WO1996011899A1 - Process for preparing aromatic carboxylic acids with efficient energy recovery - Google Patents

Process for preparing aromatic carboxylic acids with efficient energy recovery Download PDF

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Publication number
WO1996011899A1
WO1996011899A1 PCT/US1995/012255 US9512255W WO9611899A1 WO 1996011899 A1 WO1996011899 A1 WO 1996011899A1 US 9512255 W US9512255 W US 9512255W WO 9611899 A1 WO9611899 A1 WO 9611899A1
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Prior art keywords
water
add
distillation column
aromatic carboxylic
reaction
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PCT/US1995/012255
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French (fr)
Inventor
Kenneth J. Abrams
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Amoco Corporation
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Priority to JP8513236A priority Critical patent/JPH09511253A/en
Priority to AT95934533T priority patent/ATE193516T1/en
Priority to NZ294161A priority patent/NZ294161A/en
Priority to EP95934533A priority patent/EP0734372B8/en
Priority to BR9506413A priority patent/BR9506413A/en
Application filed by Amoco Corporation filed Critical Amoco Corporation
Priority to MX9602364A priority patent/MX9602364A/en
Priority to CA002178346A priority patent/CA2178346C/en
Priority to AU36844/95A priority patent/AU703997B2/en
Priority to DE69517301T priority patent/DE69517301T3/en
Publication of WO1996011899A1 publication Critical patent/WO1996011899A1/en
Priority to HK98115906A priority patent/HK1014534A1/en

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Classifications

    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/16Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
    • C07C51/21Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
    • C07C51/255Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
    • C07C51/265Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/10Process efficiency
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/10Process efficiency
    • Y02P20/129Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S203/00Distillation: processes, separatory
    • Y10S203/06Reactor-distillation
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S203/00Distillation: processes, separatory
    • Y10S203/17Saline water conversion
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S203/00Distillation: processes, separatory
    • Y10S203/21Acrylic acid or ester

Definitions

  • This invention relates to a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation of an aromatic feedstock compound. More particularly, this invention relates to a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation of an aromatic feedstock compound wherein the energy produced by the exothermic oxidation is efficiently recovered. This invention also relates to an efficient process for treating waste water produced during the preparation of aromatic carboxylic acids.
  • Aromatic carboxylic acids are useful chemical compounds and are raw materials for a wide variety of manufactured articles.
  • terephthalic acid TA
  • TA terephthalic acid
  • a single manufacturing plant can produce 100,000 to more than 750,000 metric tons of TA per year.
  • PET polyethylene terephthalate
  • PET polyethylene terephthalate
  • TA can be produced by the high pressure, exothermic oxidation of a suitable aromatic feedstock compound, such as para xylene, in a liquid-phase reaction using air or other source of molecular oxygen as the oxidant and catalyzed by one or more heavy metal compounds and one or more promoter compounds.
  • the reaction offgas contains nitrogen gas and unre acted oxygen.
  • various means can be used to control the temperature of the highly exothermic oxidation reaction, it is generally most convenient to remove heat by allowing the solvent to vaporize, i.e. boil, during the oxidation reaction.
  • the vaporized solvent which is typically a mixture of water and low- molecular weight carboxylic acid, has heretofore been condensed in one or more overhead condenser apparatus and the condensate returned to the reaction mixture.
  • the condensate is usually directed to a separation apparatus, typically a distillation column, to separate the water from the low molecular weight aliphatic acid solvent so that the water concentration in the reactor is maintained at a constant level.
  • a separation apparatus typically a distillation column
  • the offgases that are not condensed are typically vented or passed through an oxidize, to burn byproducts and form an environmentally acceptable effluent.
  • the high pressure offgas contains a considerable amount of energy.
  • prior art process have, to an extent, utilized some of the energy contained in the offgas by running the offgas through, for example, an expander or turbine, prior art processes did not fully utilize the energy available in this high pressure offgas.
  • heat removal from the reaction mixture was accomplished by condensing a portion of the reaction overhead vapor to produce moderate pressure steam.
  • the moderate pressure steam in part, was used to recover energy by a steam turbine, and a part was used to separate water from acetic acid by distillation.
  • the art therefore, needs an improved process to manufacture aromatic carboxylic acids wherein the energy generated by the highly exothermic, high pressure oxidation reaction can be economically and efficiently recovered and, in fact, serve as a net generator of energy.
  • the present invention provides such an improved process.
  • a continuous process for preparing aromatic carboxylic acids by the exothermic liquid-phase oxidation reaction of an aromatic feedstock compound wherein energy is efficiently recovered from the exothermic liquid-phase oxidation reaction comprises: a) oxidizing an aromatic feedstock compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, a low- molecular weight carboxylic acid solvent, a heavy metal oxidation catalyst and a source of molecular oxygen, under reaction conditions which produce a gaseous high pressure overhead stream comprising water, gaseous by ⁇ products, and gaseous low-molecular weight carboxylic acid solvent; b) removing in a high efficiency separation apparatus at least about 95 wt.% of the low-molecular weight carboxylic acid from the overhead stream to form a second high pressure overhead mixture substantially free of low molecular weight carboxylic acid solvent and, comprising water and gaseous byproducts formed during the oxidation reaction; and c) directing the second high pressure overhead mixture to a means for recovering energy from the
  • a high efficiency separation apparatus such as a distillation column
  • a high efficiency separation apparatus provides a means for recycling to the oxidation reactor water typically used for the purification of crude aromatic carboxylic acids.
  • Such water can be recycled as reflux to the distillation column. Any residual aromatic carboxylic acid in the water, as well as oxidation reaction intermediates, are thereby returned to the oxidation reactor and are recovered as useful product.
  • this recycle of the purification water decreases, or even eliminates the need to treat the water in a waste treatment facility. Thus, the load on the waste treatment facility is greatly reduced.
  • this invention is also a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation reaction of an aromatic feedstock compound, which process comprises oxidizing an aromatic feedstock compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, a low molecular weight carboxylic acid solvent, a heavy metal oxidation catalyst, and a source of molecular oxygen under reaction conditions which produce a gaseous overhead stream comprising water, gaseous by-products, and gaseous low-molecular weight carboxylic acid solvent; removing in a high efficiency distillation column at least about 95 weight percent of the low- molecular weight carboxylic acid from the overhead stream to form a second high pressure overhead stream comprising water and gaseous by-products formed during the oxidation reaction; separating the aromatic carboxylic acid formed in step (a) from reaction mother liquor produced during the liquid- phase oxidation reaction mixture to form crude aromatic carboxylic acid; purifying crude aromatic carboxylic acid at an elevated temperature and pressure in a purification
  • This invention is also a reactor apparatus suitable for converting an aromatic feedstock compound to an aromatic carboxylic acid by the liquid phase oxidation of the aromatic feedstock compound in a reaction mixture comprising a low molecular weight aliphatic carboxylic add and water, and providing for the efficient recovery of energy produced by the oxidation reaction,
  • reactor apparatus comprises a reactor vessel suitable for conducting the liquid phase oxidation of an aromatic feedstock compound at an elevated temperature, a high efficiency distillation column capable of separating a mixture of acetic add and water such that vapor exiting the distillation column is less than about 1.0 weight percent acetic acid, and a means for directing vapor produced by the liquid phase oxidation in the reactor to the distillation column.
  • FIG 1 shows, in schematic form, an embodiment of operating the process of this invention.
  • an aromatic feedstock compound is oxidized in an exothermic, liquid-phase oxidation reaction mixture to an aromatic carboxylic acid, and the energy generated by this highly exothermic oxidation is efficiently recovered and used, for example, to generate electricity or other forms of useful and transmittabl ⁇ energy.
  • the aromatic feedstock compound useful in the process of this invention is any aromatic compound that has oxidizable substituents which can be oxidized to a carboxylic acid group.
  • the oxidizable substituent can be an alkyl group such as a methyl, ethyl, or isopropyl group. It can also be a partially oxidized alkyl group such as an alcohol group, aldehyde group or ketone group.
  • the aromatic portion of the aromatic feedstock compound can be a benzene nucleus or it can be bi- or polycyclic, for example a naphthalene nucleus.
  • the number of oxidizable substituents on the aromatic portion of the aromatic feedstock compound can be equal to the number of sites available on the aromatic portion of the aromatic feedstock compound, but is generally fewer, and is preferably 1 to about 4, more preferably 2 or 3.
  • suitable aromatic feedstock compounds for the process of this invention include toluene, ethylbenzene, o-xylene, meta-xylene, para-xylene, 1-formyl-4- methylbenzene, 1-hydroxymethyl-4-methylbenzene, 1 ,2,4-trimethyl- benzene, 1-formyl-2,4-dimethylbenzene, 1 ,2,4,5-tetramethylbenzene, alkyl, hydroxymethyl, formyl, and acyl substituted naphthalene compounds such as 2,6- and 2 J-dimethy .naphthalene, 2-acyl-6-methylnaphthalene, 2-formyl-6-methylnaphthalene, 2-methyl-6-ethyl
  • Paraxylene for example, when oxidized produces terephthalic acid, metaxylene produces isophthalic acid and 2,6-dimethylnaphthalene produces 2,6-naphthalenedicarboxylic add.
  • suitable heavy metal oxidation catalysts include those metals having an atomic number of about 21 to about 82, inclusive, preferably a mixture of cobalt and manganese.
  • the preferred oxidation solvent is a low molecular weight aliphatic monocarboxylic add having 2 to about 6 carbon atoms, inclusive, or mixtures thereof with water. Preferably it is acetic acid or mixtures of acetic acid and' water.
  • a reaction temperature of about 145°C to about 235°C is typical, and the reaction pressure is such that the reaction mixture is under liquid phase conditions.
  • a promoter such as a low molecular weight ketone having 2 to about 6 carbon atoms or a low molecular weight aldehyde having 1 to about 6 carbon atoms can also be used.
  • Bromine promoter compounds known in the art such as hydrogen bromide, molecular bromine, sodium bromide and the like can also be used.
  • a source of molecular oxygen is also required, and typically it is air.
  • the source of molecular oxygen can vary in molecular oxygen content from that of 10% molecular oxygen, to oxygen gas. Air is the preferred source of molecular oxygen.
  • the oxygen- containing gas fed to the reactor should provide an exhaust gas-vapor mixture containing from 0.5 to 8 volume percent oxygen (measured on a solvent-free basis).
  • a feed rate of the oxygen-containing gas sufficient to provide oxygen in the amount of from 1.5 to 2.8 moles per methyl group will provide such 0.5 to 8 volume percent of oxygen (measured on a solvent-free basis) in the overhead gas-vapor mixture.
  • the catalyst employed in the oxidation step for producing crude terephthalic add preferably comprises cobalt, manganese, and bromine components, and can additionally comprise accelerators known in the art.
  • the ratio of cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst-to-p-xylene in the liquid-phase oxidation is suitably in the range of about 0.2 to about 10 milligram atoms (mga) per gram mole of p-xylene.
  • the ratio of manganese (calculated as elemental manganese) in the manganese component of the catalyst-to-cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst in the liquid-phase oxidation is suitably in the range of about 0.2 to about 10 mga per mga of cobalt.
  • the weight ratio of bromine (calculated as elemental bromine) in the bromine component of the catalyst-to-total cobalt and manganese (calculated as elemental cobalt and elemental manganese) in the cobalt and manganese components of the catalyst in the liquid-phase oxidation is suitably in the range of about 0.2 to about 1.5 mga per mga of total cobalt and manganese.
  • Each of the cobalt and manganese components can be provided in any of its known ionic or combined forms that provide soluble forms of cobalt, manganese, and bromine in the solvent in the reactor.
  • the solvent is an acetic acid medium
  • cobalt and/or manganese carbonate, acetate tetrahydrate, and/or bromine can be employed.
  • the 0.2:1.0 to 1.5:1.0 bromine-to-total cobalt and manganese milligram atom ratio is provided by a suitable source of bromine.
  • Such bromine sources include elemental bromine (Br 2 ), or ionic bromine (for example HBr, NaBr, KBr, NH Br, etc.), or organic bromides which are known to provide bromide ions at the operating temperature of the oxidation (e.g. benzylbromide, mono- and di-bromoacetic acid, bromoacetyl bromide, tetrabromoethane, ethylene-di-bromide, etc.).
  • the total bromine in molecular bromine and ionic bromide is used to determine satisfaction of the elemental bromine-to-total cobalt and manganese milligram atom ratio of 0.2:1.0 to 1.5:1.0.
  • the bromine ion released from the organic bromides at the oxidation operating conditions can be readily determined by known analytical means.
  • the minimum pressure at which the oxidation reactor is maintained is typically that pressure which will maintain a substantial liquid phase of the p-xylene and the solvent.
  • suitable reaction gauge pressures in the oxidation reactor are in the range of from about 0 kg/cm 2 to about 35 kg /cm 2 , and typically are in the range of from about 10 kg/cm 2 to about 20 kg/cm 2 .
  • the temperature range within the oxidation reactor is generally from about 120°C, preferably from about 150°C, to about 240°C, preferably to about 230°C.
  • the solvent residence time in the oxidation reactor is generally from about 20 to about 150 minutes and preferably from about 30 to about 120 minutes.
  • the process conditions described hereinabove for oxidizing paraxylene to terephthalic add can also be used to oxidize metaxylene to isophthalic add.
  • the weight ratio of monocarboxylic acid solvent to 2,6- dimethylnaphthalene is preferably about 2:1 to about 12:1
  • the mga ratio of manganese to cobalt is about 5:1 to about 0.3:1
  • the mga ratio of bromine to the total of cobalt and manganese is about 0.3:1 to about 0.8:1
  • the total of cobalt and manganese, calculated as elemental cobalt and elemental manganese is at least about 0.40 weight percent based on the weight of the solvent
  • the oxidation reaction temperature is about 185°C to about 220°C.
  • Acetic acid is the most suitable solvent for oxidation of 2,6-dimethylnaphthalene.
  • the reactor vessel used for conducting the liquid phase oxidation of the aromatic feedstock compound to the aromatic carboxylic acid is any reactor vessel that is designed to operate at the reaction conditions used for the liquid-phase oxidation reaction.
  • these reactors are constructed of an inert material such as titanium, or are lined with an inert material such as glass o.r titanium. If the oxidation reaction is conducted at an elevated pressure, the reactor must also be constructed to withstand the pressures used for the oxidation reaction.
  • the reactor can also be equipped with one or more agitators.
  • the reactor is of a cylindrical design and is positioned in a vertical manner.
  • the heat generated during the liquid-phase oxidation is dissipated by allowing the reaction solvent to vaporize from the reaction mixture along with the water present in the reaction mixture. Since the temperature at which a liquid boils is related to the pressure; the temperature of the oxidation reaction can be controlled by controlling the reaction pressure. At a reaction pressure of about 7 to about 21 kg/cm 2 , the temperature of the reaction mixture using acetic acid as the solvent, and the vapor produced therefrom, is about 170°C to about 210°C.
  • the high temperature, high pressure vapor generated by the liquid phase oxidation reaction is a considerable source of energy, particularly when one considers the amount of such vapor produced in a large-scale commercial plant producing 200,000 to 750,000 metric tons of aromatic carboxylic acid per year.
  • the vaporized reaction solvent is directed to an apparatus, such as a high effidency distillation column, that can separate the solvent, typically low molecular weight aliphatic carboxylic acid, from the water produced during the oxidation reaction.
  • an apparatus such as a high effidency distillation column
  • the apparatus used for separating the water from the solvent must be able to make a separation such that at least about 95%, more preferably about 98% and most preferably at least about 99% by weight of the low molecular weight carboxylic acid solvent in the vaporous oxidation reaction stream is removed.
  • the gaseous stream exiting the separation apparatus has a very low level of reaction solvent and, except for carbon oxides, nitrogen and oxygen gas and any by-products, it is mainly high pressure steam.
  • the reaction solvent is a low molecular weight carboxylic acid such as acetic add
  • the vapor entering the separation apparatus comprises a mixture of acetic acid and water wherein the ratio of acetic add to water, by weight, is about 20:1 to about 3:1
  • the vapor exiting the separation apparatus is generally less than about 0.5 weight percent acetic acid, more preferably less than about 0.1 weight percent acetic add and most preferably less than about 0.05 weight percent acetic acid.
  • the apparatus used to conduct this separation can be any apparatus that can separate water from the reaction solvent
  • the preferred apparatus or means for conducting such a separation is a distillation column, preferably a high-efficiency distillation column. Any high efficiency distillation column can be used; however, preferable distillation columns are those containing a high efficiency packing such as Koch Flexipac and the like or containing sieve valve or bubble cap trays.
  • the distillation column has at least about 30 theoretical plates, more preferably, at least about 50 theoretical plates.
  • the distillation column must be able to make a separation such that at least 95%, more preferably about 98% and most preferably at least about 99% by weight of the low molecular weight carboxylic acid solvent in the vaporous overhead oxidation reaction stream is removed.
  • the ratio of low molecular weight monocarboxylic add, such as acetic add, to water, by weight is typically about 20:1 to about 2:1.
  • the separation apparatus is designed to make the separation of the reaction solvent from water at elevated pressure.
  • the separation apparatus is preferably operated at a pressure equal to or slightly below the pressure of the liquid phase oxidation reaction.
  • Any means can be used to direct the vapor produced by the liquid phase oxidation reaction to the separation apparatus.
  • piping or other suitable conduit can be used.
  • the separation apparatus such as a distillation column, can be directly connected to the reactor vessel used to conduct the liquid phase oxidation reaction.
  • the vapor produced by the liquid phase oxidation reaction along with any byproduct gases formed as a result of the oxidation, any carbon oxides formed during the oxidation and, if air is used as the source of molecular oxygen, nitrogen gas, are passed through the separation apparatus to remove most of the reaction solvent.
  • the gas exiting the separation apparatus therefore generally comprises water (steam), carbon oxides, nitrogen gas, any unconsumed molecular oxygen, and oxidation reaction byproducts such as methyl bromide.
  • the gas exiting the separation apparatus is still at a high pressure and is, therefore, a valuable source of energy. While this offgas from the separation apparatus can be sent to a means for recovering energy, e.g.
  • an expander it is preferable to first remove corrosive and/or combustible byproduct materials from the high pressure offgas before it is directed to an expander or other means for energy recovery.
  • any means for removing combustible materials from the offgas is suitable, for example, a thermal oxidizer
  • a preferred method is to use a catalytic oxidation apparatus wherein the offgas is contacted with a suitable catalytic material at high temperature and high pressure in the presence of air or other source of molecular oxygen, and the corrosive and combustible byproduct materials in the offgas are cataiytically oxidized to environmentally compatible materials.
  • Such a catalytic oxidation unit can reduce or eliminate through oxidation, any residual oxidation reaction solvent present in the offgas, and it can oxidize a byproduct such as methyl bromide.
  • the separation apparatus used removes most of the reaction solvent from the reaction offgas.
  • the offgas entering the offgas catalytic oxidation unit has a low level of reaction solvent so the load on the catalytic oxidation unit is small. Otherwise, a high load of reaction solvent on the offgas catalytic oxidation unit would result in an excessively large temperature rise in the catalytic oxidation unit.
  • the combustion of the reaction solvent would be a great economic loss since it is desirable to conserve and recycle as much of the oxidation reaction solvent as possible.
  • the effluent from the catalytic oxidation unit is directed to a scrubber to remove any addic, inorganic materials such as bromine and hydrogen bromide. Bromine and hydrogen bromide would be formed by the catalytic oxidation of methyl bromide. Oxidation catalysts for such offgas oxidation are available, for example, from Engelhard Corp. or AlliedSignal Inc.
  • the gaseous, high pressure effluent from the catalytic oxidation unit and scrubber is preferably directed to a pre- heater to elevate the temperature of the offgas and thereby convert any condensed water that may be present to steam.
  • the dry, high pressure gas stream exiting the preheater is directed to an expander or other means for recovering energy from the high pressure gas stream.
  • the means for recovering energy from the high pressure offgas e.g. an expander
  • the electrical energy produced by a generator can be used to power the equipment used in the plant for manufacturing the aromatic carboxylic add, for example, it can be used to operate compressors for adding air to the liquid phase oxidation reaction, and any excess electrical energy can be transmitted to a local electric power utility.
  • the amount energy recovered in the process of this invention is at least about 0.3 and more preferably at least about 0.35 kilowatt hours per pound of terephthalic add produced.
  • the offgas After exiting the expander, the offgas is condensed and the resulting water is useful in other processes within the manufacturing plant.
  • This water is of relatively high purity containing only a small amount of dissolved gasses.
  • the condensed water can be used as a reflux for a distillation column used as a high efficiency separation apparatus.
  • the water produced by the condensation of the offgas can also be used as the solvent for a purification step where the crude aromatic carboxylic acid is treated to from a purified aromatic carboxylic add.
  • the water formed by the condensation from the reaction offgas can be used as a recrystallization solvent or as a solvent for conducting one or more chemical and/or physical treatments for the crude aromatic carboxylic acid.
  • One such purification process comprises contacting an aqueous solution or slurry of the crude aromatic carboxylic acid with hydrogen at an elevated temperature and pressure in the presence of a hydrogenation catalyst.
  • a hydrogenation catalyst such as U.S. Patent 3,584,039 to Meyer.
  • this purification procedure is conducted at an elevated temperature and pressure in a fixed catalyst bed. Both down-flow and up- flow reactors can be used.
  • the crude terephthalic acid to be purified is dissolved in water or a mixture of water and some other polar solvent such as a C1-C4 aliphatic carboxylic acid.
  • the reactor, and thus the terephthalic acid solution temperature during purification can be in the range of about 100°C to about 350°C. Preferably the temperatures are in the range of about 275°C to about 300°C.
  • Reactor pressure conditions primarily depend upon the temperature at which the purification process is carried out. Inasmuch as the temperatures at which practical amounts of the impure terephthalic acid may be dissolved are substantially above the normal boiling point of the solvent, the process pressures are necessarily considerably above atmospheric pressure to maintain the aqueous solutions in liquid phase.
  • the reactor pressure during hydrogenation can be in the range of about 200 to about 1500 pounds per square inch gauge (psig), and usually is in the range of about 900 psig to about 1 ,200 psig.
  • the hydrogen partial pressure is typically in the range of about 30 psig to about 200 psig.
  • the catalyst used for this purification step comprises one or more active hydrogenation metals such as ruthenium, rhodium, palladium or platinum on a suitable support such as carbon or titania.
  • a suitable support is an active carbon, usually derived from coconut charcoal in the form of granules having a surface area of 600 m 2 /g to 1500 m 2 /g.
  • the loading of metal on the carrier is suitably about 0.01 weight percent to about 2 weight percent.
  • Suitable materials for preparing purified aromatic carboxylic acids from crude aromatic carboxylic acids are disclosed in U.S. Patent 5,256,817 to Sikkenga et al., and in U.S. Patent Application 029,037, filed on March 10, 1993, to Schroeder et al.
  • the solution of aromatic acid in aqueous solvent is cooled to predpitate the purified aromatic carboxylic add.
  • the temperature to which the solution is cooled is such that most of the purified aromatic carboxylic acid crystallizes.
  • the crystallized purified aromatic carboxylic acid is separated from the aqueous mother liquor using a suitable solid- liquid separation device such as a centrifuge or filter.
  • the cake of purified aromatic carboxylic add can be washed with pure water, dried and sent to storage or for packaging and shipment.
  • the aqueous mother liquor separated by the centrifuge or filter contains a number of impurities, reaction intermediates and also contains suspended and dissolved aromatic carboxylic acid.
  • this stream would be sent to a waste treatment facility.
  • a major portion of this mother liquor can be diverted to the separation apparatus used for separating the oxidation reaction solvent from the water produced during the oxidation reaction.
  • the impurities, reaction intermediates and aromatic carboxylic add product are returned to the oxidation reaction mixture. Impurities are oxidized further, intermediates are converted to useful product, and aromatic carboxylic acid is recycled for recovery.
  • Such a recycle of the mother liquor from the hydrogenation reaction is particularly useful when the separation apparatus used for separating water from the oxidation reaction solvent is a distillation column.
  • the recycled aqueous mother liquor returned to the distillation column not only serves as reflux for the column, but also serves as an effective method for adding the mother liquor from the purification process to the oxidation reaction mixture.
  • the process of this invention provides for the elimination of a major waste product stream, a stream that would otherwise be sent to a waste treatment facility.
  • the mother liquor stream to the distillation column Prior to recycling the mother liquor stream to the distillation column it can be treated to remove any suspended matter, if present. For example, it can be subjected to filtration or cent rifugat ion, or it can be passed through a hydroclone to remove suspended matter.
  • the mother liquor Prior to such treatment to remove suspended matter, the mother liquor can be treated, for example, by cooling, to remove dissolved compounds that might otherwise foul the distillation column.
  • FIG. 1 shows in schematic form a preferred embodiment for operating the process of this invention.
  • agitated oxidation reactor 10 para-xylene is reacted with air in the presence of acetic add, and water as the oxidation solvent, cobalt and manganese oxidation metals and one or more bromine compounds such as hydrogen bromide as an oxidation promoter.
  • the oxidation reaction is conducted at a temperature of about 170°C to about 210°C, and at a pressure of about 7 to about 21 kg/cm 2 .
  • the heat generated by the exothermic oxidation reaction causes the reactor solvent to boil.
  • the vaporized solvent along with gaseous byproducts, carbon oxides, nitrogen from the air charged to the oxidation reaction, and unreacted oxygen pass through pipe 12 and into high pressure distillation column 20 having about 45 theoretical plates.
  • the acetic acid solvent is separated from the reaction overhead or offgas.
  • the distillation column is constructed and operated such that at least 99% of the acetic add is removed from the overhead gas.
  • the acetic acid solvent from the bottom of the distillation column is directed to surge drum 30 through pipe 25. From surge drum 30 the acetic acid solvent, which may contain some water, is returned to reactor 10 through pipe 35. The amount of solvent returned is controlled so that the proper amount of reaction solvent is maintained in the oxidation reactor.
  • the reaction overhead or offgas exiting the top of distillation tower 20 through pipe 38 contains less than about 0.1% by weight acetic acid, and is primarily water (steam), but also contains nitrogen, carbon oxides, unreacted oxygen and gaseous oxidation byproducts such as methyl bromide.
  • Offgas from pipe 38 is treated in a catalytic oxidation unit 40 where byproducts such as methyl bromide and any residual acetic acid in the offgas are catalyti ⁇ ally oxidized.
  • Catalytic oxidation unit 40 is also equipped with an aqueous scrubber to remove any bromine in the offgas exiting the catalytic oxidation unit.
  • Offgas exiting the catalytic oxidation unit 40 is directed to pipe 42.
  • a portion of the offgas from pipe 42 is directed to pipe 43 and then to condenser 45 where water is condensed from the offgas.
  • the cooled offgas is directed to knock-out drum 50 through pipe 46.
  • the water depleted gas exits the process through pipe 51.
  • the water from knock-out drum 50 is directed to PTA slurry vessel 110.
  • the offgas, which is primarily water, from pipe 42 is directed to pre- heater 60 through pipe 55.
  • the offgas is heated to a temperature of about 200°C to about 235°C and sufficient to prevent the condensation of the acetic acid depleted reactor offgas in the expander 70.
  • Pre- heated reactor offgas enters expander 70 through pipe 65.
  • Expander 70 which recovers energy from the reactor offgas, drives compressor 75 which delivers compressed air to oxidation reactor 10 through pipe 76.
  • Expander 75 also drives electric generator 80 which supplies electric power for use within the TA manufacturing plant and to the local power utility.
  • the condensed water from condenser 90 is directed to reflux drum 100 through pipe 92.
  • Water from drum 100 is directed to high pressure distillation column 20 through pipes 102 and 200. Such water returned to the column serves as reflux for the column.
  • Water from drum 100 is also directed to PTA slurry vessel 110 through pipe 105.
  • a reaction mixture slurry comprising crude terephthalic acid, water, acetic acid, catalyst metals, oxidation reaction intermediates and by- products exits oxidation reactor 10 through pipe 115 and is directed to vessel 120 where the temperature of the oxidation reaction mixture is reduced to crystallize dissolved terephthalic add.
  • Vessel 120 is optionally equipped with an air sprager to continue the oxidation reaction. Overhead gasses from vessel 120 are directed to high pressure distillation column 20 having about 45 theoretical plates, through pipe 125.
  • Oxidation reaction slurry from vessel 120 is directed to vessel 130 through pipe 128 wherein additional cooling and crystallization of terephthalic add occurs.
  • Oxidation reaction mixture slurry from vessel 130 enters separation apparatus 135 through pipe 132.
  • Separation apparatus 135 is typically one or more centrifuges or filters.
  • separation apparatus 135 crude terephthalic acid is separated from the oxidation reaction mother liquor.
  • Oxidation reaction mother liquor exits separation apparatus 135 through pipe 138 and enters mother liquor drum 140.
  • a major portion of the mother liquor containing catalyst and acetic acid is recycled to oxidation reactor 10 through line 145.
  • the other portion of the mother liquor is sent to stripper 150 through pipe 148 where acetic acid is removed and directed to vessel 130 through line 152. Bottoms from stripper 150 are sent to waste through pipe 154.
  • a slurry of crude terephthalic add and water from PTA slurry drum 110 is directed to hydrogenation reactor 160 through pipe 158.
  • reactor 160 the crude terephthalic acid dissolved in water is treated with hydrogen at an elevated temperature, for example, about 260°C to about 290°C, and elevated pressure to purify the crude terephthalic acid by, for example, reducing the levels of 4-carboxybenzaldehyde.
  • the reaction mixture from hydrogenation reactor 160 enters crystallization vessel 170 through pipe 165.
  • the slurry of purified terephthalic acid and water formed in vessel 170 is directed to separation apparatus 180 through pipe 175. Purified terephthalic acid exits separation apparatus 180 through pipe 190.
  • Separation apparatus 180 is generally a centrifuge or a rotary vacuum filter.
  • Mother liquor from separation apparatus 180 which comprises water, dissolved and suspended purified terephthalic add, and various intermediate and by-product compounds, is recycled to the top of high pressure distillation column 20 through pipe 200.
  • the return of the mother liquor from separation apparatus 180 to high pressure distillation column 20 allows for the recycle of the intermediates and by-products in the mother liquor to the oxidation reactor where they are either oxidized or converted to terephthalic acid, it also provides for the recycle of valuable terephthalic acid which would otherwise be sent to waste treatment, or which would require costly procedures for its recovery, and it eliminates treating large volumes of waste water in waste treatment facilities.

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Abstract

A process for preparing aromatic carboxylic acids by the exothermic liquid-phase oxidation reaction of an aromatic feedstock compound, wherein energy is efficiently recovered from the exothermic oxidation reaction, particularly by the use of a high efficiency distillation column for the removal of the carboxylic acid solvent and by the use of an expander for energy recovery from the high pressure offgas.

Description

PROCESS FOR PREPARING AROMATIC CARBOXYLIC ACIDS WITH EFFICIENT ENERGY RECOVERY
Field of Invention
This invention relates to a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation of an aromatic feedstock compound. More particularly, this invention relates to a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation of an aromatic feedstock compound wherein the energy produced by the exothermic oxidation is efficiently recovered. This invention also relates to an efficient process for treating waste water produced during the preparation of aromatic carboxylic acids.
BacKground of the Invention
Aromatic carboxylic acids are useful chemical compounds and are raw materials for a wide variety of manufactured articles. For example, terephthalic acid (TA) is manufactured on a world-wide basis in amounts exceeding 10 billion pounds per year. A single manufacturing plant can produce 100,000 to more than 750,000 metric tons of TA per year. TA is used, for example, to prepare polyethylene terephthalate (PET), a raw material for manufacturing polyester fibers for textile applications and polyester film for packaging and container applications. TA can be produced by the high pressure, exothermic oxidation of a suitable aromatic feedstock compound, such as para xylene, in a liquid-phase reaction using air or other source of molecular oxygen as the oxidant and catalyzed by one or more heavy metal compounds and one or more promoter compounds. Methods for oxidizing para xylene and other aromatic compounds using such liquid-phase oxidations are well known in the art. For example, S after in U.S. Patent 2,833,816 discloses a method for oxidizing aromatic feedstock compounds to their corresponding aromatic carboxylic acids. Central to these processes for preparing aromatic carboxylic acids is the use of a liquid-phase reaction employing a low molecular weight carboxylic acid, such as acetic acid, as part of the reaction solvent. A certain amount of water is also present in the oxidation reaction solvent and water is also formed as a result of the oxidation reaction. The oxidation reaction also produces a reaction off gas which generally comprises carbon dioxide, carbon monoxide and, depending on the promoter used, may contain methyl bromide. Additionally, when air is used as the source of molecular oxygen, the reaction offgas contains nitrogen gas and unre acted oxygen. Although various means can be used to control the temperature of the highly exothermic oxidation reaction, it is generally most convenient to remove heat by allowing the solvent to vaporize, i.e. boil, during the oxidation reaction. The vaporized solvent, which is typically a mixture of water and low- molecular weight carboxylic acid, has heretofore been condensed in one or more overhead condenser apparatus and the condensate returned to the reaction mixture. However, since water is also present, at least part of the condensate is usually directed to a separation apparatus, typically a distillation column, to separate the water from the low molecular weight aliphatic acid solvent so that the water concentration in the reactor is maintained at a constant level. The offgases that are not condensed are typically vented or passed through an oxidize, to burn byproducts and form an environmentally acceptable effluent.
The high pressure offgas contains a considerable amount of energy. Although prior art process have, to an extent, utilized some of the energy contained in the offgas by running the offgas through, for example, an expander or turbine, prior art processes did not fully utilize the energy available in this high pressure offgas. In prior processes, heat removal from the reaction mixture was accomplished by condensing a portion of the reaction overhead vapor to produce moderate pressure steam. The moderate pressure steam, in part, was used to recover energy by a steam turbine, and a part was used to separate water from acetic acid by distillation.
The art, therefore, needs an improved process to manufacture aromatic carboxylic acids wherein the energy generated by the highly exothermic, high pressure oxidation reaction can be economically and efficiently recovered and, in fact, serve as a net generator of energy. The present invention provides such an improved process.
Summary of the Invention
A continuous process for preparing aromatic carboxylic acids by the exothermic liquid-phase oxidation reaction of an aromatic feedstock compound wherein energy is efficiently recovered from the exothermic liquid-phase oxidation reaction, which process comprises: a) oxidizing an aromatic feedstock compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, a low- molecular weight carboxylic acid solvent, a heavy metal oxidation catalyst and a source of molecular oxygen, under reaction conditions which produce a gaseous high pressure overhead stream comprising water, gaseous by¬ products, and gaseous low-molecular weight carboxylic acid solvent; b) removing in a high efficiency separation apparatus at least about 95 wt.% of the low-molecular weight carboxylic acid from the overhead stream to form a second high pressure overhead mixture substantially free of low molecular weight carboxylic acid solvent and, comprising water and gaseous byproducts formed during the oxidation reaction; and c) directing the second high pressure overhead mixture to a means for recovering energy from the second high pressure overhead mixture.
In addition to providing for the efficient recovery of energy produced by the exothermic oxidation of the aromatic feedstock compound, the use of a high efficiency separation apparatus, such as a distillation column, provides a means for recycling to the oxidation reactor water typically used for the purification of crude aromatic carboxylic acids. Such water can be recycled as reflux to the distillation column. Any residual aromatic carboxylic acid in the water, as well as oxidation reaction intermediates, are thereby returned to the oxidation reactor and are recovered as useful product. Also, this recycle of the purification water decreases, or even eliminates the need to treat the water in a waste treatment facility. Thus, the load on the waste treatment facility is greatly reduced. Thus, this invention is also a process for preparing aromatic carboxylic acids by the exothermic, liquid-phase oxidation reaction of an aromatic feedstock compound, which process comprises oxidizing an aromatic feedstock compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, a low molecular weight carboxylic acid solvent, a heavy metal oxidation catalyst, and a source of molecular oxygen under reaction conditions which produce a gaseous overhead stream comprising water, gaseous by-products, and gaseous low-molecular weight carboxylic acid solvent; removing in a high efficiency distillation column at least about 95 weight percent of the low- molecular weight carboxylic acid from the overhead stream to form a second high pressure overhead stream comprising water and gaseous by-products formed during the oxidation reaction; separating the aromatic carboxylic acid formed in step (a) from reaction mother liquor produced during the liquid- phase oxidation reaction mixture to form crude aromatic carboxylic acid; purifying crude aromatic carboxylic acid at an elevated temperature and pressure in a purification solvent comprising water to form a mixture of purified aromatic carboxylic acid and purification mother liquor comprising water; and separating purified aromatic carboxylic add from purification mother liquor formed in step (d) and recycling at least a portion of the purification mother liquor to the high efficiency distillation column.
This invention is also a reactor apparatus suitable for converting an aromatic feedstock compound to an aromatic carboxylic acid by the liquid phase oxidation of the aromatic feedstock compound in a reaction mixture comprising a low molecular weight aliphatic carboxylic add and water, and providing for the efficient recovery of energy produced by the oxidation reaction, which reactor apparatus comprises a reactor vessel suitable for conducting the liquid phase oxidation of an aromatic feedstock compound at an elevated temperature, a high efficiency distillation column capable of separating a mixture of acetic add and water such that vapor exiting the distillation column is less than about 1.0 weight percent acetic acid, and a means for directing vapor produced by the liquid phase oxidation in the reactor to the distillation column.
Brief Description of the Figure
Figure 1 shows, in schematic form, an embodiment of operating the process of this invention.
Detailed Description of the Invention
In the process of this invention an aromatic feedstock compound is oxidized in an exothermic, liquid-phase oxidation reaction mixture to an aromatic carboxylic acid, and the energy generated by this highly exothermic oxidation is efficiently recovered and used, for example, to generate electricity or other forms of useful and transmittablβ energy.
The aromatic feedstock compound useful in the process of this invention is any aromatic compound that has oxidizable substituents which can be oxidized to a carboxylic acid group. For example, the oxidizable substituent can be an alkyl group such as a methyl, ethyl, or isopropyl group. It can also be a partially oxidized alkyl group such as an alcohol group, aldehyde group or ketone group. The aromatic portion of the aromatic feedstock compound can be a benzene nucleus or it can be bi- or polycyclic, for example a naphthalene nucleus. The number of oxidizable substituents on the aromatic portion of the aromatic feedstock compound can be equal to the number of sites available on the aromatic portion of the aromatic feedstock compound, but is generally fewer, and is preferably 1 to about 4, more preferably 2 or 3. Thus, examples of suitable aromatic feedstock compounds for the process of this invention include toluene, ethylbenzene, o-xylene, meta-xylene, para-xylene, 1-formyl-4- methylbenzene, 1-hydroxymethyl-4-methylbenzene, 1 ,2,4-trimethyl- benzene, 1-formyl-2,4-dimethylbenzene, 1 ,2,4,5-tetramethylbenzene, alkyl, hydroxymethyl, formyl, and acyl substituted naphthalene compounds such as 2,6- and 2 J-dimethy .naphthalene, 2-acyl-6-methylnaphthalene, 2-formyl-6-methylnaphthalene, 2-methyl-6-ethylnaphthalene, 2,6-diethyl- naphthalene, and the like.
Paraxylene. for example, when oxidized produces terephthalic acid, metaxylene produces isophthalic acid and 2,6-dimethylnaphthalene produces 2,6-naphthalenedicarboxylic add.
As mentioned hereinabove, methods for oxidizing aromatic feedstock to the corresponding aromatic carboxylic add using a liquid- phase, heavy-metal catalyzed oxidation reaction are well known in the art. For example, S after et al. U. S. Patent 2,833,816 discloses such processes. Other processes are disclosed in U.S. Patents 3,870,754; 4,933,491 ; 4,950,786; and 5,292,934. A particularly preferred method for oxidizing 2,6-dimethyinaphthalene to 2,6-naphthalenedicarboxylic acid is disclosed in U.S. Patent 5,183,933. However, in general, suitable heavy metal oxidation catalysts include those metals having an atomic number of about 21 to about 82, inclusive, preferably a mixture of cobalt and manganese. The preferred oxidation solvent is a low molecular weight aliphatic monocarboxylic add having 2 to about 6 carbon atoms, inclusive, or mixtures thereof with water. Preferably it is acetic acid or mixtures of acetic acid and' water. A reaction temperature of about 145°C to about 235°C is typical, and the reaction pressure is such that the reaction mixture is under liquid phase conditions. A promoter such as a low molecular weight ketone having 2 to about 6 carbon atoms or a low molecular weight aldehyde having 1 to about 6 carbon atoms can also be used. Bromine promoter compounds known in the art such as hydrogen bromide, molecular bromine, sodium bromide and the like can also be used. A source of molecular oxygen is also required, and typically it is air. For the conversion of paraxylene to terephthalic acid the source of molecular oxygen can vary in molecular oxygen content from that of 10% molecular oxygen, to oxygen gas. Air is the preferred source of molecular oxygen. In order to avoid the formation of explosive mixtures, the oxygen- containing gas fed to the reactor should provide an exhaust gas-vapor mixture containing from 0.5 to 8 volume percent oxygen (measured on a solvent-free basis). For example, a feed rate of the oxygen-containing gas sufficient to provide oxygen in the amount of from 1.5 to 2.8 moles per methyl group will provide such 0.5 to 8 volume percent of oxygen (measured on a solvent-free basis) in the overhead gas-vapor mixture.
The catalyst employed in the oxidation step for producing crude terephthalic add preferably comprises cobalt, manganese, and bromine components, and can additionally comprise accelerators known in the art. The ratio of cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst-to-p-xylene in the liquid-phase oxidation is suitably in the range of about 0.2 to about 10 milligram atoms (mga) per gram mole of p-xylene. The ratio of manganese (calculated as elemental manganese) in the manganese component of the catalyst-to-cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst in the liquid-phase oxidation is suitably in the range of about 0.2 to about 10 mga per mga of cobalt. The weight ratio of bromine (calculated as elemental bromine) in the bromine component of the catalyst-to-total cobalt and manganese (calculated as elemental cobalt and elemental manganese) in the cobalt and manganese components of the catalyst in the liquid-phase oxidation is suitably in the range of about 0.2 to about 1.5 mga per mga of total cobalt and manganese. Each of the cobalt and manganese components can be provided in any of its known ionic or combined forms that provide soluble forms of cobalt, manganese, and bromine in the solvent in the reactor. For example, when the solvent is an acetic acid medium, cobalt and/or manganese carbonate, acetate tetrahydrate, and/or bromine can be employed. The 0.2:1.0 to 1.5:1.0 bromine-to-total cobalt and manganese milligram atom ratio is provided by a suitable source of bromine. Such bromine sources include elemental bromine (Br2), or ionic bromine (for example HBr, NaBr, KBr, NH Br, etc.), or organic bromides which are known to provide bromide ions at the operating temperature of the oxidation (e.g. benzylbromide, mono- and di-bromoacetic acid, bromoacetyl bromide, tetrabromoethane, ethylene-di-bromide, etc.). The total bromine in molecular bromine and ionic bromide is used to determine satisfaction of the elemental bromine-to-total cobalt and manganese milligram atom ratio of 0.2:1.0 to 1.5:1.0. The bromine ion released from the organic bromides at the oxidation operating conditions can be readily determined by known analytical means.
For the oxidation of paraxylene to terephthalic acid, the minimum pressure at which the oxidation reactor is maintained is typically that pressure which will maintain a substantial liquid phase of the p-xylene and the solvent. When the solvent is an acetic acid-water mixture, suitable reaction gauge pressures in the oxidation reactor are in the range of from about 0 kg/cm2 to about 35 kg /cm2, and typically are in the range of from about 10 kg/cm2 to about 20 kg/cm2. The temperature range within the oxidation reactor is generally from about 120°C, preferably from about 150°C, to about 240°C, preferably to about 230°C. The solvent residence time in the oxidation reactor is generally from about 20 to about 150 minutes and preferably from about 30 to about 120 minutes. The process conditions described hereinabove for oxidizing paraxylene to terephthalic add can also be used to oxidize metaxylene to isophthalic add.
For the oxidation of 2,6-dimethylnaphthalene to 2,6-naphthalene- dicarboxylic acid the weight ratio of monocarboxylic acid solvent to 2,6- dimethylnaphthalene is preferably about 2:1 to about 12:1 , the mga ratio of manganese to cobalt is about 5:1 to about 0.3:1 , the mga ratio of bromine to the total of cobalt and manganese is about 0.3:1 to about 0.8:1 and the total of cobalt and manganese, calculated as elemental cobalt and elemental manganese is at least about 0.40 weight percent based on the weight of the solvent, and the oxidation reaction temperature is about 185°C to about 220°C. Acetic acid is the most suitable solvent for oxidation of 2,6-dimethylnaphthalene.
The reactor vessel used for conducting the liquid phase oxidation of the aromatic feedstock compound to the aromatic carboxylic acid is any reactor vessel that is designed to operate at the reaction conditions used for the liquid-phase oxidation reaction. Typically these reactors are constructed of an inert material such as titanium, or are lined with an inert material such as glass o.r titanium. If the oxidation reaction is conducted at an elevated pressure, the reactor must also be constructed to withstand the pressures used for the oxidation reaction. The reactor can also be equipped with one or more agitators. Generally, the reactor is of a cylindrical design and is positioned in a vertical manner. As stated hereinabove, the heat generated during the liquid-phase oxidation is dissipated by allowing the reaction solvent to vaporize from the reaction mixture along with the water present in the reaction mixture. Since the temperature at which a liquid boils is related to the pressure; the temperature of the oxidation reaction can be controlled by controlling the reaction pressure. At a reaction pressure of about 7 to about 21 kg/cm2, the temperature of the reaction mixture using acetic acid as the solvent, and the vapor produced therefrom, is about 170°C to about 210°C. Thus, the high temperature, high pressure vapor generated by the liquid phase oxidation reaction is a considerable source of energy, particularly when one considers the amount of such vapor produced in a large-scale commercial plant producing 200,000 to 750,000 metric tons of aromatic carboxylic acid per year.
In the process of this invention, the vaporized reaction solvent is directed to an apparatus, such as a high effidency distillation column, that can separate the solvent, typically low molecular weight aliphatic carboxylic acid, from the water produced during the oxidation reaction. For reasons discussed is more detail below, the apparatus used for separating the water from the solvent must be able to make a separation such that at least about 95%, more preferably about 98% and most preferably at least about 99% by weight of the low molecular weight carboxylic acid solvent in the vaporous oxidation reaction stream is removed. Thus, the gaseous stream exiting the separation apparatus has a very low level of reaction solvent and, except for carbon oxides, nitrogen and oxygen gas and any by-products, it is mainly high pressure steam. For example, when the reaction solvent is a low molecular weight carboxylic acid such as acetic add, the vapor entering the separation apparatus comprises a mixture of acetic acid and water wherein the ratio of acetic add to water, by weight, is about 20:1 to about 3:1 , and the vapor exiting the separation apparatus is generally less than about 0.5 weight percent acetic acid, more preferably less than about 0.1 weight percent acetic add and most preferably less than about 0.05 weight percent acetic acid.
Although the apparatus used to conduct this separation can be any apparatus that can separate water from the reaction solvent the preferred apparatus or means for conducting such a separation is a distillation column, preferably a high-efficiency distillation column. Any high efficiency distillation column can be used; however, preferable distillation columns are those containing a high efficiency packing such as Koch Flexipac and the like or containing sieve valve or bubble cap trays. Preferably, the distillation column has at least about 30 theoretical plates, more preferably, at least about 50 theoretical plates. The distillation column must be able to make a separation such that at least 95%, more preferably about 98% and most preferably at least about 99% by weight of the low molecular weight carboxylic acid solvent in the vaporous overhead oxidation reaction stream is removed. As stated above, in these overhead streams, the ratio of low molecular weight monocarboxylic add, such as acetic add, to water, by weight, is typically about 20:1 to about 2:1.
Preferably, the separation apparatus is designed to make the separation of the reaction solvent from water at elevated pressure. The separation apparatus is preferably operated at a pressure equal to or slightly below the pressure of the liquid phase oxidation reaction. Any means can be used to direct the vapor produced by the liquid phase oxidation reaction to the separation apparatus. For example, piping or other suitable conduit can be used. Additionally, the separation apparatus, such as a distillation column, can be directly connected to the reactor vessel used to conduct the liquid phase oxidation reaction. Thus, the vapor produced by the liquid phase oxidation reaction, along with any byproduct gases formed as a result of the oxidation, any carbon oxides formed during the oxidation and, if air is used as the source of molecular oxygen, nitrogen gas, are passed through the separation apparatus to remove most of the reaction solvent. The gas exiting the separation apparatus therefore generally comprises water (steam), carbon oxides, nitrogen gas, any unconsumed molecular oxygen, and oxidation reaction byproducts such as methyl bromide. Significantly, the gas exiting the separation apparatus is still at a high pressure and is, therefore, a valuable source of energy. While this offgas from the separation apparatus can be sent to a means for recovering energy, e.g. an expander , it is preferable to first remove corrosive and/or combustible byproduct materials from the high pressure offgas before it is directed to an expander or other means for energy recovery. While any means for removing combustible materials from the offgas is suitable, for example, a thermal oxidizer, a preferred method is to use a catalytic oxidation apparatus wherein the offgas is contacted with a suitable catalytic material at high temperature and high pressure in the presence of air or other source of molecular oxygen, and the corrosive and combustible byproduct materials in the offgas are cataiytically oxidized to environmentally compatible materials. Such a catalytic oxidation unit can reduce or eliminate through oxidation, any residual oxidation reaction solvent present in the offgas, and it can oxidize a byproduct such as methyl bromide. However, in the method of this invention, the separation apparatus used removes most of the reaction solvent from the reaction offgas. Thus, the offgas entering the offgas catalytic oxidation unit has a low level of reaction solvent so the load on the catalytic oxidation unit is small. Otherwise, a high load of reaction solvent on the offgas catalytic oxidation unit would result in an excessively large temperature rise in the catalytic oxidation unit. Furthermore, the combustion of the reaction solvent would be a great economic loss since it is desirable to conserve and recycle as much of the oxidation reaction solvent as possible. Generally, the effluent from the catalytic oxidation unit is directed to a scrubber to remove any addic, inorganic materials such as bromine and hydrogen bromide. Bromine and hydrogen bromide would be formed by the catalytic oxidation of methyl bromide. Oxidation catalysts for such offgas oxidation are available, for example, from Engelhard Corp. or AlliedSignal Inc. The gaseous, high pressure effluent from the catalytic oxidation unit and scrubber is preferably directed to a pre- heater to elevate the temperature of the offgas and thereby convert any condensed water that may be present to steam. The dry, high pressure gas stream exiting the preheater is directed to an expander or other means for recovering energy from the high pressure gas stream.
The means for recovering energy from the high pressure offgas, e.g. an expander, is suitably connected to an electric generator and/or to other equipment requiring mechanical work such as a compressor. The electrical energy produced by a generator can be used to power the equipment used in the plant for manufacturing the aromatic carboxylic add, for example, it can be used to operate compressors for adding air to the liquid phase oxidation reaction, and any excess electrical energy can be transmitted to a local electric power utility. For the production of terephthalic add from paraxylene feedstock, the amount energy recovered in the process of this invention is at least about 0.3 and more preferably at least about 0.35 kilowatt hours per pound of terephthalic add produced.
After exiting the expander, the offgas is condensed and the resulting water is useful in other processes within the manufacturing plant. This water is of relatively high purity containing only a small amount of dissolved gasses. For example, the condensed water can be used as a reflux for a distillation column used as a high efficiency separation apparatus. The water produced by the condensation of the offgas can also be used as the solvent for a purification step where the crude aromatic carboxylic acid is treated to from a purified aromatic carboxylic add. Thus, the water formed by the condensation from the reaction offgas can be used as a recrystallization solvent or as a solvent for conducting one or more chemical and/or physical treatments for the crude aromatic carboxylic acid. One such purification process comprises contacting an aqueous solution or slurry of the crude aromatic carboxylic acid with hydrogen at an elevated temperature and pressure in the presence of a hydrogenation catalyst. Such a process is disclosed in U.S. Patent 3,584,039 to Meyer. Using the purification of terephthalic acid as an example, this purification procedure is conducted at an elevated temperature and pressure in a fixed catalyst bed. Both down-flow and up- flow reactors can be used. The crude terephthalic acid to be purified is dissolved in water or a mixture of water and some other polar solvent such as a C1-C4 aliphatic carboxylic acid. The reactor, and thus the terephthalic acid solution temperature during purification, can be in the range of about 100°C to about 350°C. Preferably the temperatures are in the range of about 275°C to about 300°C.
Reactor pressure conditions primarily depend upon the temperature at which the purification process is carried out. Inasmuch as the temperatures at which practical amounts of the impure terephthalic acid may be dissolved are substantially above the normal boiling point of the solvent, the process pressures are necessarily considerably above atmospheric pressure to maintain the aqueous solutions in liquid phase. In general, the reactor pressure during hydrogenation can be in the range of about 200 to about 1500 pounds per square inch gauge (psig), and usually is in the range of about 900 psig to about 1 ,200 psig. The hydrogen partial pressure is typically in the range of about 30 psig to about 200 psig. The catalyst used for this purification step comprises one or more active hydrogenation metals such as ruthenium, rhodium, palladium or platinum on a suitable support such as carbon or titania. A suitable support is an active carbon, usually derived from coconut charcoal in the form of granules having a surface area of 600 m2/g to 1500 m2/g. The loading of metal on the carrier is suitably about 0.01 weight percent to about 2 weight percent. Suitable materials for preparing purified aromatic carboxylic acids from crude aromatic carboxylic acids are disclosed in U.S. Patent 5,256,817 to Sikkenga et al., and in U.S. Patent Application 029,037, filed on March 10, 1993, to Schroeder et al.
After passing through the reactor for purifying the aromatic carboxylic add, the solution of aromatic acid in aqueous solvent is cooled to predpitate the purified aromatic carboxylic add. The temperature to which the solution is cooled is such that most of the purified aromatic carboxylic acid crystallizes. The crystallized purified aromatic carboxylic acid is separated from the aqueous mother liquor using a suitable solid- liquid separation device such as a centrifuge or filter. The cake of purified aromatic carboxylic add can be washed with pure water, dried and sent to storage or for packaging and shipment.
The aqueous mother liquor separated by the centrifuge or filter contains a number of impurities, reaction intermediates and also contains suspended and dissolved aromatic carboxylic acid. In prior processes, this stream would be sent to a waste treatment facility. However, in the process of this invention, a major portion of this mother liquor can be diverted to the separation apparatus used for separating the oxidation reaction solvent from the water produced during the oxidation reaction. Thus, the impurities, reaction intermediates and aromatic carboxylic add product are returned to the oxidation reaction mixture. Impurities are oxidized further, intermediates are converted to useful product, and aromatic carboxylic acid is recycled for recovery. Such a recycle of the mother liquor from the hydrogenation reaction is particularly useful when the separation apparatus used for separating water from the oxidation reaction solvent is a distillation column. The recycled aqueous mother liquor returned to the distillation column not only serves as reflux for the column, but also serves as an effective method for adding the mother liquor from the purification process to the oxidation reaction mixture. Thus the process of this invention provides for the elimination of a major waste product stream, a stream that would otherwise be sent to a waste treatment facility. Prior to recycling the mother liquor stream to the distillation column it can be treated to remove any suspended matter, if present. For example, it can be subjected to filtration or cent rifugat ion, or it can be passed through a hydroclone to remove suspended matter. Prior to such treatment to remove suspended matter, the mother liquor can be treated, for example, by cooling, to remove dissolved compounds that might otherwise foul the distillation column.
Detailed Desnriptinn of the Figure
Figure 1 shows in schematic form a preferred embodiment for operating the process of this invention. In agitated oxidation reactor 10 para-xylene is reacted with air in the presence of acetic add, and water as the oxidation solvent, cobalt and manganese oxidation metals and one or more bromine compounds such as hydrogen bromide as an oxidation promoter. The oxidation reaction is conducted at a temperature of about 170°C to about 210°C, and at a pressure of about 7 to about 21 kg/cm2. The heat generated by the exothermic oxidation reaction causes the reactor solvent to boil. The vaporized solvent along with gaseous byproducts, carbon oxides, nitrogen from the air charged to the oxidation reaction, and unreacted oxygen pass through pipe 12 and into high pressure distillation column 20 having about 45 theoretical plates. In the distillation tower, the acetic acid solvent is separated from the reaction overhead or offgas. The distillation column is constructed and operated such that at least 99% of the acetic add is removed from the overhead gas. The acetic acid solvent from the bottom of the distillation column is directed to surge drum 30 through pipe 25. From surge drum 30 the acetic acid solvent, which may contain some water, is returned to reactor 10 through pipe 35. The amount of solvent returned is controlled so that the proper amount of reaction solvent is maintained in the oxidation reactor.
The reaction overhead or offgas exiting the top of distillation tower 20 through pipe 38 contains less than about 0.1% by weight acetic acid, and is primarily water (steam), but also contains nitrogen, carbon oxides, unreacted oxygen and gaseous oxidation byproducts such as methyl bromide. Offgas from pipe 38 is treated in a catalytic oxidation unit 40 where byproducts such as methyl bromide and any residual acetic acid in the offgas are catalytiςally oxidized. Catalytic oxidation unit 40 is also equipped with an aqueous scrubber to remove any bromine in the offgas exiting the catalytic oxidation unit. If acetic acid was not efficiently removed from the oxidation reaction overhead, it would be oxidized in the catalytic oxidation unit resulting in an economic loss. Offgas exiting the catalytic oxidation unit 40 is directed to pipe 42. A portion of the offgas from pipe 42 is directed to pipe 43 and then to condenser 45 where water is condensed from the offgas. The cooled offgas is directed to knock-out drum 50 through pipe 46. The water depleted gas exits the process through pipe 51. The water from knock-out drum 50 is directed to PTA slurry vessel 110.
The offgas, which is primarily water, from pipe 42 is directed to pre- heater 60 through pipe 55. In pre-heater 60, the offgas is heated to a temperature of about 200°C to about 235°C and sufficient to prevent the condensation of the acetic acid depleted reactor offgas in the expander 70. Pre- heated reactor offgas enters expander 70 through pipe 65. Expander 70, which recovers energy from the reactor offgas, drives compressor 75 which delivers compressed air to oxidation reactor 10 through pipe 76. Expander 75 also drives electric generator 80 which supplies electric power for use within the TA manufacturing plant and to the local power utility.
The expanded reactor offgas exits expander 70 through pipe 72 and enters condenser 90 where the water in the expanded offgas is condensed. The condensed water from condenser 90 is directed to reflux drum 100 through pipe 92. Water from drum 100 is directed to high pressure distillation column 20 through pipes 102 and 200. Such water returned to the column serves as reflux for the column. Water from drum 100 is also directed to PTA slurry vessel 110 through pipe 105.
A reaction mixture slurry comprising crude terephthalic acid, water, acetic acid, catalyst metals, oxidation reaction intermediates and by- products exits oxidation reactor 10 through pipe 115 and is directed to vessel 120 where the temperature of the oxidation reaction mixture is reduced to crystallize dissolved terephthalic add. Vessel 120 is optionally equipped with an air sprager to continue the oxidation reaction. Overhead gasses from vessel 120 are directed to high pressure distillation column 20 having about 45 theoretical plates, through pipe 125. Oxidation reaction slurry from vessel 120 is directed to vessel 130 through pipe 128 wherein additional cooling and crystallization of terephthalic add occurs. Oxidation reaction mixture slurry from vessel 130 enters separation apparatus 135 through pipe 132. Separation apparatus 135 is typically one or more centrifuges or filters. In separation apparatus 135, crude terephthalic acid is separated from the oxidation reaction mother liquor. Oxidation reaction mother liquor exits separation apparatus 135 through pipe 138 and enters mother liquor drum 140. A major portion of the mother liquor containing catalyst and acetic acid is recycled to oxidation reactor 10 through line 145. The other portion of the mother liquor is sent to stripper 150 through pipe 148 where acetic acid is removed and directed to vessel 130 through line 152. Bottoms from stripper 150 are sent to waste through pipe 154.
A slurry of crude terephthalic add and water from PTA slurry drum 110 is directed to hydrogenation reactor 160 through pipe 158. In reactor 160, the crude terephthalic acid dissolved in water is treated with hydrogen at an elevated temperature, for example, about 260°C to about 290°C, and elevated pressure to purify the crude terephthalic acid by, for example, reducing the levels of 4-carboxybenzaldehyde. The reaction mixture from hydrogenation reactor 160 enters crystallization vessel 170 through pipe 165. The slurry of purified terephthalic acid and water formed in vessel 170 is directed to separation apparatus 180 through pipe 175. Purified terephthalic acid exits separation apparatus 180 through pipe 190. Separation apparatus 180 is generally a centrifuge or a rotary vacuum filter. Mother liquor from separation apparatus 180 which comprises water, dissolved and suspended purified terephthalic add, and various intermediate and by-product compounds, is recycled to the top of high pressure distillation column 20 through pipe 200. The return of the mother liquor from separation apparatus 180 to high pressure distillation column 20 allows for the recycle of the intermediates and by-products in the mother liquor to the oxidation reactor where they are either oxidized or converted to terephthalic acid, it also provides for the recycle of valuable terephthalic acid which would otherwise be sent to waste treatment, or which would require costly procedures for its recovery, and it eliminates treating large volumes of waste water in waste treatment facilities.

Claims

Having described the invention, that which is claimed is:
1. A continuous process for preparing aromatic carboxylic acids by the exothermic liquid-phase oxidation reaction of an aromatic feedstock compound wherein energy is efficiently recovered from the exothermic liquid-phase oxidation reaction, which process comprises: a) oxidizing an aromatic feedstock compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, a low- molecular weight monocarboxylic acid solvent, a heavy metal oxidation catalyst and a source of molecular oxygen, under reaction conditions which produce a gaseous high pressure overhead stream comprising water, gaseous by products, and gaseous low-molecular weight monocarboxylic add solvent; b) removing in a high effidency separation apparatus at least about 95 wt.% of the low-molecular weight monocarboxylic add from the overhead stream to form a second high pressure overhead stream comprising water and gaseous byproducts formed during the oxidation reaction; and c) directing the second high pressure overhead mixture to a means for recovering energy from the second high pressure overhead stream.
2. The process of Claim 1 wherein the high effidency separation apparatus is a high effidency distillation column.
3. The process of Claim 2 wherein the high effidency distillation column has at least about 30 theoretical plates.
4. The process of Claim 1 wherein the means for recovering energy from the second high pressure overhead mixture is an expander.
5. The process of Claim 4 wherein the expander is connected to an electric generator.
6. The process of Claim 1 wherein the aromatic feedstock compound is para-xylene and the aromatic carboxylic acid is terephthalic acid.
7. The process of Claim 6 wherein the low-molecular weight monocarboxylic acid solvent is acetic acid.
8. The process of Claim 1 wherein water in the high pressure overhead stream is used for the purification of the aromatic carboxylic acid.
9. A process for preparing aromatic carboxylic adds by the exothermic, liquid-phase oxidation reaction of an aromatic feedstock compound, which process comprises:
(a) oxidizing an aromatic feedstock compound to an aromatic carboxylic add in a liquid-phase reaction mixture comprising water, a low molecular weight monocarboxylic add solvent, a heavy metal oxidation catalyst, and a source of molecular oxygen, under reaction conditions which produce a gaseous overhead stream comprising water, gaseous by-products, and gaseous low-molecular weight monocarboxylic acid solvent;
(b) removing in a high effidency distillation column at least about 95 weight percent of the low-molecular weight monocarboxylic acid from the overhead stream to form a second high pressure overhead stream comprising water and gaseous by-products formed during the oxidation reaction;
(c) separating the aromatic carboxylic add formed in step (a) from reaction mother liquor produced during the liquid phase oxidation reaction mixture to form crude aromatic carboxylic add;
(d) purifying crude aromatic carboxylic add at an elevated temperature and pressure in a purification solvent comprising water to form a mixture of purified aromatic carboxylic add and purification mother liquor comprising water;
(e) separating purified aromatic carboxylic add from purification mother liquor formed in step (d) and recycling at least a portion of the purification mother liquor to the high efficiency distillation column.
10. The process of Claim 9 wherein the aromatic feedstock compound is para-xylene and the aromatic carboxylic add is terephthalic acid.
11. The process of Claim 10 wherein the low molecular weight monocarboxylic add solvent is acetic add.
12. The process of Claim 9 wherein the high effidency distillation column has at least about 30 theoretical plates.
13. The process of Claim 9 wherein the purification solvent is water.
14. The process of Claim 9 wherein in step (d) hydrogen is used to purify the crude aromatic carboxylic acid.
15. The process of Claim 9 wherein at least most of the purification mother liquor is recycled to the high effidency distillation column.
16. A reactor apparatus suitable for converting an alkyl aromatic feedstock compound to an aromatic carboxylic add by the liquid phase oxidation of the aromatic feedstock compound in a reaction mixture comprising acetic acid reaction solvent and water, and which provides for the efficient recovery of energy produced by the oxidation reaction, comprising a reaction vessel suitable for conducting the liquid phase oxidation of an aromatic feedstock compound at an elevated temperature, a high effidency distillation column capable of separating a mixture of acetic add and water such that vapor exiting the distillation column is less than about 0.5 weight percent acetic add and, a means for directing vapor produced by the liquid-phase oxidation reaction in the oxidation reactor to the distillation column.
17. The reaction apparatus of Claim 16 wherein the high efficiency distillation column has at least about 30 theoretical plates.
18. The reaction apparatus of Claim 16 wherein the distillation column is capable of separating acetic add from water such that at least about 99% by weight of the acetic add in a mixture of acetic add and water fed to the distillation column is separated and not present in effluent from the top of the distillation column.
19. The reactor apparatus of Claim 16 further comprising an expander to recover energy from the vapor exiting the distillation column.
20. The reactor apparatus of Claim 19 further comprising an electric generator connected to the expander.
PCT/US1995/012255 1994-10-14 1995-09-22 Process for preparing aromatic carboxylic acids with efficient energy recovery WO1996011899A1 (en)

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DE69517301T DE69517301T3 (en) 1994-10-14 1995-09-22 PROCESS FOR THE PREPARATION OF AROMATIC CARBOXYLIC ACIDS WITH EFFECTIVE ENERGY RECOVERY
AT95934533T ATE193516T1 (en) 1994-10-14 1995-09-22 METHOD FOR PRODUCING AROMATIC CARBOXYLIC ACIDS WITH EFFECTIVE ENERGY RECOVERY
NZ294161A NZ294161A (en) 1994-10-14 1995-09-22 Preparation of aromatic carboxylic acids by reacting aromatic precursors with oxygen:- solvent and energy recovery
EP95934533A EP0734372B8 (en) 1994-10-14 1995-09-22 Process for preparing aromatic carboxylic acids with efficient energy recovery
BR9506413A BR9506413A (en) 1994-10-14 1995-09-22 Continuous process to prepare aromatic carboxylic acids and reactor
JP8513236A JPH09511253A (en) 1994-10-14 1995-09-22 Aromatic carboxylic acid production method capable of efficient energy recovery
MX9602364A MX9602364A (en) 1994-10-14 1995-09-22 Process for preparing aromatic carboxylic acids with efficient energy recovery.
CA002178346A CA2178346C (en) 1994-10-14 1995-09-22 Process for preparing aromatic carboxylic acids with efficient energy recovery
AU36844/95A AU703997B2 (en) 1994-10-14 1995-09-22 Process for preparing aromatic carboxylic acids with efficient energy recovery
HK98115906A HK1014534A1 (en) 1994-10-14 1998-12-28 Process for preparing aromatic arboxylic acids with efficient energy recovery

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996030327A1 (en) * 1995-03-27 1996-10-03 Eastman Chemical Company Process for the production of aromatic carboxylic acids
WO1996039595A1 (en) * 1995-06-05 1996-12-12 Imperial Chemical Industries Plc Effluent gas treatment
WO1997027168A1 (en) * 1996-01-25 1997-07-31 E.I. Du Pont De Nemours And Company Production of aromatic carboxylic acids
EP0818434A2 (en) * 1996-07-12 1998-01-14 Mitsubishi Gas Chemical Company, Inc. Process for the production of high-purity isophthalic acid
US5961942A (en) * 1995-06-05 1999-10-05 E. I. Du Pont De Nemours And Company Effluent gas treatment
WO2000058257A1 (en) * 1999-03-25 2000-10-05 Franco Codignola Process for the production of aromatic acids
US6143925A (en) * 1998-06-05 2000-11-07 Mitsui Chemicals, Inc. Process for producing aromatic carboxylic acid
US6833472B2 (en) 2000-07-14 2004-12-21 Eurotecnica Development And Licensing Spa Process for the purification of aromatic carboxylic acids
WO2005007606A3 (en) * 2003-07-10 2005-04-14 Eastman Chem Co A process for energy recovery in processes for the preparation of aromatic carboxylic acids
KR100527416B1 (en) * 1996-07-12 2006-03-22 미쯔비시 가스 케미칼 컴파니, 인코포레이티드 Method for producing high purity isophthalic acid
WO2006102137A1 (en) * 2005-03-21 2006-09-28 Bp Corporation North America Inc. Improved recovery of energy during the production of aromatic carboxylic acids
WO2007097543A1 (en) * 2006-02-20 2007-08-30 Amtpacific Co., Ltd. Reducing method of water from reactor outlet gas in the oxidation process of aromatic compound
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US9493387B2 (en) 2008-10-31 2016-11-15 Grupo Petrotemex, S.A. De C.V. Dicarboxylic acid production with minimal wastewater generation
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Families Citing this family (55)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19615886C1 (en) 1996-04-22 1997-07-31 Huels Chemische Werke Ag Increasing yield in crude di:methyl terephthalate prodn.
US6137001A (en) * 1998-02-11 2000-10-24 Bp Amoco Corporation Process for preparing aromatic carboxylic acids with efficient treatments of gaseous effluent
DE60002597T2 (en) * 1999-10-13 2004-08-05 Sulzer Chemtech Ag METHOD FOR THE HYDROLYTIC PRODUCTION OF A CARBOXYLIC ACID AND ALCOHOL FROM THE CORRESPONDING CARBOXYLATE
JP2003520263A (en) * 2000-01-21 2003-07-02 ビーピー・コーポレーション・ノース・アメリカ・インコーポレーテッド Production of high purity aromatic carboxylic acid by oxidation in benzoic acid / water solvent
JP4809534B2 (en) * 2001-01-22 2011-11-09 三菱瓦斯化学株式会社 Process for producing aromatic carboxylic acid
US6504051B1 (en) 2001-06-04 2003-01-07 Eastman Chemical Company Process for production of aromatic carboxylic acids with improved water removal technique
US6852879B2 (en) * 2001-10-05 2005-02-08 Bp Corporation North America Inc. Method of removing iron oxide deposits from the surface of titanium components
US6649773B2 (en) 2002-03-22 2003-11-18 General Electric Company Method for the manufacture of halophthalic acids and anhydrides
US6657067B2 (en) 2002-03-22 2003-12-02 General Electric Company Method for the manufacture of chlorophthalic anhydride
US6657068B2 (en) 2002-03-22 2003-12-02 General Electric Company Liquid phase oxidation of halogenated ortho-xylenes
US7135596B2 (en) * 2002-04-23 2006-11-14 Bp Corporation North America Inc. Method of removing iron contaminants from liquid streams during the manufacture and/or purification of aromatic acids
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US7213540B2 (en) * 2004-02-05 2007-05-08 Eastman Chemical Company Steam recompression in carboxylic acid processes
US20050256335A1 (en) * 2004-05-12 2005-11-17 Ovidiu Marin Providing gases to aromatic carboxylic acid manufacturing processes
US7541489B2 (en) * 2004-06-30 2009-06-02 Sabic Innovative Plastics Ip B.V. Method of making halophthalic acids and halophthalic anhydrides
US20060004223A1 (en) * 2004-06-30 2006-01-05 General Electric Company Method of making halophthalic acids and halophthalic anhydrides
US7608732B2 (en) * 2005-03-08 2009-10-27 Eastman Chemical Company Optimized liquid-phase oxidation
IN2015DN00761A (en) * 2004-09-02 2015-07-10 Grupo Petrotemex Sa De Cv
KR20080091453A (en) 2005-12-29 2008-10-13 비피 코포레이션 노쓰 아메리카 인코포레이티드 Ethanolysis of pet to form det and oxidation thereof
US7566802B2 (en) * 2006-05-24 2009-07-28 Eastman Chemical Company Process for energy recovery and water removal in the preparation of aromatic carboxylic acids
CN101161625A (en) * 2006-10-12 2008-04-16 高化环保技术有限公司 Process for the reduction of sulfur, nitrogen and the production of useful oxygenates from hydrocarbon materials via one-pot selective oxidation
US7465824B2 (en) * 2007-02-08 2008-12-16 Bp Corporation North America Inc. Process for the production of high purity aromatic carboxylic acids using a benzoic acid and water solvent for oxidation and purification
RU2438763C2 (en) * 2007-02-28 2012-01-10 Хитачи Плант Текнолоджиз, Лтд. Method of processing oxidation reaction waste gases and extracting power therefrom
KR100894761B1 (en) 2007-10-18 2009-04-24 주식회사 효성 Preparation method of 2,6-naphthalene dicarboxylic acid with energy recovery and recycling
US8614350B2 (en) 2008-01-15 2013-12-24 Eastman Chemical Company Carboxylic acid production process employing solvent from esterification of lignocellulosic material
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US20210380519A1 (en) 2017-08-01 2021-12-09 Bp Corporation North America Inc. Process for pre-heating boiler feed water in the manufacture of purified aromatic carboxylic acids
US11312678B2 (en) 2018-06-29 2022-04-26 Ineos Us Chemicals Company Solid-liquid separation processes using a large pore filter
CN109251139B (en) * 2018-11-02 2021-06-25 中国石油天然气集团有限公司 PIA production method and production system adopting deep oxidation
WO2020102639A1 (en) 2018-11-16 2020-05-22 Bp Corporation North America Inc. Process for manufacturing aromatic carboxylic acids
US20220380287A1 (en) 2019-10-31 2022-12-01 Ineos Us Chemicals Company Solids-Liquid Separation Processes
WO2023183864A1 (en) 2022-03-24 2023-09-28 Ineos Us Chemicals Company Process and apparatus of production of aromatic dicarboxylic acid.

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0498591A2 (en) * 1991-02-05 1992-08-12 Imperial Chemical Industries Plc Process for the production of terephthalic acid

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2064386A1 (en) 1970-12-30 1972-07-20 Franz Morat GmbH, 7000 Stuttgart-Vaihingen Device for the electronic control of textile machines or for the production of a control strip for textile machines
FR2187732A1 (en) * 1972-06-06 1974-01-18 Inst Francais Du Petrole Pure aromatic polycarboxylic acids - by oxidation of substd aromatic cpds and recycling the unreacted materials
FR2303787A3 (en) * 1975-03-14 1976-10-08 Inst Francais Du Petrole Aromatic polycarboxylic acid prodn. - esp. terephthalic acid by oxidn. of paraxylene
JPS5599517A (en) * 1979-01-22 1980-07-29 Hitachi Ltd Treatment of exhaust gas
US4202167A (en) * 1979-03-08 1980-05-13 Texaco Inc. Process for producing power
JPS5640636A (en) * 1979-09-10 1981-04-16 Cosmo Co Ltd Treatment of exhaust gas of oxidation reaction
US4471619A (en) * 1982-08-23 1984-09-18 Uop Inc. Fractionation process with power generation by depressurizing the overhead vapor stream
US5050375A (en) * 1985-12-26 1991-09-24 Dipac Associates Pressurized wet combustion at increased temperature
US4914230A (en) * 1986-07-28 1990-04-03 Amoco Corporation Catalyst recovery method
EP0478428B1 (en) * 1990-09-25 1995-03-08 Institut Français du Pétrole Process for the preparation of boron oxide by hydrolysis of methylborate and its use in the oxidation of saturated hydrocarbons to alcohols
US5102505A (en) * 1990-11-09 1992-04-07 Union Carbide Chemicals & Plastics Technology Corporation Mixed aldehyde product separation by distillation
JP3291749B2 (en) * 1992-02-06 2002-06-10 三菱化学株式会社 Method for producing aromatic carboxylic acid
JP3198711B2 (en) * 1993-03-30 2001-08-13 三井化学株式会社 Method and apparatus for producing terephthalic acid

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0498591A2 (en) * 1991-02-05 1992-08-12 Imperial Chemical Industries Plc Process for the production of terephthalic acid

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
REUMERS J.: "ENERGY CONSERVATION AT AMOCO CHEMICALS", JOURNAL A, SOFT VISION, vol. 25, no. 3, 1 July 1984 (1984-07-01), BRUSSELS, BE, pages 165 - 167, XP002028220 *

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996030327A1 (en) * 1995-03-27 1996-10-03 Eastman Chemical Company Process for the production of aromatic carboxylic acids
WO1996039595A1 (en) * 1995-06-05 1996-12-12 Imperial Chemical Industries Plc Effluent gas treatment
US5961942A (en) * 1995-06-05 1999-10-05 E. I. Du Pont De Nemours And Company Effluent gas treatment
WO1997027168A1 (en) * 1996-01-25 1997-07-31 E.I. Du Pont De Nemours And Company Production of aromatic carboxylic acids
EP0818434A2 (en) * 1996-07-12 1998-01-14 Mitsubishi Gas Chemical Company, Inc. Process for the production of high-purity isophthalic acid
EP0818434A3 (en) * 1996-07-12 1998-10-21 Mitsubishi Gas Chemical Company, Inc. Process for the production of high-purity isophthalic acid
KR100527416B1 (en) * 1996-07-12 2006-03-22 미쯔비시 가스 케미칼 컴파니, 인코포레이티드 Method for producing high purity isophthalic acid
US6143925A (en) * 1998-06-05 2000-11-07 Mitsui Chemicals, Inc. Process for producing aromatic carboxylic acid
WO2000058257A1 (en) * 1999-03-25 2000-10-05 Franco Codignola Process for the production of aromatic acids
US6761860B2 (en) 1999-03-25 2004-07-13 Franco Codignola Apparatus for the production of aromatic acids
US6833472B2 (en) 2000-07-14 2004-12-21 Eurotecnica Development And Licensing Spa Process for the purification of aromatic carboxylic acids
WO2005007606A3 (en) * 2003-07-10 2005-04-14 Eastman Chem Co A process for energy recovery in processes for the preparation of aromatic carboxylic acids
WO2006102137A1 (en) * 2005-03-21 2006-09-28 Bp Corporation North America Inc. Improved recovery of energy during the production of aromatic carboxylic acids
US7935844B2 (en) 2005-03-21 2011-05-03 Bp Corporation North America Inc. Recovery of energy during the production of aromatic carboxylic acids
KR101314005B1 (en) 2005-03-21 2013-10-01 비피 코포레이션 노쓰 아메리카 인코포레이티드 Improved recovery of energy during the production of aromatic carboxylic acids
US8779185B2 (en) 2005-03-21 2014-07-15 Bp Corporation North America Inc. Process and apparatus for manufacturing pure forms of aromatic carboxylic acids
WO2007097543A1 (en) * 2006-02-20 2007-08-30 Amtpacific Co., Ltd. Reducing method of water from reactor outlet gas in the oxidation process of aromatic compound
KR100794317B1 (en) * 2006-02-20 2008-01-11 (주)에이엠티퍼시픽 Reducing method of water from reactor outlet gas in the oxidation process of aromatic compound
AU2007218513B2 (en) * 2006-02-20 2010-03-18 Amtpacific Co., Ltd. Reducing method of water from reactor outlet gas in the oxidation process of aromatic compound
US8084639B2 (en) 2006-02-20 2011-12-27 Ki Joon Kang Method of reducing inflow of water from a reactor outlet gas to a dehydration tower for separating carboxylic acid solvent and water
EP2495405A2 (en) 2008-05-06 2012-09-05 Invista Technologies S.à.r.l. Power recovery
DE202009019033U1 (en) 2008-05-06 2015-08-20 Invista Technologies S.À.R.L. Energy recovery
US9493387B2 (en) 2008-10-31 2016-11-15 Grupo Petrotemex, S.A. De C.V. Dicarboxylic acid production with minimal wastewater generation
US9493389B2 (en) 2008-10-31 2016-11-15 Grupo Petrotemex, S.A. De C.V. Dicarboxylic acid production with enhanced energy recovery

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EG20931A (en) 2000-06-28
BR9506413A (en) 1997-09-09
ES2145927T5 (en) 2007-03-01
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TR199501268A2 (en) 1996-06-21
DE69517301D1 (en) 2000-07-06
HK1014534A1 (en) 1999-09-30
CN1083417C (en) 2002-04-24
JP2006249106A (en) 2006-09-21
CN1137266A (en) 1996-12-04
DE69517301T2 (en) 2001-01-11
ZA957905B (en) 1996-04-29
AU703997B2 (en) 1999-04-01
NZ294161A (en) 1998-03-25
US5723656A (en) 1998-03-03
KR100397242B1 (en) 2004-03-20
AU3684495A (en) 1996-05-06
MY113200A (en) 2001-12-31
EP0734372B8 (en) 2006-08-23
EP0734372A1 (en) 1996-10-02
EP0734372B2 (en) 2006-06-28
US5612007A (en) 1997-03-18
CA2178346A1 (en) 1996-04-25
CA2178346C (en) 2007-04-24
MX9602364A (en) 1997-02-28
ATE193516T1 (en) 2000-06-15
SA95160315B1 (en) 2005-07-06
JPH09511253A (en) 1997-11-11
DE69517301T3 (en) 2007-02-01
EP0734372B1 (en) 2000-05-31

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