posted on 2018-10-18, 00:00authored byHuy Quang Lê, Juha-Pekka Pokki, Marc Borrega, Petri Uusi-Kyyny, Ville Alopaeus, Herbert Sixta
We
introduce the optimization of the pulping conditions and propose
different chemical recovery options for a proven biorefinery concept
based on γ-valerolactone (GVL)/water fractionation. The pulping
process has been optimized whereby the liquor-to-wood (L:W) ratio
could be reduced to 3 L/kg without compromising the pulp properties
as raw material for textile fibers production. The recovery of the
pulping solvent was performed through combinations of lignin precipitation
by water addition, distillation at reduced pressure, and liquid CO2 extraction. With a two-step lignin precipitation coupled
with vacuum distillation, more than 90% of lignin and GVL could be
recovered from the spent liquor. However, a significant part of GVL
remained unrecoverable in the residue, which was a highly viscous
liquid with complicated phase behavior. The recovery by lignin precipitation
combined with liquid CO2 extraction could recover more
than 85% GVL and 90% lignin without forming any problematic residue
as in the distillation process. The remaining GVL remained in the
raffinate containing a low amount of lignin and other compounds, which
can be further processed to isolate the GVL and improve the recovery
rate.