U.S. patent application number 16/829458 was filed with the patent office on 2020-07-16 for acetic acid product quality improvement.
The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Shahid Azam, Sebastiano Licciulli, Roland Schmidt.
Application Number | 20200222827 16/829458 |
Document ID | / |
Family ID | 55637396 |
Filed Date | 2020-07-16 |
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United States Patent
Application |
20200222827 |
Kind Code |
A1 |
Schmidt; Roland ; et
al. |
July 16, 2020 |
ACETIC ACID PRODUCT QUALITY IMPROVEMENT
Abstract
A process of purifying acetic acid is provided. The process
includes feeding a feed stream comprising acetic acid into a bottom
half of a distillation column and distilling the acetic acid in the
presence of a homogeneous oxidizing agent in the distillation
column, to oxidize oxidizable impurities in the acetic acid,
wherein the homogeneous oxidizing agent is capable of cleaving
C.dbd.C bonds. The process further includes removing a distilled
acetic acid stream from the distillation column. Further processes
for purifying acetic acid and systems for purifying acetic acid are
also provided.
Inventors: |
Schmidt; Roland; (Wiehl,
DE) ; Licciulli; Sebastiano; (Riyadh, SA) ;
Azam; Shahid; (Riyadh, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Family ID: |
55637396 |
Appl. No.: |
16/829458 |
Filed: |
March 25, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15553761 |
Aug 25, 2017 |
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PCT/IB2016/050979 |
Feb 23, 2016 |
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16829458 |
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62120684 |
Feb 25, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 57/03 20130101;
B01D 3/009 20130101; B01D 5/0036 20130101; C01G 45/1214 20130101;
C07C 51/487 20130101; C01D 13/00 20130101; C07C 53/08 20130101;
Y02P 20/127 20151101; B01D 3/146 20130101; Y02P 20/10 20151101;
C07C 51/487 20130101; C07C 53/08 20130101 |
International
Class: |
B01D 3/00 20060101
B01D003/00; B01D 5/00 20060101 B01D005/00; C07C 51/487 20060101
C07C051/487; C07C 53/08 20060101 C07C053/08 |
Claims
1. A process for purifying acetic acid, comprising: feeding a feed
stream comprising acetic acid into a bottom half of a distillation
column; distilling the acetic acid in the presence of a homogeneous
oxidizing agent in the distillation column to oxidize oxidizable
impurities in the acetic acid, wherein the homogeneous oxidizing
agent is capable of cleaving C.dbd.C bonds; and removing a
distilled acetic acid stream from the distillation column, wherein
the homogeneous oxidizing agent is positioned in the feed
stream.
2. The process of claim 1, wherein the oxidizable impurities
comprise an .alpha.,.beta.-unsaturated carbonyl compound.
3. The process of claim 2, wherein the .alpha.,.beta.-unsaturated
carbonyl compound comprises an .alpha.,.beta.-unsaturated
carboxylic acid.
4. The process of claim 3, wherein the .alpha.,.beta.-unsaturated
carboxylic acid comprises acrylic acid.
5. The process of claim 1, wherein the distillation column
comprises a sump in the bottom half of the distillation column and
the homogeneous oxidizing agent is positioned in the sump.
6. A process for purifying acetic acid, comprising: feeding a feed
stream comprising acetic acid into a distillation column, and
distilling the acetic acid in the presence of a homogeneous
oxidizing agent, wherein: the distillation column comprises: a top
half and a bottom half; and a sump in the bottom half of the
distillation column; and wherein the feed stream is fed into the
bottom half of the distillation column; and wherein the homogeneous
oxidizing agent is positioned in the feed stream.
7. The process of claim 1, wherein the homogeneous oxidizing agent
comprises potassium permanganate.
8. The process of claim 7, wherein the potassium permanganate
comprises an aqueous solution of potassium permanganate.
9. The process of claim 7, wherein the potassium permanganate
comprises potassium permanganate on a solid support.
10. The process of claim 9, wherein the solid support is
silica.
11. The process of claim 1, wherein the process further comprises
feeding the distilled acetic acid stream through a sorbent phase
capable of removing at least one impurity selected from water, or
formic acid, or aldehydes.
12. The process of claim 1, wherein the process further comprises
additional distillation of acetic acid through an additional
distillation column.
13. The process of claim 6, wherein the homogeneous oxidizing agent
comprises potassium permanganate.
14. The process of claim 13, wherein the potassium permanganate
comprises an aqueous solution of potassium permanganate.
15. The process of claim 13, wherein the potassium permanganate
comprises potassium permanganate on a solid support.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 15/553,761 filed on Aug. 25, 2017, which is a
371 of International Application No. PCT/IB2016/050979, filed Feb.
23, 2016, which claims priority to U.S. Application No. 62/120,684,
filed Feb. 25, 2015, all of which are incorporated herein by
reference in their entirety.
TECHNICAL FIELD
[0002] The presently disclosed subject matter relates to processes
and systems for purifying acetic acid.
BACKGROUND
[0003] Acetic acid is a widely used chemical. Acetic acid has the
chemical formula CH.sub.3CO.sub.2H and is sometimes also known as
ethanoic acid or methanecarboxylic acid. It is commonly abbreviated
as MeCO.sub.2H, MeCOOH, AcOH, and AA. Acetic acid is a major
feedstock in the chemical and polymer industries. As the key
component of vinegar, acetic acid also has many applications in
food.
[0004] Acetic acid can contain various impurities, which can
include aldehydes (e.g., acetaldehyde and formaldehyde), formic
acid, acrylic acid, water, inorganic and organic salts, and various
other compounds. The levels of impurities can depend on the method
of production of acetic acid. One commonly used test of the purity
of acetic acid is the permanganate test. The permanganate test
measures oxidizable impurities present in acetic acid. A quantity
of permanganate, e.g., a standardized solution, can be added to a
concentrated sample of acetic acid, creating a colored solution.
Fading of the characteristic pink color of permanganate indicates
consumption of permanganate through reaction with oxidizable
impurities. The time over which the pink color of permanganate
survives can be described as the "permanganate time," and samples
of acetic acid with long permanganate time can be inferred to
contain low levels of oxidizable impurities. Acetic acid that
passes the permanganate test (i.e., acetic acid with low levels of
oxidizable impurities) can be particularly valuable in applications
that demand high purity acetic acid.
[0005] Industrially produced acetic acid often contains oxidizable
impurities and fails the permanganate test. Various processes and
systems for purifying acetic acid are described in the literature.
However, there remains a need in the art for improved processes and
systems for purification of acetic acid, including processes and
systems capable of removing oxidizable impurities from acetic
acid.
SUMMARY
[0006] The presently disclosed subject matter provides processes
and systems for purifying acetic acid.
[0007] A process for purifying acetic acid comprises: feeding a
stream of acetic acid into a distillation column; distilling acetic
acid in the presence of an oxidizing agent in the distillation
column, to oxidize oxidizable impurities in the acetic acid,
wherein the oxidizing agent is capable of cleaving C.dbd.C bonds;
and removing a distilled acetic acid stream from the distillation
column.
[0008] A process for purifying acetic acid comprises: feeding a
stream of acetic acid into a distillation column, wherein: the
distillation column comprises: a top and a bottom; and a sump at
the bottom of the distillation column; and wherein the stream of
acetic acid is fed into the distillation column at or near the
bottom of the distillation column; and distilling acetic acid in
the presence of an oxidizing agent, wherein the oxidizing agent is
positioned at or near the bottom of the distillation column.
[0009] A system for purifying acetic acid, comprises: a
distillation column, wherein the distillation column comprises: a
top and a bottom; and a sump at the bottom of the distillation
column; an oxidizing agent positioned at or near the bottom of the
distillation column; and an acetic acid feed line to feed acetic
acid into the distillation column positioned at or near the bottom
of the distillation column.
[0010] These and other features and characteristics are more
particularly described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The following is a brief description of the drawings wherein
like elements are numbered alike and which are presented for the
purposes of illustrating the exemplary embodiments disclosed herein
and not for the purposes of limiting the same.
[0012] The FIGURE is a schematic diagram depicting an exemplary
system for purifying acetic acid in accordance with one
non-limiting embodiment of the disclosed subject matter.
DETAILED DESCRIPTION
[0013] The presently disclosed subject matter provides processes
and systems for purifying acetic acid. Acetic acid can be purified
to remove various impurities, and overall product quality of
industrial acetic acid can be improved.
[0014] In one embodiment, a non-limiting exemplary process for
purifying acetic acid includes feeding a stream of acetic acid into
a distillation column. The process further includes distilling
acetic acid in the presence of an oxidizing agent in the
distillation column, to oxidize oxidizable impurities in the acetic
acid, wherein the oxidizing agent is capable of cleaving C.dbd.C
bonds. The process further includes removing a distilled acetic
acid stream from the distillation column.
[0015] In certain embodiments, the oxidizable impurities can
include one or more .alpha.,.beta.-unsaturated carbonyl compounds.
The one or more .alpha.,.beta.-unsaturated carbonyl compounds can
include one or more .alpha.,.beta.-unsaturated carboxylic acids.
The one or more .alpha.,.beta.-unsaturated carboxylic acids can
include acrylic acid.
[0016] In certain embodiments, the oxidizing agent can include
potassium permanganate. The potassium permanganate can include an
aqueous solution of potassium permanganate. The potassium
permanganate can include potassium permanganate on a solid support.
The solid support can be silica.
[0017] In certain embodiments, the distillation column can include
a top and a bottom, and the oxidizing agent can be positioned at or
near the bottom of the distillation column. In certain embodiments,
the distillation column can include a sump at the bottom of the
distillation column and the oxidizing agent can be positioned in
the sump.
[0018] In certain embodiments, the process can further include
feeding the distilled acetic acid stream through a sorbent phase
capable of removing at least one impurity selected from the group
consisting of water, formic acid, and aldehydes.
[0019] In certain embodiments, the process can further include
additional distillation of acetic acid through one or more
additional distillation columns.
[0020] In another embodiment, a non-limiting exemplary process for
purifying acetic acid includes feeding a stream of acetic acid into
a distillation column, wherein the distillation column includes a
top and a bottom and a sump at the bottom of the distillation
column, and wherein acetic acid is fed into the distillation column
at or near the bottom of the distillation column. The process
further includes distilling acetic acid in the presence of an
oxidizing agent, wherein the oxidizing agent is positioned at or
near the bottom of the distillation column.
[0021] In one embodiment, a non-limiting exemplary system for
purifying acetic acid includes a distillation column, wherein the
distillation column includes a top and a bottom and a sump at the
bottom of the distillation column. The system further includes an
oxidizing agent positioned at or near the bottom of the
distillation column and an acetic acid feed line to feed acetic
acid into the distillation column positioned at or near the bottom
of the distillation column.
[0022] In certain embodiments, the oxidizing agent can be
positioned on a tray near the bottom of the distillation column. In
certain embodiments, the oxidizing agent can be positioned in the
sump at the bottom of the distillation column. In certain
embodiments, the acetic acid feed line can be positioned to feed
acetic acid into the sump at the bottom of the distillation
column.
[0023] The term "about" or "approximately" means within an
acceptable error range for the particular value as determined by
one of ordinary skill in the art, which will depend in part on how
the value is measured or determined, i.e., the limitations of the
measurement system. For example, "about" can mean a range of up to
20%, up to 10%, up to 5%, and or up to 1% of a given value.
[0024] In certain embodiments, non-limiting exemplary processes and
systems for purifying acetic acid include feeding a stream of
acetic acid into a distillation column. The stream of acetic acid
can be fed from an acetic acid source. In certain embodiments, the
acetic acid source can be an existing facility for production of
acetic acid, e.g., an industrial facility. The acetic acid source
can feed a stream of acetic acid that contains various impurities,
e.g., water, inorganic and organic salts, and/or oxidizable
impurities. In this way, the acetic acid source can feed a stream
of acetic acid that is of relatively low purity.
[0025] Oxidizing Agents
[0026] Oxidizing agents are also known as oxidants and oxidizers.
By way of non-limiting example, oxidizing agents can generally
include oxygen (O.sub.2), ozone (O.sub.3), peroxides (e.g.,
hydrogen peroxide (H.sub.2O.sub.2)), peracids (also known as peroxy
acids or peroxyacids, e.g., peracetic acid), peroxyesters (also
known as peroxy esters), nitric acid (HNO.sub.3), nitrates (e.g.,
sodium nitrate (NaNO.sub.3)), sulfuric acid (H.sub.2SO.sub.4),
peroxysulfates (e.g., potassium peroxomonosulfate (OXONE.TM.) and
tetrabutylammonium peroxomonosulfate (OXONE.TM. tetrabutylammonium
salt)), halogens (e.g., F.sub.2, Cl.sub.2, Br.sub.2, and I.sub.2),
hypochlorites, chlorites, chlorates, perchlorates, hypobromites,
bromites, bromates, perbromates, hypoiodites, iodites, iodates,
periodates, permanganates, Cr(VI) complexes (e.g., CrO.sub.3), and
perborates (e.g., NaBO.sub.3).
[0027] Certain oxidizing agents are capable of cleaving C.dbd.C
bonds. C.dbd.C bonds are carbon-carbon double bonds. By way of
non-limiting example, the oxidizing agent capable of cleaving
C.dbd.C bonds can include permanganate salts, e.g., potassium
permanganate (KMnO.sub.4), ammonium permanganate
(NH.sub.4MnO.sub.4), tetraalkylammonium permanganate salts (e.g.,
tetrabutylammonium permanganate), calcium permanganate
(Ca(MnO.sub.4).sub.2), and sodium permanganate (NaMnO.sub.4). The
oxidizing agent capable of cleaving C.dbd.C bonds can also include
ozone (O.sub.3), periodate salts (e.g., sodium periodate
(NaIO.sub.4) and potassium periodate (KIO.sub.4)), perchlorate
salts (e.g., sodium perchlorate (NaClO.sub.4)), chlorate salts
(e.g., sodium chlorate (NaClO.sub.3)), peroxides (e.g., hydrogen
peroxide (H.sub.2O.sub.2), and peracids (e.g., peracetic acid
(CH.sub.3CO.sub.3H). In certain non-limiting embodiments, the
oxidizing agent capable of cleaving C.dbd.C bonds can include a
transition metal complex, e.g., a complex of Fe, Mo, Co, Cr, V, Cu,
Ag, W, Ta, Os, Rh, Ru, or Re. In certain embodiments, the
transition metal complex can be used catalytically. By way of
non-limiting example, transition metal complexes that can be used
catalytically can include
[SiRu(H.sub.2O)--W.sub.11O.sub.39]((C.sub.6H.sub.13).sub.4N).sub.5
(a ruthenium polyoxometalate, which can be used in conjunction with
a periodate, e.g., NaIO.sub.4),
[(PW.sub.4O.sub.24)](C.sub.5H.sub.5N--C.sub.16H.sub.33).sub.3 (a
peroxo form of phosphotungstic acid, which can be used in
conjunction with a peroxide, e.g., H.sub.2O.sub.2),
[cis-Ru(II)(dmp).sub.2(H.sub.2O).sub.2](PF.sub.6).sub.2, wherein
dmp is 2,9-dimethyl-1,10-phenanthroline (which can be used in
conjunction with a peroxide, e.g., H.sub.2O.sub.2),
[OsO(N-aryl-1,2-arylenediamine).sub.2], and methyltrioxorhenium
(MTO).
[0028] The oxidizing agent can include oxidizing agents in gaseous,
liquid, and/or solid forms. Gaseous oxidizing agents can include
oxygen and ozone. Liquid oxidizing agents can include solutions of
an oxidizing agent in a solvent, e.g., water and/or acetic acid.
Liquid oxidizing agents can serve as homogeneous oxidizing agents.
A liquid oxidizing agent can be used in such a way that acetic acid
and impurities can mix with, diffuse through, or bubble through the
liquid oxidizing agent. For example, in certain non-limiting
embodiments, a stream of acetic acid containing oxidizable
impurities can be mixed with an aqueous solution, e.g., an aqueous
solution of potassium permanganate.
[0029] Solid oxidizing agents can include oxidizing agents on a
solid support or solid carrier. Such oxidizing agents on a solid
support or solid carrier can include oxidizing agents adsorbed on
the solid support or solid carrier. Oxidizing agents on a solid
support or solid carrier can serve as heterogeneous oxidizing
agents. Examples of solid supports and solid carriers used to
prepare solid oxidizing agents can include various metal salts,
metalloid oxides, and metal oxides, e.g., titanium oxide, zirconium
oxide, silica (silicon oxide), alumina (aluminum oxide), magnesium
oxide, and magnesium chloride. In certain embodiments, the solid
support or solid carrier can be chosen for its high surface area.
The oxidizing agents on a solid support or solid carrier can react
with oxidizable impurities in the gas, liquid, or solid phase.
[0030] Oxidizing agents in one phase (gaseous, liquid, or solid)
can be used in conjunction with one or more additional oxidizing
agents in other phases. For example, solid oxidizing agents can be
used in conjunction with liquid and/or gaseous oxidizing agents.
For example, in certain non-limiting embodiments, an oxidizing
agent on a solid support can be used in conjunction with a gaseous
oxidant, e.g., oxygen or ozone.
[0031] Non-limiting exemplary processes and systems for purifying
acetic acid include distilling acetic acid in the presence of an
oxidizing agent in a distillation column, to oxidize oxidizable
impurities in the acetic acid. The oxidizing agent can be an
oxidizing agent capable of cleaving C.dbd.C bonds. The processes
and systems can further include removing a distilled acetic acid
stream from the distillation column. In certain embodiments, the
oxidizing agent can be potassium permanganate. The potassium
permanganate can include an aqueous solution of potassium
permanganate. The potassium permanganate can include potassium
permanganate adsorbed on a solid support. The solid support can be
silica.
[0032] The amount of oxidizing agent used can be a stoichiometric
amount with respect to the amount of oxidizable impurities in the
acetic acid. That is, the number of moles of oxidizing agent used
can be proportional to the number of moles of oxidizable impurities
in the acetic acid. The amount of oxidizing agent used can be a
super-stoichiometric amount. That is, an excess of oxidizing agent
can be used.
[0033] Impurities
[0034] Impurities in acetic acid can include aldehydes (e.g.,
acetaldehyde and formaldehyde), formic acid, acrylic acid, water,
inorganic and organic salts, and various other compounds. Some of
the impurities in acetic acid can include oxidizable impurities.
Oxidizable impurities can include aldehydes (e.g., acetaldehyde and
formaldehyde). In certain embodiments, the oxidizable impurities
can include one or more .alpha.,.beta.-unsaturated carbonyl
compounds. The one or more .alpha.,.beta.-unsaturated carbonyl
compounds can include one or more .alpha.,.beta.-unsaturated
carboxylic acids. The one or more .alpha.,.beta.-unsaturated
carboxylic acids can include acrylic acid, methacrylic acid,
2-butenoic acid (cis and/or trans), 4-methyl-2-pentenoic acid (cis
and/or trans), and 5-methyl-2-hexenoic acid (cis and/or trans). The
one or more .alpha.,.beta.-unsaturated carbonyl compounds can also
include one or more .alpha.,.beta.-unsaturated aldehydes. The one
or more .alpha.,.beta.-unsaturated aldehydes can include acrolein,
methacrolein, 2-butenal (cis and/or trans), 4-methyl-2-pentenal
(cis and/or trans), and 5-methyl-2-hexenal (cis and/or trans).
[0035] When acetic acid is distilled in the presence of an
oxidizing agent, oxidizable impurities in the acetic acid can react
with the oxidizing agent to form oxidized impurities. The oxidized
impurities can have boiling points substantially higher than those
of their precursors (the oxidizable impurities) and also
substantially higher than that of acetic acid. The oxidized
impurities can have substantially lower volatility than acetic
acid. In this way, acetic acid can be distilled while the oxidized
impurities do not distill with acetic acid, producing a purified
distilled acetic acid.
[0036] As noted above, the process for purifying acetic acid can
include distilling acetic acid in the presence of an oxidizing
agent capable of cleaving C.dbd.C bonds. Such a process can be
useful in purifying acetic acid that is contaminated with
impurities containing C.dbd.C bonds, e.g.,
.alpha.,.beta.-unsaturated carbonyl compounds, e.g., acrylic acid.
Existing processes and systems for purifying acetic acid can
emphasize treating acetic acid with an oxidizing agent to remove
acetaldehyde, formaldehyde, and other aldehyde impurities. Such
processes and systems can fail to remove certain impurities
containing C.dbd.C bonds, e.g., .alpha.,.beta.-unsaturated carbonyl
compounds, e.g., acrylic acid. Use of an oxidizing agent capable of
cleaving C.dbd.C bonds can convert .alpha.,.beta.-unsaturated
carbonyl compounds, e.g., acrylic acid, into oxidized impurities of
low volatility, which can then be separated from acetic acid to
generate acetic acid of high purity.
[0037] Processes and Systems for Purifying Acetic Acid
[0038] In certain embodiments, the distillation column can include
a top and a bottom, and the oxidizing agent can be positioned at or
near the bottom of the distillation column. For example, in certain
non-limiting embodiments, the oxidizing agent near the bottom of
the distillation column can be positioned within about 5%, within
about 10%, within about 15%, within about 20%, or within about 25%
of the distance from the bottom of the distillation column to the
top of the distillation column. In certain embodiments, the
distillation column can include a sump at the bottom of the
distillation column, and the oxidizing agent can be positioned in
the sump.
[0039] The distillation of acetic acid can be conducted under
conditions known in the art. For example, in certain non-limiting
embodiments, acetic acid can be distilled from a mixture of acetic
acid and water, e.g., an aqueous solution of acetic acid. The
aqueous solution of acetic acid can have an acidic pH. In certain
embodiments, acetic acid can be distilled at a temperature of about
50.degree. C. to about 200.degree. C. In certain embodiments,
acetic acid can be distilled at a temperature of about 90.degree.
C. to about 150.degree. C., for example at about 100.degree. C.,
about 110.degree. C., about 120.degree. C., or about 130.degree. C.
The distillation can be conducted at various pressures, including
reduced pressures, atmospheric pressure, or elevated pressures. In
certain embodiments, distillation can be conducted at a reduced
pressure, e.g., a pressure of less than 1 bar (100 kiloPascals
(kPa), about 0.5 bar (about 50 kPa), about 0.3 bar (about 30 kPa),
about 0.2 bar (about 20 kPa), about 0.1 bar (about 10 kPa), about
0.05 bar (about 5 kPa), about 0.03 bar (about 3 kPa), about 0.02
bar (about 2 kPa), about 0.01 bar (about 1 kPa), or less than 0.01
bar (about 1 kPa). Distillation can alternatively be conducted at
an elevated pressure. For example, distillation can be conducted at
a pressure between about 1 bar and about 4 bar (about 100 kPa and
about 400 kPa), e.g., at about 1 bar (about 100 kPa), about 1.5 bar
(about 150 kPa), about 2 bar (about 200 kPa), about 2.5 bar (about
250 kPa), about 3 bar (about 300 kPa), about 3.5 bar (about 350
kPa), or about 4 bar (about 400 kPa).
[0040] In certain embodiments, the processes and systems can
further include feeding the distilled acetic acid stream through a
sorbent phase capable of removing at least one impurity selected
from water, and/or formic acid, and/or aldehydes. Acetic acid can
be "polished," or further purified, by feeding through one or more
sorbent phases. High purity acetic acid with low levels of
impurities can obtained after passage through one or more sorbent
phases. By way of non-limiting example, the sorbent can include a
ROHM AND HAAS.TM. IRA sorbent, a ROHM AND HAAS.TM. XAD sorbent, a
DOW.TM. XUS sorbent, or a combination comprising at least one of
the foregoing.
[0041] In certain embodiments, the process can further include
additional distillation of acetic acid through one or more
additional distillation columns. In certain non-limiting
embodiments, acetic acid can be distilled in a first distillation
column to remove certain impurities and then further distilled in a
second distillation column to remove additional impurities. In
certain embodiments, the first distillation column can include an
oxidizing agent. In certain embodiments, the second distillation
column can include an oxidizing agent. In certain embodiments, the
first and second distillation columns can both include an oxidizing
agent. In certain embodiments, an oxidizing agent can be positioned
between the first and second distillation columns. In certain
embodiments, more than two distillation columns can be used in
series, and one, two, or more of the columns can include an
oxidizing agent.
[0042] In certain embodiments, non-limiting exemplary processes and
systems for purifying acetic acid can include feeding a stream of
acetic acid into a distillation column, wherein the distillation
column includes a top and a bottom and a sump at the bottom of the
distillation column, and wherein acetic acid is fed into the
distillation column at or near the bottom of the distillation
column. Acetic acid can be distilled in the presence of an
oxidizing agent, and the oxidizing agent can be positioned at or
near the bottom of the distillation column.
[0043] In certain embodiments, non-limiting exemplary processes and
systems for purifying acetic acid can include a distillation
column, wherein the distillation column includes a top and a bottom
and a sump at the bottom of the distillation column. An oxidizing
agent can be positioned at or near the bottom of the distillation
column, and an acetic acid feed line to feed acetic acid into the
distillation column can be positioned at or near the bottom of the
distillation column.
[0044] In certain embodiments, the oxidizing agent can be
positioned on a tray near the bottom of the distillation column.
The tray can be a diffusible tray, i.e., a tray that allows acetic
acid in liquid and/or gaseous form to contact the oxidizing agent
and that allows oxidizable impurities in the acetic acid to react
with oxidizing agent. In other embodiments, the oxidizing agent can
be positioned in the sump at the bottom of the distillation column.
In certain embodiments, oxidizing agents can be positioned both on
a tray near the bottom of the distillation column and also in the
sump at the bottom of the distillation column. In certain
embodiments, the acetic acid feed line can be positioned to feed
acetic acid into the sump at the bottom of the distillation
column.
[0045] In certain embodiments, the oxidizing agent can be
recharged. An oxidizing agent can be recharged by various
techniques known in the art. For example, an oxidizing agent can be
recharged by continuous addition of fresh oxidizing agent. By way
of non-limiting example, fresh oxidizing agent can be added as
portions of a solid oxidizing agent, as a solid dispersion of
oxidizing agent on an inert bed, and/or as a concentrated solution
of oxidizing agent in water or another solvent.
[0046] For the purpose of illustration and not limitation, the
FIGURE is a schematic representation of an exemplary system for
purifying acetic acid according to the disclosed subject matter.
The system 100 can include an acetic acid source 101. As noted
above, the acetic acid source 101 can be an existing facility for
production of acetic acid (e.g., an acetic acid reactor). The
acetic acid source 101 can be coupled to an acetic acid feed line
102, which can be further coupled to a first distillation column
103. The acetic acid feed line 102 can feed acetic acid into the
first distillation column 103. The first distillation column 103
can optionally be coupled to a high outlet line 104 positioned at
or near the top of the first distillation column 103. The high
outlet line 104 can remove water (H.sub.2O) and butyl acetate from
the first distillation column 103 and transfer it to an azeotropic
separator 105. The azeotropic separator 105 can remove water and
return butyl acetate to the first distillation column 103 through a
butyl acetate outlet line 106 that feeds butyl acetate back into
the first distillation column 103.
[0047] The first distillation column 103 can be further coupled to
a low outlet line 107 positioned at or near the bottom of the first
distillation column 103. The low outlet line 107 can remove acetic
acid from the first distillation column 103 and feed acetic acid
into a second distillation column 108. The low outlet line 107 can
be coupled to the second distillation column 108 such that the low
outlet line 107 feeds acetic acid into the second distillation
column 108 at or near the bottom of the second distillation column
108. The low outlet line 107 can optionally feed acetic acid into a
sump 110 at the bottom of the second distillation column 108. The
second distillation column 108 can include an oxidizing agent 109.
The oxidizing agent 109 can be positioned at or near the bottom of
the second distillation column 108. The oxidizing agent 109 can be
positioned on a tray near the bottom of the second distillation
column 108, as shown in the FIGURE. Alternatively or additionally,
the oxidizing agent 109 can be placed in the sump 110.
[0048] The second distillation column 108 can be coupled to a
heavies outlet line 111 positioned at or near the bottom of the
second distillation column 108. The heavies outlet line 111 can
remove "heavies," i.e., relatively non-volatile compounds with
relatively high boiling points, from the second distillation column
108. The heavies outlet line 111 can remove oxidized impurities
from the second distillation column 108. The heavies outlet line
111 can also remove inorganic and organic salts from the second
distillation column 108. The second distillation column 108 can be
further coupled to a purified acetic acid outlet line 112
positioned at or near the top of the second distillation column
108. The purified acetic acid outlet line 112 can remove purified
acetic acid from the second distillation column 108 after it has
distilled through the second distillation column 108. The purified
acetic acid outlet line 112 can be further coupled to one or more
sorbent phases 113. The sorbent phases 113 can be polishers. The
sorbent phases 113 can further purify the purified acetic acid and
provide acetic acid in high purity, with low levels of oxidizable
impurities and other impurities. The sorbent phases 113 can include
sorbent phases capable of removing water, formic acid, and/or
aldehydes.
[0049] In certain embodiments, the exemplary system 100 can include
one or more additional oxidizing agents. By way of non-limiting
example, a heterogeneous oxidizing agent can be positioned between
the acetic acid source 101 and the first distillation column 103,
e.g., in acetic acid feed line 102. Additionally or alternatively,
a heterogeneous oxidizing agent can be positioned between the first
distillation column 103 and the second distillation column 108,
e.g., in low outlet line 107. Additionally or alternatively, a
heterogeneous oxidizing agent can be positioned between the second
distillation column 108 and one or more sorbent phases 113, e.g.,
in purified acetic acid outlet line 112.
[0050] The exemplary system 100 of the presently disclosed subject
matter can be operated in continuous, semi-continuous, or batch
mode. The various sections of the system 100 can be operated
simultaneously or, alternatively, can be operated separately.
[0051] The distillation columns 103, 108 can be constructed of any
desirable materials such as, but not limited to, metals, alloys
including steel, glass, enamels, ceramics, polymers, plastics, or a
combination comprising at least one of the foregoing.
[0052] Thus the presently disclosed subject matter provides
processes and systems for purifying acetic acid which can have
advantages over certain existing processes and systems for
purifying acetic acid. As noted above, in certain embodiments the
presently disclosed subject matter provides processes and systems
that can remove impurities containing C.dbd.C bonds, including
.alpha.,.beta.-unsaturated carbonyl compounds, e.g., acrylic acid,
from acetic acid, whereas existing processes and systems for
purifying acetic acid can emphasize treating acetic acid with an
oxidizing agent to remove acetaldehyde, formaldehyde, and other
aldehyde impurities without removing impurities containing C.dbd.C
bonds.
[0053] As noted above, the presently disclosed subject matter can
include positioning an oxidizing agent on a tray near the bottom of
a distillation column or in a sump at the bottom of a distillation
column. Acetic acid can be distilled in the distillation column. As
noted above, .alpha.,.beta.-unsaturated carbonyl compounds present
in the acetic acid can be oxidized by the oxidizing agent to
oxidized impurities that are heavies, i.e., relatively non-volatile
compounds with relatively high boiling points. Because of their
relatively high boiling points, the heavies can remain in solution
rather than distilling with acetic acid. The heavies can then be
conveniently removed from the bottom of the column through a
heavies outlet line. For example, acrylic acid can be oxidized with
an oxidizing agent to oxalic acid or a salt thereof, which can be
removed through a heavies outlet line. In this way,
.alpha.,.beta.-unsaturated impurities can be efficiently removed
from acetic acid.
[0054] In certain embodiments of the presently disclosed subject
matter, acetic acid is purified by multiple means, e.g., by a first
distillation, a second distillation in the presence of an oxidizing
agent, and subsequent polishing by passage of the acetic through
one or more sorbent phases. In this way, highly purified acetic
acid can be obtained. The highly purified acetic acid can be of
higher purity and quality than acetic acid obtained from existing
purification processes and systems. The highly purified acetic can
be capable of passing the permanganate test, and can be useful in
various specialized applications requiring very low levels of
oxidizable impurities.
[0055] The processes and systems disclosed herein include at least
the following aspects:
[0056] Aspect 1: A process for purifying acetic acid, comprising:
feeding a feed stream comprising acetic acid into a bottom half of
a distillation column; distilling the acetic acid in the presence
of a homogeneous oxidizing agent in the distillation column to
oxidize oxidizable impurities in the acetic acid, wherein the
homogeneous oxidizing agent is capable of cleaving C.dbd.C bonds;
and removing a distilled acetic acid stream from the distillation
column, wherein the homogeneous oxidizing agent is positioned in
the feed stream.
[0057] Aspect 2: The process of Aspect 1, wherein the oxidizable
impurities comprise an .alpha.,.beta.-unsaturated carbonyl
compound.
[0058] Aspect 3: The process of Aspect 2, wherein the
.alpha.,.beta.-unsaturated carbonyl compound comprises an
.alpha.,.beta.-unsaturated carboxylic acid.
[0059] Aspect 4: The process of Aspect 3, wherein the
.alpha.,.beta.-unsaturated carboxylic acid comprises acrylic
acid.
[0060] Aspect 5: The process of Aspect 1, wherein the distillation
column comprises a sump in the bottom half of the distillation
column and the homogeneous oxidizing agent is positioned in the
sump.
[0061] Aspect 6: A process for purifying acetic acid, comprising:
feeding a feed stream comprising acetic acid into a distillation
column, and distilling the acetic acid in the presence of a
homogeneous oxidizing agent, wherein: the distillation column
comprises: a top half and a bottom half; and a sump in the bottom
half of the distillation column; and wherein the feed stream is fed
into the bottom half of the distillation column; and wherein the
homogeneous oxidizing agent is positioned in the feed stream.
[0062] Aspect 7: The process of Aspect 1, wherein the homogeneous
oxidizing agent comprises potassium permanganate.
[0063] Aspect 8: The process of Aspect 7, wherein the potassium
permanganate comprises an aqueous solution of potassium
permanganate.
[0064] Aspect 9: The process of Aspect 7, wherein the potassium
permanganate comprises potassium permanganate on a solid
support.
[0065] Aspect 10: The process of Aspect 9, wherein the solid
support is silica.
[0066] Aspect 11: The process of Aspect 1, wherein the process
further comprises feeding the distilled acetic acid stream through
a sorbent phase capable of removing at least one impurity selected
from water, or formic acid, or aldehydes.
[0067] Aspect 12: The process of Aspect 1, wherein the process
further comprises additional distillation of acetic acid through an
additional distillation column.
[0068] Aspect 13: The process of Aspect 6, wherein the homogeneous
oxidizing agent comprises potassium permanganate.
[0069] Aspect 14: The process of Aspect 13, wherein the potassium
permanganate comprises an aqueous solution of potassium
permanganate.
[0070] Aspect 15: The process of Aspect 13, wherein the potassium
permanganate comprises potassium permanganate on a solid
support.
[0071] In general, the invention may alternately comprise, consist
of, or consist essentially of, any appropriate components herein
disclosed. The invention may additionally, or alternatively, be
formulated so as to be devoid, or substantially free, of any
components, materials, ingredients, adjuvants or species used in
the prior art compositions or that are otherwise not necessary to
the achievement of the function and/or objectives of the present
invention. The endpoints of all ranges directed to the same
component or property are inclusive and independently combinable
(e.g., ranges of "less than or equal to 25 wt %, or 5 wt % to 20 wt
%," is inclusive of the endpoints and all intermediate values of
the ranges of "5 wt % to 25 wt %," etc.). Disclosure of a narrower
range or more specific group in addition to a broader range is not
a disclaimer of the broader range or larger group. "Combination" is
inclusive of blends, mixtures, alloys, reaction products, and the
like. Furthermore, the terms "first," "second," and the like,
herein do not denote any order, quantity, or importance, but rather
are used to denote one element from another. The terms "a" and "an"
and "the" herein do not denote a limitation of quantity, and are to
be construed to cover both the singular and the plural, unless
otherwise indicated herein or clearly contradicted by context. "Or"
means "and/or." The suffix "(s)" as used herein is intended to
include both the singular and the plural of the term that it
modifies, thereby including one or more of that term (e.g., the
film(s) includes one or more films). Reference throughout the
specification to "one embodiment", "another embodiment", "an
embodiment", and so forth, means that a particular element (e.g.,
feature, structure, and/or characteristic) described in connection
with the embodiment is included in at least one embodiment
described herein, and may or may not be present in other
embodiments. In addition, it is to be understood that the described
elements may be combined in any suitable manner in the various
embodiments.
[0072] The modifier "about" used in connection with a quantity is
inclusive of the stated value and has the meaning dictated by the
context (e.g., includes the degree of error associated with
measurement of the particular quantity). The notation ".+-.10%"
means that the indicated measurement can be from an amount that is
minus 10% to an amount that is plus 10% of the stated value. The
terms "front", "back", "bottom", and/or "top" are used herein,
unless otherwise noted, merely for convenience of description, and
are not limited to any one position or spatial orientation.
"Optional" or "optionally" means that the subsequently described
event or circumstance can or cannot occur, and that the description
includes instances where the event occurs and instances where it
does not. Unless defined otherwise, technical and scientific terms
used herein have the same meaning as is commonly understood by one
of skill in the art to which this invention belongs. A
"combination" is inclusive of blends, mixtures, alloys, reaction
products, and the like.
[0073] Unless otherwise specified herein, any reference to
standards, regulations, testing methods and the like, such as ASTM
D1003, ASTM D4935, ASTM 1746, FCC part 18, CISPR11, and CISPR 19
refer to the standard, regulation, guidance or method that is in
force at the time of filing of the present application.
[0074] All cited patents, patent applications, and other references
are incorporated herein by reference in their entirety. However, if
a term in the present application contradicts or conflicts with a
term in the incorporated reference, the term from the present
application takes precedence over the conflicting term from the
incorporated reference.
[0075] While particular embodiments have been described,
alternatives, modifications, variations, improvements, and
substantial equivalents that are or may be presently unforeseen may
arise to applicants or others skilled in the art. Accordingly, the
appended claims as filed and as they may be amended are intended to
embrace all such alternatives, modifications variations,
improvements, and substantial equivalents.
[0076] Although the presently disclosed subject matter and its
advantages have been described in detail, it should be understood
that various changes, substitutions and alterations can be made
herein without departing from the spirit and scope of the disclosed
subject matter as defined by the appended claims. Moreover, the
scope of the disclosed subject matter is not intended to be limited
to the particular embodiments described in the specification.
Accordingly, the appended claims are intended to include within
their scope such alternatives.
* * * * *