| 51. |
- Eriksson, Amanda, et al.
(författare)
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Morphology drives water storage traits in the globally widespreadlichen genus Usnea
- 2018
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Ingår i: Fungal ecology. - : Elsevier. - 1754-5048 .- 1878-0083. ; 35, s. 51-61
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Tidskriftsartikel (refereegranskat)abstract
- Links between lichen morphology, internal/external water storage and distribution patterns are poorly known. We compared mass- (WC, % H2O) and area-based (WHC, mg H2O cm−2) hydration traits in seven pendent or shrubby Usnea species from oceanic to continental climates. All species held more external than internal water. Internal WHC and WC increased with specific thallus mass (STM, mg cm−2), while external WC decreased. Shrubby species had higher STM and total WHC than pendent ones. The continental Usnea hirta (shrubby) had the highest total and external storage; the suboceanic Usnea longissima (pendent) had the lowest internal storage. Morphology drives hydration traits and explains distributions of some Usnea species, but such traits did not distinguish oceanic from widespread species. Shrubby species maximize water storage and thus prolong hydration after rainfall events and/or hydration by dew. The low internal WHC in pendent species is likely an adaptation to frequent hydration in humid air.
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| 52. |
- Erkfeldt, Sara U, 1974, et al.
(författare)
-
Alumina-supported In2O3, Ga2O3 and B2O3 catalysts for lean NOx reduction with dimethyl ether
- 2012
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 117, s. 369-383
-
Tidskriftsartikel (refereegranskat)abstract
- Alumina-supported In2O3, Ga2O3 and B2O3 were investigated as catalysts for lean NOx reduction with DME as reducing agent and compared to pure Al2O3 and In2O3. The In2O3-promoted alumina catalysts showed the highest NOx conversion at low temperatures, although with a narrow temperature window. Pure In2O3, on the other hand, was inactive for NOx reduction with DME. The Ga2O3- and B2O3-promoted alumina catalysts gave the highest NOx conversion at higher temperatures, showed a temperature window similar to pure alumina, but were less sensitive to H2O inhibition. Possible reasons for these observations are discussed.
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| 53. |
- Erkfeldt, Sara U, 1974, et al.
(författare)
-
Influence of the reducing agent for lean NOx reduction over Cu-ZSM-5
- 2011
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 102:3-4, s. 547-554
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Tidskriftsartikel (refereegranskat)abstract
- A range of ethers, alcohols and alkanes were compared as reducing agents for NOx over a Cu-ZSM-5 lean NOx catalyst. The nature of the reducing agent was found to determine the degree of NOx reduction. Methanol and DME were virtually inactive as reductants over this catalyst, while higher ethers and alcohols showed high NOx conversion. A detailed study was performed to investigate the differences. Among the studied variables, the chemical structure of the reductant was found to be especially important. Despite having a lower reducing capacity than DME, ethylene glycol was active for NOx reduction. It is concluded that a C-C bond in the reducing agent is required for lean NOx reduction over Cu-ZSM-5. The absence of this bond in DME and methanol explains their low activity for NOx reduction over this catalyst.
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| 54. |
- Erkfeldt, Sara U, 1974, et al.
(författare)
-
Lean NOx Reduction with Various Bio-Diesels as Reducing Agents
- 2011
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 54:16-18, s. 1219-1223
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Tidskriftsartikel (refereegranskat)abstract
- Commercial Cu-ZSM-5- and Ag/Al2O3-based lean NOx catalysts were evaluated in a synthetic exhaust gas bench with the fuels RME, B30, B15, Agrodiesel 15, GTL, NExBTL, and MK1 as reducing agents. The influence of reductant was larger for Ag/Al2O3, albeit moderate, whereas the Cu-zeolite showed the highest NOx conversion at lower temperature for all alternative fuels tested.
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| 55. |
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| 56. |
- Erkfeldt, Sara U, 1974, et al.
(författare)
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Promoting Effect of Triglyme on Lean NOx Reduction Over Ag/Al2O3
- 2012
-
Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 142:2, s. 183-189
-
Tidskriftsartikel (refereegranskat)abstract
- The highly oxygenated hydrocarbon triethylene glycol dimethyl ether or triglyme (CH3O-(C2H4O-)(3)CH3) was found to efficiently reduce NOx under lean conditions over Ag/Al2O3, but gave a low NOx conversion over Cu-ZSM-5. Furthermore, triglyme showed an extraordinary promoting effect when added together with propene as reducing agent for NOx over Ag/Al2O3 at low temperature. This is most likely due to that triglyme promotes the activation of propene.
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| 57. |
- Esbjörnsson Elgh, Björn Neo, 1980, et al.
(författare)
-
A facile low-temperature synthesis of TiO2 nanoparticles with excellent polymorph control
- 2015
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Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 1573-4846 .- 0928-0707. ; 76:2, s. 395-401
-
Tidskriftsartikel (refereegranskat)abstract
- A facile low-temperature synthesis method of crystalline titanium dioxide nanoparticles has been developed, and the effect of temperature and acidity on polymorph selectivity has been systematically investigated. The crystal polymorph of titanium dioxide could be tuned by carefully controlling the condensation rate of titania. Conditions providing high condensation rate favoured the formation of the anatase and brookite phases, while lowering the condensation rate yielded higher rutile content. The reaction was found to proceed either in liquid state for reactions performed at low temperatures and high acidity or in a sol–gel manner for higher temperatures and lower acidity. The aggregation behaviour was found to be strongly affected by the employed synthesis conditions and by the crystal polymorph formed. The design of a facile low-temperature synthesis system with predictive control of polymorph selectivity is important for further development of titania-based materials for applications where type of polymorph is vital, such as photocatalytic and photonic.
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| 58. |
- Esbjörnsson Elgh, Björn Neo, 1980, et al.
(författare)
-
Controlling anatase and rutile polymorph selectivity during low-temperature synthesis of mesoporous TiO2 films
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:9, s. 3024-3030
-
Tidskriftsartikel (refereegranskat)abstract
- The polymorph selectivity of a microemulsion-based synthesis solution used for evaporation-induced self-assembly preparation of ordered mesoporous titania films was studied and unexpectedly found to differ from the polymorph selectivity obtained in the films prepared from the reaction solution. While titania nanocrystallites of the rutile phase form in the reaction solution prior to film formation, crystal growth was found to continue after evaporation-induced self-assembly of titania films, resulting in a shift in polymorph selectivity to the anatase phase. Evaporation of solvent and hydrochloric acid during film formation and subsequent aging increases the concentration of the titania precursor and possibly decreases the acidity of the prepared films, both effects that increase the rate of titania condensation, thus promoting the kinetically favoured formation of anatase. The rutile content of the films can be increased by employing an extended reaction time of the synthesis solution prior to the film formation showing that preformed rutile nanocrystallites are retained and incorporated into the titania film during its formation. The crystal growth in the films could be influenced by introducing hydrochloric acid vapour during aging of the formed films, resulting in a decreased formation of anatase nanocrystallites. Such control of the polymorph selectivity in mesoporous titania films is a major advancement towards the synthesis of ordered mesoporous titania films with photocatalytically optimal anatase/rutile ratios and towards the synthesis of pure rutile mesoporous titania.
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| 59. |
- Esbjörnsson Elgh, Björn Neo, 1980, et al.
(författare)
-
Controlling morphology, mesoporosity, crystallinity, and photocatalytic activity of ordered mesoporous TiO2 films prepared at low temperature
- 2014
-
Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 2:11, s. Art. no. 113313-
-
Tidskriftsartikel (refereegranskat)abstract
- Partly ordered mesoporous titania films with anatase crystallites incorporated into the pore walls were prepared at low temperature by spin-coating a microemulsion-based reaction solution. The effect of relative humidity employed during aging of the prepared films was studied using SEM, TEM, and grazing incidence small angle X-ray scattering to evaluate the mesoscopic order, porosity, and crystallinity of the films. The study shows unambiguously that crystal growth occurs mainly during storage of the films and proceeds at room temperature largely depending on relative humidity. Porosity, pore size, mesoscopic order, crystallinity, and photocatalytic activity of the films increased with relative humidity up to an optimum around 75%.
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| 60. |
- Esbjörnsson Elgh, Björn Neo, 1980, et al.
(författare)
-
Correlating Photocatalytic Performance with Microstructure of Mesoporous Titania Influenced by Employed Synthesis Conditions
- 2013
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:32, s. 16492-16499
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Tidskriftsartikel (refereegranskat)abstract
- Ordered mesoporous anatase films can be prepared at low temperature by evaporation-induced self-assembly of a microemulsion used to preform nanocrystals of titania. Here, we study the impact of storage time of the reaction solution on the structure and photocatalytic properties of such films. The formation of anatase crystallites was found to initiate and proceed during storage of the reaction solution prior to the preparation of the titania films as expected. However, in contrast to current understanding, we find that the main part of the anatase formation occurs during aging of the prepared films in a controlled relative humidity as a consequence of the rapidly increased concentration of precursor caused by the solvent evaporation during film preparation. Ordered mesoporous films were thus obtained for reaction solutions stored up to 48 h, and the crystallinity of the pore walls was found to increase with increased storage time. Interestingly, the anatase crystallite size was found to remain between 2 and 5 nm for all films prepared from reaction solutions stored up to 48 h showing that the increased crystallinity is due to an increased number density of crystallites. Films prepared from reaction solutions stored for longer times than 48 h were found to be mesoporous but with a disordered pore arrangement. These films contained crystallites with sizes up to 10 nm, apparently too large to arrange in a meso-ordered fashion in the liquid crystalline template. The photocatalytic activity of the films was evaluated for phenol degradation and found to be higher for films prepared from reaction solutions with longer storage times of the reaction solution ascribed to their larger degree of crystallinity and larger crystallite size. Interestingly, although the degree of mesoporosity is important in providing access to high specific surface area and facile transport of reactants and products to the catalyst surface, the degree of order of the mesopores was found to be of less importance for the photocatalytic performance. In addition, this work provides new generic insight into the formation mechanism of low-temperature surfactant-templated synthesis of ordered mesoporous and crystalline materials.
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