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  • 1. Gunnarsson, Maria
    et al.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 6, p. 2427-2436Article in journal (Refereed)
    Abstract [en]

    A natural abundance of the air CO2 in NaOH(aq) at low temperature was investigated in terms of cellulose-CO2 interactions upon cellulose dissolution in this system. An organic superbase, namely 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU, known for its ability to incorporate CO2 in carbohydrates, was employed in order to shed light on this previously overlooked feature of NaOH(aq) at low temperature. The chemisorption of CO2 onto cellulose was investigated using spectroscopic methods in combination with suitable regeneration procedures. ATR-IR and NMR characterisation of regenerated celluloses showed that chemisorption of CO2 onto cellulose during its dissolution in NaOH(aq) takes place both with and without employment of the CO2-capturing superbase. The chemisorption was also observed to be reversible upon addition of water: CO2 desorbed when water was used as regenerating agent but could be preserved when instead ethanol was used. This finding could be an important parameter to take into consideration when developing processes for dissolution of cellulose based on this system.

  • 2.
    Jedvert, Kerstin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wells, Tyrone, Jr.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Analyses of wood components in mild steam explosion liquors from spruce2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 557-566Article in journal (Refereed)
    Abstract [en]

    Steam explosion at mild conditions is an intriguing pre-treatment method for future biorefineries. Here, mild steam explosion liquors, i.e. the condensed steam generated from water-impregnated and NaBH4-impregnated spruce at various steam explosion conditions, are comprehensively characterized. The characterization includes several chromatographic techniques along with nuclear magnetic resonance (NMR), in order to determine relative abundances of solubilized lignin, carbohydrates, and acetate content. The findings show that the main components in the liquors originated from hemicelluloses and, to some extent, wood extractives. Arabinose side substituents of arabinoglucuronoxylan were cleaved early during the steam treatment. The amount of (galacto) glucomannan in the liquors increased from 16% for the sample from the 4 bar (0.4 MPa) treatment, to 23% for the sample from the 7 bar treatment. The effects of different conditions on wood during NaBH4-treatment were also investigated. For this treatment, it was found that the degree of deacetylation increased at harsher conditions.

  • 3. Wojtasz-Mucha, J.
    et al.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hydrothermal pretreatment of wood by mild steam explosion and hot water extraction2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 241, p. 120-126Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step.

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