| 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. |
- Lyckeskog, Huyen, 1985, et al.
(author)
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Catalytic depolymerisation and conversion of Kraft lignin into liquid products using near-critical water
- 2014
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In: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 86, s. 67-75
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Journal article (peer-reviewed)abstract
- A high-pressure pilot plant was developed to study the conversion of LignoBoost Kraft lignin into bio-oil and chemicals in near-critical water (350◦C, 25 MPa). The conversion takes place in a continuous fixed-bed catalytic reactor (500 cm3) filled with ZrO2 pellets. Lignin (mass fraction of approximately 5.5%) is dispersed in an aqueous solution containing K2CO3(from 0.4% to 2.2%) and phenol (approximately 4.1%).The feed flow rate is 1 kg/h (reactor residence time 11 min) and the reaction mixture is recirculated internally at a rate of approximately 10 kg/h. The products consist of an aqueous phase, containing phenolic chemicals, and a bio-oil, showing an increased heat value (32 MJ/kg) with respect to the lignin feed. The 1-ring aromatic compounds produced in the process are mainly anisoles, alkylphenols, guaiacols and catechols: their overall yield increases from 17% to 27% (dry lignin basis) as K2CO3 is increased.
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| 3. |
- Ahlbom, Anders, 1993, et al.
(author)
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Using Isopropanol as a Capping Agent in the Hydrothermal Liquefaction of Kraft Lignin in Near-Critical Water
- 2021
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In: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:4
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Journal article (peer-reviewed)abstract
- In this study, Kraft lignin was depolymerised by hydrothermal liquefaction in near-critical water (290-335 degrees C, 250 bar) using Na2CO3 as an alkaline catalyst. Isopropanol was used as a co-solvent with the objective of investigating its capping effect and capability of reducing char formation. The resulting product, which was a mixture of an aqueous liquid, containing water-soluble organic compounds, and char, had a lower sulphur content than the Kraft lignin. Two-dimensional nuclear magnetic resonance studies of the organic precipitates of the aqueous phase and the char indicated that the major lignin bonds were broken. The high molar masses of the char and the water-soluble organics, nevertheless, indicate extensive repolymerisation of the organic constituents once they have been depolymerised from the lignin. With increasing temperature, the yield of char increased, although its molar mass decreased. The addition of isopropanol increased the yield of the water-soluble organic products and decreased the yield of the char as well as the molar masses of the products, which is indicative of a capping effect.
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| 4. |
- Lyckeskog, Huyen, 1985, et al.
(author)
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Storage Stability of Bio-oils Derived from the Catalytic Conversion of Softwood Kraft Lignin in Subcritical Water
- 2016
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In: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:4, s. 3097-3106
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Journal article (peer-reviewed)abstract
- The stability of lignin-derived bio-oil obtained from a continuous process [base (K2CO3)-catalyzed, using phenol as a capping agent] under subcritical conditions of water (25 MPa, 290-370 degrees C) was investigated. The lignin-derived bio-oil obtained was stored at ambient temperature for 2 years. Our results show that the base concentration in the feed solution affects the stability of this lignin-derived bio-oil during its long-term storage. It was found that, at low base concentrations (i.e., 0.4%-1.0%), the yields of all lignin-derived bio-oil fractions were relatively stable. At high base concentrations (i.e., 1.6%-2.2%), however, the yield of high-molecular-weight (high-Mw) structures increased and that of low-molecular-weight (low-Mw) structures decreased after storage. This indicated that the low-Mw materials had been polymerized to form high-Mw materials. In addition, it was found that the yield of gas chromatography-mass spectrometry (GC-MS)-identified compounds (excluding phenol) in this lignin-derived bio-oil decreased from 15% to 11%. This is probably due to the presence of solids in these lignin derived bio-oils, which promotes the catalytic polymerization reactions, suggesting that it is beneficial to remove the solids from this lignin-derived bio-oil in order to enhance its stability. Compared to the results obtained from bio-oil derived from biomass pyrolysis, our results show that bio-oil derived from the conversion of lignin in subcritical water has better chemical stability during long-term storage.
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| 5. |
- Lyckeskog, Huyen, 1985, et al.
(author)
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The effect of temperature on the catalytic conversion of Kraft lignin using near-critical water
- 2014
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 170, s. 196-203
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Journal article (peer-reviewed)abstract
- The catalytic conversion of suspended LignoBoost Kraft lignin was performed in near-critical water using ZrO2/K2CO3 as the catalytic system and phenol as the co-solvent and char suppressing agent. The reaction temperature was varied from 290 to 370 degrees C and its effect on the process was investigated in a continuous flow (1 kg/h). The yields of water-soluble organics (WSO), bio-oil and char (dry lignin basis) were in the ranges of 5-11%, 69-87% and 16-22%, respectively. The bio-oil, being partially deoxygenated, exhibited higher carbon content and heat value, but lower sulphur content than lignin. The main 1-ring aromatics (in WSO and diethylether-soluble bio-oil) were anisoles, alkylphenols, catechols and guaiacols. The results show that increasing temperature increases the yield of 1-ring aromatics remarkably, while it increases the formation of char moderately. An increase in the yields of anisoles, alkylphenols and catechols, together with a decrease in the yield of guaiacols, was also observed.
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| 6. |
- 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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| 7. |
- 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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| 8. |
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| 9. |
- 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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| 10. |
- 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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