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- Creaser, Derek, 1966, et al.
(författare)
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Kinetic modeling of selective catalytic reduction of NOx with octane over Ag-Al2O3
- 2009
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 90:1-2, s. 18-28
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic model for the selective catalytic reduction of NOx with octane over a Ag-Al2O3 catalyst was developed. Analysis of experimental data indicated that feed concentrations of NO and hydrogen had significant effects on the NOx conversion, indicating that nitrates poisoned the catalytic sites and hydrogen’s role was to reduce nitrate species. As a result nitrate poisoning was a key component of the kinetic model. Also in the model, gas phase n-octane reacted with surface oxygen to form surface hydrocarbon intermediate species that could either reduce surface NO2 species to nitrogen or be fully oxidized. An additional site was included in the model on which various oxidation reactions occurred when the NOx reduction site was fully poisoned by nitrate species. The model also accounted for experimentally observed large temperature increases due to hydrogen oxidation, during hydrogen feed. The model was constructed from transient experimental data, both with and without hydrogen feed and from a range of reactant concentrations and temperatures.
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| 7. |
- Li, Qinghua, et al.
(författare)
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Synthesis and characterization of colloidal zoned MFI crystals
- 2005
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 78:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal zoned MFI crystals, i.e., continuous crystals with a compositional gradient resulting in a ZSM-5 core covered with a silicalite-1 shell, were synthesized by the addition of ZSM-5 seeds to a silicalite-1 synthesis solution. The effect of the surface aluminum content of the ZSM-5 crystals on the synthesis of the zoned MFI crystals was investigated using SEM, TEM, XPS and XRD. An acid treatment of the ZSM-5 seeds, which removed some of the aluminum at the surface, proved favorable for the synthesis of zoned MFI crystals.
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| 10. |
- Mosca, Alessandra, et al.
(författare)
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NO2 and N2 sorption in MFI films with varying Si/Al and Na/Al ratios
- 2009
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 120:3, s. 195-205
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Tidskriftsartikel (refereegranskat)abstract
- MFI crystals or films with controlled thicknesses and different Si/Al ratios were grown on seeded cordierite monoliths using a clear synthesis mixture with template or a template-free gel. The materials were analyzed by scanning electron microscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, X-ray photoelectron spectroscopy, thermogravimetric analysis and sorption experiments using N 2 or NO 2 adsorbates. The films were uniformly distributed over the support surface. As expected, the specific monolayer N 2 adsorption capacity (mol/g zeolite ) was constant and independent of film thickness. The specific molar NO 2 adsorption capacity was significantly lower than the specific molar monolayer N 2 adsorption capacity, indicating that NO 2 is adsorbed at specific sites rather than evenly distributed in a monolayer. A number of NO 2 adsorption sites with varying strengths were observed by TPD experiments. At 30 °C, the amount of adsorbed NO 2 in the MFI films increased with increasing Al and Na content as opposed to the N 2 adsorption capacity, which was independent of these parameters. At 200 °C, the adsorbed amount of NO 2 was lower than at 30 °C and apparently independent on Al concentration in the Na-MFI films. These results indicate that different mechanisms are involved in NO 2 adsorption. NO 2 may adsorb weakly on Na + cations and also react with silanol groups and residual water in the zeolite, the latter two results in more strongly bound species. Upon NO 2 adsorption, formation of NO was observed. This work represents the first systematic study of the effects of Al and Na content on NO 2 adsorption in MFI films. © 2008 Elsevier Inc. All rights reserved.
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