| 1. |
- Acke, Filip, 1968, et al.
(författare)
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Comparison between ammonia and propene as the reducing agent in the selective catalytic reduction of NO under lean conditions over Pt black
- 1999
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Ingår i: Applied Catalysis B: Environmental. - 0926-3373 .- 1873-3883. ; 20:2, s. 133-144
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity of Pt black towards the reduction of NO under lean conditions is examined. Ammonia and propene are tested as reducing agents. A scrambling between nitrogens is observed in the formation of N2 and N2O for NH3. For C3H6, a reduction of NO to mainly N2O is found. A minor formation of N2 is only observed for high C3H6 concentrations. The role of NO2 as an intermediate in the reduction of NO is examined by using a feed gas mixture containing NO2, as well as by studying the catalytic activity of Pt black towards the NO-O2 and NO2-O2 reactions. No effect is observed in the maximum NOx conversion for C3H6 whereas for NH3 a decreased activity is found. The presented results are put in perspective of the reaction mechanisms proposed in the literature.
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| 2. |
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| 3. |
- Acke, Filip, 1968, et al.
(författare)
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Influence of the platinum-support interaction on the direct reduction of NOx under lean conditions
- 1998
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Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 116, s. 285-294
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Tidskriftsartikel (refereegranskat)abstract
- Catalysts containing Pt supported on SiC, Al2O3 and ZSM-5 were prepared and studied for NOx reduction by C3H6 in Oz excess under transient (temperature ramps) and steady-state conditions. The maximum NOx reduction activity in the heating ramp experiments was similar for Pt/SiC and Pt/ZSM-5, while Pt/Al2O3 showed higher maximum activity. Both N-2 and N2O formation was observed for all catalysts, although the respective amounts varied with the investigated system. Highest Nz selectivity was observed for Pt/Al2O3. When the NOx reduction activity was studied under steady-state conditions the activity of Pt/Al2O3 decreased substantially (mainly due to a loss in N-2 production). Pt/ZSM-5 became somewhat more selective towards Na production whereas the activity and selectivity of Pt/SiC remained at about the same values as far the heating ramp experiments. Adsorbed species on the surface of the different catalysts were investigated using in-situ FTIR in order to obtain information about the reaction mechanisms. The adsorption of species on Pt/SiC was negligible, while a number of absorption bands were observed for Pt/Al2O3 (N and C containing species, and -NCO) and Pt/ZSM-5 (HC).
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| 4. |
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| 5. |
- Acke, Filip, 1968, et al.
(författare)
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Role of adsorbed surface oxygen in the adsorption of NO on alkaline earth oxides and Pt-promoted CaO surfaces
- 1999
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Ingår i: Journal of Physical Chemistry B Materials. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 103:6, s. 972-978
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Tidskriftsartikel (refereegranskat)abstract
- Adsorbed surface oxygens are formed on CaO, SrO, and BaO during exposure to N2O, and their presence is shown to affect the room-temperature NO adsorption. Information about the adsorbed intermediates is contained in the desorption products and in the desorption temperatures during the subsequent heating ramp in Ar. The presence of adsorbed oxygen species increases the total amount of adsorbed NO for CaO and BaO substrates, whereas for SrO the adsorbed intermediate is stabilized. Two NO desorption peaks are found for CaO and SrO, one at low and one at high temperature. The former is assigned to adsorbed NO, whereas the latter is assigned to adsorbed -NO2 and/or -NO3 species. NO adsorption as -NO2 and/or -NO3 species finds evidence in the corresponding O2 desorption. Only one NO desorption peak is found for BaO. This NO desorption peak disappears in the absence of preadsorbed surface oxygens. O2 desorption is observed, even in the absence of any preadsorbed surface oxygens, for CaO and SrO substrates. This suggests NO bond dissociation upon NO adsorption. The effect of the promotion of CaO by Pt has also been investigated. The respective desorption profiles are similar to those for the unpromoted CaO with preadsorbed surface oxygens, although the amounts are significantly increased.
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| 6. |
- Acke, Filip, 1968, et al.
(författare)
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Selective reduction of NO by HNCO over Pt promoted Al2O3
- 1998
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 179:2, s. 528-536
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Tidskriftsartikel (refereegranskat)abstract
- The activity of Pt supported on gamma-Al2O3 towards HNCO oxidation and reduction of NO by HNCO under oxygen excess is examined under transient conditions (temperature ramps between 100 and 500 degrees C). Formation of N-2, N2O, NO, and NO2 is observed. Isotope labelled (NO)-N-15 is used to show the scrambling of nitrogens in N-2 ((NN)-N-14-N-15) and N2O ((NNO)-N-14-N-15). Adsorbed species on the surface are characterised by in-situ FTIR spectroscopy in order to obtain information on reaction intermediates. Adsorbed NNx species are discussed as important intermediates in the N-2 and N2O formation. The absence of Pt results in a delay in HNCO ignition and only a small N2O formation is observed.
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| 7. |
- Acke, Filip, 1968, et al.
(författare)
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Zeolite supported Pt catalysts for reduction of NO under oxygen excess: a comparison of C3H6, HNCO and NH3 as reducing agents
- 1999
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Ingår i: Applied Catalysis B: Environmental. - 0926-3373 .- 1873-3883. ; 20:3, s. 235-242
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the zeolite SiO2/Al2O3 ratio of ZSM-5 supported Pt catalysts on the reduction of NO under oxygen excess has been investigated. The activity and selectivity of three reducing agents were compared, i.e. C3H6, HNCO and NH3. The maximum NO reduction with both C3H6 and HNCO as the reducing agent was affected by the SiO2/Al2O3 ratio of the support. Although no effect was observed on the maximum NO reduction for NH3, the yields of Nz and N2O were affected. The results are put in perspective of reaction mechanisms proposed in the literature.
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| 8. |
- Amberntsson, Annika, 1974, et al.
(författare)
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Sulphur dioxide deactivation of NOx storage catalysts
- 1999
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Ingår i: Studies in Surface Science and Catalysis. - 0167-2991. ; 126, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- The influence of sulphur dioxide on the NOx storage performance of a Pt-Rh/BaO/Al2O3 model catalyst has been investigated. Addition of 2.5-25 vol.-ppm SO2 to a synthetic lean-burn exhaust, containing NO, C3H6, O2 and Ar, caused deactivation of the NOx storage function of the catalyst. The rate of deactivation was found to be proportional to the exposure of SO2. This effect is seen for temperatures between 250 and 450 degrees C. Together with in situ FTIR measurements, this leads to the conclusion that sulphur accumulates in the NOx storage component of the catalyst during the exposure. Furthermore, SO2 also inhibits the oxidation capacity of the catalyst during lean periods as is observed by a decreased NO oxidation activity. The presence of SO2 also reduces the reduction capacity of the catalyst under rich periods, which leads to an increased N2O formation and a decreased NO conversion.
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| 9. |
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| 10. |
- Dahl, Leif, et al.
(författare)
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Catalytic behavior and characterization of (CuO)1-z(La2O3)z/2 based catalysts deposited on γ-Al2O3 and prepared in situ with 0.0≤z≤1.00 with and without addition of Pd
- 1996
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Ingår i: Catalysis Letters. - 1572-879X .- 1011-372X. ; 37:1-2, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- (CuO)(1-z)(La2O3)(z/2) based catalysts with 0.0 less than or equal to z less than or equal to 1.0 supported on gamma-Al2O3 have been prepared in situ and the phases formed have been identified by XRD, SEM and TEM/EDS studies. The catalyst with z = 0.5 exhibited the best catalytic activity for oxidation of CO (T-50 = 295 and 390 degrees C with degrees of conversions of 93 and 92% at 450 degrees C under rich and lean conditions, respectively) and C3H6 (291 and 414 degrees C; 93 and 83%) and reduction of NO (405 degrees C; 60 and 0%). This catalyst contained appreciable amounts of the perovskite phase LaAl1-xCuxO3 and the enhanced catalytic properties are ascribed to the presence of this phase. Addition of Pd to this catalyst implied that the degree of conversion of NO increased and that the light-off temperatures for all involved gas species decreased. Ageing experiments revealed that LaAl1-xCuxO3 decomposed and that Cu containing Pd particles were formed during this procedure which in turn deteriorated the catalytic properties of the catalyst.
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