| 1. |
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| 2. |
- Nayeri, Moheb, 1979, et al.
(författare)
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Surface effects on the structure and mobility of the ionic liquid C(6)C(1)ImTFSI in silica gels
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 10:30, s. 5618-5627
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Tidskriftsartikel (refereegranskat)abstract
- We report on how the dynamical and structural properties of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (C(6)C(1)ImTFSI) change upon different degrees of confinement in silica gels. The apparent diffusion coefficients of the individual ions are measured by H-1 and F-19 pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy, while the intermolecular interactions in the ionogels are elucidated by Raman spectroscopy. In addition, the local structure of the ionic liquid at the silica interface is probed by solid-state NMR spectroscopy. Importantly, we extend this study to a wider range of ionic liquid-to-silica molar ratios (x) than has been investigated previously, from very low (high degree of confinement) to very high (liquid-like gels) ionic liquid contents. Diffusion NMR measurements indicate that a solvation shell, with a significantly lower mobility than the bulk ionic liquid, forms at the silica interface. Additionally, the diffusion of the C(6)C(1)Im(+) and TFSI- ions decreases more rapidly below an observed molar ratio threshold (x < 1), with the intrinsic difference in the self-diffusion coefficient between the cation and anion becoming less pronounced. For ionic liquid molar ratio of x < 1, Raman spectroscopy reveals a different conformational equilibrium for the TFSI- anions compared to the bulk ionic liquid, with an increased population of the cisoid isomers with respect to the transoid. Concomitantly, at these high degrees of confinement the TFSI- anion experiences stronger ion-ion interactions as indicated by the evolution of the TFSI- characteristic vibrational mode at similar to 740 cm(-1). Furthermore, solid-state 2D Si-29{H-1} HETCOR NMR measurements establish the interactions of the ionic liquid species with the silica surface, where the presence of adsorbed water results in weaker interactions between Si-29 surface moieties and the hydrophobic alkyl protons of the cationic C(6)C(1)Im(+) molecules.
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| 3. |
- Wassén, Sophia, 1979, et al.
(författare)
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Probe diffusion in phase-separated bicontinuous biopolymer gels
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 10:41, s. 8276-8287
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Tidskriftsartikel (refereegranskat)abstract
- Probe diffusion was determined in phase separated bicontinuous gels prepared by acid-induced gelation of the whey protein isolate-gellan gum system. The topological characterization of the phase-separated gel systems is achieved by confocal microscopy and the diffusion measurements are performed using pulsed field gradient (PFG) NMR and fluorescence recovery after photo-bleaching (FRAP). These two techniques gave complementary information about the mass transport at different time- and length scales, PFG NMR provided global diffusion rates in the gel systems, while FRAP enabled the measurements of diffusion in different phases of the phase-separated gels. The results revealed that the phase-separated gel with the largest characteristic wavelength had the fastest diffusion coefficient, while the gel with smaller microstructures had a slower probe diffusion rate. By using the diffusion data obtained by FRAP and the structural data from confocal microscopy, modelling through the lattice-Boltzmann framework was carried out to simulate the global diffusion and verify the validity of the experimental measurements. With this approach it was found that discrepancies between the two experimental techniques can be rationalized in terms of probe distribution between the different phases of the system. The combination of different techniques allowed the determination of diffusion in a phase-separated biopolymer gel and gave a clearer picture of this complex system. We also illustrate the difficulties that can arise if precautions are not taken to understand the system-probe interactions.
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| 4. |
- Achour, Abdenour, 1980, et al.
(författare)
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Evaluation of kraft and hydrolysis lignin hydroconversion over unsupported NiMoS catalyst
- 2023
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 453
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic hydroconversion of Kraft and hydrolysis lignins was for the first time compared in a batch reactor over an unsupported NiMoS-SBA catalyst. We also report the effect of key reaction parameters on the yields and properties of the products. The results obtained at 20 wt% catalyst loading for hydrolysis lignin showed the highest monomer yield of 76.0 wt%, which consisted of 39 wt% aromatics with the lowest alkylphenolics yield of 10.1 wt%. Identical operating conditions, 400 °C, 80 bar, 5 h at 10 wt% catalyst loading, were used to compare both lignins and the highest monomer yield (64.3 wt%) was found for the hydrolysis lignin, consisting of 16.0 wt% alkylphenolics and 20.1 wt% aromatic compounds. These values are considerably higher than those for Kraft lignin with its 47.0 wt% monomer yield. We suggest that the reason for high yields of monomeric units from hydrolysis lignin is that it is more reactive due to its lower ash and sulfur contents and the chemical structural differences compared to the Kraft lignin. More precisely, the bio-oil from hydrolysis lignin contained higher yields of small molecules, sourced from ring-opening of cellulose in the hydrolysis lignin, which could stabilize the reactive oligomeric groups. These yields were two to seven times higher from kraft and hydrolysis lignin, respectively, compared to those obtained without catalyst. The results showed that the NiMoS-SBA catalyst is a promising catalyst for reductive depolymerization of lignin and in addition that the regenerated catalyst had good stability for multiple reaction cycles.
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| 5. |
- Aneheim, Emma, 1982, et al.
(författare)
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Affinity of charcoals for different forms of radioactive organic iodine
- 2018
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493. ; 328, s. 228-240
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Tidskriftsartikel (refereegranskat)abstract
- During a serious nuclear reactor accident a large fraction of the radioactive iodine in the fuel can escape from the core and subsequently from the plant. While the noble gases in reactor fuel are more mobile than iodine, the iodine is often of greater concern as its chemistry and biology causes it to be more radiotoxic. Iodine has the potential to be re-concentrated in vivo in the thyroid. Filters containing charcoals are used both under normal operating conditions and during emergencies to retain iodine species, they are used in environmental sampling to estimate radioactive iodine and in respiratory protection systems such as air purifying filter respirators. During a nuclear accident iodine can exist in many forms. As the formation of organic iodine compounds other than methyl iodide has been observed in nuclear plants it can be reasoned that a failure of a charcoal to retain other organoiodines than methyl iodide could have adverse consequences. In this paper, the ability of different charcoals to capture various forms of radioactive organic iodine compounds has been explored. Besides elemental iodine used as reference methyl, chloromethyl, ethyl and isopropyl iodides have been studied together with iodoacetylene.
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| 6. |
- Baena-Moreno, Francisco, 1992, et al.
(författare)
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Effluents and residues from industrial sites for carbon dioxide capture: a review
- 2023
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Ingår i: Environmental Chemistry Letters. - : Springer Science and Business Media LLC. - 1610-3653 .- 1610-3661. ; 21:1, s. 319-337
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Forskningsöversikt (refereegranskat)abstract
- The adverse effects of climate change calls for the rapid transformation of manufacturing processes to decrease the emissions of carbon dioxide. In particular, a lower carbon footprint can be achieved by capturing carbon dioxide at the site of emission. Here we review the use of industrial effluents, waste and residues to capture carbon dioxide. Waste include steelmaking slag, municipal solid waste incinerator ashes, combustion fly ash, black liquor, paper mill waste, mining waste, cement waste, construction and demolition waste, waste from the organic industry, and flue gas desulfurization gypsum waste. Capture capacities range from 2 to 800 kg of carbon dioxide per ton of waste, depending on processes, waste type and conditions. Cement waste and flue gas desulfurization gypsum waste show the highest capture capacity per ton of waste.
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| 7. |
- Baena-Moreno, Francisco, 1992, et al.
(författare)
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Potential of organic carbonates production for efficient carbon dioxide capture, transport and storage: Reaction performance with sodium hydroxide–ethanol mixtures
- 2023
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide storage is one of the main long-term strategies for reducing carbon dioxide emissions in the atmosphere. A clear example is Norway's Longship project. If these projects should succeed, the transport of huge volumes of carbon dioxide from the emissions source to the injection points may become a complex challenge. In this work, we propose the production of sodium-based organic carbonates that could be transported to storage sites and be reconverted to CO2. Solid carbonates can be transported in considerably lower volumes than gases or pressurized liquids. Sodium-based carbonates are insoluble in most of the organic solvents and will therefore precipitate in contrast to in aqueous solutions. Particularly, here we focus on sodium hydroxide-ethanol mixtures as solvents for precipitating sodium ethyl carbonate and sodium bicarbonate. Previous works on this approach used limited sodium hydroxide concentrations, which are insufficient to prove the effectiveness of the proposed process. In this paper, we studied higher sodium hydroxide concentrations in sodium hydroxide-ethanol mixtures than previously reported in the literature. To this end, we use the following strategy: (1) In-line monitoring of the formation of carbonates using an in-line FTIR; (2) In-line measurements of the weight increase, which correspond directly to the captured carbon dioxide and reveal the absorption capacity; (3) Characterization of the solids with X-ray diffraction and scanning electron microscope. Our FTIR results confirmed that both sodium ethyl carbonate and sodium bicarbonate were formed, which agrees with X-ray diffraction and scanning electron microscope. With this reactor design, the absorption capacities reached approximately 80–93% of the theoretical values (4.8–13.3 g/L respectively). We hypothesize that full conversion is hampered because the gas might take preferential paths due to gel formation during the experiments.
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| 8. |
- Bernin, Diana, 1979, et al.
(författare)
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Microstructure of polymer hydrogels studied by pulsed field gradient NMR diffusion and TEM methods
- 2011
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 7:12, s. 5711-5716
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of various alginate gels have been studied by pulsed field gradient NMR (PFG NMR) and transmission electron microscopy (TEM). The reduced diffusivity of dendrimer diffusion within the gels has been obtained from PFG NMR diffusion experiments. The polymer strand radius, an important microstructural property, has been extracted from various diffusion models. The results agree well with the polymer strand radii obtained from image analysis of the corresponding TEM micrographs.
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| 9. |
- Bernin, Diana, 1979, et al.
(författare)
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Multi-Scale Characterization of Lyotropic Liquid Crystals Using 2H and Diffusion MRI with Spatial Resolution in Three Dimensions
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- The ability of lyotropic liquid crystals to form intricate structures on a range of length scales can be utilized for the synthesis of structurally complex inorganic materials, as well as in devices for controlled drug delivery. Here we employ magnetic resonance imaging (MRI) for non-invasive characterization of nano-, micro-, and millimeter scale structures in liquid crystals. The structure is mirrored in the translational and rotational motion of the water, which we assess by measuring spatially resolved self-diffusion tensors and spectra. Our approach differs from previous works in that the MRI parameters are mapped with spatial resolution in all three dimensions, thus allowing for detailed studies of liquid crystals with complex millimeter-scale morphologies that are stable on the measurement time-scale of 10 hours. The data conveys information on the nanometer-scale structure of the liquid crystalline phase, while the combination of diffusion and data permits an estimate of the orientational distribution of micrometer-scale anisotropic domains. We study lamellar phases consisting of the nonionic surfactant C10E3 in O, and follow their structural equilibration after a temperature jump and the cessation of shear. Our experimental approach may be useful for detailed characterization of liquid crystalline materials with structures on multiple length scales, as well as for studying the mechanisms of phase transitions.
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| 10. |
- Bernin, Diana, 1979, et al.
(författare)
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Multi-scale characterization of pasta during cooking using microscopy and real-time magnetic resonance imaging
- 2014
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969 .- 1873-7145. ; 66, s. 132-139
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Tidskriftsartikel (refereegranskat)abstract
- Macroscopic properties of pasta, such as the texture, are formed during cooking by a complex interplay of water and heat with the structuring agents starch and gluten. The impact of the starch-to-gluten ratio on microstructure and water distribution in pasta was analyzed by a multi-scale approach combining magnetic resonance imaging (MRI) and light microscopy. The cooking process and thus the water distribution was monitored non-invasively using 1H MRI in real-time with a temporal resolution of 45s. Our MRI set-up allowed following the water ingress by imaging the reduction of the uncooked core. The water ingress rate was neither dependent on pasta composition nor on the presence of salt in the cooking media (0.7% NaCl). Starch-rich samples showed a more homogeneous water distribution in the gelatinized zone, which was mirrored in a more homogeneous microstructure. In contrast, gluten-rich samples showed both a heterogeneous water distribution and microstructure. Thus, the gluten content affected local water content in the gelatinized zone but not the water ingress. © 2014 Elsevier Ltd.
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| 11. |
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| 12. |
- Bernin, Diana, 1979
(författare)
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Nuclear Magnetic Resonance Methods to Study Soft Matter Dynamics and Microstructure
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soft matter is of great importance for food, hygiene and pharmaceutical products. Gels are an example of soft matter and are found in e.g. diapers, that are able to take up large amounts of liquids. Translational motion such as diffusion and/or flow is the fundamental mechanism for transport of solutes or solvents e.g. within gels and is strongly dependent on their microstructure. In addition, interactions e.g. solutes binding to the gel surface, may alter diffusion in soft matter. In order to tailor-made materials, it is necessary to have a detailed knowledge of how microstructure and interactions influences mass transport in soft matter.Different nuclear magnetic resonance methods were applied to monitor mass transport in a variety of microstructures during steady and non-steady state conditions. Water dynamics were monitored during capillary formation in alginate gels using1H magnetic resonance imaging. This method allowed the water at the gelation front, where the growth of capillaries occurred, to be followed as a function of time. It was found that there are enhanced water dynamics at the gelation front and that the rate of gel formation occurs faster and produces a denser gel in the case of capillary formation.1H and 19F chemical shift imaging was applied to study the dynamics of water and fluoride ions dynamics during gelation of a non-aqueous cellulose solution, which forms a gel upon addition of water. The rate of gelation was followed tracking the water signal as a function of time and position.3D 1H diffusion tensor imaging combined with 3D 2H spectroscopic information mapped the microstructure of shear-induced multi-lamellar vesicles as a function of time. Furthermore, the half-life time could be estimated in a spatially resolved manner and it was found that shear-induced multi-lamellar vesicles seems to decay faster close to surfaces.The interaction of water with silica surfaces was studied with 17O relaxation measurements as a function of amount silica and salt. Upon the addition of salt, a gel is formed and a reduced amount of surface “bound” water is reported. The information obtained was then used to rationalize the diffusion of water in this systems in the framework of the cell model.
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| 13. |
- Bernin, Diana, 1979, et al.
(författare)
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Perspectives on NMR studies of CO2 adsorption
- 2018
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Ingår i: Current Opinion in Colloid & Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 33, s. 53-62
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Tidskriftsartikel (refereegranskat)abstract
- There is a consensus about a long-term goal of a carbon-neutral energy cycle, but the CO2 emissions to the atmosphere are currently very large. Carbon Capture and Storage (CCS) technologies could allow a transformation of the global energy system into a carbon-neutral one and simultaneously keeping the temperature rises within agreed bounds. The CO2 separation step of CCS is, however, very expensive, and adsorption-driven technologies have been put forward as alternatives. Hence, a recent focus has been on studying solid adsorbents for CO2, which include activated carbons, zeolites, metal-organic frameworks, and amine-modified silica. In this context, we summarize the literature concerning CO2 sorption studied with Nuclear Magnetic Resonance (NMR), outline selected NMR methods, and present an outlook for further studies. (C) 2018 Elsevier Ltd. All rights reserved.
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| 14. |
- Bernin, Diana, 1979
(författare)
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Pulsed Field Gradient NMR Studies of Diffusion in Polymer Gels
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soft biomaterials, such as gels, play an important role in different kinds of products and applications, in particular in drug delivery systems, health care products, and food. Polymer gel's great ability to control mass transport is applied on e.g. the uptake of liquids in diapers. Diffusion is one of the most essential transport mechanism, e.g. for releasing active substances. In this work, pulsed field gradient nuclear magnetic resonance (PFG NMR) techniques have been used to study diffusion on different time and length scales.The polymer strand radius, an important microstructural feature, has been extracted from reduced diffusivity in various alginate gels. The results agree well with the polymer strand radii obtained from image analysis of the corresponding transmission electron microscopy (TEM) micrographs.Chemical shift imaging (CSI), another PFG NMR method, has been used to monitor gel formation initiated by adding water to a non-aqueous cellulose solution. Diffusion rates of water molecules and fluoride ions have been obtained from one-dimensional profiles.
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| 15. |
- Bernin, Diana, 1979, et al.
(författare)
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Real time MRI to elucidate the functionality of coating films intended for modified release
- 2019
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 311-312, s. 117-124
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Tidskriftsartikel (refereegranskat)abstract
- Polymer films based on mixtures of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) have been widely used to coat pellets and tablets to modify the release profile of drugs. For three different EC/HPC films we used 1H and 19F MRI in combination with a designed release cell to monitor the drug, polymer and water in 5 dimensional (5D) datasets; three spatial, one diffusion or relaxation and a temporal dimension, in real time. We observed that the water inflow through the films correlated with the initiation of the dissolution of the drug in the tablet beneath the film. Leaching of the pore forming HPC further accelerated water penetration and resulted in a drug release onset after a hydrostatic pressure was generated below the film indicated by positional changes of the film. For the more permeable film, both water ingress and drug egress showed a large variability of release over the film surface indicating the heterogeneity of the system. Furthermore, the 1H diffusion dataset revealed the formation of a gel layer of HPC at the film surface. We conclude that the setup presented provides a significant level of details, which are not achieved with traditional methods.
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| 16. |
- Bialik, Erik, et al.
(författare)
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Ionization of Cellobiose in Aqueous Alkali and the Mechanism of Cellulose Dissolution
- 2016
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185. ; 7:24, s. 5044-5048
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.
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| 17. |
- Björnerbäck, Fredrik, et al.
(författare)
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Microporous Humins Synthesized in Concentrated Sulfuric Acid Using 5-Hydroxymethyl Furfural
- 2018
-
Ingår i: ACS OMEGA. - : American Chemical Society (ACS). - 2470-1343. ; 3:8, s. 8537-8545
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Tidskriftsartikel (refereegranskat)abstract
- A new class of highly porous organic sorbents called microporous humins is presented. These microporous humins are derived from sustainable and industrially abundant resources, have high heat of CO2 sorption, and could potentially be useful for the separation of carbon dioxide from gas mixtures. Their synthesis involves the polymerization of 5-hydroxymethyl furfural (HMF) in concentrated sulfuric acid and treatment with diethyl ether and heat. In particular, the porosities were tuned by the heat treatment. HMF is a potential platform chemical from biorefineries and a common intermediate in carbohydrate chemistry. A high uptake of CO2 (up to 5.27 mmol/g at 0 degrees C and 1 bar) and high CO2-over-N-2 and CO2-over-CH4 selectivities were observed. The microporous humins were aromatic and structurally amorphous, which was shown in a multipronged approach using C-13 nuclear magnetic resonance and Fourier transform infrared spectroscopies, elemental analysis, and wide-angle X-ray scattering.
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| 18. |
- Börjesson, Mikaela, 1987, et al.
(författare)
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Increased thermal stability of nanocellulose composites by functionalization of the sulfate groups on cellulose nanocrystals with azetidinium ions
- 2018
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 135:10
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanocrystals (CNCs) prepared via sulfuric acid hydrolysis are decorated with sulfate groups that yield a stable water suspension. To make the CNCs adaptable for use in composites, the hydroxyl groups on the surface are usually hydrophobized. In this article, an alternative hydrophobization method is described in which the sulfate groups are conjugated with azetidinium salts. The results of this study show that the sulfate groups can be functionalized with azetidinium salts and from thermal studies, it was discovered that the functionalization led to a 100 degrees C increase in thermal stability, compared with unmodified CNCs. The nanocomposites prepared by extrusion of CNC-coated low-density polyethylene powder displayed similar mechanical properties as the CNC-reference sample, but without the discoloration, due to the increased thermal stability. In conclusion, the azetidinium reagent reacts preferentially with sulfate groups, and this new type of chemical conversion of sulfate groups on polysaccharides will be beneficial in nanocomposite manufacturing. (C) 2017 Wiley Periodicals, Inc.
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| 19. |
- Church, Tamara L., et al.
(författare)
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Dispersed Uniform Nanoparticles from a Macroscopic Organosilica Powder
- 2018
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 34:6, s. 2274-2281
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Tidskriftsartikel (refereegranskat)abstract
- A colloidal dispersion of uniform organosilica nanoparticles could be produced via the disassembly of the non-surfactant-templated organosilica powder nanostructured folate material (NFM-1). This unusual reaction pathway was available because the folate and silica-containing moieties in NFM-1 are held together by noncovalent interactions. No precipitation was observed from the colloidal dispersion after a week, though particle growth occurred at a solvent-dependent rate that could be described by the Lifshitz-Slyozov-Wagner equation. An organosilica film that was prepared from the colloidal dispersion adsorbed folate-binding protein from solution but adsorbed ions from a phosphate -buffered saline solution to a larger degree. To our knowledge, this is the first instance of a colloidal dispersion of organosilica nanoparticles being derived from a macroscopic material rather than from molecular precursors.
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| 20. |
- Etman, Ahmed S., et al.
(författare)
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Insights into the Exfoliation Process of V2O5· nH2O Nanosheet Formation Using Real-Time 51V NMR
- 2019
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:6, s. 10899-10905
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2019 American Chemical Society. Nanostructured hydrated vanadium oxides (V2O5·nH2O) are actively being researched for applications in energy storage, catalysis, and gas sensors. Recently, a one-step exfoliation technique for fabricating V2O5·nH2O nanosheets in aqueous media was reported; however, the underlying mechanism of exfoliation has been challenging to study. Herein, we followed the synthesis of V2O5·nH2O nanosheets from the V2O5 and VO2 precursors in real time using solution- and solid-state 51V NMR. Solution-state 51V NMR showed that the aqueous solution contained mostly the decavanadate anion [H2V10O28]4- and the hydrated dioxovanadate cation [VO2·4H2O]+, and during the exfoliation process, decavanadate was formed, while the amount of [VO2·4H2O]+ remained constant. The conversion of the solid precursor V2O5, which was monitored with solid-state 51V NMR, was initiated when VO2 was in its monoclinic forms. The dried V2O5·nH2O nanosheets were weakly paramagnetic because of a minor content of isolated V4+. Its solid-state 51V signal was less than 20% of V2O5 and arose from diamagnetic V4+ or V5+.This study demonstrates the use of real-time NMR techniques as a powerful analysis tool for the exfoliation of bulk materials into nanosheets. A deeper understanding of this process will pave the way to tailor these important materials. ©
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| 21. |
- Feizie Ilmasani, Rojin, 1989, et al.
(författare)
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Deactivation of phosphorus-poisoned Pd/SSZ-13 for the passive adsorption of NOx
- 2022
-
Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Automotive catalysts can be exposed to various poisonous substances that can cause physical or chemical deactivation. One of such poisons is phosphorous, which originates from lubricant oils. This study focuses on the phosphorus deactivation of Pd/SSZ-13 used as a passive NOx adsorber (PNA). A clear deactivation caused by phosphorus was observed, and it was increased by increasing the content of phosphorous. It was concluded that phosphorous can cause both physical and chemical deactivation. This was evident from XPS analysis, where the presence of phosphorus pentoxide (P2O5) causes physical deactivation whereas metaphosphate (PO3-) and phosphate (PO43-) cause chemical deactivation. Also, it was shown that metaphosphates (PO3-) become the dominant phosphorous species at higher P concentrations. Lesser amounts of O2 were released in P-poisoned Pd/SSZ-13, as was found in oxygen TPD when increasing the P concentration, due to the presence of more PO3- species. Furthermore, XRD and 27Al NMR analyses revealed that phosphorus also interacted with alumina in the zeolite framework by forming Al-O-P species; this was also supported by SEM-EDX, where there was a clear overlap of P with Al and Pd spectra. DRIFTS analysis showed that OH groups in contact with the zeolite structure became contaminated by phosphorus and caused a chemical deactivation of Pd/SSZ-13. It was also found that, during multiple cycles, the PNA capacity decreased for phosphorus-poisoned samples. This was caused by the transformation of P2O5, which causes physical blocking, to PO3-, which interacts chemically with the palladium species.
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| 22. |
- Ferreira, T. M., et al.
(författare)
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NMR Studies of Nonionic Surfactants
- 2013
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Ingår i: Annual Reports on NMR Spectroscopy. - : Elsevier. - 0066-4103. ; 79, s. 73-127
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Tidskriftsartikel (refereegranskat)abstract
- NMR has contributed greatly to our current understanding of self-association, phase behaviour, and molecular dynamics in aqueous systems of oligo(ethylene oxide) mono-alkyl ether (CmEn) nonionic surfactants, which are extensively used in both basic scientific studies and technical applications as emulsifying agents and detergents. This review provides a comprehensive but concise overview of the various NMR techniques that have been applied to nonionic surfactants. We describe conventional experimental procedures, such as the measurement of quadrupole splittings, nuclear relaxation times, and self-diffusion coefficients to characterize liquid crystalline phases, micelles, and microemulsions, as well as more advanced imaging and diffusion-diffusion 2D correlation approaches to investigate the structure of phase-separated systems and the spatial organization of anisotropic liquid crystalline domains on the micro- to millimetre length scales.
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| 23. |
- Fridjonsson, E. O., et al.
(författare)
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Hydrodynamic dispersion in beta-lactoglobulin gels measured by PGSE NMR
- 2011
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Ingår i: European Physical Journal E. - : Springer Science and Business Media LLC. - 1292-8941 .- 1292-895X. ; 34:2
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Tidskriftsartikel (refereegranskat)abstract
- The displacement scale dependent molecular dynamics of solvent water molecules flowing through beta-lactoglobulin gels are measured by pulse gradient spin echo (PGSE) nuclear magnetic resonance (NMR). Gels formed under different pH conditions generate structures which are characterized by magnetic resonance imaging (MRI) and PGSE NMR measured dynamics as homogeneous and heterogeneous. The data presented clearly demonstrate the applicability of the theoretical framework for modeling hydrodynamic dispersion to the analysis of protein gels.
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| 24. |
- Ganachaud, C., et al.
(författare)
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An anomalous behavior of trypsin immobilized in alginate network
- 2013
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 97:10, s. 4403-4414
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Tidskriftsartikel (refereegranskat)abstract
- Alginate is a biopolymer used in drug formulations and for surgical purposes. In the presence of divalent cations, it forms solid gels, and such gels are of interest for immobilization of cells and enzymes. In this work, we entrapped trypsin in an alginate gel together with a known substrate, N (alpha)-benzoyl-l-arginine-4-nitroanilide hydrochloride (l-BAPNA), and in the presence or absence of d-BAPNA, which is known to be a competitive inhibitor. Interactions between alginate and the substrate as well as the enzyme were characterized with transmission electron microscopy, rheology, and nuclear magnetic resonance spectroscopy. The biocatalysis was monitored by spectrophotometry at temperatures ranging from 10 to 42 A degrees C. It was found that at 37 and 42 A degrees C a strong acceleration of the reaction was obtained, whereas at 10 A degrees C and at room temperature, the presence of d-BAPNA leads to a retardation of the reaction rate. The same effect was found when the reaction was performed in a non-cross-linked alginate solution. In alginate-free buffer solution, as well as in a solution of carboxymethylcellulose, a biopolymer that resembles alginate, the normal behavior was obtained; however, with d-BAPNA acting as an inhibitor at all temperatures. A more detailed investigation of the reaction kinetics showed that at higher temperature and in the presence of alginate, the curve of initial reaction rate versus l-BAPNA concentration had a sigmoidal shape, indicating an allosteric behavior. We believe that the anomalous behavior of trypsin in the presence of alginate is due to conformational changes caused by interactions between the positively charged trypsin and the strongly negatively charged alginate.
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| 25. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
Direct Evidence for Reaction between Cellulose and CO2 from Nuclear Magnetic Resonance
- 2021
-
Ingår i: ACS Sustainable Chemistry and Engineering. - : AMER CHEMICAL SOC. - 2168-0485. ; 9:42, s. 14006-14011
-
Tidskriftsartikel (refereegranskat)abstract
- The direct reaction between carbohydrates and CO2 has recently attracted attention in the context of cellulose dissolution and derivatization as well as carbon capture applications. We have directly demonstrated the formation of cellulose carbonate upon the introduction of CO2 into a non-aqueous cellulose solution by nuclear magnetic resonance spectroscopy. Comparison of the observed spectra with accurate electronic structure calculations of the changes in chemical shifts upon reaction allowed us to confirm the expectation that CO2 reacts with the hydroxyl group on carbon 6 of the cellulose but not exclusively this hydroxyl group. We found good agreement between predicted and measured chemical shifts using a simple computational method.
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| 26. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
Influence of urea on methyl β -D-glucopyranoside in alkali at different temperatures
- 2019
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 26:18, s. 9413-9422
-
Tidskriftsartikel (refereegranskat)abstract
- The dissolution efficiency plays an important role on the properties of regenerated cellulose-based products. Urea is known to be one of the additives aiding to improve cellulose dissolution in the NaOH(aq) system. The acting mechanism caused by urea has been debated and one of the hypothesis is that urea could induce a conformational change on cellulose, which promotes dissolution. Here we used NMR spectroscopy on a model system for cellulose, namely, methyl β -D-glucopyranoside (β -MeO-Glcp) and compared chemical shifts and J couplings, which both are indicators for conformational changes, as a function of temperature and upon the addition of urea. We found that in NaOH(aq), the hydroxymethyl group changes its conformation in favour of the population of the gt rotamer, while the presence of urea induced temperature dependent conformational changes. Heteronuclear Overhauser effect experiments showed that urea associates with cellulose but in a non-specific manner. This suggests that urea rather than binding to the carbohydrate, changes the chemical environment inducing a change in conformation of β -MeO-Glcp and likely also for cellulose when dissolved in NaOH(aq) with urea.
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| 27. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
On the interference of urea with CO 2 /CO 3 2- chemistry of cellulose model solutions in NaOH(aq)
- 2021
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 251
-
Tidskriftsartikel (refereegranskat)abstract
- The CO2/CO32− chemistry of the cellulose/NaOH(aq) solutions has been recently reported to comprise a CO2 incorporation through formation of a transient cellulose carbonate intermediate along with cellulose – CO32− interactions. This work explores on molecular interactions arising when this chemistry is brought together with urea, the most common stabiliser of these solutions. 1H, 13C and steady-state heteronuclear Overhauser effect NMR studies on the cellulose analogues (methyl-β-glucopyranoside (β-MeO-Glcp) and microcrystalline cellulose), combined with pH and ATR-FTIR measurements, reveal concurrent interactions of urea with both CO2 and CO32−– leading to increased uptake of CO2 and a buffering effect. Yet, regardless of the presence of urea, the route of conversion from CO2 to CO32-, whether going through reaction with the carbohydrate alkoxides or OH−, is likely to determine the chemical environment of the formed CO32-. These findings shed a new light on rather overlooked, albeit prominent, interactions in these solutions with the readily absorbed air CO2, essential for further development and implementation, whether towards regenerated and modified cellulose or CO2-capturing concepts.
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| 28. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
The CO 2 /CO 3 2− chemistry of the NaOH(aq) model system applicable to cellulose solutions
- 2020
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 27:2, s. 621-628
-
Tidskriftsartikel (refereegranskat)abstract
- Molecular interactions governing the recently reported CO2/CO32− chemistry of cellulose/NaOH(aq) solutions are investigated using a cellulose analogue methyl-β-D-glucopyranoside in NaOH(aq) solutions under conditions feasible with cellulose dissolution. 1H, 13C and steady-state heteronuclear Overhauser effect NMR spectroscopy complemented by pH measurements reveal carbohydrate–CO32− interactions as an important component of this chemistry. However, depending on in which order carbohydrate and CO32− are brought together in NaOH(aq) this interaction is different with different implications on stability of the CO32− in the solution.
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| 29. |
- Gunnarsson, M., et al.
(författare)
-
The CO2 capturing ability of cellulose dissolved in NaOH(aq) at low temperature
- 2018
-
Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 20:14, s. 3279-3286
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we explore the intrinsic ability of cellulose dissolved in NaOH(aq) to reversibly capture CO2. The stability of cellulose solutions differed significantly when adding CO2 prior to or after the dissolution of cellulose. ATR-IR spectroscopy on cellulose regenerated from the solutions, using ethanol, revealed the formation of a new carbonate species likely to be cellulose carbonate. To elucidate the interaction of cellulose with CO2 at the molecular level, a C-13 NMR spectrum was recorded on methyl -d-glucopyranoside (MeO-Glcp), a model compound, dissolved in NaOH(aq), which showed a difference in chemical shift when CO2 was added prior to or after the dissolution of MeO-Glcp, without a change in pH. The uptake of CO2 was found to be more than twice as high when CO2 was added to a solution after the dissolution of MeO-Glcp. Altogether, a mechanism for the observed CO2 capture is proposed, involving the formation of an intermediate cellulose carbonate upon the reaction of a cellulose alkoxide with CO2. The intermediate was observed as a captured carbonate structure only in regenerated samples, while its corresponding NMR peak in solution was absent. The reason for this is plausibly a rather fast hydrolysis of the carbonate intermediate by water, leading to the formation of CO32-, and thus increased capture of CO2. The potential of using carbohydrates as CO2 capturing agents in NaOH(aq) is shown to be simple and resource-effective in terms of the capture and regeneration of CO2.
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| 30. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
The CO2 capturing ability of cellulose dissolved in NaOH(aq) at low temperature
- 2018
-
Ingår i: Green Chemistry. - 1463-9262 .- 1463-9270. ; 20:14, s. 3279-3286
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we explore the intrinsic ability of cellulose dissolved in NaOH(aq) to reversibly capture CO2. The stability of cellulose solutions differed significantly when adding CO2 prior to or after the dissolution of cellulose. ATR-IR spectroscopy on cellulose regenerated from the solutions, using ethanol, revealed the formation of a new carbonate species likely to be cellulose carbonate. To elucidate the interaction of cellulose with CO2 at the molecular level, a C-13 NMR spectrum was recorded on methyl -d-glucopyranoside (MeO-Glcp), a model compound, dissolved in NaOH(aq), which showed a difference in chemical shift when CO2 was added prior to or after the dissolution of MeO-Glcp, without a change in pH. The uptake of CO2 was found to be more than twice as high when CO2 was added to a solution after the dissolution of MeO-Glcp. Altogether, a mechanism for the observed CO2 capture is proposed, involving the formation of an intermediate cellulose carbonate upon the reaction of a cellulose alkoxide with CO2. The intermediate was observed as a captured carbonate structure only in regenerated samples, while its corresponding NMR peak in solution was absent. The reason for this is plausibly a rather fast hydrolysis of the carbonate intermediate by water, leading to the formation of CO32-, and thus increased capture of CO2. The potential of using carbohydrates as CO2 capturing agents in NaOH(aq) is shown to be simple and resource-effective in terms of the capture and regeneration of CO2.
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| 31. |
- Gunnarsson, Maria, 1987, et al.
(författare)
-
The potential of magnetisation transfer NMR to monitor the dissolution process of cellulose in cold alkali
- 2019
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 26:18, s. 9403-9412
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose is the most important biopolymer on earth and, when derived from e.g. wood, a promising alternative to for example cotton, which exhibits a large environmental burden. The replacement depends, however, on an efficient dissolution process of cellulose. Cold aqueous alkali systems are attractive but these solvents have peculiarities, which might be overcome by understanding the acting mechanisms. Proposed dissolution mechanisms are for example the breakage of hydrophobic interactions and partly deprotonation of the cellulose hydroxyl groups. Here, we performed a mechanistic study using equimolar aqueous solutions of LiOH, NaOH and KOH to elucidate the dissolution process of microcrystalline cellulose (MCC). The pH was the highest for KOH(aq) followed by NaOH(aq) and LiOH(aq). We used a combination of conventional and advanced solution-state NMR methods to monitor the dissolution process of MCC by solely increasing the temperature from − 10 to 5 °C. KOH(aq) dissolved roughly 25% of the maximum amount of MCC while NaOH(aq) and LiOH(aq) dissolved up to 70%. Water motions on nanoscale timescales present in non-frozen water, remained unaffected on the addition of MCC. Magnetisation transfer (MT) NMR experiments monitored the semi-rigid MCC as a function of temperature. Interestingly, although NaOH(aq) and LiOH(aq) were able to dissolve a similar amount at 5 °C, MT spectra revealed differences with increasing temperature, suggesting a difference in the swollen state of MCC in LiOH(aq) already at − 10 °C. Furthermore, MT NMR shows a great potential to study the water exchange dynamics with the swollen and semi-rigid MCC fraction in these systems, which might give valuable insights into the dissolution mechanism in cold alkali.
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| 32. |
|
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| 33. |
- Hedin, Niklas, et al.
(författare)
-
Intracrystalline Transport Barriers Affecting the Self-Diffusion of CH4 in Zeolites |Na12|-A and |Na12–xKx|-A
- 2019
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 35:40, s. 12971-12978
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide must be removed from biogas or natural gas to obtain compressed or liquefied methane, and adsorption-driven isolation of CO2 could be improved by developing new adsorbents. Zeolite adsorbents can select CO2 over CH4, and the adsorption of CH4 on zeolite |Na12-xKx|-A is significantly lower for samples with a high K+ content, i.e., x > 2. Nevertheless, we show, using 1H NMR experiments, that these zeolites adsorb CH4 after long equilibration times. Pulsed-field gradient NMR experiments indicated that in large crystals of zeolites |Na12-xKx|-A, the long-time diffusion coefficients of CH4 did not vary with x, and the upper limit of the mean-square displacement was about 1.5 μm, irrespective of the diffusion time. Also for zeolite |Na12|-A samples of three different particle sizes (∼0.44, ∼2.9, and ∼10.6 μm), the upper limit of the mean-square displacement of CH4 was 1.5 μm and largely independent of the diffusion time. This similarity provided further evidence for an intracrystalline diffusion restriction for CH4 within the medium- and large-sized zeolite A crystals and possibly of clustering and close contact among the small zeolite A crystals. The upper limit of the long-time diffusion coefficient of adsorbed CH4 was (at 1 atm and 298 K) about 10-10 m2/s irrespective of the size of the zeolite particle or the studied content of K+ in zeolites |Na12-xKx|-A and |Na12|-A. The T1 relaxation time for adsorbed CH4 on zeolites |Na12-xKx|-A with x > 2 was smaller than for those with x < 2, indicating that the short-time diffusion of CH4 was hindered.
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| 34. |
- Hedin, Niklas, et al.
(författare)
-
Intracrystalline Transport Barriers Affecting the Self-Diffusion of CH4 in Zeolites vertical bar Na-12 vertical bar-A and vertical bar Na12-xKx vertical bar-A
- 2019
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:40, s. 12971-12978
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide must be removed from biogas or natural gas to obtain compressed or liquefied methane, and adsorption-driven isolation of CO2 could be improved by developing new adsorbents. Zeolite adsorbents can select CO2 over CH4, and the adsorption of CH4 on zeolite vertical bar Na12-xKx vertical bar-A is significantly lower for samples with a high K+ content, i.e., x > 2. Nevertheless, we show, using H-1 NMR experiments, that these zeolites adsorb CH4 after long equilibration times. Pulsed-field gradient NMR experiments indicated that in large crystals of zeolites vertical bar Na12-xKx vertical bar-A, the long-time diffusion coefficients of CH4 did not vary with x, and the upper limit of the mean-square displacement was about 1.5 mu m, irrespective of the diffusion time. Also for zeolite vertical bar Na-12 vertical bar-A samples of three different particle sizes (similar to 0.44, similar to 2.9, and similar to 10.6 mu m), the upper limit of the mean-square displacement of CH4 was 1.5 mu m and largely independent of the diffusion time. This similarity provided further evidence for an intracrystalline diffusion restriction for CH4 within the medium- and large-sized zeolite A crystals and possibly of clustering and close contact among the small zeolite A crystals. The upper limit of the long-time diffusion coefficient of adsorbed CH4 was (at 1 atm and 298 K) about 10(-10) m(2)/s irrespective of the size of the zeolite particle or the studied content of K+ in zeolites and vertical bar Na-12 vertical bar-A. The T-1 relaxation time for adsorbed CH4 on zeolites vertical bar Na12-xKx vertical bar-A with x > 2 was smaller than for those with x < 2, indicating that the short-time diffusion of CH4 was hindered.
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| 35. |
- Hynynen, Jonna, 1987, et al.
(författare)
-
'Lignin and extractives first' conversion of lignocellulosic residual streams using UV light from LEDs
- 2021
-
Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 23, s. 8251-8259
-
Tidskriftsartikel (refereegranskat)abstract
- Lignocellulosic biomass, especially lignin and extractives, has the potential to substitute fossil precursors in the chemical industry. The conversion of lignin has been intensively researched, but challenges remain as high temperatures and increased pressure are commonly used, which is not energy efficient. Lignin and wood extractives bear chromophoric groups that can absorb light in the ultraviolet (UV) region, which enables photochemical reactions. Ultraviolet light emitting diodes (UV-LEDs) are an emerging technology; they are cheap, versatile, and energy-efficient compared to existing mercury lamps. UV-LEDs were used in this study as a proof of concept for the valorisation of a lignocellulosic residual stream from the pulp and paper industry, sawdust. In a process at ambient temperature and pressure and without the use of a catalyst, we have shown that lignin and extractives can be valorised using light from UV-LEDs. Simplified lignin model compounds were used to pinpoint chemical reactions during irradiation, and to ease the analysis of the sawdust samples. The rate of conversion upon irradiation of the model compounds was found to be 0.7-2.3 g L-1 h(-1), depending on the concentration of the starting compounds.
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| 36. |
- Härdelin, Linda, 1977, et al.
(författare)
-
Altered Thermal and Mechanical Properties of Spruce Galactoglucomannan Films Modified with an Etherification Reaction
- 2020
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21:5, s. 1832-1840
-
Tidskriftsartikel (refereegranskat)abstract
- Native hemicellulose lacks many of the properties that make fossil fuel-based polymers excellent for use in today's industrial products and processes. The mechanical and thermal properties of the hemicellulose can, however, be modified, and its processability increased. We functionalized galactoglucomannan to lower its glass transition temperature (Tg) and thereby increase its processability. The functionalization was achieved through an etherification reaction with butyl glycidyl ether used at three molar ratios. Films were produced, and their mechanical and thermal properties were evaluated. Thermogravimetric analysis showed that increased substitution increased the degradation temperature and decreased the water content in the sample, implying increased hydrophobicity upon modification. Dynamic mechanical analysis indicated that butyl glycidyl ether functionalization alters the thermal properties of the modified films both in the absolute values of Tg and in the strength of the films. The etherification reaction resulted in a more ductile material than the unmodified galactoglucomannan (GGM).
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| 37. |
- Jansson, Helen, 1964, et al.
(författare)
-
Silicate species of water glass and insights for alkali-activated green cement
- 2015
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 5:6
-
Tidskriftsartikel (refereegranskat)abstract
- Despite that sodium silicate solutions of high pH are commonly used in industrial applications, most investigations are focused on low to medium values of pH. Therefore we have investigated such solutions in a broad modulus range and up to high pH values (similar to 14) by use of infrared (IR) spectroscopy and silicon nuclear magnetic resonance (Si-29-NMR). The results show that the modulus dependent pH value leads to more or less charged species, which affects the configurations of the silicate units. This in turn, influences the alkali-activation process of low CO2 footprint cements, i.e. materials based on industrial waste or by-products
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| 38. |
- Jansson, Helen, 1964, et al.
(författare)
-
The Initial Setting Time of Ground Granulated Blastfurnace Slag GGBS and Its Relation to the Modulus of the Alkali-Activating Solution
- 2014
-
Ingår i: 2nd International conference on Advances in chemically-activated materials (CAM'2014), RILEM Proceedings. - 1461-1147. - 9782351581421 ; 92, s. 309-318
-
Konferensbidrag (refereegranskat)abstract
- There are indications on that the initial setting time is dependent on the relative ratio of Na2O to SiO2 when sodium silicate solutions (Na2SiO3) are used for the alkali-activation of ground granulated blast-furnace slag (GGBS). One possible reason for this is that the ratio (called modulus) not only influences the pH but also the viscosity of the solution. The viscosity is, in turn dependent on the structures in the liquid. Therefore, we have investigated the structure of sodium silicate solutions of different moduli by infrared spectroscopy (IR) and silicon nuclear magnetic resonance (Si-29-NMR). The results, which show that the silica configuration is highly dependent on the modulus, will be discussed in relation to the initial setting time of corresponding measurements on GGBS hydration
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| 39. |
- Jonasson, Jenny, 1976, et al.
(författare)
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Pixel-based analysis of FRAP data with a general initial bleaching profile
- 2010
-
Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 239:2, s. 142-153
-
Tidskriftsartikel (refereegranskat)abstract
- Jonasson et al. (2008), we presented a new pixel-based maximum likelihood framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM). The main method there, called the Gaussian profile method below, is based on the assumption that the initial intensity profile after photobleaching is approximately Gaussian. In the present paper, we introduce a method, called the Monotone profile method, where the maximum likelihood framework is extended to a general initial bleaching profile only assuming that the profile is a non-decreasing function of the distance to the bleaching centre. The statistical distribution of the image noise is further assumed to be Poisson instead of normal, which should be a more realistic description of the noise in the detector. The new Monotone profile method and the Gaussian profile method are applied to FRAP data on swelling of super absorbent polymers (SAP) in water with a Fluorescein probe. The initial bleaching profile is close to a step function at low degrees of swelling and close to a Gaussian profile at high degrees of swelling. The results obtained from the analysis of the FRAP data are corroborated with NMR diffusometry analysis of SAP with a polyethylene glycol probe having size similar to the Fluorescein. The comparison of the Gaussian and Monotone profile methods is also performed by use of simulated data. It is found that the new Monotone profile method is accurate for all types of initial profiles studied, but it suffers from being computationally slow. The fast Gaussian profile method is sufficiently accurate for most of the profiles studied, but underestimates the diffusion coefficient for profiles close to a step function. We also provide a diagnostic plot, which indicates whether the Gaussian profile method is acceptable or not.
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| 40. |
- Leventaki, Emmanouela, 1996, et al.
(författare)
-
Aqueous mineral carbonation of three different industrial steel slags: Absorption capacities and product characterization
- 2024
-
Ingår i: Environmental Research. - 0013-9351 .- 1096-0953. ; 252
-
Tidskriftsartikel (refereegranskat)abstract
- Heavy carbon industries produce solid side stream materials that contain inorganic chemicals like Ca, Na, or Mg, and other metals such as Fe or Al. These inorganic compounds usually react efficiently with CO2 to form stable carbonates. Therefore, using these side streams instead of virgin chemicals to capture CO2 is an appealing approach to reduce CO2 emissions. Herein, we performed an experimental study of the mineral carbonation potential of three industrial steel slags via aqueous, direct carbonation. To this end, we studied the absorption capacities, reaction yields, and physicochemical characteristics of the carbonated samples. The absorption capacities and the reaction yields were analyzed through experiments carried out in a reactor specifically designed to work without external stirring. As for the physicochemical characterization, we used solid-state Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Using this reactor, the absorption capacities were between 5.8 and 35.3 g/L and reaction yields were in the range of 81–211 kg CO2/ton of slag. The physicochemical characterization of the solid products with solid FTIR, XRD and SEM indicated the presence of CaCO3. This suggests that there is potential to use the carbonated products in commercial applications.
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| 41. |
- Leventaki, Emmanouela, 1996, et al.
(författare)
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Experimental evaluation of black liquor carbonation for carbon dioxide capture
- 2023
-
Ingår i: Journal of CO2 Utilization. - 2212-9820. ; 72
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide is one of the main if not the most potent greenhouse gases responsible for climate change. Scientists put great efforts to tackle this problem and carbon dioxide capture seems to be a promising solution. The present study proposes a novel method of carbon dioxide capture using black liquor, a side stream from the paper and pulp industry. Its content in sodium hydroxide makes it an attractive candidate for carbon dioxide capture via carbonation. The black liquor was prepared from oat husks, a non-woody biomass, using the soda-pulping process. To estimate its carbon dioxide absorption capacity, a mixture of nitrogen and carbon dioxide (70:30%) was sparged into a bubble column reactor and computational fluid dynamics simulations of this setup were used to evaluate the mixing process. The formation of carbonate and bicarbonate ions throughout the carbonation process was followed using a Fourier-Transform Infrared (FTIR) probe and a pH meter. The absorption capacity was measured from the weight increase of the reactor. It was found to be around 30 g of carbon dioxide/L of black liquor. The carbonate and bicarbonate species in black liquor before and after carbonation were further characterized with 13C Nuclear Magnetic Resonance (NMR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and optical microscopy. Using industrial side-streams might enable an economically feasible process without the need for production of virgin absorbents or their recovery. Furthermore, this capturing process, which is performed at atmospheric conditions might reduce the overall energy consumption. The results demonstrated that black liquor could be an attractive absorbent for carbon dioxide, paving the way for a circular and resource-efficient economy.
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| 42. |
- Leventaki, Emmanouela, 1996, et al.
(författare)
-
In-Line Monitoring of Carbon Dioxide Capture with Sodium Hydroxide in a Customized 3D-Printed Reactor without Forced Mixing
- 2022
-
Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 14:17
-
Tidskriftsartikel (refereegranskat)abstract
- Many industrial processes make use of sodium because sodium is the fifth most abundant metal and the seventh most abundant element on Earth. Consequently, there are many sodium-containing industrial wastes that could potentially be used for carbon capture, paving the way towards a circular and biobased economy. For example, a common industrial chemical is NaOH, which is found in black liquor, a by-product of the paper and pulp industry. Nonetheless, the literature available on CO2 absorption capacity of aqueous NaOH is scarce for making a fair comparison with sodium-containing waste. Therefore, to fill this gap and set the foundation for future research on carbon capture, the CO2 absorption capacity of NaOH solutions in a concentration range of 1–8 w/w% was evaluated, a wider range compared with currently available data. The data set presented here enables evaluating the performance of sodium-based wastes, which are complex mixtures and might contain other compounds that enhance or worsen their carbon capture capacity. We designed a customized reactor using a 3D-printer to facilitate in-line measurements and proper mixing between phases without the energy of stirring. The mixing performance was confirmed by computational fluid dynamics simulations. The CO2 absorption capacity was measured via weight analysis and the progress of carbonation using a pH meter and an FTIR probe in-line. At 5 w/w% NaOH and higher, the reaction resulted in precipitation. The solids were analyzed with X-ray diffraction and scanning electron microscope, and nahcolite and natrite were identified. With our setup, we achieved absorption capacities in the range of 9.5 to 78.9 g CO2/L for 1 w/w% and 8 w/w% of NaOH, respectively. The results are in fair agreement with previously reported literature, suggesting that non-forced mixing reactors function for carbon capture without the need of stirring equipment and a possible lower energy consumption.
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| 43. |
- Loren, N., et al.
(författare)
-
Fluorescence recovery after photobleaching in material and life sciences: putting theory into practice
- 2015
-
Ingår i: Quarterly Reviews of Biophysics. - : Cambridge University Press (CUP). - 0033-5835 .- 1469-8994. ; 48:3, s. 323-387
-
Tidskriftsartikel (refereegranskat)abstract
- Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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| 44. |
- Lorén, Niklas, 1970, et al.
(författare)
-
Fluorescence recovery after photobleaching in material and life sciences: Putting theory into practice
- 2015
-
Ingår i: Quarterly Reviews of Biophysics. - 1469-8994 .- 0033-5835. ; 48:3, s. 323-387
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Tidskriftsartikel (refereegranskat)abstract
- Copyright © 2015 Cambridge University Press.Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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| 45. |
- Malmberg, Per, 1974, et al.
(författare)
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Molecular insights into hypomineralized enamel
- 2019
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Ingår i: European Journal of Oral Sciences. - : Wiley. - 0909-8836 .- 1600-0722. ; 127:4, s. 340-346
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Tidskriftsartikel (refereegranskat)abstract
- Hypomineralized enamel may be found in connection with the condition molar incisor hypomineralization (MIH), which has a prevalence of around 15% in most parts of the world. Molar incisor hypomineralization is associated with extensive objective and subjective problems, such as hypersensitivity of the affected teeth, enamel breakdown, and problems with retention of restorations. The etiology behind MIH has not yet been elucidated, but a number of possible factors, which affect the same or different functions of ameloblasts during their different stages of maturation, have been suggested. The aim of this study was to utilize multi-nuclear, solid-state nuclear magnetic resonance (ss-NMR) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) to elucidate any differences, at a molecular level, between enamel powder prepared from normal, healthy teeth and enamel powder prepared from teeth diagnosed with MIH. P-31 and Na-23 ss-NMR confirmed the presence of HPO42- and two different Na+ sites in hypomineralized enamel, suggesting a heterogeneous chemical composition. The content of organic components was higher in hypomineralized enamel, as shown by both C-13 ss-NMR and ToF-SIMS, indicating the presence of higher numbers of proteins and phospholipids. The interplay between both is necessary for the formation and mineralization of enamel, which might be disturbed or halted in hypomineralized enamel.
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| 46. |
- Maneval, J. E., et al.
(författare)
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Magnetic resonance analysis of capillary formation reaction front dynamics in alginate gels
- 2011
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 1097-458X .- 0749-1581. ; 49:10, s. 627-640
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Tidskriftsartikel (refereegranskat)abstract
- The formation of heterogeneous structures in biopolymer gels is of current interest for biomedical applications and is of fundamental interest to understanding the molecular level origins of structures generated from disordered solutions by reactions. The cation-mediated physical gelation of alginate by calcium and copper is analyzed using magnetic resonance measurements of spatially resolved molecular dynamics during gel front propagation. Relaxation time and pulse-field gradient methods are applied to determine the impact of ion front motion on molecular translational dynamics. The formation of capillaries in alginate copper gels is correlated to changes in translational dynamics.
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| 47. |
- Melro, Elodie, et al.
(författare)
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Levulinic Acid-Based "Green" Solvents for Lignocellulose Fractionation : On the Superior Extraction Yield and Selectivity toward Lignin
- 2023
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:7, s. 3094-3104
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Tidskriftsartikel (refereegranskat)abstract
- The high potential use of lignin in novel biomaterialsand chemicalsrepresents an important opportunity for the valorization of the mostabundant natural resource of aromatic molecules. From an environmentalperspective, it is highly desirable replacing the hazardous methodscurrently used to extract lignin from lignocellulosic biomass anddevelop more sustainable and environmentally friendly approaches.Therefore, in this work, levulinic acid (a "green" solventobtained from biomass) was successfully used, for the first time,to selectively extract high-quality lignin from pine wood sawdustresidues at 200 degrees C for 6 h (at atmospheric pressure). Moreover,the addition of catalytic concentrations of inorganic acids (i.e.,H2SO4 or HCl) was found to substantially reducethe temperature and reaction times needed (i.e., 140 degrees C, 2 h)for complete lignin extraction without compromising its purity. NMRdata suggests that condensed OH structures and acidic groups are presentin the lignin following extraction. Levulinic acid can be easily recycledand efficiently reused several times without affecting its performance.Furthermore, excellent solvent reusability and performance of extractionof other wood residues has been successfully demonstrated, thus makingthe developed levulinic acid-based procedure highly appealing andpromising to replace the traditional less sustainable methodologies.
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| 48. |
- Narvaez, Omar, et al.
(författare)
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Nonparametric distributions of tensor-valued Lorentzian diffusion spectra for model-free data inversion in multidimensional diffusion MRI
- 2024
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Ingår i: Journal of Chemical Physics. - 1089-7690 .- 0021-9606. ; 161:8
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic resonance imaging (MRI) is the method of choice for noninvasive studies of micrometer-scale structures in biological tissues via their effects on the time- and frequency-dependent (restricted) and anisotropic self-diffusion of water. While new designs of time-dependent magnetic field gradient waveforms have enabled disambiguation between different aspects of translational motion that are convolved in traditional MRI methods relying on single pairs of field gradient pulses, data analysis for complex heterogeneous materials remains a challenge. Here, we propose and demonstrate nonparametric distributions of tensor-valued Lorentzian diffusion spectra, or “D(ω) distributions,” as a general representation with sufficient flexibility to describe the MRI signal response from a wide range of model systems and biological tissues investigated with modulated gradient waveforms separating and correlating the effects of restricted and anisotropic diffusion.
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| 49. |
- Naserifar, Shirin, 1991, et al.
(författare)
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Aqueous N,N-dimethylmorpholinium hydroxide as a novel solvent for cellulose
- 2021
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 161
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Tidskriftsartikel (refereegranskat)abstract
- N,N-dimethylmorpholinium hydroxide was synthesized and its ability to dissolve microcrystalline cellulose and pulp was assessed for the first time. Microscopy and UV–Vis measurements showed that dissolution occurred over a range of 1–2 M concentration of the solvent and a maximum solubility of 7 wt% microcrystalline cellulose could be achieved. The stability of cellulose solutions was evaluated by size exclusion chromatography, which did not detect degradation to any noticeable extent. This observation was further confirmed by 13C NMR measurements. Finally, DLS studies confirmed that most of the cellulose was molecularly dissolved, with intrinsic viscosity values indicating cellulose chains expansion in this solvent.
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| 50. |
- Naserifar, Shirin, 1991, et al.
(författare)
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Cellulose gelation in aqueous hydroxide solutions by CO 2 (g): Fact and theory
- 2024
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Ingår i: Carbohydrate Polymer Technologies and Applications. - : Elsevier Ltd. - 2666-8939. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how the solvent structure affects the stability of the dissolved state and the following precipitation is important for designing future dissolution-coagulation systems for cellulose processing. In this study, two morpholinium hydroxides with different alkyl chain lengths, namely N,N-dimethylmorpholinium hydroxide (NDMMOH(aq)) and N‑butyl‑N-methyl morpholinium hydroxide (BMMorOH(aq)), were studied and compared with the previously thoroughly investigated cellulose solvent benzyltriemethylammonium hydroxide (Triton B(aq)) which is well-known for its superior ability to stabilize the dissolved state. Cellulose solutions in each solvent were characterized by NMR, flow and frequency sweeps, while cellulose coagulation by CO2(g) was followed by in situ FTIR, pH and temperature measurements. The coagulated systems were characterized by CP/MAS 13C NMR, flow, and frequency sweep measurements. Complementary molecular dynamic (MD) simulations were performed to gain a deeper insight into the observed gelation behavior. The intrinsic viscosity indicated more extended cellulose chains in the solvents with more hydrophobic moieties (Triton B and BMMorOH). Even though the course of coagulation did not show any significant differences during monitoring, both the properties of the obtained gels and the MD simulations indicated differences in formation and properties of the coagulated materials that could be related both to the choice of solvent and coagulant.
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