U.S. patent application number 12/319498 was filed with the patent office on 2009-05-21 for processes for preparing organic compounds having improved color characteristics.
Invention is credited to Jennifer L. Bailey, Gabriel R. Chapa, Kenneth Allen Windhorst.
Application Number | 20090131715 12/319498 |
Document ID | / |
Family ID | 34116348 |
Filed Date | 2009-05-21 |
United States Patent
Application |
20090131715 |
Kind Code |
A1 |
Windhorst; Kenneth Allen ;
et al. |
May 21, 2009 |
Processes for preparing organic compounds having improved color
characteristics
Abstract
Carboxylic acids, ketones, and esters having improved color
characteristics are produced by combining small quantities of water
with these compounds. An amount of water ranging from about 100 ppm
to about 50,000 ppm of the organic compound is combined to provide
lighter color compounds in comparison to these same compounds to
which no water is added. Additionally, the color characteristics of
the organic compounds may be improved by introducing a stream of
the organic compound into at least one distillation column
maintained at a temperature of about 23.degree. C. to about
250.degree. C. and at a pressure of about 10.1 kPa to about 202.6
kPa. Subjecting the organic compound stream to distillation under
these conditions allows precursors of color bodies, having boiling
points lower than the boiling point of the product being produced,
to thermally breakdown or to be removed in the overhead stream form
the distillation column.
Inventors: |
Windhorst; Kenneth Allen;
(Portland, TX) ; Bailey; Jennifer L.; (Pampa,
TX) ; Chapa; Gabriel R.; (Corpus Christi,
TX) |
Correspondence
Address: |
M. Susan SPIERING;c/o Celanese Ltd
IP Legal Dept., IZIP 701, P.O. Box 428
Bishop
TX
78343
US
|
Family ID: |
34116348 |
Appl. No.: |
12/319498 |
Filed: |
January 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10635983 |
Aug 7, 2003 |
7491839 |
|
|
12319498 |
|
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Current U.S.
Class: |
562/606 |
Current CPC
Class: |
C07C 51/44 20130101;
C07C 51/44 20130101; C07C 53/124 20130101; C07C 51/44 20130101;
C07C 53/00 20130101 |
Class at
Publication: |
562/606 |
International
Class: |
C07C 51/44 20060101
C07C051/44 |
Claims
1. A process for preparation of an organic compound, having a
stable APHA color value of 15, or less selected from the group
consisting of C.sub.1 to C.sub.6 carboxylic acids, ketones having
boiling points from 154.degree. C. to 170.degree. C., and esters
having boiling points from about 168.degree. C. to about
250.degree. C., comprising removing a product stream comprising the
organic compound from a reaction zone in which the organic compound
is prepared and introducing the product stream into a distillation
column having a lower portion and an upper portion wherein the
upper portion and the lower portion are maintained at a temperature
of about 23.degree. C. to about 250.degree. C. and at a pressure of
about 101 kPa to about 202.6 kPa.
2. The process of claim 1 wherein the organic compound is a C.sub.1
to C.sub.6 carboxylic acid.
3. The process of claim 2 wherein the carboxylic acid is butyric
acid.
4. The process of claim 3 wherein the distillation column is
operated at a temperature of about 170.degree. C. to about
180.degree. C. and at a pressure of about 101 kPa to about 202 kPa.
Description
RELATED APPLICATIONS
[0001] This is a divisional application of prior U.S. application
Ser. No. 10/635,983 filed on Aug. 7, 2003, the disclosure of which
is incorporated herein by reference.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates to processes for preparing
carboxylic acids, ketones, and esters having improved color
characteristics.
BACKGROUND INFORMATION
[0003] There are numerous known processes for producing carboxylic
acids, ketones, and esters. For example, U.S. Pat. Nos. 3,887,595,
and 6,211,405 disclose processes for producing carboxylic acids by
carbonylating olefinically unsaturated compounds such as alcohols,
ethers, and esters. U.S. Pat. No. 5,281,752 discloses a process for
producing lower carboxylic acids by reacting alkanes with carbon
dioxide. U.S. Pat. No. 5,091,587 discloses a process for the
preparation of ketones which comprises reacting a conjugated
diolefin and water in the liquid phase in the presence of a
catalyst system comprising: a group VIII metal compound and a
source of protons. U.S. Pat. No. 4,010,188 discloses a process for
the oxidation of saturated hydrocarbons in the presence of a
catalyst to produce acids. U.S. Pat. No. 3,293,292 discloses a
liquid phase oxidation of butane in the presence of a cobalt
containing catalyst system to produce carboxylic acids. U.S. Pat.
No. 4,487,720 discloses a process of the production of acids by
oxidizing saturated aliphatic aldehydes in the presence of catalyst
systems. U.S. Pat. No. 5,026,903 discloses a process for producing
of glycol esters such ethylidene diacetate by the reaction of
mixtures of dimethyl acetal, methyl acetate and carbon monoxide.
The catalyst system charged to the reactor contains rhodium atoms,
lithium iodide and optionally an organic ligand. U.S. Pat. No.
4,268,689 also discloses a process for the production of glycol
esters.
[0004] A problem associated with carboxylic acids, ketones, and
esters production and storage is color quality. To use carboxylic
acids and other organic compounds for certain applications, the
compounds must exhibit a light color. Generally speaking, the
darker color values for these organic compounds do not affect the
functionality of the compounds for most applications. However, most
purchasers of these organic compounds believe that "water white"
compounds are of higher quality than compounds possessing higher
color properties and demand water white organic compounds.
Typically, compounds exhibiting an APHA color (Pt--Co) of 15 or
less are considered to be of water white quality. If the compounds
are not of a water white quality, expensive purification schemes
must be undertaken to purify the product to achieve acceptable
color characteristics. For example, expensive and multiple
hydrogenation and acid treatment processes may be necessary to
achieve a compound having water white characteristics.
BRIEF DESCRIPTION OF DISCLOSURE
[0005] This disclosure relates to processes for preparing certain
organic compounds such as carboxylic acids, ketones, and esters
having low color characteristics. A first embodiment involves
combining water with the organic compound at a concentration of 100
ppm to 50,000 ppm water. A second embodiment involves removing a
product stream containing the organic compound from a reaction
system in which the organic compound is prepared and introducing
the product stream into a distillation column having a lower
portion and an upper portion wherein the upper and lower portions
are maintained at a temperature of from about 23.degree. C. to
about 250.degree. C. and at a pressure of about 10.1 kPa to about
202.6 kPa. Subjecting the product stream to distillation under
these conditions thermally breaks down, or removes, precursors of
color bodies, having boiling points lower than the boiling point of
the product being produced.
[0006] A third embodiment includes combining the process of the
first two embodiments by producing a product that has been
subjected to isolation and purification in a system including a
distillation column operating at the temperatures and pressures
described above and combining water with the organic compounds as
described above.
[0007] These processes may be implemented to prepare carboxylic
acid, ketone, and glycol ester products having stable APHA color
values of 15 or less. Having a stable APHA color of 15 or less
means that the products will exhibit a color value within this
range after being boiled for at least one hour at one atmosphere
(101.3 kPa) pressure.
DRAWING
[0008] FIG. 1 is a schematic diagram of an embodiment of the
process of this invention.
DETAILED DISCLOSURE
[0009] This disclosure relates to processes for preparing certain
carboxylic acids, ketones, and esters having low color properties.
The organic compounds include C.sub.1 to C.sub.6 carboxylic acids,
ketones having boiling points from 54.degree. C. to 170.degree. C.,
and esters having boiling points from about 168.degree. C. to about
250.degree. C. These various organic compounds may be the reaction
product of a variety of processes for producing these compounds.
For example, carboxylic acids are often commercially prepared by
carbonylation of alcohols, esters, or ethers to produce the
corresponding carboxylic acid. A widely used commercial
carbonylation process is the production of acetic acid from
carbonylation of methanol. Of course, the carbonylation process is
applicable to the carbonylation of higher homologues of methanol to
form acids that are the higher homologues of acetic acid. The
carboxylic acids useful in the preparation process described in
this disclosure may be the reaction product of other processes such
as oxidizing corresponding aldehydes, alkanes, and alkenes.
[0010] Additionally, the processes described here may also be used
to prepare low color value carboxylic acids that are prepared by
reacting alkanes with carbon monoxide in the presence of palladium
and/or copper catalysts and salts of peroxy acids. The carboxylic
acids may also be produced thorough the oxidation of saturated
alkanes. For example, this oxidation process may be used to produce
butyric acid through the oxidation of butane.
[0011] In summary, the C.sub.1 to C.sub.6 carboxylic acids produced
by any process, including but not limited to the exemplary
processes referred to in the BACKGROUND INFORMATION above, may
exhibit improved color properties as a result of the color
improvement processes described in this disclosure.
[0012] Any process, including but not limited to the exemplary
processes referred to in the BACKGROUND INFORMATION above, may also
produce the ketones and esters that exhibit improved color
characteristics as a result of the processes described herein.
[0013] An exemplary process scheme for the production of carboxylic
acids is depicted in FIG. 1. Specifically, the process depicted in
FIG. 1 is for the production of butyric acid through the oxidation
of butane. It is understood that the process scheme depicted may be
used to produce a variety of other carboxylic acids, including, but
not limited to, acetic acid, through the oxidation of naptha,
pentane, and other feedstocks. A liquid phase reactor 10 is charged
with air or oxygen content enriched air. The oxygen content of the
feed may be at any level, including pure oxygen. Of course, when
using pure oxygen or highly enriched air, appropriate safety
precautions should be observed to prevent fire or explosion
hazards. However, in terms of a balance of reaction efficiency and
economics, generally an enriched air feed having an oxygen content
from about 20% to about 30% is found to be useful. The reactor 10
is also charged with pure butane although a stream contain less
than pure butane may be used provided the process scheme used can
accommodate removal of any impurities included with the butane.
[0014] The butane is oxidized in the presence of any suitable
oxidation catalyst. An exemplary catalyst is cobalt salt catalyst
present at a concentration of less than 5,000 ppm. Additionally,
recycle steams as described hereinafter, may be routed to the
reactor. As the reaction proceeds, the reactor should be maintained
at temperature from about 100.degree. C. to about 200.degree. C.
and a pressure from about 6.20 Pa to about 6.89 Pa. If the feed is
naptha, the pressure should be maintained form about 3.44 Pa to
about 5.51 Pa. A crude product stream 15 is withdrawn as a
sidestream 15 from the reaction zone and introduced into a first
distillation column 20 maintained at a bottom portion temperature
ranging up to about 200.degree. C. and a top portion temperature
ranging from about 100.degree. C. to about 120.degree. C. and a
pressure of about 10.13 kPa to about 101.3 kPa to separate an
overhead light ends stream 25 and a heavy ends cut 30. The light
ends stream 25 containing alcohols is recycled to the reactor 10
and the heavy ends cut 30 is primarily waste product and may be
disposed of by any suitable means, including burning. A product
stream 35 is withdrawn as sidestream 35, which is introduced into a
first treatment unit 40. The treatment taking place in unit 40 may
be any suitable hydrogenation treatment to improve the properties
of the product stream 35. A treated product stream 45 is withdrawn
form treatment unit 40 and introduced into a second treatment unit
50 which may be any suitable treatment step to remove impurities in
the product stream, such as 3-hydroxy 2-butanone. Suitable
treatment methods are nitric acid oxidation treatment processes
that are well known, such as referred in U.S. Pat. No. 6,590,129. A
treated product stream 55 is then withdrawn from treatment unit 50
and introduced into a second distillation column 60 maintained at a
bottom portion temperature of from about 100.degree. C. to
200.degree. C. and a pressure of 10.13 kPa to 101.3 kPa. A heavy
ends cut 70 containing primarily gamma butyrolactone and crotonic
acid is removed from the bottom of the second distillation column
60. The heavy ends cut may be recycled to the reactor 10. An
overhead product stream 65 is taken from the second distillation
column 60. The overhead contains primarily propionic acid and
acetic acid and is recycled to reactor 10. The product stream 65 is
routed to a third treatment unit 55. The product stream 65 is
heated in the third treatment step. In one embodiment, the heat
treatment involves boiling the product stream for an average
residence time of one hour at atmospheric pressure. The boiling
point for the product stream is approximately 165.degree. C. The
heat treatment step will have the effect of accelerating adverse
color producing reactions that might occur upon normal aging of the
product. The heat treatment step may also remove certain impurities
through cracking or polymerization mechanisms. A treated stream 80
is withdrawn from the third treatment unit 75 and introduced into a
third distillation column 85 maintained at a bottom portion
temperature of up to 200.degree. C. and a top portion temperature
of up to 150.degree. C. and a pressure of 10.13 kPa to 101.3 kPa to
separate the butyric acid product from remaining light ends 90 and
heavy ends 95 as the product is withdrawn as sidestream 100 from
the third distillation column. Optionally, the product butyric acid
stream may be cooled.
[0015] As mentioned previously, it is desirable for many purchasers
and applications that the butyric acid, ketones, and esters
described herein have low color values. An established method for
determining the color of light colored liquids such as these
organic compounds is to determine the APHA number or the liquid.
The lower the APHA color value, the more colorless the liquid. The
procedure for determining APHA color number is set forth in ASTM
D1209-62 T and E 202-62T. With respect to C.sub.1 to C.sub.6
carboxylic acids, low color values means acids having stable APHA
colors of less than or equal to 15. For ketones, low color refers
to stable APHA color values of less than or equal to 15 and for
esters, low color refers to stable APHA values of less than or
equal to 15.
[0016] In the butyric production process depicted in FIG. 1,
typical finished product APHA color values may range from about 0
to about 5. But, the color values of the product often increase
over time as the product ages under typical storage conditions.
Often the color degradation is intensified upon exposure of the
organic compounds to heat.
[0017] To provide a product having desirable low color values, it
may be necessary to undertake expensive and time consuming
additional purification steps to produce a low APHA color value
products. It has been unexpectedly determined that stable low APHA
color value carboxylic acid, ketone, and glycol ester products may
be consistently produced without the need for additional expensive
and time consuming purification steps. The low color value products
may be produced through each of the two different processes
described in this disclosure and through the use of a combination
of the two processes.
[0018] In a first embodiment, the stable color values of the
organic compounds are improved by combining a small amount of water
with the product organic compounds. In one embodiment, the water is
added directly to the finished organic compound product under
conditions of agitation, such as stirring. In another embodiment,
the water may be conveniently added by simply adding the water to
an empty mixing vessel and then adding the organic compound to the
vessel. The addition of the organic compound will typically provide
sufficient mixing energy to form a mixed solution having a
consistent concentration of water. The water may be added to the
organic compounds over a wide range of temperatures. For example,
the water and the organic compounds may be combined at any
temperature the water and the organic compound are in liquid
phases. In general, when the organic compound is butyric acid, in
one embodiment, the water and butyric acid may be combined at a
temperature of from about 0.degree. C. to about 160.degree. C.,
depending on the pressure of the system in which combining the
water and butyric takes place. In one embodiment, the water and
butyric acid are combined at a temperature of about 20.degree. C.
to about 50.degree. C.
[0019] In one process, the water is combined with the C.sub.1 to
C.sub.6 carboxylic acids, ketones having boiling points from
54.degree. C. to 170.degree. C., and esters having boiling points
from about 168.degree. C. to about 250.degree. C. until a
concentration of about 100 ppm water to about 50,000 ppm water is
achieved. In another embodiment, water is combined with a butyric
acid product to provide a water concentration of about 100 ppm to
about 10,000 ppm. In still another embodiment, water is combined
with butyric acid to achieve a concentration of about 500 ppm water
to about 1000 ppm water.
[0020] As mentioned, the water may be combined with the organic
compounds under conditions of agitation to achieve uniform
distribution of the water throughout the organic compound product
to provide a more uniform concentration of the water throughout the
organic compound.
[0021] Alternatively, water may be added to the organic compound
products by adding water in an overhead cut product stream of any
conventional production process for producing the organic
compounds. For example, with reference to FIG. 1, water may be
added to overhead stream 65 to achieve the beneficial color
characteristics described in this disclosure.
EXAMPLES
[0022] The following Examples demonstrate the color characteristics
improvement benefits resulting from adding water to a butyric acid
product.
Example 1
[0023] A commercially produced butyric acid was found to have an
APHA color value of 4. A first sample of the butyric acid was
boiled for one hour and found to have an APHA color of 31 after
boiling. Water was added to a second sample of the same
commercially produced batch of butyric acid, while stirring at room
temperature, until a concentration level of 1000 ppm water was
reached. The water containing second sample was then boiled for one
hour in the same manner as the first sample. Following boiling, the
APHA color value of the second sample was determined to be 12.
Examples 2-4
[0024] The effect of color degradation through aging was determined
on three samples from a commercially produced butyric acid run. The
samples were prepared by successive distillations of the same
portion of the commercially produced butyric acid run. The APHA
colors of the samples were determined to be as follows:
TABLE-US-00001 Example 2 8 Example 3 4 Example 4 4
[0025] The color variance of the samples is attributable to the
fact that more color bodies were present in the first distillation
sample as compared to the second and third distillation
samples.
[0026] Each sample was allowed to stand at room temperature
undisturbed for 24 hours and the APHA colors of the samples were
determined as follows:
TABLE-US-00002 Example 2 20 Example 3 2 Example 4 9
Examples 5-7
[0027] The effect of color improvement though the addition of water
was determined on three samples from a commercially produced
butyric acid run. The samples were prepared by successive
distillations of the same portion of the commercially produced
butyric acid run. The APHA colors of the samples were determined to
be as follows:
TABLE-US-00003 Example 5 13 Example 6 3 Example 7 1
[0028] The color variance of the samples is attributable to the
fact that more color bodies were present in the first distillation
sample as compared to the second and third distillation
samples.
[0029] To each of these samples was added 20,000 ppm, water while
stirring at room temperature, to ensure uniform distribution of the
water. Following addition of the water, the APHA colors of the
samples were determined as follows:
TABLE-US-00004 Example 5 1 Example 6 1 Example 7 1
[0030] A second process by which the color of C.sub.1 to C.sub.6
carboxylic acids, ketones having boiling points from 100.degree. C.
to 170.degree. C., and esters having boiling points from about
168.degree. C. to about 250.degree. C. may be improved is the use
of high temperature conditions during the separation and
purification of product streams of these organic compounds. It has
been determined that introducing a product stream of the organic
compound into a distillation column having a lower portion and an
upper portion wherein the upper and lower portions are maintained
at a temperature of about 23.degree. C. to about 250.degree. C. and
at a pressure of about 10.1 kPa to about 202.6 kPa such that
precursors of color bodies having boiling points lower than the
boiling point of the product being produced may thermally broken
down or removed in the overhead of the distillation column. The
stream may be introduced into one or more distillation columns
operating under these outlined conditions.
[0031] An exemplary embodiment is seen by reference to FIG. 1.
Color improvement of the butyric acid product may be achieved by
operating the first distillation column 20, the second distillation
column 60, or the third distillation column 85 the upper and lower
portions at a temperature of about 23.degree. C. to about
250.degree. C. and at a pressure of about 10.1 kPa to about 202.6
kPa. Subjecting the product stream to distillation under these
conditions allows precursors of color bodies, having boiling points
lower than the boiling point of the product being produced, to be
removed in the overhead stream from the distillation column.
[0032] In another embodiment, one of the distillation columns may
be operated at upper portion and lower portion temperatures of
170.degree. C. to about 180.degree. C. and at pressures of about
101 kPa to about 202 kPa to improve color characteristics of the
butyric acid. Alternatively, all three or any two of the
distillation columns may be operated at the above-stated conditions
to achieve color improvement.
[0033] In addition to using the water addition process for color
improvement outlined above alone or the high distillation column
temperature process discussed above in isolation, the improved
color characteristics may be obtained by using the water addition
and high distillation temperature processes in combination with
each other. An additional benefit of using the heat treatment step
is the removal of low boiling impurities.
[0034] Without being bound by theory, it is believed that the
processes disclosed herein obtain improved color properties of the
organic compound products through thermally breaking down,
removing, or preventing the formation of certain color bodies, or
precursors to the color bodies, during the processes for producing
the organic compounds of interest. Specifically, it is believed
that color degradation derives from the formation of Michael
Adducts during the production of the organic compounds in
accordance with this description.
[0035] It is believed that a compound formed from an unsaturated
ketone and a carboxylic acid in the production of the relevant
organic compounds leads to formation of a Michael Adduct in
accordance with the following reaction process:
##STR00001##
[0036] As seen from this reaction process, the Michael adduct, upon
dehydration, yields color bodies thought to lead to the undesirable
darker color products. It is believed that by adding water to the
organic compound products, formation of the color bodies is
prevented. With respect to the second process involving operating
the distillation column or columns during recovery of the organic
compounds at the described temperatures and pressures, a different
mechanism, accounts for color improvement in the organic compounds
produced. In this process, the intermediate product that is a
precursor of the Michael Adduct may be broken down thermally,
thereby preventing the ultimate formation of the offensive color
bodies in the organic compound products. Alternatively, the color
precursor may be removed in the overhead of the distillation column
as long as the precursor boils at a lower temperature than the
desired product organic compound.
[0037] All patents and publications referred to herein are hereby
incorporated by reference in their entireties.
[0038] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions, and alterations could be made without departing from
the spirit and scope of the invention as defined by the following
claims.
* * * * *