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13. Promoting Effect of Ce and La on Ni–Mo/δ-Al2O3Catalysts in the Hydrodeoxygenation of Vanillin

Author

Kristensen, Tove A., Hulteberg, Christian P., Wallenberg, Reine L., Abdelaziz, Omar Y., and Blomberg, Sara

Abstract

A crucial aspect of adding an economical and environmental dimension to the upgrading of bio-oils is to develop catalysts with enhanced and prolonged activity. In the present study, the effect of doping δ-alumina (Al2O3) with oxides of cerium (Ce) and lanthanum (La) before thermal treatment was investigated. The performance of such an Al2O3-supported nickel–molybdenum (Ni–Mo) catalyst was evaluated by studying the selectivity for the direct hydrodeoxygenation (HDO) of vanillin to cresol under continuous-flow conditions. In addition, the effect of adding H2S during catalyst activation and/or performance tests was also evaluated. Overall, enhanced performance of the doped NiMo catalyst in the HDO process has been demonstrated and an increased selectivity for cresol via direct HDO observed. The advantage of adding La and Ce is supported by the characterization results, where less sintering and enhanced pore diameter of the doped Al2O3were observed after thermally inducing the transformation from the δ to θ phases. The improved characteristics and prolonged activity of the doped Al2O3were also deduced by the lower acidity of the catalyst, which resulted in reduced coke formation during the HDO process.

Published
2024
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23. Oxidative Depolymerization of Kraft Lignin to Aromatics Over Bimetallic V–Cu/ZrO2 Catalysts.

Author

Abdelaziz, Omar Y., Clemmensen, Ida, Meier, Sebastian, Bjelić, Saša, Hulteberg, Christian P., and Riisager, Anders

Subjects
*BIMETALLIC catalysts, *DEPOLYMERIZATION, *LIGNIN structure, *NUCLEAR magnetic resonance spectroscopy, *HETEROGENEOUS catalysis, *X-ray diffraction, *LIGNINS
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. [ABSTRACT FROM AUTHOR]

Published
2023
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33. On the oxidative valorization of lignin to high-value chemicals:A critical review of opportunities and challenges

Author

Abdelaziz, Omar Y., Clemmensen, Ida, Meier, Sebastian, Costa, Carina A. E., Rodrigues, Alírio E., Hulteberg, Christian P., Riisager, Anders, Abdelaziz, Omar Y., Clemmensen, Ida, Meier, Sebastian, Costa, Carina A. E., Rodrigues, Alírio E., Hulteberg, Christian P., and Riisager, Anders

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.

Published
2022

40. Lignin Conversion to Value-Added Small-Molecule Chemicals : Towards Integrated Forest Biorefineries

Author

Abdelaziz, Omar Y.

Subjects
biorefinery, renewable chemicals, catalysis, lignin depolymerization, lignin valorization, aromatic monomers, Chemical Engineering, microbial conversion, techno-economic analysis, kraft lignin
Abstract

Lignin is the most abundant aromatic biopolymer on Earth and has significant potential as a feedstock for industrial use. Due to its intrinsic heterogeneity and recalcitrance, lignin has been regarded as a low-value side-product in the pulp and paper industry and in second-generation biorefineries. However, novel technologies are currently being explored to utilize lignin as a renewable resource for bio-based chemicals, fuels, and materials. The efficient valorization of lignin would also improve the economics and sustainability of forest-based industries. Deriving value from lignin, beyond low-value heat and power, is thus essential for the success of a global circular bioeconomy employing lignocellulosic biomass as a raw material.This thesis discusses the possibility of producing high-value chemicals from technical lignin streams via thermochemical–biological methods. The work deals with four major research themes: (1) providing insights into the physicochemical properties of technical lignins that could be valuable in designing routes for their valorization, (2) developing technologies for the thermochemical depolymerization of lignin under batch and continuous-flow conditions, (3) developing strategies for the biological valorization of lignin by combining thermochemical depolymerization with microbial conversion, and (4) assessing the techno-economic viability of lignin as a feedstock for sustainable chemical production in a biorefinery.Comprehensive physicochemical characterization of technical lignins is crucial in the development of molecularly tailored lignin-based applications. Elucidating the structural and compositional features can facilitate the matching of technical lignin streams with suitable valorization strategies, including thermochemical depolymerization. Two thermochemical depolymerization approaches were investigated for the production of low-molecular-weight aromatics from technical lignin: base-catalyzed depolymerization and oxidative depolymerization. Both approaches were also found to be effective means of pretreatment enabling the microbial conversion of kraft lignin.Continuous processing allowed hydrothermal lignin treatment at exceptionally short residence times, and this is anticipated to be an important stepping-stone toward technical lignin valorization. Membrane filtration appeared to be a practical method of separating complex depolymerized lignin mixtures for product fractionation and upgrading. Bimetallic catalyst systems based on Cu, Mn, and V improved the oxidative conversion of lignosulfonate and kraft lignins into value-added aromatic compounds. Techno-economic analysis underlined the viability of large-scale chemical production from kraft lignin by oxidative depolymerization, offering opportunities for process integration with traditional pulp mills.

Published
2021

45. Oxidative Depolymerization of Kraft Lignin for Microbial Conversion

Author

Abdelaziz, Omar Y., Ravi, Krithika, Mittermeier, Fabian, Meier, Sebastian, Riisager, Anders, Lidén, Gunnar, Hulteberg, Christian P., Abdelaziz, Omar Y., Ravi, Krithika, Mittermeier, Fabian, Meier, Sebastian, Riisager, Anders, Lidén, Gunnar, and Hulteberg, Christian P.

Abstract

The valorization of lignin is being increasingly recognized as crucial to improve the economic viability of integrated biorefineries. Due to 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.

Published
2019

48. Oxidative Depolymerisation of Lignosulphonate Lignin into Low-Molecular-Weight Products with Cu–Mn/δ-Al2O3.

Author

Abdelaziz, Omar Y., Meier, Sebastian, Prothmann, Jens, Turner, Charlotta, Riisager, Anders, and Hulteberg, Christian P.

Subjects
*LIGNINS, *NUCLEAR magnetic resonance spectroscopy, *DEPOLYMERIZATION, *OXIDATIVE dehydrogenation, *SUPERCRITICAL fluid chromatography, *INDUCTIVELY coupled plasma atomic emission spectrometry, *GEL permeation chromatography, *THERMOGRAVIMETRY
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-Al2O3, 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. [ABSTRACT FROM AUTHOR]

Published
2019
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49. Oxidative Depolymerisation of Lignosulphonate Lignin into Low-Molecular-Weight Products with Cu–Mn/δ-Al2O3.

Author

Abdelaziz, Omar Y., Meier, Sebastian, Prothmann, Jens, Turner, Charlotta, Riisager, Anders, and Hulteberg, Christian P.

Subjects
LIGNINS, NUCLEAR magnetic resonance spectroscopy, DEPOLYMERIZATION, OXIDATIVE dehydrogenation, SUPERCRITICAL fluid chromatography, INDUCTIVELY coupled plasma atomic emission spectrometry, GEL permeation chromatography, THERMOGRAVIMETRY
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-Al2O3, 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. [ABSTRACT FROM AUTHOR]

Published
2019
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