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- Hubbe, Martin A., et al.
(författare)
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Lignin Recovery from Spent Alkaline Pulping Liquors Using Acidification, Membrane Separation, and Related Processing Steps : A Review
- 2019
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Ingår i: BioResources. - : NORTH CAROLINA STATE UNIV. - 1930-2126. ; 14:1, s. 2300-2351
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Tidskriftsartikel (refereegranskat)abstract
- The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomena have potential to enable higher-value uses of black liquor components, including biorefinery options, alternative ways to recover the chemicals used to cook pulp, and debottlenecking of kraft recovery processes.
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- Kihlman, Martin, et al.
(författare)
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Cellulose Dissolution in an Alkali Based Solvent : Influence of Additives and Pretreatments
- 2013
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Ingår i: Journal of the Brazilian Chemical Society. - : SOC BRASILEIRA QUIMICA, Brazil. - 0103-5053 .- 1678-4790. ; 24:2, s. 295-303
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Tidskriftsartikel (refereegranskat)abstract
- The distinction between thermodynamic and kinetics in cellulose dissolution is seldom considered in the literature. Therefore, herein an attempt to discuss this topic and illustrate our hypotheses on the basis of simple experiments was made. It is well-known that cellulose can be dissolved in a aqueous sodium hydroxide (NaOH/H2O) solvent at low temperature but it is here shown that such an alkaline solvent can be considerably improved regarding solubility, stability and rheological properties as a whole if different additives (salts and amphiphilic molecules) are used in the dissolution stage. This work probes new aqueous routes to dissolve cellulose, thereby improving the potential to commercially dissolve cellulose in an inexpensive and environmentally friendly manner.
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- Kihlman, Martin, 1986-
(författare)
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Dissolution of cellulose for textile fibre applications
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis forms part of a project with the objective of developing and implementing a novel, wood-based, process for the industrial production of cellulose textile fibres. This new process should not only be cost effective but also have far less environmental impact then current processes. Natural and man-made fibres are usually plagued with problems (e.g. economic and environmental) and are unsuitable in meeting growing demands. The focus of this thesis was therefore to investigate the dissolution of cellulose derived from various pulps in novel aqueous solvent systems. It was shown that cellulose could be dissolved in a NaOH/H2O solvent at low temperatures (<0°C) and that such an alkaline solvent can be improved regarding the solubility, stability and rheological properties of the cellulose dopes formed if different additives (salts or amphiphilic molecules) are used. The effect of different kinds of pretreatment (individually and combined) and the influence of pulp properties on cellulose accessibility and dissolution were also evaluated. These pretreatments affected, as expected, some characteristic properties of the pulps mainly by reducing the DP but also, for example, changing the composition of the carbohydrates. Not only did the pretreatment affect the solubility it also increased the stability of the cellulose dopes, resembling the effect of chemical additives to the NaOH system. According to multivariate data analysis it was established that, of the pulp properties analyzed, only the composition of carbohydrates and the DP had a significant influence on the solubility of the pulps used in this study. Finally, it was emphasized that the dissolution of cellulose pulps seemed to be controlled by a very complex interaction between both kinetic and thermodynamic parameters.
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- Kihlman, Martin, et al.
(författare)
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Dissolution of dissolving pulp in alkaline solvents after steam explosion pretreatments
- 2011
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 65:4, s. 613-617
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Konferensbidrag (refereegranskat)abstract
- In this project different aqueous based solvent systems were investigated for the dissolution of steam exploded (STEX) dissolving pulps prior to a coagulation step for preparation of textile fibers. The pulp samples studied could, to a large degree, be dissolved in a NaOH/urea/thiourea system, but there are always residuals, irrespective of the conditions. The dissolution process appeared to be kinetically controlled, as prolonged retention time decreased the amount of residuals. A pre-cooled NaOH/urea/thiourea system, and a retention time of 60 h generated the lowest amount (6%) of residuals of the STEX pretreated dissolving pulp studied. Some fundamental results are described and a model for dissolution of dissolving pulp fibers is proposed.
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- Kihlman, Martin, 1986-, et al.
(författare)
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Effect of Various Pulp Properties on The Solubility of Cellulose in Sodium Hydroxide Solutions
- 2012
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Ingår i: Holzforschung. - Berlin : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:5, s. 601-606
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution of pulps with varying characteristic properties, for example cellulose chain length or content of hemicellulose, has been investigated in two alkaline solvent systems [sodium hydroxide (NaOH)/urea/thiourea (8:8:6.5 by wt.) and NaOH/zince oxide (ZnO) (9:0.5 by wt.)]. One standard paper pulp, two dissolving pulps and three pretreated pulps were selected for this study. The dissolution parameters in focus were the fiber dimensions, average degree of polymerization (DP), polydispersity, water retention value and content of hemicelluloses. The solubility was not influenced by the fiber dimensions. The only significant properties, according to variable importance plot, were DP and composition of the hemicelluloses. It was also established that mass transfer effects during the dissolution stage plays an important role in the dissolution of cellulose derived from pulp fibers.
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- Kihlman, Martin, 1986-, et al.
(författare)
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Preparation of cellulosic fibres in semi-pilot scale from NaOH-solutions
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose is a highly interesting polymer for bio-based products and can be utilized in a wide variety of products, either in its native form or derivatized. One application for cellulose that is predicted to grow remarkably is textile fibers. It is believed that in the future a number of forest based raw materials can play a major role in replacing fossil oil based fibers and cotton to new ecological man-made fibers in both woven and nonwoven end applications.[p]The CelluNova project was initiated in early 2010 with the objective of developing a new environmentally friendly process for production of cellulose-based textile fibers. Cellulose fibers based on dissolving pulp have so far successfully been prepared from semi-pilot scale trials in a stepwise procedure. The solvent systems used were the NaOH/urea/thiourea system and the NaOH/ZnO system, at a temperature below 0°C, and a cellulose concentration as high as 6-8%.
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