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| 3. |
- Larsson, Mikael, 1967, et al.
(författare)
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The effect of reaction conditions and time on stream on the coke formed during propane dehydrogenation
- 1996
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517. ; 164:1, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- Pt/Al2O3and Pt–Sn/Al2O3catalysts, coked during propane dehydrogenation, have been studied using temperature-programmed oxidation (TPO). Time on stream, temperature, and reaction gas composition have been varied. Three different peaks were identified from the TPO profiles on the Pt–Sn catalyst and attributed to different types of coke; coke on and in the vicinity of the metal, coke on the carrier, and graphitic coke on the carrier. The amounts of these types were related to reaction conditions. The formation of the coke belonging to the first two peaks in the TPO profiles increases with temperature and partial pressure of propene. Hydrogen, on the other hand, suppresses the formation. The amount of coke that can be attributed to the third peak increases with temperature and propane partial pressure. A model is discussed where a minor part of the coke deactivates the catalyst. This coke is formed in parallel with the coke that is seen in the first two peaks in the TPO experiments. The graphitic coke formed on the carrier is not formed through this route. The experiments with different time on stream revealed that the first peak reached a constant level after about 15 h, while the second one still increased. Hydrogen was very efficient in preventing coke formation and deactivation but could not remove coke already formed on the catalyst. The hydrogenolysis and cracking mechanisms during the propane dehydrogenation are also discussed.
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| 4. |
- Olsson, Louise, 1974, et al.
(författare)
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A kinetic study of oxygen adsorption/desorption and NO oxidation over Pt/Al2O3 catalysts
- 1999
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Ingår i: Journal of Physical Chemistry B Materials. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 103:47, s. 10433-10439
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory tests and kinetic modeling were carried out in order to provide kinetic input data to a systematic investigation of the mechanism of nitrogen oxides (NO,) storage in catalysts used for lean-burn engines. In particular, we present a kinetic model of the NO oxidation to NO2 over a Pt/Al2O3 model catalyst for the temperature range 250-450 degrees C. Since the oxygen behavior at atmospheric pressure is critical for such a model, we have also studied the adsorption/desorption of oxygen by temperature-programmed desorption (TPD) experiments. The experiments show that oxygen starts to desorb at about 300 degrees C. Furthermore, the NO oxidation was studied in a temperature ramp with NO and oxygen in the gas feed. The data from this experiment and the above-determined values for the oxygen adsorption/desorption were used to construct a kinetic model for the NO oxidation. Finally, the model was validated with some transient experiments with either NO or NO2 and different oxygen concentrations in the gas feed. We found a good agreement between these experiments and the model.
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| 5. |
- Thormählen, Peter, 1969, et al.
(författare)
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Catalytic oxidation of CO in cold start emissions
- 1998
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Ingår i: 2nd World Congress on Environmental Catalysis as part of Topical Conference on Environmental Catalysis and Reaction Engineering in Miami Beach, Florida, USA, November 15-20, 1998..
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Konferensbidrag (refereegranskat)
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| 6. |
- Thormählen, Peter, 1969, et al.
(författare)
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Low temperature CO oxidation over platinum and cobalt oxide catalysts
- 1999
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 188:2, s. 300-310
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Tidskriftsartikel (refereegranskat)abstract
- The low-temperature CO oxidation activity of three monolith catalysts (Pt/Al2O3, CoOx/Al2O3, and Pt/CoOx/Al2O3) has been studied. The catalytic properties of the catalysts were investigated by using different temperature-programmed methods: CO-TPD (desorption), TPO (oxidation), TPR (reduction), TPReaction, and CO light-off. Preoxidized cobalt-oxide-containing catalysts were found to be highly active for CO oxidation at temperatures as low as 200 K,and at these low temperatures the activity is independent of the presence of platinum. The catalytic properties and how they relate to the surface reaction kinetics are discussed.
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