United States Patent [191
`Abrams
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,792,621
`Dec. 20, 1988
`
`[54] METHOD FOR CONTINUOUS
`PRODUCTION OF AROMATIC
`CARBOXYLIC ACID
`[75] Inventor:
`Kenneth J. Abrams, Naperville, Ill.
`[73] Assignee: Amoco Corporation, Chicago, Ill.
`[21] Appl. No: 890,128
`[22] Filed:
`Jul. 28, 1986
`
`[51] Int. Cl.4 .......................................... .. C07C 51/265
`[52] US. Cl. .............. ..
`[58] Field of Search .............................. .. 562/414, 416
`[56]
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,119,860 l/l964 Kalfadelis et al. ............ .. 562/416 X
`4,593,122 6/1986 Hashizume et a1. .............. .. 562/414
`Primary Examiner-Michael L. Shippen
`Attorney, Agent, or Firm-James R. Henes; William H.
`Magidson; Ralph C. Medhurst
`[57]
`ABSTRACT
`An improved method for continuously producing an
`aromatic carboxylic acid from an aromatic alkyl is dis
`closed. The reaction medium, contained Within a pres
`surized reactor, includes an aqueous monocarboxylic
`
`acid solvent, the aromatic alkyl, and an oxygen-contain
`ing gas. Heat is generated in the reactor during the
`course of the oxidation reaction, and is removed from
`the reactor by vaporization of a portion of the reaction
`medium. The vaporized reaction medium that exits the
`pressurized reactor as a vapor is partitioned in a con
`denser system, which de?nes a re?ux loop, into an aque
`ous partial condensate having a relatively lesser water
`to-solvent weight ratio and a vapor phase having a
`relatively greater water-to-solvent weight ratio. At
`least a portion of the partial condensate is returned
`directly to the reactor as an aqueous direct re?ux
`stream, while the vapor phase is withdrawn from the
`re?ux as a vapor stream. The withdrawn vapor stream
`is then subjected to further heat exchange, as its vapor
`pressure is reduced to less than the oxidation reactor
`pressure, thereby producing an aqueous aliphatic acid
`stream having a greater water concentration and a
`greater water-to-solvent weight ratio than the direct
`re?ux stream. Next, a predetermined portion of the
`aqueous aliphatic acid stream is combined, as an indirect
`recycle stream, with an aromatic alkyl feed mixture
`stream upstream of the oxidation reactor.
`
`4 Claims, 1 Drawing Sheet
`
`Petitioners' Exhibit 1023, Page 1 of 7
`
`

`
`Patent
`
`Dec. 20, 1988
`
`4,792,621
`
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`Petitioners' Exhibit 1023, Page 2 of 7
`
`

`
`1
`
`4,792,621
`
`METHOD FOR CONTINUOUS PRODUCTION OF
`AROMATIC CARBOXYLIC ACID
`
`TECHNICAL FIELD OF THE INVENTION
`This invention relates generally to the continuous,
`liquid-phase oxidation of an aromatic alkyl to an aro
`matic carboxylic acid within an oxidation reactor and in
`the presence of an aqueous aliphatic acid solvent. In
`particular the present invention is directed to a method
`which readily permits modulation of water concentra
`tion in the reactor.
`
`5
`
`10
`
`20
`
`2
`coef?cients, which systems are able to provide rela
`tively more ef?cient process control.
`The present invention provides a method for continu
`ously producing an aromatic carboxylic acid product
`that does not suffer from the foregoing problems. In the
`method of the present invention, the above-mentioned
`liquid-liquid separation step is not employed. Instead,
`the conventional knockback type of condenser is elimi
`nated, a condenser having a signi?cantly higher heat
`transfer coef?cient can be utilized, and ef?cient control
`over the amount of water present in the reactor can be
`maintained. In particular, the present method enables
`utilizing a relatively more ef?cient condenser, such as a
`downflow-type condenser, in place of the knockback
`condenser. Because a condenser that does not function
`as a liquid-liquid separator can be used, upsets caused by
`liquid carryover are eliminated. The more efficient
`condenser, moreover, can be subjected to a relatively
`higher pressure drop than was allowable for the knock
`back type of condenser. This, in turn, permits relatively
`higher gas velocities through the condenser than had
`been possible employing the conventional knockback
`condenser.
`In practicing the method of the present invention, the
`condenser produces a condensate that is relatively rich
`in water. A portion of the thus-produced water-rich
`condensate can be returned to the reactor feed, up
`stream of the oxidation reactor, to control water con
`centration within the oxidation reactor.
`
`BACKGROUND OF THE INVENTION
`Liquid-phase oxidation of an aromatic alkyl to an
`aromatic carboxylic acid is a highly exothermic chemi
`cal reaction. Typically, volatilizable aqueous solvents
`are employed to contain the reaction mixture and to
`dissipate heat of reaction.
`Liquid-phase oxidation of aromatic alkyls to aromatic
`carboxylic acid conventionally takes place in a vented,
`well-mixed oxidation reactor equipped with an over
`head condenser system. Such systems are shown in Us.
`Pat. Nos. 3,170,768 and 3,092,658, both to Baldwin. A
`substantial portion of the reaction-generated heat is
`25
`removed by evaporating a portion of the reaction mix
`ture from the reactor, partially condensing it, and re
`turning at least a portion of the condensate to the reac
`tor.
`In particular, an evaporated portion of the reaction
`mixture is withdrawn from the reactor head space.
`These vapors are then passed into an overhead con
`denser system that condenses a portion of these vapors
`and returns a resultant condensate stream to the reactor
`as re?ux.
`The non-condensed vapors that are discharged from
`the condenser system are then conventionally intro
`duced into a shell-and-tube condenser of the knockback
`variety. In addition to condensing at least a portion of
`these condenser-system discharge vapors, the knock
`40
`back condenser serves as a liquid-liquid separator to
`separate such condensed vapors into respective water
`rich and solvent-rich phases. The solvent-rich phase is
`returned to the reactor as reflux. This solvent-rich re
`?ux together with the earlier-mentioned condensate
`stream that is re?uxed to the reactor from the overhead
`condenser system de?ne a re?ux loop.
`Use of knockback condensers is undesirable for a
`variety of reasons. First, the liquid-liquid separator
`portion of the knockback condenser is provided with an
`internal baffle which separates a solvent-rich stream
`from a water-rich stream. Unscheduled process upsets
`or disturbances, which typically are costly, can arise
`when either one of the solvent-rich and water-rich
`streams carries over the baffle and combines with the
`other stream. Second, a knockback-type condenser can
`only accommodate a relatively limited gas velocity.
`That is, a gas velocity that is greater that a predeter
`mined value typically gives rise to liquid entrainment
`into the knockback condenser overhead stream. Such
`entrainment has historically given rise to numerous
`process operating problems. Third, the thermal effi
`ciency of a knockback condenser is not particularly
`desirable. For example, because of the relatively low
`gas throughput rate, heat transfer coef?cients of a
`knockback type condenser are typically relatively low.
`Accordingly, there exists a need for other process sys
`tem designs providing signi?cantly higher heat transfer
`
`35
`
`45
`
`55
`
`SUMMARY OF THE INVENTION
`The present invention facilitates the control of water
`concentration in the oxidation reactor, reduces heat
`duty of the reactor overhead condenser system and thus
`permits the use of less costly process equipment, and
`also provides the potential for operating the oxidation
`reactor at relatively lower water concentrations. The
`method of this invention contemplates partitioning the
`vapors exiting the oxidation reactor into a partial con
`densate having a relatively lesser water—to-solvent
`weight ratio and a vapor phase having a relatively
`greater water-to-solvent weight ratio. At least a portion
`of the partial condensate is returned directly to the
`reactor as a direct reflux stream while the vapor phase
`is withdrawn from the existing re?ux loop as a vapor
`stream. The withdrawn vapor stream is then subjected
`to further heat exchange, while the vapor stream pres
`sure is decreased to less than the oxidation reactor pres
`sure, to produce an aqueous aliphatic acid stream hav
`ing a water-to-solvent weight ratio greater than that of
`the direct re?ux stream. Next, a predetermined portion
`of the aqueous aliphatic acid stream is combined, as an
`indirect recycle stream, with an aromatic alkyl feed
`stream upstream of the oxidation reactor.
`Additional advantages or features of the present in
`vention will be discussed below.
`
`BRIEF DESCRIPTION OF THE FIGURE
`The accompanying FIGURE is a process flow dia
`gram illustrating a system embodying the principles of
`the method of the present invention.
`
`65
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENT
`While the present invention is susceptible to embodi
`ment in various forms, there is shown in the accompa
`nying FIGURE and hereinafter described in detail a
`
`Petitioners' Exhibit 1023, Page 3 of 7
`
`

`
`20
`
`25
`
`4,792,621
`4
`3
`p-xylene, and the trieethybenzenes. The respective aro
`preferred embodiment of the invention. The present
`matic carboxylic acid products of these aromatic alkyls
`disclosure is to be considered as an exemplification of
`the invention without limitation to the speci?c embodi
`are benzoic acid, orthophthalic acid, isophthalic acid,
`terephthalic acid (TPA), and the benzenetricarboxylic
`ment illustrated, however.
`Referring to the accompanying FIGURE, reactor
`acids. The method of this invention can be used to pro
`feed mixture from source 10 is introduced via conduit
`duce TPA, isophthalic acid, and trimellitic acid (1,2,4
`12 into oxidation reactor 14. The reactor feed mixture
`benzenetricarboxylic acid). It is particularly well suited
`comprises an aromatic alkyl, an aqueous monocarbox
`for the production of TPA.
`ylic C2 to C6 aliphatic acid solvent, and a suitable oxida
`Suitable aqueous aliphatic acid solvents useful in the
`tion catalyst. The feed mixture may further include a
`method of this invention are those that are readily vola
`suitable promoter. An oxygen-containing gas under
`tilizable at the reaction temperatures. Among such sol
`pressure from source 16 is separately introduced into
`vents are aqueous solutions of C2 to C6 monocarboxylic
`reactor 14 via a conduit 18. The preferred oxygen-con
`acids, e.g., acetic acid, propionic acid, n-butyric acid,
`taining gas is air. The reactants in reactor 14 are main
`isobutyric acid, n-valeric acid, trimethylacetic acid,
`tained at an elevated pressure sufficient to maintain the
`caproic acid, and mixtures thereof. Preferably, the vola
`contained, volatilizable reaction medium substantially
`tilizable monocarboxylic aliphatic acid solvent is an
`in the liquid state at the reaction temperature.
`aqueous acetic acid solution.
`Reactor 14 is a pressurized oxidation reactor vessel
`Suitable catalyst systems, for present invention pur
`wherein liquid-phase oxothermic oxidation of the arc
`poses, can include any catalyst system conventionally
`matic alkyl by the oxygen-containing gas takes place in
`used for liquid-phase oxidation of an aromatic alkyl. A
`the presence of the oxidation catalyst. The reaction
`suitable catalyst system, e.g., may include a mixture of
`medium contained by reactor 14 thus comprises the
`cobalt, manganese and bromine compounds or com
`oxygen-containing gas, the aromatic alkyl that is to be
`plexes, soluble in the particular volatilizable aqueous
`oxidized to an aromatic carboxylic acid product, the
`solvent employed. A preferred catalyst system is a solu
`catalyst, and a relatively volatile solvent.
`tion prepared from dry cobalt, selected manganese ace
`During the course of the oxidation reaction, exother
`tates, and water. A preferred catalyst system may also
`mic heat of reaction, generated by oxidation of the
`include a promoter such as aqueous hydrogen bromide.
`aromatic alkyl, is removed from reactor 14 by vaporiza
`As an example, as p-xylene is oxidized to produce
`tion of a portion of the reaction medium. These vapors
`TPA practicing the method of the present invention,
`pass upwardly through reactor 14 and are introduced
`the usual process conditions and parameters can be
`via a conduit 20 into a condenser system 22 that con
`summarized as follows: The contents of reactor 14 are
`denses a major portion of these vapors. The resultant
`subjected to a pressure in the range of about 15 to about
`condensate is returned to reactor 14 by pipelines 44 and
`20 kg./cm.2a. (about 215 to about 285 psia) at a tempera
`26.
`ture in the range of about 190° to about 210° C. (about
`The condenser system 22 de?nes a reflux loop for
`375° to about 4l0° F.). In the conventional process,
`reactor 14 and includes a pair of condensers 56 and 58.
`however, the oxidation reactor contents usually are
`Condensers 56 and 58 are each of the down?ow type,
`subjected to a pressure of about 27.1 kg./cm.2 a. (about
`and are connected in series by a pipeline 60. Preferably,
`385 psia) at a temperature of about 224° C. (about 435°
`each of the condensers 56 and 58, and the heat ex
`F.).
`changer 30 are of the shell-and-tube variety.
`Reduction of oxidation reactor pressure provides
`The reactor vapors which are not condensed within
`both capital-cost and operating-cost savings over the
`the reflux loop are withdrawn from this loop and sub
`conventional process. Stainless steel can be used as a
`jected to further heat exchange. Such vapors are intro
`material of construction for a heat exchanger instead of
`duced via conduit 28 into heat exchanger 30 which, in
`titanium. Capital and operating savings can be realized
`turn, cools the non-condensed reactor vapors and at the
`by employing as the oxidation reactor a pressure vessel
`same time decreases the vapor pressure of these vapors,
`having a relatively lower pressure rating, thinner walls,
`thereby producing an aqueous aliphatic acid liquid
`less weight, etc. The capital and operating costs of the
`stream that has a water-to-solvent weight ratio and
`air-compressor can also be reduced as a result of rela
`water concentration greater than that of the direct re
`tively lower process pressures.
`?ux stream.
`Moreover, operation at a lower reactor temperature
`A portion, or all, of the aqueous aliphatic acid liquid
`provides a benefit in the form of improved reactor-seal
`stream is recycled to conduit 12 via conduit 36 and
`life A reactor-seal failure typically gives rise to undesir
`thereafter combined with the reactor feed mixture up
`able process downtime and aliphatic acid solvent loss,
`stream of reactor 14. In this manner, the water concen
`both of which are economically undesirable.
`tration of the reaction medium contained within reactor
`Another advantage or feature of the present inven
`14 can be readily and expeditiously controlled.
`In operation, reactor 14 continuously produces an
`tion is that the water concentration of the reaction me
`aromatic carboxylic acid product that is continuously
`dium contained by reactor 14 can be more easily con
`trolled than conventionally possible. For example, if the
`withdrawn from reactor 14 and conveyed via a pipeline
`amount of aqueous aliphatic acid returned to reactor 14
`38 to a suitable storage or processing facility 40. Con
`via pipeline 36 is minimized, water concentration of the
`currently, the amount of water in reactor 14 is regulated
`by valve 54 by splitting the condensate from heat ex
`reaction medium within reactor 14 can be maintained as
`low as about 7.5 weight percent. Typically, however,
`changer 30 into a stream returned to reactor 14 via
`water concentration within reactor 14 is controllably
`conduit 36 and another stream passed on to solvent
`maintained at a greater value, for example, in the range
`recovery means 34 via conduit 32.
`of about 12 to about 16 weight percent water, prefera
`Suitable aromatic alkyls useful as reactor feed-mix
`ture components or ingredients in the method of the
`bly in the range of about 12 to about 14 weight percent
`present invention include toluene, o-xylene, m-xylene,
`water.
`
`40
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`45
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`50
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`65
`
`Petitioners' Exhibit 1023, Page 4 of 7
`
`

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`20
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`25
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`4,792,621
`5
`To control water concentration of the reaction me
`dium, a suitable aliquot sample can be extracted from
`reactor 14. The sample can be obtained employing, e.g.,
`a side-mounted conduit 42 or a bottom-mounted con
`duit 44, either of which can be connected to a suitable
`conventional analyzer 46 adapted to perform the analy
`sis and transmit the results thereof via communication
`link 48 to a suitable process-control unit such as a mi
`croprocessor unit 50. One such commercially available
`process-control unit is adapted to produce a pneumatic
`signal that can be conveyed via conduit 52 to an auto
`matic flow-control valve 54 that, in turn, controls the
`flow of a liquid aqueous aliphatic acid stream. When
`automatic valve 54, or the like, is incorporated in pipe
`line 36 as shown in the accompanying FIGURE, the
`sampling of the reaction medium can determine the
`amount of water to be returned to reactor 14 as a por
`tion of the aqueous aliphatic acid stream discharged
`from heat exchanger 30. Control of the water concen
`tration in reactor 14 within desired limits is thus
`achieved. The predetermined portion of the aliphatic
`acid stream is returned to reactor 14 as an indirect recy
`cle stream, upstream of reactor 14 as discussed herein
`above.
`In operation, the vaporized reaction medium exiting
`reactor 14 via conduit 20 is primarily constituted by
`vaporized acetic acid ad water. Small amounts of the
`starting material, catalyst and reaction by-products are
`also present. About 80 weight percent of the vaporized
`reaction medium supplied by conduit 20 is condensed in
`downflow condenser 56 and returned via pipeline 24 to
`an upper portion of reactor 14 as a reflux. Such re?ux
`typically is in the range of about 18 to 20 weight percent
`water and has a water-to-solvent weight ratio of about
`0.2. That portion of the vaporized reaction medium
`35
`vapors supplied by conduit 20 and not condensed in
`condenser 56 is introduced into down?ow condenser 58
`via pipeline 60. The non-condensed vapor stream within
`pipeline 60 typically has a water-to-solvent weight ratio
`of about 0.4. About 10 to about 12 weight percent of the
`vaporized reaction medium, supplied by conduit 20, is
`condensed in condenser 58 and returned via pipeline 26
`to a lower portion of reactor 14 as liquid re?ux. This
`condensed re?ux stream contains about 25 weight per
`cent water and has a water-to-solvent weight ratio of 45
`about 0.3. A portion of the total condensate in pipeline
`26 can be withdrawn therefrom via a conduit 70 as a
`trim stream and supplied to a suitable storage or further
`processing facility 72. The remainder is returned to
`reactor 14 to control the water concentration of the
`reaction medium. Liquid ?ow through conduit 70 is
`controlled in a conventional manner employing an auto
`matic ?ow-control valve 74 operatively connected to a
`liquid ?ow rate-indicating device 76.
`A typical temperature of the vapor being introduced
`into condenser 56 via conduit 20 is about 199° C. (about
`390° F.). Condenser 56 reduces the temperature of that
`vapor to about 166° C. (about 331° F.). Such cooled
`vapor, introduced into condenser 58 via pipeline 60, is
`then cooled further by condenser 58 to about 141° C.
`(about 286° F.)
`A suitable heat-transfer medium from a source 62 is
`passed through downflow condenser 56 for the purpose
`of condensing process vapors contained therein, add is
`returned to a suitable reservoir 64. Similarly, a suitable
`heat-transfer medium from another source 66 is passed
`through condenser 58, also for vapor condensing pur~
`poses, and is returned to another suitable reservoir 68.
`
`6
`Those oxidation reactor overhead vapors which are
`not condensed in condensers 56 and 58 are introduced
`into heat exchanger 30 via conduit 28. The non-con
`densed vapor stream in conduit 28 has a water-to-sol
`vent weight ratio of about 0.4-0.7.
`About 6 to about 8 weight percent of the vaporized
`reaction medium, supplied by conduit 20 is condensed
`in heat exchanger 30, and is thereafter discharged there
`from via conduit 78. This condensate contains about 30
`to about 60 weight percent water and has a water-to
`solvent weight ratio of about 0.4-0.7. The condensed
`process stream, conveyed by conduit 78, is the aqueous
`aliphatic acid liquid stream mentioned above. Conduit
`78, in turn, conveys this process stream to the above
`mentioned pipe-lines 32 and 36, which direct the ?ow of
`the aqueous aliphatic acid liquid stream upstream of
`reactor 14, and/or to storage of processing facility 34, if
`desired.
`Cooling water from a suitable source 80 is passed
`through heat exchanger 30 for purposes of condensing
`process vapors contained therein, and is then returned
`to a suitable cooling tower or reservoir 82. Those pro
`cess vapors which are not condensed in heat exchanger
`30 are conveyed therefrom via conduit 84 int gas cooler
`86. Cooling water from another source 88 is passed
`through gas cooler 86 for gas-cooling purposes, and is
`thereafter conveyed to reservoir 90.
`The 141° C. vapor being introduced into heat ex
`changer 30 via conduit 28 is reduced in temperature by
`heat exchanger 30 to about 79° C. (about 174° F.) and is
`thereafter further cooled by gas cooler 86 to about 44°
`C. (about 110° F.). This 44° C. vapor is then conveyed
`substantially at that temperature via a conduit 92 to a
`suitable storage or processing facility 94.
`Facility 92 preferably includes a vented scrubber (not
`shown) which recovers residual, unreacted p-xylene.
`The air feed rate from source 16 to reactor 14 is prefera
`bly adjusted so that the vent-gas oxygen concentration
`at the scrubber vent is in the range of about 1 to about
`3 volume percent oxygen on a volatile-free basis.
`Vapor being introduced into each of condensers 56
`and 58, and heat exchanger 30, is substantially at the
`vapor pressure within reactor 14. Heat exchanger 30
`reduces that vapor pressure by about 10 to about 15
`percent.
`Another advantage of the present invention is that
`the indirect recycle stream and the trim stream can each
`be controlled, independent of the other, to maintain
`water concentration of the reaction medium in reactor
`14. However, because the indirect recycle and the
`water trim streams are both relatively rich in water, the
`trim-stream rate through conduit 70 is necessarily re
`lated to the indirect recycle rate through conduit 36 to
`achieve a desired rate of water return to reactor 14 via
`conduits 26 and 36. That is, in operation, the rate or
`indirect recycle through conduit 36 and the rate of
`withdrawal through conduit 70 are independently con
`trollably maintained by respective automatic ?ow-con
`trol valves 54 and 74, and the rate of indirect recycle
`returned to reactor 14 via conduit 36 modulated via
`automatic ?ow-control value, to achieve a desired
`water concentration in reactor 14.
`To facilitate water concentration modulation within
`reactor 14 it has been found advantageous to monitor an
`indirect-to-direct water ratio de?ned as the weight of
`water in conduit 36 to the weight of water in pipelines
`24 and 26 taken collectively. This ratio, which in effect
`is the ratio of water indirectly recycled to reactor 14 to
`
`55
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`60
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`65
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`Petitioners' Exhibit 1023, Page 5 of 7
`
`

`
`4,792,621
`8
`7
`partitioning the vapors into a parallel condensate
`the weight of water directly refuxed into reactor 14, is
`having a relatively lesser water-to-solvent weight
`preferably maintained in a range of about 0.01 to about
`ratio and a vapor phase having a relatively greater
`0.15, more preferably in a range of about 0.02 to about
`water-to-solvent weight ratio;
`0.06. Most preferably, this ratio is maintained at a value
`returning the partial condensate directly to the oxida
`of about 0.04.
`What has been illustrated and described herein is a
`tion reactor as a direct reflux stream;
`withdrawing the vapor phase from the re?ux loop as
`method for continuously producing an aromatic car
`boxylic acid product. While the method of the present
`a vapor stream;
`subjecting the withdrawn vapor stream to heat ex
`invention has been illustrated and described with refer
`change while decreasing the vapor stream pressure
`ence to a preferred embodiment, the present invention is
`to less than the oxidation reactor pressure to
`not limited thereto. On the contrary, alternatives,
`thereby produce an aqueous aliphatic acid stream
`' changes or modi?cations may become apparent to those
`having a water-to-solvent weight ratio greater than
`skilled in the art upon reading the foregoing descrip
`tion. Accordingly, such alternatives, changes and modi
`that of the direct re?ux stream; and
`combining a predetermined portion of the aqueous
`?cations are to be considered as forming a part of the
`aliphatic acid stream with the aromatic alkyl feed
`invention insofar as they fall within the spirit and scope
`of the appended claims.
`upstream of the oxidation reactor as an indirect
`recycle stream, the predetermined portion being
`I claim:
`suf?cient to thereby control the concentration of
`1. In a method for the continuous production of an
`aromatic carboxylic acid product in a pressurized oxida
`water in the oxidation reactor within the aforesaid
`desired limits therefor.
`tion reactor by liquid-phase, exothermic oxidation of an
`2. The improvement in accordance with claim 1
`aromatic alkyl feed with an oxygen-containing gas, in
`wherein water recycled to the oxidation reactor by the
`the presence of an oxidation catalyst and in an aqueous
`monocarboxylic C2 to C6 aliphatic acid solvent medium,
`indirect recycle stream and by the direct reflux stream is
`wherein the heat generated during the course of the
`in a weight ratio of about 0.01 to about 0.15.
`3. The improvement in accordance with claim 1
`oxidation is removed from the reactor by vaporization
`wherein water recycled to the oxidation reactor by the
`of a portion of the reaction medium and water, wherein
`indirect recycle stream and by the direct re?ux stream is
`the resulting vapors are condensed in part in a re?ux
`loop externally of the oxidation reactor to produce a
`in a weight ratio of about 0.02 to about 0.06.
`4. The improvement in accordance with claim 1
`condensate and a gaseous phase, and wherein at least a
`wherein water recycled to the oxidation reactor by the
`portion of the condensate is returned to the oxidation
`indirect recycle stream and by the direct re?ux stream is
`reactor, the improvement comprising a method for
`controlling within desired limits the concentration of
`in a weight ratio of about 0.04.
`water in the oxidation reactor, which comprises:
`it
`1i!
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`Petitioners' Exhibit 1023, Page 6 of 7
`
`

`
`UNITED STATES PATENT OFFICE
`CERTIFICATE OF CORRECTION
`
`Patent No.
`
`Z+4,792L62l
`
`Dated
`
`December 20, 1988
`
`Inventor(s) Kenneth L Abrams
`
`It is certified that error appears in the above-identified patent
`and that said Letters Patent is hereby corrected as shown below:
`
`Col.
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`Line
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`1
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`3
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`4
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`4
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`5
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`5
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`6
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`7
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`8
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`58
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`33
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`1
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`53
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`27
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`"greater that" should ‘read -—greater than-
`
`"pipelines 44" should read "pipelines 24-
`
`"trieethybenzenes" should read
`-—triemthy1benzenes-
`
`"life" should read ——'life.——
`
`"ad" should read -->-ar>1d—-—
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`64
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`"add" should read —-and——-
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`I
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`24
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`"int" should read --into-
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`l
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`"refuxed'I should read —-ref1uxed-—
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`llel" h 1d read -— artial-- _
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`S1gned and Sealed th1s
`
`First Day of August, 1989
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`Arrest:
`
`DONALD J. QUIGG
`
`Petitioners' Exhibit 1023, Page 7 of 7