MXPA00012285A

MXPA00012285A - Method of purifying aromatic dicarboxylic acids

Info

Publication number: MXPA00012285A
Application number: MXPA/A/2000/012285A
Authority: MX
Inventors: Charles E Sumner Jr; Brent A Tennant
Original assignee: Eastman Chemical Company
Priority date: 1998-06-30
Filing date: 2000-12-11
Publication date: 2001-11-21

Abstract

A method of purifying an aromatic dicarboxylic acid by oxidizing m-xylene or p-xylene to produce crude isophthalic acid or crude terephthalic acid, respectively. The products of the oxidizing step are hydrogenated in the presence of a palladium catalyst. Carbon monoxide is introduced during the hydrogenation step. The palladium catalyst is provided on a carbon substrate. The products of the oxidizing step are dissolved in a solvent, which may be water, prior to the hydrogenation step. The products of the oxidizing step may be dissolved at an elevated temperature, above the normal boiling point of the solvent. The oxidation step produces isophthalic acid, 3-carboxybenzaldehyde and fluorenones in the case of oxidizing m-xylene and produces terephthalic acid, 4-carboxybenzaldehyde and fluorenones in the case of oxidizing p-xylene. It may be helpful to monitor the disappearance of 3-carboxybenzaldehyde in the case of oxidizing m-xylene and 4-carboxybenzaldehyde in the case of oxidizing p-xylene, and reducing the amount of carbon monoxide when the rate of disappearance is below a predetermined minimum. After the hydrogenation step, the isophthalic acid or terephthalic acid may be crystallized. The carbon monoxide may be maintained at a concentration of 100 to 500 ppm based on added hydrogen and carbon monoxide. Other aromatic dicarboxylic acids may also be purified by this procedure.

Description

METHOD FOR PURIFYING AROMATIC DICARBOXYLIC ACIDS ggF DESCRIPTION OF THE INVENTION The present invention is generally related to purifying aromatic dicarboxylic acids and more specifically to improving the selectivity of catalyst during the purification of the aromatic dicarboxylic acid in such a way that the product of aromatic dicarboxylic acid It is not hydrogenated. The aromatic dicarboxylic acids are used to produce a variety of polyester products. The aromatic dicarboxylic acids are generally synthesized by the catalytic oxidation of the corresponding aromatic dialkyl compound. For example, terephthalic acid (ATF) and isophthalic acid (AIF) are produced by the oxidation of liquid phase of p-xylene and m-xylene, respectively, by the following reactions.

P- TALICO ISOFTALIC ACID (AIT) In the above reactions, Co / n / Br can be used as the catalyst. The above reactions work well. However, in addition to producing the aromatic dicarboxylic acids, a number of impurities are also produced. The following are the impurities produced in the catalytic oxidation of isophthalic acid: 3 - . 3 - CBA FLUORENONA ACIDO M-T0LUIC0 The carboxybenzaldehyde (CBA) and toluic acid result from the complete oxidation of the aromatic dimethylc compound. In the oxidation of m-xylene to produce AIF, 3-CBA is produced. In the oxidation of p-xylene to produce ATF, 4-CBA is produced. Similarly, m-toluic acid is an impurity in the production of AIF and p-toluic acid is an impurity in the production of ATF. Since neither CBA nor toluic acid have two carboxylic acid groups, both can terminate the chain of a polyester produced from an unpurified dicarboxylic acid. In this way, both CBA and toluic acid are undesirable. However, toluic acid is only produced in small amounts and is soluble in water, thus eliminating in a crystallization stage. In addition to the impurities of CBA and toluic acid, the compounds generally known as "fluorenones" are produced. The fluorenone shown above is only one of several isomers. Fluorenones have two carboxylic acid groups, and therefore do not end in chain. However, fluorenones are yellow. In this way, if the fluorenones are present, the polyester produced from the aromatic dicarboxylic acid will look dirty. In view of the above, it is necessary to purify the aromatic dicarboxylic acids without purification. The dicarboxylic acids are purified by catalytic hydrogenation of the impurities in the following reactions.

CBA O TOLUIC ACID II HYDROXIMETHYLBENZOIC ACID (AH B) As can be observed, fluorenones are used. converted to "fluorenes", and the CBAs are converted to toluic acid and hydroxymethylbenzoic acid (HMBA). The fluorenos are bifuncionales, of this form no polymers that finish in 5 chain, and are white. The purification is generally carried out by dissolving the oxidation products in water at elevated temperature and pressure, followed by contacting the resulting solution with a bed of hydrogenation catalysts in the presence of a hydrogen partial pressure. The product mixture is allowed to cool which causes the purified product to crystallize. The toluic acid and HMBA remain in solution. The hydrogenation catalyst is commonly palladium on a carbon support (charcoal), the catalyst contains 0.5 percent by weight of palladium. One of the disadvantages of the purification process is the tendency to hydrogenate the aromatic dicarboxylic acid LCO to produce unwanted by-products. In the production of CBA, the following unwanted hydrocarbon reactions can occur.

ODICARBOXILI 25 AIF ACIDO CICLOHEXANODICARBOXILIC As can be seen, the AIF can be hydrogenated to cyclohexane dicarboxylic acid (CHDA) and cyclohexane carboxylic acid (CHCA). Only a small amount of CHCA is produced. The AIF can also be hydrogenated to m-toluic acid, but little mtoluic acid is produced in this route. Note that benzoic and toluic acids can also be produced from CBA. The secondary products are soluble in water, and in this way they are not totally difficult to eliminate. However, the secondary products represent a yield loss of the desired bromate dicarboxylic acid. Most of the past efforts proposed to decrease the amount of excess CHDA and CHCA produced during the purification centered around the addition of rhodium to the palladium / carbon catalyst, which is typically used in the purification process. For example, the United States Patent NO. 4,394,299 teaches the use of a Pd / Rh catalyst in bimetallic carbon for the purification of terephthalic acid to decrease the amount of 4-CBA and minimize the amount of the secondary product tm? Md ^^ a? HH ^ CHDA. The Patents of the United States NO. 4,629,715 and 4,892,972 teach the use of stratified catalyst beds consisting of a Rh / C catalyst layer before or after the volume of Pd / C catalysts. However, rhodium is very expensive. Accordingly, it is an object of the present invention to purify aromatic dicarboxylic acids to remove the chain termination byproducts and remove the yellow fluorenones. It is a further object of the present invention to catalytically hydrogenate the impurities of the oxygenation of a dialkyl aromatic while minimizing the generation of side products. It is still further an object of the present invention to minimize the hydrogenation of the desired product of dicarboxylic acid without decreasing the rate of hydrogenation of impurities such as CBA and colored bodies. It is another object of the present invention to purify aromatic dicarboxylic acid while avoiding the use of expensive rhodium catalysts. These together with other objects are made by providing a method for purifying aromatic dicarboxylic acids which oxidize m-xylene or p-xylene to produce unpurified isophthalic acid or unpurified terephthalic acid, respectively. The products of the oxidation step are hydrogenated in the presence of a palladium catalyst. The carbon monoxide is introduced during the hydrogenation step. The palladium catalyst is provided on a carbon substrate. The products of the oxidation step are dissolved in a solvent, which may be water, prior to the hydrogenation step. The products of the oxidation stage can be dissolved at an elevated temperature above the normal boiling point of the solvent. The production stage produced isophthalic acid, 3-carboxybenzaldehyde and fluorenones in the case of oxidizing m-xylene and produces terephthalic acid, 4-carboxybenzaldehyde and fluorenones in the case of oxidizing p-xylene. The step may include the step of monitoring the disappearance of 3-carboxybenzaldehyde in the case of oxidizing m-xylene and 4-carboxybenzaldehyde in the case of oxidizing p-xylene, and reducing carbon monoxide when the rate of disappearance is below a minimum default The hydrogenation step hydrogenates the 3-carboxylbenzaldehyde to m-toluic acid and 3-hydroxymethylbenzoic acid in the case of oxidizing m-xylene and hydrogenates the 4-carboxybenzaldehyde to p-tolucio acid and 4-hydroxymethylbenzoic acid in the case of oxidizing p- xylene. After the hydrogenation step, the isophthalic acid or terephthalic acid can be crystallized. Carbon monoxide can be maintained in a concentration It is obtained from 10 to 1000 ppm based on added hydrogen and carbon monoxide, and preferably maintained at 100 to 500 ppm. Other aromatic carboxylic acids can also be purified by this process. The invention will now be described with reference to the following detailed description and Examples which are given for illustration only, without limitation. According to a preferred embodiment, the products of an oxidation reaction of an aromatic dialkyl are hydrogenated in the presence of a palladium catalyst in a liquid phase reaction. The reaction by-products are dissolved in a solvent, such as water. If the water is used as the solvent, the water must be heated to ensure dissolution of the products of the oxidation reaction. For example, when producing AIF, water is heated to approximately 260 ° C. Of course, at these temperatures, the water is above its normal boiling point, and thus the solution occurs under pressure. The amount of the oxidation product that can be combined in the solvent will, of course, vary from solvent to solvent. However, for water, the water mixture oxidation product contains about 20 weight percent of the oxidation product. The hydrogenation catalyst is commonly palladium on a carbon support (charcoal), the catalyst contains 0.5 weight percent palladium. Other supports can also be used. For example, the palazzo in support of Ti02 is adequate. Hydrogenation is carried out using a partial pressure of hydrogen gas in such a way that the hydrogen goes into the solution. The hydrogen partial pressure can be 10-100 psi absolute. Carbon monoxide is added to the hydrogen feed gas to preserve the aromatic dicarboxylic acid. That is, by adding carbon monoxide to the hydrogen feed gas, the hhydrogenation of the aromatic dicarboxylic acid is suppressed such that the hydrogenated by-products are reduced. The addition of carbon monoxide has little effect on the removal of fluoresceous colored bodies of fluorenone or incomplete chain termination oxidation products, such as CBA. The amount of carbon monoxide used in the feed gas varies from about 10 ppm based on H2 + CO to 1000 ppm. Preferably, the amount of CO should be within the range of 100 to 500 ppm. The present invention works with any dicarboxylic acid, but is especially useful in the purification of isophthalic acid (AIF) and terephthalic acid (ATF). With reference to Table 1, Examples 1-7 demonstrate that the addition of small amounts of CO, typically 100 ppm to 500 ppm, serves to decrease the amount of CHDA produced after hydrogenation, while not performing the desired hydrogenation of CBA . In each of Examples 1-6, a tita or gallon autoclave equipped with a drip catalyst basket and a bottom-mounted flow valve is charged with 1400 grams of water and 25D grams of unpurified AIF. It contains 800 ppm of 3-CBA. TABLE I For examples 1-6, the autoclave is sealed and heated to 230 ° C while stirring the mixture. Afterwards, H2 is introduced to reach the various partial pressures listed in Table 1. In examples 2 and 5, the H; it contains 100 ppm of CO, and in examples 3, 6 and 7, the H2 contains 500 ppm of CO. Before the catalyst falls into the autoclave, a T = 0 sample is taken through the flow valve. At this point, the catalyst basket starts to fall into the mix. The catalyst basket contains 2 grams of palladium / carbon catalyst containing 0.5 weight percent palladium. Samples are taken from the flow valve at 10, 20", 40, 60 and 90 minutes.These samples are evaporated to dryness and analyzed for hydroxymethylbenzoic acid, toluic acid, 3-CBA, benzoic acid, cis and trans 3-CHDA and AIF .- ^ j-as constants of velocity cié first order for the disappearance of 3-CBA and the appearance drops 3-CHDA are calculated from the logarithm graphs .. Example 7 is related to the purification of ATF.For example, the ATF is dissolved without purify at a temperature of 260 ° C with other conditions that are the same .. As can be seen by comparing the rate constants for the appearance of CHDA in Table 1, the addition of small amounts of carbon monoxide in examples 2, 3 and 5-7 significantly decreases the amount of CHD ^ produced when compared to Examples 1 and 4 in which CO is not used. The more CO is used, the faster the production rate of CHDA decreases Compare Examples 2 and 3 and examples 5 and 6. In example 3, when they are introduced 500 ppm of CO with a partial pressure of H2 of 100 psi, the constant of 'speed to produce CHDA is 0.0. However, for Example 3, the rate constant for the disappearance of CBA decreases to 0.044. In this way, perhaps much more CO is used in Example 3. On the other hand, in Example 6, 500 ppm of CO are also used. However, when comparing Examples 4-6, it can be seen that the rate of disappearance of the CBA impurity is higher in Example 6 (116), which uses more CO than Examples 4 or 5. Both Examples 3 and 6 they use the same concentration of CO, 500 ppm, but Example 6 has a higher partial H2 pressure. Table 1, therefore, demonstrates that if the partial pressure of H2 is increased, it is acceptable to use more carbon monoxide. The results shown in Table 1 clearly indicate that the addition of small amounts of CO for the purification of aromatic dicarboxylic acids significantly decreases the production of unwanted by-products. In example 3, the elimination of CBA is decreased by 59%. In this way, although small amounts of carbon monoxide are desirable, much carbon monoxide is not good. The exact reason for this is not completely understood. However, how much carbon monoxide is a lot depends on the hydrogen pressure. Carbon monoxide can bind to a portion of the hydrogenation sites in palladium. Oxidation impurities (such as CBA, toluic acid and fluorenones) can be more easily hydrogenated than AIF and ATF. In this case, the addition of small amounts of carbon monoxide can not greatly affect the hydrogenation of the oxidation impurities. However, since AIF and ATF are less easily hydrogenated, the addition of small amounts of CO can decrease the hydrogenation of AIF and ATF.

There are several ways to control the amount of carbon monoxide added to the process. For example, a large amount of carbon monoxide can be added, the catalyst bed is fresh. It has been shown that a bed of fresh catalyst more easily hydrogenates aromatic dicarboxylic acids. After the final addition of CO, the hydrogenation products can be monitored. When the disappearance ratio of CBA begins to decrease, this may indicate that many sites in the catalyst have been poisoned. At this point, the carbon monoxide feed is diminished, or the source of carbon monoxide is simply removed. The deactivation of the catalyst towards the desired dicarboxylic acid is reversible. That is, after the elimination or reduction of the source of monoxide d? carbon, the catalyst will become reactivated. It is important to monitor this reactivation to ensure that the hydrogenation of the aromatic carboxylic acid AIF or ATF does not occur. For this purpose, the concentration of CBA can be monitored. After the disappearance of CBA reaches an acceptable ratio, the carbon monoxide feed can be decreased or, if the carbon monoxide feed is removed completely, the CO feed can be reintroduced. Of course, the CO feed can eventually be stabilized at the concentration Jg | U ^^ ?? L ^^^^^^^^^^^^^^^^^^^^ - ^ - ^ _ ^ - ^ ¡feg¡¡¡K == j¡¡ desired so that it is not necessary to change the proportion of CO feed. The many features and advantages of the invention are apparent from the detailed specification and, thus, it is proposed by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. In addition, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the exact construction and operation illustrated and described, and therefore all suitable and equivalent modifications can be reclassified, to fall within the scope of the invention. invention.

Claims

CLAIMS 1. A method for purifying an aromatic dicarboxylic acid, characterized in that it comprises the steps of: oxidizing an aromatic dialkyl to an aromatic dicarboxylic acid without purification; contacting the products of the oxidation step with hydrogen in the presence of a palladium catalyst; and introducing carbon monoxide during the hydrogenation step, the amount of carbon monoxide introduced that is less than or equal to 1000 ppm based on the added hydrogen and carbon monoxide.
2. A method for purifying an aromatic acido dicarboxylic acid in accordance with the claim 1, characterized in that the palladium catalyst is provided on a carbon substrate.
3. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that the products of the oxidation step are dissolved in a solvent prior to the hydrogenation step.
4. A method for purifying an aromatic dicarboxylic acid according to claim 3, characterized in that water is used as the solvent. t $ 1 '3 ~
5. A method for purifying an aromatic dicarboxylic acid according to claim 3, characterized in that the products of the oxidation step are dissolved in a solvent at a temperature 5 high, above the normal boiling point of the solvent.
6. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that the oxidation step produces colored bodies of aromatic dicarboxylic acid and an aldehyde of 10 aromatic carboxylic acid.
7. A method of purifying an aromatic dicarboxylic acid according to claim 6, characterized in that it further comprises the step of monitoring the disappearance of the acid aldehyde and reducing the 15 introduction of carbon monoxide when the rate of disappearance is below a predetermined minimum.
8. A method for purifying an aromatic dicarboxylic acid according to claim 6, characterized in that the hydrogenation step hydrogenates 20 the aromatic carboxylic acid aldehyde to an aromatic alkyl carboxylic acid and a carboxylic acid of an aromatic alcohol.
9. A method for purifying an aromatic dicarboxylic acid in accordance with claim 25 1, characterized in that carbon monoxide is introduced intermittently during the hydrogenation step.
10. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that it further comprises the step of, after the hydrogenation step, crystallizing the aromatic carboxylic acid.
11. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that the carbon monoxide is maintained at a concentration of 100 to 500 ppm, based on the added hydrogen and carbon monoxide.
12. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that the carbon monoxide is maintained at a concentration of 10 to 1000 ppm based on the added hydrogen and carbon monoxide.
13. A method for purifying an aromatic dicarboxylic acid according to claim 1, characterized in that the palladium catalyst is provided on a Ti02 substrate.
A method for purifying an aromatic dicarboxylic acid, characterized in that it comprises the steps of: oxidizing m-xylene or p-xylene to produce unpurified isophthalic acid or unpurified terephthalic acid, respectively; contracting the products of the oxidation step with hydrogen in the presence of a palladium catalyst; and introducing carbon monoxide during the hydrogenation step, the amount of carbon monoxide introduced which is less than or equal to 1000 ppm based on the added hydrogen and carbon monoxide.
15. A method for purifying an aromatic dicarboxylic acid in accordance with claim 14, characterized in that the palladium catalyst is provided on a carbon substrate.
16. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that the products of the oxidation step are dissolved in a solvent prior to the hydrogenation step.
17. A method for purifying an aromatic dicarboxylic acid according to claim 16, characterized in that water is used as the solvent.
18. A method for purifying an aromatic dicarboxylic acid according to claim 16, characterized in that the products of the oxidation step are dissolved in a solvent at an elevated temperature above the normal boiling point of the solvent. Mfegjj «j ^
19. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that the oxidation step produces" isophthalic acid, 3-carboxybenzaldehyde and fluorenones in the case of 5 oxidizes m-xylene and produces terephthalic acid, 4-carboxybenzaldehyde and fluorenones in the case of oxidizing p-xylene.
20. A method for purifying an aromatic dicarboxylic acid in accordance with the claim 10 19, further characterized because it comprises the step of monitoring the disappearance of 3-carboxybenzaldehyde in the case of oxidizing m-xylene and 4-carboxybenzaldehyde in the case of oxidizing p-xylene, and reducing the amount of carbon monoxide when the speed of disappearance is below a minimum 15 predetermined.
21. A method for purifying an aromatic dicarboxylic acid according to claim 19, characterized in that the hydrogenation step hydrogenates the 3-carboxylbenzaldehyde to m-toluic acid and 3- 20-hydroxymethylbenzoic acid in the case of oxidizing m-xylene s hydrogenated. 4-carboxybenzaldehyde to p-toluic acid and 4-hydroxymethylbenzoic acid in the case of oxidizing p-xylene.
22. A method for purifying an aromatic dicarboxylic acid in accordance with claim 25 14, characterized in that carbon monoxide is introduced intermittently during the hydrogenation step.
23. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that it further comprises the step of, after the hydrogenation step, crystallizing isophthalic acid or terephthalic acid.
24. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that the carbon monoxide is maintained at a concentration of 100 to 500 ppm based on the added hydrogen and carbon monoxide.
25. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that the carbon monoxide is maintained at a concentration of 10 to 1000 ppm based on the added hydrogen and carbon monoxide.
26. A method for purifying an aromatic dicarboxylic acid according to claim 14, characterized in that the palladium catalyst is provided on a Ti02 substrate.
27. A method for purifying an aromatic dicarboxylic acid, characterized in that it comprises the steps of: oxidizing an aromatic dialkyl to an aromatic dicarboxylic acid without purifying to produce bodies ^ ú ^ ± ín ^ mffl - C-i-rii- ^ fffl 'r rf? - * - "- ******* to *** - ^ ** colorful aromatic dicarboxylic acid and an aromatic carboxylic acid aldehyde, contact the products of the oxidation stage with hydrogen in the presence of a palladium catalyst, and introducing carbon monoxide during the hydrogenation stage, the weight of the carbon monoxide introduced which is equal to or less than 1/999 the weight of the introduced hydrogen
28. A method for purifying an aromatic dicarboxylic acid , characterized in that it comprises the steps of: oxidizing an aromatic dialkyl to an unpurified aromatic dicarboxylic acid having impurities, contacting the products of the oxidation step with hydrogen in the presence of a palladium catalyst to hydrogenate the impurities; and introducing carbon monoxide during the hydrogenation step, the amount of carbon monoxide introduced that is less than or equal to 1000 ppm based on the added hydrogen and carbon monoxide.
29. A method for purifying an aromatic dicarboxylic acid, characterized in that it comprises the steps of: oxidizing an aromatic dialkyl to an unpurified aromatic dicarboxylic acid having impurities; contacting the products of the oxidation step with hydrogen in the presence of a palladium catalyst to hydrogenate the impurities; and introducing carbon monoxide during the hydrogenation step, the weight of the carbon monoxide introduced which is equal to or less than 1/999 the weight of introduced hydrogen. . ~ * * ** te * Bu * > e. SUMMARY OF THE INVENTION A method for purifying an aromatic dicarboxylic acid by oxidizing m-xylene or p-xylene to produce unpurified isophthalic acid or unpurified terephthalic acid, respectively. The products of the oxidation step are hydrogenated in the presence of a palladium catalyst. Carbon monoxide is introduced during the hydrogenation step. The palladium catalyst is provided on a carbon substrate. The products of the oxidation stage 10 are dissolved in a solvent, which may be water, prior to the hydrogenation step. The products of the oxidation stage can be dissolved at an elevated temperature above the normal boiling point of the solvent. The oxidation step produces isophthalic acid, 3-carboxybenzaldehyde 15 and fluorenones in the case of oxidizing m-xylene and produces terephthalic acid, 4-carboxybenzaldehyde and fluorenones in the case of oxidizing p-xylene. It may be useful to monitor the disappearance of 3-carboxybenzaldehyde in the case of oxidizing m-xylene and 4-carboxybenzaldehyde in the case of oxidizing p-xylene, and reducing 20 the amount of carbon monoxide when the rate of disappearance is below a predetermined minimum. After the hydrogenation step, the isophthalic acid or terephthalic acid can be crystallized. Carbon monoxide can be maintained at a concentration of 100 to 5000 ppm in 25 based on added hydrogen and carbon monoxide. They may be ^^^ ftiiiilriffií ffffirifiw '- "^ -" - "- • -" - ** • -' also purified other aromatic dicarboxylic acids by this procedure. < ittft ^ i¿ & ^ ¿r. ^ - ^ ... * g ^ «^. J« ^ -.-- - ?? gjjirfíri ??