Promising bulk production of a potentially benign bisphenol A replacement from a hardwood lignin platform

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2018, Vol.20 (5), p.1050-1058
• Main Authors: Koelewijn, S.-F., Cooreman, C., Renders, T., Andecochea Saiz, C., Van den Bosch, S., Schutyser, W., De Leger, W., Smet, M., Van Puyvelde, P., Witters, H., Van der Bruggen, B., Sels, B. F.
• Format: Article
• Language: English
• Subjects: Benign; Bisphenol A; Catalysis; Condensates; Crystallization; Distillation; Feasibility; Feasibility studies; Fractionation; Green chemistry; Hydrogenolysis; Lignin; Phenols; Polyester resins; Polyesters; Scaffolds; Selectivity; Volatility; Wood
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C7GC02989F

A full lignin-to-chemicals valorisation chain – from hardwood over bissyringols to aromatic polyesters (APEs) – is established for renewable 4- n -propylsyringol (PS), the main product from catalytic hydrogenolysis of (native) hardwood lignin. To do so, reagent-grade PS was produced from birch wood via reductive catalytic fractionation (RCF) and isolated in 34 wt% yield on lignin basis. Additional early-stage theoretical calculations, based on both relative volatility ( α ) and distillation resistance ( Ω ) as well as Aspen Plus® simulations, predict that the isolation of PS by means of distillation is economically feasible at industrial scales ($85–95 per ton of propylphenolics at 200–400 kt a −1 scale). Subsequent stoichiometric acid-catalysed condensation with formaldehyde unveils a remarkably high 92 wt% selectivity towards the dimer 3,3′-methylenebis(4- n -propylsyringol) ( m , m ′-BSF-4P), which is isolated in >99% purity by facile single-step crystallisation. The striking dimer selectivity is ascribed to the synergetic interplay between the activating methoxy groups and the oligomerisation-inhibiting propyl chain. Next, an in vitro human oestrogen receptor α (hERα) assay was performed to ensure safe(r) chemical design. The bissyringyl scaffold displays reduced potency (∼19–45-times lower affinity than bisphenol A) and lower efficacy (∼36–45% of BPA's maximum activity). Lastly, to assess the functionality of the safe(r) bissyringol scaffold, it was converted into an APE. The APE displays a M w = 43.0 kDa, M n = 24.4 kDa, T g = 157 °C and T d,5% = 345 °C. In short, (i) the feasibility and scalability of the feedstock, (ii) the simplified process conditions, (iii) the reduced in vitro oestrogenicity, and (iv) the functionality towards polymerisation, make this bissyringol a renewable and potentially benign bisphenol replacement, capable for production at bulk scale.