Chimphango, A. F. A.
Gorgens, J. F.
ENGLISH ABSTRACT: Hemicelluloses are the most abundant plant polysaccharides available next to cellulose. The industrial usage of hemicelluloses however is very limited to nonexistent. As wood is processed in the Kraft pulping process, a large fraction of these hemicelluloses is degraded to low molecular weight isosaccharinic acids, which end up in the black liquor with the degraded lignin. The extraction of hemicelluloses prior to pulping and re-introducing them as a wet-end additive has been shown to improve the paper tensile -, burst- and tear index properties. It has also been proven that the pre-extraction of hemicelluloses does not negatively affect the downstream paper products.
The objective of this project was to study the modification of extracted wood based hemicelluloses, focusing on glucuronoxylan in Eucalyptus grandis (E. grandis), by chemical and physical methods identified from literature. The methods investigated were; cationisation, carboxymethylation and ultrasound treatment. The modified hemicelluloses were applied as a wet-end additive to E. grandis pulp to test their effect on strength properties. An addition protocol for the new hemicelluloses additives was developed in this investigation.
The E. grandis glucuronoxylan was extracted by using the mild alkali extraction method of Höije et al. The characterization of the extracted solids from the pure E. grandis chips showed that 4-O-methylglucuronoxylan was extracted with an average uronic acid content of 17.3 wt.%. The hemicelluloses yield was 50.75 wt.%, based on dry biomass, containing 40.76 wt.% xylose units. The solids still contained 26.6 wt.% lignin after extraction. The presence of lignin in the extracted solids indicated that the delignification step in the extraction method used, was not sufficient for the E. grandis biomass. The molecular weight of the extracted glucuronoxylan was 51 589 g.mol-1.
It was proven that the modification methods from literature are applicable to E. grandis glucuronoxylan, producing cationic, carboxymethyl and low uronic acid content 4-O-methylglucuronoxylan. The cationic E. grandis glucuronoxylan produced had a degree of substitution between 0.05 and 0.73 and an uronic acid content ranging between 6.12 and 12.70 wt.%. The carboxymethylated E. grandis glucuronoxylan had a degree of substitution between 0.05 and 0.11 with a uronic acid content between 10.2 and 21.4%. The sonication of E. grandis glucuronoxylan resulted in products with molecular weights ranging from 54 856 to 57 347 g.mol-1 and uronic acid contents between 13.0 and 18.4 wt.%.
Handsheet formation with the modified hemicelluloses added, showed that the cationic E. grandis glucuronoxylan improved handsheet strength and surface properties the best. Cationic E. grandis glucuronoxylan also outperformed the industrial additive, cationic starch at a dosage level of 1.0 wt.%. The addition protocol development for cationic E. grandis glucuronoxylan showed it is possible to add cationic hemicellulose before refining, which results in maximum contact time with the pulp fibres without inhibiting the effect of the additive. Cationic hemicellulose additive added before refining led to a decrease in refining energy required to reach the desired strength properties.
It was concluded that the cationisation and carboxymethylation methods chosen from literature were applicable to the South African grown E. grandis glucuronoxylan. The cationic glucuronoxylan showed the best improvement in handsheet strength and surface properties. Cationic E. grandis glucuronoxylan could be added before refining in the papermaking process for maximum effectiveness of this new strength additive. The use of hemicellulosic additives will be more sustainable than starch, due to the presence of hemicelluloses in the initial biomass that enters the pulp and paper process.
AFRIKAANSE OPSOMMING: Hemiselluloses is die mees volopste plantpolisakkariede naas sellulose, alhoewel die industriële gebruik van hierdie hemiselluloses tans nog beperk is. In die huidige verwerking van hout met behulp van die Kraft verpulpingsproses word die hemiselluloses gedegradeer na lae molukulêre massa isosakkariniese sure wat saam met die lignien in die swartloog afvalstroom eindig. Die ekstraksie van hierdie hemiselluloses vóór die verpulpingsproses, en latere byvoeging as ‘n sterktebymiddel in die papier vervaardigings proses, kan die papier treksterkte, bars-, en skeur eienskappe verbeter. Dit is aangetoon dat die ekstraksie van hemiselluloses vóór die verpulpingsproses nie die opbrengs en kwaliteit van papierprodukte negatief beïnvloed nie.
Die doelwit van hierdie projek was om die modifikasie van hemiselluloses, ge-ekstraheer uit Eucalyptus grandis (E. grandis) hout vóór verpulping, deur middle van chemiese en fisiese metodes uit literatuur te ondersoek. Die projek het spesifiek gefokus op glukuronoxilaan verkry uit E. grandis en wat gemodifiseer is met met behulp van kationisasie, karboksimetilering en ultraklank behandeling. Die gemodifiseerde hemiselluloses is daarna benut as ‘n nat-kant bymiddel tot E. grandis pulp, om die sterkte eienskappe van papier te ondersoek. ‘n Toevoegingsprotokol is vir die nuwe hemisellulose bymiddel ontwikkel in hierdie ondersoek.
Die glukuronoxilaan is deur middle van die matige alkali-ekstraksie metode van Höije geekstraheer. Karakterisering van die vastestof residu wat uit die suiwer E. grandis biomassa geekstraheer is het getoon dat 4-O-metielglukuronoxilaan geëkstraheer is, met ‘n gemiddelde glukuronosuurinhoud van 17.3 massa%. Die hemisellulose opbrengs was 50.75 massa%, gebaseer op droë biomassa, en dit het 40.76 massa% xylose-eenhede bevat. Die lignieninhoud van die soliedes was 26.6 massa% na ekstraksie. Die teenwoordigheid van die lignien het daarop gedui dat die delignifikasie (van die metode) van E. grandis biomassa nie voldoende was nie. Die molekulêre massa van die geëkstraheerde glukuronoxilaan was 51 589 g.mol-1.
Dit is bewys dat die modifikasiemetodes toepasbaar is op die E. grandis glukuronoxilaan, en dat kationiese, karboksiemetiel en lae glukuronosuur 4-0-metielglukurono-xilaan geproduseer is. Die kationiese glukuronoxilaan het ‘n graad van substitusie tussen 0.05 en 0.73 gehad, met ‘n glukuronosuur inhoud tussen 6.12 en 12.70 massa%. Die karboksiemetielglukuronoxilaan het ‘n graad van substitusie tussen 0.05 en 0.11 gehad, met glukuronosuurinhoude tussen 10.2 en 21.4 massa%. Die ultraklankbehandelde glukuronoxilaan het molekulêre massas tussen 54 856 en 57 347 g.mol-1 gehad met glukuronosuurinhoude tussen 13.0 en 18.4 massa%.
Papier handvelproduksie van die pulp waar tydens die gemodifiseerde hemiselluloses toe gevoeg is, het aangedui dat die kationiese E. grandis glukuronoxilaan die grootste sterkte- en oppervlakeienskappe verbetering getoon het. Die kationiese glukuronoxilaan het ook, in terme van verbetering van pulpeienskappe, die industrieële kationiese stysel bymiddel oortref, by ‘n doserings vlak van 1.0 massa%. Die toevoegingsprotokol ontwikkeling vir die kationiese E. grandis glukuronoxilaan het getoon dat hemiselluloses byvoeging tot die papiermaakproses vóór die raffinerings stadium die mees gunstige was, met dosering tussen 0.5 en 2.0 massa%. Die byvoeging van kationiese hemiselluloses vóór raffinering het gelei tot ‘n afname in raffineringsenergie wat benodig word om die verlangde sterkteeienskap te verkry.
Dit is bevesting gekose kationisasie- en karboksimetilerings metodes toepasbaar op die Suid Afrikaanse E. grandis glukuronoxilaan was. Die kationiese glukuronoxilaan het die grootste verbetering in pulpeienskappe, in terme van handvelsterkte en oppervlakeienskappe, getoon. Kationiese glukuronoxilaan moet vóór raffinering tot die papiermaakproses bygevoeg word vir maksimum doeltreffendheid van hierdie nuwe sterktebymiddel. Die gebruik van hemisellulose bymiddels sal meer volhoubaar wees as stysel, omdat die hemiselluloses wat in die biomassa aanwesig is, in die proses teruggrplaas word.
Dissertations -- Process engineering
Theses -- Process engineering
Extracted wood based hemicelluloses -- Modification
Hemicelluloses extraction from giant bamboo (<I>Bambusa balcooa </I>Roxburgh) prior to kraft or soda-AQ pulping and its effect on pulp physical properties
﻿ Vena PF Brienzo M Garcia-Aparicio M G�rgens JF Rypstra T
(WALTER DE GRUYTER & CO, GENTHINER STRASSE 13, BERLIN, GERMANY, D-10785, 2013)
﻿ Vena PF Garcia-Aparicio M Brienzo M G�rgens JF Rypstra T
(EDITURA ACADEMIEI ROMANE, CALEA 13 SEPTEMBRIE NR 13, SECTOR 5, BUCHAREST,ROMANIA, RO-76117, 2013)