| 1. |
- Baena-Moreno, Francisco, 1992, et al.
(author)
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Effluents and residues from industrial sites for carbon dioxide capture: a review
- 2023
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In: Environmental Chemistry Letters. - : Springer Science and Business Media LLC. - 1610-3653 .- 1610-3661. ; 21:1, s. 319-337
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Research review (peer-reviewed)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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| 2. |
- Hynynen, Jonna, 1987, et al.
(author)
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'Lignin and extractives first' conversion of lignocellulosic residual streams using UV light from LEDs
- 2021
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In: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 23, s. 8251-8259
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Journal article (peer-reviewed)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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| 3. |
- Riddell, Alexander Michael, 1996, et al.
(author)
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A 3D printed photoreactor for investigating variable reaction geometry, wavelength, and fluid flow
- 2022
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 93:8, s. 084103-
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Journal article (peer-reviewed)abstract
- Research in the field of photochemistry, including photocatalysis and photoelectrocatalysis, has been revitalized due to the potential that photochemical reactions show in the sustainable production of chemicals. Therefore, there is a need for flexible photoreactor equipment that allows for the evaluation of the geometry, light wavelength, and intensity of the vessel, along with the fluid flow in various photochemical reactions. Light emitting diodes (LEDs) have narrow emission spectra and can be either pulsed or run continuously; being flexible, they can be arranged to fit the dimensions of various types of the reactor vessel, depending on the application. This study presents a 3D printed photoreactor with the ability to adjust distances easily and switch between high-power LED light sources. The reactor design utilizes customized printed circuit boards to mount varying numbers and types of LEDs, which enables multiple wavelengths to be used simultaneously. These LED modules, comprised of heat sinks and cooling fans, fulfill the higher heat dissipation requirements of high-power LEDs. The flexibility of the reactor design is useful for optimizing the reaction geometry, flow conditions, wavelength, and intensity of photochemical reactions on a small scale. The estimates for incident light intensity under five possible reactor configurations using ferrioxalate actinometry are reported so that comparisons with other photoreactors can be made. The performance of the photoreactor for differing vessel sizes and distances, in both the flow and batch modes, is given for a photochemical reaction on 2-benzyloxyphenol-a model substance for lignin and applicable in the production of biobased chemicals.
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| 4. |
- Riddell, Alexander Michael, 1996, et al.
(author)
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Insights into Photosensitized Reactions for Upgrading Lignin
- 2023
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In: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:12, s. 4850-4859
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Journal article (peer-reviewed)abstract
- The conversion of lignin into valuable chemical products is important for the shift away from the petrochemical industry toward a more sustainable system of biorefineries. However, the recalcitrance and heterogeneity of lignin have made its selective depolymerization a difficult task. Photochemical methods of lignin conversion are being investigated because of the potential to operate photoreactors at milder temperatures and pressures than thermal methods and to achieve efficient reaction pathways. Furthermore, light-driven reactions facilitate reaction pathways that cannot be accessed by conventional/thermal methods. Most of the current research focuses on photocatalytic methods, which are interesting due to their potentially high selectivity, but come with the disadvantage of catalyst costs and separation requirements. In this work, we continue our investigation into the use of ultraviolet light-emitting diodes, which aims to utilize the advantages of photochemistry, while avoiding the use of expensive catalysts. Photosensitizers can participate in energy transfer, electron transfer, and hydrogen abstraction in photochemical reactions. Here, we investigated the effects of a common photosensitizer, benzophenone, on the photochemical conversion of lignin, and 2-(benzyloxy)phenol (2BP), a compound with an ether bond between two aromatic units. We monitored the conversion reactions using complementary techniques of 1H nuclear magnetic resonance (NMR), diffusion NMR, and in situ Fourier transform infrared (FTIR) spectroscopy. For 2BP, the reactions with benzophenone progressed slower and without a difference in the final product formation. However, several differences were observed in photoreactions utilizing Kraft lignin and benzophenone compared to those without benzophenone. For example, a faster decay of the 1H NMR peak corresponding to aromatic/phenolic protons and different changes in the shape of methoxy peaks were observed, indicating the formation of different products. This work demonstrates that benzophenone participates in the photoreactions of Kraft lignin and that the photoreactions of Kraft lignin and 2BP are different. Depolymerization of lignin into smaller fragments was confirmed with diffusion NMR, both with and without the photosensitizer.
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| 5. |
- Riddell, Alexander Michael, 1996
(author)
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Photochemical reactions of lignin: Opportunities for valorisation
- 2022
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Licentiate thesis (other academic/artistic)abstract
- Lignin is the second most abundant biopolymer after cellulose and is the largest bio-based source of aromatic compounds. However, its heterogeneous and recalcitrant structure makes it difficult to depolymerise for use in renewable chemicals production. Photochemical reactions can be performed at mild conditions and can achieve efficient reaction pathways without the use of additional reagents. The potential efficiency gains in terms of energy and use of materials have led to renewed interest in photochemistry research, as we seek to improve the environmental sustainability of industry. Concepts for valorisation of lignin through heterogenous and homogenous photocatalysis are currently being investigated. Although this photocatalyst research has shown some encouraging results, the synthesis, separation, and recycling of catalysts would add significant costs to a process. If it were possible to induce direct photochemical reactions with ultraviolet light, the difficulties associated with catalysis could be avoided, and it would bring a photochemical lignin valorisation concept closer to feasibility. This thesis deals with the topic of how ultraviolet light can induce changes in lignin. The contents in Paper I describe our early work, which demonstrated that UV light causes changes to functional groups in lignin and that UV light can be used to extract lignin from sawdust. In our more recent experiments, we use 280 nm light from UV-LEDs using a homemade 3D printed photoreactor, the details of which are covered in Paper II. The results presented here also include a comparison between acetonitrile and aqueous NaOH as solvents for the photoreactions. The evaluation of whether benzophenone can be used as a photosensitiser to increase the reaction rate or yield toward desired products in reactions of Kraft lignin and 2-(benzyloxy)phenol, a model compound used to represent an ether bond between two phenolic rings, is covered in Paper III. We also needed to access whether our conclusions are robust against changes in lignin concentration and light intensity, and an analysis of this is included in the results and discussion. Lignin has also been observed to act as a photocatalyst. The beginning of an investigation into this phenomenon is covered in this thesis using the photooxidation of methanol to formate as an example. 1H NMR is the primary analysis technique used in this work. Results based on GC-MS and diffusion NMR are included to demonstrate their intended use in future work. The analysis across all areas focuses on using the analysis methods to estimate reaction rates and selectivity toward certain products, and aims to understand the connections between these results and the details of the reactions. The results gathered so far have laid the groundwork for understanding the complex relationships between the properties of lignin, reaction conditions, and changes which occur upon irradiation with UV light. The end of the thesis discusses future plans for increasing our understanding of these photoreactions.
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