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Author:Sara, Timo
Title:Delignification of birch pulp in ionic liquid solution
Koivuselluloosan delignifiointi ionisissa nesteissä
Publication type:Master's thesis
Publication year:2014
Pages:56 s. + liitt. 2      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Sellutekniikka   (P3002)
Supervisor:Sixta, Herbert
Instructor:Hummel, Michael
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201408292537
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Location:P1 Ark Aalto  1656   | Archive
Keywords:cellulose
ionic liquids
hydrogen peroxide
dissolution
lignin
selluloosa
ioniset nesteet
vetyperoksidi
liuotus
ligniini
Abstract (eng):The objective of this thesis was to investigate the delignification efficiency of birch pulp in an ionic liquid solution.
Alkaline ionic liquids provide an appropriate environment for hydrogen peroxide bleaching of prehydrolysis-kraft (PHK) pulps, which are used for the manufacture of regenerated cellulose fibers.
Efficient bleaching in the ionic liquid solution could offer an economical alternative for the conventional multi-phase bleaching sequence.
The literature part presents the research background and information about the interaction of the chemicals applied in this work.
The feasibility of the suggested bleaching method is also evaluated.
The experimental part of this thesis was performed by dissolving unbleached PHK pulp in two different ionic liquids, 1-ethyl-3-methylimidazolium acetate ([emim]OAc) and 1-ethyl-3-methylimidazolium dimethyl phosphate ([emim]dmp).
In earlier studies, [emim]OAc has been the preferred solvent for lignocellulose material, thus it was used in most of the experiments.
The efficiency of delignification was studied by varying the process parameters (temperature, peroxide charge, bleaching time) and the results were analyzed (kappa number, intrinsic viscosity, brightness) from the regenerated pulp samples.
The effect of hydrogen peroxide stabilizers and potential process impurities was also determined.
Delignification dependency on the process parameters was in accordance with conventional bleaching although with diminished effect, thus the desired removal of residual lignin was not achieved.
The regenerated pulps experienced a reduction in brightness level due to formation of new chromophores and residual ionic liquid and its contaminants.
Overall, delignification in [emim]OAc at 90 oC and high peroxide charge produced the best results.
The intrinsic viscosity of the regenerated pulps was significantly affected even by low hydrogen peroxide charge.
However, viscosity stabilization was observed around 400 ml/g as the treatment intensity was increased.
Abstract (fin):Tämän työn tarkoituksena oli tutkia valkaisemattoman koivuselluloosan delignifioituvuutta ioninesteliuoksissa.
Alkaliset ioniset nesteet tarjoavat sopivat olosuhteet regeneroitujen selluloosakuitujen valmistuksessa käytettävän esihydrolysoidun sulfaattiselluloosan (liukosellu) vetyperoksidivalkaisuun.
Tehokas valkaisu ioninesteliuoksessa voisi tarjota taloudellisen vaihtoehdon perinteiselle monivaiheiselle valkaisusekvenssille.
Kirjallisuusosassa esitetään työssä sovellettujen kemikaalien tutkimustaustaa sekä niiden kemiallista vuorovaikutusta.
Ehdotetun valkaisumenetelmän toteutettavuus on myös arvioitu.
Työn kokeellinen osa toteutettiin liuottamalla valkaisematonta PHK-liukoselluloosaa kahteen eri ioniseen nesteeseen, 1-etyyli-3-metyyli-imidatsoliumi asetaatti ([emim]OAc) sekä 1-etyyli-3-metyyli-imidatsoliumi dimetyylifosfaatti ([emim]dmp).
Aikaisemmissa tutkimuksissa [emim]OAc on pidetty ominaisuuksiltaan parhaana lignoselluloosan liuottimena, minkä vuoksi suurin osa kokeista suoritettiin sen avulla.
Delignifiointitehokkuutta tutkittiin muuttamalla prosessiparametrejä (lämpötila, peroksidiannos, valkaisuaika) ja tulokset analysoitiin (kappaluku, rajaviskositeetti, vaaleus) regeneroiduista sellunäytteistä.
Myös vetyperoksidin stabilointiaineiden sekä mahdollisten prosessiepäpuhtauksien vaikutus arvioitiin.
Vetyperoksidilla suoritetun delignifioinnin riippuvuus prosessiparametreistä oli tavanomaisen valkaisun mukainen, tosin heikentyneellä vaikutuksella.
Siksi tavoiteltua jäännösligniinin vähennystä ei saavutettu.
Regeneroiduissa sellunäytteissä ilmeni vaaleuden alenemista johtuen uusista kromoforirakenteista ja jäljelle jääneestä ioninesteestä sekä sen epäpuhtauksista.
Kaikkiaan, delignifiointi [emim]OAc:ssa 90 oC:ssa korkealla peroksidiannoksella tuotti parhaat tulokset.
Regeneroidun sellun rajaviskositeetti muuttui merkittävästi jo alhaisella peroksidiannoksella.
Viskositeetti stabiloitui noin 400 ml/g:n kun käsittelyn intensiteettiä kasvatettiin.
ED:2014-08-31
INSSI record number: 49665
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