The application discloses a method for removing residual n-butanol in tail gas in a process for synthesizing isophorone dicarbamic acid n-butyl ester by using a urea method

Abstract

The present application relates to the technical field of IPDI synthesis, and particularly discloses a method for removing residual n-butanol in tail gas in a process for synthesizing isophorone diaminon-butyl carbamate by using a urea method, wherein the tail gas is obtained from: ammonia-containing tail gas obtained in the process for synthesizing isophorone diaminon-butyl carbamate by using the urea method, and tail gas obtained after an ammonium carbamate removal process; and the method for removing the residual n-butanol in the tail gas comprises the following steps: cooling the tail gas to 15-25 DEG C, and then adsorbing the n-butanol in the tail gas by using an adsorbent; and the adsorbent comprises molecular sieves, activated carbon and nano-polymer adsorption resin. By using the method, the content of n-butanol in the tail gas of isophorone diaminon-butyl carbamate is far lower than the industrial emission standard, no secondary pollution is caused, and the system safety is high.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of IPDI synthesis, in particular to a method for removing n-butanol in tail gas 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 an urethane 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 has hydrolyzed chlorine in the obtained isocyanate product, which affects 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 an urethane thermal decomposition method. However, most of them still stay in the laboratory stage, and only the urethane thermal decomposition method realizes device production in foreign countries. The urea method route is researched most, 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 diurethane, and the diurethane is further cracked to generate isocyanate and alcohol, and the total reaction yield can reach 90%.

[0005] The research and production of diisocyanate in China started late, but with the rapid development of China's society and economy, China has become a big country in the production and consumption of diisocyanate. On the other hand, in the field of high-performance special isocyanate, China's development is very slow, but the consumer demand is growing by more than 15% per year. Aliphatic isocyanate is mainly used in automotive topcoat, rocket propellant, anti-corrosion coating, light-cured coating and adhesive fields. 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] At present, the annual demand of HDI and IPDI in China is about 95,000 tons, which is occupied by a few multinational companies such as Wanhao and Degussa. Domestic products basically depend on imports, and some high-end military products are limited in China. It is necessary to produce aliphatic diisocyanate in China, especially by non-phosgene green synthesis technology, to promote the technological progress and industrial upgrading of related industries, and to protect the industrial security of important industries in China. It has great economic benefits and great social significance, but non-phosgene method currently only Degussa and BASF each have a 10,000 tons / year production device.

[0007] At present, the domestic industrial 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 industry safety and the reality of the backwardness of domestic production and development, the present application provides an industrial process for synthesizing isophorone diaminocarbamic acid 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 phosgene method be eliminated from the root, but also the cost can be competitive with 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 n-butanol in tail gas in the process of synthesizing isophorone diaminocarbamic acid n-butyl ester by urea method, which at least achieves 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 scheme:

[0010] The method for removing n-butanol in tail gas in the process of synthesizing isophorone diaminocarbamic acid 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 a lower temperature (this reaction is a reversible reaction, which will decompose into CO2 and ammonia at high temperature). The melting point of ammonium carbamate is 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 diaminobutyl ester by urea method is condensed to liquefy the trace amount of n-butyl alcohol in the ammonia-containing tail gas, and then the trace amount of carbon dioxide and ammonia in the ammonia-containing tail gas is reacted to generate ammonium carbamate powder.

[0024] Further, the ammonia-containing tail gas is condensed to liquefy the trace amount of n-butyl alcohol in the ammonia-containing tail gas, and carbon dioxide and ammonia components are reacted to generate ammonium carbamate. The ammonium carbamate powder and n-butyl alcohol liquid obtained by condensation are separated.

[0025] Further, the condensation temperature is 30-60℃.

[0026] Further, after the condensation, the mixture of ammonium carbamate and liquid n-butyl alcohol obtained by condensation is subjected to gas-liquid separation to obtain ammonia-containing tail gas containing ammonium carbamate powder and liquid n-butyl alcohol, and then the ammonia-containing tail gas containing ammonium carbamate powder is subjected to gas-solid separation to remove solid ammonium carbamate.

[0027] Further, the gas-solid separation treatment is: the ammonia-containing tail gas is introduced into a gas-solid separator;

[0028] 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 removed by high-temperature nitrogen gas to decompose the ammonium carbamate into ammonia component and carbon dioxide, so as to regenerate the gas-solid separator.

[0029] It is worth noting that the gas-solid separator needs to be set up two switching, one of which needs to be switched out of the process after a certain period of work, and the other one is switched on for work.

[0030] For the removal process of residual n-butanol:

[0031] It is worth noting that the formation of residual n-butanol is as follows: in the process of synthesizing isophorone diaminobutyrate by urea method, most of the n-butanol is removed by condensing the overhead condenser of the n-butanol deamination process, and then further removing the n-butanol by condensing after removing the carbamic acid ammonium, but there is still a small amount of n-butanol that cannot be condensed;

[0032] Further, the removal method of residual n-butanol is as follows: cooling the carbamic acid ammonium tail gas to 15-25℃, and then adsorbing the n-butanol in the tail gas with an adsorbent (adsorption step);

[0033] Further, the adsorbent includes at least one of molecular sieve, activated carbon and high molecular adsorption resin;

[0034] The adsorbent can selectively adsorb n-butanol, and has little adsorption of ammonia; preferably, it is a special adsorbent of Hapn nano HDV536, with particle size (0.6-1.25mm) > 95%, specific surface area 1400㎡ / g, pore volume 0.90ml / g, and pore diameter

[0035] After the adsorbent is adsorbed, a de-butanol tail gas is obtained, and the content of n-butanol in the de-butanol tail gas is less than 12mg / m 3 .

[0036] Further, the removal method of residual n-butanol further includes the following steps (desorption step): using high-temperature nitrogen to 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;

[0037] The temperature of the high-temperature inert gas is 140-160℃;

[0038] After the adsorbent is adsorbed, a de-butanol tail gas is obtained, and the content of n-butanol in the de-butanol tail gas is less than 12mg / m 3 ;

[0039] The removal method of residual n-butanol is provided with at least two sets of adsorption units, which are alternately operated for adsorption and desorption.

[0040] Further, the n-butanol obtained from the steps of removing carbamic acid ammonium and removing residual n-butanol is collected and used as raw material for the reaction of the next batch.

[0041] For the ammonia component removal treatment:

[0042] Further, the ammonia component removal treatment is that the de-butanols tail gas is passed into an acid solution to make the ammonia component in the de-butanols tail gas react with the acid to generate an ammonium salt.

[0043] 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.

[0044] 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.

[0045] Further, the catalyst comprises zinc acetate, manganese acetate, zirconium acetate, cobalt acetate; preferably, the catalyst is zirconium acetate.

[0046] Further, the carrier gas is nitrogen.

[0047] 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.

[0048] 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.

[0049] 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=0.10m3 Φ400x800 (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.

[0050] The beneficial effects of the present application are:

[0051] 1. The synthetic process flow of the present application is simple, with low pollution, high raw material utilization rate, high economic benefit, and the by-product ammonia is carried out by carrier gas and n-butanol vapor, which is conducive to promoting the rapid and efficient synthesis reaction, and through various process intensification designs, the yield of isophorone diaminonormal butyl carbamate is more than 98%, which is suitable for large-scale industrial production.

[0052] 2. The ammonium carbamate treatment process of the present application is simple, does not require manual operation, has good removal effect, and can ensure that the isophorone diaminonormal butyl carbamate synthesis tail gas treatment process is continuous and smooth.

[0053] 3. The method of the present application treats isophorone diaminonormal butyl carbamate tail gas, and the n-butanol content in the adsorbed tail gas is far lower than the industrial emission standard (12 mg / m 3 ), without secondary pollution, high system safety, and 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, thereby avoiding secondary pollution, and the system safety is high, the service life of the adsorbent is long (3-5 years), and the n-butanol adsorption rate is high (>99%). BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is the process flowchart of the present application;

[0055] Figure 2 is the specific process flowchart of the deamination of carbamic acid in the present application;

[0056] Figure 3 is the specific process flowchart of the residual n-butanol removal process in the present application. DETAILED DESCRIPTION

[0057] The technical solutions of the present application will be described in further detail below in conjunction with the drawings, but the protection scope of the present application is not limited to the following description.

[0058] I. Equipment, raw materials, process flow and detection method of IPDU-B synthesized by laboratory and industrial urea method.

[0059] Laboratory urea method uses the following equipment:

[0060] Reaction kettle: 10L; outlet condenser: Φ50x800;

[0061] Laboratory urea method raw material preparation:

[0062] Urea: GB / T 2440-2001 industrial superior product, total nitrogen (N) (on a dry basis) ≥ 46.5%;

[0063] n-Butanol: GB / T 6027-1998 superior product, main content ≥ 99.5%;

[0064] IPDA: main content ≥ 99.5%;

[0065] Catalyst (zirconium acetate): purity 99.0%.

[0066] Specific method of laboratory urea method for synthesizing n-butyl isophorone dicarbamate process:

[0067] IPDA, urea, n-butanol and catalyst were added to a 10L stainless steel reaction kettle, and the synthesis reaction was carried out at 225℃ under the condition of pressure 1.50Mpa.G for 2 hours to generate n-butyl isophorone dicarbamate, and ammonia gas was released at the same time. Ammonia was released by supplementing nitrogen and evaporating n-butanol, and n-butanol was returned to the reaction kettle by condensation, and the tail gas was absorbed with dilute sulfuric acid. After the synthesis reaction was completed, the reaction kettle was naturally cooled, and then the vacuum pump and electric heater were started to evaporate the remaining n-butanol in the kettle.

[0068] Industrial urea method used equipment:

[0069] Reaction kettle: Φ650×800, 300L, stripping ammonia removal tower: Φ273×3000 (ammonia removal tower top condenser A = 6m 2 ), falling film evaporator Φ300×1200;

[0070] Ammonia-containing tail gas condenser: A = 2.2m 2 , gas-liquid separator: V = 0.10m 3 Φ400×800 (straight pipe);

[0071] Gas-solid separator: V = 0.61m3Φ700×1300 (straight pipe);

[0072] n-Butanol adsorption tower: diameter 300mm, height 1200mm, 3 sets, operating conditions: 30-150℃ (regeneration 150℃), slightly positive pressure.

[0073] Raw material preparation:

[0074] Urea: GB / T 2440-2001 industrial superior product, actual purity 99.6%;

[0075] n-Butanol: GB / T 6027-1998 superior product, actual main content 99.8%;

[0076] IPDA: 99.5% purity;

[0077] Catalyst (zirconium acetate): 99.0% purity.

[0078] The specific method of the process for synthesizing n-butyl isophorone dicarbamate by the industrial urea method is as follows:

[0079] Liquid raw material n-butanol (excess), raw material IPDA, solid raw material urea (slightly excess), liquid catalyst zirconium acetate are added into a 300L 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, 4.5Nm 3 / h is introduced, and the temperature is raised to 225°C. The synthesis reaction is carried out under a pressure of 1.50Mpa.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 -0.090MPa for 2 hours to obtain the intermediate product n-butyl isophorone dicarbamate.

[0080] During the reaction, the gaseous material at the outlet of the reaction kettle (i.e. the synthesis tail gas) passes through a stripping ammonia removal tower and a condenser located at the top of the stripping ammonia removal tower in sequence 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 to remove most of the ammonia dissolved in the liquid material by the stripping ammonia removal tower. Finally, the n-butanol after ammonia removal returns to the reaction kettle.

[0081] The high-temperature ammonia-containing tail gas is introduced 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 ammonium carbamate is solidified. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol and ammonium carbamate solid. 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.

[0082] The ammonium carbamate tail gas containing residual n-butanol is introduced into a pre-cooler to be cooled, 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 nano adsorbent. The adsorbed tail gas is introduced into a sulfuric acid absorber to obtain ammonium salt and final tail gas.

[0083] The nano adsorbent is a special adsorbent for Heip nano HDV536, which selectively adsorbs n-butanol and does not adsorb ammonia. The particle size (0.6-1.25mm) is >95%, the specific surface area is 1400㎡ / g, the pore volume is 0.90ml / g, and the pore size is 2-3nm.

[0084] The detection method is shown in Table 1:

[0085] Table 1

[0086] 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)

[0087] II. Screening of synthesis temperature and time in the synthesis of isophorone diaminocarbonic acid n-butyl ester by laboratory urea method:

[0088] A temperature gradient of 200℃, 215℃, 225℃, 235℃, 250℃ was set, and the synthesis of isophorone diaminocarbonic acid n-butyl ester was divided into 5 groups according to the temperature gradient, and the content of isophorone diaminocarbonic acid n-butyl ester (IPDU-B) was detected and the yield was calculated at 1.5, 2, 3, 4, 5h of reaction time, respectively. The yield was calculated and shown in Table 2.

[0089] Table 2

[0090]

[0091]

[0092] 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℃ and the synthesis time is 2h, the yield of IPDU-B is more than 60%. When the reaction temperature is 215-250℃, the yield of IPDU-B is more than 90%, and the increase of temperature does not obviously improve the yield, therefore, from the economic benefit, the synthesis temperature of 200-250℃ is selected as the optimal reaction temperature, and the synthesis temperature of 215-235℃ is the optimal reaction temperature.

[0093] III. Screening of synthesis pressure in the synthesis of isophorone diaminocarbonic acid n-butyl ester by laboratory urea method:

[0094] The synthesis pressure gradient was set to 0.9, 1.1, 1.2, 1.3, 1.35, 1.4, 1.5, 1.8, 2.3 MPa, and the IPDU-B was synthesized according to the method of the laboratory urea method (IPDA: 1289 g (7.57 mol); n-butanol: 4487 g (60.6 mol); urea: 1000 g (16.5 mol)) in 9 groups of experiments according to the pressure gradient, the content of isophorone dibutyric acid carbamate (IPDU-B) was detected, and the yield was calculated, and the yield was counted in Table 3.

[0095] Table 3

[0096] 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

[0097] As can be seen from Table 3, when the reaction pressure is greater than 0.9 MPa, the yield of IPDU-B is higher than 90%, and as the reaction pressure gradually increases, the yield gradually increases, but the increasing amplitude is smaller and smaller, therefore, from the economic benefit, the reaction pressure of 0.9-2.3 MPa is selected as the optimal reaction pressure, and the reaction pressure of 1.2-1.5 MPa is the optimal reaction pressure.

[0098] Four, the selection of the amount of n-butanol in the synthesis of isophorone dibutyric acid carbamate by the laboratory urea method:

[0099] The amount of n-butanol gradient was set to 4, 5, 6, 7, 8, 9, 10 n-butanol / IPDA (mol), and the IPDU-B was synthesized according to the method of 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)) in 7 groups of experiments according to the amount of n-butanol gradient, the content of isophorone dibutyric acid carbamate (IPDU-B) was detected by GC-FID, and the yield was calculated, and the yield data was counted in Table 4.

[0100] Table 4

[0101]

[0102] Note: n-butanol / IPDA (mol) represents the molar ratio of n-butanol and IPDA.

[0103] As can be seen 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 as the amount of n-butanol added increases, it continuously increases, but when the molar ratio is greater than 5, the yield remains almost unchanged, therefore, from the economic benefit, the amount of n-butanol of n-butanol: IPDA = 4-10 is selected as the optimal n-butanol amount, and the amount of n-butanol of n-butanol: IPDA = 5-8 is the optimal n-butanol amount.

[0104] Five, the screening of urea dosage in the synthesis of isophorone diaminocarbamate n-butyl ester by laboratory urea method:

[0105] The urea dosage gradient was set as 2, 2.05, 2.1, 2.2, 2.3, and 2.5 urea / mol IPDA. Referring to the method for synthesizing IPDU-B by the laboratory urea method (IPDA: 1289 g (7.57 mol); n-butanol: 4487 g (60.6 mol); urea: 909-1147 g (15.0-18.9 mol)), isophorone diaminocarbamate n-butyl ester was synthesized in six groups of experiments according to the urea dosage gradient. The content of isophorone diaminocarbamate n-butyl ester (IPDU-B) was detected by GC-FID, and the yield was calculated. The yield data are shown in Table 5.

[0106] Table 5

[0107]

[0108] Note: Urea / IPDA (mol) represents the molar ratio of urea to IPDA.

[0109] As can be seen from 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 a relatively optimal level. The yield 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 economic benefits, the urea:n-butanol = 2-2.5 is selected as the relatively optimal urea dosage, and the urea:n-butanol = 2.2-2.5 is selected as the optimal urea dosage.

[0110] Six, verification of the effect of IPDU-B product synthesized by industrial urea method, the specific method is as follows:

[0111] Into a 300 L stainless steel reaction kettle, 158.5 kg (2.14 kmol) of liquid raw material n-butanol, 45.5 kg (0.27 kmol) of raw material IPDA, 35.5 kg (0.57 kmol) of solid raw material urea, and 318 g (0.97 mol) of liquid catalyst zirconium acetate were added. After the addition was completed, the reaction kettle was sealed, and the air in the kettle was replaced with nitrogen. Then, 4.5 Nm 3 / h of nitrogen was introduced. The temperature was raised to 225°C, and the synthesis reaction was carried out under the conditions of pressure 1.50 MPa.G for 2 hours. After the reaction was completed, part of the n-butanol was flash evaporated under reduced pressure, and then the n-butanol and intermediate product n-butyl carbamate were removed by circulating the falling film evaporator at 200°C and a vacuum degree of -0.090 MPa for 2 hours to obtain 97.5 kg of intermediate product isophorone diaminocarbamate n-butyl ester, with a product yield of 98.4% (detection method: GC-FID).

[0112] 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).

[0113] 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.

[0114] Seven, the treatment effect of waste gas in the industrial urea method for synthesizing IPDU-B, the specific method is as follows:

[0115] 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.

[0116] 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 then 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.

[0117] 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 desorbed and regenerated by 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.

[0118] 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.

[0119] Table 6

[0120] 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

[0121] 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.

[0122] 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:

[0123] (1) Raw materials

[0124] 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%);

[0125] 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.

[0126] Solvent: naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, and trinonyl trimellitate.

[0127] (2) Detection method

[0128] See the following table:

[0129]

[0130]

[0131] (3) Industrial thermal cracking reactor

[0132] 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.

[0133] (4) Industrial pyrolysis reaction process

[0134] The thermal decomposition raw material IPDU-B, solvent and catalyst enter the 1#rotary blade thermal decomposition reactor, a liquid film is forced to form on the inner wall of the reactor by the rotary blade, 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 material in the rectification column (mainly single side) enters the 2#rotary blade 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.

[0135] (5) Solvent recovery equipment

[0136] Blade evaporator: heat exchange area S=12m 2

[0137] (6) Solvent recovery method

[0138] It is emphasized that this part of the content is to process the heavy component material after the initial separation of the circulating liquid discharged from the bottom of the two rotary blade thermal decomposition reactors in (4) industrial pyrolysis reaction process.

[0139] The heavy component material produced by the thermal decomposition reaction of isophorone diaminocarbonic acid n-butyl ester is pumped to the top of the blade evaporator, a liquid film is forced to form on the inner wall of the evaporator by the rotary blade, and heated by the inner wall of the evaporator. Evaporate under vacuum conditions to obtain gaseous product and heavy component, and the gaseous product condensed by the condenser is the recovered solvent. The reaction conditions for heating and evaporation are: temperature 280℃, reaction pressure -0.096~-0.098MPa.

[0140] (7) Reaction equipment for rectification

[0141] De-light column (rectification column): Φ1200x24604, packing height 3888 / 3888 / 3888 / 3240mm

[0142] Product column (rectification column): Φ900x24348, packing height 3096 / 3096 / 4128 / 4128mm

[0143] Condenser: de-light column top condenser Φ1200x2000, heat exchange area 80m 2 ; product column top condenser Φ1000x2000, heat exchange area 90m 2

[0144] Reboiler: de-light column bottom reboiler Φ1100x2500, heat exchange area 94.5m 2 ; product column bottom reboiler Φ1400x3000, heat exchange area 190m 2

[0145] 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

[0146] 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

[0147] Control system: process operation control uses DCS system, and safety interlocking (SIS) system is provided

[0148] (8) Rectification reaction process

[0149] It should be emphasized that this part is a specific explanation of the rectification unit in (4) industrialized thermal cracking reaction process.

[0150] 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).

[0151] 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 11 mbar, the column bottom 24 mbar, the column bottom temperature 199.7℃, the column top operating temperature 25℃, and the side line temperature 160.8℃; the operating conditions of the product column were as follows: the column top 11 mbar, the column bottom 24 mbar, the column bottom temperature 194℃, the column top operating temperature 40℃, and the side line temperature 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:

[0152]

[0153]

[0154]

[0155] 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 by 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%.

[0156] 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 considered 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 teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A method for removing residual n-butanol contained in tail gas in a process for synthesizing n-butyl isophorone dicarbamate by urea method, characterized in that, The method comprises the following steps: The tail gas is obtained from the tail gas containing ammonia in the process of synthesizing isophorone diamino-n-butyl ester by urea method, and the tail gas after removing the carbamic acid ammonium by the removing process; The removing method of the residual n-butyl alcohol in the tail gas is: cooling the tail gas to 15-25℃, and then adsorbing the n-butyl alcohol in the tail gas by the adsorbent; The adsorbent is nanometer high-molecular adsorption resin HapNano HDV536 which selectively adsorbs n-butyl alcohol; The synthesis process of the isophorone diamino-n-butyl ester is: The alkoxycarbonylation reaction of organic amine is carried out by taking IPDA, n-butyl alcohol, urea and catalyst, and the by-product ammonia gas is separated by passing the carrier gas in the alkoxycarbonylation reaction, and the synthesis tail gas containing ammonia component is discharged in the reaction process, and the crude isophorone diamino-n-butyl ester is obtained after the reaction is completed; That is, the alkoxycarbonylation reaction of organic amine is carried out by taking IPDA, n-butyl alcohol, urea and catalyst in the kettle reactor, the by-product ammonia gas in the alkoxycarbonylation reaction is discharged with the evaporated excess n-butyl alcohol and carrier gas, then most of the gaseous n-butyl alcohol is liquefied by condensation, and most of the dissolved ammonia in the liquid n-butyl alcohol is removed by rectification, the tail gas containing n-butyl alcohol, carrier gas and ammonia component is discharged in the process, and the crude isophorone diamino-n-butyl ester is obtained after the reaction is completed; The crude isophorone diamino-n-butyl ester is subjected to flash evaporation and falling film evaporation to obtain the target product isophorone diamino-n-butyl ester.

2. The removal method according to claim 1, characterized in that, The removing process of the carbamic acid ammonium in the tail gas containing ammonia is: the tail gas containing ammonia is subjected to condensation treatment to liquefy the trace n-butyl alcohol in the tail gas containing ammonia, and the carbon dioxide and ammonia component react to generate the carbamic acid ammonium, and the material separation is carried out on the carbamic acid ammonium powder and n-butyl alcohol liquid obtained by condensation; The material separation is: after the condensation treatment, the mixture of the carbamic acid ammonium and liquid n-butyl alcohol obtained by condensation is subjected to gas-liquid separation to obtain the tail gas containing ammonia containing the carbamic acid ammonium powder and liquid n-butyl alcohol, and then the tail gas containing ammonia containing the carbamic acid ammonium powder is subjected to gas-solid separation to remove the solid carbamic acid ammonium.

3. The removal method of claim 1, wherein: The content of n-butanol in the de-dialcoholization tail gas after adsorption of the adsorbent is less than 12 mg / m 3 .

4. The method according to any one of claims 1-3, further comprising the following steps: The adsorbent is subjected to desorption regeneration by high-temperature nitrogen gas to obtain the regenerated adsorbent and regeneration tail gas, and then the regeneration tail gas is condensed to obtain the liquid n-butyl alcohol and inert gas containing trace n-butyl alcohol.

5. The method of claim 4, wherein: The temperature of the high-temperature inert gas is 140-160℃.

6. The removal method of claim 4, wherein: At least two sets of adsorption units are arranged to alternately carry out adsorption and desorption.

7. The removal method of claim 1, wherein: The molar ratio of the IPDA, n-butyl alcohol, 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.

8. The removal method of claim 1, wherein, The catalyst comprises at least one of zinc acetate, manganese acetate, zirconium acetate and cobalt acetate.

9. The removal method of claim 1, wherein: The carrier gas is nitrogen.

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