Industrializable IPDI synthesis process

Abstract

The present invention relates to the technical field of IPDI synthesis, specifically an industrializable IPDI synthesis process, comprising a synthesis process for n-butyl isophorone dicarbamate and a thermal cracking process for n-butyl isophorone dicarbamate. The synthesis process of the present invention has a simple flow, low pollution, high raw material utilization, high economic benefits, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of IPDI synthesis, in particular to an industrializable IPDI synthesis process. Background Art

[0002] Isocyanates are substances containing one or more NCO groups that react with polyols to synthesize polyurethane materials. Currently, isocyanates primarily include MDI, TDI, HDI, IPDI, HMDI, XDI, NDI, PPDI, and CHDI. MDI and TDI are currently the two most important types, accounting for over 90% of the total isocyanate supply. HDI, IPDI, and hydrogenated MDI have become increasingly popular in recent years due to their excellent weather resistance and yellowing resistance.

[0003] IPDI (isophorone diisocyanate, CAS No. 4098-71-9) is a preferred raw material for synthesizing light-stable, weather-resistant polyurethanes and a high-end isocyanate raw material. It is primarily used in waterborne polyurethane dispersions, anti-corrosion coatings, UV resins, adhesives, PU resins, inks, and other fields. IPDI is also used in the rocket propellant industry.

[0004] IPDI production methods primarily include phosgene and carbamate thermal decomposition. Phosgene is currently the predominant method for producing diisocyanates. Phosgene methods primarily include liquid-phase and gas-phase phosgene. However, the liquid-phase phosgene method suffers from long reaction times, large solvent requirements, low reactor space-time efficiency, and numerous byproducts, making it relatively backward. The gas-phase phosgene method presents a series of difficult engineering challenges, including safety and environmental protection, severe equipment corrosion, and high material requirements, resulting in significant equipment investment. The resulting isocyanate product contains hydrolyzed chlorine, which affects its performance. Consequently, developed countries have been committed to developing economical and simple synthesis methods, resulting in the emergence of various non-phosgene methods for synthesizing isocyanates, such as carbonylation, thermal decomposition of chloroformamide, Crutius rearrangement, reaction of amines with chloroformates, and thermal decomposition of carbamates. However, most remain at the laboratory stage, with only the thermal decomposition of carbamates achieving industrial scale production abroad. The urea method, on the other hand, is the most studied, relatively mature, and already in industrial use. The urea method for preparing isocyanate includes two major steps: the first is to react urea, diamine and alcohol to form dicarbamate, and the second is to thermally crack the dicarbamate to form isocyanate and alcohol. The total yield of the reaction can reach 90%.

[0005] my country's diisocyanate research and development and production started relatively late, but with rapid social and economic development, the country has become a major global producer and consumer of diisocyanates. Meanwhile, development in the field of high-performance specialty isocyanates has been much slower, while consumer demand is growing at an annual rate of over 15%. Aliphatic isocyanates are primarily used in automotive topcoats, rocket propellants, anti-corrosion coatings, UV-curable coatings, and adhesives. However, due to historical limitations in importing technology, high-end coatings for industries like automobiles, high-speed trains, aircraft, ships, luxury coaches, wood furniture, and construction are all dominated by foreign manufacturers. One of the limiting factors is the key raw material, aliphatic diisocyanates.

[0006] Currently, my country's annual demand for HDI and IPDI is approximately 95,000 tons, primarily captured by a handful of multinational companies like Evonik and Degussa. Domestic demand for these products is essentially entirely dependent on imports, and some high-end military-grade products are subject to sales restrictions in my country. Therefore, the production of aliphatic diisocyanates in China, particularly using green, non-phosgene synthesis technologies, is essential for promoting technological advancement and industrial upgrading in related industries, safeguarding the industrial security of key sectors in my country, and possessing enormous economic benefits and significant social significance.

[0007] The production of aliphatic diisocyanates in China, especially the use of non-phosgene green synthesis technology, is very necessary for promoting technological progress and industrial upgrading in related industries and for ensuring the industrial security of important industries in my country. It has huge economic benefits and significant social significance. However, currently only Degussa and BASF have built 10,000 tons / year production facilities each using the non-phosgene method.

[0008] At present, the domestic industrialized urea process produces IPDU-B (dimer of IPDI, with the molecular formula: ) is still a blank, and the production and synthesis technology of IPDU-B has been monopolized by foreign countries. Based on the great significance of IPDI to the national economy and industrial security and the reality of backward domestic production development, the present invention provides an industrial process for synthesizing n-butyl isophorone dicarbamate using the urea method to break the technological monopoly of developed countries on the industrial urea method for synthesizing IPDI. It is intended not only to eliminate the high process risks and environmental safety hazards of the phosgene method from the root, but also to strive to have the same competitiveness as the phosgene method in terms of cost. Summary of the Invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an industrializable IPDI synthesis process to at least achieve the effects of simple process flow, low pollution, high raw material utilization, high economic benefits, and suitability for large-scale industrial production.

[0010] The object of the present invention is achieved through the following technical solutions:

[0011] The industrializable IPDI synthesis process is characterized by comprising a synthesis process of n-butyl isophorone dicarbamate and a thermal cracking process of n-butyl isophorone dicarbamate;

[0012] The synthesis process of n-butyl isophorone dicarbamate comprises: performing an alkoxycarbonylation reaction of an organic amine with IPDA, n-butanol, urea and a catalyst, introducing a carrier gas during the alkoxycarbonylation reaction to separate the by-product ammonia, and obtaining n-butyl isophorone dicarbamate and a synthetic tail gas containing an ammonia component; subjecting the synthetic tail gas to an n-butanol deamination process to obtain deaminated n-butanol, which is then refluxed into a reactor and ammonia-containing tail gas is discharged; removing ammonium carbamate from the ammonia-containing tail gas to obtain n-butanol, ammonium carbamate and deammonium carbamate tail gas; removing residual n-butanol from the deammonium carbamate tail gas to obtain n-butanol and dealcoholization tail gas; and removing the ammonia component from the dealcoholization tail gas to obtain an ammonium salt and a final tail gas.

[0013] Specifically, the synthesis process of isophorone dicarbamate comprises the following steps:

[0014] (1) IPDA (isophorone diamine, CAS No. 2855-13-2), n-butanol, urea, and catalyst I are used in a reactor to carry out an alkoxycarbonylation reaction of an organic amine (IPDA is an organic amine containing two amino groups). The byproduct ammonia gas of the alkoxycarbonylation reaction is discharged along with the evaporated excess n-butanol and carrier gas (this mixed gas phase material is the synthesis tail gas), and the ammonia dissolved in the condensed and refluxed liquid phase n-butanol in the synthesis tail gas is largely removed by distillation (stripping deamination tower). After completion of the reaction, crude isophorone dicarbamic acid n-butyl ester (IPDU-B) is obtained. During the reaction, ammonia-containing tail gas containing n-butanol, carrier gas, and ammonia components is discharged.

[0015] The crude isophorone dicarbamate n-butyl ester is subjected to a refining process consisting of flash evaporation and falling film evaporation to obtain the target product isophorone dicarbamate n-butyl ester;

[0016] It is worth noting that in order to better separate the by-product ammonia, the carrier gas is directly introduced into the reaction liquid of the alkoxycarbonylation reaction. The carrier gas and the evaporated n-butanol vapor will carry out the tail gas containing the ammonia component, thereby accelerating the reaction speed and making the reaction more thorough.

[0017] (2) the synthetic tail gas is subjected to a n-butanol deamination process to obtain a deaminated n-butanol reflux reactor and discharge ammonia-containing tail gas;

[0018] The butanol deamination process involves removing most of the dissolved ammonia from the liquid n-butanol condensed and refluxed from the overhead condenser (stripping deamination tower) through distillation. The uncondensed gas phase discharged from the overhead condenser is an ammonia-containing tail gas containing a small amount of n-butanol and primarily carrier gas and ammonia.

[0019] Furthermore, the deaminated n-butanol is returned as a raw material to the alkoxycarbonylation reaction, which maintains the raw material ratio while greatly reducing the concentration of by-product ammonia in the reaction system, prompting the reaction equilibrium to shift to the right, improving the reaction yield, and saving a lot of industrial costs.

[0020] (3) removing ammonium carbamate from the ammonia-containing tail gas to obtain n-butanol, ammonium carbamate, and deammonium carbamate tail gas;

[0021] It's worth noting that trace amounts of water (approximately 0.3-0.5%) introduced by the raw urea hydrolyze under the IPDU synthesis reaction conditions to produce trace amounts of CO2, which is discharged with the reaction exhaust. At lower temperatures, CO2 reacts with ammonia to form ammonium carbamate (a reversible reaction that decomposes into CO2 and ammonia at higher temperatures). Ammonium carbamate has a melting point of approximately 59-60°C and can precipitate in the low-temperature sections of the process, potentially blocking pipes and valves.

[0022] The ammonium carbamate material that needs to be removed is: the ammonia-containing tail gas obtained in the process of synthesizing isophorone diaminobutyl ester by the urea method is condensed to liquefy the residual n-butanol in the ammonia-containing tail gas, and then the trace amount of carbon dioxide in the ammonia-containing tail gas reacts with the ammonia component to generate ammonium carbamate powder.

[0023] The method for removing ammonium carbamate comprises: condensing the ammonia-containing tail gas to liquefy the residual n-butanol in the ammonia-containing tail gas, reacting carbon dioxide with the ammonia component to generate ammonium carbamate, and separating the ammonium carbamate powder and n-butanol liquid obtained by condensation;

[0024] The material separation comprises the following steps: after the condensation treatment, performing gas-liquid separation on the mixture of ammonium carbamate and liquid n-butanol obtained by condensation to obtain ammonia-containing tail gas containing ammonium carbamate powder and liquid n-butanol; and then performing gas-solid separation on the ammonia-containing tail gas containing ammonium carbamate powder to remove solid ammonium carbamate.

[0025] Furthermore, the gas-solid separation treatment is carried out by: passing the ammonia-containing tail gas into a gas-solid separator;

[0026] Furthermore, the ammonium carbamate removal process also includes a gas-solid separator regeneration process, and the regeneration process includes: after ammonium carbamate is enriched in the gas-solid separator, the ammonium carbamate enriched in the gas-solid separator is blown away by high-temperature nitrogen, so that the ammonium carbamate solid is decomposed into ammonia components and carbon dioxide, so as to regenerate the gas-solid separator.

[0027] It is worth noting that two gas-solid separators need to be set up for switching use. One of them needs to be switched out of the process after a certain working cycle and regenerated by back-flushing with high-temperature inert gas. At this time, the other gas-solid separator is switched to work.

[0028] (4) removing residual n-butanol from the decarbamate tail gas to obtain n-butanol and dealcoholized tail gas;

[0029] It is worth noting that the formation process of the residual n-butanol is as follows: in the process of synthesizing isophorone diamino-n-butyl ester by the urea method, most of the n-butanol is removed by the n-butanol deamination process, and then the n-butanol is further removed by condensation through the ammonium carbamate removal process, but there is still a trace amount of n-butanol that cannot be condensed;

[0030] The method for removing the residual n-butanol is as follows: cooling the decarbamate tail gas to 15-25° C., and then adsorbing the n-butanol in the tail gas with an adsorbent (adsorption step);

[0031] The adsorbent includes: molecular sieve, activated carbon, and high molecular adsorption resin.

[0032] After adsorption by the adsorbent, a dealcohol tail gas is obtained, wherein the content of n-butanol in the dealcohol tail gas is less than 12 mg / m 3 .

[0033] The adsorbent can selectively adsorb n-butanol, but does not adsorb amino groups. It is preferably a special adsorbent of Haipu Nano HDV536, with a particle size (0.6-1.25mm)>95%, a specific surface area of ​​1400㎡ / g, a pore volume of 0.90ml / g, and a pore size of

[0034] Furthermore, the method for removing residual n-butanol further comprises the following steps (desorption step): desorbing and regenerating the adsorbent using high-temperature nitrogen to obtain a regenerated adsorbent and a regenerated tail gas, and then condensing the regenerated tail gas to obtain liquid n-butanol and an inert gas containing a trace amount of n-butanol;

[0035] The temperature of the high temperature inertness is 140-160°C;

[0036] The adsorbent is used to obtain dealcohol tail gas after adsorption, and the content of n-butanol in the dealcohol tail gas is less than 12 mg / m 3 ;

[0037] The method for removing residual n-butanol comprises setting up at least two sets of adsorption units, which perform adsorption and desorption operations alternately.

[0038] Furthermore, the n-butanol obtained in the ammonium carbamate removal and residual n-butanol removal steps is collected and used as a raw material for subsequent batch reactions.

[0039] (5) the dealcoholization tail gas is subjected to ammonia component removal treatment to obtain ammonium salt and final tail gas;

[0040] The ammonia component removal treatment is as follows: the dealcoholization tail gas is passed through an acid solution to allow the ammonia component in the dealcoholization tail gas to react with the acid to form an ammonium salt.

[0041] It is worth noting that the present invention has built an industrial device with an annual output of 100t and completed industrial verification, and is currently building an industrial device with an annual output of 2kt.

[0042] The main equipment of the industrialized plant with an annual output of 2kt to be constructed in this invention includes: Reactor: Φ1400×4253, 5.4m 3 , Stripping deamination tower: Φ500×5000 (tower top condenser A=20m 2 ), flash evaporator Φ700×1600, falling film evaporator Φ1000×2500; ammonia tail gas condenser: A=5.4m2, gas-liquid separator: V=0.61m 3 Φ700×1300 (straight tube); gas-solid separator: V=0.61m 3 Φ700×1300 (straight tube); butanol adsorption tower: diameter 1800mm, height 2000mm, 3 units, operating conditions: 30-150℃ (regeneration 150℃), slightly positive pressure.

[0043] The main equipment of the industrialized plant with an annual output of 100t of the present invention includes: reactor: Φ650×800, 300L, stripping deamination tower: Φ273×3000 (deamination tower top condenser A=6m 2 ), falling film evaporator Φ300×1200; ammonia tail gas condenser: A=2.2m 2 , gas-liquid separator: V=0.10m 3 Φ400×800 (straight tube); gas-solid separator: V=0.61m3Φ700×1300 (straight tube); butanol adsorption tower: diameter 300mm, height 1200mm, 3 units, operating conditions: 30-150℃ (regeneration 150℃), slightly positive pressure.

[0044] The thermal cracking process of isophorone diaminobutyl ester comprises:

[0045] 1) coupled thermal decomposition and distillation of n-butyl isophorone dicarbamate: n-butyl isophorone dicarbamate, a solvent, and a catalyst are introduced into a first thermal decomposition reactor for reaction to obtain a gaseous material 1, the gaseous material 1 and the gaseous material 3 are combined and introduced into a first distillation tower for distillation, n-butanol is obtained at the top of the tower, an IPDI-rich liquid is withdrawn from a middle side line, and heavy components are discharged from the bottom of the tower; the IPDI-rich liquid is introduced into a second distillation tower for operation, a small amount of a mixed liquid of n-butanol and IPDI is separated from the top of the tower, an IPDI product is withdrawn from a middle side line, and heavy components are discharged from the bottom of the tower; the heavy components discharged from the bottom of the first distillation tower and the bottom of the second distillation tower are liquid material 2, the liquid material 2 is introduced into a second thermal decomposition reactor for reaction to obtain gaseous material 3, the gaseous material 3 is returned to the first distillation tower and introduced into the first distillation tower together with the gaseous material 1 for distillation; the above process is carried out continuously.

[0046] The first thermal decomposition reactor thermally decomposes the raw material IPDU-B. The second thermal decomposition reactor thermally decomposes the contents of the first and second distillation column bottoms (both primarily consisting of isophorone isocyanato monobutyl carbamate and a small amount of IPDI), forming a circulation system with the distillation process. A circulation tank and circulation pump are located below the two thermal decomposition reactors, allowing for the recycling of solvent and catalyst. The circulation rate is adjusted based on the material quantity to maintain an appropriate ratio of raw material, solvent, and catalyst.

[0047] The gaseous material 1 and the gaseous material 3 are combined and then enter the first distillation tower at the same position, which is required for the design and stable operation of the distillation tower.

[0048] The above-mentioned isophorone isocyanate monobutyl carbamate is an intermediate product of incomplete thermal decomposition of IPDU-B, referred to as "monobutyl isophorone isocyanate".

[0049] 2) Heavy component material discharge step: The circulating materials (solvent, catalyst) of the first thermal decomposition reactor and the second thermal decomposition reactor will be enriched with heavy component materials (including by-product colloids, raw material impurities, spent catalyst, etc.) as the reaction proceeds. The first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge the circulating materials and continuously replenish the same amount of solvent and catalyst to avoid the accumulation of heavy component materials;

[0050] Furthermore, in step 1), the pressure of the first thermal decomposition reactor is controlled to be -0.08 to -0.098 MPa and the temperature is controlled to be 200 to 280°C;

[0051] And / or, in step 1), the pressure of the second thermal decomposition reactor is controlled to be -0.08 to -0.098 MPa and the temperature is controlled to be 200 to 280°C.

[0052] Furthermore, the first thermal decomposition reactor is controlled at a pressure of -0.092 to -0.098 MPa and a temperature of 220 to 260°C;

[0053] And / or, the pressure of the second thermal decomposition reactor is controlled to be -0.092 to -0.098 MPa and the temperature is controlled to be 220 to 260°C.

[0054] Furthermore, the temperature of the second thermal decomposition reactor is 1 to 10° C. higher than the temperature of the first thermal decomposition reactor.

[0055] Furthermore, in step 1), the mass ratio of isophorone dicarbamic acid n-butyl ester, solvent and catalyst is: 1:0-9:0.0025-0.015. Preferably, the mass ratio of isophorone dicarbamic acid n-butyl ester, solvent and catalyst is: 1:0.67-9:0.003-0.010.

[0056] Furthermore, in step 1), the isophorone dicarbamic acid n-butyl ester is an isophorone dicarbamic acid n-butyl ester product synthesized by the urea method; preferably, reference is made to patent 202211207615.2 applied for by the applicant in the same batch, which is an industrializable IPDI synthesis method.

[0057] The solvent is one of naphthenic oil, trioctyl trimellitate, and trinonyl trimellitate;

[0058] The catalyst is one or more of zinc picolinate, chromium picolinate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate, and zinc isooctanoate, preferably one of zinc picolinate, chromium picolinate, and MOF-5.

[0059] Furthermore, in step 1), the first thermal decomposition reactor and / or the second thermal decomposition reactor is a thin film evaporator.

[0060] Furthermore, in step 1), the thin film evaporator is a wiped film evaporator.

[0061] Furthermore, in step 2), the discharged recycled material is subjected to preliminary separation (stationary sedimentation) to obtain a primary solvent and a primary heavy component material, and the primary heavy component material is heated and evaporated to obtain a gaseous product and a residue. The primary solvent and the gaseous product can be condensed and used as the solvent in the thermal decomposition step of isophorone diaminobutyrate.

[0062] Furthermore, in step 2), when the solvent is cyclohexane oil, the heating and evaporation temperature is 280 to 350° C., and the reaction pressure is -0.096 to -0.098 MPa.

[0063] Furthermore, in step 1), the operating pressure of the first distillation tower is 10-30 mbar, the bottom temperature is 190-210°C, the top operating temperature is 20-30°C, and the side line temperature is 150-170°C; preferably, the operating pressure of the first distillation tower is 10-25 mbar, the bottom temperature is 199-202°C, the top operating temperature is 24-26°C, and the side line temperature is 159.5-161.5°C.

[0064] And / or, the operating pressure of the second distillation tower is 10-30 mbar, the bottom temperature is 190-200°C, the top operating temperature is 30-50°C, and the side line temperature is 155-160°C; preferably, the operating pressure of the second distillation tower is 10-25 mbar, the bottom temperature is 193-195°C, the top operating temperature is 39-41°C, and the side line temperature is 158-159°C.

[0065] As can be seen from the chemical formula of IPDI mentioned in the background, IPDI is highly reactive and can react with a wide variety of groups. Precisely because of this reactivity, despite the urea process comprising only two steps, domestic scientists and technicians have been unable to commercialize IPDI production using this process. The process of thermally cracking IPDU-B to produce IPDI is theoretically feasible, but despite its significant economic value, no domestic company has truly achieved industrial production. The primary reason for this is that existing technologies and companies have failed to fully understand the reasons why the urea process is infeasible for industrial IPDI synthesis. They often assume that this impossibility stems from the process's high equipment requirements, the need for high temperatures, and the relatively difficult operation. In reality, this is because industrial IPDI production presents numerous subtle issues. Industrial production of IPDI produces a large number of byproducts, the amount of which is a key determinant of the scale and viability of industrial production.

[0066] The document "Study on the Synthesis Process of Isophorone Diisocyanate" reports on pages 45-46 the research conclusions on the thermal cracking of IPDC to produce IPDI, pointing out that the NCO content in the reaction product can reach 30.1% (approximately 60.2% yield) when it is high; it also points out that the IPDI content obtained by thermal decomposition under the same reaction conditions varies greatly, with the lowest reaching 18.4% (approximately 36.4% yield). The reason for this is that a series of complex, uncontrollable, and varying degrees of chemical side reactions occur during the reaction process.

[0067] A search of the prior art reveals that a small number of patents report the ability to industrially and continuously produce IPDI with high yields (reaching 90%). In fact, Yuhshi Luh et al. conducted extensive research on the thermal decomposition of carbamates using state-of-the-art equipment, demonstrating that after the reaction is complete, the conversion of isophorone carbamate is 95%, with the maximum theoretical yield of alcohol at 90%, the maximum theoretical yield of isophorone diisocyanate at 65%, and the maximum theoretical yield of isophorone monoisocyanate at 27%. The inventors of the present application have also conducted extensive research and concluded, consistent with Yuhshi Luh et al., that even multiple cycles of thermal decomposition in a single thermal reactor cannot currently achieve high yields.

[0068] At the same time, peers do not pay attention to the research on the separation of thermal decomposition products, ignoring the existence of side reactions, the difficulty of separation design itself, and other issues. According to public information, most of them only briefly mention the separation aspect, and some are immature or even wrong.

[0069] The inventors of this application have discovered that during the thermal cracking of IPDU-B to produce IPDI, there are many types of side reactions, but the most prominent and fatal side reaction is the series of reactions between IPDI and the raw material (IPDU-B). Specifically, one secondary amine hydrogen reacts with one isocyanate group. A raw material IPDU-B molecule has two secondary amine hydrogens, which react simultaneously with the two isocyanate groups of the product IPDI and react separately with one isocyanate group of the two reactants, thus involving six types of by-products. From a kinetic point of view, as the temperature rises, the more active the secondary amine hydrogen (proton), the greater the reaction constant for dissociation, the easier it is for the reactive group to bind to the catalyst, and the activation energy of the entire side reaction decreases, which is conducive to the progress of the side reaction. Therefore, the generation of such by-products is extremely difficult to avoid. By the same principle, the intermediate product will also undergo the above-mentioned side reactions with the raw material (IPDU-B) on one side.

[0070] Furthermore, the decomposition activation energies of the primary and secondary carbamate groups in the raw material (IPDU-B) differ. The secondary carbamate groups have lower decomposition activation energies and are more easily decomposed. Consequently, the content of unimodal in the thermal decomposition products of IPDU-B is significantly higher than that of the target product (IPDI). The subsequent thermal decomposition of unimodal requires a higher temperature than the decomposition temperature of IPDU-B.

[0071] The inventors of this application have discovered that separating and purifying the pyrolysis products is also a challenge. The reaction products include n-butanol, butanol, IPDI, and solvent. The intermediate product, butanol, lacks readily available physical property data. Furthermore, side reactions between the pyrolysis products (the reverse reaction of thermal decomposition) and product self-polymerization also pose significant challenges to separation design. Among these, the rapid side reaction between the target product, IPDI, and n-butanol is the most significant issue affecting final yield and product quality.

[0072] Based on this, the inventors of this application creatively designed and implemented the above-mentioned IPDU-B thermal decomposition and product separation (distillation) process, which resolved the main contradictions, reduced side reactions to an acceptable level, and achieved satisfactory results. Its characteristics are:

[0073] 1. Two thermal decomposition reactors are used: the first performs thermal decomposition only on the raw material IPDU-B, while the second performs thermal decomposition only on one side. Compared to using a single reactor for multiple cycles of thermal decomposition, this fundamentally solves the primary problem of side reactions caused by back-mixing between the raw material IPDU-B and the product IPDI, and on one side. Furthermore, the second thermal decomposition reactor can independently control a higher temperature, eliminating the problem of single-side thermal decomposition requiring a higher temperature than IPDU-B, thereby improving reaction efficiency.

[0074] 2. Optimized distillation design minimizes the impact of side reactions and isolates qualified IPDI products. The first distillation column rapidly separates the vast majority (over 99.6% of the total) of n-butanol in the system feed, significantly reducing side reactions between IPDI and n-butanol. This also minimizes the IPDI content in the bottoms and maximizes the IPDI content in the side-stream IPDI rich solution. The second distillation column efficiently obtains qualified IPDI products through side-stream extraction.

[0075] 3. The coupled design of thermal decomposition and distillation realizes continuous thermal decomposition reaction and separation of reaction products with low risk of side reactions, as well as large-scale thermal decomposition and distillation cycles of single-side components.

[0076] The beneficial effects of the present invention are:

[0077] 1. The synthesis process of the present invention is simple, has low pollution, high raw material utilization rate, and high economic benefit. The by-product ammonia is removed by carrier gas and n-butanol vapor, which is conducive to promoting the rapid and efficient progress of the synthesis reaction. In addition, through multiple process intensification designs, the yield of isophorone dicarbamic acid n-butyl ester is above 98%, which is suitable for large-scale industrial production.

[0078] 2. The ammonium carbamate treatment process of the present invention is simple, does not require manual operation, has a good removal effect, and can ensure that the isophorone dicarbamate synthesis tail gas treatment process is continuous and smooth.

[0079] 3. The method of the present invention treats the tail gas of isophorone dicarbamate n-butyl ester, and the n-butanol content in the tail gas is far lower than the industrial emission standard (12 mg / m 3 ), there is no secondary pollution, the system is highly safe, and the desorption tail gas containing trace amounts of n-butanol and nitrogen after separation can be recycled back to the front end of the desorption tower for reuse, avoiding secondary pollution. The system is highly safe, the service life of the adsorbent is up to 3-5 years, and the n-butanol adsorption rate is high (>99%).

[0080] 4. The design of the present invention greatly improves the product yield, with the IPDI yield (calculated as IPDU-B) exceeding 90%, making it truly industrializable. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 This is a flow chart of the industrial urea synthesis process of IPDU-B;

[0082] Figure 2 This is the process flow chart for producing IPDI by thermal cracking of IPDU-B. DETAILED DESCRIPTION

[0083] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0084] 1. Equipment, raw materials, process flow and detection methods for laboratory and industrial urea-based synthesis of IPDU-B.

[0085] Equipment used in the laboratory urea method:

[0086] Reactor: 10L; outlet condenser: Φ50×800;

[0087] Preparation of raw materials for laboratory urea method:

[0088] Urea: GB / T 2440-2001 industrial superior grade, total nitrogen (N) (on dry basis) ≥ 46.5%;

[0089] n-Butanol: GB / T 6027-1998 superior quality, main content ≥99.5%;

[0090] IPDA: main content ≥99.5%;

[0091] Catalyst (zirconium acetate): purity 99.0%.

[0092] Specific method of laboratory urea method for synthesizing isophorone diaminobutyrate:

[0093] IPDA, urea, n-butanol, and a catalyst were added to a 10L stainless steel reactor. The reaction was carried out at 225°C and a pressure of 1.50 MPa.G for 2 hours to produce n-butyl isophorone dicarbamate, while simultaneously releasing ammonia. Nitrogen was added and the n-butanol evaporated, allowing the ammonia to escape. The condensed n-butanol then flowed back into the reactor, and the tail gas was absorbed with dilute sulfuric acid. After the reaction, the reactor was cooled naturally, and the vacuum pump and electric heater were then activated to evaporate the remaining n-butanol.

[0094] Equipment used in the industrial urea process:

[0095] Reactor: Φ650×800, 300L, stripping deamination tower: Φ273×3000 (deamination tower top condenser A=6m 2 ), falling film evaporator Φ300×1200;

[0096] Ammonia tail gas condenser: A=2.2m 2 , gas-liquid separator: V=0.10m 3 Φ400×800 (straight tube);

[0097] Gas-solid separator: V = 0.61m3 Φ700×1300 (straight tube);

[0098] Butanol adsorption tower: 300 mm in diameter, 1200 mm in height, 3 units, operating conditions: 30-150°C (regeneration 150°C), slightly positive pressure.

[0099] Raw materials preparation:

[0100] Urea: GB / T 2440-2001 industrial grade quality product, actual purity 99.6%;

[0101] n-Butanol: GB / T 6027-1998 superior quality, actual main content 99.8%;

[0102] IPDA: purity 99.5%;

[0103] Catalyst (zirconium acetate): purity 99.0%.

[0104] Specific method of industrial urea process for synthesizing n-butyl isophorone diaminoformate:

[0105] Add liquid raw material n-butanol (excess), raw material IPDA, solid raw material urea (slightly excess), and liquid catalyst zirconium acetate to a 300L stainless steel reactor. After the addition is completed, close the reactor and replace the air in the reactor with nitrogen. Then, add nitrogen at a rate of 4.5Nm 3 / h to 225°C, and the synthesis reaction was carried out at a pressure of 1.50 MPa.G for 2 hours. After the reaction, a portion of the n-butanol in the bottom product was flash-evaporated under reduced pressure, and then the product was cyclically dealcoholized in a falling film evaporator at 200°C and a vacuum of -0.090 MPa for 2 hours to remove unreacted n-butanol and the intermediate product n-butyl carbamate, thereby obtaining the intermediate product n-butyl isophorone dicarbamate.

[0106] During the reaction, the gaseous material (i.e., synthesis tail gas) exiting the reactor passes sequentially through a stripping deamination tower and a condenser located at the top of the tower, yielding a gaseous material and a liquid material. The gaseous material is the ammonia-containing tail gas containing a small amount of n-butanol and primarily composed of carrier gas and ammonia. The liquid material, consisting primarily of n-butanol condensed from the synthesis tail gas, is then refluxed to the top of the stripping deamination tower, where most of the dissolved ammonia in the liquid material is removed. Finally, the deaminated n-butanol returns to the reactor.

[0107] Using process nitrogen as the carrier gas, the high-temperature ammonia-containing tail gas is passed into a condenser and cooled to 59°C. At this time, most of the n-butanol contained in the ammonia-containing tail gas is liquefied and the ammonium carbamate is solidified. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol and solid ammonium carbamate. The tail gas is then passed into a gas-liquid separator to remove n-butanol, and nitrogen, ammonia and ammonium carbamate are blown into a gas-solid separator. The gas-solid separator filters and adsorbs the ammonium carbamate to obtain deammonium carbamate tail gas containing residual n-butanol.

[0108] The decarbamate tail gas containing residual n-butanol is passed into a precooler to cool down, and the outlet temperature is maintained at 20°C. The cooled tail gas is extracted and pressurized by a blower and then passed into an adsorption tower filled with a nano-adsorbent. The tail gas after adsorption is passed into a sulfuric acid pool to obtain ammonium salt and final tail gas.

[0109] The nano adsorbent is a special adsorbent of Haipu Nano HDV536, which selectively adsorbs n-butanol and does not adsorb amino groups. The particle size (0.6-1.25mm) is greater than 95%, the specific surface area is 1400㎡ / g, the pore volume is 0.90ml / g, and the pore size is

[0110] The detection methods are shown in Table 1:

[0111] Table 1

[0112] Serial number Analysis Project Detection method 1 IPDU-B content GC-FID 2 n-Butanol content GC-FID 3 Ammonia content GC-FID 4 Ammonium carbamate content <![CDATA[GC-FID (measuring CO2 peak)]]>

[0113] 2. Screening of synthesis temperature and time in the laboratory urea method for synthesizing n-butyl isophorone dicarbamate:

[0114] The synthesis temperature gradient was set at 200°C, 215°C, 225°C, 235°C, and 250°C. Referring to the laboratory urea method for synthesizing IPDU-B (IPDA: 1289 g (7.57 mol); n-butanol: 4487 g (60.6 mol); urea: 1000 g (16.5 mol)), the reaction mixture was divided into 5 groups according to the temperature gradient to synthesize n-butyl isophorone dicarbamate. The content of n-butyl isophorone dicarbamate (IPDU-B) in each group was detected at reaction times of 1.5, 2, 3, 4, and 5 h, and the yield was calculated. The statistical yields are shown in Table 1.

[0115] Table 2

[0116]

[0117]

[0118] As shown in Table 2, the yield of IPDU-B increases with increasing reaction temperature. However, if the reaction time continues to increase beyond 2 h, the synthesis rate of IPDU-B slows down, and the synthesis cost increases exponentially. Therefore, for economic considerations, a reaction time of about 2 h is preferred. When the reaction temperature is 200-250°C and the synthesis time is 2 h, the yield of IPDU-B is above 60%. When the reaction temperature is 215-250°C, the yield of IPDU-B is above 90%, and further increasing the temperature does not significantly improve the yield. For economic considerations, a synthesis temperature of 200-250°C is selected as a relatively good reaction temperature, and 215-235°C is the optimal reaction temperature.

[0119] 3. Screening of synthesis pressure in laboratory urea process for synthesizing n-butyl isophorone dicarbamate:

[0120] The synthesis pressure gradient was set to 0.9, 1.1, 1.2, 1.3, 1.35, 1.4, 1.5, 1.8, and 2.3 MPa. The laboratory urea method for synthesizing IPDU-B (IPDA: 1289 g (7.57 mol); n-butanol: 4487 g (60.6 mol); urea: 1000 g (16.5 mol)) was referred to. The experiments were divided into 9 groups according to the pressure gradient to synthesize n-butyl isophorone dicarbamate. The content of n-butyl isophorone dicarbamate (IPDU-B) was detected and the yield was calculated. The statistical yield is shown in Table 3.

[0121] Table 3

[0122] Experiment number Reaction pressure (MPa) IPDU-B yield (%) 1 0.9 91.2 2 1.1 94.4 3 1.2 96.2 4 1.3 97.5 5 1.35 98.5 6 1.4 98.1 7 1.5 98.3 8 1.8 98.2 9 2.3 98.3

[0123] As shown in Table 3, when the reaction pressure is greater than 0.9 MPa, the yield of IPDU-B is higher than 90%. As the reaction pressure gradually increases, the yield gradually increases, but the increase becomes smaller and smaller. Therefore, for economic considerations, 0.9-2.3 MPa is selected as the better reaction pressure, and 1.2-1.5 MPa is the optimal reaction pressure.

[0124] 4. Screening of the amount of n-butanol in the laboratory urea process for synthesizing n-butyl isophorone dicarbamate:

[0125] The n-butanol dosage gradient was set to 4, 5, 6, 7, 8, 9, and 10 n-butanol / IPDA (mol). The laboratory urea method for synthesizing IPDU-B was referred to (IPDA: 1289 g (7.57 mol); n-butanol: 2244-5609 g (30.3-75.7 mol); urea: 1000 g (16.5 mol)). The experiments were divided into 7 groups according to the n-butanol dosage gradient to synthesize n-butyl isophorone dicarbamate. The content of n-butyl isophorone dicarbamate (IPDU-B) was detected by GC-FID and the yield was calculated. The yield data are shown in Table 4.

[0126] Table 4

[0127]

[0128] Note: n-Butanol / IPDA (mol) represents the molar ratio of n-butanol to IPDA.

[0129] As shown in Table 4, when the molar ratio of n-butanol / IPDA is greater than 4, the yield of IPDU-B is above 75%, which is at a relatively good level, and continues to increase with the increase of n-butanol addition. However, when the molar ratio is greater than 5, the yield remains almost unchanged. Therefore, for economic considerations, n-butanol:IPDA=4-10 is selected as the preferred n-butanol dosage, and n-butanol:IPDA=5-8 is the optimal n-butanol dosage.

[0130] 5. Screening of urea dosage in laboratory urea process for synthesizing n-butyl isophorone dicarbamate:

[0131] The urea dosage gradient was set to 2, 2.05, 2.1, 2.2, 2.3, and 2.5 urea / mol IPDA. The laboratory urea method for synthesizing IPDU-B was referred to (IPDA: 1289 g (7.57 mol); n-butanol: 4487 g (60.6 mol); urea: 909-1147 g (15.0-18.9 mol)). The experiments were divided into 6 groups according to the urea dosage gradient to synthesize n-butyl isophorone dicarbamate. The content of n-butyl isophorone dicarbamate (IPDU-B) was detected by GC-FID and the yield was calculated. The yield data are shown in Table 5.

[0132] Table 5

[0133]

[0134] Note: Urea / IPDA (mol) represents the molar ratio of urea to IPDA.

[0135] As shown in Table 5, when the molar ratio of urea to n-butanol is greater than 2, the yield of IPDU-B is greater than 80%, which is at an excellent level, and continues to increase with the increase of urea addition. However, when the molar ratio is greater than 2.2, the yield remains almost unchanged. For economic considerations, urea: n-butanol = 2-2.5 is selected as the better urea dosage, and urea: n-butanol = 2.2-2.5 is the optimal urea dosage.

[0136] VI. Verification of the effectiveness of IPDU-B product synthesis using the industrial urea method. The specific method is as follows:

[0137] To a 300L stainless steel reactor, 158.5kg (2.14kmol) of liquid raw material n-butanol, 45.5kg (0.27kmol) of raw material IPDA, 35.5kg (0.57kmol) of solid raw material urea, and 318g (0.97mol) of liquid catalyst zirconium acetate were added. After the addition was completed, the reactor was sealed and the air in the reactor was replaced with nitrogen. Then, a nitrogen gas flow rate of 4.5Nm 3 / h to 225°C, and the synthesis reaction was carried out at a pressure of 1.50 MPa.G for 2 hours. After completion of the reaction, a portion of the n-butanol was flash evaporated under reduced pressure, and then the reaction was cyclically dealcoholized using a falling film evaporator at 200°C and a vacuum of -0.090 MPa for 2 hours to remove unreacted n-butanol and the intermediate product, n-butyl carbamate, to obtain 97.5 kg of the intermediate product, n-butyl isophorone dicarbamate, with a product yield of 98.4% (detection method: GC-FID).

[0138] The above verification was repeated using varying amounts of raw materials: 101.6 kg (1.37 kmol) of n-butanol, 45.5 kg (0.27 kmol) of IPDA, 37.0 kg (0.61 kmol) of solid urea, and 318 g (0.97 mol) of liquid zirconium acetate. The intermediate product, n-butyl isophorone dicarbamate, was obtained in a yield of 98.1% (detection method: GC-FID).

[0139] It can be seen that the yield of IPDU-B in industrial production is greater than 98%, indicating that the feasibility of the industrial process and industrial parameters determined by the present invention has been verified.

[0140] 7. Treatment effect of IPDU-B waste gas synthesized by industrial urea method. The specific methods are as follows:

[0141] IPDU-B was synthesized by referring to the industrial urea method (IPDA: 45.5 kg (0.27 kmol); n-butanol: 158.5 kg (2.14 kmol); urea: 35.5 kg (0.57 kmol); zirconium acetate 400 g (1.22 mol)), using process nitrogen as the carrier gas. The high-temperature ammonia-containing tail gas is passed into a condenser and cooled to 59°C. At this time, n-butanol is liquefied and ammonium carbamate is solidified. The tail gas is now a mixture of nitrogen, ammonia, liquid n-butanol and ammonium carbamate solid. The tail gas is then passed into a gas-liquid separator to remove n-butanol. Nitrogen, ammonia and ammonium carbamate are blown into a gas-solid separator. The gas-solid separator filters and adsorbs the ammonium carbamate to obtain ammonium carbamate-free tail gas containing residual n-butanol. The ammonium carbamate enriched in the gas-solid separator is blown away by high-temperature nitrogen to decompose the ammonium carbamate solid into ammonia components and carbon dioxide, thereby regenerating the gas-solid separator.

[0142] The decarbamate tail gas containing residual n-butanol was passed into a precooler to cool down, and the outlet temperature was maintained at 20°C. The cooled tail gas was extracted and pressurized by a blower and then passed into a container containing nano adsorbent (Haipu Nano HDV536 special adsorbent, particle size (0.6-1.25mm)>95%, specific surface area 1400㎡ / g, pore volume 0.90ml / g, pore diameter ) adsorption tower to obtain dealcohol tail gas. The dealcohol tail gas after adsorption is passed into a sulfuric acid absorber to obtain ammonium salt and final tail gas.

[0143] During the adsorption process, when the adsorption tower reaches the cycle time, the adsorption is stopped (a total of three adsorption towers are involved, one is adsorbing while the other two are desorbing, and the adsorption and desorption processes are alternately carried out by switching between single doors. When the adsorption tower reaches the breakthrough point, it automatically switches to the desorption process), and 150°C nitrogen is used to desorb and regenerate the adsorbent. The ammonia containing n-butanol after desorption is condensed and separated with low-temperature chilled water. The separated liquid n-butanol is collected in the n-butanol recovery tank, and the gas phase containing trace n-butanol and nitrogen returns to the front end of the adsorption tower and is merged into the decarbamate tail gas to pass through the adsorption tower to remove the trace n-butanol contained.

[0144] The contents of various components in the ammonia-containing tail gas before condensation, the ammonia-containing tail gas after condensation, the decarbamate tail gas, and the final tail gas were detected. The results are shown in Table 4.

[0145] Table 4

[0146] Ammonia (%) n-Butanol (%) Ammonium carbamate (%) Nitrogen (%) Ammonia tail gas before condensation 46.74 4.63 0.60 48.04 Ammonia tail gas after condensation 48.43 1.18 0.62 49.77 Decarbamate tail gas 48.74 1.20 0.05 50.01 Butanol tail gas 48.96 0.001 0.05 50.989 Final exhaust 0.003 Not detected Not detected 99.997

[0147] As shown in Table 4, the high-temperature ammonia-containing tail gas discharged during the synthesis of isophorone diamino n-butyl ester contains 0.62% ammonium carbamate. After the ammonium carbamate removal process, the ammonium carbamate content in the tail gas is only 0.05%, and the ammonium carbamate removal rate reaches 92%. This shows that this deammonium carbamate process can effectively remove ammonium carbamate from the urea process for synthesizing isophorone diamino n-butyl ester, preventing the pipelines and valves of industrial equipment from being blocked by ammonium carbamate. The ammonia content in the dealkanol tail gas is 48.96%, while the ammonia content in the final tail gas is only 0.003%, indicating that the deammoniation process can effectively remove ammonia from the tail gas. The content of n-butanol in the deammonium carbamate tail gas is 1.20%, while no n-butanol is detected in the final tail gas, indicating that the entire tail gas removal process can effectively remove n-butanol from the tail gas.

[0148] The thermal cracking process of isophorone diaminobutyrate is as follows:

[0149] 1. Laboratory and industrial IPDU-B pyrolysis, solvent recovery, and distillation reactors, reaction processes, raw materials, and testing methods

[0150] The applicant explains why the laboratory-scale IPDU-B pyrolysis data is included. First, the laboratory-related equipment used in this invention is small-scale equipment similar to the industrial IPDU-B pyrolysis unit. Second, the laboratory is primarily for research purposes, providing theoretical basis and production condition parameters for industrial production, which is an indispensable step before industrial implementation. This does not mean that the laboratory-scale data in this invention has no reference value. Furthermore, the laboratory also provides a comparison for industrial results, so this invention provides laboratory data.

[0151] It should also be pointed out that, in order to facilitate understanding of the meaning of each step of the present invention, the present invention describes thermal cracking, solvent recovery, and distillation separately. This does not mean that the present invention is not a continuous reaction.

[0152] (1) Laboratory pyrolysis reactor

[0153] Cracker: evaporation area 0.1m 2 ;

[0154] Circulation pump: gear pump 2.8L / h;

[0155] Distillation column: Φ50×800;

[0156] (2) Laboratory pyrolysis continuous reaction process

[0157] The raw material IPDU-B enters the thin-film evaporator (cracker) where it is heated and cracked. The cyclohexane oil and catalyst in the lower portion are then pumped back to the upper inlet of the cracker via a circulating pump. The cracked gas exiting the upper portion of the cracker enters the distillation column under vacuum. Once the heavy components begin to reflux into the cracker from the lower portion of the column, the IPDU-B feed is stopped. At this point, the cracker only thermally decomposes the refluxed material. The cracked gas exiting the upper portion of the cracker enters the distillation column under vacuum, while the light components enter the heat exchanger from the upper portion of the column, where they are condensed and flow by gravity into the crude product tank. When the reflux rate decreases to near-interruption, the IPDU-B feed is restarted, and this process is repeated until the end of the experiment.

[0158] Note: By intermittently adding IPDU-B raw material to approximately simulate IPDU-B and unilateral segmented pyrolysis, side reactions are significantly suppressed.

[0159] (3) Industrial thermal cracking reactor

[0160] IPDU-B raw material pump: Q = 2m 3 / h, H = 14m; 1# cracker: A = 30m 2 ; 1# cracking circulation pump: Q=5m 3 / h, H = 14m; 1# polymer displacement pump: Q = 2m 3 / h, H = 14m; 2# cracker: A = 25m 2 ; 2# cracking circulation pump: Q=5m 3 / h, H = 14m; 2# polymer displacement pump: Q = 2m 3 / h, H=14m.

[0161] (4) Industrial thermal cracking reaction process

[0162] The thermal decomposition raw material IPDU-B, solvent and catalyst enter the 1# rotary scraper thermal decomposition reactor, where a liquid film is forced to form on the inner wall of the reactor by the rotating scraper, and the thermal decomposition reaction is carried out by heating the inner wall of the reactor. Under vacuum conditions, the thermal decomposition products evaporate rapidly to achieve rapid separation from the reaction raw materials, greatly reducing the occurrence of side reactions. The gaseous material at the reactor outlet (gas phase material one, reaction product) enters the distillation unit. The material in the distillation tower bottom (mainly one side) enters the 2# rotary scraper thermal decomposition reactor for thermal decomposition reaction, and the gaseous material at the reactor outlet (gas phase material three, reaction product) is combined with gas phase material one and enters the distillation unit. A circulation tank and a circulation pump are provided at the bottom of the two reactors to circulate the solvent and catalyst.

[0163] (5)Solvent recovery equipment

[0164] Scraper evaporator: heat exchange area S = 12m 2

[0165] (6) Solvent recovery method

[0166] It should be emphasized that this part is about processing the heavy component materials after the initial separation (static sedimentation) of the circulating liquid discharged from the bottom of the two rotating scraper thermal decomposition reactors in the (4) industrial thermal cracking reaction process.

[0167] The heavy components produced by the thermal decomposition of n-butyl isophorone dicarbamate are pumped to the top of a scraper evaporator. Rotating scrapers force a liquid film onto the inner wall of the evaporator, which is then heated and evaporated under vacuum to produce a vapor product and heavy components. The vapor product is condensed in a condenser to recover the solvent. The heating and evaporation reaction conditions are: a temperature of 280°C and a pressure of -0.096 to -0.098 MPa.

[0168] (7) Distillation reaction equipment

[0169] Lightness removal tower (distillation tower): Φ1200×24604, packing height 3888 / 3888 / 3888 / 3240mm

[0170] Product tower (distillation tower): Φ900×24348, packing height 3096 / 3096 / 4128 / 4128mm

[0171] Condenser: Delight tower top condenser Φ1200×2000, heat exchange area 80m 2 ; Product tower top condenser Φ1000×2000, heat exchange area 90m 2

[0172] Reboiler: De-light tower bottom reboiler Φ1100×2500, heat exchange area 94.5m 2; Product tower bottom reboiler Φ1400×3000, heat exchange area 190m 2

[0173] Circulation pump: Circulation pump at the bottom of the de-light tower Q = 10.8m 3 H=40m Zone2 EEx dII BT4, product tower bottom circulation pump Q=18m 3 H=40m Zone2 EEx dII BT4

[0174] Auxiliary systems: The thermal oil system provides the required heat source, the circulating water system and the chilled water system provide the refrigerant, the nitrogen system provides nitrogen for the start-up and shutdown system replacement, and the vacuum system provides the vacuum conditions required by the device.

[0175] Control system: The process operation control adopts DCS system and is equipped with safety interlock (SIS) system

[0176] (8) Reaction process of distillation

[0177] It should be emphasized that this part of the content is a detailed explanation of the distillation unit in the (4) industrial thermal cracking reaction process.

[0178] The crude IPDI gaseous product (gas phase material 1 and gas phase material 3) enters the bottom of the degassing tower (first distillation tower) from the thermal decomposition unit, with n-butanol withdrawn from the top of the tower and IPDI-rich liquid withdrawn from the side line in the middle of the tower. The bottom material is sent to the thermal decomposition unit for cyclic thermal decomposition (second thermal decomposition reaction). The IPDI-rich liquid withdrawn from the side line of the degassing tower is pumped into the product tower (second distillation tower), with a small amount of n-butanol and IPDI withdrawn from the top of the tower and IPDI product withdrawn from the side line. The bottom material (liquid phase material 2) is sent to the thermal decomposition unit for cyclic thermal decomposition (second thermal decomposition reaction).

[0179] (9) Raw materials

[0180] Isophorone dicarbamate n-butyl ester (IPDU-B): Internal control index ≥ 99.0% (IPDU-B 99.38%, catalyst for synthesizing IPDU-B 0.46%, other 0.16%);

[0181] Thermal cracking reaction catalysts: zinc picolinate, chromium picolinate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate, zinc isooctanoate;

[0182] Solvent: naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, trinonyl trimellitate.

[0183] (10) Detection method

[0184] See Table 1:

[0185] Table 1

[0186]

[0187] (11) Statistics of raw materials, product composition and yield corresponding to each step of the present invention

[0188] Refer to the attached Figure 1 The process flow of IPDI was continuously synthesized according to the above industrial routes (4), (6) and (8). The control conditions were the optimal experimental conditions, that is, the operating pressure of the first thermal decomposition was controlled to be -0.094Mpa and the operating temperature was 240℃, and the operating pressure of the second thermal decomposition was controlled to be -0.094Mpa and the operating temperature was 245℃. The operating conditions of the light removal tower were controlled to be: 11mbar at the top of the tower, 24mbar at the bottom of the tower, 199.7℃ at the bottom of the tower, 25℃ at the top of the tower, and 160.8℃ at the side line temperature; the operating conditions of the product tower were controlled to be: 11mbar at the top of the tower, 24mbar at the bottom of the tower, 194℃ at the bottom of the tower, 40℃ at the top of the tower, and 158.3℃ at the side line temperature. After the system was running stably, the raw material feed amount, product composition and output corresponding to each step involved were statistically tabulated as follows:

[0189]

[0190]

[0191]

[0192] Note: The process of the present invention is carried out continuously. Gas phase material 1 and gas phase material 3 are materials produced at the same time in different thermal cracking reactors and are mixed together and enter the first distillation tower. IPDU raw material impurities: 0.46% of the catalyst for synthesizing IPDU-B and 0.16% of other impurities.

[0193] 2. IPDU-B thermal cracking reaction catalyst screening experiment

[0194] (1) Catalyst type screening experiment

[0195] Operating conditions: A laboratory thermal cracking reactor and reaction process were selected, and the cracking temperature of the cracker was controlled to 240°C; the operating pressure was ∼0.094 MPa; 500 g of IPDU-B, 500 g of naphthenic oil (solvent), and 3.5 g of catalyst were added to screen the catalyst types. The catalyst types and experimental results are shown in Table 2 below:

[0196] Table 2

[0197]

[0198]

[0199] Note: The main components of the colloid in the present invention are catalyst and high molecular polymer (by-product); the colloid ratio refers to the ratio of the colloid production to the raw material IPDU-B feed amount.

[0200] As shown in Table 2, the catalysts indicated in Groups 1-1 to 1-10 all have certain catalytic effects. However, when chromium picolinate, MOF-5, and zinc picolinate are selected as catalysts, the yield of IPDI is high and the content of colloids is low (fewer side reactions). Therefore, the present invention preferably uses chromium picolinate, MOF-5, or zinc picolinate as the catalyst.

[0201] (2) Catalyst dosage screening experiment

[0202] Operating conditions: A laboratory thermal cracking reactor and reaction process were selected, the cracking temperature of the cracker was controlled to 240°C; the operating pressure was ∼-0.094 MPa; 500 g of IPDU-B and 500 g of naphthenic oil were added, and chromium picolinate was selected as the catalyst. A catalyst dosage screening experiment was conducted. The catalyst dosage screening results are shown in Table 3 below:

[0203] Table 3

[0204] Experimental batch number Catalyst dosage (mass %) IPDI yield (%) Colloidal matter ratio (%) Group 2-1 0.75 91.46 2.76 Group 2-2 1.0 91.13 2.82 Group 2-3 0.5 88.25 4.33 Groups 2-4 0.3 87.75 6.23 Groups 2-5 0.25 76.88 10.94 Groups 2-6 1.25 87.93 4.67 Groups 2-7 1.5 84.73 6.87

[0205] Note: The amount of catalyst used (mass %) is relative to IPDU-B.

[0206] It can be seen from the data in Table 3 that when the amount of catalyst is too much or too little, the IPDI yield will decrease and the colloidal content will increase. The most suitable amount of catalyst is 0.3%-1%.

[0207] 3. Screening of IPDU-B thermal cracking reaction conditions

[0208] (1) Screening of thermal cracking temperature

[0209] Operating conditions: A laboratory thermal cracking reactor and reaction process were selected, and the cracking temperature of the cracker was controlled to be 240°C; the operating pressure was 0.094 MPa; 500 g of IPDU-B, 500 g of naphthenic oil, and 3.5 g of chromium picolinate were added to screen the thermal cracking temperature. The results of the thermal cracking temperature screening are shown in Table 4 below:

[0210] Table 4

[0211] Experimental batch number Cracking temperature (℃) IPDU-B conversion rate (%) IPDI yield (%) Colloidal matter ratio (%) Group 3-1 240 99.65 92.34 2.12 Group 3-2 200 3.24 2.87 0.26 Group 3-3 210 6.37 5.74 0.51 Group 3-4 220 41.12 10.23 0.62 Groups 3-5 230 97.2 84.67 1.03 Groups 3-6 260 99.82 91.13 3.87 Groups 3-7 280 99.84 87.32 8.64

[0212] As shown in Table 4, IPDI can be generated by the reaction within the temperature range of 200-280°C. Within the temperature range of 220-280°C, the conversion rate of IPDU-B increases with increasing temperature. However, when the temperature approaches 280°C, the production of colloids increases significantly. Therefore, the cracking temperature is preferably 220-260°C.

[0213] (2) Screening of vacuum degree of thermal cracking reaction

[0214] Operating conditions: A laboratory pyrolysis reactor and reaction process were selected, and the pyrolysis temperature of the pyrolysis reactor was controlled to 240°C. 500g of IPDU-B, 500g of naphthenic oil, and 3.5g of chromium picolinate were added to screen the vacuum degree of the pyrolysis reaction. The results of the vacuum degree screening of the pyrolysis reaction are shown in Table 5 below:

[0215] Table 5

[0216] Experimental batch number Vacuum degree (gauge pressure MPa) IPDI yield (%) Colloidal matter ratio (%) Group 4-1 -0.094 91.67 2.63 Group 4-2 -0.098 88.64 3.25 Group 4-3 -0.096 88.87 3.31 Group 4-4 -0.092 81.37 4.21 Group 4-5 -0.090 74.65 4.91 Groups 4-6 -0.085 58.23 6.27 Groups 4-7 -0.080 44.63 8.17

[0217] It can be seen from Table 5 that when the vacuum degree is in the range of -0.080 to -0.098, IPDI has a certain yield; when the vacuum degree is in the range of -0.092 to -0.098, IPDI has the highest yield and the colloid content is low.

[0218] 4. Screening of solvents for IPDU-B thermal decomposition

[0219] (1) Screening of solvent types for thermal cracking reactions

[0220] Operating conditions: A laboratory pyrolysis reactor and reaction process were selected, and the pyrolysis temperature of the pyrolysis reactor was controlled to 240°C and the operating pressure to -0.094 MPa. 500 g of IPDU-B, 3.5 g of chromium picolinate, and 500 g of solvent were added to screen the types of solvents for the pyrolysis reaction. The screening results of the pyrolysis reaction solvents are shown in Table 6 below:

[0221] Table 6

[0222]

[0223] As shown in Table 6, the use of solvents naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, and trinonyl trimellitate can all increase the IPDI yield and reduce the gum content, and naphthenic oil is the most suitable solvent.

[0224] (2) Screening of solvent dosage for thermal cracking reaction

[0225] Operating conditions: A laboratory thermal cracking reactor and reaction process were selected, the cracking temperature of the cracker was controlled to 240°C, the operating pressure was controlled to -0.094 MPa, 3.5 g of chromium picolinate was used, and the mass ratio of the solvent to IPDU-B in the experimental conditions was changed. The solvent was naphthenic oil KN4010, and the solvent dosage for the thermal cracking reaction was screened. The screening results of the solvent dosage for the thermal cracking reaction are shown in Table 7 below:

[0226] Table 7

[0227] Experimental batch number IPDU-B concentration (mass %) IPDI yield (%) Colloidal matter ratio (%) Group 6-1 50 92.31 2.94 Group 6-2 10 92.14 2.68 Group 6-3 20 92.34 2.74 Group 6-4 30 91.89 2.61 Group 6-5 40 92.05 2.81 Group 6-6 60 90.78 3.56 Group 6-7 70 88.43 4.37 Groups 6-8 80 85.67 8.15 Groups 6-9 90 84.91 12.31 Groups 6-10 100 79.48 15.69

[0228] As shown in Table 7, when the amount of solvent used is 0.1-9 times the amount of IPDU-B, good effects are achieved.

[0229] 5. Verification of the effect of industrial IPDU-B thermal cracking reaction

[0230] Operating Conditions: An industrial pyrolysis reactor and reaction flow were selected. The mass ratio of IPDU-B: naphthenic oil KN4010: chromium picolinate was controlled to 1:1:0.007 by circulating and replenishing the reaction volume. Four batches were run on the industrial unit. The statistical results are shown in Table 8.

[0231] Table 8

[0232]

[0233] As shown in Table 8, the yield of IPDI in industrial production is greater than 91%, indicating that the feasibility of the industrial process and industrial parameters determined by the present invention has been verified.

[0234] 6. Recovery of solvent after reaction and reuse of recovered solvent

[0235] Solvent recovery and reuse have a significant impact on industrial production, determining not only production costs but also pollutant emissions. Given this, the present invention further examined the impact of solvent recovery and reuse on the reaction. Combining an industrial pyrolysis reactor and reaction flow, heavy components were obtained after initial fractionation. Using solvent recovery equipment and a solvent recovery method, naphthenic oil KN4010 was selected for measurement, with the recovery results shown in Table 9. After the recovered solvent was reused, the properties of the pyrolysis products were measured, with the experimental results shown in Table 10.

[0236] Table 9

[0237]

[0238] Note: The reaction conditions for Group 8-1, Group 8-2, and Group 8-3 are: temperature 280°C, reaction pressure -0.096 to -0.098 MPa, temperature 300°C, reaction pressure -0.092 to -0.098 MPa, and temperature 330°C, reaction pressure -0.092 to -0.098 MPa, respectively.

[0239] Table 10

[0240]

[0241] Note: The reaction conditions of Group 9-1, Group 9-2, Group 9-3 and Group 9-4 are: the first thermal decomposition operating pressure is -0.094Mpa, the operating temperature is 240℃; the second thermal decomposition operating pressure is -0.094Mpa, the operating temperature is 245℃; the mass amount of the catalyst chromium picolinate is 0.0035 of the feed amount.

[0242] It can be seen from Tables 4, 5 and 6 that the solvent provided by the present invention can be almost completely recovered and reused, and the use of the recovered solvent has no effect on the reaction.

[0243] 7. Method for purification of crude IPDI (distillation operation)

[0244] (1) The specific composition of crude IPDI in gas phase is 19.54% n-butanol, 28.64% IPDI, 39.52% monobutylene glycol, and 12.3% naphthenic oil (solvent).

[0245] It should be noted that in this embodiment, crude gaseous IPDI refers to the product obtained by combining gaseous material 1 and gaseous material 3. Gaseous material 1 and gaseous material 3 are identical in composition, differing only in their content. Industrial production is conducted continuously (only gaseous material 1 is produced during initial startup). That is, gaseous material 1 and gaseous material 3 are produced simultaneously during industrial operation. The design and stable operation of the distillation column require that they be fed into the same location. Therefore, in the present invention, gaseous material 1 and gaseous material 3 are combined to form crude gaseous IPDI.

[0246] The operating conditions of the light removal tower (first distillation tower) are: 11 mbar at the top, 24 mbar at the bottom, 199.7°C bottom temperature, 25°C top operating temperature, and 160.8°C side line temperature; the operating conditions of the product tower (second distillation tower) are: 11 mbar at the top, 24 mbar at the bottom, 194°C bottom temperature, 40°C top operating temperature, and 158.3°C side line temperature.

[0247] The components and contents of the n-butanol extracted from the top of the lightness removal tower (first distillation tower), the IPDI-rich liquid extracted from the side stream, and the bottom stream were measured. Furthermore, a small amount of n-butanol and IPDI mixed liquid extracted from the top of the product tower (second distillation tower), the IPDI product extracted from the side stream, and the bottom stream were measured after the system stabilized. The results are shown in Table 11:

[0248] Table 11

[0249]

[0250]

[0251] (2) The specific composition of crude IPDI in gas phase is 22.94% n-butanol, 31.97% IPDI, 34.63% unilateral, and 10.46% naphthenic oil.

[0252] The operating conditions of the light removal tower (first distillation tower) are: 11 mbar at the top, 24 mbar at the bottom, 200.4°C bottom temperature, 25.5°C top operating temperature, and 161°C side line temperature; the operating conditions of the product tower (second distillation tower) are: 11 mbar at the top, 24 mbar at the bottom, 194.5°C bottom temperature, 40.5°C top operating temperature, and 158.5°C side line temperature.

[0253] The components and contents of n-butanol removed from the top of the lightness removal tower (first distillation tower), IPDI-rich liquid removed from the side stream, and the bottom stream were measured. Also, a small amount of n-butanol and IPDI mixed liquid removed from the top of the product tower (second distillation tower), IPDI product removed from the side stream, and the bottom stream were measured after the system stabilized. The results are shown in Table 12:

[0254] Table 12

[0255]

[0256] (3) The specific composition of crude IPDI in gas phase is 20.05% n-butanol, 38.21% IPDI, 31.87% unilateral, and 9.87% naphthenic oil.

[0257] The operating conditions of the light removal tower (first distillation tower) are: pressure at the top of the tower 11 mbar, bottom of the tower 24 mbar, bottom temperature of the tower 201.5°C, top operating temperature of the tower 26°C, and side line temperature of 161.2°C; the operating conditions of the product tower (second distillation tower) are: pressure at the top of the tower 11 mbar, bottom of the tower 24 mbar, bottom temperature of the tower 194.9°C, top operating temperature of the tower 41°C, and side line temperature of 158.7°C.

[0258] The components and contents of n-butanol removed from the top of the lightness removal tower (first distillation tower), IPDI-rich liquid removed from the side stream, and the bottom stream were measured. Also, a small amount of n-butanol and IPDI mixed liquid removed from the top of the product tower (second distillation tower), IPDI product removed from the side stream, and the bottom stream were measured after the system stabilized. The results are shown in Table 13:

[0259] Table 13

[0260]

[0261] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. An industrializable IPDI synthesis process, characterized by: Including a synthesis process of n-butyl isophorone dicarbamate and a thermal cracking process of n-butyl isophorone dicarbamate; The synthesis process of the isophorone diaminobutyl ester comprises the following steps: (1) IPDA, n-butanol, urea and catalyst I are used to carry out an alkoxycarbonylation reaction of an organic amine, wherein a carrier gas is introduced during the alkoxycarbonylation reaction to separate the by-product ammonia, and a synthetic tail gas containing ammonia components is discharged during the reaction. Upon completion of the reaction, a crude product of n-butyl isophorone dicarbamate is obtained; (2) The synthetic tail gas is subjected to a n-butanol deamination process to obtain deaminated n-butanol, which is then refluxed into the reactor and ammonia-containing tail gas is discharged; That is, IPDA, n-butanol, urea and catalyst I are taken to a tank reactor to carry out an alkoxycarbonylation reaction of an organic amine, and ammonia as a by-product of the alkoxycarbonylation reaction is discharged along with the evaporated excess n-butanol and carrier gas. Then, most of the gaseous n-butanol is liquefied and refluxed by condensation, and most of the ammonia dissolved in the condensed and refluxed liquid n-butanol is removed by distillation. During the process, an ammonia-containing tail gas containing n-butanol, carrier gas and ammonia components is discharged. The reaction is completed to obtain crude n-butyl isophorone dicarbamate. The crude isophorone dicarbamate product is subjected to flash evaporation and falling film evaporation to obtain the target product, isophorone dicarbamate. (3) removing ammonium carbamate from the ammonia-containing tail gas to obtain deammonium carbamate tail gas, and condensing and recovering part of n-butanol; (4) removing residual n-butanol from the decarbamate tail gas to obtain n-butanol and dealcohol tail gas; (5) The dealcoholization tail gas is treated to remove the ammonia component to obtain ammonium salt and final tail gas; The thermal cracking process of isophorone diaminobutyl ester comprises: 1) coupled thermal decomposition and distillation of n-butyl isophorone dicarbamate: n-butyl isophorone dicarbamate, a solvent, and a catalyst II are introduced into a first thermal decomposition reactor for reaction to obtain a gaseous material 1, the gaseous material 1 and the gaseous material 3 are combined and introduced into a first distillation tower for distillation, n-butanol is obtained at the top of the tower, an IPDI-rich liquid is withdrawn from a middle side line, and heavy components are discharged from the bottom of the tower; the IPDI-rich liquid is introduced into a second distillation tower for operation, a mixed liquid of n-butanol and IPDI is separated from the top of the tower, an IPDI product is withdrawn from a middle side line, and heavy components are discharged from the bottom of the tower; the heavy components discharged from the bottom of the first distillation tower and the bottom of the second distillation tower are liquid material 2, the liquid material 2 is introduced into a second thermal decomposition reactor for reaction to obtain gaseous material 3, the gaseous material 3 is returned to the first distillation tower and introduced into the first distillation tower together with the gaseous material 1 for distillation; 2) Heavy component material discharge step: The first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge the circulating material and continuously replenish the same amount of solvent and catalyst II.

2. The synthesis process according to claim 1, wherein: In the synthesis process of n-butyl isophorone dicarbamate, the molar ratio of urea, n-butanol, IPDA, and catalyst I is 1:4-10:2-2.5:0.001-0.012; the reaction temperature of the alkoxycarbonylation reaction is 200-250° C., and the reaction pressure is 0.9-2.3 MPa.

3. The synthesis process according to claim 1, wherein: The catalyst I comprises at least one of zinc acetate, manganese acetate, zirconium acetate and cobalt acetate.

4. The synthesis process according to claim 1, wherein: The carrier gas is nitrogen.

5. The synthesis process according to claim 1, wherein: In step 1) of the thermal cracking process of phorone dicarbamate n-butyl ester, the reaction pressure of the first thermal decomposition reactor is controlled to be -0.08 to -0.098 MPa, and the reaction temperature is controlled to be 200 to 280° C.; And / or, in step 1), the reaction pressure of the second thermal decomposition reactor is controlled to be -0.08 to -0.098 MPa, and the reaction temperature is controlled to be 200 to 280°C.

6. The synthesis process according to claim 1, wherein: In step 1) of the thermal cracking process of n-butyl isophorone dicarbamate, the mass ratio of n-butyl isophorone dicarbamate, solvent and catalyst II is: 1:0-9:0.0025-0.

015.

7. The synthesis process according to claim 1, wherein: In step 1) of the thermal cracking process of phorone dicarbamate n-butyl ester, the solvent is one of naphthenic oil, trioctyl trimellitate, and trinonyl trimellitate; And / or, the catalyst II is one or more of zinc picolinate, chromium picolinate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate, and zinc isooctanoate.

8. The synthesis process according to claim 1, characterized in that In step 1), the first thermal decomposition reactor and / or the second thermal decomposition reactor is a thin film evaporator.

9. The synthesis process according to claim 1, wherein: In step 1) of the thermal cracking process of phorone dicarbamate n-butyl ester, the operating pressure of the first distillation tower is 10-30 mbar, the bottom temperature is 190-210°C, the top operating temperature is 20-30°C, and the side line temperature is 150-170°C; And / or, the operating pressure of the second distillation tower is 10-30 mbar, the bottom temperature is 190-200°C, the top operating temperature is 30-0°C, and the side line temperature is 155-160°C.

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