Dissolution of cellulose from AFEX-pretreated Zoysia japonica in AMIMCl with ultrasonic vibration

Article abstract of DOI:10.1016/j.carbpol.2013.06.030

In this study, 1-allyl-3-methylimidazolium chloride (AMIMCl), an ionic liquid, was synthesized and characterized by a series of test methods. Pretreatment of Zoysia japonica by ammonia fiber expansion (AFEX) was shown to reduce significantly the mass of hemicellulose and lignin in biomass, thereby breaking the lignocellulosic structure. Z. japonica samples pretreated with AFEX showed reasonable solubility in AMIMCl upon ultrasonic treatment. The rate of cellulose regeneration from Z. japonica samples pretreated with AFEX increased with increase in applied power of ultrasonication within a certain power range from 0 to 110 W. The regeneration rate of cellulose from AFEX-pretreated Z. japonica reached a maximum of 97% when the ultrasonic power was 110 W. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses indicated that the regenerated cellulose was similar to microcrystalline cellulose.

Full text of DOI:10.1016/j.carbpol.2013.06.030

Carbohydrate Polymers 98 (2013) 412–420
Contents lists available at SciVerse ScienceDirect
Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol
Dissolution of cellulose from AFEX-pretreated Zoysia japonica in
AMIMCl with ultrasonic vibration
∗
Le Liu, Meiting Ju , Weizun Li, Qidong Hou
College of Environmental Science and Engineering, Nankai University, Tianjin 300071, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study, 1-allyl-3-methylimidazolium chloride (AMIMCl), an ionic liquid, was synthesized and char-
acterized by a series of test methods. Pretreatment of Zoysia japonica by ammonia fiber expansion (AFEX)
was shown to reduce significantly the mass of hemicellulose and lignin in biomass, thereby breaking
the lignocellulosic structure. Z. japonica samples pretreated with AFEX showed reasonable solubility in
AMIMCl upon ultrasonic treatment. The rate of cellulose regeneration from Z. japonica samples pretreated
with AFEX increased with increase in applied power of ultrasonication within a certain power range from
Received 26 March 2013
Received in revised form 13 May 2013
Accepted 18 June 2013
Available online xxx
Keywords:
0
9
to 110 W. The regeneration rate of cellulose from AFEX-pretreated Z. japonica reached a maximum of
7% when the ultrasonic power was 110 W. Fourier transform infrared spectroscopy and nuclear magnetic
1
-Allyl-3-alkylimidazolium chloride ionic
liquid
AFEX
Dissolution
resonance analyses indicated that the regenerated cellulose was similar to microcrystalline cellulose.
© 2013 Elsevier Ltd. All rights reserved.
Ultrasonic vibration
Regenerated cellulose
1
. Introduction
In China, the “National Long-Term Science and Technology
cellulose account for its aggregation tendencies (Klemm, Philipp,
Heinze, Heinze, & Wagenknecht, 1998; Oh et al., 2005).
Various pretreatment techniques may be used to enhance the
breakdown of lignocellulosic biomass. Some of the most popular
techniques are fermentative processes, which include ammonia
fiber expansion (AFEX). AFEX offers several advantages: It reduces
the production of inhibitory compounds and it precludes the wash-
ing step in removing inhibitors and pretreatment catalyst. It also
requires minimal nutrients supplied to the fermentation organisms
because the process leaves traces of residual ammonia and native
plant-derived micronutrients in the recovered pretreatment prod-
uct (Chundawat et al., 2011, 2010). In a typical AFEX process,
aqueous ammonia is added to the biomass and the resulting mix-
Development Plan (2006–2020)” points out that agricultural
biomass is one of the key development areas. Plants, which produce
1
00 billion tons of cellulose through photosynthesis annually (Zhu
et al., 2006), are regarded as an inexhaustible, renewable resource.
Plant-derived cellulose is widely used in the textile, chemical, phar-
maceutical, and energy industries because it does not contribute
to pollution and is biocompatible, biodegradable, and abundant
(
Zhang, Lv, & Luo, 2011). Moreover, agricultural solid wastes can
be used as important lignocellulosic feedstock (Heinze & Liebert,
001; Zhu et al., 2006). Although the biochemical conversion of
2
◦
biomass into energy and industrial raw materials has significant
technical and economic potential, lignocellulosic biomass is nat-
urally resistant to chemical degradation. This resistance is due to
various physical and chemical factors, such as the presence of lignin,
the crystallinity of cellulose, and the presence of covalent cross-
linkages between lignin and hemicelluloses in the plant cell wall (Li
et al., 2010). Cellulose is a linear homopolymer of ␤(1 → 4)-linked
D-glucopyranose units that may aggregate to form a highly ordered
structure. The chemical constitution and spatial conformation of
ture is heated to moderate temperatures (70–100 C) and pressures
(150–400 psi). After 5 to 30 min, the pressure is quickly released.
About 99% of the ammonia can be recovered in the gas phase
and recycled. AFEX results in partial solubilization of hemicellu-
loses (Chundawat et al., 2010; Mosier et al., 2005). The process
apparently causes the movement of solubilized hemicelluloses and
migration of lignin components to the exterior surface of the cell
walls, which increases enzyme accessibility to the cell wall polysac-
charides (Chundawat et al., 2010; Kim et al., 2008).
The development of a new type of cellulose solvent would
make a significant contribution to the sustainable and efficient use
of cellulose resources in agricultural solid waste. Several suitable
solvent systems for dissolving cellulose have been reported, e.g., N-
methylmorpholine-N-oxide (Doganand & Hilmioglu, 2009), LiCl/N,
N-dimethylacetamide (DMAc) (Nattakan, Takashi, &, Ton, 2009),
∗ Corresponding author at: College of Environmental Science and Engineering,
Nankai University, 94 Weijin Street, Tianjin 300071,
PR China. Tel.: +86 13820988813; fax: +86 2223506446.
E-mail address: jumeit@nankai.edu.cn (M. Ju).
0
144-8617/$ – see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carbpol.2013.06.030

L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
413
and NaOH/urea (Song, Zhang, Gan, Zhou, &, Zhang, 2010). Although
they can readily dissolve cellulose, their disadvantages, such as high
cost, recovery difficulties, and toxicity, limit their use (Liu & Zhang,
Mr,i
Mo,i
Rs,i
=
(1)
2
009).
Ionic liquids, also known as low-temperature molten salts or
MrZJ
MoZJ
Rl = 1 −
(2)
designable solvents, have been recognized to comprise a new kind
of green solvent (Deng, 2003). They offer various advantages that
allow them to be widely used in chemical synthesis, extraction
and separation, materials preparation, and other fields. Ionic liq-
uids consist solely of cations and anions that are present in liquid
form at or near room temperature. Ionic liquids have unique physi-
cal and chemical properties, such as low melting point (up to 173 K),
higher solubility, and designable selective dissolution.
where i represents cellulose, hemicellulose, and lignin; Rs,i is the
residual rate; Mr,i is the mass of the residual cellulose, hemicellu-
lose, or lignin in the Z. japonica sample after AFEX pretreatment;
Mo,i is the mass of cellulose, hemicellulose, or lignin in the origi-
nal Z. japonica sample; R is the mass loss rate; MrZJ is the mass of
l
the residual Z. japonica sample after AFEX pretreatment; MoZJ is the
mass of the original Z. japonica sample.
In 2002, Rogers et al. first reported the solubility of
natural cellulose in a series of ionic liquids such as 1-butyl-3-
methylimidazolium chloride (BMIMCl) (Swatloski, Spear, Holbrey,
2.3. Synthesis and characterization of AMIMCl
&
, Rogers, 2002). BMIMCl is a nonvolatile, strong solvent for cel-
The general synthesis of AMIMCl was performed according to
the method described in a previous report (Ren et al., 2003). Allyl
chloride was added dropwise to N-methylimidazole under an argon
atmosphere to the final allyl chloride/N-methylimidazole molar
ratio of approximately 1:1.2. The entire reaction was carried out
in a 500 mL glass-lined reactor at room temperature. When all of
the allyl chloride was added, the reaction mixture was refluxed
lulose and is easily recovered after processing. These attributes
prompted further research on the regulation and design of
cation–anion structures to obtain new types of ionic liquids
with superior properties. In 2003, Ren et al. introduced the allyl
group to the cationic structure of an ionic liquid to prepare 1-
allyl-3-methylimidazolium chloride (AMIMCl), which has excellent
solvent properties (Ren, Wu, Zhang, He, &, Guo, 2003).
◦
with magnetic stirring at 55 C for about 10 h. After removing the
In the present study, AMIMCl was synthesized from N-
methylimidazole and allyl chloride and was characterized by a
series of test methods. Cellulose from Zoysia japonica samples was
pretreated by AFEX (these treated samples are hereafter known as
ZJ-AFEX). We focused on the dissolution of ZJ-AFEX in AMIMCl upon
ultrasonic treatment. The regenerated cellulose was characterized
by Fourier transform infrared (FTIR) spectroscopy and nuclear mag-
netic resonance (NMR) analyses. This paper provides the necessary
theoretical basis for the development of ionic liquids for utilization
of biomass feedstock resources.
residual allyl chloride under reduced pressure, the resulting liquid
was repeatedly washed with an excess amount of ether to elim-
inate the residual N-methylimidazole. The resulting ionic liquid,
◦
AMIMCl, was dried at 80 C for 72 h. The purity of the AMIMCl was
determined by 1H NMR spectroscopy.
2.4. Dissolution of cellulose
The dissolution of Z. japonica and ZJ-AFEX samples in AMIMCl
under an argon atmosphere were investigated. For the dissolution
process, 2.00 g of sample was added to 50.00 g of ionic liquid. The
mixture was placed in a KQ3200DE ultrasonic oscillator (set at a
◦
2
. Materials and methods
specific power) at 80 C for 30 min. The remaining insoluble residue
was filtered under vacuum using a 60 mL G3 sand-core bush funnel,
◦
2.1. Materials
and then dried at 105 C for 3 h. The resulting filtrate containing the
cellulose was collected to regenerate the cellulose. The solubility of
the sample in AMIMCl was calculated as shown in Eq. (3):
Samples of Z. japonica were collected from agricultural fields
in Tianjin in northern China. After drying at 60 C in an oven for
6 h, the grass samples were ground to particles that pass through
a 0.7 mm screen. The fiber components of Z. japonica were ana-
lyzed according to the Van Soest method, using a FOSS Fibertec
010 fully automated fiber analysis system. This determination
revealed the following composition: lignin, 19.87% (w/w); hemi-
cellulose, 40.86% (w/w); cellulose, 29.71% (w/w). Microcrystalline
cellulose was purchased from Serva (Heidelberg, Germany). N-
Methylimidazole was purchased from Tianjin Xuanyang Industrial
Co., Ltd. (Tianjin, China), and purified by reduced-pressure distilla-
tion before synthesis. Allyl chloride (analytical reagent grade; 98%
pure) with a specific gravity of 0.935 kg/m3 was purchased from
Shanghai Kefeng (Shanghai) Trading Co., Ltd., Shanghai, China.
◦
Mr
1
Rd = 1 −
(3)
Mo
where R is the solubility in AMIMCl; Mr is the mass of the residual
d
sample after dissolution in AMIMCl; Mo is the mass of the original
sample.
2
2.5. Preparation of the regenerated cellulose
After dissolution of the sample in AMIMCl, the resulting fil-
trate containing cellulose was combined with an excess amount of
deionized water to regenerate the cellulose. The regenerated cellu-
◦
lose samples were dried at 80 C for 72 h. The cellulose regeneration
rate was calculated as shown in Eq. (4):
M
r−cel
2.2. AFEX pretreatment of Z. japonica
Rr = 1 −
(4)
M
o−cel
A measured amount of Z. japonica was dispersed in water by
magnetic stirring for 24 h and then diluted to 5% (w/w). Sub-
sequently, the pre-wetted Z. japonica was loaded into the AFEX
where Rr is the cellulose regeneration rate; Mr–cel is the mass of
residual cellulose in the sample after dissolution in AMIMCl; Mo–cel
is the mass of cellulose in the original sample.
reactor. The ratio of anhydrous ammonia to Z. japonica ranged from
◦
0
.5:1 to 2:1, and the reaction was carried out at 120 C and 200 psi
2.6. Recycling of AMIMCl
for 30 min. This process yielded ZJ-AFEX. The lignocellulose resid-
ual rate and mass loss rate of Z. japonica after AFEX pretreatment
were calculated according to Eqs. (1) and (2):
After sample dissolution and cellulose extraction, recovery of
the AMIMCl was accomplished by evaporating water from the

4
14
L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
filtrate. The recycled AMIMCl was used to extract cellulose, as
described in Sections 2.4 and 2.5.
on a Mercury Vx-300 with a 5 mm BBO probe at a frequency of
100.61 MHz.
2
2
2
.7. Characterization
2.7.4. Thermogravimetric analysis (TGA)
The thermal stability of AMIMCl was investigated using a
TG209 TGA instrument (NETZSCH, Ltd., Germany). Weight loss was
.7.1. FTIR
◦
All samples were ground into a powder and vacuum-dried for
4 h. The IR spectra of the samples were recorded using an FTS6000
recorded in the range of 0–550 C, and the sample was heated at a
◦
rate of 10 C/min.
Fourier Transform IR spectrometer (Bio-rad, USA). Test specimens
were prepared according to the KBr disk method.
2.7.5. Scanning electron microscopy (SEM) analysis
The original Z. japonica and ZJ-AFEX samples, obtained by air
2
.7.2. Polarization microscopy (POM)
The regenerated cellulose from ZJ-AFEX was mounted onto
drying method, were fixed to a metal-base specimen holder using
double-sided sticky tape. The samples were then coated with gold
using a vacuum sputter-coater. Afterwards, the fracture surfaces
were observed using an S-3700N scanning electron microscope
(Hitachi, Ltd., Japan).
a metal-base specimen holder using double-sided sticky tape.
The sample was then coated with the synthesized AMIMCl
using a vacuum sputter-coater. Afterward, the sample structures
◦
were observed continuously at 80 C for 60 min using a Linkam
THMSE600-BX51 polarized optical microscope (Olympus, Japan)
equipped with a hot stage and a digital camera.
3. Results and discussion
3.1. Characteristics of AMIMCl
2.7.3. NMR
Solid-state cross-polarization/magic angle spinning 13C NMR
The process developed in the current study (Wu et al., 2004;
spectra of the regenerated cellulose were obtained using a Bruker
Infinityplus-400 NMR spectrometer. The instrument was equipped
with a 4 mm MAS probe and was operated at a frequency of
Zhang, Wu, Zhang, &, He, 2005) was successfully used to synthesize
AMIMCl. The AMIMCl exhibited a considerable capacity to dissolve
cellulose in Z. japonica, as observed by polarization microscopy.
Fig. 1A and B show that dissolution of the cellulose samples com-
menced because of the dispersion of numerous cellulose fibers in
1
00.37 MHz. The structure of AMIMCl in D O at room temperature
2
1
was determined by H NMR spectroscopy. Analysis was carried out
Fig. 1. Dissolution of cellulose in Zoysia japonica in AMIMCl in the initial stage (A), partially dissolved stage (B), later dissolved stage (C) completely dissolved stage, and (D)
the micrographs were magnified two hundred times.

L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
415
Fig. 2. FT-IR spectrum of AMIMCl (A), 1H NMR spectrum of AMIMCl (B) and TGA/DTG curve of AMIMCl (C).
the ionic liquid. Eventually, the cellulose fibers disintegrated and
disappeared, while a blackburst structure emerged, as shown in the
polarization micrographs (Fig. 1D).
stretching vibration in imidazole ring), 1424 ( CH /C H bend-
2
ing vibration in side chain), 1335 (C N stretching vibration), 1175
(C H bending vibration in imidazole ring), and 997 (C H rock-
−
1
The FTIR spectrum of AMIMCl (Fig. 2A) shows the peaks at
ing vibration in allyl). The peak at 3382 cm
corresponds to
−1
the following wavenumbers (in cm ): 3058 (C
C
H stretching
trace water accumulated due to the hygroscopicity of AMIMCl.
The FTIR spectrum of the regenerated AMIMCl is similar to the
vibration), 1644 (C C stretching vibration in allyl), 1573 (C
N

4
16
L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
Fig. 3. Structures of original Zoysia japonica (A), Z. japonica sample after AFEX pretreatment with a ratio of anhydrous ammonia to Z. japonica 0.5:1 (B), ratio 1:1 (C), ratio
.5:1 (D), and ratio 2:1 (E).
1
◦
◦
spectrum of the as-synthesized AMIMCl, and shows the same
peaks.
200 C and 300 C was nearly 80%. During the rapid decomposi-
tion process, the chloride anion decomposed through dealkylation,
whereas the cation simultaneously underwent alkyl migration and
elimination (Liu et al., 2012).
The 1H NMR spectrum of AMIMCl (Fig. 2B) shows the peaks
corresponding to the following chemical shifts (in ppm): ı = 4.85,
ı = 5.56, ı = 6.05, ı = 3.93, and ı = 8.87. These shifts are related to
hydrogen atoms 1, 2, 3, 4, and 7, respectively. The peak at ı = 7.53
is related to hydrogen atoms 5 and 6. The peaks in the 1H NMR
spectrum of the regenerated AMIMCl are similar to those in this
spectrum except for the peak at ı = 3.41, which corresponds to the
signal for trace water.
3.2. Effect of AFEX pretreatment on Z. japonica
The structures of ZJ-AFEX were observed using an S-3700N scan-
ning electron microscope (Hitachi, Ltd., Japan). Fig. 3 shows that
the structures of Z. japonica were destroyed by AFEX pretreat-
ment and the surfaces of the material became rougher after AFEX
pretreatment. The pretreatment created greater pore volume in
the small pore region in comparison with that of the untreated
sample. A greater degree of structural damage accompanied an
increase in the anhydrous ammonia-to-Z. japonica ratio. AFEX
pretreatment of Z. japonica loosened the lignocellulosic matrix,
The TGA curve for AMIMCl is shown in Fig. 2C. In the thermal
◦
degradation process, the ionic liquid was stable below 200 C. The
◦
weight loss (nearly 20%) below 200 C was caused by the evapora-
tion of water and traces of remaining reactant. The decomposition
temperature corresponding to the maximum rate of weight loss
◦
(
T ) was 285.1 C, and the corresponding weight loss between
d

L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
417
Fig. 4. The component contents of ZJ-AFEX samples (A), lignocellulose residual rate after AFEX pretreatment (B), mass loss of Zoysia japonica after AFEX pretreatment (C),
Zoysia japonica and ZJ-AFEX samples dissolution in AMIMCl with ultrasonic vibration (D), and cellulose regeneration (E).
weakened intermolecular forces, and destroyed intramolecular
and intermolecular hydrogen bonds, causing a more open three-
dimensional organization of the cellulose, lignin, and hemicellulose
polymers.
A comparison of the lignocellulosic content of ZJ-AFEX samples
prepared using various ratios of anhydrous ammonia to Z. japon-
ica is shown in Fig. 4A. The cellulose content of ZJ-AFEX samples
increased relative to that of the original Z. japonica samples. How-
ever, the lignin and hemicellulose content decreased. The reduction
became more obvious when the ratio of anhydrous ammonia to
Z. japonica increased. Lignin provides a robust linkage between
polysaccharide chains that hinders chemical accessibility to cellu-
lose (Zhang & Lynd, 2004). As mentioned above, AFEX significantly
reduced the lignin content. Furthermore, levels of wax and ash were
somewhat reduced.
Fig. 4B and C show the lignocellulose residual rate and mass
loss of Z. japonica after AFEX pretreatment, respectively. AFEX
pretreatment reduced the mass of the Z. japonica sample signif-
icantly. However, hemicellulose and lignin accounted for most
of the mass loss, and the cellulose mass was not substantially
reduced. These results, combined with the analysis of the scanning
electron microscopy results, demonstrate that AFEX pretreatment
effectively disrupted the lignocellulose structure and increased the
cellulose content. Hence, during the subsequent reaction, a larger
amount of the cellulose component of ZJ-AFEX was in contact with
the ionic liquid.

4
18
L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
Fig. 5. Mechanism of the dissolution of cellulose in AMIMCl with ultrasonic vibration.
3.3. Effect of ultrasound treatment on dissolution of cellulose in
average distance between liquid molecules varies with molecu-
AMIMCl
lar vibration according to the action of the pressure wave. When
sufficient negative pressure is applied to the liquid, the distance
between molecules exceeds the critical distance and cavitation
bubbles appear (Aliyu & Hepher, 2000; Tang, Zhang, &, Chen, 2005).
High local temperatures and compressed air are produced when
the transient cavitation bubbles shrink or collapse, resulting in a
powerful shock wave and jet stream (Vinatioru & Otilia, 1997).
This promotes contact of the AMIMCl ionic liquid with the cells
in the Z. japonica and ZJ-AFEX samples and the consequent disrup-
tion of the cells. The synthesized ionic liquid has special chemical
structures, including a small chloride anion and a large 1-allyl-
3-methylimidazolium cation (Lee, Doherty, Linhardt, & Dordick,
2009; Swatloski et al., 2002). Both anions and cations are consid-
ered to be involved in the dissolution process (Pinkert, Kenneth,
Marsh,&, Mark, 2009). The oxygen and hydrogen atoms of the cel-
lulose form electron donor–electron acceptor complexes with the
charged species of the ionic liquids. The AMIMCl cations easily
bind to oxygen in the intermolecular and intramolecular H-bonds
between cellulose chains, whereas the chloride anions bind to
the hydrogen atoms. This process breaks the intermolecular and
intramolecular H-bonds of the cellulose chains, leading to the dis-
solution of the cellulose in the ionic liquid (Pinkert et al., 2009;
Zhang et al., 2005).
AMIMCl was used to dissolve the cellulose in Z. japonica and
ZJ-AFEX samples. Fig. 4D shows the solubility of Z. japonica and
ZJ-AFEX samples in AMIMCl (at 2:1 mass ratio of anhydrous ammo-
nia to Z. japonica sample), which increased at higher ultrasonic
power. However, the solubility of ZJ-AFEX sample presented a more
obvious increasing trend. Ultrasonication improved the solubil-
ity because it facilitated the penetration and diffusion of AMIMCl
in the entire structure of the samples. The lower solubility of
Z. japonica confirms the enhancement of cellulose solubilization
by AFEX pretreatment. The cellulose regeneration rate (Fig. 4E)
increased at higher values of ultrasonic power within a cer-
tain range. The regeneration rate of the cellulose in ZJ-AFEX
reached a peak of 97% when the ultrasonic power rose to 110 W.
At higher power, it began to decline. The subsequent decrease
may be due to intensified ultrasonic cavitation caused by excess
ultrasonic energy, which initiates other reactions during disso-
lution and leads to cellulose degradation (Herfoster & Wintel,
1
961).
Fig. 5 shows the mechanism of the dissolution of cellulose
in AMIMCl with ultrasound treatment. The interaction between
the ultrasonic vibrations and the medium leads to cavitation. The

L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
419
considerable capacity to dissolve cellulose. AFEX pretreatment dis-
rupted the lignocellulose structure and concomitantly increased
the cellulose content of the Z. japonica sample. The ZJ-AFEX sample
showed significant solubility in AMIMCl. Ultrasonication further
improved the solubility of cellulose because it facilitated the pen-
etration and diffusion of AMIMCl into the structure of the samples.
The cellulose regeneration rate of ZJ-AFEX reached a maximum of
9
7% when the ultrasonic power was 110 W. The regenerated cellu-
lose was similar to microcrystalline cellulose according to FTIR and
NMR analyses.
Acknowledgments
We are grateful for financial support by the “Double Five” Sci-
ence and Technology Project of the Colleges and Universities in
Tianjin, China (SW20080004).
References
Aliyu, M., & Hepher, M. J. (2000). Effects of ultrasound energy on degradation of
cellulose material. Ultrasonics Sonochemistry, 7, 265–268.
Chundawat, S. P. S., Donohoe, B. S., da Costa Sousa, L., Elder, T., Agarwal, U. P., Lu,
F., et al. (2011). Multi-scale visualization and characterization of lignocellulosic
plant cell wall deconstruction during thermochemical pretreatment. Energy &
Environmental Science, 4, 973–984.
Chundawat, S. P., Vismeh, R., Sharma, L. N., Humpula, J. F., da Costa Sousa, L., Chamb-
liss, C. K., et al. (2010). Multifaceted characterization of cell wall decomposition
products formed during ammonia fiber expansion (AFEX) and dilute acid based
pretreatments. Bioresource Technology, 101, 8429–8438.
Deng, Y. C. (2003). Ionic liquids — the green material in the 21st century. Chinese
University Technology Transfer, 10, 33–35.
Doganand, H., & Hilmioglu, N. D. (2009). Dissolution of cellulose with NMMO by
microwave heating. Carbohydrate Polymers, 75(1), 90–94.
Heinze, T., & Liebert, T. (2001). Unconventional methods in cellulose functionaliza-
tion. Progress in Polymer Science, 26, 1689–1762.
Herfoster, L., & Wintel, H. M. (1961). The Basic Principle and Application of Ultrasound.
Shanghai: Shanghai Science and Technology Press.
Fig. 6. FT-IR spectra (A) and 13C NMR spectra (B) of microcrystalline cellulose (a)
and regenerated cellulose (b).
Kim, Y., Hendrickson, R., Mosier, N. S., Ladisch, M. R., Bals, B., Balan, V., et al. (2008).
Enzyme hydrolysis and ethanol fermentation of liquid hot water and AFEX
pretreated distillers’ grains at high-solids loadings. Bioresource Technology, 99,
3.4. Characterization of regenerated cellulose
5206–5215.
Klemm, D., Philipp, B., Heinze, T., Heinze, U., & Wagenknecht, W. (1998). Compre-
hensive Cellulose Chemistry. Weinheim: Wiley-VCH.
Lee, S. H., Doherty, T. V., Linhardt, R. J., & Dordick, J. S. (2009). Ionic liquid
mediated selective extraction of lignin from wood leading to enhanced enzy-
matic cellulose hydrolysis. Biotechnology and Bioengineering, 102(5), 1368–
1376.
Li, C., Knierim, B., Manisseri, C., Arora, R., Scheller, H. V., Auer, M., et al. (2010). Com-
parison of dilute acid and ionic liquid pretreatment of switchgrass: biomass
recalcitrance, delignification and enzymatic saccharification. Bioresource Tech-
nology, 101, 4900–4906.
Liu, C. F., & Zhang, A. P. (2009). Dissolution of cellulose in novel green solvent ionic
liquids and its application. Progress in Chemistry, 21(9), 1800–1806.
Liu, D. T., Xia, K. F., Cai, W. H., Yang, R. D., Wang, L. Q., & Wang, B. (2012). Investigations
about dissolution of cellulose in the 1-allyl-3-alkylimidazolium chloride ionic
liquids. Carbohydrate Polymers, 87, 1058–1064.
To demonstrate that no other components were mixed with
13
the regenerated cellulose, we used C NMR and FTIR to compare
microcrystalline cellulose (column chromatography grade; 99.99%
purity) with regenerated cellulose from Z. japonica. As shown in
Fig. 6A, the FTIR spectrum of regenerated cellulose is compara-
ble to that of microcrystalline cellulose. The two spectra show
−
1
similar absorbance peaks (positions listed in cm ): 3343 (
stretching vibration), 2901 (C H stretching vibration), 1429 ( CH2
stretching vibration), and 1163 (C C stretching vibration).
O H
O
C O
1
3
Fig. 6B shows the C NMR spectra of microcrystalline cellulose and
regenerated cellulose. The microcrystalline cellulose has charac-
teristic peaks at 105 (C1), 90 (C4, crystalline), 85 (C4, amorphous),
Mosier, N., Wyman, C., Dale, B., Elander, R., Lee, Y. Y., Holtzapple, M., et al. (2005).
Features of promising technologies for pretreatment of lignocellulosic biomass.
Bioresource Technology, 96, 673–686.
7
5 (C3/C5), 73 (C2), 66 (C6, crystalline), and 63 (C6, amorphous)
ppm. The spectrum of regenerated cellulose also has characteristic
peaks at 105, 90, 75, and 66 ppm, but peaks at 85, 73, and 63 ppm
are not present. The reduced intensities of all the characteristic
peaks of regenerated cellulose suggest that the crystallinity of the
regenerated cellulose was lower (Wang, Li, Cao, & Tang, 2011). This
point further proves that AMIMCl effectively dissolved the cellulose
in Z. japonica through the disruption of intramolecular and inter-
molecular hydrogen bonds. In addition, multiple split peaks may
be attributed to cellulose degradation products.
Nattakan, S., Takashi, N., & Ton, P. (2009). All-cellulose composites of regener-
ated cellulose fibres by surface selective dissolution. Composites: Part A, 40(4),
321–328.
Oh, S. Y., Yoo, D. I., Shin, Y., Kim, H. C., Kim, H. Y., & Chung, Y. S. (2005). Crystalline
structure analysis of cellulose treated with sodium hydroxide and carbon diox-
ide by means of X-ray diffraction and FTIR spectroscopy. Carbohydrate Research,
3
40(15), 2376–2391.
Pinkert, A., Kenneth, N., Marsh, S. P., & Mark, P. S. (2009). Ionic liquids and their
interaction with cellulose. Chemical Reviews, 109(12), 6712–6728.
Ren, Q., Wu, J., Zhang, J., He, J. S., & Guo, M. L. (2003). Synthesis of 1-allyl, 3-
methylimidazolium-based room temperature ionic liquid and preliminary study
of its dissolving cellulose. Acta Polymerica Sinica, 3, 448–451.
Song, Y. B., Zhang, J., Gan, W. P., Zhou, J. P., & Zhang, L. N. (2010). Flocculation
properties and antimicrobial activities of quaternized celluloses synthesized in
NaOH/urea aqueous solution. Industrial & Engineering Chemistry Research, 49(3),
4
. Conclusions
1242–1246.
Swatloski, R. P., Spear, S. K., Holbrey, J. D., & Rogers, R. D. (2002). Dissolution of
cellulose with ionic liquids. Journal of the American Chemical Society, 124(18),
4974–4975.
AMIMCl was synthesized and characterized through a series
of test methods. AMIMCl exhibited high thermal stability and a

4
20
L. Liu et al. / Carbohydrate Polymers 98 (2013) 412–420
Tang, A., Zhang, H., & Chen, G. (2005). Influence of ultrasound treatment on
accessibility and regioselective oxidation reactivity of cellulose. Ultrasonics
Sonochemistry, 12, 467–472.
Zhang, H., Wu, J., Zhang, J., & He, J. S. (2005). 1-Allyl-3-methylimidazolium chloride
room temperature ionic liquid: a new and powerful nonderivatizing solvent for
cellulose. Macromolecules, 38(20), 8272–8277.
Vinatioru, M. T., & Otilia, R. (1997). The use of ultrasound for the extraction of
bioactive principles from plant materials. Ultrasonics Sonochemistry, 4, 135–
Zhang, J. M., Lv, Y. X., & Luo, N. (2011). Application research progress of ionic liquids
in cellulose chemistry. Polymer Bulletin, 10, 138–153.
1
36.
Zhang, Y. H. P., & Lynd, L. R. (2004). Toward an aggregated understanding of enzy-
matic hydrolysis of cellulose: noncomplexed cellulase systems. Biotechnology
and Bioengineering, 88, 797–824.
Zhu, S. D., Wu, Y. X., Chen, Q. M., Yu, Z. N., Wang, C. W., Jin, S. W., et al. (2006). Dis-
solution of cellulose with ionic liquids and its application: a minireview. Green
Chemistry, 8, 325–327.
Wang, X. J., Li, H. Q., Cao, Y., & Tang, Q. (2011). Cellulose extraction from wood chip
in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). Bioresource
Technology, 102, 7959–7965.
Wu, J., Zhang, J., Zhang, H., He, J. S., Ren, Q., & Guo, M. L. (2004). Homogeneous
acetylation of cellulose in a new ionic liquid. Biomacromolecules, 5(2), 266–268.