WO2009115888A1

WO2009115888A1 - Process for the recovery of water and valuable organics from wastewater in the production of aromatic carboxylic acids

Info

Publication number: WO2009115888A1
Application number: PCT/IB2009/000522
Authority: WO
Inventors: Marzio Monagheddu; Luciano Piras; Giovani Cocco
Original assignee: Dow Italia SRL
Current assignee: Dow Italia SRL
Priority date: 2008-03-20
Filing date: 2009-03-16
Publication date: 2009-09-24
Anticipated expiration: 2010-09-20
Also published as: CN102149642A; JP2011515386A; KR20100133441A

Abstract

A process for the removal and recovery of water and organics from a liquid stream in a chemical process is disclosed. The process comprises contacting the liquid stream with a polymeric adsorbent to form purified water. Subsequent steps include regenerating the polymeric adsorbent resin by contacting the polymeric adsorbent resin with polymeric adsorbent resin regeneration solution to form recovered organics, washing the polymeric adsorbent resin with a washing solution comprising substantially water, and removing remaining regeneration solution adsorbed on the polymeric adsorbent resin by contacting the resin with a fluid comprising hot water, steam, or a hot inert gas.

Description

PROCESS FOR THE RECOVERY OF WATER AND VALUABLE ORGANICS FROM WASTEWATER IN THE PRODUCTION OF AROMATIC CARBOXYLIC ACIDS

FIELD OF THE INVENTION The present invention relates to a process for recovery of water and valuable organics from wastewater during the production of aromatic carboxylic acids using polymeric absorbent resins.

BACKGROUND OF THE INVENTION Aromatic poly carboxylic acids, such as terephthalic acid, isophthalic acid and trimellitic acid, are often produced by oxidation of alkyl aromatics with oxygen containing gas, to form crude product. The crude product is mixed with a solvent to form a slurry, dissolved at high temperature, and subjected to hydrogenation to increase product purity. The effluent of the hydrogenation reactor is crystallized and then sent to two stages of solid liquid separation. The mother liquor from the first stage solid liquid separation contains water, metals, valuable organics, and other impurities, but cannot be recycled due to the high content of impurities. As a consequence, the first stage mother liquor is generally sent to disposal. There is an opportunity to recover valuable organics present in the first stage mother liquor (sometimes referred to as a purge stream), and re use at least part of the purified water in the manufacturing process, thereby reducing plant environmental impact, water consumption and production losses.

Purification of wastewater is a critical issue in the chemical industry due to environmental aspects, cost of treatment and value lost if valuable material is present. As a consequence, a number of prior art references describe wastewater treatment processes. For example, US4826600 describes a water treatment process involving aerobic or anaerobic oxidation, and JP2006272051 describes an electrolysis-based process.

Other efforts for purification of wastewater have included the use of various adsorbent materials. For example, US 5746788 and US6946077 describe processes utilizing activated carbon compounds. US5980750 and US5635071 describe processes based on one or more reverse osmosis membrane preceded by filtration. US5980750, US4540493, US3985648,

JP2000070934A, and JP58135834 all describe processes utilizing ion exchange resins to purity wastewater, while the process reported in US5236594 describes using a non-ionic macroreticular polymeric resin. Other efforts for purification of wastewater using various adsorbent materials include, for example, those described in US4079001, US4097376, JP55105636, and EP0966405.

However, the processes described in these references require pretreatment of either the adsorption material or the effluent stream in order for the purification to be effective.

US4670155 also describes a process utilizing a sorbent material. This reference recites removal of water from an organic compound by first co-sorbing an organic compound and water directly onto a particulate bed, and flowing a volatilized compound through the bed, wherein the volatilized compound preferentially volatizes water.

It would be an advantage in the art of recovery of water and valuable organic compounds in a more efficient process that does not require expensive oxidation or electrolysis equipment. It would also be an advantage in the art of recovery of water and valuable organic compounds to utilize adsorbent materials without the need for pretreatment or post-treatment steps.

SUMMARY OF THE INVENTION In a first aspect, the present invention is a process for the removal of organics and recovery of water and organics from a liquid stream in a terephthalic acid production process, an isophthalic acid process, a trimellitic acid process, or a naphthalene dicarboxylic acid process, comprising the step of contacting the liquid stream with a polymeric adsorbent to form purified water. Subsequent steps include regenerating the polymeric adsorbent resin by contacting the polymeric adsorbent resin with polymeric adsorbent resin regeneration solution to form recovered organics, washing the polymeric adsorbent resin with a washing solution comprising substantially water, and removing remaining regeneration solution adsorbed on the polymeric adsorbent resin by contacting the resin with a fluid comprising hot water, steam, or a hot inert gas. The present invention provides a method for the recovery of water and organics without the need for pretreatment of the liquid stream or extra processing steps. The use of a polymeric adsorbent resin provides an alternative to activated carbon that is significantly easier to regenerate on site resulting in smaller systems and lower costs. The polymeric adsorbent resins also have high surface area and are free of salts, metals, and minerals that can leach back into product streams or catalyze undesirable reactions. Polymeric adsorbents are engineered for regeneration under milder conditions than activated carbon, making on-site regeneration possible and allowing the organics to be returned to the process eliminating waste and cost.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves the removal of organics from water, and the recovery of water and organics from a liquid stream in a chemical process. Chemical processes suitable for employing the present invention include terephthalic acid production processes, isophthalic acid production processes, trimellitic acid processes, and naphthalene dicarboxylic acid production processes.

The liquid stream to be treated using the present invention is typically a wastewater stream in the chemical process, such wastewater stream comprising water, metals and organics. The organics in the liquid stream include mono and poly alkyl substituted aromatic mono and poly carboxylic acids; mono and poly formil substituted aromatic mono and poly carboxylic acids; aromatic alkyl aldehydes, mono and poly alkyl substituted aromatic mono and poly aldehydes; aromatic carboxylic acid, aromatic poly carboxylic acid, where the aromatic part can include one or more condensate aromatic ring; and combinations thereof.

Specific examples of said organic compounds to be removed are: toluic acid, terephthalic acid, isophthalic, carboxybenzaldehyde, benzoic acid, benzene tricarboxylic acid, trimellitic acid, dimethyl benzoic acid; methyl naphthalene-carboxylic acid; methyl benzoic acid; formyl benzene-dicarboxylic acid; diformyl benzoic acid; formyl naphthalene-carboxylic acid; formyl benzoic acid; dimethyl benzaldehyde; methylbenzene-dicarbaldehyde; naphthalene-dicarbaldehyde; benzene-dicarbaldehyde; methyl naphthalene-carbaldehyde; methyl benzaldehyde; naphthalene-dicarboxylic acid; benzene-tricarboxylic acid; benzene- dicarboxylic acid; and any combination of one of more of these. The concentration of organics in the liquid stream is typically anywhere from about 0.05% to 2% by weight. More typically, the concentration of organics in the liquid stream is from 0.1% to 1.5% by weight.

The first step of the present invention comprises contacting the liquid stream with a polymeric absorbent resin. The result is purified water, with the organics remaining adsorbed to the polymeric adsorbent resin at this stage. This first step may be performed in one or more beds in series as necessary to sufficiently separate the organics from the liquid stream. The purified water can then be, at least partially, recycled back into the chemical process.

Preferably, the first contacting step described above is conducted at a temperature of from 40 to 100 degrees C, and more preferably from 60 to 80 degrees C. The first contacting step is conducted in any conventional particulate resin bed apparatus. Those skilled in the art will know the typical resin beds that may be used, including for example, fluidized beds, and more preferably, fixed beds.

After a period of time, as with most adsorbents, the polymeric adsorbent resin will become fully loaded with organics 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 organics in the effluent stream from the resin bed will change, signaling a need for regeneration. During the regeneration step, the organics are recovered and optimally may be used in the production process for the aromatic carboxylic acids. To regenerate the polymeric adsorbent resin, the resin is contacted with a polymeric adsorbent resin regeneration solution. The polymeric adsorbent resin regeneration solution comprises an aliphatic carboxylic acid solution having a concentration of from 70 to 100% acid in solution. In a preferred embodiment, the polymeric adsorbent resin regeneration solution is an acetic acid solution with a concentration of from 80-100% acetic acid in solution, and more preferably from 90-100% acetic acid. The recovered organics can then be recycled back into the chemical process. Preferably, the regenerating step is conducted at a temperature of from 40 to 100 degrees C, and more preferably from 60 to 80 degrees C. The regeneration step is performed using any conventional pumping apparatus useful for pumping acetic acid through the resin bed. After the polymeric adsorbent resin is regenerated and the organics are recovered, the polymeric adsorbent resin is washed with a washing solution. The washing solution is comprised of 90% or greater water. If any of the polymeric adsorbent resin regeneration solution remains adsorbed on the polymeric adsorbent resin after the washing step, it is removed by contacting the resin with a fluid comprising hot water, steam, or a hot inert gas.

Suitable polymeric adsorbent resins for use in the present invention include any high surface area highly cross-linked resin. Examples of polymeric adsorbent resins include styrene polymer resins, and more preferably, styrene/divinylbenzene macroporous resins, such as those sold under the OPTIPORE trademark. OPTIPORE L-493 is a particularly preferred polymeric adsorbent resin.

Unlike ion exchange resins, which rely on the exchange of charged ions between the absorbent and the fluid to be treated, the polymeric adsorbent resins used in the present invention interact with a non-charged side of a molecule and therefore can be used with any organic compound, whether acidic, basic or neutral. Polymeric adsorbent resins utilize a combination of mechanisms in the adsorption process, including Van der Waals forces, steric interaction, hydrogen bonding, hydrophobicity, and polarity, and the presence of charged ions is not critical.

EXAMPLES Equipment:

In Examples 1 and 2 below, one jacketed column is packed with 390 ml of settled highly cross- linked styrenic polymer (OPTIPORE L-493, The Dow Chemical Company). The bed diameter is 2.54 cm and the bed height is 77 cm, for a resin bed volume of 390 ml. The process fluid is collected from the plant in the reservoir, and allowed to cool down to ambient temperature. It is then connected to the lab apparatus, heated at 75 ⁰C, and then pumped through the resin. The column is kept at 70 ⁰C by feeding hot water to the column jacket. Chemical Oxygen Demand ("COD"), a test used to measure the amount of organic compounds in water, is measured in the reservoir. COD is expressed in parts per million (ppm), which indicates the mass of oxygen consumed per liter of solution. Samples are collected on the discharge side of the column and analyzed for COD. The liquid not sampled is collected in known volume tanks and analyzed for COD. Regeneration is performed by pumping through the loaded resin 96% acetic acid 4% water solution. The column is kept at 70 ⁰C by feeding hot water to the column jacket. The whole effluent is collected in a tank and analyzed for the organic content (excluding acetic acid.)

Analytical method:

The amount of organics present in the wastewater stream is quantified in terms of COD according to ASTM D1252. After regeneration, the recovered organics can not be evaluated by ASTM D 1252 because the regenerating agent is an organic acid, and therefore they are analyzed by HPLC according to the following operating conditions:

Equipment used for the analytical method: HPLC Hitachi model L-7100 or equivalent, equipped with pumping system with 2 gradient pumps, set for 4 eluents with the following characteristics:

- operating pressure 400 bar max;

- flow 0.001 to 9.999 ml/min

- mixing range 0 to 100% with 1% increase.

- UV detector, wavelength 190 to 600 nm

- Self-sampling apparatus, model L-7200 with injection loop 0 to 100 μl Oven for column model L-7350, temperature range 5 to 100⁰C Rheodyne manual injection loop up to 20 μl

Interface between instrument and PC, equipped with printer

- HPLC column RP-18, diameter 5μ

Set the following conditions in HPLC apparatus:

- UV detector 254 nm

- Oven 35 ⁰C

Sample Preparation:

Filter about 10 ml of the sample with filter paper Whatmann no 1. Transfer about 2 ml of the filtered liquid in a vial. Insert the vial into the self-sampling unit and start the system. Those skilled in the art will know to refer to the instruction manual for information on how to set up the equipment.

Example 1

This example describes the results of adsorption. The jacketed column is fed from the top to the bottom with 95,000 ml of mother liquor from a terephthalic acid production process at a flow rate of 140 ml/min, keeping the temperature at 70 ⁰C. Table A shows the results.

Table A

* 50 bed volume means 50 x 390, or 19500 ml of sample pumped once through the column. ** 100 bed volume means 100 x 390, or 39000 ml of sample pumped once through the column. *** 200 bed volume means 200 x 390, or 78000 ml of sample pumped once through the column.

Example 2

This example describes regeneration of the resin and recovery of organic compounds. After the adsorption test described in Example 1, the jacketed column is drained and then fed, from the bottom to the top, with 4208 ml of regenerating fluid comprising 93% acetic acid and 7% water, at a flow rate of 48 ml/min, keeping the temperature at 70 ⁰C. The amount of COD adsorbed onto the resin prior to this example is 136 g. The composition of the effluent resulting from the regeneration is listed in Table B.

Table B

While the invention has been described in connection with specific embodiments thereof, it will be understood that obvious modifications and alterations that may occur to others upon reading the preceding description are to be within the scope of the claims.

Claims

WHAT IS CLAIMED IS:

1. A process for the removal of organics and recovery of water and organics from a liquid stream in a terephthalic acid production process, an isophthalic acid process, a trimellitic acid process, or a naphthalene dicarboxylic acid process, comprising the step of: contacting the liquid stream with a polymeric adsorbent to form purified water.

2. The process according to Claim 1 further comprising the step of: regenerating the polymeric adsorbent resin by contacting the polymeric adsorbent resin with polymeric adsorbent resin regeneration solution to form recovered organics.

3. The process according to Claim 2 wherein the polymeric adsorbent resin regeneration solution comprises an aliphatic carboxylic acid.

4. The process according to Claim 3 wherein the aliphatic carboxylic acid is acetic acid.

5. The process according to any of Claims 2 through 4 further comprising the step of washing the polymeric adsorbent resin with a washing solution comprising substantially water.

6. The process according to Claim 5 further comprising the step of removing remaining regeneration solution adsorbed on the polymeric adsorbent resin by contacting the resin with a fluid comprising hot water, steam, or a hot inert gas.

7. The process according to Claim 6 further comprising the step of: recycling the water into the chemical process.

8. The process according to Claim 6 or 7 further comprising the step of: recycling the organics into the chemical process.

9. The process according to any of Claims 1-8 wherein the polymeric absorbent resin is a high surface area highly cross-linked resin.

10. The process according to any of Claims 1-9 wherein the organics are selected from the group consisting of toluic acid, terephthalic acid, isophthalic, carboxybenzaldehyde, benzoic acid, benzene tricarboxylic acid, trimellitic acid, mono and poly alkyl substituted aromatic mono and poly carboxylic acids; mono and poly formyl substituted aromatic mono and poly carboxylic acids; aromatic alkyl aldehydes, mono and poly alkyl substituted aromatic mono and poly aldehydes; aromatic carboxylic acid, aromatic poly carboxylic acid, where the aromatic part can include one or more condensate aromatic ring, and a combination thereof.

11. The process according to Claim 1 wherein the contacting step is conducted at a temperature of from 40 to 100 degrees C.

12. The process according to Claim 2 wherein the regenerating step is conducted at a temperature of from 40 to 100 degrees C.

13. The process according to any of Claims 1-12 wherein the liquid stream comprises water, metals and organics.