U.S. patent application number 12/606473 was filed with the patent office on 2010-02-25 for apparatus for producing lactic acid.
This patent application is currently assigned to Heiji ENOMOTO. Invention is credited to Heiji ENOMOTO, Fangming Jin, Kenji Kakeda, Hisanori Kishida, Takehiko Moriya, Yoshitoshi Sekiguchi.
Application Number | 20100047140 12/606473 |
Document ID | / |
Family ID | 37595288 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100047140 |
Kind Code |
A1 |
ENOMOTO; Heiji ; et
al. |
February 25, 2010 |
APPARATUS FOR PRODUCING LACTIC ACID
Abstract
An apparatus for producing lactic acid according to the
invention comprises a reactor carrying out: subjecting glycerin to
a hydrothermal reaction under an alkaline condition, supplying an
alkaline solution comprising glycerin; and continuously producing
lactic acid, wherein glycerin is subjected to a hydrothermal
reaction under an alkaline condition at a temperature in the range
of 150 to 400.degree. C. and under pressure equal to or more than
the saturated vapor pressure at the temperature. The glycerin
produced from plant fats, animal fats or the like or pure product
synthesized chemically or a discharge containing glycerin generated
at the production of diesel fuel oil from fats, in which the fats
are subjected to a transesterification with alcohol in the presence
of an alkali catalyst in order to obtain fatty acid ester is
preferably used as a starting material.
Inventors: |
ENOMOTO; Heiji; (Sendai-shi,
JP) ; Jin; Fangming; (Pudong new District Shanghai,
CN) ; Moriya; Takehiko; (Sendai-shi, JP) ;
Kakeda; Kenji; (Izumiotsu-shi, JP) ; Sekiguchi;
Yoshitoshi; (Maizuru-shi, JP) ; Kishida;
Hisanori; (Osaka-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Heiji ENOMOTO
Sendai-shi
JP
HITACHI ZOSEN CORPORATION
Osaka-shi
JP
TOHOKU ELECTRIC POWER CO., INC.
Sendai-shi
JP
|
Family ID: |
37595288 |
Appl. No.: |
12/606473 |
Filed: |
October 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11994263 |
May 28, 2008 |
|
|
|
PCT/JP2006/312967 |
Jun 29, 2006 |
|
|
|
12606473 |
|
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|
Current U.S.
Class: |
422/198 |
Current CPC
Class: |
C01B 2203/02 20130101;
B01J 19/285 20130101; B01J 19/0013 20130101; C11C 3/003 20130101;
C01B 2203/1217 20130101; Y02E 50/13 20130101; C07C 51/02 20130101;
C07C 51/41 20130101; B01J 2219/00006 20130101; B01J 2219/00099
20130101; B01J 2219/00094 20130101; C01B 3/32 20130101; C01B
2203/0465 20130101; C01B 2203/066 20130101; C01B 2203/04 20130101;
C01B 3/50 20130101; Y02E 50/10 20130101; C07C 51/02 20130101; C07C
59/08 20130101; C07C 51/41 20130101; C07C 59/08 20130101 |
Class at
Publication: |
422/198 |
International
Class: |
B01J 19/00 20060101
B01J019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2005 |
JP |
2005-189182 |
Claims
1. An apparatus for producing lactic acid, wherein the apparatus
comprises a reactor carrying out: subjecting glycerin to a
hydrothermal reaction under an alkaline condition, supplying an
alkaline solution comprising glycerin; and continuously producing
lactic acid.
2. The apparatus for continuously producing lactic acid according
to claim 1, wherein the reactor carries out the hydrothermal
reaction at a temperature in a range of 150 to 400.degree. C. and
at a pressure equal to or more than a saturated vapor pressure at
the reaction temperature, wherein water maintains a liquid phase
state.
3. The apparatus for producing lactic acid according to claim 1,
wherein the apparatus further comprises a gas-liquid separator that
separates an alkaline solution comprising lactic acid from a
hydrogen gas generated in the reactor.
4. The apparatus for producing lactic acid according to claim 1,
wherein the apparatus further comprises an electrodialysis unit
comprising a bipolar membrane that separates an alkaline solution
comprising lactic acid into a solution comprising lactic acid and
an alkaline solution.
5. The apparatus for producing lactic acid according to claim 1,
wherein the apparatus further comprises a calcium crystallizer that
separates an alkaline solution comprising lactic from the
gas-liquid separator into a solid of calcium lactate and an
alkaline solution according to a crystallization process.
6. The apparatus for producing lactic acid according to claim 1,
wherein the apparatus further comprises a high-pressure pump, a
heat exchanger, and a valve for controlling a pressure and a tank
for storing a raw material.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of prior U.S.
patent application Ser. No. 11/994,263, the disclosure of which is
incorporated by reference in its entirety. U.S. Ser. No. 11/994,263
is a National Stage of PCT/JP2006/312967 filed on Jun. 29, 2006
which claims the benefit of priority under 35 U.S.C .sctn.119 from
Japanese Patent Application No. 2005-189182, filed Jun. 29, 2005,
the disclosures of which are incorporated herein by reference in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates to a process for producing lactic acid
from glycerin as a raw material and an apparatus for producing
lactic acid.
[0004] 2. Background Art
[0005] Recently, in Europe, U.S.A and other countries, a diesel
fuel oil produced from a plant oil as a raw material (so-called a
bio-diesel fuel: BDF) is actively produced. Such a diesel fuel oil
is composed of a fatty acid ester taken out from a fat consisting
of a triester of glycerin by performing a transesterification of
the fat with alcohol in the presence of an alkaline catalyst. In
this technology, the fatty acid ester taken out from fats can be
effectively used as a bio-diesel fuel oil. However, glycerin
containing the alkaline catalyst is generated as a by-product at
the production thereof in an amount of substantially 1/10 of the
raw material by weight; accordingly, there is a problem in how to
process the glycerin containing the alkaline catalyst.
[0006] Lactic acid is a raw material of plastics (lactic acid
polymer). The lactic acid polymer is considered as a material which
is applicable to sheets used for agriculture or civil engineering,
packages, shopping bags, car interiors and so on. Since the lactic
acid polymer is a biodegradable material (a material which can be
decomposed by microorganisms), it is gathering attention as one of
solutions of a waste disposal. Furthermore, since the lactic acid
polymer is derived from organisms, it is gathering an attention in
the saving of the petroleum resources and in the reduction of a
generation amount of CO.sub.2.
[0007] Accordingly, in the current situation where the wastes are
increasing, from the viewpoint of reducing an amount of wastes as
well, the lactic acid polymer is gathering attention and expected
to increase in future demand.
[0008] As a conventional process for producing lactic acid that is
a raw material of lactic acid polymer-based plastics, a
fermentation process and a synthesis process can be cited.
[0009] The fermentation process is a process where sucrose,
glucose, starch or the like derived from cultivated plants such as
corns, sugarcanes, cassayas and so on are used as raw materials and
converted into lactic acid by a fermentation action of lactic
bacteria.
[0010] As the synthesis process, the following processes can be
cited: (i) a process where hydrocyanic acid is allowed to react
with acetaldehyde to produce cyanohydrin, followed by hydrolyzing
the resultant product to obtain lactic acid, and (ii) a process
where acetaldehyde is allowed to react with carbon monoxide under
high pressure to obtain lactic acid.
[0011] However, in both processes, there is a problem in that the
cost price of lactic acid becomes high since expenses for obtaining
lactic acid (such as land and cultivation period for cultivating
cassayas and so on, a time period necessary for fermenting sugars,
a large-scale fermentation tank necessary for fermentation,
disposal of waste generated after lactic acid was obtained and so
on) are very large; accordingly a process for inexpensively
obtaining lactic acid is in demand.
[0012] Glycerin is produced as a by-product when the bio-diesel
fuel oil is produced as mentioned above. Furthermore, it is a
constituent element of fats such as plant fats, animal fats and so
on and contained a lot in a natural world. That is, in an
industrial field relating to fats, glycerin can be produced by a
removal from various kinds of fats and can be procured in a large
amount.
[0013] Accordingly, if lactic acid can be produced by a process
using glycerin which is a material capable of being inexpensively
procured, such a process is desirable because the cost for
producing lactic acid can be reduced.
[0014] A patent document JP-A-11-342379 discloses a process for
obtaining organic acids from a fish meat. The process for producing
organic acids according to the Document uses a fish meat as a raw
material and lactic acid is cited as one of organic acids obtained
variously.
[0015] However, according to the process, the resultant lactic acid
is a by-product and is produced as one of organic acids obtained
variously. That is, the process is not an efficient process for
obtaining lactic acid.
Patent Document 1: JP-A-11-342379
SUMMARY OF THE INVENTION
Disclosure of the Invention
Problem to be Solved by the Invention
[0016] The present invention was made in view of the
above-mentioned situations and intends to provide a process for
inexpensively producing lactic acid of which demand is industrially
expected, in which glycerin obtained from a wide range including
pure products, food waste oil and the like is used.
Means for Solving the Problem
[0017] In order to overcome the above mentioned problem, a process
for producing lactic acid according to the present invention is
characterized in that glycerin is subjected to a hydrothermal
reaction under an alkaline condition.
[0018] In the process according to the invention, the glycerin
produced from plant fats, animal fats or the like or pure product
synthesized chemically is preferably used as a starting
material.
[0019] In the process according to the invention, as the glycerin,
a discharge containing glycerin generated at the production of a
diesel fuel oil from fats, in which the fats are subjected to a
transesterification with alcohol in the presence of an alkaline
catalyst in order to obtain fatty acid ester, is preferably used as
a raw material.
[0020] In the process according to the invention, the process
comprises a step of performing a gas-liquid separation where an
alkali solution containing lactic acid is separated from a hydrogen
gas, both of which are generated in the hydrothermal reaction.
[0021] In the process according to the invention, preferably, the
process further comprises a step of concentrating lactic acid and
an alkaline component present in an aqueous solution after the
hydrothermal reaction according to an electrodialysis process.
[0022] In the process according to the invention, preferably, the
process further comprises a step of separating lactic acid from the
alkaline component present in the aqueous solution after the
hydrothermal reaction according to an electrodialysis process with
a bipolar membrane.
[0023] In the process according to the invention, an alkaline
component for making the glycerin under an alkaline condition is
preferably supplied when the hydrothermal reaction is carried
out.
[0024] In the process according to the invention, the alkaline
component is preferably supplied in several times.
[0025] In the process according to the invention, the alkaline
component separated from the alkaline solution containing lactic
acid is preferable used.
[0026] In the process according to the invention, unreacted
glycerin dissolved in a solution containing the alkaline component
is preferably recovered in order to reuse it as a raw material for
lactic acid.
[0027] In the process according to the invention, a generated
hydrogen gas is preferably used as a gas to be used for a fuel
battery.
[0028] Furthermore, an apparatus for producing lactic acid
according to the invention is equipped with a reactor where
glycerin is subjected to a hydrothermal reaction under an alkaline
condition, wherein a set of procedures from a supply of an alkaline
solution containing glycerin to a production of lactic acid are
continuously carried out.
[0029] In the apparatus according to the invention, preferably, the
apparatus is further equipped with a gas-liquid separator that
separates an alkaline solution containing lactic acid from a
hydrogen gas, generated in the reactor.
[0030] In the apparatus according to the invention, preferably, the
apparatus is further equipped with an electrodialysis unit with a
bipolar membrane that separates an alkaline solution containing
lactic acid from the gas-liquid separator into a solution
containing lactic acid and an alkaline solution.
[0031] In the apparatus according to the invention, preferably, the
apparatus is further equipped with a calcium crystallizer that
separates an alkaline solution containing lactic from the
gas-liquid separator into a solid of calcium lactate and an
alkaline solution according to a crystallization process.
EFFECT OF THE INVENTION
[0032] According to the invention, following effects can be
obtained.
[0033] (1) Lactic acid can be produced from glycerin discarded from
plants for a bio-deisel, oleochemical plants and so on as a raw
material. (so far, crops have to be cultivated).
[0034] (2) In many cases, an alkali used as a catalyst is contained
in the glycerin discarded from plants for bio-diesel, oleochemical
plants and so on, but such alkali can also be used efficiently in
the present invention.
[0035] (3) A time required for a conversion of glycerin into lactic
acid is from several minutes to several hours (an existing
fermentation process necessarily takes a reaction time of several
days).
[0036] (4) A conversion rate of lactic acid from glycerin is such
high as 90% and a reaction by-product is scarce. Accordingly,
treatment of waste water is relatively easily applied (in an
existing fermentation process, a culture solution for lactic acid
fermenter has to be treated).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Best Mode for Carrying Out the Invention
[0037] In what follows, methods for utilizing a discharge
containing glycerin will be described in detail with reference to
the drawings.
Embodiment 1
[0038] FIG. 1 is a flow sheet explaining a process performed using
a continuous reactor that is an example of a process for producing
lactic acid in accordance with the present invention.
[0039] In the process for producing lactic acid according to the
present invention, in the beginning, glycerin that is a raw
material is introduced into a tank for storing a raw material (1)
together with water and an alkaline component such as sodium
hydroxide or the like. An alkaline solution containing glycerin
stored in the tank for storing a raw material (1) goes through a
high-pressure pump (2), a pre-heater (3), a reactor (4) and a
cooler (5) sequentially, and, after going through a valve for
controlling a pressure (7), finally reaches a tank for storing an
alkaline solution containing lactic acid (6).
[0040] The respective configurations are described bellow.
[0041] The tank for storing a raw material (1) is a tank where an
alkaline solution containing a desired amount of glycerin and
having desired alkalinity is prepared by adding appropriate amount
of glycerin, an alkaline component and water, respectively.
[0042] Glycerin added to the tank for storing a raw material (1)
may be a product derived from a decomposition of fats such as plant
fats, animal fats or the like or a pure product synthesized
chemically. Alternatively, glycerin as a raw material may contain
impurities. For instance, as such a glycerin containing impurity,
glycerin contained in fats that can be recovered from rendering of
fish meats and animal meats, or discharge from plants for a
bio-diesel fuel oil, plants for soap and so on can be cited.
[0043] A concentration of glycerin is in the range of 1 to 80% by
weight and preferably 50% by weight or less from the viewpoint of
improving the fluidity owing to lowering of the viscosity.
[0044] As the alkaline component, any alkaline substances can be
used. Examples thereof include sodium hydroxide, potassium
hydroxide, ammonia and so on. Furthermore, a basic solid catalyst
such as calcium hydroxide can be used as well. A preferable
concentration of an alkaline component is in the range of 0.1 to
50%.
[0045] The high-pressure pump (2) applies predetermined pressure on
the alkaline solution containing glycerin from the tank for storing
a raw material (1) and water is supplied quantitatively.
[0046] The pre-heater (3) preliminarily heats the alkaline solution
containing glycerin before it is introduced in a reactor (4) where
a reaction is carried out under a high temperature and high
pressure condition. The pre-heater (3) may have a heater for
preliminarily heating. Alternatively, the alkaline solution
containing glycerin may be heated by a heat exchange at a cooler
(5) provided downstream of the reactor (4).
[0047] In the reactor (4), the alkaline solution containing
glycerin is put under a high temperature and high pressure
condition to convert glycerin in the alkaline solution to lactic
acid. Specifically, a temperature is set in the range of 150 to
400.degree. C. and pressure is set at pressure equal to or more
than the saturated vapor pressure of water at the above temperature
range so that water may retain in a liquid phase.
[0048] When a reaction is carried out at certain temperature at
pressure lower than saturated vapor pressure of water, all water
vaporizes and thereby an alkaline component precipitates as a solid
salt. In the reaction, glycerin is reacted with a hydroxide ion
OH.sup.- in an aqueous solution having alkalinity to convert it
into lactic acid; accordingly, unless in a state where water
retains a liquid phase, a reaction is difficult to proceed.
Accordingly, a reaction pressure is desirably set to a pressure
equal to or more than the saturated vapor pressure at a reaction
temperature. A reaction time is largely different depending on a
reaction temperature. The higher the reaction temperature is, or
the higher the alkaline concentration is, the shorter the reaction
time for converting it into lactic acid is.
[0049] Glycerin in the alkaline solution is converted into lactic
acid by a reaction in the reactor (4). After cooled by the cooler
(5), the resultant alkaline solution containing lactic acid is
transported to the tank for storing an alkaline solution containing
lactic acid (6) and stored in the tank for storing an alkaline
solution containing lactic acid (6). The valve for controlling a
pressure (7) is disposed between the reactor (4) and the tank for
storing an alkaline solution containing lactic acid (6) and the
high-pressure state of the alkaline solution is released by the
valve (7).
[0050] The alkaline solution containing lactic acid stored in the
tank for storing an alkaline solution containing lactic acid (6)
can be efficiently concentrated using an electrodialysis unit when
concentrations of lactic acid and alkaline component are low.
Furthermore, in the case where lactic acid and alkaline component
have to be separated, the alkaline solution containing lactic acid
stored in the tank for storing an alkaline solution containing
lactic acid (6) can be separated into lactic acid and alkaline
component according to a separator with a bipolar membrane. Still
furthermore, in the case where lactic acid and a salt of alkaline
component want to be taken out as solids from the alkaline solution
containing lactic acid stored in the tank for storing an alkaline
solution containing lactic acid (6), lactic acid and the salt of
alkaline component can be taken out as solids according to a
crystallizer.
Embodiment 2
[0051] FIG. 2 is a flow sheet explaining the apparatus for
producing lactic acid according to embodiment 2.
[0052] In the apparatus for producing lactic acid according to
embodiment 2, in the beginning, a discharge containing glycerin
from BDF plants, oleochemical plants and so on is introduced as a
raw material to a tank for storing a raw material (1). The
discharge containing glycerin from BDF plants or the like as a raw
material contains an alkaline component. When a content of the
alkaline component is scarce, an alkaline component such as NaOH or
the like is added appropriately. Furthermore, when an amount of
water is scarce, water is appropriately added.
[0053] An alkaline solution containing glycerin stored in the tank
for storing a raw material (1), after water is appropriately added
thereto, goes through a high-pressure pump (2), a heat exchanger
(3), a reactor (4), the heat exchanger (3), a valve for controlling
a pressure (7) sequentially and is finally supplied to a gas-liquid
separator (5) to separate here the solution into an alkaline
solution containing lactic acid and a hydrogen gas. The tank for
storing a raw material (1), the high-pressure pump (2) and the
reactor (4), shown in FIG. 2, are the same as those of embodiment 1
shown in FIG. 1; accordingly detailed explanations thereof are
omitted.
[0054] In the apparatus for producing lactic acid according to
embodiment 2, after pressurized to predetermined pressure by the
high-pressure pump (2), the alkaline solution containing glycerin
stored in the tank for storing a raw material is supplied to the
heat exchanger (3) to undergo heat-exchange with a gas-liquid
mixture fluid (described later) after the hydrothermal reaction.
Thereafter, the alkaline solution containing glycerin heated in the
heat exchanger (3) is supplied to the reactor (4).
[0055] Glycerin supplied to the reactor is heated by a heating
medium (overheated water vapor, silicone oil or the like)
transported from a heater for the heating medium (6) in order to be
maintained at a predetermined temperature and to undergo a
hydrothermal reaction, which leads to a decomposition of glycerin
into lactic acid and a hydrogen gas.
[0056] The fluid composed of a gas-liquid mixture leaves the
reactor (4). The fluid is heat-exchanged with the alkaline solution
containing glycerin to be supplied to the reactor (4) in order to
lower a temperature and is depressurized by the valve for
controlling a pressure (7) and then supplied to the gas-liquid
separator (5). Since a gas component generated by the hydrothermal
reaction in the reactor (4) is almost hydrogen, a pure hydrogen gas
can be obtained at the gas-liquid separator (5). In addition, since
a liquid component generated by the decomposition of glycerin is
almost alkaline solution containing lactic acid, a pure alkaline
solution containing lactic acid can be obtained. The hydrogen gas
and the alkaline solution containing lactic acid obtained by the
above reaction are taken out from the apparatus after adjusting
their pressures using valves for controlling a pressure (8) and
(9), respectively.
Embodiment 3
[0057] FIG. 3 is a flow sheet explaining the apparatus for
producing lactic acid according to embodiment 3.
[0058] The apparatus for producing lactic acid according to the
embodiment has the same constituents as those of the apparatus for
producing lactic acid according to the above mentioned embodiment
2; accordingly, in the description below, the same constituents as
those of the apparatus for producing lactic acid according to
embodiment 2 are provided with the same reference numerals and
detailed explanations are omitted.
[0059] In the apparatus for producing lactic acid according to
embodiment 3, a discharge containing glycerin from BDF plants,
oleochemical plants and so on is introduced as a raw material into
the tank for storing a raw material (1)
[0060] An alkaline solution containing glycerin stored in the tank
for storing a raw material (1), after water is appropriately added
thereto, goes through a high-pressure pump (2), the heat exchanger
(3), the reactor (4) and the heat exchanger (3) sequentially. After
going through a valve for controlling a pressure (7), the solution
is finally supplied to a gas-liquid separator (5) to separate the
solution into a solution containing sodium lactate and a hydrogen
gas. The solution containing sodium lactate obtained by separation
in the gas-liquid separator (5) is supplied to an electrodialysis
unit with a bipolar membrane (10) in order to separate the solution
into a solution containing lactic acid and an NaOH solution. The
resultant NaOH solution is supplied to the reactor (4) after
storing in the tank for storage (11).
[0061] The apparatus for producing lactic acid according to
embodiment 3 is different from the apparatus for producing lactic
acid according to embodiment 2 in that NaOH is supplied to the
reactor (4) instead of the tank for storing a raw material (1).
This is because the heat exchanger (3) and the high-pressure pump
(2) may be inhibited from corrosion due to high concentration of
NaOH. As a reaction proceeds, lactic acid is generated and consumed
by neutralization with NaOH; accordingly, NaOH is supplied to the
reactor (4) in several times. Such supply of NaOH in several times
prevents the reactor (4) from corrosion due to high concentration
of alkali as well.
[0062] The aqueous solution containing sodium lactate from the
gas-liquid separator (5) has potentially a use as a raw material
for moisturizing agents and chemicals. In the case where it is used
as a raw material for polylactic acid, a separation of the solution
into lactic acid and sodium component has to be performed. In the
apparatus for producing lactic acid according to embodiment 3, the
aqueous solution containing sodium lactate obtained by a separation
at the gas-liquid separator (5) is separated into a solution
containing lactic acid and an NaOH solution in the dialysis unit
with a bipolar membrane (10). The NaOH solution obtained by the
separation using the dialysis unit with a bipolar membrane (10) is
supplied to the reactor (4) after stored in a tank for strage (11).
Alternatively, the NaOH solution obtained by the separation may be
reused as a catalyst for a transesterification of fats.
Embodiment 4
[0063] FIG. 4 is a flow sheet explaining the apparatus for
producing lactic acid according to embodiment 4.
[0064] The apparatus for producing lactic acid according to the
embodiment has the same constituents as those of the apparatus for
producing lactic acid according to embodiment 2; accordingly, the
same constituents as those of the apparatus for producing lactic
acid according to embodiment 2 are provided with the same reference
numerals and the detailed explanations are omitted.
[0065] In the apparatus for producing lactic acid according to
embodiment 4, after the gas-liquid separation of the solution into
a solution containing sodium lactate and a hydrogen gas in the
gas-liquid separator (5), the solution containing sodium lactate
obtained by the separation is supplied to a calcium crystallizer
(12).
[0066] The addition of calcium hydroxide in the calcium
crystallizer (12) results in a precipitation of salt of calcium
lactate according to a formula bellow. The precipitated salt is
separated from an NaOH solution according to a solid-liquid
separation.
2CH.sub.3CH(OH)COONa+Ca(OH).sub.2.fwdarw.(CH.sub.3CH(OH)COO).sub.2Ca.dwn-
arw.+2NaOH
[0067] The NaOH solution obtained by the separation is supplied to
the tank for storing a raw material (1) after stored once in a
storage tank (13). The NaOH solution obtained by the separation at
the calcium crystallizer (12) dissolves unreacted glycerin. A
supply of the NaOH solution to the tank for storing a raw material
(1) leads to a recycle of the unreacted glycerin; accordingly, the
efficiency for a production of lactic acid can be improved.
[0068] The hydrogen gas generated using the apparatus for producing
lactic acid shown in each of embodiments may be combusted as an
off-gas by a flare stack or the like. Alternatively, since the
hydrogen gas generated by each of the processes has high purity as
mentioned above, it may be recovered in order to use as a gas for
fuel batteries, hydrogen engines and so on.
[0069] The lactic acid generated using the apparatus for producing
lactic acid shown in each of the embodiments has a racemic form in
which optical isomers of L and D forms are equally mixed. In order
to make use of lactic acid as a raw material of polylactic acid, an
optical resolution process (racemic resolution) has to be applied
to separate the mixture into an L form and a D form. In the optical
resolution process, known resolution processes such as a
chromatography process, a preferential crystallization process, a
diastereoisomer process, an inclusion complex process and the like
can be made use of.
[0070] In the following examples, the present invention is
explained specifically.
Example 1
[0071] In example 1, a tube made of SUS316 as shown in FIG. 5 and
sealed air-tightly with caps was used as a reactor (10). A volume
thereof is 10 ml, an allowable temperature limit is 400.degree. C.
and a withstand pressure is 300 MPa.
[0072] An aqueous solution containing 0.33 M of glycerin and 0.25 M
of sodium hydroxide was prepared. The obtained aqueous solution was
poured into the reactor (10), followed by air-tightly sealing. A
packing ratio of the solution was made not more than 60% by volume
of the reactor (10).
[0073] Then, the reactor (10) was immersed in a heating shaker
shown in FIG. 6 and shaken for a predetermined time.
[0074] A schematic diagram of the heating shaker is shown in FIG.
6. The heating shaker has a molten salt bath (21), a heater (22),
an agitator (23), a temperature controller (24) and a thermocouple
(25). The heating shaker can be controlled to a temperature in the
range of 170 to 400.degree. C. using the temperature controller
(24) and the thermocouple (25).
[0075] A reaction temperature and a reaction time in the heating
shaker were 300.degree. C. and 60 min, respectively. The pressure
was made saturated vapor pressure of water at 300.degree. C.
[0076] After performing the heating process, the reaction solution
was immersed in cold water to rapidly cool.
[0077] After performing the cooling, a solution filled in the
reactor (10) was taken out, followed by removing a solid component
with a 0.45 .mu.m filter, further followed by controlling the pH to
neutrality with sulfuric acid and the neutralized solution was
analyzed with high-performance liquid chromatography.
[0078] Here, the decomposition ratio of glycerin and the conversion
ratio to a product thereof are defined as follows based on an
amount of carbon in the substance.
Conversion ratio (% C)=carbon amount in a product/carbon amount in
the starting glycerin.times.100
Decomposition ratio (% C)=carbon amount in decomposed
glycerin/carbon amount in the starting glycerin.times.100
[0079] Analysis results by the high-performance liquid
chromatography are shown in FIG. 7 (detector: absorption detector
(UV)) and the decomposition ratios and the conversion ratios
obtained based on detected substances in a reaction solution are
shown in Table 1 below.
TABLE-US-00001 TABLE 1 Decomposition Conversion Detected Ratio
Ratio Substance (% C) (% C) Glycerin 59.8 -- (unreacted) Lactic
acid -- 58.6 Formic acid -- 0.5 Acetic acid -- 0.3 Acrylic acid --
0.1
[0080] From results of the high-performance liquid chromatography
shown in FIG. 7, the following substance can be detected in a
reaction solution: unreacted glycerin, lactic acid that is a main
product and formic acid, acetic acid and acrylic acid, which are
by-products. The decomposition ratio of glycerin was 59.8% C and
the conversion ratio to lactic acid was 58.6% C. From the results,
it is obvious that glycerin could be efficiently converted to
lactic acid.
Example 2
[0081] In example 2, the reaction time was variously altered and
the decomposition ratios of glycerin and the conversion ratios
thereof to lactic acid were measured. Other conditions were the
same as those of example 1.
[0082] Results of example 2 are shown in Table 2 below. FIG. 8 is
obtained by charting results of Table 2.
[0083] From Table 2 and FIG. 8, it is found that, as the
decomposition of glycerin proceeds, an amount of generated lactic
acid increases.
TABLE-US-00002 TABLE 2 Reaction Decomposition Conversion Time Ratio
Ratio (min) (% C) (% C) 5 16.0 6.6 10 19.5 14.5 30 43.0 39.4 60
59.8 58.6
Example 3
[0084] In example 3, in order to investigate the stability of
lactic acid in alkaline water at a high temperature and a high
pressure, an experiment of hydrothermal decomposition of lactic
acid with alkaline component was carried out. Reaction conditions
such as a temperature, a pressure and so on were made the same as
those in example 1. FIG. 9 shows results thereof. As obvious from
FIG. 9, it was found that lactic acid was very stable under an
alkaline hydrothermal condition.
Example 4
[0085] In example 4, a hydrothermal decomposition of glycerin was
carried out in a neutral aqueous solution without adding an
alkaline component. A reaction temperature was made 300.degree. C.
and a reaction time was made 10 min. FIG. 10 shows the results
thereof. FIG. 11 shows a result of the high-performance liquid
chromatography after the reaction.
[0086] From FIG. 10, lactic acid was not generated in the
hydrothermal reaction under neutral conditions. Furthermore, from
FIG. 11, it was found that acrylic acid, acrolein and so on were
generated. Thus, it was found that the reaction had to be carried
out under the alkaline condition in order to obtain lactic
acid.
Example 5
[0087] In example 5, a tube (10a) made of SUS316 as shown in FIG.
12 and capable of air-tightly sealed with caps (10b) made of the
same SUS316 at both ends thereof was used as a reactor (10). The
tube (10a) of the reactor (10) has a dimension of outer diameter:
12.7 mm, thickness: 1 mm and length: 111.3 mm, a volume of 10 ml,
the allowable temperature limit of 400.degree. C., and the
withstand pressure of 30 MPa. To one end of the tube (10a), a line
(10c) is connected. The line (10c) is connected to a high-pressure
valve (10d). The reactor (10) is closed when the high-pressure
valve (10d) is closed. when the high-pressure valve (10d) is
opened, a gas component generated in the reactor (10) is externally
taken out through the line (10c).
[0088] An experiment was carried out with the reactor (10)
according to a procedure below.
[0089] (1) An aqueous solution was prepared by adding glycerin and
NaOH to water so as to be a glycerin concentration: 0.33 M and an
NaOH concentration: 0.25 M.
[0090] (2) The aqueous solution of the (1) was charged in the
reaction tube (10) so that a volume is 40% by volume.
[0091] (3) In order to inhibit a solute from being oxidized during
the reaction, the aqueous solution was deaerated and air in the
reaction tube (10) was substituted by nitrogen gas.
[0092] (4) The reactor (10) was sealed intimately by closing the
high-pressure valve (10d) and immersed in a molten salt bath (21)
(FIG. 13) of a heating shaker (20) kept at a predetermined
temperature to start a reaction. The reaction temperature was set
at 300.degree. C. In FIG. 13, the molten salt bath (21), the heater
(22), the temperature controller (24) and the thermocouple (25) are
the same as those of the heating shaker (20) shown in FIG. 6;
accordingly, detailed explanations thereof are omitted here. A
reference numeral (26) in FIG. 13 denotes a shaker. As a
downward-extended crank-like rotation bar (26a) is rotated, a
horizontal bar (26b) moves in a horizontal direction. The reactor
(10) suspended at portions of caps (10b) to the horizontal bars
(26b) is horizontally shaken.
[0093] (5) After heated and shaken over for 60 min, the reactor
(10) is taken out from the heating shaker and rapidly cooled in
cooling water.
[0094] (6) A generated gas was recovered and gas components thereof
were analyzed by gas chromatography (GC).
[0095] (7) A reaction solution in a tube (10a) of the reactor (10),
after controlling the pH to 7 to 8, was filtered with a 0.45 .mu.m
filter to remove a solid.
[0096] (8) Components of a filtrate were analyzed by
high-performance liquid chromatography (HPLC).
[0097] In FIGS. 14 and 15, HPLC analysis results of reaction
products are shown. A graph of FIG. 14 was obtained by measuring
the absorbance of UV and a graph of FIG. 15 was obtained by
measuring the refractive index.
[0098] As obvious from FIG. 14, the reaction product was almost
made of lactic acid that is a target substance. Other reaction
products included acetic acid and acrylic acid. These are
considered to be generated by further decomposing lactic acid;
accordingly, as the reaction time becomes longer, production ratios
thereof are considered to be higher. Furthermore, as shown in the
graph of FIG. 15, the glycerin partially remains unreacted.
[0099] As the result of component analysis of the generated gas (by
GC), almost all was hydrogen (H.sub.2) gas and carbon monoxide
(CO), carbon dioxide (CO.sub.2), oxygen (O.sub.2) and the like were
not detected.
Example 6
[0100] In the example, variations with time of the reaction
products were measured. The reaction conditions were made the same
as those of example 5 except that an NaOH concentration was set to
1.25 M and, a reaction solution was subjected to a HPLC analysis
and a GC analysis at the start of the reaction and at 20, 40, 60,
80 and 100 min after the start of the reaction and the residual
ratio of glycerin and yields of lactic acid and hydrogen at each of
times are measured.
[0101] The yield of lactic acid (mol %) and the residual ratio of
glycerin (mol %) were calculated according to formulas below.
Yield of lactic acid (mol %)=amount of reaction product
(mol/L)/amount of supplied glycerin (mol/L).times.100
Residual ratio (mol %)=amount of unreacted glycerin (mol/L)/amount
of supplied glycerin (mol/L).times.100
[0102] Obtained results are shown in FIG. 16.
[0103] As shown in FIG. 16, the yield of lactic acid reached
substantially 90% at 90 min after the start of the reaction. The
yield of hydrogen as well showed substantially the same behavior as
that of lactic acid. Furthermore, at the respective times, the
yields of lactic acid were substantially the same as the
decomposition ratio of glycerin ((100-residual ratio) %). That is,
it is found that glycerin was oxidized by dehydration by the
alkaline hydrothermal reaction to convert almost portion into
lactic acid and hydrogen. On the other hand, since acid (lactic
acid) is generated from alcohol (glycerin) by the reaction, NaOH is
consumed to neutralize. The above matters can be expressed by a
stoichiometric formula (1) below.
C.sub.3H.sub.5(OH).sub.3+NaOH.fwdarw.CH.sub.3CH(OH)COO.sup.-Na.sup.++H.s-
ub.2O+H.sub.2.uparw. (1)
[0104] The stoichiometric formula shows that NaOH equal mole as
that of glycerin is necessary in order to forward a reaction
100%.
Example 7
[0105] In the example, a variation with time of the yield of lactic
acid was measured using several samples each of which has a variant
NaOH concentration from 0 to 2.5 M.
[0106] As for the experimental conditions, a reaction temperature
was made 300.degree. C. and a glycerin concentration was made 0.33
M. The yield of lactic acid was measured at the start of the
reaction and at 30, 60, 90, 120 and 150 min after the start of the
reaction. The yield of lactic acid was obtained by calculating
similarly to the example 6. Obtained results are shown in FIG.
17.
[0107] As shown in FIG. 17, when the NaOH concentration was 0 M,
lactic acid was not detected and instead thereof acrolein that is a
product generated by dehydration of glycerin was detected.
Furthermore, with an increase in the alkaline concentration, a rate
of generation of lactic acid increased and the yield of lactic acid
after 90 min reached substantially 90% when the NaOH concentration
was 1.25 M. Thus, it is thought that the alkaline component equal
to or more than equivalent mole plays a very important role in the
reaction.
Example 8
[0108] In the example, a variation with time of the yield of lactic
acid was measured using several temperature conditions varied in
the range of 220 to 340.degree. C. As for the experimental
conditions, the NaOH concentration was made 1.25 M and the glycerin
concentration was made 0.33 M. The yield of lactic acid was
measured at the start of the reaction and at 20, 40, 60, 80 and 100
min after the start of the reaction. The yield of lactic acid was
obtained by calculating similarly to example 6. Obtained results
are shown in FIG. 18.
[0109] As shown in FIG. 18, when the reaction temperature was
220.degree. C. and the reaction time was 1 hr, the generation of
lactic acid was confirmed only slightly. Furthermore, it was found
that lactic acid could be produced by continuing the reaction for a
long time even when the temperature was 150.degree. C. Still
furthermore, with an increase of the reaction temperature, the rate
of generation of lactic acid increased and the yield of lactic acid
reached substantially 90% at 300.degree. C. and 90 min. When the
reaction temperature was 340.degree. C., the yield reached 80% at
10 min; however, the yield decreased thereafter. It is considered
that lactic acid is remarkably decomposed at a temperature more
than 300.degree. C. Acetic acid and acrylic acid were detected as
products generated by decomposition of lactic acid under the
condition for the alkaline hydrothermal reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] FIG. 1 is a flow sheet for explaining a process for
producing lactic acid according to embodiment 1.
[0111] FIG. 2 is a flow sheet for explaining an apparatus for
producing lactic acid according to embodiment 2.
[0112] FIG. 3 is a flow sheet for explaining an apparatus for
producing lactic acid according to embodiment 3.
[0113] FIG. 4 is a flow sheet for explaining an apparatus for
producing lactic acid according to embodiment 4.
[0114] FIG. 5 is a schematic diagram showing a reactor used in
example 1.
[0115] FIG. 6 is a schematic diagram showing a heating shaker used
in example 1.
[0116] FIG. 7 is a graph of high-performance liquid chromatography
analysis showing results of example 1 with an absorbance detector
(UV) as a detector.
[0117] FIG. 8 is a graph showing results of example 2.
[0118] FIG. 9 is a graph showing results of example 3.
[0119] FIG. 10 is a graph showing results of example 4.
[0120] FIG. 11 is a graph showing high-performance liquid
chromatography analysis after a reaction of example 4.
[0121] FIG. 12 is a schematic diagram showing a reactor that is
used in example 5.
[0122] FIG. 13 is a schematic diagram showing a heating shaker that
is used in example 5.
[0123] FIG. 14 is a graph of high-performance liquid chromatography
analysis showing results of example 5.
[0124] FIG. 15 is a graph of high-performance liquid chromatography
analysis showing results of example 5.
[0125] FIG. 16 is a graph showing results of example 6.
[0126] FIG. 17 is a graph showing results of example 7.
[0127] FIG. 18 is a graph showing results of example 8.
EXPLANATION OF REFERENCE NUMERALS
[0128] 1: tank for storing a raw material [0129] 2: high-pressure
pump [0130] 3: pre-heater [0131] 4: reaction column [0132] 5:
cooler [0133] 6: tank for storing an alkaline solution containing
lactic acid
* * * * *