CN113024417B - Method and device for strengthening separation in isocyanate preparation - Google Patents
Method and device for strengthening separation in isocyanate preparation Download PDFInfo
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- CN113024417B CN113024417B CN202110582954.8A CN202110582954A CN113024417B CN 113024417 B CN113024417 B CN 113024417B CN 202110582954 A CN202110582954 A CN 202110582954A CN 113024417 B CN113024417 B CN 113024417B
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C263/00—Preparation of derivatives of isocyanic acid
- C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C263/00—Preparation of derivatives of isocyanic acid
- C07C263/18—Separation; Purification; Stabilisation; Use of additives
- C07C263/20—Separation; Purification
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C265/00—Derivatives of isocyanic acid
- C07C265/14—Derivatives of isocyanic acid containing at least two isocyanate groups bound to the same carbon skeleton
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Abstract
The invention provides a method and a device for strengthening separation in isocyanate preparation, wherein the method comprises the following steps: under the action of a catalyst, carrying out thermal decomposition on an organic solvent solution containing carbamate under the blowing of protective gas to obtain a first material containing isocyanate and reaction blowing gas; the first material comprises a first flow, the first flow is subjected to heat exchange and then is subjected to countercurrent purging with the reaction purge gas to obtain a purge tail gas carrying a byproduct, and the first flow subjected to countercurrent purging is circulated to thermal decomposition for reaction; the second stream produces an isocyanate product; the method obviously improves the yield and purity of the isocyanate; the device is provided with the separation device connected with the reaction device, and the first flowing strand pipeline is connected to the upper inlet of the separation device, so that the reaction and the separation of products can be simultaneously realized with lower equipment cost, the operation cost is low, and the economic benefit is high.
Description
Technical Field
The invention relates to the technical field of isocyanate preparation, in particular to the technical field of non-phosgene isocyanate preparation, and particularly relates to a method and a device for reinforced separation in isocyanate preparation.
Background
Isocyanate is a main raw material for producing polyurethane, and is widely used in the industries of elastomers, coatings, plastics, pesticides, leather and the like. At present, the demand of isocyanate is increased year by year, so the application prospect of the isocyanate is very wide. The Isocyanate products on the market are mainly Phenylisocyanate (PI), diphenylmethane Diisocyanate (MDI), Toluene Diisocyanate (TDI), and Hexamethylene Diisocyanate (HDI).
The current production method of isocyanates is mainly phosgene method, for example CN101805272A discloses a method for preparing isocyanate by interfacial phosgenation reaction, which comprises the following steps: (a) respectively flowing the polyamine solution stream and the phosgene solution stream through respective mixers, injecting the polyamine solution stream and the phosgene solution stream into a first-stage reactor at a contact included angle of 30-180 degrees, so that the polyamine solution stream and the phosgene solution stream are contacted and mixed, and carrying out a phosgenation reaction on an interface; (b) the obtained photochemical liquid enters a second-stage reactor, and photochemical reaction is continuously carried out to obtain photochemical liquid containing isocyanate; (c) separating and purifying the photochemical liquid containing the isocyanate to obtain an isocyanate product. However, the method uses highly toxic phosgene as a raw material, produces a large amount of hydrochloric acid as a byproduct, has complex production device, high requirements on equipment, more process flows and serious environmental pollution, and the byproduct in the product is not easy to separate, and is gradually eliminated, so that a non-phosgene method is developed on the basis of a phosgene method.
Currently, there is an increasing research on the preparation of isocyanates by non-phosgene methods, for example, CN1143952A discloses a process for preparing isocyanates, which uses aniline and carbon dioxide as raw materials to prepare MDI, and the process finally synthesizes MDI by using N-methyl phenyl carbamate, but the industrialization is not realized. CN103492364A discloses a method for producing toluene diisocyanate, which develops a TDI production process for synthesizing carbamate from an amino compound and carbon monoxide, and thermally hydrolyzing the carbamate to obtain isocyanate, but the method has the problems that the separation of a catalyst and a product is difficult, the catalyst corrodes equipment, and the like; WO0156977 discloses a process for producing TDI from dimethyl carbonate by reacting dimethyl carbonate with toluenediamine to form carbamate, which is then thermally decomposed to form TDI, but the process has disadvantages of long reaction time and complicated equipment, and the pyrolysis temperature of carbamate is relatively high.
Therefore, it is required to develop a method and apparatus for preparing isocyanate without phosgene, which can improve the yield of isocyanate.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a method and a device for enhanced separation in isocyanate preparation, which overcome the problems of serious environmental pollution, complex process route, difficult product concentration and separation and the like in the prior art, improve the reaction conversion rate and yield of the non-phosgene isocyanate preparation, can better realize product separation, are easy to meet the track with the prior industrial technology, can realize recycling, and are environment-friendly and pollution-free.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a process for enhancing the separation in the preparation of isocyanates, said process comprising the steps of:
under the action of a catalyst, carrying out thermal decomposition on an organic solvent solution containing carbamate under the blowing of protective gas to obtain a first material containing isocyanate and reaction blowing gas;
the first material comprises a first stream, the first stream is subjected to heat exchange and then is subjected to countercurrent purging with the reaction purge gas to obtain a purge tail gas carrying a byproduct, and the first stream subjected to countercurrent purging is circulated to thermal decomposition for reaction to generate isocyanate.
The method for enhancing the separation in the preparation of the isocyanate, which is provided by the invention, has the advantages that the product after the reaction is partially extracted, and the other part of the product is recycled to the thermal decomposition process after being swept and carried away by the reaction sweep gas and carrying the by-product with a lower boiling point, so that the content of the by-product in the thermal decomposition system is low, the heat in the reaction sweep gas is fully utilized, the reaction can be promoted to be carried out towards the direction of preparing the isocyanate, and the yield and the purity of the isocyanate product are obviously improved. The method provided by the invention reduces the separation process of the subsequent byproducts and isocyanate, and improves the economic benefit.
Preferably, the organic solvent comprises any one or a combination of at least two of an alkane, a halogenated hydrocarbon, an aromatic hydrocarbon, a halogenated aromatic hydrocarbon or an ether, wherein typical but non-limiting combinations are a combination of an alkane and a halogenated hydrocarbon, a combination of an alkane and an aromatic hydrocarbon, a combination of an aromatic hydrocarbon and a halogenated hydrocarbon, a combination of a halogenated aromatic hydrocarbon and a halogenated hydrocarbon, and a combination of an ether and a halogenated hydrocarbon.
The alkane includes any one or a combination of at least two of heptane, octane, nonane, decane, undecane, dodecane, tridecane, or the like, with typical but non-limiting combinations including heptane and nonane, heptane and octane, octane and nonane, and nonane and undecane.
The halogenated hydrocarbon includes any one or combination of at least two of chlorinated alkane, brominated alkane or iodo alkane, wherein typical but non-limiting combinations include a combination of chlorinated alkane and brominated alkane, a combination of chlorinated alkane and iodo alkane, a combination of brominated alkane and iodo alkane, such as 1-chlorooctane, 1-bromononane or 1-iododecane, and the like.
The aromatic hydrocarbon includes any one or a combination of at least two of toluene, benzene, ethylbenzene, or para-xylene, wherein typical but non-limiting combinations include a combination of toluene and benzene, a combination of toluene and ethylbenzene, a combination of benzene and ethylbenzene, and a combination of para-xylene and ethylbenzene.
The halogenated hydrocarbon includes any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, dibromobenzene or tribromobenzene, with typical but non-limiting combinations including chlorobenzene and dichlorobenzene combinations, chlorobenzene and dibromobenzene combinations, dichlorobenzene and trichlorobenzene combinations, and trichlorobenzene and tribromobenzene combinations.
Preferably, the organic solvent comprises any one of chlorobenzene, benzene, toluene or dichlorobenzene or a combination of at least two of chlorobenzene and benzene, a typical but non-limiting combination is chlorobenzene and benzene, benzene and toluene, toluene and dichlorobenzene. The organic solvent is preferable in the present invention, the carbamate can be dissolved better, and the organic solvent itself is inert and does not participate in the decomposition reaction, thereby reducing the generation of by-products.
Preferably, the urethane includes methyl toluenedicarbamate, methyl diphenylmethanedicarbamate, phenyl isophoronedicarbamate, methyl hexamethylenedicarbamate, ethyl dicyclohexylmethanedicarbamate, butyl naphthanate, propyl p-benzenedicarbamate, methyl 1, 4-cyclohexanedicarbamate, pentyl xylylenedicarbamate, hexyl cyclohexanedimethylenedicarbamate, ethyl trimethyl-1, 6-hexamethylenedicarbamate, heptyl tetramethylm-xylylenedicarbamate, phenyl norbornanedicarbamate, or the like.
Preferably, the isocyanate includes toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1, 4-cyclohexane diisocyanate, xylylene diisocyanate, cyclohexanedimethylene diisocyanate, trimethyl-1, 6-hexamethylene diisocyanate, tetramethylm-xylylene diisocyanate, norbornane diisocyanate, or the like.
The present invention is not limited to the thermal decomposition of the urethane, and any urethane can be used as long as it can be decomposed to give an isocyanate.
Preferably, the catalyst comprises an elemental metal and/or a metal oxide.
The metal in the elemental metal is selected from metal elements in group IIA, IIIA, IVA, VA, IB, IIB, IIIB, IVB, VB, VIB, VIIB or VIII of the periodic table of the elements, and may be, for example, any one or a combination of at least two of magnesium, zinc, copper, vanadium, chromium, manganese, iron, cobalt, nickel, titanium, scandium, aluminum, gallium, zirconium, rhodium, palladium or tin, with typical but non-limiting combinations being combinations of palladium and zinc, copper and vanadium, copper and manganese, vanadium and cobalt, vanadium and zirconium, cobalt and nickel, nickel and scandium.
The metal in the metal oxide is selected from the group consisting of the metal elements of groups IIA, IIIA, IVA, VA, IB, IIB, IIIB, IVB, VB, VIB, VIIB or VIII of the periodic table of the elements, and may be, for example, any one or a combination of at least two of magnesium, zinc, copper, vanadium, chromium, manganese, iron, cobalt, nickel, titanium, scandium, aluminum, gallium, zirconium, rhodium, palladium or tin, with typical but non-limiting combinations being combinations of palladium and zinc, copper and vanadium, copper and manganese, vanadium and cobalt, vanadium and zirconium, cobalt and nickel, nickel and scandium.
Preferably, the by-product comprises any one or a combination of at least two of phenol or alcohol with 1-10 carbon atoms, the number of carbon atoms can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, and the by-product is preferably any one or a combination of at least two of methanol, ethanol, propanol or phenol, wherein typical but non-limiting combinations are a combination of methanol and ethanol, a combination of methanol and phenol, a combination of ethanol and phenol, and a combination of phenol and propanol.
Preferably, the protective gas includes any one or a combination of at least two of nitrogen, argon, helium, chlorobenzene, toluene, cyclohexane, branched alkane, straight-chain alkane or chlorinated alkane, wherein the number of carbon atoms of the branched alkane, the straight-chain alkane or the chlorinated alkane is 1 to 8 independently, and the number of carbon atoms can be 1, 2, 3, 4, 5, 6, 7 or 8, and the like, wherein typical but non-limiting combinations are a combination of nitrogen and argon, a combination of nitrogen and chlorobenzene, a combination of argon and toluene, a combination of chlorobenzene and cyclohexane, a combination of cyclohexane and methane, a combination of toluene and cyclohexane, a combination of helium and chlorinated methane, a combination of propane and nitrogen, a combination of chlorinated hexane and cyclohexane, and preferably nitrogen and/or chlorobenzene.
Preferably, the temperature of the shielding gas is 230 to 300 ℃, and may be, for example, 230 ℃, 238 ℃, 246 ℃, 254 ℃, 262 ℃, 269 ℃, 277 ℃, 285 ℃, 293 ℃, or 300 ℃, but is not limited to the values listed, and other values not listed in this range are also applicable.
Preferably, the ratio of the purging rate of the protective gas to the carbamate-containing organic solvent solution is (0.1-15) L/min:1L or (5-50) L/min:1L/min, wherein the ratio of the purging rate of the protective gas to the carbamate-containing organic solvent solution is (0.1-15) L/min:1L, for example, 0.1L/min: 1L, 0.5L/min:1L, 1L/min:1L, 1.2L/min:1L, 1.5L/min:1L, 2L/min:1L, 2.5L/min: 1L, 3L/min: 1L, 3.5L/min: 1L, 4L/min: 1L, 4.5L/min: 1L, 5L/min:1L, 8L/min: 1L, 10L/min:1L during intermittent operation, 12L/min: 1L or 15L/min:1L and the like, wherein when the device continuously operates, the ratio of the purging rate of the protective gas to the carbamate-containing organic solvent solution is (5-50) L/min:1L/min, such as 5L/min:1L, 10L/min:1L, 15L/min:1L, 20L/min:1L, 25L/min:1L, 30L/min:1L, 35L/min:1L, 40L/min:1L, 45L/min:1L or 50L/min:1L and the like.
The invention further controls the purging rate of the protective gas in the range, selects the purging rate of the protective gas according to different material conditions, and is matched with the mass ratio of the first stream to the second stream during continuous operation, so that the by-product can be promoted to be separated in time, and the yield and the purity of the isocyanate can be improved.
Preferably, the first material further comprises a second stream, and the mass ratio of the first stream to the second stream is 1-50: 1, and for example, may be 1:1, 2:1, 4:1, 10:1, 15:1, 20:1, 22:1, 25:1, 28:1, 30:1, 32:1, 35:1, 38:1, 40:1, 42:1, 45:1 or 48:1, and the like, and preferably is 2-20: 1.
In continuous operation, the invention further prefers the mass ratio of the first stream and the second stream to be in the above range, which can take away the by-products in the first stream more timely and reduce the residual amount of the by-products in the isocyanate product in the final second stream.
Preferably, the thermal decomposition temperature is 230 to 300 ℃, for example, 230 ℃, 238 ℃, 246 ℃, 254 ℃, 262 ℃, 269 ℃, 277 ℃, 285 ℃, 293 ℃ or 300 ℃, but not limited to the recited values, and other values not recited in the range are also applicable.
The pressure of the thermal decomposition is 0.5 to 1.5MPa, and may be, for example, 0.5MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa or 1.5MPa, but is not limited to the values mentioned above, and other values not mentioned above within the range are also applicable.
Preferably, the thermal decomposition is carried out under stirring conditions.
The stirring conditions are not particularly limited in the present invention, and any stirring rotation speed and the like for reaction known to those skilled in the art can be used, and may be, for example, 500r/min, 400r/min or 300 r/min.
Preferably, the mass ratio of the catalyst to the aminocyanate ester is 1 (5-25), and may be, for example, 1:5, 1:7, 1:8, 1:9, 1:10, 1:12, 1:13, 1:15, 1:18, 1:20, 1:22, or 1:25, but is not limited to the recited values, and other values not recited in this range are also applicable.
Preferably, the content of the aminocyanate ester in the organic solvent solution is 1 to 10% by mass, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by mass, but not limited to the recited values, and other values not recited in the range are also applicable.
Preferably, the isocyanate product has a by-product content of 100ppm or less, such as 100ppm, 98ppm, 95ppm, 90ppm, 85ppm, 80ppm or 70ppm, but not limited to the recited values, and other values not recited in this range are equally applicable.
As a preferred technical scheme of the invention, the method comprises the following steps:
when the catalyst continuously operates, under the action of a catalyst, thermally decomposing an organic solvent solution containing 1-10% of carbamate under the blowing of a protective gas, wherein the ratio of the blowing rate of the protective gas to the organic solvent solution containing the carbamate is (5-50) L/min:1L/min, the mass ratio of the catalyst to the cyanamide is 1 (5-25), the thermal decomposition temperature is 230-300 ℃, and the pressure is 0.5-1.5 MPa, so as to obtain a first material containing isocyanate and reaction blowing gas;
the first material is divided into a first stream and a second stream, the mass ratio of the first stream to the second stream is 1-50: 1, the first stream is subjected to heat exchange and then subjected to countercurrent purging with the reaction purge gas to obtain purge tail gas carrying by-products, and the first stream subjected to countercurrent purging is circulated to thermal decomposition for reaction; the second stream produces an isocyanate product.
When the material is intermittently operated, under the action of a catalyst, thermally decomposing organic solvent solution containing 1-10% of carbamate under the blowing of protective gas, wherein the ratio of the blowing rate of the protective gas to the organic solvent solution containing carbamate is (0.1-15) L/min:1L, the mass ratio of the catalyst to the cyanamide is 1 (5-25), the thermal decomposition temperature is 230-300 ℃, and the pressure is 0.5-1.5 MPa, so as to obtain a first material containing isocyanate and reaction blowing gas;
the first material comprises a first stream, the first stream is subjected to heat exchange and then is subjected to countercurrent blowing with the reaction blowing gas to obtain blowing tail gas carrying by-products, the first stream subjected to countercurrent blowing is circulated to thermal decomposition for reaction, the thermal decomposition generates isocyanate, and after the intermittent thermal decomposition is completed, an isocyanate product is extracted.
In a second aspect, the present invention provides an apparatus for the method for enhanced separation in the preparation of isocyanates according to the first aspect, the apparatus comprising: a reaction device and a separation device. And a reaction purge gas outlet is arranged at the upper part of the reaction device, and the reaction purge gas outlet is connected with the bottom inlet of the separation device. The lower part of the reaction device is provided with a first material outlet, the first material outlet is connected with a first stream pipeline and a second stream pipeline, and the first stream pipeline is connected with the upper inlet of the separation device. And a first heat exchange device is arranged on the first stream pipeline. And a sweeping tail gas outlet is arranged at the top of the separation device.
The device provided by the invention is combined by using conventional equipment, the equipment is simple, and industrialization is easy to realize; and the device is provided with the separation device connected with the reaction device, and the first flow strand pipeline is connected to the upper inlet of the separation device, so that the reaction and the separation of products can be simultaneously realized with lower equipment cost, the operation cost is low, and the economic benefit is high.
Preferably, the upper part of the reaction device is provided with a first gas phase feed inlet.
And the first gas phase feed inlet is connected with a protective gas system.
And a second heat exchange device is arranged between the protective gas system and the first gas phase feed inlet.
According to the invention, the second heat exchange device is arranged to heat the protective gas, so that the temperature of the protective gas is consistent with the thermal decomposition temperature, and the selectivity and the reaction efficiency of the reaction are improved.
Preferably, a metering device is arranged between the protective gas system and the first gas phase feed inlet.
Preferably, the first material outlet is provided with a material conveying device.
Preferably, a stirring member is provided inside the reaction apparatus.
Preferably, the upper part of the reaction device is provided with a first liquid phase feed inlet.
Preferably, the second stream conduit is connected to an isocyanate product storage means.
Preferably, the separation device comprises a column or rectification column.
The present invention can select a column or a rectification column as a separation device according to the production yield.
Preferably, the rectification column comprises any one of a packed column, a sieve plate column or a float valve column or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of a float valve column and a sieve plate column, a combination of a packed column and a float valve column, and a combination of a float valve column and a packed column.
Preferably, the internal separation components of the column comprise any one or a combination of at least two of packing, sieve plates, trays or valves, typical but non-limiting combinations being combinations of packing and sieve plates, packing and trays, sieve plates and valves, trays and valves.
The invention has no special limitation on the entering modes of the inlets or position interfaces of the reaction device and the separation device, and can be adjusted according to the actual process, but preferably, the first liquid phase feed inlet, the first gas phase feed inlet, the upper inlet or the bottom inlet are respectively and independently provided with the bottom inserting distribution disc, and the invention can realize the high-speed injection of materials by arranging the bottom inserting distribution discs.
The device of the invention can be provided with at least two groups of devices which are connected in series, for example, 2 groups, 3 groups or 4 groups, and the like, and can be adjusted according to actual conditions.
The operation method of the device for enhancing the separation in the preparation of the isocyanate comprises the following steps:
when the continuous operation is carried out, organic solvent solution containing 1-10% of carbamate is pressurized to 0.5-1.5 MPa, then is sent into a reaction device from a first liquid phase feed inlet, is subjected to thermal decomposition at the temperature of 230-300 ℃ under the action of a catalyst, meanwhile, protective gas is preheated to the thermal decomposition temperature through a metering device and a second heat exchange device in sequence, and then is sent into the reaction device through a first gas phase feed inlet to purge the reaction device, wherein the ratio of the purging rate of the protective gas to the organic solvent solution containing carbamate is (5-50) L/min:1L/min, a first material containing isocyanate and byproducts is generated, and reaction purge gas is generated and is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream through a first stream pipeline and a second stream pipeline, wherein the mass ratio of the first stream to the second stream is 1-50: 1;
the first stream is heated by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; the first flow strand after countercurrent purging is circulated to thermal decomposition through a reaction purge gas outlet to carry out reaction; and the second flow strand draws an isocyanate product through a second flow strand pipeline.
When the intermittent operation is carried out, organic solvent solution containing 1-10% of carbamate is pressurized to 0.5-1.5 MPa and then is sent into a reaction device from a first liquid phase feed inlet, thermal decomposition is carried out at the temperature of 230-300 ℃ under the action of a catalyst, meanwhile, protective gas is preheated to the thermal decomposition temperature through a metering device and a second heat exchange device in sequence, and then is sent into the reaction device through a first gas phase feed inlet to purge the reaction device, the ratio of the purging rate of the protective gas to the organic solvent solution containing carbamate is (0.1-15) L/min:1L, first material containing isocyanate and byproducts is generated, and reaction purge gas is generated and is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and conveyed by a first stream pipeline;
the first stream is heated by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; and circulating the first strand subjected to countercurrent purging to thermal decomposition through a reaction purge gas outlet for reaction, generating isocyanate through thermal decomposition, and extracting a second strand from a second strand pipeline after the intermittent thermal decomposition to obtain an isocyanate product.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the method for enhancing the separation in the preparation of the isocyanate can effectively separate the by-product, and can reduce the residual quantity of the by-product to be less than or equal to 190ppm by using a purging process, and can reach less than 100ppm under better conditions; the method can promote the reaction to be carried out in the direction favorable for isocyanate, improves the reaction yield and the yield of equipment, and under the better condition, the yield of the isocyanate can reach more than 94 percent, and the conversion rate of the carbamate can reach more than 98 percent;
(2) the method for strengthening the separation in the preparation of the isocyanate is energy-saving and environment-friendly, can realize the recycling of the purging medium, and meets the zero-emission requirement;
(3) the device for strengthening the separation in the preparation of the isocyanate provided by the invention is combined by using conventional equipment, the equipment is simple, and the industrialization is easy to realize.
Drawings
FIG. 1 is a schematic view of an apparatus for enhancing separation in the preparation of isocyanate provided in example 1 of the present invention.
FIG. 2 is a schematic view of an apparatus for enhancing separation in the preparation of isocyanate provided in example 5 of the present invention.
FIG. 3 is a schematic diagram of an apparatus for producing isocyanates according to comparative example 1 of the present invention.
FIG. 4 is a schematic diagram of an apparatus for producing isocyanate according to comparative example 2 of the present invention.
In the figure: 1-a reaction device; 11-a stirring member; 12-a reaction purge gas outlet; 13-a first material outlet; 14-a first liquid phase feed inlet; 15-first gas phase feed; 2-a separation device; 21-upper inlet; 22-bottom inlet; 23-purging a tail gas outlet; 3-a first heat exchange device; 4-a material conveying device; 5-a second heat exchange device; 61-a first stream conduit; 62-a second stream conduit.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
In the present invention, "%" means "% by weight" unless otherwise specified.
Example 1
This example provides an apparatus for enhanced separation in the preparation of isocyanate, as shown in fig. 1, comprising: the device comprises a reaction device 1 and a separation device 2, wherein the reaction device 1 is a reaction kettle, and the separation device 2 is a rectifying column.
The reaction device 1 is provided with a reaction purge gas outlet 12 at the upper part, and the reaction purge gas outlet 12 is connected with a bottom inlet 22 of the separation device 2. The lower part of the reaction device 1 is provided with a first material outlet 13, the first material outlet 13 is connected with a first flow strand pipeline 61 and a second flow strand pipeline 62, and the first flow strand pipeline 61 is connected with the upper inlet 21 of the separation device 2. A first heat exchanging device 3 is arranged on the first stream pipe 61. The top of the separation device 2 is provided with a sweep tail gas outlet 23.
The upper part of the reaction device 1 is provided with a first gas phase feed inlet 15; the first gas phase feed port 15 is connected with a protective gas system; and a second heat exchange device 5 is arranged between the protective gas system and the first gas phase feed inlet 15. A metering device is arranged between the protective gas system and the first gas phase feed opening 15. The first material outlet 13 is provided with a material conveying device 4. The reaction apparatus 1 is provided therein with a stirring member 11. The upper part of the reaction device 1 is provided with a first liquid phase feed inlet 14. The second stream line 62 is connected to an isocyanate product storage facility.
The first liquid phase feed port 14, the first gas phase feed port 15, the upper inlet 21 and the bottom inlet 22 are all provided with bottom-inserted distribution discs.
Example 2
This example provides an apparatus for enhanced separation in the preparation of isocyanate, which is the same as example 1 except that no second heat exchange apparatus is provided.
Example 3
This example provides an apparatus for enhancing the separation in the preparation of isocyanate, which is the same as that of example 1 except that the separation apparatus is a rectifying column and a packed column is provided as a separation member in the column.
Example 4
This example provides an apparatus for enhancing separation in the preparation of isocyanate, which is the same as that of example 1 except that the separation apparatus is a rectifying column and a sieve plate column is provided as a separation member in the column.
Example 5
This example provides an apparatus for enhanced separation in the production of isocyanate, which is the same as example 1 except that the reaction apparatus and the separation apparatus in example 1 are provided as two sets of apparatuses connected in series.
Specifically, as shown in fig. 2, the apparatus includes: the device comprises a reaction device 1 and a separation device 2, wherein the reaction device 1 is a reaction kettle, and the separation device 2 is a rectifying column.
The reaction device 1 is provided with a reaction purge gas outlet 12 at the upper part, and the reaction purge gas outlet 12 is connected with a bottom inlet 22 of the separation device 2. The lower part of the reaction device 1 is provided with a first material outlet 13, the first material outlet 13 is connected with a first flow strand pipeline 61 and a second flow strand pipeline 62, and the first flow strand pipeline 61 is connected with the upper inlet 21 of the separation device 2. A first heat exchanging device 3 is arranged on the first stream pipe 61. The top of the separation device 2 is provided with a sweep tail gas outlet 23.
The upper part of the reaction device 1 is provided with a first gas phase feed inlet 15; the first gas phase feed port 15 is connected with a protective gas system; and a second heat exchange device 5 is arranged between the protective gas system and the first gas phase feed inlet 15. A metering device is arranged between the protective gas system and the first gas phase feed opening 15. The first material outlet 13 is provided with a material conveying device 4. The reaction apparatus 1 is provided therein with a stirring member 11. The upper part of the reaction device 1 is provided with a first liquid phase feed inlet 14. The first liquid phase feed port 14, the first gas phase feed port 15, the upper inlet 21 and the bottom inlet 22 are all provided with bottom-inserted distribution discs.
The reaction device 1, the separation device 2, the first heat exchange device 3 and the material conveying device 4 are all provided with two devices, wherein the purging tail gas outlet 23 of the first separation device 2 is connected with the first gas phase feed inlet 15 of the second reaction device 1, and the second stream pipeline 62 of the first reaction device 1 is connected with the first liquid phase feed inlet 14 of the second reaction device 1.
Comparative example 1
This comparative example provides an apparatus for producing isocyanate, which is the same as that of example 1 except that a separation apparatus and its related connection are not provided.
Specifically, as shown in fig. 3, the apparatus includes a reaction apparatus 1, and the reaction apparatus 1 is a reaction kettle.
The upper part of the reaction device 1 is provided with a reaction purge gas outlet 12. The lower part of the reaction device 1 is provided with a first material outlet 13, the first material outlet 13 is connected with a first flow strand pipeline 61 and a second flow strand pipeline 62, and the first flow strand pipeline 61 is connected with the upper inlet 21 of the reaction device 1. A first heat exchanging device 3 is arranged on the first stream pipe 61.
The upper part of the reaction device 1 is provided with a first gas phase feed inlet 15; the first gas phase feed port 15 is connected with a protective gas system; and a second heat exchange device 5 is arranged between the protective gas system and the first gas phase feed inlet 15. A metering device is arranged between the protective gas system and the first gas phase feed opening 15. The first material outlet 13 is provided with a material conveying device 4. The reaction apparatus 1 is provided therein with a stirring member 11. The upper part of the reaction device 1 is provided with a first liquid phase feed inlet 14. The second stream line 62 is connected to an isocyanate product storage facility.
The first liquid phase feed port 14, the first gas phase feed port 15 and the upper inlet 21 are all provided with bottom-inserted distribution discs.
Comparative example 2
This comparative example provides an apparatus for the preparation of isocyanate, which is identical to that of example 1 except that no separation apparatus is provided and that no first stream conduit and no first heat exchange apparatus are provided.
Specifically, as shown in fig. 4, the apparatus includes a reaction apparatus 1, and the reaction apparatus 1 is a reaction kettle.
The upper part of the reaction device 1 is provided with a reaction purge gas outlet 12. The lower part of the reaction device 1 is provided with a first material outlet 13, and the first material outlet 13 is connected with a second flow pipe 62.
The upper part of the reaction device 1 is provided with a first gas phase feed inlet 15; the first gas phase feed port 15 is connected with a protective gas system; and a second heat exchange device 5 is arranged between the protective gas system and the first gas phase feed inlet 15. A metering device is arranged between the protective gas system and the first gas phase feed opening 15. The first material outlet 13 is provided with a material conveying device 4. The reaction apparatus 1 is provided therein with a stirring member 11. The upper part of the reaction device 1 is provided with a first liquid phase feed inlet 14. The second stream line 62 is connected to an isocyanate product storage facility.
The first liquid phase feed port 14 and the first gas phase feed port 15 are provided with bottom-inserted distribution discs.
Application example 1
The application example provides a method for enhancing separation in isocyanate preparation, the method is carried out by adopting the device in the example 1, wherein the device in the example 1 is a combined device with the design of 30L, and the method specifically comprises the following steps:
pressurizing 18L chlorobenzene solution containing 2% diphenylmethane diamino methyl formate to 1.5MPa, then feeding the chlorobenzene solution into a reaction device from a first liquid-phase feed inlet, rapidly heating, carrying out thermal decomposition at the temperature of 280 ℃ under the action of a 5.00g ZnO catalyst, simultaneously using argon as protective gas, preheating the solution to 280 ℃ through a metering device and a second heat exchange device in sequence, feeding the solution into the reaction device through a first gas-phase feed inlet to purge the reaction device, wherein the purging rate of the protective gas is 20L/min, and the pressure in a stable control system is 1.5 MPa; generating a first material containing isocyanate and byproducts, and generating reaction purge gas which is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream through a first stream pipeline and a second stream pipeline, wherein the first stream and the second stream are subjected to intermittent reaction, and the flow rate of the second stream is 0 and is completely sent to the first stream;
the first stream is heated to 285 ℃ through the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and is subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; and circulating the first strand subjected to countercurrent purging to thermal decomposition through a reaction purge gas outlet for reaction, generating isocyanate through thermal decomposition, and after the intermittent thermal decomposition is finished, extracting a second strand from a second strand pipeline to obtain a diphenylmethane diisocyanate product, wherein the byproduct is mainly methanol.
The application example is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is carried out, so that the conversion rate of the diphenylmethane dicarbamate is 100.0%, the molar yield of the diphenylmethane diisocyanate is 98.9%, and the content of a by-product in the diphenylmethane diisocyanate product is 140 ppm.
Application example 2
The present application example provides a method for enhancing separation in the preparation of isocyanate, which is performed using the apparatus of example 1, wherein the apparatus of example 1 is a combined apparatus designed to be 30L, and specifically, the method comprises the following steps:
pressurizing 18L benzene solution containing 5% phenyl dimethylene carbamate to 1.5MPa, then feeding the benzene solution into a reaction device from a first liquid-phase feed inlet, quickly heating, carrying out thermal decomposition at 290 ℃ under the action of 200g of catalyst (the mass ratio of ZnO to aluminum oxide is 1: 10), simultaneously using methyl chloride as protective gas, preheating the protection gas to 290 ℃ sequentially through a metering device and a second heat exchange device, feeding the protection gas into the reaction device through a first gas-phase feed inlet to purge the reaction device, wherein the purging rate of the protective gas is 20L/min, and the pressure in a stable control system is 1.5 MPa; generating a first material containing isocyanate and byproducts, and generating reaction purge gas which is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream through a first stream pipeline and a second stream pipeline, wherein the first stream and the second stream are subjected to intermittent reaction, and the flow rate of the second stream is 0 and is completely sent to the first stream;
the first stream is heated to 295 ℃ by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and is subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; and circulating the first strand subjected to countercurrent purging to thermal decomposition through a reaction purge gas outlet for reaction, generating isocyanate through thermal decomposition, and after the intermittent thermal decomposition is finished, taking out the second strand from a second strand pipeline to obtain a xylylene isocyanate product, wherein the byproduct is mainly phenol.
The application example is a batch reaction, after 50min of reaction, sampling is carried out for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is used, wherein the conversion rate of the xylylene carbamate is 100%, the yield of the xylylene isocyanate is 98.5%, and the content of a byproduct in the xylylene isocyanate product is 89 ppm.
Application example 3
The present application example provides a method for enhancing separation in the preparation of isocyanate, which is performed by using the apparatus of example 1, wherein the apparatus of example 1 is a combined apparatus designed to be 200L, and specifically, the method comprises the following steps:
pressurizing 100L chlorobenzene solution containing 10% hexamethylene dicarbamic acid propyl ester to 1.0MPa, then feeding the chlorobenzene solution into a reaction device from a first liquid phase feed inlet, quickly heating, carrying out thermal decomposition under the action of 290 ℃ and 1000g of cobalt oxide catalyst (cobalt oxide is loaded on silicon dioxide, wherein the mass ratio of cobalt oxide to silicon dioxide is 1: 50), simultaneously using nitrogen as protective gas, preheating the nitrogen to 290 ℃ through a metering device and a second heat exchange device in sequence, then feeding the preheated cobalt oxide solution into the reaction device through a first gas phase feed inlet to sweep the reaction device, wherein the sweeping rate of the protective gas is 100L/min, and stably controlling the pressure in a system to be 1.0 MPa; generating a first material containing isocyanate and byproducts, and generating reaction purge gas which is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream through a first stream pipeline and a second stream pipeline, wherein the first stream and the second stream are subjected to intermittent reaction, and the flow rate of the second stream is 0 and is completely sent to the first stream;
the first stream is heated to 295 ℃ by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and is subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; and circulating the first strand subjected to countercurrent purging to thermal decomposition through a reaction purge gas outlet for reaction, generating isocyanate through thermal decomposition, and after the intermittent thermal decomposition is completed, extracting a second strand from a second strand pipeline to obtain a hexamethylene diisocyanate product, wherein the byproduct is mainly propanol.
The application example is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is adopted, so that the conversion rate of the hexamethylene dicarbamate propyl ester is 100%, the yield of the hexamethylene diisocyanate is 98.8%, and the content of a byproduct in the hexamethylene diisocyanate product is 186 ppm.
Application example 4
The present application example provides a method for enhanced separation in the preparation of isocyanates, using the apparatus of example 1, wherein the apparatus of example 1 is an assembled apparatus for carrying out a topdressing at 25m, in particular the method comprises the following steps:
10000Kg of 5% isophorone diamino ethyl formate chlorobenzene solution is pressurized to 1.0MPa and then is sent into a reaction device from a first liquid phase feed inlet, the temperature is rapidly raised, thermal decomposition is carried out at 290 ℃ under the action of 1000Kg of catalyst (zinc oxide and aluminum oxide, the mass ratio of zinc oxide to aluminum oxide is 1: 100), nitrogen is used as protective gas, the nitrogen is preheated to 295 ℃ sequentially by a metering device and a second heat exchange device, then the nitrogen is sent into the reaction device through a first gas phase feed inlet to purge the reaction device, the purging rate of the protective gas is 5000L/min, and the pressure in a stable control system is 1.0 MPa; generating a first material containing isocyanate and byproducts, and generating reaction purge gas which is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream through a first stream pipeline and a second stream pipeline, the first stream and the second stream are subjected to intermittent reaction, the flow rate of the second stream is 0, and the second stream and the first stream are all fed into the first stream;
the first stream is heated to 295 ℃ by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and is subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; and circulating the first strand subjected to countercurrent purging to thermal decomposition through a reaction purge gas outlet for reaction, generating isocyanate through thermal decomposition, and after the intermittent thermal decomposition is completed, extracting a second strand from a second strand pipeline to obtain an isophorone diisocyanate product, wherein the byproduct is mainly ethanol.
The application example is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is used, so that the conversion rate of isophorone carbamic acid ethyl ester is 100%, the yield of isophorone diisocyanate is 96.9%, and the content of a by-product in an isophorone diisocyanate product is 134 ppm.
Application example 5
The present application example provides a method for enhanced separation in the preparation of isocyanates using the apparatus of example 1, wherein the apparatus of example 5 is configured for a combined apparatus for single 25m tophan, total 25m tophan, in particular the method comprises the steps of:
pressurizing chlorobenzene solution containing 2% of methyl diphenylmethane dicarbamate to 0.8MPa at the speed of 50 m/h, then feeding the chlorobenzene solution into a reaction device from a first liquid-phase feeding hole, quickly heating, carrying out thermal decomposition at the temperature of 290 ℃ under the action of 2000Kg of catalyst (nickel oxide and silicon dioxide, the mass ratio of nickel oxide to silicon dioxide is 1: 100), simultaneously using nitrogen as protective gas, preheating to 290 ℃ through a metering device and a second heat exchange device in sequence, feeding the heated chlorobenzene solution into the reaction device through a first gas-phase feeding hole to purge the reaction device, wherein the purging speed of the protective gas is 20000L/min, and the pressure in a stable control system is 0.8 MPa; generating a first material containing isocyanate and byproducts, and generating reaction purge gas which is discharged into a separation device from a reaction purge gas outlet; the first material is discharged from a first material outlet of the reaction device, conveyed by the material conveying device and divided into a first stream and a second stream by a first stream pipeline and a second stream pipeline, and the mass ratio of the first stream to the second stream is 20: 1;
the first stream is heated to 295 ℃ by the first heat exchange device and then circulates to an inlet at the upper part of the separation device, the first stream is contacted with reaction purge gas fed from the bottom of the separation device and is subjected to countercurrent purge, the reaction purge gas carries away by-products in the first stream and is discharged from a purge tail gas outlet, and the purge tail gas is recycled as protective gas after the by-products are recovered; the first flow strand after countercurrent purging is circulated to thermal decomposition through a reaction purge gas outlet to carry out reaction; and the second flow strand is used for extracting a diphenylmethane diisocyanate product through a second flow strand pipeline. The by-product is mainly methanol.
The application example is a continuous reaction, after 3 days of continuous operation, sampling is carried out at a second flow channel of a second reaction device for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is used, wherein the conversion rate of diphenylmethane dicarbamate is 99.7%, the yield of diphenylmethane diisocyanate is 95.9%, and the content of by-products in the diphenylmethane diisocyanate product is 67 ppm.
Application example 6
This application example provides a method for enhanced separation in the preparation of isocyanate, which is the same as application example 1 except that the apparatus of example 2 is used.
Compared with the application example 6, in the application example 1, the waste heat device provided with the protective gas is arranged, the protective gas continuously introduced has almost no influence on the temperature field in the reaction system, the temperature field in the reaction system of the application example 6 fluctuates, and the conversion rate and the yield in the application example 1 are higher than those in the application example 6.
Application examples 7 to 8
Application examples 7 to 8 provide a method for enhanced separation in the preparation of isocyanate, which is the same as application example 1 except that the apparatus of examples 3 to 4 is used.
Application examples 7 to 8 can achieve similar technical effects to application example 1.
Application example 9
The present application example provides a method for enhanced separation in the preparation of isocyanate, which is the same as application example 1 except that the purge rate of the shielding gas is 100L/min.
The application example is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is adopted, so that the conversion rate of the diphenylmethane dicarbamate is 99.8%, the yield of the diphenylmethane diisocyanate is 98.6%, and the content of a byproduct in the diphenylmethane diisocyanate product is 64 ppm.
Application example 10
The present application example provides a method for enhanced separation in the preparation of isocyanate, which is the same as application example 1 except that the purge rate of the shielding gas is 2L/min.
The application example is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is adopted, so that the conversion rate of the diphenylmethane dicarbamate is 99.2%, the yield of the diphenylmethane diisocyanate is 96.7%, and the content of a byproduct in the diphenylmethane diisocyanate product is 113 ppm.
Application example 11
The application example provides a method for reinforced separation in isocyanate preparation, and the method is the same as the application example 5 except that the sweeping speed of protective gas is 40000L/min, the temperature of thermal decomposition and the temperature of argon are both 300 ℃, the pressure is 1.5MPa, and 1000Kg of catalyst is added.
The application example is a continuous reaction, after 3 days of continuous operation, a sample is taken from a second flow channel of the second reaction device for chromatographic ethanol derivatization, and the conversion rate of the diphenylmethane dicarbamate is 99.8 percent, the yield of the diphenylmethane diisocyanate is 99.1 percent, and the content of the by-product in the diphenylmethane diisocyanate product is 11ppm by using high performance liquid chromatography analysis.
Application example 12
The application example provides a method for reinforced separation in isocyanate preparation, and the method is the same as the application example 5 except that the purging rate of protective gas is 5000L/min, the temperature of thermal decomposition and the temperature of argon are both 260 ℃, the pressure is 0.5MPa, and 1000Kg of catalyst is added.
The application example is a continuous reaction, after 3 days of continuous operation, a sample is taken from a second flow channel of a second reaction device, chromatographic ethanol derivatization is carried out, and high performance liquid chromatography analysis is used, so that the conversion rate of diphenylmethane dicarbamate is 98.2%, the yield of diphenylmethane diisocyanate is 94.8%, and the content of by-products in the diphenylmethane diisocyanate product is 162 ppm.
The comprehensive application examples 1-12 show that the yield of the isocyanate in the method can reach more than 94%, the conversion rate of the carbamate can reach more than 98%, and the content of byproducts in isocyanate products is less than or equal to 190 ppm.
Application comparative example 1
Comparative example of this application provides a process for the preparation of isocyanate using the apparatus of comparative example 1, which is the same as in application example 1 except that the first stream is recycled directly to the reaction apparatus without countercurrent purging with the reaction purge gas.
The comparative example of the application is a batch reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is carried out, so that the conversion rate of the diphenylmethane dicarbamate is 87.9%, the yield of the diphenylmethane diisocyanate is 52.4%, and the content of the by-product in the diphenylmethane diisocyanate product is 892 ppm.
Comparative application example 2
Comparative example of the present application provides a method for preparing isocyanate using the apparatus of comparative example 2, which is the same as in application example 1 except that only the reaction of the reaction apparatus is performed, the circulation of the first stream and the countercurrent purge with the reaction purge gas are not provided.
The comparative example of the application is an intermittent reaction, after the reaction is carried out for 60min, a sample is taken for chromatographic ethanol derivatization, and high performance liquid chromatography analysis is used, so that the conversion rate of diphenylmethane dicarbamate is 90.1%, the yield of diphenylmethane diisocyanate is 47.4%, and the content of by-products in the diphenylmethane diisocyanate product is 946 ppm.
It can be seen from the comprehensive application examples 1 and 1-2 that, when the reaction purge gas and the circulation of the first stream are subjected to countercurrent purge in the application example 1, compared with the case that no countercurrent purge is performed in the application examples 1-2, the conversion rate of diphenylmethane dicarbamate in the application example 1 is 100.0%, the molar yield of diphenylmethane diisocyanate is 98.9%, and the content of by-products in the diphenylmethane diisocyanate product is 140ppm, while the conversion rate and the yield in the application examples 1-2 are far lower than those in the application example 1, and the content of by-products in the diphenylmethane diisocyanate product is up to 892ppm and 946ppm respectively, which indicates that the conversion rate of raw materials and the yield of products are significantly improved and the content of by-products in the product is significantly reduced by subjecting the reaction purge gas and the first stream to countercurrent purge.
In conclusion, the enhanced separation method of the invention can promote the separation of byproducts in the preparation of isocyanate by using a non-phosgene method, break through the separation residual limit of the conventional separation means, be more beneficial to the generation of isocyanate and improve the yield of isocyanate, wherein the yield of the isocyanate can reach more than 94 percent, the conversion rate of carbamate can reach more than 98 percent, and the content of the byproducts in isocyanate products is less than or equal to 190 ppm.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A process for enhanced separation in the preparation of isocyanates, said process comprising the steps of:
under the action of a catalyst, carrying out thermal decomposition on an organic solvent solution containing carbamate under the blowing of protective gas to obtain a first material containing isocyanate and reaction blowing gas;
the first material comprises a first stream, the first stream is subjected to heat exchange and then is subjected to countercurrent purging with the reaction purge gas to obtain a purge tail gas carrying a byproduct, and the first stream subjected to countercurrent purging is circulated to thermal decomposition for reaction to generate isocyanate.
2. The method for enhanced separation in the preparation of isocyanates according to claim 1, wherein the organic solvent comprises any one or a combination of at least two of alkanes, halogenated hydrocarbons, aromatic hydrocarbons, halogenated aromatic hydrocarbons or ethers.
3. The method for enhanced separation in the preparation of isocyanates according to claim 1 or 2, wherein the catalyst comprises a metal element and/or a metal oxide;
the metal in the simple metal substance is selected from metal elements in IIA, IIIA, IVA, VA, IB, IIB, IIIB, IVB, VB, VIB, VIIB or VIII groups in the periodic table of elements;
the metal in the metal oxide is selected from metal elements in IIA, IIIA, IVA, VA, IB, IIB, IIIB, IVB, VB, VIB, VIIB or VIII groups in the periodic table of elements.
4. The method for enhancing separation in the preparation of isocyanate according to claim 1, wherein the by-product comprises any one of phenol or alcohol having 1-10 carbon atoms or a combination of at least two of phenol and alcohol.
5. The method for enhancing separation in isocyanate preparation according to claim 1, wherein the shielding gas comprises any one or a combination of at least two of nitrogen, argon, helium, chlorobenzene, toluene, cyclohexane, branched alkane, linear alkane or chlorinated alkane, wherein the number of carbon atoms of the branched alkane, the linear alkane or the chlorinated alkane is 1-8 independently.
6. The method for enhancing separation in isocyanate preparation according to claim 1, wherein the ratio of the purge rate of the shielding gas to the carbamate-containing organic solvent solution is (0.1-15) L/min:1L or (5-50) L/min: 1L/min.
7. The method for enhancing separation in preparing isocyanate according to claim 1, wherein the first material further comprises a second stream, and the mass ratio of the first stream to the second stream is 1-50: 1.
8. The method for enhancing separation in the preparation of isocyanate according to claim 1, wherein the thermal decomposition temperature is 230 to 300 ℃;
the pressure of the thermal decomposition is 0.5-1.5 MPa.
9. An apparatus for the enhanced separation process in the preparation of isocyanates according to any one of claims 1 to 8, wherein the apparatus comprises: a reaction device and a separation device;
a reaction purge gas outlet is arranged at the upper part of the reaction device and is connected with the bottom inlet of the separation device;
a first material outlet is formed in the lower part of the reaction device, a first stream pipeline and a second stream pipeline are connected to the first material outlet, and the first stream pipeline is connected with an upper inlet of the separation device;
a first heat exchange device is arranged on the first stream pipeline;
a sweeping tail gas outlet is formed in the top of the separation device;
the upper part of the reaction device is provided with a first gas phase feed inlet;
the first gas phase feed port is connected with a protective gas system;
the upper part of the reaction device is provided with a first liquid phase feed inlet.
10. The apparatus of claim 9, wherein a second heat exchange device is disposed between the shielding gas system and the first gas phase feed port.
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