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Ultra-filtration of industrial kraft
pulping liquors:
Chemical structure and thermal properties of
selectively isolated lignin fractions
Short-term scientific mission Sweden-to-Italy
February 18th – March 1st , 2013
Olena Sevastyanova, PhD
Fibre and Polymer Technology/Wood Chemistry and Pulp Technology
KTH-Teknikringen 56-58
SE-100 44 Stockholm, Sweden
work: +46 8 790 6104
cell: +46 767 762 735
Fax: +46 8 790 6166
e-mail: [email protected]
http://www.kth.se/
Cost Action FP1105, Trabzon meeting, 09-10-2013, Turkey
Outline:
Ultra-filtration project at KTH: background
Preliminary results
Main results from the STSM at the University of Rome
‘Tor Vergata’ (GPC and NMR study)
Dissemination of scientific information
Cost Action FP1105, Trabzon meeting, 09-10-2013, Turkey
Availability of lignin
Lignin is one of the most abundant biopolymer, together
with cellulose (~25% of wood).
Ca. 45 and 2 million metric tons/year of kraft lignin and
lignosulfonates, respectively, are generated as result of
chemical pulp production (Hu, T., 2002)
Only 1-2 % of total amount of various technical lignins are
used in high-value applications (mostly lignosulfonates –
kraft lignin is being used internally as a low-grade fuel for
the kraft pulping operation);
 Increased pulp production without expanding the capacity
of recovery boilers (using lignin as a fuel) will result in
surplus of kraft lignin available for other applications.
Challenges for high-value applications
of kraft lignin
The main limitation for use in high-value
application is a poor quality due to:
- non-homogeneous molecular weight
distribution and chemical structure;
- impurities coming from the wood and
process elements
- unpredictable reactivity as result
Crestini et al., 2011
Cross-flow filtration
- a key separation unit in biorefinery
• Benefits of CFF for the extraction of kraft
lignin:
- decrease the load on recovery boiler
- control of the molecular mass of lignin
fractions by the membrane cut-off
Adapted from Novasep
- withdrawal of black liquor is possible in any
position;
- no need to adjust T°C or pH (ceramic
membranes)
Application:
Activated carbons for:
High
MW lignin
Medium
MW lignin
•
•
•
•
•
Environmental applications
Medical applications
Fuel storage
Gas and chemical purification
Supercapacitors
• Carbon fibres
• Thermoplastic blends
• Binders
Low
MW lignin
• Phenol formaldehyde resins
• Isocyanate binders
• Epoxy blends
• Polyurethane foams (fire retardant)
• Antioxidants
Equipment
UF-pilot plant
30 L mixing tank
Heating system
Gear-pump
Membranes:
Support TiO2/Al2O3 Layers ZrO2/ TiO2 pH 0-14, 100°C
1 and 5 kDa
Bench scale filtration unit
300 mL, pH 1-12
Membranes:
Regenerated cellulose pH 3-13, 4.7atm, 50°C
10 kDa
From Millipore
Preliminary results:
• Fractionation of lignin
• Analyses of lignin fractions
- Composition (carbohydrates and Klason lignin)
- Elemental analysis (C,H,N,S)
- Thermal properties
ISWFP 2013-06-13, Vancouver
© copyright
Fractionation scheme
Mw cut-off 5 kDa
Mw cut-off 10kDa
Mw cut-off 1 kDa
Starting material: weak black liquor from Swedish pulp and paper mill Billerud Gruvön;
pH and the dry matter content were >13 and 17.6 % percent, respectively.
Samples obtained: 0-1 kDa, 0-5 kDa, 1-5 kDa, 5-10 kDa, > 5 kDa, >10 kDa, PKL
(PKL: precipitated kraft lignin/ no fractionation)
Composition of lignin fractions
• Klason lignin 94-97%
• Higher content of carbohydrates in high-MW fractions
Carbohydrate
Klason lignin
Ash
%
1.7
5.2
3.4
0.3
0.2
0.3
0.1
%
96.9
94.4
94.9
93.8
97.8
94.3
97.2
%
0.1
0.2
0.5
n/a
0.2
1.1
2.2
Sample
PKL
> 10
>5
10-5
5-1
5-0
1-0
Acidsoluble
lignin
%
2
1
1.2
2.9
3.7
5.6
5.7
Elemental composition
Sample
PKL
> 10
>5
10-5
5-1
5-0
1-0
•
•
•
Before extraction
S
C
%
2.5
1.7
1.8
2.1
7.1
23.0
27.1
%
64.9
63
64.9
62.6
62.1
51.6
48.9
H
%
5.5
5.9
5.3
5.4
5.4
4.8
4.2
After extraction
S
C
%
1.8
1.6
1.6
1.7
3.0
4.0
4.8
%
64.7
62.1
63.5
65.1
68.5
66.1
63.4
H
%
5.9
5.9
5.8
6.0
6.4
6.3
5.9
Sulphur content decreased by solvent extraction (toluene+pentane)
Increased sulphur content in Low-MW fractions
Sulfur co-precipitated with lignin during the Klason lignin analysis (acidic
hydrolysis)
Thermal properties by TGA and DSC
Sample
PKL (Ref)
> 10
>5
10-5
5-1
<5
1-0
Decomp temp
(5 % weight loss)
°C
215
217
190
240
193
175
163
Max weight loss
Tg
°C
373
°C
144
329
290
370
320
208
209
170
159
140
94
82
70
• By CFF lignin fractions with Tg values of 70-170°C are obtained.
Dynamic Rheology: visco-elastic response
1-5 kDa
 1-5 kDa: high degree of softening;
wide processing T°C range;
Parallel plate DMA
good flow properties- should
Scan rate: 3°C/min,
Dry N atmosphere
produce continuous fibre
Frequency: 1 Hz
2
Strain: 0.1 %
>5 kDa
 5 kDa: very low degree of softening;
high Tg
high degree of cross-linking
very little flow – will be difficult to
produce fibres
Molecular mass data by GPC (URTV)
Acetobromination of lignin samples;
Calibration: polystyrene 580-50 400Da
Columns: Agilent PLgel 5, 500Å and
1000 Å
THF: Flow rate 0.5 ml/min
UV detector (280 nm)
LCC-?
Molecular mass data by GPC
Acetobromination of lignin samples;
Calibration: polystyrene 580-50 400Da
Columns: Agilent PLgel 5, 500Å and
1000 Å
THF: Flow rate 0.5 ml/min,
UV detector (280 nm)
LCC-?
Molecular mass data by GPC
•
•
Sample
Mw
Mn
PDI
PKL
20 184
4 969
4.1
>10 kDa
33 546
9 507
3.5
>5 kDa
28 153
7 958
3.5
10-5 kDa
4 953
2 283
2.2
5-1 kDa
4 725
2 045
2.3
5-0 kDa
4 061
1 718
2.4
1-0 kDa
2 668
1 241
2.1
Fractions of varied Mw are obtained by using CFF technique
PDI has been improved (more homogeneous molecular weight distribution)
Correlation between Tg and Td and Mw
of lignin
Heating rate: 10 °C/min,
0°C to 150 – 200°C,
N2 atmosphere,
Tg – midpoint T°C of
the heat capacity of
2nd heating run
Temperature (°C)
300
250
200
Tg
Td
150
100
50
0
10000
20000
Mw
30000
Functional groups by
31P
Aliph-OH
Ph-OH
-COOH
% arom.unit
% arom.unit
% arom.unit
PKL
2.15
3.5
0.36
>5
5-1
1-0
1.95
1.42
1.57
3.27
4.05
4.53
0,50
0.27
0.45
Sample
• Increased Ph-OH content in Low-MW fractions
NMR
Functional groups by QQ-HSQC NMR
Sample
β-O-4
β-5
β-β
Vinyl
protons*
α-oxidized
Other
aromatics** aliphatic H***
(% of the aromatic units)
>5
1-5
0-1
4.8
5.0
5.1
2.9
1.5
0.3
3.1
1.7
1.1
* Protons from aryl enol ethers and stilbene structures
** α-ozidized β-O-4 subunits, aryl enol ethers and stilbenes
*** etyl-ketones, diphenylmethanes
41.3
25.8
19.9
24.0
31.3
40.1
4.2
24.3
30.2
Conclusions:
• Ultra-filtration of black liquor enables an efficient
fractionation of kraft lignin
• Good correlation between thermo-mechanical properties
and Mw – lignin with Tg’s 70 to 170 °C were obtained
• low-molecular weight lignin fractions exhibits good flow
behavior as well as great high temperature cross-linking
capability – promising for fibre spinning (correlation with
MW and chemical structure)
• Ultrafiltration allows selective extraction of lignin material
with specific properties matched to intended end use.
Dissemination of STSM results
(Acknowledgement to the Cost Action FP1105) :
• ACS meeting in New Orleans, USA, April 2013 (oral
presentation);
• 17th ISFWPC in Vancouver, Canada, June 2013 (oral
presentation and Proceedings);
• Paper has been submitted to the Journal of Applied
Polymer Science (JAPS), September 2013;
• Abstract to the NWBC in Stockholm, Sweden, March
2014 has been submitted.