New synthesis of vanillin by degradation of lignin in presence of functional basic ionic liquid

Article abstract of DOI:10.14233/ajchem.2015.17372

The degradation of lignin catalyzed by functional basic ionic liquid was investigated. Higher conversion of lignin and simpler degradation product composition were obtained in the presence of basic ionic liquid, comparing with that under traditional NaOH

Full text of DOI:10.14233/ajchem.2015.17372

Asian Journal of Chemistry; Vol. 27, No. 3 (2015), 885-888
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2015.17372
New Synthesis of Vanillin by Degradation of Lignin in Presence of Functional Basic Ionic Liquid
*
FENGPING YI, XIAOYAN JIANG, JIHUA NIU, LIRONG ZHANG and ZHEN WANG
School of Perfume and Aroma Technology, Shanghai Institute of Technology, Shanghai 201418, P.R. China
*Corresponding author: Tel: +86 21 60873280; E-mail: zlir2008@163.com; yifengping@sit.edu.cn
Received: 12 February 2014;
Accepted: 21 May 2014;
Published online: 19 January 2015;
AJC-16690
The degradation of lignin catalyzed by functional basic ionic liquid was investigated. Higher conversion of lignin and simpler degradation
product composition were obtained in the presence of basic ionic liquid, comparing with that under traditional NaOH solution. The
reaction conditions were optimized. Ultrasound-assisted test proved that the ultrasound pretreatment favored the degradation process.
Keywords: Basic ionic liquid, Degradation, Lignin, Vanillin, Conversion, Selectivity.
for the wide application in organic synthesis, electrochemistry,
dealing with environmental pollution problems, rational use
of resources problems, etc14-19. Therefore, it is expected that
the functional basic ionic liquids could replace the traditional
inorganic alkaline solution to promote the lignin oxidation.
Moreover, there is no literature about the research of lignin
degradation catalyzed by ionic liquids. In this paper, we report
the results of production of vanillin by lignin degradation in
the presence of basic ionic liquids. This method provide an
efficient way to provide high conversion of lignin and selec-
tivity of vanillin.
INTRODUCTION
With the shortage of petroleum resources, it has become
a hot topic to use the renewable biomass to prepare fuels as
well as chemicals. Lignin is the second largest renewable
rebsource, which primarily exist in waste water of the paper
industry and agricultural wastes and can cause serious pollution
to the ecological environment1-3. The conversion of lignin
biomass waste into high value-added chemical products is an
economic and environmentally friendly way to improve the
utilization of biomass. The structure of lignin contains a large
number of phenyl propane units, consisting of guaiacyl
propanol, syringyl-propanol and p-hydroxy-phenyl propanol1,4.
Therefore, lignin can be degraded to obtain vanillin, syring-
aldehyde and p-hydroxybenzaldehyde under alkaline
conditions. The degradation products are widely used as spices,
pharmaceutical and pesticide intermediates5,6. Vanillin are
widely present in plants (such as vanilla, vanilla bean, benzoin,
balsam and Peru balsam properly Lu, etc.) in free form or as
glucoside form naturally7. Vanillin can be used as fixative
agents and flavoring agents in food and cosmetics8,9, but also
as plant growth promoters and ripening agent10-11. However,
due to the tedious produce process, the shortage of vanillin
limited its uses. On the other hand, the synthetic vanillin
contained some toxic substances during the production, which
hindering the application12,13. Therefore, it is an very significant
method to prepare vanillin by degradation of lignin.
EXPERIMENTAL
Chemicals were obtained from commercial suppliers and
used without further purification. Degradation reactions were
carried out as the following typical procedure. A mixture of
lignin (3 g), copper catalyst (0.2 g), ferric chloride (0.02 g),
ionic liquids [Bmim]OH (0.7 g) and water (40 mL) was heated
for the appropriate time in the three-necked flask. During the
reaction, the color of solution changed from black to brown
red. Degradation macromolecules were obtained by filtration
with the semi-permeable membrane. Then, they were dried
for 48 h at 50 °C in oven, then characterized by IR spectro-
graph. The filtrate was extracted with CHCl3, then evaporated
solvent to give the small molecules, which were subjected to
gas chromatography-mass spectrometry (GC-MS). The crude
product of reaction was measured by UV-visible spectrograph
at 297 nm. Finally, vanillin was purified by flash column
In the traditional catalytic wet air oxidation of lignin,
sodium hydroxide is used to provide basic system. However,
the condition suffers from some drawbacks, such as corrosion,
low conversion and difficulty of product separation. The ionic
liquids, green catalyst and solvent, has attracted much attention
1
chromatography. The H NMR spectra were recorded on a
BRUKERAvance III (500 MHz for 1H) in deutero-chloroform
1
(CDCl3) at room temperature. HNMR (CDCl3, 500MHz)

886 Yi et al.
Asian J. Chem.
δ:3.96 (s, 3H), 6.46 (s, 1H), 7.04 (d, J = 5 Hz, 1H ), 7.42 (s,
and [Bmim]OAc21 and one inorganic catalyst NaOH were
examined. As shown in Fig. 4, the absorbance decreased with
the reaction processing, except for the reaction with no base
added. When the degradation was catalyzed by the ionic liquid
[Bmim]OH, the absorbance did not decrease significantly after
2 h any more. The reaction completed. While, for the base of
[Bmim]OAc and NaOH, the decomposition finished after 3
and 4 h, respectively. The results suggested that the catalyst
[Bmim]OH exhibited an outstanding performance and was an
excellent catalyst for decomposition of lignin in this work.
The effect of reaction temperature on the degradation of lignin
was investigated and the results were shown in Fig. 5.
2H), 9.83 (s, 1H).
RESULTS AND DISCUSSION
Firstly, the products of degradation with and without basic
ionic liquid were characterized by IR spectra. After reaction,
the red-brown crude products were filtered through a semi
permeable membrane (0.45 µm aperture) and the IR spectra
of macromolecules on the semi permeable membrane were
carried out.As shown in Fig. 1, for the reaction in the presence
of [Bmim]OH20, the characteristic absorptions of functional
groups were mainly in the range of 1800-800 cm-1, including
frame vibrations of aromatic ring at 1600 and 1500 cm-1, C-C
bond stretching vibrations of aromatic ring at 1500-1600 cm-
1, C-H bond bending vibrations of aromatic ring at 680-880
cm-1 and C-O bond vibrations of alcohols, phenols and ether
at 1000-1300 cm-1. Comparing B with C, it was observed that
the absorption decrease at 1300-1000 cm-1 indicated the break
of C-O bond, The strong absorption at the 1750-1650 cm-1,
the characteristic peak of C-O double bond, suggested that
the formation of the carbonyl group of the degradation
macromolecules product. The IR results comparison between
before and after reaction (line B and C) proved the decompo-
sition of lignin structure. The line A was similar with line C,
which indicating that the lignin could not be degraded when
no ionic liquid added.
TABLE-1
GC-MS ANALYSIS OF MAIN PRODUCTS,
DEGRADATION CATALYZED BY BASIC IONIC LIQUIDS
Compound
Structure
N
H
O
N-butylformamide
OH
Guaiacol
O
O
4-Methyloctanoic acid
OH
HO
O
Vanillin
O
HO
3-Methoxy-4-hydroxyphenyl propane
1.10
O
O
A
OH
1.05
HO
3-Methoxy-4-hydroxy- benzoic acid
4-Hydroxy-3-methoxy-phenyl acetic acid
4-Hydroxy-3,5-dimethoxy-benzaldehyde
O
HO
1.00
O
B
O
OH
0.95
0.90
0.85
0.80
C
O
HO
O
O
4500
4000
3500
3000
2500
2000
1500
1000
Wavelength (cm–1)
Fig. 1. IR of macromolecules after decomposition,A: no ionic liquid added;
B: in presence of ionic liquid [Bmim]OH; C: lignin
Also, the filtrate of the degradation crude product filtering
by semi permeable membrane was analyzed by GC. Figs. 2
and 3 showed the GC results of lignin degradation catalyzed
by [Bmim]OH and NaOH, respectively. The peak at retention
time 16.1 min in Fig. 2 was assigned to vanillin, a major
degradation product, with content of 36.2 %. Other most of
the main products were listed in Table-1. The content of vanillin
in Fig. 3 was obviously smaller than that in Fig. 2, which
revealing the higher selectivity of vanillin. Furthermore, the
simpler composition of products obtained in the presence of
ionic liquid resulted in easy separation of decomposition
products.
16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00
The reaction conditions were optimized by UV-visible
spectrophotometer method. Two basic ionic liquids [Bmim]OH
Fig. 2. GC-MS of decomposition product (using ionic liquid as catalyst)

Vol. 27, No. 3 (2015)
New Synthesis of Vanillin by Degradation of Lignin in Presence of Functional Basic Ionic Liquid 887
TABLE- 2
EFFECT OF PRETREATMENT TIME TO THE DEGRADATION
Entry
Ultrasonic time (min) Vanillin contenta (%)
1
2
3
4
0
34.65
28.59
39.68
25.74
20
30
60
aDetermined by GC-MS; catalyst: [Bmim]OH (0.15 mol/L), reaction
time: 2 h, reaction temperature: 130 oC
2.4
2.1
1.8
1.5
1.2
0.9
16.00
18.00
20.00
22.00
24.00
Fig. 3. GC-MS of decomposition product (using NaOH as catalyst)
2.1
2.0
1.9
1.8
1.7
1.6
60
80
100
120
140
160
Temperature (°C)
Fig. 5. Relationship of reaction temperature and absorbance (catalyst:
[Bmim]OH, reaction time: 2 h)
2.0
1.8
1.6
1.4
1.5
adding NaOH
adding [Bmim]OH
adding [Bmim]OAc
no base
1.4
1.3
1.2
0
1
2
3
4
5
Time (h)
Fig. 4. Relationship of reaction time and absorbance
A great decrease in the crude product absorbance with
increasing reaction temperature was observed. Thus, the high
temperature was beneficial to the formation of degradation
products.When reaction temperature raised to 130 °C, no obvious
absorbance decrease was observed. The best degradation
temperature that we choose for the optimum condition was
130 °C. The concentration of catalyst is also a very important
parameter for the degradation. The effect of catalyst concen-
tration was evaluated and summarized in Fig. 6. The results
showed the dependence of degradation conversion on catalyst
concentration. The conversion of lignin was improved with
the dosage increase of the catalyst. When the concentration of
catalyst was higher than 0.15 mol/L, no significant absorbance
change occurred.At last, the effect of ultrasound pretreatment
to the degradation conversion was also examined. Before
heating, the reaction mixture was pretreated by ultrasound
equipment and the degradation conversion results were
summarized in Table-2. The vanillin content was highest after
treating for 0.5 h. The product vanillin was separated by
column chromatography and the structure was confirmed by
1H NMR and purity reached 99 %.
0.00
0.05
0.10
0.15
0.20
0.25
mol/L
Fig. 6. Relationship of ionic liquid dosage and absorbance (catalyst:
[Bmim]OH, reaction time: 2 h, reaction temperature: 130 °C)
Conclusion
In conclusion, functional basic ionic liquid [Bmim]OH
was used to promote the degradation of lignin to produce vanillin.
The optimized reaction conditions were obtained. Comparing
with the reaction under traditional conditions, NaOH solution,
the degradation in the presence of the ionic liquid showed high
conversion of lignin and selectivity of vanillin.
ACKNOWLEDGEMENTS
The authors thank the financial support from Program of
Local Colleges Ability Building of Science and Technology
Commission of Shanghai Municipality No. 11520502600 and
Alliance Program Project of Shanghai No. LM201247.

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