most active catalyst in the presence of O2 and NO x . The addition of potassium to the Co–Mn–Al mixed oxide apparently results in a modification of both electronic properties of active metals and acid-base function of the catalyst surface. [Copyright &y& Elsevier]

Abstract: Pure TiO2 anatase particles with a crystallite diameters ranging from 4.5 to 29nm were prepared by precipitation and sol–gel method, characterized by X-ray diffraction (XRD), BET surface area measurement, UV–vis and scanning electron microscopy (SEM) and tested in CO2 photocatalytic reduction. Methane and methanol were the main reduction products. The optimum particle size corresponding to the highest yields of both products was 14nm. The observed optimum particle size is a result of competing effects of specific surface area, charge–carrier dynamics and light absorption efficiency. [Copyright &y& Elsevier]

Abstract: The N2O catalytic reduction by carbon monoxide over Co–Mn–Al calcined hydrotalcite was studied. The effect of oxygen and that of CO/N2O molar ratio on the rate of N2O decomposition was examined. CO strongly enhanced N2O conversion when O2 was absent in the feed gas. In the presence of oxygen, carbon monoxide acts as a non-selective reductant thereby inhibiting N2O destruction. Continuing excess of CO over N2O without presence of O2 led to a very slow reduction of the catalyst, which caused noticeable N2O conversion decrease with progressing catalyst reduction. The simultaneous reduction of N2O by CO and direct N2O decomposition took place when CO was limiting reactant (CO/N2O<1) but only at temperatures, at which the direct decomposition is possible without presence of reductant. Simple reduction was observed when reactants ratio was CO/N2O≥1. [Copyright &y& Elsevier]

Abstract: Kinetics of N2O decomposition over catalyst prepared by calcination of Co–Mn hydrotalcite was examined in integral fixed-bed reactor () at various N2O and O2 initial partial pressure at temperature range of 330–450°C. Kinetic data were evaluated by linear and non-linear regression method, 15 kinetic expressions were tested. Based on the obtained results a redox model of N2O decomposition was proposed. At low pressures of O2, adsorbed oxygen is formed by the N2O decomposition; the N2O chemisorption is considered as the rate-determining step. On the contrary, at high O2 pressure it could be assumed that adsorbed oxygen species appear as a result of O2 adsorption and the Eley–Rideal mechanism is the rate determining. N2O decomposition is well described by the 1st rate law at N2O and O2 concentrations typical for waste gases. [Copyright &y& Elsevier]

Abstract: The Co–Mn–Al mixed oxide catalysts were prepared by thermal decomposition of hydrotalcite-like precursors with Co/(Mn+Al) molar ratio of 2 and Mn/Al molar ratio varying from 0 to 2. The obtained catalysts were characterized by powder XRD, XPS, BET surface area and TPR measurements and tested in N2O decomposition. The most active Co4MnAl catalyst exhibited both the optimum Mn/Al molar ratio and the optimum amount of components reducible in the temperature region in which the catalytic reaction proceeds (350–450°C). [Copyright &y& Elsevier]

Abstract: The decomposition of the nitrous oxide over catalysts prepared by thermal decomposition of Ni-(Mg)-MIII (MIII =Al or Mn) hydrotalcite-like precursors was studied. The mixed oxides obtained at 500°C were characterized using various techniques—X-ray diffraction (XRD), BET surface area measurements, temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR). The N2O decomposition was performed in the temperature range 300–450°C, at 0.05–0.15mol% inlet N2O concentrations; oxygen and nitrogen dioxide were added in some runs. The Ni-Al and Mg-Mn catalysts exhibited high catalytic activity but those containing both transition metal cations (i.e. Ni and Mn) were less active. Their lower activity was interpreted in terms of different oxidation states of manganese and nickel in the mixed oxide systems. Up to a certain value of oxygen pressure the presence of oxygen in the reaction mixture caused an inhibition of the reaction rate, while at higher oxygen pressures the N2O conversion remained nearly constant. The correlation between the observed oxygen inhibition and the proposed N2O decomposition mechanism as well as the relationship between the observed activity and the amount of reducible components determined from TPR experiments are discussed. [Copyright &y& Elsevier]

Abstract: Co/Mg-Mn/Al hydrotalcite-like compounds with Co:Mg:Mn:Al molar ratios of 4:0:2:0, 2:2:2:0, 2:2:1:1, 4:0:1:1, 4:0:0:2 and 2:2:0:2 were prepared by coprecipitation method. The mixed oxides obtained by calcination at 500°C were characterized using various techniques (XRD, IR, BET surface area measurements, TPD and TPR). The activities of calcined hydrotalcites were tested for N2O decomposition in an inert gas, and in the presence of oxygen and water vapor as well. Among the catalysts screened, the catalyst prepared from Co hydrotalcite containing Al and Mn as the trivalent cation showed the highest activity, which was retained in the presence of oxygen but was inhibited by water vapor. Redox properties of the catalysts play an important role in the reaction and optimum extent of reduction is necessary for achievement of the highest catalytic activity. [Copyright &y& Elsevier]

Abstract: Pure TiO2 and various silver-enriched TiO2 powders were prepared by the sol–gel process controlled in the reverse micellar environment. The catalysts were tested in CO2 photocatalytic reduction and characterized by X-ray diffraction (XRD), nitrogen adsorption measurement and UV–vis. Methane and methanol were the main reduction products. The yield of methane and methanol increases when modifying the TiO2 by silver incorporation is caused by two mechanisms: up to 5% of Ag in TiO2 the Ag impurity band inside the TiO2 bandgap decreases the absorption edge and increases so the electron–hole pair generation, above 5% of Ag in TiO2 Ag metallic clusters are formed in TiO2 crystals with Shottky barrier at the metal–semiconductor interface, which spatially separates electron and holes and increases their lifetime (decreases probability of their recombination). [Copyright &y& Elsevier]

Cordierite monoliths coated with ceria-zirconia supporting cobalt oxide were prepared, examined in the deep oxidation of ethanol and NO decomposition, and compared with pelletized commercial cobalt oxide catalyst. Interaction of CoO with ceria-zirconia washcoat led to formation of CoO particles with slightly worse structure ordering resulting in better reducibility than that observed for the commercial CoO catalyst. In oxidation of ethanol, activity of the CoO-containing monoliths was comparable with that of pelletized cobalt oxide catalyst with nearly seven times higher content of active components. However, conversions of NO over the monolith catalysts were lower. Nevertheless, incorporation of CoO onto ZrO-CeO washcoat increased rate of both catalytic reactions, i.e., NO decomposition and deep ethanol oxidation. Graphical Abstract: [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-based mixed oxides with alkali promoters were tested for NO decomposition. • Calcination conditions (temperature, time) strongly influence the stability of catalysts. • Deactivation caused by alkali metals vaporization occurs during first 50 h. • Rearrangement of surface species takes place below the temperature of alkali desorption. Co-Mn-Al mixed oxide and Co 3 O 4 catalysts with alkali metal promoters (K, Cs) were tested for direct NO decomposition with the aim to determine their activity and stability. The catalysts were prepared by coprecipitation with subsequent impregnation by alkali metal salts and characterized by AAS, MP-AES, XRD, N 2 physisorption and species-resolved thermal alkali desorption (SR-TAD). Long-term experiments of NO catalytic decomposition performed above the temperature of alkali metal desorption showed slow deactivation which has not yet been reported by other authors, since only short laboratory tests of NO catalytic decomposition have been presented. The reason for the observed deactivation was identified as volatilization of alkali metal promoters from the catalyst surface, which was revealed by SR-TAD and chemical analysis of alkali metals. Measurements conducted below the temperature of alkali metal desorption yielded an increase in NO conversion during the initial period of measurement, which can be explained by rearrangement of surface species. [ABSTRACT FROM AUTHOR]

Co-Mn-Al mixed oxides (Co:Mn:Al molar ratio of 4:1:1) were prepared by three different methods (i) calcination of hydrotalcite-like precursors (Co-Mn-Al-HT-ex), (ii) calcination of corresponding nitrates (Co-Mn-Al-nitr) and (iii) calcination of the product of mechanochemical reaction of Co, Mn, Al nitrates with NH 4 HCO 3 (Co-Mn-Al-carb). The catalysts were characterized by AAS, XRD, SEM, Raman spectroscopy, FTIR, TPR-H 2 , TPD-N 2 O, step response experiments and tested for N 2 O decomposition in inert gas and simulated waste gas from HNO 3 production. Different conditions of synthesis led to the formation of spinel-like phase with different structural properties leading to different catalytic activity. N 2 O conversions decreased with decreasing specific surface area in order Co-Mn-Al-carb > Co-Mn-Al-HT-ex > Co-Mn-Al-nitr. The synthesis from carbonate precursor led to the less ordered structure manifested itself in smaller crystallite size causing (i) higher surface area (ii) better reducibility and (iii) increase of mean (Co + Mn) valence. However, its highest catalyst activity was determined by the lowest bond strength of active site − oxygen while specific surface area and amount of active sites per unit surface were not decisive parameters for activities order. [ABSTRACT FROM AUTHOR]

The K-doped Co-Mn-Al mixed oxide deN2O catalyst was prepared by calcination of Co-Mn-Al layered double hydroxide, subsequent impregnation with KNO3, and shaping into tablets of 5 mm × 5 mm. Tablets were tested for N2O decomposition in pilot scale reactor connected at the bypassed tail gas from the nitric production plant downstream of the SCR NOx/NH3 catalyst with the aim to perform kinetic measurements. Special attention was paid to study the changes in the catalytic performance, which was monitored using both the long-term catalytic test and the comparison of physical-chemical properties of the fresh and used catalyst. The changes in the surface composition, caused by the time-on-stream operation for 112 days in the pilot reactor, provided stable catalytic performance; average value of N2O conversion of 90 ± 6% at 450 °C was kept (GHSV = 11 000 m³ mbed-3 h-1). The obtained kinetic data were applied in modeling of a full-scale reactor for the N2O emissions abatement and can be used for estimation of the amount of the catalyst necessary for obtaining required N2O conversion in the target plant. [ABSTRACT FROM AUTHOR]

Mixed oxide catalysts containing Co, Mn, and Al in a molar ratio of 4:1:1 were prepared by heating precursors obtained by a mechanochemical method (when appropriate nitrates were milled with ammonium hydrogen carbonate) or by coprecipitation. The precursors and related mixed oxides obtained at 500 °C were characterized by XRD, TG/DTA, UV-Vis, IR spectroscopy, TPR and NH-TPD, and were tested for activity and selectivity in ammonia oxidation to NO. The precursors prepared by mechanochemical reaction showed very similar phase composition to that of the coprecipitated product. All examined mixed oxide catalysts were active in the low temperature range (100 % conversion of NH was achieved at 250 °C), but the selectivity was sensitive to catalyst composition and the method used for preparation of the precursors. Non-modified Co-Mn-Al mixed oxide catalyst obtained from the coprecipitated precursor exhibited higher selectivity towards NO formation than the calcined product prepared by the mechanochemical method. Modification of the latter mixed oxide catalysts with cesium promoter (1 wt%) significantly increased their selectivity to nitrous oxide. The yield of NO at 250 °C was close to 100 %. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of micro-mesoporous zeolitic materials by non-templating method [•] Deposition of zeolite nanoseeds on the SBA-15 surface [•] N2O conversion over Fe-modified micro-mesoporous zeolitic catalysts [Copyright &y& Elsevier]

Abstract: ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS–CTA–MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation–reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB. [Copyright &y& Elsevier]

Abstract: Catalysts with various Ag loading (0.7–5.2wt%) in the powder form were prepared by the sol–gel process controlled in the reverse micellar environment. X-ray diffraction (XRD), nitrogen adsorption measurement, UV–vis and elemental analysis were employed for characterization of catalysts. Effect of various silver loadings on photocatalytic activity of TiO2 catalysts in N2O photocatalytic decomposition was studied. Photocatalytic decomposition of N2O was performed in annular batch reactor illuminated with 8W Hg lamp (254nm wavelength). Reaction kinetic corresponds to first-order reaction rate which is in agreement with plausible reaction mechanisms. The highest N2O conversion of 77% after 24h was reach over TiO2 modified by 3.4wt% Ag. The Ag metal clusters could provoke a decrease in the electron–hole recombination rate. [Copyright &y& Elsevier]

Abstract: A series of Co–Mn–Al/TiO2 catalysts with different Co+Mn loading (5–24wt.%) was prepared by impregnation of TiO2 support. Bulk Co–Mn–Al mixed oxides were prepared by different methods. The prepared catalysts were characterized by chemical analysis, surface area measurement, temperature programmed techniques (TPR, TPD) and tested for N2O catalytic decomposition. TiO2 acted only as a catalytic support and did not contribute to the catalytic activity. The N2O conversion over TiO2-supported Co–Mn–Al catalysts was increasing with Co+Mn loading, and was proportional to the amount of easily reducible components. Comparing the catalysts with identical amount of active components, the highest catalytic activity was achieved on the calcined precursors having carbonates in their molecules (layered double hydroxides Co–Mn–Al-HT-ex and Co–Mn–Al-carb), the lowest one on the calcined Co–Mn–Al nitrates due to the lower surface area, less advantageous porous structure and worse reducibility. [Copyright &y& Elsevier]

Abstract: Five pure and silver-enriched TiO2 catalysts with various Ag loading (0–5.2wt.%) were prepared by the sol–gel technique from nonionic surfactant Triton X-114, cyclohexane, water (or water solution of AgNO3) and metal precursor. Calcination at 400°C for 4h was applied to convert prepared gels to pure anatase crystalline powders. Effects of silver doping on titanium photocatalyst properties were evaluated by nitrogen physical adsorption, X-ray diffraction, elemental analysis, transmission electron microscopy, Raman spectroscopy, TGA analysis and UV–vis spectroscopy. Two“green” photocatalytic reactions were chosen for photocatalytic experiments: photocatalytic reduction of CO2 and photocatalytic oxidation of 4-chlorophenol (4-CP) water solution. Both photocatalytic reactions were carried at mild conditions (room temperature and ambient pressure or pH 7). The activity of titania catalysts for photocatalytic reduction of CO2 was evaluated individually with respect to various UV lamps (254 and 365nm). The UV lamp with wavelength in the range 250–420 with highest maxima at 254 and 365nm was used for photocatalytic oxidation of 4-CP. The dependence of the photocatalytic activity on increase of Ag content was evaluated for both reactions and compared with the photocatalytic activity of Degussa catalyst P25. [Copyright &y& Elsevier]

Abstract: The kaolinite/TiO2 composite was prepared using thermal hydrolysis of kaolinite/titanyl sulphate suspension and characterized by XRFS, XRPD, SEM and N2 physical adsorption. Its photocatalytic properties were evaluated by photocatalytic reduction of CO2 by water and compared with commercial TiO2 photocatalyst Degussa P25. Results showed that the yields of CO2 photocatalytic reduction products methane and methanol were higher over a kaolinite/TiO2 composite than over commercial TiO2 (Degussa P25) in spite of smaller proportion of TiO2 in the composite. Introducing of TiO2 nanoparticles into the kaolinite structure caused a decrease of anatase crystallite size. Kaolinite can also change acidobasic properties of catalyst surface, inhibit the recombination of electron–hole pairs and prevent the formation of TiO2 aggregates in suspension. These facts can contribute to the observed higher photocatalytic efficiency of kaolinite/TiO2 compared to the commercial TiO2 photocatalyst. [Copyright &y& Elsevier]

• The role of oxygen in NO decomposition was studied over Co-Mg-Mn-Al mixed oxide. • Transition metals in octahedral coordination represent sites for NO chemisorption. • Potassium ensures NO oxidation to surface nitrite intermediates. • Oxygen inhibition was ascribed to formation of stable surface nitrate species. Co-Mg-Mn-Al mixed oxide with or without K was prepared and characterized by XPS, TPR H 2 , TPD NO, TPD O 2 and TPD NO+O 2. NO decomposition was performed over catalyst activated in different atmosphere (N 2 , He, O 2). Presence of oxygen during activation changed the course of surface stabilization but did not affect NO conversion achieved at steady state. O 2 desorbed as a reaction product does not affect the reaction rate for NO inlet concentration of 400 - 8000 ppm, but presence of O 2 in inlet gas mixture (0.05 - 3 mol.%) has significant inhibiting effect. Transition metals in octahedral coordination represent sites for NO chemisorption, while potassium ensures NO oxidation to surface nitrites, which are indispensable reactive species. Oxygen desorption was the slowest reaction step, while N 2 desorption was fast. Oxygen inhibition was ascribed to oxidation of NO* species on the octahedral Co3+ and Mn3+ to more stable surface nitrates making NO* species as limiting reactant. [Display omitted] [ABSTRACT FROM AUTHOR]

• Co 3 O 4 and Co 4 MnAlO x deposited on the SiC open-cell foams by different methods. • Testing for N 2 O catalytic decomposition for the first time. • Morphology and structural properties of active phase were effected by synthesis conditions. • Foam with Co 4 MnAlO x revealed higher N 2 O conversion than with Co 3 O 4. • Active phase on the foam support could be good alternative to conventional catalyst bed. Supported Co 3 O 4 and Co 4 MnAlO x mixed oxides were prepared by deposition on the SiC open-cell foams by wet impregnation and suspension methods and characterized by AAS, BET, XRD, SEM, TEM, TPR-H 2 , XPS and nitrogen adsorption methods. Prepared supported catalysts as well as active phase Co 3 O 4 and Co 4 MnAlO x in grain form prepared from parent solutions were tested for nitrous oxide decomposition. Catalytic activity of grain active phase was governed by methods of preparation; Co 3 O 4 and Co 4 MnAlO x prepared by suspension method were significantly more active than those from solutions for impregnation method. Suspension method provided active phase with higher surface areas and sites with better reducibility, both of these factors contributed to higher N 2 O conversions. In contrast to this, N 2 O conversions over supported catalysts were dependent more on chemical composition of active phase than on method of preparation. Both catalysts containing Co 4 MnAlO x mixed oxide revealed higher conversion of N 2 O than catalysts containing Co 3 O 4. STEM analysis of the most active Co 4 MnAlO x prepared by suspension method showed (i) segregation of Co 3 O 4 nanocrystals of cuboctahedral shape containing (100) and (111) facets (this segregation was confirmed also by XPS and TPR-H 2) and (ii) Co-Mn-Al oxide nanoparticles with very small un-faceted grains assembled into elongated fiber-like agglomerates were observed by STEM. [ABSTRACT FROM AUTHOR]