WO2014121911A1

WO2014121911A1 - Method for selectively removing catalyser components from effluents of oxidation reactions of aromatic compounds, installation suitable therefor and use thereof

Info

Publication number: WO2014121911A1
Application number: PCT/EP2014/000267
Authority: WO
Inventors: Harald KÖMPEL; Ferdinand Rudolf Reif
Original assignee: Thyssenkrupp Industrial Solutions Ag
Priority date: 2013-02-05
Filing date: 2014-02-03
Publication date: 2014-08-14
Also published as: DE102013001972A1

Abstract

Disclosed is a method for purifying effluents, which contain catalyser residues, from installations for producing carbocyclically aromatic mono- or polycarboxylic acids or heterocyclically aromatic mono- or polycarboxylic acids by oxidating precursors of said mono- or polycarboxylic acids, which contain alkyl-, hydroxyalkyl-, alkoxyalkyl-, aldehyde- and/or carboxylic acid ester groups, in the presence of catalysers which contain heavy metal cations. The method is characterised in that at least one effluent from the oxidation process is brought into contact with a chelating ion exchanger that removes selected heavy metal cations selectively from the effluent such that the catalyser components can be recycled into the process, thus reducing the need for fresh catalyser. The method allows for the very efficient removal of toxic and/or expensive heavy metal cations from the effluent.

Description

description

5

Process for the selective removal of catalyst constituents from effluents of oxidation reactions of aromatic compounds, suitable plant and process

Use o The invention relates to a process for the recovery of catalyst constituents from arylcarboxylic or heteroarylcarboxylic acid plants, in particular from phthalic acid and isophthalic acid plants, and to a device suitable therefor.

Arylcarboxylic acids, such as phenylmono- or naphthylmono- or -dicarboxylic acids,

5 are obtained industrially by the catalytic oxidation of alkyl aromatics.

Thus, for example, phthalic acid or terephthalic acid can be prepared by oxidation of ortho-xylene or para-xylene or of tolyl ortho- or para-benzoic acid (ester) with the aid of catalysts. In the production of terephthalic acid, the catalysts used are usually combinations of cobalt and

: o manganese cations, as well as bromide anions or cobalt cations with a co-oxidant, for example acetaldehyde. The oxidation is generally carried out in solution using, for example, acetic acid as the solvent. In the production of phthalic acid, vanadium-containing compounds or else cobalt and manganese cations and bromine ion-containing compounds are frequently used as the oxidation catalysts. An overview of the oxidation of alkylaromatics is given in a review article by Rao et al. in E-Journal of Chemistry, Vol. 4, no. 1, pp. 1-13, January 2007.

Instead of alkylaromatics it is also possible to use aromatics with precursors of carboxylic acid groups, such as hydroxyalkyl groups, alkoxyalkyl groups and / or aldehyde groups.

CONFIRMATION COPY Analogous oxidation reactions can also be carried out on alkyl, hydroxyalkyl, alkoxyalkyl or aldehyde heteroaromatics. An example of this is the oxidation of dimethylfuran or of dihydroxyalkyl furan to furandicarboxylic acid.

5 The catalysts used in these oxidation reactions contain heavy metal cations, preferably cobalt and manganese cations, and can be carried out analogously to the oxidation of alkylbenzenes to benzene carboxylic acids.

Terephthalic acid is mainly used for the preparation of saturated polyesters with o aliphatic diols as comonomer, for example for the production of polyethylene terephthalate or of polybutylene terephthalate. To prepare the polyesters, the terephthalic acid esters, such as bis (hydroxyethyl) terephthalate or, in particular, dimethyl terephthalate, are frequently used as intermediates. Further

Areas of application of terephthalic acid is the production of aromatic polyamides, such as polyphenylene terephthalamide, eg. B for the production of highly tear-resistant fibers.

Phthalic acid is also a commonly used intermediate in the chemical industry, for example for the production of polyester resins, as a starting material for the preparation of many dyes, color pigments or plasticizers.

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Phthalic or terephthalic acid plants are often coupled with an esterification step, in which diester, for example dimethyl terephthalate, is produced from the dicarboxylic acid. Examples of such systems are described in DE 197 50 491 A1 and DE 197 52 722 C1.

! 5

In phthalic acid or terephthalic acid plants or in combinations of these systems with esterification stages in addition to the actual preparation of the dicarboxylic acid or its esters usually also one or more purification stages downstream, wherein, for example, pure terephthalic acid (hereinafter "PTA" called) or io pure terephthalic acid esters are produced An example of such a system is described in DE 39 04 586 A1. In the processes for the oxidation of (hetero) aromatics to the corresponding aromatic or heteroaromatic carboxylic acids, for example in the PTA process, process wastewater streams are produced, the traces of which are in the oxidation catalyst

contained heavy metal cations. In the case of phthalic acid and the

5 Terephthalic acid production is in the process waste water traces of the im

Oxidation catalyst contained cobalt and possibly manganese present. In a typical PTA process, cobalt acetate and manganese acetate are used for the

Preparation of terephthalic acid used as a catalyst. A portion of the dissolved acetate is discharged with the produced, poorly soluble terephthalic acid from the o oxidation reactor, typically a stirred reactor. In the

Work-up of the reaction product produces process wastewater. This contains a small amount of catalyst residues, which are typically on the order of about 10 ppm by weight. The metal (s) are dissolved as 2 ⁺ cations in the water.

5

In known processes, metal cations in process wastewater are removed by means of a so-called softener cation exchanger. Weakly acidic ion exchangers are used, but they do not selectively remove the cobalt and possibly the manganese. Other metal cations, eg Cr ² *, Mo ²⁺ and Ni ²⁺ , eg from

0 corroding stainless steels, as well as Ca ²⁺ or Fe ²⁺ are also on the

adsorbed ion exchanger resin. When the resin is regenerated, a solution of these metal cations is formed. The entire solution can not be returned to the reactor, as this would lead to a concentration of other, just mentioned metal cations. So at least a part has to be removed. There

If this heavy current is now loaded with heavy metal, it must be evaporated and disposed of, which entails high costs.

The same problem arises in the reprocessing of the catalyst in the oxidation processes of alkylaromatics or alkyl heteroaromatics. In these processes, o becomes the catalyst discharged with the effluent from the oxidation reactor

recovered and returned to the process. This recovery is generally carried out in a reclamation plant for the oxidation system the catalyst, a CRU (catalyst recovery unit), which can alternatively be operated spatially separated from the oxidation system. In the CRU, process wastewater, which is much heavier loaded with heavy metals, accumulates than in the other process effluents, which are discharged from the plant. Typical concentrations of 5 catalyst residues in the wastewater stream from the CRU amount to one

Order of magnitude of about 1000 wt. Ppm. The metal (s) are dissolved as 2 ⁺ cations in the water. The recoverable amount of heavy metal cations is significantly higher for the wastewater from the CRU than for the other process wastewater. o Another problem arises from the nature of the work-up process in the recovery of the catalyst. So far, the heavy metal cations-containing effluent from the oxidation plant in the CRU is separated by precipitation and subsequent filtration of the effluent. The filter residue is then worked up, so that the catalyst can then be recycled back into the process. It

5 would be desirable if a considerably simpler recovery process were available, in which the costly felling, filtration and processing can be omitted or the recovery process can be simplified.

Of the metal cations originating from the oxidation process, for example the process for the preparation of phthalic acid or terephthalic acid, and present in the effluents, especially cobalt must be removed, since this is toxic even in low concentrations. As a rule, today's sewage limits are between 0.1 and 1 mg / l, depending on the country, so that measures must be taken

To lower concentration. The disadvantage of the method practiced hitherto is that, in the regeneration of the softener cation exchanger, a regenerate with all bivalent metal cations is obtained as waste stream, which must be further processed, e.g. by evaporation in order to separate the metal salts and dispose of them in a landfill.

10 Processes for the recovery of catalyst components are known. Thus, DE 10 2008 040 884 A1 discloses a process for the recovery of molybdate or

Tungstate from aqueous solutions with the aid of water-insoluble, cationized inorganic carrier materials. DE 100 08 904 A1 discloses a method for

Recovery of catalyst transition metals described as salt-containing reaction mixtures. For this purpose, transition metal compounds and salts with organic impurities are separated from the reaction mixture and burned. 5 The combustion zone leaves a flue gas-salt mixture, which is mixed with water

is quenched; from the quench brine obtained is the transition metal-containing

Combustion residue separated, dried and used as feed for the

Catalyst production reused. o It has now surprisingly been found that the work-up of effluents from the oxidative preparation of arylcarboxylic acids or of heteroarylcarboxylic acids can be decisively improved if an adsorbent is used which binds selectively selected heavy metal cations.

It has also been found that the recovery of heavy metal catalyst cations and the recovery of catalyst components in the CRU of a plant for the oxidative production of arylcarboxylic acids or heteroarylcarboxylic acids can be accomplished by an adsorbent which selectively binds selected heavy metal cations.

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The present invention relates to a process for the purification of effluents containing catalyst residues from plants for the production of carbocyclic-aromatic mono- or polycarboxylic acids or heterocyclic-aromatic monocarboxylic or polycarboxylic acids by oxidation of alkyl, hydroxyalkyl, alkoxyalkyl, aldehyde

! 5 and / or carboxylic ester groups containing precursors of these mono- or

Polycarboxylic acids in the presence of heavy metal cations containing catalysts. The inventive method is characterized in that at least one effluent from the oxidation process is brought into contact with a chelating ion exchanger, which selectively selected heavy metal cations from the

! 0 outflow away. Such adsorbents, so-called "chelating" resins are known and have been developed for metallurgical plants such as cobalt production. Examples of such adsorbents can be found in DE 10 2007 034 744 A1 and in DE 101 21 163 A1.

5 If such chelating resins according to the invention for the purification of

Effluents used, such as process effluents or residues for the recovery of the catalyst from the oxidation process of (hetero) aromatics or from the effluent from the oxidation process of (hetero) aromatics intended for the recovery of the catalyst, there are two major advantages. Since only selected heavy metal cations are removed, for example, only cobalt and manganese cations, but not the other metal ²⁺ ions, the regenerate obtained from the ion exchanger is not considered waste. Especially at

Regeneration with acids, such as acetic or hydrobromic acid, directly (re) attract the catalyst constituents cobalt II and manganese II acetate or bromide,

5 which can be returned to the oxidation process. In the usual non-selective removal of all metal 2+ ions using conventional

Ion exchanger is such a circuit only partially or not at all possible, otherwise calcium or iron or other corrosion metals of stainless steels or other metallic materials would accumulate in the process streams.

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Another advantage is the elimination of the costs for the treatment of the waste-regenerated stream, for example the elimination of the evaporation of this stream and the elimination of the costs for the landfill of metal salts.

The process according to the invention thus permits, in addition to the simple purification of effluents from the oxidation process, a simple recovery of

Catalyst (s), by selective separation of selected heavy metal cations from the effluent and by simple regeneration of the loaded ion exchanger. This allows for direct recycling of catalyst (s) into the oxidation process thus and reduces the need for expensive fresh catalyst. The process according to the invention can be used in all oxidation processes

Manufacture of arylcarboxylic acids or heteroarylcarboxylic apply in which heavy metal cations containing catalysts are used.

For the purposes of this description, arylcarboxylic acids are to be understood as meaning all carbocyclic-aromatic monocarboxylic or polycarboxylic acids. These may be mononuclear or polynuclear carbocyclic aromatic compounds. at

polynuclear systems, the individual carbocyclic-aromatic rings may be fused or they are covalently bound to each other via C-C bonds or via bridging groups, such as -O-, o -CH ₂ -, -S- or -NH-. Examples of preferred

Carbocyclic-aromatic systems are naphthyl radicals or in particular phenyl radicals. These preferably carry three or especially two or one carboxyl group.

For the purposes of this description, heteroarylcarboxylic acids are understood as meaning all heterocyclic mono- or polycarboxylic acids. These may be mono- or polynuclear heterocyclic-aromatic compounds. at

polynuclear systems, the individual heterocyclic-aromatic rings may be fused or they are covalently bound to each other via C-C bonds or bridging groups, such as -O-, -CH ₂ -, -S- or -NH-. Combinations of carbocyclic-aromatic and heterocyclic-aromatic radicals may also be present.

The heteroaromatic rings usually have one to three heteroatoms,

preferably oxygen, sulfur or nitrogen, in the ring and usually consist of five or six ring atoms. Preferred heterocyclic-aromatic

Compounds have a ring heteroatom and the rest of the ring atoms are

! 5 carbon atoms. Examples of preferred heterocyclic-aromatic systems are furan, thiophene, pyrrole and pyridine radicals. These preferably carry three or

in particular two or one carboxyl group.

The (hetero) arylcarboxylic acids are obtained oxidatively from precursor compounds. These are compounds which, instead of the carboxylic acid group (s), are alkyl, preferably methyl, hydroxyalkyl, preferably hydroxymethyl, alkoxyalkyl, preferably methoxymethyl, aldehyde and / or carboxylic acid alkylester groups, preferably have carboxylic acid methyl ester groups. These precursor groups are oxidatively converted into carboxylic acid groups. In addition to these precursor groups, the precursor compounds may still have substituents that are not affected by the oxidative treatment. Examples thereof are halogen radicals, such as fluorine, chlorine, bromine or iodine, alkoxy radicals, such as methoxy or ethoxy, or nitro groups.

Examples of preferred processes are the catalytic oxidation in the presence of catalysts containing heavy metal cations of p-xylene, p-tolylbenzoic acid, p-tolylbenzoic acid ester, p-dihydroxymethylbenzene or p-dibenzaldehyde to form terephthalic acid, the oxidation of o-xylene, o-toluenobenzoic acid , o-Tolylbenzoesäureester, o-dihydroxymethylbenzene or o-dibenzaldehyde to phthalic acid, the oxidation of m-xylene, m-tolylbenzoic acid, m-tolylbenzoic acid ester, m-dihydroxymethylbenzene or m-dibenzaldehyde to isophthalic acid, the oxidation of toluene, hydroxymethylbenzene or benzaldehyde to benzoic acid , the oxidation of methylnaphthalene, hydroxy

5-methylnaphthalene or naphthalene-aldehyde to naphthalenecarboxylic acid, the oxidation of dimethylnaphthalene, methylnaphthalenecarboxylic acid, dihydroxymethylnaphthalene,

Naphthalenedialdehyde or methylnaphthalenecarboxylic acid ester to naphthalenedicarboxylic acid or the oxidation of dialkylfuran, dihydroxyfuran, hydroxymethylfuranaldehyde, methoxymethylfuranaldehyde or furandialdehyde to furandicarboxylic acid.

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The process according to the invention is preferably used in the catalytic oxidation in the presence of catalysts comprising vanadium cations or in the presence of cobalt cations and optionally manganese cation-containing catalysts of o-xylene, o-tolylbenzoic acid or o-tolylbenzoic acid esters to give phthalic acid

! 5 used. In this case, chelating ion exchangers are used, which

Vanadium cations VO ₂ ⁺ , VO ²⁺ or V ³⁺ or which cobalt cations Co ²⁺ and, if present, manganese cations Mn ^{2+ are} selectively removed from an effluent from the oxidation process, for example from a process wastewater. The process according to the invention is particularly preferably used in the catalytic oxidation of alkylaromatics or of heteroarylaromatics to arylcarboxylic acids or to Heteroarylcarboxylic acids are used in which cobalt cations and optionally manganese cation-containing catalysts are used.

Very particular preference is given to the process according to the invention in the catalytic oxidation in the presence of catalysts containing cobalt and optionally manganese cations of p-xylene, p-toluenobenzoic acid or p-tolylbenzoic acid ester

Terephthalic acid used. In this case, chelating ion exchangers are used which remove cobalt cations as Co ²⁺ and, if present, selectively remove manganese cations as Mn ²⁺ from the process wastewater.

O

Chelating ion exchangers which can be used according to the invention are known and commercially available. Examples of suitable products are Chelex ^® 100 or

Chelex ^® 20 Bio-Rad Laboratories or Amberlite ^® IRC748 of Rohm and Haas Company or Lewatit ^® MonoPlus TP 207 from Lanxess Germany GmbH.

Particularly suitable chelating ion exchangers contain, as chelating groups, iminodiacetyl groups which are covalently bound to a framework of synthetic resin, for example of polystyrene, which is optionally crosslinked. These

chelating ion exchangers were designed to be selective

To remove heavy metal cations from aqueous solutions, which are additionally large

! 0 contain amounts of cations of other metals, such as alkali metal or alkaline earth metal cations. The selectivity of these ion exchangers for selected heavy metal cations can be influenced by the pH. In contrast to conventional ion exchangers which, for example, have sulfonic acid groups and which on contact with aqueous solutions, the alkali metal and alkaline earth metal cations in the

! 5 contain excess, mainly these cations to the exchanger groups

In the case of the chelating ion exchangers, selective binding of the heavy metal cations to the exchanger groups takes place while the alkali metal and also the alkaline earth metal cations are not bound. A description of

The mode of operation and use of chelating ion exchangers can be found in Specialty Chemicals Magazine, October 2008, pp. 26-27. In a very particularly preferred variant of the process according to the invention, the catalytic oxidation of the precursors of carbocyclic-aromatic

Carboxylic acids or heterocyclic-aromatic carboxylic acids instead of in acidic solution, the regeneration of heavy metal ion-loaded selective ion exchanger 5 takes place by the acidic solvent used in the oxidation process or by other acids used in the oxidation process, for example

Hydrobromic acid, and the resulting regenerate with the catalytically active

Heavy metal ions are returned to the oxidation process. o In the case of catalytic oxidation to phthalic acid or terephthalic acid is

especially acetic acid used.

In a further very particularly preferred variant of the process according to the invention, the chelating ion exchanger is used for recovering the

5 catalyst is used by contacting an effluent from the oxidation process containing the dissolved catalyst after separation of the reaction product and solids from the reaction solution with the chelating ion exchanger to remove the heavy metal cations, the heavy metal cation-loaded chelating ion exchanger with an acid such as acetic acid

»0 or hydrobromic acid, is regenerated and the regenerate directly into the

Oxidation process is recycled.

The chelating ion exchanger can be used according to the invention in an exchange column. This is flowed through by the effluent to be cleaned from the process »5. It is also possible to combine several effluents before passing them through the exchanger column (s).

As a rule, at least two exchange columns connected in series are used and the concentration of heavy metal cation to be separated in the line is thus measured between the two exchanger columns. If the concentration there exceeds a predetermined limit, this indicates that the exchange capacity of the first exchanger column is exhausted and that it is completely filled with heavy metal cations is loaded and needs to be regenerated. The passage of the effluent through this column is stopped and the column is regenerated, for example by the use of acetic acid, to elute the bound heavy metal cations. After

Regeneration of the column, these can again be traversed by the effluent from the process. During the regeneration of the first column, the effluent may be passed through the second column or through another column (combination). It is also possible to use combinations of several columns which are operated at different pH values and allow interception of different heavy metal cations.

The invention also relates to a plant for the preparation of carbocyclic-aromatic mono- or polycarboxylic acids or heterocyclic-aromatic mono- or

Polycarboxylic acids by oxidation of alkyl, hydroxyalkyl, alkoxyalkyl, aldehyde and / or carboxylic ester groups containing precursors of this mono- or

Polycarboxylic acids in the presence of catalysts containing heavy metal cations comprising the elements:

A) oxidation reactor for the catalytic oxidation of the precursors of carbocyclic-aromatic mono- or polycarboxylic acids or heterocyclic-aromatic mono- or polycarboxylic acids,

B) Device for separating and working up the carbocyclic-aromatic mono- or polycarboxylic acids or heterocyclic-aromatic monocarboxylic or polycarboxylic acids produced in the oxidation reactor A), in which a first process wastewater stream is produced,

C) Device for the recovery of the catalyst from one of the

Device B) originating from the oxidation reaction, in which a second process wastewater stream is formed,

D) return line of the recovered catalyst into the oxidation reactor, and

E) at least one separation device for selected, contained in the catalyst heavy metal cations, which contains a chelating ion exchanger for selectively separating the selected heavy metal cations, and by which the first process wastewater stream and / or the second Process wastewater stream is passed or through which the effluent from the device B) is passed, wherein the separator is connected to the return line D).

In a preferred embodiment, the plant according to the invention contains two

Separation devices E), wherein a separation device for the purification of the first process wastewater stream and a further separation device for the purification of the second process wastewater stream is provided.

In a further preferred embodiment, the plant according to the invention comprises three separation devices E), wherein a separation device for the purification of the first process wastewater stream, a further separation device for the purification of the second process wastewater stream and still another separation device for the purification of the effluent from the device B) are provided is.

15

In an additional preferred embodiment, the separation device E) comprises two with chelating ion exchanger filled and connected in series

Exchange columns, which have at each end a supply and discharge for liquids, between which there is a sensor for determining the concentration of! 0 heavy metal cations after the first exchange column and in which the first exchange column, a supply line for the effluent to be cleaned and the second exchange column has a discharge for the purified effluent.

In a further preferred embodiment, the system according to the invention! 5 also contains a regeneration device F) for the heavy metal cation loaded

chelating ion exchanger for separating the heavy metal cations from the chelating ion exchanger. The regeneration of the loaded ion exchanger typically takes place "in situ" without removing the ion exchanger. "The invention also relates to the use of chelating ion exchangers for the selective removal of heavy metal cations from a catalytic effluent Oxidation reaction for the preparation of arylcarboxylic acids or of

Heteroaryl carboxylic acids.

The invention is exemplified by Figures 1 and 2. A restriction 5 is not intended thereby.

FIG. 1 shows schematically a version of the method according to the invention in the form of a PTA system. FIG. 2 shows an example of an interconnection of exchanger columns for use in the method according to the invention.

FIG. 1 shows a possible scheme of a PTA system which has been modified according to the invention. You can see a process air compressor (1) for

5 Compressing air (20), an oxidation reactor (2) for the oxidation of p-xylene (21), a crystallization and distillation means (3) for crystallizing the crude PTA produced and for the separation of crude acetic acid (26) (26) = Reaction solvent), a first filtration plant (4) for separating the crystallized crude PTA (24) from the liquid constituents of the distillation residue (23) from the device (3). there

! 0 remains a liquid residue (25) containing, inter alia, catalyst components, such as Co and Mn salts, and organic residues (15). These are separated in the catalyst recovery (12) and recycled as a recovered catalyst (14) in the oxidation reactor (2). In addition, the organic residues (15) and a wastewater stream (16) from the catalyst recovery (12)

! 5 discharged. The crude acetic acid (26) is treated with an acetic acid treatment plant (13) and fed into the oxidation reactor (2) as process acetic acid (22).

recycled. The crude PTA is dried in a first dryer (5), dissolved in the dissolving tank (6), subjected to a reduction treatment in the hydrogenation stage (7), recrystallized in the crystallizer (8) and separated from the second filtration plant (9)

The pure PTA obtained is dried in a second dryer (11) and discharged from the plant as product 17. The mother liquor (19) is removed from the remaining solids in a treatment plant (10) freed and leaves plant part (10) as waste water stream 2 (18). According to the invention, chelating ion exchangers (not shown) are used. These can be used to treat wastewater stream 1 (16) and / or wastewater stream 2 (18) and / or for catalyst recovery in plant part (12). Because of the

5 different loads of the individual effluents (25, 16, 18) with cobalt and manganese cations, it is recommended that the individual effluents separated with

to treat chelating ion exchangers. Alternatively, a treatment of the effluent (25) and the combined effluents (16, 18) is possible. Less preferred is a combined treatment of the effluents (25, 16, 18).

O

FIG. 2 shows a possible scheme for a plant according to the invention

Treatment of effluents from a plant for the oxidative preparation of aryl or heteroarylcarboxylic shown. Shown are exchanger column 1 (30) and

Exchange column 2 (32). These are connected in series. Between both columns (30,

5, 32), a sensor (31) is connected with which the content of cobalt cations or other heavy metal cations to be separated in the exchanger columns (30, 32) can be determined. In the operating mode, the effluent to be treated (34) is supplied exchanger column 1 (30) and leaves it as a purified effluent (36). After

Passage through sensor (31), the purified effluent (36) in the exchange column. 2

: o (32) conducts and leaves it as effluent purified from heavy metals (38). As soon as the capacity of exchanger column 1 (30) has been exhausted and this is completely laden with separated heavy metal cation, a content of this heavy metal cation or an increased content of this heavy metal cation is measured in sensor (31). By an unillustrated valve then the passage of the exhaust stream (34) through the

! 5 exchanger column 1 (30) interrupted and effluent (34) is passed via the bypass line (40) in the exchange column 2 (32). The loaded exchanger column 1 (30) is regenerated by elution with an acid used in the oxidation process, for example with acetic acid. In this case, the acid is supplied via line (33) of the exchange column 1 (30) and the eluted heavy metal salt leaves this via line (35) dissolved o in the acid and can be fed to the oxidation reactor directly as a catalyst component. After regeneration of exchanger column 1 (30), the bypass line (40) is blocked. In the further process, the combination of the exchange columns (30, 32) are now operated in reverse order. This can be done by a combination of valves, not shown. Thus, the effluent to be treated is now supplied to exchanger column 2 (32) and leaves it as purified effluent (36). After passage through the sensor (31), the purified effluent (36) in the

5 exchange column 1 (30) passed and leaves them as purified effluent. Once the capacity of the exchanger column 2 (32) is exhausted and this completely with

loaded heavy metal cation is measured, a content of this heavy metal cation or an increased content of this Schwermetallkations in sensor (31). Now the passage of the effluent to be treated is interrupted by exchanger column 2 (32) o and this is described as above for exchange column 1 (30)

regenerated. For this purpose, lines (37, 39) are provided.

Of course, other combinations of exchange columns are conceivable. Another preferred combination used corresponds to the arrangement described in Figure 2, but in each case two exchanger columns are connected in series. The two pairs of exchange columns are operated at different pH values. As a result, a targeted separation of different heavy metal cations in both pairs of columns is possible.

! 0

Claims

claims

1. A process for the purification of catalyst residues containing effluents from plants for the production of carbocyclic-aromatic mono- or polycarboxylic acids

5 or heterocyclic-aromatic mono- or polycarboxylic acids by oxidation of alkyl, hydroxyalkyl, alkoxyalkyl, aldehyde and / or carboxylic ester groups containing precursors of these mono- or polycarboxylic acids in the presence of catalysts containing heavy metal cations, characterized in that at least one effluent from the Oxidation process is brought into contact with a chelating o ion exchanger, which selected

Heavy metal cations selectively removed from the effluent.

2. The method according to claim 1, characterized in that it is in the

containing catalytic oxidation in the presence of heavy metal cations

Catalysts for the oxidation of p-xylene, p-tolylbenzoic acid, p-Tolylbenzoe- acid ester, p-dihydroxymethylbenzene or p-dibenzaldehyde to terephthalic acid, the oxidation of o-xylene, o-toluenoic, o-tolylbenzoic, o-dihydroxy- methylbenzene or o-dibenzaldehyde to phthalic acid, the oxidation of m-xylene, m-tolylbenzoic acid, m-tolylbenzoic acid ester, m-dihydroxymethylbenzene or mo dibenzaldehyde to isophthalic acid, the oxidation of toluene, hydroxymethylbenzene or benzaldehyde to benzoic acid, the oxidation of methylnaphthalene,

Hydroxymethylnaphthalene, naphthalene aldehyde to naphthalenecarboxylic acid, the oxidation of dimethylnaphthalene, methylnaphthalenecarboxylic acid, dihydroxymethylnaphthalene, naphthalenedialdehyde or methylnaphthalenecarboxylic acid esters

5 naphthalenedicarboxylic acid or the oxidation of dialkylfuran, dihydroxyfuran,

Hydroxymethylfuranaldehyde, methoxymethylfuranaldehyde or furandialdehyde to furandicarboxylic acid. o 3. The method according to claim 2, characterized in that it is in the

catalytic oxidation in the presence of catalysts containing heavy metal cations for the catalytic oxidation in the presence of vanadium cation-containing catalysts or in the presence of cobalt cations and given if catalysts containing manganese cations, wherein o-xylene, o-toluenoic or o-Tolylbenzoesäureester is oxidized to phthalic acid and wherein chelating ion exchangers are used, which Vanadiumkationen V0 ₂ ⁺ , V0 ²⁺ or V ³⁺ or which Kobaltkationen Co ²⁺ and if appropriate, selectively remove manganese cations Mn ²⁺ from an effluent from the oxidation process.

A method according to claim 1, characterized in that used in the catalytic oxidation of alkylaromatics to arylcarboxylic acids or of heteroarylaromatics to heteroarylcarboxylic cobalt cations and optionally manganese cation-containing catalysts.

A method according to claim 1, characterized in that the catalytic

Oxidation in the presence of cobalt and optionally manganese cations

In this case, p-xylene, p-tolylbenzoic acid or p-tolylbenzoic acid ester is oxidized to terephthalic acid, and chelating ion exchangers are used which selectively remove cobalt cations Co ²⁺ and optionally manganese cations Mn ²⁺ from an effluent from the oxidation process ,

A method according to claim 1, characterized in that the catalytic

Oxidation of the precursors of carbocyclic-aromatic carboxylic acids or of heterocyclic-aromatic carboxylic acids in acidic solution takes place that the regeneration of heavy metal ion-loaded selective ion exchanger by the acidic solvent used in the oxidation process or by other acids used in the oxidation process, and that the obtained regenerate with the catalytically active heavy metal cations in the

Oxidation process is traced back.

7. The method according to claim 6, characterized in that is generated by the catalytic oxidation phthalic acid or terephthalic acid and that the acidic solvent is acetic acid.

8. The method according to claim 1, characterized in that the chelating ion exchanger for recovering the catalyst is used by a dissolved catalyst containing effluent from the oxidation process after the separation of the reaction product and solids from the reaction solution with the chelating ion exchanger to remove the heavy metal cations is contacted, which is loaded with heavy metal cations chelating ion exchanger is regenerated with an acid and that the regenerate is recycled directly into the oxidation process.

9. The method according to claim 1, characterized in that at least two series-connected exchanger columns are used, and that the

Concentration of heavy metal cation to be separated is measured in the line between the two exchanger columns.

10. plant for the preparation of carbocyclic-aromatic mono- or polycarboxylic acids or heterocyclic-aromatic mono- or polycarboxylic acids by oxidation of alkyl, hydroxyalkyl, alkoxyalkyl, aldehyde and / or carboxylic ester groups containing precursors of these mono- or polycarboxylic acids in the presence of heavy metal cations containing Catalysts comprising the elements:

C) Apparatus for the recovery of the catalyst from a stream of the oxidation reaction originating from the apparatus B), in which a second process wastewater stream is produced,

D) return line of the recovered catalyst into the oxidation reactor, and E) at least one separating device for selected heavy metal cations contained in the catalyst, which contains a chelating ion exchanger for the selective separation of the selected heavy metal cations, and through which the first

Process wastewater stream and / or the second process wastewater stream is passed or through which the effluent from the device B) is passed, wherein the separator is connected to the return line D).

1 1. A system according to claim 10, characterized in that two separation devices E) are provided, wherein a separation device for the purification of the first process wastewater stream and a further separation device for the purification of the second process wastewater stream is provided.

12. Plant according to claim 10, characterized in that three separation devices E) are provided, wherein a separation device for the purification of the first process wastewater stream, a further separation device for the purification of the second process wastewater stream and still another separation device for the purification of the effluent from the Device B) is provided.

13. Plant according to claim 10, characterized in that the separation device E) comprises two filled with chelating ion exchanger and connected in series exchange columns, which at each end an inlet and outlet for

Have fluids between which a sensor for determining the

Concentration of the heavy metal cations is located after the first exchange column and in which the first exchange column, a supply line for the effluent to be cleaned and the second exchange column a derivative for the purified

Downstream has.

14. Plant according to claim 10, characterized in that this one more

Regenerator F) for the laden with heavy metal cations

containing chelating ion exchanger for separating the heavy metal cations from the chelating ion exchanger.

15. Use of chelating ion exchangers for the selective removal of heavy metal cations from an effluent of the catalytic oxidation reaction for the production of arylcarboxylic acids or of heteroarylcarboxylic acids.