U.S. patent application number 11/655317 was filed with the patent office on 2007-08-30 for versatile oxidation byproduct purge process.
Invention is credited to Philip Edward Gibson, Kenny Randolph Parker.
Application Number | 20070203359 11/655317 |
Document ID | / |
Family ID | 38330594 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070203359 |
Kind Code |
A1 |
Gibson; Philip Edward ; et
al. |
August 30, 2007 |
Versatile oxidation byproduct purge process
Abstract
Disclosed is a process and apparatus for treating a purge stream
in a carboxylic acid production process. The process employs a
purge process that allows for the separation of oxidation
byproducts into benzoic acid and non-benzoic acid oxidation
byproducts, thus providing flexibility in the treatment and use of
such oxidation byproducts.
Inventors: |
Gibson; Philip Edward;
(Kingsport, TN) ; Parker; Kenny Randolph; (Afton,
TN) |
Correspondence
Address: |
Steven A. Owen;Eastman Chemical Company
P.O. Box 511
Kingsport
TN
37662-5075
US
|
Family ID: |
38330594 |
Appl. No.: |
11/655317 |
Filed: |
January 19, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60777829 |
Mar 1, 2006 |
|
|
|
60777903 |
Mar 1, 2006 |
|
|
|
60777905 |
Mar 1, 2006 |
|
|
|
60777907 |
Mar 1, 2006 |
|
|
|
60777992 |
Feb 28, 2006 |
|
|
|
60778117 |
Mar 1, 2006 |
|
|
|
60778120 |
Mar 1, 2006 |
|
|
|
60778123 |
Mar 1, 2006 |
|
|
|
60778139 |
Mar 1, 2006 |
|
|
|
Current U.S.
Class: |
562/410 ;
562/485 |
Current CPC
Class: |
C07C 51/42 20130101;
C07C 51/265 20130101; C07C 51/48 20130101; C07C 51/48 20130101;
C07C 51/47 20130101; C07C 51/487 20130101; C07C 51/487 20130101;
C07C 51/265 20130101; C07C 51/42 20130101; C07C 63/26 20130101;
C07C 63/26 20130101; C07C 51/47 20130101; C07C 63/26 20130101; C07C
63/26 20130101; C07C 63/26 20130101 |
Class at
Publication: |
562/410 ;
562/485 |
International
Class: |
C07C 51/16 20060101
C07C051/16; C07C 51/42 20060101 C07C051/42 |
Claims
1. A process for treating a purge feed stream comprising oxidation
byproducts, wherein said oxidation byproducts include benzoic acid
(BA) and non-BA byproducts, said process comprising: separating at
least a portion of said purge feed stream into a BA rich stream and
a non-BA byproduct rich stream.
2. The process of claim 1, further comprising routing at least a
portion of said BA rich stream and at least a portion of said
non-BA byproduct rich stream to different locations.
3. The process of claim 2, wherein said oxidation byproducts are
produced in a terephthalic acid (TPA) production process.
4. The process of claim 3, wherein said routing includes directing
at least a portion of said non-BA byproduct rich stream to one or
more locations that cause at least about 5 weight percent of said
non-BA byproducts present in said non-BA byproduct rich stream to
exit said TPA production process with a TPA product produced
therein and/or to be combined with said TPA product downstream of
said TPA production process.
5. The process of claim 3, wherein said routing includes
introducing at least a portion of said non-BA byproduct rich stream
into said TPA production process at one or more locations that
cause at least a portion of said non-BA byproducts present in said
non-BA byproduct rich stream to exit said TPA production process
with a TPA product produced therein.
6. The process of claim 5, wherein at least about 10 weight percent
of said non-BA byproducts present in said non-BA byproduct rich
stream exits said TPA production process with said TPA product.
7. The process of claim 3, wherein said routing includes directing
at least a portion of said BA rich stream outside said TPA
production process for sale, waste treatment, disposal,
purification, recovery, destruction, and/or use in a subsequent
chemical process.
8. The process of claim 7, wherein at least about 50 weight percent
of said BA present in said BA rich stream is treated in a waste
treatment process.
9. The process of claim 2, wherein said different locations include
various points in a TPA production process, an isophthalic acid
(IPA) production process, a phthalic acid (PA) production process,
a BA production process, a naphthalene-dicarboxylic acid (NDA)
production process, a dimethylterephthalate (DMT) production
process, a dimethylnaphthalate (DMN) production process, a
cyclohexane dimethanol (CHDM) production process, a
dimethyl-cyclohexanedicarboxylate (DMCD) production process, a
cyclohexanedicarboxylic acid (CHDA) production process, a
polyethylene terephthalate (PET) production process, a copolyester
production process, a polymer production process employing one or
more of TPA, IPA, PA, BA, NDA, DMT, DMN, CHDM, DMCD, or CHDA as one
component and/or as a monomer, and/or outside said TPA, IPA, PA,
BA, NDA, DMT, DMN, CHDM, DMCD, CHDA, or polymer production
processes.
10. The process of claim 1, wherein said purge feed stream
comprises less than about 5 weight percent solids.
11. The process of claim 1, wherein said non-BA byproduct rich
stream comprises at least about 70 weight percent solids.
12. The process of claim 1, wherein said BA rich stream comprises
at least about 70 weight percent fluid.
13. The process of claim 1, wherein said non-BA byproduct rich
stream comprises in the range of from about 5 to about 40 weight
percent liquid.
14. The process of claim 13, further comprising drying said non-BA
byproduct rich stream to thereby produce a dried non-BA byproduct
stream comprising less than about 5 weight percent liquid.
15. The process of claim 13, further comprising adding a liquid to
said non-BA byproduct rich stream to thereby produce a reslurried
non-BA byproduct stream comprising at least about 35 weight percent
liquid.
16. The process of claim 1, wherein at least a portion of said
oxidation byproducts are byproducts from the partial oxidation of
an aromatic compound.
17. The process of claim 16, wherein said aromatic compound is
para-xylene.
18. The process of claim 1, wherein said non-BA byproducts comprise
IPA, PA, trimellitic acid, 2,5,4'-tricarboxybiphenyl,
2,5,4'-tricarboxybenzophenone, para-toluic acid (p-TAc),
4-carboxybenzaldehyde (4-CBA), naphthalene dicarboxylic acid,
monocarboxyfluorenones, monocarboxyfluorenes, and/or
dicarboxyfluorenones.
19. The process of claim 1, wherein the concentration of said BA in
said BA rich stream is at least about 1.5 times the concentration
of said BA in said purge feed stream on a weight basis.
20. The process of claim 19, wherein the concentration of said BA
in said purge feed stream is in the range of from about 500 to
about 150,000 ppmw.
21. The process of claim 1, wherein the concentration of said
non-BA byproducts in said non-BA byproduct rich stream is at least
about 1.5 times of the concentration of said non-BA byproducts in
said purge feed stream on a weight basis.
22. The process of claim 21, wherein the cumulative concentration
of said non-BA byproducts in said purge feed stream is in the range
of from about 500 to about 50,000 ppmw.
23. The process of claim 1, wherein the concentration of said BA in
said BA rich stream is at least about 5 times the concentration of
said BA in said purge feed stream on a weight basis, wherein the
concentration of said non-BA byproducts in said non-BA byproduct
rich stream is at least about 5 times the concentration of said
non-BA byproducts in said purge feed stream on a weight basis.
24. The process of claim 1, wherein said purge feed stream further
comprises at least about 75 weight percent of a solvent.
25. The process of claim 24, wherein said solvent comprises a
monocarboxylic acid.
26. The process of claim 24, wherein said solvent comprises acetic
acid and/or water.
27. The process of claim 24, further comprising directly or
indirectly routing at least a portion of said solvent back to an
oxidizer within which at least a portion of said oxidation
byproducts are formed.
28. The process of claim 27, wherein at least about 50 weight
percent of said solvent contained in said purge feed stream is
routed back to said oxidizer.
29. The process of claim 1, wherein said purge feed stream further
comprises one or more catalyst components.
30. The process of claim 29, wherein said catalyst components
comprise cobalt, manganese, and/or bromine.
31. The process of claim 29, further comprising separating said
purge feed stream into said BA rich stream, said non-BA byproduct
rich stream, and a catalyst rich stream.
32. The process of claim 31, further comprising routing at least a
portion of said BA rich stream, at least a portion of said non-BA
byproduct rich stream, and at least a portion of said catalyst rich
stream to at least two different locations.
33. The process of claim 32, wherein said oxidation byproducts are
produced in a TPA production process.
34. The process of claim 33, wherein said routing includes
introducing at least a portion of said catalyst rich stream into an
oxidizer of said TPA process within which at least a portion of
said oxidation byproducts were formed.
35. The process of claim 34, wherein at least about 50 weight
percent of said catalyst components in said catalyst rich stream
are introduced into said oxidizer.
36. The process of claim 31, wherein the cumulative concentration
of all of said catalyst components in said catalyst rich stream is
at least about 1.5 times the concentration of said catalyst
components in said purge feed stream on a weight basis.
37. The process of claim 36, wherein the cumulative concentration
of said catalyst components in said purge feed stream is in the
range of from about 500 to about 20,000 ppmw.
38. The process of claim 31, wherein the cumulative concentration
of all of said catalyst components in said catalyst rich stream is
at least about 5 times the concentration of said catalyst
components in said purge feed stream on a weight basis, wherein the
concentration of said BA in said BA rich stream is at least about 5
times the concentration of said BA in said purge feed stream on a
weight basis, wherein the concentration of said non-BA byproducts
in said non-BA byproduct rich stream is at least about 5 times the
concentration of non-BA byproducts in said purge feed stream on a
weight basis.
39. The process of claim 31, wherein said separating includes
separating said purge feed stream into said non-BA byproduct rich
stream and a catalyst and BA rich stream followed by separating
said catalyst and BA rich stream into said BA rich stream and a
catalyst rich stream.
40. The process of claim 31, wherein said separating includes
separating said purge feed stream into said BA rich stream and a
catalyst and non-BA byproduct rich stream followed by separating
said catalyst and non-BA byproduct rich stream into said non-BA
byproduct rich stream and a catalyst rich stream.
41. A terephthalic acid (TPA) production process comprising: (a)
oxidizing an aromatic compound to thereby produce a slurry
comprising TPA and oxidation byproducts, wherein said oxidation
byproducts include benzoic acid (BA) and non-BA byproducts; and (b)
substantially isolating said TPA from said slurry to thereby
produce a TPA product, wherein the cumulative rate at which said
non-BA byproducts exit said TPA production process with said TPA
product and/or are combined with said TPA product downstream of
said TPA production process is at least about 5 percent of the
make-rate of said non-BA byproducts in said TPA production
process.
42. The process of claim 41, wherein the rate at which said BA
exits said TPA production process with said TPA product and/or is
combined with said TPA product downstream of said TPA production
process is less than about 50 percent of the make-rate of said BA
in said TPA production process.
43. The process of claim 41, wherein the cumulative rate at which
said non-BA byproducts exit said TPA production process with said
TPA product and/or are combined with said TPA product downstream of
said TPA production process is at least about 10 percent the
make-rate of said non-BA byproducts in said TPA production
process.
44. The process of claim 41, wherein said isolating of step (b)
comprises subjecting said purified slurry to solid/liquid
separation to thereby produce a predominately solid phase stream
comprising at least a portion of said TPA product and a mother
liquor, wherein said mother liquor comprises at least a portion of
said oxidation byproducts and one or more catalyst components.
45. The process of claim 44, said process further comprising
directly or indirectly routing a first portion of said mother
liquor to an oxidizer where said oxidizing of step (a) is carried
out.
46. The process of claim 44, said process further comprising
diverting a second portion of said mother liquor so as to form a
purge feed stream and separating said purge feed stream into a BA
rich stream, a non-BA byproduct rich stream, and a catalyst rich
stream.
47. The process of claim 46, further comprising routing at least a
portion of said BA rich stream, at least a portion of said non-BA
byproduct rich stream, and at least a portion of said catalyst rich
stream to at least two different locations.
48. The process of claim 47, wherein said routing includes
introducing at least a portion of said catalyst rich stream into an
oxidizer where said oxidizing of step (a) is carried out.
49. The process of claim 47, wherein said routing includes
introducing at least a portion of said non-BA byproduct rich stream
into said TPA production process at one or more locations that
cause at least a portion of said non-BA byproducts present in said
non-BA byproduct rich stream to exit said TPA production process
with said TPA product.
50. The process of claim 47, wherein said routing includes
introducing at least a portion of said non-BA byproduct rich stream
into said slurry and/or said TPA product.
51. The process of claim 47, wherein said routing includes
directing at least a portion of said BA rich stream outside said
TPA production process for sale, waste treatment, disposal,
purification, recovery, destruction, and/or use in a subsequent
chemical process.
52. The process of claim 46, wherein said purge feed stream
comprises less than about 5 weight percent solids, wherein said
catalyst rich stream comprises at least about 70 weight percent
solids, wherein said BA rich stream comprises at least about 70
weight percent liquid, wherein said non-BA byproduct rich stream
comprises in the range of from about 5 to about 30 weight percent
liquid.
53. The process of claim 46, wherein the concentration of said BA
in said BA rich stream is at least about 1.5 times the
concentration of said BA in said purge feed stream on a weight
basis, wherein the concentration of said non-BA byproducts in said
non-BA byproduct rich stream is at least about 1.5 times of the
concentration of said non-BA byproducts in said purge feed stream
on a weight basis, wherein the concentration of said catalyst
components in said catalyst rich stream is at least about 1.5 times
the concentration of said catalyst components in said purge feed
stream on a weight basis.
54. The process of claim 41, step (a) further comprising subjecting
at least a portion of said slurry to purification to thereby
produce a purified slurry comprising at least a portion of said TPA
and at least a portion of said oxidation byproducts.
55. The process of claim 54, wherein said purification comprises
hydrogenation and/or oxidation.
56. The process of claim 41, wherein said non-BA byproducts
comprise IPA, PA, trimellitic acid, 2,5,4'-tricarboxybiphenyl,
2,5,4'-tricarboxybenzophenone, p-TAc, 4-CBA, naphthalene
dicarboxylic acid, monocarboxyfluorenones, monocarboxyfluorenes,
and/or dicarboxyfluorenones.
57. The process of claim 41, wherein said TPA product comprises a
cumulative concentration of mono-functional oxidation byproducts of
less than about 1,000 ppmw.
58. The process of claim 57, wherein said mono-functional oxidation
byproducts comprise BA, 4-CBA, p-TAc, monocarboxyfluorenones,
monocarboxyfluorenes, bromo-benzoic acid, and/or bromo-acetic
acid.
59. A process for treating a purge feed stream comprising
impurities and one or more catalyst components, said process
comprising: separating said purge feed stream into a
mono-functional impurity rich stream, a mono-functional impurity
depleted stream, and a catalyst rich stream.
60. The process of claim 59, wherein said impurities include
oxidation byproducts.
61. The process of claim 60, wherein said oxidation byproducts
include benzoic acid, isophthalic acid, p-toluic acid (p-TAc),
and/or 4-carboxybenzaldehyde.
62. The process of claim 59, wherein said purge feed stream further
comprises solvent, water, and/or terephthalic acid.
63. The process of claim 59, wherein said purge feed stream
comprises less than about 5 weight percent solids.
64. The process of claim 59, wherein said impurities comprise
mono-functional impurities and non-mono-functional impurities,
wherein said mono-functional impurities comprise at least one
monocarboxylic species.
65. The process of claim 64, wherein said mono-functional
impurities comprise benzoic acid, p-TAc, monocarboxyfluorenones,
monocarboxyfluorenes, bromo-benzoic acid, and/or bromo-acetic
acid.
66. The process of claim 60, wherein benzoic acid (BA) is the
primary oxidation byproduct present in said mono-functional
impurity rich stream.
67. The process of claim 60, wherein non-BA oxidation byproducts
are the primary oxidation byproducts present in said
mono-functional impurity depleted stream.
68. The process of claim 67, wherein said non-BA oxidation
byproducts include isophthalic acid and/or trimellitic acid.
69. The process of claim 59, wherein said catalyst components
comprise cobalt, manganese, and/or bromine.
70. The process of claim 59, further comprising routing at least a
portion of said mono-functional impurity rich stream, at least a
portion of said mono-functional impurity depleted stream, and at
least a portion of said catalyst rich stream to at least two
different locations.
71. The process of claim 70, wherein said impurities are produced
in a terephthalic acid (TPA) production process.
72. The process of claim 71, wherein said routing includes
directing at least a portion of said mono-functional impurity rich
stream outside said TPA production process for sale, waste
treatment, disposal, and/or destruction.
73. The process of claim 71, wherein non-mono-functional oxidation
byproducts are the primary oxidation byproducts present in said
mono-functional impurity depleted stream, wherein said routing
includes directing at least a portion of said mono-functional
impurity depleted stream to one or more locations that cause a
substantial portion of said non-mono-functional oxidation
byproducts present in said mono-functional impurity depleted stream
to exit said TPA production process with a TPA product produced
therein and/or to be combined with said TPA product downstream of
said TPA production process.
74. The process of claim 73, wherein said TPA product comprises a
cumulative concentration of mono-functional oxidation byproducts of
less than about 1,000 ppmw.
75. The process of claim 70, wherein said routing includes
introducing at least a portion of said catalyst rich stream into an
oxidizer within which said impurities are formed.
76. The process of claim 70, wherein said different locations
include various points in a polymer production process employing
terephthalic acid as one component and/or as a monomer, said TPA
production process, a polyethylene terephthalate (PET) production
process, and/or outside said polymer, TPA, or PET production
processes.
Description
RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
Provisional Pat. App. Ser. Nos. 60/777,829; 60/777,903; 60/777,905;
60/777,907; 60/777,992; 60/778,117; 60/778,120; 60/778,123; and
60/778,139, all filed Mar. 1, 2006, the entire disclosures of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a purge process
for use in the production of a carboxylic acid. More specifically,
the present invention relates to the use of a purge process for
separating and routing various oxidation byproducts formed in a
terephthalic acid production process.
[0004] 2. Description of the Prior Art
[0005] In conventional terephthalic acid (TPA) production
processes, para-xylene undergoes oxidation. In such processes,
oxidation byproducts are produced along with the formation of TPA.
Typically, such oxidation byproducts include the oxidation
intermediates and side reaction products formed in the oxidation of
para-xylene, as well as any impurities originating from the raw
materials. Some of these byproducts are detrimental to the use of
TPA in various production processes, such as for the production of
polyethylene terephthalate (PET), dimethyl terephthalate (DMT), or
cyclohexane dimethanol (CHDM). Accordingly, at least a portion of
these detrimental oxidation byproducts are typically removed from
the TPA production process in order to yield a commercially usable
TPA product. On the other hand, some oxidation byproducts are not
detrimental to these production processes. In fact, some oxidation
byproducts, such as bifunctional compounds, are actually useful in
a PET production process.
[0006] It is known in the art to employ a purge process to remove
oxidation byproducts from TPA production processes, thus rendering
the TPA product suitable for use in the various above-mentioned
production processes. A purge process typically involves separating
a portion of a mother liquor, generated from the separation of
liquid from the product stream, to form a purge feed stream. The
purge feed stream generally constitutes in the range of from 5 to
40 percent of the total mother liquor, but can be up to 100 percent
of the mother liquor. In a typical conventional purge process, the
purge feed stream contains acetic acid, catalyst, water, oxidation
byproducts, and minor amounts of terephthalic acid. The purge feed
stream in conventional processes is usually resolved into a
catalyst rich stream and an oxidation byproduct rich stream. The
catalyst rich stream is typically recycled to the oxidizer, whereas
the oxidation byproduct rich stream is usually routed out of the
TPA production process for waste treatment or destruction. In such
a conventional process, the oxidation byproduct rich stream
contains all of the different types of byproducts generated in the
oxidation step. Thus, conventional purge processes expel both
detrimental and non-detrimental oxidation byproducts from the TPA
production process.
[0007] Accordingly, there is a need for a purge process that can
differentiate detrimental oxidation byproducts from non-detrimental
and/or beneficial oxidation byproducts. Such differentiation
enables the operator to allow some or all of the non-detrimental
and/or beneficial oxidation byproducts to exit the TPA production
process along with the TPA product in order to increase product
yield and decrease costs associated with waste treatment.
SUMMARY OF THE INVENTION
[0008] One embodiment of the present invention concerns a process
for treating a purge feed stream comprising oxidation byproducts,
wherein the oxidation byproducts include benzoic acid (BA) and
non-BA byproducts. The process of this embodiment comprises:
separating at least a portion of the purge feed stream into a BA
rich stream and a non-BA byproduct rich stream.
[0009] Another embodiment of the present invention concerns a
terephthalic acid (TPA) production process comprising: (a)
oxidizing an aromatic compound to thereby produce a slurry
comprising TPA and oxidation byproducts, wherein the oxidation
byproducts include benzoic acid (BA) and non-BA byproducts; and (b)
substantially isolating the TPA from the slurry to thereby produce
a TPA product, wherein the cumulative rate at which the non-BA
byproducts exit the TPA production process with the TPA product
and/or are combined with the TPA product downstream of the TPA
production process is at least about 5 percent of the make-rate of
the non-BA byproducts in the TPA production process.
[0010] Still another embodiment of the present invention concerns a
process for treating a purge feed stream comprising impurities and
one or more catalyst components. The process of this embodiment
comprises: separating the purge feed stream into a mono-functional
impurity rich stream, a mono-functional impurity depleted stream,
and a catalyst rich stream.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0011] A preferred embodiment of the present invention is described
in detail below with reference to the attached drawing figures,
wherein:
[0012] FIG. 1 is a process flow diagram illustrating a system for
the production and purification of carboxylic acid constructed in
accordance with the present invention, particularly illustrating a
configuration where the crude slurry from the oxidation reactor is
subjected to purification, the resulting purified slurry is
subjected to product isolation, and a portion of the mother liquor
from the product isolation zone is employed as a feed to a purge
treatment system;
[0013] FIG. 2 is a process flow diagram illustrating an overview of
a purge treatment system constructed in accordance with a first
embodiment of the present invention, particularly illustrating a
configuration where the purge feed stream is subjected to
non-benzoic acid (non-BA) byproduct removal and the resulting
catalyst and benzoic acid (BA) rich mother liquor is subjected to
BA removal;
[0014] FIG. 3 is a process flow diagram illustrating in detail a
purge treatment system constructed in accordance with a first
configuration of the first embodiment of the present invention,
particularly illustrating a configuration where the purge feed
stream is subjected to concentration, the resulting concentrated
purge stream is subjected to solid/liquid separation, the resulting
catalyst and BA rich mother liquor is subjected to concentration,
and the resulting concentrated catalyst and BA rich mother liquor
is subjected to BA/catalyst separation;
[0015] FIG. 4 is a process flow diagram illustrating in detail a
purge treatment system constructed in accordance with a second
configuration of the first embodiment of the present invention,
particularly illustrating a configuration where the purge feed
stream is subjected to concentration, the resulting concentrated
purge stream is subjected to solid/liquid separation, the resulting
catalyst and BA rich mother liquor is subjected to catalyst
removal, and the resulting BA and solvent rich stream is subjected
to BA/solvent separation;
[0016] FIG. 5 is a process flow diagram illustrating an overview of
a purge treatment system constructed in accordance with a second
embodiment of the present invention, particularly illustrating a
configuration where the purge feed stream is subjected to BA
removal and the resulting catalyst and non-BA byproduct rich stream
is subjected to non-BA byproduct removal; and
[0017] FIG. 6 is a process flow diagram illustrating in detail a
purge treatment system constructed in accordance with the second
embodiment of the present invention, particularly illustrating a
configuration where the purge feed stream is subjected to
concentration, the resulting concentrated purge stream is subjected
to BA separation, the resulting catalyst and non-BA byproduct rich
stream is reslurried, and the reslurried catalyst and non-BA
byproduct rich stream is subjected to solid/liquid separation.
DETAILED DESCRIPTION
[0018] FIG. 1 illustrates an embodiment of the present invention
where carboxylic acid produced in an oxidation reactor and purified
in a purification reactor is subjected to product
isolation/catalyst removal. A portion of the resulting mother
liquor from the product isolation/catalyst removal zone is treated
in a purge treatment zone and resolved into a catalyst rich stream,
a benzoic acid (BA) rich stream, and a non-BA byproduct rich
stream. Various embodiments of the purge zone are described in
detail below with reference to FIGS. 2-6.
[0019] In the embodiment illustrated in FIG. 1, a predominately
fluid-phase feed stream containing an oxidizable compound (e.g.,
para-xylene), a solvent (e.g., acetic acid and/or water), and a
catalyst system (e.g., cobalt, manganese, and/or bromine) can be
introduced into oxidation zone 10. A predominately gas-phase
oxidant stream containing molecular oxygen can also be introduced
into oxidation zone 10. The fluid- and gas-phase feed streams form
a multi-phase reaction medium in oxidation zone 10. The oxidizable
compound can undergo partial oxidation in a liquid phase of the
reaction medium contained in oxidation zone 10.
[0020] In one embodiment of the present invention, oxidation zone
10 can comprise an agitated reactor. Agitation of the reaction
medium in oxidation zone 10 can be provided by any means known in
the art. As used herein, the term "agitation" shall denote work
dissipated into the reaction medium causing fluid flow and/or
mixing. In one embodiment, oxidation zone 10 can be a
mechanically-agitated reactor equipped with means for mechanically
agitating the reaction medium. As used herein, the term "mechanical
agitation" shall denote agitation of the reaction medium caused by
physical movement of a rigid or flexible element(s) against or
within the reaction medium. For example, mechanical agitation can
be provided by rotation, oscillation, and/or vibration of internal
stirrers, paddles, vibrators, or acoustical diaphragms located in
the reaction medium. In another embodiment of the present
invention, oxidation zone 10 can comprise a bubble column reactor.
As used herein, the term "bubble column reactor" shall denote a
reactor for facilitating chemical reactions in a multi-phase
reaction medium, wherein agitation of the reaction medium is
provided primarily by the upward movement of gas bubbles through
the reaction medium. As used herein, the terms "majority,"
"primarily," and "predominately" shall mean more than 50
percent.
[0021] The oxidizable compound present in the fluid-phase feed
stream introduced into oxidation zone 10 can comprise at least one
hydrocarbyl group. Also, the oxidizable compound can comprise an
aromatic compound. In one embodiment, the oxidizable compound can
comprise an aromatic compound with at least one attached
hydrocarbyl group or at least one attached substituted hydrocarbyl
group or at least one attached heteroatom or at least one attached
carboxylic acid function (--COOH). In another embodiment, the
oxidizable compound can comprise an aromatic compound with at least
one attached hydrocarbyl group or at least one attached substituted
hydrocarbyl group with each attached group comprising from 1 to 5
carbon atoms. In yet another embodiment, the oxidizable compound
can be an aromatic compound having exactly two attached groups with
each attached group comprising exactly one carbon atom and
consisting of methyl groups and/or substituted methyl groups and/or
at most one carboxylic acid group. Suitable examples of the
oxidizable compound include, but are not limited to, para-xylene,
meta-xylene, para-tolualdehyde, meta-tolualdehyde, para-toluic
acid, meta-toluic acid, and/or acetaldehyde. In one embodiment of
the present invention, the oxidizable compound comprises
para-xylene.
[0022] A "hydrocarbyl group," as defined herein, is at least one
carbon atom that is bonded only to hydrogen atoms and/or to other
carbon atoms. A "substituted hydrocarbyl group," as defined herein,
is at least one carbon atom bonded to at least one heteroatom and
to at least one hydrogen atom. "Heteroatoms," as defined herein,
are all atoms other than carbon and hydrogen atoms. "Aromatic
compounds," as defined herein, comprise an aromatic ring and can
comprise at least 6 carbon atoms and can also comprise only carbon
atoms as part of the ring. Suitable examples of such aromatic rings
include, but are not limited to, benzene, biphenyl, terphenyl,
naphthalene, and other carbon-based fused aromatic rings.
[0023] The amount of oxidizable compound present in the fluid-phase
feed stream introduced into oxidation zone 10 can be in the range
of from about 4 to about 20 weight percent, or in the range of from
6 to 15 weight percent.
[0024] The solvent present in the fluid-phase feed stream
introduced into primary oxidation reactor 10 can comprise an acid
component and a water component. The solvent can be present in the
fluid-phase feed stream at a concentration in the range of from
about 60 to about 98 weight percent, in the range of from about 80
to about 96 weight percent, or in the range of from 85 to 94 weight
percent. The acid component of the solvent can be an organic low
molecular weight monocarboxylic acid having from 1 to 6 carbon
atoms, or 2 carbon atoms. In one embodiment, the acid component of
the solvent can comprise acetic acid. The acid component can make
up at least about 75 weight percent of the solvent, at least about
80 weight percent of the solvent, or in the range of from 85 to 98
weight percent of the solvent, with the balance being water.
[0025] As mentioned above, the fluid-phase feed stream introduced
into oxidation zone 10 can also include a catalyst system. The
catalyst system can be a homogeneous, liquid-phase catalyst system
capable of promoting at least partial oxidation of the oxidizable
compound. Also, the catalyst system can comprise at least one
multivalent transition metal. In one embodiment, the catalyst
system can comprise cobalt, bromine, and/or manganese.
[0026] When cobalt is present in the catalyst system, the
fluid-phase feed stream can comprise cobalt in an amount such that
the concentration of cobalt in the liquid phase of the reaction
medium is maintained in the range of from about 300 to about 6,000
parts per million by weight (ppmw), in the range of from about 700
to about 4,200 ppmw, or in the range of from 1,200 to 3,000 ppmw.
When bromine is present in the catalyst system, the fluid-phase
feed stream can comprise bromine in an amount such that the
concentration of bromine in the liquid phase of the reaction medium
is maintained in the range of from about 300 to about 5,000 ppmw,
in the range of from about 600 to about 4,000 ppmw, or in the range
of from 900 to 3,000 ppmw. When manganese is present in the
catalyst system, the liquid-phase feed stream can comprise
manganese in an amount such that the concentration of manganese in
the liquid phase of the reaction medium is maintained in the range
of from about 20 to about 1,000 ppmw, in the range of from about 40
to about 500 ppmw, or in the range of from 50 to 200 ppmw.
[0027] In one embodiment of the present invention, cobalt and
bromine can both be present in the catalyst system. The weight
ratio of cobalt to bromine (Co:Br) in the catalyst system can be in
the range of from about 0.25:1 to about 4:1, in the range of from
about 0.5:1 to about 3:1, or in the range of from 0.75:1 to 2:1. In
another embodiment, cobalt and manganese can both be present in the
catalyst system. The weight ratio of cobalt to manganese (Co:Mn) in
the catalyst system can be in the range of from about 0.3:1 to
about 40:1, in the range of from about 5:1 to about 30:1, or in the
range of from 10:1 to 25:1.
[0028] During oxidation, the oxidizable compound (e.g.,
para-xylene) can be continuously introduced into oxidation zone 10
at a rate of at least about 5,000 kilograms per hour, at a rate in
the range of from about 10,000 to about 80,000 kilograms per hour,
or in the range of from 20,000 to 50,000 kilograms per hour. During
oxidation, the ratio of the mass flow rate of the solvent to the
mass flow rate of the oxidizable compound entering oxidation zone
10 can be maintained in the range of from about 2:1 to about 50:1,
in the range of from about 5:1 to about 40:1, or in the range of
from 7.5:1 to 25:1.
[0029] The predominately gas-phase oxidant stream introduced into
oxidation zone 10 can comprise in the range of from about 5 to
about 40 mole percent molecular oxygen, in the range of from about
15 to about 30 mole percent molecular oxygen, or in the range of
from 18 to 24 mole percent molecular oxygen. The balance of the
oxidant stream can be comprised primarily of a gas or gases, such
as nitrogen, that are inert to oxidation. In one embodiment, the
oxidant stream consists essentially of molecular oxygen and
nitrogen. In another embodiment, the oxidant stream can be dry air
that comprises about 21 mole percent molecular oxygen and about 78
to about 81 mole percent nitrogen. In an alternative embodiment of
the present invention, the oxidant stream can comprise
substantially pure oxygen.
[0030] During liquid-phase oxidation in oxidation zone 10, the
oxidant stream can be introduced into oxidation zone 10 in an
amount that provides molecular oxygen somewhat exceeding the
stoichiometric oxygen demand. Thus, the ratio of the mass flow rate
of the oxidant stream (e.g., air) to the mass flow rate of the
oxidizable compound (e.g., para-xylene) entering oxidation zone 10
can be maintained in the range of from about 0.5:1 to about 20:1,
in the range of from about 1:1 to about 10:1, or in the range of
from 2:1 to 6:1.
[0031] The liquid-phase oxidation reaction carried out in oxidation
zone 10 can be a precipitating reaction that generates solids. In
one embodiment, the liquid-phase oxidation carried out in oxidation
zone 10 can cause at least about 10 weight percent of the
oxidizable compound (e.g., para-xylene) introduced into oxidation
zone 10 to form solids (e.g., crude terephthalic acid (CTA)
particles) in the reaction medium. In another embodiment, the
liquid-phase oxidation carried out in oxidation zone 10 can cause
at least about 50 weight percent of the oxidizable compound (e.g.,
para-xylene) introduced into oxidation zone 10 to form solids
(e.g., CTA particles) in the reaction medium. In yet another
embodiment, the liquid-phase oxidation carried out in oxidation
zone 10 can cause at least about 90 weight percent of the
oxidizable compound (e.g., para-xylene) introduced into oxidation
zone 10 to form solids (e.g., CTA particles) in the reaction
medium. In one embodiment, the solids content of the reaction
medium can be maintained in the range of from about 5 to about 40
weight percent, in the range of from about 10 to about 35 weight
percent, or in the range of from 15 to 30 weight percent. As used
herein, the term "solids content" shall denote the weight percent
solids in a multi-phase mixture.
[0032] During oxidation in oxidation zone 10, the multi-phase
reaction medium can be maintained at an elevated temperature in the
range of from about 125 to about 200.degree. C., in the range of
from about 150 to about 180.degree. C., or in the range of from 155
to 165.degree. C. The overhead pressure in oxidation zone 10 can be
maintained in the range of from about 1 to about 20 bar gauge
(barg), in the range of from about 2 to about 12 barg, or in the
range of from 4 to 8 barg.
[0033] In the embodiment of FIG. 1, a crude slurry can be withdrawn
from an outlet of oxidation zone 10 via line 12. The solid phase of
the crude slurry in line 12 can be formed primarily of solid
particles of CTA. The liquid phase of the crude slurry in line 12
can be a liquid mother liquor comprising at least a portion of the
solvent, one or more catalyst components, and minor amounts of
dissolved terephthalic acid (TPA). The solids content of the crude
slurry in line 12 can be the same as the solids content of the
reaction medium in oxidation zone 10, discussed above.
[0034] In one embodiment of the present invention, the crude slurry
in line 12 can comprise impurities. As used herein, the term
"impurities" is defined as any substance other than TPA, solvent,
catalyst, and water. Such impurities can include oxidation
byproducts formed during the at least partial oxidation of the
above-mentioned oxidizable compound (e.g., para-xylene) including,
but not limited to, benzoic acid (BA), bromo-benzoic acid,
bromo-acetic acid, isophthalic acid, trimellitic acid,
2,5,4'-tricarboxybiphenyl, 2,5,4'-tricarboxybenzophenone,
para-toluic acid (p-TAc), 4-carboxybenzaldehyde (4-CBA),
monocarboxyfluorenones, monocarboxyfluorenes, and/or
dicarboxyfluorenones.
[0035] In one embodiment of the present invention, the impurities
in the crude slurry in line 12 can be classified according to their
functionality in a polyester polymerization process, such as, for
example, in the production of polyethylene terephthalate (PET).
Some impurities can be mono-functional while others can be
non-mono-functional in a process for producing a polyester (e.g.,
PET). As used herein, an impurity that is "mono-functional" is
defined as having only one reactive moiety in a process for
producing a polyester (e.g., PET). Typically, such reactive
moieties can include carboxyl and/or hydroxyl groups.
Mono-functional impurities include, but are not limited to, BA,
bromo-benzoic acid, bromo-acetic acid, 4-CBA, p-TAc,
monocarboxyfluorenones, and/or monocarboxyfluorenes.
Non-mono-functional impurities can comprise any impurity having
less than or greater than one reactive moiety in a process for
producing a polyester (e.g., PET). Non-mono-functional impurities
include, but are not limited to, isophthalic acid, trimellitic
acid, 2,5,4'-tricarboxybiphenyl, 2,5,4'-tricarboxybenzophenone, and
dicarboxyfluorenones.
[0036] Subsequent to removal from oxidation zone 10, the crude
slurry can optionally be introduced into purification zone 14 via
line 12. In one embodiment, the crude slurry can be treated in
purification zone 14 such that the concentration of at least one of
the above-mentioned impurities in the crude slurry is reduced,
thereby producing a purified slurry. Such reduction in the
concentration of impurities in the TPA can be accomplished by
oxidative digestion, hydrogenation, and/or
dissolution/recrystallization.
[0037] In one embodiment of the present invention, the crude slurry
fed to purification zone 14 can have a 4-CBA content of at least
about 100 parts per million based on the weight of the solids in
the crude slurry (ppmw.sub.cs), in the range of from about 200 to
about 10,000 ppmw.sub.cs, or in the range of from 800 to 5,000
ppmw.sub.cs. The crude slurry fed to purification zone 14 can have
a p-TAc content of at least about 250 ppmw.sub.cs, in the range of
from about 300 to about 5,000 ppmw.sub.cs, or in the range of from
400 to 1,500 ppmw.sub.cs. The purified slurry exiting purification
zone 14 can have a 4-CBA content of less than about 150 parts per
million based on the weight of the solids in the purified slurry
(ppmw.sub.ps), less than about 100 ppmw.sub.ps, or less than 50
ppmw.sub.ps. The purified slurry exiting purification zone 14 can
have a p-TAc content of less than about 300 ppmw.sub.ps, less than
about 200 ppmw.sub.ps, or less than 150 ppmw.sub.ps. In one
embodiment, treatment of the crude slurry in purification zone 14
can cause the purified slurry exiting purification zone 14 to have
a 4-CBA and/or p-TAc content that is at least about 50 percent less
than the 4-CBA and/or p-TAc content of the crude slurry fed to
purification zone 14, at least about 85 percent less, or at least
95 percent less. By way of illustration, if the 4-CBA content of
the crude slurry fed to purification zone 14 is 200 ppmw.sub.cs and
the 4-CBA content of the purified slurry exiting purification zone
14 is 100 ppmw.sub.ps, then the 4-CBA content of the purified
slurry is 50 percent less than the 4-CBA content of the crude
slurry.
[0038] In one embodiment of the present invention, the crude slurry
can be subjected to purification by oxidative digestion in
purification zone 14. As used herein, the term "oxidative
digestion" denotes a process step or steps where a feed comprising
solid particles is subjected to oxidation under conditions
sufficient to permit oxidation of at least a portion of the
impurities originally trapped in the solid particles. Purification
zone 14 can comprise one or more reactors or zones. In one
embodiment, purification zone 14 can comprise one or more
mechanically-agitated reactors. A secondary oxidant stream, which
can have the same composition as the gas-phase oxidant stream fed
to oxidation zone 10, can be introduced into purification zone 14
to provide the molecular oxygen required for oxidative digestion.
Additional oxidation catalyst can be added if necessary. In an
alternative embodiment of the present invention, a stream
comprising hydrogen can be introduced into purification zone 14 for
at least partial hydrogenation of the crude slurry.
[0039] When oxidative digestion is employed in purification zone
14, the temperature at which oxidative digestion is carried out can
be at least about 10.degree. C. greater than the temperature of
oxidation in oxidation zone 10, in the range of from about 20 to
about 80.degree. C. greater, or in the range of from 30 to
50.degree. C. greater. The additional heat required for the
operation of purification zone 14 can be provided by supplying a
vaporized solvent to purification zone 14 and allowing the
vaporized solvent to condense therein. The oxidative digestion
temperature in purification zone 14 can be maintained in the range
of from about 180 to about 240.degree. C., in the range of from
about 190 to about 220.degree. C., or in the range of from 200 to
210.degree. C. The oxidative digestion pressure in purification
zone 14 can be maintained in the range of from about 100 to about
350 pounds per square inch gauge (psig), in the range of from about
175 to about 275 psig, or in the range of from 185 to 225 psig.
[0040] In one embodiment of the present invention, purification
zone 14 can include two digestion reactors/zones--an initial
digester and a final digester. When purification zone 14 includes
an initial digester and a final digester, the final digester can be
operated at a lower temperature and pressure than the initial
digester. In one embodiment, the operating temperature of the final
digester can be at least about 2.degree. C. lower than the
operating temperature of the initial digester, or in the range of
from about 5 to about 15.degree. C. lower than the operating
temperature of the initial digester. In one embodiment, the
operating pressure of the final digester can be at least about 5
psig lower than the operating pressure of the initial digester, or
in the range of from about 10 to about 50 psig lower than the
operating pressure of the initial digester. The operating
temperature of the initial digester can be in the range of from
about 195 to about 225.degree. C., in the range of from 205 to
215.degree. C., or about 210.degree. C. The operating pressure of
the initial digester can be in the range of from about 215 to about
235 psig, or about 225 psig. The operating temperature of the final
digester can be in the range of from about 190 to about 220.degree.
C., in the range of from 200 to 210.degree. C., or about
205.degree. C. The operating pressure of the final digester can be
in the range of from about 190 to 210 psig, or about 200 psig.
[0041] In one embodiment of the present invention, purification
zone 14 can comprise optional first and second solvent swap zones.
Optional first and second solvent swap zones can operate to replace
at least a portion of the existing solvent in a slurry with a
replacement solvent. Equipment suitable for such replacement
includes, but is not limited to, a decanter centrifuge followed by
a reslurry with replacement solvent, a disc stack centrifuge, an
advancing front crystallizer, or multiple decanter centrifuges with
optional counter current washing. The replacement oxidation solvent
can have substantially the same composition as the solvent
introduced into oxidation zone 10, as described above.
[0042] In one embodiment, the crude slurry fed to purification zone
14 can be treated in the optional first solvent swap zone prior to
purification of the crude slurry by the above-mentioned oxidative
digestion. In another embodiment, a purified slurry resulting from
oxidative digestion of the crude slurry can be treated in the
optional second solvent swap zone.
[0043] Optionally, at least a portion of the displaced oxidation
solvent from the optional first and/or second solvent swap zones
can be discharged from purification zone 14 via line 38. At least a
portion of the displaced oxidation solvent in line 38 can be routed
to solids removal zone 32 via line 40, purge treatment zone 100 via
line 38a, and/or oxidation zone 10 via line 38b.
[0044] In another embodiment of the present invention, purification
zone 14 can comprise an optional crystallization zone and/or an
optional cooling zone. A purified slurry resulting from the
above-mentioned oxidative digestion of the crude slurry can be
treated in the optional crystallization zone to at least partially
increase the particle size distribution of the purified slurry.
Optional crystallization zone can comprise any equipment known in
the art that can operate to increase the particle size distribution
of the purified slurry. When an optional cooling zone is employed,
the purified slurry can be cooled therein to a temperature in the
range of from about 20 to about 195.degree. C. When both a
crystallization zone and a cooling zone are employed, the purified
slurry can be treated first in the crystallization zone and
subsequently in the cooling zone.
[0045] Referring again to FIG. 1, a purified slurry can be
withdrawn from an outlet of purification zone 14 via line 16. The
solid phase of the purified slurry can be formed primarily of
purified terephthalic acid (PTA) particles, while the liquid phase
can be formed of a mother liquor. The solids content of the
purified slurry in line 16 can be in the range of from about 1 to
about 50 percent by weight, in the range of from about 5 to about
40 weight percent, or in the range of from 20 to 35 weight percent.
The purified slurry in line 16 can be introduced into product
isolation/catalyst removal zone 18 for at least partial recovery of
the solid PTA particles.
[0046] Optionally, at least a portion of the crude slurry in line
12 can be introduced into product isolation/catalyst removal zone
18 via line 12a. As mentioned above, the solid phase of the crude
slurry can be formed primarily of CTA particles, while the liquid
phase can be formed of a mother liquor. The solids content of the
crude slurry in line 12a can be in the range of from about 1 to
about 50 percent by weight, in the range of from about 5 to about
40 weight percent by weight, or in the range of from 20 to 35
percent by weight. The crude slurry in line 12a can be introduced
into product isolation/catalyst removal zone 18 for recovery of the
solid CTA particles.
[0047] Product isolation/catalyst removal zone 18 can separate the
crude slurry and/or the purified slurry into a predominately fluid
phase mother liquor and a wet cake. Product isolation/catalyst
removal zone 18 can comprise any method of solid/liquid separation
known in the art that is capable of generating a wet cake and a
mother liquor stream. In addition, it may be desirable for product
isolation/catalyst removal zone 18 to have the capability of
washing the wet cake. Suitable equipment for use in product
isolation/catalyst removal zone 18 includes, but is not limited to,
a pressure drum filter, a vacuum drum filter, a vacuum belt filter,
multiple solid bowl centrifuges with optional counter current wash,
or a perforated centrifuge.
[0048] In one embodiment of the present invention, a wash stream
can be introduced into product isolation/catalyst removal zone 18
to wash at least a portion of the wet cake generated in product
isolation/catalyst removal zone 18, thereby producing a washed wet
cake. In one embodiment, the wash stream can comprise acetic acid
and/or water. Optionally, after washing the wet cake, the used wash
liquor can be withdrawn from product isolation/catalyst removal
zone 18, and at least a portion of the wash liquor can be routed,
either directly or indirectly, to oxidation zone 10.
[0049] The above-mentioned wet cake generated in product
isolation/catalyst removal zone 18 can be discharged via line 20.
In one embodiment of the present invention, the wet cake generated
in product isolation/catalyst removal zone 18 can primarily
comprise solid particles of TPA. The solid TPA particles can
comprise CTA and/or PTA particles. The wet cake can comprise in the
range of from about 5 to about 30 weight percent liquid, in the
range of from about 10 to about 25 weight percent liquid, or in the
range of from 12 to 23 weight percent liquid. Additionally, the TPA
product wet cake in line 20 can comprise oxidation byproducts, as
discussed above. In one embodiment, the TPA product in line 20 can
comprise a cumulative concentration of mono-functional oxidation
byproducts of less than about 1,000 ppmw, less than about 750 ppmw,
or less than 500 ppmw.
[0050] In one embodiment of the present invention, the wet cake in
line 20 can be introduced into drying zone 22 via line 20 to
thereby produce a dry TPA particulate product comprising solid TPA
particles. Drying zone 22 can comprise any drying device known in
the art that can produce a dried TPA particulate product comprising
less than about 5 weight percent liquid, less than about 3 weight
percent liquid, or less than 1 weight percent liquid. Dried TPA
particulate product can be discharged from drying zone 22 via line
24.
[0051] In another embodiment, the wet cake in line 20 can be
introduced into solvent swap zone 26 to produce a wet TPA
particulate product comprising solid TPA particles. Solvent swap
zone 26 can operate to replace at least a portion of the liquid in
the wet cake with a replacement solvent. Equipment suitable for
such replacement includes, but is not limited to, a decanter
centrifuge followed by a reslurry with replacement solvent, a disc
stack centrifuge, an advancing front crystallizer, or multiple
decanter centrifuges with counter current washing. Wet TPA
particulate product can be discharged from solvent swap zone 26 via
line 28. The wet TPA particulate product can comprise in the range
of from about 5 to about 30 weight percent liquid, in the range of
from about 10 to about 25 weight percent liquid, or in the range of
from 12 to 23 weight percent liquid.
[0052] Referring still to FIG. 1, the above-mentioned mother liquor
can be discharged from product isolation/catalyst removal zone 18
via line 30. In one embodiment of the present invention, at least a
portion of the mother liquor can optionally be introduced into
solids removal zone 32. Solids removal zone 32 can comprise any
equipment known in the art that is operable to remove a sufficient
amount of solids from the mother liquor to produce a
solids-depleted mother liquor comprising less than about 5 weight
percent solids, less than about 2 weight percent solids, or less
than 1 weight percent solids. Suitable equipment that may be
employed in solids removal zone 32 includes a pressure filter, such
as, for example, a filter press, a candle filter, a pressure leaf
filter, and/or a cartridge filter. In one embodiment, solids
removal zone 32 can be operated at a temperature in the range of
from about 20 to about 195.degree. C. and a pressure in the range
of from about 750 to about 3750 torr during solids removal. The
solids-depleted mother liquor can be discharged from solids removal
zone 32 via line 34. In one embodiment of the present invention, at
least a portion of the solids removed from the mother liquor in
solids removal zone 32 can be discharged via line 36 and can be
routed to product isolation/catalyst removal zone 18 via line 36a
and/or to line 20 via line 36b.
[0053] As mentioned above, at least a portion of the displaced
oxidation solvent from purification zone 14 can also optionally be
treated in solids removal zone 32. Such displaced oxidation solvent
can be withdrawn from purification zone 14 via line 38 and
introduced into solids removal zone 32 via line 40. When displaced
oxidation solvent from oxidation zone 14 is treated in solids
removal zone 32, the resulting solids-depleted displaced oxidation
solvent can be combined with the solids-depleted mother liquor and
can be discharged via line 34.
[0054] In one embodiment of the present invention, at least a
portion of the optionally solids-depleted mother liquor in line 34
can be withdrawn from line 34 via line 42 to form a purge feed
stream. The amount of mother liquor withdrawn by line 42 to form
the purge feed stream can be in the range of from about 1 to about
55 percent of the total weight of the mother liquor, in the range
of from about 5 to about 45 percent by weight, or in the range of
from 10 to 35 percent by weight. Optionally, at least a portion of
the displaced oxidation solvent discharged from purification zone
14 in line 38 can be combined with the purge feed stream via line
38a. In another embodiment, at least a portion of the remaining
mother liquor in line 34 can be routed, either directly or
indirectly, to oxidation zone 10 via line 44. Optionally, at least
a portion of the wash liquor discharged from product
isolation/catalyst removal zone 18 can be combined with at least a
portion of the mother liquor in line 44 prior to introduction into
oxidation zone 10.
[0055] In one embodiment of the present invention, the mother
liquor in line 34, and consequently the purge feed stream in line
42, can comprise solvent, one or more catalyst components,
oxidation byproducts, and TPA. The solvent in the mother liquor in
line 34 and the purge feed stream in line 42 can comprise a
monocarboxylic acid. In one embodiment, the solvent can comprise
water and/or acetic acid. The mother liquor in line 34 and the
purge feed stream in line 42 can comprise solvent in an amount of
at least about 85 weight percent, at least about 95 weight percent,
or at least 99 weight percent.
[0056] The catalyst components in the mother liquor in line 34 and
the purge feed stream in line 42 can comprise the catalyst
components as described above with reference to the catalyst system
introduced into oxidation zone 10. In one embodiment, the catalyst
components can comprise cobalt, manganese, and/or bromine. The
mother liquor in line 34 and the purge feed stream in line 42 can
have a cumulative concentration of all of the catalyst components
in the range of from about 500 to about 20,000 ppmw, in the range
of from about 1,000 to about 15,000 ppmw, or in the range of from
1,500 to 10,000 ppmw.
[0057] The oxidation byproducts in the mother liquor in line 34 and
the purge feed stream in line 42 can comprise one or more of the
oxidation byproducts discussed above. In one embodiment, the
oxidation byproducts in the mother liquor in line 34 and the purge
feed stream in line 42 can comprise both BA and non-BA byproducts.
As used herein, the term "non-BA byproducts" is defined as any
oxidation byproduct that is not benzoic acid. Non-BA byproducts
include, but are not limited to, isophthalic acid (IPA), phthalic
acid (PA), trimellitic acid, 2,5,4'-tricarboxybiphenyl,
2,5,4'-tricarboxybenzophenone, p-TAc, 4-CBA, naphthalene
dicarboxylic acid, monocarboxyfluorenones, monocarboxyfluorenes,
and/or dicarboxyfluorenones. In one embodiment, the mother liquor
in line 34 and the purge feed stream in line 42 can comprise BA in
an amount in the range of from about 500 to about 150,000 ppmw
based on the weight of the purge feed stream, in the range of from
about 1,000 to about 100,000 ppmw, or in the range of from 2,000 to
50,000 ppmw. Additionally, the mother liquor in line 34 and the
purge feed stream in line 42 can have a cumulative concentration of
non-BA byproducts in the range of from about 500 to about 50,000
ppmw, in the range of from about 1,000 to about 20,000 ppmw, or in
the range of from 2,000 to 10,000 ppmw.
[0058] In one embodiment of the present invention, the mother
liquor in line 34 and the purge feed stream in line 42 can comprise
solids in an amount of less than about 5 weight percent, less than
about 2 weight percent, or less than 1 weight percent.
Additionally, the purge feed stream can have a temperature of less
than about 240.degree. C., in the range of from about 20 to about
200.degree. C., or in the range of from 50 to 100.degree. C.
[0059] Referring still to FIG. 1, the purge feed stream can be
introduced into a purge treatment zone 100 via line 42. As will be
discussed in greater detail below, the purge treatment zone 100 can
separate the purge feed stream into a catalyst rich stream, a BA
rich stream (i.e., a mono-functional impurity rich stream), and a
non-BA byproduct rich stream (i.e., a mono-functional impurity
depleted stream). The BA rich stream can be discharged from purge
treatment zone 100 via line 48, the catalyst rich stream can be
discharged from purge treatment zone 100 via line 50, and the
non-BA byproduct rich stream can be discharged from purge treatment
zone 100 via line 52.
[0060] The BA rich stream in line 48 can have a relatively higher
concentration of BA on a weight basis compared to the BA
concentration of the purge feed stream in line 42. In one
embodiment of the present invention, the BA rich stream in line 48
can have a concentration of BA that is at least about 1.5 times the
concentration of BA in the purge feed stream on a weight basis, at
least about 5 times the concentration of BA in the purge feed
stream on a weight basis, or at least 10 times the concentration of
BA in the purge feed stream on a weight basis. In one embodiment,
BA can be the primary oxidation byproduct in the BA rich stream.
Depending of the temperature and pressure of the BA rich stream
upon exiting purge treatment zone 100, the BA rich stream in line
48 can predominately comprise solids or fluid. Thus, in one
embodiment, the BA rich stream in line 48 can comprise at least
about 50 weight percent fluid, at least about 70 weight percent
fluid, or at least 90 weight percent fluid. In an alternate
embodiment, the BA rich stream in line 48 can comprise at least
about 50 weight percent solids, at least about 70 weight percent
solids, or at least 90 weight percent solids.
[0061] The catalyst rich stream in line 50 can have a relatively
higher cumulative concentration of all of the catalyst components
on a weight basis compared to the cumulative concentration of all
of the catalyst components in the purge feed stream in line 42. In
one embodiment of the present invention, the catalyst rich stream
in line 50 can have a cumulative concentration of all of the
catalyst components that is at least about 1.5 times the cumulative
concentration of all of the catalyst components in the purge feed
stream on a weight basis, at least about 5 times the cumulative
concentration of all of the catalyst components in the purge feed
stream on a weight basis, or at least 10 times the cumulative
concentration of all of the catalyst components in the purge feed
stream on a weight basis. Depending of the temperature and pressure
of the catalyst rich stream upon exiting purge treatment zone 100,
the catalyst rich stream in line 50 can predominately comprise
solids or fluid. Thus, in one embodiment, the catalyst rich stream
in line 50 can comprise at least about 50 weight percent fluid, at
least about 70 weight percent fluid, or at least 90 weight percent
fluid. In an alternate embodiment, the catalyst rich stream in line
50 can comprise at least about 50 weight percent solids, at least
about 70 weight percent solids, or at least 90 weight percent
solids.
[0062] The non-BA byproduct rich stream in line 52 can have a
relatively higher cumulative concentration of non-BA byproducts on
a weight basis compared to the cumulative concentration of non-BA
byproducts in the purge feed stream in line 42. In one embodiment
of the present invention, the non-BA byproduct rich stream in line
52 can have a cumulative concentration of non-BA byproducts that is
at least about 1.5 times the cumulative concentration of non-BA
byproducts in the purge feed stream on a weight basis, at least
about 5 times the cumulative concentration of non-BA byproducts in
the purge feed stream on a weight basis, or at least 10 times the
cumulative concentration of non-BA byproducts in the purge feed
stream on a weight basis. In one embodiment, non-BA byproducts can
cumulatively be the primary oxidation byproducts in the non-BA
byproduct rich stream. The non-BA byproduct rich stream in line 52
can be in the form of a wet cake, comprising in the range of from
about 5 to about 30 weight percent liquid, in the range of from 10
to about 25 weight percent liquid, or in the range of from 12 to 23
weight percent liquid.
[0063] In one embodiment of the present invention, at least a
portion of the BA rich stream, the catalyst rich stream, and the
non-BA byproduct rich stream can be routed to different locations.
Such locations include, but are not limited to, various points in a
TPA production process, an IPA production process, a phthalic acid
(PA) production process, a BA production process, a
naphthalene-dicarboxylic acid (NDA) production process, a
dimethylterephthalate (DMT) production process, a
dimethylnaphthalate (DMN) production process, a cyclohexane
dimethanol (CHDM) production process, a
dimethyl-cyclohexanedicarboxylate (DMCD) production process, a
cyclohexanedicarboxylic acid (CHDA) production process, a
polyethylene terephthalate (PET) production process, a production
process for any isomers of NDA, DMT, DMN, CHDM, DMCD, CHDA, a
copolyester production process, a polymer production process
employing one or more of TPA, IPA, PA, BA, NDA, DMT, DMN, CHDM,
DMCD, CHDA, or any isomers thereof as one component and/or as a
monomer, and/or outside the TPA, IPA, PA, BA, NDA, DMT, DMN, CHDM,
DMCD, CHDA, PET, or polymer production processes.
[0064] In one embodiment, the amount of BA that exits the TPA
production process with the TPA product and/or is combined with the
TPA product downstream of the TPA production process can be
sufficient to result in a TPA product comprising BA in an amount of
less than about 1000 ppmw, less than about 500 ppmw, or less than
250 ppmw. In another embodiment, the rate at which BA exits the TPA
production process with the TPA product and/or is combined with the
TPA product downstream of the TPA production process can be less
than about 50 percent, less than about 10 percent, less than about
1 percent, or less than 0.1 percent of the make-rate of BA in the
TPA production process. As used herein with reference to BA, when
no purification step (e.g., purification zone 14) is employed in
the TPA production process, the term "make-rate" is defined as the
difference between the mass per unit time of BA entering the
oxidation step (e.g., oxidation zone 10) and the mass per unit time
of BA exiting the oxidation step. When a purification step is
employed in the TPA production process, the term "make-rate" when
referring to BA is defined as the difference between the mass per
unit time of BA entering the oxidation step (e.g., oxidation zone
10) and the mass per unit time of BA exiting the purification step
(e.g., purification zone 14). By way of illustration, for a TPA
production process that employs a purification step, if BA enters
the oxidation step of the TPA production process at a rate of 50
kilograms per hour (kg/hr), and BA exits the purification step at a
rate of 150 kg/hr, then the make-rate of BA in the TPA production
process is 100 kg/hr.
[0065] In another embodiment, at least a portion of the BA rich
stream can exit the process depicted in FIG. 1 and be routed to a
purification and recovery process, a subsequent chemical process,
and/or a waste treatment or disposal process. Such waste treatment
or disposal processes include, but are not limited to, sale,
burial, incineration, neutralization, anaerobic and/or aerobic
digestion, treatment in a waste oxidizer, and/or treatment in a
waste reactor. In one embodiment of the present invention, at least
a portion of the BA rich stream can be routed to a waste treatment
process where at least about 50 weight percent, at least about 60
weight percent, or at least 70 weight percent of the BA present in
the BA rich stream is treated.
[0066] As mentioned above, the catalyst rich stream in line 50 can
be routed to various points in a TPA production process. In one
embodiment of the present invention, at least a portion of the
catalyst rich stream in line 50 can be routed, either directly or
indirectly, to oxidation zone 10, where at least about 50 weight
percent, at least about 60 weight percent, or at least 70 weight
percent of the catalyst components of the catalyst rich stream are
introduced into oxidization zone 10. In one embodiment, prior to
routing, a liquid can optionally be added to the catalyst rich
stream in line 50 to produce a reslurried catalyst rich stream. The
reslurried catalyst rich stream can comprise at least about 35
weight percent liquid, at least about 50 weight percent liquid, or
at least 65 weight percent liquid. The liquid added to the catalyst
rich stream can be, for example, acetic acid and/or water.
[0067] Referring still to FIG. 1, as noted above, the non-BA
byproduct rich stream in line 52 can be routed to various points in
the depicted TPA production process. Such routing includes, but is
not limited to, returning at least a portion of the non-BA
byproduct rich stream, either directly or indirectly, to oxidation
zone 10 and/or purification zone 14. In one embodiment, at least a
portion of the non-BA byproduct rich stream can be routed such that
at least a portion of the non-BA byproducts in said non-BA
byproduct rich stream exit the TPA production process with the dry
TPA product discharged from line 24 and/or with the wet TPA product
discharged from line 28. For example, at least a portion of the
non-BA byproduct rich stream can be introduced into the purified
slurry in line 16 and/or into the product slurry/cake in line 20
and allowed to exit the TPA production process with the TPA
product. In another embodiment, at least a portion of the non-BA
byproducts in the non-BA byproduct rich stream can be combined with
the TPA product downstream of the TPA production process. In one
embodiment, at least about 5 weight percent, at least about 25
weight percent, at least about 50 weight percent, or at least 75
weight percent of the non-BA byproducts in the non-BA byproduct
rich stream can be allowed to exit the TPA production process with
the TPA product and/or can be combined with the TPA product
downstream of the TPA production process.
[0068] In one embodiment, the cumulative rate at which the non-BA
byproducts exit the TPA production process with the TPA product
and/or are combined with the TPA product downstream of the TPA
production process can be at least about 5 percent, at least about
10 percent, at least about 20 percent, or at least 50 percent of
the make-rate of the non-BA byproducts in the TPA production
process. As used herein with reference to non-BA byproducts, when
no purification step (e.g., purification zone 14) is employed in
the TPA production process, the term "make-rate" is defined as the
difference between the mass per unit time of non-BA byproducts
entering the oxidation step (e.g., oxidation zone 10) and the mass
per unit time of non-BA byproducts exiting the oxidation step. When
a purification step is employed in the TPA production process, the
term "make-rate" when referring to non-BA byproducts is defined as
the difference between the mass per unit time of non-BA byproducts
entering the oxidation step (e.g., oxidation zone 10) and the mass
per unit time of non-BA byproducts exiting the purification step
(e.g., purification zone 14). By way of illustration, for a TPA
production process that employs a purification step, if non-BA
byproducts enter the oxidation step of the TPA production process
at a rate of 50 kg/hr, and non-BA byproducts exit the purification
step at a rate of 150 kg/hr, then the make-rate of non-BA
byproducts in the TPA production process is 100 kg/hr.
[0069] In another embodiment, the non-BA byproduct rich stream can
exit the process depicted in FIG. 1 and can be routed to a
purification and recovery process, a process utilizing non-BA
byproducts for making non-BA byproduct derivatives, and/or a waste
treatment or disposal process. Such waste treatment or disposal
processes include, but are not limited to, sale, burial,
incineration, neutralization, anaerobic and/or aerobic digestion,
treatment in a waste oxidizer, and/or treatment in a waste
reactor.
[0070] As mentioned above, the non-BA byproduct rich stream in line
52 can be in the form of a wet cake. In one embodiment of the
present invention, prior to routing the non-BA byproduct rich
stream, at least a portion the non-BA byproduct rich stream may
optionally be dried in drying zone 54. Drying zone 54 can comprise
any drying device known in the art that can produce a dried non-BA
byproduct rich stream comprising less than about 5 weight percent
liquid, less than about 3 weight percent liquid, or less than 1
weight percent liquid. The optionally dried non-BA byproduct rich
stream can be discharged from drying zone 54 via line 56.
[0071] In another embodiment, prior to routing the non-BA byproduct
rich stream, a liquid may be added to at least a portion of the
non-BA byproduct rich stream in reslurry zone 58 to produce a
reslurried non-BA byproduct rich stream. The reslurried non-BA
byproduct rich stream can be discharged from reslurry zone 58 via
line 60. The reslurried non-BA byproduct rich stream can comprise
at least about 35 weight percent liquid, at least about 50 weight
percent liquid, or at least 65 weight percent liquid. The liquid
added to the non-BA byproduct rich stream in reslurry zone 58 can
comprise acetic acid and/or water.
[0072] FIG. 2 illustrates an overview of one embodiment of purge
treatment zone 100, briefly discussed above with reference to FIG.
1. In the embodiment of FIG. 2, purge treatment zone 100 comprises
a non-BA byproduct removal zone 102 and a BA removal zone 104. The
purge feed stream in line 42 can initially be introduced into
non-BA byproduct removal zone 102. As will be discussed in greater
detail below, non-BA byproduct removal zone 102 can separate the
purge feed stream into the above-mentioned non-BA byproduct rich
stream and a catalyst and BA rich mother liquor (i.e., a catalyst
and mono-functional impurity rich mother liquor). The non-BA
byproduct rich stream can be discharged from non-BA byproduct
removal zone 102 via line 52, and the catalyst and BA rich mother
liquor can be discharged via line 106.
[0073] In one embodiment of the present invention, the catalyst and
BA rich mother liquor in line 106 can comprise one or more catalyst
components, BA, and solvent. The catalyst and BA rich mother liquor
can comprise solids in an amount of less than about 5 weight
percent, less than about 3 weight percent, or less than 1 weight
percent. The solvent in the catalyst and BA rich mother liquor can
comprise acetic acid and/or water. The catalyst components in the
catalyst and BA rich mother liquor can comprise cobalt, manganese,
and/or bromine, as discussed above in relation to the catalyst
system introduced into oxidation zone 10 of FIG. 1.
[0074] The catalyst and BA rich mother liquor in line 106 can have
a relatively higher concentration of BA and catalyst components on
a weight basis compared to the concentration of BA and catalyst
components in the purge feed stream in line 42. In one embodiment,
the catalyst and BA rich mother liquor in line 106 can have a
cumulative concentration of all of the catalyst components that is
at least about 1.5 times the cumulative concentration of all of the
catalyst components in the purge feed stream on a weight basis, at
least about 5 times the cumulative concentration of all of the
catalyst components in the purge feed stream on a weight basis, or
at least 10 times the cumulative concentration of all of the
catalyst components in the purge feed stream on a weight basis.
Furthermore, the catalyst and BA rich mother liquor in line 106 can
have a concentration of BA that is at least about 1.5 times the
concentration of BA in the purge feed stream on a weight basis, at
least about 5 times the concentration of BA in the purge feed
stream on a weight basis, or at least 10 times the concentration of
BA in the purge feed stream on a weight basis.
[0075] In the embodiment of FIG. 2, the catalyst and BA rich mother
liquor can be introduced into BA removal zone 104 via line 106. As
will be discussed in greater detail below, BA removal zone 104 can
separate the catalyst and BA rich mother liquor into the
above-mentioned BA rich stream and the above-mentioned catalyst
rich stream. The BA rich stream can be discharged from BA removal
zone 104 via line 48 and the catalyst rich stream can be discharged
via line 50.
[0076] FIG. 3 illustrates in detail one configuration of non-BA
byproduct removal zone 102 and BA removal zone 104. In the
embodiment of FIG. 3, non-BA byproduct removal zone 102 comprises
concentration section 202 and solid/liquid separation section 208.
In this embodiment, the purge feed stream can initially be
introduced into concentration section 202 via line 42.
Concentration section 202 can operate to remove at least a portion
of the volatile compounds contained in the purge feed stream. In
one embodiment, the volatile compounds comprise at least a portion
of the solvent in the purge feed stream. The solvent can comprise
water and/or acetic acid. Concentration section 202 can remove at
least about 30, at least about 45, or at least 60 weight percent of
the volatile compounds in the purge feed stream. Volatile compounds
can be discharged from concentration section 202 via line 204. In
one embodiment of the present invention, at least a portion of the
volatiles in line 204 can be routed, either directly or indirectly,
to oxidation zone 10 depicted in FIG. 1.
[0077] Any equipment known in the industry capable of removing at
least a portion of the volatile compounds from the purge feed
stream may be employed in concentration section 202. Examples of
suitable equipment include, but are not limited to, one or more
evaporators. In one embodiment, concentration section 202 can
comprise at least two evaporators. When two evaporators are
employed, each one individually can be operated under vacuum at
reduced temperature, or can be operated at elevated temperature and
pressure. In one embodiment, each evaporator can be operated at a
temperature in the range of from about 40 to about 180.degree. C.
and a pressure in the range of from about 50 to about 4500 torr
during concentration. Suitable equipment for use in concentration
section 202 includes, but is not limited to, a simple agitated
tank, a flash evaporator, an advancing front crystallizer, a thin
film evaporator, a scraped thin film evaporator, and/or a falling
film evaporator.
[0078] In the embodiment of FIG. 3, a concentrated purge feed
stream can be discharged from concentration section 202 via line
206. The solids content of the concentrated purge feed stream in
line 206 can be at least about 1.5 times, at least about 5 times,
or at least 10 times the solids content of the unconcentrated purge
feed stream in line 42, where solids content is measured on a
weight basis. The concentrated purge feed stream can comprise
solids in an amount in the range of from about 5 to about 70 weight
percent, or in the range of from 10 to 40 weight percent. Also, the
concentrated purge feed stream can comprise one or more catalyst
components, BA and non-BA oxidation byproducts, TPA particles, and
solvent, each as discussed above.
[0079] The concentrated purge feed stream can be introduced into
solid/liquid separation section 208 via line 206. Solid/liquid
separation section 208 can separate the concentrated purge feed
stream into a predominately fluid phase catalyst and BA rich mother
liquor and a wet cake. In the embodiment of FIG. 3, solid/liquid
separation section 208 comprises mother liquor removal section 208a
and wash section 208b. Mother liquor removal section 208a can
operate to separate the concentrated purge feed stream into the
above-mentioned catalyst and BA rich mother liquor and an initial
wet cake. The catalyst and BA rich mother liquor can be discharged
from mother liquor removal section 208a via line 106. The initial
wet cake can be introduced into wash section 208b. At least a
portion of the initial wet cake can then be washed with the wash
feed introduced into wash section 208b via line 210 to produce a
washed wet cake. The wash feed in line 210 can comprise water
and/or acetic acid. Furthermore, the wash feed can have a
temperature in the range of from about the freezing point of the
wash feed to about the boiling point of the wash feed, in the range
of from about 20 to about 110.degree. C., or in the range of from
40 to 90.degree. C. The wash feed can operate to remove at least a
portion of catalyst components from the wet cake. After washing the
wet cake, the resulting wash liquor can be discharged from wash
section 208b via line 212, and the washed wet cake can be
discharged via line 52. In one embodiment, the above-mentioned
non-BA byproduct rich stream comprises at least a portion of the
washed wet cake.
[0080] Solid/liquid separation section 208 can comprise any
solid/liquid separation device known in the art. Suitable equipment
for use in solid/liquid separation section 208 includes, but is not
limited to, a pressure drum filter, a vacuum drum filter, a vacuum
belt filter, multiple solid bowl centrifuges with counter current
wash, or a perforated centrifuge. In one embodiment, solid/liquid
separation section 208 can be operated at a temperature in the
range of from about 20 to about 170.degree. C. and a pressure in
the range of from about 375 to about 4500 torr during
separation.
[0081] As mentioned above, the wash liquor can be discharged from
solid/liquid separation section 208 via line 212. In one
embodiment, at least a portion of the wash liquor in line 212 can
be routed, either directly or indirectly, to oxidation zone 10 as
depicted in FIG. 1. Optionally, at least a portion of the wash
liquor in line 212 can be concentrated prior to introduction in
oxidation zone 10. The optional concentrator can be any device
known in the art capable of concentrating the wash liquor stream,
such as, for example, membrane separation or evaporation. In
another embodiment, at least a portion of the wash liquor in line
212 can be routed to a waste treatment facility.
[0082] Referring still to FIG. 3, BA removal zone 104 comprises
concentration section 214 and BA/catalyst separation section 220.
In one embodiment, the catalyst and BA rich mother liquor in line
106 can initially be introduced into concentration section 214.
Concentration section 214 can operate to remove at least a portion
of the volatile compounds contained in the catalyst and BA rich
mother liquor. In one embodiment, the volatile compounds comprise
at least a portion of the solvent in the catalyst and BA rich
mother liquor. The solvent can comprise water and/or acetic acid.
Concentration section 214 can remove at least about 50, at least
about 70, or at least 90 weight percent of the solvent in the
catalyst and BA rich mother liquor. Evaporated compounds can be
discharged from concentration section 214 via line 216.
[0083] Any equipment known in the industry capable of removing at
least a portion of the volatile compounds from the catalyst and BA
rich mother liquor can be employed in concentration section 214.
Examples of suitable equipment include, but are not limited to, a
simple agitated tank, a flash evaporator, an advancing front
crystallizer, a thin film evaporator, a scraped thin film
evaporator, or a falling film evaporator. In one embodiment,
concentration section 214 can be operated at a pressure in the
range of from about 50 to about 800 torr during concentration.
Additionally, concentration section 214 can be operated at a
temperature of at least about 120.degree. C., or at least
130.degree. C. during concentration.
[0084] In the embodiment of FIG. 3, a concentrated catalyst and BA
rich mother liquor (i.e., a mono-functional impurity rich slurry)
can be discharged from concentration section 214 via line 218. The
concentrated catalyst and BA rich mother liquor can comprise one or
more catalyst components, BA, and solvent. The concentration of all
the catalyst components and BA of the concentrated catalyst and BA
rich mother liquor can be at least about 1.5 times, at least about
5 times, or at least 10 times the concentration of all the catalyst
components and BA of the unconcentrated catalyst and BA rich mother
liquor in line 106.
[0085] The concentrated catalyst and BA rich mother liquor can be
introduced into BA/catalyst separation section (i.e.,
mono-functional impurity removal section) 220 via line 218.
BA/catalyst separation section 220 operates to separate the
concentrated catalyst and BA rich mother liquor into the
above-mentioned catalyst rich stream and the above-mentioned BA
rich stream. In one embodiment, separation of the concentrated
catalyst and BA rich mother liquor can be accomplished by
evaporating and removing at least a portion of the BA in the
concentrated catalyst and BA rich mother liquor. Any dryer known in
the art that can evaporate and remove at least about 50 weight
percent, at least about 70 weight percent, or at least 90 weight
percent of the BA in the concentrated catalyst and BA rich mother
liquor can be used. A suitable example of a commercially available
dryer that can be employed in BA/catalyst separation section 220
includes, but is not limited to, a LIST dryer. In one embodiment,
BA/catalyst separation section 220 can be operated at a temperature
in the range of from about 170 to about 250.degree. C. and a
pressure in the range of from about 50 to about 760 torr during
separation. The catalyst rich stream can be discharged from
BA/catalyst separation section 220 via line 50, and the BA rich
stream can be discharged via line 48.
[0086] FIG. 4 illustrates in detail a second configuration of
non-BA byproduct removal zone 102 and BA removal zone 104. Non-BA
byproduct removal zone 102 comprises concentration section 302 and
solid/liquid separation section 308. In the embodiment of FIG. 4,
concentration section 302 and solid/liquid separation section 308
are operated in substantially the same manner as discussed above
with reference to concentration section 202 and solid/liquid
separation section 208 of FIG. 3. Additionally, the composition and
treatment of the volatiles in line 304, the concentrated purge feed
stream in line 306, the wash feed in line 310, and the wash liquor
in line 312 are substantially the same as discussed above with
reference to the volatiles in line 204, the concentrated purge feed
stream in line 206, the wash feed in line 210, and the wash liquor
in line 212 of FIG. 3. The above-mentioned non-BA byproduct rich
stream can be discharged from solid/liquid separation section 308
via line 52, and the above-mentioned catalyst and BA rich mother
liquor can be discharged via line 106.
[0087] In the embodiment of FIG. 4, BA removal zone 104 comprises
catalyst removal section 314 and BA/solvent separation section 318.
In one embodiment, the catalyst and BA rich mother liquor in line
106 can initially be introduced into catalyst removal section 314.
Catalyst removal section 314 can operate to remove at least a
portion of the BA and solvent in the catalyst and BA rich mother
liquor, generating the above-mentioned catalyst rich stream and a
BA and solvent rich stream (i.e., a mono-functional impurity and
solvent rich stream). Removal of BA and solvent in catalyst removal
section 314 can be accomplished by evaporating and removing at
least a portion of the BA and solvent from the catalyst and BA rich
mother liquor. In one embodiment, at least about 50 weight percent,
at least about 70 weight percent, or at least 90 weight percent of
the BA and solvent in the catalyst and BA rich mother liquor can be
removed in catalyst removal section 314. Any dryer known in the art
that can evaporate and remove at least a portion of the BA and
solvent in the catalyst and BA rich mother liquor can be used. A
suitable example of a commercially available dryer that can be
employed in catalyst removal section 314 includes, but is not
limited to, a LIST dryer. In one embodiment, catalyst removal 314
can be operated at a temperature in the range of from about 170 to
about 250.degree. C. and a pressure in the range of from about 50
to about 760 torr during catalyst removal.
[0088] As mentioned above, catalyst removal zone 314 generates the
catalyst rich stream and a BA and solvent rich stream. The catalyst
rich stream can be discharged from catalyst removal zone 314 via
line 50. The BA and solvent rich stream can be discharged from
catalyst removal section 314 via line 316. In one embodiment, the
BA and solvent rich stream can be a predominately fluid phase
stream and can comprise at least two portions having different
volatilities (i.e., a lower volatility portion and a higher
volatility portion). The lower volatility portion can comprise BA
and the higher volatility portion can comprise solvent. The solvent
can comprise acetic acid and/or water.
[0089] In the embodiment of FIG. 4, the BA and solvent rich stream
can be introduced into BA/solvent separation section (i.e.,
mono-functional impurity/solvent separation section) 318 via line
316. BA/solvent separation section 318 can separate the BA and
solvent rich stream into the above-mentioned BA rich stream and a
solvent rich stream. The separation of the BA and solvent rich
stream can be accomplished by fluid/fluid separation. Any
fluid/fluid separation device known in the art capable of
separating two fluid phases may be used in BA/solvent separation
section 318. Such devices include, but are not limited to, a dryer,
an evaporator, a partial condenser, and/or distillation devices. In
one embodiment, BA/solvent separation section 318 can be operated
at a temperature in the range of from about 170 to about
250.degree. C. and a pressure in the range of from about 50 to
about 760 torr during separation.
[0090] The BA rich stream can be discharged from BA/solvent
separation section 318 via line 48. The solvent rich stream can be
discharged from BA/solvent separation section 314 via line 320. In
one embodiment, the solvent rich stream can comprise a higher
concentration of solvent than the BA and solvent rich stream in
line 316. The solvent rich stream can have a concentration of
solvent that is at least about 1.5 times the concentration of
solvent in the BA and solvent rich stream on a weight basis, at
least about 5 times the concentration of solvent in the solvent and
BA rich stream on a weight basis, or at least 10 times the
concentration of solvent in the solvent and BA rich stream on a
weight basis. In one embodiment, at least a portion of the solvent
rich stream in line 320 can be routed, either directly or
indirectly, to oxidation zone 10 depicted in FIG. 1.
[0091] FIG. 5 illustrates an overview of another embodiment of
purge treatment zone 100, briefly discussed above with reference to
FIG. 1. In the embodiment of FIG. 5, purge treatment zone 100
comprises BA removal zone 400 and non-BA byproduct removal zone
402. The purge feed stream in line 42 can initially be introduced
into BA removal zone 400. As will be discussed in greater detail
below, BA removal zone 400 can separate the purge feed stream into
the above-mentioned BA rich stream and a catalyst and non-BA
byproduct rich stream (i.e., a catalyst and non-mono-functional
impurity rich stream). The BA rich stream can be discharged from BA
removal zone 400 via line 48, and the catalyst and non-BA byproduct
rich stream can be discharged via line 404.
[0092] In one embodiment of the present invention, the catalyst and
non-BA byproduct rich stream can comprise one or more catalyst
components, non-BA byproducts, and solvent. Depending of the
temperature and pressure of the catalyst and non-BA byproduct rich
stream upon exiting BA removal zone 400, the catalyst and non-BA
byproduct rich stream in line 404 can predominately comprise solids
or fluid. Thus, in one embodiment, the catalyst and non-BA
byproduct rich stream in line 404 can comprise at least about 50
weight percent fluid, at least about 70 weight percent fluid, or at
least 90 weight percent fluid. In an alternate embodiment, the
catalyst and non-BA byproduct rich stream in line 404 can comprise
at least about 50 weight percent solids, at least about 70 weight
percent solids, or at least 90 weight percent solids. The solvent
in the catalyst and non-BA byproduct rich stream can comprise
acetic acid and/or water. The catalyst components in the catalyst
and non-BA byproduct rich stream can comprise cobalt, manganese,
and/or bromine, as discussed above in relation to the catalyst
system introduced into oxidation zone 10 of FIG. 1.
[0093] The catalyst and non-BA byproduct rich stream in line 404
can have a relatively higher concentration of catalyst components
and non-BA byproducts on a weight basis compared to the
concentration of catalyst components and non-BA byproducts in the
purge feed stream in line 42. In one embodiment, the catalyst and
non-BA byproduct rich stream in line 404 can have a cumulative
concentration of all of the catalyst components that is at least
about 1.5 times the cumulative concentration of all of the catalyst
components in the purge feed stream on a weight basis, at least
about 5 times the cumulative concentration of all of the catalyst
components in the purge feed stream on a weight basis, or at least
10 times the cumulative concentration of all of the catalyst
components in the purge feed stream on a weight basis. Furthermore,
the catalyst and non-BA byproduct rich stream in line 404 can have
a cumulative concentration of non-BA byproducts that is at least
about 1.5 times the cumulative concentration of non-BA byproducts
in the purge feed stream on a weight basis, at least about 5 times
the cumulative concentration of non-BA byproducts in the purge feed
stream on a weight basis, or at least 10 times the cumulative
concentration of non-BA byproducts in the purge feed stream on a
weight basis.
[0094] In the embodiment of FIG. 5, the catalyst and non-BA
byproduct rich stream can be introduced into non-BA byproduct
removal zone 402 via line 404. As will be discussed in greater
detail below, non-BA byproduct removal zone 402 can separate the
catalyst and non-BA byproduct rich stream into the above-mentioned
non-BA byproduct rich stream and the above-mentioned catalyst rich
stream. The non-BA byproduct rich stream can be discharged from
non-BA byproduct removal zone 402 via line 52 and the catalyst rich
stream can be discharged via line 50.
[0095] FIG. 6 illustrates in detail one configuration of BA removal
zone 400 and non-BA byproduct removal zone 402. In the embodiment
of FIG. 6, BA removal zone 400 comprises concentration section 502
and BA separation section 508. In this embodiment, the purge feed
stream in line 42 can initially be introduced into concentration
section 502. Concentration section 502 can operate to remove at
least a portion of the volatile compounds contained in the purge
feed stream. Concentration section 502 is operated in substantially
the same manner as discussed above with reference to concentration
section 202 of FIG. 3. Volatiles can be discharged from
concentration section 502 via line 504. The composition and
treatment of the volatiles in line 504 is substantially the same as
discussed above with reference to the volatiles in line 204 of FIG.
3. A concentrated purge feed stream can be discharged from
concentration section 502 via line 506. The composition of the
concentrated purge feed stream in line 506 is substantially the
same as discussed above with reference to the concentrated purge
feed stream in line 206 of FIG. 3.
[0096] Referring still to FIG. 6, the concentrated purge feed
stream in line 506 can be introduced into BA separation section
(i.e., mono-functional impurity removal section) 508. BA separation
section 508 can operate to separate the concentrated purge feed
stream into the above-mentioned BA rich stream and the
above-mentioned catalyst and non-BA byproduct rich stream. In one
embodiment, BA separation can be achieved by evaporating and
removing at least a portion of the BA from the concentrated purge
feed stream. The evaporation can be achieved by heating the
concentrated purge feed stream in BA separation section 508 to at
least about 123.degree. C. at atmospheric pressure. In another
embodiment, BA separation section 508 can be operated at a pressure
in the range of from about 50 to about 760 torr during evaporation.
Additionally, BA separation section 508 can be operated at a
temperature in the range of from about 123 to about 250.degree. C.
during evaporation. At least about 40 weight percent, at least
about 70 weight percent, or at least 90 weight percent of the BA
contained in the concentrated purge feed stream can be removed in
BA separation section 508. Equipment suitable for use in BA
separation section 508 includes, but is not limited to, a LIST
dryer, a pot distillation device, a partial condenser, or a thin
film evaporator. The BA rich stream can be discharged from BA
separation section 508 via line 48, and the catalyst and non-BA
byproduct rich stream can be discharged via line 404.
[0097] In the embodiment of FIG. 6, non-BA byproduct removal zone
402 comprises reslurry section 510 and solid/liquid separation
section 516. In one embodiment, the catalyst and non-BA byproduct
rich stream in line 404 can initially be introduced into reslurry
section 510. Reslurry section 510 can be operated to add a liquid
to the catalyst and non-BA byproduct rich stream, thereby
generating a reslurried catalyst and non-BA byproduct rich stream.
The liquid added to the catalyst and non-BA byproduct rich stream
in reslurry section 510 can be introduced into reslurry section 510
via line 512. In one embodiment, the liquid in line 512 can be a
solvent, which can comprise acetic acid and/or water. Equipment
suitable for use in reslurry section 510 can include any equipment
known in the art that can accomplish mixing a liquid stream and a
solid stream to generate a slurry. Optionally, reslurry section 510
can comprise a step of crystallization in order to increase
particle size distribution.
[0098] The reslurried catalyst and non-BA byproduct rich stream can
be discharged from reslurry section 510 via line 514. In one
embodiment, the reslurried catalyst and non-BA byproduct rich
stream can comprise one or more catalyst components, non-BA
byproducts, and/or solvent. The solvent can comprise acetic acid
and/or water. The catalyst components can comprise cobalt,
manganese, and/or bromine, as discussed above in relation to the
catalyst system introduced into oxidation zone 10 of FIG. 1. The
reslurried catalyst and non-BA byproduct rich stream can comprise
solids in an amount in the range of from about 0 to about 65 weight
percent, or in the range of from 10 to 40 weight percent.
[0099] The reslurried catalyst and non-BA byproduct rich stream can
be introduced into solid/liquid separation section 516 via line
514. Solid/liquid separation section 514 can separate the
reslurried catalyst and non-BA byproduct rich stream into a
predominately fluid phase mother liquor (e.g., the above-mentioned
catalyst rich stream) and a wet cake. In the embodiment of FIG. 6,
solid/liquid separation section 516 comprises mother liquor removal
section 516a and wash section 516b. Mother liquor removal section
516a can operate to separate the reslurried catalyst and non-BA
byproduct rich stream into the above-mentioned catalyst rich stream
and an initial wet cake. The catalyst rich stream can be discharged
from mother liquor removal section 516a via line 50. The initial
wet cake can be introduced into wash section 516b. At least a
portion of the initial wet cake can then be washed with the wash
feed introduced into wash section 516b via line 518 to produce a
washed wet cake. The wash feed in line 518 can comprise water
and/or acetic acid. The wash feed can operate to remove at least a
portion of catalyst components from the wet cake. After washing the
wet cake, the resulting wash liquor can be discharged from wash
section 516b via line 520, and the washed wet cake can be
discharged via line 52. In one embodiment, the above-mentioned
non-BA byproduct rich stream can comprise at least a portion of the
washed wet cake.
[0100] Solid/liquid separation section 516 can comprise any
solid/liquid separation device known in the art. Suitable equipment
that can be used in solid/liquid separation section 516 includes,
but is not limited to, a pressure drum filter, a vacuum drum
filter, a vacuum belt filter, multiple solid bowl centrifuges with
counter current wash, or a perforated centrifuge. In one
embodiment, solid/liquid separation section 516 can be operated at
a temperature in the range of from about 20 to about 170.degree. C.
and a pressure in the range of from about 375 to about 4500 torr
during separation.
[0101] As mentioned above, the wash liquor can be discharged from
solid/liquid separation section 516 via line 520. In one
embodiment, at least a portion of the wash liquor in line 520 can
be routed, either directly or indirectly, to oxidation zone 10, as
depicted in FIG. 1. Optionally, the wash liquor in line 520 can be
concentrated prior to introduction in oxidation zone 10. The
optional concentrator can be any device known in the art capable of
concentrating the wash liquor stream, such as, for example,
membrane separation or evaporation. In another embodiment, at least
a portion of the wash liquor in line 520 can be routed to a waste
treatment facility.
[0102] It will be understood by one skilled in the art that each of
the above-described embodiments, as well as any sub-parts of those
embodiments, may be operated in a continuous or a non-continuous
manner. Non-continuous operations include, but are not limited to,
batch-wise operations, cyclical operations, and/or intermittent
operations.
[0103] In some of the embodiments above, temperature ranges are
provided for a specified operation. For each of the above
embodiments where a temperature range is provided, the temperature
is defined as the average temperature of the substance in the given
zone or section. By way of illustration, as discussed above with
reference to FIG. 1, a portion of the mother liquor in line 30 can
optionally be treated in solids removal zone 32, where solids
removal zone 32 can be operated at a temperature in the range of
from about 20 to about 195.degree. C. This means that the average
temperature of the mother liquor while in solids removal zone 32
can be in the range of from about 20 to about 195.degree. C.
Numerical Ranges
[0104] The present description uses numerical ranges to quantify
certain parameters relating to the invention. It should be
understood that when numerical ranges are provided, such ranges are
to be construed as providing literal support for claim limitations
that only recite the lower value of the range as well as claims
limitation that only recite the upper value of the range. For
example, a disclosed numerical range of 10 to 100 provides literal
support for a claim reciting "greater than 10" (with no upper
bounds) and a claim reciting "less than 100" (with no lower
bounds).
Definitions
[0105] As used herein, the terms "comprising," "comprises," and
"comprise" are open-ended transition terms used to transition from
a subject recited before the term to one or more elements recited
after the term, where the element or elements listed after the
transition term are not necessarily the only elements that make up
the subject.
[0106] As used herein, the terms "including," "includes," and
"include" have the same open-ended meaning as "comprising,"
"comprises," and "comprise."
[0107] As used herein, the terms "having," "has," and "have" have
the same open-ended meaning as "comprising," "comprises," and
"comprise."
[0108] As used herein, the terms "containing," "contains," and
"contain" have the same open-ended meaning as "comprising,"
"comprises," and "comprise."
[0109] As used herein, the terms "a," "an," "the," and "said" mean
one or more.
[0110] As used herein, the term "and/or," when used in a list of
two or more items, means that any one of the listed items can be
employed by itself or any combination of two or more of the listed
items can be employed. For example, if a composition is described
as containing components A, B, and/or C, the composition can
contain A alone; B alone; C alone; A and B in combination; A and C
in combination; B and C in combination; or A, B, and C in
combination.
CLAIMS NOT LIMITED TO DISCLOSED EMBODIMENTS
[0111] The forms of the invention described above are to be used as
illustration only, and should not be used in a limiting sense to
interpret the scope of the present invention. Obvious modifications
to the exemplary embodiments, set forth above, could be readily
made by those skilled in the art without departing from the spirit
of the present invention.
[0112] The inventors hereby state their intent to rely on the
Doctrine of Equivalents to determine and assess the reasonably fair
scope of the present invention as pertains to any apparatus not
materially departing from but outside the literal scope of the
invention as set forth in the following claims.
* * * * *