Influence of base-catalyzed organosolv fractionation of larch wood sawdust on fraction yields and lignin properties

Markus Hochegger, Gregor Trimmel, Betty Cottyn-Boitte, Laurent Cézard, Amel Majira, Sigurd Schober, Martin Mittelbach

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Abstract

Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel dependency. As of now, the fractionation is still the most difficult step of the whole process. The objective of this study is to investigate the potential of a base-catalyzed organosolv process as a fractionation technique for European larch sawdust. A solvent system comprising methanol, water, sodium hydroxide as catalyst, and anthraquinone as co-catalyst is tested. The influence of three independent process variables, temperature (443–446 K), catalyst loading (20–30% w/w), and alcohol-to-water ratio (30–70% v/v), is studied. The process conditions were determined using a fractional factorial experiment. One star point (443 K, 30% v/v MeOH, 30% w/w NaOH) resulted in the most promising results, with a cellulose recovery of 89%, delignification efficiency of 91%, pure lignin yield of 82%, residual carbohydrate content of 2.98% w/w, and an ash content of 1.24% w/w. The isolated lignin fractions show promising glass transition temperatures (≥424 K) with high thermal stabilities and preferential O/C and H/C ratios. This, together with high contents of phenolic hydroxyl (≥1.83 mmol/g) and carboxyl groups (≥0.52 mmol/g), indicates a high valorization potential. Additionally, Bjorkman lignin was isolated, and two reference Kraft cooks and a comparison to three acid-catalyzed organosolv fractionations were conducted.

Original languageEnglish
Article number996
JournalCatalysts
Volume9
Issue number12
DOIs
Publication statusPublished - 1 Dec 2019

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Keywords

  • Characterization
  • European larch
  • Fractionation
  • Lignin
  • Organosolv

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Fields of Expertise

  • Advanced Materials Science

Treatment code (Nähere Zuordnung)

  • Experimental

Cooperations

  • NAWI Graz

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