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Prehydrolysis in softwood pulping produces a valuable biorefinery fraction for material utilization
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-1631-1781
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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2012 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, no 15, 8389-8396 p.Article in journal (Refereed) Published
Abstract [en]

A scaled-up prehydrolysis process was elaborated to demonstrate an industrially feasible operation step in a pulping process that generates a valuable side product in addition to the cellulose pulp. The valuable side product is aqueous process liquor, a softwood hydrolysate (SWH) herein produced in 60 L batches, and its components were recovered and utilized as materials. The process parameters were shown to influence the yield, composition, and quality of the obtained hydrolysates. Furthermore, the process conditions were shown to influence the ability of SWHs to form free-standing, foldable films in blends with either microfibrillated cellulose (MFC) or carboxymethyl cellulose (CMC). Films with oxygen permeabilities (OP) as low as 0.35 cm 3 ÎŒm day -1 m -2 kPa -1 at 50% relative humidity, were produced from aqueous solutions providing a viable and green alternative to petroleum-based packaging barriers. The OPs were very low regardless of SWH film composition and upgrading conditions, whereas the films' tensile performance was directly controlled by the ratio of SWH to cocomponent.

Place, publisher, year, edition, pages
2012. Vol. 46, no 15, 8389-8396 p.
Keyword [en]
Wood Hydrolysate, Films, Hemicelluloses, Cellulose, Oxygen
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-101525DOI: 10.1021/es301699nISI: 000307199800061ScopusID: 2-s2.0-84864693939OAI: diva2:549253

QC 20120904

Available from: 2012-09-04 Created: 2012-08-30 Last updated: 2014-11-14Bibliographically approved
In thesis
1. Bio-based barriers from wood hydrolysates: A pilot-scale approach
Open this publication in new window or tab >>Bio-based barriers from wood hydrolysates: A pilot-scale approach
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wood hydrolysates (WHs) are liquids extracted from the hydrothermal treatment of wood. They exist as the byproduct of forestry industries such as the dissolving pulp and fiberboard industries. WHs are hemicellulose-based with a large share of lignin in the chemical composition. In this thesis, methods for utilizing pilot-scale produced WH are shown for production of oxygen barriers. The key materials for fabricating oxygen-barriers are WHs with minor upgrade through ultrafiltration/diafiltration. These barriers have a great potential to be used in the food packaging industry.

WHs were produced via hydrothermal treatments of spruce and birch chips in a pilot-scale digester, which mimicked a prehydrolysis plant in a dissolving pulp mill. The produced WHs were used in their crude state or after upgrading through ultrafiltration/diafiltration to form freestanding films and coatings. As shown in previous studies from our group, WHs can provide an inexpensive alternative for the production of oxygen barriers. Compared with purified hemicellulose, they perform better due to the presence of the lignin and lignin carbohydrate molecular interactions forming a denser and less permeable matrix.     

Careful analyses and characterizations were conducted on the WHs to assess the influence of cooking conditions and upgrading parameters on the chemical composition and molecular weight of the WHs, which consequently affect the oxygen barrier and mechanical properties of the freestanding films. The optimum cooking and upgrading parameters were chosen to produce pilot-scale WH, which were further used in coating formulations applied in multilayer barriers. Three different green co-components were chosen to blend with the WH to mechanically reinforce the matrix: carboxymethyl cellulose and microfibrillated cellulose (MFC) were blended with spruce and/or birch WH, and poly L-lactide (PLLA) was blended with softwood hydrolysates from a fiberboard mill (Masonite AB). Freestanding films with different formulations were produced through casting, and the mechanical and oxygen barrier properties were compared.

To proceed toward industrialization of the oxygen barrier, barrier coatings based on pilot-scale produced WH along with different carboxymethyl celluloses as co-component were applied using a semi-pilot scale Hirano coater to form multilayer barriers. The oxygen barrier properties, mechanical properties and coating/substrate interaction were analyzed for the multilayer barriers.     

In a different approach, softwood hydrolysate from Masonite AB fiberboard mill was functionalized through a ring-opening polymerization of L-lactide in which L-lactide oligomers were grafted from the acetylated galactoglucomannan (AcGGM) backbone. This copolymer was then used as a compatibilizer in the hydrolysate/PLLA blend films. The introduction of only a minor amount of copolymer (1% w/w) into hydrolysate/PLLA matrix caused a significant increase in the tensile ductility (~ 400%).

Freestanding films based on spruce and birch hydrolysates containing carboxymethyl cellulose and/or MFC as co-component demonstrated excellent barrier performances with oxygen permeability (OP) values as low as 0.3 cm3 µm day-1 m-2 kPa-1 at 50% relative humidity (RH). Although at higher RH (80%) the barrier properties of the films diminished, the OP values were still less than 30 cm3 µm day-1 m-2 kPa-1; hence, they were still considered good barriers. These good barrier properties cause these films to be ready to compete with most petroleum-based polymers such as polyethylene terephthalate (PET) and Ethylene vinyl alcohol (EVOH) for the packaging industry.


Abstract [sv]

Vedhydrolysat är hemicellulosa-rika vätskor som utvinns från vattenbaserade procesströmmar vid hydrotermisk behandling av trä. Få industriella tillämpningar har skapats för denna grupp av material. Här presenteras metoder för att utnyttja vedhydrolysat i laboratorieskala och pilotskala som en råvara för att skapa goda syrgasbarriärer med potential för förpackningar inom livsmedelsindustrin.

Vedhydrolysat från gran- och björkflis har genererats i pilotskala som imiterar förhydrolysen i en pappersmassaprocess. Hydrolysaten uppgraderas sedan via ultrafiltrering och diafiltrering genom membraner med olika cut-offs. Tidigare studier från vår grupp har visat att vedhydrolysat i orenad form är ett billigt alternativ för produktion av syrgasbarriärer och dessutom bättre barriärer jämfört med ren hemicellulosa tack vare innehållet av lignin som leder till tätare och mindre permeabel molekylpackning.

Processparametrarna vid hydrolys och uppgradering var faktorer som påverkade kemisk sammansättning och molekylvikter hos hydrolysaten vilka därmed påverkade de mekaniska egenskaperna och syrgasbarriäregenskaperna hos filmerna.  

För att förstärka de fristående filmerna användes olika gröna samkomponenter som karboximetylcellulosa, mikrofibrillerad cellulosa (MFC) och poly-L-laktid (PLLA). Barrvedshydrolysat från granflis eller björkflis blandades antingen med karboximetylcellulosa eller med MFC. PLLA användades som samkomponent för barrvedshydrolysat från Masonite AB.

Barriärbeläggningar baserade på hydrolysat producerat i pilotskala tillsammans med olika typer av karboximetylcellulosa som samkomponent applicerades på papper eller PET substrat. Beläggningar skapades i semi-pilotskala med en Hirano coater. Dessa flerskiktsbarriärer analyserades sedan med avseende på dess syrgasbarriärsegenskaper, dess mekaniska egenskaper och dessutom interaktionen mellan beläggning och substrat.

Barrvedshydrolysatet från Masonite AB funktionaliserades med L-laktid-oligomerer genom ringöppningspolymerisation där laktid ympades på hemicellulosakedjorna. Ympsampolymeren fungerade som en kompatibilisator i blandningsfilmerna hydrolysat/PLLA. Tillsatsen av PLLA förbättrade dessutom de draghållfasthetsegenskaperna hos hydrolysat/PLLA matrisen. En tillsats på endast 1 vikts-% av den syntetiserade kompatibilisatorn ledde till en 400% ökning i seghet hos matriserna utan att syrgasbarriäregenskaperna påverkades.

Både fristående filmer och flerskiktsbarriärer presterade bra i olika relativa fuktigheter (50%, 80%). Syrgaspermeabiliteten var så låg som 0,3 cm3 µm day-1 m-2 kPa-1 vid 50% relativ fuktighet och syrgaspermeabiliteten var mindre än 30 cm3 µm day-1 m-2 kPa-1 vid 80% relativ fuktighet.  Dessa egenskaper gör det möjligt att med dessa filmer konkurrera med många oljebaserade plaster inom livsmedelsförpackningsindustrin såsom PET och EVOH.




Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. 69 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:44
Wood hydrolysate, biorefinery, oxygen permeability, multilayer barriers, food packaging., vedhydrolysat, syrgaspermeabilitet, barriärskikt, livsmedelsförpackning
National Category
Polymer Technologies
urn:nbn:se:kth:diva-155882 (URN)978-91-7595-325-0 (ISBN)
Public defence
2014-12-03, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 10:00 (English)

QC 20141114

Available from: 2014-11-14 Created: 2014-11-13 Last updated: 2014-11-14Bibliographically approved

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