Device and method for continuously preparing 1, 5-pentamethylene diisocyanate through thermal cracking

Abstract

The invention belongs to the technical field of fine chemical synthesis, and particularly relates to a device and a method for continuously preparing 1, 5-pentamethylene diisocyanate through thermal cracking. The method comprises the following steps: mixing and preheating a 1, 5-pentamethylene dicarbamate compound and bismuth neodecanoate, pumping the mixture into a reaction kettle filled with tetraethylene glycol dimethyl ether, carrying out a thermal cracking reaction, carrying out primary purification on the obtained reaction liquid, and continuously carrying out secondary purification to obtain the 1, 5-pentamethylene diisocyanate. According to the device and method for continuously preparing 1, 5-pentamethylene diisocyanate through thermal cracking, a non-phosgene method is adopted in the preparation process, the device and method are environmentally friendly, small in potential safety hazard, mild in reaction condition and simple and convenient in technology, the yield of 1, 5-pentamethylene diisocyanate reaches 80% or above, and the purity reaches 99%.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical synthesis, and particularly relates to a device and method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking. Background Art

[0002] Polyurethane is a polymer with excellent thermal properties, mechanical properties, viscoelasticity, wear resistance and biological properties. Therefore, it is widely used in coatings, fibers, adhesives, thermosetting materials, thermoplastic materials, bionic materials and nanocomposites. The main raw material of polyurethane is isocyanate, including aromatic isocyanates such as toluene diisocyanate and aliphatic isocyanates such as 1,6-hexamethylene diisocyanate. Among them, 1,6-hexamethylene diisocyanate is the first choice for high-end polyurethane coatings due to the excellence of its linear aliphatic structure. However, with the improvement of green environmental protection requirements, bio-based materials have gradually become the focus of research by scientific researchers. Therefore, compared with 1,6-hexamethylene diisocyanate, which relies on petrochemical resources for production, 1,5-pentamethylene diisocyanate synthesized from bio-based raw materials will have broader development potential.

[0003] Usually in industrial production, isocyanates are mainly synthesized by the phosgene method, but this method still has some difficult to solve problems. The first is that the phosgene method requires the use of excessive phosgene during the synthesis process. Phosgene is a highly toxic substance that will bring higher safety hazards to production and bring risks to enterprises. Secondly, the phosgene method will generate highly corrosive hydrochloric acid byproducts, which can easily damage production equipment and increase equipment management and maintenance costs. Finally, isocyanates produced by the phosgene method often contain chloride impurities that are difficult to remove, such as hydrolyzed chlorine, etc. These impurities will reduce the activity of isocyanates and affect the subsequent reaction efficiency. Therefore, from the perspective of environmental protection and health safety, non-phosgene methods have become an important means to achieve green isocyanate synthesis and related processes.

[0004] The one-step pathways of non-phosgene synthesis that have been reported mainly include the reductive carbonylation of nitro groups, the oxidative carbonylation of amino groups, and the rearrangement method. The two-step pathway is mainly the thermal decomposition of carbamates, which first synthesizes carbamates and then thermally cracks them to obtain the corresponding isocyanates. The two-step pathway has been studied by a large number of researchers due to its feasibility in synthesis. Chinese patent CN108689884A reports a method for manufacturing 1,5-pentanediisocyanate, which directly reacts the extraction mixture of 1,5-pentanediamine with urea to generate carbamates, and then thermally cracks the carbamates to obtain 1,5-pentanediisocyanate, but its PDI yield is low, about 50%, making it difficult to achieve industrial production.

[0005] Therefore, in the process of thermal cracking of carbamate, it is of great significance to use new thermal cracking solvents and new catalysts to carry out the reaction and to develop a thermal cracking method for continuously preparing 1,5-pentamethylene diisocyanate. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a device and method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking in view of the deficiencies in the prior art. The method provided by the present invention adopts a new thermal cracking solvent and a new catalyst for reaction, and adopts a continuous reaction separation coupling device at the same time, which is pollution-free, has little safety hazard, has few by-products, and has high yield and high purity of 1,5-pentamethylene diisocyanate.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] The invention discloses a method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking. A 1,5-pentamethylene diurethane compound, tetraethylene glycol dimethyl ether and bismuth neodecanoate are mixed and then subjected to thermal cracking reaction. The obtained reaction liquid is separated and purified to obtain 1,5-pentamethylene diisocyanate.

[0009] In some embodiments, the 1,5-pentamethylenediamino formate compound is any one of 1,5-pentamethylenediamino formic acid methyl ester, 1,5-pentamethylenediamino formic acid ethyl ester and 1,5-pentamethylenediamino formic acid butyl ester or a combination thereof, preferably 1,5-pentamethylenediamino formic acid butyl ester.

[0010] In some embodiments, there is no special requirement for the amount of tetraethylene glycol dimethyl ether, as long as the raw materials are dispersed or dissolved evenly and the viscosity is moderate; preferably, the mass of the 1,5-pentamethylene diamino formate compound accounts for 5% to 20% of the mass of the tetraethylene glycol dimethyl ether.

[0011] In some embodiments, the mass of the bismuth neodecanoate accounts for 3% to 10% of the mass of the 1,5-pentamethylene diamino formate compound.

[0012] In some embodiments, preferably, the mass of the bismuth neodecanoate accounts for 3% to 9% of the mass of the 1,5-pentamethylenediaminoformate compound, more preferably 5% to 9%, and even more preferably 5% to 7%.

[0013] In some embodiments, the thermal cracking reaction has a reaction temperature of 180-260° C., a reaction time of 0.5-3 h, and a reaction pressure of 0.02-0.08 MPa.

[0014] In some embodiments, preferably, the thermal cracking reaction has a reaction temperature of 220-250°C, more preferably 230-250°C, and even more preferably 230-240°C.

[0015] In some embodiments, preferably, the thermal cracking reaction has a reaction time of 0.5 to 1.5 h.

[0016] In some embodiments, preferably, the thermal cracking reaction has a reaction pressure of 0.04 to 0.08 MPa, and more preferably 0.04 to 0.06 MPa.

[0017] In some embodiments, the thermal cracking reaction is carried out under the protection of an inert gas.

[0018] Wherein, the inert gas is any one or a combination of helium, nitrogen and argon, preferably nitrogen.

[0019] In some embodiments, a 1,5-pentamethylene dicarbamate compound and bismuth neodecanoate are mixed and preheated and then pumped into a reactor filled with tetraethylene glycol dimethyl ether for thermal cracking reaction, and the obtained reaction solution is subjected to primary purification, and then further subjected to secondary purification to obtain 1,5-pentamethylene diisocyanate;

[0020] Wherein, the reactor is purged with inert gas.

[0021] The 1,5-pentamethylene diamino formate compound and bismuth neodecanoate are mixed and preheated, and the preheating temperature is 40°C to 100°C, preferably 70°C to 90°C, and more preferably 80°C to 90°C.

[0022] Wherein, the inert gas is any one or a combination of helium, nitrogen and argon, preferably nitrogen.

[0023] The flow rate of preheating the mixture of 1,5-pentamethylene dicarbamate compound and bismuth neodecanoate and pumping it into the reactor filled with tetraethylene glycol dimethyl ether is 180 g / h to 450 g / h, preferably 200 g / h to 400 g / h, and more preferably 300 g / h to 400 g / h.

[0024] In some embodiments, during the primary purification process, the separation temperature is 140-300°C, the rotation speed is 150-500rpm, and the reaction pressure is 0.002-0.100MPa; during the secondary purification process, the separation temperature is 160-350°C, the rotation speed is 150-500rpm, and the reaction pressure is 0.002-0.100MPa; the purge flow rate of the purge inert gas is 20-300mL / min.

[0025] In some embodiments, preferably, during the primary purification process, the separation temperature is 150-170°C, and more preferably 160-170°C.

[0026] In some embodiments, preferably, during the primary purification process, the rotation speed is 200-400 rpm, more preferably 300-400 rpm, and even more preferably 350-400 rpm.

[0027] In some embodiments, preferably, during the primary purification process, the reaction pressure is 0.002-0.010 MPa, and more preferably 0.002-0.005 MPa.

[0028] In some embodiments, preferably, during the secondary purification process, the separation temperature is 160-200°C, more preferably 170-190°C, and even more preferably 180-190°C.

[0029] In some embodiments, preferably, during the secondary purification process, the rotation speed is 200-400 rpm, more preferably 300-400 rpm, and even more preferably 350-400 rpm.

[0030] In some embodiments, preferably, during the secondary purification process, the reaction pressure is 0.002-0.010 MPa, and more preferably 0.002-0.005 MPa.

[0031] In some embodiments, preferably, the purge flow rate of the purge inert gas is 50 to 300 mL / min.

[0032] Furthermore, the present invention discloses a device for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking, the device comprising a connecting pipeline, a raw material preheater, an inert gas interface, a first stirring device, a reactor, a condenser, a second stirring device, a first-stage falling film reactor, a first light component discharge port, a first heavy component discharge port, a third stirring device, a second-stage falling film reactor, a second light component discharge port and a second heavy component discharge port; the raw material preheater is connected in series with the reactor, the first-stage falling film reactor and the second-stage falling film reactor in sequence through pipelines; wherein the discharge port of the raw material preheater is connected with the feed port of the reactor through a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the reactor; the discharge port of the reactor and the feed port of the first-stage falling film reactor are connected through a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the first-stage falling film reactor; the first heavy component discharge port of the first-stage falling film reactor is connected with the feed port of the second-stage falling film reactor through a pipeline.

[0033] In some embodiments, the falling film reactor is a scraped film evaporation reactor with a built-in condenser or a roller falling film evaporation reactor with a built-in condenser. Preferably, the falling film reactor is a roller falling film evaporation reactor with a built-in condenser.

[0034] In some embodiments, the reactor is provided with an inert gas interface for inputting inert gas; and the reactor is provided with a first stirring device for stirring the material.

[0035] In some embodiments, the discharge port of the reactor and the feed port of the first-stage falling film reactor are connected by a pipeline, and a condenser is provided on the connecting pipeline for cooling the material; a second stirring device is provided in the first-stage falling film reactor for stirring the material; and the first-stage falling film reactor is provided with a first light component discharge port.

[0036] In some embodiments, the second-stage falling film reactor is provided with a third stirring device for stirring the material; the second-stage falling film reactor is provided with a second light component discharge port for outputting the product 1,5-pentamethylene diisocyanate; and the second-stage falling film reactor is provided with a second heavy component discharge port.

[0037] Specifically, the above-mentioned device is used to continuously prepare 1,5-pentamethylene diisocyanate by thermal cracking method, including the following process:

[0038] A 1,5-pentamethylene dicarbamate compound and bismuth neodecanoate are mixed and placed in a raw material preheater for preheating. After the preheating, the mixed material is pumped into a reactor and stirred for thermal cracking reaction, and the inert gas is purged from the inert gas interface in the reactor. The reaction liquid obtained after the thermal cracking reaction is pumped into a first-stage falling film reactor for primary purification, and the reaction liquid is cooled by a condenser during the pumping process. After the primary purification, the reaction liquid flows out through the first heavy component discharge port of the first-stage falling film reactor, and continues to flow into the second-stage falling film reactor for secondary purification. After the secondary purification, 1,5-pentamethylene diisocyanate flows out from the second light component discharge port of the second-stage falling film reactor. Among them, the substances flowing out of the first light component discharge port provided in the first-stage falling film reactor are mainly by-product alcohol substances, and the substances flowing out of the second heavy component discharge port of the second-stage falling film reactor are mainly residual high-boiling point solvents.

[0039] Beneficial effects:

[0040] The invention provides a device and method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking. The preparation process adopts a non-phosgene method, is green and environmentally friendly, and has little potential safety hazard. In the thermal cracking process of 1,5-pentamethylene dicarbamate, the invention adopts a new thermal cracking solvent and a new catalyst to carry out the reaction, and simultaneously adopts a continuous reaction separation coupling device, so that the reaction conditions are mild and the process is simple. The yield of 1,5-pentamethylene diisocyanate reaches more than 80%, and the purity reaches 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0042] Figure 1 This is a diagram of a reaction device for preparing 1,5-pentamethylene diisocyanate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0044] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0045] Figure 1 A diagram of a reaction device for preparing 1,5-pentamethylene diisocyanate in an embodiment of the present invention; in the diagram: 1-raw material preheater; 2-nitrogen interface; 3-first stirring device; 4-reactor; 5-condenser; 6-second stirring device; 7-first falling film reactor; 8-first light component discharge port; 9-first heavy component discharge port; 10-third stirring device; 11-second falling film reactor; 12-second light component discharge port; 13-second heavy component discharge port. The first falling film reactor and the second falling film reactor are both roller falling film evaporation reactors.

[0046] Among them, the raw material preheater 1 is connected in series with the reactor 4, the first-stage falling film reactor 7, and the second-stage falling film reactor 11 in sequence through pipelines. The discharge port of the raw material preheater 1 is connected to the feed port of the reactor 4 through a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the reactor 4; a nitrogen interface 2 is provided on the reactor 4 for inputting nitrogen; a first stirring device 3 is provided in the reactor 4 for stirring the materials. The discharge port of the reactor 4 and the feed port of the first-stage falling film reactor 7 are connected through a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the first-stage falling film reactor 7. At the same time, a condenser 5 is provided on the connecting pipeline for cooling the materials; a second stirring device 6 is provided in the first-stage falling film reactor 7 for stirring the materials; the first light component discharge port 8 of the first-stage falling film reactor 7 is used to separate by-product alcohol substances. The first heavy component discharge port 9 of the first falling film reactor 7 is connected to the feed port of the second falling film reactor 11 through a pipeline; a third stirring device 10 is provided in the second falling film reactor 11 for stirring the material; a second heavy component discharge port 13 of the second falling film reactor 11 is used to separate the residual high boiling point solvent; and a second light component discharge port 12 of the second falling film reactor 11 is used to output the product 1,5-pentamethylene diisocyanate.

[0047] Embodiment 1:

[0048] Bismuth neodecanoate and 1,5-pentamethylenediaminobutyl are mixed, placed in a raw material preheater and preheated to 70° C., wherein the bismuth neodecanoate is 3% of the mass fraction of 1,5-pentamethylenediaminobutyl. Subsequently, the mixed material was pumped into a reactor filled with tetraethylene glycol dimethyl ether at a flow rate of 200 g / h (1,5-pentamethylene dicarbamic acid butyl ester was 12% of the mass fraction of tetraethylene glycol dimethyl ether), and the reaction was carried out for 0.5 hours under the conditions of reaction temperature of 220°C, reaction pressure of 0.02 MPa, and nitrogen purge flow rate of 50 mL / min. After the reaction was completed, the reaction liquid was cooled by a condenser and pumped into a first-stage roller falling film evaporation reactor, and the first step of separation and removal of by-product alcohol was carried out under the conditions of separation temperature of 150°C, roller speed of 300 rpm and reaction pressure of 0.01 MPa; then it flowed into a second-stage roller falling film evaporation reactor, and the second step of separation and removal of residual solvent was carried out under the conditions of separation temperature of 170°C, roller speed of 300 rpm and reaction pressure of 0.01 MPa, and finally 1,5-pentamethylene diisocyanate was obtained.

[0049] Embodiment 2:

[0050] Bismuth neodecanoate and 1,5-pentamethylenediaminobutyl ester are mixed, placed in a raw material preheater and preheated to 80° C., wherein the bismuth neodecanoate is 5% of the mass fraction of 1,5-pentamethylenediaminobutyl ester. Subsequently, the mixed material was pumped into a reactor filled with tetraethylene glycol dimethyl ether at a flow rate of 300 g / h (1,5-pentamethylene diaminobutyl ester was 12% of the mass fraction of tetraethylene glycol dimethyl ether), and the reaction was carried out for 1 hour under the conditions of a reaction temperature of 230°C, a reaction pressure of 0.04 MPa, and a nitrogen purge flow rate of 100 mL / min. After the reaction was completed, the reaction liquid was cooled by a condenser and pumped into a first-stage roller falling film evaporator reactor, and the first step of separation and removal of by-product alcohol was carried out under the conditions of a separation temperature of 160°C, a roller speed of 350 rpm, and a reaction pressure of 0.005 MPa; and then the mixture was flowed into a second-stage roller falling film evaporator reactor, and the second step of separation and removal of residual solvent was carried out under the conditions of a separation temperature of 180°C, a roller speed of 350 rpm, and a reaction pressure of 0.005 MPa, to finally obtain 1,5-pentamethylene diisocyanate.

[0051] Embodiment 3:

[0052] Bismuth neodecanoate and 1,5-pentamethylenediaminobutyl are mixed, placed in a raw material preheater and preheated to 90° C., wherein the bismuth neodecanoate is 7% of the mass fraction of 1,5-pentamethylenediaminobutyl. Subsequently, the mixed material was pumped into a reactor filled with tetraethylene glycol dimethyl ether at a flow rate of 400 g / h (1,5-pentamethylene dicarbamic acid butyl ester was 12% of the mass fraction of tetraethylene glycol dimethyl ether), and the reaction was carried out for 1.5 hours under the conditions of a reaction temperature of 240°C, a reaction pressure of 0.06 MPa, and a nitrogen purge flow rate of 150 mL / min. After the reaction was completed, the reaction liquid was cooled by a condenser and pumped into a first-stage roller falling film evaporation reactor, and the first step of separation and removal of by-product alcohol was carried out under the conditions of a separation temperature of 170°C, a roller speed of 400 rpm, and a reaction pressure of 0.002 MPa; and then the mixture was flowed into a second-stage roller falling film evaporation reactor, and the second step of separation and removal of residual solvent was carried out under the conditions of a separation temperature of 190°C, a roller speed of 400 rpm, and a reaction pressure of 0.002 MPa, to finally obtain 1,5-pentamethylene diisocyanate.

[0053] Embodiment 4:

[0054] Bismuth neodecanoate and 1,5-pentamethylenediaminobutyl are mixed, placed in a raw material preheater and preheated to 90° C., wherein the bismuth neodecanoate is 9% of the mass fraction of 1,5-pentamethylenediaminobutyl. Subsequently, the mixed material was pumped into a reactor filled with tetraethylene glycol dimethyl ether at a flow rate of 350 g / h (1,5-pentamethylene dicarbamic acid butyl ester was 12% of the mass fraction of tetraethylene glycol dimethyl ether), and the reaction was carried out for 1 hour under the conditions of a reaction temperature of 250°C, a reaction pressure of 0.08 MPa, and a nitrogen purge flow rate of 200 mL / min. After the reaction was completed, the reaction liquid was cooled by a condenser and pumped into a first-stage roller falling film evaporation reactor, and the first step of separation and removal of by-product alcohol was carried out under the conditions of a separation temperature of 160°C, a roller speed of 350 rpm, and a reaction pressure of 0.005 MPa; and then the mixture was flowed into a second-stage roller falling film evaporation reactor, and the second step of separation and removal of residual solvent was carried out under the conditions of a separation temperature of 180°C, a roller speed of 350 rpm, and a reaction pressure of 0.005 MPa, to finally obtain 1,5-pentamethylene diisocyanate.

[0055] Embodiment 5:

[0056] Bismuth neodecanoate and 1,5-pentamethylenediaminobutyl are mixed, placed in a raw material preheater and preheated to 90° C., wherein the bismuth neodecanoate is 9% of the mass fraction of 1,5-pentamethylenediaminobutyl. Subsequently, the mixed material was pumped into a reactor filled with tetraethylene glycol dimethyl ether at a flow rate of 350 g / h (1,5-pentamethylene diaminobutyl ester was 12% of the mass fraction of tetraethylene glycol dimethyl ether), and the reaction was carried out for 1 hour under the conditions of a reaction temperature of 250°C, a reaction pressure of 0.08 MPa, and a nitrogen purge flow rate of 300 mL / min. After the reaction was completed, the reaction liquid was cooled by a condenser and pumped into a first-stage roller falling film evaporation reactor, and the first step of separation and removal of by-product alcohol was carried out under the conditions of a separation temperature of 170°C, a roller speed of 400 rpm, and a reaction pressure of 0.002 MPa; and then the mixture was flowed into a second-stage roller falling film evaporation reactor, and the second step of separation and removal of residual solvent was carried out under the conditions of a separation temperature of 190°C, a roller speed of 400 rpm, and a reaction pressure of 0.002 MPa, to finally obtain 1,5-pentamethylene diisocyanate.

[0057] Comparative Example 1:

[0058] This comparative example provides a thermal cracking preparation method and process of 1,5-pentamethylene diisocyanate, which is the same as Example 2 except that the solvent is replaced by dibutyl sebacate.

[0059] Comparative Example 2:

[0060] This comparative example provides a thermal cracking preparation method and process of 1,5-pentamethylene diisocyanate, which is the same as Example 2 except that the solvent is replaced by dioctyl azelate.

[0061] Comparative Example 3:

[0062] This comparative example provides a thermal cracking preparation method and process of 1,5-pentamethylene diisocyanate, which is the same as Example 2 except that the solvent is replaced by dioctyl phthalate.

[0063] Comparative Example 4:

[0064] This comparative example provides a thermal cracking preparation method and process of 1,5-pentamethylene diisocyanate, which is the same as Example 2 except that the solvent is replaced by p-xylene.

[0065] Comparative Example 5:

[0066] This comparative example provides a method and process for preparing 1,5-pentamethylene diisocyanate by thermal cracking. The method is the same as Example 2 except that the catalyst is replaced by zinc acetate.

[0067] Comparative Example 6:

[0068] This comparative example provides a method and process for preparing 1,5-pentamethylene diisocyanate by thermal cracking. The method is the same as Example 2 except that the catalyst is replaced by zinc oxide.

[0069] Comparative Example 7:

[0070] This comparative example provides a method and process for preparing 1,5-pentamethylene diisocyanate by thermal cracking. The method is the same as Example 2 except that the catalyst is replaced by ferric oxide.

[0071] Comparative Example 8:

[0072] This comparative example provides a method and process for preparing 1,5-pentamethylene diisocyanate by thermal cracking. The method is the same as Example 2 except that the catalyst is replaced by bismuth trioxide.

[0073] Comparative Example 9:

[0074] This comparative example provides a thermal cracking preparation method and process of 1,5-pentamethylene diisocyanate. The method is the same as Example 2, except that the reaction liquid obtained by the reaction in the reactor is not separated and purified by a two-stage roller falling film evaporation reactor to directly obtain 1,5-pentamethylene diisocyanate.

[0075] The mass of 1,5-pentamethylene diisocyanate after the reaction in Example 1-5 and Comparative Example 1-9 was measured, and the mass yield and purity of 1,5-pentamethylene diisocyanate were calculated. The results are shown in Table 1.

[0076] Purity detection method of 1,5-pentamethylene diisocyanate: The product was analyzed by an Agilent 7890B gas chromatograph equipped with an Agilent DB-17 (30m×0.32mm×0.25μm) capillary column and a flame ionization detector (FID). The injection temperature and detector temperature were 280°C and 300°C, respectively. The temperature program of GC analysis was maintained at 120°C for 5 minutes, from 120°C to 300°C at 20°C / min, and then maintained at 300°C for 5 minutes. Nitrogen and tetradecane were used as carrier gas and internal standard for quantitative analysis, respectively.

[0077] Table 1 Mass yield and purity of 1,5-pentamethylene diisocyanate in different embodiments and comparative examples

[0078]

[0079]

[0080] The following conclusions can be drawn from Table 1:

[0081] (1) It can be seen from Examples 1-5 that after optimizing the reaction process, in the method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking provided by the present invention, the mass yield of 1,5-pentamethylene diisocyanate can reach 83.7% and the purity can reach 99.6%;

[0082] (2) Combining Example 2 with Comparative Examples 1-4, it can be seen that the solvent used in Example 2 is tetraethylene glycol dimethyl ether, compared with the solvents used in Comparative Examples 1-4, which are dibutyl sebacate, dioctyl azelate, dioctyl phthalate and p-xylene, respectively. The mass yield of 1,5-pentamethylene diisocyanate in Example 2 is 83.7%, while the mass yields of 1,5-pentamethylene diisocyanate in Comparative Examples 1-4 are 67.1%, 63.5%, 54.8% and 61.5%, respectively, which are far less than the mass yield of Example 2; thus, it is shown that when tetraethylene glycol dimethyl ether is preferably used as the solvent in the present invention, the mass yield of the prepared 1,5-pentamethylene diisocyanate is higher;

[0083] (3) It can be seen from comparative examples 6-8 that comparative example 8 uses bismuth trioxide as a catalyst for the reaction. Compared with comparative examples 6 and 7, which use zinc oxide and ferric oxide as catalysts for the reaction, respectively, the mass yield of 1,5-pentamethylene diisocyanate prepared in comparative example 8 is greater than that in comparative examples 6 and 7; this indicates that the catalyst containing metallic bismuth in the present invention has a higher catalytic efficiency;

[0084] (4) It can be seen from Example 2 and Comparative Examples 5-8 that the catalyst used in Example 2 is bismuth neodecanoate, which is higher than the catalysts used in Comparative Examples 5-8, namely zinc acetate, zinc oxide, ferric oxide and bismuth trioxide. The mass yield of 1,5-pentamethylene diisocyanate in Example 2 is higher; thus, it is shown that when bismuth neodecanoate is preferably used as the catalyst in the present invention, the catalytic activity is high and the mass yield of 1,5-pentamethylene diisocyanate can be greatly improved.

[0085] In summary, in the method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking provided by the present invention, tetraethylene glycol dimethyl ether is used as a solvent and bismuth neodecanoate is used as a catalyst, which has a high catalytic efficiency for the thermal cracking system and achieves a high yield of 1,5-pentamethylene diisocyanate. At the same time, a continuous reaction separation coupling device is used to obtain high-purity 1,5-pentamethylene diisocyanate. The reaction conditions are mild, the process is simple, and the method has good prospects for industrial application.

[0086] The present invention provides a device and method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking, characterized in that: The 1,5-pentamethylene dicarbamate compound, tetraethylene glycol dimethyl ether and bismuth neodecanoate are mixed and subjected to thermal cracking reaction, and the obtained reaction liquid is separated and purified to obtain 1,5-pentamethylene diisocyanate.

2. The method according to claim 1, characterized in that The 1,5-pentamethylenediamino formic acid ester compound is any one of 1,5-pentamethylenediamino formic acid methyl ester, 1,5-pentamethylenediamino formic acid ethyl ester and 1,5-pentamethylenediamino formic acid butyl ester or a combination of several thereof.

3. The method according to claim 1, characterized in that The mass of the bismuth neodecanoate accounts for 3% to 10% of the mass of the 1,5-pentamethylene diamino formate compound.

4. The method according to claim 1, characterized in that: The thermal cracking reaction has a reaction temperature of 180-260° C., a reaction time of 0.5-3 h, and a reaction pressure of 0.02-0.08 MPa.

5. The method according to claim 1, characterized in that The thermal cracking reaction is carried out under the protection of inert gas.

6. The method according to claim 1, characterized in that The 1,5-pentamethylene dicarbamate compound and bismuth neodecanoate are mixed and preheated, and then pumped into a reactor filled with tetraethylene glycol dimethyl ether for thermal cracking reaction, and the obtained reaction solution is subjected to primary purification, and then further subjected to secondary purification to obtain 1,5-pentamethylene diisocyanate; Wherein, the reactor is purged with inert gas.

7. The method according to claim 1, characterized in that During the primary purification process, the separation temperature is 140-300°C, the rotation speed is 150-500rpm, and the reaction pressure is 0.002-0.100MPa; during the secondary purification process, the separation temperature is 160-350°C, the rotation speed is 150-500rpm, and the reaction pressure is 0.002-0.100MPa; the purge flow rate of the purge inert gas is 20-300mL / min.

8. A device for continuously preparing 1,5-pentamethylene diisocyanate by thermal cracking, characterized in that: The device comprises a connecting pipeline, a raw material preheater (1), an inert gas interface (2), a first stirring device (3), a reactor (4), a condenser (5), a second stirring device (6), a first falling film reactor (7), a first light component discharge port (8), a first heavy component discharge port (9), a third stirring device (10), a second falling film reactor (11), a second light component discharge port (12) and a second heavy component discharge port (13); the raw material preheater (1) and the reactor (4), the first falling film reactor (7), the second falling film reactor (11), the second light component discharge port (12) and the second heavy component discharge port (13) are connected. The reactors (11) are connected in series via pipelines; wherein the discharge port of the raw material preheater (1) is connected to the feed port of the reactor (4) via a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the reactor (4); the discharge port of the reactor (4) is connected to the feed port of the first-stage falling film reactor (7) via a pipeline, and a feed pump is provided on the connecting pipeline for conveying materials into the first-stage falling film reactor (7); the first heavy component discharge port (9) of the first-stage falling film reactor (7) is connected to the feed port of the second-stage falling film reactor (11) via a pipeline.

9. The device according to claim 8, characterized in that The falling film reactor is a scraped film evaporation reactor with a built-in condenser or a roller falling film evaporation reactor with a built-in condenser. Preferably, the falling film reactor is a roller falling film evaporation reactor with a built-in condenser.

10. The device according to claim 8, characterized in that The reactor (4) is provided with an inert gas interface (2) for inputting inert gas; the reactor (4) is provided with a first stirring device (3) for stirring the material; The discharge port of the reaction kettle (4) and the feed port of the first-stage falling film reactor (7) are connected via a pipeline, and a condenser (5) is provided on the connecting pipeline for cooling the material; a second stirring device (6) is provided in the first-stage falling film reactor (7) for stirring the material; and the first-stage falling film reactor (7) is provided with a first light component discharge port (8); The second-stage falling film reactor (11) is provided with a third stirring device (10) for stirring the material; the second-stage falling film reactor (11) is provided with a second light component discharge port (12) for outputting the product 1,5-pentamethylene diisocyanate; and the second-stage falling film reactor (11) is provided with a second heavy component discharge port (13).

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