EP2158039A2

EP2158039A2 - Process for the recovery of oxidation catalyst using ion exchange resins

Info

Publication number: EP2158039A2
Application number: EP08827459A
Authority: EP
Inventors: Marzio Monagheddu; Luciano Piras; Giovanni Cocco
Original assignee: Dow Italia SRL
Current assignee: Dow Italia SRL
Priority date: 2007-05-31
Filing date: 2008-05-16
Publication date: 2010-03-03
Also published as: WO2009022237A3; JP2010527785A; CN101952039B; RU2009149338A; KR20100017447A; WO2009022237A2; WO2009022237A9; KR101467603B1; JP5296781B2; CN101952039A; BRPI0811377A2

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 THE RECOVERY OF OXIDATION CATALYST USING ION

EXCHANGE RESINS

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of United States Provisional Application Number

60/932,400, filed May 31, 2007.

FIELD OF THE INVENTION

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

BACKGROUND OF THE INVENTION

Production of aromatic carboxylic acids often occurs by way of direct oxidation of an aromatic hydrocarbon. Among these, terephthalic acid is one such carboxylic acid that is used in the production of many different polymers, including polyethylene terephthalate (PET). Terephthalic Acid is produced by direct oxidation of p-xylene, catalyzed by heavy metals, such as Co and Mn, and a radical initiator, such as bromine. The oxidized product is subsequently crystallized and subjected to solid liquid separation, producing i) a solid stream comprising the product, ii) a mother liquor stream to be partially recycled to the oxidation process, and iii) a liquid stream. The liquid stream is processed for solvent recovery, and in this solvent recovery operation, the catalysts and radical initiators present in the liquid stream are either lost or only partially recovered by means of low-efficient chemical and/or physical methods. Moreover when low purity feed stocks are used for the production of aromatic carboxylic acids, the liquid stream has to be increased relative to the other streams, increasing the value of the catalysts and initiator lost through the liquid stream.

Recent efforts have attempted to address the loss of catalysts during the manufacture of aromatic carboxylic acids. For example, US 2002/0016500 Al, US 3,959,449, US 4,202,797, US 4,162,991, and JP 10015390A all describe various methods for recovering components of a catalyst such as heavy metals and/or halogens. However, the above mentioned prior art references describe methods that require pretreatment of one or more of the streams involved in the process of recovering the heavy metals or halogens, and/or methods that require extra processing steps that require the use of expensive capital equipment.

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

It would be an advantage in the art of recovery of heavy metals and halogens to recover and purify a higher quantity of heavy metals and halogens in a more efficient process that does not require extra processing steps or pretreatment of the stream containing the heavy metals and halogens. It would also be an advantage in the art of recovery of heavy metals and halogens to utilize ion exchange resins in a manner that optimizes the recovery of the heavy metals and halogens.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is 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 comprising the steps of: a) contacting the liquid stream with a strong base anion exchange resin; and b) contacting a discharge stream from step (a) 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. In a second aspect, the present invention is a process for the removal and recovery of i) at least one heavy metal selected from the group consisting of Co, Mn, and a combination thereof, and ii) bromine, from a liquid stream in a chemical process, the process for the removal and recovery comprising the steps of: a) contacting the liquid stream with a strong base anion exchange resin in halogenide form; b) contacting a discharge stream from step (a) with a chelating cation exchange resin; c) regenerating the anion exchange resin in step a by contacting the anion exchange resin with an anion exchange resin regeneration solution comprising water and acetic acid to form recovered heavy metals and bromine; d) regenerating the chelating cation exchange resin by contacting the chelating cation exchange resin with a regeneration primer comprising HBr and thereafter contacting the chelating cation exchange resin 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 metals and bromine in the chemical process.

The present invention provides a method for the recovery of metals and halogens without the need for pretreatment of the liquid stream or extra processing steps.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a method for the recovery of catalyst used in a chemical process. In one aspect, the chemical process is a liquid phase oxidation process of alkyl aromatics, including but not limited to di- and tri methylbenzene that produces one or more liquid streams containing the catalyst. In one embodiment, the liquid stream(s) is withdrawn from the oxidation process, then separated to produce a solid-containing product stream, a mother liquor stream, and a liquid stream, wherein the liquid stream comprises catalysts, reaction solvent, reaction intermediates, reaction byproducts and corrosion products. Examples of liquid phase oxidation processes include the production of terephthalic acid, isophthalic acid and trimellitic acid. The production of terephthalic acid, for example, comprises the oxidation of p-xylene to form terephthalic acid. The catalysts used in the liquid phase oxidation and ending up in the liquid stream comprise heavy metals and/or halogens. In many embodiments, such as, for example, terephthalic acid, isophthalic acid and trimellitic acid processes, the heavy metals comprise one or more of cobalt, manganese, cerium, zirconium and hafnium; and the halogen comprises bromine. Figure 1 shows one embodiment of a recovery system 10 that can be used for the present invention. As shown, recovery system 10 comprises a reservoir 11, a column 13 containing an ion exchange resin, and a bed 17 containing a chelating resin.

As shown in Fig. 1, a liquid stream 12 is withdrawn from reservoir 11. The configuration of reservoir 11 is not critical to the present invention, and as with most chemical processing systems, the nature of the chemical process will dictate the configuration and materials of construction of the reservoir 11 and other auxiliary equipment. The concentration of heavy metals and halogens in the liquid stream 12 is not critical to the present invention, and the present invention is effective with nearly any concentration of heavy metals and/or halogens. Typical concentration ranges of heavy metals and halogens in a liquid stream can be, for example, a bromide concentration of between 200 and 1000 parts per million (ppm); a cobalt concentration of between 100 ppm and 800 ppm; and a manganese concentration of between 200 ppm and 1000 ppm.

The liquid stream is fed from reservoir 11 to ion exchange resin bed 13, where the liquid stream comes into contact with at least one ion exchange resin as it passes through ion exchange resin bed 13. Optimally, the temperature of the liquid stream 12 when contacting the ion exchange resin is in the range of from 20 - 150 ⁰C, more preferably from 40-100 ⁰C, and most preferably from 65-100 ⁰C.

The ion exchange resin is a strong base anion exchange resin selected to absorb at least a portion of 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, and more preferably a chlorinated or brominated anion exchange resin. Preferably, the strong base anion exchange 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. For anion exchange resins that are in the brominated form, as is known in the art, the conversion of a strong base anion exchange resin to the bromide form can be obtained by washing the bed of the resin, in any form, with 10-50 times the resin bed volume (defined herein as the volume of the ion exchange resin bed) of a strong base solution and then with 5- 20 resin bed volume of a solution containing bromide, preferably at a concentration of at least 3 wt % bromide. The strong base anion exchange resin can be supported on any matrix. Preferably, the strong base anion exchange resin is supported on a styrene-based matrix, and more preferably a styrene-divinylbenzene matrix.

The direction of flow of the liquid stream through resin bed 13 is not critical. However, as shown in Figure 1 , typically the liquid stream will be fed to the top of resin bed 13 such that it flows downward through resin bed 13.

Discharge stream 16 from column 13 comprises the reaction solvent, residual catalysts not absorbed by the strong base anion exchange resin, reaction byproducts, reaction intermediates and corrosion products. Discharge stream 16 is fed to bed 17 where it comes into contact with a chelating resin. The chelating resin absorbs remaining heavy metals and/or halogens such that the resulting effluent stream 18 is substantially free of heavy metal catalysts and/or halogens. Effluent stream 18 thus consists essentially of reaction byproducts, reaction intermediates, most of the corrosion products.

The chelating resin in bed 17 is a resin selected to absorb heavy metals and/or halogens, and 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 an imido diacetic acid resin. The chelating resin can be in any form such as, for example, the sodium or hydrogen form, and more preferably the hydrogen form. The chelating resin can be supported on any matrix. Preferably, the chelating resin is supported on a styrene-based matrix, and more preferably a styrene-divinylbenzene matrix.

The direction of flow of discharge stream 16 through chelating resin bed 17 is not critical. However, as shown in Figure 1, typically the discharge stream 16 will be fed to the top of bed 17 such that it flows downward through bed 17.

After a period of time, as with most ion exchange resins and chelating resins, the anion exchange resin in column 13 and the chelating resin in bed 17 will become fully loaded with heavy metals and/or halogens and therefore must be regenerated. Those skilled in the art understand that a resin bed is typically sized to last for a specified period of time before regeneration is required, or that the concentration levels of heavy metals and/or halogens in effluent stream 18 will change, signaling a need for regeneration. During the regeneration step, the heavy metals and/or halogens are recovered and optimally may be used in the production process for the aromatic carboxylic acids.

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 from 10 to 100% by weight, and more preferably from 30 to 70 % by weight. Preferably the concentration of acetic acid in the anion exchange resin regeneration solution is from 90 to 0% by weight, and more preferably from 70 to 30 % by weight. To regenerate the chelating resin, the chelating resin is first contacted with a regeneration primer and then contacted with a chelating cation exchange resin regeneration solution.

The regeneration primer comprises 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 regeneration primer is from 1-20% by weight, more preferably from 2-10% by weight, and even more preferably from 3-6% by weight. Preferably the concentration of acetic acid in the regeneration primer is from 0 to 98% by weight, more preferably from 10-95% by weight, and even more preferably from 85-90% by weight. Optionally, water can be added to the regeneration primer in a preferred concentration of from 1.5-100% by weight, more preferably from 3-50% by weight, and even more preferably from 4-35% by weight. The volume of the regeneration primer used is selected in order to feed to the resin 3-10 g of bromide for every 1 gram of absorbed metal. During this step, together with the absorption of bromide by the resin, a portion of the heavy metals are recovered. For example, when cobalt and manganese are the heavy metals, up to 10% of the cobalt and 50% of the manganese loaded on the chelating resin may be recovered from the chelating resin during this step.

Preferably, the chelating cation exchange resin regeneration solution comprises water or a combination of water and acetic acid. Preferably the concentration of water in the chelating cation exchange resin regeneration solution is from 30 to 100 weight %, more preferably from 50 to 100 wt %, and even more preferably from 80 to 100 wt%. and the concentration of acetic acid in the chelating cation exchange resin regeneration solution is from 0 to 30%. The resulting stream contains the recovered heavy metals and halogens in a ratio of halide to heavy metals of from about 3 to about 10. In a PTA process, for example, the ratio of Br- : (Co + Mn) is from about 2 to about 10, more preferably from 2 to 8, and even more preferably from 2 to 5. This stream containing the recovered heavy metals and halogens is then purified, as described below. Referring now to Figure 2, an alternative embodiment of a recovery system 20 is also possible. The recovery system 20 in Figure 2 comprises reservoir 21 , and chelating resin bed 23. As shown, the chelating resin is selected such that only the chelating resin is needed to recover the heavy metals and halogens, and an anion exchange resin is not needed. Otherwise, bed 23 operates in the same manner as bed 17 in the embodiment depicted in Figure 1. Effluent stream 24 has similar properties to those of effluent stream 18 in the embodiment depicted in Figure 1.

Optimally, the recovered heavy metals and/or halogens are purified before being used in the aromatic carboxylic acid process. Such purification step involves contacting the recovered heavy metals and halogens with a strong base anion exchange resin. Preferably, the strong base anion exchange resin used for purification is in hydroxide or acetate form, and more preferably in the 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 stream 19 or feed stream 25 is fed to a bed 40 containing the strong base anion exchange resin used for purification. Feed stream 19 or feed stream 25 can be fed to bed 40 either in series with the strong base anion resin bed and chelating cation exchange resin beds 17/23, or by means of a buffer vessel 30 equipped with a pump. Feed stream 19 or feed stream 25 optimally also comprises at least 35% water so as to optimize the efficiency of the purification step and of the operation of the strong base anion exchange resin in the OH- form, 40, as illustrated in Fig. 2. After the purification step, stream 41, containing purified heavy metals and halogens may be fed back to the oxidation process.

When the strong base anion exchange resin in bed 40 is fully loaded with bromide, it must be regenerated. Those skilled in the art understand that a resin bed is typically sized to last for a specified period of time before regeneration is required, or that the concentration levels of heavy metals and/or halogens in the outlet stream will change, signaling a need for regeneration. As illustrated in Fig. 2, the regeneration of this strong base anion exchange resin in bed 40 is carried out by washing with a regeneration agent that is a hot strong base solution, 42, such as, for example, NaOH solution or a KOH solution. The resulting solution from the outlet 43 is either sent for appropriate disposal or recycled.

EXAMPLES

Defined terms used in the Examples: "DOWEX 2 IK-XLT" means a strong base anion exchange resin in chloride form, manufactured by The Dow Chemical Company.

"DOWEX IDA-I" means a chelating cation exchange resin manufactured by The Dow Chemical Company.

"Column A" means a jacketed glass column packed with 250 ml of DOWEX 2 IK-XLT. "Column B" means a jacketed glass column packed with 250 ml of DOWEX 2 IK-XLT. "Column C" means a jacketed glass column packed with 390 ml of DOWEX IDA-I. "Feed" means a liquid stream from a PTA process to be treated according to the present invention.

"Effluent" means the discharge stream from Column A, B, or C. "Eluted catalyst" means the catalyst regenerated from column A, B, or C according to the present invention.

Procedures Used in the Examples:

Procedure for converting anion exchange resin to bromide form: DOWEX 2 IK-XLT was converted in bromide form as follows: 12 liters of NaOH 4% by weight aqueous solution were passed through the resin bed in column A, recirculating water at 70 ⁰C in the column jacket. Water was then passed through the resin bed up to neutral pH on the discharge side and then the resin bed was washed with 1000ml aqueous solution of HBr 4% by weight.

Procedure for converting anion exchange resin to OH- form: DOWEX 2 IK-XLT in column B was converted in OH- form as follows: 12 liters of NaOH 4% by weight aqueous solution were passed through the resin bed in Column B, recirculating water at 70 °C in the column jacket. Water was then passed through the resin bed, up to neutral pH on the discharge side.

Procedure for determining concentration of metal ions: The concentration of metal ions was determined using an Atomic Absorption Spectrophotometer Analyst 300 by Perkin Elmer. The samples to be analyzed were appropriately diluted with water, and the absorbance values were measured using the following operating condition:

Absorbance values of samples were compared with absorbance of standards for atomic absorption spectrophotometry in Normex vials containing solutions with concentrations certified by the manufacturer. The concentrations in mg/1 of each single metal is calculated automatically by the control software of the instrument.

Procedure for measuring Bromide concentration:

Bromide was measured by titration with silver nitrate (AgNO₃) according to the following procedure: Weigh about 30g of the sample.

Add 5 ml of iron ammonium sulfate solution and 5 ml of 1 : 1 nitric acid into the flask. The final color of the solution is yellow-green.

Add 2-3 drops of the 0.02 N ammonium thiocianate (NH₄CNS) solution. The solution will become orange-red. Add 0.02 N AgNO₃ in excess, to the point where the orange-red color disappears.

Titrate the excess AgNO₃ with the NH₄CNS up to the new appearance of the orange-red color. The calculation of bromide concentration is made using the formula: Br = (A- B)*N*79.9*100/P*1000, where: A= ml of AgNO₃ consumed; B=ml of NH₄CNS consumed;

N=Normality of the solution for titrations (0.02N); and P=sample weight.

Example 1

Columns A and C are put in series, similar to the configuration shown in Fig. 1 , where resin bed 13 is Column A and resin bed 17 is Column C. The feed stream to column A comprises heavy metals and halogens, reaction solvent, oxidation reaction byproducts and oxidation reaction intermediates and corrosion product, with specific concentrations reported in Table 1. The feed stream is heated to 70 C. 500 ml of glacial acetic acid are pumped through the two resin beds, and then the stream to be tested is fed to the resin beds and recovered on the discharge side of the last bed. The column jacket temperatures are kept constant during the test. After absorption the tested stream is removed from the columns by pumping through the two beds glacial acetic acid. The regeneration was carried out by using 100% water as regenerating agent for column A, a solution composed of acetic acid/HBr/Water = 90/4/6 % by weight as primer for column C and a solution 100% water as regenerating solution for column C. At the end of the test the two resin beds are washed with glacial acetic acid. Relevant data are reported in Table 1.

Table 1

Example 2

The procedures used in Example 1 are repeated, except that only Column C is tested , such that the configuration is similar to that shown in Figure 2 where Column C is resin bed 23. Regeneration was carried out by using a solution composed of acetic acid/HBr/Water = 90/4/6 % by weight as primer for column C and a solution 100% water as regenerating solution for column C. Relevant data are reported in Table 1.

Example 3

Column B is tested, such that the configuration is similar to that shown in Figure 1 and

Figure 2 where Column B is resin bed 40. The feed stream composition, representing composition of stream 19 and 25 in Figure 1 and 2 respectively, is reported in Table 1. 500 ml of glacial acetic acid are pumped through the resin bed, and then the stream to be tested is fed to the resin bed and recovered on the discharge side of the bed 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 are reported in Table 1.

Example 4

The same procedures performed in Example 3 are repeated except that the water concentration of the feed stream is increased to 35% by weight. Relevant results are reported in Table 1.

Claims

WHAT IS CLAIMED IS:

1. 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 comprising the steps of: a) contacting the liquid stream with a strong base anion exchange resin; and b) contacting a discharge stream from step (a) with a chelating cation exchange resin.

2. The process according to Claim 1 further comprising the step of: 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.

3. The process according to Claim 2 wherein the anion exchange resin regeneration solution comprises water and acetic acid.

4. The process according to any of Claims 1 through 3 further comprising the step of: d) regenerating the chelating cation exchange resin to form recovered heavy metals and halogens.

5. The process according to Claim 4 wherein step (d) comprises contacting the chelating cation exchange resin with a regeneration primer and thereafter contacting the chelating cation exchange resin with a chelating cation exchange resin regeneration solution.

6. The process according to Claim 5 wherein the regeneration primer comprises hydrogen bromide or hydrogen chloride.

7. The process according to Claims 5 or 6 wherein the the chelating cation exchange resin regeneration solution is water.

8. The process according to any of Claims 1-7 further comprising the step of: e) purifying the recovered heavy metals and halogens.

9. The process according to Claim 8 wherein step (e) comprises contacting the recovered heavy metals and halogens with a strong base anion exchange resin in hydroxide or acetate form to form purified heavy metals and halogens.

10. The process according to Claim 9 further comprising the step of: f) using the purified heavy metals and halogens in the chemical process.

11. The process according to any of Claims 1-10 wherein the heavy metal is Co, Mn, Ce, Zr, Hf, or a combination thereof.

12. The process according to any of Claims 1-11 wherein the chemical process is a terephthalic acid production process, an isophthalic acid process or a trimellitic acid process.

13. The process according to any of Claims 1-12 wherein the halogen is Br.

14. The process according to any of Claims 1-13 wherein the anion exchange resin in step a is a halogenated anion exchange resin.

15. The process according to Claim 14 wherein the anion exchange resin is a brominated anion exchange resin.

16. The process according to any of Claims 1-15 wherein the chelating exchange resin in step (b) is an imido diacetic acid resin.

17. A process for the removal and recovery of i) at least one heavy metal selected from the group consisting of Co, Mn, Ce, Zr, Hf, and a combination thereof, and ii) bromine, from a liquid stream in a chemical process, the process for the removal and recovery comprising the steps of: a) contacting the liquid stream with a strong base anion exchange resin in halogenide form; b) contacting a discharge stream from step (a) with a chelating cation exchange resin; c) regenerating the anion exchange resin in step (a) by contacting the anion exchange resin with an anion exchange resin regeneration solution comprising water and acetic acid to form recovered heavy metals and bromine; d) regenerating the chelating cation exchange resin by contacting the chelating cation exchange resin with a regeneration primer comprising HBr and thereafter contacting the chelating cation exchange resin 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 metals and bromine in the chemical process. 17. The process according to Claim 16 wherein the strong base anion exchange resin in step a is a brominated anion exchange resin.

18. The process according to Claim 16 or 17 wherein the chelating cation exchange resin is an imido diacetic acid resin.

19. A process for the removal and recovery of i) at least one heavy metal selected from the group consisting of Co, Mn, and combinations thereof, and ii) bromine, from a liquid stream in a PTA process, the process for the removal and recovery comprising the steps of: a) contacting the liquid stream with a chelating cation exchange resin; b) regenerating the chelating cation exchange resin by contacting the chelating cation exchange resin with a regeneration primer comprising HBr and thereafter contacting the chelating cation exchange resin 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 metals and bromine in the PTA process.

20. The process according to Claim 19 wherein the chelating cation exchange resin is an imido diacetic acid resin.