1. Regeneration of Cellulose from Ionic Liquid and Effects
of Co-Solvent Addition using Different Coagulants
www.nottingham.ac.uk
Raymond L. H. Ting
Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, NG7 2RD
Introduction
• The use of 3D ink-jet printing is well known in utilizing support materials
to produce tailored design structures in fabrication process.
• Cellulose, the most widespread biopolymer, has attracted significant
interest to reduce the dependency on fuels.
• Ionic Liquid (IL) such as [BMIM][Ac] has shown to be capable of
dissolving considerable amount of cellulose with the use of aprotic co-
solvent, DMSO.
• Addition of coagulants lead to the reconstitution of cellulose from the IL.
nd, linked by β (1-4) D-glucose units (i.e. gluco-
hydroxyl groups along the chains are connected
ds (H-bonds) in both parallel and anti-parallel
ted in Fig. 1. As a consequence of the H-bond
possesses strong mechanical strength and cannot
in common solvents.
pread utilization of cellulose, the prime step in
lulose dissolution. Traditionally, two types of
zing and nonderivatizing) are suggested to dis-
he derivatizing solvents such as sodium hydro-
fide or sodium hydroxide/urea mixtures interact
he hydroxyl groups of cellulose and form inter-
et al., 2005; Pinkert et al., 2009). In contrast, the
olvents such as N-methylmorpholine-N-oxide
Ndimethylacetamide/LiCl and dimethylsulfoxide
lammonium fluoride trihydrate (TBAF) do not
es (Hermanutz et al., 2008; Rosenau et al., 2001;
). Although these solvents are available and used
re not environmentally benign due to the lack of
he requirement of high temperature and pres-
hu et al., 2006). Therefore, there is a critical need
ative solvents to dissolve cellulose.
s of solvents, ionic liquids (ILs) have attracted
est. ILs are unique ionic materials with melting
er than 100 1C, substantially lower than normal
If the melting temperatures are below room
y are coined as room temperature ILs (RTILs).
on cations in ILs are bulky, asymmetric and
such as imidazolium, pyridinium, pyrrolidinium,
phonium, piperidinium, pyrazolium, thiazolium,
nions may range from simple halides, inorganic
nic ions. Fig. 2 depicts the chemical structures of
d anions in ILs (Plechkova and Seddon, 2008).
racteristics distinguishing ILs from conventional
wide range of melting temperature (À40 to
mal stability (up to 400 1C), low vapor pressure,
ng properties, low flammability, high conductiv-
d thermal), and broad electrochemical potential
V). Their physical and chemical properties can be
mutation of cations and anions, which is barely
entional solvents (Freudenmann et al., 2011).
ve been considered as a good substitute for
traditional volatile solvents and hence classified as “green”
solvents for a broad spectrum of potential applications in both
industrial-scale (Plechkova and Seddon, 2008) and laboratory
scale (Olivier-Bourbigou et al., 2010).
Among various applications schematically demonstrated in
Fig. 3, ILs have been recommended for cellulose dissolution and
regeneration. The first attempt using IL for cellulose dissolution
was dated back to 1934 by Graenacher, who used N-ethylpyridi-
nium chloride in the presence of N-containing bases (Graenacher,
1934). At that time, however, the practical importance of ILs was
not realized. Only in 2002, Swatloski et al. found that 1-n-butyl-3-
methylimidazolium chloride [C4mim][Cl] could dissolve cellulose
up to 25 wt% by microwave heating. They further reported that the
dissolved cellulose could be readily regenerated by adding anti-
solvents such as water, ethanol, and acetone (Swatloski et al.,
2002). Thereafter, 1-n-allyl-3-methylimidazolium chloride [Amim]
Cl was tested for cellulose dissolution as well as regeneration
(Zhang et al., 2005). Cellulose dissolution in six ClÀ
and [Ac]À
-based ILs and its regeneration using water were investigated
Plant Biomass
Inter-chain
H-bond
Intra-chain H-bond
Cellulose
Fig. 1. Cellulose network in plant biomass.
Fig. 2. Typical cations and anions in ILs.
K.M. Gupta, J. Jiang / Chemical Engineering Science 121 (2015) 180–189 181
Figure 1: Cellulose network in plant biomass (Krisha M. Gupta, 2014)1
Aims & Objective
• To discover the role of other coagulants in regenerating cellulose from
cellulose/[BMIM][Ac] solution instead of water.
• Properties of regenerated cellulose to be studied in various volume of
coagulants, temperatures and regeneration times.
• Evaluate the effect of co-solvent addition prior to cellulose dissolution
on the properties of regenerated cellulose.
• Develop the best coagulants and its parameter for further
development of the research.
Research Methodology
Dissolution
Amount to Dissolve:
• 5 wt% Cellulose in
[BMIM][Ac].
• 5 wt% Cellulose in 50
wt% [BMIM][Ac]/
DMSO
Regeneration
Coagulants:
• Distilled Water
• Ethanol
• Acetonitrile
Studies on Effect:
• Volumes
• Temperatures
• Regeneration Times
• Addition of DMSO
Analysis
Equipment:
• ATR-FTIR
Spectrometer
• TGA Analyzer
Figure 2: Summarized Experimental Procedures Flow Chart
Acknowledgements
Results and Discussions
Figure 3: Appearance of Regenerated Cellulose in 20 mL of Coagulants at 20oC
(A) Distilled Water, (B) Ethanol, (C) Acetonitrile
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300 350 400 450 500 550
Mass/mg
Temperature/oC
AC, 20 mL
ET, 20 mL
DS, 20 mL
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200 250 300 350 400 450 500 550
Mass/mg
Temperature/oC
DMSO.DS, 20 mL
DMSO.ET, 20 mL
DMSO.AC, 20 mL
Figure 4: Thermal analysis of regenerated cellulose in 20 mL
mediums
Figure 5: Thermal analysis of regenerated cellulose
in 20 mL mediums with addition of co-solvent
40
50
60
70
80
90
100
500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000
Transmittance/%T
Wavelength/cm-1
DS, 20 mL ET, 20 mL AC, 20 mL
DMSO.DS, 20 mL DMSO.ET, 20 mL DMSO.AC, 20 mL
Components/ 20 mL Mediums Td ( oC )
Native Cellulose 325
Distilled Water 255
Ethanol 249
Acetonitrile 234
Distilled Water with addition of Co-
Solvent
260
Ethanol with addition of Co-Solvent 255
Acetonitrile with addition of Co-Solvent 251
Figure 6: FTIR spectra of regenerated cellulose in 20 mL mediums and
effects of co-solvent addition
Figure 7: Decomposition temperature of
regenerated and native cellulose
• The regeneration of cellulose in water can also be easily regenerated in ethanol but not
in acetonitrile mediums. Condition of regenerated cellulose in higher volume of
coagulants give a better result than temperature and times.
• Thermal stability of regenerated cellulose with addition of co-solvent was improved
further and the absorption peaks for C-H bonds were more prominent due to higher
degree of crystallization between cellulose chain interactions.
• Coagulants of ethanol and acetonitrile, did not outperform the reconstitution of cellulose
in water during regeneration process.
[Ac]−
H2O
[Ac]−
Fig. 12. A mechanism of cellulose regeneration by adding H2O in cellulose/[C4mim][Ac].
Reproduced with permission: Copyright 2013, Royal Society of Chemistry.
B.E. = −75.58 B.E. = −73.97 B.E.= −55.92
Fig. 13. Binding energies (kJ/mol) of [Ac]À
with (a) water, (b) ethanol and (c) acetone.
Reproduced with permission: Copyright 2013, Royal Society of Chemistry.
K.M. Gupta, J. Jiang / Chemical Engineering Science 121 (2015) 180–189188
The author would like to thank Prof. R. Wildman, Dr. Victor Sans Sangorrin and Dr. Anna
Croft/Derek Irvine for their guidance. Special gratitude to Zhang Fan, Yin Feng and
Deshani for their assistance and support in operating the equipment.
Conclusion and Recommendations Figure 8: A mechanism of cellulose
regeneration by adding H2O in cellulose and
[BMIM][Ac] solution (Krisha M. Gupta, 2014)1
Taken from Royal Society of Chemistry
• A decrease in crystallinity and transformation of cellulose I to cellulose
II during regeneration process. Regenerated cellulose showed a lower
thermodynamic stability compared to native cellulose.
• Further research on saturation volume of coagulants used in regeneration.
References
1. Krisha M. Gupta, J. J. (2014). Cellulose dissolution and regeneration in ionic liquids: A computational
perspective. Chemical Engineering Science , 121 (2015), 180-189. 2. Zhenghui Liu, X. S. (2015).
Preparation and characterization of regenerated cellulose from ionic liquid using different methods.
Carbohydrate Polymer , 117, 99-105.