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COST FP1105
Changes On Lignin Structure Influenced By The Ionic Liquid
Raquel Pradoa, Xabier Erdociab, Jalel Labidib, Tom Weltona
Department of chemistry, Imperial College London, London, UK a
Chemical and Environmental Engineering Department, University of the Basque Country, San Sebastian, Spain b
COST FP1105
Lignin
Lignin properties:
Polyphenol polymer
Aromatics source
50 million tons as residue per
year
Applications:
Adhesive
Bioactive
Binder
Antioxidant
% Softwood Hardwood Grasses
Coumaryl 5
Coniferyl 90-95 50 75
Sinapyl 5-10 50 25
B-O-4 46 60
A-O-4 6-8 6-8
4-O-5 3.5-4 6.5
B-5 9-12 6
B-1 7 7
B-B’ 2 3
5-5’ 9.5-11 4.5
COST FP1105
Ionic Liquids
Definition
They are salts in the liquid state
Their melting points are lower than 100 °C
Are composed by low symmetry cations and anions
Properties
Low melting point
Low vapour pressure
High thermal stability
High chemical stability
High ionic conductivity
Applications
Organic synthesis Solvent and catalyst
Separation processes
Electrochemistry
Tribology
Biorefinery
COST FP1105
Miscanthus characterization
Miscanthus composition
• Miscanthus is a rapid growth plant
% Standard Miscanthus
Moisture content TAPPI T264 cm-97 8.80±0.03
Ash TAPPI T211 om-93 4.2±0.5
Hot water solubility TAPPI T207 om-93 12.4±0.2
NaOH solubility TAPPI T212 om-98 36.8±0.7
Extractives TAPPI T204 cm-97 7.9±0.4
Lignin TAPPI T222 om-98 18.4±0.4
Hollocellulose 30±2
α-cellulose 36.2±0.2
COST FP1105
Experimental conditions
Synthesis of [HC4im][HSO4]
Drop-wise addition of H2SO4 on butyl imidazole
H2SO4 :butyl imidazole mass ratio 1:1
Magnetically stirred for 24 h and dried under vacuum
Synthesis of [Et3NH][HSO4]
Drop-wise addition of H2SO4 5 M on triethylamine
H2SO4 : triethylamine mass ratio 1:1
Magnetically stirred for 24 h and dried under vacuum
COST FP1105
Experimental conditions
Pretreatment
Miscanthus, water and IL ([Et3NH][HSO4] or
[HC4im][HSO4]) were homogeneously mixed in
a 1:2:8 mass ratio.
The mixtures were subjected to different
pretreatment times at 120 °C (8 h and 22 h).
Lignin precipitation
2 volumes of water were added to black liquor
It was centrifuged at 4000 rpm during 15 min
Washed with distilled water and dried at 70 ºC
during 16 h
IL + H2O + Miscanthus
Black liquor
Lignin
IL
Pulp
COST FP1105
Yields results
PretreatmentSample Solved
biomass (%)Lignin (%) S/GIL Time
[HC4im][HSO4]8 h Im 8 60 ± 1 14.64 ± 0.03 1.14
22 h Im 22 63.9 ± 0.5 30 ± 7 1.11
[Et3NH][HSO4]8 h Am 8 43.7±0.6 9.05 0.94
22 h Am 22 46.1±0.6 11.7±0.4 0.87
[HC4im][HSO4] was more active on biomass solubility and lignin extraction than [Et3NH][HSO4].
IL affect to S/G ratio:
[HC4im][HSO4] leads to higher amount of syringyl units.
[Et3NH][HSO4] leads to higher amount of guaiacyl and in both with the pretreatment time
syringyl units decreased.
COST FP1105
ATR-IR Characterization
[HC4im][HSO4]: at 2874 and 3143 cm-1 appeared
peaks assigned to stretching on imidazole ring due
to IL contamination.
[Et3NH][HSO4]: at 1268 and 1326 cm-1
appeared bands related with guaiacyl ring
stretching and deformation.
COST FP1105
Py-GCMS characterization
Butyl imidazole
Sugars Phenolics Fatty acids [HC4im][HSO4]: There was butyl
imidazole contamination and
higher proportion of sugar.
[Et3NH][HSO4]: Fatty acid
proportion was higher and there
was no IL contamination.
COST FP1105
HPSEC Characterization
Sample MW Mn PolydispersityIm 8 6,820 1108 5.65Im 22 14,726 2824 5.22Am 8 36,156 1760 20.99Am 22 10,142 1643 6.17
[HC4im][HSO4]: Mw increased
with the pretreatment time,
but polydispersity decreased.
[Et3NH][HSO4]: Mw and
polydispersity decreased with
the pretreatment time.
COST FP1105
Conclusion
[HC4im][HSO4] showed higher reactivity. But the obtained lignin was contaminated by
imidazole ring.
S/G ratio was also affected by the IL, as it was observed by ATR-IR and py-GCMS:
[HC4im][HSO4] lignin had higher amount of syringyl.
[Et3NH][HSO4] lignin had higher amount of guaiacyl.
Lignin structure was affected by the IL.