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Conversion of Wood and Non-Wood Paper- Grade Pulps to Dissolving-Grade Pulps

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Conversion of Wood and Non-Wood Paper- Grade Pulps to Dissolving-Grade Pulps Conversion of Wood and Non-wood Paper- grade Pulps to Dissolving-grade Pulps Viviana Köpcke Doctoral Thesis Royal Institute of Technology School of Chemical Science and Engineering Department of Fibre and Polymer Technology Division of Wood Chemistry and Pulp Technology Stockholm 2010 Conversion of Wood and Non-wood Paper- grade Pulps to Dissolving-grade Pulps Supervisor Associate Professor Monica Ek AKADEMISK AVHANDLING Som med tillstånd av Kungliga Tekniska Högskolan framläggs till offentlig granskning för avläggande av teknologie doktorsexamen, fredagen den 3 december 2010 kl. 13.00 i sal F3, Lindstedsvägen 26, KTH, Stockholm. Avhandlingen försvaras på engelska. ©Viviana Köpcke Stockholm 2010 TRITA-CHE-Report 2010:46 ISSN 1654-1081 ISBN 978-91-7415-777-2 Abstract Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose. In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose- binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps. The main focus of the forest industry is the production of paper-grade pulps. Paper- grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps. Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps. Sammanfattning Dissolvingmassor används vanligen för framställning av cellulosaregenerat och cellulosaderivat. För att erhålla högkvalitativa produkter måste dessa så kallade specialmassor uppfylla vissa krav som t ex högt cellulosainnehåll, låg hemicellulosahalt, en homogen molekylviktsfördelning samt hög cellulosareaktivitet. De flesta kommersiella dissolvingmassorna uppfyller dessa egenskaper i viss utsträckning. Men att uppnå hög tillgänglighet, löslighet samt reaktivitet, är inte enkelt på grund av cellulosans kompakta och komplexa struktur. I avhandlingens första del undersöktes monokomponent endoglukanasers förmåga att öka cellulosans tillgänglighet och reaktivitet för en lövvedsbaserad dissolvingmassa. Ett monokomponent endoglukanas med en cellulosabindande domän (CBD) visade sig signifikant öka cellulosans tillgänglighet och reaktivitet. Motsvarande försök testades även på pappersmassor. Skogsindustrins fokus är framförallt framställning av pappersmassor. Dessa framställs främst med sulfatprocessen. Dissolvingmassor däremot framställs från sulfitprocessen alternativt förhydrolyserad sulfat, på grund av kravet på hög renhet för dessa massor. Sulfatprocessen är känd för att vara den mest effektiva processen med avseende på energi och återvinningsaspekter, vilket leder till att produktionskostnaderna blir lägre för pappersmassor än sulfitdissolvingmassor. Detta har lett till försök att konvertera pappersmassor till dissolvingmassa. Detta är emellertid inte en lätt uppgift, framförallt eftersom pappersmassor innehåller lägre halter cellulosa och högre halter hemicellulosor än dissolvingmassor. Pappersmassor visar även lägre reaktivitet och en inhomogen molekylviktsfördelning. Som en konsekvens av detta, fokuserades arbetet i den andra delen av denna studie på möjligheten att omvandla sulfatmassa till dissolvingmassa. Ett flertal sekvenser av olika behandlingar av lövved och ettårsväxter undersöktes i detta arbete. Den bästa sekvensen för respektive massa bestämdes, och de ingående parametrarna optimerades. Efter flertal försök visades att massor från björk, eukalyptus och sisal uppfyllde kraven för en kommersiell dissolvingmassa för viskostillverkning. Detta efter att ha behandlats med en sekvens, bestående av två kommersiella enzymer, ett xylanas och ett monokomponent endoglukanas, samt alkalisteg. List of Publications This thesis is based on the following papers which are referred to by roman numbers and that are appended at the end. Paper I Increasing accessibility and reactivity of paper grade pulp by enzymatic treatment for use as dissolving pulp V. Köpcke, D. Ibarra and M. Ek (2008), Nordic Pulp and Paper Research Journal, Vol. 23(4), pp. 363−368. Paper II Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps D. Ibarra, V. Köpcke and M. Ek (2009), Holzforschung, Vol. 63, pp. 721−730 Paper III Optimization of treatment sequences for the production of dissolving pulp from birch kraft pulp V. Köpcke, D. Ibarra, P.T. Larsson and M. Ek (2010), Nordic Pulp and Paper Research Journal, Vol. 1, pp. 191−198. Paper IV Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp V. Köpcke, D. Ibarra, P.T. Larsson and M. Ek (2010), Polymers from Renewable Resources, Vol. 1, pp. 17−34 Paper V Combination of alkaline and enzymatic treatments as a process for upgrading sisal paper-grade pulp to dissolving-grade pulp D. Ibarra, V. Köpcke, P.T. Larsson, A-S. Jääskeläinen, and M. Ek (2010), Bioresource Technology, Vol. 101, pp. 7416−7423. Paper VI Behaviour of different monocomponent endoglucanase on the accessibility and reactivity of dissolving-grade pulps for viscose process D. Ibarra, V. Köpcke, and M. Ek, (2010), Enzyme and Microbial Technology, Vol. 47, pp. 355-362. Author contribution: Paper I: Principal author, planned and performed the experimental work together with Dr. D. Ibarra. Paper II: Co-author, contributed to plan the experimental work together with Dr. D. Ibarra. Paper III: Principal author, planned and performed all the experimental work except for the 13CP/MAS NMR performed by P.T Larsson. Paper IV: Principal author, responsible for planning the experimental work. The 13CP/MAS NMR was performed by P.T Larsson Paper V: Co-author, contributed to plan the experimental work together with Dr. David Ibarra. A-S. Jääskeläinen performed the Raman Spectroscopy and P.T. Larsson the 13CP/MAS NMR spectroscopy. Paper VI: Co-author, contributed to plan the experimental work together with Dr. D. Ibarra Results from the above publications have been presented at: Influence of Mechanical and Enzymatic Treatment on Cellulose Accessibility V. Hermosilla, H. Nanko and M. Ek. 14th ISWFPC: International Symposium on Wood, Fibre and Pulping Chemistry, June 25-28, Durban, South Africa, 2007. Conference Proceedings, abstract 117. Study on the feasibility of converting kraft pulps into dissolving pulps: accessibility and reactivity V. Köpcke, D. Ibarra, and M. Ek 235th American Chemical Society (ACS) National meeting, April 6-11, New Orleans, USA, 2008. Abstract of papers CELL-257 Exploring enzymatic and chemical pretreatments to upgrade eucalyptus globulus paper-grade pulp into dissolving-grade pulp D. Ibarra, V. Köpcke, and Ek, M. 4th International Colloquium on Eucalyptus Kraft Pulp (ICEP). May 4-6, Concepción, Chile, 2009 Structural characterization of dissolving-grade pulps produced by paper-grade pulp V. Köpcke, D. Ibarra, G. Henriksson, P.T. Larsson and M. Ek 15th ISWFPC: International Symposium on Wood, Fibre and Pulping Chemistry, June 15-18, Oslo, Norway, 2009. Proceedings, abstract O-030. Feasibility study on converting paper-grade pulps to dissolving-grade pulps V. Köpcke, D. Ibarra, P.T. Larsson and M. Ek 11th European Workshop on Lignocellulosics and Pulp, EWLP, August 16-19, Hamburg, Germany, 2010. Table of contents 1 Introduction..................................................................................................................1 1.1 Objectives...........................................................................................................................
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