| 1. |
- Arnby, Karl, 1974, et al.
(författare)
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Characterization of Pt/γ-Al2O3 catalysts deactivated by hexamethyldisiloxane
- 2004
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 54:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The deactivation of alumina supported platinum and iron catalysts by hexamethyldisiloxane (HMDS) exposure has been investigated. Three catalysts (Pt/Al2O3, Fe/Al2O3 and Fe/Pt/Al2O3) were prepared and the influence of short- and long-term deactivation on the activity for oxidation of ethyl acetate was studied. The catalysts were characterized using BET, ICP-AES, XPS, SEM and CO chemisorption. The deactivation was found to proceed by deposition of silicon-species in form of silicate (SixOy) that block the active sites on the surface of the catalysts. The silicon seems to rather attach to platinum and iron sites than to the alumina surface. The Pt/Al2O3 catalyst was moderately deactivated by HMDS even though the silicate was blocking almost the entire platinum surface. Adding iron to the catalyst increased the tolerance towards HMDS as fewer Pt sites were blocked for the Fe/Pt/Al2O3 sample. The deactivation of the two platinum containing samples was reversible since the silicate could partly be removed from the Pt sites by regeneration whereby most of the activity was restored. However, for the Fe/Al2O3 sample the deactivation was more severe and irreversible.
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| 2. |
- Augustsson, Ola
(creator_code:cre_t)
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A catalyst for catalytic oxidation of hydrocarbons
- 2004
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- A catalyst having resistance towards Si and/or P deactivation in catalytic oxidation of organic hydrocarbons is disclosed. The catalyst comprises a catalytically inert support, a catalytically active layer of metallic Pt and/or Pd and deposited on said catalytically active layer at least one oxide ...
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| 3. |
- Bengtsson, Peter, 1974-, et al.
(författare)
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Evaluation of hydrocarbon emissions from heart- and sapwood of Scots pine using a laboratory-scale wood drier
- 2004
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Ingår i: Holzforschung. - : Walter de Gruyter. - 1437-434X .- 0018-3830. ; 58:6, s. 660-665
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Tidskriftsartikel (refereegranskat)abstract
- The subject of study is the emission of Volatile Organic Compounds (VOC) during the drying of wood. Heartwood and sapwood from Scots pine were dried at different temperatures (50, 70 and 90°C) in a laboratory kiln. The sampling method, Solid Phase Microextraction was used to collect the different volatile organic compounds during the drying. The gas chromatograph and mass spectrometer was used to identify and quantify the organic matter. The total hydrocarbons were measured with a flame ionization detector. Primarily, different monoterpenes were released during the drying process. 3-carene and α-pinene were most common and were also analytically quantified. The diterpene, pimaral, was found in an estimated large amount in the later stage of the drying process but was not exactly quantified. Large differences in both release behaviour and total amount of released hydrocarbon between heart- and sapwood were obtained. Emissions of VOC from heartwood were of a magnitude approximately three times higher than that from sapwood.
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| 4. |
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| 5. |
- Lillieblad, Lena, et al.
(författare)
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Boiler operation influence on the emissions of submicrometer-sized particles and polycyclic aromatic hydrocarbons from biomass-fired grate boilers
- 2004
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 18:2, s. 410-417
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Tidskriftsartikel (refereegranskat)abstract
- The emissions of particles, and gaseous compounds, into the ambient air from biomass-fired moving grate boilers were characterized under different boiler operation conditions. The boilers had a thermal capacity of similar to1 MW. The flue gas cleaning systems consisted of multicyclones for the removal of coarse particles. Dry wood fuel that consisted of shavings, wood chips, and sawdust from a local wood industry and wood pellets were fired at two plants. The influence of boiler load on the emissions was characterized. An electrical low-pressure impactor (ELPI) was used to determine the particle number concentration with high time resolution. A low-pressure cascade impactor (LPI) was utilized for the mass size distribution and the size-differentiated chemical composition. Elemental analysis of the fly ash collected on impactor substrates was made by particle-induced X-ray emission (PIXE) analysis. The concentration of elemental carbon under different load conditions was also measured. In addition, emissions of polycyclic aromatic hydrocarbons (PAHs) from the boiler that was operating on dry wood fuel were compared with PAH emissions from two different biomass-fired boilers (one was operating on forest residues and the other on pellets). The boiler load had little influence on the particle mass concentration of submicrometer-sized particles, which was in the range of 50-75 mg/m(3) (0 degreesC, 101.3 kPa, dry gas, 13% CO2). The total particle number concentration increased and the particle size decreased as the boiler load increased. The elemental analysis revealed that potassium and sulfur were the dominating components in the submicrometer size range, whereas potassium and calcium were major components in the coarse fraction. The PAH emissions between the three boilers varied by almost 3 orders of magnitude.
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| 6. |
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| 7. |
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| 8. |
- Moradi, Farokhbag, et al.
(författare)
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Deactivation of oxidation and SCR catalysts used in flue gas cleaning by exposure to aerosols of high- and low melting point salts, potassium salts and zinc chloride
- 2003
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier. - 0926-3373 .- 1873-3883. ; 46:1, s. 65-76
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Tidskriftsartikel (refereegranskat)abstract
- For the purpose of this deactivation study, Pt- and vanadia supported catalysts were used. The catalysts have been exposed to aerosol particles of inorganic salts, with high- or low melting points. The average diameter of the generated salt particle was kept constant at around 70 nm. The aerosol particle penetration depth for the samples exposed to potassium salt, was 1 μm as measured by scanning electron microscopy (SEM). The corresponding depth for zinc chloride salt (ZnCl2) was 5 μm. In order to validate the dependency of the catalytic decay rate to exposure temperature, Pt/wire-mesh catalyst was treated with potassium chloride at two temperatures, namely 300 and 500 °C. Pt/supported catalyst was also treated with ZnCl2 salt at 190 and 300 °C. The extent of decay was tested in the oxidation of CO for particle treated Pt/wire-mesh samples. The degree of the deactivation for the aerosol particle deactivated vanadia supported catalysts were also examined in the reduction of NOx. When the Pt/wire-mesh catalyst have been exposed to the poisons aerosol particles at higher temperature lead to the strongest deactivation in the CO oxidation. The Pt-supported catalysts that were treated with aerosol particles from potassium carbonate and potassium sulphate revealed a minor deactivation in the CO oxidation reaction. No significant deactivation was observed for the salt treated vanadia supported monolith samples used in selective catalytic reduction (SCR). A slight pronunced deactivation effect appeared when the vanadia supported wire-mesh catalysts were salt treated. Generally, the obtained results in this study do not indicate any correlation between the salt melting point and the degree of catalytic decay. The obtained results indicate that the exposure temperature during the deactivation procedure is the most critical parameter. Also, the higher the exposing temperature the stronger deactivated sample is produced.
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| 9. |
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| 10. |
- Pagels, Joakim, et al.
(författare)
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Characteristics of aerosol particles formed during grate combustion of moist forest residue
- 2003
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 34:8, s. 1043-1059
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of aerosol particles formed during combustion of moist forest residue were studied as a function of load in a I MW moving grate boiler and at almost full load in a similar larger 6 MW boiler. The coarse (1 mum < d(ae) < 10 mum) particle number and mass concentration increased by more than one order of magnitude and the fine particle mean diameter, total volume and mass decreased when the load was increased from 50% to 75%. The combined effects led to an increase in PM10 with increasing load. The number and mass concentration and the size distribution were similar in the two boilers when operated at high load. The dominant elements (Z > 12) were K, S and Cl in the fine mode and Ca, K and S in the coarse mode. The dominant ions in the fine mode were K+, SO42- and CO32-. The fine mode particles had hygroscopic growth factors of around 1.65 at RH=90%, with a deliquescence point at a relative humidity between 30% and 60%. It was assessed that K2CO3 is responsible for the low deliquescence point. Fine mode particles of a given dry diameter had similar chemical composition. (C) 2003 Elsevier Ltd. All rights reserved.
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