Title of Invention

INDUSTRIAL PROCESS FOR PRODUCTION OF DIOL

Abstract It is an object of the present invention to provide a specific apparatus and process for producing a diol by taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, continuously feeding the starting materials into a continuous multi-stage distillation column A in which a catalyst is present, carrying out reactive distillation in the column A, continuously withdrawing a low boiling point reaction mixture AT containing a produced dialkyl carbonate and the aliphatic monohydric alcohol from an upper portion of the column A in a gaseous form, continuously withdrawing a high boiling point reaction mixture AB containing a produced diol from a lower portion of the column A in a liquid form, continuously feeding the high boiling point reaction mixture AB into a continuous multi-stage distillation column C, distilling off material having a lower boiling point than that of the diol contained in the high boiling point reaction mixture AB as a column top component CT and a side cut component Cs so as to obtain a column bottom component CB, continuously feeding the column bottom component CB into a continuous multi-stage distillation column C, and obtaining the diol as a side cut component Es from a side cut outlet of the continuous multi-stage distillation column C. Moreover, it is an object to thus provide a specific industrial apparatus and industrial production process that are inexpensive and, for example, enable the diol to be produced in an amount of not less than 1 ton / hr, preferably not less than 2 tons / hr, more preferably not less than 3 tons / hr, stably for a prolonged period of time (e.g. not less than 1000 hours, preferably not less than 3000 hours, more preferably not less than 5000 hours). According to the present invention, the above objects can be attained by using a continuous multi-stage distillation column C having a specified structure, and withdrawing a liquid component from the side cut outlet, which is installed at the bottom of a chimney tray having a specified structure installed in an enrichment section of the continuous multi-stage distillation column C.
Full Text

INDUSTRIAL PROCESS FOR PRODUCTION OF DIOL
Technical Field
The present invention relates to a process for producing a diol
industrially in a large amount stably for a prolonged period of time by
continuously feeding a cyclic carbonate and an aliphatic monohydric
alcohol into a reactive distillation column, carrying out a reactive
distillation process, and obtaining a high boiling point reaction mixture
having the diol as a main component thereof which is continuously
withdrawn from the bottom of the reactive distillation column, and then
continuously feeding the high boiling point reaction mixture into a
continuous multi-stage distillation column for separating off material
having a lower boiling point than that of the diol contained in the high
boiling point reaction mixture, continuously obtaining the material having
a lower boiling point than that of the diol as a column top component and
a side cut component, and continuously obtaining the diol substantially
not containing the material having a lower boiling point than that of the
diol as a column bottom component.
Background Art
A reactive distillation process for producing a dialkyl carbonate
and a diol through reaction between a cyclic carbonate and an aliphatic
monohydric alcohol has been first disclosed by the present inventors
(see Patent Document 1: Japanese Patent Application Laid-Open No.
4-198141, Patent Document 2: Japanese Patent Application Laid-Open
No. 4-230243, Patent Document 3: Japanese Patent Application

Laid-Open No. 9-176061, Patent Document 4: Japanese Patent
Application Laid-Open No. 9-183744, Patent Document 5: Japanese
Patent Application Laid-Open No. 9-194435, Patent Document 6:
International Publication No. W097/23445 (corresponding to European
Patent No. 0889025, and U.S. Patent No. 5847189), Patent Document 7:
International Publication No. W099/64382 (corresponding to European
Patent No. 1086940, and U.S. Patent No. 6346638), Patent Document 8:
International Publication No. WO00/51954 (corresponding to European
Patent No. 1174406, and U.S. Patent No. 6479689), Patent Document 9:
Japanese Patent Application Laid-Open No. 2002-308804, Patent
Document 10: Japanese Patent Application Laid-Open No. 2004-131394),
and patent applications in which such a reactive distillation system is
used have subsequently also been filed by other companies (see Patent
Document 11: Japanese Patent Application Laid-Open No. 5-213830
(corresponding to European Patent No. 0530615, and U.S. Patent No.
5231212), Patent Document 12: Japanese Patent Application Laid-Open
No. 6-9507 (corresponding to European Patent No. 0569812, and U.S.
Patent No. 5359118), Patent Document 13: Japanese Patent Application
Laid-Open No. 2003-119168 (corresponding to International Publication
No. WO03/006418), Patent Document 14: Japanese Patent Application
Laid-Open No. 2003-300936, Patent Document 15: Japanese Patent
Application Laid-Open No. 2003-342209). In the case of using a
reactive distillation system for this reaction, the reaction can be made to
proceed with a high conversion. However, reactive distillation
processes proposed hitherto have related to producing the dialkyl
carbonate and the diol either in small amounts or for a short period of

time, and have not related to carrying out the production on an industrial
scale stably for a prolonged period of time. That is, these processes
have not attained the object of producing a diol continuously in a large
amount (e.g. not less than 1 ton / hr) stably for a prolonged period of
time (e.g. not less than 1000 hours, preferably not less than 3000 hours,
more preferably not less than 5000 hours).
For example, the maximum values of the height (H: cm), diameter
(D: cm), and number of stages (n) of the reactive distillation column, the
amount produced P (kg / hr) of ethylene glycol, and the continuous
production time T (hr) in examples disclosed for the production of
dimethyl carbonate (DMC) and ethylene glycol (EG) from ethylene
carbonate and methanol are as in Table 1.
Table 1


In Patent Document 14 (Japanese Patent Application Laid-Open
No. 2003-300936), it is stated at paragraph 0060 "The present example
uses the same process flow as for the preferred mode shown in FIG. 1
described above, and was carried out with the object of operating a
commercial scale apparatus for producing dimethyl carbonate and
ethylene glycol through transesterification by a catalytic conversion
reaction between ethylene carbonate and methanol. Note that the
following numerical values in the present example can be adequately
used in the operation of an actual apparatus", and as that example it is
stated that 2490 kg / hr of ethylene glycol was specifically produced.

The scale described in that example corresponds to an annual production
of 30,000 or more tons of dimethyl carbonate, and hence this implies that
operation of the world's largest scale commercial plant using this process
had been carried out at the time of the filing of the patent application for
Patent Document 14 (Japanese Patent Application Laid-Open No.
2003-300936) (April 9, 2002). However, even at the time of filing the
present application, there is not the above fact at all. Moreover, in the
example of Patent Document 14 (Japanese Patent Application Laid-Open
No. 2003-300936), exactly the same value as the theoretically calculated
value is stated for the amount of dimethyl carbonate produced, but the
yield for ethylene glycol is approximately 85.6%, and the selectivity is
approximately 88.4%, and hence it cannot really be said that a high yield
and high selectivity have been attained. In particular, the low selectivity
indicates that this process has a fatal drawback as an industrial
production process. (Note also that Patent Document 14 (Japanese
Patent Application Laid-Open No. 2003-300936) was deemed to have
been withdrawn on July 26, 2005 due to examination not having been
requested).
With such a reactive distillation process, there are very many
causes of fluctuation such as composition variation due to reaction and
composition variation due to distillation in the distillation column, and
temperature variation and pressure variation in the column, and hence
continuing stable operation for a prolonged period of time is often
accompanied by difficulties, and in particular these difficulties are further
increased in the case of handling large amounts. To continue mass
production of a dialkyl carbonate and a diol using a reactive distillation

process stably for a prolonged period of time while maintaining high yield
and high selectivity, and thus produce a diol, the process must be
cleverly devised. However, the only description of continuous stable
production for a prolonged period of time with a reactive distillation
process proposed hitherto has been the 200 to 400 hours in Patent
Document 1 (Japanese Patent Application Laid-Open No. 4-198141) and
Patent Document 2 (Japanese Patent Application Laid-Open No.
4-230243).
The present inventors have proposed an industrial reactive
distillation process that enables a dialkyl carbonate and a diol to be
mass-produced continuously and stably for a prolonged period of time
with high yield and high selectivity, but in addition to this, a process
enabling a diol to be separated out and purified in a large amount stably
for a prolonged period of time from a high boiling point reaction mixture
continuously withdrawn in a large amount from a lower portion of the
distillation column is also required, a process for producing a large
amount of a diol with a high yield having been called for. The present
invention has been devised to attain this object.
As shown in Table 1, with the exception of Patent Document 14
(Japanese Patent Application Laid-Open No. 2003-300936), the amount
of the diol produced per hour using reactive distillation processes
proposed hitherto has been a small amount. Moreover, with the process
of Patent Document 14 (Japanese Patent Application Laid-Open No.
2003-300936), it is stated that approximately 2490 kg / hr of ethylene
glycol containing approximately 130 kg / hr of unreacted ethylene
carbonate and approximately 226 kg / hr of dihydroxyethyl carbonate was

obtained as a column bottom component from a fourth step distillation
column. However, this is merely a statement of the composition of the
reaction mixture, there being no description whatsoever of production of
a diol.
As a process for producing a diol of relatively high purity using
reactive distillation and a diol purifying column, a process is known in
which the diol is obtained from a side cut of the diol purifying column.
For example, in the example (FIG. 5) in Patent Document 12 (Japanese
Patent Application Laid-Open No. 6-9507 (corresponding to European
Patent No. 0569812, and U.S. Patent No. 5359118)), a high boiling point
reaction mixture withdrawn from a lower portion of a reactive distillation
column is fed into a thin film evaporator (III), high boiling point material
obtained therefrom is fed into a thin film evaporator (IV), low boiling point
evaporated material obtained therefrom is fed into a distillation column
(VII), and ethylene glycol is obtained as a side cut component 22 from a
concentrating portion of the distillation column (VII), and then purification
is further carried out using a purifier (IX), whereby ethylene glycol is
produced in an amount of 255 g / hr. That is, in the process of Patent
Document 12 (Japanese Patent Application Laid-Open No. 6-9507
(corresponding to European Patent No. 0569812, and U.S. Patent No.
5359118)), ethylene glycol is not obtained from the high boiling point
reaction mixture until four purifying apparatuses have been used.
Furthermore, the process of Patent Document 12 (Japanese Patent
Application Laid-Open No. 6-9507 (corresponding to European Patent No.
0569812, and U.S. Patent No. 5359118)) is a process in which a small
amount of ethylene glycol is produced, there being no suggestions

whatsoever regarding a process for producing a large amount (e.g. not
less than 1 ton / hr) of a diol stably for a prolonged period of time (e.g.
not less than 5000 hours).
Moreover, in, for example, example 1 (FIG. 5) in Patent Document
15 (Japanese Patent Application Laid-Open No. 2003-342209), a high
boiling point reaction mixture withdrawn from a lower portion of a
reactive distillation column is fed into a second distillation column 4, high
boiling point material obtained therefrom is fed into a hydrolysis reactor 7,
the reaction mixture therefrom is fed into a decarboxylation tank
(gas-liquid separator 8), a liquid component obtained therefrom is fed
into a third distillation column 10, and ethylene glycol is produced in an
amount of 19 kg / hr as a side cut component from a stripping section of
the third distillation column 10. However, with the process of Patent
Document 15 (Japanese Patent Application Laid-Open No. 2003-342209),
the ethylene glycol obtained contains 0.2 % by weight of diethylene
glycol. To obtain ethylene glycol as required as a starting material for a
PET fiber or a PET resin using the process of Patent Document 15
(Japanese Patent Application Laid-Open No. 2003-342209), at least one
further purifying apparatus is thus required. That is, with the process of
Patent Document 15 (Japanese Patent Application Laid-Open No.
2003-342209), ethylene glycol is obtained from a side cut outlet installed
in the stripping section, which is below an inlet for feeding into the
distillation column, but the purity of the ethylene glycol is insufficient,
and moreover the process of Patent Document 15 (Japanese Patent
Application Laid-Open No. 2003-342209) is a process in which a small
amount of ethylene glycol is produced, there being no suggestions

whatsoever regarding a process for producing a large amount (e.g. not
less than 1 ton / hr) of a diol stably for a prolonged period of time (e.g.
not less than 5000 hours).
Moreover, in, for example, example 10 (FIG. 6) in Patent
Document 8 (International Publication No. WO00/51954 (corresponding
to European Patent No. 1174406, and U.S. Patent No. 6479689)) and
example 1 (FIG. 1) in Patent Document 9 (Japanese Patent Application
Laid-Open No. 2002-308804), ethylene glycol is obtained from a side cut
outlet installed in an enrichment section of an EG purifying column 41,
which is above an inlet for feeding into the column, but in each case the
amount produced is a small amount of less than 200 g / hr, there being
no suggestions whatsoever regarding a process for producing a large
amount (e.g. not less than 1 ton / hr) of a diol stably for a prolonged
period of time (e.g. not less than 5000 hours).
Approximately 16 million tons per year (2004) of ethylene glycol is
produced worldwide, but hitherto all of this has been through a hydration
method in which water is added to ethylene oxide. However, as shown
by the statement "Production of EG (ethylene glycol) is by a hydration
reaction of EO (ethylene oxide), the reaction generally being carried out
... at 150 to 200 °C. At this time, not only is the target substance MEG
(monoethylene glycol) produced, but moreover DEG (diethylene glycol)
and TEG (triethylene glycol) are also by-produced. The proportions of
these products depend on the water / EO ratio, and to obtain MEG with a
selectivity of approximately 90%, the water / EO ratio must be made to
be approximately 20 as a molar ratio. A large amount of water must
thus be distilled off in an EG purification step, and a large amount of

thermal energy is consumed in this. ... With regard to synthesis of EG
from EO, it is not an overstatement to say that this is an imperfect
process from the viewpoint of energy efficiency." in Non-Patent
Document 1 (Japan Petroleum Institute (ed.), "Sekiyu-kagaku Purosesu"
("Petrochemical Processes"), pages 120 to 125, Kodansha, 2001), this
industrial production process has great drawbacks both from the
perspective of the ethylene glycol yield and selectivity, and the
perspective of energy saving.
Disclosure of Invention
Problems to be Solved by the Invention
It is an object of the present invention to provide a specific
apparatus and process for producing a diol by taking a cyclic carbonate
and an aliphatic monohydric alcohol as starting materials, continuously
feeding the starting materials into a continuous multi-stage distillation
column A in which a catalyst is present, carrying out reactive distillation
in the column A, continuously withdrawing a low boiling point reaction
mixture AT containing a produced dialkyl carbonate and the aliphatic
monohydric alcohol from an upper portion of the column A in a gaseous
form, continuously withdrawing a high boiling point reaction mixture AB
containing a produced diol from a lower portion of the column A in a
liquid form, then continuously feeding the high boiling point reaction
mixture AB into a continuous multi-stage distillation column C for
separating off material having a lower boiling point than that of the diol
contained in the high boiling point reaction mixture AB, continuously
obtaining the material having a lower boiling point than that of the diol as

a column top component CT and / or a side cut component Cs, and
continuously obtaining the diol substantially not containing the material
having a lower boiling point than that of the diol as a column bottom
component CB- Moreover, it is an object to thus provide a specific
industrial apparatus and industrial production process that are
inexpensive and, for example, enable the diol to be produced in an
amount of not less than 1 ton / hr stably for a prolonged period of time
(e.g. not less than 1000 hours, preferably not less than 3000 hours, more
preferably not less than 5000 hours).
Means for Solving the Problems
That is, according to the first aspect of the present invention,
there are provided:
1. in an industrial process for the production of a diol in which a diol is
produced by taking a cyclic carbonate and an aliphatic monohydric
alcohol as starting materials, continuously feeding the starting materials
into a continuous multi-stage distillation column A in which a catalyst is
present, carrying out reactive distillation in said column A, continuously
withdrawing a low boiling point reaction mixture AT containing a produced
dialkyl carbonate and said aliphatic monohydric alcohol from an upper
portion of the column A in a gaseous form, continuously withdrawing a
high boiling point reaction mixture AB containing a produced diol from a
lower portion of the column A in a liquid form, then continuously feeding
said high boiling point reaction mixture AB into a continuous multi-stage
distillation column C for separating off material having a lower boiling
point than that of the diol contained in said high boiling point reaction
mixture AB, continuously obtaining the material having a lower boiling

point than the diol as a column top component d and a side cut
component Cs, and continuously obtaining the diol substantially not
containing the material having a lower boiling point than that of the diol
as a column bottom component CB, wherein the improvement comprises:
(a) said continuous multi-stage distillation column C comprises a
continuous multi-stage distillation column comprising a stripping section
having a length L1 (cm), an inside diameter D1 (cm) and an internal with
a number of stages ni thereinside, and an enrichment section having a
length L2 (cm), an inside diameter D2 (cm) and an internal with a number
of stages n2 thereinside, wherein L1, D1, n1, L2, D2, and n2 satisfy the
following formulae (1) to (9):
300 50 3 3 1000 50 10 20 DS^DT (9);
(b) the enrichment section of said continuous multi-stage
distillation column C has at least one chimney tray installed therein as an
internal, said chimney tray having installed therein one or more chimneys
each having an opening having a cross-sectional area S (cm2) satisfying
the formula (10):
200
and each of the chimneys being such that a height h (cm) from said
opening of said chimney to a gas outlet of said chimney satisfies the
formula (i ■,
10 (c) a side cut outlet is connected to a liquid collecting portion of
said chimney tray of said continuous multi-stage distillation column C,
2. the process according to item 1, wherein an amount produced of the
diol is not less than 1 ton / hr,
3. the process according to item 1 or 2, wherein a plurality (n3 stages)
of trays K are further provided in a lower portion of the internals in a
lowermost portion of the stripping section which is in a lower portion of
said continuous multi-stage distillation column C, a liquid is continuously
withdrawn from an uppermost stage of said trays K, and after heat is
given to require for distillation in a reboiler, the heated liquid is returned
into the distillation column C from a feeding port provided between the
uppermost stage of the trays K and the internal in the lowermost portion
of the stripping section, while a remainder of the liquid is fed into a lower
tray in order,
4. the process according to item 3, wherein each of the trays K is a
baffle tray,
5. the process according to item 3 or 4, wherein an inside diameter D3
of said continuous multi-stage distillation column C where the trays K are
present satisfies D1 6. the process according to any one of items 3 to 5, wherein l_i, D1, L1 /
D1, n^ L2, D2, L.2 / D2, n2, and n3for said continuous multi-stage
distillation column C satisfy respectively 500
5 D2 7. the process according to any one of items 1 to 6, wherein the
internal in the stripping section of said continuous multi-stage distillation
column C and the internal excluding the chimney tray in the enrichment
section are trays and / or packings,
8. the process according to item 7, wherein the internal in the stripping
section of said continuous multi-stage distillation column C is the tray,
and the internal excluding the chimney tray in the enrichment section are
trays and / or structured packings,
9. the process according to item 7 or 8, wherein said tray is a sieve
tray,

10. the process according to item 9, wherein said sieve tray has 100 to
1000 holes / m2 in a sieve portion thereof, and a cross-sectional area per
hole in a range of from 0.5 to 5 cm2,
11. the process according to item 9 or 10, wherein an aperture ratio (a
ratio of a total cross-sectional area of the hole in one tray stage to an
area of the tray) of said sieve tray in the enrichment section of said
continuous multi-stage distillation column C is in a range of from 2 to
15%,
12. the process according to any one of items 9 to 11, wherein an
aperture ratio (a ratio of a total cross-sectional area of the hole in one
tray stage to an area of the tray) of said sieve tray in the enrichment
section of said continuous multi-stage distillation column C is in a range
of from 1.5 to 12%,
13. the process according to any one of items 1 to 12, wherein an

aperture ratio (a ratio of a total cross-sectional area of the opening in the
chimney to an area of the chimney tray including a total cross-sectional
area of the opening) of said chimney tray is in a range of from 10 to 40%,
14. the process according to any one of items 1 to 13, wherein said
continuous multi-stage distillation column C has a column bottom
temperature in a range of from 150 to 250 °C,
15. the process according to any one of items 1 to 14, wherein said
continuous multi-stage distillation column C has a column top pressure in
a range of from 50000 to 300000 Pa,
16. the process according to any one of items 1 to 15, wherein said
continuous multi-stage distillation column C has a reflux ratio in a range
of from 0.3 to 5,
17. the process according to any one of items 1 to 16, wherein a
content of the diol in said column top component Cj is not more than 100
ppm,
18. the process according to any one of items 1 to 17, wherein a
content of the diol in said side cut component Cs is not more than 0.5%
of the diol fed into said continuous multi-stage distillation column C.
In addition, according to the second aspect of the present
invention, there are provided:
19. a continuous multi-stage distillation column being a continuous
multi-stage distillation column C for producing a diol by taking a cyclic
carbonate and an aliphatic monohydric alcohol as starting materials,
continuously feeding the starting materials into a continuous multi-stage
distillation column A in which a catalyst is present, carrying out reactive
distillation in said column A, continuously withdrawing a low boiling point

reaction mixture AT containing a produced dialkyl carbonate and the
aliphatic monohydric alcohol from an upper portion of the column A in a
gaseous form, continuously withdrawing a high boiling point reaction
mixture As containing a produced diol from a lower portion of the column
A in a liquid form, then continuously feeding said high boiling point
reaction mixture AB into a continuous multi-stage distillation column C for
separating off material having a lower boiling point than that of the diol
contained in said high boiling point reaction mixture AB, continuously
obtaining the material having a lower boiling point than that of the diol as
a column top component Cj and a side cut component Cs, and
continuously obtaining the diol substantially not containing the material
having a lower boiling point than that of the diol as a column bottom
component CB, wherein the improvement comprises:
(a) said continuous multi-stage distillation column C comprises a
distillation column comprising a stripping section having a length L1 (cm),
an inside diameter D1 (cm) and an internal with a number of stages ni
thereinside, and an enrichment section having a length L2 (cm), an inside
diameter D2 (cm) and an internal with a number of stages n2 thereinside,
wherein U, D^ n1, L2, D2, and n2 satisfy the following formulae (1) to (9):
300 50 3 3 1000 50 10
20 Dz^D, (9);
(b) the enrichment section of said continuous multi-stage
distillation column C has at least one chimney tray installed therein as an
internal, the chimney tray having installed therein one or more chimneys
each having an opening having a cross-sectional area S (cm2) satisfying
the formula (10):
200 and each of the chimneys being such that a height h (cm) from said
opening of said chimney to a gas outlet of the chimney satisfies the
formula (11):
10 (c) a side cut outlet is connected to a liquid collecting portion of
said chimney tray of said continuous multi-stage distillation column C,
20. the continuous multi-stage distillation column according to item 19,
wherein a plurality (n3 stages) of trays K are further provided in a lower
portion of the internals in a lowermost portion of the stripping section
which is in a lower portion of said continuous multi-stage distillation
column C, a liquid is continuously withdrawn from an uppermost stage of
the trays K, and after heat is given to require for distillation in a reboiler,
the heated liquid is returned into the distillation column C from a feeding
port provided between the uppermost stage of the trays K and the
internal in the lowermost portion of the stripping section, while a
remainder of the liquid is fed into a lower tray in order.
21. the continuous multi-stage distillation column according to item 20,
wherein each of the trays K is a baffle tray,

22. the continuous multi-stage distillation column according to item 20
or 21, wherein an inside diameter D3 of said column where the trays K
are present satisfies D^ 23. the continuous multi-stage distillation column according to any one
of items 19 to 22, wherein L1? D1, U / D1, n1, L2, D2, L2 / D2, n2, and n3
satisfy respectively 500 nn and 3 24. the continuous multi-stage distillation column according to any of
items 19 to 23, wherein the internal in the stripping section of the
stripping section and the internal excluding the chimney tray in the
enrichment section are trays and / or packings,
25. the continuous multi-stage distillation column according to item 24,
wherein the internal in the stripping section is a tray, and the internal
excluding the chimney tray in the enrichment section is a tray and/or a
structured packing,
26. the continuous multi-stage distillation column according to item 24
or 25, wherein said tray is a sieve tray,
27. the continuous multi-stage distillation column according to item 26,
wherein said sieve tray has 100 to 1000 holes / m2 in a sieve portion
thereof, and a cross-sectional area per hole in a range of from 0.5 to 5
cm2,
28. the continuous multi-stage distillation column according to item 26
or 27, wherein an aperture ratio (a ratio of a total cross-sectional area of
the hole in one tray stage to an area of the tray) of said sieve tray in the
stripping section is in a range of from 2 to 15%,

29. the continuous multi-stage distillation column according to any one
of items 26 to 28, wherem an aperture ratio (a ratio of a total
cross-sectional area of the hole in one tray stage to an area of the tray)
of said sieve trays in the enrichment section is in a range of from 1.5 to
12%,
30. the continuous multi-stage distillation column according to any one
of items 19 to 29, wherein an aperture ratio (a ratio of a total
cross-sectional area of the opening in the chimneys to an area of the
chimney tray including a total cross-sectional area of the opening) of said
chimney tray is in a range of from 10 to 40%.
Advantageous Effects of Invention
According to the specific apparatus and process provided by the
present invention, there are provided an industrial apparatus and
industrial production process that are inexpensive and enable a diol
substantially not containing material having a lower boiling point than
that of the diol to be produced, from a cyclic carbonate and an aliphatic
monohydric alcohol, with a high yield (e.g. generally not less than 97%,
preferably not less than 98%, more preferably not less than 99%, based
on the cyclic carbonate used) on an industrial scale of not less than 1 ton
/ hr, preferably not less than 2 tons / hr, more preferably not less than 3
tons / hr stably for a prolonged period of time of, for example, not less
than 1000 hours, preferably not less than 3000 hours, more preferably
not less than 5000 hours.
Moreover, the process according to the present invention differs
from an existing ethylene glycol production process in that ethylene

glycol can be produced by the process according to the present invention
with a high yield and a high selectivity without using a large amount of
water, and thus achieves excellent effects as an industrial production
process that simultaneously solves two long-standing problems with the
existing industrial production process (low selectivity, high energy use).
Brief Description of Drawing
FIG. 1 is a schematic view showing an example of a continuous
multi-stage distillation column C preferable for carrying out the present
invention, ni stages of trays being installed in a stripping section, and
trays being installed in a lower portion and structured packings in an
upper portion (total number of stages n2) in an enrichment section, as an
internal in a trunk portion of the column, and one chimney tray stage
being installed in the concentrating portion above an inlet 1 (Note that in
FIG. 1, the trays excluding the chimney tray in the stripping section and
the enrichment section are omitted), and a diameter D3 of the lower
portion of the column is greater than a diameter D^ of the enrichment
section, trays K (n3 stages) being provided therein.
Description of Reference Numerals
1: inlet, 2: outlet of column top component d, 3: outlet of column
bottom component CB, 4: outlet of side cut component Cs, 5: internal
(packing), 6: heat exchanger, 7: reboiler, 8: inlet of reflux liquid, 9:
chimney tray, h: height (cm) from an opening of chimney to a gas outlet
of chimney, l_i: length (cm) of stripping section of continuous
multi-stage distillation column C, L2: length (cm) of enrichment section

of continuous multi-stage distillation column C, D^ inside diameter (cm)
of stripping section of continuous multi-stage distillation column C, D2:
inside diameter (cm) of enrichment section of continuous multi-stage
distillation column C, K: tray.
Best Mode for Carrying Out the Invention
Following is a detailed description of the present invention.
The reaction of the present invention is a reversible equilibrium
transesterification reaction represented by the following formula in which
a dialkyl carbonate and a diol are produced from a cyclic carbonate and
an aliphatic monohydric alcohol:

wherein R1 represents a bivalent group -(CH2)m- (m is an integer from 2
to 6), one or more of the hydrogens thereof being optionally substituted
with an alkyl group or aryl group having 1 to 10 carbon atoms. Moreover,
R2 represents a monovalent aliphatic group having 1 to 12 carbon atoms,
one or more of the hydrogens thereof being optionally substituted with an
alkyl group or aryl group having 1 to 10 carbon atoms.
The cyclic carbonate used as a starting material in the present
invention is a compound represented by (A) in the above formula. For
example, an alkylene carbonate such as ethylene carbonate or propylene
carbonate, or 1,3-dioxacyclohexa-2-one, 1,3-dioxacyclohepta-2-one, or

the like can be preferably used, ethylene carbonate or propylene
carbonate being more preferably used due to ease of procurement and
so on, and ethylene carbonate being particularly preferably used.
Moreover, the aliphatic monohydric alcohol used as the other
starting material is a compound represented by (B) in the above formula,
one having a lower boiling point than that of the diol produced being
used. Although possibly varying depending on the type of the cyclic
carbonate used, examples of the cyclic carbonate include methanol,
ethanol, propanol (isomers), allyl alcohol, butanol (isomers), 3-buten-1-ol,
amyl alcohol (isomers), hexyl alcohol (isomers), heptyl alcohol (isomers),
octyl alcohol (isomers), nonyl alcohol (isomers), decyl alcohol (isomers),
undecyl alcohol (isomers), dodecyl alcohol (isomers), cyclopentanol,
cyclohexanol, cycloheptanol, cyclooctanol, methylcyclopentanol
(isomers), ethylcyclopentanol (isomers), methylcyclohexanol (isomers),
ethylcyclohexanol (isomers), dimethylcyclohexanol (isomers),
diethylcyclohexanol (isomers), phenylcyclohexanol (isomers), benzyl
alcohol, phenethyl alcohol (isomers), phenylpropanol (isomers), and so
on. Furthermore, these aliphatic monohydric alcohols may be
substituted with substituents such as halogens, lower alkoxy groups,
cyano groups, alkoxycarbonyl groups, aryloxycarbonyl groups, acyloxy
groups, and nitro groups.
Of such aliphatic monohydric alcohols, ones preferably used are
alcohols having 1 to 6 carbon atoms, more preferably alcohols having 1
to 4 carbon atoms, i.e. methanol, ethanol, propanol (isomers), and
butanol (isomers). In the case of using ethylene carbonate or propylene
carbonate as the cyclic carbonate, preferable aliphatic monohydric

alcohols are methanol and ethanol, methanol being particularly
preferable.
In the process of the present invention, a catalyst is made to be
present in a reactive distillation column A. The method of making the
catalyst be present in the reactive distillation column A may be any
method, but in the case, for example, of a homogeneous catalyst that
dissolves in the reaction liquid under the reaction conditions, the catalyst
can be made to be present in a liquid phase in the reactive distillation
column by feeding the catalyst into the reactive distillation column
continuously, or in the case of a heterogeneous catalyst that does not
dissolve in the reaction liquid under the reaction conditions, the catalyst
can be made to be present in the reaction system by disposing the
catalyst as a solid in the reactive distillation column; these methods may
also be used in combination.
In the case that a homogeneous catalyst is continuously fed into
the reactive distillation column, the homogeneous catalyst may be fed in
together with the cyclic carbonate and/or the aliphatic monohydric
alcohol, or may be fed in at a different position to the starting materials.
The reaction actually proceeds in the distillation column in a region
below the position at which the catalyst is fed in, and hence it is
preferable to feed the catalyst into a region between the top of the
column and the position(s) at which the starting materials are fed in.
The catalyst must be present in at least 5 stages, preferably at least 7
stages, more preferably at least 10 stages.
Moreover, in the case of using a heterogeneous solid catalyst, the
catalyst must be present in at least 5 stages, preferably at least 7 stages,

more preferably at least 10 stages. A solid catalyst that also has an
effect as a packing in the distillation column may also be used.
As the catalyst used in the present invention, any of various
catalysts known from hitherto can be used. Examples of the catalyst
include:
alkali metals and alkaline earth metals such as lithium, sodium,
potassium, rubidium, cesium, magnesium, calcium, strontium, and
barium;
basic compounds of alkali metals and alkaline earth metals such
as hydrides, hydroxides, alkoxides, aryloxides, and amides;
basic compounds of alkali metals and alkaline earth metals such
as carbonates, bicarbonates, and organic acid salts;
tertiary amines such as triethylamine, tributylamine, trihexylamine,
and benzyldiethylamine;
nitrogen-containing heteroaromatic compounds such as
N-alkylpyrroles, N-alkylindoles, oxazoles, N-alkylimidazoles,
N-alkylpyrazoles, oxadiazoles, pyridine, alkylpyridines, quinoline,
alkylquinolines, isoquinoline, alkylisoquinolines, acridine, alkylacridines,
phenanthroline, alkylphenanthrolines, pyrimidine, alkylpyrimidines,
pyrazine, alkylpyrazines, triazines, and alkyltriazines;
cyclic amidines such as diazobicycloundecene (DBU) and
diazobicyclononene (DBN);
thallium compounds such as thallium oxide, thallium halides,
thallium hydroxide, thallium carbonate, thallium nitrate, thallium sulfate,
and thallium organic acid salts;
tin compounds such as tributylmethoxytin, tributylethoxytin,

dibutyldimethoxytin, diethyldiethoxytin, dibutyldiethoxytin,
dibutylphenoxytin, diphenylmethoxytin, dibutyltin acetate, tributyltin
chloride, and tin 2-ethylhexanoate;
zinc compounds such as dimethoxyzinc, diethoxyzinc,
ethylenedioxyzinc, and dibutoxyzinc;
aluminum compounds such as aluminum trimethoxide, aluminum
triisopropoxide, and aluminum tributoxide;
titanium compounds such as tetramethoxytitanium,
tetraethoxytitanium, tetrabutoxytitanium, dichlorodimethoxytitanium,
tetraisopropoxytitanium, titanium acetate, and titanium acetylacetonate;
phosphorus compounds such as trimethylphosphine,
triethylphosphine, tributylphosphine, triphenylphosphine,
tributylmethylphosphonium halides, trioctylbutylphosphonium halides,
and triphenylmethylphosphonium halides;
zirconium compounds such as zirconium halides, zirconium
acetylacetonate, zirconium alkoxides, and zirconium acetate;
lead and lead-containing compounds, for example lead oxides
such as PbO, Pb02, and Pb304;
lead sulfides such as PbS, Pb2S3, and PbS2;
lead hydroxides such as Pb(OH)2, Pb302(OH)2, Pb2[Pb02(OH)2],
and Pb20(OH)2;
plumbites such as Na2Pb02, K2Pb02, NaHPb02, and KHPb02;
plumbates such as Na2Pb03, Na2H2Pb04, K2Pb03, K2[Pb(0H)6],
K4Pb04, Ca2Pb04, and CaPb03;
lead carbonates and basic salts thereof such as PbC03 and
2PbC03Pb(OH)2;

alkoxylead compounds and aryloxylead compounds such as
Pb(OCH3)2, (CH30)Pb(OPh), and Pb(OPh)2;
lead salts of organic acids, and carbonates and basic salts thereof,
such as Pb(OCOCH3)2, Pb(OCOCH3)4, and Pb(0C0CH3)2PbO3H20;
organolead compounds such as Bu4Pb, Ph4Pb, Bu3PbCI, Ph3PbBr,
Ph3Pb (or Ph6Pb2), Bu3PbOH, and Ph2PbO (wherein Bu represents a
butyl group, and Ph represents a phenyl group);
lead alloys such as Pb-Na, Pb-Ca, Pb-Ba, Pb-Sn, and Pb-Sb;
lead minerals such as galena and zinc blende; and hydrates of
such lead compounds.
In the case that the compound used dissolves in a starting
material of the reaction, the reaction mixture, a reaction by-product or
the like, the compound can be used as a homogeneous catalyst, whereas
in the case that the compound does not dissolve, the compound can be
used as a solid catalyst. Furthermore, it is also preferable to use, as a
homogeneous catalyst, a mixture obtained by dissolving a compound as
above in a starting material of the reaction, the reaction mixture, a
reaction by-product or the like in advance, or by reacting to bring about
dissolution.
Furthermore, ion exchangers such as anion exchange resins
having tertiary amino groups, ion exchange resins having amide groups,
ion exchange resins having at least one type of exchange groups
selected from sulfonate groups, carboxylate groups and phosphate
groups, and solid strongly basic anion exchangers having quaternary
ammonium groups as exchange groups; solid inorganic compounds such
as silica, silica-alumina, silica-magnesia, aluminosilicates, gallium

silicate, various zeolites, various metal-exchanged zeolites, and
ammonium-exchanged zeolites, and so on can also be used as a
heterogeneous catalyst.
As a heterogeneous catalyst, a particularly preferably used one is
a solid strongly basic anion exchanger having quaternary ammonium
groups as exchange groups, examples thereof including a strongly basic
anion exchange resin having quaternary ammonium groups as exchange
groups, a cellulose strongly basic anion exchanger having quaternary
ammonium groups as exchange groups, and an inorganic carrier
supported type strongly basic anion exchanger having quaternary
ammonium groups as exchange groups. As a strongly basic anion
exchange resin having quaternary ammonium groups as exchange groups,
for example a styrene type strongly basic anion exchange resin or the
like can be preferably used. A styrene type strongly basic anion
exchange resin is a strongly basic anion exchange resin having a
copolymer of styrene and divinylbenzene as a parent material, and
having quaternary ammonium groups (type I or type II) as exchange
groups, and can be schematically represented, for example, by the
following formula:


wherein X represents an anion; as X, generally at least one type of anion
selected from F", CI", Br", I", HC03\ C032", CH3C02", HC02", I03", Br03",
and CI03" is used, preferably at least one type of anion selected from CI",
Br", HCO3", and C032". Moreover, as the structure of the resin parent
material, either a gel type one or a macroreticular (MR) type one can be
used, the MR type being particularly preferable due to the organic
solvent resistance being high.
An example of a cellulose strongly basic anion exchanger having
quaternary ammonium groups as exchange groups is cellulose having
-OCH2CH2NR3X exchange groups obtained by converting some or all of
the -OH groups in the cellulose into trialkylaminoethyl groups. Here, R
represents an alkyl group; methyl, ethyl, propyl, butyl or the like is
generally used, preferably methyl or ethyl. Moreover, X represents an
anion as above.

An inorganic carrier supported type strongly basic anion
exchanger having quaternary ammonium groups as exchange groups that
can be used in the present invention means an inorganic carrier that has
had -0(CH2)nNR3X quaternary ammonium groups introduced thereto by
modifying some or all of the -OH surface hydroxyl groups of the
inorganic carrier. Here, R and X are defined as above, n is generally
an integer from 1 to 6, preferably n = 2. As the inorganic carrier, silica,
alumina, silica-alumina, titania, a zeolite, or the like can be used, it being
preferable to use silica, alumina, or silica-alumina, particularly preferably
silica. Any method can be used as the method of modifying the surface
hydroxyl groups of the inorganic carrier.
As the solid strongly basic anion exchanger having quaternary
ammonium groups as exchange groups, a commercially available one
may be used. In this case, the anion exchanger may also be used as
the transesterification catalyst after being subjected to ion exchange with
a desired anionic species in advance as pretreatment.
Moreover, a solid catalyst containing a macroreticular or gel-type
organic polymer having bonded thereto heterocyclic groups each
containing at least one nitrogen atom, or an inorganic carrier having
bonded thereto heterocyclic groups each containing at least one nitrogen
atom can also be preferably used as the transesterification catalyst.
Furthermore, a solid catalyst in which some or all of these
nitrogen-containing heterocyclic groups have been converted into a
quaternary salt can be similarly used. Note that a solid catalyst such as
an ion exchanger may also act as a packing in the present invention.
The amount of the catalyst used in the present invention varies

depending on the type of the catalyst used, but in the case of
continuously feeding in a homogeneous catalyst that dissolves in the
reaction liquid under the reaction conditions, the amount used is
generally in a range of from 0.0001 to 50 % by weight, preferably from
0.005 to 20 % by weight, more preferably from 0.01 to 10 % by weight, as
a proportion of the total weight of the cyclic carbonate and the aliphatic
monohydric alcohol fed in as the starting materials. Moreover, in the
case of using a solid catalyst installed in the distillation column, the
catalyst is preferably used in an amount in a range of from 0.01 to 75
vol%, more preferably from 0.05 to 60 vol%, yet more preferably from 0.1
to 60 vol%, based on the empty column volume of the distillation column.
There are no particular limitations on the method of continuously
feeding the cyclic carbonate and the aliphatic monohydric alcohol into
the continuous multi-stage distillation column A constituting the reactive
distillation column in the present invention; any feeding method may be
used so long as the cyclic carbonate and the aliphatic monohydric
alcohol can be made to contact the catalyst in a region of at least 5
stages, preferably at least 7 stages, more preferably at least 10 stages,
of the distillation column A. That is, the cyclic carbonate and the
aliphatic monohydric alcohol can be continuously fed in from a required
number of inlets in stages of the continuous multi-stage distillation
column A satisfying the conditions described earlier. Moreover, the
cyclic carbonate and the aliphatic monohydric alcohol may be introduced
into the same stage of the distillation column, or may be introduced into
different stages to one another.
The starting materials may be fed continuously into the distillation

column A in a liquid form, in a gaseous form, or as a mixture of a liquid
and a gas. Other than feeding the starting materials into the distillation
column A in this way, it is also preferable to additionally feed in a
gaseous starting material intermittently or continuously from the lower
portion of the distillation column A. Moreover, another preferable
method is one in which the cyclic carbonate is continuously fed in a liquid
form or a gas / liquid mixed form into a stage of the distillation column A
above the stages in which the catalyst is present, and the aliphatic
monohydric alcohol is continuously fed in a gaseous form and / or a
liquid form into the lower portion of the distillation column A. In this
case, the cyclic carbonate may of course contain the aliphatic
monohydric alcohol.
In the present invention, the starting materials fed in may contain
the product dialkyl carbonate and / or diol. The content thereof is, for
the dialkyl carbonate, generally in a range of from 0 to 40 % by weight,
preferably from 0 to 30 % by weight, more preferably from 0 to 20 % by
weight, in terms of the percentage by mass of the dialkyl carbonate in the
aliphatic monohydric alcohol / dialkyl carbonate mixture, and is, for the
diol, generally in a range of from 0 to 10 % by weight, preferably 0 to 7 %
by weight, more preferably 0 to 5 % by weight, in terms of the percentage
by weight of the diol in the cyclic carbonate / diol mixture.
When carrying out the present reaction industrially, besides fresh
cyclic carbonate and / or aliphatic monohydric alcohol newly introduced
into the reaction system, material having the cyclic carbonate and / or
the aliphatic monohydric alcohol as a main component thereof recovered
from this process and / or another process can also be preferably used

for the starting materials. It is an excellent characteristic feature of the
present invention that this is possible. An example of another process
is a process in which a diaryl carbonate is produced from the dialkyl
carbonate and an aromatic monohydroxy compound, the aliphatic
monohydric alcohol being by-produced in this process and recovered.
The recovered by-produced aliphatic monohydric alcohol generally often
contains the dialkyl carbonate, the aromatic monohydroxy compound, an
alkyl aryl ether and so on, and may also contain small amounts of an
alkyl aryl carbonate, the diaryl carbonate and so on. The by-produced
aliphatic monohydric alcohol may be used as is as a starting material in
the present invention, or may be used as a starting material after the
amount of contained material having a higher boiling point than the
aliphatic monohydric alcohol has been reduced through distillation or the
like.
A cyclic carbonate preferably used in the present invention is one
produced through reaction between, for example, an alkylene oxide such
as ethylene oxide, propylene oxide or styrene oxide and carbon dioxide;
a cyclic carbonate containing small amounts of such starting material
compounds or the like may be used as a starting material in the present
invention.
In the present invention, a ratio between the amounts of the cyclic
carbonate and the aliphatic monohydric alcohol fed into the reactive
distillation column A varies according to the type and amount of the
transesterification catalyst and the reaction conditions, but a molar ratio
of the aliphatic monohydric alcohol to the cyclic carbonate fed in is
generally in a range of from 0.01 to 1000 times. To increase the cyclic

carbonate conversion, it is preferable to feed in the aliphatic monohydric
alcohol in an excess of at least 2 times the number of mols of the cyclic
carbonate. However, if an amount of the aliphatic monohydric alcohol
used is too great, then it is necessary to make the apparatus larger. For
such reasons, a molar ratio of the aliphatic monohydric alcohol to the
cyclic carbonate is preferably in a range of from 2 to 20, more preferably
from 3 to 15, yet more preferably from 5 to 12. Furthermore, if much
unreacted cyclic carbonate remains, then the unreacted cyclic carbonate
may react with the product diol to by-produce oligomers such as a dimer
or a trimer, and hence in the case of industrial implementation, it is
preferable to reduce the amount of unreacted cyclic carbonate remaining
as much as possible. In the process of the present invention, even if
the above molar ratio is not more than 10, the cyclic carbonate
conversion can be made to be not less than 98%, preferably not less
than 99%, more preferably not less than 99.9%. This is another
characteristic feature of the present invention.
In the present invention, preferably not less than approximately 1
ton / hr of a high boiling point reaction mixture AB containing the diol is
continuously produced in the reactive distillation column A, this being fed
into a continuous multi-stage distillation column C, so as to produce not
less than approximately 1 ton / hr of the diol substantially not containing
material having a lower boiling point than that of the diol as a column
bottom component CB; the minimum amount of the cyclic carbonate
continuously fed in to achieve this is generally 1.55 P ton / hr, preferably
1.5 P ton / hr, more preferably 1.45 P ton / hr, based on the amount P
(ton / hr) of the diol to be produced. In a yet more preferable case, this

amount can be made to be less than 1.43 P ton / hr.
There are no particular limitations on the continuous multi-stage
distillation column A for carrying out the reactive distillation process in
the present invention, but the continuous multi-stage distillation column A
is preferably one that enables not only distillation but also reaction to be
carried out at the same time so as to be able to produce preferably not
less than 1.5 ton / hr of the dialkyl carbonate and/or preferably not less
than 1 ton / hr of the diol stably for a prolonged period of time.
In the present invention, the diol is produced by taking the cyclic
carbonate and the aliphatic monohydric alcohol as starting materials,
continuously feeding the starting materials into the continuous
multi-stage distillation column A in which the catalyst is present, carrying
out reactive distillation in the column A, continuously withdrawing a low
boiling point reaction mixture AT containing a produced dialkyl carbonate
and the aliphatic monohydric alcohol from an upper portion of the column
A in a gaseous form, continuously withdrawing a high boiling point
reaction mixture AB containing a produced diol from a lower portion of the
column A in a liquid form, continuously feeding the high boiling point
reaction mixture AB into a continuous multi-stage distillation column C,
continuously obtaining material having a lower boiling point than that of
the diol contained in the high boiling point reaction mixture AB as a
column top component CT and / or a side cut component Cs, and
continuously obtaining the diol substantially not containing the material
having a lower boiling point than that of the diol. The continuous
multi-stage distillation column C must thus have a function of enabling
the material having a lower boiling point than that of the diol contained in

the high boiling point reaction mixture AB to be removed efficiently as the
column top component CT and / or the side cut component Cs; the
present invention provides an industrial distillation apparatus having a
specified structure having this function, and it has been discovered that
by using this apparatus, the object of the present invention can be
attained.
The high boiling point reaction mixture AB may contain a trace to a
small amount of unreacted cyclic carbonate. In this case, it is
preferable to make it such that such unreacted cyclic carbonate is
substantially not present in the column bottom component CB from the
continuous multi-stage distillation column C. To achieve this, it is
preferable to add a small amount of water into the continuous multi-stage
distillation column C so that the unreacted cyclic carbonate is converted
into the diol through hydrolysis, and/or devise the continuous multi-stage
distillation column C such that the unreacted cyclic carbonate is reacted
with the diol and thus converted into a dialkylene glycol or the like (e.g.
for a temperature and residence time required for this reaction to
proceed to completion to be secured, for back mixing of the column
bottom component to be reduced, etc.). As a result, it can be made to
be such that there is substantially no unreacted cyclic carbonate in the
column bottom component CB from the continuous multi-stage distillation
column C, this being preferable when carrying out the present invention.
Note that the term "substantially not containing" used in the
present invention means that the content is not more than 50 ppm,
preferably not more than 10 ppm, more preferably not more than 5 ppm.
To attain the above object, the continuous multi-stage distillation

column C used in the present invention must be made to simultaneously
satisfy various conditions.
Specifically, the continuous multi-stage distillation column C must
be as follows:
(a) the continuous multi-stage distillation column C comprises a
distillation column comprising a stripping section having a length L1 (cm),
an inside diameter D1 (cm) and an internal with a number of stages ni
thereinside, and an enrichment section having a length L2 (cm), an inside
diameter D2 (cm) and an internal with a number of stages n2 thereinside,
wherein L1, D1, n^ L2, D2, and n2 satisfy the following formulae (1) to (9):
300 50 3 3 1000 50 10 20 D2 (b) the enrichment section of the continuous multi-stage
distillation column C has at least one chimney tray installed therein as
the internal, the chimney tray having installed therein one or more
chimneys each having an opening having a cross-sectional area S (cm2)
satisfying the formula (10):
200 and each of the chimneys being such that a height h (cm) from the

opening of the chimney to a gas outlet of the chimney satisfies the
formula (11):
10 (c) a side cut outlet is connected to a liquid collecting portion of
the chimney tray of the continuous multi-stage distillation column C.
It has been discovered that by using such a continuous
multi-stage distillation column C, a column bottom component CB
substantially not containing material having a lower boiling point than
that of the diol can be produced on an industrial scale of not less than 1
ton / hr, preferably not less than 2 tons / hr, more preferably not less
than 3 tons / hr, stably for a prolonged period of time of, for example, not
less than 1000 hours, preferably not less than 3000 hours, more
preferably not less than 5000 hours, from a large amount of the high
boiling point reaction mixture AB which has been produced through a
reactive distillation process between the cyclic carbonate and the
aliphatic monohydric alcohol. The reason why it has become possible to
separate out and purify the diol on an industrial scale with such excellent
effects by implementing the process according to the present invention is
not clear, but this is supposed to be due to a composite effect brought
about when the conditions of the formulae (1) to (11) are combined.
Preferable ranges for the respective factors are described below.
If L1 (cm) is less than 300, then the separation efficiency for the
stripping section decreases, and hence the desired separation efficiency
cannot be attained. Moreover, to keep down the equipment cost while
securing the desired separation efficiency, L1 must be made to be not
more than 3000. Furthermore, if L1 is greater than 3000, then the

pressure difference between the top and bottom of the column becomes
too great, and hence prolonged stable operation becomes difficult, and
moreover it becomes necessary to increase the temperature in the lower
portion of the column, and hence side reactions become liable to occur.
A more preferable range for L^ (cm) is 500 1500 being yet more preferable.
If D1 (cm) is less than 50, then it is not possible to attain the
desired distillation amount. Moreover, to keep down the equipment cost
while attaining the desired distillation amount, D1 must be made to be not
more than 700. A more preferable range for D^ (cm) is 70 with 190 If L1 I D1 is less than 3 or greater than 30, then prolonged stable
operation becomes difficult. A more preferable range for L1 / D^ is 4 If ni is less than 3, then the separation efficiency for the stripping
section decreases and hence the desired separation efficiency cannot be
attained. Moreover, to keep down the equipment cost while securing the
desired separation efficiency, ni must be made to be not more than 30.
Furthermore, if ni is greater than 30, then the pressure difference
between the top and bottom of the column becomes too great, and hence
prolonged stable operation becomes difficult, and moreover it becomes
necessary to increase the temperature in the lower portion of the column,
and hence side reactions become liable to occur. A more preferable
range for ni is 5 If L2 (cm) is less than 1000, then the separation efficiency for the
enrichment section decreases, and hence the desired separation

efficiency cannot be attained. Moreover, to keep down the equipment
cost while securing the desired separation efficiency, L2 must be made to
be not more than 5000. Furthermore, if L2 is greater than 5000, then the
pressure difference between the top and bottom of the column becomes
too great, and hence prolonged stable operation 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.
A more preferable range for L2 (cm) is 1500 3500 being yet more preferable.
If D2 (cm) is less than 50, then it is not possible to attain the
desired distillation amount. Moreover, to keep down the equipment cost
while attaining the desired distillation amount, D2 must be made to be not
more than 500. A more preferable range for D2 (cm) is 70 with 90 If L2 / D2 is less than 10 or greater than 50, then prolonged stable
operation becomes difficult. A more preferable range for L2 / D2 is 15 L2 / D2 If n2 is less than 20, then the separation efficiency for the
enrichment section decreases and hence the desired separation
efficiency cannot be attained. Moreover, to keep down the equipment
cost while securing the desired separation efficiency, n2 must be made to
be not more than 100. Furthermore, if n2 is greater than 100, then the
pressure difference between the top and bottom of the column becomes
too great, and hence prolonged stable operation 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.

A more preferable range for n2 is 30 yet more preferable. Note that in the present invention, at least one
chimney tray must be installed in the concentrating portion, and the
number of stages therefor is included in n2 above. Moreover, for the
continuous multi-stage distillation column C of the present invention,
preferably D2 Furthermore, in the case that the high boiling point reaction
mixture AB fed into the continuous multi-stage distillation column C
contains a small amount of unreacted cyclic carbonate, it is preferable
for it to be devised such that the unreacted cyclic carbonate is made to
undergo reaction in a lower portion of the column, so that substantially
no unreacted cyclic carbonate is contained in the column bottom
component CB- Accordingly, in a preferable embodiment of the present
invention, a plurality (n3 stages) of trays K are further provided in a lower
portion of the internals in a lowermost portion of the stripping section
which is in the lower portion of the continuous multi-stage distillation
column C, some liquid are continuously withdrawn from an uppermost
stage of the trays K, and given heat required for distillation and reaction
in a reboiler, and then the heated liquid is returned into the distillation
column C from a feeding port provided between the uppermost stage of
the trays K and the internals in a lowermost portion of the enrichment
section, while a remainder of the liquid is fed into lower trays in order.
By devising the continuous multi-stage distillation column C in this
way, the residence time of liquid in the lower portion of the column can
be increased. Moreover, by making a diameter D3 of the column at and
below the stages where the trays K are present be greater than the

diameter D1 of the enrichment section {D^ held can be increased and hence the residence time can be increased,
and thus a sufficient reaction time can be maintained. Furthermore, by
making the column bottom liquid level be lower than the lowermost one of
the trays K, back mixing of the liquid in the lower portion of the column
can be prevented. As a result of the above, in the present invention,
even in the case that a small amount of unreacted cyclic carbonate is
contained, the unreacted cyclic carbonate can be reacted with the diol,
which is generally present in a large excess, and thus converted
completely into a dialkylene glycol having a high boiling point or the like.
The trays K may be any type of trays so long as these trays fulfill
the role described above, but in terms of the relationship between
performance and equipment cost, a sieve tray or a baffle trays is
preferable, the baffle tray being particularly preferable. In the case of
the sieve tray or the baffle tray, a weir is preferably provided, it
preferably being made to be such that liquid overflowing the weir
continuously falls down from a downcomer portion into lower stage trays.
In this case, the weir height is preferably in a range of from 4 to 30 cm,
more preferably from 6 to 20 cm, yet more preferably from 8 to 15 cm.
In the case of the baffle tray, a simple tray in which the weir is the baffle
is particularly preferable.
A preferable range for D3 is 1.2Di 1.5Di Moreover, n3 is not less than 2, a preferable range for n3 being 3 n3 The chimney tray installed in the enrichment section of the

continuous multi-stage distillation column C has provided therein at least
one chimneys each having an opening having a cross-sectional area S
(cm2) in the plane of the tray. Moreover, a chimney cover is preferably
installed on an upper opening of each of the chimneys. This chimney
cover plays a role in a gaseous component that rises up from lower
stages flowing sideways at the upper opening (gas outlet) of the chimney,
and moreover plays a role in preventing a liquid component that falls
down from upper stages from falling down directly into the lower stages.
The cross-sectional shape of each of the chimneys may be any of
triangular, square, polygonal, circular, elliptical, star-shaped or the like,
but a square shape or a circular shape is preferably used. Moreover, for
each of the chimneys, the cross-sectional shape and area may vary from
an upper portion to a lower portion of the chimney, but is preferably
constant since then manufacture is simple and inexpensive. Moreover,
the at least two chimneys may have different shapes to one another, but
preferably have the same shape as one another.
In the present invention, the cross-sectional area S (cm2) of the
opening (the part of the chimney having the smallest cross section) of
each of the chimneys connected to the chimney tray must satisfy the
formula (10):
200 If S is less than 200, then a large number of chimneys are
required to attain a predetermined production amount, and hence the
equipment cost becomes high. If S is greater than 1000, then the flow
of gas in the chimney tray stage is prone to becoming ununiform, and
hence prolonged stable operation becomes difficult. A more preferable

range for S (cm2) is 300 preferable.
Moreover, the height h (cm) from the opening of each of the
chimneys to the gas outlet (a lower end of the upper opening of the
chimney) of that chimney must satisfy the formula (11):
10 The chimney tray used in the present invention generally has
installed therein a downcomer portion for allowing the liquid component
to fall down into lower stages, and a weir for holding the liquid
component. The height of the weir depends on h, but is generally set to
approximately 5 to 20 cm less than h. Consequently, if h is less than 10,
then the amount of liquid held in the chimney tray becomes low, and
hence prolonged stable operation becomes difficult. Moreover, if h is
greater than 80, then the amount of liquid held increases, and hence the
strength of the equipment must be increased, and thus the equipment
cost becomes high, and moreover the residence time of the purified diol
in the column increases, which is undesirable. A more preferable range
for h (cm) is 15 An aperture ratio (the ratio of the total cross-sectional area of the
openings in the chimneys to the area of the chimney tray including the
total cross-sectional area of the openings) of the chimney tray is
preferably in a range of from 10 to 40%. If the aperture ratio is less
than 10%, then prolonged stable operation becomes difficult. Moreover,
if the aperture ratio is greater than 40%, then the number of chimneys
must be increased, or each of the chimneys must be made higher, and in
either case the equipment cost becomes high. A more preferable range

for the aperture ratio is 13 to 35%, with 15 to 30% being yet more
preferable.
In the present invention, the at least one chimney tray is installed
in the enrichment section (a portion above an inlet for feeding into the
column but below the top of the column) of the multi-stage distillation
column C, and a fraction having as a main component thereof
intermediate boiling point material having a lower boiling point than that
of the diol but a higher boiling point than that of the aliphatic monohydric
alcohol is continuously withdrawn from the side cut outlet which is
connected to the bottom of the liquid collecting portion of the chimney
tray. The number of chimney trays can be made to be two or more if
required, but is generally one. The stage at which the chimney tray is
installed may be at any position in the enrichment section, but is
preferably a stage that is at least 3 stages from the bottom of the stages
in the enrichment section and at least 10 stages from the top of the
stages in the enrichment section, more preferably a stage that is at least
4 stages from the bottom of the stages in the enrichment section and at
least 15 stages from the top of the stages in the enrichment section, yet
more preferably a stage that is at least 5 stages from the bottom of the
stages in the enrichment section and at least 4 stages from the top of the
stages in the enrichment section.
The continuous multi-stage distillation column C of the present
invention preferably comprises a distillation column having trays and/or
packings as internals in each of the stripping section and the enrichment
section. The term "internal" used in the present invention means a part
in the distillation column where gas and liquid are actually brought into

contact with one another. Examples of the tray include a bubble-cap
tray, a sieve tray, a ripple tray, a ballast tray, a valve tray, a counterflow
tray, an Unifrax tray, a Superfrac tray, a Maxfrac tray, a dual flow tray, a
grid plate tray, a turbogrid plate tray, a Kittel tray, or the like. Examples
of the packing include random 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 structured packings such as
Mellapak, Gempak, Techno-pack, Flexipac, a Sulzer packings, a Goodroll
packing or Glitschgrid. A multi-stage distillation column having both a
tray portion and a portion packed with packings can also be used.
Furthermore, the term "number of stages ni or n2 of the internal" used in
the present invention means the number of trays in the case of trays, and
the theoretical number of stages in the case of packings, ni or n2 in the
case of a continuous multi-stage distillation column having both a tray
portion and a portion packed with packings is thus the sum of the number
of trays and the theoretical number of stages.
In the present invention, the internals in the stripping section of
the continuous multi-stage distillation column C and the internals
excluding the chimney tray in the enrichment section are preferably trays
and/or packings. Furthermore, it has been discovered that it is
particularly preferable if the internals in the stripping section are trays,
and the internals excluding the chimney tray in the enrichment section
are trays and/or structured packings. Moreover, it has been discovered
that sieve trays each having a sieve portion and a downcomer portion are
particularly good as the trays in terms of the relationship between
performance and equipment cost. It has also been discovered that each

sieve tray preferably has 100 to 1000 holes / m2 in the sieve portion
thereof. A more preferable number of holes is from 150 to 900 holes /
m2, yet more preferably from 200 to 800 holes / m2. Moreover, it has
been discovered that the cross-sectional area per hole of each sieve tray
is preferably in a range of from 0.5 to 5 cm2. A more preferable
cross-sectional area per hole is from 0.7 to 4 cm2, yet more preferably
from 0.9 to 3 cm2. Furthermore, it has been discovered that it is
particularly preferable if each sieve tray has 150 to 1200 holes / m2 in
the sieve portion thereof, and the cross-sectional area per hole is in a
range of from 0.5 to 5 cm2.
An aperture ratio (the ratio of the total cross-sectional area of the
holes in one tray stage to the area of the tray) of each of the sieve trays
in the enrichment section of the continuous multi-stage distillation
column C is preferably in a range of from 2 to 15%, more preferably from
2.5 to 12%, yet more preferably from 3 to 10%. Moreover, an aperture
ratio (the ratio of the total cross-sectional area of the holes in one tray
stage to the area of the tray) of each of the sieve trays in the enrichment
section of the continuous multi-stage distillation column C is preferably in
a range of from 1.5 to 12%, more preferably from 2 to 11%, yet more
preferably from 2.5 to 10%. Note that in the present invention, the
chimney tray installed in the enrichment section is counted in the number
of stages, but as described above, the aperture ratio for the chimney tray
is different to the aperture ratio for the sieve trays.
It has been shown that by adding the above conditions to the
continuous multi-stage distillation column C, the object of the present
invention can be attained more easily.

In the present invention, the dialkyl carbonate produced through
the reactive distillation in the continuous multi-stage distillation column A
is continuously withdrawn from the upper portion of the column in a
gaseous form as the low boiling point reaction mixture AT together with
aliphatic monohydric alcohol that has remained unreacted due to
generally being used in excess. Moreover, the high boiling point
reaction mixture AB containing the produced diol is continuously
withdrawn from the lower portion of the column in a liquid form. The
high boiling point reaction mixture AB having the diol as a main
component thereof generally contains 10 to 45 % by weight of residual
aliphatic monohydric alcohol, a trace of the dialkyl carbonate, a very
small amount (generally not more than 0.2 % by weight) of unreacted
cyclic carbonate, a small amount (generally not more than 0.4 % by
weight) of by-products having a lower boiling point than the diol (a
2-alkoxyethanol etc.), and a small amount (generally not more than 0.4 %
by weight) of by-products having a higher boiling point than the diol (e.g.
a dialkylene glycol) including catalyst.
Material having a lower boiling point than that of the diol (the
aliphatic monohydric alcohol, a trace of the dialkyl carbonate and
by-produced C02, low boiling point by-products) and a small amount of
the diol in the high boiling point reaction mixture AB continuously fed into
the continuous multi-stage distillation column C are thus continuously
withdrawn as the column top component CT and / or the side cut
component Cs, while the diol containing the catalyst and a small amount
of high boiling point by-products is continuously withdrawn as the column
bottom component CB. In the present invention, the concentration of the

diol in the column bottom component CB is generally not less than 95 %
by weight, preferably not less than 97 % by weight, more preferably not
less than 98 % by weight.
Moreover, in the process of the present invention, a very small
amount (generally not more than 0.2 % by weight) of unreacted cyclic
carbonate fed into the continuous multi-stage distillation column C can
be reacted with the diol, which is present in a large amount in the
continuous multi-stage distillation column C, to produce a dialkylene
glycol, and hence it is easy to make the amount of unreacted cyclic
carbonate present substantially zero; in the present invention, the
column bottom component CB generally having substantially no unreacted
cyclic carbonate therein is continuously obtained.
Note that, generally, with an objective of obtaining an ultra high
purity diol having a further reduced content of an aldehyde which may be
contained in the diol in trace amount, or an ultra high purity diol having a
high UV transmissivity, it is also preferable to feed a small amount of
water into the lower portion of the continuous multi-stage distillation
column C in accordance with the process described in Patent Document
9 (Japanese Patent Application Laid-Open No. 2002-308804) or Patent
Document 10 (Japanese Patent Application Laid-Open No. 2004-131394).
The distillation conditions for the continuous multi-stage
distillation column C used in the present invention vary depending on the
form of the internals in the distillation column and the number of stages,
the type, composition and amount of the high boiling point reaction
mixture AB fed in, the purity of the diol required, and so on. The column
bottom temperature is generally preferably a specified temperature in a

range of from 150 to 250 °C. A more preferable column bottom
temperature range is from 170 to 230 °C, yet more preferably from 190 to
210 °C. The column bottom pressure varies depending on the
composition in the column and the column bottom temperature used, but
is generally in a range of from 50000 to 300000 Pa, preferably from
80000 to 250000 Pa, more preferably from 100000 to 200000 Pa.
Moreover, the reflux ratio for the continuous multi-stage distillation
column C is preferably in a range of from 0.3 to 5, more preferably from
0.5 to 3, yet more preferably from 0.8 to 2.
In the present invention, the content of the diol in the column top
component CT from the continuous multi-stage distillation column C is
generally not more than 100 ppm, preferably not more than 50 ppm, more
preferably not more than 10 ppm, yet more preferably not more than 5
ppm. In the present invention, it is even possible to make the content of
the diol in the column top component CT be zero.
The side cut component Cs from the continuous multi-stage
distillation column C generally contains the aliphatic monohydric alcohol,
by-products having a lower boiling point than that of the diol (a
2-alkoxyethanol etc.), the diol, and a small amount of impurities having a
higher boiling point than that of the diol (e.g. a dialkylene glycol). The
amount of the side cut component Cs is generally not more than 4%,
preferably not more than 3%, more preferably not more than 2%, of the
high boiling point reaction mixture AB fed into the continuous multi-stage
distillation column C.
Moreover, in the present invention, the content of the diol in the
side cut component Cs can generally easily be made to be not more than

0.5%, preferably not more than 0.4%, more preferably not more than
0.3%, of the diol fed into the continuous multi-stage distillation column C.
As the column bottom component CB from the continuous
multi-stage distillation column C, the diol can be continuously obtained
containing generally not more than 2%, preferably not more than 1.5%,
more preferably not more than 1%, of by-products having a higher boiling
point than that of the diol (e.g. a dialkylene glycol) and a small amount of
catalyst component. The diol obtained as the column bottom component
CB is generally not less than 99.5%, preferably not less than 99.6%,
more preferably not less than 99.7%, of the diol fed into the continuous
multi-stage distillation column C. It is a characteristic feature of the
present invention that the diol can be obtained with such a high recovery.
Moreover, in a preferable embodiment of the present invention,
the reaction is carried out using starting materials and a catalyst not
containing a halogen, and hence the produced diol can be made to not
contain a halogen at all. In the present invention, a diol having a
halogen content of not more than 0.1 ppm, preferably not more than 1
ppb, can thus be easily produced.
In the present invention, the reaction yield and the purification
yield are thus high, and hence the diol can be produced with a high yield
of generally not less than 97%, preferably not less than 98%, more
preferably not less than 99%, based on the cyclic carbonate used.
The material constituting each of the continuous multi-stage
distillation columns A and C 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 dialkyl carbonate and diol to be produced,

stainless steel is preferable.
EXAMPLES
Following is a more detailed description of the present invention
through examples. However, the present invention is not limited to the
following examples. Note that the halogen content was measured using
ion chromatography.
Example 1:
A continuous multi-stage distillation column C as shown in FIG. 1
having L1 = 1100 cm, D1 = 110 cm, L1 / D1 = 10, m = 10, L2 = 3000 cm,
D2 = 110 cm, L2 / D2 = 27.3, and n2 = 60 was used. The inside diameter
(D3) was increased to 200 cm over approximately 500 cm from the bottom
of the column, and in this portion there were installed 8 stages of baffle
trays K having a downcomer portion and for which a weir (height 10 cm)
was the baffle. It was devised such that some liquid was continuously
withdrawn from a lower portion of the uppermost stage of the baffle trays
K, the withdrawn liquid being heated by a reboiler, and then fed back into
an upper portion of this stage. Moreover, in the enrichment section, an
upper portion was packed with Mellapak with a theoretical number of
stages of 52, one chimney tray stage was installed below the Mellapak,
and 8 stages of trays were provided below the chimney tray. In this
example, sieve trays were used as the internals in the stripping section,
and sieve trays were used as the trays in the enrichment section. These
sieve trays had a cross-sectional area per hole of approximately 1.3 cm2.
In the stripping section, the number of holes in each of the sieve trays

was approximately 250 to 300 / m2, and the aperture ratio was in a range
of from 3 to 4%. Moreover, in the enrichment section, the number of
holes in each of the sieve trays was approximately 150 to 300 / m2, and
the aperture ratio was in a range of from 2.8 to 3.6%. The chimney tray
had four chimneys therein, each of the chimneys having S =
approximately 500 cm2 and h = 25 cm, and the aperture ratio being in a
range of from 18 to 25%. The chimney tray had a downcomer portion,
the weir height being 10 cm.
A starting material containing ethylene carbonate (EC) and
methanol (MeOH) (molar ratio MeOH / EC = 8.4) and a catalyst (KOH in
ethylene glycol subjected to thermal dehydration treatment; K
concentration 0.1 % by weight based on EC) was continuously fed into a
continuous multi-stage distillation column A, and reactive distillation was
carried out, whereby 3.205 ton / hr of a column bottom component AB
was continuously withdrawn. The ethylene carbonate conversion was
100%, and the ethylene glycol selectivity was 99.8%. The column
bottom component AB, which contained 0.99 ton / hr of methanol, 0.001
ton / hr of dimethyl carbonate, 0.009 ton / hr of 2-methoxyethanol, 2.186
ton / hr of ethylene glycol, and 0.019 ton / hr of diethylene glycol and
catalyst component, was continuously fed into a continuous multi-stage
distillation column C from an inlet. This inlet was installed between the
trays in the 10th and 11th stages from the bottom of the continuous
multi-stage distillation column C.
The continuous multi-stage distillation column C was operated
continuously with a column bottom temperature of approximately 200 °C,
a column top pressure of approximately 11000 Pa, and a reflux ratio of

0.9. Moreover, the column bottom liquid level was kept below the
lowermost one of the trays K.
It was possible to attain stable steady state operation after 24
hours.
A column top component CT containing 0.968 ton / hr of methanol,
and 0.001 ton / hr of dimethyl carbonate, a side cut component Cs
containing 0.022 ton / hr of methanol, 0.009 ton / hr of 2-methoxyethanol,
and 0.004 ton / hr of ethylene glycol, and a column bottom component CB
containing 2.182 ton / hr of ethylene glycol, and 0.019 ton / hr of
diethylene glycol, catalyst component and high boiling point by-products
were continuously withdrawn from the continuous multi-stage distillation
column C.
The content of ethylene glycol in the column top component CT
was not more than 5 ppm, i.e. substantially zero. Moreover, the content
of ethylene glycol in the side cut component Cs was 0.18% of the
ethylene glycol fed into the continuous multi-stage distillation column C.
The concentration of ethylene glycol in the column bottom
component CB was 99.1 % by weight. Moreover, 99.82% of the ethylene
glycol fed into the continuous multi-stage distillation column C was
recovered as the column bottom component CB- The ethylene glycol
yield based on the ethylene carbonate was 99.6%.
Prolonged continuous operation was carried out under these
conditions. After 500 hours, 2000 hours, 4000 hours, 5000 hours, and
6000 hours, the produced amounts of ethylene glycol per hour were
2.182 ton, 2.182 ton, 2.182 ton, 2.182 ton, and 2.182 ton, and hence
operation was very stable.

Example 2:
A starting material containing ethylene carbonate (3.565 ton / hr)
and methanol (molar ratio MeOH / EC = 8) and a catalyst (KOH in
ethylene glycol subjected to thermal dehydration treatment; K
concentration 0.1 % by weight based on EC) was continuously fed into a
continuous multi-stage distillation column A, and reactive distillation was
carried out, whereby dimethyl carbonate and ethylene glycol were
produced with similar reaction results to in Example 1, a column bottom
component AB having ethylene glycol as a main component thereof being
continuously withdrawn. The ethylene glycol was separated out by
distillation using the same continuous multi-stage distillation column C as
in Example 1 and a similar process.
It was possible to attain stable steady state operation after 24
hours.
The column bottom component CB, which was continuously
withdrawn from the continuous multi-stage distillation column C at 2.472
ton / hr, contained 2.439 ton / hr of ethylene glycol, and 0.033 ton / hr of
diethylene glycol, catalyst component and high boiling point by-products.
The concentration of ethylene glycol in the column bottom component CB
was 99.1 % by weight. Moreover, 99.8% of the ethylene glycol fed into
the continuous multi-stage distillation column C was recovered as the
column bottom component CB. The ethylene glycol yield based on the
ethylene carbonate was 99.5%.
Prolonged continuous operation was carried out under these
conditions. After 1000 hours, 2000 hours, 3000 hours, and 5000 hours,

the produced amounts of ethylene glycol per hour were 2.439 ton, 2.439
ton, 2.439 ton, and 2.439 ton, and hence operation was very stable.
Example 3:
A continuous multi-stage distillation column C very similar to that
used in Example 1 was used. However, the number of holes in each of
the sieve trays in the stripping section and the enrichment section was
approximately 550 to 650 / m2, and the aperture ratio was in a range of
from 6.5 to 8.5%.
A starting material containing ethylene carbonate (8.20 ton / hr)
and methanol (molar ratio MeOH / EC = 9) and a catalyst (KOH in
ethylene glycol subjected to thermal dehydration treatment; K
concentration 0.1 % by weight based on EC) was continuously fed into a
continuous multi-stage distillation column A, and reactive distillation was
carried out, whereby dimethyl carbonate and ethylene glycol were
produced with similar reaction results to in Example 1, a column bottom
component AB having ethylene glycol as a main component thereof being
continuously withdrawn. The ethylene glycol was separated out by
distillation using the continuous multi-stage distillation column C and a
similar process to Example 1.
It was possible to attain stable steady state operation after 24
hours.
The column bottom component CB, which was continuously
withdrawn from the continuous multi-stage distillation column C at 5.852
ton / hr, contained 5.754 ton / hr of ethylene glycol, and 0.098 ton / hr of
diethylene glycol, catalyst component and high boiling point by-products.

The concentration of ethylene glycol in the column bottom component CB
was 98.3 % by weight. Moreover, 99.8% of the ethylene glycol fed into
the continuous multi-stage distillation column C was recovered as the
column bottom component CB. The ethylene glycol yield based on the
ethylene carbonate was 99.6%.
Prolonged continuous operation was carried out under these
conditions. After 500 hours, 1000 hours, and 1500 hours, the produced
amounts of ethylene glycol per hour were 5.754 ton, 5.754 ton, and 5.754
ton, and hence operation was very stable.
Industrial Applicability
According to the present invention, there are provided a specific
industrial apparatus and industrial production process that are
inexpensive and enable a diol to be produced in an amount of not less
than 1 ton / hr, preferably not less than 2 tons / hr, more preferably 3
tons / hr, stably for a prolonged period of time (e.g. not less than 1000
hours, preferably not less than 3000 hours, more preferably not less than
5000 hours) by taking a cyclic carbonate and an aliphatic monohydric
alcohol as starting materials, continuously feeding the starting materials
into a continuous multi-stage distillation column A in which a catalyst is
present, carrying out reactive distillation in the column A, continuously
withdrawing a low boiling point reaction mixture AT containing a produced
dialkyl carbonate and the aliphatic monohydric alcohol from an upper
portion of the column A in a gaseous form, continuously withdrawing a
high boiling point reaction mixture AB containing a produced diol from a
lower portion of the column A in a liquid form, then continuously feeding

the high boiling point reaction mixture AB into a continuous multi-stage
distillation column C for separating off material having a lower boiling
point than that of the diol contained in the high boiling point reaction
mixture As, continuously obtaining the material having a lower boiling
point than that of the diol as a column top component d and a side cut
component Cs, and continuously obtaining the diol substantially not
containing the material having a lower boiling point than that of the diol
as a column bottom component CB- The present invention is thus very
useful industrially.

CLAIMS
We claim:
1. An am industrial process for the production of a diol in which a diol is produced by taking a cyclic carbonate and an aliphatic
monohydric alcohol as starting materials, continuously feeding the
starting materials into a continuous multi-stage distillation column A in
which a catalyst is present, carrying out reactive distillation in said
column A, continuously withdrawing a low boiling point reaction mixture
AT containing a produced dialkyl carbonate and said aliphatic monohydric
alcohol from an upper portion of the column A in a gaseous form,
continuously withdrawing a high boiling point reaction mixture AB
containing a produced diol from a lower portion of the column A in a
liquid form, then continuously feeding said high boiling point reaction
mixture AB into a continuous multi-stage distillation column C for
separating off material having a lower boiling point than that of the diol
contained in said high boiling point reaction mixture AB, continuously
obtaining the material having a lower boiling point than the diol as a
column top component CT and a side cut component Cs, and
continuously obtaining the diol substantially not containing the material
having a lower boiling point than that of the diol as a column bottom
component CB, wherein the improvement comprises:
(a) said continuous multi-stage distillation column C comprises a
continuous multi-stage distillation column comprising a stripping section
having a length L1 (cm), an inside diameter D1 (cm) and an internal with
a number of stages n1 thereinside, and an enrichment section having a
length L2 (cm), an inside diameter D2 (cm) and an internal with a number

of stages n2 thereinside, wherein L1, D1, n1, L2, D2, and n2 satisfy the
following formulae (1) to (9):
300 50 3 3 1000 50 10 20 D2 (b) the enrichment section of said continuous multi-stage
distillation column C has at least one chimney tray installed therein as an
internal, said chimney tray having installed therein one or more chimneys
each having an opening having a cross-sectional area S (cm2) satisfying
the formula (10):
200 and each of the chimneys being such that a height h (cm) from said
opening of said chimney to a gas outlet of said chimney satisfies the
formula (11):
10 (c) a side cut outlet is connected to a liquid collecting portion of
said chimney tray of said continuous multi-stage distillation column C.
2. The process according to Claim 1, wherein an amount
produced of the diol is not less than 1 ton / hr.

3. The process according to Claim 1 or 2, wherein a plurality
(n3 stages) of trays K are further provided in a lower portion of the
internals in a lowermost portion of the stripping section which is in a
lower portion of said continuous multi-stage distillation column C, a liquid
is continuously withdrawn from an uppermost stage of said trays K, and
after heat is given to require for distillation in a reboiler, the heated liquid
is returned into the distillation column C from a feeding port provided
between the uppermost stage of the trays K and the internal in the
lowermost portion of the stripping section, while a remainder of the liquid
is fed into a lower tray in order.
4. The process according to Claim 3, wherein each of the
trays K is a baffle tray.
5. The process according to Claim 3 or 4, wherein an inside
diameter D3 of said continuous multi-stage distillation column C where
the trays K are present satisfies D1 6. The process according to any one of Claims 3 to 5, wherein
L1, D1, L1 / D1, n1, L2, D2, L2 / D2, n2, and n3for said continuous
multi-stage distillation column C satisfy respectively 500 15 7. The process according to any one of Claims 1 to 6, wherein

the internal in the stripping section of said continuous multi-stage
distillation column C and the internal excluding the chimney tray in the
enrichment section are trays and / or packings.
8. The process according to Claim 7, wherein the internal in
the stripping section of said continuous multi-stage distillation column C
is the tray, and the internal excluding the chimney tray in the enrichment
section are trays and / or structured packings.
9. The process according to Claim 7 or 8, wherein said tray is
a sieve tray.
10. The process according to Claim 9, wherein said sieve tray
has 100 to 1000 holes / m2 in a sieve portion thereof, and a
cross-sectional area per hole in a range of from 0.5 to 5 cm2.
11. The process according to Claim 9 or 10, wherein an
aperture ratio (a ratio of a total cross-sectional area of the hole in one
tray stage to an area of the tray) of said sieve tray in the enrichment
section of said continuous multi-stage distillation column C is in a range
of from 2 to 15%.
12. The process according to any one of Claims 9 to 11,
wherein an aperture ratio (a ratio of a total cross-sectional area of the
hole in one tray stage to an area of the tray) of said sieve tray in the
enrichment section of said continuous multi-stage distillation column C is

in a range of from 1.5 to 12%.
13. The process according to any one of Claims 1 to 12,
wherein an aperture ratio (a ratio of a total cross-sectional area of the
opening in the chimney to an area of the chimney tray including a total
cross-sectional area of the opening) of said chimney tray is in a range of
from 10 to 40%.
14. The process according to any one of Claims 1 to 13,
wherein said continuous multi-stage distillation column C has a column
bottom temperature in a range of from 150 to 250 °C.
15. The process according to any one of Claims 1 to 14,
wherein said continuous multi-stage distillation column C has a column
top pressure in a range of from 50000 to 300000 Pa.
16. The process according to any one of Claims 1 to 15,
wherein said continuous multi-stage distillation column C has a reflux
ratio in a range of from 0.3 to 5.
17. The process according to any one of Claims 1 to 16,
wherein a content of the diol in said column top component CT is not
more than 100 ppm.
18. The process according to any one of Claims 1 to 17,
wherein a content of the diol in said side cut component Cs is not more

than 0.5% of the diol fed into said continuous multi-stage distillation
column C.
19. A continuous multi-stage distillation column being a
continuous multi-stage distillation column C for producing a diol by taking
a cyclic carbonate and an aliphatic monohydric alcohol as starting
materials, continuously feeding the starting materials into a continuous
multi-stage distillation column A in which a catalyst is present, carrying
out reactive distillation in said column A, continuously withdrawing a low
boiling point reaction mixture AT containing a produced dialkyl carbonate
and the aliphatic monohydric alcohol from an upper portion of the column
A in a gaseous form, continuously withdrawing a high boiling point
reaction mixture AB containing a produced diol from a lower portion of the
column A in a liquid form, then continuously feeding said high boiling
point reaction mixture AB into a continuous multi-stage distillation column
C for separating off material having a lower boiling point than that of the
diol contained in said high boiling point reaction mixture AB, continuously
obtaining the material having a lower boiling point than that of the diol as
a column top component CT and a side cut component Cs, and
continuously obtaining the diol substantially not containing the material
having a lower boiling point than that of the diol as a column bottom
component CB, wherein the improvement comprises:
(a) said continuous multi-stage distillation column C comprises a
distillation column comprising a stripping section having a length L1 (cm),
an inside diameter D1 (cm) and an internal with a number of stages n1
thereinside, and an enrichment section having a length L2 (cm), an inside

diameter D2 (cm) and an internal with a number of stages n2 thereinside, wherein L1, D1,
n1, L2, D2 and n2 satisfy the following formulae (1) to (9):

(b) the enrichment section of said continuous multi-stage distillation column C
has at least one chimney tray (9) installed therein as an internal, the chimney tray (9)
having installed therein one or more chimneys each having an opening having a cross-
sectional area S (sm2) satisfying the formula (10):

and each of the chimneys being such that a height h (cm) from said opening of said
chimney to a gas outlet of the chimney satisfies the formula (11):

(c) a side cut outlet (4) is connected to a liquid collecting portion of said
chimney tray of said continuous multi-stage distillation column C.
20. The continuous multi-stage distillation column according to Claim 19,
wherein a plurarity (n3 stages) of trays K are further provided in

a lower portion of the internals in a lowermost portion of the stripping
section which is in a lower portion of said continuous multi-stage
distillation column C, a liquid is continuously withdrawn from an
uppermost stage of the trays K, and after heat is given to require for
distillation in a reboiler, the heated liquid is returned into the distillation
column C from a feeding port provided between the uppermost stage of
the trays K and the internal in the lowermost portion of the stripping
section, while a remainder of the liquid is fed into a lower tray in order.
2A. The continuous multi-stage distillation column according to
Claim 20, wherein each of the trays K is a baffle tray.
22. The continuous multi-stage distillation column according to
Claim 20 or 21, wherein an inside diameter D3 of said column where the
trays K are present satisfies D1 23. The continuous multi-stage distillation column according to
any one of Claims 19 to 22, wherein L1, D1, L1 / D1, n1, L2, D2, L2 / D2, n2,
and n3 satisfy respectively 500 20, 5 n2 24. The continuous multi-stage distillation column according to
any of Claims 19 to 23, wherein the internal in the stripping section of
the stripping section and the internal excluding the chimney tray in the
enrichment section are trays and / or packings.

25. The continuous multi-stage distillation column according to
Claim 24, wherein the internal in the stripping section is a tray, and the
internal excluding the chimney tray in the enrichment section is a tray
and/or a structured packing.
26. The continuous multi-stage distillation column according to
Claim 24 or 25, wherein said tray is a sieve tray.
27. The continuous multi-stage distillation column according to
Claim 26, wherein said sieve tray has 100 to 1000 holes / m2 in a sieve
portion thereof, and a cross-sectional area per hole in a range of from
0.5 to 5 cm2.
28. The continuous multi-stage distillation column according to
Claim 26 or 27, wherein an aperture ratio (a ratio of a total
cross-sectional area of the hole in one tray stage to an area of the tray)
of said sieve tray in the stripping section is in a range of from 2 to 15%.
29. The continuous multi-stage distillation column according to
any one of Claims 26 to 28, wherein an aperture ratio (a ratio of a total
cross-sectional area of the hole in one tray stage to an area of the tray)
of said sieve trays in the enrichment section is in a range of from 1.5 to
12%.
30. The continuous multi-stage distillation column according to

any one of Claims 19 to 29, wherein an aperture ratio (a ratio of a total
cross-sectional area of the opening in the chimneys to an area of the
chimney tray including a total cross-sectional area of the opening) of said
chimney tray is in a range of from 10 to 40%.



ABSTRACT OF THE DISCLOSURE


TITLE OF THE INVENTION :- INDUSTRIAL PROCESS FOR THE
PRODUCTION OF DIOL.
It is an object of the present invention to provide a specific
apparatus and process for producing a diol by taking a cyclic carbonate
and an aliphatic monohydric alcohol as starting materials, continuously
feeding the starting materials into a continuous multi-stage distillation
column A in which a catalyst is present, carrying out reactive distillation
in the column A, continuously withdrawing a low boiling point reaction
mixture AT containing a produced dialkyl carbonate and the aliphatic
monohydric alcohol from an upper portion of the column A in a gaseous
form, continuously withdrawing a high boiling point reaction mixture AB
containing a produced diol from a lower portion of the column A in a
liquid form, continuously feeding the high boiling point reaction mixture
AB into a continuous multi-stage distillation column C, distilling off
material having a lower boiling point than that of the diol contained in the
high boiling point reaction mixture AB as a column top component CT and
a side cut component Cs so as to obtain a column bottom component CB,
continuously feeding the column bottom component CB into a continuous
multi-stage distillation column C, and obtaining the diol as a side cut
component Es from a side cut outlet of the continuous multi-stage
distillation column C. Moreover, it is an object to thus provide a specific
industrial apparatus and industrial production process that are
inexpensive and, for example, enable the diol to be produced in an
amount of not less than 1 ton / hr, preferably not less than 2 tons / hr,
more preferably not less than 3 tons / hr, stably for a prolonged period of
time (e.g. not less than 1000 hours, preferably not less than 3000 hours,

more preferably not less than 5000 hours). According to the present
invention, the above objects can be attained by using a continuous
multi-stage distillation column C having a specified structure, and
withdrawing a liquid component from the side cut outlet, which is
installed at the bottom of a chimney tray having a specified structure
installed in an enrichment section of the continuous multi-stage
distillation column C.

Documents:

00953-kolnp-2008-abstract.pdf

00953-kolnp-2008-claims.pdf

00953-kolnp-2008-correspondence others.pdf

00953-kolnp-2008-description complete.pdf

00953-kolnp-2008-drawings.pdf

00953-kolnp-2008-form 1.pdf

00953-kolnp-2008-form 2.pdf

00953-kolnp-2008-form 3.pdf

00953-kolnp-2008-form 5.pdf

00953-kolnp-2008-gpa.pdf

00953-kolnp-2008-international publication.pdf

00953-kolnp-2008-international search report.pdf

00953-kolnp-2008-others pct form.pdf

00953-kolnp-2008-pct priority document notification.pdf

00953-kolnp-2008-pct request form.pdf

00953-kolnp-2008-translated copy of priority document.pdf

953-KOLNP-2008-(08-11-2011)-ABSTRACT.pdf

953-KOLNP-2008-(08-11-2011)-AMANDED CLAIMS.pdf

953-KOLNP-2008-(08-11-2011)-DESCRIPTION (COMPLETE).pdf

953-KOLNP-2008-(08-11-2011)-DRAWINGS.pdf

953-KOLNP-2008-(08-11-2011)-EXAMINATION REPORT REPLY RECIEVED.pdf

953-KOLNP-2008-(08-11-2011)-FORM 1.pdf

953-KOLNP-2008-(08-11-2011)-FORM 2.pdf

953-KOLNP-2008-(08-11-2011)-FORM 3.pdf

953-KOLNP-2008-(08-11-2011)-OTHERS.pdf

953-KOLNP-2008-(08-11-2012)-ANNEXURE TO FORM 3.pdf

953-KOLNP-2008-(08-11-2012)-CORRESPONDENCE.pdf

953-KOLNP-2008-(09-10-2013)-ANNEXURE TO FORM 3.pdf

953-KOLNP-2008-(09-10-2013)-CORRESPONDENCE.pdf

953-KOLNP-2008-(21-11-2012)-ANNEXURE TO FORM 3.pdf

953-KOLNP-2008-(21-11-2012)-CORRESPONDENCE.pdf

953-KOLNP-2008-(25-07-2013)-CORRESPONDENCE.pdf

953-KOLNP-2008-(26-09-2012)-CORRESPONDENCE.pdf

953-KOLNP-2008-(30-07-2012)-PETITION UNDER RULE 137.pdf

953-KOLNP-2008-CORRESPONDENCE OTHERS 1.1.pdf

953-KOLNP-2008-CORRESPONDENCE.pdf

953-KOLNP-2008-EXAMINATION REPORT.pdf

953-KOLNP-2008-FORM 18.pdf

953-KOLNP-2008-GPA.pdf

953-KOLNP-2008-GRANTED-ABSTRACT.pdf

953-KOLNP-2008-GRANTED-CLAIMS.pdf

953-KOLNP-2008-GRANTED-DESCRIPTION (COMPLETE).pdf

953-KOLNP-2008-GRANTED-DRAWINGS.pdf

953-KOLNP-2008-GRANTED-FORM 1.pdf

953-KOLNP-2008-GRANTED-FORM 2.pdf

953-KOLNP-2008-GRANTED-FORM 3.pdf

953-KOLNP-2008-GRANTED-FORM 5.pdf

953-KOLNP-2008-GRANTED-SPECIFICATION-COMPLETE.pdf

953-KOLNP-2008-INTERNATIONAL PUBLICATION.pdf

953-KOLNP-2008-INTERNATIONAL SEARCH REPORT & OTHERS.pdf

953-KOLNP-2008-OTHERS-.pdf

953-KOLNP-2008-OTHERS.pdf

953-KOLNP-2008-PETITION UNDER RULE 12.pdf

953-KOLNP-2008-REPLY TO EXAMINATION REPORT.pdf

953-KOLNP-2008-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf


Patent Number 258391
Indian Patent Application Number 953/KOLNP/2008
PG Journal Number 02/2014
Publication Date 10-Jan-2014
Grant Date 06-Jan-2014
Date of Filing 04-Mar-2008
Name of Patentee ASAHI KASEI CHEMICALS CORPORATION
Applicant Address 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 SHINSUKE FUKUOKA 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
2 HIROSHI HACHIYA 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
3 KAZUHIKO MATSUZAKI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
4 HIRONORI MIYAJI 1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
PCT International Classification Number C07C 27/02,B01D 3/14
PCT International Application Number PCT/JP2007/050810
PCT International Filing date 2007-01-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2006-017520 2006-01-26 Japan