CN102675154B - Separation and purification device and method for preparing methylene diphenyl diisocyanate (MDI) complex product by utilizing pyrolysis of carbamate - Google Patents
Separation and purification device and method for preparing methylene diphenyl diisocyanate (MDI) complex product by utilizing pyrolysis of carbamate Download PDFInfo
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Abstract
The invention relates to a separation and purification device and a method for preparing an MDI complex product by utilizing pyrolysis of carbamate. The separation and purification device comprises a solvent dehydration tower (2), a cooling and crystallization system (4), a heat filter (5) and a de-heavy fractionator (6), reboilers (3) are arranged at the bottoms of the solvent dehydration tower (2) and the de-heavy fractionator (6) respectively, and condensers (1) are arranged at the tops of the solvent dehydration tower (2) and the de-heavy fractionator (6) respectively. The method includes adding a mixing material containing solvents, raw materials, by-products and the MDI product to the solvent dehydration tower (2) for rectification and separation so as to achieve recycling of the solvents, adding the obtained liquid containing the MDI product to the cooling and crystallization system (4) for cooling and crystallization, obtaining a part of the raw materials, by-product solid and filtrate containing the MDI product after the filtration of the heat filter (5), and adding the filtrate to the de-heavy fractionator (6) for separation to obtain the MDI product. The separation and purification device and the method for preparing the MDI complex product by utilizing the pyrolysis of carbamate have the advantages of being simple in process, easy to operate and capable of achieving continuous operation.
Description
Technical field
The present invention relates to the separation field of MDI, particularly, the present invention relates to separating refining device and method that a kind of carbamate pyrolysis prepares the complicated product of MDI.
Background technology
Diphenylmethanediisocyanate (being called for short MDI) is the main foundation raw material of polyurethane industrial.Position according to two-NCO group on phenyl ring is different, can have 2,2 '-MDI, 2,4 '-MDI and 4,4 '-three kinds of MDI isomers.
At present, produce MDI both at home and abroad and mainly adopt phosgenation, prepare diamines and the polyamines of diphenylmethane by the condensation reaction of aniline and formaldehyde, then react vulcabond (MDI) and the polyisocyanates of preparation diphenylmethane series by phosgenation.Owing to introducing phosgene, in its product system, chlorine-containing compound is arranged, comprise in addition three kinds of isomerss, polyisocyanates and the light naphthas etc. of MDI.
Because phosgenation technique is used hypertoxic raw material phosgene, and the strong hydrochloric acid of by-product macro-corrosion, exist environmental pollution, severe reaction conditions, equipment corrosion and residual chlorine to affect the problems such as quality product, development environment close friend's non-phosgene prepares MDI technique and receives much attention.
At present the more non-phosgene technique of report concentrates on take Urethylane as raw material, thermolysis or directly aspect gas phase high temperature pyrolysis synthesizing isocyanate under the liquid phase solvent system.The reaction mechanism that is isocyanic ester due to the Urethylane pyrolysis belongs to the reversible thermo-negative reaction of consecutive, at two-NHCOOCH
3All pyrolysis generates in two purpose product group-NCO processes, and will inevitably generate intermediate product is that an end contains-NHCOOCH
3Group, an end contain-material of NCO group; Simultaneously, contain in MDI active-the NCO group, easily make two MDI that polycondensation occurs under comparatively high temps and generate dimer, the rough sledding such as coking further appear, therefore the pyrolytic reaction time can not be oversize, thereby limited the transformation efficiency of carbamate, often contained some unconverted complete raw material in the product system.Therefore, prepare in MDI technique in the carbamate pyrolysis, the product system of its product system and existing phosgenation technique is completely different, except three kinds of isomerss that contain equally MDI, also contains intermediate product, the unconverted component of raw material, solvent carrier etc. completely.Develop a kind of brand-new product system separation and refining method, to remove intermediate product, unconverted raw material completely etc., obtain the mixture of highly purified MDI isomers, further the refining product that obtains the different isomerss of MDI, be to determine that the carbamate pyrolysis prepares the important factor of this technological feasibility of MDI and ripening degree.
The carbamate pyrolysis prepares MDI technique, and not only product composition is very complicated, and its two contained components are that the complete carbamate raw material of intermediate product and unreacted also has following singularity, has increased the difficulty of separating technology.
First, the complete carbamate of intermediate product and unreacted is heat-sensitive substance, decomposition reaction easily occurs when excess Temperature generate MDI and methyl alcohol, if their too high levels, the methyl alcohol that perhaps generates can not in time be discharged in separation system, all can affect the purity of purpose product MDI.
Second, all contain active-NCO group in intermediate product and MDI, be easy to make between two MDI, MDI and intermediate product or two intermediate products polycondensation generation dimer occurs, the rough sledding such as coking further appear, therefore, the separation system temperature can not be too high, and the residence time of separating under hot environment can not be oversize.
At present, produce MDI technique by the carbamate pyrolysis, more about the report of its preparation aspect, and to the separation of its complicated product system and refining, all do not hear with the report and the research that obtain high-purity MDI isomers product.
Summary of the invention
To the object of the invention is in order addressing the above problem, to provide a kind of carbamate pyrolysis to prepare the separating refining device of the complicated product of MDI.
A further object of the present invention has been to provide a kind of carbamate pyrolysis to prepare the separation and refining method of the complicated product of MDI.
In order to address the above problem, the separating refining device that carbamate pyrolysis provided by the present invention prepares the complicated product of MDI comprises: desolventizing tower 2, crystallisation by cooling system 4, hot filter 5 and weight-removing column 6, bottom at desolventizing tower 2 and weight-removing column 6 arranges respectively reboiler 3, at the top of desolventizing tower 2 and weight-removing column 6, condenser 1 is set respectively;
The mixture that will contain solvent, raw material, by product and product MDI adds desolventizing tower 2 to carry out rectifying separation, and the solvent condenser 1 that gasification enters desolventizing tower 2 tops under reboiler 3 effects in desolventizing tower 2 reclaims, recycles solvent; The raw material that the tower reactor of desolventizing tower 2 obtains, by product and product MDI enter crystallisation by cooling system 4 and carry out cooling and crystallization, separate out part material and by product, filter by hot filter 5 filter cake that obtains raw material and by product, the filtrate of containing the MDI product enters weight-removing column 6 and separates, the MDI gasification enters weight-removing column 6 evaporator overhead condensers 1 under the effect of reboiler 3, condensation obtains product, and raw material, by product are discharged in tower reactor with liquid form, realizes the separation of the complicated product of MDI.
As a kind of improvement of such scheme, described condenser 1 is shell-and tube condenser; Described reboiler 3 is falling film evaporator.
Another improvement as such scheme, described mixture is carbamate pyrolysis products therefrom system, its Raw is ditan diamino-methyl formate (being called for short MDC), by product is 4-Urethylane-4-isocyanic ester ditan (being called for short MMI), product is 2,2 '-MDI, 2,4 '-MDI, 4,4 '-MDI.
The inventive system comprises: desolventizing tower 2, crystallisation by cooling system 4, hot filter 5, weight-removing column 6 etc.MDI, MMI, the incoming mixtures such as MDC are rectifying separation in desolventizing tower 2, the tower top gained is high-purity light naphtha, can get back to the reuse of carbamate pyrolytic reaction systemic circulation, the tower reactor material enters the crystal of crystallisation by cooling system 4 and hot filter 5 remove portion MMI and MDC, filtrate enters weight-removing column 6, weight-removing column tower top gained is high-purity MDI isomer mixt, can further utilize the refining product that obtains the different isomerss of MDI of existing technique, tower reactor is MMI and MDC, can with the filter cake of heat filtering system get back to together carbamate pyrolytic reaction system again pyrolysis prepare MDI, thereby obtain cyclically utilizing, improve the yield of MDI product.
In crystallisation by cooling system 4 and hot filter 5 that the present invention adopts, crystallization and filtration temperature are 40～200 ℃, and the crystallizer residence time is 5～240min; Before weight-removing column separates MDI and MMI, MDC, MMI and the MDC of crystallisation by cooling system and hot filter remove portion thermo-sensitivity are set, reduce the MMI and the MDC content that enter in weight-removing column, the amount of MMI and MDC pyrolysis methanol is reduced, thereby guarantee the purity of product MDI; Simultaneously, realized partial condensation at the condenser of weight-removing column tower top by arranging of temperature, made the methyl alcohol of generation in time discharge system with gaseous phase, above two aspects guarantee to obtain highly purified MDI isomers product.
In order to realize another object of the present invention, the present invention also provides a kind of carbamate pyrolysis to prepare the separation and refining method of the complicated product of MDI, and the method comprises the following steps:
The mixture that 1) will contain solvent, raw material, by product and product MDI adds in desolventizing tower 2, control the tower reactor temperature lower than 250 ℃, tower top pressure is that 0.2～50KPa separates, solvent gasifies under the effect of reboiler 3 and enters the condenser 1 at desolventizing tower 2 tops, obtain liquid solvent, obtain simultaneously the mixing liquid of raw material, by product and product MDI in tower reactor;
2) with step 1) in solvent be for recycling and reuse, step 1) mixing liquid of the raw material in, by product and product MDI enters crystallisation by cooling system 4 and carries out crystallization, obtain the crystal of part material, by product, filter by hot filter 5, obtain the filter cake and the filtrate of containing product MDI of raw material and by product;
3) filtrate of containing product MDI step 2) enters weight-removing column 6, control the interior tower reactor temperature of weight-removing column 6 lower than 250 ℃, tower top pressure is 0.2～10KPa, separate, the condenser 1 that product MDI gasification enters weight-removing column 6 tops under reboiler 3 effect carries out condensation, obtain product, raw material, by product are discharged from tower reactor with liquid form, realize the separation of the complicated product of MDI.
A kind of improvement as such scheme, in described step 2) in, described mixture is carbamate pyrolysis products therefrom system, wherein solvent comprises one or more in chlorobenzene, orthodichlorobenzene or its isomers, and raw material is MDC, and by product is MMI, product is 2,2 '-MDI, 2,4 '-MDI, 4,4 '-MDI.
As another improvement of such scheme, described step 2) in the temperature of crystallization and filtration be 40～150 ℃, crystallization time is 5～120min.
Another improvement as such scheme, described step 3) in, condenser is shell-and tube condenser, controlling its temperature is 40～150 ℃, wherein gaseous product MDI is converted into liquid state and collects after condenser 1, and the methyl alcohol of generation is in time discharged with gaseous phase after condenser 1 and realized the partial condensation of gas in the condenser.
In method of the present invention, the raw material feeding liquid is first sloughed light naphtha in the desolventizing tower, and wherein, light naphtha comprises the mixture of chlorobenzene, orthodichlorobenzene or its isomers; Then enter crystallisation by cooling and the hot filter remove portion MMI of system and MDC, the thick MDI mixture of gained enters weight-removing column and further removes MMI and MDC, namely obtains highly purified MDI isomer mixt.
The invention has the advantages that, carbamate pyrolysis of the present invention prepares separating refining device and the method for the complicated product of MDI, realized that the carbamate pyrolysis prepares the separation of complicated product system in the MDI process and makes with extra care, and described device and method adopts technique and the technology of industrial maturation, have that technique is simple, ripe, reliable, easy to operate, device and the advantage such as facility investment is little, and can realize technique serialization operation.
Description of drawings
Fig. 1 is the schematic diagram that carbamate pyrolysis of the present invention prepares the separating refining device of the complicated product of MDI.
The accompanying drawing sign
1, condenser 2, desolventizing tower 3, reboiler
4, crystallisation by cooling system 5, hot filter 6, weight-removing column
Embodiment
Below in conjunction with accompanying drawing, device and method of the present invention is described in detail.
As shown in Figure 1, the inventive system comprises: desolventizing tower 2, crystallisation by cooling system 4, hot filter 5, the reboiler 3 that the bottom of weight-removing column 6 and the condenser 1 that arranges respectively at the top of desolventizing tower 2 and weight-removing column 6, desolventizing tower 2 and weight-removing column 6 arranges respectively.solvent, MDI, MMI, the mixtures such as MDC are rectifying separation in desolventizing tower 2, 1 condensation obtains high-purity light naphtha to overhead gas through condenser, can get back to the reuse of carbamate pyrolytic reaction systemic circulation, the tower reactor material enters the crystal of crystallisation by cooling system 4 and hot filter 5 remove portion MMI and MDC, filtrate enters weight-removing column 6, weight-removing column tower top gained is high-purity MDI isomer mixt, can further utilize the refining product that obtains the different isomerss of MDI of existing technique, tower reactor is MMI and MDC liquid, can with the filter cake of hot filter 5 get back to together carbamate pyrolytic reaction system again pyrolysis prepare MDI, thereby obtain cyclically utilizing, improve the yield of MDI product.
The desolventizing tower 2 tower reactor temperature that the present invention adopts are controlled at and are no more than 250 ℃, and tower top pressure is controlled at 0.2～50KPa, and reboiler is that falling film evaporator is rapidly heated with realization, and condenser is shell-and tube condenser; Crystallisation by cooling system 4 and hot filter, crystallization and filtration temperature are 40～150 ℃, and the crystallizer residence time is 5～120min, can remove portion MMI and MDC, the MMI and the MDC content that enter weight-removing column are reduced, and the amount of decomposing methanol reduces, thereby guarantees the purity of product MDI; Weight-removing column tower reactor temperature is controlled at and is no more than 250 ℃, tower top pressure is controlled at 0.2～10KPa, reboiler is that falling film evaporator is rapidly heated with realization, tower top condensing system adopts the partial condensation mode, the methyl alcohol that generates is in time discharged with gaseous phase, guarantee that the gained phlegma is highly purified MDI isomer mixt, condenser temperature is controlled at 40～150 ℃.
in method of the present invention, a stream gang a is the raw material incoming flow, at least comprise 2, 2 '-MDI, 2, 4 '-MDI, 4, 4 '-MDI, MMI, MDC, light naphtha, a stream gang b is desolventizing tower 2 overhead condensate, be high-purity light naphtha, a stream gang c extracts out in tower reactor, main ingredient is 2, 2 '-MDI, 2, 4 '-MDI, 4, 4 '-MDI, MMI, MDC, a stream gang d is filtrate, be thick MDI isomer mixt, and part MMI and MDC, a stream gang e is filter cake, main ingredient is MMI and MDC solid, a stream gang f is the condenser system Exhaust Gas, main ingredient is methyl alcohol, a stream gang g is the phlegma of condenser system, it is high-purity MDI isomer mixt, a stream gang h is tower bottoms, main ingredient is MMI and MDC liquid.
Embodiment 1
In embodiment 1, take the 664g composition and comprise 2,2 '-the stream thigh a of MDI, 2,4 '-MDI, 4,4 '-MDI, MMI, MDC, chlorobenzene, reduce to 3.16% through chlorobenzene content in stream gang c after the desolventizing tower, stream gang c is through crystallisation by cooling and heat filtering system, and in gained stream gang d, MMI and MDC content reduce to respectively 13.7%, 4.97%, and stream gang d is through after weight-removing column, a gained stream gang f consists of chlorobenzene, methyl alcohol does not detect, and stream gang g is the mixture that purity reaches high-purity MDI isomers of 97%.
In embodiment 2, take the 616.8g composition and comprise 2,2 '-the stream thigh a of MDI, 2,4 '-MDI, 4,4 '-MDI, MMI, MDC, chlorobenzene, reduce to 2.79% through chlorobenzene content in stream gang c after the desolventizing tower, stream gang c is through crystallisation by cooling and heat filtering system, and in gained stream gang d, MMI and MDC content reduce to respectively 9.07%, 0.57%, and stream gang d is through after weight-removing column, a gained stream gang f consists of chlorobenzene, methyl alcohol does not detect, and stream gang g is the mixture that purity reaches high-purity MDI isomers of 96.8%.
The invention provides separating refining device and method that a kind of carbamate pyrolysis prepares the complicated product of MDI, realized that the carbamate pyrolysis prepares the separation of complicated product system in the MDI process and makes with extra care, the various drawbacks that previous methods prepares MDI have been solved, and can find out by embodiment 1 and 2, apparatus and method of the present invention have good effect, and the mixture purity of the MDI isomers that is isolated to all reaches more than 96%.
Claims (9)
1. a carbamate pyrolysis prepares the separating refining device of the complicated product of MDI, it is characterized in that, described separating refining device comprises: desolventizing tower (2), crystallisation by cooling system (4), hot filter (5) and weight-removing column (6), the bottom of described desolventizing tower (2) and weight-removing column (6) arranges respectively reboiler (3), and the top of described desolventizing tower (2) and weight-removing column (6) arranges respectively condenser (1);
The mixture that will contain solvent, raw material, by product and product MDI adds desolventizing tower (2) to carry out rectifying separation, solvent gasifies under reboiler (3) effect in desolventizing tower (2) and enters the condenser (1) at desolventizing tower (2) top, condensation obtains liquid solvent, and solvent is reclaimed, recycles; The liquid that contains raw material, by product and product MDI that the tower reactor of desolventizing tower (2) obtains enters crystallisation by cooling system (4) and carries out cooling and crystallization, separate out part solid material and by product, filter the filtrate that obtains the filter cake of raw material and by product and contain product MDI by hot filter (5), filtrate enters weight-removing column (6) and separates, the MDI gasification enters the condenser (1) at weight-removing column (6) top under the effect of reboiler (3), condensation obtains product MDI, raw material, by product are discharged with liquid form in tower reactor, realize the separation of the complicated product of MDI.
2. carbamate pyrolysis according to claim 1 prepares the separating refining device of the complicated product of MDI, it is characterized in that, described condenser (1) is shell-and tube condenser.
3. carbamate pyrolysis according to claim 1 prepares the separating refining device of the complicated product of MDI, it is characterized in that, described reboiler (3) is falling film evaporator.
4. carbamate pyrolysis according to claim 1 prepares the separating refining device of the complicated product of MDI, it is characterized in that, described mixture is carbamate pyrolysis products therefrom system, its Raw is the ditan diamino-methyl formate, by product is 4-Urethylane-4-isocyanic ester ditan, product is 2,2 '-MDI, 2,4 '-MDI, 4,4 '-MDI.
5. a carbamate pyrolysis prepares the separation and refining method of the complicated product of MDI, and the method comprises the following steps:
The mixture that 1) will contain solvent, raw material, by product and product MDI adds in desolventizing tower (2), control the tower reactor temperature lower than 250 ℃, tower top pressure is that 0.2～50KPa separates, solvent gasifies under the effect of reboiler (3) and enters the condenser (1) at desolventizing tower (2) top, obtain liquid solvent, obtain simultaneously the mixing liquid of raw material, by product and product MDI in tower reactor;
2) solvent in step 1) is for recycling and reuse, the mixing liquid of raw material in step 1), by product and product MDI enters crystallisation by cooling system (4) and carries out cooling and crystallization, obtain the crystal of part material, by product, filter by hot filter (5), remove the filter cake of raw material and by product, thereby reduced the amount of the methanol gas of raw material and by product generation, obtained simultaneously containing the filtrate of product MDI;
3) filtrate of containing product MDI step 2) enters weight-removing column (6), control the interior tower reactor temperature of weight-removing column (6) lower than 250 ℃, tower top pressure is 0.2～10KPa, separate, carry out condensation at the lower product MDI of reboiler (3) the effect condenser (1) that enters weight-removing column (6) top that gasifies, obtain product, raw material, by product are discharged from tower reactor with liquid form, realize the separation of the complicated product of MDI.
6. carbamate pyrolysis according to claim 5 prepares the separation and refining method of the complicated product of MDI, it is characterized in that, in described step 1), described mixture is carbamate pyrolysis products therefrom system, wherein solvent comprises one or more in chlorobenzene, orthodichlorobenzene or its isomers, raw material is the ditan diamino-methyl formate, by product is 4-Urethylane-4-isocyanic ester ditan, product is 2,2 '-MDI, 2,4 '-MDI, 4,4 '-MDI.
7. carbamate pyrolysis according to claim 5 prepares the separation and refining method of the complicated product of MDI, it is characterized in that described step 2) in the temperature of crystallization and filtration be 40～150 ℃, crystallization time is 5～120min.
8. carbamate pyrolysis according to claim 5 prepares the separation and refining method of the complicated product of MDI, it is characterized in that, in described step 3), condenser is shell-and tube condenser, controlling its temperature is 40～150 ℃, wherein gaseous product MDI is converted into liquid state and collects after condenser (1), methyl alcohol is still discharged with gas form through condenser (1), has realized the partial condensation of gas in the condenser.
9. carbamate pyrolysis according to claim 5 prepares the separation and refining method of the complicated product of MDI, it is characterized in that, described method also comprises step 4): with step 2) in obtain in the filter cake of raw material and by product and step 3) discharging from tower reactor the pyrolysis that raw material, by product be further used for carbamate and prepare MDI.
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| CN105837471B (en) * | 2015-01-16 | 2018-01-12 | 中国科学院过程工程研究所 | A kind of liquid phase pressurization thermal decomposition method prepares the two level pyrolysis installation and method for pyrolysis of poly methylene poly phenyl poly isocyanate |
| CN110483337B (en) * | 2018-05-14 | 2020-08-28 | 中国科学院过程工程研究所 | System and method for separating and refining xylylene diisocyanate product |
| CN114984601A (en) * | 2022-07-05 | 2022-09-02 | 中国科学院过程工程研究所 | Device system and method for separating and refining 1, 5-pentamethylene diisocyanate by non-phosgene method |
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