| 1. |
- Kattge, Jens, et al.
(author)
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TRY plant trait database - enhanced coverage and open access
- 2020
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In: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Journal article (peer-reviewed)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 2. |
- Bergman, Susanna L., et al.
(author)
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In-situ studies of oxidation/reduction of copper in Cu-CHA SCR catalysts: Comparison of fresh and SO2-poisoned catalysts
- 2020
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In: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 269
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Journal article (peer-reviewed)abstract
- SO2-poisoning results in deactivation of Cu-CHA SCR under standard SCR conditions; however regeneration at 700 °C completely restores the SCR performance. To understand the nature of these effects, Cu-species in the fresh and poisoned catalysts were characterized by in-situ temperature-dependent time-resolved Cu K-edge X-ray absorption spectroscopy using the multivariate curve resolution alternating least squares (MCR-ALS) approach and continuous Cauchy wavelet transforms. The extracted chemically-meaningful reference spectra of Cu-species were analyzed by DFT-assisted XANES calculations. Cu-bisulfates were found as the most energetically favorable poisoned Cu-species. The response of Cu-species to a reducing environment differs in the fresh and SO2-poisoned catalysts. Differences in reducibility are related to the formation of quasi-linear Cu-complexes in the SO2-poisoned catalyst formed during heating in H2/He. Heating in H2/He leads to partial desulfurization of the poisoned catalyst. Cooling in H2/He after heating results in more facile formation of Cu-metal clusters in fresh catalyst than in SO2-poisoned.
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| 3. |
- Dahlin, Sandra
(author)
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Deactivation of emission control catalysts for heavy-duty vehicles : Impact of biofuel and lube oil-derived contaminants
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Catalytic emission control is used to reduce the negative impact of pollutants from diesel exhausts on our health and on the environment. For a heavy-duty truck, such a system consists of a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, and an ammonia slip catalyst (ASC). Due to greenhouse-gas induced global warming, it is necessary to decrease the emissions of such gases. Two strategies for this reduction are: 1) to produce engines that are more fuel efficient, 2) to use sustainably produced renewable fuels such as biodiesel and HVO. However, both these strategies may pose additional challenges for the emission control system: a colder exhaust due to the higher fuel-efficiency requires the use of highly active catalysts; catalyst deactivation related to impurities in biofuels, which requires very robust catalysts. The objective of this thesis was to study the impact of biofuel as well as lubrication oil-related contaminants on the performance of emission control catalysts (DOC and SCR catalysts) for heavy-duty diesel engines. The main focus has been on the low-temperature performance of V2O5-WO3/TiO2 (VWTi) and Cu-SSZ-13 SCR catalysts. Results from the project have shown that both Cu-SSZ-13 and VWTi catalysts capture and can be deactivated by phosphorus (P), while only the Cu-SSZ-13 is deactivated by sulfur (S). The degree of the P-related deactivation depends on the concentration in the catalyst, which depends on content of P in the exhaust and the exposure time, as well as the type of catalyst. S-deactivation of Cu-SSZ-13 is observed at low temperatures, where un-poisoned Cu-SSZ-13 are significantly more active than VWTi catalysts. As a contrast, the VWTi-performance can even be improved by sulfur; but alkali metals are severe poisons to VWTi catalysts. Partial performance-recovery of S-poisoned Cu-SSZ-13 can be obtained by exposing it to sulfur-free exhausts at elevated temperatures. The use of an upstream DOC, providing fast SCR conditions to the SCR catalyst, considerably improves the low-temperature performance of the VWTi, as well as sulfur-poisoned Cu-SSZ-13 catalysts. An upstream DOC also protects the SCR catalysts from phosphorus deactivation, as it can trap large amounts of P. However, if too much phosphorus is captured by the DOC, severe deactivation of this catalyst results, which lowers the overall performance of the exhaust treatment system. Insights from this project will guide the development of robust exhaust treatment systems for various applications. Additionally, it could aid in developing more durable emission control catalysts.
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| 4. |
- Englund, Johanna, 1988, et al.
(author)
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Deactivation of a Vanadium-Based SCR Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation
- 2020
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In: Catalysts. - : MDPI AG. - 2073-4344. ; 10:5
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Journal article (peer-reviewed)abstract
- We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NO(x)reduction performance in terms of standard, fast and NO2-rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NO(x)reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V4+/V(5+)ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V(4+)to V(5+)is partially hindered, blocking the redox cycle for parts of the active sites.
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| 5. |
- Wang, Aiyong, 1989, et al.
(author)
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A deactivation mechanism study of phosphorus-poisoned diesel oxidation catalysts: Model and supplier catalysts
- 2020
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In: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 10:16, s. 5602-5617
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Journal article (peer-reviewed)abstract
- The effect of phosphorus poisoning on the catalytic behavior of diesel oxidation catalysts was investigated over model and supplier monolith catalysts, i.e., Pd-Pt/Al2O3. The results of ICP and XPS from the vapor-phase poisoning over model catalysts suggested that the temperature of phosphorus poisoning affects both the overall content of phosphorus and the dispersion of phosphorus (i.e., inlet/outlet and surface/bulk). Phosphorus oxide (P2O5), metaphosphate (PO3-), and phosphate (PO43-) were identified in the poisoned model and supplier catalysts. The distribution of these species on poisoned model catalysts was highly dependent on the poisoning temperature, i.e., a higher temperature resulted in a higher concentration of PO43-. The outlets of the monoliths contained more PO43- and less P2O5 than the inlets. Both active sites and surface OH groups on model and supplier catalysts were contaminated upon phosphorus poisoning. It is found that PO43- had a stronger influence on the active sites than P2O5. One significant finding in this study is that the vapor-phase phosphorus poisoning could be a practical and cost efficient approach to simulate an accelerated aging/poisoning process.
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