U.S. patent application number 14/704783 was filed with the patent office on 2015-08-20 for method and device for carboxylic acid production.
The applicant listed for this patent is Ceramatec, Inc.. Invention is credited to SAI Bhavaraju, Kean Duffey.
Application Number | 20150233002 14/704783 |
Document ID | / |
Family ID | 45555291 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150233002 |
Kind Code |
A1 |
Bhavaraju; SAI ; et
al. |
August 20, 2015 |
METHOD AND DEVICE FOR CARBOXYLIC ACID PRODUCTION
Abstract
A multi-compartment electrolysis cell includes an anodic
compartment, a cathodic compartment, and a solid alkali ion
transporting membrane (such as a NaSICON membrane). An anolyte is
added to the anodic compartment. The anolyte comprises an alkali
salt of a carboxylic acid, a first solvent, and a second solvent.
The alkali salt of the carboxylic acid is partitioned into the
first solvent. The anolyte is then electrolyzed to produce a
carboxylic acid, wherein the produced carboxylic acid is
partitioned into the second solvent. The second solvent may then be
separated from the first solvent and the produced carboxylic acid
may be recovered from the second solvent. The first solvent may be
water and the second solvent may be an organic solvent.
Inventors: |
Bhavaraju; SAI; (West
Jordan, UT) ; Duffey; Kean; (Allston, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ceramatec, Inc. |
Salt Lake City |
UT |
US |
|
|
Family ID: |
45555291 |
Appl. No.: |
14/704783 |
Filed: |
May 5, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13103716 |
May 9, 2011 |
9057137 |
|
|
14704783 |
|
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61371113 |
Aug 5, 2010 |
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Current U.S.
Class: |
204/237 ;
204/252 |
Current CPC
Class: |
C25B 1/02 20130101; C25B
13/04 20130101; C25B 15/08 20130101; C25B 3/00 20130101; C25B 3/02
20130101; B01D 61/422 20130101 |
International
Class: |
C25B 13/04 20060101
C25B013/04; C25B 3/02 20060101 C25B003/02; C25B 15/08 20060101
C25B015/08 |
Claims
1. A device for producing carboxylic acid comprising: a
multi-compartment electrolysis cell comprising an anodic
compartment, a cathodic compartment, and a solid alkali ion
transporting membrane; an anode in communication with the anodic
compartment; a cathode in communication with the cathodic
compartment; a power source in communication with the anode and the
cathode for creating a current therebetween; and an anolyte
comprising an alkali salt of a carboxylic acid, a first solvent and
a second solvent, wherein the alkali salt of the carboxylic acid is
partitioned into the first solvent, wherein a carboxylic acid
produced in the cell is partitioned into the second solvent.
2. The device of claim 1, wherein the first solvent comprises
water, the second solvent comprises an organic solvent and the
solid alkali ion transporting membrane comprises a NaSICON
membrane.
3. The device of claim 1, wherein the solid alkali ion transporting
membrane separates the anodic compartment from the cathodic
compartment.
4. The device of claim 1, wherein the multi-compartment
electrolysis cell further comprises a middle compartment, wherein
the solid alkali ion transporting membrane separates the cathodic
compartment from the middle compartment, and wherein an anionic
membrane separates the middle compartment from the anodic
compartment.
5. The device of claim 1, wherein the anolyte is housed within the
anodic compartment, wherein a portion of the second solvent may be
removed from the anodic compartment and separated from the produced
carboxylic acid.
6. The device of claim 1, further comprising a catholyte housed in
the cathodic compartment, and wherein the device is configured to
continuously remove a portion of the catholyte and feed said
portion back into the cathodic compartment.
7. A device for producing carboxylic acid comprising: a
multi-compartment electrolysis cell comprising an anodic
compartment, a cathodic compartment, and a NaSICON membrane
separating the anodic compartment and the cathodic compartment; an
anode in communication with the anodic compartment; a cathode in
communication with the cathodic compartment; a power source in
communication with the anode and the cathode for creating a current
therebetween; and an anolyte comprising an alkali salt of a
carboxylic acid, a first solvent comprising water and a second
solvent comprising an organic solvent, wherein the alkali salt of
the carboxylic acid is partitioned into the first solvent, wherein
a carboxylic acid produced in the cell is partitioned into the
second solvent.
8. The device of claim 7, wherein the multi-compartment
electrolysis cell further comprises a middle compartment, wherein
the solid alkali ion transporting membrane separates the cathodic
compartment from the middle compartment, and wherein an anionic
membrane separates the middle compartment from the anodic
compartment.
9. The device of claim 7, wherein the anolyte is housed within the
anodic compartment, wherein a portion of the second solvent may be
removed from the anodic compartment and separated from the produced
carboxylic acid.
10. The device of claim 7, further comprising a catholyte housed in
the cathodic compartment, and wherein the device is configured to
continuously remove a portion of the catholyte and feed said
portion back into the cathodic compartment.
11. A device for producing carboxylic acid comprising: a
multi-compartment electrolysis cell comprising an anodic
compartment, a cathodic compartment, a middle compartment, and a
solid alkali ion transporting membrane separates the cathodic
compartment from the middle compartment, and wherein an anionic
membrane separates the middle compartment from the anodic
compartment; an anode in communication with the anodic compartment;
a cathode in communication with the cathodic compartment; a power
source in communication with the anode and the cathode for creating
a current therebetween; and an anolyte comprising an alkali salt of
a carboxylic acid, a first solvent comprising water and a second
solvent comprising an organic solvent, wherein the alkali salt of
the carboxylic acid is partitioned into the first solvent, wherein
a carboxylic acid produced in the cell is partitioned into the
second solvent.
12. The device of claim 11, wherein the anolyte is housed within
the anodic compartment, wherein a portion of the second solvent may
be removed from the anodic compartment and separated from the
produced carboxylic acid.
13. The device of claim 11, further comprising a catholyte housed
in the cathodic compartment, and wherein the device is configured
to continuously remove a portion of the catholyte and feed said
portion back into the cathodic compartment.
Description
RELATED APPLICATION
[0001] The application is a divisional of and claims priority to
U.S. patent application Ser. No. 13/103,716, filed on May 9, 2011
(the '716 application). The '716 application claims the benefit of
U.S. Provisional Patent Application Ser. No. 61/371,113 filed Aug.
5, 2010, entitled "Method and Device for Carboxylic Acid
Production." These applications are expressly incorporated herein
by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a method of forming lactic
acid (or other carboxylic acids) using an electrolysis cell. More
specifically, the present disclosure relates to forming lactic acid
(or other carboxylic acids) using an electrolysis cell without
having the cell's solid ion conducting membrane (e.g., NaSICON
membrane) be fouled (poisoned) by the formed acid.
BACKGROUND
[0003] Lactic acid is a common chemical encountered in foodstuffs,
medicines and other products. Lactic acid is a naturally occurring
chemical and has the formula CH.sub.3CH(OH)COOH. The corresponding
lactate anion has the formula CH.sub.3CH(OH)COO.sup.- However, for
convenience, lactic acid and the lactate anion are often
represented by their stoichiometric formulas, namely
C.sub.3H.sub.6O.sub.3 and C.sub.3H.sub.5O.sub.3.sup.-.
[0004] Lactic acid is a desirable product because it may be
converted into a biodegradable polymer that may be used to form
bottles and other useful products. Accordingly, the market for
lactic acid is continuously growing. There are known ways to make
lactic acid, including using gypsum as a reactant.
[0005] Various attempts have been made to produce lactic acid using
electrolysis (e.g., in an electrolysis cell). In general, this
reaction involves sodium lactate aqueous solution (under the
influence of an applied voltage) to produce lactic acid at the
cell's anode. This chemical oxidation reaction of the cell's
anolyte solution is represented as follows:
C.sub.3H.sub.5O.sub.3Na+H.sub.2O.fwdarw.C.sub.3H.sub.6O.sub.3+1/2O.sub.2-
+2Na.sup.++2e.sup.- [0006] (sodium lactate) (lactic acid)
[0007] In many electrolytic cells designed to accomplish this
conversion of lactate anion to lactic acid, a solid ion conducting
membrane, such as a NaSICON membrane, is used. During the chemical
reaction, the produced sodium ions (Na+) flow through the cell's
membrane (e.g., towards the cathode). However, lactic acid is an
organic acid, and as such, the lactic acid produced in this
reaction would decrease the pH of the anolyte solution. This
decrease in the pH operates to stop the conduction of the sodium
ions through the membrane. This is referred to as "poisoning" or
"fouling" of the membrane. Once the pH of the anolyte reaches a
certain acidic level, the sodium ions can no longer flow through
the membrane and the formation of lactic acid in the cell
ceases.
[0008] It should be noted that although the prior example was given
with respect to lactic acid, attempts have been made to form other
carboxylic acids (such as, for example, citric acid, oleic acid,
adapic acid, decanoic acid, etc.) from their corresponding alkali
salts using similar reactions in electrolysis cells. However, as
all of these carboxylic acids are acidic chemicals, these
electrolytic chemical reactions also suffer from a similar type of
"poisoning" of the membrane that was described above. Accordingly,
there is a need in the art for a new type of electrolysis cell that
can be used to form lactic acid (or another type of carboxylic
acid), wherein the membrane will not be poisoned (fouled) by the
production of the acid. Such a new type of electrolytic cell is
disclosed herein.
SUMMARY
[0009] The present embodiments address the acidic poisoning of a
membrane (such as a NaSICON membrane) in an electrolysis cell by
using a two phase electrolysis approach. The present embodiments
use a mixture of aqueous (or more polar) and non-aqueous (or less
polar) solvents in the anolyte. In one embodiment, the lactic acid
(or another carboxylic acid) that is produced in the anolyte is
removed into the non-aqueous (organic) second phase. The second
phase (organic phase) therefore preferentially absorbs the lactic
acid from the aqueous phase, leaving sodium lactate anions in the
aqueous phase. This phenomenon is called partitioning. More
specifically, sodium lactate, which is more polar than lactic acid,
prefers the polar solvent (water) while lactic acid, which is less
polar, prefers a less polar or non-polar (organic) solvent. The
lactic acid that migrates into the non-aqueous (non-polar) phase
will not dissociate to form H.sup.+ ions. As a result, the pH of
the anolyte in the aqueous phase is generally governed by the
presence of the lactate anion (which is a basic entity). The pH of
the anolyte thus does not substantially drop upon the formation of
the lactic acid and as such, the lactic acid will not poison the
NaSICON membrane. Rather, the cell operates at the basic (or
perhaps neutral) pH and the membrane conducts the sodium ions into
the catholyte until all the sodium lactate is consumed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] In order that the manner in which the above-recited and
other features and advantages of the invention are obtained will be
readily understood, a more particular description of the invention
briefly described above will be rendered by reference to specific
embodiments thereof which are illustrated in the appended drawings.
Understanding that these drawings depict only typical embodiments
of the invention and are not therefore to be considered to be
limiting of its scope, the invention will be described and
explained with additional specificity and detail through the use of
the accompanying drawings in which:
[0011] FIG. 1 shows a flow diagram of a method of producing
carboxylic acids (and other products) from biomass;
[0012] FIG. 2 shows a schematic diagram of a multi-compartment
electrolysis cell according to the present embodiments;
[0013] FIG. 3 shows a schematic diagram of another embodiment of a
multi-compartment electrolysis cell;
[0014] FIG. 4 shows a flow diagram of a method of producing
carboxylic acids and other products using the present
embodiments;
[0015] FIG. 5 is a flow diagram of another embodiment of a method
of producing carboxylic acids and other products; and
[0016] FIG. 6 shows a schematic diagram of a computer-simulated
method for separating a carboxylic acid from an anolyte
mixture.
DETAILED DESCRIPTION
[0017] The presently preferred embodiments of the present invention
will be best understood by reference to the drawings, wherein like
parts are designated by like numerals throughout. It will be
readily understood that the components of the present invention, as
generally described and illustrated in the figures herein, could be
arranged and designed in a wide variety of different
configurations. Thus, the following more detailed description of
the embodiments of the present invention, as represented in the
Figures, is not intended to limit the scope of the invention, as
claimed, but is merely representative of embodiments of the
invention.
[0018] With respect to FIG. 1, an overall process 100 is shown for
producing a carboxylic acid. As will be described, the process 100
produces a carboxylic acid in an electrolysis cell 104. The
electrolysis cell 104 has an ion conducting membrane. The process
100 begins by obtaining the corresponding anion for the carboxylic
acid. In some embodiments, this anion may be obtained from a
quantity of biomass 102. Obviously, given its abundance in nature,
it is desirable to find a way to use this biomass as a starting
material to form a useable carboxylic acid product. As used herein,
"biomass" 102 may comprise, for example, carbohydrates, lipids
(such as fats or oils), lignins, tall oil and/or resins from plant,
algal, or animal origin. Other examples of biomass include wood
chips, forestry residue, energy crops (switch grass, miscanthus,
sorghum, energy cane and other genetically modified plants), algae,
cyanobacteria, jatropha, soy bean, corn, palm, coconut, canola,
rapeseed, Chinese tallow, animal fats products of genetically
modified organisms, and the like.
[0019] As indicated above, the biomass 102 may be from algal,
animal, microbial, or plant origins (such as wood, etc.). In one
embodiment, any type of biomass may be used, whether the source of
this biomass 102 is natural, synthetic, man-made, or even
genetically altered (such as in the case of microbes,
microorganisms, or animals). If the biomass is from an algal
material, the algae may be synthesized, genetically-altered, or may
be naturally occurring. Mixtures of different types of biomass may
also be used. As explained in detail herein, the biomass 102 may be
used as a starting material to ultimately arrive at a carboxylic
acid (such as, for example, lactic acid).
[0020] As shown in FIG. 1, the quantity of the biomass 102 may be
obtained. This biomass 102 may be converted 110 into an alkali salt
of a carboxylic acid 112 (which may be also referred to as a
"carboxylate"). Other products 114 may also be formed. In some
embodiments, this conversion 110 of the biomass 102 may involve an
alkaline fermentation reaction and may occur at an alkaline
fermentation refinery 106 or at another similar facility. Other
processing steps, either in addition to or in lieu of the
fermentation reaction (e.g. hydrolysis of biomass in alkaline
media), may also be used to produce the carboxylate 112. Those
skilled in the art are familiar with the steps, chemical processes,
treatments, etc., that are necessary to form the carboxylates 112
from biomass 102. In some embodiments, the alkali salt of a
carboxylic acid 112 will be a sodium salt.
[0021] The alkali salt of a carboxylic acid 112 and/or the other
products 114 may optionally be subjected to a water removal step
120 and/or other processing. Once the alkali salt of a carboxylic
acid 112 has been processed, it may be added 105 to the
electrolysis cell 104 (having the ion conducting membrane.) The
process 109 that is used by the cell 104 is described herein in
greater detail. This process 109 forms a carboxylic acid 130 as
well as other usable products 132. The carboxylic acid 130 and the
other products 132 may then undergo a purification step 140 to
produce a concentrated supply of the carboxylic acid 144, other
byproducts 146 and a concentrated supply of caustic 150 (such as
NaOH). The steps associated with the purification 140 are known to
a skilled artisan and some of these steps are described herein.
Further, as will be described in greater detail in conjunction with
FIGS. 2 and 3, the electrolysis cell 104 may be a multi-compartment
electrolysis cell 104 that uses an organic phase to separate the
formed carboxylic acid from an aqueous phase.
[0022] Referring now to FIG. 2, an exemplary embodiment of an
electrolysis cell 104 is illustrated. The electrolysis cell 104 may
be used to convert biomass to a carboxylic acid. Specifically, the
electrolysis cell 104 may be a multi-compartment electrolysis cell.
Accordingly the cell 104 may comprise two separate compartments,
namely a cathodic compartment 204 and an anodic compartment 206.
The cathodic compartment 204 may be in communication with a cathode
210. In some embodiments, the cathode 210 may be wholly located
within the cathodic compartment 204. In other embodiments, at least
part of the cathode 210 is not located within the cathodic
compartment 204. The anodic compartment 206 may be in communication
with an anode 212. In some embodiments, the anode 212 may be wholly
located within the anodic compartment 206. In other embodiments, at
least part of the anode 212 is not located within the anodic
compartment 206. Those skilled in the art will appreciate how to
construct the cathode 210, the anode 212, the cathodic compartment
204 and/or the anodic compartment 206 so that an electrolysis
(electrolytic) reaction may occur within the electrolysis cell 104.
A power source 218 is in communication with the anode 212 and the
cathode 210 and operates to create a current between the cathode
210 and the anode 212 (e.g., an applied current within the cell 104
to generate current or vice-versa).
[0023] The electrolysis cell 104 may further comprise a solid
alkali ion transporting membrane 220. The solid alkali ion
transporting membrane 220 may separate the anodic compartment 206
from the cathodic compartment 204. In many embodiments, the solid
alkali ion transporting membrane 220 may be capable of transporting
alkali metal ions from the anodic compartment 206 to the cathodic
compartment 204. In some embodiments where the alkali metal is
sodium, the membrane 220 may be a NaSICON membrane. NaSICON is a
material known in the art and may be used to form the membrane.
Some NaSICON membranes are commercially available from Ceramatec,
Inc., of Salt Lake City, Utah. NaSICON typically has a relatively
high ionic conductivity for sodium ions at room temperature.
Alternatively, if the alkali metal is lithium, then a particularly
well suited material that may be used to construct an embodiment of
the membrane is LiSICON. Alternatively, if the alkali metal is
potassium, then a particularly well suited material that may be
used to construct an embodiment of the membrane is KSICON. Other
examples of such solid electrolyte membranes include those
membranes based on the NaSICON structure, sodium conducting
glasses, beta alumina and solid polymeric sodium ion conductors.
Such materials are commercially available. Moreover, such membranes
are tolerant of impurities that may be in the anolyte and will not
allow the impurities to mix with the catholyte. Thus, the
impurities (which may be derived from the biomass) do not
necessarily have to be removed prior to placing the anolyte in the
cell 104. Likewise, such membranes may also be desirable because
they are not subject to degradation by polymers, as is possible
with other types of polymer membranes.
[0024] The electrolysis cell 104 may comprise an anolyte 230 and a
catholyte 226. The catholyte 226 may comprise an aqueous solution.
The catholyte 226 may be housed, at least partially, within the
cathodic compartment 204. The anolyte 230 may be housed, at least
partially, within the anodic compartment 206. The anolyte 230
comprises a first solvent 234 and a second solvent 232. The two
solvents 232, 234 are generally immiscible or partially immiscible
such that they separate out from each other. Examples of the types
of solvents that may be used comprise water and an organic solvent
(such as, for example, hexanol cyclohexanol, octonal, or butanol).
Of course, other types of organic solvents may also be used. The
first solvent 234 may comprise water (or an aqueous phase) whereas
the second solvent 232 may comprise an organic solvent. The anolyte
230 may also comprise a quantity of an alkali salt of a carboxylic
acid 224 (which, as noted above, may be derived from biomass).
[0025] The chemical reactions that occur within the anodic
compartment 206 and cathodic compartment 204 (based upon the
voltage applied by the source 218) will now be described. In this
example, the alkali metal is sodium and the alkali salt of a
carboxylic acid 224 is sodium lactate:
Basic Anolyte Reactions Within the Anodic Compartment:
[0026] H.sub.2O.fwdarw.1/2O.sub.2+2H.sup.++2e.sup.-(Water
Oxidation)
2H.sup.++2C.sub.3H.sub.5O.sub.3Na.fwdarw.2C.sub.3H.sub.6O.sub.3+2Na.sup.-
+
Basic Catholyte Reactions Within the Cathodic Compartment:
[0027] 2H.sub.2O+2e.sup.-.fwdarw.H.sub.2+2OH.sup.-(Water
Reduction)
2OH.sup.-+2Na.sup.+.fwdarw.2NaOH
[0028] As can be seen from these reactions, water (H.sub.2O) is
oxidized on the anode 212 to release oxygen gas (O.sub.2) and
protons (H.sup.+). These protons (H.sup.+) then react with sodium
lactate (C.sub.3H.sub.5O.sub.3Na) to form free sodium ions
(Na.sup.+) and lactic acid (C.sub.3H.sub.6O.sub.3). The sodium ions
(Na.sup.+) may be transported across the NaSICON membrane 220,
while the lactic acid (C.sub.3H.sub.6O.sub.3) 228 may be
partitioned into the second solvent 232 (organic phase) of the
anolyte 230. The acid 228 may be partitioned into the second
solvent 232 based on its solubility preference for this organic
phase. (This extraction is described as happening within the
electrolytic cell 104, although in some embodiments, the extraction
occurs partially or wholly outside of the cell.)
[0029] This liquid-liquid extraction reduces pH effects on the
anolyte 230 (caused by the formation of the acid 228) and protects
the NaSICON membrane. More specifically, when the lactic acid 228
partitions into the second solvent 232, the lactic acid 228 does
not dissociate into H.sup.+ ions and lactate anions. Rather, the
lactic acid remains in its neutral (molecular) form in the organic
phase. Further, when the lactic acid 228 partitions into the second
solvent 232, the alkali salt of a carboxylic acid 224 (e.g., sodium
lactate) is left in the first solvent 234 (e.g., the water or
aqueous phase). The alkali salt of a carboxylic acid 224 is a basic
chemical, and as such, the pH of the anolyte 230 does not drop to
an acidic level upon the formation of the acid 228. NaSICON
membranes have been known to foul or be poisoned in an acidic pH,
such as, for example, a pH of 6 or lower. However, by maintaining
the anolyte 230 at a basic pH (due to the presence of the alkali
salt of a carboxylic acid 224), the anolyte 230 does not achieve an
acidic pH and the NaSICON membrane 220 is not fouled.
[0030] By separating the first solvent 234 from the second solvent
232, the carboxylic acid 228 may be extracted and isolated. This
separation may occur by removing the anolyte 230 from the cell 104
(after it has been electrolyzed). (Alternatively, the separation of
the first solvent 234 and the second solvent 232 may occur within
the cell 104.) Once removed, the water and organic phases may be
easily separated via known techniques. The carboxylic acid 228 may
then be recovered (separated) from the organic second solvent 232,
thereby achieving a supply of the desired carboxylic acid 228.
After the carboxylic acid 228 has been recovered, the anolyte 230
that was removed from the cell 104 may be returned (re-fed) into
the cell 104 so that the cell 104 may be reused. In one embodiment,
after the carboxylic acid 228 has been recovered, the second
solvent, devoid of carboxylic acid product, is recombined with the
first solvent to remake the anolyte 230 that may be returned
(re-fed) into the cell 104 so that the cell 104 may be reused.
Those skilled in the art will appreciate that the separation
process(es) used to separate the water and the organic solvent may
be implemented as a continuous process, wherein sodium carboxylate
is continuously being added to the anolyte and/or first solvent and
the anolyte is re-fed into the cell 104 and carboxylic acid is
continuously recovered.
[0031] In the reaction that occurs in the anolyte 230, sodium ions
(Na.sup.+) are produced. These sodium ions (Na.sup.+) may be
transported across the NaSICON membrane 220 and enter the catholyte
226. Once in the catholyte 226, the sodium ions (Na+) may react
with hydroxide ions (OH) (which were formed during water (H.sub.2O)
reduction on the cathode 210) to form pure caustic (NaOH). Hydrogen
gas (H.sub.2) may also be formed in the cathodic compartment
204.
[0032] Referring now to FIG. 3, another exemplary embodiment of an
electrolysis cell 104a is illustrated. The electrolysis cell 104a
that is shown in FIG. 3 is similar to that which was shown in FIG.
2 and may be used in the process 100 of FIG. 1. Accordingly, for
purposes of brevity, much of the discussion of the
features/elements of FIG. 3 that are similar to that which was
found in FIGS. 1 and 2 will be omitted.
[0033] Like the embodiments shown above, electrolysis cell 104a is
a multi-compartment electrolysis cell. However, unlike the
two-compartment cell (having a cathodic compartment and an anodic
compartment) shown in FIG. 2, the electrolysis cell 104a of FIG. 3
is a three-compartment cell. Specifically, the electrolysis cell
104a comprises a cathodic compartment 204, an anodic compartment
206 as well as a middle compartment 310. The middle compartment 310
may be interposed between the cathodic compartment 204 and the
anodic compartment 206. Specifically, the middle compartment 310
may be separated from the cathodic compartment 204 by the solid
alkali ion transporting membrane 220 (such as, for example, the
NaSICON membrane). The middle compartment 310 may be separated from
the anodic compartment 206 by an anionic membrane 312. An anionic
membrane 312 may allow anions to pass through (e.g., exit the
middle compartment 310 and enter the anodic compartment 206), but
will prevent cations from passing through the anionic membrane
312.
[0034] The electrolysis cell 104a of FIG. 3 may operate to form a
carboxylic acid 228. An example of how the cell 104a may be used to
create a carboxylic acid 228 will now be provided in which the
alkali metal is sodium and the alkali salt of the carboxylic acid
is sodium lactate (C.sub.3H.sub.5O.sub.3Na).
[0035] In this embodiment, an inlet stream 340 enters the middle
compartment 310. The introduction of this stream 340 means that
there may be a liquid 301 in the middle compartment 310. This
liquid 301 may contain the alkali salt of a carboxylic acid (e.g.,
sodium lactate). The lactate anions (C.sub.3H.sub.5O.sub.3.sup.-)
224 move (under the influence of the applied voltage supplied by
the voltage source 218) from the middle compartment 310 through an
anionic membrane 312 into the anodic compartment 206. The
positively charged sodium ions (Na.sup.+) are not allowed to pass
through the anionic membrane 312. Instead, sodium ions (Na.sup.+)
move from the middle compartment 310 through the cationic NaSICON
membrane 220 into the cathodic compartment 204.
[0036] The chemical reactions of the anolyte 230 within the anodic
compartment 206 as well as the chemical reactions of the catholyte
226 within the cathodic compartment 204 operate identically to the
process described in FIG. 2. When the sodium ions (Na.sup.+) move
through the NaSICON membrane 220 into the cathodic compartment 204,
these cations enter the catholyte 226. Once in the catholyte 226,
the sodium ions (Na.sup.+) may react with hydroxide ions (OH.sup.-)
(which were formed during water (H.sub.2O) reduction on the cathode
210) to form pure caustic (NaOH). Hydrogen gas (H.sub.2) may also
be formed in the cathodic compartment 204.
[0037] When the anions 224 move through the anionic membrane 312,
these anions enter the anolyte 230. In the anodic compartment 206,
water (H.sub.2O) from the anolyte 230 is oxidized on the anode 212
to release oxygen gas (O.sub.2) and protons (H.sup.+). These
protons (H.sup.+) then react with the lactate
(C.sub.3H.sub.5O.sub.3.sup.-) anions 224 (which have migrated from
the middle compartment 310 via the anionic membrane 312) to form
lactic acid 228 (C.sub.3H.sub.6O.sub.3). The lactic acid
(C.sub.3H.sub.6O.sub.3) 228 is partitioned into the second solvent
232 (organic phase) of the anolyte 230 based on its solubility
preference for this phase. While the lactic acid 228 partitions
into the second solvent 232, the lactate 224 anion partitions into
the first solvent 234 (e.g., the water or aqueous phase). The
lactate anion 224 is a basic chemical, and as such, the pH of the
anolyte 230 does not drop upon the formation of the acid 228. The
lactic acid in the second solvent 232 does not dissociate and form
H.sup.+ and thus, the pH in the anodic compartment remains basic
(or neutral) and above a pH of about 6.
[0038] In the three-compartment embodiment shown in FIG. 3, there
is added protection of the NaSICON membrane (e.g., another
compartment) that prevents the lowering of the pH around the
NaSICON membrane. Rather, the pH of the liquid 301 in the middle
compartment 310 (e.g., around the NaSICON membrane) is set by the
basic lactate anion. Accordingly, the NaSICON membrane 220 in the
cell 104a is not fouled.
[0039] FIGS. 4 and 5 represent two different Process Flow Diagrams
(PFD) that show continuous processes of how embodiments may be
constructed and used to produce lactic acid/carboxylic acids. Both
FIG. 4 and FIG. 5 show continuous processes, although both concepts
could also be demonstrated using batch processes. FIGS. 4 and 5
show a possible process flow scheme in which the acid generated is
separated from the water phase (e.g., the first solvent) external
of the cell (e.g., in a separate liquid-liquid separation tank).
However, embodiments could also be made in which no liquid-liquid
separation tank is used in which the separation of the water from
the organic phase occurs within the cell itself. It should be noted
that the process shown in FIG. 4 provides extra protection of the
NaSICON membrane from the produced acid (particularly when using a
two compartment cell as shown in FIG. 2) because the acid can be
removed from the water phase immediately upon its formation. On the
other hand, the approach shown in FIG. 5 also has its advantages in
that it does not require a well-mixed solution to enter the cell
and thus could possibly require less solvent (although it may
indeed require higher cell throughput).
[0040] Each PFD shown in FIGS. 4 and 5 is designed to provide
control over the water/solvent ratio for a liquid-liquid extraction
that occurs either inside or outside of the electrolytic cell. The
ratio of water to solvent should be tailored to the specific
process and solvent being used, thereby achieving maximum acid
removal with minimal solvent. Theoretically, the water is only
required in the process to (1) keep all sodium lactate and other
inlet stream constituents dissolved and (2) provide protons
(H.sup.+) for the production of the acid. Thus, excess water in the
anolyte may be avoided. In fact, from a practical standpoint, water
removal from a post-fermentation stream may be beneficial prior to
the stream entering the electrolytic process (as indicated by the
water removal step 120 in FIG. 1).
[0041] Referring now to FIG. 4, a process 400 is shown that may be
used to produce a carboxylic acid. In the process 400, an inlet
broth 401 may be obtained. (As explained herein, this broth 401 may
be derived from biomass.) The broth 401 may be added to a mixing
tank 403. The inlet broth 401 may comprise the products generated
by the conversion reaction 110 (for example, the fermentation
reaction) of FIG. 1. A pump 405 and/or one or more valves 407 (as
needed) may be used to introduce the inlet broth 401 from the
mixing tank 403 into the electrolysis cell 104 (or 104a).
[0042] In the process 400, an electrolysis cell 104/104a may be
used to produce a carboxylic acid. As described above, the
catholyte 226 (not shown in FIG. 4) may be used to produce
concentrated caustic (e.g., NaOH). Accordingly, a solution 404 of
the catholyte 226 may be extracted from the cell 104/104a. This
solution may then be subjected to a heat exchange/temperature
exchange 408 (that may be powered by one or more utilities 410).
(One or more valves 412 may be used to introduce the coolant
chemicals that may be needed in the heat exchange/temperature
exchange.) Those skilled in the art will appreciate the
processes/conditions necessary to accomplish this heat
exchange/temperature exchange 408. From this tank 416, hydrogen gas
420 may be extracted. (As noted above, hydrogen gas (H.sub.2) was
produced in the cathodic compartment 204 (not shown in FIG. 4), and
thus, this gas 420 may be collected so that it may be sold,
disposed of, re-used, etc.). Also, because water is consumed as
part of the reaction in the catholyte 226, the water in the
catholyte 226 may become depleted. Accordingly, water 424 may be
added to the tank 416, as needed. Further, caustic (NaOH) 428 is
produced in the catholyte 226, and as such, a quantity (such as a
concentrated quantity) of NaOH 428 may be removed from the tank
416, as needed. (This caustic 428 may be sold, disposed of,
re-used, etc.). It should be noted however, that caustic NaOH may
be used in the conversion reaction 110 of FIG. 1. Accordingly, this
produced caustic 428 may then be recycled and reused in that
conversion reaction 110, thus lowering the overall costs associated
with the present embodiments.
[0043] The catholyte 226 that is found in the catholyte
recirculation tank 416 may be returned (re-fed) back 430 into the
cell 104/104a, thus replenishing the supply of catholyte in the
cell 104/104a. As needed, a pump 432 (and/or a valve 431) may be
used to push the replenished catholyte from the tank 416 into the
cell 104/104a. This processing of the catholyte 226 that was
described above may be referred to as the "caustic loop" 434 of the
overall process 400. This caustic loop 434 operates to replenish
and renew the catholyte 226 in the cell 104/104a so that the
overall process may be operated continuously. Thus, a fresh,
updated supply of the catholyte 226 may continuously be present in
the cell 104/104a.
[0044] In addition to a caustic loop 434, the process 400 also may
include a solvent loop 440 that may be used to extract the produced
carboxylic acid from the anolyte 230 (not shown in FIG. 4) and/or
replenish/update the anolyte 230. As noted above, the anolyte 230
in the anodic compartment 206 (not shown in FIG. 4) may comprise a
first solvent 234 (not shown in FIG. 4) and a second solvent 232
(not shown in FIG. 4). (The first solvent 234 may be water and the
second solvent 232 may be an organic solvent). The alkali salt of
the carboxylic acid 224 (not shown in FIG. 4) is preferentially
present in the first solvent 234 and the formed carboxylic acid 228
(not shown in FIG. 4) is preferentially present in the second
solvent 232. The anolyte 230 may be extracted 441 from the cell
104/104a and added to a liquid-liquid separation tank 442. The
separation tank 442 contains a first solvent (water phase) 495 and
a second solvent (organic solvent) 497. The second solvent (organic
phase) 497 contains the formed carboxylic acid 228 and is separated
445 from the water 495 (first solvent).
[0045] This separated second solvent 497 may, as needed, be
subjected to a heat exchange/temperature exchange reaction 447
(that may be powered by one or more utilities 449 such as steam).
One or more valves 452 may be used to introduce the chemicals that
may be needed in the heat exchange/temperature exchange process
447. Those skilled in the art will appreciate the processes
necessary to accomplish this heat exchange/temperature exchange.
The utility (such as steam) may be collected and reused 451 after
this heat exchange/temperature exchange 447 has occurred.
[0046] After finishing the heat exchange/temperature exchange
reaction 447, a distillation may be performed upon the second
solvent 497. This distillation (or other separation process) may
occur within a distillation column 455. The distillation column 455
separates out the various components from the second solvent 497.
For example, the carboxylic acid 457 (such as lactic acid) that was
found in the second solvent 232 may be extracted and processed
further, concentrated, used, etc. Any water 461 that may have been
present in the second solvent 497 may also be removed and re-used,
treated, disposed of, etc. Likewise, any oxygen gas 459 (which was
produced in the anolyte reaction) may also be removed from the tank
442 and collected, disposed of, sold, used, etc.
[0047] After removing these substances from the second solvent 497,
the second solvent 497 may leave 469 the distillation column 455.
Specifically, the second solvent 497 may then be combined with
anolyte 230 that has been extracted from the liquid-liquid
separation tank 416. As shown by arrows 499 and 499a, a portion of
the water phase 495 and the organic phase 497 may be extracted from
the separation tank 442 and combined 493 together. This combined
flow may then be added to the flow 469 after it leaves the
distillation column 455. Accordingly, the process in FIG. 4 shows
an embodiment, where a two-phase liquid solution is introduced into
the electrolytic cell, providing for some partitioning of the
solution within the cell, and therefore possible pH buffering
within the cell.
[0048] This combined liquid may then be filtered 473, as desired,
to remove contaminants 474. Once filtered, this combined liquid may
then be subjected to a heat exchange/temperature exchange process
478 (that may be powered by one or more utilities 480). One or more
valves 482 may be used to introduce chemicals that may be needed in
the heat exchange/temperature exchange. Those skilled in the art
will appreciate the processes necessary to accomplish this heat
exchange/temperature exchange 478. The products of this heat
exchange/temperature exchange 478 may be then added 491 to the
mixing tank 403 for use, and may ultimately be reused, in the cell
104/104a.
[0049] Thus, the process 400 represents a continuous process where
the products are continuously being produced and removed from the
system. Thus, a fresh, update supply of the anolyte 230 may
continuously be present in the cell 104/104a. This process 400 also
provides an external liquid-liquid extraction process using the
tank 442.
[0050] Referring now to FIG. 5, a different process 500 is shown
that may be used to produce a carboxylic acid. In the process 500,
an inlet broth 501 may be obtained and be added to an anolyte
recirculation tank 503. The inlet broth 501 may comprise the
products generated by the conversion reaction 110 (such as, for
example, a fermentation reaction) of FIG. 1. A pump 505 and/or one
or more valves 507 (as needed) may be used to introduce the inlet
broth 501 from the mixing tank 503 into the electrolysis cell 104
(or 104a).
[0051] It should be noted that the caustic loop 434 of the process
500 (which is associated with the catholyte) operates in the same
manner as the caustic loop 434 of FIG. 4. Accordingly, for purposes
of brevity, a discussion of the caustic loop 434 will not be
repeated.
[0052] In addition to a caustic loop 434, the process 500 also may
include a solvent loop 540 that may be used to extract the produced
carboxylic acid from the anolyte 230 (not shown in FIG. 5). As
noted above, the anolyte 230 in the anodic compartment 206 (not
shown in FIG. 5) may comprise a first solvent 234 (not shown in
FIG. 5) and a second solvent 232 (not shown in FIG. 5). (The first
solvent 234 may be water and the second solvent 232 may be an
organic solvent). The alkali salt of the carboxylic acid 224 (not
shown in FIG. 5) is preferentially present in the first solvent 234
and the formed carboxylic acid 228 (not shown in FIG. 5) is
preferentially present in the second solvent 232. The anolyte 230
may be extracted 441 from the cell 104/104a and added to a
liquid-liquid separation tank 442. The separation tank 442 contains
a first solvent (water phase) 495 and a second solvent (organic
solvent) 497. The second solvent (organic phase) 497 contains the
formed carboxylic acid 228 and is separated 445 from the water 495
(first solvent).
[0053] This separated second solvent 497 may, as needed, be
subjected to a heat exchange/temperature exchange 447 (that may be
powered by one or more utilities 449 such as steam). One or more
valves 452 may be used to introduce chemicals that may be needed in
the heat exchange/temperature exchange 447. Those skilled in the
art will appreciate the processes necessary to accomplish this heat
exchange/temperature exchange. The utility (such as steam) may be
recollected and reused 451 after this heat exchange/temperature
exchange 447 has occurred.
[0054] After finishing the heat exchange/temperature exchange
reaction 447, a distillation reaction may occur upon the second
solvent 497. This distillation process (or other separation
process) may occur within a distillation column 455. The
distillation column 455 separates out the various components from
the second solvent 497. For example, the carboxylic acid 457 (such
as lactic acid) that was found in the second solvent 232 may be
extracted and processed further, concentrated, used, etc. Any water
461 that may have been present in the second solvent 497 may also
be removed and re-used, treated, disposed of, etc. Likewise, any
oxygen gas 459 (which was produced in the anolyte reaction) may
also be removed from the tank 442 and collected, disposed of, sold,
used, etc.
[0055] However, unlike the embodiment of FIG. 4, the solvent 497
from the distillation column 455 may be extracted 571 and be
returned 572 to the liquid-liquid separation tank 442, where it may
re-mix with the other anolyte 230 and be reused.
[0056] The process 500 may also include a water loop 570. The water
loop 570 begins when a portion of the water phase 495 (e.g., the
first solvent) is removed 581 from the liquid-liquid separation
tank 442. This removed liquid may then be filtered 583 to remove
contaminants 585.
[0057] Once filtered, the water phase 495 may then be subjected to
a heat exchange/temperature exchange 578 (that may be powered by
one or more utilities 580). One or more valves 582 may be used to
introduce chemicals that may be needed in the heat
exchange/temperature exchange. Those skilled in the art will
appreciate the processes necessary to accomplish this heat
exchange/temperature exchange 578. The products of this heat
exchange/temperature exchange 578 are then added 591 to the tank
503 so that they may ultimately be reused in the cell 104/104a. In
one embodiment, only the water phase is introduced into the cell,
thus simplifying the process, but risking a lower pH within the
cell. In such an embodiment, higher flow rates through the cell may
be utilized to manage this risk.
[0058] Thus, the process 500 represents a continuous process where
the products are continuously being produced and removed from the
system. Thus, a fresh, updated supply of the anolyte 230 and
catholyte 226 (not shown in FIG. 5) may continuously be present in
the cell 104/104a. This process 500 provides an external
liquid-liquid extraction process using the tank 442.
[0059] Referring now to FIG. 6, a computer simulation using
CHEMCAD.RTM. software was performed to analyze a separation process
that may be used in the present embodiments. This
computer-simulated process 600 is shown in FIG. 6. This
computer-simulated process 600 involves separating out a carboxylic
acid from a mixture of water and an organic solvent (which may be,
for example hexanol, cyclohexanol, octonal, and butanol or other
solvents). Specifically, an anolyte mixture of two different
solvents is simulated. This mixture comprises a solution 602 of 20%
lactic acid/80% water and a solution of hexanol 604. The solutions
602, 604 are mixed in a liquid-liquid extractor 606. In the
simulation of FIG. 6, 4.5 L of the hexanol 604 is mixed with every
1 L of the water solution 602. Thus, there is substantially more
hexanol in the simulated mixture than there is water.
[0060] As shown by FIG. 6, the liquid-liquid extractor 606 is able
to separate the water from the hexanol and the lactic acid.
Specifically, water may be extracted 610 from the extractor 606.
According to the simulation, the water 611 will be about 99% (with
the remainder being hexanol and lactic acid). Likewise, a mixture
of hexanol and lactic acid may also be extracted 612 from the
liquid-liquid extractor 606.
[0061] According to the simulation of FIG. 6, the mixture 601 of
hexanol/lactic acid, which may or may not contain a minor fraction
of water, may then be subjected to a distillation column 616. This
distillation column 616 operates to separate the lactic acid from
the hexanol. Specifically, the lactic acid is extracted 620 from
the column 616 (and subjected to a heat exchange/temperature
exchange process or other purification process 630 as needed). The
simulation indicates that the quantity of lactic acid 636 that may
be obtained from such processes is over 99% pure.
[0062] Similarly, the hexanol may be extracted 640 from the column
616 (and may be subjected to a heat exchange/temperature exchange
process or other purification reaction 650) as needed). The
simulation indicates that the quantity of hexanol 646 that that may
be obtained from such processes is 90% pure (with some water
contained therein).
[0063] As shown by the dashed arrows 655, 656, in one embodiment,
if the samples are not properly treated by heat
exchange/temperature exchange processes 630, 650, a sample may be
returned to the column 616, as needed, in order to properly treat
the flows. In one embodiment, the "reflux ratio" of a distillation
column may be used to determine how much of the sample is removed
from the top or bottom of the column 616 compared to how much is
sent back into the column 616. Other ways know to those of skill in
the art may be used to operate the column 616 in order to improve
the separation of chemicals.
[0064] As can be seen from the present embodiments, it may be
desirable to separate some of the products (such as the carboxylic
acid) during an electrolysis process, so that these chemicals do
not poison a NaSICON (or other similar) membrane. However, those of
skill in the art will recognize that the embodiments and techniques
disclosed herein may also be used in order to isolate one or more
reactants (as needed) from the NaSICON membrane, thereby preventing
the reactants from fouling the membrane. It may be desirable to
separate reactants and/or products during electrolysis in a NaSICON
membrane-containing electrolytic cell because: [0065] (1) either
the reactant(s) or the product(s) affect the performance of the
anode; [0066] (2) either the reactant(s) or the product(s) affect
the performance of the membrane; [0067] (3) continuous (not batch)
production and separation of the product(s) are more easily
accomplished; and [0068] (4) the separation of the reactant(s) or
product(s) from the anolyte may increase the operational current
density.
[0069] It should further be noted that embodiments may be
constructed in which the particular organic solvent used is
specifically selected/tailored to the particular carboxylic acid.
For example, if the produced carboxylic acid is lactic acid, there
may be other impurities (or other types of carboxylic acids) that
are present in the anolyte. It may be possible to construct
embodiments in which the organic solvent preferentially dissolves
the desired product (the lactic acid) and does not dissolve (or
perhaps dissolves to a lesser extent) the other organic impurities
and/or other carboxylic acids in the anolyte, thereby increasing
the purity of the obtained carboxylic acid. Those skilled in the
art would appreciate how to select these solvents for each
particular system/produced carboxylic acid.
[0070] While many of the examples provided herein involve the
formation of lactic acid as the carboxylic acid product, the
teachings of this disclosure can be used to produce other types of
carboxylic, including citric acid, oleic acid, adapic acid,
decanoic acid and other acids from their corresponding alkali
salts.
[0071] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the systems, methods, and
apparatus described herein without departing from the scope of the
claims.
* * * * *