Title of Invention

INDUSTRIAL PROCESS FOR PRODUCTION OF HIGH-PURITY DIPHENYL CARBONATE

Abstract It is an object of the present invention to provide a specific process that enables a high-purity diphenyl carbonate that can be used as a raw material of a high-quality and high-performance polycarbonate to be produced stably for a prolonged period of time on an industrial scale of not less than 1 ton / hr from a reaction mixture containing a catalyst and reaction by-products that has been obtained through transesterification reaction and the like using a dialkyl carbonate and a phenol as a starting material. Although there have been various proposals regarding processes for the production of reaction mixtures containing aromatic carbonates by means of a reactive distillation method, these have all been on a small scale and short operating time laboratory level, and there have been no disclosures on a specific process or apparatus enabling mass production on an industrial scale from such a reaction mixture to a high-purity diphenyl carbonate that can be used as a raw material of a high-quality and high-performance polycarbonate. According to the present invention, there are provided a high boiling point material separating column A and a diphenyl carbonate purifying column B each comprising a continuous multi-stage distillation column having specified structures, and there is provided a specific process that enables a high-purity diphenyl carbonate which is important as a raw material of a high-quality and high-performance polycarbonate to be produced stably for a prolonged period of time on an industrial scale of not less than 1 ton / hr from a reaction mixture containing the diphenyl carbonate using an apparatus in which these two continuous multi-stage distillation columns are connected together.
Full Text Technical Field
The present invention relates to an industrial process for the production of a
high-purity diphenyl carbonate. More particularly, the present invention relates to an
industrial process for the production of a high-purity diphenyl carbonate, which is
useful as a raw material of a transesterification method polycarbonate, by using two
continuous multi-stage distillation columns having specified structures, from a
reaction mixture containing a diphenyl carbonate obtained by carrying out a
transesterification reaction between a dialkyl carbonate and a phenol and/or a
disproportionation reaction of an alkyl phenyl carbonate and/or a transesterification
reaction between an alkyl phenyl carbonate and a phenol.
Background Art
A high-purity diphenyl carbonate is important as a raw material for the
production of an aromatic polycarbonate, which is the most widely used engineering
plastics, without using toxic phosgene. As a process for producing an aromatic
carbonate, a process of reacting an aromatic monohydroxy compound with
phosgene has been known from long ago, and has also been the subject of a variety
of studies in recent years. However, this process has the problem of using
phosgene, and in addition chlorinated impurities that are difficult to separate out are
present in the aromatic carbonate produced using this process, and hence this
aromatic carbonate cannot be used as a raw material for the production of the
aromatic polycarbonate. Because such chlorinated impurities markedly inhibit the
polymerization reaction in the transesterification method which is carried out in the
presence of an extremely small amount of a basic catalyst; for example, even if such
chlorinated impurities are present in an amount of only 1 ppm, the polymerization
hardly proceeds at all. To make the aromatic carbonate capable of using as a raw
material of a transesterification method polycarbonate, a troublesome multi-stage
separation/purification processes such as enough washing with a dilute aqueous
alkaline solution and hot water, oil / water separation, distillation and so on are thus
required. Furthermore, the yield of aromatic carbonate decreases due to hydrolysis
loss and distillation loss during this separation/purification processes. Therefore,
there are many problems in carrying out this method economically on an industrial
scale.
On the other hand, a process for producing aromatic carbonates through
transesterification reactions between dialkyl carbonates and aromatic monohydroxy
compounds are also known. However, such transesterification reactions are all
equilibrium reactions. Since the equilibriums are biased extremely toward the
original system and the reaction rates are slow, there have been many difficulties in
producing the aromatic carbonate industrially in large amounts using this method.
Two types of proposals have been made to improve on the above difficulties. One
of these relates to development of a catalyst to increase the reaction rate, and many
metal compounds have been proposed as the catalyst for the above type of the
transesterification reactions. For example, Lewis acids such as transition metal
halides and Lewis acid-forming compounds (see Patent Documents 1: Japanese
Patent Application Laid-Open No. 51-105032, Japanese Patent Application
Laid-Open No. 56-123948, Japanese Patent Application Laid-Open No. 56-123949
(corresponding to West German Patent Application No. 2528412, British Patent No.
1499530, and U.S. Patent No. 4182726), Japanese Patent Application Laid-Open No.
51-75044 (corresponding to West German Patent Application No. 2552907, and U.S.
Patent No. 4045464)), tin compounds such as organotin alkoxides and organotin
oxides (see Patent Documents 2: Japanese Patent Application Laid-Open No.
54-48733 (corresponding to West German Patent Application No. 2736062),
Japanese Patent Application Laid-Open No. 54-63023, Japanese Patent Application
Laid-Open No. 60-169444 (corresponding to U.S. Patent No. 4554110), Japanese
Patent Application Laid-Open No. 60-169445 (corresponding to U.S. Patent No.
4552704), Japanese Patent Application Laid-Open No. 62-277345, Japanese Patent
Application Laid-Open No. 1-265063), salts and alkoxides of alkali metals and
alkaline earth metals (see Patent Document 3: Japanese Patent Application
Laid-Open No. 57-176932), lead compounds (see Patent Documents 4: Japanese
Patent Application Laid-Open No. 57-176932, Japanese Patent Application
Laid-Open No. 1-93560), complexes of metals such as copper, iron and zirconium
(see Patent Document 5: Japanese Patent Application Laid-Open No. 57-183745),
titanic acid esters (see Patent Documents 6: Japanese Patent Application Laid-Open
No. 58-185536 (corresponding to U.S. Patent No. 4410464), Japanese Patent
Application Laid-Open No. 1 -265062), mixtures of a Lewis acid and protonic acid
(see Patent Document 7: Japanese Patent Application Laid-Open No. 60-173016
(corresponding to U.S. Patent No. 4609501)), compounds of Sc, Mo, Mn, Bi, Te or
the like (see Patent Documents 8: Japanese Patent Application Laid-Open No.
1 -265064), ferric acetate (see Patent Document 9: Japanese Patent Application
Laid-Open No. 61-172852), and so on have been proposed.
Since the problem of the disadvantageous equilibrium cannot be solved
merely by developing the catalyst, as the other type of the proposals, attempts have
been made to devise a reaction system so as to shift the equilibrium toward the
product system as much as possible, thus improving the aromatic carbonate yield.
For example, for the reaction between dimethyl carbonate and phenol, there have
been proposed a method in which methanol produced as a by-product is distilled off
by azeotropy together with an azeotrope-forming agent (see Patent Documents 10:
Japanese Patent Application Laid-Open No. 54-48732 (corresponding to West
German Patent Application No. 736063, and U.S. Patent No. 4252737)), and a
method in which the methanol produced as a by-product is removed by being
adsorbed onto a molecular sieve (see Patent Documents 11: Japanese Patent
Application Laid-Open No. 58-185536 (corresponding to U.S. Patent No. 410464)).
Moreover, a method has also been proposed in which, using an apparatus in which a
distillation column is provided on top of a reactor, an alcohol produced as a
by-product in the reaction is separated off from the reaction mixture, and at the same
time an unreacted starting material that evaporates is separated off by distillation
(see Patent Documents 12: examples in Japanese Patent Application Laid-Open No.
56-123948 (corresponding to U.S. Patent No. 4182726), examples in Japanese
Patent Application Laid-Open No. 56-25138, examples in Japanese Patent
Application Laid-Open No. 60-169444 (corresponding to U.S. Patent No. 4554110),
examples in Japanese Patent Application Laid-Open No. 60-169445 (corresponding
to U.S. Patent No. 4552704), examples in Japanese Patent Application Laid-Open
No. 60-173016 (corresponding to U.S. Patent No. 4609501), examples in Japanese
Patent Application Laid-Open No. 61-172852, examples in Japanese Patent
Application Laid-Open No. 61-291545, examples in Japanese Patent Application
Laid-Open No. 62-277345).
However, these reaction systems have basically been batch system or
switchover system. Because there are limitations in the improvement of the
reaction rate through catalyst development for such transesterification reactions, and
the reaction rates are still slow, and thus it has been thought that the batch system is
preferable to a continuous system. Of these, a continuous stirring tank reactor
(CSTR) system in which a distillation column is provided on the top of the reactor has
been proposed as the continuous system, but there are problems such as the
reaction rate being slow, and a gas-liquid interface in the reactor being small, based
on the volume of the liquid. Hence it is not possible to make the reaction ratio high.
Accordingly, it is difficult to attain the object of producing the aromatic carbonate
continuously in large amounts stably for a prolonged period of time by means of the
above-mentioned methods, and many issues remain to be resolved before
economical industrial implementation is possible.
The present inventors have developed reactive distillation methods in which
such a transesterification reaction is carried out in a continuous multi-stage
distillation column simultaneously with separation by distillation, and have been the
first in the world to disclose that such a reactive distillation system is useful for such
a transesterification reaction, for example, a reactive distillation method in which a
dialkyl carbonate and an aromatic hydroxy compound are continuously fed into the
multi-stage distillation column, and the reaction is carried out continuously inside the
column in which a catalyst is present, while continuously withdrawing a low boiling
point component containing an alcohol produced as a by-product by distillation and
continuously withdrawing a component containing a produced alkyl aryl carbonate
from a lower portion of the column (see Patent Document 13: Japanese Patent
Application Laid-Open No. 3-291257), a reactive distillation method in which an alkyl
aryl carbonate is continuously fed into the multi-stage distillation column, and the
reaction is carried out continuously inside the column in which a catalyst is present,
while continuously withdrawing a low boiling point component containing a dialkyl
carbonate produced as a by-product by distillation, and continuously withdrawing a
component containing a produced diaryl carbonate from a lower portion of the
column (see Patent document 14: Japanese Patent Application Laid-Open No.
4-9358), a reactive distillation method in which these reactions are carried out using
two continuous multi-stage distillation columns, and hence a diaryl carbonate is
produced continuously while efficiently recycling a dialkyl carbonate produced as a
by-product (see Patent document 15: Japanese Patent Application Laid-Open No.
4-211038), and a reactive distillation method in which a dialkyl carbonate and an
aromatic hydroxy compound or the like are continuously fed into the multi-stage
distillation column, and a liquid that flows down through the column is withdrawn from
a side outlet provided at an intermediate stage and/or a lowermost stage of the
distillation column, and is introduced into a reactor provided outside the distillation
column so as to bring about reaction, and is then introduced back through a
circulating inlet provided at a stage above the stage where the outlet is provided,
whereby reaction is carried out in both the reactor and the distillation column (see
Patent Documents 16: Japanese Patent Application Laid-Open No. 4-224547,
Japanese Patent Application Laid-Open No. 4-230242, Japanese Patent Application
Laid-Open No. 4-235951).
These reactive distillation methods proposed by the present inventors are the
first to enable aromatic carbonates to be produced continuously and efficiently, and
many similar reactive distillation systems based on the above disclosures have been
proposed thereafter (see Patent Documents 17 to 32: Patent Document 17:
International Publication No. 00/18720 (corresponding to U.S. Patent No. 5362901),
Patent Document 18: Italian Patent No. 01255746, Patent Document 19: Japanese
Patent Application Laid-Open No. 6-9506 (corresponding to European Patent No.
0560159, and U.S. Patent No. 5282965), Patent Document 20: Japanese Patent
Application Laid-Open No. 6-41022 (corresponding to European Patent No. 0572870,
and U.S. Patent No. 5362901), Patent Documents 21: Japanese Patent Application
Laid-Open No. 6-157424 (corresponding to European Patent No. 0582931, and U.S.
Patent No. 5334742), Japanese Patent Application Laid-Open No. 6-184058
(corresponding to European Patent No. 0582930, and U.S. Patent No. 5344954),
Patent Document 22: Japanese Patent Application Laid-Open No. 7-304713, Patent
Document 23: Japanese Patent Application Laid-Open No. 9-40616, Patent
Document 24: Japanese Patent Application Laid-Open No. 9-59225, Patent
Document 25: Japanese Patent Application Laid-Open No. 9-110805, Patent
Document 26: Japanese Patent Application Laid-Open No. 9-165357, Patent
Document 27: Japanese Patent Application Laid-Open No. 9-173819, Patent
Documents 28: Japanese Patent Application Laid-Open No. 9-176094, Japanese
Patent Application Laid-Open No. 2000-191596, Japanese Patent Application
Laid-Open No. 2000-191597, Patent Documents 29: Japanese Patent Application
Laid-Open No. 9-194436 (corresponding to European Patent No. 0785184, and U.S.
Patent No. 5705673), Patent Documents 30: International Publication No. 00/18720
(corresponding to U.S. Patent No. 6093842), International Publication No. 01/042187
(corresponding to Published Japanese Translation of PCT Application No.
2003-516376), Patent Documents 31: Japanese Patent Application Laid-Open No.
2001-64234, Japanese Patent Application Laid-Open No. 2001-64235, Patent
Document 32: International Publication No. 02/40439 (corresponding to U.S. Patent
No. 6596894, U.S. Patent No. 6596895, and U.S. Patent No. 6600061)).
Among the reactive distillation systems, the present applicants have further
proposed, as a method that enables highly pure aromatic carbonates to be produced
stably for a prolonged period of time without a large amount of a catalyst being
required, a method in which a high boiling point material containing a catalyst
component is reacted with an active substance and then separated off, and the
catalyst component is recycled (see Patent Documents 33: International Publication
No. 97/11049 (corresponding to European Patent No. 0855384, and U.S. Patent No.
5872275)), and a method carried out while keeping the weight ratio of a polyhydric
aromatic hydroxy compound in the reaction system to a catalyst metal at not more
than 2.0 (see Patent Documents 34: Japanese Patent Application Laid-Open No.
11-92429 (corresponding to European Patent No. 1016648, and U.S. Patent No.
6262210)). Furthermore, the present inventors have also proposed a method in
which 70 to 99 % by weight of phenol produced as a by-product in a polymerization
process is used as a starting material, and diphenyl carbonate can be produced by
means of the reactive distillation method. This diphenyl carbonate can be used as
the raw material for polymerization to produce aromatic polycarbonates (see Patent
Documents 35: Japanese Patent Application Laid-Open No. 9-255772
(corresponding to European Patent No. 0892001, and U.S. Patent No. 5747609)).
However, in all of these prior art documents in which the production of the
aromatic carbonates using the reactive distillation method is proposed, there is no
disclosure whatsoever of a specific process or apparatus enabling mass production
on an industrial scale (e.g. more than 1 ton per hr), nor is there any description
suggesting such a process or apparatus. For example, the descriptions regarding
heights (H1 and H2: cm), diameters (D1 and D2: cm), the numbers of stages (N1 and
N2), and the feeding rates of the raw materials (Q1 and Q2: kg/hr) for two reactive
distillation columns disclosed for producing mainly diphenyl carbonate (DPC) from
dimethyl carbonate and phenol are as summarized in the following table.
TABLE 1

In other words, the biggest continuous multi-stage distillation columns used
when carrying out this reaction using the reactive distillation system are those
disclosed by the present applicants in Patent Documents 33 and 34. As can be
seen from Table 1, the maximum values of the various conditions for the continuous
multi-stage distillation columns disclosed for the above reaction are H1 = 1200 cm,
H2 = 600 cm, D1 = 20 cm, D2 = 25 cm, N1 = N2 = 50 (Patent Document 25), Q1 = 86
kg/hr, and Q2 = 31 kg/hr, and the total amount of diphenyl carbonate produced was
only approximately 6.7 kg/hr, which was not an amount produced on an industrial
scale.
As methods for separating the diphenyl carbonate from the reaction mixture
containing a diphenyl carbonate that has been produced through transesterification
reaction and the like between a dialkyl carbonate and a phenol as a starting material
as described above, and then purifying the diphenyl carbonate, crystallization
methods, distillation methods and the like have been proposed. With regard to the
distillation methods, three methods have been proposed. One is a method in which
the diphenyl carbonate is obtained as a column top component from a distillation
column; for example, there are:
I) a method in which the reaction mixture containing the catalyst is distilled as
is in a batch type distillation column, and the diphenyl carbonate is obtained as the
column top component (see example of Patent Document 10, example 2 of Patent
Document 19);
II) a method in which the reaction mixture containing the catalyst is subjected
to flash evaporation, and thus separated into a high boiling point material containing
most of the catalyst and a low boiling point material, and then the low boiling point
material is distilled in a distillation column for starting material recovery, and a
catalyst-containing diphenyl carbonate is obtained as a column bottom material, and
then this column bottom material is distilled in a purifying column, whereby the
diphenyl carbonate is obtained as a column top component (see Patent Document
37: example 1 in Japanese Patent Application Laid-open No. 4-100824, Patent
Document 38: Japanese Patent Application Laid-open No. 9-169704); and
III) a method in which the reaction mixture containing the catalyst is distilled
in a distillation column (or evaporator), and thus separated into a high boiling point
material containing most of the catalyst and a low boiling point material, and then the
low boiling point material is subjected to continuous sequential distillation using a
distillation apparatus comprising three columns, i.e. a light fraction separating column,
a methyl phenyl carbonate separating column, and a diphenyl carbonate separating
column, whereby diphenyl carbonate is obtained as a column top component (see
Patent Document 25).
Another is a method in which the diphenyl carbonate is obtained as a column
bottom component from a distillation column; for example, there is:
IV) a method in which the reaction mixture containing the catalyst is distilled
in a distillation column, and thus separated into a high boiling point material
containing most of the catalyst and a low boiling point material, and then the low
boiling point material is distilled in a distillation column, and the diphenyl carbonate is
obtained as a column bottom component (see Patent Document 31).
The other is a method in which the diphenyl carbonate is obtained as a side
cut component from a distillation column; for example, there are:
V) a method in which the reaction mixture containing the catalyst is
introduced into a third reactive distillation column, and further reaction and distillation
are carried out, whereby the diphenyl carbonate is obtained as a side cut component
from the reactive distillation column (see Patent Document 21);
VI) a method in which the reaction mixture containing the catalyst is
subjected to flash evaporation, and thus separated into a high boiling point material
containing most of the catalyst and a low boiling point material, and then the low
boiling point material is introduced into a distillation column and distillation is carried
out, whereby the diphenyl carbonate is obtained as a side cut component from the
reactive distillation column (see Patent Documents 34 and 35, Patent Document 39:
International Publication No. 92/18458 (corresponding to U.S. Patent No. 5426207);
VII) a method in which the reaction mixture containing the catalyst is distilled
in a first purifying column, and thus separated into a high boiling point material
containing most of the catalyst and a low boiling point material, and then the low
boiling point material is introduced into a second purifying column and distillation is
carried out, whereby the diphenyl carbonate is obtained as a side cut component
from the second purifying column (see Patent Document 40: Japanese Patent
Application Laid-open No. 11-49727); and
VIII) a method in which diphenyl carbonate containing phenyl salicylate is
introduced into a distillation column having the number of theoretical stages being
from 5 to 15, and distillation is carried out at a column bottom temperature of not less
than 150°C, whereby the diphenyl carbonate is obtained as a side cut component
from the distillation column (see Patent Document 36: Japanese Patent Application
Laid-open No. 9-194437 (corresponding to European Patent No. 0784048)).
However, it has been shown that various problems remain with such diphenyl
carbonate separation/purification methods using these distillations. More
specifically, the purity of the diphenyl carbonate obtained through the above I) is low,
and moreover this is a batch process and hence is not suitable for mass production
on an industrial scale. Regarding the above II), the method of Patent Document 37
is a batch method, and the diphenyl carbonate which was obtained through the
method disclosed in Patent Document 38 contains a titanium catalyst, albeit in an
amount of not more than 1 ppm, and hence is not suitable as a raw material for the
production of a high-purity discolored polycarbonate. With the method of the above
III), since the diphenyl carbonate is heated to a high temperature at the bottom of
each of two of the distillation columns, i.e. the light fraction separating column and
the methyl phenyl carbonate separating column, and is then subjected to a high
temperature in the diphenyl carbonate separating column, the diphenyl carbonate is
altered, bringing about a decrease in the purity and a decrease in the yield.
Moreover, the method of the above IV) in which the diphenyl carbonate is
obtained from the column bottom is unsuitable, because the purity is low and hence
a desired polycarbonate cannot be produced.
With the method of the above V), the reaction mixture containing the catalyst,
the unreacted starting material and the impurities obtained from the bottom of the
second reactive distillation column is introduced into the third reactive distillation
column from an upper portion thereof, and the diphenyl carbonate is withdrawn from
the side of the third reactive distillation column. Vapor or mist of the catalyst, the
starting material, the impurities and the like may thus be entrained, and hence the
purity of the diphenyl carbonate is low. With the method of the above VI), the
amount of diphenyl carbonate produced is 6.7 kg/hr (example 3 of Patent Document
34) or 3.9 kg/hr (example 1 of Patent Document 35), which is not on an industrial
scale. The method of the above VII) is a preferable process, but the amount of
diphenyl carbonate produced is small at 2 kg/hr (example 8 of Patent Document 40),
which is not on an industrial scale. Moreover, the method is carried out with the
column top pressure in the first purifying column at a high vacuum of 200 Pa, and
hence industrial implementation would be difficult, because a very large distillation
column would be required so that the high vacuum could be maintained.
Moreover, with the method of the above VIII), although it is stated that the
content of phenyl salicylate is reduced from 3000 ppm to 50 ppm (example 2 of
Patent Document 36), nothing is stated whatsoever for other impurities. For
example, even though the diphenyl carbonate is produced using the phosgene
method in this example, and hence this is definitely a purification method for diphenyl
carbonate containing chlorinated impurities, nothing is stated whatsoever with regard
to the chlorinated impurities (which have an adverse effect on the polymerization to
produce a polycarbonate and the properties of the polycarbonate even in an
extremely small amount of only a few tens of ppb). With this method, such
chlorinated impurities will not be separated out sufficiently, and hence it will not be
possible to use the diphenyl carbonate as a raw material for a polycarbonate. This
is as described in comparative example 1 (in which the alkali column is not used) of
the purification method (in which after washing twice with alkaline hot water, washing
with hot water is carried out, and then the diphenyl carbonate is dehydrated through
distillation and then passed through a column filled with a solid alkali, before being
subjected to reduced pressure distillation in the multi-stage distillation column) of
Patent Document 41 (Japanese Patent Application Laid-Open No. 9-194437), which
was filed more than one year after the filing of Patent Document 36.
Furthermore, in Patent Document 36, the temperature and time at which
phenol starts to be distilled off in the case that reaction is carried out with bisphenol A
are given as a method of evaluating the purity of the diphenyl carbonate obtained
through the distillation, but evaluation of whether the diphenyl carbonate is suitable
for polymerization cannot be carried out using this test method. This is because
even for diphenyl carbonate of low purity such that a polycarbonate of the required
degree of polymerization cannot be produced, the initial reaction in which phenol is
eliminated occurs sufficiently. Moreover, since with this evaluation method, a large
amount of 2.3 ppm of NaOH based on the bisphenol A is used as a catalyst, even for
diphenyl carbonate containing, for example, 1 ppm of chlorinated impurities, an
incorrect evaluation that the diphenyl carbonate is of high purity and is suitable as a
raw material for a polycarbonate would be obtained. As stated earlier, the diphenyl
carbonate containing 1 ppm of chlorinated impurities cannot be used as the raw
material for the polycarbonate at all. In ordinary polymerization, since such a large
amount of an alkaline catalyst is not used, this evaluation method is not suitable for
evaluating the purity of diphenyl carbonate to be used for producing polycarbonate.
Further, in Patent Document 36, there is no specific description whatsoever of
purification of diphenyl carbonate that has been obtained using the transesterification
method. Since the types and contents of impurities differ between diphenyl
carbonate obtained through the phosgene method and diphenyl carbonate obtained
using the transesterification method, it cannot be said that diphenyl carbonate of the
same purity will be obtained through the same purification method. It thus cannot
be said at all that diphenyl carbonate having the required purity for the raw material
of the polycarbonate would be obtained through the purification method of Patent
Document 36. Furthermore, the amount of purified diphenyl carbonate disclosed in
Patent Document 36 is 0.57 kg/hr, which is not on an industrial scale.
A reaction mixture obtained through transesterification reaction between a
dialkyl carbonate and a phenol as a starting material in the presence of a
homogeneous catalyst generally contains various reaction by-products. In particular,
if a diphenyl carbonate containing the amounts of high boiling point by-products
having a higher boiling point than that of the diphenyl carbonate, such as phenyl
salicylate, xanthone, phenyl methoxybenzoate,
1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene and the like which have not been
reduced down to a sufficient level is used as the raw material of the
transesterification method polycarbonate, then these high boiling point by-products
will cause coloration and deterioration in properties. It is thus preferable to reduce
the amounts of such impurities as much as possible. However, such high boiling
point by-products are difficult to separate out, and with methods proposed hitherto, it
has not been possible to reduce the amounts of such high boiling point by-products
down to a sufficient level. In particular, there has been no proposal whatsoever of a
process for the production on an industrial scale of not less than 1 ton / hr of a
high-purity diphenyl carbonate required for the raw material of a high-quality and
high-performance polycarbonate.
Disclosure of Invention
It is an object of the present invention to provide a specific process that
enables a high-purity diphenyl carbonate that can be used as a raw material of a
high-quality and high-performance polycarbonate to be produced stably for a
prolonged period of time on an industrial scale of not less than 1 ton / hr from a
reaction mixture containing a catalyst and reaction by-products that has been
obtained through transesterification reaction and the like using a dialkyl carbonate
and a phenol as a starting material.
Since the present inventors disclosed a process for producing aromatic
carbonates using the continuous multi-stage distillation column, various proposals
regarding processes for the production of reaction mixtures containing aromatic
carbonates by means of the reactive distillation method have been made. However,
these have all been on a small scale and a short operating time laboratory level, and
there have been no disclosures on a specific process or apparatus enabling mass
production on an industrial scale from such a reaction mixture to a high-purity
diphenyl carbonate that can be used as the raw material of a high-quality and
high-performance polycarbonate. In view of these circumstances, the present
inventors carried out studies aimed at discovering a specific process enabling a
high-purity diphenyl carbonate which is important as the raw material of the
high-quality and high-performance polycarbonate to be produced stably for a
prolonged period of time on an industrial scale of not less than 1 ton / hr. As a
result, the present inventors have reached to the present invention.
That is, in the first aspect of the present invention, there is provided:
1. In an industrial process for the production of a high-purity diphenyl carbonate
which is produced continuously from a reaction mixture containing a diphenyl
carbonate, which has been obtained by carrying out a transesterification reaction
between a dialkyl carbonate and a phenol and/or a disproportionation reaction of an
alkyl phenyl carbonate and/or a transesterification reaction between an alkyl phenyl
carbonate and a phenol in the presence of a homogeneous catalyst, by continuously
introducing said reaction mixture into a high boiling point material separating column
A, and continuously carrying out separation by distillation into a column top
component At containing the diphenyl carbonate and a column bottom component
Ab containing the catalyst, and then continuously introducing said column top
component At into a diphenyl carbonate purifying column B having a side cut outlet,
and continuously carrying out separation by distillation into a column top component
BT, a side cut component Bs and a column bottom component Bb, the improvement
which comprises:
(a) said high boiling point material separating column A comprises a
continuous multi-stage distillation column having a length La (cm), an inside diameter
Da (cm), and an internal with a number of stages nA thereinside, wherein La, Da, and
nA satisfy the following formulae (1) to (3);
800 = LA = 3000 (1)
100 = DA = 1000 (2)
20 = nA = 100 (3);
(b) a distillation operation of said high boiling point material separating
column A is carried out under conditions of a column bottom temperature TA in a
range of from 185 to 280°C, and a column top pressure PA in a range of from 1000 to
20000 Pa;
(c) said diphenyl carbonate purifying column B comprises a continuous
multi-stage distillation column having a length Lb (cm), an inside diameter Db (cm),
an internal thereinside, an inlet B1 at a middle portion of the column, and a side cut
outlet B2 between said inlet B1 and the column bottom, in which a number of stages
of the internal above the inlet B1 is n1, a number of stages of the internal between
the inlet B1 and the side cut outlet B2 is n2, a number of stages of the internals below
the side cut outlet B2 is n3, and a total number of stages is nB (= n1 + n2 + n3),
wherein LB, DB, n1, n2, n3, and nB satisfy the following formulae (4) to (9);
1000 = LB = 5000 (4)
100 = DB = 1000 (5)
5 = m = 20 (6)
12 = n2 = 40 (7)
3 = n3 = 15 (8)
20 = nB = 70 (9);
(d) a distillation operation of said diphenyl carbonate purifying column B is
carried out under conditions of a column bottom temperature Tb in a range of from
185 to 280°C, and a column top pressure PB in a range of from 1000 to 20000 Pa;
and
(e) not less than 1 ton / hr of the high-purity diphenyl carbonate is obtained
continuously as the side cut component Bs.
2. The process according to item 1, wherein La, Da, and nA for said high boiling
point material separating column A satisfy the following formulae: 1000 = La =
2500, 200 = DA = 600, and 30 = nA = 70, respectively,
Lb, Db, n1, n2, n3, and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 = LB = 3000,150 = DB = 500,7 = m = 15,12 =
n2 = 30, 3 = n3 = 10, and 25 = nB = 55, respectively,
TA is in a range of from 190 to 240°C, PA is in a range of from 2000 to 15000 Pa,
TB is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000 Pa.
3. The process according to item 1 or 2, wherein each of said high boiling point
material separating column A and said diphenyl carbonate purifying column B is a
distillation column having a tray and/or a packing as said internal.
4. The process according to item 3, wherein said internal of each of said high
boiling point material separating column A and said diphenyl carbonate purifying
column B is a packing.
5. The process according to item 4, wherein said packing is a structured packing
which is at least one selected from the group consisting of Mellapak, Gempak,
Techno-pack, Flexipac, a Sulzer packing, a Goodloe packing, and a Glitsch, as
described hereinafter.
In the second aspect of the present invention, there is provided:
6. A high-purity diphenyl carbonate containing a halogen content of not more
than -0.1 ppm, and a content of by-products having a higher boiling point than
that of the diphenyl carbonate of not more than 100 ppm, produced by the
process according to any one of claims 1 to 5.
7. The high-purity diphenyl carbonate according to item 6, wherein the halogen
content is not more than 10 ppb, and the content of each of phenyl salicylate,
xanthone, phenyl methoxybenzoate, and
l-phenoxycarbonyl-2-phenoxycarboxy-phenylene, which are the by-products
having the higher boiling point than that of the dipenyl carbonate, is not more
than 30 ppm.
8. The high-purity diphenyl carbonate according to item 7, wherein the content
of the by-products having the higher boiling point than that of the diphenyl
carbonate is not more than 50 ppm.
9. The high-purity diphenyl carbonate according to item 8, wherein the halogen
content is not more than 1 ppb, and the content of the by-products having the
higher boiling point than that of the diphenyl carbonate is not more than 10
ppm.
In the third aspect of the present invention, there is provided:
10. An apparatus for producing a high-purity diphenyl carbonate which is
produced from a reaction mixture containing a diphenyl carbonate, which has
been obtained by carrying out a transesterificatipn reaction between a dialkyl
carbonate and a phenol and/or a disproportionation reaction of an alkyl
carbonate and/or a transesterification reaction between an alkyl phenyl
carbonate and a phenol in the presence of a homogeneous catalyst, the
apparatus comprises;
a high boiling point material separating column A which receives said
reaction mixture, and which carries out separation by distillation into a column top
component At containing the diphenyl carbonate and a column bottom component
Ab containing the catalyst; and
a diphenyl carbonate purifying column B having a side cut outlet B2, which is
connected with said high boiling point material separating column A, and which
receives said column top component At therefrom, wherein separation by distillation
is carried out into a column top component Bt, a side cut component Bs and a
column bottom component Bb; wherein
(a) said high boiling point material separating column A comprises a
continuous multi-stage distillation column having a length La (cm), an inside diameter
Da (cm), and an internal with a number of stages nA thereinside, wherein lA, Da, and
nA satisfy the following formulae (1) to (3);
800 = LA = 3000 (1)
100 = DA = 1000 (2)
20 = nA = 100 (3);
(b) said diphenyl carbonate purifying column B comprises a continuous
multi-stage distillation column having a length Lb (cm), an inside diameter DB (cm),
an internal thereinside, an inlet B1 at a middle portion of the column, and the side cut
outlet B2 between said inlet B1 and the column bottom, in which a number of stages
of the internal above the inlet B1 is n1, a number of stages of the internal between
the inlet B1 and the side cut outlet B2 is n2, a number of stages of the internals below
the side cut outlet B2 is n3, and a total number of stages is nB (= n1 + n2 + n3),
wherein LB, DB, n1, N2, n3, and nB satisfy the following formulae (4) to (9);
1000 = LB = 5000 (4)
100 = DB = 1000 (5)
5 = m = 20 (6)
12 = n2 = 40 (7)
3 = n3 = 15 (8)
20 = nB = 70 (9).
11. The apparatus according to item 10, wherein a distillation operation of said high
boiling point material separating column A is carried out under conditions of a column
bottom temperature TA in a range of from 185 to 280°C, and a column top pressure
PA in a range of from 1000 to 20000 Pa.
12. The apparatus according to item 10 or 11, wherein a distillation operation of
said diphenyl carbonate purifying column B is carried out under conditions of a
column bottom temperature Tb in a range of from 185 to 280°C, and a column top
pressure PB in a range of from 1000 to 20000 Pa.
13. The apparatus according to any one of items 10 to 12, wherein not less than 1
ton / hr of the high-purity diphenyl carbonate is obtained as the side cut component
Bs.
14. The apparatus according to any one of items 10 to 13, wherein LA, DA, and nA
for said high boiling point material separating column A satisfy the following formulae:
1000 = LA = 2500, 200 = DA = 600, and 30 = nA = 70, respectively,
Lb, Db, n1, n2, n3, and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 = LB = 3000, 150 = DB = 500,7 = n1 = 15, 12=
n2 = 30, 3 = n3 = 10, and 25 = nB = 55, respectively,
TA is in a range of from 190 to 240°C, PA is in a range of from 2000 to 15000 Pa,
TB is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000 Pa
15. The apparatus according to any one of items 10 to 14, wherein each of said
high boiling point material separating column A and said diphenyl carbonate purifying
column B is a distillation column having a tray and/or a packing as said internal.
16. The apparatus according to item 15, wherein said internal of each of said high
boiling point material separating column A and said diphenyl carbonate
purifying column B is a packing.
17. The apparatus according to item 16, wherein said packing is a structured
packing which is at least one selected from the group consisting of Mellapak,
Gempak, Techno-pack, Flexipac, a Sulzer packing, Goodloe packing and a
Glitsch, as described hereinafter.
In another aspect of the process according to the present invention, there is
provided:
18. A process for the production of a high-purity diphenyl carbonate, the process
comprising the steps of:
(i) carrying out a transesterification reaction between a dialkyl carbonate
and a phenol and/or a disproportionation reaction of an alkyl carbonate and/or
a transesterification reaction between an alkyl phenyl carbonate and a phenol in
the presence of a homogeneous catalyst, so as to form a reaction mixture
containing a diphenyl carbonate;
(ii) carrying out separation by distillation in a high boiling point material
separating column A into a column top component At containing the diphenyl
carbonate and a column bottom component Ab containing the catalyst
(iii) carrying out separation by distillation of said column top component At
in a diphenyl carbonate purifying column B having a side cut outlet into a
column top component Bt, a side cut component Bs and a column bottom
component Bb, said column top component At introducing from the side cut
outlet into the column B; wherein
(a) said high boiling point material separating column A comprises a
continuous multi-stage distillation column having a length LA(cm), an inside
diameter Da (cm), and an internal with a number of stages nA thereinside,
wherein La, Da, and
nA satisfy the following formulae (1) to (3);
800 = LA = 3000 (1)
100 = DA = 1000 (2)
20 = nA = 100 (3);
(b) said diphenyl carbonate purifying column B comprises a
continuous multi-stage distillation column having a length Lb (cm), an inside diameter
DB (cm), an internal thereinside, an inlet B1 at a middle portion of the column, and a
side cut outlet B2 between said inlet B1 and the column bottom, in which a number
of stages of the internal above the inlet B1 is n1, a number of stages of the internal
between the inlet B1 and the side cut outlet B2 is n2, a number of stages of the
internals below the side cut outlet B2 is n3, and a total number of stages is nB (= n1 +
n2 + n3), wherein LB, Db, n1, n2, n3, and nB satisfy the following formulae (4) to (9);
1000 = LB = 5000 (4)
100 = DB = 1000 (5)
5 = m = 20 (6)
12 = n2 = 40 (7)
3 = n3 = 15 (8)
20 = nB = 70 (9).
19. The process according to item 18, wherein not less than 1 ton / hr of the
high-purity diphenyl carbonate is obtained as the side cut component Bs.
20. The process according to item 18 or 19, wherein La, Da, and nA for said high
boiling point material separating column A satisfy the following formulae: 1000 = La
= 2500, 200 = DA = 600, and 30 = nA = 70, respectively,
Lb, DB, n1, n2, n3, and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 = LB = 3000, 150 = DB = 500,7 = n1 = 15, 12 =
n2 = 30, 3 = n3 = 10, and 25 = nB = 55, respectively,
TA is in a range of from 190 to 240°C, Pa is in a range of from 2000 to 15000 Pa,
Tb is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000
Pa.
21. The process according to any one of items 18 to 20, wherein each of said
high boiling point material separating column A and said diphenyl carbonate
purifying column B is a distillation column having a tray and/or a packing as
said internal.
22. The process according to item 21, wherein said internal of each of said high
boiling point material separating column A and said diphenyl carbonate
purifying column B is a packing.
23. The process according to item 22, wherein said packing is a structured
packing which is at least one selected from the -group consisting of Mellapak,
Gempak, Techno-pack, Flexipac, a Sulzer packing, a Goodloe packing, and a
Glitsch, as described hereinafter.
Advantageous Effect of the Invention
It has been discovered that by implementing the present invention, a
high-purity diphenyl carbonate that can be used as a raw material of a
high-quality and high-performance polycarbonate can be produced on an
industrial scale of not less than 1 ton / hr, preferably not less than 2 ton / hr,
more preferably not less than 3 ton / hr, stably for a prolonged period of time of
not less than 2000 hours, preferably not less than 3000 hours, more preferably
not less than 5000 hours, from a reaction mixture containing the diphenyl
carbonate that has been obtained by carrying out a transesterification reaction
between a dialkyl carbonate and a phenol and/or a disproportionation reaction
of an alkyl phenyl carbonate and/or a transesterification reaction between the
alkyl phenyl carbonate and the phenol in the presence of a homogeneous
catalyst.
Brief Description of Drawing
FIG. 1 is a schematic view of an example showing a continuous separating /
purifying apparatus for carrying out the present invention in which a high boiling point
material separating column A and a diphenyl carbonate purifying column B are
connected together. As one example, each of these continuous multi-stage
distillation columns has installed therein an internal comprising a structured packing
having a predetermined number of stages.
A1 and B1: inlet; B2: outlet; 11: outlet for a column bottom component of high boiling
point material column A; 13 and 23: column top gas outlet; 14, 24, 18, 28, and 38:
heat exchanger; 15 and 25; reflux liquid inlet; 16: outlet for a column top component
of high boiling point material column A; 17 and 27; column bottom liquid outlet; 26:
outlet for a column top component of diphenyl carbonate purifying column B; 31:
outlet for a column bottom component of diphenyl carbonate purifying column B; 33:
outlet for a side cut component of diphenyl carbonate purifying column B.
Best Mode for Carrying our the Invention
In the following, the present invention is described in detail.
Adialkyl carbonate used in the present invention is a compound represented
by the general formula (10);
R1OCOOR1 (10)
wherein R1 represents an alkyl group having 1 to 10 carbon atoms, an alicyclic group
having 3 to 10 carbon atoms, or an aralkyl group having 6 to 10 carbon atoms.
Examples of R1 include an alkyl group such as methyl, ethyl, propyl (isomers), allyl,
butyl (isomers), butenyl (isomers), pentyl (isomers), hexyl (isomers), heptyl (isomers),
octyl (isomers), nonyl (isomers), decyl (isomers) and cyclohexylmethyl; an alicyclic
group such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl; and
an aralkyl group such as benzyl, phenethyl (isomers), phenylpropyl (isomers),
phenylbutyl (isomers) and methylbenzyl (isomers). The above-mentioned alkyl
groups, alicyclic group and aralkyl group may be substituted with other substituents
such as la ower alkyl group, a lower alkoxy group, a cyano group or a halogen atom,
and may also contain an unsaturated bond therein.
Examples of dialkyl carbonates having such R1 include dimethyl carbonate,
diethyl carbonate, dipropyl carbonate (isomers), diallyl carbonate, dibutenyl
carbonate (isomers), dibutyl carbonate (isomers), dipentyl carbonate (isomers),
dihexyl carbonate (isomers), diheptyl carbonate (isomers), dioctyl carbonate
(isomers), dinonyl carbonate (isomers), didecyl carbonate (isomers), dicyclopentyl
carbonate, dicyclohexyl carbonate, dicycloheptyl carbonate, dibenzyl carbonate,
diphenethyl carbonate (isomers), di(phenylpropyl) carbonate (isomers),
di(phenylbutyl) carbonate (isomers), di(chlorobenzyl) carbonate (isomers),
di(methoxybenzyl) carbonate (isomers), di(methoxymethyl) carbonate,
di(methoxyethyl) carbonate (isomers), di(chloroethyl) carbonate (isomers) and
di(cyanoethyl) carbonate (isomers).
Of these dialkyl carbonates, ones preferably used in the present invention
are dialkyl carbonates in which R1 is an alkyl group having not more than four carbon
atoms and not containing a halogen atom. A particularly preferable one is dimethyl
carbonate. Moreover, of preferable dialkyl carbonates, particularly preferable ones
are dialkyl carbonates produced in a state substantially not containing a halogen, for
example ones produced from an alkylene carbonate substantially not containing a
halogen and an alcohol substantially not containing a halogen.
A phenol used in the present invention is one in which one hydroxyl group is
bonded to a phenyl group, and may be phenol itself or a substituted phenol.
Examples of the substituted phenols include various alkylphenols such as cresol
(isomers), xylenol (isomers), trimethylphenol (isomers), tetramethylphenol (isomers),
ethylphenol (isomers), propylphenol (isomers), butylphenol (isomers), diethyl phenol
(isomers), methylethylphenol (isomers), methylpropylphenol (isomers),
dipropylphenol (isomers), methylbutylphenol (isomers), pentylphenol (isomers),
hexylphenol (isomers) and cyclohexylphenol (isomers); various alkoxyphenols such
as methoxyphenol (isomers) and ethoxyphenol (isomers); and arylalkylphenols such
as phenyl propyl phenol (isomers). Of unsubstituted phenol and such substituted
phenols, unsubstituted phenol is particularly preferable used in the present invention.
Moreover, of these phenols, ones substantially not containing a halogen are
preferably used in the present invention.
The molar ratio of the dialkyl carbonate to the phenol used in the starting
material for use in the present invention must be in a range of from 0.1 to 10.
Outside this range, the amount of unreacted starting material remaining relative to a
prescribed amount of the desired diphenyl carbonate produced becomes high, which
is not efficient, and moreover much energy is required to recover the unreacted
starting material. For that reason, the above molar ratio is more preferably in a
range of from 0.5 to 5, yet more preferably from 1 to 3.
A catalyst used in the present invention is a homogeneous catalyst which
contains a metal such as Pb, Cu, Zn, Fe, Co, Ni, Al, Ti, V, Sn and the like, and which
dissolves in the reaction system. A catalyst in which such a metallic component is
bonded to organic groups can thus be preferably used. The catalyst component
may of course have been reacted with an organic compound present in the reaction
system such as aliphatic alcohols, phenols, alkyl phenyl carbonates, diphenyl
carbonates or dialkyl carbonates, or may have been subjected to heating treatment
with the starting material or products prior to the reaction. The catalyst used in the
present invention is preferably one that has a high solubility in the reaction liquid
under the reaction conditions. Examples of preferable catalysts in this sense
include PbO, Pb(OH)2 and Pb(OPh)2; TiCI4, Ti(0Me)4, (MeO)Ti(OPh)3)
(MeO)2Ti(OPh)2l (MeO)3Ti(OPh) and Ti(OPh)4; SnCI4, Sn(OPh)4, Bu2SnO and
Bu2Sn(OPh)2; FeCI3, Fe(OH)3 and Fe(OPh)3; and such catalysts that have been
treated with phenol, the reaction liquid and the like.
In the present invention, it is particularly preferable to use a starting material
and catalyst not containing a halogen. In this case, the diphenyl carbonate
produced does not contain a halogen at all, and hence it is important as a raw
material when industrially producing a polycarbonate by means of a
transesterification method. The reason is that even if a halogen is present in the
raw material for the polymerization in even an amount less than, for example, 1 ppm,
then this halogen does inhibit the polymerization reaction, and cause a deterioration
in the properties of the polycarbonate produced, and cause discoloration of the
polycarbonate.
The process for the production of the reaction mixture containing the
diphenyl carbonate using such a homogeneous catalyst with the dialkyl carbonate
and the phenol as a starting material may be any process, but one particularly
preferable for industrial implementation is a process in which two continuous
multi-stage distillation columns are used as reactive distillation columns as previously
proposed by the present inventors. This is a process in which a transesterification
reaction between the dialkyl carbonate and the phenol is carried out in the presence
of the homogeneous catalyst in the first continuous multi-stage distillation column to
obtain a column bottom reaction mixture having an alkyl phenyl carbonate as a main
product therein, and this column bottom reaction mixture is introduced into the
second continuous multi-stage distillation column, where conversion of the alkyl
phenyl carbonate into the diphenyl carbonate and the dialkyl carbonate occurs
r»o
mainly through a disproportionation reaction. The diphenyl carbonate may of
course also be produced through a transesterification reaction between the alkyl
phenyl carbonate and the phenol in the reactive distillation columns. The column
bottom reaction mixture from the second continuous multi-stage distillation column
thus obtained is preferably taken as the reaction mixture containing the diphenyl
carbonate used in the present invention.
Note that since the disproportionation reaction is a transesterification
reaction between two of the same molecular species, the "reaction mixture
containing the diphenyl carbonate, which has been obtained by carrying out a
transesterification reaction between a dialkyl carbonate and a phenol and/or a
disproportionation reaction of an alkyl phenyl carbonate and/or a transesterification
reaction between the alkyl phenyl carbonate and the phenol in the presence of a
homogeneous catalyst" used in the present invention can also be referred to as a
"reaction mixture containing the diphenyl carbonate, which has been obtained
through transesterification reaction between a dialkyl carbonate and a phenol as a
starting material in the presence of a homogeneous catalyst". When "reaction
mixture" is used merely in the present invention, such a reaction mixture is meant.
In addition to the diphenyl carbonate, the reaction mixture used in the
present invention contains the catalyst, unreacted starting materials, the alkyl phenyl
carbonate, by-products and so on. As the by-products, there are relatively low
boiling point by-products such as an alkyl phenyl ether, and the high boiling point
by-products such as Fries rearrangement products of the alkyl phenyl carbonate or
the diphenyl carbonate and derivatives thereof, degeneration products of the
diphenyl carbonate, and other high boiling point material of an unknown structure.
For example, in the case of producing diphenyl carbonate using dimethyl
carbonate and phenol as a starting material, reaction by-products are anisole, methyl
salicylate, phenyl salicylate, xanthone, phenyl methoxybenzoate,
1-phenoxycarbonyl-2-phenoxycarboxy-phenylene and so on, and typically a small
amount of high boiling point by-products of unknown structure thought to be
produced through further reaction of these reaction by-products is also contained.
In one embodiment of the present invention, such a reaction mixture is
continuously introduced into a high boiling point material separating column A, and
continuously separated into a column top component At containing the diphenyl
carbonate and a column bottom component Ab containing the catalyst, and then the
column top component At is continuously introduced into a diphenyl carbonate
purifying column B having a side cut outlet, and continuously separated by distillation
into a column top component Bt, a side cut component Bs and a column bottom
component BB. In this way, not less than 1 ton / hr of a high-purity diphenyl
carbonate is obtained continuously as the side cut component Bs. For this purpose,
the high boiling point material separating column A and the diphenyl carbonate
purifying column B must each be made to be a continuous multi-stage distillation
column having a specified structure, and must be used in combination with one
another.
The reaction mixture used in the present invention generally contains 50 to
80 % by weight of the diphenyl carbonate based on 100 % by weight of the reaction
mixture, and hence to obtain not less than 1 ton / hr of the high-purity diphenyl
carbonate, the amount of the reaction mixture continuously introduced into the high
boiling point material separating column A is not less than approximately 1.3 to 2 ton
/ hr, although this amount varies depending on the content of the diphenyl carbonate.
It is generally necessary to subject more than 2 ton / hr of the reaction mixture to the
separation/purification.
Figure 1 illustrates a schematic view of an example showing a continuous
separating / purifying apparatus for carrying out the present invention in which a high
boiling point material separating column A and a diphenyl carbonate purifying column
B are connected together. As one example, each of the high boiling point material
separating column A and the diphenyl carbonate purifying column comprises a
continuous multi-stage distillation columns having therein an internal comprising, but
is not limited to, a structured packing having a predetermined number of stages.
Note that the columns A and B comprise the following structures, respectively, in
order to carry out the producing process according to the present invention.
In the producing process according to the present invention, the high boiling
point material separating column A must be a continuous multi-stage distillation
column having a length La (cm), an inside diameter DA (cm), and an internal with a
number of stages nA thereinside, wherein La, Da, and nA satisfy the following
formulae (1) to (3):
800 = LA = 3000 (1)
100 = DA = 1000 (2)
20 = nA = 100 (3).
Moreover, the distillation conditions for the high boiling point material
separating column A must be a column bottom temperature Ta in a range of from 185
to 280°C, and a column top pressure PA in a range of from 1000 to 20000 Pa.
Furthermore, the diphenyl carbonate purifying column B must be a
continuous multi-stage distillation column having a length Lb (cm), an inside diameter
DB (cm), an internal thereinside, an inlet B1 at a middle portion of the column, and a
side cut outlet B2 between said inlet B1 and the column bottom, in which a number
of stages of the internal above the inlet B1 is n1, a number of stages of the internal
between the inlet B1 and the side cut outlet B2 is n2, a number of stages of the
internals below the side cut outlet B2 is n3, and a total number of stages is nB (= n1 +
n2 + n3), wherein LB, DB, m, n2, n3, and nB satisfy the following formulae (4) to (9) :
1000= LB = 5000 (4)
100 = DB = 1000 (5)
5 = m = 20 (6)
12 = n2 = 40 (7)
3 = n3 = 15 (8)
20 = nB = 70 (9)
Moreover, the distillation conditions for the diphenyl carbonate purifying
column B must be a column bottom temperature TB in a range of from 185 to 280°C,
and a column top pressure PB in a range of from 1000 to 20000 Pa.
It has been discovered that by using the high boiling point material
separating column A and the diphenyl carbonate purifying column B simultaneously
satisfying all of these conditions, a high-purity diphenyl carbonate can be purified
and produced on an industrial scale of not less than 1 ton / hr stably for a prolonged
period of time, for example not less than 2000 hours, preferably not less than 3000
hours, more preferably not less than 5000 hours, from a reaction mixture containing
the diphenyl carbonate that has been obtained through transesterification reaction
between a dialkyl carbonate and a phenol as a starting material in the presence of a
homogeneous catalyst. The reason why it has become possible to produce the
high-purity diphenyl carbonate on an industrial scale with such excellent effects by
implementing the process of the present invention is not clear, but this is supposed
to be due to a combined effect between the distillation conditions and an effect
brought about when the conditions of formulae (1) to (9) are combined. Preferable
ranges for the respective factors are described below.
If LA (cm) is less than 800, since a height of the internal which can be
installed in the high boiling point material separating column A becomes limited, the
separation efficiency decreases, and it is thus undesirable for La (cm). Moreover, to
keep down the equipment cost while attaining the desired separation efficiency, La
must be made to be not more than 3000. A more preferable range for LA (cm) is
1000 = LA = 2500, with 1200 = LA = 2000 being yet more preferable.
If DA (cm) is less than 100, then it is not possible to attain the desired
production amount. Moreover, to keep down the equipment cost while attaining the
desired production amount, Da must be made to be not more than 1000. A more
preferable range for DA (cm) is 200 = DA = 600, with 250 = DA = 450 being yet
more preferable.
If nA is less than 20, then the separation efficiency decreases, and hence the
desired high purity cannot be attained. Moreover, to keep down the equipment cost
while attaining the desired separation efficiency, nA must be made to be not more
than 100. Furthermore, if nA is greater than 100, then the pressure difference
between the top and bottom of the column becomes too great, and hence prolonged
stable operation of the high boiling point material separating column A becomes
difficult. Moreover, it becomes necessary to increase the temperature in the lower
portion of the column, and hence side reactions become liable to occur, which is
undesirable. A more preferable range for nA is 30 = nA = 70, with 35 = nA =
60 being yet more preferable.
If Ta is less than 185°C, since the column top pressure must be reduced,
equipment for maintaining a high vacuum must be used, and moreover the
equipment increases in size. Moreover, it is undesirable for Ta to be greater than
280°C, because the high boiling point by-products are produced during the distillation.
A more preferable range for TA is from 190 to 240°C, with from 195 to 230°C being
yet more preferable.
It is undesirable for Pa to be less than 1000 Pa, since then large equipment
enabling a high vacuum to be maintained must be used. Moreover, it is undesirable
for PA to be greater than 20000 Pa, since then the distillation temperature must be
increased and hence production of by-products increases. A more preferable range
for PA is from 2000 to 15000 Pa, with from 3000 to 13000 Pa being yet more
preferable.
If Lb (cm) is less than 1000, since a height of the internal which can be
installed in the diphenyl carbonate purifying column B becomes limited, the
separation efficiency decreases, and it is thus undesirable for Lb (cm). Moreover, to
keep down the equipment cost while attaining the desired separation efficiency, Lb
must be made to be not more than 5000. A more preferable range for LB (cm) is
1500 = LB = 3000, with 1700 = LB = 2500 being yet more preferable.
If Db (cm) is less than 100, then it is not possible to attain the desired
production amount. Moreover, to keep down the equipment cost while attaining the
desired production amount, Db must be made to be not more than 1000. A more
preferable range for DB (cm) is 150 = DB = 500, with 200 = DB = 400 being yet
more preferable.
If nB is less than 20, then the separation efficiency for the column as a whole
decreases, and hence the desired high purity cannot be attained. Moreover, to
keep down the equipment cost while attaining the desired separation efficiency, nB
must be made to be not more than 70. Furthermore, if nB is greater than 70, then
the pressure difference between the top and bottom of the column becomes too
great, and hence prolonged stable operation of the diphenyl carbonate purifying
column B becomes difficult. Moreover, it becomes necessary to increase the
temperature in the lower portion of the column, and hence side reactions become
liable to occur, which is undesirable. A more preferable range for nB is 25 = nB =
55, with 30 = nB = 50 being yet more preferable. Furthermore, it has been
ascertained that to obtain the desired high-purity diphenyl carbonate stably for a
prolonged period of time, n1, n2, and n3 must be in the ranges 5 = n1 = 20, 12 =
n2 = 40, and 3 = n3 = 15, respectively. More preferable ranges are 7 = n1 =
15,12 = n2 = 30, and 3 = n3 = 10.
It is undesirable for Tb to be less than 185°C, since then the column top
pressure must be reduced, and hence equipment for maintaining a high vacuum
must be used, and moreover the equipment increases in size. Moreover, it is
undesirable for Tb to be greater than 280°C, since then high boiling point by-products
are produced during the distillation. A more preferable range for Tb is from 190 to
240°C, with from 195 to 230°C being yet more preferable.
It is undesirable for PB to be less than 1000 Pa, since then large equipment
enabling a high vacuum to be maintained must be used. Moreover, it is undesirable
for PB to be greater than 20000 Pa, since then the distillation temperature must be
increased and hence production of by-products increases. A more preferable range
for PB is from 2000 to 15000 Pa, with from 3000 to 13000 Pa being yet more
preferable.
For the high boiling point material separating column A and the diphenyl
carbonate purifying column B, so long as Da and Db are within the above ranges,
each of the columns may have the same inside diameter from the upper portion
thereof to the lower portion thereof, or the inside diameter may differ in different
portions. For example, for each of the continuous multi-stage distillation columns,
the inside diameter of the upper portion of the column may be smaller than, or larger
than, the inside diameter of the lower portion of the column.
Each of the high boiling point material separating column A and the diphenyl
carbonate purifying column B used in the present invention is a distillation column
having a tray and/or a packing as the internal. The term "internal" used in the
present invention means the parts in the distillation column where gas and
liquid are actually brought into contact with one another. As the tray, for
example, a bubble-cap tray, a sieve tray, a valve tray, a counterflow tray, a
Superfrac tray, a Maxfrac tray or the like are preferable. As the packing,
irregular packings such as a Raschig ring, a Lessing ring, a Pall ring, a Berl
saddle, an Intalox saddle, a Dixon packing, a McMahon packing or Heli-Pak, or a
structured packing such as Techno-pack (Sanrei Techno Corporation's
homepage (http: / / www.sanrei-techno.co.jp); and Mellapak, Gempak, Flexipac a
Sulzer packing, a Goodloe packing or a Glitsch ( all as described in "Distillation
Design", Henry Z. Kister, McGraw Hill (1992)) are preferable. The multi-stage
distillation column having both a tray portion and a portion packed with the
packing can also be used. Note that the term "number of stages (n) of an
internal" used in the present invention means that the total number of trays in
the case of a tray, and the theoretical number of stages in the case of the
packing. Accordingly, in the case of the multi-stage column having both the
tray portion and the portion packed with the packing, n means the sum of the
total number of trays and the theoretical number of stages of the packing.
It has been ascertained that the high boiling point material separating
column A according to the present invention preferably comprises the packing
as the internal, and furthermore a structured packing is preferable as the
packing. It has also been discovered that the diphenyl carbonate purifying
column B according to the present invention preferably comprises the packing
as the internal, particularly preferably one or more of the structured packing.
A process in which transesterification reaction is carried out with a
dialkyl carbonate and a phenol as a starting material in the presence of a
homogeneous catalyst using an apparatus in which two reactive distillation
columns are connected together is a preferable process for obtaining the reaction
mixture that acts as the starting material in the present invention. In this case,
a column bottom liquid continuously withdrawn from the bottom of the second
reactive distillation column
can be used as the reaction mixture used in the present invention. This reaction
mixture continuously withdrawn from the bottom of the second reactive distillation
column generally contains 0.05 to 2 % by weight of the dialkyl carbonate, 1 to 20 %
by weight of the phenol, 0.05 to 2 % by weight of an alkyl phenyl ether, 10 to 45 % by
weight of an alkyl phenyl carbonate, 50 to 80 % by weight of the diphenyl carbonate,
0.1 to 5 % by weight of high boiling point by-products, and 0.001 to 5 % by weight of
the catalyst, based on the 100 % by weight of the reaction mixture.
The composition of the reaction mixture varies depending on the conditions
of the transesterification reaction between the dialkyl carbonate and the phenol, the
type and amount of the catalyst and so on, but so long as the transesterification
reaction is carried out under constant conditions, a reaction mixture of approximately
constant composition can be produced, and hence the composition of the reaction
mixture fed into the high boiling point material separating column A may be
approximately constant. However, in the present invention, so long as the
composition of the reaction mixture is within the above range, then even if this
composition fluctuates somewhat, the separation can still be carried out with
approximately the same separation efficiency. This is one of the characteristic
features of the present invention.
In the present invention, when continuously feeding the reaction mixture that
acts as the starting material into the high boiling point material separating column A,
the reaction mixture may be fed in a liquid from into inlet(s) provided in one or a
plurality of positions below a middle portion of the separating column A, or it is also
preferable to feed the reaction mixture into the column via a reboiler of the
separating column A from piping provided at a lower portion of the reboiler. The
amount of the reaction mixture fed into the high boiling point material separating
column A varies depending on the amount of the high-purity diphenyl carbonate to be
produced, the concentration of the diphenyl carbonate in the reaction mixture, the
separation conditions for the separating column A and so on, but the above amount
is generally not less than 2 ton / hr, preferably not less than 6 ton / hr, more
preferably not less than 10 ton / hr. The upper limit of the amount of the reaction
mixture fed into varies depending on the size of the apparatus, the required
production amount and so on, but the upper limit is generally 200 ton / hr. The
reaction mixture fed continuously into the high boiling point material separating
column A is separated into a column top component (At) containing most of the
diphenyl carbonate and most of compounds having a lower boiling point than that of
the diphenyl carbonate, such as unreacted starting material, an alkyl phenyl ether
and an alkyl phenyl carbonate, and a column bottom component (Ab) containing the
catalyst, high boiling point by-products and a small amount of the diphenyl
carbonate.
The column bottom component (AB) may contain a small amount of the alkyl
phenyl carbonate. Such organic material in the column bottom component (Ab)
plays a useful role in dissolving the catalyst component and thus maintaining a liquid
state of the column bottom component (Ab). All or some of the column bottom
component (AB) is generally reused by recycling to the first reactive distillation
column as a transesterification reaction catalyst component, but in some cases the
catalyst may be recycled after being separated from the organic material in a catalyst
recovery process, and then reused by recycling to the first reactive distillation
column.
It is a characteristic feature of the present invention that the catalyst
component and by-products having a higher boiling point than that of the diphenyl
carbonate such as phenyl salicylate, xanthone, phenyl methoxybenzoate and
1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene are almost completely removed as
the column bottom component (AB) in the high boiling point material separating
column A, it being easy to make the content thereof in the column top component
(AT) be generally not more than 200 ppm, preferably not more than 100 ppm, more
preferably not more than 50 ppm. It is another characteristic feature of the present
invention that despite making the column top component (At) hardly contain any
such high boiling point by-products, most of the diphenyl carbonate in the reaction
mixture introduced can be withdrawn from the top of the column. In the present
invention, not less than 95%, preferably not less than 96%, more preferably not less
than 98%, of the diphenyl carbonate in the reaction mixture continuously fed into the
high boiling point material separating column A can be withdrawn from the top of the
column. Moreover, in the present invention, although dependent on the
composition of the reaction mixture fed into the separating column A, typically 90 to
97 % by weight of the liquid continuously fed in is continuously withdrawn from the
top of the column as the column top component (At), with 10 to 3% being
continuously withdrawn from the bottom of the column as the column bottom
component (AB). The composition of the column top component (AT) is generally
0.05 to 2 % by weight of the dialkyl carbonate, 1 to 21 % by weight of the phenol,
0.05 to 2 % by weight of an alkyl phenyl ether, 11 to 47 % by weight of the alkyl
phenyl carbonate, and 52 to 84 % by weight of the diphenyl carbonate, based on
100 % by weight of the column top component (At). The content of the high boiling
point by-products is generally not more than 200 ppm, preferably not more than 100
ppm, more preferably not more than 50 ppm.
In the present invention, the reflux ratio for the high boiling point material
separating column A is in a range of from 0.01 to 10, preferably from 0.08 to 5, more
preferably from 0.1 to 3.
As stated above, the amount of the column top component (At) continuously
withdrawn from the top of the high boiling point material separating column A is
generally approximately 90 to 97% of the reaction mixture fed into the separating
column A. This column top component (Ay) is continuously fed into the diphenyl
carbonate purifying column B from the inlet B1 provided at an intermediate portion of
the purifying column B, and is continuously separated into three components, i.e. a
column top component (Bt), a side cut component (Bs), and a column bottom
component (Bb). All of components having a lower boiling point than that of the
diphenyl carbonate contained in the column top component (At) from the separating
column A fed into the purifying column B are continuously withdrawn from the top of
the purifying column B as the column top component (By), and a small amount of
liquid is continuously withdrawn from the bottom of the purifying column B. A small
amount of the diphenyl carbonate is contained in the column top component (Bt),
this amount generally being 1 to 9%, preferably 3 to 8%, of the diphenyl carbonate
fed in. The diphenyl carbonate in the column top component (Bt) is separated out
and thus recovered in another distillation column used for separating the column top
component (Bt). Alternatively, a method in which this diphenyl carbonate is
separated off as the column bottom component from this other distillation column,
and is then recovered by being returned into the high boiling point material
separating column A and/or the diphenyl carbonate purifying column B is also
preferable.
The column bottom component (Bb) contains the diphenyl carbonate, and a
small amount of high boiling point by-products concentrated to approximately a few
percent. Another characteristic feature of the present invention is that the amount
of the diphenyl carbonate in the column bottom component (Bb) withdrawn from the
bottom of the purifying column B can be kept very low. This amount is generally
0.05 to 0.5% of the diphenyl carbonate fed in.
The high-purity diphenyl carbonate is continuously withdrawn from the side
cut outlet B2 at a flow rate of generally not less than 1 ton / hr, preferably not less
than 3 ton / hr, more preferably not less than 5 ton / hr. This amount generally
corresponds to approximately 90 to 96% of the diphenyl carbonate fed into the
purifying column B.
The purity of the diphenyl carbonate obtained as the side cut component (Bs)
in the present invention is generally not less than 99.9%, preferably not less than
99.99%, more preferably not less than 99.999%. The contents of high boiling point
impurities when carrying out the present invention with dimethyl carbonate and
phenol as the starting material are not more than 30 ppm, preferably not more than
10 ppm, more preferably not more than 1 ppm for phenyl salicylate, not more than 30
ppm, preferably not more than 10 ppm, more preferably not more than 1 ppm for
xanthone, not more than 30 ppm, preferably not more than 10 ppm, more preferably
not more than 1 ppm for phenyl methoxybenzoate, and not more than 30 ppm,
preferably not more than 10 ppm, more preferably not more than 5 ppm for
1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene. Moreover, the total content of
these high boiling point by-products is not more than 100 ppm, preferably not more
than 50 ppm, more preferably not more than 10 ppm. Note that the term
"high-purity diphenyl carbonate" used in the present invention means that the purity
of the diphenyl carbonate is not less than 99.9 and the diphenyl carbonate contains
not more than 100 ppm of high boiling point by-products.
Moreover, in the present invention, a starting material and catalyst not
containing a halogen are generally used, and hence the halogen content of the
diphenyl carbonate obtained is not more than 0.1 ppm, preferably not more than 10
ppb, more preferably not more than 1 ppb.
In the present invention, the reflux ratio for the diphenyl carbonate purifying
column B is in a range of from 0.01 to 10, preferably from 0.1 to 8, more preferably
from 0.5 to 5.
The material constituting the high boiling point material separating column A,
the diphenyl carbonate purifying column B, and other liquid-contacting parts which
are used in the present invention is generally a metallic material such as carbon steel
or stainless steel. In terms of the quality of the diphenyl carbonate produced,
stainless steel is preferable.
Examples
Hereinbelow, the present invention will be described in more detail with
reference to the following Examples, but the present invention is not limited to the
following Examples.
The purity of the diphenyl carbonate, and the contents of impurities were
measured by means of a gas chromatography method, and the halogen content was
measured by means of an ion chromatography method.
Example 1:

A continuous multi-stage distillation column as shown in FIG. 1 having La =
1700 cm and DA = 340 cm, and having Mellapak with nA = 30 installed therein as the
internal was used as the separating column A.

A continuous multi-stage distillation column as shown in FIG. 1 having Lb =
2200 cm and Db = 280 cm, and having three sets of Mellapak with n1 = 12, n2 = 18,
and n3 = 5 installed therein as the internal was used as the purifying column B.

An apparatus in which two reactive distillation columns (a first reactive
distillation column and a second reactive distillation column) were connected
together was used, the reaction liquid in the first reactive distillation column was
made to contain 100 ppm of Pb(OPh)2 as a catalyst, reactive distillation was carried
out using dimethyl carbonate and phenol as a starting material, and a reaction
mixture containing diphenyl carbonate was continuously withdrawn at 13.1 ton / hr
from the column bottom of the second reactive distillation column. Note that
halogens were not detected in the starting material or the catalyst used in the
reaction.
The composition of the reaction mixture was 0.1 % by weight of dimethyl
carbonate, 0.1 % by weight of anisole, 6.3 % by weight of phenol, 32.2 % by weight
of methyl phenyl carbonate, 58.6 % by weight of diphenyl carbonate, and 2.7 % by
weight of high boiling point by-products including the catalyst.

Using an apparatus comprising the high boiling point material separating
column A and the diphenyl carbonate purifying column B as shown in FIG. 1, the
reaction mixture obtained through the reactive distillation described above was
continuously introduced at 13.1 ton / hr into the separating column A from the inlet A1.
The column bottom temperature (TA) was made to be 206°C and the column top
pressure (PA) was made to be 3800 Pa in the separating column A, distillation was
carried out continuously with a reflux ratio of 0.6, a column top component (AT) was
continuously withdrawn at 12.5 ton / hr via a conduit 16, and a column bottom
component (Ab) was continuously withdrawn at 0.6 ton / hr via a conduit 11. The
column top component (Ay) was continuously introduced as is into the purifying
column B from the inlet B1. The column bottom temperature (Tb) was made to be
213°C and the column top pressure (PB) was made to be 5000 Pa in the purifying
column B, distillation was carried out continuously with a reflux ratio of 1.5, a column
top component (BT) was continuously withdrawn at 5.3 ton / hr via a conduit 26, a
column bottom component (Bb) was continuously withdrawn at 0.03 ton / hr via a
conduit 31, and a side cut component (Bs) was continuously withdrawn at 7.17 ton /
hr via a conduit 33.
The compositions of the components at 24 hours after the system had
become completely stable were as follows.
At: 0.1 % by weight of dimethyl carbonate, 0.1 % by weight of anisole, 6.6 % by
weight of phenol, 33.8 % by weight of methyl phenyl carbonate, 59.4 % by weight of
diphenyl carbonate;
Ab: 41.0 % by weight of diphenyl carbonate, 59.0 % by weight of high boiling point
material including a catalyst component and by-products having a higher boiling
point than that of diphenyl carbonate such as phenyl salicylate, xanthone, phenyl
methoxybenzoate and 1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene;
Bt: 0.25 % by weight of dimethyl carbonate, 0.25 % by weight of anisole, 15.6 % by
weight of phenol, 79.6 % by weight of methyl phenyl carbonate, 4.3 % by weight of
diphenyl carbonate;
BB: 95.0 % by weight of diphenyl carbonate, 5.0 % by weight of the high boiling point
material.
The content of each of phenyl salicylate, xanthone and phenyl
methoxybenzoate in the side cut component was not more than 1 ppm, and the
content of 1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene was 4 ppm. Moreover,
the halogen content was not more than 1 ppb. It was thus found that the purity of
the diphenyl carbonate obtained from the side cut was not less than 99.999%.
Moreover, the amount of this high-purity diphenyl carbonate produced was 7.17 ton /
Prolonged continuous operation was carried out under these conditions.
The amount of diphenyl carbonate produced and the purity were substantially
unchanged after 500 hours, 2000 hours, 4000 hours, 5000 hours, and 6000 hours.
Example 2:

An apparatus in which two reactive distillation columns (a first reactive
distillation column and a second reactive distillation column) were connected
together was used, the reaction liquid in the first reactive distillation column was
made to contain 250 ppm of Pb(OPh)2 as a catalyst, reactive distillation was carried
out using dimethyl carbonate and phenol as a starting material, and a reaction
mixture containing diphenyl carbonate was continuously withdrawn at 11.3 ton / hr
from the column bottom of the second reactive distillation column. Note that
halogens were not detected in the starting material or the catalyst used in the
reaction.
The composition of the reaction mixture was 0.1 % by weight of dimethyl
carbonate, 0.1 % by weight of anisole, 2.5 % by weight of phenol, 33.2 % by weight
of methyl phenyl carbonate, 62.5 % by weight of diphenyl carbonate, and 1.6 % by
weight of high boiling point by-products including the catalyst.

Using an apparatus comprising the high boiling point material separating
column A and the diphenyl carbonate purifying column B as shown in Example 1, the
reaction mixture obtained through the reactive distillation described above was
continuously introduced at 11.3 ton / hr into the separating column A from the inlet A1.
The column bottom temperature (TA) was made to be 205°C and the column top
pressure (PA) was made to be 4000 Pa in the separating column A, distillation was
carried out continuously with a reflux ratio of 0.7, a column top component (At) was
continuously withdrawn at 11.0 ton / hr via the conduit 16, and a column bottom
component (Ab) was continuously withdrawn at 0.3 ton / hr via the conduit 11. The
column top component (At) was continuously introduced as is into the purifying
column B from the inlet B1. The column bottom temperature (Tb) was made to be
210°C and the column top pressure (Pb) was made to be 4500 Pa in the purifying
column B, distillation was carried out continuously with a reflux ratio of 2.0, a column
top component (BT) was continuously withdrawn at 4.7 ton / hr via the conduit 26, a
column bottom component (Bb) was continuously withdrawn at 0.03 ton / hr via the
conduit 31, and a side cut component (Bs) was continuously withdrawn at 6.27 ton /
hr via the conduit 33.
The compositions of the components at 24 hours after the system had
become completely stable were as follows.
At: 0.1 % by weight of dimethyl carbonate, 0.1 % by weight of anisole, 2.6 % by
weight of phenol, 34.1 % by weight of methyl phenyl carbonate, 63.1 % by weight of
di phenyl carbonate;
AB: 40.2 % by weight of diphenyl carbonate, 59.8 % by weight of the high boiling
point material including a catalyst component and by-products having a higher
boiling point than that of diphenyl carbonate such as phenyl salicylate, xanthone,
phenyl methoxybenzoate and 1-phenoxycarbonyl-2-phenoxycarboxy-phenylene;
Bt: 0.3 % by weight of dimethyl carbonate, 0.2 % by weight of anisole, 6.1 % by
weight of phenol, 79.8 % by weight of methyl phenyl carbonate, 13.6 % by weight of
diphenyl carbonate;
BB: 96.0 % by weight of diphenyl carbonate, 4.0 % by weight of the high boiling point
material.
The content of each of phenyl salicylate, xanthone and phenyl
methoxybenzoate in the side cut component was not more than 1 ppm, and the
content of 1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene was 3 ppm. Moreover,
the halogen content was not more than 1 ppb. It was thus found that the purity of
the diphenyl carbonate obtained from the side cut was not less than 99.999%.
Moreover, the amount of this high-purity diphenyl carbonate produced was 6.27 ton /
hr.
Prolonged continuous operation was carried out under these conditions.
The amount of diphenyl carbonate produced and the purity were substantially
unchanged after 500 hours, 1000 hours, and 2000 hours.
Example 3:

An apparatus in which two reactive distillation columns (a first reactive
distillation column and a second reactive distillation column) were connected
together was used, the reaction liquid in the first reactive distillation column was
made to contain 150 ppm of Pb(OPh)2 as a catalyst, reactive distillation was carried
out using dimethyl carbonate and phenol as a starting material, and a reaction
mixture containing diphenyl carbonate was continuously withdrawn at 17.2 ton / hr
from the bottom of the second reactive distillation column. Note that halogens were
not detected in the starting material or the catalyst used in the reaction.
The composition of the reaction mixture was 0.2 % by weight of dimethyl
carbonate, 0.1 % by weight of anisole, 6.6 % by weight of phenol, 30.2 % by weight
of methyl phenyl carbonate, 60.1 % by weight of diphenyl carbonate, and 2.8 % by
weight of high boiling point by-products including the catalyst.

Using an apparatus comprising a high boiling point material separating
column A and a diphenyl carbonate purifying column B as shown in Example 1, the
reaction mixture obtained through the reactive distillation described above was
continuously introduced at 17.2 ton / hr into the separating column A from the inlet A1.
The column bottom temperature (TA) was made to be 207°C and the column top
pressure (Pa) was made to be 4100 Pa in the separating column A, distillation was
carried out continuously with a reflux ratio of 0.61, a column top component (At) was
continuously withdrawn at 16.4 ton / hr via the conduit 16, and a column bottom
component (Ab) was continuously withdrawn at 0.8 ton / hr via the conduit 11. The
column top component (At) was continuously introduced as is into the purifying
column B from the inlet B1. The column bottom temperature (Tb) was made to be
220°C and the column top pressure (PB) was made to be 6600 Pa in the purifying
column B, distillation was carried out continuously with a reflux ratio of 1.49, a
column top component (Bt) was continuously withdrawn at 7.1 ton / hr via the
conduit 26, a column bottom component (Bb) was continuously withdrawn at 0.05 ton
/ hr via the conduit 31, and a side cut component (Bs) was continuously withdrawn at
9.25 ton / hr via the conduit 33.
The compositions of the components at 24 hours after the system had
become completely stable were as follows.
At: 02 % by weight of dimethyl carbonate, 0.1 % by weight of anisole, 6.9 % by
weight of phenol, 31.7 % by weight of methyl phenyl carbonate, 61.1 % by weight of
diphenyl carbonate;
AB: 39.8 % by weight of diphenyl carbonate, 61.2 % by weight of high boiling point
material including a catalyst component and by-products having a higher boiling
point than that of diphenyl carbonate such as phenyl salicylate, xanthone, phenyl
methoxybenzoate and 1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene;
BT: 0.5 % by weight of dimethyl carbonate, 0.2 % by weight of anisole, 16.0 % by
weight of phenol, 73.2 % by weight of methyl phenyl carbonate, 10.1 % by weight of
diphenyl carbonate;
BB: 94.0 % by weight of diphenyl carbonate, 6.0 % by weight of high boiling point
material.
The content of each of phenyl salicylate, xanthone and phenyl
methoxybenzoate in the side cut component was not more than 1 ppm, and the
content of 1 -phenoxycarbonyl-2-phenoxycarboxy-phenylene was 4 ppm. Moreover,
the halogen content was not more than 1 ppb. It was thus found that the purity of
the diphenyl carbonate obtained from the side cut was not less than 99.999%.
Moreover, the amount produced of this high-purity diphenyl carbonate was 9.25 ton /
hr.
Prolonged continuous operation was carried out under these conditions.
The amount of diphenyl carbonate produced and the purity were substantially
unchanged after 500 hours, 1000 hours, and 2000 hours.
Industrial Applicability
The present invention can be suitably used in the field of producing a
high-purity diphenyl carbonate, which can be used as a raw material of a high-quality
and high-performance polycarbonate, stably for a prolonged period of time on an
industrial scale of not less than 1 ton / hr from a reaction mixture containing a
catalyst and reaction by-products that has been obtained through transesterification
reaction or the like using a dialkyl carbonate and a phenol as a starting material.
WE CLAIM:
1. A process for the production of a high-purity diphenyl carbonate which is
produced continuously from a reaction mixture containing a diphenyl carbonate, which
has been obtained by carrying out a transesterification reaction between a dialkyl
carbonate such as herein described, and a phenol and/or a disproportionation reaction of
an alkyl phenyl carbonate such as herein described, and/or a transesterification reaction
between an alkyl phenyl carbonate and a phenol in the presence of a homogeneous
catalyst, such as herein described, by continuously introducing said reaction mixture into
a high boiling point material separating column A, and continuously carrying out
separation by distillation into a column top component AT containing the diphenyl
carbonate and a column bottom component AB containing the catalyst, such as herein
described, and then continuously introducing said column top component At into a
diphenyl carbonate purifying column B having a side cut outlet, and continuously carrying
out separation by distillation into a column top component BT, a side cut component Bs
and a column bottom component BB, characterized in that,
(a) said high boiling point material separating column A comprises a continuous
multi-stage distillation column having a length La (cm), an inside diameter DA (cm), and
an internal with a number of stages nA thereinside, wherein LA, DA, and nA satisfy the
following formulae (1) to (3);
800= A =3000 (1)
100=DA =1000 (2)
20=nA=100 (3);
(b) a distillation operation of said high boiling point material separating column A
- is carried out under conditions of a column bottom temperature TA in a range of from 185
to 280°C, and a column top pressure Pa in a range of from 1000 to 20000 Pa;
(c) said diphenyl carbonate purifying column B comprises a continuous
multi-stage distillation column having a length Lb (cm), an inside diameter Db (cm), an
internal thereinside, an inlet B1 at a middle portion of the column, and a side cut outlet B2
between said inlet B1 and the column bottom, in which a number of stages of the internal
above the inlet B1 is n1, a number of stages n2 of the internal between the inlet B1 and
the side cut outlet B2 is n2, a number of stages n3 of the internals below the side cut
outlet B2 is n3, and a total number of stages is nB (= n1 + n2 + n3), wherein LB, Db, n1 n2
n3, and nB satisfy the following formulae (4) to (9);
1000= LB = 5000 (4)
100= DB=1000 (5)
5 = m= 20 (6)
12 = n2 = 40 (7)
3 = n3 = 15 (8)
20 = nB = 70 (9);
(d) a distillation operation of said diphenyl carbonate purifying column B is carried
out under conditions of a column bottom temperature TB in a range of from 185 to 280°C,
and a column top pressure Pb in a range of from 1000 to 20000 Pa; and
(e) not less than 1 ton / hr of the high-purity diphenyl carbonate is obtained
continuously as the side cut component B$.
2. The process as claimed in claim 1, wherein La, Da, and nA for said high boiling point
material separating column A satisfy the following formulae: 1000 = LA = 2500, 200 = DA
= 600, and 30 = nA = 70, respectively,
Lb, DB, n1, n2, n3, and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 =LB= 3000, 150 = DB = 500, 7= m = 15, 12 = n2 = 30, 3 = n3
=10, and 25 = na = 55, respectively,
TA is in a range of from 190 to 240°C, PA is in a range of from 2000 to 15000 Pa,
TB is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000 Pa.
3. The process as claimed in claim 1 or 2, wherein each of said high boiling point
material separating column A and said diphenyl carbonate purifying column B is a
distillation column having a tray and/or a packing as said internal.
4. The process as claimed in claim 3, wherein said internal of each of said high
boiling point material separating column A and said diphenyl carbonate purifying column
B is a packing.
5. The process as claimed in claim 4, wherein said packing is a structured
packing which is at least one selected from the group such as herein described.
6. An apparatus for producing a high-purity diphenyl carbonate which is
produced from a reaction mixture containing a diphenyl carbonate, which has been
obtained by carrying out a transesterification reaction between a dialkyl carbonate and a
phenol and/or a disproportionation reaction of an alkyl carbonate and/or a
transesterification reaction between an alkyl phenyl carbonate and a phenol in the
presence of a homogeneous catalyst, the apparatus comprises;
a high boiling point material separating column A which receives said reaction
mixture, and which carries out separation by distillation into a column top component AT
containing the diphenyl carbonate and a column bottom component Ab containing the
catalyst; and
a diphenyl carbonate purifying column B having a side cut outlet B2, which is
connected with said high boiling point material separating column A, and which receives
said column top component AT therefrom, wherein separation by distillation is carried out
into a column top component BT, a side cut component Bs and a column bottom
component Bb; wherein
(a) said high boiling point material separating column A comprises a continuous
multi-stage distillation column having a length LA (cm), an inside diameter DA (cm), and
an internal with a number of stages nA thereinside, wherein La, Da, and nA satisfy the
following formulae (1) to (3);
800 =LA= 3000 (1)
100 = DA =1000 (2)
20 =nA= 100 (3);
(b) said diphenyl carbonate purifying column B comprises a continuous
multi-stage distillation column having a length Lb (cm), an inside diameter Db (cm), an
internal thereinside, an inlet B1 at a middle portion of the column, and the side cut outlet
B2 between said inlet B1 and the column bottom, in which a number of stages of the
internal above the inlet B1 is n1, a number of stages of the internal between the inlet B1
and the side cut outlet B2 is n2, a number of stages of the internals below the side cut
outlet B2 is n3, and a total number of stages is nB (= n1 + n2 + n3),
wherein Lb, Db, n1, n2, n3 and nB satisfy the following formulae (4) to (9);
1000 = LB = 5000 (4)
100= DB=1000 (5)
5 = n1 = 20 (6)
12= n2=40 (7)
3= n3=15 (8)
20= nB=70 (9)
* 7. The apparatus as clajmed in claim 6, wherein a distillation operation of said
high boiling point material separating column A is carried out under conditions of a
column bottom temperature Ta in a range of from 185 to 280°C, and a column top
pressure Pa in a range of from 1000 to 20000 Pa.
8. The apparatus as claimed in claim 6 or 7, wherein a distillation operation of
said diphenyl carbonate purifying column B is carried out under conditions of a column
bottom temperature Tb in a range of from 185 to 280°C, and a column top pressure Pb in
a range of from 1000 to 20000 Pa.
9. The apparatus as claimed in any one of claims 6 to 8, wherein not less than 1
ton / hr of the high-purity diphenyl carbonate is obtained as the side cut component Bs.
10. The apparatus as claimed in any one of claims 6 to 9, wherein La, Da, and
nA for said high boiling point material separating column A satisfy the following formulae:
1000 = LA = 2500, 200 = DA = 600, and 30 = nA = 70, respectively,
LB, Db, n1 n2, n3 and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 = LB = 3000, 150 = DB = 500, 7 = ni = 15, 12 = n2 = 30, 3 =
n3 = 10, and 25 = nB = 55, respectively,
Ta is in a range of from 190 to 240°C, PA is in a range of from 2000 to 15000 Pa,
TB is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000 Pa
11. The apparatus as claimed in any one of claims 6 to 10, wherein each of said
high boiling point material separating column A and said diphenyl carbonate purifying
column B is a distillation column having a tray and/or a packing as said internal.
12. The apparatus as claimed in claim 11, wherein said internal of each of said
high boiling point material separating column A and said diphenyl carbonate purifying
column B is a packing.
13. The apparatus as claimed in claim 12, wherein said packing is a structured
packing which is at least one selected from the group such as herein described.
14. A process for the production of a high-purity diphenyl carbonate, the
process comprising the steps of:
(i) carrying out a transesterification reaction between a dialkyl carbonate and a
phenol and/or a disproportionation reaction of an alkyl carbonate and/or a
transesterification reaction between an alkyl phenyl carbonate and a phenol in the
presence of a homogeneous catalyst, so as to form a reaction mixture containing a
diphenyl carbonate;
(ii) carrying out separation by distillation in a high boiling point material separating
column A into a column top component AT containing the diphenyl carbonate and a
column bottom component Ab containing the catalyst
* (iii) carrying out separation by distillation of said column top component At in a
diphenyl carbonate purifying column B having a side cut outlet into a column top
component BT, a side cut component Bs and a column bottom component Bb, said
column top component At introducing from the side cut outlet into the column B; wherein
(a) said high boiling point material separating column A comprises a
continuous multi-stage distillation column having a length La (cm), an inside diameter DA
(cm), and an internal with a number of stages nA thereinside, wherein La, Da, and nA
satisfy the following formulae (1) to (3);
800= LA =3000 (1)
100= DA =1000 ' (2)
20= nA= 100 (3);
(b) said diphenyl carbonate purifying column B comprises a continuous
multi-stage distillation column having a length LB (cm), an inside diameter DB (cm), an
internal thereinside, an inlet B1 at a middle portion of the column, and a side cut outlet B2
between said inlet B1 and the column bottom, in which a number of stages of the internal
above the inlet B1 is n1, a number of stages n2 of the internal between the inlet B1 and
the side cut outlet B2 is n2, a number of stages n3 of the internals below the side cut
outlet B2 is n3, and a total number of stages is nB (= n1 + n2 + n3), wherein LB, DB, n1, n2,
n3, and nB satisfy the following formulae (4) to (9);
15. The process as claimed in claim 14, wherein not less than 1 ton / hr of the-
high-purity diphenyl carbonate is obtained as the side cut component Bs.
16. The process as claimed in claim 14 or 15, wherein LA, Da, and nA for said high
boiling point material separating column A satisfy the following formulae: 1000 =
LA = 2500, 200 = DA = 600, and 30 = nA = 70, respectively,
Lb, Db, n1, n2, n3, and nB for said diphenyl carbonate purifying column B satisfy the
following formulae: 1500 = LB = 3000, 150 = DB = 500, 7 = m = 15, 12= n2 = 30, 3 = n3
=10, and 25 = nB = 55, respectively,
TA is in a range of from 190 to 240°C, PA is in a range of from 2000 to 15000 Pa,
TB is in a range of from 190 to 240°C, and PB is in a range of from 2000 to 15000 Pa.
17. The process as claimed in any one of claims 14 to 16, wherein each of said
high boiling point material separating column A and said diphenyl carbonate purifying
column B is a distillation column having a tray and/or a packing as said internal.
18. The process as claimed in claim 17, wherein said internal of each of said
high boiling point material separating column A and said diphenyl carbonate purifying
column B is a packing.
19. The process as claimed in claim 18, wherein said packing is a structured
packing which is at least one selected from the group such as herein described.


It is an object of the present invention to provide a specific process that
enables a high-purity diphenyl carbonate that can be used as a raw material of a
high-quality and high-performance polycarbonate to be produced stably for a
prolonged period of time on an industrial scale of not less than 1 ton / hr from a
reaction mixture containing a catalyst and reaction by-products that has been
obtained through transesterification reaction and the like using a dialkyl carbonate
and a phenol as a starting material. Although there have been various proposals
regarding processes for the production of reaction mixtures containing aromatic
carbonates by means of a reactive distillation method, these have all been on a small
scale and short operating time laboratory level, and there have been no disclosures
on a specific process or apparatus enabling mass production on an industrial scale
from such a reaction mixture to a high-purity diphenyl carbonate that can be used as
a raw material of a high-quality and high-performance polycarbonate. According to
the present invention, there are provided a high boiling point material separating
column A and a diphenyl carbonate purifying column B each comprising a continuous
multi-stage distillation column having specified structures, and there is provided a
specific process that enables a high-purity diphenyl carbonate which is important as
a raw material of a high-quality and high-performance polycarbonate to be produced
stably for a prolonged period of time on an industrial scale of not less than 1 ton / hr
from a reaction mixture containing the diphenyl carbonate using an apparatus in
which these two continuous multi-stage distillation columns are connected together.

Documents:

00463-kolnp-2007-correspondence-1.1.pdf

00463-kolnp-2007-form-18.pdf

0463-kolnp-2007 abstract.pdf

0463-kolnp-2007 claims.pdf

0463-kolnp-2007 correspondence others.pdf

0463-kolnp-2007 description(complete).pdf

0463-kolnp-2007 drawings.pdf

0463-kolnp-2007 form-1.pdf

0463-kolnp-2007 form-2.pdf

0463-kolnp-2007 form-3.pdf

0463-kolnp-2007 form-5.pdf

0463-kolnp-2007 g.p.a.pdf

0463-kolnp-2007 international publication.pdf

0463-kolnp-2007 international search authority report.pdf

0463-kolnp-2007 others.pdf

0463-kolnp-2007 pct form.pdf

0463-kolnp-2007 priority document.pdf

463-KOLNP-2007-ABSTRACT.pdf

463-KOLNP-2007-AMENDED CLAIMS.pdf

463-KOLNP-2007-CANCELLED PAGES.pdf

463-KOLNP-2007-CLAIMS.pdf

463-kolnp-2007-correspondence-1.1.pdf

463-KOLNP-2007-CORRESPONDENCE.pdf

463-KOLNP-2007-DESCRIPTION (COMPLETE).pdf

463-kolnp-2007-examination report.pdf

463-KOLNP-2007-FORM 1.pdf

463-kolnp-2007-form 18.pdf

463-KOLNP-2007-FORM 2.pdf

463-KOLNP-2007-FORM 3-1.1.pdf

463-KOLNP-2007-FORM 3-1.2.pdf

463-kolnp-2007-form 5.pdf

463-KOLNP-2007-FORM-27.pdf

463-kolnp-2007-gpa.pdf

463-kolnp-2007-granted-abstract.pdf

463-kolnp-2007-granted-claims.pdf

463-kolnp-2007-granted-description (complete).pdf

463-kolnp-2007-granted-drawings.pdf

463-kolnp-2007-granted-form 1.pdf

463-kolnp-2007-granted-form 2.pdf

463-kolnp-2007-granted-specification.pdf

463-kolnp-2007-others-1.1.pdf

463-KOLNP-2007-OTHERS.pdf

463-KOLNP-2007-PETITION UNDER RULE 137.pdf

463-KOLNP-2007-PRIORITY DOCUMENT.pdf

463-kolnp-2007-reply to examination report-1.1.pdf

463-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-00463-kolnp-2007.jpg


Patent Number 247499
Indian Patent Application Number 463/KOLNP/2007
PG Journal Number 15/2011
Publication Date 15-Apr-2011
Grant Date 12-Apr-2011
Date of Filing 08-Feb-2007
Name of Patentee ASAHI KASEI CHEMICALS CORPORATION
Applicant Address 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
Inventors:
# Inventor's Name Inventor's Address
1 SHINSUKE FUKUOKA 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
2 KAZUHIKO MATSUZAKI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
3 HIRONORI MIYAJI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
4 HIROSHI HACHIYA 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
PCT International Classification Number C07C 68/06,B01D 3/16
PCT International Application Number PCT/JP2005/015343
PCT International Filing date 2005-08-24
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2004-245758 2004-08-25 Japan