U.S. patent application number 16/115136 was filed with the patent office on 2018-12-20 for method for phosgenating compounds containing hydroxyl, thiol, amino and/or formamide groups.
The applicant listed for this patent is Bayer Aktiengesellschaft. Invention is credited to Konstantinos METAXAS, Leslaw MLECZKO, Jens Stefan ROGGAN, Ralph SCHELLEN, Aurel WOLF.
Application Number | 20180361349 16/115136 |
Document ID | / |
Family ID | 54064280 |
Filed Date | 2018-12-20 |
United States Patent
Application |
20180361349 |
Kind Code |
A1 |
MLECZKO; Leslaw ; et
al. |
December 20, 2018 |
METHOD FOR PHOSGENATING COMPOUNDS CONTAINING HYDROXYL, THIOL, AMINO
AND/OR FORMAMIDE GROUPS
Abstract
The invention relates to a method particularly for reacting
phosgene with compounds that contain hydroxyl, thiol, amino and/or
formamide groups, comprising the steps of: (I) providing a reactor
which has a first reaction chamber (300, 310, 320, 330, 340, 350)
and a second reaction chamber (200, 210, 220, 230, 240, 250, 260),
the first and the second reaction chambers being separated from one
another by means of a porous carbon membrane (100, 110, 120, 130,
140, 150); (II) providing carbon monoxide and chlorine in the first
reaction chamber; and simultaneously (III) providing a compound
containing hydroxyl, thiol, amino and/or formamide groups in the
second reaction chamber. The porous carbon membrane is configured
to catalyse the reaction of carbon monoxide and chlorine to obtain
phosgene, and to allow this formed phosgene to pass into the second
reaction chamber. The invention also relates to a reactor that is
suitable for carrying out the claimed method.
Inventors: |
MLECZKO; Leslaw; (Dormagen,
DE) ; WOLF; Aurel; (Wulfrath, DE) ; SCHELLEN;
Ralph; (Dormagen, DE) ; METAXAS; Konstantinos;
(Koln, DE) ; ROGGAN; Jens Stefan; (Koln,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bayer Aktiengesellschaft |
Leverkusen |
|
DE |
|
|
Family ID: |
54064280 |
Appl. No.: |
16/115136 |
Filed: |
August 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15503855 |
Feb 14, 2017 |
10105675 |
|
|
PCT/EP2015/068811 |
Aug 17, 2015 |
|
|
|
16115136 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 7/01 20130101; C07C
263/10 20130101; B01J 19/0013 20130101; C07C 68/02 20130101; C01F
7/02 20130101; C07C 69/96 20130101; B01J 19/2475 20130101; C01B
32/80 20170801; C07C 68/02 20130101; B01J 2523/31 20130101; B01J
19/1893 20130101; B01J 31/0231 20130101; B01J 2219/00085 20130101;
C07C 69/96 20130101 |
International
Class: |
B01J 19/18 20060101
B01J019/18; B01J 19/00 20060101 B01J019/00; B01J 19/24 20060101
B01J019/24; B01J 31/02 20060101 B01J031/02; C07C 69/96 20060101
C07C069/96; C01B 7/01 20060101 C01B007/01; C01B 32/80 20170101
C01B032/80; C07C 68/02 20060101 C07C068/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2014 |
DE |
10 2014 111 902.9 |
Claims
1. A reactor for reaction of phosgene with one or more_compounds
containing one or more hydroxyl, thiol, amino and/or formamide
groups, comprising: a first reaction space and a second reaction
space, wherein the first and second reaction spaces are separated
from one another by a porous carbon membrane; and a catalyst for
the reaction of phosgene with the compound containing hydroxyl,
thiol, amino and/or formamide groups, arranged at least partly on
the side of the porous carbon membrane facing the second reaction
space.
2. The reactor as claimed in claim 1, wherein an open-cell foam is
additionally present in the first reaction space.
3. The reactor as claimed in claim 1, wherein the reactor comprises
a multitude of first reaction spaces surrounded by a common second
reaction space.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a Divisional Application of U.S. patent application
Ser. No. 15/503,855, filed Aug. 17, 2015, which is a .sctn. 371
National Stage Application of PCT/EP2015/068811, filed Aug. 17,
2015, which claims priority to German Application No. 10 2014 111
902.9 filed Aug. 20, 2014. Each of these applications is
incorporated by reference in its entirety.
BACKGROUND
Field of the Invention
[0002] The studies that led to this invention were supported under
Grant Agreement No. 245988-1 as part of the Seventh Framework
Programme of the European Union (FP7/2007-2013)-INCAS (Integration
of Nanoreactor and multisite Catalysis for a Sustainable chemical
production).
Description of Related Art
[0003] The present invention relates to a method of reaction of
phosgene with compounds containing hydroxyl, thiol, amino and/or
formamide groups, comprising the steps of: (I) providing a reactor
comprising a first reaction space and a second reaction space,
wherein the first and second reaction spaces are separated from one
another by a porous carbon membrane; (II) providing carbon monoxide
and chlorine in the first reaction space; and simultaneously (III)
providing a compound containing hydroxyl, thiol, amino and/or
formamide groups in the second reaction space. It further relates
to a reactor suitable for performing the method of the
invention.
[0004] Phosgene (COCl.sub.2) is a key reagent in the production of
pharmaceuticals, polyurethanes and polycarbonates. It is a very
reactive but also very toxic chemical, and the industrial scale
production process, because of the amounts of phosgene (hold-up)
present in a plant, always harbors risks to the environment in the
event of an unintended release resulting from leaks in pipelines or
other damage to plant components.
[0005] One example of the industrial scale use of phosgene as key
reagent is the preparation of diphenyl carbonate (DPC). DPC is an
important intermediate for the synthesis of high-quality
polycarbonates, for example through transesterification with
bisphenol A. The synthesis of DPC proceeding from phenol and
phosgene (direct phosgenation) proceeds in two steps: the first
step comprises the preparation of phosgene in a gas phase reaction
of carbon monoxide and chlorine, which typically occurs over
activated carbon catalysts in a multitube fixed bed reactor.
According to the boiling temperature of the cooling medium in the
reactors, a distinction is made between phosgene preparation in
cold combiners or hot combiners. By reaction of phenol with
phosgene in the presence of a suitable catalyst, DPC is ultimately
obtained. DPC preparation via direct phenol phosgenation, in
comparison with the conventional interfacial methods (reaction of
sodium phenoxide with phosgene), offers the advantage that the
formation of large amounts of NaCl waste products is avoided.
[0006] Both the phosgene synthesis and the DPC synthesis are highly
exothermic reactions with enthalpies of reaction of -107 and -54
kJ/mol. Particularly the exothermicity of the phosgene synthesis in
the gas phase requires efficient cooling systems, but it is not
possible to prevent hotspots in the reactor with local temperatures
of more than 500.degree. C. (cf. Mitchell et al., Catal. Sci.
Technol., 2012). The occurrence of temperatures of more than
300.degree. C. does not just lead to elevated material stress in
the reactor but also adversely affects the equilibrium reaction of
phosgene formation (the breakdown of phosgene predominates at more
than 300.degree. C.) and additionally increases the rate of
deactivation of the catalyst, such that there is an overall drop in
space-time yield and process efficient.
[0007] From the point of view of smaller hold-up volumes for
improvement of process safety, microstructured reactors are of
interest. For instance, U.S. Pat. No. 6,932,951 describes a
microstructured reactor for the hydrogenation of cyclohexene to
cyclohexane as an example application.
[0008] CN 101757859 A describes a carbon membrane reactor and a
method for use thereof. It is a feature of the carbon membrane
reactor that a defect-free carbon membrane is bonded to the housing
of the reactor and a cavity is formed within the housing of the
reactor, with the cavity that communicates with a charge orifice
and an outlet orifice for coreactants forming a charge side and the
cavity with an inlet and an outlet for purge gas communicates
forming a passage side. The defect-free carbon membrane is filled
with catalysts; alternatively, the catalysts are presented on the
defect-free carbon membrane.
[0009] A review article on the topic of carbon membranes is "A
review on the latest development of carbon membranes for gas
separation", A. F. Ismail, L. I. B. David/Journal of Membrane
Science 193 (2001) 1-18. A further publication is "Porous,
catalytically active ceramic membranes for gas-liquid reactions: a
comparison between catalytic diffuser and forced through flow
concept", M. Reif, R. Dittmeyer, Catalysis Today 82 (2003)
3-14.
SUMMARY
[0010] Considering the present state of development, a demand for a
method with the reduced phosgene hold-up is apparent. In the
context of the invention, such a method is provided. More
particularly, it was an object of the invention to provide a
phosgenation method in which minimum amounts of free phosgene are
present in the reaction system.
[0011] This object is achieved in accordance with the invention by
a method of reacting a first compound with a second compound,
[0012] wherein the first compound has a GHS hazard identification
of GHS06 and is obtainable from the reaction of at least one first
fluid precursor compound and a second fluid precursor compound
[0013] and wherein the second compound is capable of a chemical
reaction with the first compound,
[0014] comprising the steps of:
[0015] (I) providing a reactor comprising a first reaction space
and a second reaction space, wherein the first and second reaction
spaces are separated from one another by a porous carbon
membrane;
[0016] (II) providing the first and second precursor compounds in
the first reaction space;
[0017] and simultaneously
[0018] (III) providing the second compound in the second reaction
space;
[0019] wherein the porous carbon membrane is set up to: [0020]
catalyze the reaction of the first and second precursor compounds
to give the first compound and [0021] allow the first compound
formed to move into the second reaction space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1-8 depict embodiments as described herein.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0023] It is envisaged in accordance with the invention that the
first compound has a hazard identification according to GHS
(Globally Harmonized System of Classification, Labelling and
Packaging of Chemicals of the United Nations) of GHS06. In the
European Union, this is legislated for by Directive (EC) No.
1272/2008, also called CLP Regulation. The classification GHS06
refers to toxic or very toxic substances.
[0024] With regard to the first fluid precursor compound and the
second fluid precursor compound, gases and liquids are envisaged in
accordance with the invention, including solutions of solids in a
solvent.
[0025] More particularly, the first compound may be phosgene, the
first precursor compound may be carbon monoxide, the second
precursor compound may be chlorine and the second compound may be a
compound containing hydroxyl, thiol, amino and/or formamide
groups.
[0026] Because of the major importance of the reaction of phosgene
with a compound containing hydroxyl, thiol, amino and/or formamide
groups, the present invention is elucidated in connection with this
first and second compound, without being restricted thereto.
[0027] In the method of the invention, phosgene occurs only as a
comparatively short-lived intermediate. The gas mixture of carbon
monoxide and chlorine present in the first reaction space reacts on
passage through the catalytically active carbon membrane to give
phosgene. The phosgene formed in situ passes from the pores of the
carbon membrane into the second reaction space, where it reacts
with the compound containing hydroxyl, thiol, amino and/or
formamide groups.
[0028] The method of the invention can avoid the presence of any
great amounts of phosgene in the reaction system. A further
advantage is the avoidance of local hotspots in the phosgene
synthesis, as known from conventional plants. The compound
containing hydroxyl, thiol, amino and/or formamide groups also
serves to remove the heat of reaction. A low thickness of the
membrane likewise promotes the removal of heat. In addition, the
formation of NaCl as by-product is avoided with respect to the
conventional phase transfer method. Overall, the integration of two
reactions in one method results in an increase in the space-time
yield of the method over a longer period and the thermal stress on
the plant is reduced.
[0029] In step (I) of the method of the invention, a reactor is
provided. The design of the reactor is not stipulated further at
first and may, for example, be a tubular reactor for continuous
operation or a tank reactor for a batchwise mode of operation. The
reactor has two reaction spaces separated from one another by a
porous carbon membrane. One reaction space is envisaged for the
phosgene formation and one reaction space for the phosgenation.
Through the choice of suitable liquid and gas pressures in the two
reaction spaces, the passage of liquid reactants from the second
reaction space into the first reaction space can be prevented.
[0030] The porous carbon membrane may be a self-supporting membrane
or a membrane supported by a gas-permeable substrate. It can be
obtained by pyrolysis of organic precursor compounds or else from
carbon material produced beforehand, such as activated carbon,
graphene or carbon nanotubes (CNTs). If the porosity of the
membrane is suitable for the passage of phosgene, with the proviso
of catalytic activity for the phosgene synthesis, carbon membranes
from the industrial gas separation sector can be used.
[0031] The term "porous" in connection with the carbon membranes
means here that pores connected to one another that are present in
the membrane enable a path through the membrane at least for the
phosgene molecules formed.
[0032] Steps (II) and (III) of the method of the invention are
conducted simultaneously, in order that the phosgene formed in situ
can react further very quickly. Examples of suitable compounds
containing hydroxyl, thiol, amino and/or formamide groups are
aromatic alcohols such as phenol, aliphatic alcohols, primary
aromatic amines, secondary aromatic amines, primary aliphatic
amines, secondary aliphatic amines, N,N-dimethylformamide and
N-methylformanilide. Especially aromatic and aliphatic alcohols and
formamides are preferred; the former because of the use of the
reaction products in polycarbonate production and the latter
because of their use in Vilsmeier-Haack formylations. Preference is
further given to primary amines, since they can be converted by
phosgenation to the corresponding isocyanates which are used in
polyurethane production.
[0033] Overall, the membrane can thus also be regarded as a pore
reactor.
[0034] Corrosion-sensitive surfaces in the reactor can be
protected, for example, by means of a stainless steel or SiO.sub.2
coating.
[0035] With regard to the reaction conditions in the method of the
invention, the reaction temperature for the phosgene synthesis may
advantageously be between 80 and 300.degree. C. and for the
phosgenation (especially of phenol) between 150 and 300.degree. C.
Particular preference is given to a reaction temperature in the
first and second reaction space of 190 to 210.degree. C.
[0036] The pressure in the first and second reaction space may, for
example, be 1 to 29 bar. Preference is given to a pressure of 24 to
26 bar. Especially within the preferred range, it is possible to
reduce the residence time such that it is a few minutes (by
contrast with one hour or more).
[0037] It is additionally advantageous in phosgenation reactions
when the porous carbon membrane is also set up in order to prevent
contact of Cl.sub.2 with the starting materials and products in the
second reaction space. In this way, it is possible to prevent the
formation of chlorination products, for example chlorophenols.
[0038] Further embodiments and aspects of the present invention are
elucidated hereinafter. They can be combined with one another as
desired unless the opposite is apparent from the context.
[0039] In one embodiment of the method of the invention, the porous
carbon membrane has a nominal pore size, determined by means of
mercury porosimetry (ISO 15901-1), of .gtoreq.0.01 to .ltoreq.10
.mu.m. The nominal pore size is understood as usual to mean the
maximum of the pore size distribution. Preferred nominal pore sizes
are .gtoreq.0.1 to .ltoreq.1.0 .mu.m.
[0040] The membrane preferably in each case independently has the
following further properties:
[0041] Thickness: .gtoreq.1 to .ltoreq.10 mm
[0042] Specific surface area (BET): .gtoreq.100 to .ltoreq.2000
m.sup.2/g
[0043] Porosity: .gtoreq.0.1 to .ltoreq.0.5
[0044] Tortuosity: .gtoreq.1 to .ltoreq.15
[0045] Thermal conductivity: .gtoreq.1 to .ltoreq.175 W/m/K
[0046] Membrane loading in the reactor: .gtoreq.300 to .ltoreq.800
kg/m.sup.3
[0047] In a further embodiment of the method of the invention, the
porous carbon membrane further comprises a catalyst for the
reaction of the first compound (preferably of phosgene) with the
second compound (preferably the compound containing hydroxyl,
thiol, amino and/or formamide groups), arranged at least partly on
the side of the porous carbon membrane facing the second reaction
space. Appropriately, the catalyst is a heterogeneous catalyst. In
the case of the phosgenation of aromatic alcohols such as phenol,
it is possible to use Al.sub.2O.sub.3, for example
[0048] In a further embodiment of the method of the invention, a
homogeneous catalyst is additionally present in the second reaction
space. The catalyst, preferably for the reaction of phosgene with
the compound containing hydroxyl, thiol, amino and/or formamide
groups, is thus dissolved in the reaction medium present in the
second reaction space. In the case of the phosgenation of aromatic
alcohols such as phenol, it is possible to use TiCl.sub.4 or
pyridine, for example.
[0049] In a further embodiment of the method of the invention, an
open-cell foam is additionally present in the first reaction space.
In principle, suitable foam materials are all of those that are
stable at the temperatures that exist in the phosgene synthesis and
especially up to 300.degree. C. The foam is preferably a metal or
ceramic foam. As well as better mixing of the CO and Cl .sub.2
reactants, a foam additionally has the property that the first
reaction space can be mechanically supported thereby. This is
advantageous especially in multilayer reactors.
[0050] In a further embodiment of the method of the invention, the
reactor further comprises a cavity to accommodate a heat transfer
fluid. In this way, it is possible to implement heat exchangers,
especially crossflow heat exchangers. Heat transfer fluids used may
be liquids such as water or oil or else gases such as air.
[0051] In a further embodiment of the method of the invention, the
reactor further comprises a dwell zone to complete the reaction of
the first compound (preferably phosgene) with the second compound
(preferably with the compound containing hydroxyl, thiol, amino
and/or formamide groups). Specifically in the case of multistage
reactions in which, for example, the reaction of phenol with
phosgene to give the chloroformate formed as an intermediate
proceeds quickly but the further reaction of the chloroformate with
phenol to give DPC proceeds more slowly, a dwell zone can result in
an increase in the yield of the reaction in the second reaction
space in flow direction after the phosgene synthesis (such that no
additional phosgene moves into the second reaction space).
[0052] In a further embodiment of the method of the invention, the
compound containing hydroxyl, thiol, amino and/or formamide groups
is phenol, dimethylformamide or N-methylformanilide.
[0053] In a further embodiment of the method of the invention, the
reactor comprises a multitude of first reaction spaces, second
reaction spaces and porous carbon membranes, wherein one first and
one second reaction space are separated from one another in each
case by a porous carbon membrane. It is thus possible to obtain
flat, multilayer and modular membrane reactors.
[0054] In a further embodiment of the method of the invention, the
reactor has a cylindrical construction with first reaction space
and second reaction spaces arranged concentrically from the inside
outward, wherein the first and second reaction spaces are separated
from one another by the porous carbon membrane. In that case, the
reactor behaves in principle like a bubble column reactor.
Preferably, two or more of these reactors are combined to form a
shell and tube reactor.
[0055] The individual cylindrical reactor may independently have
the following properties:
[0056] Diameter of the second reaction space: .gtoreq.3 to
.ltoreq.10 cm
[0057] Length of the second reaction space: .gtoreq.3 to .ltoreq.20
m
[0058] Dwell time of the reaction mixture in the second reaction
space: .gtoreq.1 to .ltoreq.60 minutes
[0059] Molar excess of phenol: .gtoreq.4 to .ltoreq.6
[0060] In a further embodiment of the method of the invention, the
first reaction space and/or the second reaction space have a
cross-sectional area at right angles to the flow direction of the
fluid flowing through of .gtoreq.810.sup.-5 to .ltoreq.810.sup.-4
m.sup.2. Preferably, the cross-sectional area is .gtoreq.110.sup.-4
to .ltoreq.710.sup.-4 m.sup.2 and more preferably
.gtoreq.210.sup.-4 to .ltoreq.610.sup.-4 m.sup.2.
[0061] In a further embodiment of the method of the invention, the
reactor comprises a multitude of first reaction spaces surrounded
by a common second reaction space.
[0062] As well as the planar design, preference is given to a form
of the carbon membrane in which it takes the form of a hollow
cylinder closed at one end.
[0063] The invention further relates to a reactor for reaction of
phosgene with compounds containing hydroxyl, thiol, amino and/or
formamide groups, comprising:
[0064] a first reaction space and a second reaction space, wherein
the first and second reaction spaces are separated from one another
by a porous carbon membrane;
[0065] and
[0066] a catalyst for the reaction of phosgene with the compound
containing hydroxyl, thiol, amino and/or formamide groups, arranged
at least partly on the side of the porous carbon membrane facing
the second reaction space.
[0067] Appropriately, the catalyst is a heterogeneous catalyst. In
the case of the phosgenation of aromatic alcohols such as phenol,
it is possible to use Al.sub.2O.sub.3, for example.
[0068] In one embodiment of the reactor of the invention, an
open-cell foam is additionally present in the first reaction space.
In principle, suitable foam materials are all of those that are
stable at the temperatures that exist in the phenol synthesis and
especially up to 300.degree. C. The foam is preferably a metal or
ceramic foam. As well as better mixing of the CO and Cl.sub.2
reactants, a foam has the further property that the first reaction
space can be mechanically supported. This is advantageous
especially in multilayer reactors.
[0069] In a further embodiment of the reactor of the invention, the
first reaction space and/or the second reaction space have a
cross-sectional area at right angles to the flow direction of the
fluid flowing through of .gtoreq.810.sup.-5 to .ltoreq.810.sup.-4
m.sup.2.
[0070] In a further embodiment of the reactor of the invention, the
porous carbon membrane has a nominal pore size, determined by means
of mercury porosimetry (ISO 15901-1), of .gtoreq.0.01 to .ltoreq.10
.mu.m. The nominal pore size is understood as usual to mean the
maximum of the pore size distribution. Preferred nominal pore sizes
are .gtoreq.0.1 to .ltoreq.1 .mu.m.
[0071] The membrane preferably in each case independently has the
following further properties:
[0072] Thickness: .gtoreq.1 to .ltoreq.10 mm
[0073] Specific surface area (BET): .gtoreq.100 to .ltoreq.2000
m.sup.2/g
[0074] Porosity: .gtoreq.0.1 to .ltoreq.0.5
[0075] Tortuosity: .gtoreq.1 to .ltoreq.15
[0076] Thermal conductivity: .gtoreq.1 to .ltoreq.175 W/m/K
[0077] Membrane loading in the reactor: .gtoreq.300 to .ltoreq.800
kg/m.sup.3
[0078] In a further embodiment of the reactor of the invention, the
reactor further comprises a cavity to accommodate a heat transfer
fluid. It is thus possible to implement heat exchangers, especially
crossflow heat exchangers. Heat transfer fluids used may be liquids
such as water or oil or else gases such as air.
[0079] In a further embodiment of the reactor of the invention, the
reactor further comprises a dwell zone to complete the reaction of
phosgene with the compound containing hydroxyl, thiol, amino and/or
formamide groups. Specifically in the case of multistage reactions
in which, for example, the reaction of phenol with phosgene to give
the chloroformate proceeds quickly but the reaction of the
chloroformate with phenol to give DPC proceeds more slowly, a dwell
zone can result in destruction of phosgene in the second reaction
space in flow direction after the phosgene synthesis (such that no
additional phosgene moves into the second reaction space).
[0080] In a further embodiment of the reactor of the invention, the
reactor comprises a multitude of first reaction spaces, second
reaction spaces and porous carbon membranes, wherein one first and
one second reaction space are separated from one another in each
case by a porous carbon membrane. It is thus possible to obtain
flat, multilayer and modular membrane reactors.
[0081] In a further embodiment of the reactor of the invention, the
reactor has a cylindrical construction with first reaction space
and second reaction space arranged concentrically from the inside
outward, wherein the first and second reaction spaces are separated
from one another by the porous carbon membrane. In that case, the
reactor behaves in principle like a bubble column reactor.
Preferably, two or more of these reactors are combined to form a
shell and tube reactor.
[0082] The individual cylindrical reactor may independently have
the following properties:
[0083] Diameter of the second reaction space: .gtoreq.3 to
.ltoreq.10 cm
[0084] Length of the second reaction space: .gtoreq.3 to .ltoreq.20
m
[0085] In a further embodiment of the reactor of the invention, the
first reaction space and/or the second reaction space have a
cross-sectional area at right angles to the flow direction of the
fluid flowing through of .gtoreq.810.sup.-5 to .ltoreq.810.sup.4
m.sup.2.
[0086] In a further embodiment of the reactor of the invention, the
reactor comprises a multitude of first reaction spaces surrounded
by a common second reaction space.
[0087] The present invention is illustrated in detail by the
figures which follow, but without being restricted thereto. The
figures show:
[0088] FIG. 1 a cross section through a reactor for the method of
the invention
[0089] FIG. 2 a cross section through a further reactor for the
method of the invention
[0090] FIG. 3 a cross section through a further reactor for the
method of the invention
[0091] FIG. 4 a cross section through a further reactor for the
method of the invention
[0092] FIG. 5 a cross section through a further reactor for the
method of the invention
[0093] FIG. 6 a cross section through a further reactor for the
method of the invention
[0094] FIG. 7 simulation results for a method of the invention
[0095] FIG. 8 a cross section through a further reactor for the
method of the invention
[0096] FIG. 1 shows a schematic cross section through a reactor as
usable in the method of the invention. Two porous carbon membranes
100, 110 each separate a first reaction space 300, 310 from second
reaction spaces 200, 210. Arranged centrally is a further cavity
400 through which a heat transfer fluid can flow, such that the
cavity 400 can assume the function of a heat exchanger. The first
reaction spaces 300, 310 contain an open-pore foam which, as well
as a supporting function, also brings about better gas mixing. This
may, for example, be an open-pore metal foam. Carbon monoxide and
chlorine are introduced into the first reaction spaces 300, 310 and
react under catalysis by the membranes 100, 110 to give phosgene.
This phosgene passes through the pores of the membranes 100, 110
into the second reaction spaces 200, 210. In the second reaction
spaces 200, 210, a compound containing hydroxyl, thiol, amino
and/or formamide groups, such as phenol, is present, and reacts
with the phosgene. To promote this reaction, a catalyst may be
used. This may take the form of a homogeneous catalyst in second
reaction spaces 200, 210. Alternatively or additionally, a
heterogeneous catalyst may be present on the side of the membranes
100, 110 facing the second reaction spaces 200, 210.
[0097] FIG. 2 shows a schematic cross section through a further
reactor as usable in the method of the invention. The reactor shown
here differs from the reactor according to FIG. 1 by the central
arrangement of the first reaction space 320 which is delimited from
second reaction spaces 220, 230 at the top and bottom by porous
carbon membranes 120, 130. Arranged adjoining the second reaction
spaces 220, 230 are cavities 410, 420 to accommodate a heat
transfer fluid. The reactor shown in FIG. 2 is advantageous when a
greater amount of heat of reaction has to be removed compared to
the reactor from FIG. 1.
[0098] FIG. 3 shows a schematic cross section through a further
reactor as usable in the method of the invention. The reactor has a
concentric design, and so it is possible to implement a tubular
reactor or shell and tube reactor. The view shown here is a cross
section at right angles to the main axis of the reactor. On the
inside is the first reaction space 330 with an open-pore foam as
already described above. The porous carbon membrane 140 separates
the first reaction space 330 from the second reaction space 240.
Cavity 430 again serves to accommodate a heat transfer fluid.
[0099] FIG. 4 shows a schematic cross section through a further
reactor as usable in the method of the invention. The reactor is as
described in FIG. 1. DPC synthesis is to be elucidated here by way
of example. CO gas and Cl.sub.2 gas are introduced into the first
reaction spaces 300, 310 and form phosgene on passage through the
catalytically active carbon membrane 100, 110. On entry into the
second reaction spaces 200, 210, the phosgene formed in the
membrane 100, 110 reacts with phenol (PhOH) via the chloroformate
intermediate to give diphenyl carbonate (DPC). The streams of
phenol and of CO and Cl.sub.2 run orthogonally to one another.
Appropriately, a heat transfer fluid flows through the cavity 400,
likewise orthogonally to the flow direction of the phenol and
counter to the CO and Cl.sub.2 stream. In that case, it is possible
to implement a crossflow heat exchanger.
[0100] FIG. 5 shows a schematic cross section through a further
reactor as usable in the method of the invention. This is a tubular
reactor which may likewise be part of a shell and tube reactor. CO
gas and Cl.sub.2 gas are introduced into the first reaction space
340 and react on passage through the catalytically active, porous
carbon membrane 140 to form phosgene. On entry of phosgene into the
second reaction space 250, it reacts, for example, with phenol to
give diphenyl carbonate, with intermediate formation of the
chloroformate intermediate. The reaction product leaves the tubular
reactor at the upper end. In the case of the tubular reactors or
shell and tube reactors, direct cooling from the outside is
possible by means of a free-flowing heat transfer medium, such that
a separate cavity as in the reactors outlined above is
dispensable.
[0101] In the arrangement shown in FIG. 6, the difference from the
reactor according to FIG. 5 is that, in the second reaction space
250, in a dwell zone 500 present downstream of the porous carbon
membrane 150 viewed in flow direction of the phenol, the reaction
that proceeds in the second reaction space 250 can progress
further. Thus, if required, the overall conversion of the reaction
can be increased further.
[0102] FIG. 7 shows simulation results for a method of the
invention. The synthesis of DPC by phosgenation of phenol was
modeled on the basis of known kinetic information. Kinetics for
homogeneous and heterogeneous catalyses were introduced into the
model from in-house results. The physical properties were taken
from the Aspen Properties.RTM. software package and, where
possible, compared with the experimental Detherm database. The
specifications employed were: 99.9% conversion of Cl.sub.2 in the
phosgene synthesis, 100% conversion of the phosgene in the
phosgenation of phenol (no phosgene at the reactor outlet), maximum
temperature 300.degree. C. at the membrane. The pressure used was
25 bar, in order to effectively dissolve phosgene in the liquid
phenol and therefore to significantly reduce the lifetime thereof.
The molar ratio of phenol to phosgene required for 100% phosgene
conversion and for cooling of the reactor was >4:1. The reactor
used for the modeling corresponds to the setup shown in FIG. 6 and
therefore had a dwell zone 500. In FIG. 7, the phenol conversion
X(PhOH) and the temperature at the porous carbon membrane T are
plotted against the length of the tubular reactor. The reactor had
a total length of 4.5 meters. The section from 3 meters onward
corresponds to the dwell zone for full phosgene conversion; the
actual phosgene synthesis proceeds in the first 3 meters of the
reactor. The starting temperature of the phenol was 140.degree.
C.
[0103] An annual production of DPC of about 20 000 metric tonnes
can be achieved according to the above model calculation in a shell
and tube reactor with about 400 reactors according to FIG. 6.
[0104] FIG. 8 shows a schematic cross section through a further
reactor for the method of the invention. As can be seen, a
multitude of first reaction spaces 350 open at one end are present,
separated by membranes 150 from a common second reaction space 260.
At the lower end of the reactor, CO and chlorine gas are
introduced. The gas mixture passes into the first reaction spaces
and reacts under catalysis by the membranes to give phosgene, which
passes through the membranes. This is shown schematically by arrows
and the gas bubbles 600. At the lower end of the second reaction
space, phenol is introduced. This is in the liquid phase, for
example in molten form or in solution. The surface of the liquid
phase in the second reaction space is shown by the dotted line 700.
Accordingly, a gas phase is present above the liquid phase. In the
second reaction space, the phenol introduced reacts with the
phosgene that has passed through the membranes to give DPC. The
product mixture of DPC and unconverted phenol ("PhOH(exc.)") is
withdrawn at the upper end of the second reaction space. At the
upper end of the reactor, HCl as gaseous product and unconverted CO
("CO(exc.)") are discharged.
[0105] An annual production of DPC of about 20 000 metric tonnes
can be achieved according to the aforementioned model calculation
in a reactor with about 400 first reaction spaces according to FIG.
8.
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