Note: Descriptions are shown in the official language in which they were submitted.
1()~;~0~4
This invention relat~s to a process for producing a
phthalic acid which comprises oxidizing the corresponding
tolua]dehyde with molecular oxygen or a molecular oxygen-
containing gas in a liquid phase by using a lower aliphaticmonocarboxylic acid as a solvent, and a heavy metal salt(s)
containing at least one manganese salt, and at least one
bromine comp~und as a catalyst and more particularly relates
to a process for producing a phthalic acid from the cor-
responding tolualdehyde, characterized in that the manganesesalt is used in such an amount that the proportion of manga-
nese atom in the reaction system is 40 ppm by weight or less
based on the combined weight of solvent and water in the
reaction system thereby preventing blackened of the result-
ing phthalic acid.
Japanese Patent Publication No. 2666/1959 filed onMay 4~ 1955 discloses that when an at least one aliphatic
group~substituted aromatic compound is oxidized with molecu- -
lar 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 sal-t and at least one bromine compound as a
catalyst, the corresponding aromatic carboxylic acid is
- formed. Each of terephthalic acid and isophthalic acid
has been prepared from p-xylene and m-xylene 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 from the corresponding aliphatic
~0 group-substituted aromatic compound. The publication
discloses that a cobalt salt also is an excellent catalyst.
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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 bromine compound to obtain
terephthalic acid, Journal of Industrial Chemistry, Vol.
` 70, 1967, page 1155 discloses that a cobalt salt is the most
effective catalyst 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 acid from p-xylene.
Japanese Patent Publication No. 36732/1970 filed on June 26,
1967 discloses that polymerizable terephthalic acid of high
` 15 purity can be obtained by oxidizing p-xylene and that a
- cobalt salt has an excellent catalytic action for the oxi-
- dization reaction. Considering these prior art techniques
together, it was known that a mixture of a cobalt salt and
~ a manganese salt have excellent catalytic action for oxidiz-
20 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 o~ Industrial Chemistry, Vol. 67, 1964, 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
,,'~'' .
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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 formed.
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 produced from
p-tolualdehyde. We have also folmd that blackening of the
resulting terephthalic acid is caused by mixing of the
- m~nganese salt employed as one component of the catalyst
in the resulting terephthalic acid. It is a matter of
. ~
course that even if the dark gray terephthalic acid produced
from p-tolualdehyde reacts with glycols, polyesters having
. ~ .
high whiteness can not be obtained. It was also found that
even if 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 found 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
terephthalic acid.
In the prior art, terephthalic acid has been produced
- 4 -
~O~Z0~4
from p-xylene as a starting material on an industrial scale,
because the technique of 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 terephthalic acid is produced by com-
; plicated processes, such as isomerization 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 reacting toluene with carbon monoxide in the
presence of hydrogen fluoride and boron trifluoride 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 from 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 for the production of terephthalic acid.
However, as mentioned above, the technique for the production
of terephthalic acid from p-xylene can not be applied to the
technique for the production of terephthalic acid from p-
- 25 tolualdehyde as it is.
.
The inventors of this invention have carried out a
; wide range of research to find an industrially valuable
process for producing a phthalic acid which comprises
oxidizing the corresponding tolualdehyde with molecular
.
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1()4;~014
oxygen or a molecular oxygen-containing gas in a liquid
phase by using a lower aliphatic monocarboxylic acid as a
solvent, and a heavy metal salt containing at least one
manganese salt, and at least one bromine compound as a
catalyst. As a result, we have found that in case of
oxidizing p-tolualdehyde with molecular oxygen or a molecu-
lar oxygen-containing gas in a liquid phase by using a lower
aliphatic monocarboxylic acid as a solvent in the presence
ofa heav~ metal saltcontaining at least one manganese salt,
and a bromine compound to form terephthalic acid, the pro
portion of manganese atom in the reaction system has a great
influence on the blackering of terephthalic acid caused by -
mixing of manganese therein.
We have found that a non-blackened phthalic acid can
be produced from the corresponding tolualdehyde, when the
~` proportion of manganese atom in the reaction system is
` maintained at less than 40 ppm by weight based on the com- --
bined weight of water and the solvent in the reaction system.
The solution consisting of water and solvent in the reaction
system is hereinafter called a reaction solution. In other
words, we have found that no blackening of the phthalic acid
occurs under any conditions for oxidizing the corresponding
tolualdehyde with molecular oxygen or a molecular oxygen-
containing gas~ if the proportion of the manganese atom in
the reaction system is maintained at less than 40 ppm based
on the weight of the reaction solution. This invention 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.
-- 6 --
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~o~zo~
This invention relates to a process for producing a
non-blackened phthalic acid from the corresponding tolualde-
hyde which comprises oxidizing the tolualdehyde with molecu-
lar 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, especially both manganese and
cobalt salts and at least one bromine compound as a catalyst,
characterized in that the manganese salt is used in such an
amount that the proportion of manganese atom in the reaction
system is not more than 40 parts per million ~40 ppm) based
on the weight of the reaction solution. The term "blackening
of terephthalic acid" in the specification and the claims
means that terephthalic acid in black, dark gray or grayish
brown, etc. is formed.
~` It is critical to add to the reaction system the
manganese salt in such an amount that the proportion of
manganese atom in the reaction system is not more than 40
ppm based on the weight of the reaction solution, and prefer-
ably the manganese salt is added in such an amount that the
proportion of the manganese atom in the reaction system
ranges from 5 ppm to 40 ppm based on the weight of the
reaction solution. When p-tolualdehyde is oxidized in the
presence of said solvent and said catalyst while maintaining
the proportion of the manganese atom in the reaction system
at less than 40 ppm based on the weight of the reaction
solution, terephthalic acid which has ~igh whiteness and is
industrially valuable can be produced. When the proportion
of the manganese atom in the reaction system is more than
- ,
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.. ......
40 ppm based on the weight of the reaction solution, dark
gray terephthalic acid is produced from p-tolualdehyde under
conventional conditions.
- The catalyst employed in this invention consists of
heavy metal salt(s), such as a manganese salt and/or a
cobalt salt, and a 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 amount of the cobalt salt added to the reaction
system and the amount of the bromine compound added to the
reaction system are not critical in this invention. These
components are used in a catalytic amount sufficient to
oxidize a tolualdehyde to the corresponding phthalic acid. -~
Independent of the amount of the cobalt salt, the amount of
the bromine compound and the water content in the reaction
solution, a non-blackened phthalic acid can be produced -
from the corresponding tolualdehyde by limiting the propor-
tion of the manganese atom in the reaction system to a
-~ specific value. In general, the cobalt salt may be used
; in such an amount that the proportion of cobalt atom ranges
from 100 ppm to 5000 ppm based on the weight of the solvent.
The bromine compound includes an inorganic salt, such as,
for example ammonium bromide, sodium bromide, potassium
bromide or hydrogen bromide, etc. and an organic bromide,
such as, for example tetrabromoethane or tetrabromo-p-xylene,
etc. The bromine compound is used in such an amount that
: the proportion of bromine atom in the reaction system ranges
from 500 ppm to 5000 ppm based on the weight of the solvent.
. .
.-
-- 8 --
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10420~L
Reaction temperature is not critical. However,
elevated temperature accelerates the reaction and a temper-
ature ranging from about 120C to about 240C is advanta-
geously employed. The oxidization reaction of this invention
is carried out in the liquid phase. Therefore, it is prefer-
red that the oxidization reaction be carried out at one or
superatmosphere so as to keep the tolualdehyde and the
solvent introduced into the reaction system in the liquid
state. The oxidization reaction is conveniently carried
out at a pressure ranging from 1 to 50 atms.
Molecular oxygen or a molecular oxygen-containing
gas is used as an oxidizing agent. From an economic point
of view, air is the preferred oxidizing agent.
A lower aliphatic monocarboxylic acid9 such as acetic
acid, propionic acid or butyric acid, etc. is conveniently
used as the solvent. Acetic acid is preferred. The amount
of the lower aliphatic monocarboxyl acid used is conveniently
at least two times as much as the tolualdehyde on a weight
basis.
The history of the tolualdehyde is not of a limiting
nature to the process of this invention. In other words,
all tolualdehydes, whatever the method which have been pre-
- pared, can be used in the process of this invention, P-
tolualdehyde obtained by reaction of toluene with 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, because it is more available.
The present process is particularly suitable ~or
oxidizing p-tolualdehyde to form terephthalic acid. This
is because not only p-tolualdehyde is commercially available
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1~4ZO~L
and the resulting terephthalic acid is useful9 but also the
effect of this invention is advantageous in case of the
oxidation of p-tolualdehyde. This invention is more suitable
for continuous or semi-continuous oxidization of p-tolualde-
hyde.
The present lnvention is further illustrated by the ~ -
following Examples and comparative Examples. However, this
invention should not be limited by these examples, and the
- changes and modifications within the spirit and scope of
this invention can be effected. The percent, ppm and parts ~ ~
in the Examples are based on weight unless otherwise specified. ~ `
Example 1
Into a 500 m~ pressure reactor made of titanium equip- ~
ped with reflux condenser, stirring means, heating means, `
inlet for raw material, inlet for raw material gas and exit ~ `
for gas were charged 0.790 gr of cobalt acetate tetrahydrate,
0.0375 gr of manganese acetate tetrahydrate, 0.324 gr of
sodium bromide and 208.8 gr of acetic acid. The proportions
of Co, Mn and Br in the resulting mixture were in the
following-
Co proportion 890 ppm (based on solvent)
Mn proportion 40 ppm (based on reaction solution)
~r proportion 1200 ppm (based on solvent)
The pressure in the reactor was raised to 10 Kg/cm2G
by blowing nitrogen gas into the reactor, and thereafter thetemperature of the reactor was raised to 200C by heating
means. Thereafter, 80 gr of p-tolualdehyde was added to the `
reactor at 200C at 20 Kg/cm2 over one hour while blowing
air into the reactor~ After addition of p-tolualdehyde was
completed, air was blown into the reactor for another five
.,
-- 10 --
,~04ZO:~
minutes. Thereafter, the reactor was cooled to room temper-
ature, and the resulting reaction product was removed.
The product in a slurry state was filtered and cake
was separated from the filtrate. The cake was washed with
- 5 acetic acid and then water. The resulting terephthalic acid
was dried at 110C. The yield of terephthalic acid and the
properties thereof are shown in Table 1.
Example 2
The procedure of Example 1 was repeated except that
the proportion of the manganese was 20 ppm based on the
reaction solution. The yield of the resulting terephthalic
acid and the properties thereof are shown in Table 1.
- Example 3
The procedure of Example 1 was repeated except that
the proportion of the manganese was 10 ppm based on the
reaction solution. The yield of the resulting terephthalic
acid and the properties thereof are shown in Table 1.
Comparative Example 1
The procedure of Example 1 was repeated except that
the proportion of the manganese was 90 ppm based on the
reaction solution. The yield of the resulting terephthalic
acid and the properties thereof are shown in Table 1.
Comparative ExamPle 2
The procedure of Example 1 was repeated except that
- 25 the proportion of Co, Br and Mn were 890 ppm, 1200 ppm and
60 ppm based on the reaction solution. respectively. The
... :.
yield of the resulting terephthalic acid and the properties
thereof are shown in Table 1.
The water content in the reaction solution in Examples
1 through 3 and Comparative Examples 1 and 2 was 16.3% at the
. ~ .
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10~0 :a~
end point of the reaction.
TABLE 1
_ Properties of the resulting Yield of
Mn propor- terephthalic acid terephthalic
N tion based or _ _ acid
o. the reaction Appear- 4CBA Alkaline Ash ~percent on
solutionance content color* content a mole basis)
(ppm) (ppm)
. . .
Example 1 40 white 750 0.518 5.2 95.8
Example 2 20 white 700 0.430 4.1 96.0
. ..
Example 3 10 white B70 0.442 4.3 95.4
Comparative _ _ Grayish . ~
: Example 1 brown 1000 ~ 46 95.1
Comparative Pale
Example 2 60yellow 970 1.84 29 95.7
* 2 gr of the terephthalic acid was dissolved in 25 m~
of a 2 normal solution of potassium hydroxide. The resulting
reaction product was placed in 50 mm cell. The cell was
exposed to light having wavelength of 340 m~ to determine
optical density. The alkaline color expresses the resulting
optical density.
Each of the terephthalic acid obtained in Examples 1
through 3 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 lowered to 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 less than 10 ppm
terephthalic acid
alkaline color less than 0.090
. ~
- 12 -
1042014
The resulting purified terephthalic acid reacted
with ethylene glycol to form polyethylene terephthalate.
The resulting polyethylene terephthalate was clear.
The terephthalic acid obtained in Comparative Example
1 was hydrogenated and was recrystallized in hot water as
disclosed in Japanese Patent Publication No. 16860/1966.
The properties of the resulting terephthalic acid were in
the following:
Appearance dark gray
4CBA contained in the 10 ppm
terephthalic acid
Alkaline color ~
The terephthalic acid which was hydrogenated and
- recrystallized reacted with ethylene glycol to form poly-
-- ethylene terephthalate. The resulting polyethylene tere-
phthalate was dark gray.
Example 4
Into the reactor employed in Example 1 were charged
0.790 gr of cobalt acetate tetrahydrate 9 0.0262 gr of man-
ganese acetate, 0.324 gr of sodium bromide and 208.9 gr of
` 20 acetic acid (having water content therein of 5%). The
- contents of Co, Mn and Br in the resulting mixture were
; in the following proportions~
Co proportion 890 ppm (based on solvent)
Mn proportion 28 ppm (based on reaction solution) `
v 25 Br proportion 1200 ppm (based on solvent)
The pressure in the reactor was raised to 10 Kg/cm by
blowing nitrogen gas into the reactor, and thereafter the
temperature of the reactor was raised to 200C. Thereafter,
80 gr of p-tolualdehyde was added to the reactor at 190C
.
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014
at 18 Kg/cm2G over one hour while blowing air into the
reactor. After addition of p tolualdehyde was completed,
air was blown into the reactor for another five minutes.
Thereafter, the reactor was cooled to room temperature, and
the resulting reaction product was removed.
The product in a slurry state was filtered and cake
was separated from the filt-rate. The cake was washed with
acetic acid and then water. The resulting terephthalic
acid was dried at 110C. The yield of the terephthalic
acid and the properties thereof are shown in Table 2.
; Examples 5 and 6
The procedures of Example 4 were repeated except
that acetic acid having the water content of 10~ (Example 5)
or 15% (Example 6) was used. The yield of the resulting
terephthalic acid and the properties thereof are shown in
Table 2.
ComParative Ex~ ~3
; The procedure of Example 4 was repeated except that
,'7' the proportion of the manganese was 60 ppm based on the
reaction solution. The yield of the resulting terephthalic
acid and the properties thereof are shown in Table 2.
Comparative Example 4
The procedure of Example 4 was repeated except that
the proportion of the manganese was 60 ppm based on the
reaction solution, and acetic acid having the water content
of 10% was used. The yield of the resulting terephthalic
acid and the properties thereof are shown in Table 2.
The procedure of Example 4 was repeated except that
- 30 the proportion of the manganese was 60 ppm based on the
- - 14 -
.
lO~ZOl~
reaction solution, and acetic acid having the water content
of 15% was used. The yield of the resulting terephthalic
- acid and the properties thereof are shown in Table 2.
~ TABLE 2
.
; Properties of the resulting Yield of
l~Jater terephthalic acid terephthalic
No.content Appear- 4CBA Alkaline Ash acid
acid added ance c ntent color content a mole basis)
Example 4 white 990 0.513 4.5 96.6
Example 510 white 1180 0.573 4.8 96.0
. ..
Example 615 whlte 1350 0.700 6.0 95.0
Comparative grayish
Example 3 5 brown 1030 ~0 53 95.2
., _ _ . . . .
Comparative
Example 410 gray 1390 64 95.0
Comparative dark
Example 515 gray 1500 ~o 95.0 94.1
.. j l . ~ ,. . ,_
Each of the terephthalic acid obtained in Examples
. 4 - 6 was hydrogenated and was recrystallized as disclosed
in Japanese Patent Publication No. 16860/1965, whereby white
'~ terephthalic acid crystals were obtained in all cases.
On the other hand, though each of the terephthalic
acid obtained in Comparative Examples 3 - 5 was hydrogenated
and was recrystallized as disclosed in Japanese Patent
Publication No. 16860/1966, white terephthalic acid crystals
can not be obtained. Alkaline color of the purified tere-
phthalic acid was ~ .
Example 7
.
Into the reactor employed in Example 1 were charged
1.58 gr of cobalt acetate tetrahydrate, 0.0262 gr of manga-
nese acetate 9 0.324 gr of sodium bromide and 208.1 gr of
- 15 -
~4'Z~14
.
- acetic acid having the water content of 5%. The proportion
of Co, Mn and Br in the resulting mixture were in the
following:
Co proportion 1780 ppm (based on solvent)
Mn proportion 28 ppm (based on reaction solution)
Br proportion 1200 ppm (based on solvent)
The pressure in the reactor was raised to 10 Kg/cm
~ by blowing nitrogen gas into the reactor, and thereafter
: the temperature in the reactor was raised to 200C. There-
. : .
` 10 after, 40 gr of p-tolualdehyde was added to the reactor at
200C at 18 Kg/cm2G over one hour while blowing air into
- the reactor. After addition of p-tolualdehyde was completed,
air was blown into the reactor for another five minutes.
The resulting reaction product was subjected to the same
treatment as used in Example 1. The yield of the resulting
terephthalic acid and the properties thereof are shown in
Table 3.
Com~arative Example 6
. .
The procedure of Example 7 was repeated except that
the proportion of the manganese was 90 ppm based on the
;- reaction solution. The yield of the resulting terephthalic
. .
;; acid and the properties thereof are shown in Table 3.
TABLE 3
,
..,.
Proportion Properties of the resulting Yield of
of Mn terephthalic acid terephthali
based on the ~acid
No. reaction Appear- 4CBA Alkaline Ash (percent
solution ance content color content on a mole
(ppm) (ppm) (ppm) basis)
'.' .
Example 7 28 white 290 0.294 4.5 94.2
. . . . . .
Comparative dark
Example 6 90 gray 850 ~ 87 94.0
_ _ l .. ~ .
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- 16 -
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1~4ZOl~
Though the terephthalic acid obtained in Comparative
Example 6 was hydrogenated and recrystallized9 the dark gray
color could not be removed from the terephthallc acid.
Example 8
Into the reactor employed in Example 1 were charged
3.16 gr of cobalt acetate tetrahydrate, 0.0375 gr of manga-
nese acetate, 1.026 gr of sodium bromide and 205.8 gr of
acetic acid having the water content of 5~0. The proportion
- of Co, Mn and Br in the resulting mixture were in the
following:
Co proportion 3560 ppm (based on solvent)
Mn proportion 40 ppm (based on reaction solution)
~ Br proportion 3600 ppm (based on solvent) :
The pressure in the reactor was raised to 10 Kg/cm2 ~ :
by blowing nitrogen gas into the reactor, and thereafter
the temperature of the reactor was raised to 200C, There-
. after, 30 gr of p-tolualdehyde was added to the reactor at ~ -
;~. 205C at 20 Kg/cm2G over one hour while blowing air into
the reactor. After addition of p-tolualdehyde was completed,
air was blown into the reactor for another five minutes.
The resulting reaction product was subjected to the same
.. ~ treatment as that of Example 1. The yield of the resulting
terephthalic acid and the properties thereof are shown in
the following
Appearance white
4CBA con-tent 210 ppm
Alkaline color 0.100
Ash content 3.2 ppm
. Yield of tere-
-. phthalic acid 95.0% on a mole basis
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Example 9
Continuous oxidization of p-tolualdehyde was carried
out in an apparatus for continuous oxidization reaction
comprising a 2.5 liter pressure reactor made of titanium
equipped with refl~x condenser, stirring means, heating
means, inlet for raw material, inlet for raw material gas,
exit for gas, exit for reaction product, and two receivers
for the reaction product connected to the exit for reaction
product of the reactor.
Into the reactor were charged 500 gr of acetic acid
having a water content of 15%, 1.26 gr of cobalt acetate
tetrahydrate, 0.087 gr of manganese acetate tetrahydrate
. and 0.515 gr of sodium bromide. The pressure in the reactor
: was raised to 10 Kg/cm G, and then the temperature of the
reactor was raised to 200C. Feeding solution havlng the ~ -
following components was prepared in ~nother container:
. Cobalt acetate tetrahydrate (Co content
~ in the feeding solution 594 ppm)
-~ manganese acetate tetrahydrate (Mn -
content in the feeding solution 39.1 ppm)
sodium bromide (Br content in the feeding
solution 805 ppm)
The feeding solution was continuously fed into the
reactor at the rate of 780 gr/hr, and p-tolualdehyde was
continuously fed into the reactor at the rate of 260 gr/hr
at 200C at 16.5 Kg/cm2 gauge. At the same time, air was
blown into the reactor at such a rate as to maintain the
oxygen content in the gas withdrawn from the exit for gas
of the reactor at ~%. The reaction product was continuously
withdrawn into the receiver so as to keep the level of the
` reaction solution constant.
':`,
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- - 18 -
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104~0~4
The reaction product in a slurry state was filtered,
and cake was separated from the filtrate. The cake was
- washed with acetic acid and then water, and was dried to
obtain terephthalic acid. The yield of terephthalic acid
5 was 94.4% on the mole basis. The terephthalic acid had the
following properties:
Appearance white
4CBA content 184~ ppm
Alkaline color 0.801
-~ 10 Ash content 3.3 ppm
Mn in the ash based on the acid 1~6 ppm
- The resulting terephthalic acid was hydrogenated with
molecular hydrogen in the presence of a catalyst and was
recrystalli7ed in hot water as disclosed in Japanese Patent
: 15 Publication No. 16860/1966. The purified terephthalic acid
,
had the following properties-
J`.'' Appearance white `
4CBA content less than 10 ppm
Alkaline color 0.090
~ 20 The purified terephthalic acid reacted with polyethyl-
- ~ ene glycol to form polyethylene terephthalate. The resulting
polyethylene terephthalate was clear.
Comparative Example 7
The procedure of Example 9 was repeated except that
the feeding solution having Co content of 594 ppm, Mn content
of 55.4 ppm and Br content of 805 ppm was used.
The properties of the resulting terephthalic acid
` and the yield thereof were in the followingo
Appearance gray
4CBA content 1880 ppm
... .
: . , .
.: 9 .. ..
; .~,.
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10420~4
Alkaline color
Ash content 47.4 ppm
Mn304 in the ash 35.0 ppm
based on the
telephthalic
- acid
- Yield 92.0% on a mole basis
The water content in the reaction solution was 16.7%
at the end point of the reaction. Though the resulting
terephthalic acid was hydrogenated and was recrystallized
` as disclosed in Japanese Patent Publication No. 16860/1966,
~ the gray color was not removed from the terephthalic acid.
- 10 The purified terephthalic acid reacted with ethylene glycol
to form polyethylene terephthalate. However, the resulting
polyethylene terephthalate was gray.
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