Recently,
lignin utilization in advanced applications has gained
much interest. Due to the limitation of the current use of standard
lignin, lignin particles have recently gained attention in overcoming
the challenge. In this work, the spherical lignin particles obtained
from organosolv lignin (OL) were prepared using the dialysis method
with tetrahydrofuran (THF) or ethanol as the solvent. From the result,
it was found that the types of lignin and solvent, initial lignin
concentration, and stirring rate strongly affected the size of fabricated
particles. Moreover, the preparation of lignin particles using THF
as a solvent showed more uniform and symmetric spherical lignin particles.
The stability of the particle dispersion was examined under various
pH conditions. Moreover, lignin samples were also introduced into
the poly(vinyl alcohol) (PVA) for the production of ultraviolet (UV)-blocking
composite film. Mechanical and optical properties of composite film
were also observed. As a result, the prepared lignin–PVA composite
film showed great ultraviolet (UV) protective potential in both UVA
and UVB regions.
We
develop a sequential fractionation of palm empty fruit bunches
(EFB) and microwave-assisted depolymerization of lignin for producing
monophenolic compounds with high yields. EFB has been known as a low-priced
and abandoned residue from the palm oil milling process due to its
low heating value and generation of toxic gases upon burning; therefore,
valorization of EFB has been an important task for circular economy.
In this study, a subsequent alkaline hot compressed water fractionation
to separate hemicellulose and lignin from cellulose has been studied.
The lignin separation by lignin precipitation and a filtration process
followed by microwave-assisted lignin oxidative depolymerization to
high value phenolic compounds was proposed. We systematically screened
many catalysts as well as investigated reaction conditions (such as
the concentration of hydrogen peroxide, reaction time, etc.) to achieve
the highest yield of lignin-derived phenolic compounds. It was found
that the optimal conditions for depolymerization of pretreated EFB
lignin were (i) NaOH solution with 2.5% (w/w) hydrogen peroxide, (ii)
microwave (300 W) for 15 min, and (iii) bimetallic Cu(OH)2 and Fe2O3 catalysts. The highest percentage
of the total phenolic compound concentration peak area is 91.78%,
including 42.84% of syringol, 5.42% of vanillin, 8.71% of acetovanillone,
6.65% of syringaldehyde, and 28.16% of acetosyringone. The proposed
sequential fractionation and microwave-assisted treatment would be
promising for converting other lignocellulosic raw biomass to useful
phenolic compounds.
This work aims to enhance the value of palm empty fruit bunches (EFBs), an abundant residue from the palm oil industry, as a precursor for the synthesis of luminescent carbon dots (CDs). The mechanism of fIuorimetric sensing using carbon dots for either enhancing or quenching photoluminescence properties when binding with analytes is useful for the detection of ultra-low amounts of analytes. This study revealed that EFB-derived CDs via hydrothermal synthesis exceptionally exhibited luminescence properties. In addition, surface modification for specific binding to a target molecule substantially augmented their PL characteristics. Among the different nitrogen and sulfur (N and S) doping agents used, including urea (U), sulfate (S), p-phenylenediamine (P), and sodium thiosulfate (TS), the results showed that PTS-CDs from the co-doping of p-phenylenediamine and sodium thiosulfate exhibited the highest PL properties. From this study on the fluorimetric sensing of several metal ions, PTS-CDs could effectively detect Fe3+ with the highest selectivity by fluorescence quenching to 79.1% at a limit of detection (LOD) of 0.1 µmol L−1. The PL quenching of PTS-CDs was linearly correlated with the wide range of Fe3+ concentration, ranging from 5 to 400 µmol L−1 (R2 = 0.9933).
Hydrodeoxygenation
(HDO) of bio-oil derived from liquefaction of
a palm empty fruit bunch (EFB) in glycerol was investigated. To enhance
the heating value and reduce the oxygen content of upgraded bio-oil,
hydrodeoxygenation of light bio-oil over Ni- and Co-based catalysts
on an Al2O3 support was performed in a rotating-bed
reactor. Two consecutive steps were conducted to produce bio-oil from
EFB including (1) microwave-assisted wet torrefaction of EFB and (2)
solvothermolysis liquefaction of treated EFB in a Na2CO3/glycerol system. The HDO of as-prepared bio-oil was subsequently
performed in a unique design reactor possessing a rotating catalyst
bed for efficient interaction of a catalyst with bio-oil and facile
separation of the catalyst from upgraded bio-oil after the reaction.
The reaction was carried out in the presence of each mono- or bimetallic
catalyst, namely, Co/Al2O3, Ni/Al2O3, NiMo/Al2O3, and CoMo/Al2O3, packed in the rotating-mesh host with a rotation
speed of 250 rpm and kept at 300 and 350 °C, 2 MPa hydrogen for
1 h. From the results, the qualities of upgraded bio-oil were substantially
improved for all catalysts tested in terms of oxygen reduction and
increased high heating value (HHV). Particularly, the NiMo/Al2O3 catalyst exhibited the most promising catalyst,
providing favorable bio-oil yield and HHV. Remarkably greater energy
ratios and carbon recovery together with high H/O, C/O, and H/C ratios
were additionally achieved from the NiMo/Al2O3 catalyst compared with other catalysts. Cyclopentanone and cyclopentene
were the main olefins found in hydrodeoxygenated bio-oil derived from
liquefied EFB. It was observed that cyclopentene was first generated
and subsequently converted to cyclopentanone under the hydrogenation
reaction. These compounds can be further used as a building block
in the synthesis of jet-fuel range cycloalkanes.
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