| 1. |
- Belkheiri, Tallal, 1985, et al.
(author)
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Kraft Lignin Depolymerization in Near-Critical Water: Effect of Changing Co-Solvent
- 2014
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In: Cellulose Chemistry and Technology. - 0576-9787. ; 48:9-10, s. 813-818
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Journal article (peer-reviewed)abstract
- As part of developing a process to valorize lignin in a pulp mill with lignin separation, the depolymerisation of lignin to valuable chemicals was investigated in near-critical water. This was done by using methanol as co-solvent and hydrogen donor, phenol to suppress repolymerization (e.g. formation of char), and ZrO2 as a heterogeneous catalyst, with potassium carbonate as a co-catalyst. The reaction was carried out in a continuous flow fixed-bed reactor (500 cm(3)), at 280-350 degrees C and 25MPa. An important aspect is to suppress char formation. Therefore, the char formation was studied by using different concentrations of methanol and phenol. The char yield varied between 14% and 26%. When using methanol as the only co-solvent, the char yield decreased with increasing methanol concentration. Adding phenol resulted in a further decrease. The reactor outlet consisted mainly of two liquid phases, an aqueous and an oil phase, mixed together. The chemical analysis of the aqueous phase showed the presence of mainly phenolic compounds, for instance guaiacol, catechol, phenol and cresol.
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| 2. |
- Nguyen Lyckeskog, Huyen, 1985, et al.
(author)
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Accelerated aging of bio-oil from lignin conversion in subcritical water
- 2017
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In: Tappi Journal. - : TAPPI. - 0734-1415. ; 16:3, s. 123-141
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Journal article (other academic/artistic)abstract
- Accelerated aging of bio-oil derived from lignin was investigated at different aging temperatures (50 degrees C and 80 degrees C) and times (1 hour, 1 day, 1 week, and 1 month). The bio-oil used was produced by the hydrothermal liquefaction of kraft lignin, using phenol as the capping agent, and base (potassium carbonate and potassium hydroxide) and zirconium dioxide as the catalytic system in subcritical water. Elemental composition, molecular weight (by using gel permeation chromatography), and chemical composition (by using gas chromatography-mass spectrometry and 2D nuclear magnetic resonance [18.8 T, DMSO-d(6)]) of the bio-oil were measured to gain better understanding of the changes that occurred after being subjected to an accelerated aging process. The lignin-derived hydrothermal liquefaction bio-oil was quite stable compared with biomass-pyrolysis bio-oil. The yield of the low molecular weight fraction (light oil) decreased from 64.1% to 58.1% and that of tetrahydrofuran insoluble fraction increased from 16.5% to 22.2% after aging at 80 degrees C for 1 month. Phenol and phenolic dimers (Ar-CH2-Ar) had high reactivity compared with other aromatic substituents (i.e., methoxyl and aldehyde groups); these may participate in the polymerization/condensation reactions in the hydrothermal liquefaction bio-oil during accelerated aging. Moreover, the 2D heteronuclear single quantum coherence nuclear magnetic resonance spectra of the high molecular weight fraction (heavy oil) in the aged raw oil in the aromatic region showed that the structure of this fraction was a combination of phenol-alkyl patterns, and the guaiacol cross-peaks of Ar-2, Ar-5, and Ar-6 after aging indicate that a new polymer was formed during the aging process. Application: Pulp mill personnel can use this information when considering technology to extract lignin from black liquor and process it further into bio-oil.
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| 3. |
- Nguyen Lyckeskog, Huyen, 1985
(author)
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Catalytic conversion of LignoBoost Kraft lignin into liquid products in near-critical water
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Lignin, one of the three main components of lignocellulosic biomass, is the second most abundant organic polymer found on Earth. Due to its aromatic nature, lignin is recognized as being a potential feedstock for producing transportation fuel and high value-added chemicals. Nowadays, most of the lignin (almost 99%) produced in the Kraft pulping process is used as internal fuel. A modern Kraft mill has an energy surplus and, therefore, the potential of being a large scale biorefinery: one option is to extract lignin from black liquor, make it a new source of specialty chemicals and fuel. Furthermore, a new process, called “LignoBoost”, has recently been developed to extract a high quantity of pure lignin and has gained commercial status. Therefore, in years to come, a huge amount of LignoBoost Kraft lignin is expected to be available for valorisation.In this work, the catalytic conversion of LignoBoost Kraft lignin into liquid products at near-critical condition in water, using ZrO2/K2CO3 as the catalytic system and phenol as the co-solvent, was carried out in the small pilot unit, developed by, and located at, Chalmers University of Technology in Gothenburg, Sweden. The plant, operated in continuous mode, was fed with lignin slurry at a flow rate of 1 kg/h. The analytical procedure for the reaction products has been developed in order to determine the composition of the liquid products. In addition, the influence of K2CO3 concentration and reaction temperature was investigated in order to optimise the yields of the liquid products obtained.The results show that the K2CO3 concentration and reaction temperature exert different effects in terms of the composition and yields of the resulting products. The reaction products obtained from this process consist of water-soluble organics (5–11% on a dry lignin basis), lignin-oil (69–88%) and char (16–22%). The main 1-ring aromatic compounds (found in water-soluble organics and diethyl ether-soluble lignin-oil) are anisoles, alkylphenols, guaiacols and catechols, showing different trends with K2CO3 concentration and reaction temperature. In addition, the reaction temperature has a relatively large effect on alkylphenols, whereas K2CO3 has a relatively large effect on anisoles. The lignin-oil, being partially deoxygenated, has higher carbon content and heat value, but lower content of sulphur, than lignin in the feed.
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| 4. |
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| 5. |
- Nguyen Lyckeskog, Huyen, 1985
(author)
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Hydrothermal Liquefaction of Lignin into Bio-Oil
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Lignin, one of the three main components of lignocellulosic biomass, is the second most abundant organic polymer found on Earth. Nowadays, most of the lignin (almost 99%) produced in the Kraft pulping process is used as internal fuel. However, modern Kraft mills have an energy surplus, which provides an opportunity for extracting lignin that can be used as a new source of specialty chemicals as well as transportation fuel. Furthermore, a new process, called “LignoBoostTM”, has been developed recently to extract a large quantity of pure lignin and has gained commercial status.In this work, hydrothermal liquefaction (HTL) was used to produce bio-oil from LignoBoostTM Kraft lignin in subcritical water, using ZrO2/K2CO3/KOH as the catalytic system and phenol as the capping agent, in a small pilot unit (in continuous mode) developed and located at Chalmers University of Technology in Gothenburg, Sweden. An analytical procedure for the reaction products was developed in order to analyse the liquid products. In addition, the influence of the concentration of K2CO3 and the reaction temperature was investigated to optimise the yields and quality of the resulting liquid products. The stability of bio-oil is a significant factor to study since it influences the further upgrading of bio-oil into fuel to be used in industry: high stability makes it more versatile and thus suitable for wider range of applications. The stability of the resulting bio-oil was, therefore, studied under natural (room temperature, 2 years) and accelerated aging (up to 80°C, up to 1 month); the accelerated aging of bio-oil fractions was also studied to obtain a deeper understanding of the aging mechanism.The results show that these two variables, i.e. the concentration of K2CO3 and the reaction temperature, affect the products obtained differently: these products consist of bio-oil (69–88%), water-soluble organics (5–11%) and char (16–22%). The main monomers are anisoles, alkyl phenols, guaiacols and catechols, the relative amounts of which varied with the reaction conditions. Being partially deoxygenated, lignin HTL bio-oil has low contents of water and ash, which is beneficial for achieving bio-oil of high quality. This bio-oil was found to be remarkably stable at both room temperature and elevated temperature. Furthermore, its stability was found to be enhanced by the removal of insoluble high Mw molecules.
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| 6. |
- Nguyen Lyckeskog, Huyen, 1985, et al.
(author)
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Importance of Decomposition Reactions for Catalytic Conversion of Tar and Light Hydrocarbons: An Application with an Ilmenite Catalyst
- 2016
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 55:46, s. 11900-11909
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Journal article (peer-reviewed)abstract
- This work elucidates the contributions of different decomposition reactions, namely, steam reforming, hydro-cracking, dry reforming, and (thermal) cracking reactions, to the conversion of tar and light hydrocarbons during the catalytic cleaning of a biomass derived raw gas. A raw gas that contained a high content of steam and that was produced in the Chalmers indirect biomass gasifier was taken as the reference. The representative reactions associated with the upgrading of the given raw gas were identified to investigate the individual effects and thereafter reassembled to investigate the synergistic effects. Ilmenite was used as the catalyst, and the temperature range of 750 degrees-900 degrees C was the focus. For this process, it was discovered that the complete steam reforming, steam dealkylation, and hydro-cracking reactions are important, whereas the dry reforming reaction is not relevant. In addition, the water gas shift reaction occurs significantly and can promote the hydron-cracking reaction. These results provide insights into the most important reactions for inclusion in kinetic models of catalytic gas cleaning.
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| 7. |
- Nguyen Lyckeskog, Huyen, 1985, et al.
(author)
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Storage stability of bio-oils derived from the catatytic conversion of kraft lignin in subcritical water
- 2016
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In: European Biomass Conference and Exhibition Proceedings. - 2282-5819. ; 2016:24thEUBCE, s. 1107-1110
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Conference paper (peer-reviewed)abstract
- In the efforts of replacing fossil raw material with renewable resources, most attention has been on carbohydrates (e.g. 2nd generation ethanol). However, during the last period of time the interest in lignin has raised due to its aromatic nature and that it now has started to be more abundant. The conversion of lignin in subcritical water into smaller aromatic units is a promising process because of the relatively mild operating temperatures, which allows the aromatic structures to be retained. In this work, we have investigated the storage stability of lignin-derived bio-oil obtained from the continuous process at subcritical conditions of water (25 MPa, 350oC). The bio-oil was stored at an ambient temperature for 1–2 years. The changes in water concentration (Karl Fischer measurement), chemical composition (GC-MS and elemental analysis) and molecular weight (GPC analysis) of bio-oils were evaluated before and after the storage. The bio-oil was fractionated into: light oil (a low Mw fraction), heavy oil and solids (the high Mw fractions) and all three fractions were analyzed in order to obtain a better understanding about the stability of monomeric as well as oligomeric structures.
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| 8. |
- Nguyen Lyckeskog, Huyen, 1985, et al.
(author)
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Thermal stability of low and high Mw fractions of bio-oil derived from lignin conversion in subcritical water
- 2017
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In: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 7:4, s. 401-414
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Journal article (peer-reviewed)abstract
- The thermal stability of bio-oil influences its application in industry and is, therefore, a very important factor that must be taken into consideration. In this study, the stability of low and high molecular weight (Mw) fractions of bio-oil obtained from the hydrothermal liquefaction (HTL) of lignin in subcritical water was studied at an elevated temperature (80 °C) for a period of 1 h, 1 day and 1 week. The changes in molecular weight (gel permeation chromatography (GPC)) and chemical composition (gas chromatography–mass spectrometry (GC–MS) and 2D heteronuclear single quantum correlation (HSQC) NMR (18.8 T, DMSO-d6)) of low and high Mw fractions of the HTL bio-oil (i.e. light oil (LO) and heavy oil (HO)) were evaluated before and after ageing. It was found that only a slight formation of high Mw insoluble structures was obtained during ageing at elevated temperature for 1 week: 0.5% for the LO and 3.1% for the HO. These higher Mw moieties might be formed from different polymerisation/condensation reactions of the reactive compounds (i.e. anisoles, guaiacols, phenols, methylene (–CH2–) groups in phenolic dimers and xanthene). The high Mw insolubles in both the LO and the HO were analysed for structural composition using 2D HSQC NMR to obtain a better understanding of the changes in the composition of bio-oil fractions during the accelerated ageing process. In addition, a chemical shift database in DMSO-d6 was analysed for a subset of phenolic model compounds to simplify the interpretation of the 2D HSQC NMR spectra.
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