CA1042459A - Process for producing a non-blackened phthalic acid from the corresponding tolualdehyde - Google Patents
Process for producing a non-blackened phthalic acid from the corresponding tolualdehydeInfo
- Publication number
- CA1042459A CA1042459A CA244,015A CA244015A CA1042459A CA 1042459 A CA1042459 A CA 1042459A CA 244015 A CA244015 A CA 244015A CA 1042459 A CA1042459 A CA 1042459A
- Authority
- CA
- Canada
- Prior art keywords
- tolualdehyde
- terephthalic acid
- solvent
- acid
- reaction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
- C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
A PROCESS FOR PRODUCING A NON-BLACKENED PHTHALIC ACID
FROM THE CORRESPONDING TOLUALDEHYDE
Abstract of the Disclosure:
A process for producing a non-blackened phthalic acid from the corresponding tolualdehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent and heavy metal salt(s) containing at least one manganese salt, especially both manganese and cobalt salts, and at least one bromine com-pound as a catalyst, characterized in that the water con-tent in the reaction solution into which the tolualdehyde is introduced is maintained at less than 10% by weight based on the combined weight of the solvent and water in the solution is disclosed.
FROM THE CORRESPONDING TOLUALDEHYDE
Abstract of the Disclosure:
A process for producing a non-blackened phthalic acid from the corresponding tolualdehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent and heavy metal salt(s) containing at least one manganese salt, especially both manganese and cobalt salts, and at least one bromine com-pound as a catalyst, characterized in that the water con-tent in the reaction solution into which the tolualdehyde is introduced is maintained at less than 10% by weight based on the combined weight of the solvent and water in the solution is disclosed.
Description
~L~34~5i9 This invention relates to a process ~or producing a phthalic acid which comprises oxidizing the corresponding tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphaticmonocarboxylic acid as a solvent and heavy metal salt(s) containing as at least one manganese salt and at least one bromine compound as catal~st and more particularly relates to a process for producing a phthalic acid from the cor-responding tolualdehyde, characterized in that the watercontent o~ the reaction solution into which the tolualdehyde is introduced is maintained at less than 10% by weight based on the weight of the solution9 thereby preventing blackening of t~e resulting phthalic acid.
Japanese Patent Publication No. 2666/1959 filed on May 4, 1955 discloses that when an at least one aliphatic group-substituted aromatic compound is oxidized with molecular oxygen or a molecular oxygen-containing gas in a liquld phase by using a lower aliphatic monocarboxylic acid as a solvent and a heavy metal salt containing a manganese salt and a bromine compound as a catalyst, the corresponding aromatic carboxylic acid is formed. Terephthalic acid and iso-phthalic acid have been prepared from p-xylene and m-xylene, respectively, on an industrial scale by using the above mentioned process.
Japanese Patent Publication No. 2666/1959 discloses that a manganese salt is an excellent catalyst for producing an aromatic carboxylic acid ~rom the corresponding aliphatic group-substituted aromatic compound. The publication dis-closes that a cobalt salt also is an excellent catalyst~
Japanese Patent Publication No. 2666/1959 filed on May 4, 1955 discloses that when an at least one aliphatic group-substituted aromatic compound is oxidized with molecular oxygen or a molecular oxygen-containing gas in a liquld phase by using a lower aliphatic monocarboxylic acid as a solvent and a heavy metal salt containing a manganese salt and a bromine compound as a catalyst, the corresponding aromatic carboxylic acid is formed. Terephthalic acid and iso-phthalic acid have been prepared from p-xylene and m-xylene, respectively, on an industrial scale by using the above mentioned process.
Japanese Patent Publication No. 2666/1959 discloses that a manganese salt is an excellent catalyst for producing an aromatic carboxylic acid ~rom the corresponding aliphatic group-substituted aromatic compound. The publication dis-closes that a cobalt salt also is an excellent catalyst~
- 2 -':: ' , ' ."'' . .
... , ' . . .. .
~V~f~
In case of oxidizing p-xylene with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using acetic acid, etc. as a solvent, and a catalyst consisting of a heavy metal salt and a brom:ine sompound to obtain terephthalic acid, Journal of Industrial Chemistry~ Vol, 70, 1967, page 1155 discloses that a cobalt salt i~ the most effective ca-talyst of the heavy metal salts~ and that a manganese salt ranks next. Also, Organic Oxidation Reaction, written by Yoshio Kamiya, published by Gihodo in 1974 dis-closes that the heavy metal salts obtained by adding a manganese salt to a cobalt salt have a synergistic effect as a catalyst for producing terephthalic ac~d ~rom p-xylene.
Japanese Patent Publication No~ 367~2/1970 filed on June 26, 1967 discloses that polymerizable terephthalic acid of high i~ 15 purity can be ob-tained by oxidizing p-xylene and that a cobalt salt has an excellent catalytic action for the oxi-dization reaction. Considering these prior art technlques together, it was known that a mixture of a cobalt salt and a manganese salt have excellent catalytic action ~or oxidiz-ing p-xylene with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and a bromine compound - and a heavy metal salt as a catalyst to obtain terephthalic acid.
Journal of Industrial Chemistry, Vol. 67, 19649 page 1396 discloses that when p-xylene is oxidized in a system comprising a manganese salt as a metal component p-xylene is oxidized to terephthalic acid via p-toluic acid and 4-carboxy benzaldehyde (hereinunder abbreviated as 4CBA~.
Therefore, it seems self-evident that terephthalic acid can , ~ . , .: - . ~ ;
~ . . .
- . -be easily produced from p~tolualdehyde using the same catalyst as the one for producing terephthalic acid from p-xylene in the same way as -the prior artO
The inventors of`-the present invention, however, have found that when p-tolualdehyde is oxidized in place of p-xylene under the same continuous oxidizing conditions as those under which p-xylene is oxidized to terephthalic acid, dark gray terephthalic acid is surprisingly ~ormed~
In other words, we have found that a technical problem which does not occur in case of producing terephthalic acid from p-xylene occurs when terephthalic acid is prodùced from "
p-tolualdehyde. We have also found that blackening of the resulting terephthalic acid is caused by mixing o~ the manganese salt employed as one component of the catalyst in the resulting terephthalic acid. I-t is a matter o~
course that even if the dark gray terephthalic acid produced from p-tolualdehyde reacts wi-th glycols, polyesters having high whiteness can not be obtained. It was also ~ound that even i~ the dark gray terephthalic acid is washed with acetic acid, etc. the dark gray color can not be removed from the terephthalic acid. Similarly, we have ~ound that neither recrystallization of the dark gray terephthalic acid in acetic acid or water, nor particular recrystalliza-tion as disclosed in Japanese Patent Publication No. 16860/
1966 on March 27, 1964 removes the dark gray from the terephthalic acid. In other words, it was found that industrially valuable terephthalic acid can not be obtained from p-tolualdehyde as it is when p-xylene is oxidized to tereph-thalic acid.
In the prior art, terephthalic acid has been produced ,-: .. - . - :
.
s~
from p-xylene as a starting material on an industrial scale, because the technique o~ producing terephthalic acid from p-xylene has progressed by practicing the inventions dis closed in Japanese Patent Publication Nos. 2666/1959 and 36732/1970.
P-xylene which is employed as a starting material for the production of terephthallc acid is produced b~ com-plicated processes, such as isomerlzation of xylenes and separation of xylenes. On the other hand, it was known -that p-tolualdehyde can be easily produced from toluene and carbon monoxide. Recently, p-tolualdehyde has been produced by reac-ting -toluene with carbon mopo~ide in the presence of hydrogen fluoride and boron tri~luoride as a catalyst as disclosed in Japanese Patent Publication No~
29760/1964. Toluene can be more easily produced on an industrial scale than xylene. For example, separation of "
toluene ~rom aromatic hydrocarbons and purification of toluene are easier than those of p-xylene. Also, toluene is cheaper than p-xylene. Therefore, it is advantageous -~
that p-tolualdehyde produced from toluene can be used as a starting material ~or the production of terephthalic acid However, as mentioned above9 the technique for the production o~ terephthalic acid from p-xylene can not be applied to the technique for the production o~ terephthalic acid ~rom p-~5 tolualdehyde as it is.
The inventors of this invention have carried out awide range of research to ~ind an industrially valuable process for producing a phthalic acid which comprises oxidizing the corresponding tolualdehyde with molecular ,~; ~ , .
oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and heavy metal salt(s) containing at least one manganese salt and at least one bromine co`mpound as a catalyst.
As a result, we have found that in case of oxidizing p-tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using lower aliphatic monocarboxylic acid as a solvent in the presence of heavy metal salt containing at leas-t one manganese salt to ~or~
terephthalic acid, the water content in the lower aliphatic monocarboxylic acid has a great influence on the bYackening of terephthalic acid caused by mixing of manganese ~herein.
We have found that when p-tolualdehyde i~ oxidized in the liquid monocarboxylic acid by maintaining the w~ter content in a reaction solution into which p-tolualdehyde is introduced at less than 10% by weight based on the com~ined weight of the solvent and water in the reaction solution~ terephthalic acid which has high whiteness and is industrially ~aluable can be produced. This in~ent~on is based on these discovery.
Therefore, an object of this invention is to provide a process for producing a non-blackened phthalic acid from the corresponding tolualdehyde.
This invention relates to a process ~or producing a non-blackened phthalic acid from the corresponding tolu-aldehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and heavy metal salt(s) containing at ; .
'.. ~' ~ . -.':'' ,,, ;., ' 1.. ~ , , .... .
~ ~ ~ 2 4S~
least one rnanganese sal-t, especially bo-th manganese and cobalt sal-ts, and a bromine compound as a catalyst, charac~
terized in that the water content in a reaction solution into which -the tolualdehyde is introduced is maintained at less than 10% by weight based on the combined weight of the solvent and water in the solu-tion.
The term "reaction solution" means a mixture of the lower aliphatic monocarboxylic acid and water in the reaction system. In other words, when the oxidization reaction is contlnuously carried out in a reaction vessel of continuously agitating type, the term l'water content in a reaction solu-tion" means the concentration of water contained in ~he reaction solution which contacts with the tolualdehyde at the time it is introduced into the reaction system. The term "blackening of terephthalic acid" means that terephthalic acid in black, dark gray or gra~ish brown, etc~ is ~or~edO
Water which is present in the reaction solution comprises water contained in the solvent and water formed during oxidizing the tolualdehyde.
Even when the oxidization of p-tolualdehyde is carried out at such a high concentration of manganese at ~hich the oxidization of p-xylene is conventionally carried out~ -manganese is not mixed in the reaction terephthalic acid by maintaining the water content in the reaction solution at less 10% by weight based on the comblned weight of the solvent and water in the solution according -to this inven-tion. Therefore~ according to this invention, white tere-phthalic acid can be obtained.
The history of the tolualdehyde is not of a limiting ~0 nature to the process of this invention. In other words, . ~ ., . ~ , .
--.: . . . .. . . :
all tolualdehydes which have been prepared by a variety of methods can be used in the process of this invention. The tolualdehyde obtained by reaction o~ toluene wi-th carbon monoxide in the presence of hydrogen fluoride and boron trifluoride as a catalyst is preferably used as a starting material in the present process.
The catalyst employed in this invention may consist of heavy metal salt containing one or more manganese salt and one or more bromine compound. The catalyst may also consist of heavy metal salts containing one or more manganese salt and one or more cobalt salt, and one or more bromine -compound. The heavy metal salt includes inorganic salt or organic salt of manganese and inorganic or organic salt of cobalt. It is preferred that the heavy metal salt be soluble in the lower aliphatic monocarboxylic acid employed as a solvent. The proportion o~ the components constituting the catalyst of this invention in the reaction system is not critical in this invention. Independent of the amount o~
the components constituting the ca-talyst, a non-blackened phthalic acid can be obtained from the corresponding tolu-aldehyde by limiting the water content in the solution to a specific value. The manganese sal-t may be used in such amoun-t that the manganese atoms in the reaction solution ranges from 0.005% to 0.5% by weight based on the weight of the solvent. The cobalt salt may be used in such an amount that the proportion o~ cobalt atoms in the solution ranges from 0.01% to 0~3% by weight based on the weight o~ the solvent. The bromine compound includes an inorganic salt9 such as, for example ammonium bromide, sodium bromide, potassium bromide or hydrogen bromide, etc. and an organic .... - ~ ~ .
.: : , ; .
bromide, such as, for example te~rabromoe-thane or tetrabromo p-xylene, etc. The bromine compound may be used in such an amount that the proportion of bromine atoms in the solution ranges from 0.05% to 0.5% by weight based on the weight o~
the solvent.
Solution temperature is not critical. However, elevated temperature speeds the process and a temperature ranging from about 120CC to about 240C is advantageously employed. The oxidization reaction o~ this invention is carried out in the liquid phase. Therefore, it is preferred that the oxidization reaction be carried out under one or superatmosphere so as to keep the tolualdehyde and the solvent introduced into the reaction system in the liquid state~ The oxidization reac-tion is conveniently carried out under a pressure ranging from 1 to 50 atoms.
Molecular oxygen or a molecular oxygen-containing ; gas is used as an oæidizing agent. From an economic point ; of viaw air is the preferred oxidizing agent.
A lower aliphatic noncarboxylic acid9 such as acetic acid, propionic acid or butyric acid, etc. is conveniently used as the solvent. Acetic acid is preferred. The amount of lower aliphatic monocarboxylic acid used is conveniently at least two times as much as the tolualdehyde on the weight basis.
The presen-t process is particularly suitable ~or oxidizing p-tolualdehyde to form terephthalic acid. This is because not only p tolualdehyde is commercially available and the resulting terephthalic acid is useful, but also the effect of this invention is advantageous in case o~ the oxidation of p--tolualdehyde. This invention is more ~ : .
sui-table for continous or semi-continuous oxidizatlon of p-tolualdehyde.
The present invention is ~urther illustrated by the following Examples and Compara-tive Examples, However, this invention should not be limited by these examples7 and the changes and modifications wi-thin the spirit and scope of this invention can be effected. The percent and parts in the Examples are based on weight unless otherwise speci~ied.
~LL
Continuous oxidization of p ~olualdehyde was carried out in an apparatus for continuous oxidization reaction comprising a 2.5 ~ pressure reactor made o~ ti-tanium equipped with reflux condenser, stirring means, hea-ting means~ inlet for raw material, inlet for raw material gas, exit ~or gas exit for reaction product, and two receivers for the reaction product connected to the exit for reaction product of the reactor.
500 gr of acetic acid (having water content of 5%) containing 0.598 gr of cobalt acetate tetrahydrate, 1,265 gr o~ manganese acetate and 0.654 gr of tetrabromoethane was charged into the reactor. The pressure in the reactor was - raised to 10 Kg/cm2 by blowing nitrogen gas into the reactor9 and thereafter the temperature in the reactor was raised to 210C. Feeding solution having the following components was prepared in another container:
cobalt acetate te-tra hydrate (Co content in the feeding solution 0.0283%~
manganese acetate (Mn content in the feeding solution 0.0567%) tetrabromo ethane ( Br content in the feeding solution 0.121%) balance of acetic acid (having water con-tent of 0.03%~
The feeding solution was continuously fed into the reactor at the rate of 1120 gr/hr, and p-tolualdehyde was continuously fed into the reactor at the rate o~ 225 gr/hr at 210C and at 18.0 Kg/cm2 gauge. At the same time9 air was blown into the reactor at such a rate as to maintain oxygen content in the gas withdrawn from the exit for gas of the reactor at 3%. The water content in the reaction solution was 9.80% in the stationary sta-te. The reaction product in the slurry state was continuously withdrawn from the reactor to the receiver. The reaction product was filtered, and cake was separated from the filtrate. The cake was washed twice with acetic acid solution twice as much as the cake and then was washed twice with water twice as much as the cake, and was dried to obtain terephthalic ~-acid. The yield of terephthalic acid was 96.6/~ on the mol basis.
The resulting terephthalic acid had the following properties:
Appearance white 4CBA contained the terephthalic acid 1420 ppm Alkaline color* 0.637 Ash contained in the terephthalic acid 8.0 ppm * 2 gr of the terephthalic acid was dissolved in 25 ml of a 2 normal solution of potassium hydroxide. The resulting solution was placed in 50 mm cell~ The cell was exposed to light having wavelength of 340 m~ to determine ... .. . . . . : ..
4~9 optical density. The alkaline color expresses the resulting optical density.
The resulting terephthalic~ acid was hydrogenated with molecular hydrogen in the presence of a catalyst and was recrystallized in hot water as disclosed in Japanese Patent Publication No. 16860/1966. The solution was lowerad to a room temperature, and the terephthalic acid was removed from the solution. The resulting terephthalic acid had the following properties:
Appearance white 4CBA contained in the terephthalic acid less than 10 ppm alkaline color 0~090 The resulting terephthalic acid reacted with ethylene glycol to form polyethylene terephthalate. The resulting polyethylene terephthalate was clear.
f~
500 gr o~ acetic acid (having water content of 15%) containing 0.598 gr of cobalt acetate tetrahydrate, 1.265 gr of manganese acetate and 0.654 gr o~ tetrabromoethane was charged into the reactor employed in Example 1. The pressure in the reactor was raised to 10 Kg/cm2 by blowing nitrogen gas into the reactor, and thereafter the temperature in the reactor was raised to 220C. Feeding solution having the following components was prepared in another container:
cobalt acetate tetra hydra-te (Co content in the feeding solution 0.0283%) manganese acetate (Mn content in the feeding solution 0.0567%) . ~ . :~ : . .
,. . ~ , , 2~9 tetrabromo ethane (Br content in the feeding solution 0.121%) balance o~ ace-tic acid (having wa-ter content o~ 5%) The feeding solution was continuously ed into the reactor at the rate of 782 gr/hr, and p-tolualdehyde was continuously fed into the reactor at the rate of 295 ~r/hr at 220C and at 23.8 Kg/cm2 Gauge. At the same time alr was blown into the reactor at such a rate as to maintain the oxygen content in the gas wi-thdrawn from the exit for gas in the reactor at 3%. The water content in the reaction solution was 13~2% in the stationary state. The reaction product in a slurry state was continuously withdrawn from the reactor. The resulting product was treated in the same way as in Example 1.
The resulting terephthalic acid had the following propertieso Appearance dark gray 4CBA contained in the terephthalic acid 1210 ppm ;
Alkaline color Ash contained in the terephthalic acid 1100 ppm Mn304 in the ash (based on the weight of ~ the terephthalic acid) 765 ppm ; The yield of terephthalic acid was 88.1% on the mole basis. However, even if the terephthalic acid was re~rystal-lized in hot water, the black color of the terephthalic acid caused by manganese remained. The terephthalic acid was - hydrogenated and was recrystallized in hot water in the same way as that of Example 1. The resulting terephthalic acid was dark gray. The terephthalic acid which was hydro-genated and recrystallized reacted with ethylene glycol to ,.,; .. . . . . . . . .
',',: ~ . : ~
455~
form polyethylene -terephthalate. The resul-ting polyethylene terephthalate was dark gray.
Example 2 The procedure of Example 1 was repeated except that 500 gr of acetic acid (having water conten-t of 5%) contain-ing 1~52 gr of cobalt acetate tet;rahydrate, 0.402 gr o~
manganese acetate and 0.654 gr of tetrabromoethane was charged into the reactor before introducing p-tolualdehyde into the reactor, the feeding solution (containing 720 ppm of Co, 180 ppm of Mn and 280 ppm o~ Br) was continuously introduced into the reactor, the temperature of the rea~tor was 206C, and the feeding rate of p-tolualdehyde is 217 gr/hr and the feeding rate of the feeding solution was 108~ gr/hr.
The water content in the reaction solution was 7.80%
in the stationary state.
The resulting terephthalic acid had the following propertieso Appearance white 4CBA contained in the terephthalic acid 1160 ppm Alkaline color 0.650 Ash contained in the terephthalic acid 10 ppm The yield of terephthalic acid was 96.8% on the mole basis. The terephthalic acid was hydrogenated and recrystal-lized in the same way as in Example 1. The resulting tere-phthalic acid had the same properties as those of Example 1.The polyethylene terephthalate obtained by reacting ethylene glycol therewi-th was clear.
~L ' ,.
The procedure of Example 2 was repeated except that the water content of the acetic acid charged into the . ' ' . . ' ,' ~ ~2~S~
reaction sys-tem before introducing p-tolualdehyde into the reactor was 10%, the ~eeding rate o~ p-tolualdehyde was 296 gr/hr and the feeding rate o~ the feeding solution wa8 786 gr/hr, and the pressure in the reactor Was 17.5 Kg/cm2 Gauge. The water con-tent in the reaction solution was 11.2%
in the stationary state.
The resulting terephthalic acid had the following propertles~
Appearance - dark gray 4CBA contained in the terephthalic acid lZ10 ppm Alkaline color ~-~O
Ash contained in the terephthalic acid 500 ppm And the yield of terephthalic acid was 92.3% on the mole basisO The terephthalic acid was hy~rogenated and recrystallized in the same way as in Example 1. The result-ing terephthalic acid was black. The terephthalic acld which was hydrogenated and recrystallized reacted with ethylene glycol to form polyethylene terephthalate. The resulting polyethylene terephthalate was dark gray, ~ 15 -, .. . . . . . . . .
;.'. ,': . ;. . ~ ' ' ' . .
... , ' . . .. .
~V~f~
In case of oxidizing p-xylene with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using acetic acid, etc. as a solvent, and a catalyst consisting of a heavy metal salt and a brom:ine sompound to obtain terephthalic acid, Journal of Industrial Chemistry~ Vol, 70, 1967, page 1155 discloses that a cobalt salt i~ the most effective ca-talyst of the heavy metal salts~ and that a manganese salt ranks next. Also, Organic Oxidation Reaction, written by Yoshio Kamiya, published by Gihodo in 1974 dis-closes that the heavy metal salts obtained by adding a manganese salt to a cobalt salt have a synergistic effect as a catalyst for producing terephthalic ac~d ~rom p-xylene.
Japanese Patent Publication No~ 367~2/1970 filed on June 26, 1967 discloses that polymerizable terephthalic acid of high i~ 15 purity can be ob-tained by oxidizing p-xylene and that a cobalt salt has an excellent catalytic action for the oxi-dization reaction. Considering these prior art technlques together, it was known that a mixture of a cobalt salt and a manganese salt have excellent catalytic action ~or oxidiz-ing p-xylene with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and a bromine compound - and a heavy metal salt as a catalyst to obtain terephthalic acid.
Journal of Industrial Chemistry, Vol. 67, 19649 page 1396 discloses that when p-xylene is oxidized in a system comprising a manganese salt as a metal component p-xylene is oxidized to terephthalic acid via p-toluic acid and 4-carboxy benzaldehyde (hereinunder abbreviated as 4CBA~.
Therefore, it seems self-evident that terephthalic acid can , ~ . , .: - . ~ ;
~ . . .
- . -be easily produced from p~tolualdehyde using the same catalyst as the one for producing terephthalic acid from p-xylene in the same way as -the prior artO
The inventors of`-the present invention, however, have found that when p-tolualdehyde is oxidized in place of p-xylene under the same continuous oxidizing conditions as those under which p-xylene is oxidized to terephthalic acid, dark gray terephthalic acid is surprisingly ~ormed~
In other words, we have found that a technical problem which does not occur in case of producing terephthalic acid from p-xylene occurs when terephthalic acid is prodùced from "
p-tolualdehyde. We have also found that blackening of the resulting terephthalic acid is caused by mixing o~ the manganese salt employed as one component of the catalyst in the resulting terephthalic acid. I-t is a matter o~
course that even if the dark gray terephthalic acid produced from p-tolualdehyde reacts wi-th glycols, polyesters having high whiteness can not be obtained. It was also ~ound that even i~ the dark gray terephthalic acid is washed with acetic acid, etc. the dark gray color can not be removed from the terephthalic acid. Similarly, we have ~ound that neither recrystallization of the dark gray terephthalic acid in acetic acid or water, nor particular recrystalliza-tion as disclosed in Japanese Patent Publication No. 16860/
1966 on March 27, 1964 removes the dark gray from the terephthalic acid. In other words, it was found that industrially valuable terephthalic acid can not be obtained from p-tolualdehyde as it is when p-xylene is oxidized to tereph-thalic acid.
In the prior art, terephthalic acid has been produced ,-: .. - . - :
.
s~
from p-xylene as a starting material on an industrial scale, because the technique o~ producing terephthalic acid from p-xylene has progressed by practicing the inventions dis closed in Japanese Patent Publication Nos. 2666/1959 and 36732/1970.
P-xylene which is employed as a starting material for the production of terephthallc acid is produced b~ com-plicated processes, such as isomerlzation of xylenes and separation of xylenes. On the other hand, it was known -that p-tolualdehyde can be easily produced from toluene and carbon monoxide. Recently, p-tolualdehyde has been produced by reac-ting -toluene with carbon mopo~ide in the presence of hydrogen fluoride and boron tri~luoride as a catalyst as disclosed in Japanese Patent Publication No~
29760/1964. Toluene can be more easily produced on an industrial scale than xylene. For example, separation of "
toluene ~rom aromatic hydrocarbons and purification of toluene are easier than those of p-xylene. Also, toluene is cheaper than p-xylene. Therefore, it is advantageous -~
that p-tolualdehyde produced from toluene can be used as a starting material ~or the production of terephthalic acid However, as mentioned above9 the technique for the production o~ terephthalic acid from p-xylene can not be applied to the technique for the production o~ terephthalic acid ~rom p-~5 tolualdehyde as it is.
The inventors of this invention have carried out awide range of research to ~ind an industrially valuable process for producing a phthalic acid which comprises oxidizing the corresponding tolualdehyde with molecular ,~; ~ , .
oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and heavy metal salt(s) containing at least one manganese salt and at least one bromine co`mpound as a catalyst.
As a result, we have found that in case of oxidizing p-tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using lower aliphatic monocarboxylic acid as a solvent in the presence of heavy metal salt containing at leas-t one manganese salt to ~or~
terephthalic acid, the water content in the lower aliphatic monocarboxylic acid has a great influence on the bYackening of terephthalic acid caused by mixing of manganese ~herein.
We have found that when p-tolualdehyde i~ oxidized in the liquid monocarboxylic acid by maintaining the w~ter content in a reaction solution into which p-tolualdehyde is introduced at less than 10% by weight based on the com~ined weight of the solvent and water in the reaction solution~ terephthalic acid which has high whiteness and is industrially ~aluable can be produced. This in~ent~on is based on these discovery.
Therefore, an object of this invention is to provide a process for producing a non-blackened phthalic acid from the corresponding tolualdehyde.
This invention relates to a process ~or producing a non-blackened phthalic acid from the corresponding tolu-aldehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and heavy metal salt(s) containing at ; .
'.. ~' ~ . -.':'' ,,, ;., ' 1.. ~ , , .... .
~ ~ ~ 2 4S~
least one rnanganese sal-t, especially bo-th manganese and cobalt sal-ts, and a bromine compound as a catalyst, charac~
terized in that the water content in a reaction solution into which -the tolualdehyde is introduced is maintained at less than 10% by weight based on the combined weight of the solvent and water in the solu-tion.
The term "reaction solution" means a mixture of the lower aliphatic monocarboxylic acid and water in the reaction system. In other words, when the oxidization reaction is contlnuously carried out in a reaction vessel of continuously agitating type, the term l'water content in a reaction solu-tion" means the concentration of water contained in ~he reaction solution which contacts with the tolualdehyde at the time it is introduced into the reaction system. The term "blackening of terephthalic acid" means that terephthalic acid in black, dark gray or gra~ish brown, etc~ is ~or~edO
Water which is present in the reaction solution comprises water contained in the solvent and water formed during oxidizing the tolualdehyde.
Even when the oxidization of p-tolualdehyde is carried out at such a high concentration of manganese at ~hich the oxidization of p-xylene is conventionally carried out~ -manganese is not mixed in the reaction terephthalic acid by maintaining the water content in the reaction solution at less 10% by weight based on the comblned weight of the solvent and water in the solution according -to this inven-tion. Therefore~ according to this invention, white tere-phthalic acid can be obtained.
The history of the tolualdehyde is not of a limiting ~0 nature to the process of this invention. In other words, . ~ ., . ~ , .
--.: . . . .. . . :
all tolualdehydes which have been prepared by a variety of methods can be used in the process of this invention. The tolualdehyde obtained by reaction o~ toluene wi-th carbon monoxide in the presence of hydrogen fluoride and boron trifluoride as a catalyst is preferably used as a starting material in the present process.
The catalyst employed in this invention may consist of heavy metal salt containing one or more manganese salt and one or more bromine compound. The catalyst may also consist of heavy metal salts containing one or more manganese salt and one or more cobalt salt, and one or more bromine -compound. The heavy metal salt includes inorganic salt or organic salt of manganese and inorganic or organic salt of cobalt. It is preferred that the heavy metal salt be soluble in the lower aliphatic monocarboxylic acid employed as a solvent. The proportion o~ the components constituting the catalyst of this invention in the reaction system is not critical in this invention. Independent of the amount o~
the components constituting the ca-talyst, a non-blackened phthalic acid can be obtained from the corresponding tolu-aldehyde by limiting the water content in the solution to a specific value. The manganese sal-t may be used in such amoun-t that the manganese atoms in the reaction solution ranges from 0.005% to 0.5% by weight based on the weight of the solvent. The cobalt salt may be used in such an amount that the proportion o~ cobalt atoms in the solution ranges from 0.01% to 0~3% by weight based on the weight o~ the solvent. The bromine compound includes an inorganic salt9 such as, for example ammonium bromide, sodium bromide, potassium bromide or hydrogen bromide, etc. and an organic .... - ~ ~ .
.: : , ; .
bromide, such as, for example te~rabromoe-thane or tetrabromo p-xylene, etc. The bromine compound may be used in such an amount that the proportion of bromine atoms in the solution ranges from 0.05% to 0.5% by weight based on the weight o~
the solvent.
Solution temperature is not critical. However, elevated temperature speeds the process and a temperature ranging from about 120CC to about 240C is advantageously employed. The oxidization reaction o~ this invention is carried out in the liquid phase. Therefore, it is preferred that the oxidization reaction be carried out under one or superatmosphere so as to keep the tolualdehyde and the solvent introduced into the reaction system in the liquid state~ The oxidization reac-tion is conveniently carried out under a pressure ranging from 1 to 50 atoms.
Molecular oxygen or a molecular oxygen-containing ; gas is used as an oæidizing agent. From an economic point ; of viaw air is the preferred oxidizing agent.
A lower aliphatic noncarboxylic acid9 such as acetic acid, propionic acid or butyric acid, etc. is conveniently used as the solvent. Acetic acid is preferred. The amount of lower aliphatic monocarboxylic acid used is conveniently at least two times as much as the tolualdehyde on the weight basis.
The presen-t process is particularly suitable ~or oxidizing p-tolualdehyde to form terephthalic acid. This is because not only p tolualdehyde is commercially available and the resulting terephthalic acid is useful, but also the effect of this invention is advantageous in case o~ the oxidation of p--tolualdehyde. This invention is more ~ : .
sui-table for continous or semi-continuous oxidizatlon of p-tolualdehyde.
The present invention is ~urther illustrated by the following Examples and Compara-tive Examples, However, this invention should not be limited by these examples7 and the changes and modifications wi-thin the spirit and scope of this invention can be effected. The percent and parts in the Examples are based on weight unless otherwise speci~ied.
~LL
Continuous oxidization of p ~olualdehyde was carried out in an apparatus for continuous oxidization reaction comprising a 2.5 ~ pressure reactor made o~ ti-tanium equipped with reflux condenser, stirring means, hea-ting means~ inlet for raw material, inlet for raw material gas, exit ~or gas exit for reaction product, and two receivers for the reaction product connected to the exit for reaction product of the reactor.
500 gr of acetic acid (having water content of 5%) containing 0.598 gr of cobalt acetate tetrahydrate, 1,265 gr o~ manganese acetate and 0.654 gr of tetrabromoethane was charged into the reactor. The pressure in the reactor was - raised to 10 Kg/cm2 by blowing nitrogen gas into the reactor9 and thereafter the temperature in the reactor was raised to 210C. Feeding solution having the following components was prepared in another container:
cobalt acetate te-tra hydrate (Co content in the feeding solution 0.0283%~
manganese acetate (Mn content in the feeding solution 0.0567%) tetrabromo ethane ( Br content in the feeding solution 0.121%) balance of acetic acid (having water con-tent of 0.03%~
The feeding solution was continuously fed into the reactor at the rate of 1120 gr/hr, and p-tolualdehyde was continuously fed into the reactor at the rate o~ 225 gr/hr at 210C and at 18.0 Kg/cm2 gauge. At the same time9 air was blown into the reactor at such a rate as to maintain oxygen content in the gas withdrawn from the exit for gas of the reactor at 3%. The water content in the reaction solution was 9.80% in the stationary sta-te. The reaction product in the slurry state was continuously withdrawn from the reactor to the receiver. The reaction product was filtered, and cake was separated from the filtrate. The cake was washed twice with acetic acid solution twice as much as the cake and then was washed twice with water twice as much as the cake, and was dried to obtain terephthalic ~-acid. The yield of terephthalic acid was 96.6/~ on the mol basis.
The resulting terephthalic acid had the following properties:
Appearance white 4CBA contained the terephthalic acid 1420 ppm Alkaline color* 0.637 Ash contained in the terephthalic acid 8.0 ppm * 2 gr of the terephthalic acid was dissolved in 25 ml of a 2 normal solution of potassium hydroxide. The resulting solution was placed in 50 mm cell~ The cell was exposed to light having wavelength of 340 m~ to determine ... .. . . . . : ..
4~9 optical density. The alkaline color expresses the resulting optical density.
The resulting terephthalic~ acid was hydrogenated with molecular hydrogen in the presence of a catalyst and was recrystallized in hot water as disclosed in Japanese Patent Publication No. 16860/1966. The solution was lowerad to a room temperature, and the terephthalic acid was removed from the solution. The resulting terephthalic acid had the following properties:
Appearance white 4CBA contained in the terephthalic acid less than 10 ppm alkaline color 0~090 The resulting terephthalic acid reacted with ethylene glycol to form polyethylene terephthalate. The resulting polyethylene terephthalate was clear.
f~
500 gr o~ acetic acid (having water content of 15%) containing 0.598 gr of cobalt acetate tetrahydrate, 1.265 gr of manganese acetate and 0.654 gr o~ tetrabromoethane was charged into the reactor employed in Example 1. The pressure in the reactor was raised to 10 Kg/cm2 by blowing nitrogen gas into the reactor, and thereafter the temperature in the reactor was raised to 220C. Feeding solution having the following components was prepared in another container:
cobalt acetate tetra hydra-te (Co content in the feeding solution 0.0283%) manganese acetate (Mn content in the feeding solution 0.0567%) . ~ . :~ : . .
,. . ~ , , 2~9 tetrabromo ethane (Br content in the feeding solution 0.121%) balance o~ ace-tic acid (having wa-ter content o~ 5%) The feeding solution was continuously ed into the reactor at the rate of 782 gr/hr, and p-tolualdehyde was continuously fed into the reactor at the rate of 295 ~r/hr at 220C and at 23.8 Kg/cm2 Gauge. At the same time alr was blown into the reactor at such a rate as to maintain the oxygen content in the gas wi-thdrawn from the exit for gas in the reactor at 3%. The water content in the reaction solution was 13~2% in the stationary state. The reaction product in a slurry state was continuously withdrawn from the reactor. The resulting product was treated in the same way as in Example 1.
The resulting terephthalic acid had the following propertieso Appearance dark gray 4CBA contained in the terephthalic acid 1210 ppm ;
Alkaline color Ash contained in the terephthalic acid 1100 ppm Mn304 in the ash (based on the weight of ~ the terephthalic acid) 765 ppm ; The yield of terephthalic acid was 88.1% on the mole basis. However, even if the terephthalic acid was re~rystal-lized in hot water, the black color of the terephthalic acid caused by manganese remained. The terephthalic acid was - hydrogenated and was recrystallized in hot water in the same way as that of Example 1. The resulting terephthalic acid was dark gray. The terephthalic acid which was hydro-genated and recrystallized reacted with ethylene glycol to ,.,; .. . . . . . . . .
',',: ~ . : ~
455~
form polyethylene -terephthalate. The resul-ting polyethylene terephthalate was dark gray.
Example 2 The procedure of Example 1 was repeated except that 500 gr of acetic acid (having water conten-t of 5%) contain-ing 1~52 gr of cobalt acetate tet;rahydrate, 0.402 gr o~
manganese acetate and 0.654 gr of tetrabromoethane was charged into the reactor before introducing p-tolualdehyde into the reactor, the feeding solution (containing 720 ppm of Co, 180 ppm of Mn and 280 ppm o~ Br) was continuously introduced into the reactor, the temperature of the rea~tor was 206C, and the feeding rate of p-tolualdehyde is 217 gr/hr and the feeding rate of the feeding solution was 108~ gr/hr.
The water content in the reaction solution was 7.80%
in the stationary state.
The resulting terephthalic acid had the following propertieso Appearance white 4CBA contained in the terephthalic acid 1160 ppm Alkaline color 0.650 Ash contained in the terephthalic acid 10 ppm The yield of terephthalic acid was 96.8% on the mole basis. The terephthalic acid was hydrogenated and recrystal-lized in the same way as in Example 1. The resulting tere-phthalic acid had the same properties as those of Example 1.The polyethylene terephthalate obtained by reacting ethylene glycol therewi-th was clear.
~L ' ,.
The procedure of Example 2 was repeated except that the water content of the acetic acid charged into the . ' ' . . ' ,' ~ ~2~S~
reaction sys-tem before introducing p-tolualdehyde into the reactor was 10%, the ~eeding rate o~ p-tolualdehyde was 296 gr/hr and the feeding rate o~ the feeding solution wa8 786 gr/hr, and the pressure in the reactor Was 17.5 Kg/cm2 Gauge. The water con-tent in the reaction solution was 11.2%
in the stationary state.
The resulting terephthalic acid had the following propertles~
Appearance - dark gray 4CBA contained in the terephthalic acid lZ10 ppm Alkaline color ~-~O
Ash contained in the terephthalic acid 500 ppm And the yield of terephthalic acid was 92.3% on the mole basisO The terephthalic acid was hy~rogenated and recrystallized in the same way as in Example 1. The result-ing terephthalic acid was black. The terephthalic acld which was hydrogenated and recrystallized reacted with ethylene glycol to form polyethylene terephthalate. The resulting polyethylene terephthalate was dark gray, ~ 15 -, .. . . . . . . . .
;.'. ,': . ;. . ~ ' ' ' . .
Claims (9)
1. A process for producing a non-blackened terephthalic acid from the corresponding tolualdehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid reaction system containing a lower aliphatic monocarboxylic acid as a solvent and heavy metal salt(s) containing at least one manganese salt and at least one bromine compound as a catalyst, characterized in that the water content in the reaction solution into which the tolualdehyde is introduced is maintained at less than 10%
by weight based on the combined weight of the solvent and water in the solution.
by weight based on the combined weight of the solvent and water in the solution.
2. A process as claimed in claim 1 wherein the starting material is p-tolualdehyde obtained by reacting toluene with carbon monoxide in the presence of hydrogen fluoride and boron trifluoride as a catalyst.
3. A process as claimed in claim 1 wherein the oxidization reaction is carried out at a temperature ranging from about 120°C to about 240°C.
4. A process as claimed in claim 1 wherein the oxidization reaction is carried out at a pressure ranging from 1 to 50 atoms.
5. A process for producing a non-blackened terephthalic acid from the corresponding tolualdehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and at least
5. A process for producing a non-blackened terephthalic acid from the corresponding tolualdehyde which comprises oxidizing the tolualdehyde with molecular oxygen or a molecular oxygen-containing gas in a liquid phase by using a lower aliphatic monocarboxylic acid as a solvent, and at least
Claim 5 continued....
one cobalt salt, at least one manganese salt and at least one bromine compound as a catalyst characterized in that the water content in the reaction solution into which the tolualdehyde is introduced is maintained at less than 10%
by weight based on the combined weight of the solvent and water in the solution.
one cobalt salt, at least one manganese salt and at least one bromine compound as a catalyst characterized in that the water content in the reaction solution into which the tolualdehyde is introduced is maintained at less than 10%
by weight based on the combined weight of the solvent and water in the solution.
6. A process as claimed in claim 5 wherein the proportion of cobalt atoms in the reaction solution ranges from 0.01%
to 0.3% by weight based on the weight of the solvent.
to 0.3% by weight based on the weight of the solvent.
7. A process as claimed in claim 5 wherein the starting material is p-tolualdehyde obtained by reacting toluene with carbon monoxide in the presence of hydrogen fluoride and boron trifluoride as a catalyst.
8. A process as claimed in claim 5 wherein the oxidization reaction is carried out at a temperature ranging from about 120°C to about 240°C.
9. A process as claimed in claim 5 wherein the oxidization reaction is carried out at a pressure ranging from 1 to 50 atoms.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1212875A JPS5186437A (en) | 1975-01-28 | 1975-01-28 | FUTARUSANNOKOKUSHOKUKABOSHIHO |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042459A true CA1042459A (en) | 1978-11-14 |
Family
ID=11796885
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA244,015A Expired CA1042459A (en) | 1975-01-28 | 1976-01-21 | Process for producing a non-blackened phthalic acid from the corresponding tolualdehyde |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5186437A (en) |
| BE (1) | BE837945A (en) |
| CA (1) | CA1042459A (en) |
| DE (1) | DE2603173A1 (en) |
| FR (1) | FR2299306A1 (en) |
| GB (1) | GB1518881A (en) |
| IT (1) | IT1057065B (en) |
| NL (1) | NL7600873A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5195034A (en) * | 1975-02-14 | 1976-08-20 | Futarusanno kokushokukaboshihoho | |
| JPS5432434A (en) * | 1977-08-12 | 1979-03-09 | Ici Ltd | Method of preparing phthalicacid by oxidation of trialdehyde |
| EP0953561A1 (en) * | 1998-04-29 | 1999-11-03 | ARTEVA TECHNOLOGIES S.à.r.l. | Preparation of dimethylterephthalate via the air oxidation of p-tolualdehyde |
| WO2013111782A1 (en) | 2012-01-26 | 2013-08-01 | 東レ株式会社 | METHOD FOR PRODUCING p-XYLENE AND/OR p-TOLUALDEHYDE |
| US20150299086A1 (en) * | 2012-11-23 | 2015-10-22 | Eth Zurich | Method for the production of polyethylene terephthalate with a low carbon footprint |
| WO2022172968A1 (en) | 2021-02-10 | 2022-08-18 | 学校法人幾徳学園 | Method for producing terephthalic acid from biomass resource, and method for producing polyester from biomass resource |
-
1975
- 1975-01-28 JP JP1212875A patent/JPS5186437A/en active Granted
-
1976
- 1976-01-21 CA CA244,015A patent/CA1042459A/en not_active Expired
- 1976-01-21 GB GB236476A patent/GB1518881A/en not_active Expired
- 1976-01-26 IT IT6716576A patent/IT1057065B/en active
- 1976-01-27 BE BE163833A patent/BE837945A/en not_active IP Right Cessation
- 1976-01-27 FR FR7602164A patent/FR2299306A1/en active Granted
- 1976-01-28 DE DE19762603173 patent/DE2603173A1/en not_active Ceased
- 1976-01-28 NL NL7600873A patent/NL7600873A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5186437A (en) | 1976-07-29 |
| DE2603173A1 (en) | 1976-07-29 |
| FR2299306A1 (en) | 1976-08-27 |
| FR2299306B1 (en) | 1980-04-18 |
| NL7600873A (en) | 1976-07-30 |
| BE837945A (en) | 1976-05-14 |
| GB1518881A (en) | 1978-07-26 |
| IT1057065B (en) | 1982-03-10 |
| JPS5744653B2 (en) | 1982-09-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0111784B1 (en) | Process for producing terephthalic acid suitable for use in direct polymerization | |
| EP1140765B1 (en) | A production method of aromatic carboxylic acids | |
| US4051178A (en) | Process for producing terephthalic acid | |
| US6175038B1 (en) | Method of producing aromatic carboxylic acids by oxidizing alkyl aromatic compounds or partially oxidized intermediates thereof with oxygen-enriched gas | |
| US4241220A (en) | Process for producing terephthalic acid | |
| CA1042459A (en) | Process for producing a non-blackened phthalic acid from the corresponding tolualdehyde | |
| KR100549107B1 (en) | Production method of aromatic polycarboxylic acids | |
| US3846487A (en) | Process for the production of fiber grade terephthalic acid | |
| US2853514A (en) | Process for the preparation of aromatic carboxylic acids | |
| EP1856019B1 (en) | Processes for producing aromatic dicarboxylic acids | |
| US2963509A (en) | Process for oxidation of mono-alkyl benzene | |
| US4853479A (en) | Process for the manufacture of aromatic dicarboxylic acids and derivatives thereof | |
| US6180822B1 (en) | Method of producing aromatic carboxylic acids by oxidizing alkyl aromatic compounds or partially oxidized intermediates thereof with carbon dioxide containing gas | |
| CA1042014A (en) | Process for producing a non-blackened phthalic acid from the corresponding tolualdehyde | |
| US4297507A (en) | Process and apparatus for producing terephthalic acid with high purity | |
| JPH0567132B2 (en) | ||
| US4886906A (en) | Process for producing 2,6-naphthalene dicarboxylic acid | |
| US3674845A (en) | Method of producing aromatic carboxylic acids from alkylbenzenes | |
| US4214100A (en) | Process for preventing blackening of phthalic acid | |
| CA1085879A (en) | Continuous process for the removal of non-paraffinic hydrocarbons from paraffinic hydrocarbons | |
| US20060205974A1 (en) | Processes for producing aromatic dicarboxylic acids | |
| KR820000653B1 (en) | Process for preparation of terephthalic acid | |
| US3778471A (en) | Process for producing aliphatic carboxylic acids and aromatic carboxylic acids | |
| JPS5915895B2 (en) | Method for producing aromatic carboxylic acid | |
| JPH06172260A (en) | Production of naphthalenecarboxylic acid |