Wood biorefinery concept based on γ-valerolactone/water fractionation

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School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2018-11-16
Degree programme
88 + app. 92
Aalto University publication series DOCTORAL DISSERTATIONS, 225/2018
This thesis introduces a novel biorefinery concept based on the uncatalyzed pulping of hardwood biomass in an aqueous solution of gamma-valerolactone (GVL). The optimum conditions were determined as 50 wt% GVL, liquor-to-wood ratio (L:W) of 3 – 4 L/kg, 180°C and 90 – 150 minutes. Eucalyptus globulus (E. globulus) wood was effectively fractionated in a single step into its principal components. The pulp fraction was of viscose grade with similar properties to those of a dissolving pulp produced from acid sulfite pulping of hardwood. GVL unbleached and bleached pulps were readily converted to textile fibers with mechanical properties comparable to the current commercial products. Lignin-containing nanofibrillated cellulose (NFC) was also produced from unbleached GVL pulps and subjected to morphological and rheological characterizations, revealing potential applications related to the water retention and structural recovery of the NFC suspensions. Most of the hemicelluloses and lignin in wood were extracted and dissolved into the spent liquor. The dissolved hemicellulose-based fraction can be upgraded to furanic platform chemicals in subsequent catalytic conversion processes in GVL-rich medium. Lignin was precipitated by water addition or by GVL removal. The sulfur-free lignin was characterized by low impurity content, rich in functionalities, relatively low polydispersity and low molecular mass. Fundamental study on the solubility of lignin in GVL/water resulted in a ternary phase diagram with information applicable to the recovery process. Hildebrand solubility theory estimated an optimum dissolution of lignin in a solution containing about 92 – 96 wt% GVL (70 – 80 mol% GVL). The solvent recovery was conducted with vacuum distillation and liquid CO2 extraction as the core techniques. A lignin and GVL recovery rate of ca. 90% was achieved, which can still be improved by the equipment modification, operational parameters optimization and the adoption of advanced lignin treatments. The GVL fractionation process is sulfur-free and the high pulp bleachability offers the possibility for a total-chlorine-free bleaching sequence, thus making the process environmentally friendly. Furthermore, initial assessment demonstrated that the proposed GVL biorefinery could be energetically self-sustained by the steam and electricity generated from the combustion of isolated lignin. Altogether, our concept fulfills the requirements of a modern biorefinery. 
Supervising professor
Sixta, Herbert, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
Thesis advisor
Pokki, Juha-Pekka, Dr., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
Borrega, Marc, Dr., Technical Research Centre of Finland VTT, Finland
gamma-valerolactone, GVL, eucalyptus globulus, hardwood biomass, biorefinery, pulping, organosolv fractionation, vacuum distillation, liquid-liquid extraction, liquid-CO2 extraction
Other note
  • [Publication 1]: Huy Quang Lê, Anna Zaitseva, Juha-Pekka Pokki, Marina Ståhl, Ville Alopaeus, Herbert Sixta. Solubility of organosolv lignin in y-valerolactone/water binary mixtures. ChemSusChem, 2016, volume 9, issue 20, pp. 2939-2947.
    DOI: 10.1002/cssc.201600655 View at publisher
  • [Publication 2]: Huy Quang Lê, Yibo Ma, Marc Borrega,Herbert Sixta. Wood biorefinery based on y-valerolactone/water fractionation. Green Chemistry, 2016, volume 18, issue 20, pages 5466-5476.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201703233153
    DOI: 10.1039/c6gc01692h View at publisher
  • [Publication 3]: Huy Quang Lê, Katarina Dimic-Misic, Leena-Sisko Johansson, Thaddeus Maloney, Herbert Sixta. Effect of lignin on the morphology and rheological properties of nanofibrillated cellulose produced from y-valerolactone/water fractionation process. 2016, Cellulose, volume 25, issue 1, pp. 179-194.
    DOI: 10.1007/s10570-017-1602-5 View at publisher
  • [Publication 4]: Huy Quang Lê, Juha-Pekka Pokki, Marc Borrega, Petri Uusi-Kyyny, Ville Alopaeus, Herbert Sixta. Chemical recovery of y-valerolactone/water biorefinery. Industrial and Engineering Chemistry Research, accepted in 2018.
    DOI: 10.1021/acs.iecr.8b03723 View at publisher