| 1. |
- Abdelaziz, Omar Y, et al.
(författare)
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Lignin Depolymerisation under Continuous-Flow Conditions : Highlights of Recent Developments
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 13:17, s. 4382-4384
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is a poly-aromatic polymer contained in the plant cell wall, and it is considered the most abundant non-carbohydrate polymer on Earth. The aromaticity and richness of its functional groups render lignin an attractive starting biomacromolecule for conversion into a variety of value-added products. The development of successful strategies for lignin valorisation infers the design of effective depolymerisation protocols. Most research on lignin depolymerisation have focused on batch-mode processing, whereas only a few studies have tackled such lignin transformation in continuous reactor systems. In the present paper, we highlight the emerging developments within the concept of continuous lignin processing and the challenges remaining in realising the efficient valorisation of lignin using this technology concept. A special focus is set on the hydrothermal conversion of technical lignin under continuous-flow conditions, together with suggestions for future research.
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| 2. |
- Abdelaziz, Omar Y., et al.
(författare)
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On the Oxidative Valorization of Lignin to High-Value Chemicals : A Critical Review of Opportunities and Challenges
- 2022
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 15:20
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Forskningsöversikt (refereegranskat)abstract
- The efficient valorization of lignin is crucial if we are to replace current petroleum-based feedstock and establish more sustainable and competitive lignocellulosic biorefineries. Pulp and paper mills and second-generation biorefineries produce large quantities of low-value technical lignin as a by-product, which is often combusted on-site for energy recovery. This Review focuses on the conversion of technical lignins by oxidative depolymerization employing heterogeneous catalysts. It scrutinizes the current literature describing the use of various heterogeneous catalysts in the oxidative depolymerization of lignin and includes a comparison of the methods, catalyst loadings, reaction media, and types of catalyst applied, as well as the reaction products and yields. Furthermore, current techniques for the determination of product yields and product recovery are discussed. Finally, challenges and suggestions for future approaches are outlined.
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| 3. |
- Argyropoulos, Dimitris D. S., et al.
(författare)
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Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges
- 2023
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Ingår i: ChemSusChem. - : John Wiley and Sons Inc. - 1864-5631 .- 1864-564X. ; 16:23
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Forskningsöversikt (refereegranskat)abstract
- Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.
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| 4. |
- Hamidi, Hassan, et al.
(författare)
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Photocurrent Generation from Thylakoid Membranes on Osmium-Redox-Polymer-Modified Electrodes.
- 2015
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 8:6, s. 990-993
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Tidskriftsartikel (refereegranskat)abstract
- Thylakoid membranes (TMs) are uniquely suited for photosynthesis owing to their distinctive structure and composition. Substantial efforts have been directed towards use of isolated photosynthetic reaction centers (PRCs) for solar energy harvesting, however, few studies investigate the communication between whole TMs and electrode surfaces, due to their complex structure. Here we report on a promising approach to generate photosynthesis-derived bioelectricity upon illumination of TMs wired with an osmium-redox-polymer modified graphite electrode, and generate a photocurrent density of 42.4 μA cm(-2) .
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| 5. |
- Li, Chuanshuai, et al.
(författare)
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Electron Transfer Mediated by Iron Carbonyl Clusters Enhance Light-Driven Hydrogen Evolution in Water by Quantum Dots
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:12, s. 3252-3260
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Tidskriftsartikel (refereegranskat)abstract
- Photocatalytic water splitting has become a promising strategy for converting solar energy into clean and carbon-neutral solar fuels in a low-cost and environmentally benign way. Hydrogen gas is such a potential solar fuel/energy carrier. In a classical artificial photosynthetic system, a photosensitizer is generally associated with a co-catalyst to convert photogenerated charge into (a) chemical bond(s). In the present study, assemblies consisting of CdSe quantum dots that are coupled with one of two molecular complexes/catalysts, that is, [Fe2S2(CO)6] or [Fe3Te2(CO)9], using an interface-directed approach, have been tested as catalytic systems for hydrogen production in aqueous solution/organic solution. In the presence of ascorbic acid as a sacrificial electron donor and proton source, these assemblies exhibit enhanced activities for the rate of hydrogen production under visible light irradiation for 8 h in aqueous solution at pH 4.0 with up to 110 μmol of H2 per mg of assembly, almost 8.5 times that of pure CdSe quantum dots under the same conditions. Transient absorption and time-resolved photoluminescence spectroscopies have been used to investigate the charge carrier transfer dynamics in the quantum dot/iron carbonyl cluster assemblies. The spectroscopic results indicate that effective electron transfer from the molecular iron complex to the valence band of the excited CdSe quantum dots significantly inhibits the recombination of photogenerated charge carriers, boosting the photocatalytic activity for hydrogen generation; that is, the iron clusters function as effective intermediaries for electron transfer from the sacrificial electron donor to the valence band of the quantum dots.
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| 6. |
- Polukeev, Alexey V., et al.
(författare)
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Iridium Catalyzed Dehydrogenation in a Continuous Flow Reactor as a Tool Towards Practical On-Board Hydrogen Generation From LOHCs
- 2022
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 15:8
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Tidskriftsartikel (refereegranskat)abstract
- To enable the large-scale use of hydrogen fuel cells for mobility applications, convenient methods for on-board hydrogen storage and release need to be developed. A promising approach is liquid organic hydrogen carriers (LOHCs), since these are safe, available on a large scale and compatible with existing re-fuelling infrastructure. Usually, LOHC dehydrogenation is carried out in batch-type reactors by transition metals and their complexes and suffers from slow H 2 release kinetics and/or inability to reach high energy density by weight due to low conversion or the need to dilute the reaction mixture. Here we report the use of a continuous flow reactor in combination with a heterogenized iridium pincer complex, which enables a tremendous increase in LOHC dehydrogenation rates. Thus, dehydrogenation of isopropanol is performed in a regime that in terms of gravimetric energy density, hydrogen generation rate and precious metal content is potentially compatible with applications in a fuel-cell powered car.
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| 7. |
- Prothmann, Jens, et al.
(författare)
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Non-targeted analysis strategy for the identification of phenolic compounds in complex technical lignin samples
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 13:17, s. 4605-4612
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is the second most abundant biopolymer in nature and a promising renewable resource for aromatic chemicals. For the understanding of different lignin isolation and conversion processes, the identification of phenolic compounds is of importance. However, due to the vast number of possible chemical transformations, the prediction of produced phenolic structures is challenging, and a non-targeted analysis method is therefore needed. In this study, we present a non-targeted analysis method for the identification of phenolic compounds using ultra-high-performance supercritical fluid chromatography/high-resolution multiple stage tandem mass spectrometry combined with a Kendrick mass defect-based classification model. The method was applied to a Lignoboost Kraft lignin (LKL), a sodium Lignosulphonate lignin (SLS) and a depolymerised Kraft lignin (DKL) sample. In total, 260 tentative phenolic compounds were identified in the LKL sample, 50 in the SLS sample and 77 in the DKL sample.
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| 8. |
- Takamuku, Shogo, et al.
(författare)
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Segmented tetrasulfonated copoly(arylene ether sulfone)s: improving proton transport properties by extending the ionic sequence
- 2013
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 6:2, s. 308-319
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Tidskriftsartikel (refereegranskat)abstract
- The morphologies and proton-transport efficiencies of segmented copoly(arylene ether sulfone) ionomers that contain tetrasulfonated sequences are compared with the corresponding copolymers with disulfonated sequences. Tetrasulfonated 4,4′-bis[(4-chlorophenyl)sulfonyl]-1,1′-biphenyl (sBCPSBP) is synthesized by metalation and sulfination. This new monomer is then used in K2CO3-mediated polycondensations of mixtures with 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-dihydroxybiphenyl in dimethyl sulfoxide at 110 °C to prepare segmented copolymers with tetrasulfonated units. The corresponding disulfonated copolymers are prepared by using disulfonated DCDPS instead of sBCPSBP. Small-angle X-ray scattering measurements of the fully aromatic copolymer membranes show ionomer peaks that indicate significantly larger characteristic separation lengths of the tetrasulfonated copolymers compared to those of the corresponding disulfonated copolymers with similar ionic contents. This implies a much more efficient phase separation of the ionic groups in the segmented tetrasulfonated copolymer membranes, especially at low-to-medium ionic contents. The enhanced phase separation has a pronounced positive effect on water uptake characteristics and proton transport properties. Under a reduced relative humidity (RH), the tetrasulfonated copolymer membranes show a significantly higher conductivity than the disulfonated ones, particularly at low-to-medium ionic contents. At an ion-exchange capacity of 1 meq g−1, the conductivity of the tetrasulfonated copolymer membrane at 30 % RH is higher than that of the disulfonated membrane at 90 % RH. Because of their relative ease of synthesis, segmented copolymers based on well-designed multisulfonated monomers may provide a viable alternative to the more complex sulfonated block and graft copolymers for use as fuel-cell membranes.
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| 9. |
- Weiber, Annika, et al.
(författare)
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Ion distribution in quaternary ammonium functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion exchange membranes
- 2014
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 7:9, s. 2621-2630
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Tidskriftsartikel (refereegranskat)abstract
- A series of copoly(arylene ether sulfone)s having precisely two, three or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion exchange membranes. The copolymers are synthesized via condensation polymerizations involving either di-, tri- or tetramethylhydroquinone, followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows an excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ionexchangecapacity (IEC) of 2.1 meq. g-1, the water uptake decrease with an increasing local density of QA groups. Moreover, at moderate IECs at 20 °C the Br- conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, placing multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells.
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| 10. |
- Fredin, Lisa A., et al.
(författare)
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Molecular and Interfacial Calculations of Iron(II) Light Harvesters
- 2016
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631. ; 9:7, s. 667-675
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Tidskriftsartikel (refereegranskat)abstract
- Iron-carbene complexes show considerable promise as earth-abundant light-harvesters, and adsorption onto nanostructured TiO2 is a crucial step for developing solar energy applications. Intrinsic electron injection capabilities of such promising FeII N-heterocyclic complexes (Fe-NHC) to TiO2 are calculated here, and found to correlate well with recent experimental findings of highly efficient interfacial injection. First, we examine the special bonding characteristics of Fe-NHC light harvesters. The excited-state surfaces are examined using density functional theory (DFT) and time-dependent DFT (TD-DFT) to explore relaxed excited-state properties. Finally, by relaxing an Fe-NHC adsorbed on a TiO2 nanocluster, we show favorable injection properties in terms of interfacial energy level alignment and electronic coupling suitable for efficient electron injection of excited electrons from the Fe complex into the TiO2 conduction band on ∼100 fs time scales.
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