Energy Conversion and Management 51 (2010) 346–349
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Energy Conversion and Management
journal homepage: www.elsevier.com/locate/enconman
Preliminary investigation on concentrating of acetol from wood vinegar
Ze Wang, Weigang Lin, Wenli Song *, Jianzhong Yao
State Key Laboratory of Multi-Phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
a r t i c l e
i n f o
Article history:
Received 23 February 2009
Accepted 30 September 2009
Available online 6 November 2009
Keywords:
Wood vinegar
Pyrolysis liquid
Acetol
Concentrating
a b s t r a c t
Acetol, as one of the components in biomass pyrolysis liquid, is a high value added compound for medicine synthesis. Benefit may be obtained if acetol can be extracted from the pyrolysis liquid, while the
instability of acetol makes the concentrating difficult. In this paper, the concentrating of acetol from
wood vinegar is preliminarily investigated, and the conditions of distillation, solvent extraction, and
Na2CO3 effect on the concentrating result are discussed. Herein the content of acetol can be concentrated
from below 4% in the raw wood vinegar to above 60%, and the number of main components reduce from
over 20 to 5, while the yield of acetol is still rather low. It was found that in the organic solution distillation process, acetol can be easily concentrated from 1% to above 40%, while a further distillation of the
concentrated acetol system was rather hard. The conversion of acetol in the distillation process was probably an important cause to the low yield of acetol, and a lower distillation temperature was advantageous
for the concentrating of acetol.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
With declining petroleum resources, and more environmental
concerns on fossil fuels, it is imperative to develop sustainable
fuels and chemicals from renewable resources [1–4]. As one of
the important renewable resources, biomass can be converted to
liquid products by thermochemical approach for pyrolysis-oil and
chemicals [2–7]. Pyrolysis-oil may be used as a transport fuel after
upgrading treatment [8–12] or by emulsion with diesel [13].
Chemicals like methanol, acetic acid can be obtained from the
pyrolysis liquid a long time ago [3]. Recently, hydrothermal approach was applied in treating the biomass to produce chemicals
like liquid alkanes [2,6,14,15] or the unique compound like 2-(4hydroxy-benzyl)-4-methyl-phenol [16]. The bio-refinery is getting
prosperous these years while the high value added chemicals that
can be obtained are still rather few, compared with the number of
components found in the pyrolysis-oil.
Acetol (1-hydroxy-2-propanone), as one of the major component in the liquid product by pyrolysis of biomass, is a valuable
compound for medicine synthesis [17]. At present, there are two
main approaches in producing acetol [18]. The first, acetol can be
synthesized by the reaction between bromoacetone and sodium
or potassium formate or acetate, followed by hydrolysis of the ester with methyl alcohol. The second, acetol can be prepared by the
treatment of glycerol or propylene glycol at 200–300 °C with a
dehydrogenating catalyst. While the two methods are both in high
* Corresponding author. Tel.: +86 010 82627078.
E-mail addresses: [email protected] (Z. Wang), [email protected]
(W. Song).
0196-8904/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.enconman.2009.09.031
cost due to the expensive bromoacetone or catalyst. So it is worthwhile to take efforts to extract acetol from the pyrolysis liquid.
While the instability of acetol makes the concentrating difficult.
Till now there is no report on the method of extraction of acetol
from pyrolysis liquid.
In this paper, the concentrating of acetol from wood vinegar
was preliminarily probed. The conditions of distillation, solvent
extraction, and Na2CO3 effect on the concentrating result were
tested and phenomena were discussed.
2. Analytical method
The wood vinegar and the concentrated products were analyzed
by GC–MS apparatus (Agilent-6890-5972). The column was ABFFAP (30 m 0.25 mm 0.25 lm). Analytical conditions: inlet
heater, 275 °C; MSD temperature, 150–155 °C; temperature program, initial 50 °C for 5 min, increase to 110 °C by 20 °C/min for
5 min, and finally to 230 °C by 20 °C/min for 6.5 min. The contents
of the components in different systems were represented by peak
area percentages for relative comparisons under different conditions, since the aim of the work was for qualitative probe.
3. Results and discussion
The raw wood vinegar was analyzed by GC–MS, the total ion
chromatogram (TIC) was shown in Fig. 1, and the composition
was listed in Table 1. It can be seen from Fig. 1 that water
(80.97%) was the predominant component in wood vinegar, and
the other main components were acetic acid (7.28%), methyl
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Z. Wang et al. / Energy Conversion and Management 51 (2010) 346–349
Fig. 1. Total ion chromatogram of the raw wood vinegar.
Table 1
Composition of raw wood vinegar and latter 50% evaporated fraction.
RT/min
ID
Area%Raw
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
2.11
2.42
2.46
2.84–2.88
3.69
6.1–7.24
7.5
9.37
9.7
10.41
10.52
10.8
11.49
12.51
13.91
14.78
Acetaldehyde
Acetone
Acetic acid, methyl ester
Methyl alcohol
2,3-Butanedione
Water
Propanenitrile
Formamide
2-Propanone, 1-hydroxy2-Cyclopenten-1-one
2-Cyclopenten-1-one, 2-methylButanoic acid, 2-oxoAcetic acid
Furfural
Propanoic acid
2-Furancarboxaldehyde, 5methylButanoic acid
1-Penten-3-one, 2-methylCyclooctane
Phenol, 2-methoxyPhenol, 2-methoxy-4-methylPhenol
0.12
0.99
0.44
4.55
0.06
80.97
0.03
0.02
3.41
0.04
0.01
0.1
7.28
0.61
0.7
0.02
17
18
19
20
21
22
15.43
15.95
17.81
18.1
18.87
19.16
0.03
0.03
0.06
0.33
0.11
0.11
,
Methyl Alcohol
,
2-Propanone, 1-hydroxy,
Acetic acid
,
Furfural
,
Phenolic derivatives
solide--slow to fast
hollow--fast to slow
Area%L50%
22
0.038
0.182
79.715
4.182
14.241
0.078
0.972
0.034
0.128
0.025
0.099
Raw – raw wood vinegar.
L50% – later 50% evaporated fraction.
alcohol (4.55%), acetol (3.4%), acetone (0.99%), propanoic acid
(0.7%), furfural (0.61%), and phenol derivatives (0.55%). Among
the main components, acetol was most distinct in the ratio of content to market price, indicating that it was worthwhile to take efforts to extract acetol from the wood vinegar.
The raw wood vinegar (100 ml) was firstly distilled at atmospheric pressure. Two heating rates were tested, one case was slow
heating in the beginning and fast heating later, and the other case
was from fast to slow. With distillation going, the evaporated fractions were collected in the order of 3 ml, 10.5 ml 8, and 4 ml. The
composition of each evaporated fraction was analyzed, and the
change of the composition with distillation process was shown in
Fig. 2. The composition of the latter 50% evaporated fraction was
listed in Table 1.
It can be seen from Fig. 2 that the heating rate had very little
influence on the content of acetol during the distillation process,
and therefore a constant heating rate for distillation was adopted.
The contents of methanol, furfural, phenol derivatives were higher
relative content (%)
No.
24
20
10
8
6
4
2
0
0
20
40
60
80
100
volume of distillate (ml)
Fig. 2. Components in different distillation fractions under two distilling
conditions.
in the early 45% evaporated fraction, and then the contents of
theirs decreased with distillation going. The contents of acetol
and acetic acid were lower in the early distilled fractions, and then
increased distinctly after 45% volumetric fraction. it can be seen
from Table 1 that the content of acetol in the latter 50% fraction
was higher, and the contents of volatile components and phenol
derivatives were lower than those in the original raw wood vinegar. So the latter 50% evaporated fraction can be used as the source
material for further treatment.
Acetol (145 °C) has similar boiling point with acetic acid
(117.9 °C) and has high solubility in water, so the separation of acetol by direct distillation of the water solution with much acetic acid
inside is hard. So solvent extraction to transfer acetol from water
phase to organic phase was considered. According to the like dissolves the like principle, the solvent like acetone must have high
solubility to acetol, but these solvents dissolve with water very
well too, so the screen for appropriate solvent is needed. Herein
four solvents of toluene, chloroform, ethyl acetate, hypnone were
tested. Raw wood vinegar (5 ml) was blended with solvent (5 ml)
in a test tube, mixing by fast shaking up and down for 5 min, laying
aside for 10 min, and then the organic layer was analyzed by GC–
MS. The peak areas of the main components in different solvents
were shown in Fig. 3. It can be seen from Fig. 3 that the ratio of ace-
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Z. Wang et al. / Energy Conversion and Management 51 (2010) 346–349
tol to acetic acid in chloroform was the highest, while ethyl acetate
had the highest solubility. Herein ethyl acetate was chosen as the
extracting solvent, since acetic acid may be eliminated by base
treatment.
The latter 50% evaporated fraction (5 ml) was treated by Na2CO3
in a test tube, and then blended with ethyl acetate (5 ml) for solvent extraction. After standing for 10 min the organic layer was
analyzed. The influence of the amount of Na2CO3 on the composition of the organic solution was shown in Fig. 4.
It can be seen from Fig. 4 that when Na2CO3 was 0.156 g, the
amount of acetic acid, propanoic acid were rather high; acetic acid
and propanoic acid disappeared when Na2CO3 was over 0.34 g; the
content of acetol increased with increasing amount of Na2CO3, and
researched the highest level at 2.15 g; too much Na2CO3 of
3.1001 g made the content of acetol lower. The content of water
had a reverse order with acetol. The content of phenol derivatives
increased first and then fell off with increasing amount of Na2CO3.
It can be explained that acid can be neutralized by Na2CO3, and
meanwhile water reacts with excessive Na2CO3 to form hydrates
like Na2CO310H2O or Na2CO37H2O or Na2CO3H2O. The deduced
content of water makes acetol concentrated, while the overmuch
Na2CO3 may absorb acetol and makes the content of acetol lower
instead.
The distillation of ethyl acetate solution was tested. It was
found that acetol can be easily concentrated from 1% to above
40% with bottom temperature of 85–145 °C at atmospheric pressure, while a further distillation of the concentrated acetol system
(>40%) was rather hard. The bottom solution (27 ml) of acetol
(46.5%) was distilled under a vacuum condition with bottom temperature of 50–125 °C, and 12 ml bottom solution was left after
distillation. In the bottom solution, the content of ethyl acetate
was distinctly decreased from 29.1% to 3.2%, but the content of acetol did not rise accordingly; instead it slightly declined from 46.5%
to 44.7%, while the content of 2-hydroxy-3-methyl-2-cyclopenten1-one (HMCPO) distinctly increased from 8.6% to 13.5%. In the
evaporated phase, the content of ethyl acetate was the highest of
85%, the content of acetol was just 1.2%, and no other heavier components were detected. The last bottom solution (7 ml) was further
distilled under a vacuum condition with bottom temperature of
72–150 °C to transfer acetol to the evaporated phase. After distillation, 3 ml evaporated phase was obtained. In the evaporated phase,
the content of acetol increased a little to 50.8%, while an unknown
compound appeared in a remarkable abundance of 21.4%. It indicates that during the distillation process acetol may convert to
some other compounds, and the unknown compound and HMCPO
Fig. 4. Effect of the amount of Na2CO3 on the contents of main components in ethyl
acetate solutions.
may be the compounds that formed from acetol. The unknown
compound was speculated as 5-methyl-6H-pyran-3-one (MPO).
The identification of MPO and the possible formation routes of
HMCPO and MPO were systematically discussed in another paper.
Herein, the possible formation route from acetol to HMCPO is representatively illustrated in Fig. 5. TIC of the evaporated liquid is
shown in Fig. 6.
By finely distillation condition control the content of acetol can
be increased to some extent. Till now the best level of acetol was
62.4% (area percentage), the second abundant component was its
homolog 1-hydroxy-2-butanone (19.6%), the other major components were ethyl acetate (8.1%), acetic acid (6.2%), and water
(1.1%), while the yield of acetol was still quite low (4.9%). Herein
O
OH
HOCH2CCH3
HO-CH2CCH3
2 CH3 CCH2OH
O
H-CH2 CCHOH
CH3CCH2OH
O
O
A
D
B
_ H
2O
1728000
1719000
area of the peaks
1710000
1-hydroxy-2-Propanone
Acetic acid
Phenolic derivatives
Propanoic acid
OH
_ H
2O
1701000
O
1692000
300000
250000
OH
O
O
G
F
CH2CCH3
CH2 CCHOH
_
O
E
H2O
_HO
2
200000
150000
CH2
100000
50000
0
toluene
chloroform
Ethyl Acetate
extraction solvent
Fig. 3. Extraction ability of different extraction solvents on main components in
wood vinegar.
OH
OH
hypnone
O
O
H
I
Fig. 5. Deduced reaction routes for formation of HMCPO (F).
Z. Wang et al. / Energy Conversion and Management 51 (2010) 346–349
349
4. Conclusion
Fig. 6. Total ion chromatogram of the concentrated acetol solution under higher
distillation temperature.
The acetol concentrating from wood vinegar was preliminarily
investigated. It was found that in the process of wood vinegar distillation, heating rate had very little influence on the content of
acetol with distillation going. The contents of methanol, furfural,
phenol derivatives were higher, and the contents of acetol and acetic acid were lower in the early 45% distilled fraction, and then
methanol, furfural, phenol derivatives decreased, and acetol, acetic
acid increased distinctly. Ethyl acetate had the highest solubility
among the four solvents of toluene, chloroform, ethyl acetate,
and hypnone. Excessive Na2CO3 made the content of water decrease and acetol increase, while overmuch Na2CO3 made the content of acetol lower instead. In the organic solution distillation
process, acetol can be easily concentrated to above 40%, while a
further distillation of the concentrated system is hard. Conversion
of acetol during distillation process may be an important cause to
the low yield of acetol, and a lower treating temperature is advantageous for the increasing of acetol.
Acknowledgments
The work is supported by the National Basic Research Program
(973 Program), No. 2004CB719704.
References
Fig. 7. Total ion chromatogram of the concentrated acetol solution under lower
distillation temperature.
the yield of acetol is defined as the ratio of acetol obtained (product
of the area percentage of acetol and the volume of the concentrated
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atmospheric pressure; the bottom solution was treated by Na2CO3
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indicates that the distillation temperature is sensitive to the content of acetol and the lower treating temperature is advantageous
for the increasing of acetol by lessening the conversion of acetol
and reducing the transfer of heavier components into the distillate.
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