Doctoral Course on Cellulose Chemistry
(PUU 23.6080 – Aalto University)
Heterogeneous Cellulose
Chemistry
Alistair W. T. King
(Docent in Organic Chemistry, University of Helsinki)
Osasto / Henkilön nimi
22.06.2016
/ Esityksen nimi
21.6.2
016
1
Cellulose Chemistry
Homogeneous Processing (Selectivity Control - Research)
Analytics (NMR, GPC, IR)
Heterogeneous Processing (Specified Products - Industrial)
Nanocellulose Surface Modification
Cellulose Chemistry
Why is cellulose not use more extensively?
14000
Polymeric Feedstock Cost (€/ton)
12000
10000
High purity grade of cellulose
8000
12400
6000
4000
2000
0
14
480
665
740
810
950
1100
1130
1450
Zauba.com
Why is cellulose not already used
similar to petrochemical polymers?
• 1st Semi-Synthetic Polymer - Cellulose II (Textiles, Mercerisation - 1844)
• 1st Synthetic Plastic - Cellulose Nitrate (Parkesine, 1862)
• 1st regenerated cellulose fibre - CuproCellulose (‘Bemberg Silk’, 1897)
• Cellulose Xanthate (viscose/cellophane), CMC, MCC, Cellulose Acetate, etc.
• Cellulose does not have a melting point. Therefore….....
it cannot be melt-processed
• It must be plasticised by swelling in a solvent or chemically modification
’Traditional’
Heterogeneous Processes
Mercerisation (John Mercer - 1844)
Cellulose I
Cellulose II
•
stronger
fibres
•
easier to dye
•
more silk-like
appearance
•
increased
reactivity
Sobue et al., Z. Phys. Chem., 1939, 43, 309.
Cellulose Nitrate
(highly flammable or explosive)
Xyloidine: Henry Braconnot (1833) – nitration of cotton to low DS in nitric acid
Gun Cotton (DS3): Christian Schönbein (1846) – addition of sulphuric acid
Colloidon: Schönbein – control of DS to give soluble cellulose nitrate for films
Parkesine: Alexander Parkes (1862) – 1st plastic made from cellulose nitrate (waterproofing woven fabrics)
Celluloid: John Hyatt (1870) –cellulose nitrate plasticised & stabilised with camphor (billiard balls, photo film)
Chardonnet Silk: Hilaire de Chardonnet (1889) – 1st cellulose-based fibres
?
Still used: Explosives, lacquers &
Inorganic Esters of Cellulose
Cellulose Sulphate: polyelectrolyte – viscosity
modifier, emulsion stabiliser, binder, gelator,
sulphate esters used in nanocellulose (CNC)
stabilisation
Cellulose Phosphate: polyelectrolyte, calcium
binding drug, chromatography, potential for fibre
spinning (formation of liquid crystalline phases)
Cellulose Xanthate: viscose & cellophane
Cellulose Xanthate (Viscose)
Edward Bevin &
Charles Cross (1892)
Cellulose Xanthate (Viscose)
Wet-spinning (Viscose fibres) or film-formation (cellophane)
Cellulose Carbamate
Carbon Disulphide (CS2) is toxic and flammable
Urea is not toxic…....however......
isocyanic acid and ammonia area also toxic
Carbamate and Xanthate are isoelectronic
excess urea must also be recycled somehow
Saxell et al. Stora Enso: https://www.google.com/patents/WO2015198218A1?cl=en
Cellulose Ethers
CMC Production
• Ground cellulose is suspended in isopropanol or slurried in ethanol
• Aqueous caustic soda is dosed, followed by chloroacetic acid
• Exothermic reaction is performed at 50-110 oC
• Product is filtered and washed with alcohol as the product is water soluble
• A portion of chloroacetic acid hydrolyses to glycolic acid
• Solvents are recovered and recycled by distillation
All alkylating agents are highly toxic!
Cellulose Ethers,Ullmann’sEncyclopediaofIndustrialChem.
CMC Production
•
Cellulose I à Na-Cell I/II
•
Alcohols used to aid in penetration of the fibre
•
65-80 % yield, based on ClCH2COOH with the
rest hydrolysed
•
Product produced in varying purity grades
•
Water soluble dependent on DS
•
Non-statistical (block-like) modification
Kiessig,Hess,Sobue,Z.Phys.Chem.,1939,43,309
Cellulose Ethers,Ullmann’sEncyclopediaofIndustrialChem.
MC Production
•
Ground cellulose is slurried in water to high dosing in alcohols
•
Stoichometric caustic soda is dosed
•
MeCl (bp -24 oC) is dosed in the gas state or liquid state at up to 30 bar pressure.
•
The reaction is exothermic, performed at 70-120 oC
•
MC is flocculated in hot water to purify (LCST behaviour).
•
Solvents are recovered and recycled by distillation
•
MeCl and 2 eq of NaOH are consumed to give DME as byproduct
All alkylating agents are highly toxic!
Cellulose Ethers,Ullmann’sEncyclopediaofIndustrialChem.
HEC/HPC
•
Ground cellulose is slurried in water to high dosing in alcohols
•
Catalytic caustic soda is dosed: enough to get the reaction to work but not too much as it consumes the
alkylating reagents
•
Ethylene oxide (bp 11 oC) or propylene oxide (bp 34 oC) are dosed, at pressure if required
•
The exothermic reaction is performed at 70-120 oC
•
Like MC, HPC is flocculated in hot water to purify (LCST behaviour).
•
HEC is washed with alcohol-water mixtures (no flocculation point)
•
Solvents are recovered and recycled by distillation
•
Glycols are the byproducts
All alkylating agents are highly toxic!
Cellulose Ethers,Ullmann’sEncyclopediaofIndustrialChem.
Cellulose Acetate (CTA)
Initial (DS 0)
5 min (DS 0.2)
10 min (DS 0.4)
15 min (DS 0.8)
‘Homogeneous’ Conversion
(Hetero-Homo Conversion)
30 min (DS 2.3)
Ac2O as acetylating agent
‘Homogeneous’
‘Fibrous’
(Acetic acid: swelling)
(Toluene: non-swelling)
Sassi & Chanzy, Cellulose 1995, 2, 111
Cellulose Acetate (CTA)
DS cannot be
controlled!
(DS3-uniform modification)
Fibre surface is pre-activated with H2SO 4 à
AcOH soluble Cell-OAc-SO4H
à
Transesterified with Ac2O à Insoluble CTA
Luo et al., Bioresources 2013, 2708.
Cellulose Acetate (CTA)
Saponification to Cellulose Acetate (CA)
ATR-IR for Surface Modification
NaOH-HCl titration for bulk modification
Braun, Biomacromol. 2005, 152
Cellulose Ethers
Tim Liebert
Low liquids slurries (CMC)
Quell-schicht = Swelling layer
Tim Liebert
Cellulose Ethers
Tim Liebert
Chromatographic Analyses
Liebert et al. Ch8, Esterification of Polysaccharides. (Springer) 2006, p.163
Nanocellulose Production
Amorphous (Disordered) Regions
Fibrillar Bundle
Crystalline Regions (Cellulose I)
Eero Kontturi – Aalto University
Nanocellulose Production
MCC
Tunicate
Typically
40 nm diameter
from hardwood
pulp
Cotton
Ramie
Controlled Acid Hydrolysis
Mechanical Shearing
Nanocellulose Modification
The removal of water
from these solutions is
techno-economically
challenging without
aggregating the material
Certain chemical
modifications are
impossible in presence
of water
1-5 wt % Cellulose
Sustainable Surface Modification
• Solvent Redispersion
• Reactive Ball Milling
• Activated intermediates
• Green Fischer Esterification (SolReact)
• Periodate Oxidation (aqueous based, reductive amination)
• Radical Reactions (polymer grafting, poor kinetic control)
• TEMPO Oxidation (C6-OH à COOH, aqueous based)
• Surface Adsorption & The ‘Double-Click’ Method
Solvent Redispersion
•
HCl or H2SO4 digested, neutralised, filtered and redispersed in molecular solvents
•
SO4-TW were much easier to redisperse than the HCl-TW due to electrostatic repulsion
•
Formic acid allows for formation of formate esters (labile).
•
Potential for transesterification in the dispersed state
van den Berg, Biomacromol., 2007, 8, 1353
Reactive Ball Milling
•
Preparation of dispersed modified nanocelluloses directly from filter paper
•
Synergistic action of mechanical treatment and ball milling
•
Energy intensive
Huang et al., ChemSusChem, 2012, 5, 2319.
Activated Intermediates
•
Acid Chlorides & Isocyanates (moderately expensive, corrosive, water sensitive)
•
Carbodiimides (rather expensive, severe sensitizers, water sensitive)
•
Click Chemistry (work in water but very expensive)
Thiol-ene Reaction
‘Green’ Fischer Esterification
(SolReact)*
•
Acid-catalysed esterification in a
water-free melt of organoacids
•
H2SO4 digestion of MCC
•
Dialysis and pH adjust
•
Excess organoacid
•
Water evaporation
•
Fischer esterification (130 oC)
•
EtOH dispersion/centrifugation
*Espino-Pérez et al. Biomacromol., 2014, 15, 4551
Periodate Oxidation (in water)
Laitinen et al. Ind. Eng. Chem. Res., 2014, 53, 20092
Radical Reactions
(not quenched by water)
CNCs
(i) Ceric Ammonium
Nitrate & Nitric Acid
(ii) Methylmethacrylate (MMA)
(nanostructure maintained!)
PMMA-g-CNC’s
Kedzior, Cranston et al., Can. J. Chem. Eng., 2016, 10.1002/cjce.22456
TEMPO Oxidation (in water)
•
Applied to introduce
electrostatic charge
during NFC fibrillation
•
Considerable energy
reduction to produce
NFC gels
•
Also allows for
introduction of COOH
groups for further
chemical modification
Isogai et al., Nanoscale, 2011, 3, 71–85
‘Double Click’ Method
Filpponen et al. Biomacromol., 2012, 13, 736
Still costly but cheap CMC modification may allow for application to a wide range of surfaces!
IONIC LIQUIDS?
(non-distillable & stabilise cellulose)
Neither dissolve cellulose!
Dewatering CNCs
(80 oC/Rotary Evap. down to ~ 15 mbar)
Regenerated CNCs (Still Nano-Scaled)
1 – CNC in TEGO P9
2 – CNC in [emim][OTf]
(DMF Added)
(Precipitation – Poor Stabilisation)
Dewatering NFC
(80 oC/Rotary Evap. down to ~ 15 mbar)
Regenerated NFC (Still NFC)
Opportunities for Chemical Modification
(in the absence of water)
More aggregated & lower DS
* Missoum & Bras et al. Soft Matter, 2012, 8338.
NFC
Solution (aq)
Solvent
Exchange*
Chemical*
Modification
(4 x Centrifugation
with Acetone)
(in [bmim][PF6])*
IL Evap.**
Chemical**
Modification
(in [emim][OTf])
** King, Filpponen, Helminen & Kilpeläinen, Patent Filing FI2015/5635.
Wide potential for
chemical modification
Summary
Heterogeneous reactions are much more economical than homogeneous due to
ease of separation and recycling of waste streams
The cost is a lack of flexibility to tune the product (DS, regioselectivity)
The instability of nanocellulose in aqueous solution requires new approaches to
chemical modification to prevent aggregation
Non-aqueous reactions are typically not performed and few methods are
sustainable
Ionic liquids seem to offer the possibility of stabilisation of nanocellulose surfaces
and the opportunity to do chemical reactions in a water-free environment.