Advances in Ma terials Physics and Che mist ry, 2012, 2, 154-157
doi:10.4236/ampc.2012.24B040 Published Online December 2012 (htt p:// ampc)
Copyright © 2012 SciRes. AMPC
Aqueous Two Phase Extraction for the Recovery of
1,3-Propanediol from Its Aqueous Solutions
Min Hee Chung1, Yeon Ki Ho ng1, Hyoung Wook Lee2, Sung-Jun Park3
1Department of Chemical and Biological Engineering, Korea National Univers ity of Tra nspor tation, Chungju, Chungbuk, Korea
2Department of Energy Syst em En g ineering , Korea National University of Transportation, Chungju, Chungbuk Korea
3Department of Mech anic al Engi neering, Korea National University of Transportation, Chungju, Chungbuk Korea
Email: hongyk@ut .ac .kr, hwle e @ut.a,
Received 2012
As the biodiesel production is rapidly enhanced, the crude glycerol, which is by-product of biodiesel processes, is state of surplus.
1,3-PDO (1,3-propanediol), a valuable monomer of poly(trimethylene terephthalate) (PTT), can be produced from the fermentation
process using crude glycerin as a carbon source. For the economic biological production of 1,3-PDO, the low cost and high efficient
separation processes is essential. In this study, aqueous two-phase system composed of various hydrophilic alcohols and salt was
used as a primary separation step for 1,3-PDO. It was found that the aqueous two-phas e systems are easi l y formed with d ecreasi ng o f
the pol arit y of alcoho ls . The extr actio n efficienc y is proportional to the polarity of alcohols. In case of methanol or ethanol/K2HPO4,
the extraction efficiency was more than 90%. It was concluded that the aqueous two-phase extraction using methanol or etha-
nol/K2HPO4 can be applied for the primary separation of 1,3-PDO as an alternative to a conventional primary separation pro cesses.
Keywords: 1,3 -Propanediol; Alcohols; Phase Separation; Extraction Efficiency
1. Introduction
Over the last decade, biodiesel has emerged as an alternative
fuel of fossil diesel. However, the production of biodiesel is not
profitable without government subsidies due to its high produc-
tion cost. For the economic production of biodiesel, finding
new applications of glycerol which is a by-product from bio-
diesel production is important. Generally, for every 9 kg of
biodiesel produced, 1 kg of a crude glycerol by-product is pro-
duced . There is a larg e amount of crude gl ycerol on t he market
available fo r very low pri ce due to the rap id increase of biodie-
sel prod uc t ion [1.2] .
Glycerol can be u sed as a carb on source fo r the fer ment ative
production of 1,3-PDO (1,3-propanediol) which is a monomer
of PTT(Poly(trimethyleneterephthalate). PTT is a polyester
with sup erior str etching and stretch r ecovery characteri stics an d
has various usage for textile, carpets and upholstery manufac-
turing [3].
Before two decades, 1,3-PDO had been produced by hydra-
tion of acrolein or hydroformylation of ethylene oxide. In early
2003, DuPont developed a commercial biological process for
1,3-PDO based on the fermentation of glucose. Such a
bio-based PDO made a petroleum-based PTT to be bioplastic.
In spite of energy saving of glucose based fermentation by Du-
Pont, the cost of 1,3-PDO has been still high and its price can
depend on the price of glucose [4]. The low price of glycerol
due to the rapid increasing of biodiesel production makes its
usage of a promising alternative carbon source be possible.
A biological production of 1,3-PDO has several advantages
compared with the conventional chemical production because
of low cost and more eco-friendly process. 1,3-PDO had been
synthesized by various microbes such as Klebsiella pneumonia,
Clostridium butyricum and Citrobactor freundii [5-7]. It was
reported that the final concentration of 1,3-PDO in fermentation
broth was low, ranging from 30 to 130 g/L. In addition, the
fermentation broth contains a mixture of 1,3-PDO,
2,3-butanediol, glycerol, lactate, acetate, succinate and other
impurities which make the downstream processing of 1,3-PDO
fermentation broth be dif ficul t [8].
The downstream processes of biologically produced 1,3-PDO
includes three main steps. In the first step, microbial cells are
removed by using flocculation, filtration, and centrifugation.
The secon d step contains the primary reco very processes fo r the
removal of impurities such as acid salts and ethanol and the
evaporation of water. In this step, evaporation, solvent extrac-
tion, precipitation, electrodialysis and chromatography
processes can be used. In the last step, the final purification of
1,3-PDO is carried out by vacuum distillation process [9].
Figu re 1. PTT synthes is from 1,3-PDO.
Copyright © 2012 SciRes. AMPC
Among these steps, the most important step is primary separa-
tion step which requires a large amount of energy for the re-
moval of water from fermentation broth. Furthermore, the re-
moval of acid salts from broth is not easy. For the cost effective
biological production of 1,3-PDO, a low energy required sepa-
ration processes with a high efficiency is essential.
For the economic removal of impurities, s everal pro cesses as
the primary separation step have been suggested. Broekhuis et
al proposed reactive extraction by formaldehyde or acetalde-
hyde where 1,3-PDO was converted into a compound without
hydroxyl groups and then recovered it by solvent extraction
[10]. Hao et al used propionaldehyde, butylaldehyde and iso-
butylaldehyde as extractants for the recovery of 1,3-PDO [11].
However, th e organic salts th at are for med d uring fermentatio n
would decline the recovery efficiency. In some cases, electro-
dialysis was used for the removal of organic acids salts but low
product yield, membrane pollution, and high maintenance cost
make this process undesirable. Recently, Hong reports that the
amine-based extraction process is effective for the removal of
acid salts from 1,3-PDO aque o us s ol utions [8 ].
Aqueous liquid-liquid two-phase systems are formed when
two polymers or polymer/salt are dissolved together above
certain concentration. The general characteristic feature of these
systems is that both phases are aqueous, allowing partition of
target molecules. In case of polymer/polymer or polymer/salt
systems, it is difficult to use in a commercial scale due to their
high cost. Therefore, for the bulk chemical such as 1,3-PDO,
the ch eap aqueous two-phase s ystems are essenti al.
In this study, aqueous two-phase systems composed of alco-
hol solvents and inorganic salts was used for the extraction of
1,3-PDO from its artificial aqueous solutions. The phase sepa-
ration of two-phases containing alcohols/salt and the effect of
concentration of 1,3-PDO and solvent on separation yield was
2. Materials and Methods
2.1. Materials and Reagents
1,3-PDO (Aldrich, 99.9%) were used as received to prepare its
aqueous solutions. The concentrations of 1,3-PDO ranged from
50 g/L to 100 g/L. These concentrations were based on the
concentration of practical fermentation broth produced by K.
Pneumoniae. Hydrophilic alcohols such as methanol (Aldrich
99.9%), ethanol (Aldrich 99.9%) and isopropanol (Aldrich
99.9%) were also used as received without any further purifica-
tion. The salt used in this study was K2HPO4.
2.2. Experimental Procedure
For the investigation of effect of 1,3-PDO concen tration, 2 g of
K2HPO4 and 10 ml of alcohol were added to the 10 ml of
1,3-PDO aqueous solution. After stirred for 2 min, the mixtures
were held for 10h at room temperature.
For the study of effect of solvent amounts, the specific con-
centration of 1,3-PDO aqueous solution and 2 g of K2HPO4
were added to alcohols with various volumes.
The concentration of 1,3-PDO in the top and bottom phases
were measured b y gas chromatography.
3. Results and Discussion
3.1. Phase Diagram
Phase diagram data are essential for the selection of optimized
two-phase systems. The phase diagram was prepared by a tur-
bidimetric titration method [12]. The concentrations of alcohols
and K2HPO4 were calculated by the following equations.
wm mmm
= =
wm mmm
= =
are the amount of alcohols, K2HPO4,
and water, respectively.
are the mass fraction of
alcohol and K2HPO4.
The bimodal curves determined at room temperature for the
alcohols/K2HPO4 systems were shown in Figure 2. These bi-
modal curves provide information about the concentrations of
phase which are able to form a aqueous two-phase. Figure 2
shows that aqueous two-phase systems can be formed by add-
ing appropriate amount of K2HPO4 to aqueous alcohol solu-
tions. It is found that the ability of the alcohols for phase sepa-
ration follows the order: isopropanol>ethanol>methanol, which
is in accordance with the order of polarity of the alcohols. From
Figure 2, isopropanol has the best phase-forming abilities
among hydrophilic alcohols used in this study. And Figure 2
shows that the ability of the alcohols for phase separation in-
creased with the weight fracti on of K2HPO4. The anion HPO42-
that strongly interacts with water molecules enable to form
aqueous two-phase.
In this study, partition coefficients of 1,3-PDO between two
phases ar e as fo llows:
are equilibrium concentrations of 1,3-PDO
in top phase and bottom phase, respectively. Extraction effi-
ciency of 1,3-PDO can be calcu lated as follows:
(s alt )
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
w2(sal t) vs w1(MeOH)
w2(sal t) vs w1(EtOH)
w2(sal t) vs w1(BuOH)
w2(sal t) vs w1(IPA)
Figure 2. Phase diagram of alcohols/salt aqueous two-phase sys-
te ms .
Copyright © 2012 SciRes. AMPC
In itial c onc entr at ion of 1, 3- PDO (g/ L)
020 40 60 80100
Figure 3. Effect of 1,3-PDO concentration on extraction efficiency
in an aqueous two-phase systems composed of Alcohols/K2HPO4.
Weight fr action of alcohols ( w /w )
0.0 0.2 0.4 0.6
Y (%)
Figure 4. Effect of weight fraction of various alcohols on extraction
efficiency in an aqueous two-phase systems composed alco-
tt bb
+ (4)
are volu me of each phase.
Figure 3 shows the effect of 1,3-PDO concentration on ex-
traction efficiency in aqueous two-phase systems composed of
various alcohols and K2HPO4. The extraction efficiency does
not depend on the 1,3-PDO concent rati on. However , th e extrac-
tion efficien cy increased with the polar ity of alcohol s. It can be
presumed that the solubility of alcohols for 1,3-PDO and the
hydrogen bonding between alcohols and 1,3-PDO are propor-
tional to their polarities. Because 1-butanol is hydrophobic, its
extraction efficiency is low compared to other hydrophilic al-
cohols. Considering the economics of 1,3-PDO separation
proces ses, it is found that the only single extraction step is ap-
plicable to the primary separation of 1,3-PDO by using more
than 50 %(w/w) of methanol or ethanol. In case of isopropanol,
multiple or continuous extraction is required.
4. Conclusions
In this study, the extraction of 1,3-PDO in hydrophilic alco-
hols/K2HPO4 was demonstrated to be effective. It is found that
the aqueous two phases are easily formed with decreasing of
the polarity of alcohols. However, the extraction efficiency is
proportional to the polarity of alcohols. It can be concluded that
methanol or ethanol is suitable for the extraction of 1,3-PDO b y
using aqueous two-phase. Considering the toxicity of solvents,
ethanol is more suitable than methanol. Compared with other
primary separation processes such as evaporation, electrodialy-
sis and conventional solvent extraction, aqueous two-phase
extraction has the advantages of low energy cost, quick phase
separati on and hi gh extraction efficiency for 1, 3-PDO.
5. Acknowledgements
This research was supported by a grant from the Academic
Research P rogram of Korea Nati onal University o f Transp orta-
tion in 2012. (Hyoung Wook Lee)
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