Preparation method and preparation device of isocyanate

Abstract

The invention relates to a preparation method and a preparation device of isocyanate, and the preparation method comprises the following steps: carrying out cold reaction on a phosgene solution and an amine solution in a cold reactor to obtain an intermediate mixed solution; separating the intermediate mixed solution by adopting a cyclone, obtaining a carbamoyl chloride mixed solution from an underflow port of the cyclone, and obtaining an amine hydrochloride mixed solution from an overflow port of the cyclone; the carbamyl chloride mixed solution enters a first thermal reactor for thermal reaction to obtain a first reaction product, and the amine hydrochloride mixed solution enters a second thermal reactor for thermal reaction to obtain a second reaction product; mixing the first reaction product and the second reaction product in a staying reactor to obtain an isocyanate reaction solution; and carrying out post-treatment on the isocyanate reaction liquid to obtain the isocyanate. The method can reduce the generation amount of urea by-products, further inhibits the generation of other subsequent by-products, reduces the chromaticity of the product, and improves the quality of isocyanate.

Description

Technical Field

[0001] This invention relates to the field of isocyanate technology, and in particular to methods and apparatus for preparing isocyanates. Background Technology

[0002] The liquid-phase phosgene method is an effective and crucial step in the preparation of isocyanates, typically consisting of two stages: a cold reaction and a hot reaction. According to the reaction mechanism (main reaction, using aromatic amines as an example): in the cold reaction stage, the amine reacts with phosgene to produce carbamoyl chloride and hydrogen chloride. The generated hydrogen chloride then reacts with the amine to form amine hydrochloride. In the hot reaction stage, carbamoyl chloride directly decomposes into isocyanate, while the amine hydrochloride first decomposes into free amine, which then further reacts with phosgene to form isocyanate.

[0003]

[0004] However, free amines can also react with carbamoyl chloride or isocyanates to form urea byproducts (see side reactions). Moreover, based on reactivity analysis, free amines are more reactive with carbamoyl chloride, which may be the main way urea byproducts are formed.

[0005] Meanwhile, urea byproducts are solids with extremely poor solubility. Their formation not only clogs reactors and downstream equipment, affecting continuous operation, but also reduces product quality and impacts the application of subsequent products (such as foaming performance and polyurethane hardness). Furthermore, urea, as an intermediate, can further react with phosgene to generate impurities such as carbodiimide, urea ketimide, and phosgene adducts (colored substances) (see side reactions), increasing the variety of impurities, product color, acidity, and hydrolyzed chlorine, further reducing product quality. Therefore, effectively controlling the reaction between free amines formed from the decomposition of amine hydrochloride during the thermal reaction stage and carbamoyl chloride to control the formation of urea byproducts is particularly important.

[0006]

[0007] To suppress the formation of byproducts such as urea, and thus solve a series of problems such as production instability and low product quality caused by the formation of urea, the prior art discloses the following methods:

[0008] Patent CN114749116A discloses a combined reactor, with a tubular reactor for the cold reaction section and a reaction tower or reactor for the hot reaction section, which suppresses monofunctional and polyfunctional impurities through process condition control. However, the hot reaction section of this patent only suppresses the conversion of monofunctional impurities from the cold reaction into polyfunctional impurities, and cannot control the interaction between intermediates such as amine hydrochloride to produce byproducts such as urea.

[0009] Patent CN101811018A discloses a slanted paddle-type cold photochemical reactor, which has a good high-speed shear effect, allowing phosgene and amines to mix thoroughly, thereby suppressing the formation of amine hydrochloride, reducing thermal reaction time, and reducing the formation of byproducts such as urea. However, this process only reduces the formation of byproducts by decreasing the amount of amine hydrochloride formed, and it still cannot suppress side reactions between intermediates such as amine hydrochloride.

[0010] Patent CN104892458A discloses a method for preparing isocyanates using reactive distillation. High-pressure distillation can effectively reduce the HCl content in the circulating phosgene solution, yielding high-purity recycled phosgene. However, this method only reduces amine hydrochloride formation by lowering the HCl content in the raw phosgene; it cannot control the reaction between the HCl produced during the reaction and the amines to form amine hydrochloride. Furthermore, the high-pressure distillation apparatus carries a high risk of phosgene leakage.

[0011] Patent CN115925581A discloses a method for preparing isocyanates with low urea content. This method uses a blocking agent to control the formation of side reactions such as urea. Although the urea content is controlled to a certain extent, new substances are introduced into the reaction system, which inevitably enter the product, affecting the product quality and downstream applications.

[0012] In summary, existing technologies mainly control the formation of byproducts such as urea by means of reactor type, purity of raw materials and auxiliary materials, and isocyanate protection, but the effect is not significant enough. Summary of the Invention

[0013] Therefore, it is necessary to provide a method and apparatus for preparing isocyanate to address the above problems. The preparation method can reduce the amount of urea byproducts generated, thereby inhibiting the generation of other subsequent byproducts, reducing product color, and improving the quality of isocyanate.

[0014] A method for preparing an isocyanate, comprising the following steps:

[0015] Phosgene solution and amine solution undergo a cold reaction in a cold reactor to obtain an intermediate mixture.

[0016] The intermediate mixture is separated using a hydrocyclone, with a carbamoyl chloride mixture obtained from the underflow outlet of the hydrocyclone and an amine hydrochloride mixture obtained from the overflow outlet of the hydrocyclone.

[0017] The carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product.

[0018] The first reaction product and the second reaction product are mixed in a residence reactor to obtain an isocyanate reaction solution;

[0019] The isocyanate reaction solution was post-treated to obtain isocyanate.

[0020] In one embodiment, the step of cold reaction of the phosgene solution and the amine solution in a cold reactor simultaneously satisfies the following conditions:

[0021] (1) Temperature is 30℃-80℃, pressure is 2bar-40bar;

[0022] (2) The mass concentration of phosgene solution is 20%-90%, the mass concentration of amine solution is 10%-60%, and the molar ratio of phosgene to amine is 3:1-8:1.

[0023] In one embodiment, there are two hydrocyclones, including a first hydrocyclone and a second hydrocyclone. The intermediate mixture first enters the first hydrocyclone for separation, and the carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone. The material obtained from the overflow port of the first hydrocyclone enters the second hydrocyclone for separation, and the amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone. The material obtained from the underflow port of the second hydrocyclone is returned to the first hydrocyclone.

[0024] In one embodiment, at least one hydrocyclone is further included to further separate the carbamoyl chloride mixture obtained from the underflow port of the first hydrocyclone, and / or to further separate the amine hydrochloride mixture obtained from the overflow port of the second hydrocyclone.

[0025] In one embodiment, the step of the carbamoyl chloride mixture entering the first thermal reactor for thermal reaction simultaneously satisfies the following conditions:

[0026] (1) Pressure is 2 bar to 10 bar;

[0027] (2) A three-stage gradient temperature is adopted, with the first stage temperature being 50℃-80℃, the second stage temperature being 80℃-100℃, and the third stage temperature being 100℃-130℃;

[0028] (3) The stay time is 30min-100min.

[0029] In one embodiment, the step of the amine hydrochloride mixture entering the second thermal reactor for thermal reaction simultaneously satisfies the following conditions:

[0030] (1) Pressure is 2 bar to 10 bar;

[0031] (2) A three-stage gradient temperature is adopted, with the first stage temperature being 50℃-80℃, the second stage temperature being 80℃-100℃, and the third stage temperature being 100℃-130℃;

[0032] (3) The stay time is 50min-120min.

[0033] In one embodiment, the pressure of the residence reactor is controlled at 2 bar to 10 bar, and the temperature is controlled at 110°C to 140°C.

[0034] In one embodiment, there are two or more residence reactors, and the two or more residence reactors are connected in series. The first reaction product and the second reaction product are mixed in the first residence reactor and then pass through the series of residence reactors in sequence. The pressure of the residence reactors decreases sequentially according to the series sequence.

[0035] In one embodiment, the number of residence reactors is 2 to 6;

[0036] And / or, the pressure of the residence reactor decreases sequentially in increments of 0.2 bar to 1 bar.

[0037] In one embodiment, the post-processing step includes at least a light removal process, wherein the light removal process is carried out at a pressure of 2-10 bar and a temperature of 150°C-200°C.

[0038] In one embodiment, the amine in the amine solution is selected from methylene diphenyl diamine, polymethylene polyphenyl polyamine, a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine, 2,4-toluenediamine, a mixture of 2,4-toluenediamine and 2,6-toluenediamine, m-phenylenediamine and its isomers, p-phenylenediamine and its isomers, tetramethylxylenediamine, 1,3-dimethylaminocyclohexane, 2,6-dimethylamine, 1,5-naphthyldiamine, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 4,4'-dicyclohexylmethanediamine, 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentane Diamine, 2,4,4 (or 2,2,4)-trimethyl-1,6-diaminocyclohexane, 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- or 2,6-diamino-1-methylcyclohexane, 1-amino-1-methyl-4(3)-aminomethylcyclohexane, 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane At least one of the following: alkyl, bis(aminomethyl)norbornene, triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

[0039] A method for preparing the isocyanate described above uses a preparation apparatus comprising at least a cold reactor, a hydrocyclone, a first thermal reactor, a second thermal reactor, and a residence reactor. The cold reactor is connected to the hydrocyclone, the underflow outlet of the hydrocyclone is connected to the first thermal reactor, the overflow outlet of the hydrocyclone is connected to the second thermal reactor, and the residence reactor is connected to both the first thermal reactor and the second thermal reactor.

[0040] In one embodiment, there are two hydrocyclones, including a first hydrocyclone and a second hydrocyclone. The feed inlet of the first hydrocyclone is connected to the cold reactor, the underflow outlet of the first hydrocyclone is connected to the first hot reactor, the overflow outlet of the first hydrocyclone is connected to the feed inlet of the second hydrocyclone, the overflow outlet of the second hydrocyclone is connected to the second hot reactor, and the underflow outlet of the second hydrocyclone is connected to the feed inlet of the first hydrocyclone.

[0041] In one embodiment, at least one hydrocyclone is further included, sequentially connected to the first hydrocyclone, and / or sequentially connected to the second hydrocyclone.

[0042] In one embodiment, there are two or more residence reactors, and the two or more residence reactors are connected in series, wherein the first residence reactor is simultaneously connected to the first thermal reactor and the second thermal reactor.

[0043] In one embodiment, the number of residence reactors is 2 to 6.

[0044] In one embodiment, the first thermal reactor and the second thermal reactor are selected from a reaction tower, and the residence reactor is selected from a stirred tank reactor.

[0045] In one embodiment, the preparation apparatus further includes at least a light removal tower in communication with the residence reactor.

[0046] In the intermediate mixture obtained by cold reaction of phosgene solution and amine solution, the particle size difference between carbamoyl chloride and amine hydrochloride is relatively large. This invention utilizes this characteristic, first using a hydrocyclone to separate carbamoyl chloride and amine hydrochloride in the intermediate mixture, and then carbamoyl chloride and amine hydrochloride are respectively fed into independent thermal reactors for thermal reaction, avoiding contact between carbamoyl chloride and amine hydrochloride in the thermal reactor, thereby reducing the amount of urea byproducts generated, which in turn can inhibit the generation of other subsequent byproducts, reduce product color, and improve the quality of isocyanate. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the apparatus for preparing isocyanate according to the present invention.

[0049] In the diagram: 10, cold reactor; 21, first hydrocyclone; 22, second hydrocyclone; 31, first hot reactor; 32, second hot reactor; 40, residence reactor; 50, dephosphorization tower; 101, phosgene solution feed pipe; 102, amine solution feed pipe; 103, gas phase recovery pipe. Detailed Implementation

[0050] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0052] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0053] Combination Figure 1 As shown, the method for preparing isocyanate provided by the present invention includes the following steps:

[0054] Phosgene solution and amine solution undergo a cold reaction in cold reactor 10 to obtain an intermediate mixture;

[0055] The intermediate mixture is separated using a hydrocyclone, with a carbamoyl chloride mixture obtained from the underflow outlet of the hydrocyclone and an amine hydrochloride mixture obtained from the overflow outlet of the hydrocyclone.

[0056] The carbamoyl chloride mixture enters the first thermal reactor 31 for thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor 32 for thermal reaction to obtain the second reaction product.

[0057] The first reaction product and the second reaction product are mixed in residence reactor 40 to obtain an isocyanate reaction solution;

[0058] The isocyanate reaction solution was post-treated to obtain isocyanate.

[0059] This invention does not impose any special restrictions on the phosgene solution, amine solution, or cold reaction process conditions during the cold reaction stage. The phosgene solution is obtained by mixing phosgene with a first solvent. In some embodiments, the mass concentration of the phosgene solution is preferably 20%-90%. The first solvent is selected from organic solvents, more preferably benzene-based solvents, such as toluene, chlorobenzene, and o-dichlorobenzene.

[0060] The amine solution is obtained by mixing an amine with a second solvent. In some embodiments, the mass concentration of the amine solution is preferably 10%-60%. The second solvent is selected from organic solvents, more preferably benzene-based solvents, such as toluene, chlorobenzene, and o-dichlorobenzene. The amine is selected from methylene diphenyl diamine (mMDA), polymethylene polyphenyl polyamine (pMDA), a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA), 2,4-toluenediamine (TDA-100), a mixture of 2,4-toluenediamine and 2,6-toluenediamine (TDA-80 or TDA-65), m-phenylenediamine (XDA), and others. Isomers, p-phenylenediamine (PPDA) and its isomers, tetramethylxylenediamine (TMXDA), 1,3-dimethylaminocyclohexane (H6XDA), 2,6-dimethylamine, 1,5-naphthyldiamine (1,5-NDA), 1,4-diaminobutane, 1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA), 4,4'-dicyclohexylmethanediamine (H12MDA), 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diamino Nonane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentanediamine (MPDA), 2,4,4 (or 2,2,4)-trimethyl-1,6-diaminohexane (TMDA), 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4- or 2,6-diamino-1-methylcyclohexane (H6-TDA), 1-amino-1-methyl-4(3 1,3-(and / or 1,4)-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornene (NBDA), triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

[0061] The first solvent used in the phosgene solution is the same as the second solvent used in the amine solution.

[0062] In some embodiments, when the phosgene solution and the amine solution undergo a cold reaction in the cold reactor 10, the temperature is preferably 30°C-80°C, the pressure is preferably 2 bar-40 bar, and the molar ratio of phosgene to amine (phosgene-amine ratio) is preferably 3:1-8:1.

[0063] When the amine solution and phosgene solution undergo a cold reaction in the cold reactor 10, an intermediate mixture of amine hydrochloride and carbamoyl chloride is generated. Both carbamoyl chloride and amine hydrochloride are solid particles, and due to their different crystallization kinetics, the resulting carbamoyl chloride and amine hydrochloride have different particle sizes. For example, in the intermediate mixture obtained during the cold reaction stage using the spray mixing method of this invention, the average particle size of carbamoyl chloride is 100μm-300μm, and the average particle size of amine hydrochloride is 30μm-80μm. Therefore, carbamoyl chloride and amine hydrochloride can be separated by a hydrocyclone. Then, carbamoyl chloride and amine hydrochloride are separately introduced into independent hot reactors for hot reaction, which avoids contact between carbamoyl chloride and amine hydrochloride in the hot reactor, thereby reducing the amount of urea byproducts generated, inhibiting the generation of other subsequent byproducts, reducing product color, and improving the quality of isocyanate.

[0064] When amine solution and phosgene solution undergo a cold reaction in cold reactor 10, different reaction methods and process conditions result in different average particle sizes of carbamoyl chloride and amine hydrochloride. Therefore, the number of hydrocyclones and the separation method can be selected according to the specific average particle size of carbamoyl chloride and amine hydrochloride. Generally, the smaller the particle size difference, the more hydrocyclones are required.

[0065] For example, when a single hydrocyclone can separate carbamoyl chloride and amine hydrochloride, the intermediate mixture enters the hydrocyclone, the carbamoyl chloride mixture is obtained from the underflow outlet of the hydrocyclone, and the amine hydrochloride mixture is obtained from the overflow outlet of the hydrocyclone. When the carbamoyl chloride mixture obtained by a single hydrocyclone contains a small amount of amine hydrochloride, and / or the amine hydrochloride mixture contains a small amount of carbamoyl chloride, hydrocyclones can be used again to separate the obtained carbamoyl chloride mixture and / or amine hydrochloride mixture. In this case, the number of hydrocyclones is two or more.

[0066] In conjunction with the cold reaction of the present invention, the present invention preferably uses two hydrocyclones, including a first hydrocyclone 21 and a second hydrocyclone 22. In this case, the intermediate mixture first enters the first hydrocyclone 21 for separation. The carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone 21, which is basically free of amine hydrochloride. The material obtained from the overflow port of the first hydrocyclone 21 is a mixture of a small amount of carbamoyl chloride and amine hydrochloride. The material enters the second hydrocyclone 22 again for separation. The amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone 22, which is basically free of carbamoyl chloride. The material obtained from the underflow port of the second hydrocyclone 22 is returned to the first hydrocyclone 21.

[0067] It is understood that when at least one hydrocyclone is included, and the number of hydrocyclones is three or more, hydrocyclones can be used to further separate the carbamoyl chloride mixture obtained from the underflow port of the first hydrocyclone 21. During separation, the carbamoyl chloride mixture is obtained from the underflow port of the hydrocyclone, and the material from the overflow port can be returned to the first hydrocyclone 21 and / or the second hydrocyclone 22. Similarly, when hydrocyclones are used to further separate the amine hydrochloride mixture obtained from the overflow port of the second hydrocyclone 22, the amine hydrochloride is obtained from the overflow port of the hydrocyclone, and the material from the underflow port can be returned to the first hydrocyclone 21 and / or the second hydrocyclone 22. Hydrocyclones can be added in this manner.

[0068] Referring to the main reaction, when the carbamoyl chloride mixture enters the first thermal reactor 31 for a thermal reaction, the carbamoyl chloride directly decomposes into isocyanate and generates hydrogen chloride gas. In some embodiments, during the step of the carbamoyl chloride mixture entering the first thermal reactor 31 for a thermal reaction, the pressure is preferably 2 bar to 10 bar, the temperature is preferably 50°C to 130°C, and the residence time is preferably 30 min to 100 min. Since the thermal reaction is a reversible endothermic reaction, preferably, the first thermal reactor 31 is divided into at least two temperature zones, and the thermal reaction adopts two or more stages of gradient heating. The temperature of each stage can be kept constant. For example, when the first thermal reactor 31 is a reaction vessel, the first thermal reactor 31 is divided into three temperature zones and adopts three stages of gradient heating. The first temperature zone generally corresponds to the lower temperature zone of the first thermal reactor 31, and the first stage temperature corresponding to the first temperature zone is 50℃-80℃. The second temperature zone generally corresponds to the middle temperature zone of the first thermal reactor 31, and the second stage temperature corresponding to the second temperature zone is 80℃-100℃. The third temperature zone generally corresponds to the upper temperature zone of the first thermal reactor 31, and the third stage temperature corresponding to the third temperature zone is 100℃-130℃. Furthermore, the heights of the first, second, and third temperature zones are equal, and / or the first, second, and third stage temperatures corresponding to the first, second, and third temperature zones are kept constant. This helps to ensure that the equilibrium effectively shifts towards the positive reaction direction while reducing the amount of impurities generated.

[0069] Referring to the main reaction, when the amine hydrochloride mixture enters the second thermal reactor 32 for thermal reaction, the amine hydrochloride first decomposes into free amine, which then reacts with residual phosgene to generate carbamoyl chloride, which further decomposes into isocyanate and hydrogen chloride gas. In some embodiments, in the step of the amine hydrochloride mixture entering the second thermal reactor 32 for thermal reaction, the pressure is preferably 2 bar-10 bar, the temperature is preferably 50°C-130°C, and the residence time is preferably 50 min-120 min. Referring to the carbamoyl chloride mixture entering the first thermal reactor 31 for thermal reaction, when the amine hydrochloride mixture enters the second thermal reactor 32 for thermal reaction, it is preferable to use a two-stage or more gradient temperature increase, more preferably a three-stage gradient temperature increase, with the first stage temperature being 50°C-80°C, the second stage temperature being 80°C-100°C, and the third stage temperature being 100°C-130°C.

[0070] It is understandable that hydrogen chloride gas is generated when the carbamoyl chloride mixture undergoes a thermal reaction in the first thermal reactor 31 and the amine hydrochloride mixture undergoes a thermal reaction in the second thermal reactor 32. Therefore, gas-liquid separation is performed in both cases, and the gas phase is recovered.

[0071] Since both the first and second reaction products obtained by this invention are isocyanates, it is preferable to mix the first and second reaction products in a residence reactor 40. The residence reactor 40 can act as a protection and buffer, allowing any unreacted intermediates in the first and second reaction products to continue reacting completely, resulting in an isocyanate reaction solution. In some embodiments, the pressure of the residence reactor 40 is controlled at 2 bar to 10 bar, and the temperature is controlled at 110°C to 140°C.

[0072] Furthermore, the number of residence reactors 40 is preferably two or more, and the two or more residence reactors 40 are connected in series. The first reaction product and the second reaction product are mixed in the first residence reactor 40 and then pass through the series-connected residence reactors 40 in sequence. The pressure of the residence reactors 40 decreases in sequence according to the series connection, so that the generated hydrogen chloride gas can be discharged in time, improving the reversible decomposition reaction efficiency of the intermediate and shortening the residence time.

[0073] Preferably, the number of residence reactors 40 is 2 to 6, and the pressure of the residence reactors 40 decreases sequentially in increments of 0.2 bar to 1 bar.

[0074] The present invention does not impose special restrictions on the post-processing steps of the isocyanate reaction solution, which generally include de-lighting, desolventizing and purification, for example, the pressure of the de-lighting is 2 bar-10 bar and the temperature is 150℃-200℃.

[0075] See also Figure 1 The present invention also provides a preparation apparatus for the preparation method of the isocyanate, the preparation apparatus comprising at least a cold reactor 10, a hydrocyclone, a first hot reactor 31, a second hot reactor 32, and a residence reactor 40.

[0076] The cold reactor is preferably a static mixer, and more preferably a nozzle mixer. The cold reactor 10 is connected to a phosgene solution feed pipe 101 and an amine solution feed pipe 102. The phosgene solution and the amine solution enter the cold reactor 10 through the phosgene solution feed pipe 101 and the amine solution feed pipe 102, respectively, and undergo a cold reaction in the cold reactor 10.

[0077] The hydrocyclone is connected to the cold reactor 10. The intermediate mixture obtained in the cold reactor 10 enters the hydrocyclone and is separated into a carbamoyl chloride mixture and an amine hydrochloride mixture by the hydrocyclone. In addition, the underflow port of the hydrocyclone is connected to the first hot reactor 31. The carbamoyl chloride mixture obtained by the hydrocyclone separation enters the first hot reactor 31 for thermal reaction. The overflow port of the hydrocyclone is connected to the second hot reactor 32. The amine hydrochloride mixture obtained by the hydrocyclone separation enters the second hot reactor 32 for thermal reaction.

[0078] Both the first thermal reactor 31 and the second thermal reactor 32 are preferably reaction towers, and each reaction tower is equipped with a sieve plate, preferably 4-10 sieve plates. At the same time, the reaction tower is equipped with a jacketed heat exchanger.

[0079] like Figure 1 As shown, the present invention preferably has two hydrocyclones, including a first hydrocyclone 21 and a second hydrocyclone 22. The feed inlet of the first hydrocyclone 21 is connected to the cold reactor 10, the underflow outlet of the first hydrocyclone 21 is connected to the first hot reactor 31, the overflow outlet of the first hydrocyclone 21 is connected to the feed inlet of the second hydrocyclone 22, the overflow outlet of the second hydrocyclone 22 is connected to the second hot reactor 32, and the underflow outlet of the second hydrocyclone 22 is connected to the feed inlet of the first hydrocyclone 21.

[0080] Furthermore, the preparation apparatus further includes at least one hydrocyclone, which is sequentially connected to the first hydrocyclone 21 and / or sequentially connected to the second hydrocyclone 22. It can be understood that the sequential connection is in the same manner as the connection between the first hydrocyclone 21 and the second hydrocyclone 22, and is used to continue to separate the obtained carbamoyl chloride mixture and amine hydrochloride mixture.

[0081] Both the first thermal reactor 31 and the second thermal reactor 32 are connected to a residence reactor 40, which can be selected from a stirred tank reactor, a trough reactor, or a tubular reactor, preferably a stirred tank reactor. The first reaction product obtained in the first thermal reactor 31 and the second reaction product obtained in the second thermal reactor 32 are mixed in the residence reactor 40 and then enter a post-processing device.

[0082] Preferably, there are two or more residence reactors 40, and the two or more residence reactors 40 are connected in series. The first residence reactor 40 is connected to both the first thermal reactor 31 and the second thermal reactor 32. The first reaction product obtained from the first thermal reactor 31 and the second reaction product obtained from the second thermal reactor 32 are mixed in the first residence reactor 40, and then pass through the series-connected residence reactors 40 in sequence before finally entering the post-processing device.

[0083] Furthermore, the number of residence reactors 40 is 2 to 6.

[0084] In this invention, the post-processing device includes at least a de-glazing tower 50 connected to the residence reactor 40, for de-glazing treatment of the isocyanate reaction solution obtained from the residence reactor 40.

[0085] See also Figure 1 The preparation apparatus further includes a gas phase recovery pipe 103. The first thermal reactor 31, the second thermal reactor 32, the residence reactor 40 and the decolorization tower 50 are all connected to the gas phase recovery pipe 103, so that the generated gas can be recovered and reused through the gas phase recovery pipe 103.

[0086] The preparation method and apparatus for the isocyanate will be further described below through specific embodiments. The yield is calculated based on the amount of isocyanate generated, i.e.: Yield % = (Molar amount of isocyanate measured in the product) / (Theoretically, molar amount of isocyanate generated from amino groups in the raw material) × 100.

[0087] Example 1:

[0088] This embodiment uses a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials to prepare MDI products.

[0089] First, chlorobenzene solutions of phosgene and MDA are injected into a nozzle mixer for a cold reaction to obtain an intermediate mixture. The concentrations of phosgene and MDA are 50 wt% and 30 wt%, respectively, the phosgene-to-amine ratio is 4:1, and the reaction temperature is controlled at 80°C. oAt C, with a pressure of 15 bar, the average particle size of carbamoyl chloride in the resulting intermediate mixture was 281 μm, and the average particle size of amine hydrochloride was 77 μm.

[0090] Then, the intermediate mixture enters the first hydrocyclone for separation. The carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone, and the material obtained from the overflow port enters the second hydrocyclone for separation. The amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone, and the material obtained from the underflow port is returned to the first hydrocyclone.

[0091] Then, the carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product. The temperature of the three-stage gradient heating in both the first and second thermal reactors is controlled at 80°C. o C, 100 o C and 120 o C, the pressure is 3.5 bar, the residence time of the first thermal reactor is 100 min, and the residence time of the second thermal reactor is 120 min.

[0092] Then, the first and second reaction products are mixed in a residence reactor to obtain an isocyanate reaction solution. There are five residence reactors connected in series, all at a temperature of 120°C. o C, with pressures of 3.5 bar, 3.0 bar, 2.5 bar, 2.0 bar, and 1.5 bar respectively, the first and second reaction products are mixed in the first residence reactor, and then passed through a series of residence reactors in sequence, with the isocyanate reaction solution obtained in the last residence reactor.

[0093] Then, the isocyanate reaction solution is pumped into the dephosgene tower to remove phosgene at 180°C and 2.5 bar to obtain the dephosgene reaction solution. Finally, the dephosgene reaction solution undergoes desolvation and purification operations to obtain various MDI products with a total product yield of 99.8%, of which MDI-50 has a colorimetric value (APHA) of 12 and MDI-100 has a colorimetric value (APHA) of 8.

[0094] Example 2:

[0095] This embodiment uses toluene diamine (TDA-80) as a raw material to prepare toluene diisocyanate (TDI-80).

[0096] First, a solution of o-dichlorobenzene containing phosgene and a solution of o-dichlorobenzene containing TDA-80 were injected into a nozzle mixer for a cold reaction to obtain an intermediate mixture. The concentrations of phosgene and TDA-80 were 50 wt% and 30 wt%, respectively, the phosgene-amine ratio was 5:1, and the reaction temperature was controlled at 60°C. oAt C, with a pressure of 10 bar, the average particle size of carbamoyl chloride in the resulting intermediate mixture was 187 μm, and the average particle size of amine hydrochloride was 51 μm.

[0097] Then, the intermediate mixture enters the first hydrocyclone for separation. The carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone, and the material obtained from the overflow port enters the second hydrocyclone for separation. The amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone, and the material obtained from the underflow port is returned to the first hydrocyclone.

[0098] Then, the carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product. The temperature of the three-stage gradient heating in both the first and second thermal reactors is controlled at 60°C. o C, 100 o C and 130 o C, the pressure is 3.0 bar, the residence time of the first thermal reactor is 90 min, and the residence time of the second thermal reactor is 110 min.

[0099] Then, the first and second reaction products are mixed in a residence reactor to obtain an isocyanate reaction solution. There are four residence reactors connected in series, all at a temperature of 130°C. o C, with pressures of 3.0 bar, 2.5 bar, 2.0 bar, and 1.5 bar respectively, the first and second reaction products are mixed in the first residence reactor, and then passed through a series of residence reactors in sequence, with the isocyanate reaction solution obtained in the last residence reactor.

[0100] Then, the isocyanate reaction solution is pumped into the dephosgene tower to remove phosgene at 180°C and 2.0 bar to obtain the dephosgene reaction solution. Finally, the dephosgene reaction solution undergoes desolventizing and purification operations to obtain TDI-80 product with a product yield of 98.7% and a color (APHA) of 10.

[0101] Example 3:

[0102] This embodiment uses m-phenylenediamine (XDA) as a raw material to prepare m-phenylenediethylene diisocyanate (XDI).

[0103] First, a solution of o-dichlorobenzene containing phosgene and a solution of o-dichlorobenzene containing XDA were injected into a nozzle mixer for a cold reaction to obtain an intermediate mixture. The concentrations of phosgene and XDA were 40 wt% and 35 wt%, respectively, the phosgene-to-amine ratio was 6:1, and the reaction temperature was controlled at 70°C. oAt C, with a pressure of 15 bar, the average particle size of carbamoyl chloride in the resulting intermediate mixture was 119 μm, and the average particle size of amine hydrochloride was 32 μm.

[0104] Then, the intermediate mixture enters the first hydrocyclone for separation. The carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone, and the material obtained from the overflow port enters the second hydrocyclone for separation. The amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone, and the material obtained from the underflow port is returned to the first hydrocyclone.

[0105] Then, the carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product. The temperature of the three-stage gradient heating in both the first and second thermal reactors is controlled at 70°C. o C, 90 o C and 110 o C, the pressure is 5.0 bar, the residence time of the first thermal reactor is 80 min, and the residence time of the second thermal reactor is 100 min.

[0106] Then, the first and second reaction products are mixed in a residence reactor to obtain an isocyanate reaction solution. There are three residence reactors connected in series, all at a temperature of 110°C. o C, with pressures of 5.0 bar, 4.0 bar, and 3.0 bar respectively, the first and second reaction products are mixed in the first residence reactor, and then passed through a series of residence reactors in sequence, with the isocyanate reaction solution obtained in the last residence reactor.

[0107] Then, the isocyanate reaction solution is pumped into the dephosgene tower to remove phosgene at 200°C and 5.0 bar to obtain the dephosgene reaction solution. Finally, the dephosgene reaction solution undergoes desolvation and purification operations to obtain the XDI product with a yield of 98.8% and a color (APHA) of 17.

[0108] Example 4:

[0109] This embodiment uses 4,4'-dicyclohexylmethanediamine (H12MDA) as a raw material to prepare 4,4'-dicyclohexylmethane diisocyanate (H12MDI).

[0110] First, a chlorobenzene solution of phosgene and a chlorobenzene solution of H12MDA are injected into a nozzle mixer for a cold reaction to obtain an intermediate mixture. The concentrations of phosgene and H12MDA are 60 wt% and 40 wt%, respectively, the phosgene-amine ratio is 8:1, and the reaction temperature is controlled at 50°C. oAt C, with a pressure of 10 bar, the average particle size of carbamoyl chloride in the resulting intermediate mixture was 169 μm, and the average particle size of amine hydrochloride was 45 μm.

[0111] Then, the intermediate mixture enters the first hydrocyclone for separation. The carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone, and the material obtained from the overflow port enters the second hydrocyclone for separation. The amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone, and the material obtained from the underflow port is returned to the first hydrocyclone.

[0112] Then, the carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product. The temperature of the three-stage gradient heating in both the first and second thermal reactors is controlled at 50°C. o C, 90 o C and 120 o C, the pressure is 4.0 bar, the residence time of the first thermal reactor is 80 min, and the residence time of the second thermal reactor is 100 min.

[0113] Then, the first and second reaction products are mixed in a residence reactor to obtain an isocyanate reaction solution. There are three residence reactors connected in series, all at a temperature of 120°C. o C, with pressures of 4.0 bar, 3.0 bar, and 2.0 bar respectively, the first and second reaction products are mixed in the first residence reactor, and then passed through a series of residence reactors in sequence, with the isocyanate reaction solution obtained in the last residence reactor.

[0114] Then, the isocyanate reaction solution is pumped into the dephosgene tower to remove phosgene at 160°C and 3.0 bar to obtain the dephosgene reaction solution. Finally, the dephosgene reaction solution undergoes desolvation and purification operations to obtain H12MDI product with a total product yield of 98.4% and a color (APHA) of 14.

[0115] Comparative Example 1:

[0116] This comparative example uses a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials to prepare MDI products.

[0117] First, chlorobenzene solutions of phosgene and MDA are injected into a nozzle mixer for a cold reaction to obtain an intermediate mixture. The concentrations of phosgene and MDA are 50 wt% and 30 wt%, respectively, the phosgene-to-amine ratio is 4:1, and the reaction temperature is controlled at 80°C. oAt C, with a pressure of 15 bar, the average particle size of carbamoyl chloride in the resulting intermediate mixture was 281 μm, and the average particle size of amine hydrochloride was 77 μm.

[0118] Then, the intermediate mixture was sequentially fed into six hot reactors at a temperature of 120°C. o At C, with a pressure of 3.5 bar, an isocyanate reaction solution was obtained. Finally, the isocyanate reaction solution was subjected to dephosgene, desolventization, and purification operations to obtain various MDI products. The total product yield was 95.5%, of which MDI-50 had a color intensity (APHA) of 33 and MDI-100 had a color intensity (APHA) of 24.

[0119] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an isocyanate, characterized in that, Includes the following steps: Phosgene solution and amine solution undergo a cold reaction in a cold reactor to obtain an intermediate mixture. The intermediate mixture is separated using a hydrocyclone, with a carbamoyl chloride mixture obtained from the underflow outlet of the hydrocyclone and an amine hydrochloride mixture obtained from the overflow outlet of the hydrocyclone. The carbamoyl chloride mixture enters the first thermal reactor for a thermal reaction to obtain the first reaction product, and the amine hydrochloride mixture enters the second thermal reactor for a thermal reaction to obtain the second reaction product. The first reaction product and the second reaction product are mixed in a residence reactor to obtain an isocyanate reaction solution; The isocyanate reaction solution was post-treated to obtain isocyanate.

2. The method for preparing isocyanate according to claim 1, characterized in that, The cold reaction step involving phosgene solution and amine solution in a cold reactor simultaneously satisfies the following conditions: (1) Temperature is 30℃-80℃, pressure is 2bar-40bar; (2) The mass concentration of phosgene solution is 20%-90%, the mass concentration of amine solution is 10%-60%, and the molar ratio of phosgene to amine is 3:1-8:

1.

3. The method for preparing isocyanate according to claim 1, characterized in that, The number of hydrocyclones is two, including a first hydrocyclone and a second hydrocyclone. The intermediate mixture first enters the first hydrocyclone for separation, and the carbamoyl chloride mixture is obtained from the underflow port of the first hydrocyclone. The material obtained from the overflow port of the first hydrocyclone enters the second hydrocyclone for separation, and the amine hydrochloride mixture is obtained from the overflow port of the second hydrocyclone. The material obtained from the underflow port of the second hydrocyclone is returned to the first hydrocyclone.

4. The method for preparing isocyanate according to claim 3, characterized in that, It also includes at least one hydrocyclone for further separation of the carbamoyl chloride mixture obtained from the underflow port of the first hydrocyclone, and / or for further separation of the amine hydrochloride mixture obtained from the overflow port of the second hydrocyclone.

5. The method for preparing isocyanate according to claim 1, characterized in that, The step of the carbamoyl chloride mixture entering the first thermal reactor for thermal reaction simultaneously satisfies the following conditions: (1) Pressure is 2 bar to 10 bar; (2) A three-stage gradient temperature is adopted, with the first stage temperature being 50℃-80℃, the second stage temperature being 80℃-100℃, and the third stage temperature being 100℃-130℃; (3) The stay time is 30min-100min.

6. The method for preparing isocyanate according to claim 1, characterized in that, The step of the amine hydrochloride mixture entering the second thermal reactor for thermal reaction simultaneously satisfies the following conditions: (1) Pressure is 2 bar to 10 bar; (2) A three-stage gradient temperature is adopted, with the first stage temperature being 50℃-80℃, the second stage temperature being 80℃-100℃, and the third stage temperature being 100℃-130℃; (3) The stay time is 50min-120min.

7. The method for preparing isocyanate according to claim 1, characterized in that, The pressure of the residence reactor is controlled at 2 bar-10 bar, and the temperature is controlled at 110℃-140℃.

8. The method for preparing isocyanate according to claim 7, characterized in that, The number of residence reactors is two or more, and the two or more residence reactors are connected in series. The first reaction product and the second reaction product are mixed in the first residence reactor and then pass through the series of residence reactors in sequence. The pressure of the residence reactors decreases sequentially according to the series sequence.

9. The method for preparing isocyanate according to claim 8, characterized in that, The number of residence reactors is 2 to 6; And / or, the pressure of the residence reactor decreases sequentially in increments of 0.2 bar to 1 bar.

10. The method for preparing isocyanate according to claim 1, characterized in that, The post-processing steps include at least a light removal process, wherein the light removal process is carried out at a pressure of 2-10 bar and a temperature of 150-200°C.

11. The method for preparing isocyanate according to claim 1, characterized in that, The amine in the amine solution is selected from methylene diphenyl diamine, polymethylene polyphenyl polyamine, a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine, 2,4-toluenediamine, a mixture of 2,4-toluenediamine and 2,6-toluenediamine, m-phenylenediamine and its isomers, p-phenylenediamine and its isomers, tetramethylxylenediamine, 1,3-dimethylaminocyclohexane, 2,6-dimethylamine, 1,5-naphthyldiamine, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 4,4'-dicyclohexylmethanediamine, 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentanediamine, 2, 4,4 (or 2,2,4)-trimethyl-1,6-diaminocyclohexane, 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- or 2,6-diamino-1-methylcyclohexane, 1-amino-1-methyl-4(3)-aminomethylcyclohexane, 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane, bis At least one of (aminomethyl)norbornene, triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

12. A preparation apparatus used in the method for preparing the isocyanate according to any one of claims 1-11, characterized in that, The preparation apparatus includes at least a cold reactor, a hydrocyclone, a first thermal reactor, a second thermal reactor, and a residence reactor, wherein the cold reactor is connected to the hydrocyclone, the underflow port of the hydrocyclone is connected to the first thermal reactor, the overflow port of the hydrocyclone is connected to the second thermal reactor, and the residence reactor is connected to both the first thermal reactor and the second thermal reactor.

13. The preparation apparatus according to claim 12, characterized in that, The number of hydrocyclones is two, including a first hydrocyclone and a second hydrocyclone. The feed inlet of the first hydrocyclone is connected to the cold reactor, the underflow outlet of the first hydrocyclone is connected to the first hot reactor, the overflow outlet of the first hydrocyclone is connected to the feed inlet of the second hydrocyclone, the overflow outlet of the second hydrocyclone is connected to the second hot reactor, and the underflow outlet of the second hydrocyclone is connected to the feed inlet of the first hydrocyclone.

14. The preparation apparatus according to claim 13, characterized in that, It also includes at least one hydrocyclone, which is sequentially connected to the first hydrocyclone, and / or sequentially connected to the second hydrocyclone.

15. The preparation apparatus according to claim 12, characterized in that, The number of residence reactors is two or more, and the two or more residence reactors are connected in series in sequence, wherein the first residence reactor is simultaneously connected to the first thermal reactor and the second thermal reactor.

16. The preparation apparatus according to claim 15, characterized in that, The number of residence reactors is 2 to 6.

17. The preparation apparatus according to claim 12, characterized in that, The first thermal reactor and the second thermal reactor are selected from reaction towers, and the residence reactor is selected from stirred tank reactors.

18. The preparation apparatus according to claim 12, characterized in that, The preparation apparatus further includes at least a light removal tower connected to the residence reactor.

Images