Method for removing ammonium carbamate in isophorone di-n-butyl carbamate synthesis process by urea method

Abstract

The present application relates to the field of IPDI synthesis, in particular to a method for removing by-product ammonium carbamate in the process for synthesizing n-butyl isophorone dicarbamate by urea method, the material of the ammonium carbamate to be removed is: ammonia-containing tail gas obtained in the process for synthesizing n-butyl isophorone dicarbamate by urea method is subjected to condensation treatment, trace n-butanol in the ammonia-containing tail gas is liquefied, and then ammonium carbamate powder is generated by the reaction of carbon dioxide and ammonia components; the removal method of the ammonium carbamate is: the ammonia-containing tail gas is subjected to condensation treatment, trace n-butanol in the ammonia-containing tail gas is liquefied, and ammonium carbamate is generated by the reaction of carbon dioxide and ammonia components, and the ammonium carbamate powder and n-butanol liquid obtained by condensation are subjected to material separation. The ammonium carbamate treatment process of the present application is simple, does not need manual operation, has good removal effect, and can ensure that the tail gas treatment process for synthesizing n-butyl isophorone dicarbamate is continuously and smoothly operated.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of IPDI synthesis, in particular to a method for removing ammonium carbamate in a process for synthesizing n-butyl isophorone dicarbamate by adopting a urea method. BACKGROUND

[0002] Diisocyanate refers to a substance containing two NCO groups, which is reacted with a polyol to synthesize a polyurethane material. At present, isocyanates mainly include MDI, TDI, HDI, IPDI, HMDI, XDI, NDI, PPDI, CHDI and the like. Among them, MDI and TDI are currently the two most important varieties, accounting for more than 85% of the total amount of diisocyanate, and HDI, IPDI and hydrogenated MDI are applied more and more widely in recent years due to excellent weather resistance and yellowing resistance.

[0003] IPDI (isophorone diisocyanate, CAS No. 4098-71-9) is a preferred raw material for synthesizing light-stable and weather-resistant polyurethane, and belongs to a high-end product in isocyanate raw materials. It is mainly used in the fields of water-based polyurethane dispersion, anticorrosive coating, UV resin, adhesive, PU resin, ink and the like. Meanwhile, IPDI can also be used in the rocket propellant industry.

[0004] The production methods of IPDI mainly include a phosgene method and a carbamate thermal cracking method. The phosgene method is currently the main production method of diisocyanate. The phosgene method mainly includes a liquid phase phosgene method and a gas phase phosgene method. However, the liquid phase phosgene method has long reaction time, needs a large amount of solvent, has low space-time efficiency of the reactor, has many by-products and is relatively backward. The gas phase phosgene method has a series of engineering technical problems such as safety and environmental protection which are difficult to solve, is seriously corroded to equipment, has relatively high requirements on the material of the equipment, has large corresponding equipment investment and contains hydrolyzed chlorine in the obtained isocyanate product, thereby affecting the use performance of the product. Therefore, developed countries have been committed to developing an economic and simple synthesis method, so that various non-phosgene methods for synthesizing isocyanate appear, such as a carbonylation method, a chloroformamide thermal decomposition method, a crutius rearrangement method, an amine and chloroformate reaction method and a carbamate thermal decomposition method. However, most of them still stay in the laboratory stage, and only the carbamate thermal decomposition method realizes device production in foreign countries. The urea method is the most researched route, the method is relatively mature and has been applied in foreign industry. The urea method for preparing isocyanate includes two steps, that is, urea, diamine and alcohol are reacted to generate dicarbamate, and the dicarbamate is further cracked to generate isocyanate and alcohol, and the total reaction yield can reach 90%.

[0005] The research and development and production of diisocyanate in China started late, but with the rapid development of society and economy in China, China has become a big country in the production and consumption of diisocyanate in the world. On the other hand, in the field of high-performance special isocyanate, China develops very slowly, and the consumption demand grows by more than 15% per year. Aliphatic isocyanate is mainly used in the fields of automobile topcoat, rocket propellant, anti-corrosion coating, light-cured coating and adhesive, etc. Due to historical reasons of introducing technology, high-grade coatings for automobiles, high-speed trains, airplanes, ships, luxury passenger cars, wooden furniture, buildings and other industries in China are all occupied by foreign products, one of the factors restricting them is the key raw material aliphatic diisocyanate.

[0006] It is necessary to produce aliphatic diisocyanate in China, especially by using non-phosgene green synthesis technology, to promote the technological progress and industrial upgrading of related industries, and to ensure the industrial safety of important industries in China. It has great economic benefits and great social significance, but non-phosgene method currently only has 10,000 tons / year production device of Degussa and BASF.

[0007] At present, the industrialized urea method for producing IPDU-B (molecular formula is: 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 safety and the reality of the backwardness of domestic production and development, the present application provides an industrial process for synthesizing isophorone diaminocarbamate n-butyl ester by urea method to break the technical monopoly of developed countries on the industrial urea method for synthesizing IPDI. Not only can the high-risk process and environmental safety hazards of the phosgene method be eliminated from the root, but also the cost can be competitive with the phosgene method. SUMMARY

[0008] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method for removing ammonium carbamate in the process of synthesizing isophorone diaminocarbamate n-butyl ester by urea method, so as to at least achieve the effects of simple process, little pollution, high raw material utilization rate, high economic benefit and suitability for large-scale industrial production.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] The industrial process for synthesizing isophorone diaminocarbamate n-butyl ester by urea method comprises the following steps:

[0011] Take IPDA (isophorone diamine, CAS number 2855-13-2), n-butanol, urea and catalyst in a kettle test reactor to carry out the alkoxy carbonylation reaction of organic amine (IPDA is an organic amine containing two amino groups), the byproduct ammonia gas of the alkoxy carbonylation reaction is discharged with the evaporated excess n-butanol and carrier gas (this mixed gas phase material is the synthesis tail gas), most of the gas phase n-butanol in the synthesis tail gas is liquefied backflow by condensation, and most of the dissolved ammonia in the liquid phase n-butanol of the condensation backflow is removed by rectification (stripping ammonia removal tower), and the ammonia-containing tail gas containing n-butanol, carrier gas and ammonia components is discharged, and the crude isophorone diaminoformic acid n-butyl ester (IPDU-B) is obtained after the reaction is completed;

[0012] The crude isophorone diaminoformic acid n-butyl ester is subjected to a refining process composed of flash evaporation and falling film evaporation to obtain the target product isophorone diaminoformic acid n-butyl ester;

[0013] It is worth noting that in order to better separate the byproduct ammonia gas, the carrier gas is directly introduced into the reaction liquid of the alkoxy carbonylation reaction, and the carrier gas and the evaporated n-butanol vapor will bring out the tail gas containing ammonia components, so that the reaction equilibrium moves to the direction of the target product (to the right), and the reaction degree is more thorough.

[0014] The synthesis tail gas is subjected to an n-butanol ammonia removal process to obtain the n-butanol backflow reaction kettle after ammonia removal and discharge the ammonia-containing tail gas (main components: ammonia gas, nitrogen gas, carbon dioxide and n-butanol);

[0015] The ammonia-containing tail gas is subjected to removal of ammonium carbamate to obtain the ammonia-removed ammonium carbamate tail gas (main components: ammonia gas, nitrogen gas, residual n-butanol), and part of the n-butanol is recovered by condensation, and the removed ammonium carbamate is removed by heating and blowing;

[0016] The ammonia-removed ammonium carbamate tail gas is subjected to removal of residual n-butanol to obtain n-butanol and n-butanol-removed tail gas (main components: nitrogen gas, ammonia gas);

[0017] The n-butanol-removed tail gas is subjected to ammonia component removal treatment to obtain ammonium salt, and the final tail gas (main component: nitrogen gas) meeting the discharge standard is discharged.

[0018] For the n-butanol ammonia removal process:

[0019] The n-butanol ammonia removal specifically refers to that most of the dissolved ammonia in the liquid phase n-butanol of the condensation backflow of the overhead condenser is removed by rectification (stripping ammonia removal tower). The gaseous phase not condensed in the overhead condenser is discharged, that is, the ammonia-containing tail gas containing a small amount of n-butanol and mainly composed of carrier gas and ammonia components;

[0020] Further, the deamination n-butyl alcohol is returned to the alkoxycarbonylation reaction as raw material, the concentration of byproduct ammonia in the reaction system is greatly reduced while maintaining the ratio of reaction raw materials, the reaction equilibrium is shifted to the right, the reaction yield is improved, and a large amount of industrial cost is saved.

[0021] For the removal process of ammonium carbamate:

[0022] It is worth noting that: due to the trace amount of water (about 0.3-0.5%) brought by the raw material urea, trace amount of CO2 is obtained by hydrolysis of urea under the synthesis reaction conditions of IPDU, and is discharged with the reaction tail gas. CO2 and ammonia will generate ammonium carbamate at low temperature (this reaction is a reversible reaction, which will decompose into CO2 and ammonia at high temperature) with a melting point of about 59-60℃, which will precipitate at low temperature and block the pipeline and valve.

[0023] Further, the material to be removed is: the ammonia-containing tail gas obtained by the process of synthesizing isophorone diamino-n-butyl ester by 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.

[0024] Further, the ammonia-containing tail gas is condensed to liquefy the residual n-butanol in the ammonia-containing tail gas, and carbon dioxide reacts with the ammonia component to generate ammonium carbamate. The ammonium carbamate powder and n-butanol liquid obtained by condensation are separated.

[0025] Further, the material separation is: after the condensation treatment, the mixture of ammonium carbamate and liquid n-butanol obtained by condensation is separated by gas-liquid separation to obtain ammonia-containing tail gas containing ammonium carbamate powder and liquid n-butanol, and then the ammonia-containing tail gas containing ammonium carbamate powder is gas-solid separated to remove solid ammonium carbamate.

[0026] Further, the gas-solid separation treatment is: the ammonia-containing tail gas is introduced into a gas-solid separator;

[0027] Further, the ammonium carbamate removal process further includes a regeneration process of the gas-solid separator, and the regeneration process includes: when ammonium carbamate is enriched in the gas-solid separator, the enriched ammonium carbamate in the gas-solid separator is blown off by high-temperature nitrogen gas to decompose the ammonium carbamate into ammonia component and carbon dioxide, so as to regenerate the gas-solid separator.

[0028] It is worth noting that the gas-solid separator needs to be set up with two reverse switching, one of which needs to be switched out of the process after a certain period of work and regenerated by high-temperature inert gas blowing, at which time the other gas-solid separator is switched on.

[0029] The removal process of residual n-butanol is as follows:

[0030] It is worth noting that the residual n-butanol is formed in the process of synthesizing isophorone diaminobutyrate by urea method, most of which is removed by the overhead condenser of the n-butanol deamination process tower, and then further removed by condensation through the removal process of ammonium carbamate, but there is still a small amount of n-butanol that cannot be condensed.

[0031] Further, the removal method of the residual n-butanol is as follows: cooling the deamination ammonium carbamate tail gas to 15-25℃, and then adsorbing the n-butanol in the tail gas with an adsorbent (adsorption step);

[0032] Further, the adsorbent includes at least one of molecular sieve, activated carbon and high molecular adsorption resin.

[0033] The adsorbent can selectively adsorb n-butanol and is substantially not adsorbed by ammonia; preferably, it is a special adsorbent of Hapn Nano HDV536, the particle size (0.6-1.25mm) is >95%, the specific surface area is 1400㎡ / g, the pore volume is 0.90ml / g, and the pore size is 2-3nm.

[0034] After the adsorbent is adsorbed, a de-n-butanol tail gas is obtained, and the content of n-butanol in the de-n-butanol tail gas is less than 12mg / m 3 .

[0035] Further, the removal method of the residual n-butanol further includes the following steps (desorption step): using high-temperature nitrogen gas to desorb and regenerate the adsorbent, obtaining regenerated adsorbent and regeneration tail gas, and then condensing the regeneration tail gas to obtain liquid n-butanol and inert gas containing a small amount of n-butanol.

[0036] The temperature of the high-temperature inert gas is 140-160℃.

[0037] After the adsorbent is adsorbed, a de-n-butanol tail gas is obtained, and the content of n-butanol in the de-n-butanol tail gas is less than 12mg / m 3 .

[0038] The removal method of the residual n-butanol is provided with at least two sets of adsorption units, which are alternately operated for adsorption and desorption.

[0039] Further, the n-butanol obtained from the steps of removing ammonium carbamate and removing residual n-butanol is collected and used as raw material for the reaction of the next batch.

[0040] For the removal of ammonia components:

[0041] Further, the ammonia component removal treatment is that the de-butanol tail gas is introduced into an acid solution to make the ammonia component in the de-butanol gas react with the acid to generate an ammonium salt.

[0042] Further, the molar ratio of the IPDA, n-butanol, urea and the catalyst is 1:4-10:2-2.5:0.001-0.012; the reaction temperature of the alkoxycarbonylation reaction is 200-250℃, and the reaction pressure is 0.9-2.3 MPa.

[0043] Preferably, the molar ratio of the IPDA, n-butanol, urea and the catalyst is 1:5-8:2-2.3:0.004-0.01; preferably, the reaction temperature is 215-235℃, and the reaction pressure is 1.2-1.5 MPa.

[0044] Further, the catalyst comprises zinc acetate, manganese acetate, zirconium acetate and cobalt acetate; preferably, the catalyst is zirconium acetate.

[0045] Further, the carrier gas is nitrogen.

[0046] Further, the present application has built an industrial device of 100t per year and completed industrial verification, and is building an industrial device of 2kt per year.

[0047] The main equipment of the industrial device of 2kt per year built by the present application comprises: a reaction kettle: Φ1400×4253, 5.4m 3 , a stripping ammonia removal tower: Φ500×5000 (a tower top condenser A=20m 2 ), a flasher Φ700×1600, a falling film evaporator Φ1000×2500; an ammonia-containing tail gas condenser: A=5.4m2, a gas-liquid separator: V=0.61m 3 Φ700×1300 (straight pipe); a gas-solid separator: V=0.61m 3 Φ700×1300 (straight pipe); a n-butanol adsorption tower: a diameter of 1800mm, a height of 2000mm, 3, operating conditions: 30-150℃ (regeneration 150℃), slightly positive pressure.

[0048] The main equipment of the industrial device of 100t per year built by the present application comprises: a reaction kettle: Φ650×800, 300L, a stripping ammonia removal tower: Φ273×5000 (an ammonia removal tower top condenser A=6m 2 ), a falling film evaporator Φ300×1200; an ammonia-containing tail gas condenser: A=2.2m 2 , a gas-liquid separator: V=0.10m 3Φ400x800 (straight pipe) ; gas-solid separator: V = 0.61 m3Φ700x1300 (straight pipe) ; n-butanol adsorption tower: diameter 300 mm, height 1200 mm, 3, operating conditions: 30-150℃ (regeneration 150℃), micro-positive pressure.

[0049] The beneficial effects of the present application are:

[0050] 1、The synthetic process flow of the present application is simple, pollution is small, raw material utilization rate is high, economic benefit is high, byproduct ammonia is carried out by carrier gas and n-butanol vapor, which is conducive to promoting the rapid and efficient progress of the synthesis reaction, and through various process intensification designs, the yield of isophorone diaminonormal butylcarbamate is more than 98%, which is suitable for large-scale industrial production.

[0051] 2、The ammonium carbamate treatment process of the present application is simple, does not need manual operation, has good removal effect, and can ensure that the isophorone diaminonormal butylcarbamate synthesis tail gas treatment process is continuous and smooth.

[0052] 3、The method of the present application treats isophorone diaminonormal butylcarbamate tail gas, the content of n-butanol in the adsorbed tail gas is far lower than the industrial emission standard (12 mg / m 3 ), there is no secondary pollution, the system safety is high, the desorbed tail gas containing trace n-butanol and nitrogen after separation can be recycled to the front end of the desorption tower for adsorption, and is used again, secondary pollution is avoided, the system safety is high, the service life of the adsorbent is 3-5 years, and the n-butanol adsorption rate is high (>99%). BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is the process flowchart of the present application;

[0054] Figure 2 is the specific process flowchart of the deaminocarbamate process in the present application;

[0055] Figure 3 is the specific process flowchart of the residual n-butanol removal process in the present application. DETAILED DESCRIPTION

[0056] I. Equipment, raw materials, process flow and detection method of IPDU-B synthesized by laboratory and industrial urea method.

[0057] Equipment used in laboratory urea method:

[0058] Reaction kettle: 10L; outlet condenser: Φ50x800;

[0059] Preparation of raw materials for laboratory urea method:

[0060] Urea: GB / T 2440-2001 Industrial Grade, total nitrogen (N) (on dry basis) ≥ 46.5%;

[0061] n-Butanol: GB / T 6027-1998 Industrial Grade, main content ≥ 99.5%;

[0062] IPDA: main content ≥ 99.5%;

[0063] Catalyst (zirconium acetate): purity 99.0%.

[0064] Specific method of synthesis of n-butyl isophorone dicarbamate by urea method in laboratory:

[0065] Into a 10 L stainless steel reactor, IPDA, urea, n-butanol and catalyst were added, and the synthesis reaction was carried out at 225°C under a pressure of 1.50 MPa.G for 2 hours to generate n-butyl isophorone dicarbamate, and ammonia was released. The ammonia was allowed to escape by supplementing nitrogen and evaporating n-butanol, and the n-butanol was returned to the reactor by condensation, and the tail gas was absorbed by dilute sulfuric acid. After the synthesis reaction was completed, the reactor was naturally cooled, and the vacuum pump and electric heater were turned on to evaporate the remaining n-butanol in the reactor.

[0066] Equipment used in industrial urea method:

[0067] Reactor: Φ650x800, 300L, stripping ammonia removal tower: Φ273x3000 (ammonia removal tower top condenser A=6m 2 ), falling film evaporator Φ300x1200;

[0068] Ammonia-containing tail gas condenser: A=2.2m 2 , gas-liquid separator: V=0.10m 3 Φ400x800 (straight pipe);

[0069] Gas-solid separator: V=0.61m3Φ700x1300 (straight pipe);

[0070] n-Butanol adsorption tower: diameter 300mm, height 1200mm, 3 units, operating conditions: 30-150°C (regeneration 150°C), slightly positive pressure.

[0071] Raw material preparation:

[0072] Urea: GB / T 2440-2001 Industrial Grade, actual purity 99.6%;

[0073] n-Butanol: GB / T 6027-1998 Industrial Grade, actual main content 99.8%;

[0074] IPDA: purity 99.5%;

[0075] Catalyst (zirconium acetate): purity 99.0%.

[0076] The specific method of the process for synthesizing n-butyl isophorone dicarbamate by the industrial urea method is as follows:

[0077] Liquid raw material n-butanol (excess), raw material IPDA, solid raw material urea (slightly excess), and liquid catalyst zirconium acetate are added into a 300 L stainless steel reaction kettle. After the addition is completed, the reaction kettle is closed and the air in the kettle is replaced with nitrogen. Then, 4.5 Nm 3 / h of nitrogen is introduced. The temperature is raised to 225°C, and the synthesis reaction is carried out under a pressure of 1.50 MPa.G for 2 hours. After the reaction is completed, the product at the bottom of the kettle is flash evaporated under reduced pressure to remove part of the n-butanol. Then, the n-butanol and intermediate product n-butyl carbamate are removed by circulating the product through a falling film evaporator at a temperature of 200°C and a vacuum degree of -0.090 MPa for 2 hours to obtain the intermediate product n-butyl isophorone dicarbamate.

[0078] During the reaction, the gaseous material at the outlet of the reaction kettle (i.e., the synthesis tail gas) is sequentially passed through a stripping ammonia removal tower and a condenser located at the top of the stripping ammonia removal tower to obtain gaseous material and liquid material. The gaseous material is the ammonia-containing tail gas mainly composed of a small amount of n-butanol and carrier gas and ammonia components. The liquid material is most of the n-butanol condensed from the synthesis tail gas. The liquid material is then refluxed to the top of the stripping ammonia removal tower, most of the ammonia dissolved in the liquid material is removed by the stripping ammonia removal tower, and finally the n-butanol after ammonia removal returns to the reaction kettle.

[0079] The high-temperature ammonia-containing tail gas is introduced into the condenser and cooled to 59°C. At this time, most of the n-butanol contained in the ammonia-containing tail gas is liquefied, and ammonium carbamate is solidified. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol, and ammonium carbamate solids. The tail gas is then introduced into a gas-liquid separator to remove the 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 an ammonium carbamate tail gas containing residual n-butanol.

[0080] The ammonium carbamate tail gas containing residual n-butanol is introduced into a pre-cooler for cooling, and the outlet temperature is maintained at 20°C. The cooled tail gas is extracted and pressurized by a fan and then introduced into an adsorption tower containing a nano adsorbent. The adsorbed tail gas is introduced into a sulfuric acid absorber to obtain an ammonium salt and a final tail gas.

[0081] The nano adsorbent is a special adsorbent for Heip nano HDV536, which selectively adsorbs n-butanol and does not adsorb ammonia. The particle size (0.6-1.25 mm) is >95%, the specific surface area is 1400 m

[0082] The detection method is shown in Table 1:

[0083] Table 1

[0084] Serial number Analysis item Detection method 1 IPDU-B content GC-FID 2 n-Butanol content GC-FID 3 Ammonia content GC-FID 5 Ammonium carbamate content GC-FID (measure CO2 peak)

[0085] II. Screening of synthesis temperature and time in the synthesis of isophorone diaminobutyric urea by laboratory urea method:

[0086] A synthesis temperature gradient of 200°C, 215°C, 225°C, 235°C, 250°C was set, and isophorone diaminobutyric urea was synthesized by laboratory urea method (IPDA: 1289g (7.57mol); n-butanol: 4487g (60.6mol); urea: 1000g (16.5mol)) according to the temperature gradient, and the content of isophorone diaminobutyric urea (IPDU-B) was detected and the yield was calculated at 1.5, 2, 3, 4, 5h of reaction time, respectively, and the yield was counted in Table 2.

[0087] Table 2

[0088] Experiment number Reaction temperature (°C) 1.5h 2h 3h 4h 5h 1 200 65.7％ 69.8％ 73.4％ 77.1％ 81.2％ 2 215 78.4％ 91.47％ 93.6％ 97.2％ 97.7％ 3 225 92.7％ 96.9％ 98.5％ 98.7％ 97.6％ 4 235 92.3％ 94.6％ 97.7％ 98.3％ 98.4％ 5 250 91.6％ 96.3％ 98.1％ 97.5％ 97.1％

[0089] As can be seen from Table 2, with the increase of reaction temperature, the yield of IPDU-B increases, but when the reaction time is more than 2h, the synthesis rate of IPDU-B becomes slower and slower, but the synthesis cost increases exponentially, therefore, from the economic benefit, the reaction time of about 2h is selected. When the reaction temperature is 200-250°C and the synthesis time is 2h, the yield of IPDU-B is more than 60%. When the reaction temperature is 215-250°C, the yield of IPDU-B is more than 90%, and the yield does not increase obviously with the increase of temperature, therefore, from the economic benefit, the synthesis temperature of 200-250°C is selected as the optimal reaction temperature, and the synthesis temperature of 215-235°C is the optimal reaction temperature.

[0090] III. Screening of synthesis pressure in the synthesis of isophorone diaminobutyric urea by laboratory urea method:

[0091] A synthesis pressure gradient of 0.9, 1.1, 1.2, 1.3, 1.35, 1.4, 1.5, 1.8, 2.3MPa was set, and isophorone diaminobutyric urea was synthesized by laboratory urea method (IPDA: 1289g (7.57mol); n-butanol: 4487g (60.6mol); urea: 1000g (16.5mol)) according to the pressure gradient, and the content of isophorone diaminobutyric urea (IPDU-B) was detected and the yield was calculated, and the yield was counted in Table 3.

[0092] Table 3

[0093] 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

[0094] From Table 3, when the reaction pressure is greater than 0.9 MPa, the yield of IPDU-B is higher than 90%, and with the gradual increase of the reaction pressure, the yield gradually increases, but the increasing amplitude is smaller and smaller, therefore, from the economic benefit consideration, 0.9-2.3 MPa is selected as the relatively optimal reaction pressure, and 1.2-1.5 MPa is the optimal reaction pressure.

[0095] Four, screening of the amount of n-butanol in the synthesis of n-butyl isophorone dicarbamate by the laboratory urea method:

[0096] The amount of n-butanol gradient is set to 4, 5, 6, 7, 8, 9, 10 n-butanol / IPDA (mol), and referring to the method of synthesizing IPDU-B by the laboratory urea method (IPDA: 1289 g (7.57 mol); n-butanol: 2244-5609 g (30.3-75.7 mol); urea: 1000 g (16.5 mol)), seven groups of experiments are divided according to the n-butanol amount gradient to synthesize n-butyl isophorone dicarbamate, respectively, and the content of n-butyl isophorone dicarbamate (IPDU-B) is detected by GC-FID and the yield is calculated, and the yield data is shown in Table 4.

[0097] Table 4

[0098]

[0099]

[0100] Note: n-butanol / IPDA (mol) represents the molar ratio of n-butanol and IPDA.

[0101] From 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 optimal level, and with the increasing amount of n-butanol, the yield continuously increases, but when the molar ratio is greater than 5, the yield remains almost unchanged, therefore, from the economic benefit consideration, n-butanol: IPDA = 4-10 is selected as the relatively optimal n-butanol amount, and n-butanol: IPDA = 5-8 is the optimal n-butanol amount.

[0102] Five, screening of the amount of urea in the synthesis of n-butyl isophorone dicarbamate by the laboratory urea method:

[0103] The urea dosage gradient 2, 2.05, 2.1, 2.2, 2.3, 2.5 urea / mol IPDA, reference laboratory urea method synthesis IPDU-B method (IPDA: 1289g (7.57mol); n-butanol: 4487g (60.6mol); urea: 909-1147g (15.0-18.9mol)) according to the urea dosage gradient is divided into 6 groups of experiments respectively synthesis of isophorone diaminocarbamic acid n-butyl ester, respectively using GC-FID detection isophorone diaminocarbamic acid n-butyl ester (IPDU-B) content and calculate the yield, the yield data in table 5.

[0104] Table 5

[0105] Experiment number Urea / IPDA (mol) IPDU-B yield (%) 1 2 83.6 2 2.05 91.2 3 2.1 96.2 4 2.2 97.5 5 2.3 97.6 6 2.5 97.6

[0106] Note: urea / IPDA (mol) represents the molar ratio of urea and IPDA.

[0107] From table 5, when the molar ratio of urea / n-butanol dosage is greater than 2, the yield of IPDU-B is greater than 80%, which is at a relatively optimal level, and continuously increases with the increase of urea addition amount, but when the molar ratio is greater than 2.2, the yield remains almost unchanged, considering the economic benefit, the urea:n-butanol=2-2.5 is selected as the optimal urea dosage, and the urea:n-butanol=2.2-2.5 is the optimal urea dosage.

[0108] Six, the verification of the effect of IPDU-B product synthesized by industrial urea method, the specific method is as follows:

[0109] Into the 300L stainless steel reactor liquid raw material n-butanol 158.5kg (2.14komol), raw material IPDA 45.5kg (0.27kmol), solid raw material urea 35.5kg (0.57kmol), liquid catalyst zirconium acetate 318g (0.97mol), after adding, the reactor is sealed, and the air in the reactor is replaced with nitrogen, then the nitrogen is introduced at the amount of 4.5Nm 3 / h, heated to 225℃, and the synthesis reaction is carried out under the condition of pressure 1.50Mpa.G for 2 hours. After the reaction is completed, part of the n-butanol is flash evaporated under reduced pressure, and then the n-butanol and intermediate product n-butyl carbamate are removed by circulating the falling film evaporator at 200℃ and vacuum degree-0.090MPa for 2 hours, to obtain 97.5kg of intermediate product isophorone diaminocarbamic acid n-butyl ester, and the product yield is 98.4% (detection method is GC-FID).

[0110] The above verification was carried out by changing the amount of raw materials, using 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 catalyst zirconium acetate. The intermediate product, n-butyl isophorone dicarbamate, was obtained in an amount of 97.2 kg, and the product yield was 98.1% (detection method: GC-FID).

[0111] It can be seen that the yield of IPDU-B in industrial production is greater than 98%, which verifies the feasibility of the industrial process and the determined industrial parameters.

[0112] Seven, the treatment effect of waste gas in the industrial urea method for synthesizing IPDU-B, the specific method is as follows:

[0113] Referring to the method of industrial urea method for synthesizing IPDU-B (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 introduced into the condenser and cooled to 59°C, at which point the n-butanol is liquefied and the ammonium carbamate is solidified. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol, and ammonium carbamate solids. The tail gas is then introduced into a gas-liquid separator to remove the n-butanol, and the nitrogen, ammonia, and ammonium carbamate are blown into a gas-solid separator. The gas-solid separator filters and adsorbs the ammonium carbamate, obtaining a deaminocarbamic acid ammonium tail gas containing residual n-butanol. The ammonium carbamate enriched in the gas-solid separator is blown off by high-temperature nitrogen to decompose the ammonium carbamate solids into ammonia and carbon dioxide, thereby regenerating the gas-solid separator.

[0114] The deaminocarbamic acid ammonium tail gas containing residual n-butanol is introduced into a pre-cooler to cool, and the outlet temperature is maintained at 20°C. The cooled tail gas is extracted and pressurized by a fan and introduced into an adsorption tower containing a nano adsorbent, obtaining a de-butanol tail gas. The de-butanol tail gas after adsorption is introduced into a sulfuric acid absorber, obtaining an ammonium salt and a final tail gas.

[0115] The above adsorption process stops when the adsorption tower reaches the cycle time (a total of three adsorption towers are involved, one is adsorbed at the same time, and the other two are desorbed, and the adsorption and desorption processes are alternately carried out by switching between valves, and the adsorption tower automatically switches to the desorption process when it reaches the breakthrough point). The adsorbent is regenerated by desorption using 150°C nitrogen, and the n-butanol-containing ammonia gas after desorption is separated by low-temperature chilled water condensation. The liquid phase n-butanol after separation is collected into a 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 introduced into the deaminocarbamic acid ammonium tail gas to remove the trace n-butanol contained therein.

[0116] The content of each component in the ammonia-containing tail gas before condensation, the ammonia-containing tail gas after condensation, the ammonium carbamate-removed tail gas, and the final tail gas was detected, and the results are shown in Table 6.

[0117] Table 6

[0118] Ammonia (%) n-Butanol (%) Ammonium carbamate (%) Nitrogen (%) Ammonia-containing tail gas before condensation 46.74 4.63 0.60 48.04 Ammonia-containing tail gas after condensation 48.43 1.18 0.62 49.77 Ammonium carbamate removal tail gas 48.74 1.20 0.05 50.01 Butanol removal tail gas 48.96 0.001 0.05 50.989 Final tail gas 0.003 Not detected Not detected 99.997

[0119] As can be seen from Table 6, the high-temperature ammonia-containing tail gas discharged in the synthesis of isophorone diamino-n-butyl carbamate contains 0.62% of ammonium carbamate, and after the ammonium carbamate removal process, the content of ammonium carbamate in the tail gas is only 0.05%, and the removal rate of ammonium carbamate reaches 92%, indicating that the ammonium carbamate removal process can effectively remove ammonium carbamate in the synthesis of isophorone diamino-n-butyl carbamate by urea method, and can prevent the pipes and valves of industrial equipment from being blocked by ammonium carbamate. The content of ammonia in the butanol-removed tail gas is 48.96%, and the content of ammonia in the final tail gas is only 0.003%, indicating that the deamination process can effectively remove ammonia in the tail gas. The content of n-butanol in the ammonium carbamate-removed tail gas is 1.20%, and no n-butanol is detected in the final tail gas, indicating that the entire tail gas removal process can effectively remove n-butanol in the tail gas.

[0120] Eight, the intermediate product isophorone diamino-n-butyl carbamate, which is synthesized into IPDI through a thermal cracking process, and the thermal cracking process is preferably the following scheme:

[0121] (1) Raw materials

[0122] Isophorone diamino-n-butyl carbamate (IPDU-B) component: internal control index ≥ 99.0% (IPDU-B 99.38%, catalyst for synthesizing IPDU-B 0.46%, and others 0.16%);

[0123] Thermal cracking reaction catalyst: zinc picolinate, chromium picolinate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate, and zinc iso-octoate.

[0124] Solvent: naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, and trinonyl trimellitate.

[0125] (2) Detection method

[0126] See the following table:

[0127]

[0128]

[0129] (3) Industrial thermal cracking reactor

[0130] IPDU-B raw material pump: Q=2m 3 / h, H=14m; 1#cracking vessel: A=30m 2 ; 1#cracking circulating pump: Q=5m 3 / h, H=14m; 1#polymer discharge pump: Q=2m 3 / h, H=14m; 2#cracking vessel: A=25m 2 ; 2#cracking circulating pump: Q=5m 3 / h, H=14m; 2#polymer discharge pump: Q=2m 3 / h, H=14m.

[0131] (4) Industrial pyrolysis reaction process

[0132] The thermal decomposition raw material IPDU-B, solvent and catalyst enter the 1#rotary scraper thermal decomposition reactor, a liquid film is forced to form on the inner wall of the reactor by the rotary scraper, and thermal decomposition reaction is carried out by heating the inner wall of the reactor. Under vacuum conditions, the thermal decomposition products are rapidly evaporated to achieve rapid separation from the reaction raw materials, greatly reducing the generation of side reactions. The gaseous material at the outlet of the reactor (gaseous material one, reaction product) enters the rectification unit. The rectification column material (mainly single side) enters the 2#rotary scraper thermal decomposition reactor for thermal decomposition reaction, and the gaseous material at the outlet of the reactor (gaseous material three, reaction product) is combined with the gaseous material one and enters the rectification unit. The bottom of the two reactors is provided with a circulating tank and a circulating pump, and the solvent and catalyst are circulated.

[0133] (5) Solvent recovery equipment

[0134] Scraper evaporator: heat exchange area S=12m 2

[0135] (6) Solvent recovery method

[0136] It is emphasized that this part is to process the heavy component material of the circulating liquid discharged from the bottom of the two rotary scraper thermal decomposition reactors in (4) industrial pyrolysis reaction process after preliminary separation.

[0137] The heavy component material produced by the thermal decomposition reaction of isophorone diaminocarbamate n-butyl ester is pumped to the top of the scraper evaporator, a liquid film is forced to form on the inner wall of the evaporator by the rotary scraper, and the inner wall of the evaporator is heated under vacuum conditions to obtain gaseous product and heavy component. The gaseous product is condensed by a condenser to obtain the recovered solvent. The reaction conditions for heating evaporation are: temperature is 280℃, and reaction pressure is -0.096~-0.098MPa.

[0138] (7) Rectification reaction equipment

[0139] De-light column (rectification column): Φ1200x24604, packing height 3888 / 3888 / 3888 / 3240mm

[0140] Product column (rectification column): Φ900x24348, packing height 3096 / 3096 / 4128 / 4128mm

[0141] Condenser: de-light column top condenser Φ1200x2000, heat exchange area 80m 2 ; product column top condenser Φ1000x2000, heat exchange area 90m 2

[0142] Reboiler: de-light column bottom reboiler Φ1100x2500, heat exchange area 94.5m 2 ; product column bottom reboiler Φ1400x3000, heat exchange area 190m 2

[0143] Circulating pump: de-light column bottom circulating pump Q=10.8m 3 H=40m Zone2 EEx dII BT4, product column bottom circulating pump Q=18m 3 H=40m Zone2 EEx dII BT4

[0144] Auxiliary system: heat conduction oil system provides required heat source, circulating water system and refrigerated water system provide refrigerant, nitrogen system provides nitrogen for start-up and shutdown system replacement, vacuum system provides required vacuum conditions for the device

[0145] Control system: process operation control uses DCS system, and safety interlocking (SIS) system is provided

[0146] (8) Rectification reaction process

[0147] It should be emphasized that this part of the content belongs to the specific explanation of the rectification unit in (4) industrialized thermal cracking reaction process.

[0148] Gas phase IPDI crude (gas phase material one and gas phase material three) enters the de-light column bottom (first rectification column) from the thermal decomposition unit, n-butanol is collected at the top of the column, IPDI rich liquid is collected at the middle side line of the column, and the column bottom material goes to the thermal decomposition unit for cyclic thermal decomposition (second thermal decomposition reaction). The IPDI rich liquid collected from the side line of the de-light column is pumped into the product column (second rectification column), a small amount of n-butanol+IPDI is collected at the top of the column, IPDI product is collected at the side line, and the column bottom material (liquid phase material two) goes to the thermal decomposition unit for cyclic thermal decomposition (second thermal decomposition reaction).

[0149] The IPDI was continuously synthesized according to the above industrialized routes (4), (6), (8), and the control conditions were the optimal experimental conditions, i.e., the operating pressure of the first thermal decomposition was -0.094 Mpa, and the operating temperature was 240 ℃; the operating pressure of the second thermal decomposition was -0.094 Mpa, and the operating temperature was 245 ℃. The operating conditions of the light-removing column were as follows: the column top was 11 mbar, the column bottom was 24 mbar, the column bottom temperature was 199.7 ℃, the operating temperature of the column top was 25 ℃, and the side line temperature was 160.8 ℃; the operating conditions of the product column were as follows: the column top was 11 mbar, the column bottom was 24 mbar, the column bottom temperature was 194 ℃, the operating temperature of the column top was 40 ℃, and the side line temperature was 158.3 ℃. After the system was stably operated, the raw material feeding amount, the product composition and the product yield of each step were as follows:

[0150]

[0151]

[0152]

[0153] Note: The process of the present application is continuously performed, and the gas phase material one and the gas phase material three are materials produced at the same time in different thermal cracking reactors, which are mixed into the first rectifying column; the IPDI raw material impurities: the catalyst for synthesizing IPDI-B is 0.46%, and other impurities are 0.16%.

[0154] The above description is only the preferred embodiments of the present application, and it should be understood that the present application is not limited to the forms disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concepts described herein, by the above-mentioned teaching or related technical or knowledge. The modifications and changes made by those skilled in the art without departing from the spirit and scope of the present application should be within the protection scope of the appended claims of the present application.

Claims

1. A method for removing by-product ammonium carbamate in the process for synthesizing n-butyl isophorone dicarbamate by urea method, characterized in that: The material containing ammonium carbamate to be removed is the ammonia-containing tail gas obtained in the process of synthesizing n-butyl isophorone dicarbamate by urea method, which is condensed at 59℃, so that the residual n-butanol in the ammonia-containing tail gas is liquefied, and then the ammonium carbamate powder generated by the reaction of carbon dioxide and ammonia component; The removal of the ammonium carbamate is carried out by separating the ammonium carbamate powder and n-butanol liquid obtained by condensation; The separation of the material is carried out by separating the mixture of ammonium carbamate and liquid n-butanol obtained by condensation by gas-liquid separation to obtain the ammonia-containing tail gas containing ammonium carbamate powder and liquid n-butanol, and then separating the ammonia-containing tail gas containing ammonium carbamate powder by gas-solid separation to remove the solid ammonium carbamate.

2. The removal method of claim 1, wherein: The process of synthesizing n-butyl isophorone dicarbamate by urea method includes: The alkoxycarbonylation reaction of organic amine is carried out by taking IPDA, n-butanol, urea and catalyst, and carrier gas is introduced during the reaction to separate the by-product ammonia component, so that n-butyl isophorone dicarbamate and synthesis tail gas containing ammonia component are obtained, and the synthesis tail gas is further subjected to n-butanol deamination process; The n-butanol deamination process includes separating the n-butanol and ammonia component in the synthesis tail gas by rectification to obtain heavy n-butanol and light ammonia-containing tail gas.

3. The removal method of claim 1, wherein: The gas-solid separation treatment is carried out by introducing the ammonia-containing tail gas into a gas-solid separator.

4. The removal method of claim 1, wherein: The ammonia-containing tail gas is further subjected to ammonia component removal treatment after the gas-solid separation treatment; The ammonia removal process is to introduce the gas-solid separation treated deamination carbamate tail gas into an acid solution to react the ammonia component in the deamination carbamate tail gas with the acid to generate ammonium salt.

5. The removal method of claim 2, wherein: The carrier gas is nitrogen.

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