Upload
others
View
10
Download
0
Embed Size (px)
Citation preview
Effects of Organosolv Fractionation Process on the Properties of
Switchgrass Lignin as a Precusor for Carbon Products Pyoungchung Kim,
1* Darren Baker1, Nicole Labbé
1
1Center for Renewable Carbon, University of Tennessee, Knoxville TN 37996
* Corresponding Author. Email: [email protected]
Introduction
Feedstock : Switchgrass
Extractives Removal
Accelerated Solvent Extractor (ASE)
H2O extraction
• 100 oC, 7 min/cycle, 3 cycles
EtOH extraction
• 100 oC, 7 min/cycle, 3 cycles
Solvent Fractionation : Extractive-free
feedstock
Solvent mixture
H2O (50%), EtOH (36%), MIBK (14%),
Catalyst : H2SO4 (0.6 %, 0.05 M)
Study variables
Reaction time : 10, 20, 30, 40, 60, 80 min
10 min/cycle
Pressure : 1600 – 1700 psi
Temperature : 140, 160, 180 oC
Products
Cellulose : washed with DI water (2L)
Lignin : washed with DI water (2L)
Moisture content Extractives Ash Cellulose Hemicellulose Lignin
Average (%) 7.4 6.3 2.4 33.7 28.1 22.3
St dev (%) 0 0.0 0.3 0.7 0.9 0.6
Time (min)
0 20 40 60 80 100
Rem
ain
ed
bio
mass
(%
)
20
40
60
80140 oC
160 oC
180 oC
Time (min)
0 20 40 60 80 100
Hem
icellu
lose
(%
)
0
10
20
30
40
50
60
140 oC
160 oC
180 oC
Time (min)
0 20 40 60 80 100
Cellu
lose
(%
)
50
60
70
80
90
100
110
120
140 oC
160 oC
180 oC
Time (min)
0 20 40 60 80 100
Lig
nin
(%
)
0
10
20
30
40
50
60
140 oC
160 oC
180 oC
Biomass recovery Cellulose in solid fraction
Hemicellulose in
solid fraction
Lignin in solid fraction
Biomass loss in the reactor showed a gradual increase by reaction time under different temperature
and presented a loss up to 45 % at 140 oC, 55 % at 160 oC and 64 % at 180 oC for 60 min reaction
time.
Of the solid fraction, cellulose decreased less than 3 % under 140 oC, 7 % under 160 oC for 60 min,
and 30 % under 180 oC for 60 min.
Hemicellulose fraction significantly decreased for 60 min to 78 % under 140 oC, 88 % under 160 oC
and 95 % under 180 oC.
Simultaneously, lignin fraction also decreased to 72 % under 140 oC, 87 % under 160 oC and 87 %
for 30 min and did not decreased by time under 180 oC.
Principal component analysis (PCA) of FTIR spectra of lignin showed that lignins produced at 180 oC were apparently separated with other lignins produced 140 and 160 oC by the first principal
component (PC1, accounting for 75% of the total spectral variance) (Scores plot).
TGA showed that lignins produced at high temperature produced more residues (40.8±1.0%)
than lignins produced at low temperature (35.6±2.1% – 36±1.0%). This indicates that lignins at
high temperature may contain more condensed aromatic structures, which is more thermally
stable.
Derivative thermograms (DTG) showed that the first stage of maximum degradation (Tmax) at 280 oC is related to thermally weak side chains such as β-O-4 linkage in lignin. The second stage of
Tmax at 380 oC is related to lignin itself. The third stage of Tmax at higher than 650 oC is related to
functional groups present in lignins and their derivatives leading to complex crosslinked
structures that are thermally stable.
With increasing reaction time and temperature to isolate lignin from biomass, side chains were
broken and decreased.
Experimental set-up
Chemical composition (switchgrass)
Biomass recovery by Wet chemistry
Lignin by FT-IR
Introduction The desire to reduce fossil fuel derived products and mitigate greenhouse gas emissions with
increasing demand for natural products has led to the rapid expansion of the biomass-based
industry. The application of biomass fractionation provides clean product streams to produce a wide
range of value added products such as materials, chemicals, fuel, heat and power.
Clean fractionation is a type of organosolv pre-treatment that upgrades biomass feedstocks for a
biorefinery by separating the cellulose, hemicellulose, and lignin into pure streams for conversion
into value-added products.
Organosolv fractionation uses a mixture of an organic solvent and water to cleanly separate the
three major components of biomass. Through this solvent fractionation technique, the extraction
efficiency is improved, which reduces conversion times and increases yields, allowing the biomass
to be processed more economically. After fractionation, the solvent fraction is rich in lignin and
hemicellulose components and cellulose is present in the solid phase.
Objective The objective of this study was to optimize processing parameters of organosolv fractionation,
including time and temperature in terms of producing a derived lignin for carbon based materials
production
Switchgrass
ASE
(H2O, EtOH, MIBK, H2SO4)
Cellulose
Liquid fraction
extractivesASE
(H2O, EtOH)
Lignin
Hemicellulose
Solid fraction
Evaporation
Washing
Accelerated Solvent
Extractor (ASE)
Scores plot of PC2 (12%) showed that lignins
were also separated by longer reaction time with
higher temperature.
Loadings plot of PC2 indicate that lignins
produced at longer reaction time with higher
temperature were more oxidized.
Loadings plot by PC1 indicate that more
condensed aromatic structures are produced from
lignins produced at 180 oC
Lignin by Pyrolysis-GC/MS
Lignin by Thermogravimetric analysis
Gas chromatograms produced by pyrolysis at 450 oC for 12 s showed that lignins produced at
different temperature and time contained dominantly peaks of guaiacyl and syringyl subunits
and small peaks of carbohydrates (acetic acid, furfural) that were chemically bonded to lignin
even after washed by deionized water.
0 5 10 15 20 25 30 35 40
Inte
nsit
y (
a.u
.)
Time (min)
Furfural
MIBK
Acetic acid
Acetic acid Phenol
Methyl
Phenol
Guaiacol
Dimethyl
phenol
Methyl
guaiacol Mehtyl
benzalde
hyde
Ethylguai
acol
Vinyl
guaiacol
Propenyl
guaiacol
Syringol
Vanillin
Vanillic
acid
Acetosyringone
Methoxy
methylbenzo
furan
Methyl
eugenol
Vanillin Coniferyl
aldehyce
140-80
160-80
180-80
Temp (oC)
100 200 300 400 500 600 700 800 900
Wt
(%)
0
20
40
60
80
100
DT
G (
dw
t(%
)/dte
mp)
-0.06
-0.04
-0.02
0.00
180 oC-80min 180 oC-40min 160 oC-80min 160 oC-40min 140 oC-80min 140 oC-40min
Maximum yield of lignin was produced at 160 oC for 60 min and 180 oC for 30 min.
Increasing temperature and reaction time produced more condensed aromatic skeleton and less β-
O-4 linkage.
Lignins produced from switchgrass contained complex crosslinked structures with functional groups
and their derivatives.
Future work Structural features of lignin by Nuclear Magnetic Resonance.
Molecular weight distribution by Gel Permeation Chromatography.
References
Conclusion and Future work
Sing et al. “Lignin–carbohydrate complexes from sugarcane bagasse: Preparation, purification, and
characterization, Carbohydrate Polymers, 62, 57-66 (2005)
Bozell et al. “Biomass fractionation for the biorefinery: Heteronuclear mulitple quantum coherence-nuclear
magnetic resonance investigation of lignin isolated from solvent fractionation of switchgrass, Agriculture and
food chemistry, 59 9232-42 (2011)
SunGrant Initiative
Acknowledgement Wavenumber (cm-1
)
60080010001200140016001800
Loadin
g p
lot
(PC
1 7
5%
)
-0.10
-0.05
0.00
0.05
0.10 Loadings plot of PC1
Wavenumber (cm-1
)
60080010001200140016001800
Loadin
gs
plo
t (P
C2 1
2%
)-0.10
-0.05
0.00
0.05
0.10
0.15
1600 1504
G
1464
G
1408
1123
G
1030
1530
1719 1295
1220
G1157
830
Loadings plot of PC2
PC1 (76%)
-6 -4 -2 0 2 4 6
PC
2 (
12
%)
-2
-1
0
1
2
3
140-60
140-80
160-60
160-80
180-30
180-40
180-50
180-60
180-80
Scores plot