| 61. |
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| 62. |
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| 63. |
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| 64. |
- Persson, Katarina, et al.
(författare)
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Influence of co-metals on bimetallic palladium catalysts for methane combustion
- 2005
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 231, s. 139-150
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic combustion of methane has been investigated over eight different bimetallic palladium catalysts, comprising the co-metals Co, Rh, Ir, Ni, Pt, Cu, Ag, or An. The catalysts were characterized by TEM, EDS, PXRD, and temperature-programmed oxidation (TPO). It was found that a catalyst containing both Pd and Pt was the most promising, as it had a high activity that did not decline with time. The catalyst containing Pd and Ag was also a promising candidate, but its activity was slightly lower. For PdCo and PdNi, the co-metals formed spinel structures with the alumina support, with the result that the co-metals did not affect the combustion performance of palladium. For PdRh, PdIr, PdCu, and PdAg, the co-metals formed separate particles consisting of the corresponding metal oxide. These catalysts, except PdRh, showed a stable activity. For PdPt and PdAu, the co-metals formed alloys with palladium, and both catalysts showed a stable activity.
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| 65. |
- Persson, Katarina, et al.
(författare)
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Supported palladium-platinum catalyst for methane combustion at high pressure
- 2005
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 100, s. 479-483
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic combustion of methane over a supported bimetallic Pd-Pt catalyst and a monometallic Pd catalyst has been investigated experimentally. Two different reactor configurations were used in the study, i.e. a tubular lab-scale reactor working at atmospheric pressure and a high-pressure reactor working at up to 15 bar. The results showed that the bimetallic catalyst has a clearly more stable activity during steady-state operation compare to the palladium only catalyst. The activity of the bimetallic catalyst was slightly higher than for the palladium catalyst. These results were established in both test facilities. Further, the impact of pressure on the combustion activity has been studied experimentally. The tests showed that the methane conversion decreases with increasing pressure. However, the impact of pressure is more prominent at lower pressures and levels out for pressures above 10 bar
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| 66. |
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| 67. |
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| 68. |
- Johansson, Rebecka, et al.
(författare)
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Phenotypic modulation of cultured bladder smooth muscle cells and the expression of inducible nitric oxide synthase.
- 2004
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Ingår i: American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 286:4, s. 642-648
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Tidskriftsartikel (refereegranskat)abstract
- Phenotypic modulation of smooth muscle is associated with various pathological conditions, including bladder dysfunction. Cytoskeletal dynamics modulate the cell phenotype and were recently shown to be involved in regulation of inducible nitric oxide synthase ( iNOS). We tested the hypothesis that the cell differentiation status affects iNOS expression, and that iNOS is preferentially expressed in immature dedifferentiated bladder smooth muscle cells (BSMC). Isolated rat BSMC were put into different stages of differentiation by serum deprivation on laminin-coated plates in the presence of IGF-I and by interaction with Rho signaling and actin polymerization. iNOS and smooth muscle-myosin heavy chain (SM-MHC) protein expression were investigated with Western blot analysis. Our results showed iNOS protein in BSMC exposed to interleukin-1beta ( 2 ng/ml) + TNF-alpha ( 50 ng/ml). Growth of BSMC in serum-free medium on laminin in the presence of IGF-I increased SM-MHC expression, whereas cytokine-induced iNOS was inhibited. Disruption of F-actin with latrunculin B ( 0.5 muM) potentiated iNOS expression and decreased SM-MHC expression. Rho inhibition with C3 (2.5 mug/ml) increased iNOS expression, whereas SM-MHC expression was slightly decreased. Rho-kinase inhibition with Y-27632 ( 10 muM) mediated a decrease in iNOS and a slight increase in SM-MHC expression. In conclusion, the capacity of BSMC to express iNOS was negatively correlated to differentiation status measured as SM-MHC expression. Actin cytoskeletal dynamics and Rho signaling are involved in regulation of cytokine-induced iNOS expression in BSMC. Phenotypic changes and impairment in actin cytoskeleton formation may potentiate cytokine activation and in turn increase nitric oxide production in the bladder during disease.
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| 69. |
- Persson, Katarina
(författare)
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Bimetallic palladium catalysts for catalytic combustion of methane
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Catalytic combustion is a promising combustion technique in gas turbines, which results in ultra low levels of NOx, CO and unburned hydrocarbons. Due to the low combustion temperature achieved in catalytic combustion almost no thermal NOx is formed. The focus in this thesis will be on the first stage in a catalytic combustion chamber, i.e. the ignition catalyst. The catalyst used for this application is often a supported palladium-based catalyst due to its excellent activity for methane combustion. However, this type of catalyst has a serious drawback; the methane conversion decreases with time during operation. The unstable activity will result in increasing difficulties to ignite the fuel. The objective of the work presented in this thesis has been to improve the catalytic performance of supported palladium catalysts, with focus on stabilizing the methane conversion. The first part gives a general background to gas turbines and catalytic combustion. The second part concerns the monometallic palladium catalysts; their behaviour during methane combustion is addressed. The third part describes different bimetallic catalysts, which all have palladium as one of the active components. Results from the activity tests of methane combustion showed that it is possible to stabilize the activity by adding certain co-metals into the palladium catalyst. The morphology of the various bimetallic catalysts has been studied to gain a better understanding of the various combustion behaviours. Finally, the influence of pressure on the catalytic performance is evaluated. The catalysts were tested under more realistic conditions for gas turbines, with elevated pressure, in a high-pressure test facility with a 100 kW fuel power.
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| 70. |
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