United States Patent [191
`Huber, Jr. et a1.
`
`USOO5099064A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,099,064
`Mar. 24, 1992
`
`[54]
`
`[75]
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`[73]
`
`[21]
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`[22]
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`[51]
`[52]
`[53]
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`[56]
`
`METHOD FOR INCREASING CONVERSION
`EFFICIENCY FOR OXIDATION OF AN
`ALKYL AROMATIC COMPOUND TO AN
`AROMATIC CARBOXYLIC ACID
`
`Inventors: William F. Huber, Jr.; Martin A.
`Zeitlin, both of Naperville, Ill.
`
`Assignee: Amoco Corporation, Chicago, Ill.
`
`App]. No.: 814,655
`
`Filed:
`
`Dec. 30, 1985
`
`Int. Cl.5 ................... .. CO7C 51/265; CO7C 59/84
`U.S. Cl. .................................................. .. 562/414
`Field of Search .... ..
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`2,788,367 4/1957 Bills et al. ......................... .. 562/414
`2,906,775 9/1959 Taplin
`.
`.
`.... .. 562/414
`3,928,433 12/1975 Onopchenko et al.
`.... .. 562/414
`3,970,696 7/1976 Shigeyasu et a1. ................ .. 562/414
`
`FOREIGN PATENT DOCUMENTS
`
`1262259 3/1968 Fed. Rep. of Germany .... .. 562/414
`Primary Examiner-Vivian Garner
`Attorney, Agent, or Firm-James R. Henes; William H.
`Magidson; Ralph C. Medhurst
`[57]
`msmcr
`A method and system for increasing conversion effi
`ciency of aromatic alkyl reactant to aromatic carboxylic
`acid product and for improving the quality of the prod
`uct, are disclosed. The method and system provide for
`the continuous production of an aromatic carboxylic
`acid by the liquid phase, exothermic oxidation of an
`aromatic alkyl in a vaporizable solvent in an oxidation
`reactor. The reactor makes use of a vented, overhead
`condenser system and a separator system for condensa
`tion of vaporized reactor material, separation of the
`condensed solvent therefrom, and re?ux of separated
`solvent back into the reactor. The improvement com
`prises combining the reactor liquid feedstream with the
`re?uxed solvent upstream from the oxidation reactor.
`
`7 Claims, 2 Drawing Sheets
`
`Petitioners' Exhibit 1025, Page 1 of 7
`
`

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`US. Patent
`
`Mar. 24, 1992
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`Sheet 1 of 2
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`5,099,064
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`00
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`ow Nw
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`Petitioners' Exhibit 1025, Page 2 of 7
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`

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`U.S. Patent
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`Mar. 24, 1992
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`Sheet 2 of 2
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`A
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`Petitioners' Exhibit 1025, Page 3 of 7
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`

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`1
`
`METHOD FOR INCREASING CONVERSION
`EFFICIENCY FOR OXIDATION OF AN ALKYL
`AROMATIC COMPOUND TO AN AROMATIC
`CARBOXYLIC ACID
`
`FIELD OF THE INVENTION
`This invention relates generally to the continuous,
`liquid phase oxidation of an aromatic alkyl to an aro
`matic carboxylic acid. More particularly, the present
`invention concerns a method and system for increasing
`reactor conversion ef?ciency and for improving the
`aromatic carboxylic acid product quality as well.
`
`5,099,064
`2
`oxidation of aromatic alkyls, however, it is highly desir
`able to improve the reactor conversion efficiency and
`quality of aromatic carboxylic acids produced by the
`oxidation of aromatic alkyls.
`The invention disclosed herein tends to diminish so
`called reactor “entrance” effects, thought to be caused
`by an oxygen de?ciency at the point where the reactor
`feedstrearn feeds the reactor. The invention disclosed
`herein also tends to minimize color-body generation,
`known to limit aromatic carboxylic acid plant operating
`?exibility and capacity.
`
`BACKGROUND OF THE INVENTION
`Liquid phase oxidation of an aromatic alkyl to an
`aromatic carboxylic acid is a highly exothermic chemi
`cal reaction. Volatilizable aqueous acidic solvents are
`used to contain the reaction mixture and to dissipate the
`heat of reaction. conventionally, the oxidation‘of aro
`matic alkyls in the liquid phase to form aromatic car
`boxylic acids is generally performed in a vented, well
`mixed oxidation reactor, with a substantial portion of
`the heat generated by the exothermic oxidation reaction
`being removed by evaporating directly from the reac
`tion mixture a portion of the aqueous solvent and aro
`matic alkyl contained within the reactor.
`The materials vaporized as a result of the heat gener
`ated in the exothermic reaction, together with unre
`acted oxygen and other aqueous components that may
`be present, pass upwardly through the reactor and are
`withdrawn from the reactor at a point above the reac
`tion mixture liquid level for the reactor. The vapors are
`passed upwardly and out of the reactor to an overhead
`re?ux condenser system where the vaporized solvent,
`water and aromatic alkyl are condensed. The resultant
`condensate is thereafter separated, e. g., in a re?ux split
`ter, into a portion having a relatively higher water con
`centration and a portion having a relatively lower water
`concentration. The separated portion having a rela
`tively lower water concentration, now at a temperature
`less than the reactor contents’ temperature, is re?uxed
`back into the reactor by gravity. conventionally, the
`re?uxed portion of the condensate is returned directly
`to the reactor through a process line external to the
`reactor. The non-condensable gases, carried along with
`the vaporized reactor material, are vented.
`In operation, the reactor is fed by a liquid feed stream
`containing the aromatic alkyl, aqueous acidic solvent
`and an oxidation catalyst. An oxygen-containing gas is
`separately introduced into the reactor for oxidizing the
`aromatic alkyl to the aromatic carboxylic 'acid in the
`presence of the catalyst.
`The reaction mixture contained in the reactor typi
`cally comprises a suspension of crystalline aromatic
`carboxylic acid in liquid, volatilizable, aqueous acidic
`solvent as mother liquor. The mother liquor contains, in
`addition to dissolved catalyst, some dissolved aromatic
`carboxylic acid product and lesser amounts of partially
`converted species of such product. The mother liquor
`can also include a minor amount of unreacted, aromatic
`alkyl.
`Aromatic carboxylic acid product quality is mea
`sured by optical density. At present, optical density of
`the obtained product limits the oxidation reactor oper
`65
`ating temperature and pressure, as well as the reactor
`throughput and mother liquor recycle rate into the
`reactor. Because of the commercial importance of the
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`SUMMARY OF THE INVENTION
`The present invention is an improvement in a method
`and in a system for the continuous production of an
`aromatic carboxylic acid by liquid phase oxidation of an
`aromatic alkyl in an oxydation reactor. The improve
`ment includes combining upstream from the reactor a
`liquid feed stream, containing an aromatic alkyl, with
`condensed acidic solvent medium that is re?uxed back
`into the reactor, thereby providing a re?ux-containing
`feed mixture, and then introducing the re?ux-contain
`ing feed mixture into the oxidation reactor. A system
`embodying the present invention includes a liquid-liq
`uid mixing means for effecting the “combining” step.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1- is a schematic process ?ow diagram of one
`embodiment of the present invention;
`FIG. 2 is a schematic process ?ow diagram of an
`other embodiment of the present invention; and
`FIG. 3 is a detail on an enlarged scale showing a
`preferred liquid-liquid mixing means.
`The drawings of FIGS. 1 and 2, being process ?ow
`diagrams, are mere schematic illustrations. Accord
`ingly, details which are not necessary for an under
`standing of the present invention have been omitted.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`Aromatic carboxylic acid is produced in an oxidation
`reactor at an elevated temperature and pressure by
`liquid phase, exothermic oxidation of an aromatic alkyl
`by an oxygen-containing gas in a vaporizable, aqueous
`acidic solvent medium. Oxidation of the aromatic alkyl
`to the aromatic carboxylic acid takes place in the aque
`ous acidic solvent medium in the presence of an oxida
`tion catalyst. The conversion of aromatic alkyl to aro
`matic carboxylic acid is exothermic. Heat generated in
`the oxidation reaction is at least partially dissipated by
`vaporization of a portion of the solvent, water, aromatic
`alkyl and other vaporizable constituents of the reaction
`mixture present in the oxidation reactor. Vaporized
`reaction mixture constituents are withdrawn from the
`oxidation reactor, condensed in an overhead condenser
`system, and separated in a re?ux splitter or a similar
`device into condensate portions having different water
`concentrations. Condensate portion having a relatively
`lower water concentration, and thus a relatively higher
`acidic solvent concentration, is fed back into the oxida
`tion reactor.
`A liquid feedstream for the oxidation reactor contains
`the aromatic alkyl, the acidic solvent medium, and an
`effective amount of an oxidation catalyst for effecting in
`the reactor a liquid phase oxidation of the aromatic
`alkyl, in the presence of oxygen, to the aromatic carbox
`ylic acid. The improvement of the present invention
`
`Petitioners' Exhibit 1025, Page 4 of 7
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`5,099,064
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`comprises combining the re?uxed condensate portion
`with the oxidation reactor liquid feed stream upstream
`from the oxidation reactor to produce a re?ux-contain
`ing liquid feed mixture which is at a temperature below
`the reactor contents’ temperature. The re?ux-contain
`ing feed mixture is then introduced into the oxidation
`I'CHCIOI'.
`Referring to FIG. 1, an elongated, vertically-dis
`posed, continuous stirred-tank oxidation reactor 10 for
`oxidizing an aromatic alkyl to an aromatic carboxylic
`acid is shown. The oxidation reaction is continuous and
`proceeds in the liquid phase. The reactor 10 includes an
`agitator 12 which drives impeller blades 14, ?xed to an
`agitator shaft 15. The reactor 10 further includes inter
`nal baffles (not shown). Each impeller blade 14 is ro
`tated by the shaft 15 in a generally horizontal plane at a
`pre-selected rotational speed so that the contents of the
`reactor 10 are well mixed.
`The contents of the reactor 10 are subjected to an
`elevated pressure and temperature sufficient to maintain
`the contained volatilizable solvent and aromatic alkyl
`substantially in the liquid state.
`An aromatic alkyl, such as para-xylene, from a source
`16, and a volatilizable aqueous acidic solvent medium,
`such as a catalyst-containing aqueous acetic acid solu
`tion, from a source 18, are combined to form a mixture.
`A liquid, reactor re?ux stream from re?ux splitter 48,
`contained in transfer pipe 32 and having a relatively
`higher acetic acid concentration than the non-re?uxed
`condensate portion exiting via discharge pipe 48, is
`further combined with the formed mixture and is intro
`duced into the reactor 10, via side inlet 36, as will be
`described in greater detail below. An oxygen-contain
`ing gas from a source 20 is introduced into the bottom of
`the reactor 10 via a gas inlet line 66. The oxygen-con
`35
`taining gas serves to oxidize the aromatic alkyl to an
`aromatic carboxylic acid in the presence of the catalyst.
`Localized pockets of relatively low oxygen concen
`tration or relatively high aromatic alkyl or catalyst
`concentration, such as are in the vicinity of the reactor
`inlet or the reactor baf?es, are thought to reduce con
`version efliciency of aromatic alkyl to aromatic carbox
`ylic acid. To counteract these so-called “entrance” and
`“other” effects, it has been discovered that, when the
`reactor feed stream containing the aromatic alkyl and
`the volatilizable aqueous acidic solvent medium (the
`solvent medium containing the oxidation catalyst) is
`combined with the liquid reactor re?ux stream to pro
`duce a re?ux-containing mixture and the re?ux-contain
`ing mixture is then introduced into the reactor 10, the
`overall conversion efficiency of aromatic alkyl to am‘
`matic carboxylic acid is increased and the product qual
`ity is improved as well. i
`The prior art teaches recycling the re?ux stream to
`the bottom of the reactor 10 and introducing the feed
`stream into the side of the reactor 10. The present in
`vention, however, contemplates introducing the com
`bined re?ux-containing liquid feed mixture either at the
`bottom or the side of the reactor 10, as desired.
`Accordingly, in one embodiment of this invention, a
`liquid-liquid mixing means, such as the piping “T” con
`nection 28 (FIG. 1), is provided. The aromatic alkyl is
`supplied to the “T” connection 28 by an inlet pipe 30
`which carries the aromatic alkyl feed stream from
`source 16 via pipe 22 and the aqueous acidic solvent
`(containing the oxidation catalyst) from source 18 via
`pipe 24. The aromatic alkyl and aqueous acidic solvent
`mixture is further combined with the reactor re?ux
`
`4
`stream in “T" connection 28, with the re?ux stream
`being introduced into “T” connection 28 by transfer
`pipe 32. The resultant re?ux-containing reactor feed
`exiting the “T” connection 28 is transferred via dis
`charge pipe 34 into the reactor 10 either at side inlet 36,
`bottom inlet 38, or both, as desired. The reactor side
`inlet 36 is located below the reactor liquid level D. The
`temperature of the re?ux-containing feed mixture is less
`than the reactor temperature.
`The source of oxygen for the oxidation of this inven
`tion can vary. Air and oxygen-enriched gas such as
`oxygen-enriched air or gaseous oxygen can be used.
`The oxygen-containing gas, from whatever source,
`supplied to the reactor 10 provides sufficient oxygen to
`result in an exhaust gas-vapor mixture containing from
`about two to about eight volume percent oxygen (mea
`sured on a solvent-free basis) when the oxidation reac
`tor is in operation. For example, when each alkyl sub
`stituent on the aromatic ring of the aromatic alkyl is a
`methyl group, a feed rate of the oxygen-containing gas
`sufficient to provide oxygen in the amount of from
`about 1.4 to about 2.8 moles per methyl group will
`provide such two to eight volume percent oxygen con
`centration in the gas-vapor mixture in the condenser 40.
`In operation, the minimum pressure at which the
`reactor 10 is maintained is that pressure which will
`maintain a substantial amount of the aromatic alkyl
`present in the liquid phase and at least about 70 percent
`of the volatilizable, aqueous acidic solvent in the liquid
`phase. When the aqueous acidic solvent is an acetic
`acid-water mixture, suitable gauge pressures in the reac
`tor 10 can be up to about 35 kg/crn2 and typically are in
`the range of about 10 kg/cm2 to about 30 kg/cm2.
`The process temperature employed is, on the one
`hand, low enough that the oxidation occurs with rela
`tively low heat losses but, on the other hand, is high
`enough so that an economically desirable degree of
`conversion of the aromatic alkyl to the corresponding
`aromatic carboxylic acid is obtained. Process tempera~
`tures suitable for use in practicing the method of this
`invention generally are in the range of about 120° C. to
`about 240° C., preferably about 150' C. to about 230° C.
`Various narrower ranges may be preferred for a partic
`ular aromatic alkyl being oxidized. For example, when
`the aromatic alkyl is para-xylene, the preferred overall
`temperature range within the reactor 10 is about 175° C.
`to about 225° C., and the preferred temperature of the
`re?ux-containing liquid feed mixture is about 85° C.
`The residence time of the reactor is de?ned as the
`quotient of the reactor liquid volume divided by the
`liquid feed-stream ?ow rate into the reactor 10. Typi
`cally, in a commercial operation, the residence time in
`the reactor 10 is in the range of about 20 to about 90
`minutes.
`Suitable aromatic alkyls for use in the method of this
`invention include toluene, ortho-, meta‘, and para
`xylene, and the trimethylbenzenes. The respective aro
`matic carboxylic acid products are benzoic acid, or
`thophthalic acid, isophthalic acid, terephthalic acid, and
`the benzenektricarboxylic acids. Preferably, the method
`of this invention is used to produce terephthalic acid,
`isophthalic acid, and trimellitic acid (1, 2, 4-benzene~
`tricarboxylic acid). More preferably, the method of this
`invention is used to produce terephthalic acid.
`Suitable volatilizable, aqueous acidic solvents for use
`in the method of this invention can be aqueous solutions
`of any C2-C6 fatty acid such as acetic acid, propionic
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`Petitioners' Exhibit 1025, Page 5 of 7
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`acid, n-butyric acid, isobutyric acid, n-valeric acid,
`Chemical Engineers’ Handbook, 6th Ed., published 1984
`trimethylacetic acid, caproic acid, and mixtures thereof.
`by McGraw-Hill, at pages 21-64 through 21-83.)
`The volatilizable acidic solvent preferably is aqueous
`The amount of acidic solvent contained in the re
`?uxed portion of the condensed solvent, being dictated
`acetic acid. When combined with the liquid feed, the
`by the operation of the re?ux splitter 46 and the overall
`volatilizable aqueous solvent preferably contains from
`about 0.5 to about 20 weight percent of water. How
`plant economics, of course, can vary. However, a major
`portion of the water produced by the liquid phase oxi
`ever, after being combined with the re?ux stream, the
`resultant reflux-containing liquid feed fed to reactor 10
`dation of the aromatic alkyl is removed in the non
`re?uxed portion of the condensate in reflux splitter 46
`can contain up to about 35 weight percent of water.
`Suitable catalysts for present purposes include any
`via discharge pipe 48 from the re?ux splitter 46 to stor
`_ catalyst system conventionally used for liquid phase
`age means 50 for further use, or to waste, as desired.
`The non-re?uxed portion of the condensate contains
`oxidation of an aromatic alkyl. A suitable catalyst sys
`tem preferably includes a mixture of cobalt, manganese
`water, a relatively lower concentration of aromatic
`carboxylic acid, and a minor amount of aromatic alkyl.
`and bromine compounds or complexes, that are soluble
`in the particular volatilizable, aqueous acidic solvent
`The re?uxed portion of the condensate from the re
`employed. When the catalyst system comprises soluble
`?ux splitter 46, containing aromatic alkyl, water, a rela
`tively higher acidic solvent concentration, and aromatic
`forms of cobalt, manganese or bromine, the cobalt (cal
`carboxylic acid, is returned from re?ux splitter 46 into
`culated as elemental cobalt) preferably is present in the
`range about 0.1 to about 10.0 milligram atoms (mga) per
`reactor 10 via transfer line 32, and is combined with the
`gram mole of the aromatic alkyl. Similarly, the manga
`aromatic alkyl in the “T” connection 28, as described
`nese (calculated as elemental manganese) is preferably
`above. A pump 54 can be used to assist ?ow of re?ux
`through line 32 into the “T” connection 28, if desired.
`present in the ratio of about 0.1 to about 10.0 mga per
`In this manner, localized oxygen starvation in pockets
`mga of the cobalt. Further, the bromine (calculated as
`of high aromatic alkyl and catalyst concentrations
`elemental bromine) is preferably present in the ratio of
`within the reactor 10 is avoided.
`from about 0.2 to about 1.5 mga per mga of total cobalt
`To effect condensation, coolant is introduced into the
`and manganese (both on an elemental basis).
`condenser 40 through coolant inlet pipe 56 and exits via
`In the method and system embodiments of this inven
`tion in which the catalyst system employed comprises a
`coolant discharge pipe 58. The condensate from con
`denser 40 ?ows generally downwardly and through
`mixture of soluble forms of cobalt, manganese and bro
`transfer line 44, and upwardly into the splitter 46. Non
`mine, and the solvent is aqueous acetic acid, each of
`condensable gases, included with the vaporized reactor
`cobalt and manganese can be provided in any of its
`material introduced into the condenser 40, are vented
`known ionic or combined forms that are soluble in aque
`from the separator 46 through a vent pipe 60 which
`ous acetic acid solutions. For example, such forms can
`includes a ?ow-control valve 62. Preferably, the oxy
`include cobalt and/or manganese carbonate, acetate
`tetrahydrate, and/or bromide. However, the desired
`gen concentration from the vent gas is about three to
`catalysis cannot be effected by bromides of both cobalt
`about four percent oxygen by volume, but can be in the
`and manganese. Rather, the catalysis can be effected by
`overall range of about two to about eight percent oxy
`gen by volume.
`appropriate ratios of the bromide salts and other aque
`The reaction mixture, which typically comprises a
`ous acetic acid-soluble forms containing no bromide; for
`suspension of crystalline aromatic carboxylic acid in
`example, the acetates. As a practical matter, and by way
`liquid, volatilizable, aqueous acidic solvent mother li
`of non-limiting example, a 01:1 to 10:1 ratio of manga
`quor, is conventionally transferred by a discharge pipe
`nese mga to cobalt mga is provided through use of the
`64 to suitable crystallizers (not shown). The discharge
`aqueous, acetic acid-soluble forms other than bromides;
`pipe 64 is located below the reactor liquid level D. The
`for example, both as acetate tetrahydrates. A 0.2:1 to
`1.5:1 ratio of elemental bromine mga to total cobalt and
`reactor feed pipe 36 is preferably located on the reactor
`10 lower than the reactor discharge pipe 64 and is
`manganese mga is provided by a source of bromine.
`spaced about 180 degrees therefrom to minimize the
`Such bromine sources include elemental bromine (Br;),
`and ionic bromides (for example, HBr, NaBr, KBr,
`likelihood of any aromatic alkyl, introduced by inlet 36,
`NH4Br, etc.).
`being in the reactor 10 for less than the desired resi
`Heat of reaction in the reactor 10 vaporizes the vola
`dence time.
`In the reactor 10, the aromatic alkyl is oxidized by
`tilizable solvent, water and reaction mixture contained
`therein. A substantial portion of the heat generated by
`oxygen, usually introduced as air at the bottom of reac
`tor 10 by inlet pipe 66, in the presence of the catalyst, to
`the exothermic reaction in the reactor 10 is removed
`from the reaction mixture by vaporization of the aque
`form the desired aromatic carboxylic acid and interme
`ous solvent and, to a lesser extent, the aromatic alkyl.
`diates thereto. A product stream is withdrawn as an
`The vaporized material and any unreacted oxygen and
`effluent stream from the reactor 10 via the discharge
`other components of the oxygen-containing gas fed to
`pipe 64. The product stream is thereafter treated using
`the reactor 10 pass upwardly through the reactor 10 and
`conventional techniques to separate its components and
`are withdrawn from the reactor 10 via the exit pipe 42.
`to recover the aromatic carboxylic acid contained
`therein, usually by crystallization.
`The vaporized materials contained within pipe 42 are
`A further embodiment of the present invention is
`received into an overhead condenser system such as the
`illustrated in FIG. 2. As between FIGS. 1 and 2, like
`condenser 40, are condensed, and are conveyed by a
`transfer line 44 into a re?ux splitter 46 in which the
`reference numerals have been assigned to like parts or
`condensed solvent phase is separated into two portions
`elements of the present invention. Further, for the sake
`having different acid, and thus water, concentrations.
`of brevity, and because the function of many of the parts
`Such liquid-liquid splitters are well-known in the art
`or elements appearing in FIG. 2 have been described in
`and will not be described herein. (See, e.g., Perry’s
`connection with FIG. 1, only those parts or elements of
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`Petitioners' Exhibit 1025, Page 6 of 7
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`FIG. 2 which have not been discussed heretofore will
`be discussed at length hereinbelow.
`As shown in FIG. 2, a liquid-liquid mixing means 68
`is used to combine the aromatic alkyl and aqueous
`acidic solvent from line 30 with the re?ux from line 32
`to provide the re?ux-containing liquid feed mixture to
`be fed via side-inlet line 36 or bottom-inlet line 38 into
`the reactor 10. Such a liquid-liquid mixing means can be
`a so~called “static” mixer or any one of a large number
`of other ?ow or line mixers well-known in the art. (See,
`e.g., Perry’s Chemical Engineers’ Handbook, 6th Ed, at
`pages 21-57 through 21-64.) Preferably, the choice of a
`liquid-liquid mixing means 68 is such that it does not
`require the use of a pump such as the optional pump 54
`in transfer pipe line 32.
`Such liquid-liquid mixing means can be a liquid-han
`dling device conventionally referred to as a jet pump. A
`jet pump is a suitable liquid-handling device which
`makes use of the momentum of one fluid to move an
`other. The preferred liquid-liquid mixing means, shown
`in FIG. 3, is a liquid-liquid ejector 70, a type of jet pump
`which is well-known in the art.
`The liquid-liquid ejector 70 shown in FIG. 3 includes
`an aromatic alkyl and aqueous solvent mixture inlet port
`72, a reactor re?ux suction port 74 and a discharge port
`76. Fluid momentum originating at the sources 16 and
`/or 18 forces the aromatic alkyl and aqueous solvent
`mixture into and through the ?rst venturi 78 which
`feeds the second venturi 80 thereby creating suction at
`suction port 74 and causing the reactor re?ux stream to
`enter the suction port 74 and flow into the ejector ?uid
`suction chamber 82. From the suction chamber 82 the
`re?ux stream enters the ?uid-mixing chamber 83 where
`the liquid-phase solvent re?ux is combined and mixes
`with the mixture of aromatic alkyl and aqueous acidic
`solvent. The ?uid momentum provided at sources 16
`and 18 usually is sufficient to discharge the resultant
`mixture from the liquid-liquid ejector 70 via discharge
`port 76 and through side inlet 36 or bottom inlet 38 into
`the reactor 10, as desired. To facilitate clean-out of the
`liquid-liquid ejector 70, ?rst and second threaded clean
`out plugs 84 and 86 are provided.
`Combining the reactor-re?ux stream with the reac
`tor~feed stream increases the ratio of acidic solvent to
`aromatic alkyl in the resulting combined feed stream. It
`has been found that this tends to increase overall con
`version ef?ciency of aromatic alkyl to aromatic car
`boxyl acid as well. The prior art method of recycling
`re?ux from the re?ux splitter 46 into the reactor 10
`teaches introducing the reactor feed stream (containing
`the aromatic alkyl and aqueous solvent) at a reactor
`location point spaced from the re?ux return point.
`When the aromatic alkyl is para-xylene and the aqueous
`solvent is aqueous acetic acid, the ratio of acetic acid to
`para-xylene in the reactor feed under the prior art
`scheme is about 3:1 (volumetric basis). In contradistinc~
`tion, when the aromatic alkyl and aqueous acidic sol
`vent mixture is combined with the reactor re?ux, as
`Adiscussed above in connection with the present inven
`tion, the re?uxed portion of the condensate has a rela
`tively higher acetic acid concentration and the ratio of
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`acetic acid to para-xylene in the resultant reactor feed
`stream is about 14:] (volumetric basis).
`The foregoing description exempli?es preferred em
`bodiments of the present invention. Still other varia
`tions and rearrangements of component parts are possi
`ble without departing from the spirit and scope of this
`invention and will readily present themselves to one
`skilled in the art.
`What is claimed is:
`1. In a method for the continuous production of an
`aromatic carboxylic acid product by the liquid phase,
`exothermic oxidation of an aromatic alkyl with an oxy
`gen~containing gas and aqueous acidic solvent medium
`present in an oxidation reactor and in the presence of an
`oxidation catalyst, wherein heat generated in the oxida
`tion reactor is at least partially dissipated by vaporiza
`tion of the aqueous solvent medium therein, the vapor
`ized aqueous acidic solvent medium is withdrawn from
`the oxidation reactor and condensed in a re?ux con
`denser system, the improvement which comprises:
`providing a liquid feedstream for the oxidation reac
`tor, the liquid feedstream containing the aromatic
`alkyl and the aqueous acidic solvent medium;
`combining a separated portion of the condensed sol
`vent medium having relatively lower water con
`tent with the liquid feedstream, thereby providing
`a solvent re?ux-containing feed mixture; and
`introducing the solvent re?ux-containing feed mix
`ture into the oxidation reactor.
`2. The method in accordance with claim 1 wherein
`the aromatic carboxylic acid is terephthalic acid, iso
`phthalic acid or trimellitic acid.
`3. The method in accordance with claim 1 wherein
`the aromatic alkyl is para-xylene and wherein the aro
`matic carboxylic acid is terephthalic acid.
`4. The method in accordance with claim 3 wherein
`the aqueous acidic solvent medium and the condensed
`solvent are aqueous acetic acid and the portion of the
`condensed aqueous solvent medium re?uxed to the
`reactor contains a relatively higher concentration of
`acetic acid than the portion of the condensed aqueous
`solvent medium not re?uxed.
`'
`5. The method in accordance with claim 4 wherein
`the volume ratio of acetic acid to para-xylene is about
`3:1 in the liquid feedstream and is about 14:1 in the
`solvent re?ux-containing feed mixture.
`6. The method in accordance with claim 1 wherein
`the aqueous solvent medium and the condensed solvent
`phase are aqueous acetic acid and the portion of the
`condensed aqueous acidic solvent medium re?uxed to
`the reactor contains a higher concentration of acetic
`acid than the portion of the condensed aqueous acidic
`solvent medium not re?uxed.
`7. The method in accordance with claim 1 wherein
`the solvent medium in the oxidation reaction is at a
`pre-selected temperature in the range of from about
`120° C. to about 240° C. and wherein the solvent re?ux
`containing feed mixture is at a temperature less than the
`pre-selected temperature.
`a ‘e
`
`a a a
`
`Petitioners' Exhibit 1025, Page 7 of 7