Coconut Coir Pith
(CCP) is a relatively unexplored type of lignocellulosic
waste from the coconut industry. As a feedstock that is highly enriched
in lignin (Klason lignin content of 40.9 wt % found in this study),
CCP is a potential source for renewable lignin-derived materials.
We have performed a systematic study on the characterization and valorization
of lignin from CCP. We have investigated two different valorization
approaches: reductive catalytic fractionation (RCF) and soda pulping
followed by catalytic hydrodeoxygenation. During RCF, the lignin was
converted into monomeric products in 7.6 wt %. Using soda pulping
conditions, we were able to isolate lignin from CCP in 74% yield.
Subsequent hydrotreatment of the lignin over a Pt/MoO3/TiO2 catalyst resulted in the formation of hydrogenated oil in
43 wt % yield, suitable for the production of biobased diesel fuels
and lubricant base oils.
The increased interest in utilizing lignin as a feedstock
to produce
various aromatic compounds requires advanced chemical analysis methods
to provide qualitative and quantitative characterization of lignin
samples along different technology streamlines. However, due to the
lack of commercially available chemical standards, routine quantification
of industrially relevant lignin oligomers in complex lignin samples
remains a challenge. This study presents a novel method for universal
quantification of lignin dimers based on supercritical fluid chromatography
with charged aerosol detection (CAD). A series of lignin-derived dimeric
compounds that have been reported from reductive catalytic fractionation
(RCF) were synthesized and used as standards. The applicability of
using linear regression instead of quadratic calibration curves was
evaluated over a concentration range of 15–125 mg/L, demonstrating
that the former calibration method is as appropriate as the latter.
The response factors of lignin dimeric compounds were compared to
assess the uniformity of the CAD signal, revealing that the CAD response
for the tested lignin dimers did not differ substantially. It was
also found that the response factors were not dependent on the number
of methoxy groups or linkage motifs, ultimately enabling the use of
only one calibrant for these compounds. The importance of chromatographic
peak resolution in CAD was stressed, and the use of a digital peak
sharpening technique was adopted and applied to address this challenge.
The developed method was verified and used for the quantification
of lignin dimers in an oil obtained by a RCF of birch sawdust.
Valorizing industrial streams that are burnt to a low value is important to make biorefining more sustainable. In this work, hemicellulose obtained as a pre-hydrolysis liquor from kraft pulping was...
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