| 1. |
- Abdulhamid, Hussam, 1974, et al.
(author)
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A combined transient in situ FTIR and flow reactor study of NOx storage and reduction over M/BaCO3/Al2O3 (M=Pt, Pd or Rh) catalysts
- 2006
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In: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 244:2, s. 169-182
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Journal article (peer-reviewed)abstract
- Transient in situ DRIFTS and flow-reactor experiments were performed to study the storage and reduction of NOX over Pt/BaCO3/Al2O3, Pd/BaCO3/Al2O3, and Rh/BaCO3/Al2O3 samples using CO, H-2, C3H6, or C3H8 as the reducing agent. The DRIFTS results show that exposure of the examined samples to NO2 results in the formation of nitrite/nitrate peaks over alumina and barium and that the reduction of stored NOX is influenced by the type of precious metal and reducing agent. Using CO as the reductant results in a lower NOX reduction capacity for Pt/BaCO3/Al2O3 compared with Pd- and Rh-based samples, whereas H-2 shows a significant ability to reduce the stored NOX on all samples examined. In addition, the reduction with CO and C3H6 proceeds via the formation of isocyanate species over both barium and alumina sites. The intensity of barium-isocyanate species for Pt/BaCO3/Al2O3 is significantly lower than the corresponding intensity for the Pd- and Rh-based samples, suggesting that the interaction between barium and Pt is lower than the corresponding interaction in the Pd/BaCO3/Al2O3 and Rh/BaCO3/Al2O3 samples. (c) 2006 Elsevier Inc. All rights reserved.
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| 2. |
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| 3. |
- Abdulhamid, Hussam, 1974, et al.
(author)
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In situ FTIR study of SO2 interaction with Pt/BaCO3/Al2O3 NOx storage catalysts under lean and rich conditions
- 2006
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In: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 241:1, s. 200-210
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Journal article (peer-reviewed)abstract
- The interaction of SO2 with Pt/BaCO3/Al2O3 NOx storage catalysts under lean and rich conditions in the absence and presence of water was investigated by means of in situ FTIR spectroscopy at 350 degrees C. For the lean condition (SO2 + O-2), surface and bulk barium sulfates were formed in addition to sulfites and surface sulfates on alumina. Pt does not appear to play an essential role in the formation of these species under lean conditions. In contrast, under reducing conditions (SO2 + H-2), Pt catalysed the reduction of SO2 with H-2 to form reduced sulfur species that accumulate on both Pt and barium sites. A subsequent treatment with NO2 resulted in the reduction of NO2 in the oxidation of these sulfur-containing species to form bulk barium sulfate instead of being stored over barium sites. Introducing water significantly affected sulfur trapping over the catalyst surface. During the lean conditions, the presence of water resulted in almost no surface barium sulfate formation. Meanwhile, the formation of bulk barium sulfate was increased, probably due to enhanced sulfate formation. However, the presence of H2O under reducing conditions resulted in significantly lower sulfur storage on both barium and alumina in comparison with humid lean exposure conditions.
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| 4. |
- Abdulhamid, Hussam, 1974, et al.
(author)
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Influence of the type of reducing agent (H2, CO, C3H6 and C3H8) on the reduction of stored NOX in a Pt/BaO/Al2O3 model catalyst
- 2004
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In: Topics in Catalysis. - 1572-9028 .- 1022-5528. ; 30-31:1-4, s. 161-168
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Journal article (peer-reviewed)abstract
- In this investigation, a comparative study for a NOx storage catalytic system was performed focusing on the parameters that affect the reduction by using different reductants (H2, CO, C3H6 and C3H8) and different temperatures (350, 250 and 150 degrees C), for a Pt/BaO/Al2O3 catalyst. Transient experiments show that H2 and CO are highly efficient reductants compared to C3H6 which is somewhat less efficient. H2 shows a significant reduction effect at relatively low temperature (150 degrees C) but with a low storage capacity. We find that C3H8 does not show any NOx reduction ability for NOx stored in Pt/BaO/Al2O3 at any of the temperatures. The formation of ammonia and nitrous oxide is also discussed.
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| 5. |
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| 6. |
- Abdulhamid, Hussam, 1974, et al.
(author)
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The reduction phase in NOx storage catalysis: Effect of type of precious metal and reducing agent
- 2006
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 62:3-4, s. 319-328
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Journal article (peer-reviewed)abstract
- The effect of different reducing agents (H2, CO, C3H6 and C3H8) on the reduction of stored NOx over PM/BaO/Al2O3 catalysts (PM = Pt, Pd or Rh) at 350, 250 and 150 °C was studied by the use of both NO2-TPD and transient reactor experiments. With the aim of comparing the different reducing agents and precious metals, constant molar reduction capacity was used during the reduction period for samples with the same molar amount of precious metal. The results reveal that H2 and CO have a relatively high NOx reduction efficiency compared to C3H6 and especially C3H8 that does not show any NOx reduction ability except at 350 °C over Pd/BaO/Al2O3. The type of precious metals affects the NOx storage-reduction properties, where the Pd/BaO/Al2O3 catalyst shows both a high storage and a high reduction ability. The Rh/BaO/Al2O3 catalyst shows a high reduction ability but a relatively low NOx storage capacity.
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| 7. |
- DAWODY, JAZAER, 1959, et al.
(author)
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Platinum dispersion measurements for Pt/BaO/Al2O3, NOx storage catalysts
- 2005
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In: Applied Catalysis A: General. - : Elsevier BV. - 1873-3875 .- 0926-860X. ; 296:2, s. 157-168
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Journal article (peer-reviewed)abstract
- In this investigation different experimental methods to determine the platinum dispersion of Pt/BaO/Al2O3 NOx storage catalysts are compared. The dispersion of platinum is determined independently using temperature programmed desorption of CO, dissociation of N2O, static volumetric CO and H2 chemisorption, dynamic CO chemisorption and transmission electron microscopy. For Pt/BaO/Al2O3, reproducible results are obtained when the platinum dispersion is determined from N2O dissociation, CO and H2 chemisorption. However, repeated CO-TPD experiments result in decreased amount of desorbed CO, which limits this method to determine platinum dispersion for Pt/BaO/Al2O3 samples. For Pt/Al2O3, similar values for platinum dispersion are obtained for all methods used in the study.In addition to the platinum dispersion investigations, the surface morphology of Pt/BaO/Al2O3 samples and the distribution of different elements are studied using SEM-EDS. The SEM-EDS analyses show that the platinum is evenly distributed over the entire sample surface, while the distribution of barium is more uneven.
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| 8. |
- Fridell, Erik, 1963, et al.
(author)
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Regeneration of NOx storage catalysts
- 2004
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In: 13th International Congress on Catalysis, Paris, France, July 11-16, 2004.
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Conference paper (peer-reviewed)
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| 9. |
- Malik, Azhar, et al.
(author)
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A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot
- 2011
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In: AEROSOL SCIENCE AND TECHNOLOGY. - : Taylor and Francis. - 0278-6826 .- 1521-7388. ; 45:2, s. 284-294
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Journal article (peer-reviewed)abstract
- Miniaturized detection systems for nanometer-sized airborne particles are in demand, for example in applications for onboard diagnostics downstream particulate filters in modern diesel engines. A soot sensor based on resistivity measurements was developed and characterized. This involved generation of soot particles using a quenched co-flow diffusion flame; depositing the particles onto a sensor substrate using thermophoresis and particle detection using a finger electrode structure, patterned on thermally oxidized silicon substrate. The generated soot particles were characterized using techniques including Scanning Mobility Particle Sizer for mobility size distributions, Differential Mobility Analyzer-Aerosol Particle Mass analyzer for the mass-mobility relationship, and Transmission Electron Microscopy for morphology. The generated particles were similar to particles from diesel engines in concentration, mobility size distribution, and mass fractal dimension. The primary particle size, effective density and organic mass fraction were slightly lower than values reported for diesel engines. The response measured with the sensors was largely dependent on particle mass concentration, but increased with increasing soot aggregate mobility size. Detection down to cumulative mass as small as 20-30 mu g has been demonstrated. The detection limit can be improved by using a more sensitive resistance meter, modified deposition cell, larger flow rates of soot aerosol and modifying the sensor surface.
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