| 1. |
- Abdelaziz, Omar Y., et al.
(författare)
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Biological valorization of low molecular weight lignin
- 2016
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 34:8, s. 1318-1346
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Forskningsöversikt (refereegranskat)abstract
- Lignin is a major component of lignocellulosic biomass and as such, it is processed in enormous amounts in the pulp and paper industry worldwide. In such industry it mainly serves the purpose of a fuel to provide process steam and electricity, and to a minor extent to provide low grade heat for external purposes. Also from other biorefinery concepts, including 2nd generation ethanol, increasing amounts of lignin will be generated. Other uses for lignin – apart from fuel production – are of increasing interest not least in these new biorefinery concepts. These new uses can broadly be divided into application of the polymer as such, native or modified, or the use of lignin as a feedstock for the production of chemicals. The present review focuses on the latter and in particular the advances in the biological routes for chemicals production from lignin. Such a biological route will likely involve an initial depolymerization, which is followed by biological conversion of the obtained smaller lignin fragments. The conversion can be either a short catalytic conversion into desired chemicals, or a longer metabolic conversion. In this review, we give a brief summary of sources of lignin, methods of depolymerization, biological pathways for conversion of the lignin monomers and the analytical tools necessary for characterizing and evaluating key lignin attributes.
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| 2. |
- Abdelaziz, Omar Y., et al.
(författare)
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Conceptual Design of a Kraft Lignin Biorefinery for the Production of Valuable Chemicals via Oxidative Depolymerization
- 2020
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Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:23, s. 8823-8829
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is the most abundant aromatic biopolymer on Earth, and its aromatic structure makes it a promising platform for the production of biobased chemicals and other valuable building blocks. The valorization of lignin into chemicals currently presents a challenge, and its facilitation is key in the development of viable lignocellulosic biorefinery processes. This study presents a conceptual design for a recently demonstrated process for lignin oxidative depolymerization. Modeling, simulation, and analysis were performed based on experimental data to assess the viability of the process. Mass and energy balances and main design data were determined for a 700 t/y kraft lignin biorefinery. The production capacity of aromatic chemicals, including vanillin, vanillic acid, guaiacol, and acetovanillone, was 0.3 kg aromatics/kg net lignin use. A heat-integrated process design is suggested, and the energy demands and the CO2 emissions are evaluated and compared. Assuming an interest rate of 10% and a plant lifetime of 10 years, the return on investment was calculated to be 14%, indicating that such a biorefinery is viable. A sensitivity analysis was carried out to assess the impact of the vanillin selling price and the cost of lignin on the profitability of the process. A quantitative investigation of process sustainability resulted in an E-factor of ∼1.6 for the entire synthetic route, that is, 38% material efficiency. The findings of this study underline the need for further research to develop efficient lignin conversion technologies with attractive yields in order to increase profitability on an industrial scale.
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| 3. |
- Abdelaziz, Omar Y., et al.
(författare)
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Membrane filtration of alkali-depolymerised kraft lignin for biological conversion
- 2019
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Ingår i: Bioresource Technology Reports. - : Elsevier BV. - 2589-014X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have investigated the possibility of membrane filtration as a means for obtaining a fraction containing mainly low-molecular-weight (LMW) compounds from depolymerised lignin (DL) for subsequent microbial conversion. A DL stream from continuous-mode alkali depolymerisation of a softwood kraft lignin produced at a temperature of 220 °C and a residence time of 2 min, using a NaOH/lignin weight ratio of 1 with 5 wt% lignin loading was fractionated using a polymeric membrane with a molecular weight cut-off of 500–700 Da. The permeate (DLP) volume recovery of LMW phenolics (250–450 Da) was 70% after filtration for 3.7 h. The DLP was used as a carbon source for growth of three bacterial strains; Pseudomonas fluorescens, P. putida EM42 and Rhodococcus opacus, and good growth was obtained by the first two microorganisms. This proof-of-concept study demonstrates a novel strategy for technical lignin valorisation by combining depolymerisation, nanofiltration and bioconversion.
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| 4. |
- 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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| 5. |
- Abdelaziz, Omar Y., et al.
(författare)
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Oxidative Depolymerisation of Lignosulphonate Lignin into Low-Molecular-Weight Products with Cu–Mn/δ-Al2O3
- 2019
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 62, s. 639-648
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Tidskriftsartikel (refereegranskat)abstract
- Lignin depolymerisation receives great attention due to the pressing need to find sustainable alternatives to fossil sources for production of fuels and chemicals. In this study, alumina-supported Cu–Mn and Ni–Mo catalysts were tested for oxidative depolymerisation of a technical lignin stream—sodium lignosulphonates—to produce valuable low-molecular-weight aromatics that may be considered for applications in the fuels and chemicals sector. The reactions were performed at elevated temperature and oxygen pressure, and the product mixtures were analysed by size exclusion chromatography, two-dimensional nuclear magnetic resonance spectroscopy and supercritical fluid chromatography mass spectrometry. The best performance was obtained with Cu–Mn/δ-Al 2 O 3 , which was thoroughly characterised before and after use by nitrogen physisorption, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, thermal gravimetric analysis, inductively coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. Major products identified were vanillin, p-hydroxybenzaldehyde, vanillic acid and p-hydroxybenzoic acid as well as smaller aliphatic aldehydes, acids and lactones.
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| 6. |
- Abdelaziz, Omar Y., et al.
(författare)
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Oxidative Depolymerization of Kraft Lignin for Microbial Conversion
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:13, s. 11640-11652
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Tidskriftsartikel (refereegranskat)abstract
- The valorization of lignin is being increasingly recognized as crucial to improve the economic viability of integrated biorefineries. Because of its inherent heterogeneity and recalcitrance, lignin has been treated as a waste product in the pulp and paper industry, but new technologies are now being explored to transform lignin into a sustainable resource and enhance its value chain. In the present study, alkaline oxidative depolymerization was investigated as a potential form of pretreatment to enable further biological conversion of LignoBoost kraft lignin (LB). LB lignin oxidation reactions were studied at various temperatures (120-200 °C) and O2 partial pressures (3-15 bar) to identify the optimal conditions for obtaining a biocompatible, oxidatively depolymerized lignin (ODLB) stream. The low molecular weight compounds resulting from this treatment consisted mainly of aromatic monomers and carboxylic acids. The highest yield of aromatic monomers, 3 wt %, was obtained at 160 °C and 3 bar O2. The yield of carboxylic acids increased with both increasing temperature and O2 pressure, exceeding 13% under the harshest conditions investigated. The growth of four aromatic-catabolizing bacterial strains was examined on reaction product mixtures, all of which showed growth on agar plates utilizing ODLB as the sole source of carbon and energy. Rhodococcus opacus and Sphingobium sp. SYK-6 were found to consume most of the aromatic monomers present in the ODLB (e.g., vanillin, vanillate, acetovanillone, and guaiacol). The findings of this study indicate that pretreatment by oxidative depolymerization has potential in the biological valorization of technical lignin streams, for the production of valuable chemicals and materials.
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| 7. |
- Abdelaziz, Omar Y., et al.
(författare)
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Oxidative Depolymerization of Kraft Lignin to Aromatics Over Bimetallic V–Cu/ZrO2 Catalysts
- 2023
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Ingår i: Topics in Catalysis. - 1022-5528. ; 66:17-18, s. 1369-1380
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Tidskriftsartikel (refereegranskat)abstract
- Zirconia-supported vanadium–copper catalysts (VCux:yZr) were used for the oxidative depolymerization of softwood LignoBoost Kraft lignin (LB). Various VCux:yZr catalysts were prepared (x:y = 0:1, 1:4, 1:2, 3:4, 1:1, and 1:0) by incipient wetness impregnation, and reactions were performed in alkaline water at 150 °C under an O2 pressure of 5 bar for 10 min. 1H–13C HSQC NMR spectroscopy was used for product identification and quantification. The most promising catalyst was VCu1:2Zr, giving a total monomer yield of 9 wt% and the highest selectivity for vanillin (59%). This catalyst was characterized before and after use by N2 physisorption, XRD, TGA, SEM-EDS, and XPS. Cleavage of the main interunit linkages in LB, including the β-O-4 bonds and recalcitrant C–C bonds, was also observed. The findings of this study demonstrate the potential of the V–Cu/ZrO2 catalyst system in the production of value-added aromatics from technical lignin under relatively mild conditions. This would contribute to the more sustainable use of an underutilized side-stream in forest-based industries, provided catalyst reuse can be successfully demonstrated.
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| 8. |
- Abdelaziz, Omar Y., et al.
(författare)
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Physicochemical Characterisation of Technical Lignins for Their Potential Valorisation
- 2017
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Ingår i: Waste and Biomass Valorization. - : Springer Science and Business Media LLC. - 1877-265X .- 1877-2641. ; 8:3, s. 859-869
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, the second most abundant natural polymer, has emerged as a potential alternative material to petroleum-based chemicals and renewable resource for the production of diverse forms of aromatics, biofuels, and bio-based materials. Thus, it is becoming important to understand its structure and properties to provide key features and insights for better/efficient lignin valorisation. In this work, the physicochemical characterisation of two types of industrial (technical) lignins, namely LignoBoost lignin and alkali-treated lignin was performed. Characterisation has been conducted using Brunauer–Emmett–Teller N2 adsorption, particle size distribution, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, gel permeation chromatography, and thermogravimetric analysis. It was found that the pretreatment severity considerably influenced the lignin composition and functional properties. The measured physicochemical properties helped in proposing potential valorisation routes for these lignins in the context of a biorefinery, focusing on their depolymerisation and subsequent biological conversion to value-added chemicals and fuels.
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| 9. |
- Abdelaziz, Omar Y., et al.
(författare)
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Recent strides toward transforming lignin into plastics and aqueous electrolytes for flow batteries
- 2024
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Ingår i: iScience. - : Elsevier Inc.. - 2589-0042. ; 27:4
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Forskningsöversikt (refereegranskat)abstract
- Lignin is an abundant polyaromatic polymer with a wide range of potential future uses. However, the conversion of lignin into valuable products comes at a cost, and medium- to high-value applications are thus appropriate. Two examples of these are polymers (e.g., as fibers, plasticizers, or additives) and flow batteries (e.g., as redox species). Both of these areas would benefit from lignin-derived molecules with potentially low molecular weight and high (electro)chemical functionality. A promising route to obtain these molecules is oxidative lignin depolymerization, as it enables the formation of targeted compounds with multiple functionalities. An application with high potential in the production of plastics is the synthesis of new sustainable polymers. Employing organic molecules, such as quinones and heterocycles, would constitute an important step toward the sustainability of aqueous flow batteries, and lignin and its derivatives are emerging as redox species, mainly due to their low cost and renewability.
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| 10. |
- Ajao, Olumoye, et al.
(författare)
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Green solvents-based fractionation process for kraft lignin with controlled dispersity and molecular weight
- 2019
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524. ; 291
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to develop a novel green solvent based sustainable process to refine lignin into low molecular weight (LMW) and high molecular weight (HMW) fractions. Lignin dispersity reduction were experimentally determined using four solvent mixtures, and benchmarked against eight pure solvents. Data outputs were used for modelling the integrated fractionation process. Dispersity reduction of up to 73% was achieved for the high value LMW fraction. Also, a 90% reduction of energy requirement was achieved with an optimized process incorporating a mechanical vapor compression system. This study showed that solvent mixtures involving water can significantly reduce the cost, environment, health and safety impacts of lignin fractionation. Techno-economic evaluation confirmed the economic viability of a large-scale process processing 50 tonne/day of lignin.
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