Industrial method for producing IPDI by thermal cracking of n-butyl isophorone dicarbamate

Abstract

The present invention relates to the technical field of industrial urea method for synthesizing IPDI, specifically an industrial method for continuously thermally cracking IPDU-B to produce IPDI. The industrial method includes the following continuous processes: 1) Using two thermal decomposition reactors (the first thermal decomposition reactor and the second thermal decomposition reactor), combining with distillation operation to carry out two-stage thermal decomposition reaction to prepare a reaction product containing a high IPDI content; 2) Discharging the recycled heavy components of the two-stage thermal decomposition reactors and recovering the solvent; 3) Distillation operation step: Separating the thermal decomposition product, using a two-column process of a first distillation column (light component removal column) and a second distillation column (product column), separating almost all of the n-butanol (more than 99.6% of the total amount) at the top of the first column, and taking out the crude product and the product from the side lines of the two columns respectively. The thermal cracking method provided by the present invention achieves the effects of industrial continuous production of IPDI with a yield greater than 90% and a purity greater than 99.7%.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial synthesis of IPDI by urea method, specifically an industrial method for the thermal cracking of n-butyl isophorone dicarbamate (IPDU-B) to produce IPDI. Background Art

[0002] The chemical name of isophorone diisocyanate is 3-isocyanatomethylene-3,5,5-trimethylcyclohexyl isocyanate, abbreviated as IPDI in English. The molecular formula is C 12 H 18 N 2 O 2 , and the structural formula is The relative molecular mass is 222.29. It is a colorless or light yellow liquid with a camphor-like odor and is completely miscible with organic solvents such as esters, ketones, ethers, aromatic hydrocarbons, and aliphatic hydrocarbons.

[0003] Diisocyanates contain two -N=C=O groups. Due to electron imbalance and unsaturation, diisocyanates have high reactivity. Common chemical reactions are as follows:

[0004] Reaction with water:

[0005] Diisocyanates react with water to form unstable carbamic acid and rapidly decompose into diisocyanate-based diamine and release carbon dioxide. This reaction can occur at room temperature.

[0006]

[0007] If the diisocyanate is in excess, the formed diamine will continue to react with the diisocyanate to form urea and further react to form biuret.

[0008] OCNRCH 2 NCO+NH 2 RCH 2 NH 2 →OCNRCH 2 NHCONHRCH 2 NH 2

[0009] OCNRCH 2 NCO+OCNRCH 2 NHCONHRCH 2 NH 2

[0010] →OCNRCH 2 NHCONHRCH 2 NHCNHRCH 2 NCO

[0011] Reaction with hydroxyl groups:

[0012] Generally, substances containing -OH such as alcohols and phenols react with diisocyanates to form urethanes and react with polyols with two or more hydroxyl groups to form polyurethanes.

[0013] OCNRNCO + 2R'OH → R'OCONHRCH 2 NHCOOR'

[0014]

[0015] This is also the production principle of the main use of diisocyanates, namely polyurethanes.

[0016] Reaction with amines:

[0017] Reaction with primary amines and secondary amines produces substituted ureas (polyurea elastomers), while tertiary amines do not contain active hydrogen and diisocyanates do not react with tertiary amines.

[0018] OCNRCH 2 NCO + NH 2 R' → CONRCH 2 NHCONHR'

[0019] OCNRCH 2 NCO + 2NH 2 R' → R'NHOCNHRCH 2 NHCONHR'

[0020] OCNRCH 2 NCO + NHR'R" → CONRCH 2 NHCONR'R"

[0021] Based on the above reactions, in the production of polyurethanes, diamines are often used as crosslinking agents and chain extenders, while triethylamine is used as a neutralizing agent. However, on the other hand, in the cracking units of HDI and IPDI, since the cracking raw material dicarbamate contains two secondary amino groups (-NH), and the by-products of dicarbamate at high temperatures may contain amine substances such as amines and diamines, the product IPDI reacts with the raw materials and further polymerizes. Therefore, to a certain extent, the production of polyurethanes and the cracking of ADU can be regarded as a reversible two-way reaction, which is the utilization of a pair of contradictions.

[0022] Reaction with carbamate:

[0023]

[0024] This reaction has low activity and will only occur above 120 °C to form allophanate products.

[0025] Reaction with acid anhydride:

[0026] The reaction of isocyanate with anhydride generates an imide ring with high heat resistance, and further reaction can produce polyimide (PI) with higher thermal stability.

[0027]

[0028] Reaction with amide:

[0029] The reaction of isocyanate with amide produces acylurea.

[0030] RNCO + H 2 NCOR' → RNHCONHCOR'

[0031] Self-polymerization reaction:

[0032] Under the action of heating and a catalyst (such as dibutyltin dilaurate), IPDI will undergo a self-polymerization reaction to form dimers and trimers, and even form polymers at higher temperatures.

[0033] Two IPDIs self-polymerize into IPDI dimer:

[0034]

[0035] The dimer is an unstable compound, which decomposes and reduces to IPDI when heated, or continues to polymerize into a trimer.

[0036]

[0037] Different from the dimer, the reaction of the trimer is irreversible, and the decomposition product of the trimer when heated is not IPDI. The trimer has a stable structure, is not easily decomposed under high-temperature conditions, has good thermal stability, good wear resistance, good corrosion resistance, etc., can quickly release the solvent, and has high reactivity due to still containing the -N=C=O group, and is often used as a polyurethane curing agent and is widely used in industries such as furniture, automobiles, and aviation.

[0038] The main production methods of isophorone diisocyanate are the phosgene method and the urethane pyrolysis method. The phosgene method is still the main production method of diisocyanate at present. Only Degussa and BASF have built 10,000-ton / year production plants using the non-phosgene method, and domestic production is still blank.

[0039] The gas-phase phosgenation method is a process for preparing isocyanates by feeding gaseous amines, diluted with an inert gas or the vapor of an inert solvent, together with phosgene into a mixing reactor and reacting at a temperature between 200 and 600 °C. The gas-phase method is the newest phosgenation method. Compared with the traditional liquid-phase phosgenation method, the gas-phase method has the advantages of less phosgene consumption, extremely fast reaction rate, high yield (up to over 98%), and low risk. Currently, Bayer uses this method to produce HDI and IPDI, and its production accounts for over 70% of HDI production. The only IPDI producer in China also uses this process.

[0040] The amine phosgenation method mainly has the following problems: ① Phosgene is a highly toxic gas, and a series of engineering and technical problems such as safety and environmental protection in the production process are difficult to solve; ② There are a large number of by-products of hydrogen chloride in the phosgenation production. If the absorption treatment is not perfect, it will also leak, causing environmental pollution; ③ The by-product hydrogen chloride seriously corrodes the equipment in the production process, has relatively high requirements for the equipment material, and the corresponding equipment investment is large; ④ The isocyanate product obtained by the phosgenation method contains hydrolyzable chlorine, which affects the use performance of the product.

[0041] Due to the above-mentioned disadvantages of the phosgenation method, developed countries have been committed to developing economical and simple synthesis methods, and various non-phosgenation methods for synthesizing isocyanates have emerged, such as carbonylation method, thermal decomposition method of chlorocarboxamide, crutius rearrangement method, reaction method of amine and chloroformate, thermal decomposition method of carbamate, etc. However, most of them are still at the laboratory stage, and only the thermal decomposition method of carbamate has achieved industrial production abroad.

[0042] From the raw materials used to prepare carbamate, there are mainly the urea method and the dialkyl carbonate method.

[0043] The process of preparing carbamate by the dimethyl carbonate method and then thermally cracking it to obtain ADI has attracted people's attention. This method has the characteristics of easy reaction, simple control, and relatively high yield. The methanol produced can be recycled and further made into dimethyl carbonate. However, the manufacturing cost of dimethyl carbonate is relatively high, which limits the industrial application of this method.

[0044] The urea method route has been studied the most, the method is relatively mature, and it has been applied industrially (abroad). The process of preparing isocyanates by the urea method includes two major steps. One is to react urea, diamine, and alcohol to form diurethane, and the other is to thermally crack diurethane to form isocyanate and alcohol. The total reaction yield can reach 90%.

[0045] The pyrolysis reaction can be carried out in the liquid phase or in the gas phase. Gas-phase pyrolysis is a high-temperature process, generally with a temperature higher than 300 °C, and the reaction can proceed with or without a catalyst; the temperature in the liquid-phase pyrolysis process is generally lower than 300 °C, and usually a catalyst and a high-boiling solvent need to be added. During the thermal decomposition process, many side reactions often occur, such as the formation of tar and resinous polymer by-products, which not only reduces the yield but also clogs the reactor and other equipment.

[0046] The components of the thermal decomposition products are numerous, and there are no ready physical property data for many intermediate products. Side reactions (reverse reactions of thermal decomposition) between thermal decomposition products, product self-polymerization reactions, etc. also pose great difficulties to the separation design. Among them, the side reaction between the target product IPDI and n-butanol is very rapid. The data can be found in "Reaction Kinetics Study Based on Isophorone Diisocyanate" (East China University of Science and Technology, Zhang Liwei, 2010)

[0047] The research and development and production of diisocyanates in China started relatively late. However, with the rapid development of China's society and economy, China has become a global producer and consumer of diisocyanates, among which MDI and TDI account for more than 85% of the total diisocyanate output. On the other hand, in the field of high-performance special isocyanates, China's development is very slow, while the consumption demand is growing at a rate of more than 15% per year. Aliphatic isocyanates are mainly used in automotive topcoats, rocket propellants, anti-corrosion coatings, UV-curable coatings, adhesives and other fields. Due to historical reasons of introducing technologies, high-grade coatings used in industries such as automobiles, high-speed trains, airplanes, ships, luxury buses, wooden furniture, and buildings in China are all occupied by foreign products. One of the restrictive factors is the key raw material aliphatic diisocyanates.

[0048] At present, the annual demand for HDI and IPDI in China is about 95,000 tons, mainly occupied by a few multinational companies such as Evonik and Degussa. Domestically, only Bayer has a 30,000-ton / year plant in Caojing, Shanghai and a 15,000-ton / year plant in Yantai Wanhua, and most of Bayer's products are exported, with high prices; domestically, only Yantai Wanhua has built a 15,000-ton / year plant using the phosgene method for IPDI, and only a small amount of products enter the market. The domestic product demand basically mainly relies on imports. Due to well-known reasons, due to the fact that non-phosgene IPDI products do not contain chlorine and can be used in the production of high-end microelectronics industries and high-end military products, they are restricted from being sold to China.

[0049] Based on the great significance of IPDI to the national economy and industrial safety and the reality of the backward domestic production and development. The present invention provides an industrial method for producing IPDI by pyrolysis of IPDU-B, breaking the technical monopoly of developed countries on the industrial urea method for synthesizing IPDI. Summary of the Invention

[0050] The object of the present invention is to provide an industrial method for continuously producing IPDI by thermal cracking of IPDU-B.

[0051] The object of the present invention is achieved by the following technical solutions: an industrial method for continuously producing IPDI by coupling thermal cracking and rectification of n-butyl isophorone dicarbamate, the industrial method comprising the following steps:

[0052] 1) Step of coupling thermal decomposition and rectification of n-butyl isophorone dicarbamate: Feed n-butyl isophorone dicarbamate, solvent and catalyst into the first thermal decomposition reactor for reaction to obtain a first gaseous material. Combine the first gaseous material and the third gaseous material and feed them into the first rectification column for rectification operation. n-Butanol is obtained at the top of the column, an IPDI-rich liquid is withdrawn from the middle side line, and heavy components are discharged from the bottom of the column. The IPDI-rich liquid enters the second rectification column for operation. A small amount of a mixture of n-butanol and IPDI is separated at the top of the column, the IPDI product is withdrawn from the middle side line, and heavy components are discharged from the bottom of the column. The heavy components discharged from the bottom of the first rectification column and the bottom of the second rectification column are the second liquid material. Feed the second liquid material into the second thermal decomposition reactor for reaction to obtain the third gaseous material. The third gaseous material is returned to the first rectification column and enters the first rectification column together with the first gaseous material for rectification operation; the above process is carried out continuously.

[0053] The first thermal decomposition reactor thermally decomposes the raw material IPDU-B. The second thermal decomposition reactor thermally decomposes the materials at the bottom of the first rectification column and the bottom of the second rectification column (the physical components are mainly n-butyl isocyanatoisophorone monocarbonate and a small amount of IPDI), and forms a circulating system with rectification. A circulating tank and a circulating pump are provided at the lower part of the two thermal decomposition reactors. The solvent and catalyst are recycled, and the circulation amount is adjusted according to the material amount to maintain an appropriate ratio of the raw material to the solvent and catalyst.

[0054] The first gaseous material and the third gaseous material are combined and enter the first rectification column at the same position, which is required for the design and stable operation of the rectification column.

[0055] The above-mentioned n-butyl isocyanatoisophorone monocarbonate is an intermediate product of incomplete thermal decomposition of IPDU-B, abbreviated as "single side".

[0056] 2) Step of discharging heavy component materials: The circulating materials (solvent, catalyst) of the first thermal decomposition reactor and the second thermal decomposition reactor will also enrich heavy component materials (including by-product colloids, raw material impurities, deactivated catalysts, etc.) as the reaction proceeds. The first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge the circulating materials and continuously supplement an equal amount of solvent and catalyst to avoid the accumulation of heavy component materials;

[0057] Further, in step 1), the pressure controlled by the first thermal decomposition reactor is -0.08 to -0.098 MPa, and the temperature is 200 to 280 °C;

[0058] And / or, in step 1), the pressure controlled by the second thermal decomposition reactor is -0.08 to -0.098 MPa, and the temperature is 200 to 280 °C.

[0059] Furthermore, the pressure controlled by the first thermal decomposition reactor is -0.092 to -0.098 MPa, and the temperature is 220 to 260 °C;

[0060] And / or, the pressure controlled by the second thermal decomposition reactor is -0.092 to -0.098 MPa, and the temperature is 220 to 260 °C.

[0061] Further, the temperature of the second thermal decomposition reactor is 1 to 10 °C higher than that of the first thermal decomposition reactor.

[0062] Further, in step 1), the mass ratio of the n-butyl isophorone dicarbamate, the solvent and the catalyst is: 1:0 - 9:0.0025 - 0.015. Preferably, the mass ratio of the n-butyl isophorone dicarbamate, the solvent and the catalyst is: 1:0.67 - 9:0.003 - 0.010.

[0063] Further, in step 1), the n-butyl isophorone dicarbamate is a product of n-butyl isophorone dicarbamate synthesized by the urea method; preferably referring to the patent 202211207615.2 applied by the applicant in the same batch, an industrializable IPDI synthesis method.

[0064] The solvent is one of naphthenic oil, trioctyl trimellitate, and trinonyl trimellitate;

[0065] The catalyst is one or more of zinc pyridinecarboxylate, chromium pyridinecarboxylate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate, and zinc isooctanoate. Preferably, it is one of zinc pyridinecarboxylate, chromium pyridinecarboxylate, and MOF-5.

[0066] Further, in step 1), the first thermal decomposition reactor and / or the second thermal decomposition reactor is a thin-film evaporator.

[0067] Further, in step 1), the thin-film evaporator is a wiped-film evaporator.

[0068] Further, in step 2), the discharged recycled material is preliminarily separated (by static settlement) to obtain a preliminarily separated solvent and a preliminarily separated heavy component material. The preliminarily separated heavy component material is heated and evaporated to obtain a gas-phase product and a residue. After condensation, the preliminarily separated solvent and the gas-phase product can be used as solvents in the pyrolysis step of isophorone diisocyanate n-butyl carbamate.

[0069] Further, in step 2), when the solvent is naphthenic oil, the temperature of the heating evaporation is 280-350 °C, and the reaction pressure is -0.096 to -0.098 MPa.

[0070] Further, in step 1), the operating pressure of the first distillation column is 10-30 mbar, the bottom temperature is 190-210 °C, the top operating temperature is 20-30 °C, and the side line temperature is 150-170 °C; preferably, the operating pressure of the first distillation column is 10-25 mbar, the bottom temperature is 199-202 °C, the top operating temperature is 24-26 °C, and the side line temperature is 159.5-161.5 °C.

[0071] And / or, the operating pressure of the second distillation column is 10-30 mbar, the bottom temperature is 190-200 °C, the top operating temperature is 30-50 °C, and the side line temperature is 155-160 °C; preferably, the operating pressure of the second distillation column is 10-25 mbar, the bottom temperature is 193-195 °C, the top operating temperature is 39-41 °C, and the side line temperature is 158-159 °C.

[0072] It can be seen from the chemical formula involved in IPDI in the background technology that IPDI has very active properties and can react with various groups. Due to the very active properties of IPDI, although the reaction steps for synthesizing IPDI by the urea method are only two steps, domestic scientific and technical personnel are unable to industrialize the production of IPDI by this process route. The process of IPDU-B pyrolysis to generate IPDI is absolutely feasible in principle. However, despite the great economic value of synthesizing IPDI, no domestic enterprise has been able to truly industrialize the synthesis of IPDI. The main reason is that the existing technologies / enterprises have not been able to correctly understand the reasons why the urea method cannot be industrialized to synthesize IPDI. Existing technologies / enterprises often think that the reason for the inability to achieve is that this process has relatively high requirements for equipment, requires relatively high temperatures, and is relatively difficult to operate. In fact, when industrially producing IPDI, there will be many problems that are difficult to notice. A large number of by-products are generated during the industrial production of IPDI, and the amount of by-products generated is the main determining factor for the industrial production scale and whether industrial production can be carried out.

[0073] The research conclusion of the thermal cracking of IPDC to produce IPDI was reported on pages 45-46 of the literature "Research on the Synthesis Process of Isophorone Diisocyanate", indicating that the content of NCO in the reaction product can reach as high as 30.1% (yield of about 60.2%); it was also pointed out that the difference in the content of IPDI obtained by pyrolysis under the same reaction conditions is very large, and the lowest can reach 18.4% (yield of about 36.4%). The reason lies in a series of complex, uncontrollable and varying degrees of chemical side reactions occurring during the reaction process.

[0074] By querying the prior art, it is known that a small number of patents have reported that it can continuously produce IPDI industrially with a very high yield (reaching 90%). In fact, Yuhshi Luh et al. have conducted a large number of studies on the thermal decomposition of carbamate using the most advanced equipment, indicating that after the reaction is complete, the conversion rate of isophorone carbamate is 95%. At this time, the highest theoretical yield of alcohol is 90%, the highest theoretical yield of isophorone diisocyanate is 65%, and the highest theoretical yield of isophorone monoisocyanate is 27%. The inventors of this application have also conducted a large number of studies, and the conclusions are the same as those of Yuhshi Luh et al. That is, even with multiple cycles of thermal cracking reactions in a single thermal cracking reactor, it is still impossible to achieve a high-yield effect.

[0075] At the same time, peers do not pay attention to the research on the separation problem of thermal decomposition products, ignoring problems such as the existence of side reactions and the difficulty of separation design itself. From the publicly available information, most only simply mention separation, and some are immature or even have incorrect understandings.

[0076] The inventors of this application have found that during the process of thermal cracking of IPDU-B to produce IPDI, there are many types of side reactions, but the most prominent and fatal side reaction is a series of reactions between IPDI and the raw material (IPDU-B). Specifically: one secondary amine hydrogen reacts with one isocyanate group. One molecule of the raw material IPDU-B has two secondary amine hydrogens, which will react with the two isocyanate groups of one molecule of the product IPDI simultaneously and also react with one isocyanate group of the two reactants separately. Therefore, 6 kinds of by-products are involved. From a kinetic perspective, as the temperature increases, the secondary amine hydrogen (proton) becomes more active, the dissociation reaction constant becomes larger, the reaction group is more likely to combine with the catalyst, and the activation energy of the entire side reaction decreases, which is conducive to the progress of the side reaction. Therefore, the generation of this type of by-product is extremely difficult to avoid. By the same principle, the intermediate on one side will also have the above-mentioned side reaction with the raw material (IPDU-B).

[0077] Meanwhile, there are differences in the decomposition activation energies of the carbamate groups at the primary and secondary positions of the raw material (IPDU-B). The decomposition activation energy of the carbamate group at the secondary position is lower and it is easier to decompose. Therefore, the content of the single side in the single thermal decomposition product of IPDU-B is much greater than that of the target product (IPDI). When the single side undergoes re-thermal decomposition, the required temperature is higher than the thermal decomposition temperature of IPDU-B.

[0078] The inventors of the present application have found through research that the separation and purification of the pyrolysis products is also a difficult problem. The reaction products include n-butanol, single side, IPDI, solvent, etc. There are no ready physical property data for the intermediate product single side. Side reactions (reverse reactions of thermal decomposition), product self-polymerization reactions, etc. among the thermal decomposition products have also caused great difficulties in the separation design. Among them, the side reaction between the target product IPDI and n-butanol is very rapid, which is the most prominent problem affecting the final yield and product quality.

[0079] Based on this, the inventors of the present application have creatively designed and implemented the above-mentioned IPDU-B thermal decomposition and product separation (rectification) processes, solved the main contradictions, reduced the side reactions to an acceptable level, and achieved satisfactory results. Its characteristics are as follows:

[0080] 1. Use 2 thermal decomposition reactors. The first thermal decomposition reactor only conducts thermal decomposition reactions on the raw material IPDU-B, and the second thermal decomposition reactor only conducts thermal decomposition reactions on the single side. Compared with the method of using a single reactor for multiple cycle thermal decomposition reactions, the most important side reaction problem caused by the backmixing contact between the raw material IPDU-B and the products IPDI and single side is fundamentally solved. At the same time, the second thermal decomposition reactor can be independently controlled at a higher temperature, solving the problem that the required temperature for the thermal decomposition of the single side is higher than the thermal decomposition temperature of IPDU-B, and improving the reaction efficiency.

[0081] 2. The optimized rectification design minimizes the influence of side reactions and separates qualified IPDI products. The first rectification column first quickly separates most (more than 99.6% of the total amount) of the n-butanol in the system materials, greatly reducing the side reaction between IPDI and n-butanol, and at the same time minimizing the IPDI content in the bottom materials of the column and maximizing the IPDI content in the IPDI-rich liquid taken from the side line. The second rectification column efficiently obtains qualified IPDI products through the method of side line extraction.

[0082] 3. The coupled design of thermal decomposition and rectification realizes continuous thermal decomposition reactions and reaction product separation with low side reaction risks, as well as the large cycle of thermal decomposition and rectification of the single side component.

[0083] The beneficial effects of the present invention are as follows:

[0084] 1) The design of the present invention greatly improves the product yield, and the IPDI yield (calculated based on IPDU-B) is greater than 90%. It can truly be industrialized.

[0085] 2) The method provided by the present invention achieves an effect that the solvent recovery rate is greater than 95%, and the recovered solvent can be directly used as the solvent for the pyrolysis reaction of n-butyl isophorone dicarbamate without purification.

[0086] 3) The zinc pyridinecarboxylate, chromium pyridinecarboxylate and MOF-5 selected in the present invention are used for the industrial urea method of the pyrolysis catalyst of n-butyl isophorone dicarbamate, and have the effects of good selectivity, few side reactions and high product yield.

[0087] 4) The solvent for the industrial urea method IPDU-B pyrolysis provided by the present invention itself has the characteristics of being compatible with IPDU-B, chemical stability, good catalyst dispersion and heat resistance. When used in the IPDU-B pyrolysis reaction, it can increase the IPDI yield and reduce the formation of by-products.

[0088] 5) After being treated by the industrial method (rectification operation) for purifying the crude IPDI of the present invention, the purity of the obtained IPDI product is greater than 99.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is the process flow diagram for the production of IPDI by IPDU-B pyrolysis;

[0090] Figure 2 It is the data recorded in the literature "Research on the Reaction Kinetics Based on Isophorone Diisocyanate". DETAILED DESCRIPTION OF THE INVENTION

[0091] The technical solutions of the present invention will be further described in detail below, but the protection scope of the present invention is not limited to the following.

[0092] I. Reactors, reaction processes, raw materials and detection methods for IPDU-B pyrolysis, solvent recovery and rectification in the laboratory and industrial production

[0093] The applicant explains the reasons for involving the laboratory IPDU-B pyrolysis data. First of all, the laboratory-related equipment of the present invention uses small-scale equipment similar to the industrial IPDU-B pyrolysis device. Moreover, the laboratory is mainly for research purposes, providing theoretical basis and production condition parameters for industrial production, which is an indispensable step before industrial implementation. This does not mean that the laboratory-scale data of the present invention has no reference significance; in addition, the laboratory also provides a comparison for the industrial effect, so the present invention provides the laboratory data.

[0094] It should also be pointed out first that for the convenience of understanding the meaning of each step of the present invention, the present invention writes the pyrolysis, solvent recovery and rectification separately, which does not mean that the present invention is not a continuous reaction.

[0095] (1) Laboratory thermal cracking reactor

[0096] Cracker: Evaporation area 0.1 m 2 ;

[0097] Circulation pump: Gear pump 2.8 L / h;

[0098] Rectifying column: Φ50×800;

[0099] (2) Laboratory thermal cracking continuous reaction process

[0100] The raw material IPDU-B enters the thin-film evaporator (cracker) and is heated and cracked. The naphthenic oil and catalyst at the lower part are pumped back to the upper inlet of the cracker through the circulation pump. The cracked gas coming out of the upper part of the cracker enters the rectifying column under the action of vacuum. When a large amount of the heavy components start to flow back into the cracker from the lower part of the rectifying column, the feeding of IPDU-B is stopped. At this time, the cracker only thermally decomposes the reflux material. The cracked gas coming out of the upper part of the cracker enters the rectifying column under the action of vacuum, and the light components enter the heat exchanger from the upper part of the rectifying column, are condensed and then flow into the crude product tank by themselves. When the reflux flow rate decreases to near interruption, the feeding of IPDU-B is started again, and the operation is repeated like this until the test ends.

[0101] Note: By adding the IPDU-B raw material intermittently, the IPDU-B and unilateral segmented pyrolysis are approximately simulated, and the side reactions are significantly inhibited.

[0102] (3) Industrial thermal cracking reactor

[0103] IPDU-B raw material pump: Q = 2 m 3 / h, H = 14 m; 1# cracker: A = 30 m 2 ; 1# cracking circulation pump: Q = 5 m 3 / h, H = 14 m; 1# polymer drain pump: Q = 2 m 3 / h, H = 14 m; 2# cracker: A = 25 m 2 ; 2# cracking circulation pump: Q = 5 m 3 / h, H = 14 m; 2# polymer drain pump: Q = 2 m 3 / h, H = 14 m.

[0104] (4) Industrial thermal cracking reaction process

[0105] The pyrolysis raw material IPDU-B, solvent, and catalyst enter the No. 1 rotary scraper pyrolysis reactor. The rotary scraper forces the formation of a liquid film on the inner wall of the reactor, and pyrolysis reaction occurs through heating the inner wall of the reactor. Under vacuum conditions, the pyrolysis products evaporate rapidly to achieve rapid separation from the reaction raw materials, greatly reducing the generation of side reactions. The gas-phase material (gas-phase material 1, reaction product) at the reactor outlet enters the rectification unit. The material at the bottom of the rectification column (mainly the single side) enters the No. 2 rotary scraper pyrolysis reactor for pyrolysis reaction. The gas-phase material (gas-phase material 3, reaction product) at the reactor outlet is combined with gas-phase material 1 and enters the rectification unit. A circulation tank and a circulation pump are provided at the bottom of the two reactors, and the solvent and catalyst are circulated.

[0106] (5) Solvent recovery equipment

[0107] Scraped surface evaporator: Heat transfer area S = 12m 2

[0108] (6) Solvent recovery method

[0109] It should be emphasized that this part of the content is to process the heavy component material after preliminary separation (static settlement) of the circulating liquid discharged from the bottom of the two rotary scraper pyrolysis reactors in the (4) industrial pyrolysis reaction process.

[0110] The heavy component material generated by the pyrolysis reaction of n-butyl isophorone dicarbamate is pumped to the top of the scraped surface evaporator. The rotary scraper forces the formation of a liquid film on the inner wall of the evaporator, and it is heated through the inner wall of the evaporator and evaporated under vacuum conditions to obtain gas-phase products and heavy components. The gas-phase products are condensed using a condenser to obtain the recovered solvent. Reaction conditions for heating and evaporation: temperature is 280 °C, and reaction pressure is -0.096 to -0.098 MPa.

[0111] (7) Rectification reaction equipment

[0112] Light component removal tower (rectification column): Φ1200×24604, packing height 3888 / 3888 / 3888 / 3240 mm

[0113] Product tower (rectification column): Φ900×24348, packing height 3096 / 3096 / 4128 / 4128 mm

[0114] Condenser: Light component removal tower top condenser Φ1200×2000, heat transfer area 80m 2 ; Product tower top condenser Φ1000×2000, heat transfer area 90m 2

[0115] Reboiler: Light component removal tower bottom reboiler Φ1100×2500, heat transfer area 94.5m 2; The reboiler at the bottom of the product tower is Φ1400×3000, with a heat transfer area of 190 m 2

[0116] Circulation pump: The circulation pump at the bottom of the light component removal tower has Q = 10.8 m 3 H = 40 m, Zone2 EEx dII BT4, and the circulation pump at the bottom of the product tower has Q = 18 m 3 H = 40 m, Zone2 EEx dII BT4

[0117] Auxiliary system: The heat transfer oil system provides the required heat source, the circulating water system and the chilled water system provide the refrigerant, the nitrogen system provides nitrogen for purging during startup and shutdown, and the vacuum system provides the required vacuum conditions for the unit

[0118] Control system: The process operation control adopts the DCS system and is equipped with a safety interlock (SIS) system

[0119] (8) Reaction process of rectification

[0120] It should be emphasized that this part of the content belongs to a specific explanation of the rectification unit in the (4) industrial thermal cracking reaction process

[0121] The gaseous crude IPDI (gaseous material one and gaseous material three) enters the bottom of the light component removal tower (the first rectification tower) from the thermal decomposition unit. n-Butanol is taken out from the top of the tower, the IPDI-rich liquid is taken out from the middle side line of the tower, and the bottom material of the tower goes to the thermal decomposition unit for cyclic thermal decomposition (the second thermal decomposition reaction). The IPDI-rich liquid taken out from the side line of the light component removal tower is pumped into the product tower (the second rectification tower). A small amount of n-butanol + IPDI is taken out from the top of the tower, the IPDI product is taken out from the side line, and the bottom material of the tower (liquid material two) goes to the thermal decomposition unit for cyclic thermal decomposition (the second thermal decomposition reaction).

[0122] (9) Raw materials

[0123] Composition of n-butyl isophthalate diisocyanate (IPDU-B): The internal control index is ≥99.0% (IPDU-B 99.38%, catalyst for synthesizing IPDU-B 0.46%, others 0.16%);

[0124] Catalysts for thermal cracking reaction: Zinc pyridinecarboxylate, chromium pyridinecarboxylate, MOF-5, zinc oxide, bismuth trioxide, zinc ionic liquid, zinc chloride, zinc acetate, zinc acrylate, zinc isooctanoate;

[0125] Solvents: Naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, trinonyl trimellitate

[0126] (10) Detection methods

[0127] See Table 1:

[0128] Table 1

[0129]

[0130] (11) Statistics of raw materials, product components and yields corresponding to each step of the present invention

[0131] Refer to the attached Figure 1 According to the process flow of, continuous synthesis of IPDI is carried out in accordance with the above industrialization routes (4), (6), and (8). The control conditions are the optimal experimental conditions, that is, the operating pressure of the first thermal decomposition is -0.094 Mpa, the operating temperature is 240 °C, the operating pressure of the second thermal decomposition is -0.094 Mpa, and the operating temperature is 245 °C. The operating conditions of the light removal tower are controlled as follows: the top of the tower is 11 mbar, the bottom of the tower is 24 mbar, the bottom temperature of the tower is 199.7 °C, the operating temperature at the top of the tower is 25 °C, and the side line temperature is 160.8 °C; the operating conditions of the product tower are: the top of the tower is 11 mbar, the bottom of the tower is 24 mbar, the bottom temperature of the tower is 194 °C, the operating temperature at the top of the tower is 40 °C, and the side line temperature is 158.3 °C. After the system runs stably, the feed rates of raw materials, product components and yields corresponding to each step involved are listed as follows:

[0132]

[0133]

[0134]

[0135] Note: The process of the present invention is carried out continuously. Gas-phase material 1 and gas-phase material 3 are materials generated at the same moment in different thermal cracking reactors and are mixed together and fed into the first distillation column; IPDU raw material impurities: 0.46% of the catalyst for synthesizing IPDU-B, and 0.16% of other impurities.

[0136] II. Catalyst screening experiment for thermal cracking reaction of IPDU-B

[0137] (1) Catalyst type screening experiment

[0138] Operating conditions: Select a laboratory thermal cracking reactor and reaction process, and control the cracking temperature of the cracker to ~240 °C; the operating pressure to ~ -0.094 Mpa; put in 500 g of IPDU-B, 500 g of naphthenic oil (solvent), and 3.5 g of catalyst to screen the catalyst type. The types of catalysts and experimental results are shown in Table 2 below:

[0139] Table 2

[0140] Experiment Batch Number Catalyst Reaction Completion Time (min) IPDI Yield (%) Gelatinous Substance Ratio (%) Group 1-1 Chromium Picolinate 45 91.59 2.65 Group 1-2 MOF-5 33 92.02 3.58 Group 1-3 Zinc Picolinate 37 91.32 3.49 Group 1-4 Zinc Oxide 44 79.04 9.24 Group 1-5 Bismuth Oxide 49 57.04 10.06 Group 1-6 Ionic Liquid Zinc 75 49.07 14.68 Group 1-7 Zinc Chloride 43 53.06 13.88 Group 1-8 Zinc Acetate 55 56.72 13.68 Group 1-9 Zinc Acrylate 52 59.79 12.45 Group 1-10 Zinc Isooctanoate 54 60.95 12.68

[0141] Note: The main components of the gum in the present invention are catalysts and high molecular polymers (by-products); the gum ratio refers to the ratio of the amount of gum produced to the feeding amount of raw material IPDU-B.

[0142] As can be seen from Table 2, the catalysts pointed out in Group 1-1 to Group 1-10 all have a certain catalytic effect. However, when chromium picolinate, MOF-5 and zinc picolinate are selected as catalysts, the yield of IPDI is high and the content of gum is low (less side reactions). Therefore, the present invention preferably uses chromium picolinate, MOF-5 or zinc picolinate as catalysts.

[0143] (2) Screening experiment on catalyst dosage

[0144] Operating conditions: Select a laboratory pyrolysis reactor and reaction process, control the pyrolysis temperature of the pyrolyzer to ~240°C; operating pressure to ~ -0.094 Mpa; put in 500 g of IPDU-B and 500 g of naphthenic oil, and select chromium picolinate as the catalyst to conduct an experiment on screening the catalyst dosage. The screening results of the catalyst dosage are shown in Table 3 below:

[0145] Table 3

[0146] Experiment Batch Number Catalyst Dosage (mass%) IPDI Yield (%) Gelatinous Substance Ratio (%) Group 2-1 0.75 91.46 2.76 Group 2-2 1.0 91.13 2.82 Group 2-3 0.5 88.25 4.33 Group 2-4 0.3 87.75 6.23 Group 2-5 0.25 76.88 10.94 Group 2-6 1.25 87.93 4.67 Group 2-7 1.5 84.73 6.87

[0147] Note: The catalyst dosage (mass %) is relative to IPDU-B.

[0148] It can be seen from the data in Table 3 that when the catalyst dosage is too much or too little, the yield of IPDI will decrease and the content of gum will increase. The most suitable dosage of the catalyst is 0.3% - 1%.

[0149] III. Screening of IPDU-B pyrolysis reaction conditions

[0150] (1) Screening of pyrolysis temperature

[0151] Operating conditions: Select a laboratory pyrolysis reactor and reaction process, control the pyrolysis temperature of the pyrolyzer to ~240°C; operating pressure to ~ -0.094 Mpa; put in 500 g of IPDU-B, 500 g of naphthenic oil and 3.5 g of chromium picolinate to screen the pyrolysis temperature. The screening results of the pyrolysis temperature are shown in Table 4 below:

[0152] Table 4

[0153] Experiment Batch Number Pyrolysis Temperature (°C) IPDU-B Conversion Rate (%) IPDI Yield (%) Gelatinous Substance Ratio (%) Group 3-1 240 99.65 92.34 2.12 Group 3-2 200 3.24 2.87 0.26 Group 3-3 210 6.37 5.74 0.51 Group 3-4 220 41.12 10.23 0.62 Group 3-5 230 97.2 84.67 1.03 Group 3-6 260 99.82 91.13 3.87 Group 3-7 280 99.84 87.32 8.64

[0154] As can be seen from Table 4, IPDI can be generated by reaction within the temperature range of 200 - 280°C. Within the temperature range of 220 - 280°C, the conversion rate of IPDU-B increases with the increase in temperature. However, when the temperature approaches 280°C, the generation of gum substances increases significantly. Therefore, the cracking temperature is preferably 220 - 260°C.

[0155] (2) Screening of the vacuum degree of the thermal cracking reaction

[0156] Operating conditions: Select a laboratory thermal cracking reactor and reaction process, control the cracking temperature of the cracker to ~240°C; put in 500 g of IPDU-B, 500 g of naphthenic oil, and 3.5 g of chromium picolinate, and screen the vacuum degree of the thermal cracking reaction. The screening results of the vacuum degree of the thermal cracking reaction are shown in Table 5 below:

[0157] Table 5

[0158]

[0159]

[0160] As can be seen from Table 5, within the vacuum degree range of -0.080 to -0.098, IPDI has a certain yield; within the vacuum degree range of -0.092 to -0.098, the IPDI yield is the highest and the gum content is low.

[0161] IV. Screening of the solvent for the thermal cracking reaction of IPDU-B

[0162] (1) Screening of the types of solvents for the thermal cracking reaction

[0163] Operating conditions: Select a laboratory thermal cracking reactor and reaction process, control the cracking temperature of the cracker to ~240°C, and the operating pressure to ~ -0.094 Mpa; put in 500 g of IPDU-B, 3.5 g of chromium picolinate, and 500 g of the solvent amount, and screen the types of solvents for the thermal cracking reaction. The screening results of the solvents for the thermal cracking reaction are shown in Table 6 below:

[0164] Table 6

[0165] Experiment Batch Number Solvent IPDI Yield (%) Gelatinous Substance Ratio (%) Group 5-1 Naphthenic Oil KN4010 92.10％ 2.87％ Group 5-2 Solvent-Free 79.48％ 15.69％ Group 5-3 Naphthenic Oil KN4006 90.20％ 3.26％ Group 5-4 Naphthenic Oil KN4016 91.00％ 3.07％ Group 5-5 Trioctyl Trimellitate 88.30％ 5.83％ Group 5-6 Trinonyl Trimellitate 89.23％ 5.24％

[0166] As can be seen from Table 6, the use of solvents such as naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate, and trinonyl trimellitate can all increase the IPDI yield and reduce the gum content, and naphthenic oil is most suitable for use as a solvent.

[0167] (2) Screening of the solvent amount for the thermal cracking reaction

[0168] Operating conditions: Select a laboratory pyrolysis reactor and reaction process, control the pyrolysis temperature of the pyrolyzer at ~240 °C, and the operating pressure at ~ -0.094 Mpa; use 3.5 g of chromium picolinate, change the mass ratio of the solvent to IPDU-B in the experimental conditions, with the solvent being naphthenic oil KN4010, and screen the solvent dosage for the pyrolysis reaction. The screening results of the pyrolysis reaction solvent dosage are shown in Table 7 below:

[0169] Table 7

[0170]

[0171]

[0172] As can be seen from Table 7, when the solvent dosage is 0.1 - 9 times the dosage of IPDU-B, good results are obtained in all cases.

[0173] V. Verification of the Effect of Industrial IPDU-B Pyrolysis Reaction

[0174] Operating conditions: Select an industrial pyrolysis reactor and reaction process, control the mass ratio of IPDU-B : naphthenic oil KN4010 : chromium picolinate at 1 : 1 : 0.007 through the circulation rate and make-up rate; implement 4 batches on the industrial device. The statistical results are shown in Table 8 below.

[0175] Table 8

[0176]

[0177] As can be seen from Table 8, the IPDI yield in industrial production is greater than 91%, indicating that the feasibility of the industrial process and the determined industrial parameters of the present invention have been verified.

[0178] VI. Recovery of the Solvent after the Reaction and Reuse of the Recovered Solvent

[0179] The recovery and reuse of the solvent are crucial for industrial production, as it not only determines the production cost but also the pollutant emissions. In view of this, the present invention further examines the recovery of the above solvent and its impact on the reaction during reuse. Combining the industrial pyrolysis reactor and reaction process, the heavy fraction material after preliminary separation is obtained. Using the solvent recovery equipment and in accordance with the solvent recovery method, the recovery results of naphthenic oil KN4010 are measured as shown in Table 9. After the recovered solvent is reused, the properties of the pyrolysis products are measured, and the experimental results are shown in Table 10 below.

[0180] Table 9

[0181]

[0182] Note: The reaction conditions for Group 8-1, Group 8-2, and Group 8-3 are as follows: temperature is 280°C, reaction pressure is -0.096 to -0.098 MPa; temperature is 300°C, reaction pressure is -0.092 to -0.098 MPa; temperature is 330°C, reaction pressure is -0.092 to -0.098 MPa.

[0183] Table 10

[0184]

[0185] Note: The reaction conditions for Group 9-1, Group 9-2, Group 9-3, and Group 9-4 are all as follows: the pressure for the first thermal decomposition operation is -0.094 Mpa, the operating temperature is 240°C; the pressure for the second thermal decomposition operation is -0.094 Mpa, the operating temperature is 245°C; the mass dosage of the catalyst chromium picolinate is 0.0035 of the feeding amount.

[0186] It can be seen from Tables 4, 5, and 6 that the solvent provided by the present invention can be almost completely recovered and reused, and the use of the recovered solvent has no influence on the reaction.

[0187] VII. Method for purifying crude IPDI (rectification operation)

[0188] (1) The specific components of the gaseous-phase crude IPDI are 19.54% n-butanol, 28.64% IPDI, 39.52% unilateral, and 12.3% naphthenic oil (solvent).

[0189] It should be explained that in this embodiment, the gaseous-phase crude IPDI refers to the product obtained by combining gaseous-phase material one and gaseous-phase material three. The components of gaseous-phase material one and gaseous-phase material three are the same, and the difference lies only in the content of the components. The industrialization is carried out continuously (only gaseous-phase material one is generated at the beginning of startup), that is, gaseous-phase material one and gaseous-phase material three are generated simultaneously during industrial operation. The design and stable operation of the rectification tower require them to be fed at the same position. Therefore, the present invention combines gaseous-phase material one and gaseous-phase material three as the gaseous-phase crude IPDI.

[0190] Control the operating conditions of the light component removal tower (the first rectification tower) as follows: top pressure 11 mbar, bottom pressure 24 mbar, bottom temperature 199.7°C, top operating temperature 25°C, side line temperature 160.8°C; the operating conditions of the product tower (the second rectification tower) are: top pressure 11 mbar, bottom pressure 24 mbar, bottom temperature 194°C, top operating temperature 40°C, side line temperature 158.3°C.

[0191] Take the n-butanol drawn from the top of the light removal column (the first rectification column), the IPDI-rich liquid drawn from the middle side line of the column, and the bottom material; and take the small amount of n-butanol and IPDI mixture drawn from the top of the product column (the second rectification column), the IPDI product drawn from the middle side line of the column, and the bottom material. After the system runs stably, the components and contents are measured respectively, and the relevant results are shown in Table 11 below:

[0192] Table 11

[0193]

[0194] (2) The specific components of the crude IPDI in the gas phase are 22.94% n-butanol, 31.97% IPDI, 34.63% mono-side, and 10.46% naphthenic oil.

[0195] Control the operating conditions of the light removal column (the first rectification column) as follows: the top pressure is 11 mbar, the bottom pressure is 24 mbar, the bottom temperature is 200.4 °C, the top operating temperature is 25.5 °C, and the side line temperature is 161 °C; the operating conditions of the product column (the second rectification column) are: the top pressure is 11 mbar, the bottom pressure is 24 mbar, the bottom temperature is 194.5 °C, the top operating temperature is 40.5 °C, and the side line temperature is 158.5 °C.

[0196] Take the n-butanol drawn from the top of the light removal column (the first rectification column), the IPDI-rich liquid drawn from the middle side line of the column, and the bottom material; and take the small amount of n-butanol and IPDI mixture drawn from the top of the product column (the second rectification column), the IPDI product drawn from the middle side line of the column, and the bottom material. After the system runs stably, the components and contents are measured respectively, and the relevant results are shown in Table 12 below:

[0197] Table 12

[0198]

[0199]

[0200] (3) The specific components of the crude IPDI in the gas phase are 20.05% n-butanol, 38.21% IPDI, 31.87% mono-side, and 9.87% naphthenic oil.

[0201] Control the operating conditions of the light removal column (the first rectification column) as follows: the pressure at the top is 11 mbar, the pressure at the bottom is 24 mbar, the bottom temperature is 201.5 °C, the top operating temperature is 26 °C, and the side line temperature is 161.2 °C; the operating conditions of the product column (the second rectification column) are: the pressure at the top is 11 mbar, the pressure at the bottom is 24 mbar, the bottom temperature is 194.9 °C, the top operating temperature is 41 °C, and the side line temperature is 158.7 °C.

[0202] Take the n-butanol taken from the top of the light removal tower (the first rectification tower), the IPDI-rich liquid taken from the middle side line of the tower, and the bottom material of the tower; and take a small amount of the n-butanol and IPDI mixture taken from the top of the product tower (the second rectification tower), the IPDI product taken from the middle side line of the tower, and the bottom material of the tower. After the system runs stably, the components and contents are measured respectively, and the relevant results are shown in Table 13 below:

[0203] Table 13

[0204]

[0205] Furthermore, the method for synthesizing n-butyl isophorone dicarbamate by the urea method is preferably as follows:

[0206] I. Equipment, raw materials, process flow and detection methods for synthesizing IPDU-B by the urea method in the laboratory and industrialization.

[0207] (1) Equipment used in the industrial urea method:

[0208] Reaction kettle: Φ650×800, 300L, Stripping ammonia tower: Φ273×3000 (the condenser at the top of the ammonia stripping tower A = 6m 2 ), Falling film evaporator Φ300×1200;

[0209] Ammonia-containing tail gas condenser: A = 2.2m 2 , Gas-liquid separator: V = 0.10m 3 Φ400×800 (straight pipe);

[0210] Gas-solid separator: V = 0.61m3 Φ700×1300 (straight pipe);

[0211] n-Butanol adsorption tower: diameter 300mm, height 1200mm, 3 units, operating conditions: 30 - 150 °C (regeneration at 150 °C), slightly positive pressure.

[0212] (2) Raw material preparation:

[0213] Urea: GB / T 2440-2001 industrial first-class product, actual purity 99.6%;

[0214] n-Butanol: GB / T 6027-1998 first-class product, actual main content 99.8%;

[0215] IPDA: purity 99.5%;

[0216] Catalyst (zirconium acetate): purity 99.0%.

[0217] (3) Specific method for synthesizing n-butyl isophorone dicarbamate by the industrial urea method:

[0218] Add liquid raw materials n-butanol (in excess), raw material IPDA, solid raw material urea (slightly in excess), and liquid catalyst zirconium acetate to a 300L stainless steel reactor. After feeding, seal the reactor and displace the air in the reactor with nitrogen. Then, heat it to 225°C at a nitrogen flow rate of 4.5 Nm 3 / h and carry out the synthesis reaction for 2 hours under the condition of a pressure of 1.50 Mpa.G. After the reaction is completed, flash off part of the n-butanol from the bottom product of the reactor, and then carry out circulating alcohol removal for 2 hours through a falling film evaporator at 200°C and a vacuum degree of -0.090 MPa to remove the unreacted n-butanol and the intermediate product n-butyl carbamate, obtaining the intermediate product n-butyl isophorone dicarbamate.

[0219] During the reaction process, the gas-phase material at the outlet of the reactor (i.e., the synthesis tail gas) passes through a stripping deammoniation tower and a condenser located at the top of the stripping deammoniation tower in sequence to obtain a gas-phase material and a liquid-phase material. The gas-phase material is an ammonia-containing tail gas mainly composed of a small amount of n-butanol, carrier gas, and ammonia components. The liquid-phase material is most of the n-butanol condensed from the synthesis tail gas. This liquid-phase material is then refluxed to the top of the stripping deammoniation tower, and most of the ammonia dissolved in this liquid-phase material is removed through the stripping deammoniation tower. Finally, the deammoniated n-butanol returns to the reactor.

[0220] Pass the high-temperature ammonia-containing tail gas into a condenser to cool it down to 59°C. At this time, most of the n-butanol contained in the ammonia-containing tail gas is liquefied and ammonium carbamate solidifies. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol, and ammonium carbamate solid. Then, pass the tail gas into a gas-liquid separator to remove n-butanol, and nitrogen, ammonia, and ammonium carbamate are blown into a gas-solid separator. The gas-solid separator filters and adsorbs ammonium carbamate to obtain a deammonium carbamate tail gas containing residual n-butanol.

[0221] Pass the deammonium carbamate tail gas containing residual n-butanol into a pre-cooler to cool it down, and keep the outlet temperature at 20°C. Then, extract and pressurize the cooled tail gas with a fan and pass it into an adsorption tower filled with a nano adsorbent. The adsorbed tail gas is passed into a sulfuric acid absorber to obtain an ammonium salt and a final tail gas.

[0222] The nano adsorbent is the special adsorbent Hap nano HDV536, which selectively adsorbs n-butanol and basically does not adsorb ammonia. The particle size (0.6 - 1.25 mm) > 95%, the specific surface area is 1400 ㎡ / g, the pore volume is 0.90 ml / g, and the pore diameter

[0223] The detection method is shown in the following table:

[0224]

[0225]

[0226] II. Verification of the effect of synthesizing IPDU-B by industrial urea method. The specific method is as follows:

[0227] Add 158.5 kg of liquid raw material n-butanol, 45.5 kg of raw material IPDA, 35.5 kg of solid raw material urea, and 318 g of liquid catalyst zirconium acetate into a 300 L stainless steel reactor. After feeding, seal the reactor and displace the air in the reactor with nitrogen. Then, heat it to 225 °C at a nitrogen inlet flow rate of 4.5 Nm 3 / h and carry out the synthesis reaction for 2 hours under the condition of a pressure of 1.50 Mpa.G. After the reaction is completed, flash off part of the n-butanol under reduced pressure, and then circulate and remove alcohol for 2 hours through a falling film evaporator at 200 °C and a vacuum degree of -0.090 MPa to remove unreacted n-butanol and the intermediate n-butyl carbamate, obtaining 97.5 kg of the intermediate product n-butyl isophorone dicarbamate, and the product yield is 98.4% (the detection method is GC-FID).

[0228] It can be seen that the yield of industrial production of IPDU-B is greater than 98%, indicating that the feasibility of the industrial process and the determined industrial parameters of the present invention have been verified.

[0229] III. Treatment effect of the waste gas from synthesizing IPDU-B by industrial urea method. The specific method is as follows:

[0230] Refer to the method of synthesizing IPDU-B by industrial urea method (IPDA: 45.5 kg (0.27 kmol); n-butanol: 158.5 kg (2.14 kmol); urea: 35.5 kg (0.57 kmol); zirconium acetate 400 g (1.22 mol)), using process nitrogen as the carrier gas. Pass the high-temperature ammonia-containing tail gas into a condenser to cool it down to 59 °C. At this time, n-butanol liquefies and ammonium carbamate solidifies. At this time, the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol and ammonium carbamate solid. Then, pass the tail gas into a gas-liquid separator to remove n-butanol. Nitrogen, ammonia and ammonium carbamate are blown into a gas-solid separator. The gas-solid separator filters and adsorbs ammonium carbamate to obtain the de-ammonium carbamate tail gas containing residual n-butanol. The ammonium carbamate enriched in the gas-solid separator is decomposed into ammonia components and carbon dioxide by blowing with high-temperature nitrogen to regenerate the gas-solid separator.

[0231] Pass the de-ammonium carbamate tail gas containing residual n-butanol into a pre-cooler to cool it down, and keep the outlet temperature at 20 °C. Extract and pressurize the cooled tail gas with a blower and then pass it into an adsorption tower filled with a nano adsorbent to obtain the de-butanol tail gas. The adsorbed de-butanol tail gas is passed into a sulfuric acid absorber to obtain ammonium salt and the final tail gas.

[0232] In the above adsorption process, adsorption stops when the adsorption tower reaches the cycle time (a total of three adsorption towers are involved. While one tower is adsorbing, the other two are desorbing. The adsorption and desorption processes are alternated by switching valves. When the adsorption tower reaches the breakthrough point, it automatically switches to the desorption process). Nitrogen at 150 °C is used to desorb and regenerate the adsorbent. The ammonia gas containing n-butanol after desorption is condensed and separated by low-temperature chilled water. The liquid-phase n-butanol after separation is collected in the n-butanol recovery tank. The gas phase containing trace amounts of n-butanol and nitrogen returns to the front end of the adsorption tower and is combined with the ammonium carbamate removal tail gas to remove the trace n-butanol contained through the adsorption tower.

[0233] The contents of each component in the ammonia-containing tail gas before condensation, the ammonia-containing tail gas after condensation, the ammonium carbamate removal tail gas, and the final tail gas were detected, and the results are shown in the following table.

[0234]

[0235]

[0236] As can be seen from the above table, the high-temperature ammonia-containing tail gas discharged during the synthesis of isophorone diaminobutyl ester contains 0.62% of ammonium carbamate. After passing through the ammonium carbamate removal process, the content of ammonium carbamate in the tail gas is only 0.05%, and the ammonium carbamate removal rate reaches 92%. This shows that the ammonium carbamate removal process of the present invention can effectively remove ammonium carbamate in the process of synthesizing isophorone diaminobutyl ester by the urea method and can prevent the pipelines and valves of industrial equipment from being blocked by ammonium carbamate. The ammonia content in the n-butanol removal tail gas is 48.96%, while the ammonia content in the final tail gas is only 0.003%. This shows that the ammonia removal process can effectively remove ammonia in the tail gas. The n-butanol content in the ammonium carbamate removal tail gas is 1.20%, while n-butanol is not detected in the final tail gas. This shows that the entire tail gas removal process can effectively remove n-butanol in the tail gas.

[0237] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. An industrial method for producing IPDI by thermal cracking of n-butyl isophorone dicarbamate, characterized in that, the industrial method comprises the following steps: 1) A step of coupling thermal decomposition and rectification of n-butyl isophorone dicarbamate: n-butyl isophorone dicarbamate, a solvent and a catalyst enter a first thermal decomposition reactor for reaction to obtain a first gaseous material. The first gaseous material and a third gaseous material are combined and enter a first rectification column for rectification operation. n-Butanol is obtained at the top of the column, an IPDI-rich liquid is withdrawn from the middle side line, and heavy components are discharged from the bottom of the column. The IPDI-rich liquid enters a second rectification column for operation. A mixture of n-butanol and IPDI is separated at the top of the column, an IPDI product is withdrawn from the middle side line, and heavy components are discharged from the bottom of the column. The heavy components discharged from the bottom of the first rectification column and the bottom of the second rectification column are the second liquid material. The second liquid material enters a second thermal decomposition reactor for reaction to obtain a third gaseous material, and the third gaseous material returns to the first rectification column and enters the first rectification column together with the first gaseous material for rectification; A step of discharging heavy component materials: The first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge circulating materials, and the mass ratio of n-butyl isophorone dicarbamate: solvent: catalyst is controlled to be 1:1:0.007 by the circulation amount and the supplementary amount; In step 1), the reaction pressure controlled by the first thermal decomposition reactor is -0.08 to -0.098 MPa, and the reaction temperature is 200 to 280 °C; and / or, in step 1), the reaction pressure controlled by the second thermal decomposition reactor is -0.08 to -0.098 MPa, and the reaction temperature is 200 to 280 °C; In step 1), the reaction temperature of the second thermal decomposition reactor is 1 to 10 °C higher than the reaction temperature of the first thermal decomposition reactor.

2. The industrial method according to claim 1, characterized in that, in step 1), the n-butyl isophorone dicarbamate is a product of n-butyl isophorone dicarbamate synthesized by the urea method; the solvent is one of naphthenic oil, trioctyl trimellitate, and trinonyl trimellitate; the catalyst is one or more of zinc pyridinecarboxylate, chromium pyridinecarboxylate, MOF-5, zinc oxide, bismuth trioxide, zinc ionic liquid, zinc chloride, zinc acetate, zinc acrylate, and zinc isooctanoate.

3. The industrial method according to claim 1, characterized in that, in step 1), the first thermal decomposition reactor and / or the second thermal decomposition reactor is a thin-film evaporator.

4. The industrial method according to claim 3, characterized in that, in step 1), the thin-film evaporator is a wiped-film evaporator.

5. The industrial method according to claim 2, characterized in that, in step 2), the discharged circulating materials are preliminarily separated to obtain a preliminarily separated solvent and a preliminarily separated heavy component material. The preliminarily separated heavy component material is heated and evaporated to obtain a gaseous product and a residue. The preliminarily separated solvent and the gaseous product can be used as solvents in the thermal decomposition step of n-butyl isophorone dicarbamate after condensation.

6. The industrial method according to claim 5, characterized in that, In step 2), when the solvent is naphthenic oil, the temperature for heating and evaporation is 280 to 350 °C, and the reaction pressure is -0.096 to -0.098 MPa.

7. According to the industrial method described in claim 1, characterized in that in step 1), the operating pressure of the first distillation column is 10 - 30 mbar, the bottom temperature is 190 - 210 °C, the top operating temperature is 20 - 30 °C, and the side line temperature is 150 - 170 °C; and / or, the operating pressure of the second distillation column is 10 - 30 mbar, the bottom temperature is 190 - 200 °C, the top operating temperature is 30 - 50 °C, and the side line temperature is 155 - 160 °C.

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