Organosolv pretreatment
represents one of the most promising biomass
valorization strategies for renewable carbon-based products; meanwhile,
there is an overall lack of holistic approach to how extraction conditions
affect the suitable end-usages. In this context, lignin extracted
from silver birch (
Betula pendula
L.)
by a novel hybrid organosolv/steam-explosion treatment at varying
process conditions (EtOH %; time; catalyst %) was analyzed by quantitative
NMR (
1
H–
13
C HSQC;
13
C NMR;
31
P NMR), gel permeation chromatography, Fourier transform
infrared (FT-IR), Pyr-gas chromatography–mass spectroscopy
(GC/MS), and thermogravimetric analysis, and the physicochemical characteristics
of the lignins were discussed regarding their potential usages. Characteristic
lignin interunit bonding motifs, such as β-
O
-4′, β-β′, and β-5′, were
found to dominate in the extracted lignins, with their abundance varying
with treatment conditions. Low-molecular-weight lignins with fairly
unaltered characteristics were generated via extraction with the highest
ethanol content potentially suitable for subsequent production of
free phenolics. Furthermore, β-β′ and β-5′
structures were predominant at higher acid catalyst contents and prolonged
treatment times. Higher acid catalyst content led to oxidation and
ethoxylation of side-chains, with the concomitant gradual disappearance
of
p
-hydroxycinnamyl alcohol and cinnamaldehyde.
This said, the increasing application of acid generated a broad set
of lignin characteristics with potential applications such as antioxidants,
carbon fiber, nanoparticles, and water remediation purposes.
Halophytes present major potentials in biorefinery as these salt tolerant crops prospect an alternative for energy demands and products with reduced effects in food security and environmental damages when compared...
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