A new generation of organosolv biorefinery: Birch fractionation in gamma-valerolactone, full valorization of pulping streams, and solvent recovery

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2023-08-25
Degree programme
78 + app. 96
Aalto University publication series DOCTORAL THESES, 119/2023
This thesis presents a comprehensive biorefinery concept based on wood fractionation in gamma-valerolactone. Firstly, the stability of gamma-valerolactone (GVL) was evaluated in a wide range of pH (pH = 0-9) with a focus on pulping conditions (150-180°C). GVL hydrolyzes in a highly acidic environment and forms equilibrium with 4-hydroxyvaleric acid (4-HVA) (4 mol%) while under highly alkaline conditions GVL ring irreversibly opens and forms 4-hydroxyvalerate (>10 mol%). Nevertheless, GVL/ 4-HVA equilibrium remains stable under typical pulping conditions. The second part of this thesis investigated the alkaline-catalyzed fractionation with prehydrolysis, acid-catalyzed and alkaline-catalyzed fractionation of silver birch in 50 wt% GVL (180°C, 120 min). Although prehydrolysis could remove a substantial amount of hemicelluloses, the alkaline catalysis did not improve the overall quality of pulp in comparison to uncatalyzed or acid-catalyzed fractionation. Acid-catalyzed fractionation produced highly pure but significantly destroyed cellulose. After the optimization of fractionation conditions, the temperature of 150°C, time of 120 min, 55 wt % GVL, and the liquor-to-wood ratio of 4 were selected as the optimal conditions for dissolving pulp production.The produced dissolving pulp resembled the properties of commercial acid sulfite pulp, and it could be readily converted to fibers by Ioncell® technology. The mechanical properties of spun GVL-fibers and GVL-yarn exceeded the ones of commercially regenerated cellulose fibers and yarns. 70 % of dissolved lignin was isolated from the spent liquor by the addition of water (1:1), which was further processed as a polyol via an isocyanate-free route into polyhydroxyurethane. Most of the hemicelluloses were dissolved into spent liquor mostly in the form of monomeric xylose. It was demonstrated that xylose can be easily isolated by cooling crystallization from spent liquor in the presence of residual GVL.The last part of the thesis focused on GVL recovery from spent liquor by liquid CO2 extraction. In the laboratory setup, the recovery of GVL was 67 %, while 9 % of GVL remained in the raffinate. The low recovery rate was limited by the number of separation stages and short column height. Nevertheless, the advanced modeling validated based on laboratory experiments demonstrated that almost 99% of GVL could be recovered and recycled back to pulping
Supervising professor
Alopaeus, Ville, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Thesis advisor
Sixta, Herbert, Prof., Aalto University, Finland
Quang, Lê Huy, Dr., Aalto University, Finland
biorefinery, organosolv, gamma-valerolactone, cellulose
Other note
  • [Publication 1]: Granatier, Marianna; Schlapp-Hackl, Inge; Lê Huy, Quang; Nieminen, Kaarlo; Pitkänen Leena; Sixta, Herbert. 2021. Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery. Cellulose. 28. 11567-11578. 0969-0239.
    DOI: 10.1007/s10570-021-04243-5 View at publisher
  • [Publication 2]: Granatier, Marianna; Lê Huy, Quang; Carmona González, Eva; Sixta, Herbert. 2023. Birch fractionation in γ-valerolactone with the emphasis on pulp properties: prehydrolysis, acid-catalyzed, and alkaline-catalyzed concept. RSC Sustainability. 1. 97-106.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202305082971
    DOI: 10.1039/d2su00046f View at publisher
  • [Publication 3]: Granatier, Marianna; Lê Huy, Quang; Ma, Yibo; Rissanen, Marja; Schlapp-Hackl, Inge; Diment, Daryna; Zaykovskaya, Anna; Pokki, Juha-Pekka; Balakshin, Mikhail; Louhi-Kultanen, Marjatta; Alopaeus, Ville; Sixta, Herbert. 2023. Gamma-valerolactone biorefinery: Catalyzed birch fractionation and valorization of pulping streams with solvent recovery. Heliyon. 9. 6. e17423.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202308014523
    DOI: 10.1016/j.heliyon.2023.e17423 View at publisher