KR20100017447A - Process for the recovery of oxidation catalyst using ion exchange resins - Google Patents

Abstract

A process for the removal and recovery of at least one heavy metal and at least one halogen from a liquid stream in a chemical process is disclosed. The process comprises the steps of contacting the liquid stream with a strong base anion exchange resin; and contacting a discharge stream from the first step with a chelating cation exchange resin. The recovery process optionally includes a step regenerating the anion exchange resin by contacting the anion exchange resin with an anion exchange resin regeneration solution to form recovered heavy metals and halogens. Optimally, the recovery process of the present invention also includes a step of regenerating the chelating cation exchange resin to form recovered heavy metals and halogens.

Description

Process for recovering oxidation catalyst using ion exchange resin {PROCESS FOR THE RECOVERY OF OXIDATION CATALYST USING ION EXCHANGE RESINS}

The present invention relates to a method for recovering heavy metals and halogens using a series of ion exchange and chelating resins.

Cross Reference with Related Application

This application claims priority to US Provisional Application No. 60 / 932,400, filed May 31, 2007.

Background technology

The production of aromatic carboxylic acids is often caused by the direct oxidation of aromatic hydrocarbons. Among others, terephthalic acid is one such carboxylic acid used in the preparation of various other polymers including polyethylene terephthalate (PET). Terephthalic acid is prepared by the direct oxidation of p -xylene by catalysis of heavy metals such as Co and Mn and radical initiators such as bromine. The oxidized product is subsequently crystallized and then subjected to solid liquid separation to produce i) a solid stream comprising the product, ii) a mother liquor stream which is partially recycled to the oxidation process and iii) a liquid stream. The liquid stream is treated for solvent recovery, in which solvent and radical initiators present in the liquid stream are lost or only partially recovered by chemical and / or physical methods with low efficiency. Moreover, when low purity feedstocks are used in the production of aromatic carboxylic acids, the liquid stream must be increased relative to other streams, which increases the number of catalysts and initiators lost through the liquid stream.

Attempts have been made to address the loss of catalysts during the production of aromatic carboxylic acids. For example, US 2002/0016500 A1, US 3,959,449, US 4,202,797, US 4,162,991 and JP10015390A all disclose various methods for recovering components of catalysts such as heavy metals and / or halogens. However, the abovementioned prior art documents describe methods that require the pretreatment of one or more streams involved in the recovery of heavy metals and / or halogens and / or require separate process steps that require the use of expensive equipment. have.

Other efforts described for heavy metal and halogen recovery include the use of ion exchange resins. For example, US 4,238,294, US 5,880,313 and US 5,955,394 disclose methods for recovering heavy metal ions and / or halogens through the use of ion exchange resins. However, these documents require extensive pretreatment steps or other processing steps that require expensive equipment.

Recovery and purification of larger amounts of heavy metals and halogens in a more efficient process that does not require pretreatment or separate treatment steps of the streams containing heavy metals and halogens would be beneficial to the field of recovery of heavy metals and halogens. The use of ion exchange resins in a manner that optimizes the recovery of heavy metals and halogens will also benefit the recovery of heavy metals and halogens.

Summary of the Invention

A first aspect of the invention is a method of removing and recovering one or more heavy metals and one or more halogens from a liquid stream of a chemical process, the method comprising: a) contacting the liquid stream with a strong base anion exchange resin; And b) contacting the discharge stream from step a) with a chelated cation exchange resin. The recovery method optionally includes regenerating the anion exchange resin by contacting the anion exchange resin with an anion exchange resin regeneration solution to form recovered heavy metals and halogens. Preferably, the recovery method of the present invention also includes the step of regenerating the chelated cation exchange resin to form recovered heavy metals and halogens.

A second aspect of the present invention provides a method for removing and recovering at least one heavy metal selected from the group consisting of i) Co, Mn and combinations thereof and ii) bromine from a liquid stream of a chemical process, wherein the removal and recovery method comprises: a Contacting the liquid stream with a strong base anion exchange resin in the form of a halide; b) contacting the discharge stream from step a) with a chelated cation exchange resin; c) regenerating the anion exchange resin by contacting the anion exchange resin of step a) with an anion exchange resin regeneration solution comprising water and acetic acid to form recovered heavy metals and bromine; d) regenerating the chelated cation exchange resin by contacting the chelated cation exchange resin with a regeneration primer comprising HBr followed by contact with a regeneration solution comprising water to form recovered heavy metals and bromine; e) purifying the recovered heavy metals and bromine by contacting the recovered heavy metals and bromine with a strong base anion exchange resin in hydroxide form to form purified heavy metals and bromine; And f) the purified heavy metals and bromine ′ for use in the chemical process.

The present invention provides a process for the recovery of metals and halogens that does not require pretreatment or separate treatment steps of the liquid stream.

1 is a schematic diagram of one embodiment of a recovery system of the present invention.

2 is a schematic diagram of another embodiment of a recovery system of the present invention.

The present invention is a method for recovering a catalyst used in a chemical process. In a first embodiment, the chemical process is a liquid phase oxidation process of an alkyl aromatic, including but not limited to di- and trimethylbenzene, which produces one or more liquid streams containing the catalyst. In one embodiment, the liquid stream is withdrawn from the oxidation process and then separated into a solid-containing product stream, a mother liquor stream and a liquid stream, wherein the liquid stream separates the catalyst, reaction solvent, reaction intermediates, reaction by-products and corrosion products. Include. Examples of liquid phase oxidation processes include the preparation of terephthalic acid, isophthalic acid and trimellitic acid. The preparation of terephthalic acid includes, for example, oxidation of p -xylene to form terephthalic acid. Catalysts used in liquid phase oxidation to the liquid stream include heavy metals and / or halogens. For example, in many embodiments, such as terephthalic acid, isophthalic acid and trimellitic acid, heavy metals include one or more of cobalt, manganese, cerium, zirconium and hafnium, and halogens include bromine.

1 illustrates one embodiment of a recovery system 10 that can be used in the present invention. As shown, the recovery system 10 includes a reservoir 11, a column 13 containing an ion exchange resin and a layer 17 containing a chelating resin.

As shown in FIG. 1, liquid stream 12 exits reservoir 11. The structure of the reservoir 11 is not critical to the present invention and, like most chemical process systems, the properties of the chemical process depend on the construction and materials of the reservoir 11 and other auxiliary device structures.

The concentrations of heavy metals and halogens in the liquid stream 12 are not critical to the present invention and the present invention is effective for almost all concentrations of heavy metals and / or halogens. Typical concentration ranges of heavy metals and halogens in the liquid stream include, for example, bromide concentrations of 200 to 1000 parts per million (ppm); Cobalt concentration of 100 ppm to 800 ppm; And manganese concentrations of 200 ppm to 1000 ppm.

The liquid stream is fed from the reservoir 11 to the ion exchange resin layer 13, where the liquid stream comes into contact with one or more ion exchange resins while passing through the ion exchange resin layer 13. Optimally, the temperature of the liquid stream 12 in contact with the ion exchange resin ranges from 20 to 150 ° C, more preferably from 40 to 100 ° C, most preferably from 65 to 100 ° C.

Ion exchange resins are strong base anion exchange resins selected to absorb at least some of the heavy metals and halogens from the liquid stream. Preferably, the strong base anion exchange resin is a strong base anion exchange resin in the halide form, more preferably a chlorinated or brominated anion exchange resin. Preferably, the strong base anion exchange resin functional group is an amine group. Most preferably, the strong base anion exchange resin is a strong base quaternary amine anion exchange resin in the bromide form. In the case of anion exchange resins in brominated form, the conversion of the strong base anion exchange resins to the bromide form, as known in the art, involves the formation of any type of resin layer into the resin layer volume (herein the ion exchange resin layer). Obtained by washing with a 10 to 50 times strong base solution of a volume), and then with a solution containing 5 to 20 times the bromide of the volume of the resin layer, preferably at a concentration of bromide of at least 3% by weight. have.

The strong base anion exchange resin can be supported on any substrate. Preferably, the strong base anion exchange resin is supported on a styrene-based substrate, more preferably a styrene-divinylbenzene substrate.

The direction of flow of the liquid stream through the resin layer 13 is not critical. However, as shown in FIG. 1, typically the liquid stream will be fed to the top of the resin layer 13 and flow down through the resin layer 13.

The discharge stream 16 from column 13 comprises a reaction solvent, residual catalyst not absorbed by the strong base anion exchange resin, reaction by-products, reaction intermediates and corrosion products. Egress stream 16 is fed to layer 17 where it comes into contact with the chelating resin. Since the chelating resin absorbs the remaining heavy metals and / or halogens, the product effluent stream 18 is substantially free of heavy metals and / or halogens. Thus, effluent stream 18 consists essentially of reaction by-products, reaction intermediates and large amounts of corrosion products.

The chelating resin in layer 17 is a resin selected to absorb heavy metals and / or halogens, more particularly cobalt, manganese, cerium, zirconium, hafnium, bromine, from the liquid stream. Preferably, the chelating group of the chelating resin is a carboxylic acid chelating group, more preferably a dicarboxylic acid group. Most preferably, the chelating resin is already diacetic acid resin. The chelating resin may be in any form, for example sodium or hydrogen form, and more preferably in hydrogen form.

The chelated resin can be supported on any substrate. Preferably, the chelating resin is supported on a styrene-based substrate, more preferably a styrene-divinylbenzene substrate.

The direction of flow of the discharge stream 16 through the chelated resin layer 17 is not critical. However, as shown in FIG. 1, typically, the discharge stream 16 will be fed to the top of layer 17 and flow down through layer 17.

After a certain period of time, like most ion exchange resins and chelating resins, the anion exchange resin in column 13 and the chelating resin in layer 17 will be completely loaded with heavy metals and / or halogens to be regenerated. do. One skilled in the art will typically size the resin bed to last for a certain time before regeneration is necessary, or the concentration levels of heavy metals and / or halogens in the effluent stream 18 will change to signal a need for regeneration. I understand. During the regeneration phase, heavy metals and / or halogens are recovered and can be optimally used in the preparation of aromatic carboxylic acids.

In order to regenerate the anion exchange resin, the anion exchange resin is contacted with an anion exchange resin regeneration solution. Preferably, the anion exchange resin regeneration solution comprises water or a combination of water and acetic acid. Preferably, the concentration of water in the anion exchange resin regeneration solution is 10 to 100% by weight, more preferably 30 to 70% by weight. Preferably, the concentration of acetic acid in the anion exchange resin is 90 to 0% by weight, more preferably 70 to 30% by weight.

To regenerate the chelated resin, the chelated resin is first contacted with the regeneration primer and then with the chelated cation exchange resin regeneration solution.

The regenerated primer includes an acid, such as hydrochloric acid or hydrobromic acid, and may also include acetic acid. Preferably, the concentration of hydrobromic acid or hydrochloric acid in the regenerated primer is from 1 to 20% by weight, more preferably from 2 to 10% by weight, even more preferably from 3 to 6% by weight. Preferably, the concentration of acetic acid in the regenerated primer is from 0 to 98% by weight, more preferably from 10 to 95% by weight, even more preferably from 85 to 90% by weight. Optionally, the concentration of water that can be added to the regenerated primer is preferably 1.5 to 100% by weight, more preferably 3 to 50% by weight, even more preferably 4 to 35% by weight. The use volume of the regenerated primer is selected to supply 3-10 g bromide to the resin for every 1 g of metal absorbed. During this step, with the absorption of bromide by the resin, part of the heavy metal is recovered. For example, when cobalt and manganese are the heavy metals, up to 10% cobalt and 50% manganese loaded on the chelating resin can be recovered from the chelating resin during this step.

Preferably, the chelated cation exchange resin regeneration solution comprises water or a combination of water and acetic acid. Preferably, the concentration of water in the chelated cation exchange resin regeneration solution is 30 to 100% by weight, more preferably 50 to 100% by weight, even more preferably 80 to 100% by weight, and the chelated cation exchange resin The concentration of acetic acid in the regeneration solution is 0-30% by weight. The resulting stream contains the recovered heavy metals and halogens at a ratio of about 3 to 10 halides to heavy metals. In the PTA process, for example, the ratio of Br-:( Co + Mn) is about 2-10, more preferably 2-8, even more preferably 2-5. The stream containing the recovered heavy metals and halogens is then purified as described below.

Referring now to FIG. 2, other embodiments of the recovery system 20 are also possible. The recovery system 20 of FIG. 2 includes a reservoir 21 and a chelated resin layer 23. As shown, chelating resins are chosen such that only chelating resins are needed to recover heavy metals and halogens, but not anion exchange resins. Alternatively, layer 23 operates in the same manner as layer 17 in the embodiment shown in FIG. 1. Effluent stream 24 has similar characteristics to effluent stream 18 of the embodiment shown in FIG. 1.

Optimally, the recovered heavy metals and / or halogens are purified prior to use in the aromatic carboxylic acid process. This purification step involves contacting the recovered heavy metal and halogen with a strong base anion exchange resin. Preferably, the strong base anion exchange resin used for purification is in hydroxide or acetate form, more preferably in hydroxide form.

As shown in FIG. 1, feed stream 19 contains the recovered heavy metals and halogens to be purified. In the embodiment shown in FIG. 2, feed stream 25 contains the recovered heavy metals and halogens to be purified. Feed streams 19 and 25 are fed to layer 40 containing the strong base anion exchange resin used for purification. Feed stream 19 or 25 is fed to layer 40 in series with the strong base anion exchange resin layer and the chelated cation exchange resin layer 17/23 or by a buffer vessel 30 equipped with a pump. Can be. As shown in FIG. 2, feed stream 19 or 25 also optimally contains at least 35% water such that the efficiency of the purification step and the operation of the strong base anion exchange resin 40 in OH- form is optimized. . After the purification step, stream 41 containing purified heavy metals and halogens can be fed back to the oxidation process.

If the strong base anion exchange resin in layer 40 is fully loaded with bromide, it must be regenerated. One skilled in the art will typically understand that the resin layer will be sized to last for a certain time before regeneration is necessary, or the concentration levels of heavy metals and / or halogens in the effluent stream will change to signal a need for regeneration. As shown in FIG. 2, the regeneration of this strong base anion exchange resin in layer 40 is performed by washing with a regenerant, for example a hot strong base solution 42 such as a NaOH solution or a KOH solution. The solution obtained from outlet 43 is either properly disposed of or sent for recirculation.

Example  Definition of terms used:

"DOWEX 21K-XLT" refers to a strong base anion exchange resin in chloride form prepared by The Dow Chemical Company.

"DOWEX IDA-1" means a chelated cation exchange resin prepared by The Dow Chemical Company.

"Column A" means a jacketed glass column filled with 250 ml of DOWEX 21K-XLT.

"Column B" means a jacketed glass column filled with 250 ml of DOWEX 21K-XLT.

"Column C" means a jacketed glass column filled with 390 ml of DOWEX IDA-1.

"Feed" means a liquid stream from a PTA process treated according to the present invention.

"Effluent" means the discharge stream from column A, B or C.

By "eluted catalyst" is meant a catalyst regenerated from column A, B or C according to the invention.

Example  Process used:

Process for converting anion exchange resin to bromide form:

The DOWEX 21K-XLT was converted to the bromide form as follows: 12 liters of 4% aqueous NaOH solution was passed through the resin bed of column A and water was recycled at 70 ° C. in the column jacket. Subsequently, water was passed through the resin layer so that the pH at the discharge side became neutral or less, and the resin layer was then washed with 1000 ml aqueous solution of 4% by weight of HBr.

Anion exchange resin OH -Process for conversion to form:

The DOWEX 21K-XLT in column B was converted to OH-form as follows: 12 liters of 4% by weight aqueous NaOH solution was passed through the resin bed of column B and water was recycled at 70 ° C. in the column jacket. Next, water was passed through the resin layer, and the pH at the discharge side was made neutral or less.

Procedure for determining the concentration of metal ions:

The concentration of metal ions was measured using a Perkin Elmer Atomic Absorption Spectrophotometer Analyst 300. Samples to be analyzed were appropriately diluted with water and absorbance values were determined using the following operating conditions:

ion Wavelength (nm) C ₂ H ₂ flow (ml / min) Flow (ml / min) Slit (nm) cobalt 240.7 1.5 10 in the air 0.2 iron 248.3 1.5 8 in the air 0.7 manganese 279.5 1.5 10 in the air 0.2

The absorbance values of the samples were compared with the absorbance of standard samples for atomic absorption spectrophotometers in a Normex vial containing a solution having a manufacturer-certified concentration. The mg / l concentration of each single metal was automatically calculated by the instrument's control software.

Bromide Concentration Process:

The bromide was determined by titration with silver nitrate (AgNO ₃ ) according to the following procedure:

Weigh about 30 g of sample.

5 ml ammonium sulfate solution and 5 ml 1: 1 nitric acid are added to the flask. The final color of the solution is tan.

Add 2-3 drops of 0.02 N ammonium thiocyanate (NH ₄ CNS) solution. The solution is orange-red.

An excess of 0.02 N AgNO ₃ is added until the orange-red disappears.

Excess AgNO ₃ is titrated with NH ₄ CNS until new orange-red appears.

The bromide concentration is calculated using the formula Br = (A-B) * N * 79.9 * 100 / P * 1000, where

A = ml of AgNO ₃ consumed;

B = ml of NH ₄ CNS consumed;

N = normal concentration (0.02 N) of the solution to be titrated; And

P = sample weight.

Example  One

Columns A and C, in which the resin layer 13 is column A and the resin layer 17 is column C, are arranged in series similarly to the structure shown in FIG. The feed stream to column A comprises heavy metals, halogens, reaction solvents, oxidation reaction by-products, oxidation reaction intermediates and corrosion products at the specific concentrations listed in Table 1. The feed stream is heated to 70 ° C. 500 ml of glacial acetic acid is popped through two layers of resin, then the stream to be tested is fed to the resin layer and recovered on the discharge side of the last layer. The column jacket temperature is kept constant during the test. After absorption, the tested stream is removed from the column by pumping glacial acetic acid through the two layers. 100% water as regenerant for column A, acetic acid / HBr / water = 90/4/6% by weight as primer for column C, and 100% water solution as regeneration solution for column C To perform the playback. At the end of the test, the two resin layers are washed with glacial acetic acid. Relevant data is shown in Table 1.

Example 1 Example 2 Example 3 Example 4 Tested columns A C C B B Resin type DOWEX 21K-XLT (in column A, first contact) DOWEX IDA-1 (in column C, second contact) DOWEX IDA-1 DOWEX 21K-XLT DOWEX-21K-XLT Flow rate (ml / min) 58 70 50 50 Volume of solution supplied (ml) 36800 23800 2550 2550 Jacket temperature (℃) 60 60 35 35 Feed composition: Br (ppm) Co (ppm) Mn (ppm) Fe (ppm) H ₂ O  390 200 422 2.5  416 295 520 3.3  32000 (77% absorbed) 1800 (74% absorbed) 2980 (44% absorbed) 20%  23200 (49% absorbed) 1400 (3% absorbed) 2310 (4% absorbed) 35% Effluent Composition: Br (ppm) Co (ppm) Mn (ppm) Fe (ppm)  30 13 125 1.3  80 63 161 2.6 Eluted catalyst composition: Br (ppm) Co (ppm) Mn (ppm) Fe (ppm)  23924 2350 5188 6  19 118 2199 3561 8

Example  2

The procedure used in Example 1 was repeated except that only column C was tested, and the structure is similar to the structure shown in FIG. 2 where column C is the resin layer 23. Regeneration is performed using a solution consisting of acetic acid / HBr / water = 90/4/6% by weight as the primer for column C and a 100% water solution as the regeneration solution for column C. Relevant data is shown in Table 1.

Example  3

Column B, in which column B is the resin layer 40, was tested and the structure is similar to the structure shown in FIGS. Feed stream compositions representing the compositions of streams 19 and 25 of FIGS. 1 and 2 are shown in Table 1, respectively. 500 ml of glacial acetic acid is popped through the resin layer and then the stream to be tested is fed to the resin layer and recovered at the discharge side of the layer itself. The column jacket temperature is kept constant during the test. After absorption, the tested stream is removed from the column by pumping water through the bed. Relevant data is shown in Table 1.

Example  4

The same procedure as in Example 3 was repeated except that the water concentration of the feed stream was increased to 35% by weight. Relevant data is shown in Table 1.

Claims (21)

A method of removing and recovering one or more heavy metals and one or more halogens from a liquid stream of a chemical process, a) contacting said liquid stream with a strong base anion exchange resin; And b) contacting the discharge stream from step a) with a chelated cation exchange resin Including, the method. The method of claim 1, c) regenerating the anion exchange resin by contacting the anion exchange resin with an anion exchange resin regeneration solution to form recovered heavy metals and halogens. The method of claim 2, Wherein said anion exchange resin regeneration solution comprises water and acetic acid. The method according to any one of claims 1 to 3, d) regenerating the chelated cation exchange resin to form recovered heavy metals and halogens. The method of claim 4, wherein Wherein step d) comprises contacting the chelated cation exchange resin with a regeneration primer followed by contact with a chelated cation exchange resin regeneration solution. The method of claim 5, Wherein said regenerating primer comprises hydrogen bromide or hydrogen chloride. The method according to claim 5 or 6, Wherein said chelated cation exchange resin regeneration solution is water. The method according to any one of claims 1 to 7, e) purifying the recovered heavy metals and halogens. The method of claim 8, Wherein step e) comprises contacting the recovered heavy metal and halogen with a strong base anion exchange resin in hydroxide or acetate form to form purified heavy metal and halogen. The method of claim 9, f) using the purified heavy metal and halogen in the chemical process. The method according to any one of claims 1 to 10, The heavy metal is Co, Mn, Ce, Zr, Hf or a combination thereof. The method according to any one of claims 1 to 11, The chemical process is a terephthalic acid production process, isophthalic acid production process or trimellitic acid production process. The method according to any one of claims 1 to 12, Wherein said halogen is Br. The method according to any one of claims 1 to 13, The anion exchange resin in step a) is a halogenated anion exchange resin. The method of claim 14, Wherein said anion exchange resin is a brominated anion exchange resin. The method according to any one of claims 1 to 15, The chelation exchange resin in step b) is already a diacetic acid resin. A process for removing and recovering from a liquid stream of a chemical process one or more heavy metals selected from the group consisting of i) Co, Mn, Ce, Zr, Hf and combinations thereof and ii) bromine, a) contacting said liquid stream with a strong base anion exchange resin in the form of a halide; b) contacting the discharge stream from step a) with a chelated cation exchange resin; c) regenerating the anion exchange resin by contacting the anion exchange resin of step a) with an anion exchange resin regeneration solution comprising water and acetic acid to form recovered heavy metals and bromine; d) regenerating the chelated cation exchange resin by contacting the chelated cation exchange resin with a regeneration primer comprising HBr followed by contact with a regeneration solution comprising water to form recovered heavy metals and bromine; e) purifying the recovered heavy metals and bromine by contacting the recovered heavy metals and bromine with a strong base anion exchange resin in hydroxide form to form purified heavy metals and bromine; And f) using the purified heavy metal and bromine in the chemical process Including, the method. The method of claim 16, Wherein the strong base anion exchange resin in step a) is a brominated anion exchange resin. The method according to claim 16 or 17, Wherein said chelated cation exchange resin is an imido diacetic acid resin. A process for removing and recovering from a liquid stream of a PTA process i) one or more heavy metals selected from the group consisting of Co, Mn and combinations thereof and ii) bromine, a) contacting said liquid stream with a chelated cation exchange resin; b) regenerating the chelated cation exchange resin by contacting the chelated cation exchange resin with a regeneration primer comprising HBr followed by contact with a regeneration solution comprising water to form recovered heavy metals and bromine; c) purifying the recovered heavy metals and bromine by contacting the recovered heavy metals and bromine with a strong base anion exchange resin in hydroxide form to form purified heavy metals and bromine; And d) using the purified heavy metal and bromine in the PTA process Including, the method. The method of claim 20, Wherein said chelated cation exchange resin is an imido diacetic acid resin.

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