This study focused on maximizing yields of oligomeric and monomeric products while minimizing coke formation in the depolymerization of lignin from an organosolv medium. A design of experiments (DoE) with temperature, time, and ethanol‐water ratio as factors was established and tested. Optimized reaction conditions were found at 185.4°C with 7.5 wt% sodium hydroxide as catalyst, an ethanol‐water ratio of 48.6% (v/v), and a residence time of 30 minutes. With these optimized parameters, maximum monomer and oligomer yields of 9.4 wt% and 86.2 wt% and minimized coke formation of 0.5 wt% were achieved. The oligomeric and monomeric products were characterized by GPC, GC‐MS, and OH‐group determination (Folin‐Ciocalteu).
More wood for technical valorization is to be expected in Europe over the coming years, due to climate change and the bark beetle. To further independence from fossil-fuel resources a novel approach to the base-catalyzed depolymerization (BCD) of organosolv lignin into monomers and oligomers, while maximizing yields and minimizing coke formation, was scaled up in a theoretical wood-based biorefinery with a yearly input of 40 000 t of wood chips. Other process steps were modeled from the literature. A novel work-up approach was evaluated under laboratory conditions, implemented, and compared with a simulation-based pervaporation technique. The life-cycle assessment (LCA) showed that the biorefinery provided a significantly lower global warming potential (GWP) (excluding biogenic carbon) than its fossil counterparts. Moreover, the majority of impacts on the other midpoint categories was also smaller than for the fossil reference. However, after allocating the GWPs, it was evident that subsequent conversion of the C6 fraction to value-added products is necessary for optimal results. The discounted cash flow analyses for the biorefinery setups (40 to 400 kt year -1 ) showed that they were not profitable with prices based on fossil references. However, when using higher prices/t from the literature, such as €1615 for monomers, €2000 for oligomers, and €510 for C6 sugars, a positive net present value could be reached at
This study demonstrates that bio-based products of lignin depolymerisation can potentially replace common antioxidants and UV absorbers in the plastics and cosmetics industries. The kraft lignin Indulin AT was used to obtain low-MW lignin and monomers & oligomers rich in phenolic hydroxyl groups. Both thermo-oxidative stability and antioxidant activity significantly improved upon lignin depolymerisation. The results from oxidation induction time differential scanning calorimetry (OIT-DSC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) measurements show that the lignin based depolymerisation products are comparable with commercial antioxidants like pentaerythritol-tetrakis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate) (Irganox 1010). UV/vis spectroscopy was investigated to confirm absorption of the depolymerisation products in the UVA and UVB range (280–400 nm).
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