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Патент USA US3043856

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Unite States Patent
lC€
3,@43,845
Patented July 10, 1962
2
1
ture. Such acids are derived, for example, from pyridine,
3,043,846
pyrazine, pyrimidine, pyridazine, a-pyran, furan, thio
POLYCARBQX LlC ACIDS
phene, thiazole,-.quinoline, isoquinoline, indole, benzo
_PROCESS FOR THE PRODUCTION OF AROMATIC
triazole 0nd benzimidazole.
In all of these carboxylic acids the aromatic ring or
the heterocyclic ring having an aromatic structure may in
signors to Henkel & Cie G.m.b.H., Dusseldorf-Holt
hausen, Germany, a corporation of Germany
addition to the carboxyl group also carry other sub
No IPrawing. Filed Nov. 12, 1958, Ser. No. 773,157
stituents such as halogen atoms or alkyl radicals, provided
Claims priority, application Germany Mar. 5, 1956
that they do not decompose at temperatures below the
8 Ciairns. (Cl. 260—295)
10 reaction temperature. The term aromatic carboxylic acids
Bruno Blaser, Dusseldorf-Urdenbach, and Bernhard
Raccke and Hubert Schirp, Dusseldorf, Germany, as
is, therefore, intended to include both compounds having
This invention relates to a process for the production
of aromatic or aromatic heterocyclic di- and tricarboxylic
acids from aromatic or aromatic heterocyclic monocar
boxylic acids.
As the applicants had previously found, the alkali metal
salts of carboxylic acids, the carboxyl groups of which
a homocyclic aromatic ring and compounds having a
heterocyclic ring.
‘
The above-named carboxylic acids are used in the form
15 of their salts for the process according to this invention.
Advantageously, the alkali metal salts are used, and pref
erably the potassium salts and in addition also the sodium
salts. The lithium, rubidium and cesium salts which may
also be employed must generally be excluded because of
are attached to aromatic ring systems or to heterocyclic
rings having an aromatic structure, can ‘be transformed
into salts of other aromatic carboxylic acids with at least
two carboxyl groups in the molecule, by heating to ele 20 economic reasons. It is often advantageous to use mix
tures of salts of two different metals, for example, mix
vated temperatures. When salts of monocarboxylic acids
tures of the sodium and potassium salts, because in many
are used as starting materials, the salts of di- and tri
cases the mechanical properties of the reaction material
carboxylic acids are obtained as reaction products. The
industrially valuable reaction products formed thereby
are, for example, terephthalic acid, trimesic acid, naph 25
thalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic
acid, pyridine-2,5-dicarboxylic acid, pyridine-2,4,6-tri
carboxylic acid, furan-2,5-dicarboxylic acid, thiophene
2,5 dicarboxylic acid and many others.
The ring sys
tems free from carboxyl groups are obtained as by
products. These processes were carried out with or with
are improved thereby.
>
.
In place of such salts, reaction materials which form
the ‘salts may be used. Particularly suitable materials are
carboxylic acid anhydrides or also carboxylic acid esters
and acid-binding metal compounds, such as alkali metal
carbonates. These mixtures do not need to ‘be provided
30 in stoichiometric ratios; One or the other component may
be used in excess.
It is advantageous to carry out the reaction according
out pressure in the presence of an inert protective gas,
to this invention in the presence of acid-binding agents,
preferably carbon dioxide. When pressure has been used
preferably in the presence of alkali metal carbonates,
heretofore, the reaction has been carried out at pressures
35 alkali metal formates or alkali metal oxalates. The above
up to about 250 atmospheres.
mentioned acide'binding agents do not need to be em
It is an object of this invention to produce desired
ployed in stoichiometric quantities. They may be pro
aromatic carboxylic acids in increased yield in an aro
Vided in quantities less than the stoichiometric amount or
matic carboxylic acid conversion process conducted at
carbon dioxide pressures in excess of 400 atmospheres.
also in excess.
The salts or salt mixtures to be subjected to the re
Another object is to avoid the formation of undesirable
action are preferably provided in as dry a condition as
side products in the production of aromatic or heterocyclic
possible. If the salts ‘are available in the form of their
di- and tricarboxylic acids from the corresponding mono
aqueous solutions they may be transformed into dry
carboxylic acids.
powders in accordance With known methods, preferably
A further object of the present invention is a process
for the production of aromatic or aromatic heterocyclic 45 by spray-drying, and if necessary, subjected to a subse
quent drying treatment to remove minute residual quan
di- and tricarboxylic acids from the corresponding mono
carboxylic acids which is carried out at lower tempera
tities of moisture.
It has further been found that the reaction according
tures than heretofore.
to the present invention is favorably in?uenced by the
These and other objects will become apparent as the
presence of catalysts. Metals such as zinc, cadmium,
description of this invention proceeds.
mercury, lead and iron, as Well as compounds of these
We have found that the transformation of salts of
metals, such as their oxides, or their inorganic or organic
aromatic monocarboxylic acids or of heterocyclic mono
acid salts, for example, their carbonates, bicarbonates, hal
carboxylic acids having an aromatic structure into salts
ides, sulfates, phosphates, acetates, formates, oxalates, fatty
of di- or tricarboxylic acids may be carried out especially
advantageously by heating the starting materials in the 55 acid salts or also the salts of the above-mentioned metals
formed from those acids which are employed as start
presence of acid binding agents to elevated temperatures
ing materials for the reaction according to the inven
under carbon dioxide pressure and by working under
pressures above 400 atmospheres.
tion or which are formed during the reaction, for ex
'
ample, their benzoates, phthalates or terephthalates, may
The starting materials for the lprocess according to this
invention are salts of aromatic monocarboxylic acids. 60 be used as catalysts. The amount of catalyst may vary
Within wide limits and may range from 0 to 15%
Such acids are, for example, benzoic acid, a- and 5
naphthoic acid, diphenylmonocarboxylic acids.
Also,
monocarboxylic acids in which the carboxyl groups are
attached to another aromatic ring system such as to an
thracene, terphenyl, diphenylmethane or benzophenone
radicals, are suitable as starting materials for the process
in accordance with the invention.
by weight, preferably from 0.5 to 5% by weight,
based on the weight of reaction mixture. The catalyst
may be uniformly and ?nely distributed throughout the
65 reaction ‘mixture by spray-drying or otherwise transform
ing an aqueous solution of the salts serving as the start
ing material, which has the catalyst dissolved or sus
pended therein, into a dry powder. The above-named
Similarly, the starting materials for the process accord
catalysts may also be employed in conjunction with
ing to the invention may be salts of monobasic hetero 70 known carrier, for example, with kieselguhr.
cyclic carboxylic acids, the carboxyl groups of which are
The reaction according to the present invention may
attached to heterocyclic rings having an aromatic struc
not only be carried out in the presence of these catalysts
aoaaeae
3
aluminum oxide, ?nely divided silicic acid, or also, inert
a substantial improvement in the yield and the amount of
by-product consisting of the ‘ring system free from car
boxyl groups is reduced and even completely eliminated.
A further substantial advantage of carrying out the re
salts such as sodium sulfate. In many cases the mechani
action at pressures above '400 atmospheres in accord
but also in the presence of liquid or solid additives, for
example, in the presence of sand, metal powder, metal
shavings, kieselguhr, activated charcoal, ?nely divided
ance with the present invention is that in many cases
cal properties of the reaction mixture are improved by
the optimum reaction temperature is considerably re
these additives. In place of the solid inert materials,
duced. Furthermore, the process according to the present
inert liquids which do not decompose under the prevail
invention permits the production with good yields also of
ing reaction conditions may also be used, such as toluene,
10 those reaction products which were not accessible at all
benzene or the like._
or only in minute quantities by the procedures heretofore
The high pressure required for the reaction which
used.
'
exceeds 400 atmospheres, and preferably more than 500
The following examples are set forth to enable persons
atmospheres, may be produced in a very simple fashion,
for example, by suitable pumps or compressors.
skilled in the art to understand and practice our invention
The
high pressures may, however, also be produced by pass 15 but we do not intend to be limited thereby.
ing liquid carbon dioxide from a pressure cylinder or
Example I
another storage vessel into the cooled andevacuated
30
gm.
potassium
benzoate,
13 gm. anhydrous potas
reaction vessel, and thereafter heating the same. In place
sium carbonate (molar ratio 1:05) and 1 gm. cadmium
of liquid carbon dioxide, solid carbon dioxide may also
Pressures of 1500 ‘to 2000 atmospheres 'are 20 ?uoride were milled in a ball mil-l and the mixture was
placed into an autoclave having -_a net volume of 0.2 liter.
About 150 gm. liquid carbon dioxide were then introduced,
‘the reaction, depending upon the amount of carbon di
and the contents of the autoclave were heated for 7 ‘hours
oxide introduced into the reaction vessel. Otherwise
at 360° C. whereby a maximum pressure of 1540 atmos
there is no upper pressure limit but the upper limit de
pends largely upon the strength of the available apparatus. 25 pheres developed. The reaction temperature was meas
ured in this and the following Examples II-XI by means
As a rule, the reaction begins at temperatures between
of a thermoelectric couple which was in the center of the
300 and 400“ C. The optimum reaction temperature _
be used.
developed thereby due to the temperature required ‘for
is different and. depends upon the starting materials used.
Sometimes it is advantageous toemploy a reaction ‘tem
perature below 400° C., but the upper temperature limit
for the process is determined only by the decomposition
temperature of the organic starting materials and reaction
products.
In carrying out the reaction in ‘accordance with this
invention, it may be advantageous to'maintain the re
action material in motion in order to avoid local over
heating and decomposition caused thereby and also to
prevent the reaction mixture from sintering or'caking.
This may, for example, be accomplished by performing
the reaction in vessels. provided with a stirring device,
in'roeking autoclaves or in rotary autoclaves. Uniform
heating of ‘the reaction material may also’be eifected by
' distributing thereaction material ,in thin layers with or
‘without agitation. However, good 'yields are alsorob
tained without applying these particular measures, pro
vided care ‘is taken that strong ‘local overheating is
avoided.
~
,
The separation of the reaction product from the re
action material may take place in known fashion. The
raw product is ?rst dissolved in water or in dilute acids
and thereafter puri?ed by ?ltration or by treatment with
activated charcoal or with other decoloring agents, if
necessary. Subsequently the salts formed by the re
action may be transformed into the corresponding free
acids by acidi?cation with organic or inorganic acids or
also by passing carbon dioxide therethrough with or
without, pressure. Thefree acids may be separated by
making use of their different 'solubilities or volatilities,
and may thereafter be isolated in relatively pure form
reaction chamber. According to'experience the wall tem
perature lies about 20~50° C. higher thanJthe measured
30
temperature.
‘
The reaction vproduct was dissolved in water and the
terephthalic acid formed by the reaction was precipitated ,
‘with hydrochloric acid. 20.7 gm. terephthalic acid were
obtained which was pure. From the mother liquors 1.3%
of the quantity of benzoic acid originally used were re
covered. Taking into consideration the amount of re
covered benzoic acid, the yield of terephthalic acid was
65.6% of theory. The calculation of the yield was made
under the assumption that 1 mol benzoic acid forms 1 mol
‘terephthalic acid.
Example II
30 gm. potassium benzoate, 13 gm. anhydrous potas
sium carbonate, '1 gm. cadmium fluoride and about 150
gm. liquid carbon dioxide were heated for 7 hours at
380° C. in the same manner as described in Example I
whereby a maximum pressure of about 1600 atmospheres
was reached. After‘ further processing of the reaction
mixture, no benzoic acid was recovered. The yield of
terephthalic acid was 61.5%, calculated on the assump
tiog that 1 mol benzoic acid ‘forms 1 mol terephthalic
aci
.
Example III
30 gm. potassium benzoate, 13 :gm. anhydrous potas
siumcarbonate, 1 gm. cadmium ?uoride and about 150
gm. liquid carbon dioxide were heated for 7"hours at
350° C. under the same conditions as ‘those described in
the two preceding examples, whereby a maximum pres
sure of 1300 atmospheres was reached.
Taking into con
and, if desired, transformed into their derivatives. The 00 sideration the 4.4 gm. 'of recovered benzoic acid, a ter
ephthalic acid yield of 65.6% was obtained.
:salt mixtures produced by the reaction may also be trans
formed directly into derivatives of the acids, for example,
Example IV
into their esters or halides, and these derivatives may
then ‘be puri?ed by fractional distillation, if desired.
The process in accordance with this invention produces
industrially valuable di-~ and polycarboxylic acids or their
salts, or derivatives, such as terephthalic acid, trimesic
acid, naphthalene-2,6-dicarboxylic acid, pyridine-2,5-di
carboxylic acid, pyridine-2,4,6-tricarboxylic acid, furan
2,5-dicarboxylic acid, thiophene-2,5-dicarboxylic acid, and
many others.
.
.
.The advantage of the process according to the pres
ent invention over the methods heretofore used in which
pressures upto a maximum of 250.atmospheres were
43 gm. of a mixture consisting of'potassium benzoate
and potassium carbonate in a molar ratio of 12-1 (corre
sponding to 23.1 gm. potassium benzoate) which was
produced by simultaneously spray-drying corresponding
solutions, were admixed with 2 gm. cadmium fluoride in
a ball mill and the resulting mixture was placed into an
autoclave having a net volume of 0.2 liter. About 150
gm. liquid carbon dioxide were added thereto. Subse
quently, the contents of the autoclave were heated for 7
hours at 360° C. whereby a maximum pressure of about
1000 atmospheres was reached. Upon working up the
employed, resides in that the present'procedure produces 75 reaction mixture in the same manner as described in Ex
3,043,846
ample I, 34% of the amount of benzoic acid originally
used were recovered. The yield of terephthalic acid was
11.45 gm., which corresponds to 72.8% of the theoretical
yield.
Example V
43 gm. of an equimolar mixture of potassium benzoate
and potassium carbonate and about 150 gm. liquid carbon
dioxide were heated for 21 hours at 330° C. under the
same conditions as those described in Example IV. A
volume of 0.2 liter. About 140 gm. liquid carbon dioxide
were added thereto. Subsequently, the contents of the
autoclave were heated for 30 hours at 300° C. whereby a
maximum pressure of 670 atmospheres was reached.
After treatment of the reaction product in the same man
her as described in Example I, 13.20 gm. benzoic acid
were recovered. The yield of terephthalic acid was 3.6
gm. Taking into consideration the amount of benzoic
acid recovered, this corresponds to a yield of 60.1% of
theory.
maximum pressure of about 1100 atmospheres was 10
Example XI
reached. After further processing of the reaction mixture,
40 gm. of a mixture consisting of sodium benzoate and
3 gm. benzoic acid were recovered. The yield of ter
sodium carbonate (molar ratio 1:05) and 2 gm. cadmium
ephthalic acid was 15.6 gm. which corresponds to.79% of
?uoride were placed into an autoclave having a net volume
the theoretical vield.
15 of 0.2 liter. About 150 gm. liquid carbon dioxide were
Example VI
added thereto. Subsequently, the contents of the auto
A homogeneous mixture of 30 gm. potassium benzoate,
clave were heated for 7 hours at 360° C. whereby a maxi
13 gm., anhydrous potassium carbonate and 2 gm. of
mum pressure of 1400 atmospheres was reached. After
cadmium ?uoride was placed into an autoclave having a
further processing of the reaction mixture in accordance
net volume of 0.2 liter. About 160 gm. liquid carbon 20 with the method described in Example I, 8.8 gm. benzoic
dioxide were added thereto. The contents of the auto
acid were recovered. The yield of terephthalic acid was
clave were then heated for 7 hours at 360° 0, whereby a
4.15 gm. Taking into consideration the amount of ben
pressure of about 1600 atmospheres was reached. The
zoic acid recovered, this corresponds to a yield of 19.0%
reaction mixture was further processed in the manner de
of theory.
scribed in Example I. 0.3 gm. benzoic acid was recovered 25
Example XII
from the mother liquid. The yield of terepht/halic acid
For this experiment and the experiment described in
was 20.7 gm. Taking into consideration the amount of
benzoic acid recovered, this corresponds to a yield of
Example XIII a high-pressure autoclave having a net
69.9% of theory.
volume of about 600 cc. was used.
Example VII _
A homogeneous mixture of 30 gm. potassium benzoate
and 13 gm. anhydrous potassium carbonate was placed
into an autoclave having a net volume of 0.2 liter.
About
The autoclave was
heated on all sides by an aluminum block. The tempera
ture was controlled with the aid of eight platinum resist—
ance thermometers. Three of these were located in the
aluminum block, three others in apertures in the wall of
the autoclave, one in the bottom of the autoclave and an
160 gm. liquid carbon dioxide were added thereto. There 35 other in a thermometer ?tting submerged in the reaction
after the contents of the autoclave were heated for 7
mixture. The heating of the autoclave was controlled in
hours at 360° (3., whereby a pressure of about 1600
such a way that no excess heat was developed in the wall
atmospheres was reached. After further processing of
the reaction product in the same manner as described
of the autoclave. After the reaction temperature was
reached, the temperature measured in the reaction mix
in Example I, 4.95 gm. benzoic acid were recovered. The 40 ture was [lower by only 10 to 15° than the temperature in
yield of terephthalic acid was 9 gm. which corresponds
the wall of the autoclave;
. .
to a yield of 52.8% of theory, taking into consideration
132 gm. of an equimolar mixture of potassium benzoate
the amount of benzoic acid recovered.
‘
and‘ potassium carbonate was intimately admixed with 5.5
'
gm. cadmium ?uoride in a ball mill, and the mixture was
Example VIII
45 then placed into the high-pressure autoclave above de
40 gm. potassium benzoate and about 160 gm. liquid
carbon dioxide were placed into an autoclave having a
scribed. After the autoclave was cooled to 0° C., 400 gm.
of liquid carbon dioxide were added. Thereafter, the
autoclave was heated for 10 hours to a wall temperature
of 400° C., during which the internal pressure rose to ap
net volume of 0.2 liter. Subsequently, the contents of
the autoclave were heated for 7 hours at 360° C. whereby
a pressure of about 1600 atmospheres was reached. After 50 proximately 1500‘ atmospheres. .The temperature meas
ured in the reaction mixture'was about 390° C. .
treatment of the reaction mixture in the samemanner as
The reaction product, which weighed 148 gm., was
described in Example I, 18.55 gm. benzoic acid. were re
worked up in the manner described above. 54.1 gm.
covered. The yield of terephthalic acid was-6.1 gm,
terephthalic acid were obtained, corresponding to a yield
which corresponds to a yield of 37.4% of theory when
taking into consideration the amount of benzoic acid re 55 of 73.8% of theory. 7.4 gm. benzoic acid were recov
covered.
4
‘
Example IX
A homogeneous mixture of 30 gm. potassium benzoate,
ered from the mother liquor. ‘
' Example XIII
131 gm. of an equimolar mixture of potassium benzoate
13 gm. anhydrous potassium carbonate and 2 gm. cad
60 and potassium carbonate were intimately admixed with
mium ?uoride was placed into an autoclave having a net
8 gm. of the complex salt K2(CdF2Cl2) in a ball mill, and
volume of 0.2 liter. About 40 gm. liquid carbon dioxide
the mixture was placed into the high-pressure autoclave
were added thereto. Thereafter the contents of the auto
described in Example XII. 400 gm. liquid carbon dioxide
clave were heated for 7 hours at 380° C. whereby a pres
sure of 500 atmospheres was reached. The reaction mix
were added thereto. Thereafter the autoclave was heated
65 for 10 hours to a wall temperature of 415° C. (internal
ture was worked up in the same manner as described in
temperature 400-405 ° C.) , during which the internal pres~
Example 1. vFrom the mother liquid 1.25 ‘gm. benzoic
acid were recovered. The yield of terephthalic acid was
' sure reached about 1500 atmospheres. The reaction prod
net, which weighed 156 gm., was worked up in the manner
12.65 gm. 7 Taking into consideration the amount of hen
described above. 65.7 gm. terephthalic acid were ob
zoic acid recovered, this corresponds to a yield of 56.9%
70 tained, corresponding to a yield of 91.4% of theory.
of theory.
.
_
-
Example X
A homogeneous mixture of 30 gm. potassium benzoate,
13 gm. anhydrous potassium carbonate and 2 gm. cad
Example XIV .
A mixture of 16.1 gm. of the potassium salt of nicotinic
acid (pyridine-?-carboxylic acid), 138 gm. potassium car
mium ?uoride was placed into an autoclave having a net 75 bonate and 1.0 gm.' cadmium ?uoride was heated for 8
7
hours-at 350° C. in an autoclave having a capacity of 0.2
liter. At the beginning of the run, 180 gm. carbon dioxide
were introduced into the autoclave.
At 350” C. a pres
sure of 1800 atmospheres developed. After cooling and
releasing the pressure from the autoclave, the reaction
ous application Serial No. 643,952, ?led March 5, 1957,
now abandoned.
'
'
We claim:
‘
1. In the method of producing alkali metal salts of
aromatic carboxylic acids, selected from the group con
product, which weighed 32 gm., was dissolved in 400 cc.
sisting of mono- and dicyclic aromatic and aromatic
hot water.
heterocyclic di- and tricarboxylic acids from the corre
sponding mono- and dicyclic aromatic and aromatic het
The solution was ?ltered, acidi?ed with hy
drochloric acid and then evaporated to one-half its vol
ume. Upon cooling to 0° C., 16.1 gm. of the monopotas
erocyclic mono-carboxylic acid ‘salts which ‘comprises,
sium salt of isocinchomeric acid (pyridine-2,5-dicarboxylic 10 heating the mono-carboxylic salts to be converted to a
temperature above 300° C. and below the temperature
at which said salt and the reaction products substan
tially decompose in a substantially oxygen-free inert car
A mixture of 52.5 gm. of the potassium salt of B-naph
bon dioxide atmosphere and in the presence of an acid
thoic acid, 34.5 gm. potassium carbonate and 217 gm. cad~
binding agent,~for a time suf?cient to effect said conver
rnium ?uoride was heated ‘for 6 hours at 420~430° C. in 15
sion, the improvement which comprises conducting the
an'autoclave having a capacity of 0.6 liter. Prior to
reaction under a pressure of at least 400 atmospheres,
heating, 480 gm. carbon dioxide were introduced into the
thereby obtaining a molar yield of the di- and tricar
‘autoclave, which produced a pressure of 1350 atmospheres
acid product salts which is more than 50% of
at the reaction temperature. After cooling and releasing 20 boxylic
the monocarboxylic acid salts undergoing conversion.
‘the pressure from the autoclave, the reaction product was
2. In the method of producing alkali metal salts of
dissolved in water and the solution was ?ltered. The ?l
aromatic carboxylic acids, selected from the group con
trate was acidi?ed with concentrated hydrochloric acid.
sisting of mono- and dicyclic aromatic and aromatic _
The crystals which separated out were ?ltered o? while
heterocyclic
monocarboxylic acid salts which comprises,
the solution was still hot and were repeatedly washed with 25 heating the monocarboxylic salts to be converted to a
hot alcohol and then dried at 140° C. The yield of naph
temperature above 300° C. and below the temperature at
thalene-2,6-dicarboxylic acid was 26.5 gm. From the
which said salt and the reaction products substantially
wash alcohol 8.5 gm. B-naphthoic acid were recovered.
decompose, in the presence ofa catalyst containing a
‘Example XVI
catalytically- active bivalent metal selected from the
A mixture of 22.0;gm. of the potassium salt of thio 30 group consisting of cadmium, zinc, mercury, lead and
‘iron, in a substantially oxygen-free carbon dioxide at
phene-a-carboxylic acid, 27.6 gm.- potassium carbonate
' acid) crystallized out.
Example XV
and 2.0 gm. cadmium ?uoride was heated in an autoclave
for 31/2 hours at 340° C. Before heating, the air was dis
placed with carbon dioxide and thereafter su?icient car
bon dioxide was introduced into the autoclave to produce 35
an internal pressure of 800 atmospheres at the reaction
. temperature.
The reaction product, which weighed 54.2
gm., was dissolved in 600 cc. hot water.
The solution
_ 1 was ?ltered, and the ?ltrate was acidi?ed with hydrochloric
acid. The thiophene-‘Z,5'-dicarboxylic acid precipitated
' thereby was ?ltered off, washed with water and dried.
The yield was 17.0 gm. By extraction with ether, 12.2
gm. of amixture of thiophene-monocarboxylic and dicar
boxylic acids having an acid number of 5 95 was recovered
‘from the mother liquor and the wash water.
Example XVII
mosphere and in the presence of a metallic salt acid
binding agent, for a time sufficient to effect said con
version, the improvement which comprises conducting the
reaction under a pressure of at least 400 atmospheres,
thereby'obtaining a molar yield of the di- and tri
carboxylic acid product salts which is more than 50% of
the monocarboxylic acid salts undergoing conversion.
3. In a process for the production of terephthalic acid
from potassium benzoate which comprises the steps of
heating said potassium benzoate at a temperature of at
least, 300° C. but not greater than the temperature at
which said salts and the reaction products will substan
tially decompose, in the presence of a cadmium-contain
ing catalyst and potassium carbonate in a carbon dioxide
atmosphere, for a time su?icient to e?ect said conver
sion, whereby said potassium benzoate undergoes a con
version to dipotassium terephthalate, and treating said
A mixture of 32.2 gm. of the potassium salt of iso
terephthalate with and acid substance to liberate ter
nicotinicacid, 27.6 gm. potassium carbonate and 3.0 gm.
cadmium ?uoride was heated for 16 hours at 390° C. in 50 ephthalic acid, the improvement which comprises con
an autoclave'having a capacity of '600 cc.
Prior to heat
ing, the: air in the autoclave was displaced with carbon
dioxide, and then sul?cient carbon dioxide was introduced,
under pressure to produce an internal pressure of 1500
atmospheres rat the reaction temperature. The reaction
product, which weighed 64.5 gm." was dissolved in hot
"water. The solution was ?ltered, and the clearr?ltrate
was acidi?ed with a quantity of hydrochloric acid equiva
ducting the reaction under a pressure of at least 400
atmospheres, thereby obtaining a molar yield of tereph
thalic acid which is more than 50% based on the hen
zoate salts undergoing conversion.
4. The process of claim 3 wherein sodium benzoate
is admixed with the reaction mixture.
‘
5. In a process for the production of naphthalene
2,6-dicarboxylic acid by the thermal conversion of the
potassium salt of ?-naphthoic acid which comprises the
lent to the calculated amount of potassium present. Upon
steps of heating said potassium salt of IS-naphthoic acid
60
cooling, 26.2, gm. of the monopotassium salt of trirnestinic
at a temperature of at least 300° C. but not greater than'
acid (pyridine-2,4,6-tricarboxylic acid) crystallized out.
the temperature at which said salts and the reaction
By extraction of the mother liquor, 2.76 gm. additional
products will substantially decompose, in the presence of
pyridine-tricarboxylic acid were obtained.
.
a cadmium-containing catalyst and potassium ‘carbonate '
Other alkali metal salts such as the lithium, rubidium
and cesium salts or the alkaline earth metal or thallium 65 in a carbon dioxide atmosphere, for a time suf?cient to
salts may be employed in place of the potassium and
sodium salts, with similar results.
In all of the above '
effect said conversion, whereby said potassium salt of 5
naphthoic acid undergoes a conversion to the dipotas~
sium salt of naphthalene-2,6-dicarboxylic acid and treat
examples, yields have been‘ calculated on the assumption
ing said dipotassium salt of naphthalene-2,6-dicarboxylic
‘that ’1 mol benzoic acid forms 1 mol terephthalic acid.
While we have set forth vspeci?c examples and modes 70 acid with an acid substance to liberate naphthalene-2,6
dicarboxylic acid, the improvement which comprises con
of practice for our invention, it should be understood
ducting the reaction under a pressure of at least 400 at;
that various modi?cations may be made in the invention
mospheres, thereby obtaining a molar yield of 2,6-dicar
without departing from the spirit thereof or the scope of
‘the following claims.
‘
This application is acontinuation-in-part of our previ
boxylic acid which is more than 50% based on the ,8
naphthoic acid salt undergoing conversion.
3,043,846
9
6. In a process for the production of isocinchomeric
acid from potassium nicotinate, which comprises the
steps of heating said potassium nicotinate at a tempera
10
thereby, obtaining a product yield greater than 50% based
on the amount of starting material.
8. In a process for the production of pyridine-2,4,6
tricarboxy-lic acid from the potassium salt of isonicotinic
acid, which comprises'the steps of heating said potassium
perature at which said salts and the reaction products
salt of isonicotinic acid at a temperature of at least 300°
will substantially decompose, in the presence of a cadmi
C. but not greater than the temperature at which said
um-containing catalyst and potassium carbonate in a car
salts and the reaction products will substantially decom~
bon dioxide atmosphere, for a time su?icient to eifect
pose, in the presence of a cadmium-containing catalyst
said conversion, whereby said potassium nicotinate un
dergoes a conversion to the dipotassium salt of iso 10 and potassium carbonate in a carbon dioxide atmosphere,
for a time su?icient to effect said conversion, whereby said
cinchomeric and treating said dipotassium salt of iso
potassium salt of isonicotinic acid undergoes a conversion
cinchomeric with an acid substance to liberate iso
to the potassium salt of pyridine 2,4,6-tricarboxylic acid
cinchomeric 'acid, the improvement which comprises
ture of at least 300° C. but not greater than the tem
and treating said potassium salt of pyridine 2,4,6-tricar
atmospheres, thereby obtaining a product yield greater 15 boxylic acid with an acid substance to liberate pyridine
2,4,6-tricarboxylic acid, the improvement which comprises
than 50% based on the amount of starting material.
conducting the reaction under a pressure of at least 400
7. In a process for the production of thiophene-2,5
dicarboxylic acid from the potassium salt of thiophene-a
carboxylic acid, which comprises the steps of heating said
potassium salt of thiophene-a-carboxylic acid at a tem 20
perature of at least 300° C. but not greater than the tem
perature at which said salts and the reaction products will
substantially decompose, in the presence of a cadmium
containing catalyst and potassium carbonate in a carbon
dioxide atmosphere, for a time suiiicient to etfect said 25
conversion, whereby said potassium salt of thiophene-a
carboxylic acid undergoes a conversion to the dipotassium
salt of thiophene-Z,S-dicarboxylic acid and treating said
dipotassium salt of thiophene-2,5-dicarboxylic acid with
an acid substance to liberate thiophene-2,5-dicarboxylic 30
conducting the reaction under a pressure of at least 400
atmospheres, thereby obtaining a product yield greater
than 50% based on the amount of starting material.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,794,830
2,823,229
2,823,230
2,823,231
2,848,487
2,900,386
Raecke et a1. __________ __ June 4,
Raecke et a1 ___________ __ Feb. 11,
Raecke et al ___________ __ Feb. 11,
Raecke et al ___________ .._ Feb. 11,
Keen ________________ __ Aug. 19,
Raecke et al ___________ __ Aug. 18,
2,906,774
Raecke et a1 ___________ __ Sept. 29, 1959
524,035
Belgium ______________ __ Mar. 2, 1956
FOREIGN PATENTS
acid, the improvement which comprises conducting the
reaction under a pressure of at least 400 atmospheres,
1957
1958
1958
1958
1958
1959
UNITED STATES PATENT OFFICE
CERTIFICATE OF CORRECTION
Patent No, 3,043,846
July 10, 1962
Bruno Blaser et a1a
It is hereby certified that error appears in the above numbered pat
ent requiring correction and that the said Letters Patent should read as
corrected below.
Column 4, line 73, for "3600 C. " read —— 340° C. ——.
Signed and sealed this 13th day of November 1962.,
SEAL)
\ttest:
IRNEIST w. SWIDER
DAVID L' LADD
Ittesting Officer
Commissioner of Patents
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