CN117326980A - Industrial method for producing IPDI by thermal cracking of isophorone dicarbamate - Google Patents

Abstract

The invention relates to the technical field of industrial urea method synthesis of IPDI, in particular to an industrial method for producing IPDI by continuous thermal cracking of IPDI-B. The industrial process comprises the following continuous processes: 1) Two thermal decomposition reactors (a first thermal decomposition reactor and a second thermal decomposition reactor) are used for carrying out two-stage thermal decomposition reaction in combination with rectification operation to prepare a reaction product with higher IPDI content; 2) Discharging the circulating heavy component materials of the two-stage thermal decomposition reactor and recovering the solvent; 3) The rectification operation steps are as follows: the thermal decomposition products are separated by using a first rectifying tower (light component removing tower) and a second rectifying tower (product tower), almost all n-butanol (more than 99.6% of the total amount) is separated at the top of the first tower, and crude products and products are respectively extracted at the side lines of the two towers. The thermal cracking method provided by the invention realizes the effects of industrial continuous production of IPDI with yield more than 90% and purity more than 99.7%.

Description

Industrial method for producing IPDI by thermal cracking of isophorone dicarbamate

Technical Field

The invention relates to the technical field of industrial urea method synthesis of IPDI, in particular to an industrial method for producing IPDI by thermal cracking of isophorone dicarbamic acid n-butyl ester (IPDU-B).

Background

Isophorone diisocyanate is known as 3-isocyanatomethylene-3, 5-trimethylcyclohexyl isocyanate, and is abbreviated as IPDI in English. Molecular formula C ₁₂ H ₁₈ N ₂ O ₂ Structural formulaThe relative molecular weight of 222.29 is colorless or pale yellow liquid, has camphor-like smell, and is completely mixed with organic solvents such as esters, ketones, ethers, aromatic hydrocarbons, aliphatic hydrocarbons and the like.

Diisocyanates contain two-n=c=o groups, which are highly reactive due to electronic imbalance and unsaturation. The usual chemical reactions are as follows:

reaction with water:

the diisocyanate reacts with water to form unstable carbamic acid and rapidly decomposes into diisocyanate bulk diamine and emits carbon dioxide, and the reaction can occur at normal temperature.

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

OCNRCH ₂ NCO+NH ₂ RCH ₂ NH ₂ →OCNRCH ₂ NHCONHRCH ₂ NH ₂

OCNRCH ₂ NCO+OCNRCH ₂ NHCONHRCH ₂ NH ₂

→OCNRCH ₂ NHCONHRCH ₂ NHCNHRCH ₂ NCO

Reaction with hydroxyl groups:

in general, an OH-containing substance such as an alcohol or phenol is reacted with a diisocyanate to produce a urethane, and reacted with a dihydric or higher polyol to produce a polyurethane.

OCNRNCO+2R'OH→R'OCONHRCH ₂ NHCOOR'

This is also the principle of production of the diisocyanate, the polyurethane, which is the primary use.

Reaction with amine:

reaction with primary and secondary amines produces substituted ureas (polyurea elastomers), whereas tertiary amines do not contain active hydrogen and diisocyanates do not react with tertiary amines.

OCNRCH ₂ NCO+NH ₂ R'→CONRCH ₂ NHCONHR'

OCNRCH ₂ NCO+2NH ₂ R'→R'NHOCNHRCH ₂ NHCONHR'

OCNRCH ₂ NCO+NHR'R"→CONRCH ₂ NHCONR'R"

It is based on the above reaction that in the production of polyurethanes, diamines are often used as crosslinking agents and chain extenders, while triethylamine is used as a neutralizing agent. On the other hand, in the cleavage unit of HDI and IPDI, since the cleavage starting material of the dicarbamate contains two secondary amino groups (-NH), and the dicarbamate may contain amine substances such as amine and diamine in byproducts under high temperature conditions, the product IPDI reacts with the starting material and further polymerizes. Thus, to some extent, cleavage of the production polyurethane to ADU can be considered a reversible bi-directional reaction, a pair of contradictory bodies of use.

Reaction with carbamates:

the reactivity is low, and more than 120 ℃ is needed to react to generate allophanate products.

Reaction with anhydride:

the isocyanate reacts with the anhydride to form an imide ring with high heat resistance, and the further reaction can form Polyimide (PI) with higher heat stability.

Reaction with an amide:

the isocyanate reacts with the amide to form an acyl urea.

RNCO+H ₂ NCOR'→RNHCONHCOR'

Self-polymerization:

Under the action of heat and a catalyst (such as dibutyl tin dilaurate), the IPDI can undergo self-polymerization to form dimers and trimers, and even form polymers at higher temperature.

Two IPDI self-polymerize into an IPDI dimer:

dimers are unstable compounds that decompose under heating to reduce to IPDI, or continue to polymerize to trimers.

Unlike dimers, the reaction of trimers is irreversible and the trimer heat decomposition products are not IPDI. The trimer has stable structure, is not easy to decompose under high temperature conditions, has the advantages of good thermal stability, good wear resistance, good corrosion resistance and the like, can quickly release a solvent, has higher reactivity because of still containing-N=C=O groups, and is widely applied to industries such as furniture, automobiles, aviation and the like as a polyurethane curing agent.

The production method of isophorone diisocyanate mainly comprises a phosgene method and a carbamate thermal cracking method. The phosgene method is still the main production method of diisocyanate at present, and only the Desoxel and the Basoff are respectively built with 1 ten thousand tons/year production devices by the non-phosgene method, and the domestic production is still blank.

The gas-phase phosgenation process is a process for preparing isocyanates by diluting gaseous amines or with inert gases or vapors of inert solvents, and then feeding them into a mixing reactor together with phosgene, and reacting them at 200 to 600 ℃. The gas phase method is the most novel phosgenation method, and has the advantages of less phosgene consumption, extremely fast reaction rate, high yield (up to more than 98 percent) and low risk compared with the traditional liquid phase phosgenation method. At present, bayer company adopts the method to produce HDI and IPDI, and the yield of the product is over 70% of that of the HDI. The only IPDI production enterprise in China also adopts the process.

The amine phosgene process has mainly the following problems: (1) phosgene is extremely toxic gas, and a series of engineering technical problems such as safety, environmental protection and the like in the production process are difficult to solve; (2) a large amount of byproduct hydrogen chloride exists in the production of the phosgene method, and if the absorption treatment is imperfect, the byproduct hydrogen chloride also leaks, so that the environment is polluted; (3) the byproduct hydrogen chloride has serious corrosion to equipment in the production process, has higher requirements on equipment materials and has larger corresponding equipment investment; (4) the isocyanate product produced by the phosgene method contains hydrolytic chlorine, which affects the usability of the product.

Because of the above disadvantages of the phosgene method, developed countries have been devoted to develop economical and simple synthetic methods, and thus various methods for synthesizing isocyanates by non-phosgene methods have emerged, such as a carbonylation method, a chloroformyl amide thermal decomposition method, a critium rearrangement method, an amine and chloroformyl ester reaction method, a carbamate thermal decomposition method, etc., but most of them remain in laboratory stages, and only the carbamate thermal decomposition method realizes the production of the device abroad.

From the raw materials used for the preparation of carbamates, there are mainly urea processes and dialkyl carbonate processes.

The process for preparing the carbamate by the dimethyl carbonate method and preparing the ADI by the reheat cracking method has attracted attention, and the method has the characteristics of easy reaction, simple control and higher yield, and the produced methanol can be recycled to further prepare the dimethyl carbonate. But the manufacturing cost of the dimethyl carbonate is high, which limits the application of the method in industry.

The urea process route is most studied, the process is mature and has been used industrially (abroad). The urea method isocyanate preparation process comprises two steps, namely, reacting urea, diamine and alcohol to generate the dicarbamate, and performing reheat pyrolysis on the dicarbamate to generate isocyanate and alcohol, wherein the total reaction yield can reach 90%.

The thermal cracking reaction may be carried out in a liquid phase or in a gas phase. The gas phase thermal cracking is a high temperature process, the temperature is generally higher than 300 ℃, and the reaction can be carried out with or without a catalyst; the thermal cracking process temperature of the liquid phase process is generally below 300 ℃, and a catalyst and a high boiling point solvent are generally required to be added. The thermal decomposition process is often accompanied by the formation of a number of side reactions, such as tar, resinous polymeric byproducts, which not only reduce the yield but also can plug reactors and other equipment.

The components of the thermal decomposition products are more, many intermediate products have no ready physical data, side reactions (reverse reaction of thermal decomposition) between the thermal decomposition products, self-polymerization of the products and the like, and the separation design is also extremely difficult. Wherein, the side reaction of the target product IPDI and n-butanol is very rapid. Data are found in "study of kinetics of isophorone diisocyanate-based reaction" (university of eastern China, zhang Liwei, 2010)

The development and production of diisocyanate in China are relatively late, but with the rapid development of society and economy in China, china becomes a global country for producing and consuming diisocyanate, wherein MDI and TDI account for more than 85% of the total amount of diisocyanate. On the other hand, in the field of high-performance special isocyanate, the development of China is very slow, and the consumption demand is increased by more than 15% in year. The aliphatic isocyanate is mainly applied to the fields of automotive finishing paint, rocket propellant, anti-corrosion paint, photo-curing paint, adhesive and the like. Because of the history of the introduction technology, the high-grade paint for industries such as automobiles, high-speed trains, airplanes, ships, luxury buses, wood furniture, buildings and the like in China is fully occupied by foreign products, wherein one of restriction factors is the key raw material aliphatic diisocyanate.

At present, the annual demand of HDI and IPDI in China is about 9.5 ten thousand tons, and the HDI and IPDI are mainly occupied by a few nationwide companies such as winning, de-Gusai and the like. Only Bayer Shanghai channel jing in HDI country has 3 ten thousand tons/year, smoke station Wanhua 1.5 ten thousand tons/year device, and most of Bayer products are exported, and the price is high; only the smoke table Wanhua in IPDI China adopts a phosgene method to construct a 1.5 ten thousand tons/year device, and only a small amount of products enter the market. Domestic product demand basically depends mainly on import. For the well known reasons, the IPDI product of the non-phosgene method does not contain chlorine, and can be used for the production of high-end microelectronics industry and high-end military varieties and is limited and sold in China.

The IPDI-based method has great significance for national economy and industry safety and the realization of lagging domestic production and development. The invention provides an industrial method for producing IPDI by thermal cracking of IPDI-B, which breaks through the technical monopoly of industrialized urea method for IPDI synthesis in developed countries.

Disclosure of Invention

The invention aims to provide an industrial method for continuously producing IPDI by thermal cracking of IPDI-B.

The aim of the invention is realized by the following technical scheme: an industrial method for continuously producing IPDI by coupling thermal cracking and rectifying of isophorone dicarbamate, comprising the following steps:

1) Pyrolyzing and rectifying the isophorone dicarbamic acid n-butyl ester to couple the steps: allowing isophorone dicarbamic acid n-butyl ester, a solvent and a catalyst to enter a first thermal decomposition reactor for reaction to obtain a gas phase material I, merging the gas phase material I and the gas phase material III, entering a first rectifying tower for rectifying operation, obtaining n-butanol at the top of the tower, extracting IPDI rich liquid from the middle side line, and discharging heavy components from the tower bottom; the IPDI rich liquid enters a second rectifying tower for operation, a small amount of mixed liquid of n-butanol and IPDI is separated from the tower top, an IPDI product is extracted from the middle side line, and heavy components are discharged from the tower bottom; heavy components discharged from the bottoms of the first rectifying tower and the second rectifying tower are liquid-phase materials II, the liquid-phase materials II enter a second thermal decomposition reactor to react, a gas-phase material III is obtained, and the gas-phase material III returns to the first rectifying tower and enters the first rectifying tower together with the gas-phase material I to carry out rectifying operation; the above process is carried out continuously.

The first thermal decomposition reactor is used for thermally decomposing the raw material IPDU-B. The second thermal decomposition reactor carries out thermal decomposition on the materials at the bottom of the first rectifying tower and the materials at the bottom of the second rectifying tower (the physical components are mainly isophorone isocyanate group n-butyl monocarbamate and a small amount of IPDI) and forms a circulating system with rectification. The lower parts of the two thermal decomposition reactors are provided with a circulating tank and a circulating pump, the solvent and the catalyst are recycled, and the circulating quantity is regulated according to the material quantity so as to keep the proper proportion of the raw materials, the solvent and the catalyst.

The gas phase material I and the gas phase material III are combined and then enter the first rectifying tower at the same position, which is required by the design and stable operation of the rectifying tower.

The isophorone isocyanate group mono-n-butyl carbamate is an intermediate product of incomplete thermal decomposition of IPDU-B, and is called as a single side for short.

2) And heavy component material discharging: circulating materials (solvents and catalysts) of the first thermal decomposition reactor and the second thermal decomposition reactor can enrich heavy component materials (including byproduct colloid, raw material impurities, spent catalysts and the like) along with the progress of the reaction, and the first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge the circulating materials and continuously supplement the same amount of solvents and catalysts so as to avoid accumulation of the heavy component materials;

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

and/or, in the step 1), the pressure controlled by the second thermal decomposition reactor is-0.08 to-0.098 MPa, and the temperature is 200-280 ℃.

Further, the pressure controlled by the first thermal decomposition reactor is-0.092 to-0.098 MPa, and the temperature is 220-260 ℃;

and/or the pressure controlled by the second thermal decomposition reactor is-0.092 to-0.098 MPa, and the temperature is 220-260 ℃.

Further, the temperature of the second thermal decomposition reactor is 1-10 ℃ higher than the temperature of the first thermal decomposition reactor.

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

Further, in the step 1), the isophorone dicarbamic acid n-butyl ester is an isophorone dicarbamic acid n-butyl ester product synthesized by a urea method; preference is given to industrially applicable methods for IPDI synthesis, with reference to patent 202211207615.2 filed by the same applicant.

The solvent is one of naphthenic oil, trioctyl trimellitate and trionyl trimellitate;

the catalyst is one or more of zinc picolinate, chromium picolinate, MOF-5, zinc oxide, bismuth trioxide, ionic liquid zinc, zinc chloride, zinc acetate, zinc acrylate and zinc isooctanoate. Preferably zinc picolinate, chromium picolinate, MOF-5.

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

Further, in step 1), the thin film evaporator is a wiped film evaporator.

Further, in the step 2), the discharged circulating material is subjected to preliminary separation (standing sedimentation) to obtain a primary component solvent and a primary component heavy component material, the primary component heavy component material is heated and evaporated to obtain a gas phase product and residues, and the primary component solvent and the gas phase product can be used as a solvent in the pyrolysis step of isophorone dicarbamate after being condensed.

Further, in the step 2), when the solvent is naphthenic oil, the heating evaporation temperature is 280-350 ℃, and the reaction pressure is-0.096 to-0.098 MPa.

Further, in the step 1), the operation pressure of the first rectifying tower is 10-30mbar, the temperature of a tower bottom is 190-210 ℃, the operation temperature of the tower top is 20-30 ℃, and the side line temperature is 150-170 ℃; preferably, the operating pressure of the first rectifying tower is 10-25mbar, the temperature of the tower bottom is 199-202 ℃, the operating temperature of the tower top is 24-26 ℃, and the lateral line temperature is 159.5-161.5 ℃.

And/or the operating pressure of the second rectifying tower is 10-30mbar, the temperature of the tower bottom is 190-200 ℃, the operating temperature of the tower top is 30-50 ℃, and the lateral line temperature is 155-160 ℃; preferably, the operating pressure of the second rectifying tower is 10-25mbar, the temperature of the tower bottom is 193-195 ℃, the operating temperature of the tower top is 39-41 ℃, and the lateral line temperature is 158-159 ℃.

From the chemical formulae referred to in the art for IPDI, it can be seen that IPDI has very reactive properties and that IPDI reacts with a wide variety of groups. Since IPDI has very active property, although the reaction step for synthesizing IPDI by urea method is only two steps, domestic scientists cannot realize industrial production of IPDI by the process route. The process for producing the IPDI by thermally cracking the IPDI is absolutely feasible in principle, but although the synthesis of the IPDI has great economic value, no enterprise can really and industrially synthesize the IPDI in China. The main reasons are that the prior art/enterprises cannot correctly recognize the reason that the industrial synthesis of the IPDI by the urea method cannot be realized, and the prior art/enterprises often consider the reason that the process has higher requirements on equipment, needs higher temperature and is relatively difficult to operate. In fact, many problems which are difficult to notice occur when IPDI is produced industrially. Industrial production of IPDI produces a large amount of by-products, and the amount of by-products is a major determinant for determining the scale of industrial production and whether industrial production is possible.

The literature, "study of the synthesis process of isophorone diisocyanate", pages 45-46 reports the conclusion of the study of the thermal cleavage of IPDC to IPDI, indicating that the NCO content of the reaction product can be up to 30.1% (about 60.2% yield); it has also been pointed out that the difference in the content of IPDI obtained by pyrolysis under the same reaction conditions is very large, at a minimum up to 18.4% (about 36.4% yield), owing to the series of complex, uncontrollable, different degrees of chemical side reactions that occur during the reaction.

According to the prior art, a small number of patents report that the method can continuously produce the IPDI in an industrialized mode, and the yield is high (reaching 90%). In fact, yuhshi Luh et al have conducted extensive studies on thermal decomposition of urethane using the most advanced equipment, indicating that after the reaction is completed, the conversion of isophorone urethane is 95%, at which time the theoretical yield of alcohol is 90% at the highest, the theoretical yield of isophorone diisocyanate is 65% at the highest, and the theoretical yield of isophorone monoisocyanate is 27% at the highest. The inventor of the present application also makes a great deal of research, and the conclusion is consistent with yuhshi Luh and the like, and even if the single pyrolysis reactor is used for multiple circulation pyrolysis reactions, the effect of high yield cannot be realized at present.

Meanwhile, the research on the separation problem of thermal decomposition products is not paid attention to, the problems of side reaction existence, difficulty of separation design and the like are ignored, and the published data show that the separation aspect is mainly simply mentioned, and some are immature and even wrongly known.

The inventor of the present application has found that during the thermal cracking process of IPDI from IPDI-B, the types of side reactions are particularly numerous, but the most prominent and deadly side reactions are a series of reactions between IPDI and raw material (IPDI-B), specifically: one secondary amine hydrogen reacts with one isocyanate group, and one raw material IPDU-B molecule has two secondary amine hydrogens, which react with two isocyanate groups of one product IPDI at the same time, and react with one isocyanate group of two reactants respectively, thus involving 6 byproducts. From the kinetic point of view, as the temperature increases, the more active the secondary amine hydrogen (proton) is, the larger the dissociated reaction constant is, the more easily the reactive group is combined with the catalyst, and the reduction of the activation energy of the whole side reaction is favorable for the progress of the side reaction, so that the generation of the side products is extremely difficult to avoid. In the same principle, the intermediate product has a side reaction with the raw material (IPDU-B) as described above.

Meanwhile, the decomposition and activation energy of the carbamate groups of the primary position and the secondary position of the raw material (IPDU-B) are different, and the decomposition and activation energy of the carbamate groups of the secondary position is lower and easier to decompose. So that the single-side content of the thermal decomposition product of the IPDU-B is far greater than that of the target product (IPDI). In single-sided reheat decomposition, the required temperature is higher than the thermal decomposition temperature of IPDU-B.

The inventor of the application researches and discovers that separation and purification of pyrolysis products are also difficult, reaction products comprise n-butanol, unilateral, IPDI, solvent and the like, unilateral intermediate products have no ready physical data, side reactions (thermal decomposition reverse reaction) between thermal decomposition products, product self-polymerization reaction and the like are also difficult to separate and design. Among them, the side reaction of the objective product IPDI with n-butanol is very rapid, which is the most prominent problem affecting the final yield and product quality.

Based on the above, the inventor creatively designs and implements the thermal decomposition and product separation (rectification) process of the IPDU-B, solves the main contradiction, reduces the side reaction to an acceptable degree and obtains a satisfactory effect. The method is characterized in that:

1. the 2 thermal decomposition reactors were used, the first thermal decomposition reactor was used for thermal decomposition of only the starting material IPDU-B, and the second thermal decomposition reactor was used for thermal decomposition of only one side. Compared with the mode of using a single reactor for multiple circulating thermal decomposition reactions, the method fundamentally solves the most main side reaction problem caused by back mixing contact between the raw material IPDU-B and the product IPDI and single side. Meanwhile, the second thermal decomposition reactor can independently control higher temperature, so that the problem that the temperature required by single-side thermal decomposition is higher than the thermal decomposition temperature of IPDU-B is solved, and the reaction efficiency is improved.

2. The optimized rectification design reduces the influence of side reaction as much as possible and separates out qualified IPDI products. The first rectifying tower is used for separating most of n-butanol (more than 99.6% of total amount) in the system materials rapidly, so that side reactions of IPDI and n-butanol are reduced greatly, the content of IPDI in tower kettle materials is reduced as much as possible, and the content of IPDI in side-stream extracted IPDI rich liquid is increased as much as possible. And the second rectifying tower efficiently obtains the qualified IPDI product through a side-draw mode.

3. The coupling design of thermal decomposition and rectification realizes continuous thermal decomposition reaction with low side reaction risk, reaction product separation and thermal decomposition and rectification large circulation of unilateral components.

The beneficial effects of the invention are as follows:

1) The design of the invention greatly improves the product yield, and the IPDI yield (calculated by IPDI-B) is more than 90 percent. Can really realize industrialization.

2) The method provided by the invention realizes the effect that the recovery rate of the solvent is more than 95%, and the recovered solvent can be directly used as the solvent for the pyrolysis reaction of isophorone dicarbamic acid n-butyl ester without purification.

3) The zinc picolinate, chromium picolinate and MOF-5 selected by the invention are used for the industrial urea-process isophorone dicarbamate n-butyl ester thermal cracking catalyst, and have the effects of good selectivity, less side reaction and high product yield.

4) The thermal cracking solvent for industrial urea method IPDI-B provided by the invention has the characteristics of compatibility with IPDI-B, chemical stability, good catalyst dispersion and heat resistance, and can increase the yield of IPDI and reduce the generation of byproducts when being used for the thermal cracking reaction of IPDI-B.

5) After the industrial method (rectification operation) for purifying the crude IPDI product is adopted, the purity of the obtained IPDI product is more than 99.7 percent.

Drawings

FIG. 1 is a process flow diagram for producing IPDI by thermal cracking of IPDI;

FIG. 2 is data recorded in the literature on study of kinetics of isophorone diisocyanate-based reaction.

Detailed Description

The technical scheme of the present invention is described in further detail below, but the scope of the present invention is not limited to the following.

1. Laboratory and industrial IPDU-B thermal cracking, solvent recovery, rectification reactor, reaction flow, raw material and detection method

The applicant has explained that it relates to laboratory ipdi-B thermal cracking data, and first, the laboratory related apparatus of the present invention employs small-sized apparatus similar to commercial ipdi-B thermal cracking apparatus. Furthermore, the laboratory is mainly used for research, provides theoretical basis and production condition parameters for industrial production, is an indispensable step before industrial implementation, and does not represent that the laboratory-scale data of the invention have no reference significance; in addition, the laboratory also provides a comparison of the industrialization effect, so the invention provides laboratory data.

It is also first pointed out that the invention has been written with thermal cracking, solvent recovery, rectification apart in order to facilitate an understanding of the meaning of each step of the invention, which does not indicate that the invention is not a continuous reaction.

(1) Laboratory thermal cracking reactor

A cracker: evaporation area 0.1m ² ；

And (3) a circulating pump: gear pump 2.8L/h;

rectifying column: Φ50X100;

(2) Continuous thermal cracking reaction process in laboratory

The raw material IPDU-B enters a thin film evaporator (cracker) to be heated and cracked, and naphthenic oil and catalyst at the lower part are pumped back to an inlet at the upper part of the cracker through a circulating pump. And (3) introducing pyrolysis gas from the upper part of the cracker into a rectifying column under the vacuum effect, and stopping feeding the IPDU-B when heavy components start to flow back into the cracker in a large amount from the lower part of the rectifying column. At this time, the cracker only carries out thermal decomposition to the reflux material, and the pyrolysis gas that the cracker upper portion was come out gets into the rectifying column under the vacuum effect, and light component then gets into heat exchanger from rectifying column upper portion, flows into crude product jar by the self-flow after being condensed. And when the reflux quantity is reduced to be close to the interruption, starting the feeding of the IPDU-B, and repeating the operation until the test is finished.

Note that: the batch feeding mode of the IPDU-B raw material is used for approximately simulating the IPDU-B and unilateral segmented pyrolysis, so that side reactions are obviously inhibited.

(3) Industrial thermal cracking reactor

IPDU-B feed pump: q=2m ³ H, h=14m; 1# cracker: a=30m ² The method comprises the steps of carrying out a first treatment on the surface of the 1# pyrolysis circulation pump: q=5m ³ H, h=14m; 1# high polymer drainage pump: q=2m ³ H, h=14m; 2# cracker: a=25m ² The method comprises the steps of carrying out a first treatment on the surface of the 2# pyrolysis circulation pump: q=5m ³ H, h=14m; 2# high polymer drainage pump: q=2m ³ /h，H＝14m。

(4) Industrial thermal cracking reaction flow

The thermal decomposition raw material IPDU-B, solvent and catalyst enter a No. 1 rotary scraping plate thermal decomposition reactor, a liquid film is forcedly formed on the inner wall of the reactor by the rotary scraping plate, and the thermal decomposition reaction is carried out by heating the inner wall of the reactor. Under the vacuum condition, the thermal decomposition products are rapidly evaporated to realize rapid separation from the reaction raw materials, thereby greatly reducing the generation of side reactions. The gas phase material (gas phase material I, reaction product) at the outlet of the reactor enters a rectifying unit. The material (mainly single side) at the bottom of the rectifying tower enters a No. 2 rotary scraping plate thermal decomposition reactor for thermal decomposition reaction, and the gas-phase material (gas-phase material III, reaction product) at the outlet of the reactor and the gas-phase material I are combined and enter a rectifying unit. The bottoms of the two reactors are provided with a circulating tank and a circulating pump, and the solvent and the catalyst circulate.

(5) Solvent recovery device

Scraper evaporator: heat exchange area s=12m ²

(6) Method for recovering solvent

It should be emphasized that this part is to treat the heavy component materials after the primary separation (standing sedimentation) of the circulating liquid discharged from the bottoms of the two rotary scraper thermal decomposition reactors in the industrialized thermal cracking reaction flow of (4).

Heavy component materials generated by the pyrolysis reaction of isophorone dicarbamate are pumped to the top of a scraper evaporator, a liquid film is forcedly formed on the inner wall of the evaporator through a rotary scraper, the liquid film is heated through the inner wall of the evaporator, the vapor phase product and the heavy component are obtained through evaporation under the vacuum condition, and the vapor phase product is condensed by a condenser to obtain the recovered solvent. Reaction conditions for heating evaporation: the temperature is 280 ℃, and the reaction pressure is-0.096 to-0.098 MPa.

(7) Reaction equipment for rectification

Light component removal column (rectifying column): phi 1200X 24604, filler height 3888/3888/3888/3240mm

Product column (rectifying column): phi 900X 24348 and packing height 3096/3096/4128/4128mm

And (3) a condenser: light component removing tower top condenser phi 1200 x 2000, heat exchange area 80m ² The method comprises the steps of carrying out a first treatment on the surface of the Product tower top condenser phi 1000 multiplied by 2000, heat exchange area 90m ²

Reboiler: the reboiler phi at the bottom of the light component removal tower is 1100 multiplied by 2500, and the heat exchange area is 94.5m ² The method comprises the steps of carrying out a first treatment on the surface of the The reboiler at the bottom of the product tower is phi 1400 multiplied by 3000, and the heat exchange area is 190m ²

And (3) a circulating pump: light component removal tower bottom circulating pump Q=10.8m ³ H= 40m Zone2 EEx dII BT4, product bottom circulation pump q=18m ³ H＝40m Zone2 EEx dII BT4

Auxiliary system: the heat conduction oil system provides a required heat source, the circulating water system and the chilled water system provide refrigerants, the nitrogen system provides nitrogen for the start-stop system to replace, and the vacuum system provides vacuum conditions required by the device

And (3) a control system: the process operation control adopts a DCS system and is provided with a Safety Interlock (SIS) system

(8) Reaction scheme of rectification

It is emphasized that this section belongs to the specific explanation of the rectification unit in the industrial thermal cracking reaction scheme of (4).

The crude product of the gas-phase IPDI (gas-phase material I and gas-phase material III) enters the light component removal tower bottom (first rectifying tower) from the thermal decomposition unit, n-butanol is extracted from the tower top, IPDI rich liquid is extracted from the side line in the middle of the tower, and the material in the tower bottom is circularly thermally decomposed (second thermal decomposition reaction) by the thermal decomposition unit. The IPDI rich liquid extracted from the side line of the light component removal tower is pumped into a product tower (a second rectifying tower), a small amount of n-butanol and IPDI are extracted from the top of the product tower, the IPDI product is extracted from the side line, and the material in the tower bottom (liquid phase material II) is subjected to cyclic thermal decomposition (a second thermal decomposition reaction) by a thermal decomposition unit.

(9) Raw materials

N-butyl isophorone dicarbamate (IPDU-B) component: the internal control index is more than or equal to 99.0 percent (99.38 percent of IPDU-B, 0.46 percent of catalyst for synthesizing the IPDU-B and the other 0.16 percent);

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

solvent: naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate and trionyl trimellitate.

(10) Detection method

See table 1:

TABLE 1

(11) The raw materials corresponding to each step of the invention, the obtained product components and the yield statistics

Referring to the process flow of FIG. 1, IPDI is continuously synthesized according to the industrialized routes (4), (6) and (8), and the control conditions are optimal experimental conditions, namely, the operation pressure of the first thermal decomposition is controlled to be-0.094 Mpa, the operation temperature is controlled to be 240 ℃, the operation pressure of the second thermal decomposition is controlled to be-0.094 Mpa, and the operation temperature is controlled to be 245 ℃. The operating conditions for controlling the light ends removal column are: 11mbar at the top of the tower, 24mbar at the bottom of the tower, 199.7 ℃ at the bottom of the tower, 25 ℃ at the top of the tower and 160.8 ℃ at the side line temperature; the operating conditions of the product column were: 11mbar at the top of the column, 24mbar at the bottom of the column, 194℃at the top of the column, 40℃at the top of the column and 158.3℃at the side line. After the system is running stably, the statistics of the raw material feeding amount, the obtained product components and the yield corresponding to each step are listed as follows:

And (3) injection: the process is continuously carried out, and a gas phase material I and a gas phase material III are produced by different thermal cracking reactors at the same time and are mixed together to enter a first rectifying tower; IPDU feedstock impurities: catalyst for synthesizing IPDU-B0.46% and other impurities 0.16%.

2. Screening experiment of catalyst for thermal cracking reaction of IPDU-B

(1) Catalyst species screening experiments

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃; the operating pressure is minus 0.094Mpa; 500g of IPDU-B, 500g of naphthenic oil (solvent) and 3.5g of catalyst were charged, and the types of the catalysts were selected and the experimental results were shown in Table 2 below:

TABLE 2

Experiment lot number	Catalyst	Reaction completion time (min)	IPDI yield (%)	Gum ratio (%)
					Group 1-1	Pyridinecarboxylic acid chromium salt	45	91.59	2.65
Group 1-2	MOF-5	33	92.02	3.58
					Groups 1-3	Zinc picolinate	37	91.32	3.49
Groups 1-4	Zinc oxide	44	79.04	9.24
					Groups 1-5	Bismuth oxide	49	57.04	10.06
Groups 1-6	Ionic liquid zinc	75	49.07	14.68
					Groups 1-7	Zinc chloride	43	53.06	13.88
Groups 1-8	Zinc acetate	55	56.72	13.68
					Groups 1-9	Zinc acrylate	52	59.79	12.45
Groups 1-10	Zinc iso-octoate	54	60.95	12.68

Note that: the main components of the colloid in the invention are catalyst and high molecular polymer (by-product); the gum ratio refers to the ratio of the gum production to the feed of the raw material IPDU-B.

As is clear from Table 2, the catalysts indicated in groups 1-1 to 1-10 all have a certain catalytic effect, but when chromium picolinate, MOF-5 and zinc picolinate are selected as catalysts, the yield of IPDI is high and the content of colloid is low (side reaction is small), so chromium picolinate, MOF-5 or zinc picolinate is preferable as catalysts in the present invention.

(2) Catalyst dosage screening experiments

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃; the operating pressure is minus 0.094Mpa; 500g of IPDU-B and 500g of naphthenic oil are put into the reactor, chromium picolinate is selected as a catalyst, and a catalyst dosage screening experiment is carried out, wherein the catalyst dosage screening result is shown in the following table 3:

TABLE 3 Table 3

Experiment lot number	Catalyst amount (mass%)	IPDI yield (%)	Gum ratio (%)
				Group 2-1	0.75	91.46	2.76
Group 2-2	1.0	91.13	2.82
				Groups 2-3	0.5	88.25	4.33
Groups 2-4	0.3	87.75	6.23
				Groups 2-5	0.25	76.88	10.94
Groups 2-6	1.25	87.93	4.67
				Groups 2-7	1.5	84.73	6.87

Note that: the catalyst amount (% by mass) is relative to IPDU-B.

As can be seen from the data in Table 3, when the catalyst is used in an excessive or too small amount, the IPDI yield is lowered, the gum content is increased, and the catalyst is most suitably used in an amount of 0.3% -1%.

3. Screening of thermal cracking reaction conditions of IPDU-B

(1) Screening of thermal cracking temperatures

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃; the operating pressure is minus 0.094Mpa; 500g of IPDU-B, 500g of naphthenic oil and 3.5g of chromium picolinate were charged, and the thermal cracking temperature was selected as shown in Table 4 below:

TABLE 4 Table 4

Experiment lot number	Cracking temperature (. Degree. C.)	IPDU-B conversion (%)	IPDI yield (%)	Gum 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
Groups 3-4	220	41.12	10.23	0.62
					Groups 3 to 5	230	97.2	84.67	1.03
Groups 3 to 6	260	99.82	91.13	3.87
					Groups 3 to 7	280	99.84	87.32	8.64

As can be seen from Table 4, IPDI was produced by the reaction at a temperature in the range of 200 to 280 ℃; in the temperature range 220-280 ℃, the conversion of ipdi-B increases with increasing temperature, but as the temperature approaches 280 ℃, the gum production increases substantially, so the cleavage temperature is preferably 220-260 ℃.

(2) Screening of vacuum degree of thermal cracking reaction

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃; 500g of IPDU-B, 500g of naphthenic oil and 3.5g of chromium picolinate are put into the reactor, and the vacuum degree of the thermal cracking reaction is screened, and the screening result of the vacuum degree of the thermal cracking reaction is shown in the following table 5:

TABLE 5

As is clear from Table 5, when the vacuum degree is within the range of-0.080 to-0.098, the IPDI yields are constant; when the vacuum degree is within the range of-0.092 to-0.098, the yield of IPDI is highest, and the content of colloid is low.

4. Screening of solvents for thermal cracking reactions of IPDU-B

(1) Screening of solvent types for thermal cracking reactions

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃ and the operating pressure to-0.094 Mpa; 500g of IPDU-B, 3.5g of chromium picolinate and 500g of solvent are added, and the solvent type of the thermal cracking reaction is screened, and the screening result of the thermal cracking reaction solvent is shown in the following table 6:

TABLE 6

Experiment lot number	Solvent(s)	IPDI yield (%)	Gum 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％
Groups 5-4	Naphthenic oil KN4016	91.00％	3.07％
				Groups 5-5	Trioctyl trimellitate	88.30％	5.83％
Groups 5-6	Trinonyl trimellitate	89.23％	5.24％

As can be seen from Table 6, the use of the solvents naphthenic oil KN4010, naphthenic oil KN4006, naphthenic oil KN4016, trioctyl trimellitate and trionyl trimellitate all increased the IPDI yield and reduced the gum content, and the naphthenic oil was most suitable for use as a solvent.

(2) Screening of solvent dosage for thermal cracking reaction

Operating conditions: selecting a laboratory thermal cracking reactor and a reaction flow, and controlling the cracking temperature of the cracker to 240 ℃ and the operating pressure to-0.094 Mpa; 3.5g of chromium picolinate, changing the mass ratio of the solvent to IPDU-B in experimental conditions, wherein the solvent is naphthenic oil KN4010, and screening the solvent dosage of the thermal cracking reaction, wherein the screening result of the solvent dosage of the thermal cracking reaction is shown in the following table 7:

TABLE 7

As shown in Table 7, the solvent was used in an amount of 0.1 to 9 times the amount of IPDU-B, and the effect was excellent.

5. Verification of thermal cracking reaction effect of industrial IPDU-B

Operating conditions: selecting an industrial thermal cracking reactor and a reaction flow, and controlling the IPDU-B through a circulation amount and a supplement amount: naphthenic oil KN4010: the mass ratio of the chromium picolinate is 1:1:0.007; 4 batches were performed on an industrial plant. The statistical results are shown in Table 8 below.

TABLE 8

As can be seen from Table 8, the yield of industrial IPDI was greater than 91%, which indicates that the feasibility of the industrial process and the industrial parameters determined by the invention was verified.

6. Recovery of solvent after reaction and reuse of recovered solvent

The influence of the recovery and reuse of the solvent on the industrial production is important, not only the production cost but also the pollutant discharge amount are determined, and therefore, the invention further examines the influence of the recovery and reuse of the solvent on the reaction. Combining an industrial thermal cracking reactor and a reaction flow to obtain a heavy component material after primary separation, using a solvent recovery device and according to a solvent recovery method, selecting naphthenic oil KN4010 to measure recovery results as shown in table 9, and measuring properties of thermal cracking products after reusing the recovered solvent, wherein experimental results are shown in table 10.

TABLE 9

Note that: the reaction conditions for group 8-1, group 8-2 and group 8-3 were: the temperature is 280 ℃, and the reaction pressure is-0.096 to-0.098 MPa. The temperature is 300 ℃, and the reaction pressure is-0.092 to-0.098 MPa. The temperature is 330 ℃, and the reaction pressure is minus 0.092 to minus 0.098MPa.

Table 10

Note that: the reaction conditions for group 9-1, group 9-2, group 9-3 and group 9-4 are: the first thermal decomposition operating pressure is-0.094 Mpa, and the operating temperature is 240 ℃; the second thermal decomposition operating pressure is-0.094 Mpa, and the operating temperature is 245 ℃; the mass dosage of the catalyst chromium picolinate is 0.0035 of the feeding amount.

As can be seen from tables 4, 5 and 6, 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.

7. Method for purifying crude IPDI (rectification operation)

(1) The specific components of the gas phase IPDI crude product are 19.54% of n-butanol, 28.64% of IPDI, 39.52% of unilateral side and 12.3% of naphthenic oil (solvent).

It should be explained that the crude gas-phase IPDI in this embodiment refers to a product obtained by combining the gas-phase material one and the gas-phase material three, which are identical in that the content of the components is different, industrialization is continuously performed (only the gas-phase material one is generated when starting), that is, the gas-phase material one and the gas-phase material three are simultaneously generated in the industrialized operation, and the rectification column is designed and stable to operate so as to require that they are fed at the same position. The present invention thus combines gas phase feed one and gas phase stream three as crude gas phase IPDI.

The operating conditions of the light component removal column (first rectifying column) are controlled as follows: 11mbar at the top of the tower, 24mbar at the bottom of the tower, 199.7 ℃ at the bottom of the tower, 25 ℃ at the top of the tower and 160.8 ℃ at the side line temperature; the operating conditions of the product column (second rectification column) were: 11mbar at the top of the column, 24mbar at the bottom of the column, 194℃at the top of the column, 40℃at the top of the column and 158.3℃at the side line.

Taking n-butanol extracted from the top of a light component removal tower (a first rectifying tower), IPDI rich liquid extracted from the side line of the middle part of the tower, and tower kettle materials; and taking a small amount of mixed liquid of n-butanol and IPDI from the top of a product tower (a second rectifying tower), and taking the IPDI product from the side line of the middle part of the tower, and tower kettle materials. After the system was stably operated, the components and contents were measured, respectively, and the results are shown in Table 11 below:

TABLE 11

(2) The specific components of the gas phase IPDI crude product are 22.94% of n-butanol, 31.97% of IPDI, 34.63% of unilateral side and 10.46% of naphthenic oil.

The operating conditions of the light component removal column (first rectifying column) are controlled as follows: 11mbar at the top of the tower, 24mbar at the bottom of the tower, 200.4 ℃ at the temperature of the bottom of the tower, 25.5 ℃ at the operating temperature of the top of the tower and 161 ℃ at the side line temperature; the operating conditions of the product column (second rectification column) were: 11mbar at the top of the column, 24mbar at the bottom of the column, 194.5℃at the top of the column, 40.5℃at the side stream and 158.5 ℃.

Taking n-butanol extracted from the top of a light component removal tower (a first rectifying tower), IPDI rich liquid extracted from the side line of the middle part of the tower, and tower kettle materials; and taking a small amount of mixed liquid of n-butanol and IPDI from the top of a product tower (a second rectifying tower), and taking the IPDI product from the side line of the middle part of the tower, and tower kettle materials. After the system was stably operated, the components and contents were measured, respectively, and the results are shown in Table 12 below:

table 12

(3) The specific components of the gas phase IPDI crude product are 20.05% of n-butanol, 38.21% of IPDI, 31.87% of unilateral side and 9.87% of naphthenic oil.

The operating conditions of the light component removal column (first rectifying column) are controlled as follows: 11mbar on the pressure tower top, 24mbar on the tower bottom, 201.5 ℃ on the tower bottom, 26 ℃ on the tower top operation temperature and 161.2 ℃ on the side line; the operating conditions of the product column (second rectification column) were: the pressure at the top of the column was 11mbar, the temperature at the bottom of the column was 24mbar, the operating temperature at the top of the column was 194.9℃and the side stream temperature was 158.7 ℃.

Taking n-butanol extracted from the top of a light component removal tower (a first rectifying tower), IPDI rich liquid extracted from the side line of the middle part of the tower, and tower kettle materials; and taking a small amount of mixed liquid of n-butanol and IPDI from the top of a product tower (a second rectifying tower), and taking the IPDI product from the side line of the middle part of the tower, and tower kettle materials. After the system was stably operated, the components and contents were measured, respectively, and the results were as shown in Table 13 below:

TABLE 13

Further, the urea method for synthesizing isophorone dicarbamate is preferably as follows:

1. equipment, raw materials, process flow and detection method for synthesizing IPDU-B by laboratory and industrial urea method.

(1) Equipment used in the industrialized urea method:

and (3) a reaction kettle: Φ650×800, 300L, stripping deamination column: phi 273 x 3000 (deamination tower top condenser a=6m) ² ) Falling film evaporator phi 300 multiplied by 1200;

an ammonia-containing tail gas condenser: a=2.2m ² Gas-liquid separator: v=0.10m ³ Φ400×800 (straight tube);

gas-solid separator: v=0.61 m3 Φ700×1300 (straight tube);

n-butanol adsorption tower: diameter 300mm, height 1200mm,3 stations, operating conditions: 30-150 ℃ (regeneration 150 ℃), micro positive pressure.

(2) Raw material preparation:

urea: GB/T2440-2001 industrial high-grade product with actual purity of 99.6%;

n-butanol: GB/T6027-1998 superior products with actual main content of 99.8%;

IPDA: purity 99.5%;

catalyst (zirconium acetate): the purity was 99.0%.

(3) The specific method for synthesizing isophorone dicarbamic acid n-butyl ester by the industrialized urea method comprises the following steps:

adding liquid raw material n-butanol (excessive), raw material IPDA, solid raw material urea (slightly excessive) and liquid catalyst zirconium acetate into a 300L stainless steel reaction kettle, sealing the reaction kettle after the addition, replacing air in the kettle with nitrogen, and introducing 4.5Nm according to the nitrogen ³ The temperature is raised to 225 ℃ and the synthesis reaction is carried out for 2 hours under the condition of the pressure of 1.50 Mpa.G. After the reaction is finished, decompressing and flashing part of n-butanol of the bottom product of the kettle, and then passing through a falling film evaporator at 200And (3) circularly dealcoholizing for 2 hours under the conditions of the temperature of between DEG C and the vacuum degree of-0.090 MPa, and removing unreacted n-butyl alcohol and an intermediate product n-butyl carbamate to obtain the intermediate product isophorone diamino n-butyl carbamate.

In the reaction process, gas-phase materials (namely synthetic tail gas) at the outlet of the reaction kettle sequentially pass through a stripping deamination tower and a condenser positioned at the top of the stripping deamination tower to obtain gas-phase materials and liquid-phase materials, wherein the gas-phase materials are ammonia-containing tail gas which contains a small amount of n-butanol and mainly contains carrier gas and ammonia components. The liquid phase material is most of n-butanol condensed from the synthesis tail gas, the liquid phase material is refluxed to the top of the stripping deamination tower, most of ammonia dissolved in the liquid phase material is removed by the stripping deamination tower, and finally the n-butanol after deamination returns to the reaction kettle.

Introducing high-temperature ammonia-containing tail gas into a condenser, cooling to 59 ℃, liquefying most of n-butanol contained in the ammonia-containing tail gas at the moment, solidifying ammonium carbamate, wherein the tail gas is a mixture of nitrogen, ammonia, liquid n-butanol and ammonium carbamate solids, introducing the tail gas into a gas-liquid separator to remove n-butanol, blowing the nitrogen, the ammonia and the ammonium carbamate into the gas-solid separator, and filtering and adsorbing the ammonium carbamate by the gas-solid separator to obtain the ammonia-removed tail gas containing residual n-butanol.

And (3) introducing the ammonia carbamate tail gas containing the residual n-butanol into a precooler for cooling, keeping the outlet temperature at 20 ℃, pumping and pressurizing the cooled tail gas by a fan, and introducing the tail gas into an adsorption tower filled with the nano adsorbent. And introducing the absorbed tail gas into a sulfuric acid absorber to obtain ammonium salt and final tail gas.

The nano adsorbent is special for the Haima nano HDV536, selectively adsorbs n-butanol and does not basically adsorb ammonia. Particle size (0.6-1.25 mm) > 95%, specific surface area 1400 square meter/g, pore volume 0.90ml/g, pore diameter

The detection method is shown in the following table:

2. the industrial urea method for verifying the effect of synthesizing the IPDU-B product comprises the following steps:

158.5kg of liquid raw material n-butanol, 45.5kg of raw material IPDA, 35.5kg of solid raw material urea and 318g of liquid catalyst zirconium acetate are added into a 300L stainless steel reaction kettle, the reaction kettle is closed after the feeding is finished, the air in the kettle is replaced by nitrogen, and then 4.5Nm of nitrogen is introduced into the reaction kettle according to the nitrogen introducing amount ³ The temperature is raised to 225 ℃ and the synthesis reaction is carried out for 2 hours under the condition of the pressure of 1.50 Mpa.G. After the reaction is finished, decompressing and flashing part of n-butyl alcohol, circularly dealcoholizing for 2 hours by a falling film evaporator under the conditions of 200 ℃ and vacuum degree of-0.090 MPa, removing unreacted n-butyl alcohol and intermediate product n-butyl carbamate to obtain 97.5kg of intermediate product isophorone diamino n-butyl carbamate and the product yield is 98.4% (the detection method is GC-FID).

It can be seen that the yield of industrial production IPDU-B is greater than 98%, which shows that the feasibility of the industrial process and the industrial parameters are verified.

3. The treatment effect of industrial urea method for synthesizing IPDU-B waste gas is as follows:

the industrial urea process was used to synthesize IPDA-B (IPDA: 45.5kg (0.27 kmol), n-butanol: 158.5kg (2.14 kmol), urea: 35.5kg (0.57 kmol), zirconium acetate 400g (1.22 mol)), and process nitrogen was used as a carrier gas. Introducing high-temperature ammonia-containing tail gas into a condenser, cooling to 59 ℃, liquefying n-butanol at the moment, solidifying ammonium carbamate, introducing the tail gas into a gas-liquid separator again to remove n-butanol, introducing nitrogen, ammonia and ammonium carbamate into the gas-solid separator, filtering and adsorbing the ammonium carbamate by the gas-solid separator to obtain the ammonia-free tail gas containing residual n-butanol, and blowing out the enriched ammonium carbamate in the gas-solid separator by high-temperature nitrogen to decompose the ammonium carbamate solid into ammonia components and carbon dioxide so as to regenerate the gas-solid separator.

And (3) introducing the ammonium carbamate tail gas containing the residual n-butanol into a precooler for cooling, keeping the outlet temperature at 20 ℃, pumping and pressurizing the cooled tail gas by a fan, and introducing the tail gas into an adsorption tower filled with a nano adsorbent to obtain the butanol-removed tail gas. And introducing the adsorbed butanol-removed tail gas into a sulfuric acid absorber to obtain ammonium salt and final tail gas.

And stopping adsorption when the adsorption tower reaches the cycle time (three adsorption towers and one adsorption tower are involved, simultaneously, the other two adsorption towers are used for desorption, the adsorption and desorption processes are alternately carried out through switching between valves, the adsorption tower is automatically switched to the desorption process when reaching the penetration point), the adsorbent is desorbed and regenerated by adopting nitrogen at 150 ℃, the ammonia containing n-butanol after desorption is separated by low-temperature freezing water condensation, the separated liquid phase n-butanol is collected to an 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 incorporated into the ammonia-deamination tail gas to remove the trace n-butanol through the adsorption tower.

The contents of each component in the ammonia-containing tail gas before condensation, the ammonia-containing tail gas after condensation, the deaminated ammonium tail gas and the final tail gas are detected, and the results are shown in the following table.

As shown in the table above, the high temperature ammonia-containing tail gas discharged in isophorone diamino n-butyl ester synthesis contains 0.62% of ammonium carbamate, and after the ammonia carbamate removal process, the ammonium carbamate content in the tail gas is only 0.05%, and the ammonium carbamate removal rate reaches 92%, which indicates that the ammonium carbamate removal process can effectively remove ammonium carbamate in the urea process for synthesizing isophorone diamino n-butyl ester, and can prevent pipelines and valves of industrial equipment from being blocked by ammonium carbamate. The ammonia content in the butanol-removing tail gas is 48.96%, and the ammonia content in the final tail gas is only 0.003%, which indicates that the ammonia in the tail gas can be effectively removed by the deamination process. The content of n-butanol in the deaminated ammonium formate tail gas is 1.20%, and no n-butanol is detected in the final tail gas, which indicates that the whole tail gas removal process can effectively remove n-butanol in the tail gas.

The foregoing is merely a preferred embodiment of the invention, and it is to be understood that the invention is not limited to the form disclosed herein but is not to be construed as excluding other embodiments, but is capable of numerous other combinations, modifications and environments and is capable of modifications within the scope of the inventive concept, either as taught or as a matter of routine skill or knowledge in the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims (10)

1. An industrial method for producing IPDI by thermal cracking of isophorone dicarbamate is characterized by comprising the following steps:

1) Pyrolyzing and rectifying the isophorone dicarbamic acid n-butyl ester to couple the steps: allowing isophorone dicarbamic acid n-butyl ester, a solvent and a catalyst to enter a first thermal decomposition reactor for reaction to obtain a gas phase material I, merging the gas phase material I and the gas phase material III, entering a first rectifying tower for rectifying operation, obtaining n-butanol at the top of the tower, extracting IPDI rich liquid from the middle side line, and discharging heavy components from the tower bottom; the IPDI rich liquid enters a second rectifying tower for operation, the mixed liquid of n-butanol and IPDI is separated from the tower top, the IPDI product is extracted from the middle side line, and the heavy component is discharged from the tower bottom; heavy components discharged from the bottoms of the first rectifying tower and the second rectifying tower are liquid-phase materials II, the liquid-phase materials II enter a second thermal decomposition reactor to react, a gas-phase material III is obtained, and the gas-phase material III returns to the first rectifying tower and enters the first rectifying tower together with the gas-phase material I to carry out rectification;

2) And heavy component material discharging: the first thermal decomposition reactor and the second thermal decomposition reactor need to continuously discharge circulating materials and continuously supplement the same amount of solvent and catalyst.

2. The industrial process according to claim 1, wherein 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 ℃;

and/or, in the step 1), the reaction pressure controlled by the second thermal decomposition reactor is-0.08 to-0.098 MPa, and the reaction temperature is 200-280 ℃.

3. The industrial process according to claim 1, wherein in step 1), the reaction temperature of the second thermal decomposition reactor is 1 to 10 ℃ higher than the reaction temperature of the first thermal decomposition reactor.

4. The industrial process according to claim 1, wherein in step 1), the mass ratio of isophorone dicarbamate to solvent to catalyst is: 1:0-9:0.0025-0.015.

5. The industrial process according to claim 1, wherein in step 1), the n-butyl isophorone dicarbamate is an n-butyl isophorone dicarbamate product synthesized by a urea process;

The solvent is one of naphthenic oil, trioctyl trimellitate and trionyl trimellitate;

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

6. The industrial process according to claim 1, wherein in step 1), the first thermal decomposition reactor and/or the second thermal decomposition reactor is a thin film evaporator.

7. The industrial process according to claim 6, wherein in step 1), the thin film evaporator is a wiped film evaporator.

8. The method according to claim 5, wherein in step 2), the discharged recycle material is subjected to preliminary separation to obtain a primary solvent and a primary heavy component material, the primary heavy component material is heated and evaporated to obtain a gas phase product and a residue, and the primary solvent and the gas phase product are condensed and can be used as the solvent in the pyrolysis step of isophorone dicarbamate n-butyl.

9. The industrial process according to claim 8, wherein in step 2), when the solvent is naphthenic oil, the temperature of the heating evaporation is 280 to 350 ℃, and the reaction pressure is-0.096 to-0.098 MPa.

10. The method according to claim 1, wherein in step 1), the operation pressure of the first rectifying column is 10-30mbar, the column bottom temperature is 190-210 ℃, the column top operation temperature is 20-30 ℃, and the side line temperature is 150-170 ℃;

and/or the operating pressure of the second rectifying tower is 10-30mbar, the temperature of the tower bottom is 190-200 ℃, the operating temperature of the tower top is 30-50 ℃, and the lateral line temperature is 155-160 ℃.