Influence of base-catalyzed organosolv fractionation of larch wood sawdust on fraction yields and lignin properties
2019
Hochegger, Markus | Trimmel, Gregor | Cottyn Boitte, Betty | Cezard, Laurent | Majira, Amel | Schober, Sigurd | Mittelbach, Martin | Universität Graz = University of Graz | Graz University of Technology [Graz] (TU Graz) | Institut Jean-Pierre Bourgin (IJPB) ; Institut National de la Recherche Agronomique (INRA)-AgroParisTech | Université Paris Saclay (COmUE) | Centre National de la Recherche Scientifique (CNRS)
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Show more [+] Less [-]English. 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.
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