Lignin valorization through the
development of carbon materials
Darren Baker
LIGHTer Workshop, Borås, 3rd February 2016
Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
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The need for alternative precursors
● Structured carbons are produced from PAN, pitches and regenerated celluloses
● Regenerated celluloses used for fibres are the most expensive because:
… additional fibre treatment needed, slow conversion, low carbon yields
● Pitches, used for fibres, foams, and monoliths, are the next most expensive because:
… they are highly refined petroleum fractions, need a certain pretreatment, small market
● PAN, used for fibres and nanofibres, are the least expensive ranging from €30 per kg
… expensive precursor and conversion
● In each case the precursor is industrially optimized for final utilization
Structured carbons in fibre, nanofibre, foam, monolith and other formats are needed
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Potential uses of carbon materials
● Cost is a significant barrier but it is the carbon morphology that determines use
● There are many applications that would use carbon fibre, nanofibre, foams and monoliths
preferentially if they were lower cost
… insulation, filtration, activated carbon applications, composite materials
● There are also high value applications for which more appropriate morphology is needed
… energy storage, composite electrodes, functional electrodes, exchange media, catalysis
● Chopped carbon fibre applications are also an area of interest
… short PAN carbon fibre can be more expensive than filament PAN carbon fibre
… it is an area of growing interest (e.g. SMC – Sheet Moulding Composites)
● In each case cost and benefits will need to be assessed against each precursor
Opportunities to tailor carbon morphology to the application!
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Carbon morphology
● Carbon fibres, for example, are engineered for strength, modulus and/or thermal properties
● Precursors are developed and optimised to provide this on conversion
● PAN: the carbon fibre has a turbostratic structure which contains planes oriented along the fibre length
which is interrupted by amorphous regions
… high tensile, medium modulus, low thermal and electrical conductivity
● Mesophase pitch: extensive graphitic planes radially oriented and with structure along the fibre
… lower tensile, high modulus, high thermal and electrical conductivity
● Isotropic pitch: highly amorphous structure
… low tensile, low modulus, high thermal resistivity
None of these are optimal for:
electrochemical energy storage, gas storage, catalyst support, activation for sorption …
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Carbon morphology
PAN
Mesophase Pitch
Layer spacing, d= 0.335 nm
(perfect)
d= 0.344 nm
“turbostratic”
(Ogale, Clemson University, USA)
Even if d-spacing is appropriate:
- accessibility is limited
- activation very difficult
- carbon yields low
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0.335 < d < 0.344
“graphitic”
Mesophase pitch carbon morphology development
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● Current carbon fibres are cylindrical or eliptical
● What if a carbon fibre support could be made
inexpensively and with unique shape?
… capillary action, hollow, high surface area
… self supporting, activated
● Mesophase pitch is melt spinnable, but is very expensive
● Isotropic pitch is melt spinnable, but conversion is very
expensive
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(PE CF, Advanced Materials 24, 2386–2389 (2012))
Fibre morphology
Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
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Lignin carbons
Lignin: a melt processed carbon precursor which provides an alternative carbon morphology
- graphitic, like MPP, but these are smaller and discontinuous
- turbostratic, like PAN, but discontinuous … more amorphous
- tensile properties are therefore lower
Carbon structure can be tuned to favour one or the other:
- lignin carbons are easily activated to generate porosity / functionality
- porosity is highly defined and carbon yields high
- d-spacing can be tuned for electrochemical storage applications
- active agents can be incorporated in the structure easily
Lignin carbons are much lower in cost to produce
- raw material is a fraction of the cost
- conversion of the raw material to carbon material can be very low cost
Why has lignin become interesting?
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Lignin: Valorisation is a bioeconomy question
Recovery Boiler Capacity
Lignin Revenue
eg: limiting pulp production
How much can we increase the
value of lignin?
Renewable Fuels Standards
15 to 30% LIGNIN
eg: US 36 billion gallons by 2022
Ethanol/butanol waste product
with a 12c/kg fuel value
Fuel Economy
Lighter vehicles
eg: CAFE U.S.: 35.5 mpg in 2017
54.5 mpg for 2025.
Creating a demand for low cost
carbon fiber
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Lignin is not just any old lignin
Lignins are a family of polymers whose structures depend on the
biomass and on the delignification and recovery conditions used
Chemical structure determines usefulness in
manufacturing lignin products.
Annual biomasses (e.g. energy crops) contains
various ratios of Guaiacyl and Syringyl alcohols
and also Hydroxyphenyl.
p-Coumaryl alcohol
(hydroxyphenyl)
X=Y=H
HO
O
Coniferyl alcohol
(guaiacyl alcohol)
X = OCH3 and Y = H
HO
Y
X
Sinapyl alcohol
(syringyl alcohol)
X = Y = OCH3
O
n
Lignin is around 90-99% of one or more of
SGH plus another 15 monomers, and several
types of links between monomers
(β-0-4 shown)
Softwood Lignin
> 90% coniferyl alcohol,
plus p-coumaryl alcohol
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Hardwood Lignin
ratios of coniferyl
and sinapyl alcohols
Lignin is not usually just lignin
Lignins are recovered as a result of processes designed for carbohydrate
recovery. Impurities are usually included.
● Impurities must be removed or controlled as they give rise to flaws in later processing, these are
cellulose, hemicellulose, inorganics, volatiles and extractives
● Lignins are defined by chemical properties
… monomer composition, linkages, pendent groups, elemental composition
● They are defined by there macromolecular properties
… molecular mass, Tg, Ts, melt and/or solution rheology, thermogravimetric response
● The polymers can then be classified for particular process and end use
… resins, solution spun fibre, foams, monoliths
… melt spun fibre, nanofibre, conversion to phenolic monomers or fuels
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Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
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Typical scheme for carbon material production
We consider lignin a precursor to
making an engineering polymer
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Our strategy: Biorefining = Oil refining
The production of lignin using the LignoBoost process (Source: Valmet)
Scale
gram in laboratory
kg in small pilot
kgs in large pilot
tonne in Bäckhammar
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High throughput lignin fractionation
● Capabilities for high capacity ultrafiltration,
pH fractionation and other methods
● Lignins can be tailored towards utilization on
the basis of molecular mass
● Lignin chemistry can also be altered
depending on the method used
Properties of fractions optimized for particular
processes and products
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Separation of a softwood lignin
into fractions of differing Tg
Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
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Melt spinning of lignin
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Conversion of lignin fibre to carbon fibre is complex
● Each thermal processing step has an optimum for extracting the best possible properties
Thermox 1
Thermox n
Carbon 1
Carbon 2
(R1 / T1 / t1 / ε1)
(Rn / Tn / tn / εn)
(R3 / T3 / t3 / ε3)
(R4 / T4 / t4 / ε4)
Lignin fibre
R1 – Rate at which temperature is reached (dependent on t1)
Fibre tow enter furnace and have a balistic temperature change
T1 – Isothermal temperature set point
Temperature is set to initiate crosslinking of the lignin fibres
t1 – Isothermal temperature dwell time
Dwell time is set to optimally crosslink the lignin fibres
ε1 – Strain controlled by relative fibre speed at start and end of process
Strain is induced at an optimal level once other parameters optimized
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Example: effect of carbonization rate
Too slow
Medium
Too fast
Incomplete
Porosity / activation
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Example: effect of graphitization temperature
1.2
1000 C
1800 C
2100 C
2400 C
2700 C
PAN (T300)
Normalized Intensity .
1.0
1000°C
0.8
0.6
1800°C
2100°C
0.4
2400°C
0.2 PAN CF (T300)
2700°C
0.0
16
20
24
28
32
2 theta
Graphitic structure evolution in Alcell-based carbon fiber as a function of heat
treatment temperature. PAN-based T300 is provided for comparison, where ……. is d002
spacing and ------- is stacking height, Lc
(Baker, F. S.; Baker, D. A.; Gallego, N. C. Proceeding, SAMPE ’10 Conference and Exhibition, Seattle, WA, May 17–20, 2010.)
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Published state of the art
Process
Reported data for lignin CF development uses batch conversion processes
Strength
Around 1.2 GPa tensile strength is the maximum so far reported
Modulus
Around 85 GPa tensile modulus is the maximum so far reported
Extension
Around 1.8 to 2.2% extensibility before break
Future?
Most studies performed without tensioning and property development is optimized
during continuous conversion
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Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
www.innventia.com © 2015  24
Lignin conversion: melt vs solution processes
Lignins for electrospinning
have very high Tg and Ts
Rapid conversion
High yield
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Lignin-based carbon nanofibers
● Preparation of fibrous products with differing morphologies and diameters
● High throughput: solutions are up to 50% wt. lignin compared to 7% wt. with PAN
● The ability to add components to functionalise the carbon nanofibres
● Ability to tune carbon morphology and to easily activate giving unique well-defined porosity
● Rapid conversion kinetics because the high molecular mass lignins used
Example of the effect of spinning solution concentration on nanofibre morphology
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Lignin nanofibre non-woven
35%
40%
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45%
Nanofibre non-woven (pilot)
First attempt at pilot scale electrospinning was successful even though the fibres were large
indicating work needs to be done to optimize solvent system and other variables …
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Lignin valorization through the development of carbon materials
● The need for alternative carbon material precursors
● Lignin as a carbon material precursor
● Our strategy for lignin production and use
● Examples of lignin carbon fibres
● Examples of lignin carbon nanofibres
● Portfolio of lignin programs at Innventia
www.innventia.com © 2015  29
Innventia lignin portfolio
Summary of lignin research at Innventia
Lignin manufacture – Various scales of pilot facilities for lignin recovery and modification
Research projects – Carbon fibre, nanofibre, resins, chemical conversions, activated carbons (incl. fibre), fuels
Processing – Differing scales of fibrous product production
Conversion – Different scales of batchwise conversion … investigating continuous conversion
Analytical – State of the art analytical support from biomass through to final product
Future – Pilot scale conversion line
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