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The Use of Membrane Filtration to Improve the Properties of Extracted Wood Components
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The forest is alarge and important natural resourcein Sweden, and approximately 70% of the country’s land area is woodland. Wood is an excellent raw material for the replacement of oil-based products because it is renewable, biodegradable and carbon neutral. Furthermore, the forest industry is searching for new processes and methods to utilise by-product streams in a so-called integrated biorefinery. A key to the success of producing new products from wood could be pure and homogenous raw materials. Because wood contains a large variety of components with different characteristics and sizes, cross-flow filtration (CFF) will be a key separation technique to obtain homogenous and pure raw materials in the biorefinery concept.

Different wood material components have been studied in this thesis. The first part of this work focuses on kraft lignin. Kraft lignin is interesting because approximately 3.5-4 million metric tonnes are produced in Sweden annually (~7million tonnes of kraft pulp/year in 2012), and today it is mainly used as fuel. The second part of this thesis deals with materials in hot water extract (i.e.,  galactoglucomannan, but also other components). These extracted materials are interesting because similar materials are extracted in thermomechanical pulping process by-product streams. Finally, nanocellulose has been studied since it is an interesting raw material for future applications.

Through CFF, kraft lignin from black liquor has been fractionated into raw material samples with more homogeneous characteristics such as molecular weight, aromatic hydroxyl groups and thermal properties. From dynamic mechanical analysis, low molecular weight fractions were found to have the highest degree softening. To precipitate low molecular weight fractions (<1000 Dacut-off) into a convenient solid, lower temperatures than forhigh molecular weight fractions were needed. To produce low molecular weight lignin (<5000 Da cut-off) from re-dissolved LignoBoost lignin, lower lignin concentrations and higher pH and ionic strength were found to increase the permeate fluxat the tested conditions.

Nanocellulose has been producedby a novel process called nanopulping and has subsequently been size fractionated by CFF to obtain more homogenous nanocellulose.

CFF and adsorption chromatography can be used to isolate dissolved wood components, yielding several upgraded products: lignin, lignin-carbohydrate complexes, and galactoglucomannan.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 59 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014.9
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-143954OAI: oai:DiVA.org:kth-143954DiVA: diva2:709871
Public defence
2014-04-25, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140404

Available from: 2014-04-04 Created: 2014-04-03 Last updated: 2014-04-04Bibliographically approved
List of papers
1. Fractionation of Technical Lignin: Molecular Mass and pH Effects
Open this publication in new window or tab >>Fractionation of Technical Lignin: Molecular Mass and pH Effects
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2013 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, 2270-2282 p.Article in journal (Refereed) Published
Abstract [en]

Today, lignin from kraft pulping is used mainly as fuel, with only very small amounts being used as raw material for chemicals and materials. This work focuses on using a convenient method for separating large amounts of low molecular weight lignin from the kraft process. Low molecular weight lignin contains larger amounts of phenolic structural units, which are possible modification sites and can be used as antioxidants. Moreover, a product that has reduced polydispersity, low molecular weight, and purified lignin could be a potential material for new applications. The studied process for separating lignin from weak black liquor used a membrane with a cut-off of 1000 Da. During precipitation of the 1000 Da permeate, it is necessary to prevent formation of fairly large, rigid particles/agglomerates of lignin by keeping the temperature low. To improve the dead-end filtration, higher ionic strength is needed for the weak black liquor. Additionally, reducing the end pH will cause more material to precipitate. More sulfur was found in the low molecular weight lignin and at lower precipitation pH, indicating that most sulfur left in the lignin samples might be bound to low molecular weight lignin.

Keyword
Lignin, Weak black liquor, Low molecular weight, Cross-flow filtration, Ultrafiltration, Molar mass, Precipitation, Dead-end filtration
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-125775 (URN)000320185500019 ()2-s2.0-84877984168 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20130814

Available from: 2013-08-14 Created: 2013-08-13 Last updated: 2017-12-06Bibliographically approved
2. Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration
Open this publication in new window or tab >>Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration
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2014 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 18, 9505-9515 p.Article in journal (Refereed) Published
Abstract [en]

This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (T-g) between 70 and 170 degrees C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (M-n) and T-g's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (M-w > 5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step.

Keyword
biopolymers and renewable polymers, crosslinking, glass transition, rheology, thermal properties
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-143949 (URN)10.1002/app.40799 (DOI)000337623600057 ()2-s2.0-84902544032 (Scopus ID)
Note

QC 20140806. Updated from manuscript to article in journal.

Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-12-05Bibliographically approved
3. Parameters Affecting the Cross-flow Filtration of Dissolved LignoBoost Kraft Lignin
Open this publication in new window or tab >>Parameters Affecting the Cross-flow Filtration of Dissolved LignoBoost Kraft Lignin
2015 (English)In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 36, no 1, 1-8 p.Article in journal (Other academic) Published
Abstract [en]

In the kraft pulping process, the lignin-containing by-product kraft black liquor is currently combusted as an energy source. LignoBoost is a technique that extracts lignin from kraft black liquor, resulting in a lignin-lean black liquor, which is returned to the process, and an extracted kraft lignin. To facilitate the use of the extracted kraft lignin in high-value applications, it can be refined via fractionation to produce a more homogeneous starting raw material. Hence, the aim of this study is to investigate the behavior of dissolved softwood kraft lignin during cross-flow filtration. The effects of the lignin concentration, pH, and ionic strength on the fractionation of the dissolved lignin during cross-flow filtration are investigated. The results indicate that large amounts of low-molecular-weight kraft lignin can be produced from solutions having a low lignin concentration. Furthermore, the effects of pH and ionic strength on the fractionation of low-molecular-weight lignin are identified within the studied ranges.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2015
Keyword
Cross-flow filtration, ultrafiltration, kraft lignin, low molecular weight
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-143952 (URN)10.1080/02773813.2015.1025284 (DOI)000364850100001 ()2-s2.0-84944871166 (Scopus ID)
Note

QC 20151214

Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-12-05Bibliographically approved
4. A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration
Open this publication in new window or tab >>A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration
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2012 (English)In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 16, 1871-1875 p.Article in journal (Refereed) Published
Abstract [en]

A novel energy-efficient method called nanopulping (patent pending) to produce nanocellulose from chemical pulp, and a novel cross-flow ultra-filtration method to separate nanofibrils fractions of different size were applied in this study. Pretreatment with endoglucanase or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation seems to enhance the nanopulping process. Results were evaluated with atomic force microscope and ultrafiltration. The nanopulping produced a relatively inhomogeneous material with larger particles/ fibers in addition to nanofibers. However, by ultrafiltration of the material it was possible to obtain more homogeneous material in different dimensions with methods industrially acceptable.

Keyword
Cross flow ultra-filtration, Endoglucanase pretreatment, Microfibrillated cellulose, Nanocellulose, Nanopulping, TEMPO pretreatment
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-101522 (URN)10.2174/138527212802651197 (DOI)000307867800006 ()2-s2.0-84864563327 (Scopus ID)
Note

QC 20120904

Available from: 2012-09-04 Created: 2012-08-30 Last updated: 2017-12-07Bibliographically approved
5. Separation Of Galactoglucomannans, Lignin, And Lignin-Carbohydrate Complexes From Hot-Water-Extracted Norway Spruce By Cross-Flow Filtration And Adsorption Chromatography
Open this publication in new window or tab >>Separation Of Galactoglucomannans, Lignin, And Lignin-Carbohydrate Complexes From Hot-Water-Extracted Norway Spruce By Cross-Flow Filtration And Adsorption Chromatography
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2012 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 4, 4501-4516 p.Article in journal (Refereed) Published
Abstract [en]

A simple method to simultaneously recover polymeric carbohydrates, mainly galactoglucomannans (GGM), lignin, and lignin-carbohydrate complex (LCC) from hot-water-extracted Norway spruce wood is presented. The isolation method consists of cross-flow filtration, where high and low molecular mass species are removed, followed by fixed-bed adsorption on a hydrophobic polymeric resin (XAD-16) to remove lignins and lignans. In the second step of fixed-bed adsorption, a phenylic reversed-phase analytical chromatography column, where mass transport resistance is minimized and a very high selectivity towards aromatic compounds have been observed, was used to separate LCC from GGM. The isolated LCC fraction contained about 10% aromatics, whereas the upgraded GGM fraction contained about 1.5% aromatics and the lignin fraction contained about 56% aromatics. Polymeric xylan was accumulated in the GGM fraction, while mannose was the dominant sugar found in the LCC fraction. As products, approximately 7% was recovered in the lignin fraction in the first adsorptive step, 5% was recovered as LCC, and 88% as upgraded hemicelluloses.

Keyword
LCC, Lignin carbohydrate complex, GGM, galactoglucomannan, Norway spruce, Biorefinery, Separation, Sorption, Chromatography, Ultrafiltration
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-109587 (URN)000311336800005 ()2-s2.0-84872773250 (Scopus ID)
Note

QC 20130108

Available from: 2013-01-08 Created: 2013-01-08 Last updated: 2017-12-06Bibliographically approved

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