| 1. |
- Anugwom, Ikenna, et al.
(författare)
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Switchable ionic liquids as delignification solvents for lignocellulosic materials
- 2014
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Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 7:4, s. 1170-1176
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Tidskriftsartikel (refereegranskat)abstract
- The transformation of lignocellulosic materials into potentially valuable resources is compromised by their complicated structure. Consequently, new economical and feasible conversion/fractionation techniques that render value-added products are intensely investigated. Herein an unorthodox and feasible fractionation method of birch chips (B. pendula) using a switchable ionic liquid (SIL) derived from an alkanol amine (monoethanol amine, MEA) and an organic super base (1,8-diazabicyclo-[5.4.0]-undec-7-ene, DBU) with two different trigger acid gases (CO2 and SO2 ) is studied. After SIL treatment, the dissolved fractions were selectively separated by a step-wise method using an antisolvent to induce precipitation. The SIL was recycled after concentration and evaporation of anti-solvent. The composition of undissolved wood after MEA-SO2 -SIL treatment resulted in 80 wt % cellulose, 10 wt % hemicelluloses, and 3 wt % lignin, whereas MEA-CO2 -SIL treatment resulted in 66 wt % cellulose, 12 wt % hemicelluloses and 11 wt % lignin. Thus, the MEA-SO2 -SIL proved more efficient than the MEA-CO2 -SIL, and a better solvent for lignin removal. All fractions were analyzed by gas chromatography (GC), Fourier transform infrared spectroscopy (FT-IR), (13) C nuclear magnetic resonance spectroscopy (NMR) and Gel permeation chromatography (GPC).
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| 2. |
- Anugwom, Ikenna, et al.
(författare)
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Towards optimal selective fractionation for Nordic woody biomass using novel amine–organic superbase derived switchable ionic liquids (SILs)
- 2014
-
Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 70, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Improved fractionation process conditions for wood dissolution with switchable ionic liquids (SILs) were determined. The short time, high temperature (STHT) system was introduced as a selective and efficient way to extract components from lignocellulosic material. A SIL based on monoethanol amine (MEA) and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) formed via coupling with SO2, was applied as a solvent in a 1:3 weight ratio with water. In essence, selective dissolution of mainly lignin was achieved by means of the aqueous SIL at 160 °C (∼6.1 bar corresponding to the vapor pressure of water) in 2 h and in a pressure vessel, for both hard- and soft-wood. About 95 wt-% of wood lignin was extracted. The dissolved components in the spent SIL were recovered by the addition of an anti-solvent whereupon over 70% of the dissolved components were recovered; the recovered fraction contained 19 wt-% hemicellulose while the rest of the material was in essence lignin. The non-dissolved, fluffy material contained ∼70 wt-% cellulose and ∼20 wt-% hemicellulose – a consistency resembling that of Kraft pulp.
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| 3. |
- Asaadi, Shirin, et al.
(författare)
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Structural analysis of Ioncell-F fibres from birch wood
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 181, s. 893-901
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Tidskriftsartikel (refereegranskat)abstract
- Quite recently, the Ioncell-F process, a novel and promising Lyocell fibre process, has been developed. The ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH]OAc) utilized in this process, was identified as an excellent cellulose solvent for dry-jet wet fibre spinning. Fibres spun from cellulose-[DBNH]OAc solution have shown excellent mechanical properties. Herein, various structural features of these ionic liquid-based fibres were analyzed and correlated with their mechanical properties. The highest slope of tenacity increase of these Ioncell-F fibres (from birch wood) observed at low draw ratios (DRs), while a continuous but slower increase occurs to partly very high draws. The improvements in the mechanical properties do not seem to correlate with changes in the crystallite size or the crystalline orientation based on wide-angle X-ray scattering (WAXS) results. More significant differences were seen for the sample crystallinity, the amorphous orientation (measured by birefringence), the orientation of the voids, the specific surface (measured by small-angle X-ray scattering (SAXS)), and the sorption/desorption properties of the fibres.
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| 4. |
- Baird, Zachariah Steven, et al.
(författare)
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Vapor-Liquid Equilibrium of Ionic Liquid 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium Acetate and Its Mixtures with Water
- 2020
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 65:5, s. 2405-2421
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids have the potential to be used forextracting valuable chemicals from raw materials. These processesoften involve water, and after extraction, the water or otherchemicals must be removed from the ionic liquid, so it can bereused. To help in designing such processes, we present data onthe vapor−liquid equilibrium of the system containing protic ionicliquid 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium acetate,water, acetic acid, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Earlier studies have only focused on mixtures of water and anionic liquid with a stoichiometric ratio of the ions. Here, we alsoinvestigated mixtures containing an excess of the acid or basecomponent because in real systems with protic ionic liquids, theamount of acid and base in the mixture can vary. We modeled thedata using both the ePC-SAFT and NRTL models, and we compared the performance of different modeling strategies. We alsoexperimentally determined the vapor composition for a few of the samples, but none of the modeling strategies tested couldaccurately predict the concentration of the acid and base components in the vapor phase.
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| 5. |
- Borrega, Marc, et al.
(författare)
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Birch wood pre-hydrolysis vs pulp post-hydrolysis for the production of xylan-based compounds and cellulose for viscose application
- 2018
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 190, s. 212-221
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal treatments of birch wood and kraft pulp were compared for their ability to extract the xylan and produce viscose-grade pulp. Water post-hydrolysis of kraft pulp produced a high-purity cellulosic pulp with lower viscosity but higher cellulose yield than traditional pre-hydrolysis kraft pulping of wood. Post-hydrolysis of pulp also increased the crystallite dimensions and degree of crystallinity in cellulose, and promoted a higher extent of fibril aggregation. The lower specific surface area in post-hydrolyzed pulps, derived from their larger fibril aggregates, decreased the accessibility of –OH groups. However, this lower accessibility did not seem to decrease the pulp reactivity to derivatizing chemicals. In the aqueous side-stream, the xylose yield was similar in both pre- and post-hydrolysates, although conducting post-hydrolysis of pulp in a flow-through system enabled the recovery of high purity and molar mass (∌10 kDa) xylan for high-value applications.
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| 6. |
- Brännvall, Elisabet
(författare)
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Aspects on Strenght Delivery and Higher Utilisation of the Strength Potential of Kraft Pulp Fibres
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Studies on strength delivery and related fields have so far concentrated on finding the locations in the mill where fibres are damaged and what the damages consist of. However, fibres will invariably encounter mechanical stresses along the fibreline and in this thesis a new concept is introduced; the vulnerability of fibres to mechanical treatment. It is hypothesised that fibres with different properties have different abilities to withstand the mechanical forces they endure as they are discharged from the digester and transported through valves, pumps and various washing and bleaching equipment. In the thesis, results are presented from trials where pulps with significantly different hemicellulose compositions were high-intensity mixed at pH 13, 70°C and 10% pulp consistency and pulp strength evaluated. By varying alkalinity and temperature, pulps with different carbohydrate composition could be obtained. High alkali concentration and low temperature resulted in high glucomannan content and low xylan content, whereas cooking at low alkali concentration and high temperature rendered a pulp with low glucomannan and high xylan content. The high alkalinity pulp was stronger, determined as tear index at given tensile index. The pulp viscosity was also higher for this pulp. However, when the pulps were subjected to high-intensity mixing, the high alkalinity pulp lost in tear strength and the re-wetted zero-span tensile strength was substantially reduced. The pulp cooked at high alkalinity was thus interpreted as being more vulnerable to mechanical treatment than the pulp obtained by cooking at low alkalinity. Another pair of pulps was manufactured at high and low sodium ion concentrations, but otherwise with similar chemical charges. The pulp obtained by cooking at low sodium ion concentration became stronger, evaluated as tear index at a given tensile index and the curl index was substantially lower, 8% compared to 12% for the pulp cooked at a high sodium ion concentration. The viscosity was 170 ml/g higher for the pulp manufactured at low sodium ion concentration. When the pulps were subjected to high-intensity mixing, the tear strength of the pulp manufactured at high sodium ion concentration was reduced. The re-wetted zero-span tensile index decreased also after mixing. The pulp obtained by cooking at higher sodium ion concentration was thus interpreted as being more vulnerable to mechanical treatment than the pulp manufactured at lower sodium ion concentration. In the thesis, two reasons for the low strength delivery of industrially produced pulps compared to laboratory-cooked pulps are put forward. Since the ionic strength of mill cooking liquor systems is much higher than is normally used in laboratory cooking, this can partly explain the difference in strength between mill- and laboratory-cooked pulp. A higher sodium ion concentration was shown in this thesis work to give a pulp of lower strength. Secondly, it is suggested that the difference in retention time of the black liquor in laboratory cooking and continuous mill cooking systems can explain the difference in tensile strength between laboratory-cooked and mill-produced pulp. The black liquor in a continuous digester has a longer retention time in the digester than the chips. This gives a longer time for the dissolved xylan to degrade and, as a consequence, the xylan deposited on the mill pulp fibres will be more degraded than the xylan deposited on the laboratory-cooked pulp fibres. In the thesis, results are also presented from studies using different strength-enhancing chemicals. The fibre surfaces of bleached never-dried and once-dried pulp were modified by the polyelectrolyte multilayer technique using cationic and anionic starch. Although the pulps absorbed the same amount of starch, the never-dried pulp reached a higher tensile index than the once-dried pulp. When the starch-treated never-dried pulp was dried and reslushed it still had higher tensile index than the never-dried untreated pulp. The starch layers were thus able to counteract part of the hornification effect. The never-dried starch treated pulps were subsequently dried, reslushed and beaten. Pulp with starch layers had a better beatability evaluated as the tensile index obtained after given number of PFI revolutions than dried untreated pulp. Hence, there is a potential to increase the tensile index of market pulp by utilising the polyelectrolyte multilayer technique before drying. Addition of CMC to bleached mill pulp and laboratory-cooked pulp increased the tensile strength to the same degree for both pulps. CMC addition had a straightening effect on the fibres, the shape factor increased and this increased the zero-span tensile strength also.
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| 7. |
- Chawachart, Niwat, et al.
(författare)
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Thermal behaviour and tolerance to ionic liquid [emim] OAc in GH10 xylanase from Thermoascus aurantiacus SL16W
- 2014
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Ingår i: Extremophiles. - : Springer Japan. - 1431-0651 .- 1433-4909. ; 18:6, s. 1023-1034
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Tidskriftsartikel (refereegranskat)abstract
- GH10 xylanase from Thermoascus aurantiacus strain SL16W (TasXyn10A) showed high stability and activity up to 70–75 C. The enzyme’s half-lives were 101 h, 65 h, 63 min and 6 min at 60, 70, 75 and 80 C, respectively. The melting point (Tm), as measured by DSC, was 78.5 C, which is in line with a strong activity decrease at 75–80 C. The biomass-dissolving ionic liquid 1-ethyl-3-methylimidazolium acetate ([emim]OAc) in 30 % concentration had a small effect on the stability of TasXyn10A; Tm decreased by only 5 C. It was also observed that [emim]OAc inhibited much less GH10 xylanase (TasXyn10A) than the studied GH11 xylanases. The Km of TasXyn10A increased 3.5-fold in 15 % [emim]OAc with xylan as the substrate, whereas the approximate level of Vmax was not altered. The inhibition of enzyme activity by [emim]OAc was lesser at higher substrate concentrations. Therefore, high solid concentrations in industrial conditions may mitigate the inhibition of enzyme activity by ionic liquids. Molecular docking experiments indicated that the [emim] cation has major binding sites near the catalytic residues but in lower amounts in GH10 than in GH11 xylanases. Therefore, [emim] cation likely competes with the substrate when binding to the active site. The docking results indicated why the effect is lower in GH10.
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| 8. |
- Colson, Jérôme, et al.
(författare)
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Adhesion properties of regenerated lignocellulosic fibres towards poly(lactic acid) microspheres assessed by colloidal probe technique
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 532, s. 819-829
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Tidskriftsartikel (refereegranskat)abstract
- In the field of polymer reinforcement, it is important to understand the interactions involved between the polymer matrix and the reinforcing component. This paper is a contribution to the fundamental understanding of the adhesion mechanisms involved in natural fibre reinforced composites. We report on the use of the colloidal probe technique for the assessment of the adhesion behaviour between poly(lactic acid) microspheres and embedded cross-sections of regenerated lignocellulosic fibres. These fibres consisted of tailored mixtures of cellulose, lignin and xylan, the amount of which was determined beforehand. The influence of the chemical composition of the fibres on the adhesion behaviour was studied in ambient air and in dry atmosphere. In ambient air, capillary forces resulted in larger adhesion between the sphere and the fibres. Changing the ambient medium to a dry nitrogen atmosphere allowed reducing the capillary forces, leading to a drop in the adhesion forces. Differences between fibres of distinct chemical compositions could be measured only on freshly cut surfaces. Moreover, the surface energy of the fibres was assessed by inverse gas chromatography. Compared to fibres containing solely cellulose, the presence of lignin and/or hemicellulose led to higher adhesion and lower surface energy, suggesting that these chemicals could serve as natural coupling agents between hydrophobic and hydrophilic components.
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| 9. |
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| 10. |
- Darabi, Sozan, 1994, et al.
(författare)
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Green Conducting Cellulose Yarns for Machine-Sewn Electronic Textiles
- 2020
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 12:50, s. 56403-56412
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of "green"electronics is a response to the pressing global situation where conventional electronics contribute to resource depletion and a global build-up of waste. For wearable applications, green electronic textile (e-textile) materials present an opportunity to unobtrusively incorporate sensing, energy harvesting, and other functionality into the clothes we wear. Here, we demonstrate electrically conducting wood-based yarns produced by a roll-to-roll coating process with an ink based on the biocompatible polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The developed e-textile yarns display a, for cellulose yarns, record-high bulk conductivity of 36 Scm-1, which could be further increased to 181 Scm-1 by adding silver nanowires. The PEDOT:PSS-coated yarn could be machine washed at least five times without loss in conductivity. We demonstrate the electrochemical functionality of the yarn through incorporation into organic electrochemical transistors (OECTs). Moreover, by using a household sewing machine, we have manufactured an out-of-plane thermoelectric textile device, which can produce 0.2 μW at a temperature gradient of 37 K.
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| 11. |
- Darabi, Sozan, 1994, et al.
(författare)
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Huge potential for electronic textiles made with new cellulose thread
- 2021
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Ingår i: Technische Textilien. - 0323-3243. ; 64:3, s. 158-159
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Electronic textiles offer very interesting new opportunities in various fields, in particular in healthcare. However, to be sustainable, they need to be made of renewable materials. A research team led by Chalmers University of Technology, Gothenburg/Sweden, now presents a thread made of conductive cellulose, which offers interesting and practical possibilities for electronic textiles.
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| 12. |
- Darabi, Sozan, 1994, et al.
(författare)
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Polymer-Based n-Type Yarn for Organic Thermoelectric Textiles
- 2023
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X .- 2199-160X. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- A conjugated-polymer-based n-type yarn for thermoelectric textiles is presented. Thermoelectric textile devices are intriguing power sources for wearable electronic devices. The use of yarns comprising conjugated polymers is desirable because of their potentially superior mechanical properties compared to other thermoelectric materials. While several examples of p-type conducting yarns exist, there is a lack of polymer-based n-type yarns. Here, a regenerated cellulose yarn is spray-coated with an n-type conducting-polymer-based ink composed of poly(benzimidazobenzophenanthroline) (BBL) and poly(ethyleneimine) (PEI). The n-type yarns display a bulk electrical conductivity of 8 × 10−3 S cm−1 and Seebeck coefficient of −79 µV K−1. A promising level of air-stability for at least 13 days can be achieved by applying an additional thermoplastic elastomer coating. A prototype in-plane thermoelectric textile, produced with the developed n-type yarns and p-type yarns, composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-coated regenerated cellulose, displays a stable device performance in air for at least 4 days with an open-circuit voltage per temperature difference of 1 mV °C−1. Evidently, polymer-based n-type yarns are a viable component for the construction of thermoelectric textile devices.
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| 13. |
- Deb, Somdatta, et al.
(författare)
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Application of mild autohydrolysis to facilitate the dissolution of wood chips in direct-dissolution solvents
- 2016
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 18:11, s. 3286-3294
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Tidskriftsartikel (refereegranskat)abstract
- Wood is not fully soluble in current non-derivatising direct-dissolution solvents, contrary to the many reports in the literature quoting wood 'dissolution' in ionic liquids. Herein, we demonstrate that the application of autohydrolysis, as a green and economical wood pre-treatment method, allows for a massive increase in solubility compared to untreated wood. This is demonstrated by the application of two derivitising methods (phosphitylation and acetylation), followed by NMR analysis, in the cellulose-dissolving ionic liquids 1-allyl-3-methylimidazolium chloride ([amim]Cl) and 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH][OAc]. In addition, the non-derivitising tetrabutylphosphonium acetate ([P-4444][OAc]) : DMSO-d6 electrolyte also allowed for dissolution of the autohydrolysed wood samples. By combination of different particle sizes and P-factors (autohydrolysis intensity), it has been clearly demonstrated that the solubility of even wood chips can be drastically increased by application of autohydrolysis. The physiochemical factors affecting wood solubility after autohydrolysis are also discussed.
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| 14. |
- Ek, Monica, et al.
(författare)
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WOBAMA : wood based materials and fuels
- 2014
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Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 48:9-10, s. 773-779
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Tidskriftsartikel (refereegranskat)abstract
- WOBAMA - Wood Based Materials and Fuels is a biorefinery oriented scientific research project supported by Wood Wisdom-Net Research Programme and ERA-NET Bioenergy. In this project, the wood based raw materials were converted to a range of value added products through unconventional techniques. So far, many demonstrators have been prepared, such as the dissolving pulps with high cellulose content, the regenerated cellulose films with high tenacity, the hydrophobic materials based on cellulose and birch bark suberin, as well as the adhesives based on polysaccharides.
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| 15. |
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| 16. |
- Gentile, Luigi, et al.
(författare)
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A novel X-ray diffraction approach to assess the crystallinity of regenerated cellulose fibers
- 2022
-
Ingår i: IUCrJ. - 2052-2525. ; 9, s. 492-496
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Tidskriftsartikel (refereegranskat)abstract
- Here, a new accurate approach is presented to quantify the degree of crystallinity of regenerated cellulose textile fibers using wide-angle X-ray scattering. The approach is based on the observation that the contributions to the scattering from crystalline and amorphous domains of the fibers can be separated due to their different degree of orientation with respect to the fiber direction. The method is tested on Ioncell-F fibers, dry jet wet spun with different draw ratios from an ionic liquid solution. The analysis output includes, apart from an accurate estimate of the fiber crystallinity, the degrees of orientation of the cellulose nanocrystals and the cellulose chains in the amorphous domains.
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| 17. |
- Gubitosi, Marta, et al.
(författare)
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The colloidal structure of a cellulose fiber
- 2021
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 28:5, s. 2779-2789
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: We present a small angle X-ray scattering (SAXS) study of the colloidal structure of regenerated cellulose fibers, air-gap spun from an ionic liquid solution. Based on the data, and a different interpretation of the anisotropic SAXS pattern, we propose a slightly different colloidal structure of the fibers, than what is commonly assumed for regenerated cellulose fibers. Fibers with two different degrees of orientation, as produced by different draw ratios, DR = 2 and 15, respectively, are analyzed. The 2D SAXS pattern is highly anisotropic with striking cross-like pattern, having scattering predominantly perpendicular and parallel to the fiber axis. This cross-like pattern suggest a colloidal structure with oriented crystalline lamellae of ca. 10 nm thickness, embedded within a continuous matrix of amorphous cellulose. The lamellae are oriented with their normal parallel with the fiber axis. Complementary wide angle X-ray diffraction data confirm that the lamellae normal direction corresponds to the cellulose chain direction (c-direction) in the monoclinic cellulose crystal (Cellulose II). Graphic abstract: [Figure not available: see fulltext.].
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| 18. |
- Gusenbauer, Claudia, et al.
(författare)
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Differences in surface chemistry of regenerated lignocellulose fibers determined by chemically sensitive scanning probe microscopy
- 2020
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 165, s. 2520-2527
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the composition of regenerated lignocellulosic fibers in the production process enables targeting of specific material properties. In composite materials, such properties could be manipulated by controlled heterogeneous distribution of chemical components of regenerated fibers. This attribute requires a visualization method to show their inherent chemical characteristics. We compared complementary microscopic techniques to analyze the surface chemistry of four differently tuned regenerated lignocellulosic fibers. Adhesion properties were visualized with chemical force microscopy and showed contrasts towards hydrophilic and hydrophobic atomic force microscopy tips. Fibers containing xylan showed heterogeneous adhesion properties within the fiber structure towards hydrophilic tips. Additionally, peak force infrared microscopy mapped spectroscopic contrasts with nanometer resolution and provided point infrared spectra, which were consistent to classical infrared microscopy data. With this setup, infrared signals with a spatial resolution below 20 nm reveal chemical gradients in specific fiber types.
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| 19. |
- Kvarnlöf, Niklas, 1971-
(författare)
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Activation of dissolving pulps prior to viscose preparation
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The conventional viscose manufacturing process is a mature process that needs to be improved with respect to its environmental impact and its production cost structure. Therefore a research study has been done with the aim to improve the reactivity of the dissolving pulp used, in order to reduce the chemical demand in the viscose process and thus reduce the cost and indirectly the environmental impact.The work described in this thesis has shown that it is possible to enhance the pulp reactivity and to use less carbon disulphide in the production of viscose, while maintaining a good quality viscose dope, by two entirely different pretreatment methods, one chemical and one enzymatic.The chemical method used pressurized oxygen after the mercerisation step, which increased the reactivity of the alkali cellulose. The viscose dopes produced from the pressurized oxygen treated alkali cellulose had lower filter clogging values, Kw, compared to conventionally produced viscoses. The temperature and the oxygen treatment time of the alkali cellulose were however crucial for the viscose quality.The best performing enzyme of several tested was a cellulase of the mono component endoglucanase preparation Carezyme®. This enzymatic treatment was optimized with respect to viscose dope preparation. The study showed that the enzyme treatment could be carried out under industrially interesting conditions with respect to temperature, enzyme dose and reaction time. A re-circulation study of the enzyme showed that it was possible to re-use the spent press water from the enzymatic treatment step several times, and thus lower the production cost. Some of the viscose process stages were modified to properly fit the enzymatically treated dissolving pulp and a comparison between viscose made from enzyme-treated pulp and viscose made from conventional pulp, showed that the enzyme-treated samples had a lower filter clogging value, Kw. This indirectly indicates that the enzyme pretreatment could reduce the carbon disulphide charge in the viscose manufacturing process. An initial study of how the Carezyme® influenced different cellulosic sources was also performed.
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| 20. |
- Köpcke, Viviana
(författare)
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Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose. In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose-binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps. The main focus of the forest industry is the production of paper-grade pulps. Paper-grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps. Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps.
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| 21. |
- Li, He, et al.
(författare)
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Thermostabilization of extremophilic Dictyoglomus thermophilum GH11 xylanase by an N-terminal disulfide bridge and the effect of ionic liquid [emim] OAc on the enzymatic performance
- 2013
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Ingår i: Enzyme and microbial technology. - : Elsevier. - 0141-0229 .- 1879-0909. ; 53:6-7, s. 414-419
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, an extremophilic GH11 xylanase was stabilized by an engineered N-terminal disulphide bridge. The effect of the stabilization was then tested against high temperatures and in the presence of a biomass-dissolving ionic liquid, 1-ethyl-3-methylimidazolium acetate ([emim]OAc). The N-terminal disulfide bridge increased the half-life of a GH11 xylanase (XYNB) from the hyperthermophilic bacterium Dictyoglomus thermophilum by 10-fold at 100 °C. The apparent temperature optimum increased only by ∼5 °C, which is less than the corresponding increase in mesophilic (∼15 °C) and moderately thermophilic (∼10 °C) xylanases. The performance of the enzyme was increased significantly at 100–110 °C. The increasing concentration of [emim]OAc almost linearly increased the inactivation level of the enzyme activity and 25% [emim]OAc inactivated the enzyme almost fully. On the contrary, the apparent temperature optimum did not decrease to a similar extent, and the degree of denaturation of the enzyme was also much lower according to the residual activity assays. Also, 5% [emim]OAc largely counteracted the benefit obtained by the stabilizing disulfide bridge in the temperature-dependent activity assays, but not in the stability assays. Km was increased in the presence of [emim]OAc, indicating that [emim]OAc interfered the substrate–enzyme interactions. These results indicate that the effect of [emim]OAc is targeted more to the functioning of the enzyme than the basic stability of the hyperthermophilic GH11 xylanase.
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| 22. |
- Nypelö, Tiina, 1982, et al.
(författare)
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Conversion of wood-biopolymers into macrofibers with tunable surface energy via dry-jet wet-spinning
- 2018
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 25:9, s. 5297-5307
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Tidskriftsartikel (refereegranskat)abstract
- Surface chemistry of regenerated all-wood-biopolymer fibers that are fine-tuned by composition of cellulose, lignin and xylan is elucidated via revealing their surface energy and adhesion. Xylan additive resulted in thin fibers and decreased surface energy of the fiber outer surfaces compared to the cellulose fibers, or when lignin was used as an additive. Lignin increased the water contact angle on the fiber surface and decreased adhesion force between the fiber cross section and a hydrophilic probe, confirming that lignin reduced fiber surface affinity to water. Lignin and xylan enabled fiber decoration with charged groups that could tune the adhesion force between the fiber and an AFM probe. The fibers swelled in water: the neat cellulose fiber cross section area increased 9.2%, the fibers with lignin as the main additive 9.1%, with xylan 6.8%, and the 3-component fibers 5.5%. This indicates that dimensional stability in elevated humidity is improved in the case of 3-component fiber compared to 2-component fibers. Xylan or lignin as an additive neither improved strength nor elongation at break. However, improved deformability was achieved when all the three components were incorporated into the fibers. Graphical Abstract: [Figure not available: see fulltext.].
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| 23. |
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| 24. |
- Persson, Anders, 1963-, et al.
(författare)
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Ioncell-F: ionic liquid-based cellulosic textile fibers as an alternative to viscose and Lyocell
- 2016
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Ingår i: Textile research journal. - : Sage Publications. - 0040-5175 .- 1746-7748. ; 86:5, s. 543-552
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Tidskriftsartikel (refereegranskat)abstract
- Ioncell-F, a recently developed process for the production of man-made cellulosic fibers from ionic liquid solutions by dry-jet wet spinning, is presented as an alternative to the viscose and N-methylmorpholine N-oxide (NMMO)-based Lyocell processes. The ionic liquid 1,5-diazabicyclo[4.3.0]non-5-ene acetate was identified as excellent cellulose solvent allowing for a rapid dissolution at moderate temperatures and subsequent shaping into continuous filaments. The highly oriented cellulose fibers obtained upon coagulation in cold water exhibited superior tenacity, exceeding that of commercial viscose and NMMO-based Lyocell (Tencel) fibers. The respective staple fibers, which have been converted into two-ply yarn by ring spinning technology, presented very high tenacity. Furthermore, the Ioncell yarn showed very good behavior during the knitting and weaving processes, reflecting the quality of the produced yarn. The successfully knitted and woven garments from the Ioncell yarn demonstrate the suitability of this particular ionic liquid for the production of man-made cellulosic fibers and thus give a promising outlook for the future of the Ioncell-F process.
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| 25. |
- Salmen, Lennart, et al.
(författare)
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Enzymatic chip treatment for TMP - Prospects
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference. - : PI.
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Konferensbidrag (refereegranskat)abstract
- In order to evaluate enzyme pre-treatments of chips as means of lowering the energy demand in mechanical pulping, impregnation and refining trials were performed. Wing refining showed that property development was similar to that of reference pulps in the case of pectinase and xylanase while for chips treated with mannanase a less favourable development of the tensile index was noted. Considering the highly increased possibility for enzymatic interactions reached with greater disintegration of chips it could well be that the possibilities for enzymes to attack desired fibre wall structures may have been too few even in the case of Impressafiner treated material used here.
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| 26. |
- Santamala, Harri, et al.
(författare)
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Advantages of regenerated cellulose fibres as compared to flax fibres in the processability and mechanical performance of thermoset composites
- 2016
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Ingår i: Composites Part A: Applied Science and Manufacturing. - : Elsevier. - 1359-835X. ; 84, s. 377-385
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Tidskriftsartikel (refereegranskat)abstract
- Man-made cellulosic fibres (MMCFs) have attracted widespread interest as the next generation of fibre reinforced composite. However, most studies focused entirely on their performance on single fibre level and little attention has been paid to their behaviour on a larger application scale. In this study, MMCFs were utilized as reinforcement in unidirectionally (UD) manufactured thermoset composites and compared to several commercial UD flax fibre products. Specimens were prepared using a vacuum bag based resin infusion technique and the respective laminates characterized in terms of void fraction and mechanical properties. MMCF laminates had comparable or better mechanical performance when compared to flax fibre laminates. Failure mechanisms of MMCF laminates were noted to differ from those of flax-reinforced laminates. The results demonstrate the potential of MMCFs as a viable alternative to glass fibre for reinforcement on a larger scale of UD laminates. These results were utilized in the Biofore biomaterial demonstration vehicle.
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| 27. |
- Schlapp-Hackl, Inge, et al.
(författare)
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Application-Related Consideration of the Thermal Stability of [mTBDH][OAc] Compared to Amidine-Based Ionic Liquids in the Presence of Various Amounts of Water
- 2022
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 61:1, s. 259-268
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Tidskriftsartikel (refereegranskat)abstract
- The hydrolysis kinetics of 7-methyl-1,5,7triazabicyclo[4.4.0]dec-5-enium acetate [mTBDH][OAc] was investigated in a comprehensive study by the utilization of the well-known Schlenk technique to achieve a better understanding of its stability for dry-jet wet spinning applications (e.g., Ioncell) and due to the course of operation for recovery methods like fractional distillation. Decomposition behavior as a function of temperature, time, acid-base stoichiometry, and water content was extensively analyzed and characterized by nuclear magnetic resonance spectroscopy (NMR), capillary electrophoresis (CE), and thermogravimetric analysis (TGA). Furthermore, kinetic models were formulated for the prediction of the stability and the results were compared with the closely related amidine-based analogues 1,5diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] and 1,8-diazabicyclo[5.4.0]undec-7-enium acetate [DBUH][OAc].
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| 28. |
- Testova, Lidia, et al.
(författare)
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Dissolving-grade birch pulps produced under various prehydrolysis intensities : Quality, structure and applications
- 2014
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:3, s. 2007-2021
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous-phase prehydrolysis followed by alkaline pulping is a viable process to produce wood-based dissolving pulps. However, detailed characterisation of the achievable pulp quality, performance and cellulose structure is yet lacking. In this study, the production of hemicellulose-lean birch soda-anthraquinone pulps after prehydrolysis under various intensities was investigated. Increasing prehydrolysis intensity resulted in pulps of higher purity but lower cellulose yield and degree of polymerisation. Higher cellulose yield by using sodium borohydride during pulping was achieved at the expense of reducing pulp purity. Cellulose crystallinity was similar in all pulps indicating simultaneous degradation of both crystalline and amorphous cellulose regions. Reinforced prehydrolysis seemingly increased the cellulose crystal size and the interfibrillar distances. Moderate intensity prehydrolysis (170 °C) resulted in a pulp well suited for viscose application, whereas reinforced prehydrolysis favoured the production of acceptable cellulose triacetate dope. The performance of the pulps in viscose and acetate applications was strongly related to the chemical and structural properties.
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| 29. |
- Tolonen, Lasse K., et al.
(författare)
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Solubility of Cellulose in Supercritical Water Studied by Molecular Dynamics Simulations
- 2015
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 119:13, s. 4739-4748
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Tidskriftsartikel (refereegranskat)abstract
- The insolubility of cellulose in ambient water and most aqueous systems presents a major scientific and practical challenge. Intriguingly though, the dissolution of cellulose has been reported to occur in supercritical water. In this study, cellulose solubility in ambient and supercritical water of varying density (0.2, 0.7, and 1.0 g cm(-3)) was studied by atomistic molecular dynamics simulations using the CHARMM36 force field and TIP3P water. The Gibbs energy of dissolution was determined between a nanocrystal (4 x 4 x 20 anhydroglucose residues) and a fully dissociated state using the two-phase thermodynamics model. The analysis of Gibbs energy suggested that cellulose is soluble in supercritical water at each of the studied densities and that cellulose dissolution is typically driven by the entropy gain upon the chain dissociation while simultaneously hindered by the loss of solvent entropy. Chain dissociation caused density augmentation around the cellulose chains, which improved water-water bonding in low density supercritical water whereas the opposite occurred in ambient and high density supercritical water.
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| 30. |
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| 31. |
- Wedin, Helena, et al.
(författare)
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Evaluation of post-consumer cellulosic textile waste for chemical recycling based on cellulose degree of polymerization and molar mass distribution
- 2019
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Ingår i: Textile research journal. - : SAGE Publications Ltd. - 0040-5175 .- 1746-7748. ; 89:23-24, s. 5067-5075
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to improve the understanding of which end-of-life cellulosic textiles can be used for chemical recycling according to their composition, wear life and laundering—domestic versus service sector. For that purpose, end-of-life textiles were generated through laboratorial laundering of virgin fabrics under domestic and industrial conditions, and the cellulose content and its intrinsic viscosity and molar mass distribution were measured in all samples after two, 10, 20, and 50 laundering cycles. Results presented herein also address the knowledge gap concerning polymer properties of end-of-life man-made cellulosic fabrics—viscose and Lyocell. The results show that post-consumer textiles from the home consumer sector, using domestic laundering, can be assumed to have a similar, or only slightly lower, degree of polymerization than the virgin textiles (−15%). Post-consumer textiles from the service sector, using industrial laundering, can be assumed to have a substantially lower degree of polymerization. An approximate decrease of up to 80% of the original degree of polymerization can be expected when they are worn out. A higher relative decrease for cotton than man-made cellulosic textiles is expected. Furthermore, in these laboratorial laundering trials, no evidence evolved that the cellulose content in blended polyester fabrics would be significantly affected by domestic or industrial laundering. With respect to molar mass distribution, domestic post-consumer cotton waste seems to be the most suitable feedstock for chemical textile recycling using Lyocell-type processes, although a pre-treatment step might be required to remove contaminants and lower the intrinsic viscosity to 400–500 ml/g. © The Author(s) 2019.
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