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Fraktionering av rapshalmrester: Cellulosa och lignin
KTH, School of Chemical Science and Engineering (CHE).
2016 (Swedish)Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesisAlternative title
Fractionation of Rapeseed Straw Residues: Cellulose and Lignin (English)
Abstract [sv]

Med rapsfrön som en eftertraktad produkt från raps kvarstår rapshalm, vilket anses vara en avfallsprodukt. Dock är rapshalmen en god källa till biopolymerer och kan spela en potentiell roll som råvara till materialframställning.

Det övergripande målet med detta examensarbete var att fullständigt separera lignin och cellulosa från varandra i den halmrest som återstår efter hydrotermisk extraktion av rapshalm vilket delprojekt 1 har behandlat. Den huvudmetod som har tillämpats under projektet var alkalisk delignifiering, med bestämd tid, temperatur och koncentrationen NaOH. Två prover av halmrester valdes för behandling i detta projekt varav den första har extraherats med närvaro av bikarbonat som buffertlösning medan den andra har extraherats vid en högre temperatur. Ytterligare metoder för att erhålla lignin och cellulosa var ligninfällning och defibrering. Av den erhållna cellulosamassan framställdes papper. De erhållna produkterna med kolhydratanalys (IC), askhalt (TGA), och bestämning av funktionella grupper (FTIR). Cellulosamassan analyserades med SEM och ljusmikroskopi. De framställda pappersarken analyserades med dragprovning för bestämning av mekaniska egenskaper.

Det totala utbytet av lignin inte så högt, en tredjedel av ligninmängden i rapshalm. Det första provet gav ett högre utbyte än det andra, däremot gav det andra ett mer ligninrikt utbyte. Fibermassan från det andra provet hade en högre halt cellulosa. Mikroskopianalyser visade att fibrerna inte frilagts fullständigt från varandra, med kvarvarande biomassa som bibehåller sin originalstruktur. Mängden frilagda fibrer var högre i det första provet samt fiberstrukturen på de spiralformade fibrerna höll kvar sin primära form. Enligt resultaten från dragprovningsanalysen hade papperet från det första provet en signifikant högre brottgräns och E-modul än det andra.

Abstract [en]

The oil rich seeds from the rapeseed are products of interest, which leaves the straws as a waste product. Rapeseed straw is a good source of biopolymers which have potential as material resources.

The overall aim of this degree project was to fully separate lignin from cellulose in pretreated straws. The main method applied was delignification with alkali under specified conditions including time, temperature, and the concentration of sodium hydroxide. Two samples of preextracted straw were chosen. The first sample was extracted in the presence of a buffer while the second was extracted at a higher temperature. Other methods were also used, such as kraft lignin precipitation for a better yield of lignin, and defibration of the cellulosic fibre mass. Paper sheets were made from the obtained fibre mass. The products were analyzed with a variety of analytic methods, including IC, TGA, and FTIR. The straws and the cellulosic mass were further analyzed with SEM and optical microscopy. The obtained paper materials were analyzed mechanically by tensile testing.

The total yield of lignin was not so high, about a third of the total lignin content in the rapeseed straw. The first sample gave a higher than the second sample, however the second sample gave a more lignin rich yield. The obtained fibre mass in the second sample had a considerably higher content of cellulose. Microscopy analyses showed that the fibres did not fully separate, and there were remains of biomass in their current structure. The amount of separated fibres were higher in the first sample as well as the spiral-shaped fibres maintained their structure. The results from the tensile test showed that the paper prepared from the first sample had a significantly higher tensile strength than the paper obtained from the second sample.

Place, publisher, year, edition, pages
2016.
Keyword [sv]
alkalisk delignifiering, rapshalm, cellulosa, lignin
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-187042OAI: oai:DiVA.org:kth-187042DiVA: diva2:928707
Educational program
Bachelor of Science in Engineering - Chemical Engineering
Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2016-05-16Bibliographically approved

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