novel ionic liquids and wood fractionation mechanisms

$: Novel ionic liquids and wood fractionation mechanisms$
FuBio 2 | JR2 | WP2 Novel Ionic Liquids and Fractionation Mechanisms

Alistair W. T. King University of Helsinki

Overview – Work Package Status & Highlights

•  Why ionic liquids?

•  Wood & Wood Biopolymer Solubility

•  Wood & Pulp Fractionation Mechanisms

•  Brief Highlights: Autohydrolysis, Fibrillation, IONCELL

•  Novel and Recyclable Ionic Liquids

•  Conclusions

2

WP2: Objectives

•  FuBio (Future Biorefinery) –  Research oriented (process development)

–  Cellulose

–  Joint Research 2

•  Work Package 2 –  Novel Biomass Fractionation (Ionic Liquids)

•  The main objective is to develop efficient and sustainable methods for biomass fractionation using recyclable ionic liquids

3 Alistair W. T. King

What is an Ionic Liquid?


‘Ionic Liquids’ are essentially ‘molten salts’ containing one or more organic ions! Unsolvated ‘Molten Salts’ (m.p.)

–  NaCl 801 oC –  [mmim]Cl 125 oC –  [emim]Cl 87 oC –  [emim][NTf2] -3 oC –  [emim][OAc] -45 oC

Ionic Liquid Anatomy & Cellulose Dissolution


N NMe

Cl-

π−ππ−π

VDVH

H-bond acidity

H-bond bacisity

COLUMBIC

VDVProperties are dictated by the interplay of Columbic, Polar, H-bonding

and dispersion interactions

Cellulose dissolution dependent on H-bond basicity & acidity. Hydrophobic interactions may also play a part

What Makes Ionic Liquids Unique?

Cellulose

Lignin Hemicellulose

Hot Water

Organic Solvents

Basic Ionic Liquids Solubility for each component dependent on entropic component of Gibbs equation (MW, Temp) and chemical stability of components in the solvents

Alistair W. T. King

Wood Processing – Idealised Schemes

7

Dissolution (Homogeneous)

Degradation

Selective Precipitation

Chemical Modification

Regeneration

Extraction (Heterogeneous)

Chips or Sawdust

Pure fractions, e.g. Cellulose, hemis, lignin

+ LCCs

Biofuels & Chemicals

Pure fractions, e.g. Cellulose, hemis, lignin & LCCs

Materials, e.g. Films, Fibres,

Composites, Moldable

Variable degrees of cellulose

swelling

Parameterising Wood Solubility

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Swell/Dissolve (90 oC, 18 hr)

Wood Meal + Ionic Liquid ([amim]Cl)

Phosphitylate Hydroxyls

Quantitative 31P NMR

Integrate in Solution-state

•  Pre-dissolution/swelling occurs into [amim]Cl under mild conditions •  Quantitative 31P NMR as a measure of wood ‘solubility’

•  Kyllönen, et al., On the solubility of wood in ionic liquids., Green Chem., DOI:10.1039/C3GC41273C, 2013.

Wood ‘solubility’

Wood Solubility vs Particle Size (micro)

9

0

2

4

6

8

10

12

-1 4 9 14 19 24

Tota

l Hyd

roxy

ls (m

mol

/g)

Planetary Milling Time (hr)

Spruce

Birch

•  Sawdust (0 hr) planetary milled and subjected to 31P NMR •  Both hard and softwoods are not soluble until finely pulverised

Birch Wood Solubility vs Chip Size

10

10.7

3.2

1.3 1.7 1.8

0.3 0.0 0.0

2.0

4.0

6.0

8.0

10.0

12.0

PM 24 hr <0.16mm 0.16-0.4mm 0.4-1mm 1-3mm 3-6mm >6mm

Tota

l Hyd

roxy

ls (m

mol

/g)

Planetary Milling Time or Particle Size Range

•  As particle size increases towards chip size, solubility decreases drastically

Highlight: Autohydrolysis (PHWE)


•  Hauru, Sixta et al. RSC Advances, 2013 (‘Enhancement of ionic liquid-aided fractionation of birchwood. Part 1: Autohydrolysis pretreatment’)

•  Autohydrolysis (pressurised hot water extraction) is an existing industrial wood pre-treatment method (pre-hydrolysis kraft pulp)

Effect of Autohydrolysis on Wood Solubility

12

•  Birch chips were autohydrolysed and then Wiley-milled to pass a 1mm sieve •  After autohydrolysis, even very low P-factors increase solubility drastically

10.7

1.4

5.3

11.9 11.5

13.4 11.9

12.6 12.8 12.8

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

PM 24 hr

0 50 170 260 770 1060 1320 3600 8170

Tota

l Hyd

roxy

ls (m

mol

/g)

Planetary Milling Time or P-Factor

Autohydrolysed Wood Solubility vs Chip Size

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10.7 11.9 11.9

12.6

10.8 10.8 12.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

PM 24 hr <0.16mm 0.16-0.4mm 0.4-1mm 1-3mm 3-6mm >6mm

Tota

l Hyd

roxy

ls (m

mol

/g)

Planetary Milling Time or Particle Size Range

•  For a P-Factor of 1060, solubility is now consistent over a wide particle size range, unlike the untreated birch which is essentially insoluble approaching 1 mm.

A Significant FuBio Result

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•  Allow for true homogeneous processing of wood using an existing pulping pre-treatment (pre-hydrolysis)

•  Degradation of the cellulosic fraction is minimised during this pre-treatment

•  An extracted hemicellulose fraction can add value to the process

•  Industrial-sized chips can now be used (sawdust or further milling not required)

Highlight: Fibrillation


Fibrillation of Wood Chips in Ionic Liquid

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•  When chips are treated with ionic liquid they fibrillate, not dissolve.

•  Fibre yield is high (typically > 90%) •  Thought to be a result of removal of pectin

from the middle lamella. Lignin is preserved •  Materials are now being assessed by partners

for potential applications

[emim] [Me2PO4]

140 oC / 6 hr

Highlight: IONCELL


IONCELL: Kraft Pulp Fractionation

Alistair W. T. King

pure Cellulose I

+

3 4 5 6 70,0

0,5

1,0

1,5

dm/d

(log

MM

)

log MMHemi-rich Kraft pulp

pure Hemi

Ionic Liquid + Co-Solvent 3 4 5 6 7

0,0

0,5

1,0

1,5dm

/dlo

g(M

M)

log MM

3 4 5 6 70,0

0,5

1,0

1,5

dm/d

(log

MM

)

log MM

Poster: IONCELL: Selective xylan extraction with ionic liquids, A. Roselli, M. Hummel, H. Sixta (Aalto University)

High selectivity of extraction and recovery of pure fractions

Predominant Structures Studied in FuBio


Ionic Liquid: Imidazoliums ‘Distillable’ ‘Switchable’ Applicability Cellulose Dissolution & Wood

Chip Fibrillation/ Hemicellulose Extraction (IONCELL)

Cellulose Dissolution/Wood Fractionation

Wood Extraction

Thermal Stability Moderate Stability/Variable Unstable Unstable

Recyclability Low Distillable Distillable

Water Miscibility Most Fully Yes Yes

Toxicity Moderate-Low Moderate-Low High-Low

Cost (> ton) High (< 60 €/kg) Low (15-60 €/kg) Low (< 20 €/kg)

Alternative Structures Studied in FuBio


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Ionic Liquid: Hydrophobic & Non-basic imidazoliums

Phosphonium Carboxylates

Cholinium Carboxylates

Applicability Can selectively dissolve lignin over polysaccharide

DMSO electrolytes dissolve polysaccharide but neat ILs are selective for lignin (tuneable)

Known to dissolve lignin but not cellulose

Thermal Stability Relatively High Stability Highest Stability Lowest Stability

Recyclability Low Phase-separable Low

Water Miscibility Miscible Tunable miscibility Fully Miscible

Toxicity Moderate Toxicity Moderate-High Toxicity Lowest

Cost High High Low

* BASF patent does not cover these structures!

Distillable Ionic Liquids (DILs)


[emim][OAc] Distillability

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Kugelrohr 0.3 mbar/170-180 oC alkylimidazoles recovered

Sublimation Apparatus (wt boiling stones) 0.03 mbar/130-145 oC ‘Pure’ [emim][OAc] recovered

Distillable only below 170 oC

using short-path distillation apparatus

BASF Patent (WO 09027250)

0.05 mbar / 170 oC

Distillable acid-base conjugates

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King et al, Distillable acid-base conjugate ionic liquids for cellulose dissolution and processing. Angew. Chem. Int. Ed., 2011, 50, 6301.

[TMGH][OAc] Extract Distillation

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• [emim][OAc] distillation:

• 130 oC / 0.05 mbar

• [TMGH][OAc] distillation

• 130 oC / 5 mbar!

[TMGH][OAc] Pine extract distilled at JBEI

Switchable Ionic Liquids (SILs)


Switchable Ionic Liquids (SILs): The Concept

26

§  Solvent before and after switching mixed with Nile red dye to show the transformation from low polarity to high polarity

§  Solvent is ‘switched’ back again by bubbling N2 or heating.

+ CO2

Switchable Ionic Liquids (SILs): The Concept

27

N

N+

NH+

N

CO2+

CO2-NH2OH

NH2O

O

O-

Gas flow in Gas flow out

MEA SIL

Poster: Different pre-treatment methods and their effects before SIL wood fractionation, I. Anugwom, P. Virtanen, P. Mäki-Arvela, J-P. Mikkola (Åbo Akademi University)

DBU

Phase-Separable Ionic Liquids (PSILs)


Hydrophobic ‘Phase-Separable’ Ionic Liquids (PSILs)

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Chlorides, provided by CYTEC, were converted to the acetates using ion exchange resin.

HSQC of MCC Dissolved in [P8881][OAc]/d6-DMSO (7 % MCC, 50 oC)

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1H NMR of MCC Dissolved in [P8881][OAc]/d6-DMSO (7 % MCC, 50 oC)

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C1 C6

C3 C4

C5

C2

Polymeric AGU C1-1H Anomeric Glu C1-1H (reducing end) Terminal Glu C1-1H

Assignment of C1-1H NMR Resonances

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Based on 2D NMR assignments of low to high DP samples: •  Cellobiose (DP 2) •  sc-H2O extracted MCC (DP 15) •  MCC & Avicel (DP 100) •  Bahia PHK pulp (DP 500) •  Borregaard Super VS sulfite

pulp (DP 1000)

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Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi

% Recovery of [P8881][OAc] Per Cycle at Different Co-Solvent Compositions

Gibbs Diagram: [P8881][OAc], DMSO & Water

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Poster: An NMR study of wood and wood biopolymers dissolved in phase-separable ionic liquids (PSILs), A. Holding, V. Mäkelä, J. Helminen, L. Tolonen, H. Sixta, I. Kilpeläinen, A. King (Aalto & U. Helsinki)

Conclusions

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•  Basic ionic liquids are highly effective media for homogeneous processing of wood

•  True homogeneous processing requires pre-treatment methods such as pre-hydrolysis/autohydrolysis

•  It is possible to fibrillate wood chips upon treatment with certain ionic liquids

•  It is possible to convert kraft pulp to high purity cellulose and xylan with ionic liquid-co-solvent treatments (IONCELL)

•  New recyclable ionic liquids for lignocellulose processing have been developed: Switchable (SIL), distillable (DIL), phase-separable (PSIL)

•  PSIL-DMSO electrolytes are excellent media for cellulose dissolution and NMR analysis.

Acknowledgements

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•  Ilkka Kilpeläinen (University of Helsinki) •  Ionic Liquid Development •  Arno Parviainen, Ashley Holding, Somdatta Deb, Pirkko

Karuhnen, Jorma Matikainen, Laura Lemetti, Tia Kakko, Valtteri Mäkelä

•  Herbert Sixta (Aalto University) •  Fractionation Scheme Development •  Application of ILs for fibre spinning •  Yibo Ma, Lasse Tolonen, Lauri Hauru, Michael Hummel, Anne

Michud, Annariika Roselli

•  Jyri-Pekka Mikkola (Åbo Akademi University) •  Switchable Ionic Liquids

•  Ikenna Anugwom, Valerie Eta, Pasi Virtanen, Paivi Mäki-Arvela

•  Martin Lawoko (Wallenberg Wood Science Center, KTH) •  Seema Singh (Joint Bioenergy Institute, CA, USA)

PROC ESS C HEMISTRY C ENTRE ÅAÅBO AKADEMIUN IV E R S I TY

novel ionic liquids and wood fractionation mechanisms

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