CA1120056A

CA1120056A - Process for producing isomerized aromatic carboxylic acids and terephthalic acid

Info

Publication number: CA1120056A
Application number: CA000322877A
Authority: CA
Inventors: Geoffrey E. Dolbear; Raymond A. Schep
Original assignee: Occidental Research Corp
Current assignee: Occidental Research Corp
Priority date: 1978-03-06
Filing date: 1979-03-05
Publication date: 1982-03-16

Abstract

?-77 /js PROCESS FOR PRODUCING ISOMERIZED AROMATIC

CARBOXYLIC ACIDS AND TEREPHTHALIC ACID

ABSTRACT

Isomerized aromatic carboxylic acid is produced from benzoic acid and another aromatic material by treating a mixture of an aromatic material, water, and a water soluble reagent comprising a Group Ia or IIa metal, the reagent producing an alkaline solution by hydrolysis, with oxygen, under conditions sufficient to convert at least a portion of the aromatic material to an aromatic carboxylic acid salt of the metal of the reagent; adding benzoic acid to the mixture;
and isomerizing the aromatic carboxylic acid salt by heating without converting the aromatic carboxylic acid salt to an aromatic carboxylic acid salt of a different Group Ia or IIa metal prior to isomerizing. The isomerized aromatic carboxylic acid salt is then converted to isomerized aromatic carboxylic acid and the reagent is regenerated. The isomerized aromatic carboxylic acid is recovered and the reagent is recycled to supply a portion of the reagent required for producing said aromatic carboxylic acid salt.

In an alternate embodiment, the benzoic acid is added to the mixture and is in the mixture while the mixture is treated with oxygen and the soluble reagent.

In another embodiment, the water soluble reagent comprises a Group Ia or IIa metal formate, acetate, or propionate.

In another embodiment, the isomerized aromatic carboxylic acid salt is treated with an acid of the reagent to convert the isomerized aromatic carboxylic acid salt to an isomerized aromatic carboxylic acid precipitate and the reagent.

In another embodiment, the water soluble reagent is potassium carbonate, or potassium bicarbonate or mixtures thereof.

The invention is especially useful for producing tereph-thalic acid.

Description

FIELD F INVENTION

The field of the invention relates to ~he production of isomerized aromatic carboxylic acids from aromatic materials, such as coal, petroleum residium, shale oil, and tar sands.
The invention is particularly useful for the production of lS~ terephthalic acid from bituminous coa~.

PRIOR_ART

U~S. Patent 2,785,198 discloses a process for producing polycarboxylic acids from bituminous coal, lignites; peat and ;the like or their carbonization products such as coal, tar, or pitch by thermal treatment with oxidizing agents such as nitric acid, chromic acid, permanganate, or oxygen or air under super-atmospheric pressure in an alkaline medium.

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The crude oxidation product is subject to an extraction treatment with a polar organic solvent for both the monocyclic aromatic and high molecular weight polycarboxylic acids, and treating the thusly formed solution with water to extract the 5I monocyclic aromatic polycarboxylic acids from the remainder of the mixture.

~j The alkaline medium disclosed by Grosskinsky et al is sodium hydroxide.

ll U.S. Patent 2,193,337 discloses a process for producing 10 1 organic acids by heating carbonaceous material such as sawdust, wood chips, peat, or coal with oxygen-containing gases at 1 elevated pressures and temperatures in the presence of at least i! 10 times the weight of the carbonaceous material of water and Il preferably an oxide or hydroxide of an alkali or alkaline earth 15l metal. Oxalic acid and other organic acids which are formed, such as mellitic and benzoic acid or acetic acid, may be isolated from the resulting reaction mixture as salts of the i alkali or alkaline earth metals. The caustic material disclosed ' is an oxide or hydroxide of an alkali metal or an alkaline earth metal and specifically lime, quick-lime, and caustic soda.

U.S. Patent 2,786,074 discloses a process for making organic acids by oxidizing carbonaceous materials at elevated , temperatures and pressures with gaseous oxygen in the presence 25 ~ of an alkaline solution. Alkalis which are suitable for use in a high pressure reactor are specified as sodium hydroxide, ,I potassium hyd~oxide, and mixtures thereof.

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i6 U.S. Patent 2,461,740 discloses a process for oxidizing i carbonaceous material to aromatic acids using a two-stage I oxidation process.

I In the first stage, the carbonaceous material is oxidized 5l to a state where it is soluble in aqueous alkali such, for example, as a solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate, especially at elevated ¦ temperatures.

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Ij Any acid or acid anhydride with suitable oxidizing pro-101l perties which can be regenerated by air and recycled in the process can be employed, for example sulfur trioxide, oxides of nitrogen, or the acids formed by reaction of ~hese compounds with water. Specifically disclosed are sulfur trioxide, Il N2O3, and N2s-i1 .
15'l In the second stage, U.S. Patent 2,461,740 discloses the use of a high pressure elevated temperature reaction of oxygen ¦ gas in aqueous alkali. The aqueous alkali employed is a solution of sodium hydroxide, potassium hydroxide, sodium 1'l carbonate, or potassium carbonate.

20 l U.S. Patent 3,023,217 disc1Oses a process for introducing 'I carboxyl groups into aromatic compounds free from carboxyl ,I groups, such as aromatic carbocyclic hydrocarbons and aromatic .j .
heterocyclic hydrocarbons. The patent discloses a process for I introducing into aromatic carbocyclic or aromatic heterocyclic compounds free from carboxyl groups by reacting such materials I

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1 in the absence of substantial amounts of oxygen, such as a j non-oxidative atmosphere and under anhydrous conditions, with I alkali metal salts of aliphatic carboxylic acids at elevated I temperatures and pressures in the presence of catalysts.
As disclosed in the process, it is necessary to exclude the presence of substantial quantities of oxygen. Examples of aliphatic carboxylic acids which are used in the form of their alkali metal salts, especially their potassium salts, are il oxalic acid, malonic acid, maleic acid, and trichloroacetic 101 acid.
l . '~. , Examples of suitable compounds free from carboxyl groups which may be used as starting materials for the process are Il aromatic carbocyclic compounds free from carboxyl groups such Il as monocyclic aromatic hydrocarbons such as benzene or its 15,1 derivatives having saturated alkyl or cycloalkyl substitutes attached thereto, and dicyclic aromatic hydrocarbons such as naphthalenes, diphenyl, and other polycyclic aromatic hydro-carbon compounds. Similarly, aromatic heterocyclic compounds I free from carboxyl groups which may be used as starting mate-20¦ rials are heterocyclic compounds which contain one or more ¦l heteroatoms in the ring and which are designated as having an ¦l aromatic character because of their chemical behavior.
, U.S. Patent 2,948,750 discloses a process for carboxylating j aromatic hydrocarbons by direct introduction o~ carbon dioxide to produce polycarboxylic acids.

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Suitable starting materials which are disclosed arearomatic hydrocarbons, especially benzene but also toluene, xylene, cumene and diisopropyl benzene and other benzenes 1 substituted with saturated or unsaturated alkyl or cycloalkyl radicals, naphthalene, diphenyl, diphenylmethane and other aromatic compounds which may also be substituted with hydro-carbon radicals.

Selective earboxylation is accomplished by heating the l! starting materials in the presenee of an acid-binding agent, 10ll and earbon dioxide under anhydrous eonditions. Examples of the aeid-binding agent are earbonates of alkali metals, espeeially jl potassium earbonate, the salts of other weak aeids such as il bicarbonates, formates, or oxalates. Similarly, the corres-1l ponding eompounds of other metals are suitable; for example, 15l the earbonates of the alkali earth metals.

U.S. Patent 3,023,216 discloses a method of introducing -earboxyl groups into aromatie earboeyelie compounds free from I carboxyl groups by reaeting these eompounds in a non-oxidative I atmosphere with alkali metal salts of aromatie carbocyelie or 20l aromatie heteroeyelic carboxylie aeids.

¦ Suitable eompounds whieh are free from carboxyl groups which may be used as starting compounds in this patent are similar to the starting compounds in U.S. Patent 2,948,750.

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U.S. Patent 3,023,216 discloses reacting aromatic car-bocyclic compounds free from carboxyl groups with aromatic carboxylic acids in the form of their alkali metal salts.

The requirements of both patents to Blaser et al require 5; essentially specific chemical compounds as starting materials.
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, U.S. Patent 2,833~816 discloses a process for oxidizing ¦I aromatic compounds using a catalyst comprising a lower aliphatic !i carboxylate salt of a heavy metal and bromine. Examples of a ¦i heavy metal are manganese, cobalt, nickel, chromium, vanadium, mol~bdenum, tungsten, tin, and cerium.

The metals may be supplied in the form of metal salts;
for example such as manganese acetate. The bromine may be supplied as ionic bromine, or other bromine compounds soluble i in the reaction medium such as potassium bromate.
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151l Thus, the process requires the conjoint presence of Il bromine and a heavy metal oxidation catalyst.

¦I The starting material required is an aromatic compound containing one or more aliphatic substltuents to produce I corresponding aromatic carboxylic acids.

20il U.S. Patent 3,064,043 discloses a process ~or oxidizing ~ para-toluic acid or para-formyl toluene to produce terephthalic ¦ acid.

U.S. Patent 3,064,0~6 discloses a process for oxidizing ll toluic acid or formyl toluene to produce orthophthalic acid or 251' isophthalic ac,id.

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Both patents to Taylor et al require specific starting materials to be oxidized.
United States Patent 3,558,458 discloses a process for preparing aromatic acids by treating an alkyl aryl ketone with water at an elevated temperature in the presence of a reaction promoting agent. The reaction promoting agent may comprise an alkaline catalyst, a transition metal salt, or actinic light.
Examples of an alkaline catalyst include potassium acetate, lithium acetate, rubidium acetate, and cesium acetate. The process is conducted in water at a temperature of about 200C
to 400C.
The art discloses processes for the alkaline oxidation of coal employing large amounts of chemicals relative to the amount of water soluble coal acids produced,see United States -~ -Patent 2,786,074 and a report entitled "Production of Chemicals by Oxidation of Coal", Battelle Laboratory, Columbus, Ohio of ;
March 31, 1975. The report also suggests the use of potassium acetate and acetic acid in a cyclic process for the Henkel reaction at page 19.
Recovery of caustic soda and sodium carbonate was dis-~ closed by Industrial and Engineering Chemlstry, Volume 44 ~1952), at page 2791 in an article entitled "Water-Soluble Polycarboxylic Acids by OxidatioD of Coal" beginning at page 2784.
Japanese Patent 18,365 discloses the reclamation of alkali by recrystallization and requires the consumption of one part by weight of the alkali and 1.5 parts of sulfuric acid for eacn two parts of coal consumed.

Non-alkaline oxidation of coal generally yields about 10 parts by weight of water soluble coal acids based on 100 parts of coal carbon consumed. Alkaline oxidation yields have been about 30 to about 42 parts per 100 parts of coal carbon consumed. Therefore, alkaline oxidation processes are favored because of the higher yield possible.

In systems like HCl/KCl, H2SO4/K2SO4, and HNO3/KNO3 the salts do not produce an alkali solution by hydrolysis because the acids involved are too strong. These systems over oxidize the coal and therefore result in much lower yield of coal acids.

~nother disadvantage of treatment of coals with strong acids is the production of unwanted by-products by chlorination, sulfation, or nitration of the aromatic nuclei of the coal~

Coal acids have been prepared by nitric acid oxidation, U.S. Patents 3,468,943; 3,709,931; 2,555,410; in the presence of nitrogen catalyst, U.S. Patent 3,702,340; and oxidation in a non-alkaline aqueous medium, U.S. Patent 3,259,650.

The caustic-oxygen treatment of coal has been described in U.S. Bureau of Mines Information Circular ~o. 8234 at pages 7~ to 98.

., In another process, U.S. Patent 3,259,650 discloses the 25 use of a non-alkaline medium and produces lower yields of water soluble coal açids~

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~ nited States Patent 2,927,130 discloses a process for the recovery of alkalis and terephthalic acid from aqueous solu-tions containing alkali salts of terephthalic acid. Alkalis of interest are sodium, potassium and ammonium. The patent dis-closes that dialkali salts of terephthalic acid in aqueous solu-tion can easily be divided into difficultly soluble monoalkali salts and alkali bicarbonate by introducing carbon dioxide into the solution, and that the difficultly soluble monoalkali salts of terephthalic acid can be hydrolyzed with water into free terephthalic acid and dialkali salts of terephthalic acid. The free terephthalic acid separates out as a solid, while the di-alkali terephthalate remains in solution.

.. ' ''' ,.,, ' ' ~ ~t - 9a -` ' ~20~156 Although oxidation can be carried out in reclaimable acidic media, these processes are not as desirable because of lower yields and unwanted by-products due to chlorination, sulfation, and nitration.

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5j The art discloses a process for preparing terephthalic acid by heating pure potassium phthalate, or pure potassium isophthalate, or pure potassium benzoate in the presence of I, catalyst such as cadmium, zinc and other metals, as reported Il in the Journal of American Chemical Society, Volume 79, pages 6005 to 6008.

The art discloses a catalytic process for preparing terephthalic acid from toluene by oxidizing toluene to benzoic acid, reacting the thusly formed benzoic acid with potassium l terephthalate in a methathesis reaction to produce terephthalic 15l acid and potassium benzoate, and heating the thusly formed potassium benzoic in the presence of a catalyst to produce potassium terephthalate and benzene by a disproportionation , reaction. Terephthalic acid and benzene are recovered and the thus formed potassium terephthalate is recycled to the methathe-20l sis reaction. The process is reviewed in Stanford ResearchInstitute Report No. PEP'7~-2~3 of Eebruary, 1977.

The use of the applicant's invention allows reclamation of the reagent, higher yields, and less production of undesirable l by-products. In the applicant's invention, the material 25l principally consumed in the process is benzoic acid and the , aromatic material. Almost all other reagents are almost fully !
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recoverable and completely reusable. In one embodiment of the applicantls invention, -the applicant has found that 92 to 95 percent by weight of potassium could be recovered as potassium acetate.

SUMMAl~Y OF THE INVENTION
According to the present invention, there is provided a process for producing isomerized aromatie earboxylie aeid from aromatic material comprising:
a. treating a mixture of an aromatie material, water, and a water soluble reagent comprising a C-roup Ia or IIa metal, said reagent producin~ an alkaline solution by hydrolysis, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said Group Ia or Ila metal of said reagent;
b. mixing benzoic acid with said mixture;
c. isomerizing said aromatic earboxylie aeid salt by heating to produee an isomerized aromatic carboxylic acid salt without converting said aromatic carboxylic aeid salt to an aromatic earboxylie acid salt of a different Group Ia or IIa metal prior to isomerizing said aromatic carboxylie acid salt;
d. converting said isomerized aromatic carboxylic acid salt to isomerized aromatie earboxylic acid, and -regenerating said reagent comprising said Group Ia or IIa metal;
e. recovering said isomerized aromatic carboxylic acid;
and f. recycling said reagent comprising said Group Ia or-IIa metal thusly regenerated to step (a) to supply a portion of said reagent required for producing said aromatic ear~oxyl1c acid salt.

~.! - 11 -Z~9~56 There is also provided in a process for producing isomer-ized aromatic carboxylic acid from aromatic material wherein carbonaceous material is oxidized in an aqueous-caustic envir-onment to produce an aromatic carboxylic acid salt and the aro-matic carboxylic acid salt is isomerized in the presence of a catalyst, the improvement which comprises oxidizing an aromatic material in the presence of a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, to form an aromatic carboxylic acid salt of said reagent, mixing ben-zoic acid with said-mixture; isomerizing said aromatic carbox-ylic acid salt produced by the oxidatio~ of the aromatic mater-ial in the presence of said reagent without treating said aro-matic carboxylic acid salt, or converting said salt to its aro-matic carboxylic acid and treating, with a compound ~hich con-tains a Group Ia or IIa metal prior to isomerization; and separating said isomerized aromatic carboxylic acid formed from said reagent.
This invention provides an improved process for the production of isomerized aromatic carboxylic acids from benzoic acid and another aromatic material.

A mixture of an aromatic material, water, and a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate is first formed. The Group Ia or IIa metal formate, acetate, or propionate is such that it will produce an alkaline solution by hydrolysis. Thus, hydrogen is excluded from the group comprising Group Ia or IIa metals.

Examples of such soluble reagents are potassium acetate, potassium formate, potassium propionate, sodium acetate, sodium formate, sodium propionate, lithium acetate, lithium formate, ~ - lla .... ~ ~ ,. . .

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lithium propionate, magnesium acetate, calcium acetate, barium acetate, beryllium acetate, etc.

The aromatic material may be coal, especially bituminous coal, petroleum residium, lignite, peat, pitch, tar, coke, char, oil shale, oil rom oil shale, and any other material containing or capable of evolving or producing aromatic material either liquid or solid.

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Any kind of coal, including lignite, anthracite, or coke or char can be used, but bituminous coals give the best yields.
~ Yields of benzene carboxylic acid ~rom anthracite coal are low " because anthracite is too aromatized. Anthracitic coals 5 l produce a product having a high percentage of polynuclear aromatic acids.

¦~ Yields from lignites are low because lignite produces little aromatic material, thus the yield of aromatic carboxylic ¦¦ acids will be low.

10ll Pure water is not required and in Eact process water may be used over and over at least in part.

i The mixture can be formed in any manner in a mixing zone using mixers suitable for handling slurries!containing solids Il if a solid or solid-like aromatic material is to be converted, 15¦¦ or mixers suitable for handling liquids if a liquid aromatic material is to be converted.

The mixture is removed from the mixing zone and fed I to a reaction zone wherein the mixture is reacted with oxygen, Il or an oxygen-containing gas such as air, The reaction zone and 20 1I the mixing zone can-be, if desired, in the same vessel as in ¦ some batch-type processes, or they may be separate vessels as in some continuous processes.

In one embodiment benzoic acid is added to the mixing 1,' zone or to the oxidation-reaction zone. Excess carboxylic 25 ¦I groups attached to the aromatic material and formed in the Z~56 . .
reaction zone are subsequently transferred to the benzoic acid thereby carboxylating the benzoic to phthalic acid and isophthalic acid.

The mixture is treated with oxygen under conditions sufficient to convert the aromatic material to an aromatic carboxylic acid salt of the reagent. In general, a temperature of about 209C to about 350C is required. The pressure in the reaction zone should be sufficient to maintain a liquid state I in the reaction zone. Generally this requires a pressure o-f at 10l least abouc 250 psig. Preferred reaction zone conditions are about 270C and about 900 psig.

Reaction times in the reaction zone depend upon the temperature, degree of agitation, the proportion of aromatic Il material, water, and water soluble reagent,,the solid-to-liquid 15¦ ratio, and the particle size of the solid material. Generally, ¦ reaction times of from about ten minutes to about three hours are required.

During oxidation carboxylic acids are formed which react Ii with the reagent to form carboxylic acid salts, and the volatile acid of the reagent, the latter of which can be reclaimed by venting vapor from the reactor.

After treating the mixture with oxygen, or an oxygen-containing gas such as air, to convert the aromatic material , into aromatic carboxylic acid, water is removed from the 25,l mixture in a dewatering zone. In the dewatering zone, an amount of water is removed which is sufficient to allow the aromatic carboxylic acid salt to be isomerized.

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, (356 The dewatering zone can be in the same vessel as the reaction zone as in some batch processes, or it can be in a Il separate vessel as in some continuous processes.

,I The water from the dewatering zone can be used in the mixing zone to supply at least part of the water requirements in the mixing zone.

In another embodiment, benzoic acid is mixed with the mixture from the dewatering zone prior to isomerization.

¦~ Whether the benzoic acid is mixed with the aromatic 10l before, during or after treatment of the mixture in the oxida-tion zone, the mixture after water removal in the dewatering zone is treated in an isomerization zone by heating the mixture to a temperature sufficiently high in the presence of a catalyst -l to isomerize the aromatic material and to produce terephthalic 15l acid salt from the carboxylate benzoic acid salt.

The isomerized aromatic carboxylic acid salt mixture is ¦ then cooled, dissolved in water, and treated in an acidification ¦ zone with an acid of the reagent which was used to form the Il original mixture of aromatic feed material, water, and reagent.

20ll As used herein and claimed herein, the expression "an acid of the reagent" means an acid which is formed by the replacement of the Group Ia or IIa metal atom of the water soluble reagent i with hydrogen. The acid, therefore, will either be formic, acetic, or propionic acid, or mixtures thereof.

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The treatment of the isomerized aromatic carboxylic acid salt mixture in the acidification zone with an acid of the reagent causes isomerized aromatic carboxylic acid salts to be I converted to their corresponding acids which are insoluble and 5j form a precipitate. Reagent is also formed in the conversion reaction.

For example, potassium phthalate treated with acetic acid is converted to phthalic acid and potassium acetate. Separation can also be achieved by solvent extraction or other suitable means'.

10~l The acidification zone may be in the same vessel as the I isomerization zone as in some batch processes, or it can be in a separate acidification vessel as in some continuous processes.

Sufficient acid is added to the mixture to effect the Il conversion of the aromatic carboxylate to the aromatic carboxy- ' j 15li lic acid and terephthalic acid salt to terephthalic acid and to ¦ cause precipitation.

j Where separation is by precipitation, the conditions in i' I
the acidification zone must be such that the species of aromatic ,I carboxylic acid desired to precipitate will in fact precipitate.
20l, These conditions, especially temperature, will vary depending I upon the species or species of aromatic carboxylic acids which are desired to form precipitates.

~l After forming the aromatic carboxylic acid precipitate, 1~ the precipitate is separated from the mlxture in a separation zone. Any apparatus capable of separating sollds from liquids 1.' ' - 15 - i i , . , :! I

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,1 may be used such as a filter. The separated solid comprises the aromatic carboxylic acid precipitate and terephthalic acid.

¦ The separated liquid from the separation zone is treated Il in a regeneration zone to recover the reagent from the liquid.

5~¦ The liquid stream from the acidification zone contains both the reagent and an acid of the reagent. The reagent and ¦ the acid of the reagent are separated in a separation zone.
The separated reagent can be used for additional treatment o.
I fresh aromatic material in the mixing zone whether the process 10,¦ is batch or continuous.

I¦ The separated acid of the reagent can be used to acidify ¦l additional material in the acidification zone whether the process is batch or continuousO

Il Thus the invention can be seen to comprise the use of 15l' an alkaline~acid-system. Examples of alkaline-acid-systerns ¦ which may be used in the invention are potassium acetate-acet c ¦ acid, or potassium formate~formic acid, or potassium propionate-propionic acid. Any alkaline-acid buffer system can be used Il from which a component is volatile or extractable. Since 20 ¦I potassium acetate is the most soluble, it is therefore preferred.

In another embodiment isomerized aromatic carboxylic acid is produced from aromatic materials by treating a mixture of an Il aromatic material, water, and a water soluble reagent comprising ¦l a Group Ia or IIa metal, the reagent producing an alkaline 25 , solution by hydrolysis, with oxygen under conditions sufficient 5~

to convert at least a portion of the aromatic material to an aromatic carboxylie aeid salt of the metal of the reagent;
adding benzoic aeid to the mixture; and isomerizing the aromatic ~ earboxylie acid salt by heating without converting the aromatic 5, earboxylie aeid salt to an aromatic earboxylie aeid salt of a different Group Ia or IIa metal prior to isomerizing. The isomerized aromatic carboxylic aeid salt is then converted to isomerized aromatie earboxylic aeid and the reagent is regen-, erated. The isomerized aromatic earboxylic aeid is recovered 10, and the reagent is reeyeled to supply a portion of the reagentrequired for producing said aromatie carboxylie aeld salt.

Preferably the Group Ia or IIa metal of the reagent is potassium.

,¦ Preferably the aromatie earbonaeeous material is eoal, and lSi espeeially preferably bituminous eoal.

Preferably the benzoie acid is added after the oxygen treatment, but it may be added during or before the oxygen treatment.

I As mentioned earlier, systems like HCl/KCl, H2S04/K2S04, 20 1l and HN03/KN03 are unsuitable beeause the salts do not ¦, produee an alkali solution by hydrolysis sinee the aeids involved are too strong. Equally important is the fact that ¦ unwanted by-products are formed by ehlorination, sulfation, or nitration of aromatie nuelei.

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~z~0~6 , . , BRIEF DESCRIPTION OF T~E D~AWINGS

~ igure 1 is a schematic flow diagram for the process for 1, the production of terephthalic acid from bituminous coal with ,I the addition of benzoic acid after the oxidation of the coal.
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5, Figure 2 is a schematic flow diagram for the process for ,1, the production of terephthalic acid from bituminous coal and ¦' benzoic acid with the addition of benzoic acid before or during the oxidation of the coal. ' ! DESCRIPTION OF PREFERRED EMBODIMENT

10ll Referring to Figure 1, a finely divided bituminous coal ,I through stream 10, water through stream 12 and potassium ¦i acetate through stream 14 are introduced in,to mixer 20. About ,I five parts water by weight and about 1 to 5 parts by weight of I¦ potassium acetate are added to the mixer per part by weight of 15l,l coal. Any type of mixer may be used. After mixing, the j mixture is removed from mixer 20 through stream 22 and intro-duced into autoclave 30. Air or oxygen is introduced into 11 autoclave 30 through line 24. About two parts by weight of ,~
' oxygen per part by weight of coal is charged to autoclave 30.
!! , ' 201 The coal is oxidized in autoclave 30 to produce aromatic ,l carboxylic acids comprising benzene carboxylic acids, poly-nuclear aromatic acids, carbon dioxide and water. The potassium l! acetate reacts with the thusly formed acids to produce potassium ,i salts thereof and acetic acid.

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; The autoclave is operated at a temperature of about 200 to about 350C, preferably about 270C, and at a pressure of about 250 psig to about 2000 psig, preferably about 900 psig.
Temperatures below about 200C are not desirable because the formation of polynuclear aromatic carboxylic acids are favored and temperatures above about 350C are not desirable because the formation of carbon dioxide is favored. Pressures outside this range, however, can be used. Lower pressures are not , desirable because kinetic rates are lower. Higher pressures lOIi are not desirable because of the cost of high pressure equipment and compression costs. Preferably the contents of autoclave 30 are agitated to increase product yield and to lower reaction ' time.

I Gases comprising carbon dioxide, acetic acid and water 1511 vapor are removed from autoclave 30 through line 31 and fed into condenser 350. In condenser 350 the vaporous acetic acid and water vapor are condensed. The condensate and gases are removed from condenser 350 through line 360 and fed to separator ~' 370. The condensate comprising aqueous acetic acid is separated 20l' from the gas comprising carbon dioxide in separator 370. The gas is removed from separator 370 through line 380 and the condensate through line 390. Both of streams 380 and 390 are fed to subsequent steps in the process as will be described Il later.

25l The thusl~ formed aromatic acid salts are dischar~ed from autoclave 30 through line 32 to fil~er 40.
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Filter 40 is used to separate the liquid product from residual solids. Filter 40 may be any type of filter, such as I a precoated revolving drum filter or a vacuum filter. The , liquid product containing the dissolved thusly formed potassium 5, acid salts is removed from filter 40 through line 42. The solids which contain unreacted coal and ash are removed from filter 40 through line 44 and recycled to mixer 20. The Il filtration step is optional and is not needed if the solids in ¦ stream 32 will not interfere with a subsequent isomerization step as described later.

i Liquid stream 42 from filter 40 together with benzoic acid from line 45 is charged to mixer 46. Mixer 46 may be any type of mixer such as a stirred tank. Benzoic acid is converted Il in mixer 46 to potassium benzoate. The temperature in mixer 46 15 1! is from about 0C to about 100C if the mixing is performed at ¦i ambient pressure. Preferably the mixing temperature is ambient.

l The mixed stream 48 from mixer 46 is charged to evaporator , 50 where most of the water therein is removed. The damp solids ~i containing the thusly formed potassium benzoate and potassium 20,i carboxylic acid salts are removed from the evaporator 50 through line 52 and enter dryer 60. Water from evaporator 50 is removed through line 54 and recycled to mixer 20.
il In an alternate embodiment (not shown), benzoic acid can ~ `

l, be mixed with stream 52 before it enters dryer 60 in lieu of 25; mixing with stream 42.

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~ 'Z~56 i In dryer ~0, the remaining water which contains acetic acid is removed from the damp solids. I'he thusly formed dry solids are removed from dryer 60 through line 52 and charged to , isomerization reactor ~0. It is important to dry the solids 5,~ charged to the isomerization reactor sufficiently to prevent excessive reaction between water and aromatic carboxylic acids in the isomerization reactor.

ll In still another embodiment (not shown), benzoic acid ¦i can be dry mixed with stream 62 before it enters isomerization 10,, reactor 80 in lieu of mixing with stream 46.

¦ In an alternate embodiment, potassium benzoate can be ! introduced, as through line 66, into isomerization reactor 80 Il to simultaneously undergo conversion to terephthalic acid.
,' ! i I In isomerization reactor 80, potassium benzoate is car-15l boxylated and the dry aromatlc carboxylic acid salts are catalytically isomerized at a temperature of from about 400C
to about 440C at a pressure of about 10 atmospheres~ and for a ij , period of time of about 10 to about 100 minutes, to cause isomerization of the dry potassium acid salts to more valuable 20, products such as terephthalate and other isomerized aromatic acid salts. During isomerization the potassium benzoate combines with the excess carboxyl groups of the aromatic carboxylic acid salts to form polycarboxyl benzene carboxylic !l acid salts which are then isomerized to potassium terephthalate.

25l Preferably a carbon dioxide environment is maintained in the isomerization reactor. Especially preferably the carbon dioxide is produced in the oxidation step as mentioned earlier ... .

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Il i 'i 0(3~6 and is fed to the isomerization reactor ~0 through line 380.
If free oxygen is present in the gas in line 380 then it must be removed or converted to carbon dioxide (not shown) before the gas is fed to isomerization reactor 80. Stream 380 ~ay be ~ -5~, used as a source of carbon dioxide without any subsequent puri-fication or treatment, if it does not contain free oxygen, since it is not necessary to use pure carbon dioxide. In still ~I another embodiment, any inert atmosphere, such as nitrogen, may , be used.

10l, Examples o~ catalysts useful for promoting the isomeri-zation are the oxides, carbonates, or halides of zinc or cadmium. Organic salts, particularly carboxylates such as cadmium benzoate, are particularly good catalysts. Cadmium , iodide is a preferred catalyst, in concentrations varying from l5il 1 to 15 parts by weight per 100 parts by weight of aromatic carboxylic acid salts. The preferred concentration of cadmium l~l iodide is about 5 parts by weight per 100 parts by weight of ll¦ the aromatic carboxylic acid salt mixture.

Il The products are removed from isomerization reactor 80 20 ' through line 82 and enter cooler 90 where the products are -cooled to a temperature of about 200C to about 100C, pre-ferably about 100~. It is necessary to cool the products because decomposition occurs at higher temperatures when ex-i posed to water or oxygen. For example, exposure to water can cause potassium terephthalate to decompose to benzoic acid and potassium bicarbonate; and exposure to oxygen can cause potas-sium terephthalate to decompose to carbon dioxide and potassium bicarbonate.

' I .

~: , The cooled products removed from cooler 90 through line 92, together with water from line 94, are charged to dissolver 100. In dissolver 100 the potassium acid salts are completely I dissolved.

5l The mixture is removed from dissolver 100 through line 102 ¦l and enters filter 110 where any undissolved solids are separated I from the liquid portion of the mixture. The thusly separated liquid portion is removed from filter 110 through line 112 and I charged to precipitator 120. Treatment of the solution with 101l activated charcoal to remove any impurities which impart a color to the terephthalic acid solution can be performed ¦ prior to the precipitation step if desired.

I The thusly separated solids, which consist essentially !' Of char and ash, are removed from filter 110 through line 114 15l and a portion thereof is recycled to mixer 20 by way of line 116, or alternately the solids are recycled to autoclave 30 Il (not shown), to undergo further oxidation to produce additional ¦I carboxylic acids. In order to prevent buildup of solids, , principally ash, in the system, another portion of the solids 20'll is removed from the system through line 118.

In still another embodiment (not shown), solids from ¦, filter liO are mechanically treated or floated to separate the ash material from the carbonaceous material. The carbonaceous ¦ material can be returned to mixer 20, or alternately to auto-25 1l clave 30, while the separated ash fraction i5 removed from the li system.
" .

I I .

5~
. . ..
Returning to dryer 60, the vapor stream, removed from the dryer through line 64, is fed to condenser 70 whereupon water vapor containing acetic acid vapors is condensed to produce ` aqueous acetic acid. The condensate and any gases are removed 5l from condenser 70 through line 72 and fed to separator 75 which separates the aqueous acetic acid from the gases. The separated aqueous acetic acid is removed from separator 75 through line ,¦ 76 and then charged to precipitator 120. Make-up acetic acid ¦l is fed to precipitator 120 through line 124. An excess of acetic acid is maintained in the precipitator to effect preci-pitation of terephthalic acid. A pH of about 3 to about 7, preferably about 4.7 to about S.S, is maintained in precipitator 1~ 120 to cause conversion of the potassium terephthalate to the li terephthalic acid. By controlling the pH in the precipitator 15~l in this range, i.e. about 3 to about 7, terephthalic acid will !~ be formed from the potassium acid salt and will be caused to precipitate. Other aromatic carboxylic acids are more soluble than terephthalic acid and will remain in solution. A low pH, lll for example below about 3, in the precipitator is undesirable because this will cause impurities to co-precipitate with !, terephthalic acid, while a high pH, for example over about 7, is undesirable because insufficient precipitation of terephthalic acid will result, thereby reducing the yield.

¦I The temperature in the precipitator must be controlled 25~l below the temperature at which significant product begins to dissolve. This temperature is about 5C to about 25C when the principal product is terephthalic acid. Precipitator 120 may be any type, such as a continuous stirred tank reactor.

" .

i , i, .
' Gases removed from separator 75 through line 77, which comprise carbon dioxide, can be used to maintain at least part of carbon dioxide atmosphere in the isomerization reactor 23.
` These gases are fed to reactor 80 through line 78 or vented through line 79. If gases from separator 75 contain free oxygen then the free oxygen must be removed or converted to carbon dioxide (not shown) before the yases are fed to lsomerization reactor 80.

!1 All of the products are removed from precipitator 120 lO~ through line 122 and enter filter 130. Filter 130 may be any il type, such as a precoated revolving drum filter.

The solid product, terephthalic acid, is removed from filter 130 through line 131 and stored in storage vessel ~ 135.

15l The liquids are separated from the solid terephthalic acid in filter 130 and the liquid is removed from the filter through line 132. If it i5 desired to remove more soluble carboxylic acids from the acid solution, then liquids in line i 132 are fed to separator 140.

20,l Separator 140 may be a liquid-liquid extraction apparatus.
The separated carboxylic acids are removed from the separator 140 through line 152 and are fed to purifier 160. Purification of the carboxylic acid in purifier 16C may be by conventional ~I means. The purified carboxylic acids are removed from the purifier 160 through line 162 and sent to storaye vessel 170.
The impurities, consisting principally of potassium salts and water solublelaromatic acids, are removed from purifier 160 ., .
.:

s~

through line 164. These impurities may be recycled to the autoclave.

In an alterna-te embodiment (not shown), if it is not desirable to remove the more soluble carboxylic acids from liquid stream 132, then stream 132 is fed directly to separator 190 instead of stream 142 for separation of acetic acid from potassium acetate. In this embodiment, elements 140, 142, 152, 160, 162, 164, and 170 are omitted.

Returning to separator 140, stream 142, which does not contain the separated aromatic carboxylic acid but which contains potassium acetate and acetic acid, is fed to separator 190 for separation of acetic acid from potassium acetate.
Acetic acid may be separated from potassium acetate in separator ~190 by distillation or by steam distillation, or by solvent extraction or by other standard procedures.

The separated acetic acid is removed from separator 190 through line 194 and is recycled to precipitator 120 through line 126. Make-up acetic acid may be added to precipitator 120 ~-through line 124.
: . :
Potassium acetate is removed from separator 190 through line 192 and enters reactor 200 whereupon it is treated with lime which is introduced to reactor 200 through line 196. The purpose of the lime treatment is to prevent buildup of sulfate in the recycle stream and thereby liberate potassium for recycle. Reactor 200 can be a continuous stirred tank reactor.

.. . . .

The product from reactor 200 is removed therefrom througA
line 202 and enters filter 210 whereupon calcium sulphate is separated as a solid from the li~uid stream containing the dissolved potassium acetate. Filter 210 may be any type, such 5l as a vacuum filter. Calcium sulphate is removed from filter 210 by line 212. The calcium sulphate may be used in the making of portland cement, gypsum or pool acid or disposed of i¦ by landfill. The potassium acetate stream is removed from !~ filter 210 through line 214 and is recycled to mixer 20.
10 ¦ Make-up potassium acetate may be added to mixer 20 through line 14.

Alternately, if there is no desire to produce isomerized carboxylic acids, stream 32 can be fed directly to filter 110 ll and the steps involving elements 40 through 102 are omitted.
15',, The alternate process is shown in Figure 2. This process, although similar, still has considerable value because of the regeneration and recycling of potassium acetate, line 214, to mixer 20 or, alternately, to autoclave 30 ~not shown). However, ~i by eliminating the isomerization step, an aromatic carboxylic 20 ~ acid of different constituents is produced and the yield of ¦ terephthalic acid will be reduced. This carboxylic acid mixture is useful in detergent manufacturing.

In an alternate embodiment of this invention, as shown I in Figure 2, the benzoic acid can be added directly to mixer 20 through line 16. The benzoic acid and potassium acid react to i form potassium benzoate under the temperature conditions l imposed in autoclave 30. In this embodiment, mixer 46 of ! Figure 1 is not required.
. ~ .

.
, ~L~,.oa~ 56 In an alternate embodiment, benzoic acid can be added directly to autoclave 30 through line 26.

Although the Figures illustrate the addition of benzoic acid at two specific locations in the process, it may occur to one skilled in the art to add benzoic acid at other locations prior to the isomerization reaction.

In another embodiment, the product from the isomerization reactor 80, preferably havin~ been cooled in cooler 90, dis- -solved in dissolver 100 and filtered in filter 110 to remove undissolved solids, is sent to a precipitator for treatment with ; carbon dioxide. ~n this embodiment, the precipitator is used to precipitate the monopotassium salt of terephthalic acid by -treatment with carbon dioxide. Thus, the aqueous solution containing dipotassium terephthalate in stream 112 is treated -; in the precipitator wi~h carbon dioxide to produce the mono-; potassium salt of terephthalic acid and potassium bicarbonate.In this embodiment, which is not shown in either Figure 1 or 2, acetic acid is not charged to the precipitator. The precipitator is maintained at a temperature below about 50QC, preferably below 30~C, and especially preferably at about 0C to enhance the dissolving of carbon dioxide in the solution.

The monopotassium salt of terephthalic acid, a precipitate, is separated from the aqueous solution of potassium bicarbonate in a separation zone which may be a filter. The separated monopotassium salt of terephthalic acid is then charged to a hydrolyzer where it is treated with water to form dipotassium . ~ ; , 5~;

terephthalate and terephthalic acid. The dipotassium tereph-thalate remains in solution while the terephthalic acid preci-pitates~ The terephthalic acid may then be separated from the dipotassium terephthalate solution and the dipotassium tereph-thalate solution recycled to the precipitator above, or treatedin another zone. In either case, the dipotassium terephthalate is treated with carbon dioxide to convert the dipotassium terephthalate to monopotassium salt of terephthalic acid and additional potassium bicarbonate.

The monopotassium salt of terephthalic acid can be neutral-ized by other means, if desired, such as treatment with carbon dioxide in an aqueous solution.
!
The potassium bicarbonate solution after separation from the monopotassium solid terephthalic acid can be recycled to mixer 20, or alternately to autoclave 30, as the water soluble reagent comprising a Group Ia or IIa metal. In this embodiment, the water soluble reagent comprising a Group Ia or IIa metal ~does not require the use of a formate, acetate or propionate of such metal.

Furthermore, in this embodiment the alkali metal reagent, which is potassium in the above description, is recovered and recycled in the process. As can be seen, no conversion of the potassium aromatic carboxylic acid salt prior to isomerization is required in the process. That is to say, it is not necessary to convert the potassium acid salt to a sodium acid salt, or vice versa, prior to isomerization.

:i `
.: . . , ,-, .: :

0~5~

The proeess of this invention has the advantage over prior art for producing terephthalic acid in that it is not necessary to prepare the salts of the aromatic earboxylie acids, then to separate the benzene earobyxlie aeids from the remaining polynuelear earboxylie aeids; and then to convert the benzene earboxylie acids to the potassium salt of the aeids prior to isomerization.

. .
Another advantage o~ this invention is that it is not neeessary to prepare the salts in a separate zone apart from the oxidation zone sinee in this invention the salts are t prepared direetly in the.oxidation zone.

Another advantage o~ this invention is that it is not .neeessary to t~eat the aromatic earboxylie aeid salts, or eonvert the aromatie carboxylic acid salts to their aromatie carboxylie acids and then treat, with a compound which contains a Group Ia or IIa metal prior to isomerization.

Similarly, another advantage o~ this invention is that it is not necessary to convert the aromatie carboxylic aeid salts to their aromatie earboxylie aeids and to treat the aromatic carboxylie aeids with a Group Ia or IIa metal prior to isomeri-zation.

....... ., . . .. ... . _ _ _ _ _ .. .. .. .. .

3L~Z~)~56 ;,1 1I Still another advantage of this invention is that after '` the aromatic material is oxidized in the presence of a first compound comprising a Group Ia or IIa metal to form an aromatic ~ carboxylic acid salt of the Group Ia or IIa metal, it is not 5 1 necessary to convert the aromatic carboxylic acid salt of the ~ Group Ia~or IIa metal to another aromatic carboxylic acid salt !~ of another Group Ia or IIa metal prior to isomerization.

¦¦ For example it is not necessary to first form a sodium l aromatic carboxylic acid salt and then to convert that salt to 10¦! a potassium aromatic carboxylic acid salt prior to isomerization of the salt.

Another advantage is that the reagent is regenerated by j the process.

EXAMPLE I

Regeneration of Reagent The following is an example of the conversion of an aromatic carboxylic acid with a metal acetate to a metal aromatic carboxylate followed by the conversion of the metal aromatic carboxylate by treating with an excess acetic acid to I convert the metal aromatic carboxylate to aromatic carboxylic 1, acid. (Thls corresponds to Step Nos. 30~ 40, 50, 60, 120, 130, 1 ~;
,l and 190 of the Figures.) 18.82 gr of dry reagent grade trimesic acid (1, 3, 5 'l benzene-tricarboxylic acid) was added to a flask together with `~ 39.50 gr of potassium acetate and 300 gr of water. This mixture was boiled until all of the trimesic acid was dissolved. ¦
(This corresponds to the state found in autoclave 30 of the 15 , Figures.) The mixture was then evaporated to dryness. It is estimated that at least 80% of the acid was converted to its ; potassium salt. (This corresponds to the state found in dryer 60 of the Figures.) The condensate consisted of acetic acid and water.

i Three extractions of the acid salt took place using 80 cm3 ! f a mixture containing 90~ glacial acetic acid and io~ by weight ;, of water for each extraction. Each extraction took place at , 60C with stirring for 15 minutes. Each time the acetic acid .. . .
- 31 - i `
''I i .',1 . I
, ~ZO~)~6 water mixture containing newly formed potassium acetate was passed through a 50-60 ASTM sintered glass filter, with the newly formed trimesic acid remaining behind. (This corresponds to steps 120 and 130 of the Figures.) The extract was evaporated to dryness by heating to 200C under vacuum. 37.53 gr of extract or 95% by weight of the original potassium acetate was recovered. The weight of i the remaining dry trimesic acid was 20.22 gr. It thus con-tained the remaining potassium. (This corresponds to step 190 of the Figures.) The fact that the reclaimed potassium acetate may contain some potassium trimesate and trimesic acid in this experiment , is of no consequence to the process of this invention because it is intended that the reclaimed potassium acetate be recycled.
15` However, should a higher reclamation factor be desired, the extraction with the acetic acid water mixture can be repeated i~
with the results being predicted by a fractionation curve as used in distillation.

EXAMPLE II

Oxidation of Coal~
.. . .
About 28 gr of coal, 170 gr of potassium acetate~ and 400 gr of water were charged to a stirred autoclave.

The mixture was treated with oxygen at a total pressure of 1700 psig at a temperature of 500F for 30 minutes with continuous stirring taking place.
.

.
.~' , I

5~

The autoclave contents were analyzed and 12.8 gr of coal acids were found to be present. About 6.4 gr of this was benzene-carboxylic acids, which represents a 28% yield on a dry ash free coal basis.

EXAMPLE III

~ Regeneration of Reagent, Specifically Potassium Acetate ! To demonstrate the regeneration of potassium acetate, the , following experiment was carried out~

! ~ .
! Pyromellitic acid, a typical constituent of coal acids, 10 was used. - -,.
18.82 gr of pyromellitic acid were reacted with 39~5 gr of potassium acetate to give 30.4 gr of tetrapotassium pyromellate ' -and an unmeasured amount of acetic acid. The acetic acid is recoverable by distillation. The salt was extracted with a water/acetic acid mixture, and 37.5 gr of potassium acetate was recovered.

The salt was converted back to pyromellitic acid. Thus, 95% potassium acetate was reclaimed after forming the potassium salt of pyromellitic acid.
,, j .
EXAMPLE IV

Precipitation of Aromatic Carboxylic Acid, Specifically Terephthalic Acid !
A prepared solution of potassium terephthalate consisting of 10 gr of potassium terephthalate in 100 gr of water was :, ' ~Z~)~56 treated with 100 ml of 6~ acetic acid solution and immediately produced 6.7 gr of a white precipitate of terephthalic acid.

EXAMPLE V

Isomerization of Coal Acids About 9.3 gr of coal acids were converted to their corresponding potassium salts. 0.5 gr of cadmium oxide was thoroughly mixed with the salts. The mixture was then dried to ilremove moisture.
.i ', The mixture was charged to an autoclave which was pres- i surized to 130 psig with carbon dioxide. It was heated to 400C and maintained at that temperature for four hours while at 130 psig.
, I !
After cooling, the mixture was dissolved in boiling water ! `
'and filtered to remove char containing the cadmium.

Upon acidification of the mixture with 100 ml of 6%
acetic acid solution, a yield of 3.2 gr of terephthalic acid was obtained. This corresponds to a 36~ yield from the coal acids.

, EXAMPLE VI

Conversion of Coal_to Terephthalic Acid 100 gr potassium acetate and 30 gr of bituminous coal are mixed with 400 gr of water. The mixture is charged to an oxidation autoclave and heated to 260C. Oxygen is slowly added to the autoclave until a total pressure of 1500 psig is 25 achieved. A product gas consisting of carbon dioxide, steam, _ 34 -. . .
~' I

, : : . :
' ' `'" ~' ' ' ~LZ~)~56 and acetic acid is periodically vented from the autoclave, and the autoclave is repressurized with oxygen to 1500 psig each time. After half an hour of treatment with o~ygen, the auto-clave contents are cooled to room temperature and discharged from the autoclave.

The oxidized mixture is dried by boiling until almost dry and the vapors condensed. A total of 407.6 gr of liquid condensate is collected by combining the condensate from the -product gas and the drying operation. The total condensate comprises of 16.6 gr of acetic acid. The moist oxidized mixture is thoroughly dried under vacuum for three hours.

About 2.0 gr of cadmium iodide, as catalyst, is intimately mixed with the dried, oxidized mixture. The mixture is then charged to an isomerization autoclave and heated to 150F.
Remaining moisture is purged from the autoclave using dry carbon dioxide. The autoclave is heated to 395C for 2.5 hours with 600 psig of carbon dioxide pressure.

The autoclave is then cooled to room temperature. The solid material is removed from the autoclave and dissolved in 100 gr of hot water. The solution is filtered to remove char and solidsO

The condensate from the oxidization and drying steps, which contains acetic acid, is added to the solution. A

precipitate of 10.2 gr of crude terephthalic acid is formed.
The terephthalic acid precipitate is separated by filtration.

.

The filtrate, or mother liquor, is evaporated to form a condensate containing 0.9 gr of acetic acid dissolved in 450 gr of water. 102 gr of solid residue, containing 98.5 gr of potassium acetate is obtained. The solid residue is recycled to the next oxidation step.

The 450 gr of water is reduced in weight to 400 gr and 1.5 gr of makeup potassium carbonate is added, converting the remaining acetic acid in solution to potassium acetate.
The solution is recycled to the oxidation step. It can be seen that nearly all of the original potassium acetate is recovered and recycled.

The following table summarizes the mass flows in Example VI.

Weight of Coal ~ 30.0 gr Weight of Potassium Acetate100.0 gr Weight of Recovered Potassium Acetate 9a.5 gr Weight of Unused Acetic Acid0.9 gr Weiyht of Potassium Carbonate Required to Regenerate Potassium Acetate from Acetic Acid 1.5 gr .
- ,~' ' ' .' ~

~ zo~56 EXAMPLE VII

The following experiment illustrates the yield of tereph-thalic acid obtained from a mixture of benzenecarboxylic acids and polyaromatic carboxylic acids obtained from the oxidation of coal in an aqueous caustic medium.

In a first experiment, a slurry of 10 gr of aromatic car- I ;
boxylic acids produced from the oxidation of coal, and having the composition as given below, was brought to a pH of 7.8 by ¦ -the addition of potassium carbonate.

Composition of Aromatic Carboxylic Acids Produced _ From the Oxidation of_Coal Acids Weight ~ Acid Polyaromatic Carboxylic 44.5 Benzene Carboxylic 47.5 lSIl Pyridine Carboxylic 4.2 I Thiophene Carboxylic 3.8 ''' 1 0 0 . 0 : ~ .

1.4 gr of cadmium iodide was added to the solution as a I catalyst. The ~nixture was then dried under vacuum at 110C for four hours. A11 traces of moisture were removed`from the mlxture during drying.

The dried mixture was then charged to a 2 liter autoclave, which was sealed and pressurized to 175 psig with carbon ' dioxide. The mixture was then heated at 400C for 1.5 hours to effect the isomerization of the acid salts.

,1 . .' .1 .

,: . -` ':

~Z~56 The resulting mixture was dissolved in water, filtered, and treated with acetic acid to yield a precipitate containing 0.8 gr of terephthalic acid.

By comparison, in a second experiment 10 gr of the above aromatic carboxylic acid produced from the oxidation of coal, and having the same composition as used with the above experi-ment, were mixed with 3 gr of benzoic acid. Exactly the same procedure was followed as in the first experiment, except that ¦1.82 gr of cadmium iodide were added to maintain a catalyst 10 ' concentration of 14% by weight of carboxylic acids. After isomerization, 3.3 gr of terephthalic acid were found to be present in the precipitate.

While we do not wish to be bound by theory, if benæoic acid produced terephthalic acid purely by a disproportionation 15 ; reaction with itself, i.e., 2 moles of benzoic acid producing 1 mole of terephthalic acid and 1 mole of benzene, then the 3 gr of benzoic acid could produce a maximum yield of terephthalate of 2.04 gr. The 2.04 gr theoretical maximum yield of tereph-thalic acid by disproportionation plus the 0.8 gr produced by 20 ; the first of the above experiments without benzoic acid total , 2084 gr, which is less than the 3.3 gr achieved in the second experiment.

Thus, the second experiment can be seen to produce a yield 16~ greater than the sum of the yield from the first experiment and the maximum theoretical yield based on a disproportionation of benzoic acid to terephthalic acid~

! `

` . ~

Rather than 100% of theoretical yield of terephthalic acid from benzoic acid by disproportionation, 57.6% was repo~ted in the Journal of the American Chemical Society, Volume 79, page 6006. Based on a 57.6% yield of terephthalic acid from benzoic S acid, 1.18 gr of terephthalic acid would be expected to be produced from 3 gr of benzoic acid. Adding the 1.18 gr to the 0.8 gr of terephthalic acid produced by the first experiment ` total to 1.98 grams. Therefore the second experiment can be seen to produce a yield 51~ greater than the sum of the yield from the first experiment and the expected yield based on a disproportionation reaction of benzoic acid to terephthalic ~ I
acid.

5~

EXAMPLE VIII

Conversi_n of Coal Char to Terephthalic Acid 100 gr potassium acetate and 30 gr of coal char are mixed with ~00 gr of water. The coal char is produced by pyrolyzing a bituminous coal at 1500F for 20 minutes in a fluidized bed reactor. The mixture is charged to an oxidation autoclave and heated to 260C. Oxygen is slowly added to the autoclave until a total pressure of 1500 psig is achieved.
A product gas consisting of carbon dioxide, steam, and acetic acid is periodically vented from the autoclave, and the auto-clave is repressurized with oxygen to 1500 psig each time.
After half an hour of treatment with oxygen, the autoclave contents are cooled to room temperature and discharged from the autoclave.

lS The oxidized mixture is dried by boiling until almost dry ~
and the vapors condensed. A total of 407.6 gr of liquid --condensate is collected by combining the condensate from the product gas and the drying operation. The total condensate comprises of 16.6 gr of acetic~ acid. The moist oxidized mixture is thoroughly dried under vacuum for three hours.

About 2.0 gr of cadmium iodide, as catalyst, is intimately mixed with the dried, oxidized mixture. The mixture is then charged to an isomerization autoclave and heated tc 150F.
Remaining moisture is purged from the autoclave using dry carbon dioxide. The autoclave is heated to 395C for 2.5 hours with 600 psig of carbon dioxide pressure.

~LZ~56 The autoclave is then cooled to room temperature. The solid material is removed from the autoclave and dissolved in 100 gr of hot water. The solution is filtered to remove char and solids.

The condensate from the o~idization and drying steps, which contains acetic acid, is added to the solution. A precipitate of 6.3 gr of crude terephthalic acid is formed~ The terephthalic acid precipltate is separated by filtration.

The filtrate, or mother liquor, is evaporated to form a condensate containing 0O9 gr of acetic acid dissolved in 450 gr of water. 102 gr of solid residue, containing 98.5 gr of potassiu~
acetate is obtained. The solid residue is recycled to the next o~idation step.

The 450 gr of water is reduced in weight to 400 gr and 1.5 gr of makeup potassium carbonate is added, converting the remaining acetic acid in solution to potassium acetate. The solution is recycled to the oxidation step. It can be seen that nearly all of the original potassium acetate is recovered and recycled.

The following table summarizes the mass flows in Example VIII.

Weight of Coal Char 30.0 gr Weight of Potassium Acetate100.0 gr Weight of Recovered Potassium Acetate 98.5 gr Weight of Unused Acetic Acid0.9 gr Weight of Potassium Carbonate Required to Regenerate Potassium Acetate from Acetic Acid 1.5 gr i ~ - ~

EXAMPLE I~

Con~ersion of Coal Tar to Terephthalic Acid 100 gr potassium acetate and 30 gr of coal tar are mixed with 400 gr of water. The coal tar is produced by pyrolyzing a bituminous coal to 1500F for 20 minutes in a fluidized bed, cooling the product vapors, and recovering the condensed coal tar. The mixture is charged to an oxidation autoclave and heated to 260C. Oxygen is slowly added to the autoclave until a total pressure of 1500 psig is achieved. A product gas consisting of carbon dioxide, steam, and acetic acld is periodically vented from the autoclave, and the autoclave is repressurized with oxygen to 1500 psig each time. After half an hour of treatment with oxygen, the autoc~ave contents are ~cooled to room temperature and discharged from the autoclave.

lS The oxidized mixture is dried by boiling until almost dry and the vapors condensed. A total of 407.6 gr of liquid condensate is collected by combining the condensate from the product gas and the drying operation. The total condensate comprises of 16.6 gr of acetic acid. The moist oxidized ~mixture is thoroughly dried under vacuum for three hours.
' About 2.0 gr of cadmium iodide, as catalyst, is intimately mixed with the dried, oxidized mixture. The mixture is then charged to an isomeri2ation autoclave and heated to 150F.
Remaining moisture is purged from the autoclave using dry carbon dioxide. The autoclave is heated to 395C for 2.5 hours with 600 psig of carbon dioxide pressure.

, ''' ., ~L~,f~ ~5~6 The autoclave is then cooled to room temperature. The solid material is removed from the autoclave and dissolved in 100 gr of hot water. The solution is filtered to remove char and solids.

The condensate from the oxidization and drying steps, which contains acetic acid, is added to the solution. A precipitate of 11.8 gr of crude terephthalic acid is formed. The terephthalic acid precipitate is separated by filtration.

The filtrate, or mother liquor, is evaporated to form a condensate containing 0.9 gr of acetic acid dissolved in 450 gr of water. 102 gr of solid residue, containing 98.5 gr of potassium `acetate is obtained. The solid residue is recycled to the next oxidation step.

The 450 gr of water is reduced in weight to 400 gr and 1.5 gr of makeup potassiu~ carbonate is added, converting the remaining acetic acid in solution to potassium acetate. The solution is recycled to the oxldation step. It can be seen that nearly all of the original potassium acetate is recovered and recycled.

The following table summarizes the mass flows in Example IX.

Weight of Coal Tar 30.0 gr Weight of Potassium Acetate lO0.0 gr Weight of Recovered Potassium Acetate 98.5 gr Weight of Unused Acetic Acid O.g gr Weight of Potassium Carbonate Required to Regenerate Potassium Acetate from Acetic Acid 1.5 gr 5~

EXAMPL~ X

Conversion of Heavy Residual Oil to Terephthalic Acid 100 gr potassium acetate and 30 gr of heavy residual oil from a naphthenic crude oil are mixed with ~00 gr of water.
The mixture is charged to an oxidation autoclave and heated to 260C~ Oxygen is slowly added to the autoclave until a total pressure of 1500 psig is achieved. A product gas consisting of carbon dioxide, steam, and acetic acid is periodically vented ; -from the autoclave, and the autoclave is repressurized with ~ -oxygen to 1500 psig each time~ After half an hour of treatment with oxygen, the autoclave contents are cooled to room tempera-ture and discharged from the autoclave.

The oxidized mixture i5 dried by boiling until almost dry and the vapors condensed. A total of 407.6 gr of liquid condensate is collected by combining the condensate from the product gas and the drying operation. The total condensate comprises of 16.6 gr of acetlc acid. The moist oxidized mixture is thoroughly dried under vacuum for three hours.

About 2.0 gr of cadmium iodide, as catalyst, is intimately mixed with the dried, oxidized mixture. The mixture is then charged to an isomerization autoclave and heated to 150F.
Remaining moisture is purged from the autoclave using dry carbon dioxide. The autoclave is heated to 395C for 2.5 hours with 600 psig of carbon dioxide pressure.

- 44 - `

~ -The autoclave is then cooled to room temperature. The solid material is removed from the autoclave and dissolved in 100 gr o hot water. The solution is filtered to remove char and solids.

The condensate from the oxidization and drying steps, which contains acetic acid, is added to the solution. A precipitate of 3.8 gr of crude terephthalic acid is formed. The terephthalic acid precipitate is separated by filtration.

The filtrate, or mother liquor, is evaporated to form a condensate containing 0.9 gr of acetic acid dissolved in 450 gr of water. 102 gr of solid residue~ containing 98.5 gr of potassium acetate is obtained. The solid residue is recycled to the next oxidation step.

The 450 gr of water is reduced in weight to 400 gr and 1.5 gr of makeup potassium carbonate is added, converting the remaining acetic acid in solution to potassium acetate. The solution is recycled to the oxidation step. It can be seen that nearly all of the original potassium acetate is recovered and recycled.

The following table summarizes ~he mass flows in Example X. :

Weight of Heavy Residual Oil 30.0 gr Weight of Potassium Acetate 100.0 gr Weight of Recovered Potassium Acetate98.5 gr Weight of Unused Acetic Acid 0.9 gr Weight of Potassium Carbonate Required to Regenerate Potassium Acetate from Acetic Acid 1.5 gr o~6 EXAMPLE XI

Conversion of Dipotassium Terephthalate to Terephthalic Acid Using Carbon Dioxide 29 gr of dipotassium terephthalate were dissolved in 200 ml of hot deionized water and the solution was filtered to remove any insoluble solids. Carbon dioxide was bubbled through the solution as it was cooled in an ice bath. White crystals immediately began to form. After the suspension of crystals in the solution had cooled to a temperature of less than -2C (28F) and let stand for thirty minutes, it was then vacuum filtered. The white needles on the filter were washed with ice water, dried in a vacuum oven, and weighed. Approxi-mately 16.2 gr of precipitate were recovered. A sample was analyzed and found to have the composition: !

Ele % by Weight C 47.4 H 2.8 K 18.1 0 31.7 (by difference) Pure potassium hydrogen terephthalate has the following composition:

Element~ by Wei~ht C 47.0 H 2.5 K 19.2 0 31.3 Thus, the precipitate is potassium hydrogen terephthalate.

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The potassium hydrogen terephthalate was then dissolved in 160 ml of water and boiled for 5 minutes. About 6.5 gr of terephthalic acid were recovered by filtering the solution.
The solution, which contains dipotassium terephthalate, can be S concentrated and recycled to the carbon dioxide precipitation step.

EXAMPLE XII

Conversion of Dipotassium Terephthalate to_Terephthalic Acid Using Carbon Dioxide 29 gr of dipotassium terephthalate were dissolved in 200 ml of hot deionized water and the solution was filtered to remove any insoluble solids. Carbon dioxide was then bubbled through the solution (cooled to 25C) in a pressure filtration apparatus at 800 psig. About 20 gr of potassium hydrogen terephthalate were recovered after filtration. This was then dissolved in 200 ml of water and boiled for five minutes.
About 8.0 gr of terephthalic acid were recovered by filtration of the solution.

The process of the invention has been described generally and by example with reference of clarity and illustration only.
It will be apparent to those skilled in the art from the foregoing that various modifications of the process and the S materials disclosed herein can be made without departure from the spirit of the invention.
. ~

Accordingly, the invention is not to be construed or limited to the specific embodiments illustrated, but only as -de~ined in the following claims.
_ . _ . ~ . _ . . .. ... _ . .. , _ _ . , , . , . . I

Claims

What is claimed is:

1. A process for producing isomerized aromatic carboxylic acid from aromatic materials comprising:
a. treating a mixture of an aromatic material, water, and a water soluble reagent comprising a Group Ia or IIa metal, said reagent producing an alkaline solution by hydrolysis, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said Group Ia or IIa metal of said reagent;
b. mixing benzoic acid with said mixture;
c. isomerizing said aromatic carboxylic acid salt by heating to produce an isomerized aromatic carboxylic acid salt without converting said aromatic carboxylic acid salt to an aromatic carboxylic acid salt of a different Group Ia or IIa metal prior to isomerizing said aromatic carboxylic acid salt;
d. converting said isomerized aromatic carboxylic acid salt to isomerized aromatic carboxylic acid, and regenerating said reagent comprising said Group Ia or IIa metal;
e. recovering said isomerized aromatic carboxylic acid;
and f. recycling said reagent comprising said Group Ia or IIa metal thusly regenerated to step (a) to supply a portion of said reagent required for producing said aromatic carboxylic acid salt.

2. The process of claim 1 wherein said aromatic material is coal.

3. The process of claim 1 wherein said Group Ia or IIa metal is potassium.

4. The process of claim 3 wherein said aromatic material is coal.

5. The process of claim 1 wherein said benzoic acid is mixed with said mixture and said mixture is treated with oxygen.

6. The process of claim 1 wherein said benzoic acid is mixed with said mixture after said mixture is treated with oxygen.

7. A process for producing isomerized aromatic carboxylic acid from aromatic materials comprising:
a. treating a mixture of i. an aromatic material, ii. water, and iii. a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said reagent;
b. mixing benzoic acid with said mixture after treating in step (a);
c. removing sufficient water from said mixture from step (b) so that said aromatic carboxylic acid salt in said mixture can be isomerized;
d. forming an isomerized aromatic carboxylic acid salt from said aromatic carboxylic acid salt by heating said mixture from step (c) to a temperature suffi-ciently high in the presence of a catalyst;
e. treating said mixture from step (d) with an acid of said reagent to convert at least a portion of said isomerized aromatic carboxylic acid salt to isomerized aromatic carboxylic acid, and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
and f. separating said isomerized aromatic carboxylic acid formed in step (e) from said reagent.

8. The process of claim 7 wherein said aromatic material is coal.

9. The process of claim 7 wherein said reagent is potassium acetate.

10. The process of claim 7 further comprising recovering and recycling said reagent from step (f) to step (a) to provide at least part of said reagent of said mixture.

11. The process of claim 7 wherein step (e) is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

12. The process of claim 7 wherein carbon dioxide is formed in step (a) and further comprising removing a gas stream comprising carbon dioxide from said mixture in step (a).

13. A process for producing isomerized aromatic carboxylic acid from aromatic materials comprising:
a. treating a mixture of i. an aromatic material, ii. water, and iii. a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said reagent;

_ 52 -b. mixing benzoic acid with said mixture after treating in step (a);
c. removing sufficient water from said mixture from step (b) so that said aromatic carboxylic acid salt in said mixture can be isomerized;
d. forming an isomerized aromatic carboxylic acid salt from said aromatic carboxylic acid salt by heating said mixture from step (c) to a temperature suffi-ciently high in the presence of a catalyst;
e. treating said mixture from step (d) with an acid of said reagent to convert at least a portion of said isomerized aromatic carboxylic acid salt to isomerized aromatic carboxylic acid, and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
f. separating said isomerized aromatic carboxylic acid formed in step (e) from said mixture from step (e), thereby forming a first stream containing the thusly separated isomerized aromatic carboxylic acid and a second stream comprising said reagent and said acid of said reagent;
g. separating said acid of said reagent from said reagent;
h. recycling said thusly separated reagent from step (g) to step (a) to provide at least part of said reagent of said mixture; and i. recycling said thusly separated acid of said reagent from step (g) to step (e) to provide at least part of said acid of said reagent required for step (e).

14. The process of claim 13 wherein said aromatic material is coal.

15. The process of claim 13 wherein said aromatic material is bituminous coal.

16. The process of claim 13 wherein said reagent is potassium acetate.

17. The process of claim 13 wherein said catalyst is cadmium benzoate.

18. The process of claim 13 wherein said catalyst is cadmium iodide.

19. The process of claim 13 wherein step (e) is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

20. The process of claim 13 wherein carbon dioxide is formed in step (a) and further comprising removing a gas stream comprising carbon dioxide from said mixture in step (a).

21. The process of claim 13 wherein said aromatic material is bituminous coal and said reagent is potassium acetate.

22. A process for producing isomerized aromatic carboxylic acid from aromatic materials comprising:
a. treating a mixture of i. an aromatic material, ii. water, iii. a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, and iv. benzoic acid, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said reagent;
b. removing sufficient water from said mixture from step (a) so that said aromatic carboxylic acid salt in said mixture can be isomerized;
c. forming an isomerized aromatic carboxylic acid salt from said aromatic carboxylic acid salt by heating said mixture from step (b) to a temperature suffi-ciently high in the presence of a catalyst;
d. treating said mixture from step (c) with an acid of said reagent to convert at least a portion of said isomerized aromatic carboxylic acid salt to isomerized aromatic carboxylic acid, and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
and e. separating said isomerized aromatic carboxylic acid formed in step (d) from said reagent.

23. The process of claim 22 wherein said aromatic material is coal.

24. The process of claim 22 wherein said reagent is potassium acetate.

25. The process of claim 22 further comprising recovering and recycling said reagent from step (e) to step (a) to provide at least part of said reagent of said mixture.

26. The process of claim 22 wherein step (d) is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

27. The process of claim 22 wherein carbon dioxide is formed in step (a) and further comprising removing a gas stream comprising carbon dioxide from said mixture in step (a).

28. A process for producing isomerized aromatic carboxylic acid from aromatic materials comprising:
a. treating a mixture of i. an aromatic material, ii. water, iii. a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, and iv. benzoic acid, with oxygen under conditions sufficient to convert at least a portion of said aromatic material to an aromatic carboxylic acid salt of said reagent;

b. removing sufficient water from said mixture from step (a) so that said aromatic carboxylic acid salt in said mixture can be isomerized;
c. forming an isomerized aromatic carboxylic acid salt from said aromatic carboxylic acid salt by heating said mixture from step (b) to a temperature suffi-ciently high in the presence of a catalyst;
d. treating said mixture from step (c) with an acid of said reagent to convert at least a portion of said isomerized aromatic carboxylic acid salt to isomerized aromatic carboxylic acid, and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
e. separating said isomerized aromatic carboxylic acid formed in step (d) from said mixture from step (d), thereby forming a first stream containing the thusly separated isomerized aromatic carboxylic acid and a second stream comprising said reagent and said acid of said reagent;
f. separating said acid of said reagent from said reagent;
g. recycling said thusly separated reagent from step (f) to step (a) to provide at least part of said reagent of said mixture; and h. recycling said thusly separated acid of said reagent from step (f) to step (d) to provide at least part of said acid of said reagent required for step (d).

29. The process of claim 28 wherein said aromatic material is coal.

30. The process of claim 28 wherein said aromatic material is bituminous coal.

31. The process of claim 28 wherein said reagent is potassium acetate.

32. The process of claim 28 wherein said catalyst is cadmium benzoate.

33. The process of claim 28 wherein said catalyst is cadmium iodide.

34. The process of claim 28 wherein step (d) is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

35. The process of claim 28 wherein carbon dioxide is formed in step (a) and further comprising removing a gas stream comprising carbon dioxide from said mixture in step (a).

36. The process of claim 28 wherein said aromatic material is bituminous coal and said reagent is potassium acetate.

37. In a process for producing isomerized aromatic carboxylic acid from aromatic material wherein carbonaceous material is oxidized in an aqueous-caustic environment to produce an aromatic carboxylic acid salt and the aromatic carboxylic acid salt is isomerized in the presence of a catalyst, the improvement which comprises oxidizing an aromatic material in the presence of a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, to form an aromatic carboxylic acid salt of said reagent, mixing benzoic acid with said mixture;
isomerizing said aromatic carboxylic acid salt produced by the oxidation of the aromatic material in the presence of said reagent without treating said aromatic carboxylic acid salt, or converting said salt to its aromatic carbox-ylic acid and treating, with a compound which contains a Group Ia or IIa metal prior to isomerization; and separating said isomerized aromatic carboxylic acid formed from said reagent.

38. The process of claim 37 wherein said aromatic material is coal and said reagent is potassium acetate.

39. The process of claim 37 further comprising recovering and recycling said reagent to provide at least part of said reagent used during oxidation of said aromatic material.

40. The process of claim 37 wherein said reagent after separating from said isomerized aromatic carboxylic acid is in a mixture which comprises said acid of said reagent;
and further comprising treating said isomerized aromatic carboxylic acid salt with an acid of said reagent to form isomerized aromatic carboxylic acid and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
separating said acid of said reagent from said reagent;
recycling said thusly separated reagent to provide at least part of said reagent used during oxidation of said aromatic material; and recycling said thusly separated acid of said reagent to provide at least part of said acid of said reagent required for precipitating said isomerized aromatic carboxylic acid.

41. The process of claim 40 wherein said treating of said isomerized aromatic carboxylic acid salt with an acid of said reagent is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

42. In a process for producing isomerized aromatic carboxylic acid from aromatic material wherein carbonaceous material is oxidized in an aqueous-caustic environment to produce an aromatic carboxylic acid salt and the aromatic carbox-ylic acid salt is isomerized in the presence of a catalyst, the improvement which comprises oxidizing benzoic acid and an aromatic material in the presence of a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, to form an aromatic carboxylic acid salt of said reagent; isomerizing said aromatic carboxylic acid salt produced by the oxidation of the aromatic material in the presence of said reagent without treating said aromatic carboxylic acid salt, or converting said salt to its aromatic carboxylic acid and treating, with a compound which contains a Group Ia or IIa metal prior to isomerization; and separating said isomerized aromatic carboxylic acid formed from said reagent.

43. The process of claim 42 wherein said aromatic material is coal and said reagent is potassium acetate.

44. The process of claim 42 further comprising recovering and recycling said reagent to provide at least part of said reagent used during oxidation of said aromatic material.

45. The process of claim 42 wherein said reagent after separating from said isomerized aromatic carboxylic acid is in a mixture which comprises said acid of said reagent;
and further comprising treating said isomerized aromatic carboxylic acid salt with an acid of said reagent to form isomerized aromatic carboxylic acid and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
separating said acid of said reagent from said reagent;
recycling said thusly separated reagent to provide at least part of said reagent used during oxidation of said aromatic material; and recycling said thusly separated acid of said reagent to provide at least part of said acid of said reagent required for precipitating said isomerized aromatic carboxylic acid.

45. The process of claim 45 wherein said treating of said isomerized aromatic carboxylic acid salt with an acid of said reagent is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

47. In a process for producing isomerized aromatic carboxylic acid from aromatic material wherein carbonaceous material is oxidized in an aqueous-caustic environment to produce an aromatic carboxylic acid salt and the aromatic carbox-ylic acid salt is isomerized in the presence of a catalyst, the improvement which comprises oxidizing an aromatic material in the presence of a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, to form an aromatic carboxylic acid salt of said reagent, mixing benzoic acid with said mixture;
isomerizing said aromatic carboxylic acid salt produced by the oxidation of the aromatic material in the presence of said reagent without converting said aromatic carboxylic acid salt to aromatic carboxylic acid and treating said aromatic carboxylic acid with a compound which contains a Group Ia or IIa metal prior to isomerization; and separating said isomerized aromatic carboxylic acid formed from said reagent.

48. The process of claim 47 wherein said aromatic material is coal and said reagent is potassium acetate.

49. The process of claim 47 further comprising recovering and recycling said reagent to provide at least part of said reagent used during oxidation of said aromatic material.

50. The process of claim 47 wherein said reagent after separating from said isomerized aromatic carboxylic acid is in a mixture which comprises said acid of said reagent;

and further comprising treating said isomerized aromatic carboxylic acid salt with an acid of said reagent to form isomerized aromatic carboxylic acid and said reagent, and to precipitate said isomerized aromatic carboxylic acid;
separating said acid of said reagent from said reagent;
recycling said thusly separated reagent to provide at least part of said reagent used during oxidation of said aromatic material; and recycling said thusly separated acid of said reagent to provide at least part of said acid of said reagent required for precipitating said isomerized aromatic carboxylic acid.

51. The process of claim 50 wherein said treating of said isomerized aromatic carboxylic acid salt with an acid of said reagent is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

52. In a process for producing isomerized aromatic carboxylic acid from aromatic material wherein carbonaceous material is oxidized in an aqueous-caustic environment to produce an aromatic carboxylic acid salt and the aromatic carbox-ylic acid salt is isomerized in the presence of a catalyst, the improvement which comprises oxidizing benzoic acid and an aromatic material in the presence of a water soluble reagent comprising a Group Ia or IIa metal formate, acetate, or propionate, said reagent producing an alkaline solution by hydrolysis, to form an aromatic carboxylic acid salt of said reagent; isomerizing said aromatic carboxylic acid salt produced by the oxidation of the aromatic material in the presence of said reagent without converting said aromatic carboxylic acid salt, or con-verting said salt to aromatic carboxylic acid and treating said aromatic carboxylic acid with a compound which contains a Group Ia or IIa metal prior to isomerization;
and separating said isomerized aromatic carboxylic acid formed from said reagent.

53. The process of claim 52 wherein said aromatic material is coal and said reagent is potassium acetate.

54. The process of claim 52 further comprising recovering and recycling said reagent to provide at least part of said reagent used during oxidation of said aromatic material.

55. The process of claim 52 wherein said reagent after separating from said isomerized aromatic carboxylic acid is in a mixture which comprises said acid of said reagent;
and further comprising treating an isomerized aromatic carboxylic acid salt with an acid of said reagent to form isomerized aromatic carboxylic acid and said reagent, and to precipitate said isomerized aromatic carboxylic acid, separating said acid of said reagent from said reagent;
recycling said thusly separated reagent to provide at least part of said reagent used during oxidation of said aromatic material; and recycling said thusly separated acid of said reagent to provide at least part of said acid of said reagent required for precipitating said isomerized aromatic carboxylic acid.

56. The process of claim 55 wherein said treating of said isomerized aromatic carboxylic acid salt with an acid of said reagent is conducted at a pH of about 4.7 to about 5.5 and said precipitated isomerized aromatic carboxylic acid is terephthalic acid.

57. The process of claim 1 wherein said reagent comprises potassium carbonate.

58. The process of claim 1 wherein said reagent comprises potassium bicarbonate.

59. The process of claim 3 wherein said isomerized aromatic carboxylic acid salt comprises dipotassium terephthalate and wherein said dipotassium terephthalate is treated in an aqueous solution with carbon dioxide to produce an acid potassium terephthalate and potassium bicarbonate, said acid potassium terephthalate is converted to terephthalic acid, and said potassium bicarbonate is used as said potassium reagent.

60. The process of claim 59 wherein said acid potassium terephthalate is converted to terephthalic acid by treat-ment with carbon dioxide.

61. The process of claim 59 wherein said acid potassium terephthalate is converted to terephthalic acid by hydrolyzing with water.

62. The process of claim 1 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

63. The process of claim 7 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

64. The process of claim 13 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

65. The process of claim 22 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

66. The process of claim 28 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

67. The process of claim 37 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

68. The process of claim 42 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

69. The process of claim 47 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.

70. The process of claim 52 wherein said isomerized aromatic carboxylic acid comprises terephthalic acid.