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I
Method of Producing Butanol
Background of the Invention
Field of the Invention
[0001]
The present invention relates to a method of producing butanol by separating
butanol from a butanol-containing solution. More particularly, the present
invention relates to a method for producing butanol, which method comprises a
step
of removing inorganic salts, sugars, proteins, catalytic components and/or the
like
remaining in a butanol-containing solution with a nanofiltration membrane.
Description of the Related Art
[0002]
Butanol is a compound which is industrially very important as a raw material
of chemicals and pharmaceutical agents, as a solvent, and as a fuel material.
It is
well known that butanol can be industrially synthesized from acetaldehyde by
the
Wacker process, or from propylene, carbon monoxide and water by the Reppe
process, and it also has long been known that these can be produced by acetone-
butanol fermentation. Production of butanol by acetone-butanol fermentation
have
problems in that the cost of the substrate to be used as the nutrient source
for
microorganisms and the cost of purification of the product are high, so that
production of butanol has become dependent on chemical synthesis. However,
because of the recent decrease in the crude oil resource and substantial rise
in its
price, production methods of butanol using biomass have been expected to be
useful
as alternatives to chemical synthesis, and therefore reduction of the
production cost
in acetone-butanol fermentation is demanded.
[0003]
In general, as the method for purifying butanol, solvent extraction or
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distillation is employed. In solvent extraction, in cases where the desired
product is
a lower alcohol, which is highly soluble in water, distribution of the lower
alcohol
into the organic phase is difficult, so that use of a special extraction
solvent or
multistep extraction may be required, which leads to increase in the cost
(Patent
Document 1). Further, in purification by distillation, since the concentration
of
butanol in the fermentation broth is low, water, whose boiling point is lower
than that
of butanol, needs to be distilled off in a large amount, so that a method that
enables
efficient concentration of butanol is demanded. As a solution to solve the
problem,
a method for concentrating a fermentation alcohol using a separation membrane
has
been devised. In Patent Document 2, a method for concentrating an alcohol by
the
pervaporation separation method using a silicone rubber membrane is disclosed.
However, this method is the so called batch filtration concentration wherein
purified
fermentation broth is recovered from a fermenter and then treated in a
pervaporation
apparatus under specific conditions, which is not rational in view of device
configuration.
[0004]
Examples of the continuous method for alcohol concentration as an
alternative to the batch process include the method using a silicalite
membrane
coated with silicone rubber, which is disclosed in Patent Document 3. In cases
where the operation of concentration is carried out by introducing a
silicalite
membrane into a fermenter, fouling occurs with time due to organic acids such
as
succinic acid and malic acid produced as by-products. By coating the surface
of the
silicalite membrane with the silicone rubber to make the membrane surface
hydrophobic, this fouling is suppressed. However, since fouling substances
accumulate with time also on the surface of the silicone rubber, the
performance of
the separation membrane may decrease with time.
[0005]
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Further, in case where an alcohol is distilled from a fermentation broth,
sugars,
amino acids, side metabolites such as organic acids, and the like remaining in
the
fermentation broth are heated to yield by-products, which are then
contaminated in
the distillate fraction as impurities, which is problematic. Therefore,
purification of
the fermentation broth is also an important problem. As methods for purifying
an
alcohol, a method for purifying 1,3-propanediol wherein distillation is
carried out in
combination with microfiltration, ultrafiltration, nanofiltration or ion
exchange
(Patent Document 4); and a method for separating diol using a reverse osmosis
membrane or a nanofiltration membrane (Patent Document 5) are disclosed.
However, these prior arts do not disclose the effect of difference in the
material of the
nanofiltration membrane on the permeation selectivity and on purification of
butanol.
Prior Art References
Patent Documents
[0006]
Patent Document 1 US 2007/193960 A
Patent Document 2 JP 57-136905 A
Patent Document 3 JP 2003-135090 A
Patent Document 4 US 2005/069997 A
Patent Document 5 US 2006/065600 A
Summary of the Invention
[0007]
In view of the above-mentioned purpose, that is, purification of butanol, the
present invention aims to provide a method by which butanol can be separated
and
collected at higher purity and at lower cost than by the conventional methods.
[0008]
The present inventors intensively studied to solve the above problems and
discovered that high-purity butanol can be obtained by filtering a butanol-
containing
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solution through a nanofiltration membrane having a functional layer
containing a
polyamide, and that the cost of distillation can be effectively reduced by
this process,
thereby completing the present invention.
[0009]
That is, the present invention provides the following (1) to (7):
(1) A method of producing butanol, the method comprising the steps of:
filtering
a butanol-containing solution through a nanofiltration membrane; and
collecting
butanol-containing solution from the permeate flow of the nanofiltration
membrane.
(2) The method according to (1), wherein the butanol-containing solution is a
fermentation broth obtained by microbial fermentation.
(3) The method according to (1), wherein the nanofiltration membrane has a
functional layer comprising a polyamide.
(4) The method according to (3), wherein the polyamide comprises a cross-
linked
piperazine polyamide as a major component, and a constituting component
represented by Formula [I]:
N\-CH2 JN-
R R
[I]
wherein R represents -H or -CH3, and n represents an integer of 0 to 3.
(5) The method according to (1), further comprising the step of filtering the
collected butanol-containing solution through a reverse osmosis membrane to
increase the butanol concentration.
(6) The method according to (1), further comprising the step of distilling the
collected butanol-containing solution under a pressure of not less than I Pa
and not
more than atmospheric pressure, at 25 C to 200 C.
(7) The method according to (5), further comprising the step of distilling the
butanol-containing solution after concentration through the reverse osmosis
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membrane under a pressure of not less than 1 Pa and not more than atmospheric
pressure, at 25 C to 200 C.
[0010]
By the present invention, metal catalysts, inorganic salts and/or sugars
5 existing in a butanol-containing chemically synthesized reaction solution or
fermentation broth can be removed by a simple process, and therefore the
distillation
efficiency can be increased and the cost can be reduced, so that highly pure
butanol
can be produced at low cost.
Brief Description of the Drawings
[0011]
Fig. 1 is a schematic view showing an embodiment of the separation
apparatus used in the present invention having a nanofiltration membrane and a
reverse osmosis membrane.
Fig. 2 is a schematic view showing an embodiment of a cross-sectional view
of a cell in the separation apparatus used in the present invention having a
nanofiltration membrane and a reverse osmosis membrane, which cell has the
reverse
osmosis membrane attached thereto.
Description of Symbols in Drawings
[0012]
1 Feed tank
2 Cell equipped with nanofiltration membrane or reverse osmosis
membrane
3 High-pressure pump
4 Permeate flow which has pass through membrane
5 Retentate flow which has been concentrated with membrane
6 Feed flow sent by high-pressure pump 7 Nanofiltration
membrane or reverse osmosis membrane
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8 Supporting plate
Best Mode for Carrying out the Invention
[0013]
The present invention will now be described more concretely.
The method of the present invention for producing butanol is a method for
producing butanol by separating butanol from a butanol-containing solution,
and
relates to a method for producing butanol, comprising a step of allowing the
butanol-
containing solution to pass through a nanofiltration membrane to remove metal
catalysts, inorganic salts, sugars and/or the like.
[0014]
In the present invention, butanol means a collective name of compounds
having a hydroxyl group and four carbon atoms, and examples thereof include n-
butanol, isobutanol, 2-butanol and 2-methyl-2-propanol. In the present
invention, a
butanol may comprise a single type of butanol or may be a mixture of plural
types of
butanols.
[0015]
The method used in the present invention for producing a butanol-containing
solution is not restricted as long as it is known to those skilled in the art,
and
examples of the method include a method wherein the solution is prepared by
the
Wacker process from acetaldehyde and a method wherein the solution is prepared
by
Reppe process from propylene, carbon monoxide and water, as mentioned above,
in
cases where a chemical synthesis method is used. In terms of fermentation
culture,
the solution is produced by anaerobic culture of Clostridium butylicum. A
preferred
method for the butanol-containing solution used in the present invention is
the
method by fermentation culture of a microorganism, and, in this case, the
fermentation broth itself containing butanol can be used as the butanol-
containing
solution to be applied to the nanofiltration membrane.
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[0016]
The nanofiltration membrane used in the present invention is also called NF
membrane, and generally defined as a "membrane that allows permeation of
monovalent ions but blocks divalent ions". The membrane is considered to have
voids of as small as several nanometers, and mainly used for rejection
microparticles,
molecules, ions, salts and/or the like in water.
[0017]
By filtering the butanol-containing solution through the nanofiltration
membrane, impurities (substances other than butanol) are removed at the feed
flow of
the nanofiltration membrane and the butanol-containing solution is collected
from the
permeate flow of the nanofiltration membrane.
[0018]
Examples of known materials of nano filtration membranes generally include
polymer materials such as cellulose acetate polymers; polyamides; polyesters;
polyimides; vinyl polymers including polyvinyl alcohols; and polysulfones,
which
can be used in the present invention. Among these, a nanofiltration membrane
having a polyamide in its functional layer is preferably used in the present
invention
since high purification efficiency can be attained therewith. Other plural
membrane
materials may also be contained in the membrane as long as the functional
layer
contains a polyamide. In terms of the membrane structure, either an asymmetric
membrane wherein at least one side of the membrane has a dense layer, which
membrane has micropores having a diameter that gradually increases from the
dense
layer to the inside of the membrane or to the other side of the membrane, or a
composite membrane having on the dense layer of an asymmetric membrane a very
thin functional layer formed by another material can be used. Examples of the
composite membrane which may be used include the composite membrane described
in JP 62-201606 A, wherein a nanofiltration membrane having a polyamide
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functional layer was placed on a support membrane made of a polysulfone
membrane
material.
[0019]
The nanofiltration membrane having a polyamide functional layer preferably
used in the present invention is preferably a composite membrane having a high
pressure resistance, a high permeability and a high solute rejection
performance.
Further, in order to allow maintenance of durability against the operation
pressure, a
high permeability and a high rejection performance, the membrane preferably
has a
polyamide functional layer which is retained by a support made of a porous
membrane and/or a non-woven fabric. In a nanofiltration membrane having a
polyamide functional layer, preferred examples of the carboxylic component,
expressed in terms of monomers, constituting the polyamide include aromatic
carboxylic acids such as trimesic acid, benzophenone tetracarboxylic acid,
trimellitic
acid, pyromellitic acid, isophthalic acid, terephthalic acid,
naphthalenedicarboxylic
acid, diphenylcarboxylic acid and pyridinecarboxylic acid, and, in view of
solubility
to the film-forming solvent, trimesic acid, isophthalic acid or terephthalic
acid, or a
mixture thereof is more preferred.
[0020]
Preferred examples of the amine component, expressed in terms of monomers,
constituting the polyamide include primary diamines having an aromatic
ring(s), such
as m-phenylenediamine, p-phenylenediamine, benzidine, methylenebisdianiline,
4,4'-
diaminobiphenyl ether, dianisidine, 3,3',4-tiaminobiphenyl ether, 3,3',4,4'-
tetraaminobiphenyl ether, 3,3'-dioxybenzidine, 1,8-naphthalenediamine, m(p)-
monomethylphenylenediamine, 3,3'-monomethylamino-4,4'-diaminobiphenyl ether,
4,N,N'-(4-aminobenzoyl)-p(m)-phenylenediamine-2,2'-bis(4-aminophenyl
benzimidazol), 2,2'-bis(4-aminophenyl benzoxazol), 2,2'-bis(4-aminophenyl
benzothiazole); and secondary diamines such as piperazine and piperidine and
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derivatives thereof; and, in particular, a nanofiltration membrane having a
functional
layer composed of a cross-linked polyamide containing piperazine or
piperidine,
expressed in terms of monomers, has a high pressure resistance and durability
as well
as heat resistance and chemical resistance, and is therefore preferably used.
The
functional layer of the nanofiltration membrane more preferably comprises a
cross-
linked piperazine polyamide or a cross-linked piperidine polyamide as a major
component; the polyamide still more preferably comprises a cross-linked
piperazine
polyamide or a cross-linked piperidine polyamide as a major component and
further
comprises a constituting component represented by the Formula [I]; and the
polyamide still more preferably comprises a cross-linked piperazine polyamide
as a
major component and further comprises a constituting component represented by
the
Formula [I]. Further, preferably, in the Formula [I], n=3. Examples of the
nanofiltration membrane comprising a cross-linked piperazine polyamide as a
major
component and further comprises a constituting component represented by the
Formula [I] include the one described in JP 62-201606 A, and particular
examples of
the nanofiltration membrane include a cross-linked piperazine polyamide
nanofiltration membrane UTC60 manufactured by TORAY INDUSTRIES, INC.
[0021]
A nanofiltration membrane is generally used as a spiral-wound membrane
element, and the nanofiltration membrane used in the present invention can
also be
preferably used a spiral-wound membrane element. Particular examples of a
preferred nanofiltration membrane which may be used include SU-2 10, SU-220,
SU-
600 and SU-6 10, which are nanofiltration modules manufactured by TORAY
INDUSTRIES, INC. using UTC60 manufactured by the same manufacturer, which
nanofiltration modules have a polyamide functional layer comprising a cross-
linked
piperazine polyamide as a major component and further a constituting component
represented by the Formula [I]. Further particular examples of the membrane
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include nanofiltration membranes NF-45, NF-90, NF-200 and NF-400 manufactured
by FilmTec Corporation, which have a functional layer made of a cross-linked
piperazine polyamide, and nanofiltration membranes NF99, NF97 and NF99HF
manufactured by Alfa-Laval, which have a polyamide functional layer.
5 [0022]
In the present invention, the filtration of the butanol-containing solution
through a nanofiltration membrane may be carried out under pressure. With a
filtration pressure lower than 0.1 MPa, the membrane permeation flux
decreases, and
with a filtration pressure higher than 8 MPa, the membrane is damaged.
Therefore,
10 the filtration pressure is preferably within the range of 0.1 MPa to 8 MPa,
and, in
cases where it is within the range of 0.5 MPa to 7 MPa, the membrane
permeation
flux is high, so that butanol can be allowed to pass through the membrane
efficiently
with less possibility of causing damage to the membrane. A filtration pressure
of 1
MPa to 6 MPa is especially preferred.
[0023]
In the present invention, in the filtration of a butanol-containing solution
through a nanofiltration membrane, the recovery of butanol can be increased by
returning the retentate to the feed solution and repeating the filtration. The
recovery
of butanol can be calculated by measuring the total amount of butanol
contained
before the nanofiltration and the total amount of butanol permeated through
the
nanofiltration membrane, followed by calculation by Equation 1.
[0024]
Recovery of butanol (%) = (total amount of butanol permeated through
nanofiltration membrane / total amount of butanol contained before
nanofiltration) x
100 ... (Equation 1).
[0025]
In terms of the membrane separation performance of the nanofiltration
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membrane used in the present invention, the membrane preferably shows a salt
rejection rate of not less than 45% when an aqueous sodium chloride solution
(500
mg/L) at 25 C, pH 6.5 is filtered under a filtration pressure of 0.75 MPa.
Here, the
salt rejection rate can be calculated by measuring the salt concentration of
the
permeated aqueous sodium chloride solution, followed by calculation by
Equation 2.
[0026]
Salt rejection rate = 100 x { 1-(salt concentration of permeate / salt
concentration of feed solution} ... (Equation 2).
[0027]
Further, in terms of the permeation performance of the nanofiltration
membrane, the membrane preferably shows a membrane permeation flux (m3/(m2
day)) of not less than 0.3 with aqueous sodium chloride solution (500 mg/L)
under a
filtration pressure of 0.3 MPa. The membrane permeation flux can be calculated
by
measuring the amount of the permeant, the length of time required for
collecting this
amount of the permeant, and the membrane area, followed by calculation by
Equation 3.
[0028]
Membrane permeation flux (m3/(m2 = day)) = amount of permeant /
(membrane area x collection time) ... (Equation 3).
[0029]
In the present invention, examples of the impurities separated from the
butanol-containing solution into the feed flow by the nanofiltration membrane
include inorganic substances such as calcium, sodium, sulfuric acid, nitric
acid and
phosphoric acid; sugars such as glucose, fructose, xylose, sucrose, galactose
and
starch; and proteins; and mixtures thereof can also be preferably separated.
[0030]
The permeability of the nanofiltration membrane to butanol in the present
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invention can be evaluated by calculating the permeation rate of butanol. The
permeation rate of butanol can be calculated by measuring the concentration of
butanol (butanol concentration of feed solution) contained in the feed
solution
(butanol-containing solution) and the concentration of butanol (butanol
concentration
of permeate) contained in the permeate (butanol solution) by analysis
represented by
high performance liquid chromatography and gas chromatography, followed by
calculation by Equation 4.
[0031]
Permeation rate of butanol (butanol concentration of permeate / butanol
concentration of feed solution) x 100 ... (Equation 4).
[0032]
The permeate from the nanofiltration membrane is preferably concentrated in
cases where the concentration of the substance of interest is low. In terms of
the
method for concentrating the permeate from the nanofiltration membrane,
methods
using a concentrator represented by an evaporator are commonly employed and
also
applicable to the present invention, but, since the heat capacity of water is
much
larger than those of organic solvents, enormous energy and time are required
for the
concentration. On the other hand, concentration by a reverse osmosis membrane
is
superior to concentration using an evaporator in view of reduction in the
energy/cost,
and therefore preferably applied to the present invention.
[0033]
The reverse osmosis membrane in the present invention is a filter for
removing ions and/or low molecular-weight molecules using a pressure
difference
larger than the osmotic pressure of the solution to be treated, and examples
thereof
which can be used include cellulose membranes such as those made of cellulose
acetate and membranes wherein a multifunctional amine compound and a
multifunctional acid halide were polycondensed to provide a separation
functional
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layer made of a polyamide on a microporous support membrane. In order to
suppress dirt, that is, fouling, on the surface of the reverse osmosis
membrane, a low-
fouling reverse osmosis membrane, which is mainly for sewage treatment, can
also
be preferably employed, which reverse osmosis membrane is prepared by covering
the surface of a separation functional layer made of a polyamide with an
aqueous
solution of a compound having at least one reactive group reactive with an
acid
halide group, thereby allowing acid halide groups remaining on the surface the
separation functional layer to form covalent bonds with the reactive groups.
Since
most of the divalent ions have been removed in the step of filtering through
the
nanofiltration membrane of the present invention, stable membrane
concentration can
be carried out without formation of scale on the surface of the reverse
osmosis
membrane.
[0034]
Further, the term "filtering through the reverse osmosis membrane" means
that the butanol-containing solution permeated through the nanofiltration
membrane
is concentrated by being allowed to pass through the reverse osmosis membrane,
followed by collecting the resulting solution containing butanol in the
concentrate
flow.
[0035]
Examples of the reverse osmosis membrane preferably used in the present
invention include composite membranes having a cellulose acetate polymer as a
functional layer (hereinafter referred to as cellulose acetate reverse osmosis
membranes) and composite membranes having a polyamide functional layer
(hereinafter referred to as polyamide reverse osmosis membranes). Here,
examples
of the cellulose acetate polymer include polymers prepared with organic acid
esters
of cellulose such as cellulose acetate, cellulose diacetate, cellulose
triacetate,
cellulose propionate and cellulose butyrate, which may be used solely, as a
mixture,
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or as a mixed ester. Examples of the polyamide include linear polymers and
cross-
linked polymers constituted by aliphatic and/or aromatic diamine monomers.
Examples of the form of the membrane which may be used as appropriate include
the
flat membrane, spiral-wound membrane and hollow fiber membrane.
[0036]
Particular examples of the reverse osmosis membrane used in the present
invention include polyamide reverse osmosis membrane modules manufactured by
TORAY INDUSTRIES, INC., such as low-pressure type modules SU-710, SU-720,
SU-720F, SU-710L, SU-720L, SU-720LF, SU-720R, SU-71 OP and SU-720P, as well
as high-pressure type modules SU-810, SU-820, SU-820L and SU-820FA containing
UTC70 as the reverse osmosis membrane; cellulose acetate reverse osmosis
membranes manufactured by the same manufacturer SC-L100R, SC-1,200R, SC-
1100, SC-1200, SC-2100, SC-2200, SC-3100, SC-3200, SC-8100 and SC-8200;
NTR-759HR, NTR-729HF, NTR-70SWC, ES10-D, ES20-D, ES20-U, ESI5-D,
ES 15-U and LF10-D manufactured by Nitto Denko Corporation; RO98pHt, R099,
HR98PP and CE404OC-30D manufactured by Alfa-Laval; GE Sepa manufactured by
GE; and BW30-4040, TW30-4040, XLE-4040, LP-4040, LE-4040, SW30-4040 and
SW30HRLE-4040 manufactured by FilmTec Corporation.
[0037]
In the present invention, filtration of the permeate from the nanofiltration
membrane with the reverse osmosis membrane is carried out under pressure, and
the
filtration pressure is preferably within the range of 1 MPa to 8 MPa since,
with a
filtration pressure lower than 1 MPa, the membrane permeation flux decreases,
and
with a filtration pressure higher than 8 MPa, the membrane is damaged.
Further,
since, with a filtration pressure within the range of 1 MPa to 7 MPa, the
membrane
permeation flux is high, the butanol solution can be efficiently concentrated.
The
filtration pressure is most preferably within the range of 2 MPa to 6 MPa
since there
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is less possibility of causing damage to the membrane in this case.
[0038]
Further, in the present invention, by subjecting the permeate from the
nanofiltration membrane to a step of distilling the permeate, highly pure
butanol can
5 be obtained. The distillation step is carried out preferably under a reduced
pressure
of not less than 1 Pa and not more than atmospheric pressure (normal pressure,
about
101 kPa), more preferably under a reduced pressure of not less than 100 Pa and
not
more than 15 kPa. In cases where the distillation is carried out under reduced
pressure, the distillation temperature is preferably 20 C to 200 C, more
preferably
10 50 C to 150 C.
Examples
[0039]
The present invention will now be described more concretely by way of
Examples, but the present invention is not restricted to the Examples below.
15 [0040]
Reference Example 1
Evaluation of Permeability of Nanofiltration Membrane to Butanol
To 20 L of ultrapure water, 20 g of n-butanol (both of which were
manufactured from Wako Pure Chemical Industries, Ltd.) was added, and the
resulting mixture was stirred at 25 C for 30 minutes, thereby preparing l Og/L
butanol
solution. Subsequently, 20 L of the thus prepared aqueous butanol solution was
fed
to a feed tank 1 of the membrane filtration apparatus shown in Fig. 1. As the
904
nanofiltration membrane indicated by Symbol 7 in Fig. 2, each of a cross-
linked
piperazine polyamide nanofiltration membrane "UTC60" (nanofiltration membrane
1; manufactured by TORAY INDUSTRIES, INC.), a polyamide nanofiltration
membrane "NF99" (nanofiltration membrane 2, manufactured by Alfa-Laval), a
cellulose acetate nanofiltration membrane "GE Sepa" (nanofiltration membrane
3;
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manufactured by GE Osmonics) , and a cross-linked piperazine polyamide
nanofiltration membrane "NF-400" (nanofiltration membrane 4; manufactured by
FilmTec Corporation) was placed in a cell made of stainless steel (SUS316),
and the
temperature of the feed solution was adjusted to 25 C and the pressure of a
high-
pressure pump 3 was adjusted to 1 MPa, followed by collecting the permeate 4.
The concentration of butanol contained in each of the feed tank 1 and the
permeate 4
was analyzed with a gas chromatography: GC-2010 (manufactured by Shimadzu
Corporation) under the following conditions, thereby calculating the
permeation rate
of butanol.
Column: TC-1, 0.53 mm I.D. x 15 m, df l.5 pm (GL Science)
Mobile phase: helium gas (7.9 mL/min., 50 to 100 C: 5 C/min.)
Detection: FID 250 C.
[0041]
The results are shown in Table 1.
[0042]
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0
0)
00 0 N rn 00
0 0
y rn v .-~ 00
0 00 t~ 0; 00
~ O O O O
U U
U
a)
c
N U 1
OR 0
U
171 0 o
0
0
0 c oll p, H
w H Q
N O M O
0 cr-O g,
o O E, o o
z z z
CA 02735505 2011-03-30
18
[0043]
As shown by the results in Table 1, butanol permeated through any of the
nanofiltration membranes. Further, since the permeation rates of butanol were
high,
a possibility that butanol can be purified from nonorganic salts and sugars at
high
efficiency was suggested. The differences in the permeation rate of butanol
among
the different types of the membrane materials were small, but the cross-linked
piperazine polyamide nanofiltration membranes showed higher permeation rates
of
butanol, and the polyamide nanofiltration membrane showed a somewhat lower
permeation rate.
[0044]
(Examples 1 to 9)
Purification of Butanol from Fermentation Broth Using Nanofiltration Membrane
<n-Butanol Fermentation>
Two liters of the medium shown in Table 2 was prepared and adjusted to pH
6.5. The resulting medium was autoclaved (121 C, 15 minutes) and then allowed
to
cool to 37 C, followed by addition of 25 mL of inoculum thereto to carry out
main
culture. The inoculum used was prepared by culturing Clostridium butylicum at
37 C for 24 hours in the same medium as that shown in Table 2 except that the
glucose concentration was 50 g/L. The main culture was carried out by
anaerobic
culture under stirring at 100 rpm at 37 C for 72 hours. After the culture, the
bacterial cells were precipitated by centrifugation, and the culture
supernatant was
collected as an n-butanol-containing solution.
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[0045]
Table 2
Medium component Concentration [g/L]
Glucose 150
KH2PO4 0.8
K2HPO4 0.8
MgSO4 2
MnSO4 = H2O 0.01
FeSO4.7H2O 0.01
NaCl 1
Cysteine 0.5
Asparagine 2
Yeast extract 5
[0046]
<Purification of n-Butanol with Nano filtration Membrane>
Thereafter, 2 L of the culture supernatant obtained as described above was fed
to the feed tank 1 of the membrane filtration apparatus shown in Fig. 1. As
the
90~ nanofiltration membrane indicated by Symbol 7 in Fig. 2, each of the above
nanofiltration membranes 1 to 3 was placed in a cell made of stainless steel
(SUS316), and the pressure by the high-pressure pump 3 was adjusted to 1 MPa,
3
MPa or 5 MPa, followed by collecting the permeate 4 under the respective
pressures.
The concentration of n-butanol contained in each of the feed tank 1 and the
permeate
4 was analyzed under the same conditions as those in Reference Example 1 using
a
gas chromatography (manufactured by Shimadzu Corporation). Further, the sugar
concentrations (glucose, fructose and sucrose) were analyzed with a high
performance liquid chromatography (manufactured by Shimadzu Corporation) under
the following conditions.
Column: Luna 5u NH2 100A (manufactured by Phenomenex, Inc.), 30 C
Mobile phase: water:acetonitrile = 1:3, 0.6 mL/min.
Detector: RI.
[0047]
CA 02735505 2011-03-30
The results are shown in Table 3.
[0048]
CA 02735505 2011-03-30
21
o 0
O O O O O O O O tn c:) O O
o =N ON ON ON O, C ON rn ON C, Q, O1 C
=~ al H
cd
C." a)
CO O fl N v v~ N O ao r k L
~D~D 0 0 0 0 0 O O O O O
cn
c
E i v) vn vn N N N N N- N N- N N
a)
a)
o ..
o a N 00 -, \O N CO N Q, N
o, N ~r 00 \~O d ri Co tf 4
00 00 00 tN ID lD O, 00 00 00 00 00
a) H
w
a)
o
O 00 of Q\ \IR N & ct 00 O V7
O\ 00 00 N ,0 "0 0, Co 00 00 00 00
W a
c:) C) O O o 0 C) 0 O o o O
a)
a)
~C b N M 0 M M 'd' N N M 1r 't O
N oo N O CO ' '-1 ~t N v 1 ,0 O
Gi -, ~t N N cn 00 N vi 00 '-+ N
C
O r~
N z
Q Q C C C
o o D N o o
ai ^ a) ,~ a) cd :, a) o
z
N M ct cn ,O N Co Q, O N
sc x x x sc k k X
F' W W W W W W W W W W W W
CA 02735505 2011-03-30
22
[0049]
As shown in Table 3, with all the nanofiltration membranes and under all the
filtration pressures, the sugars were removed and n-butanol solutions were
obtained.
Further, since a colorless transparent solution was obtained from the brown-
colored
broth, it was assumed that the other impurities were also mostly removed.
Further,
when an operation in which 1.5 L of the permeate was collected and 1.5 L of
distilled
water was added thereto, followed by collecting the permeate again was
repeated
three times in order to increase the recovery of n-butanol shown by (Equation
1), the
recovery became 94%.
[0050]
<Distillation from Solution Concentrated Using Reverse Osmosis Membrane >
Among the n-butanol solutions obtained as described above, those of
Example 2, Example 5, Example 8 and Example 11 were subjected to the study. To
the feed tank 1 of the membrane filtration apparatus shown in Fig. 1, 4.5 L of
the
solution was fed. As the 904 reverse osmosis membrane indicated by Symbol 7 in
Fig. 2, a polyamide reverse osmosis membrane (UTC-70, manufactured by TORAY
INDUSTRIES, INC.) was attached to a cell made of stainless steel (SUS316), and
membrane filtration was carried out by adjusting the pressure by the high-
pressure
pump 3 to 5 MPa and the temperature of the feed solution to 35 C, thereby
removing
4.4 L of the permeate 4 from the reverse osmosis membrane. One hundred
milliliter
of the thus obtained concentrate was subjected to atmospheric distillation at
117 C.
The results of the distillation are shown in Table 4.
[0051]
CA 02735505 2011-03-30
23
0
rn Oo Iq O,
C O: o; of
rn o. rn ON
U
-ts
0 0
rn rn rn C
.~
0
'.o M 00
V U O1 .-+ 00 00
~. M M M M
o
U
O
O
00 0\ '
06 06 06
O
U
N
c2
p p p p
o o o o
z z El z 02 z E
N yr 00
W W W W
CA 02735505 2011-03-30
24
[0052]
From these results, it was shown that the present invention allows highly
efficient production of high-purity n-butanol at low cost.
[0053]
(Comparative Example 1)
Purification of 1,3-Propanediol with Nanofiltration Membrane
A model broth containing 1,3-propanediol was filtered through a
nanofiltration membrane as follows.
[0054]
In terms of the culture medium, 2.5 L of a culture medium containing 60 g/L
of Yutosei (MUSO Co., Ltd.) and 1.5 g/L of ammonium sulfate was prepared and
then autoclaved (121 C, 15 minutes). First, an yeast strain NBRC 10505 was
cultured in 5 ml of the above raw material sugar medium in a test tube
overnight with
shaking (pre-preculture). The pre-preculture broth was inoculated to 100 ml of
a
fresh lot of the above raw material sugar medium, and culture was carried out
in a
500-m1 Sakaguchi flask for 24 hours with shaking (preculture). The preculture
broth was added to 2L of the above raw material sugar medium, and culture was
carried out while adjusting temperature and pH in ajar fermenter. The
operating
conditions of the jar fermenter were as shown below.
[0055]
Reaction vessel volume (amount of lactic acid fermentation medium), 2 (L);
temperature adjustment, 30 ( C); ventilation volume for the reaction vessel,
0.2
(L/min.); stirring rate of the reaction vessel, 400 rpm; pH adjustment,
adjusted to pH
5 with 1 N calcium hydroxide.
[0056]
After 24 hours of the culture, the fermentation broth was centrifuged to
remove the yeast cells, and the supernatant was collected. To this broth, 1,3-
CA 02735505 2011-03-30
propanediol was added to 10 g/L. This broth was subjected to treatment with
the
nanofiltration membrane in the same manner as in the above Example 2. The
resultant was further concentrated using the reverse osmosis membrane in the
same
manner as in the above Example 2, followed by distillation under reduced
pressure (5
5 mmHg) at 97 C.
[0057]
As a result, the distillation yield of 1,3-propanediol was 95%, and the GC
purity was 99.7%. Thus, it was suggested that usage of the nanofiltration
membrane
allows purification of high-purity 1,3-propanediol. However, since the
membrane
10 permeability of 1,3-propanediol with respect to the nano filtration
membrane I
(UTC60) was as low as 26%, the yield of 1,3-propanediol was lower than that of
butanol. Thus, it was shown that, although 1,3-propanediol and butanol
described
in Example 2 have almost the same molecular weights, n-butanol shows a higher
permeation rate with respect to the nanofiltration membrane, so that butanol
is a
15 compound more suitable for purification with the nanofiltration membrane.
