Cobalt Species Active for Nitrous Oxide (N2O) Decomposition within a Temperature Range of 300–600°C (original) (raw)
Related papers
Direct nitrous oxide decomposition with a cobalt oxide catalyst
Applied Catalysis A: General, 2010
The influence of individual components of the gas mixture, which is found directly downstream of the platinum-rhodium gauze in ammonia oxidation, i.e. nitric oxide, oxygen and water vapor, on the state of Co 3 O 4 under high-temperature nitrous oxide decomposition conditions has been determined. A variety of characterization techniques, such as: nitrogen physisorption, XRD, XPS and TG-DTA-MS, was applied.
Reaction Kinetics, Mechanisms and Catalysis, 2018
The influence of co-fed gases (O 2 , CO 2 , CH 4 , and H 2 O) on the N 2 O decomposition over (Co or Fe)-BETA and (Co, Fe)-ZSM-5 catalysts prepared by ion exchange method was investigated. Co 2+ ions and oxo dinuclear Co species were identified in Co-ZSM-5 and Co-BETA catalysts. Isolated and oligomeric Fe 3+ species in cationic sites and Fe 2 O 3 particles were found on surface of the Fe-ZSM-5 and Fe-BETA catalysts. Cobalt catalysts were more actives than iron catalysts for the direct decomposition of N 2 O. Conversion of N 2 O over Fe-BETA and Fe-ZSM-5 was remained stable when co-fed O 2 , CO 2 , and CH 4 , but decreases with water vapor. However, Co-BETA and Co-ZSM-5 showed much larger reaction rate for N 2 O decomposition and were very stable when co-fed O 2 , CO 2 , CH 4 , and especially H 2 O. The results showed that the higher CH 4 consumption during N 2 O reaction over Co-BETA and Co-ZSM-5 was due to CH 4 combustion. Keywords N 2 O decomposition • Co-fed gases • Iron species • Cobalt species • ZSM-5 zeolite • BETA zeolite
Catalysts
Nitrous oxide (N2O), produced from several human activities, is considered a greenhouse gas with significant environmental impacts. The most promising abatement technology consists of the catalytic decomposition of N2O into nitrogen and oxygen. Many recently published papers dealing with N2O catalytic decomposition over Ni-substituted Co3O4 are related to the treatment of N2O concentrations less than 2 vol% in the feed stream. The present work is focused on developing catalysts active in the presence of a gaseous stream richer in N2O, up to 20 vol%, both as powder and in structured configurations suitable for industrial application. With this aim, different nickel-cobalt mixed oxides (NixCo1−xCo2O4) were prepared, characterized, and tested. Subsequently, since alumina-based slurries assure successful deposition of the catalytic species on the structured carrier, a screening was performed on three nickel-cobalt-alumina mixed oxides. As the latter samples turned out to be excellent ca...
Applied Catalysis B: …, 2000
CoO x /ZrO 2 samples, prepared by adsorption from cobalt solutions or by impregnation, were characterized by means of DRS, XPS, FTIR and volumetric CO adsorption. In samples prepared by adsorption the maximum Co-uptake was 2.2 atoms nm −2. XPS evidenced cobalt dispersion up to about 2 atoms nm −2. DRS evidenced Co 3 O 4 above 2 atoms nm −2. Volumetric CO adsorption, combined with FTIR, showed that cobalt was highly dispersed on the ZrO 2 surface in samples containing 0.4 and 0.9 atoms nm −2. The selective catalytic reduction (SCR) of NO with C 3 H 6 in the presence of excess O 2 was studied on samples containing up to 4.8 Co atoms nm −2 with a reactant mixture containing NO=4000 ppm, C 3 H 6 =2000 ppm, O 2 =2%. Isolated cobalt in CoO x /ZrO 2 containing up to about 2 atoms nm −2 is active and selective for NO reduction in the presence of excess O 2. Aggregated cobalt present as Co 3 O 4 in more concentrated samples is active for C 3 H 6 combustion, thus rendering the relevant CoO x /ZrO 2 samples non-selective.
A study on N2O catalytic decomposition over Co/MgO catalysts
Journal of Hazardous Materials, 2009
a b s t r a c t Different oxide supported cobalt catalysts were prepared by co-precipitation method and tested for the decomposition of nitrous oxide. Co/MgO with cobalt loading of 15% showed the best activity and a 100% N 2 O conversion was obtained at temperatures higher than 700 K. The active phase of cobalt species in Co/MgO catalysts was Co 3 O 4 highly dispersed in the matrices of MgO, based on XRD and XPS results as well as the kinetic analysis. The existence of NO, O 2 and H 2 O in reaction system showed different negative effects on N 2 O decomposition. Nevertheless, a 100% N 2 O conversion could be achieved at 800 K under simulated conditions of tail gas from nitric acid plant. Moreover, Co/MgO catalyst exhibited quite good durability and no obvious activity loss was observed in the 100 h stability test.
Effect of Zinc on the Structure and Activity of the Cobalt Oxide Catalysts for NO Decomposition
Catalysts
Co4−iZniMnAlOx mixed oxides (i = 0, 0.5 and 1) were prepared by coprecipitation, subsequently modified with potassium (2 or 4 wt.% K), and investigated for direct catalytic NO decomposition, one of the most attractive and challenging NOx abatement processes. The catalysts were characterised by atomic absorption spectroscopy, powder X-ray diffraction, Raman and infrared spectroscopy, temperature-programmed reduction by hydrogen, the temperature-programmed desorption of CO2 and NO, X-ray photoelectron spectroscopy, scanning electron microscopy, the work function, and N2 physisorption. The partial substitution of cobalt increased the specific surface area, decreased the pore sizes, influenced the surface composition, and obtained acid-base properties as a result of the higher availability of medium and strong basic sites. No visible changes in the morphology, crystallite size, and work function were observed upon the cobalt substitution. The conversion of NO increased after the Co subs...
Co-ZSM-5 catalysts for N2O decomposition
Applied Catalysis B: Environmental, 1998
The catalytic properties of cobalt containing ZSM-5 zeolites prepared by various methods were compared. TPR, XRD, N 2 -BET, XPS, FTIR and UV±vis spectroscopy were used for characterizing the samples. Well-dispersed cobalt oxide-like species and isolated Co 2 ions in charge compensation positions were found in the zeolite. Catalysts prepared using a single step cation exchange method showed high activity for N 2 O decomposition in a temperature range 300±5508C, in the presence of 0± 5% O 2 , and high stability in the presence of 10% H 2 O to the feed. UV±vis spectra and TPR experiments indicated the presence of some cobalt oxides, not detected by DRX, in a Co-ZSM-5 catalyst containing 3.76 wt% Co, prepared by a solid-state reaction procedure. The N 2 O conversion over this catalyst was strongly affected by addition of both O 2 and H 2 O to the feed. #