{"id":{"repo_id":"aalto","oai_identifier":"oai:aaltodoc.aalto.fi:123456789/13329"},"canonical_url":"https://search.dev.ndltd.org/etd/aalto/oai:aaltodoc.aalto.fi:123456789/13329","repository":{"repo_id":"aalto","name":"Aalto University","base_url":"https://aaltodoc.aalto.fi/server/oai/request"},"display":{"title":"Changes in accessibility of cellulose for kraft pulps measured by deuterium exchange","abstract":"The emerging biorefinery processes and products set distinct processing and quality requirements compared to pulp and paper. Therefore, fundamental properties of cell wall, such as cellulose accessibility, require a more thorough understanding in the future.The aim of this study was to increase an understanding on the changes in cellulose accessibility throughout the chemical refining of wood, including kraft pulping, bleaching, drying, and further processing of the pulp. The characteristic physicochemical conditions in each subprocess were simulated with laboratory setups. In part, the analysis was based solely on literature. Cellulose accessibility was directly evaluated by deuteration, both in the liquid phase (deuteration combined with Fourier transform infrared spectroscopy) and in the vapor phase (dynamic vapor sorption with deuteration). The analytical methods based on deuterium exchange provided kinetic information on the underlying phenomena and revealed the reversible nature of cellulose microfibril coalescence. During kraft pulping, the proposed cellulose microfibril coalescence occurs mainly during the heat-up period and follows the first order dynamics. The active alkali (AA) content has a significant effect on the phenomenon. Hot acidic treatments, typical of ECF pulp bleaching, induce the formation of inaccessible regions in pulp similar to drying. Alkaline treatments, in contrast, induce a dynamic equilibrium state either between microfibrils and microfibril aggregates or between the amorphous and crystalline parts of cellulose. The equilibrium shifts towards disengagement at higher pH and temperature.The changes in cellulose accessibility in alkali are dependent on the drying history of the pulp. In addition, hemicellulose dissolution may affect the accessibility. Thus, TEMPO catalyzed oxidation of birch kraft pulp can be radically intensified by a short treatment with relatively mild alkali at room temperature. Multiple drying cycles or prolonged exposure to humid atmosphere increase cellulose microfibril coalescence, but this effect diminishes gradually. As a conclusion, many steps in processing wood and pulp reduce cellulose accessibility, presumably by microfibril coalescence. However, alkaline treatments of pulp induce an equilibrium state, which can increase the accessibility prior to further processing steps, e.g., catalytic oxidation of primary alcohols. Analytical methods applying deuteration provide valuable information on the changes in cellulose accessibility and their dynamics.","abstract_html":"The emerging biorefinery processes and products set distinct processing and quality requirements compared to pulp and paper. Therefore, fundamental properties of cell wall, such as cellulose accessibility, require a more thorough understanding in the future.The aim of this study was to increase an understanding on the changes in cellulose accessibility throughout the chemical refining of wood, including kraft pulping, bleaching, drying, and further processing of the pulp. The characteristic physicochemical conditions in each subprocess were simulated with laboratory setups. In part, the analysis was based solely on literature. Cellulose accessibility was directly evaluated by deuteration, both in the liquid phase (deuteration combined with Fourier transform infrared spectroscopy) and in the vapor phase (dynamic vapor sorption with deuteration). The analytical methods based on deuterium exchange provided kinetic information on the underlying phenomena and revealed the reversible nature of cellulose microfibril coalescence. During kraft pulping, the proposed cellulose microfibril coalescence occurs mainly during the heat-up period and follows the first order dynamics. The active alkali (AA) content has a significant effect on the phenomenon. Hot acidic treatments, typical of ECF pulp bleaching, induce the formation of inaccessible regions in pulp similar to drying. Alkaline treatments, in contrast, induce a dynamic equilibrium state either between microfibrils and microfibril aggregates or between the amorphous and crystalline parts of cellulose. The equilibrium shifts towards disengagement at higher pH and temperature.The changes in cellulose accessibility in alkali are dependent on the drying history of the pulp. In addition, hemicellulose dissolution may affect the accessibility. Thus, TEMPO catalyzed oxidation of birch kraft pulp can be radically intensified by a short treatment with relatively mild alkali at room temperature. Multiple drying cycles or prolonged exposure to humid atmosphere increase cellulose microfibril coalescence, but this effect diminishes gradually. As a conclusion, many steps in processing wood and pulp reduce cellulose accessibility, presumably by microfibril coalescence. However, alkaline treatments of pulp induce an equilibrium state, which can increase the accessibility prior to further processing steps, e.g., catalytic oxidation of primary alcohols. Analytical methods applying deuteration provide valuable information on the changes in cellulose accessibility and their dynamics.","abstract_has_math":false,"creators":["Pönni, Raili"],"institution":"Aalto University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Puunjalostustekniikan laitos","school":null,"contributors":["Aalto-yliopisto","Aalto University"],"advisors":["Kontturi, Eero, Dr., Aalto University, Department of Forests Products Technology, Finland","Vuorinen, Tapani, Prof., Aalto University, Department of Forests Products Technology, Finland"],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014","date_published":"2014","updated_at":"2026-08-21T16:42:07Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aaltodoc.aalto.fi/handle/123456789/13329","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"source_record":{"url":"https://aaltodoc.aalto.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aaaltodoc.aalto.fi%3A123456789%2F13329","prefix":"dim"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Aalto-yliopisto","Aalto University"]},{"key":"dc:contributor.advisor","label":"Advisor","values":["Kontturi, Eero, Dr., Aalto University, Department of Forests Products Technology, Finland"]},{"key":"dc:contributor.department","label":"Department","values":["Puunjalostustekniikan laitos","Department of Forest Products Technology"]},{"key":"dc:contributor.supervisor","label":"Supervisor","values":["Vuorinen, Tapani, Prof., Aalto University, Department of Forests Products Technology, Finland"]},{"key":"dc:creator","label":"Author","values":["Pönni, Raili"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-06-10T09:00:20Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-06-10T09:00:20Z"]},{"key":"dc:date.issued","label":"Date","values":["2014"]},{"key":"dc:publisher","label":"Institution","values":["Aalto University","Aalto-yliopisto"]},{"key":"dc:type","label":"Dc Type","values":["G5 Artikkeliväitöskirja"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["text"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://aaltodoc.aalto.fi/handle/123456789/13329"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The emerging biorefinery processes and products set distinct processing and quality requirements compared to pulp and paper. Therefore, fundamental properties of cell wall, such as cellulose accessibility, require a more thorough understanding in the future.The aim of this study was to increase an understanding on the changes in cellulose accessibility throughout the chemical refining of wood, including kraft pulping, bleaching, drying, and further processing of the pulp. The characteristic physicochemical conditions in each subprocess were simulated with laboratory setups. In part, the analysis was based solely on literature. Cellulose accessibility was directly evaluated by deuteration, both in the liquid phase (deuteration combined with Fourier transform infrared spectroscopy) and in the vapor phase (dynamic vapor sorption with deuteration). The analytical methods based on deuterium exchange provided kinetic information on the underlying phenomena and revealed the reversible nature of cellulose microfibril coalescence. During kraft pulping, the proposed cellulose microfibril coalescence occurs mainly during the heat-up period and follows the first order dynamics. The active alkali (AA) content has a significant effect on the phenomenon. Hot acidic treatments, typical of ECF pulp bleaching, induce the formation of inaccessible regions in pulp similar to drying. Alkaline treatments, in contrast, induce a dynamic equilibrium state either between microfibrils and microfibril aggregates or between the amorphous and crystalline parts of cellulose. The equilibrium shifts towards disengagement at higher pH and temperature.The changes in cellulose accessibility in alkali are dependent on the drying history of the pulp. In addition, hemicellulose dissolution may affect the accessibility. Thus, TEMPO catalyzed oxidation of birch kraft pulp can be radically intensified by a short treatment with relatively mild alkali at room temperature. Multiple drying cycles or prolonged exposure to humid atmosphere increase cellulose microfibril coalescence, but this effect diminishes gradually. As a conclusion, many steps in processing wood and pulp reduce cellulose accessibility, presumably by microfibril coalescence. However, alkaline treatments of pulp induce an equilibrium state, which can increase the accessibility prior to further processing steps, e.g., catalytic oxidation of primary alcohols. Analytical methods applying deuteration provide valuable information on the changes in cellulose accessibility and their dynamics.","Metsäteollisuuden uusien biojalostamoihin keskittyvien prosessien ja tuotteiden valmistuksessa tarvitaan tietoa puuraaka-aineesta ja erityisesti puun soluseinästä. Eräs merkittävä ominaisuus on selluloosan reaktiivisuus, jota voidaan kuvata selluloosan saavutettavuudella. Tämän työn tarkoituksena oli tutkia muutoksia selluloosan saavutettavuudessa koko puu prosessointiketjun aikana. Työ kattaa sulfaattisellun valmistuksen, valkaisun, kuivauksen ja sellun jatkojalostuksen. Näitä osaprosesseja simuloitiin laboratoriokokeilla. Osin työ perustui kirjallisuustarkasteluun. Työssä käytettiin deuteriumvaihtoa sekä nestefaasissa (deuterointi yhdistettynä Fourier-muunnos infrapunaspektroskopiaan) että kaasufaasissa (dynaaminen kaasusorptio deuteriumvaihdolla). Deuteriumvaihtotekniikoilla saavutettavuutta pystyttiin arvioimaan suoraan. Lisäksi voitiin seurata ilmiöiden kinetiikkaa ja todeta selluloosamikrofibrillien aggregoitumisen palautuva luonne. Sulfaattikeiton aikana selluloosamikrofibrillit aggregoituvat jo keittolämpötilan nosto-vaiheen aikana. Vaikuttava alkalipitoisuus keitossa on merkittävä muuttuja aggregoitumisen kannalta. ECF valkaisusekvensseille tyypilliset, kuumat ja happamat vaiheet, aiheuttavat vastaavia muutoksia mikrofibrilleissä kuin kuivaus. Alkaliset vaiheet puolestaan johtavat dynaamiseen tasapainotilaan, jonka oletetaan olevan mikrofibrillien ja mikrofibrilli-aggregaattien välinen tai kiteisten ja amorfisten alueiden välinen. Tasapaino siirtyy kohti suurempaa saavutettavuutta kun lämpötilaa ja alkalisuutta kasvatetaan. Sellun kuivauksella ennen alkalikäsittelyä on suuri merkitys selluloosan saavutettavuuteen. Myös hemisellu-loosien liukeneminen alkalikäsittelyn aikana vaikuttaa saavutettavuuteen. Koivusellun TEMPO-katalysoitua hapetusta voidaan tehostaa merkittävästi lyhyellä alkalikäsittelyllä huoneenlämmössä. Kuivauksessa saavutettavuus laskee ajan funktiona sekä toistettaessa kuivaussyklejä, mutta vaikutus pienenee vähitellen. Yhteenvetona voidaan todeta, että useat puun ja sellun prosessointivaiheet aiheuttavat muutoksia selluloosan saavutettavuudessa, olettavasti mikrofibrillien aggregoitumisen johdosta. Toisaalta alkaliset käsittelyt voivat palauttaa aiemmin heikentynyttä saavutettavuutta ja siten parantaa raaka-aineen reaktiivisuutta esim. katalyyttisen hapetuksen aikana. Deuterointia käyttävät mittaustekniikat antavat merkittävää tietoa selluloosan reaktiivisuudesta ja kinetiikasta."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Changes in accessibility of cellulose for kraft pulps measured by deuterium exchange","Sulfaattisellun saavutettavuuden arviointi deuteriumvaihtomenetelmillä"]}]}],"canonical_facts":{"dc:contributor":["Aalto-yliopisto","Aalto University"],"dc:contributor.advisor":["Kontturi, Eero, Dr., Aalto University, Department of Forests Products Technology, Finland"],"dc:contributor.department":["Puunjalostustekniikan laitos","Department of Forest Products Technology"],"dc:contributor.supervisor":["Vuorinen, Tapani, Prof., Aalto University, Department of Forests Products Technology, Finland"],"dc:creator":["Pönni, Raili"],"dc:date.accessioned":["2014-06-10T09:00:20Z"],"dc:date.available":["2014-06-10T09:00:20Z"],"dc:date.issued":["2014"],"dc:description.abstract":["The emerging biorefinery processes and products set distinct processing and quality requirements compared to pulp and paper. Therefore, fundamental properties of cell wall, such as cellulose accessibility, require a more thorough understanding in the future.The aim of this study was to increase an understanding on the changes in cellulose accessibility throughout the chemical refining of wood, including kraft pulping, bleaching, drying, and further processing of the pulp. The characteristic physicochemical conditions in each subprocess were simulated with laboratory setups. In part, the analysis was based solely on literature. Cellulose accessibility was directly evaluated by deuteration, both in the liquid phase (deuteration combined with Fourier transform infrared spectroscopy) and in the vapor phase (dynamic vapor sorption with deuteration). The analytical methods based on deuterium exchange provided kinetic information on the underlying phenomena and revealed the reversible nature of cellulose microfibril coalescence. During kraft pulping, the proposed cellulose microfibril coalescence occurs mainly during the heat-up period and follows the first order dynamics. The active alkali (AA) content has a significant effect on the phenomenon. Hot acidic treatments, typical of ECF pulp bleaching, induce the formation of inaccessible regions in pulp similar to drying. Alkaline treatments, in contrast, induce a dynamic equilibrium state either between microfibrils and microfibril aggregates or between the amorphous and crystalline parts of cellulose. The equilibrium shifts towards disengagement at higher pH and temperature.The changes in cellulose accessibility in alkali are dependent on the drying history of the pulp. In addition, hemicellulose dissolution may affect the accessibility. Thus, TEMPO catalyzed oxidation of birch kraft pulp can be radically intensified by a short treatment with relatively mild alkali at room temperature. Multiple drying cycles or prolonged exposure to humid atmosphere increase cellulose microfibril coalescence, but this effect diminishes gradually. As a conclusion, many steps in processing wood and pulp reduce cellulose accessibility, presumably by microfibril coalescence. However, alkaline treatments of pulp induce an equilibrium state, which can increase the accessibility prior to further processing steps, e.g., catalytic oxidation of primary alcohols. Analytical methods applying deuteration provide valuable information on the changes in cellulose accessibility and their dynamics.","Metsäteollisuuden uusien biojalostamoihin keskittyvien prosessien ja tuotteiden valmistuksessa tarvitaan tietoa puuraaka-aineesta ja erityisesti puun soluseinästä. Eräs merkittävä ominaisuus on selluloosan reaktiivisuus, jota voidaan kuvata selluloosan saavutettavuudella. Tämän työn tarkoituksena oli tutkia muutoksia selluloosan saavutettavuudessa koko puu prosessointiketjun aikana. Työ kattaa sulfaattisellun valmistuksen, valkaisun, kuivauksen ja sellun jatkojalostuksen. Näitä osaprosesseja simuloitiin laboratoriokokeilla. Osin työ perustui kirjallisuustarkasteluun. Työssä käytettiin deuteriumvaihtoa sekä nestefaasissa (deuterointi yhdistettynä Fourier-muunnos infrapunaspektroskopiaan) että kaasufaasissa (dynaaminen kaasusorptio deuteriumvaihdolla). Deuteriumvaihtotekniikoilla saavutettavuutta pystyttiin arvioimaan suoraan. Lisäksi voitiin seurata ilmiöiden kinetiikkaa ja todeta selluloosamikrofibrillien aggregoitumisen palautuva luonne. Sulfaattikeiton aikana selluloosamikrofibrillit aggregoituvat jo keittolämpötilan nosto-vaiheen aikana. Vaikuttava alkalipitoisuus keitossa on merkittävä muuttuja aggregoitumisen kannalta. ECF valkaisusekvensseille tyypilliset, kuumat ja happamat vaiheet, aiheuttavat vastaavia muutoksia mikrofibrilleissä kuin kuivaus. Alkaliset vaiheet puolestaan johtavat dynaamiseen tasapainotilaan, jonka oletetaan olevan mikrofibrillien ja mikrofibrilli-aggregaattien välinen tai kiteisten ja amorfisten alueiden välinen. Tasapaino siirtyy kohti suurempaa saavutettavuutta kun lämpötilaa ja alkalisuutta kasvatetaan. Sellun kuivauksella ennen alkalikäsittelyä on suuri merkitys selluloosan saavutettavuuteen. Myös hemisellu-loosien liukeneminen alkalikäsittelyn aikana vaikuttaa saavutettavuuteen. Koivusellun TEMPO-katalysoitua hapetusta voidaan tehostaa merkittävästi lyhyellä alkalikäsittelyllä huoneenlämmössä. Kuivauksessa saavutettavuus laskee ajan funktiona sekä toistettaessa kuivaussyklejä, mutta vaikutus pienenee vähitellen. Yhteenvetona voidaan todeta, että useat puun ja sellun prosessointivaiheet aiheuttavat muutoksia selluloosan saavutettavuudessa, olettavasti mikrofibrillien aggregoitumisen johdosta. Toisaalta alkaliset käsittelyt voivat palauttaa aiemmin heikentynyttä saavutettavuutta ja siten parantaa raaka-aineen reaktiivisuutta esim. katalyyttisen hapetuksen aikana. Deuterointia käyttävät mittaustekniikat antavat merkittävää tietoa selluloosan reaktiivisuudesta ja kinetiikasta."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["https://aaltodoc.aalto.fi/handle/123456789/13329"],"dc:language.iso":["en"],"dc:publisher":["Aalto University","Aalto-yliopisto"],"dc:title":["Changes in accessibility of cellulose for kraft pulps measured by deuterium exchange","Sulfaattisellun saavutettavuuden arviointi deuteriumvaihtomenetelmillä"],"dc:type":["G5 Artikkeliväitöskirja"],"dc:type.dcmitype":["text"]},"updated_at":"2026-08-21T16:42:07Z"}