METHOD FOR THE SYNTHESIS OF AN OXETEAN COMPOUND BY A MICROREACTOR

Description

TECHNICAL FIELD

[0001] The invention relates to the field of organic synthesis, in particular to a method for synthesizing an oxetane compound by a microreactor.BACKGROUND

[0002] 3-Ethyl-3-hydroxymethyloxetane and bis[1-ethyl(3-oxetanyl)methyl]ether are the most widely used monomers in the photocurable cationic system and are extensively applied in the fields of photocurable coatings, inks, adhesives, and the like. Their structural formulas are as follows:

[0003] The cyclocarbonate cracking method is commonly used in industry to prepare oxetane products. For example, the reaction process for producing 3-ethyl-3-hydroxymethyloxetane by the cyclocarbonate cracking method is as follows:

[0004] In the formula, R is alkyl, generally methyl or ethyl.

[0005] The process is as follows: trimethylolpropane and carbonate ester are subjected to the transesterification reaction in a rectifying still at a temperature of 80°C to 120°C, the alcohol as by-product is continuously fractionated out during the reaction, the excess carbonate ester is removed by distillation after the reaction has been completed, and the transesterification procedure takes 10 h to 12 h; then the cracking procedure is started, wherein the cracking is conducted at a temperature of 160°C to 200°C for 12 h to 15 h to remove carbon dioxide and the finished product is finally obtained by rectification under negative pressure. The whole process takes 30 h to 40 h to complete, and the production efficiency is relatively low. The cracking reaction is conducted at high temperature for a long time, which will lead to the production of high-boiling by-products, so the yield of the finished product is low (65% to 75%), and a large amount of distillation residues will be generated after the completion of rectification, which can only be disposed as solid wastes.

[0006] JP H 1112261A relates to a method for producing oxetanes from a triol compound (for example, 1,1,1-trimethylolalkane) and a carbonate by reacting the triol compound with dimethyl carbonate in the presence of a catalyst while removing methanol as a by-product to form a cyclic carbonate and then decarboxylating the carbonate. Oxetanes are compounds that are useful as materials for photocationically curable resins.

[0007] JP 4,604,531 B2 relates to a process for producing cyclic carbonates and oxetanes from a triol compound such as 1,1,1-trimethylolalkane and dimethyl carbonate. In the preparation method of the cyclic carbonates, the triol compound is reacted with the dimethyl carbonate while selectively removing by-product methanol by a gas permeation membrane. In the preparation method of the oxetanes, the cyclic carbonates are prepared through the above-mentioned preparation method, and the cyclic carbonates are subsequently subjected to decarbonation.

[0008] JP 3,840,695 B2 relates to production of hydroxy-bearing oxetane compound. First, a reaction is carried out between (A) a triol compound and (B) a 2-4C alkyl or 2-4C alkylene carbonate compound to form (C) a cyclic carbonate compound. Subsequently, the compound C is decarboxylated in the presence of a basic catalyst to obtain the objective hydroxy-bearing oxetane compound.

[0009] US 5,721,020 A relates to an ultraviolet-curing coating composition for cans, capable of forming a coating film which can be cured by irradiation with ultraviolet rays and which, when cured, is superior in processability, adhesivity, hardness, mar resistance, etc. and particularly in appearance and retort resistance; and a process for producing a coated metal can by using the above composition. The ultraviolet-curing coating composition for cans comprises: (A) a cation-polymerizable compound, (B) a compound having at least one oxetane ring in the molecule, (C) a cationic initiator which generates a cation when irradiated with ultraviolet rays, and (D) a lubricity-imparting agent.

[0010] It is described in "Review of the applications of microreactors" , Xingjun YAO ET AL, RENEWABLE ANO SUSTAINABLE ENERGY REVIEWS, vol. 47, 30 March 2015 (2015-03-30), pages 519-539 that micro-reactors offer excellent mass and heat transfer performance for extraction and multiphase reactions. They provide a powerful tool for process intensification and micro scale processing. This paper reviews the structures of micro-reactors and units, and their applications on the synthesis of nanoparticles, organics, polymers and bio-substances. The structural evolution and properties of the commercialized and lab-made micro-structured reactors are introduced in detail. Recent developments of the fabrication, structures, and applications of micro-structured reactors are highlighted. The promising direction in micro-reaction technology is also discussed. In view of the existence of the above problems, it is necessary to provide a method for synthesizing an oxetane compound with relatively high yield and short reaction time.SUMMARY

[0011] A main object of the invention is to provide a method for synthesizing an oxetane compound by a microreactor, so as to solve the problems present in the existing synthesis methods for oxetane compounds such as low yield and long reaction time. In view of this, the invention further provides a method for adjusting the product distribution by controlling relevant parameters in the reaction process, to realize the co-production of three oxetane compounds.

[0012] In order to achieve the above object, the invention provides a method for synthesizing an oxetane compound by a microreactor, including feeding trimethylolpropane and a carbonate ester into a microreactor in the presence of a basic catalyst, and synthesizing the oxetane compound under solvent or solvent-free condition through a microreaction continuous flow process.

[0013] The basic catalyst comprises a first basic catalyst and a second basic catalyst, and the method for synthesizing an oxetane compound by a microreactor includes: continuously feeding the first basic catalyst, trimethylolpropane, and carbonate ester into a first microreactor for transesterification reaction, to obtain a reaction product system containing an esterified intermediate; extracting the esterified intermediate from the reaction product system containing the esterified intermediate; feeding the esterified intermediate and the second basic catalyst into a second microreactor for cracking reaction, to obtain a cracked reaction product system; and subjecting the cracked reaction product system to gas-liquid separation treatment, to obtain the oxetane compound.

[0014] Further, the solvent is one or more of the group consisting of halogenated hydrocarbons, benzene, toluene, xylene, nitrobenzene, and acetonitrile.

[0015] Further, the temperature of the first microreactor is 50 to 300°C, the residence time of the first microreactor is 1 to 60 min; and the reaction temperature of the second microreactor is 150 to 400°C, and the residence time of the second microreactor is 1 to 8 min.

[0016] Further, the temperature of the first microreactor is 100 to 200°C; and the reaction temperature of the second microreactor is 200 to 300°C.

[0017] Further, the molar ratio of trimethylolpropane to carbonate ester is 1:(1 to 5), and the content of the basic catalyst is 100 ppm to 50,000 ppm.

[0018] Further, the molar ratio of trimethylolpropane to carbonate ester is 1:(1.5 to 3), and the content of the basic catalyst is 100 ppm to 10,000 ppm.

[0019] Further, the carbonate ester is selected from one or more of the group consisting of dimethyl carbonate, diethyl carbonate, and dipropyl carbonate; and the basic catalyst is selected from one or more of alkali metal hydroxides, sodium alkoxides, potassium alkoxides, or alkali metal carbonates.

[0020] Further, the first basic catalyst and the second basic catalyst are independently selected from one or more of alkali metal hydroxides, sodium alkoxides, potassium alkoxides, or alkali metal carbonates, respectively; preferably, the first basic catalyst and the second basic catalyst are independently selected from one or more of the group consisting of sodium methoxide, sodium ethoxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate, respectively; preferably, the amount of the first basic catalyst is 200 to 500 ppm, and the amount of the second basic catalyst is 300 to 3,000 ppm.

[0021] Further, in the process of the cracking reaction, the synthesis method further includes: adding water to the esterified intermediate, and the water content of the system in the process of the cracking reaction is 10 to 100,000 ppm.

[0022] The first microreactor has a reaction channel having an inner diameter selected from 200 to 10,000 µm, and the second microreactor has a reaction channel having an inner diameter independently selected from 200 to 10,000 µm respectively; preferably, the first microreactor has a reaction channel having an inner diameter selected from 200 to 2,000 µm, and the second microreactor has a reaction channel having an inner diameter selected from 500 to 10,000 µm.

[0023] Further, the device used in the extraction process is selected from a thin-film evaporator or a rectification tower.

[0024] By applying the technical solution of the invention, the microreactor has the advantages such as high heat and mass transfer coefficient, good mixing performance, easy temperature control, and safe and controllable process as compared to conventional reactors. Making use of the advantages of the microreactor to produce the above three oxetane products can greatly improve the mass and heat transfer performances of the reaction system, reduce the reaction time, improve the production efficiency, especially avoid the long-term high temperature process in the cracking procedure and reduce the production of high-boiling by-products, improve the yield, realize the process continuity and automation, and improve the process safety. In addition, the above synthesis process requires small size for reaction device, small floor space for production site, and less human resources, and has high safety.DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawing as a part of the subject application is used to provide further understandings on the invention. The exemplary embodiments and their descriptions in the invention are used to explain the invention and do not serve as improper limitations to the invention. In the accompanying drawing: FIG. 1 shows a schematic diagram for the structure of a synthesis device for oxetane compound provided according to a typical embodiment of invention.

[0026] The above drawing includes the following reference signs: 10. Raw material storage tank; 11. First feeding pump; 20. First microreactor; 30. Thin-film evaporator; 40. Esterified intermediate storage tank; 41. Second feeding pump; 50. Light end collection tank ; 60. Second microreactor; 70. Micro heat exchanger; 80. Gas-liquid separation tank; 90. Rectification device.DESCRIPTION OF EMBODIMENTS

[0027] It should be noted that, in the case of no conflict, the embodiments in the subject application as well as the features therein can be combined with each other. The invention will be described in detail below with reference to the embodiments.

[0028] As described in the background, the existing synthesis methods for oxetane compounds have problems such as low yield and long reaction time. In order to solve the above technical problems, the invention provides a method for synthesizing an oxetane compound by a microreactor, including: feeding trimethylolpropane and a carbonate ester into a microreactor in the presence of a basic catalyst, and synthesizing the oxetane compound under inert solvent or solvent-free condition through a microreaction continuous flow process.

[0029] The microreactor has the advantages such as high heat and mass transfer coefficient, good mixing performance, easy temperature control, and safe and controllable process as compared to conventional reactors. Making use of the advantages of the microreactor to produce the above three oxetane products can greatly improve the mass and heat transfer performances of the reaction system, reduce the reaction time, improve the production efficiency, especially avoid the long-term high temperature process in the cracking procedure and reduce the production of high-boiling by-products, improve the yield, realize the process continuity and automation, and improve the process safety. In addition, the above synthesis process requires small size for reaction device, small floor space for production site, and less human resources, and has high safety.

[0030] The basic catalyst comprises a first basic catalyst and a second basic catalyst, and the method for synthesizing an oxetane compound by a microreactor includes: continuously feeding the first basic catalyst, trimethylolpropane, and carbonate ester into a first microreactor for transesterification reaction, to obtain a reaction product system containing an esterified intermediate; extracting the esterified intermediate from the reaction product system containing the esterified intermediate; feeding the esterified intermediate and the second basic catalyst into a second microreactor for cracking reaction, to obtain a cracked reaction product system; and subjecting the cracked reaction product system to gas-liquid separation treatment, to obtain the oxetane compound.

[0031] After the above gas-liquid separation, the resulting product is a mixture, which can be further separated by those skilled in the art as required. The separation method includes but is not limited to distillation.

[0032] The solvent used in the above synthesis method can be selected from those commonly used in the art. In a preferred embodiment, the solvent includes but is not limited to one or more of the group consisting of halogenated hydrocarbons, benzene, toluene, xylene, nitrobenzene, and acetonitrile. Under comprehensive consideration of cost factors, the solvent-free condition is preferred.

[0033] In a preferred embodiment, the temperature of the first microreactor is 50 to 300°C, the residence time of the first microreactor is 1 to 60 min; and the reaction temperature of the second microreactor is 150 to 400°C, and the residence time of the second microreactor is 1 to 8 min. Compared with the uncontrollability of the product composition in the conventional process, limiting the process conditions of the transesterification reaction and the cracking reaction to the above ranges in the subject application can improve the total yield of oxetane products. At the same time, the method of the subject application can also control the distribution of different products, realize the co-production of three oxetane compounds, and improve the economic values. For example, the temperature of the first microreactor can be 50°C, 80°C, 100°C, 160°C, 200°C, or 300°C; and the reaction temperature of the second microreactor can be 150°C, 200°C, 260°C, 300°C, or 400°C.

[0034] In a preferred embodiment, the temperature of the first microreactor is 100 to 200°C; and the reaction temperature of the second microreactor is 200 to 300°C. The temperature of the first microreactor and the temperature of the second microreactor include but are not limited to the above ranges, while limiting them to the above ranges is beneficial to further improving the yield of target product and shortening the reaction time.

[0035] In a preferred embodiment, in the process of transesterification reaction, the molar ratio of trimethylolpropane to carbonate ester is 1:(1 to 5), and the content of the basic catalyst is 100 ppm to 50,000 ppm. The amounts of trimethylolpropane, carbonate ester, and basic catalyst include but are not limited to the above ranges, while limiting them to the above ranges is beneficial to further improving the conversion rate of reaction raw materials. More preferably, the molar ratio of trimethylolpropane to carbonate ester is 1:(1.5 to 3), and the content of the basic catalyst is 100 ppm to 10,000 ppm.

[0036] In the above synthesis method, the carbonate ester and the basic catalyst can be selected from those commonly used in the art. In a preferred embodiment, the carbonate ester includes but is not limited to one or more of the group consisting of dimethyl carbonate, diethyl carbonate, and dipropyl carbonate.

[0037] In a preferred embodiment, the first basic catalyst and the second basic catalyst are independently selected from one or more of hydroxides formed by alkali metals, sodium alkoxides, potassium alkoxides, and carbonates formed by alkali metals, respectively. More preferably, the first basic catalyst and the second basic catalyst are independently selected from one or more of the group consisting of sodium methoxide, sodium ethoxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate.

[0038] In order to further improve the catalytic effect and shorten the reaction time, further preferably, the first basic catalyst and the second basic catalyst are independently selected from one or more of sodium methoxide, sodium ethoxide, sodium hydroxide, or potassium hydroxide, respectively; and the amount of the first basic catalyst is 200 to 500 ppm, and the amount of the second basic catalyst is 300 to 3,000 ppm.

[0039] In a preferred embodiment, in the process of the cracking reaction, the above synthesis method further includes: adding water to the esterified intermediate, and the water content of the system in the process of the cracking reaction is 10 to 100,000 ppm. Compared with other ranges, limiting the water content of the system in the process of the cracking reaction to the above range is beneficial to improving the cracking rate of the esterified intermediate, thereby contributing to the yield of the oxetane compound.

[0040] The first microreactor has a reaction channel having an inner diameter selected from 200 to 10,000 µm, and the second microreactor has a reaction channel having an inner diameter selected from 200 to 10,000 µm. Compared with other ranges, limiting the reaction channel of the first microreactor and the reaction channel of the second microreactor to the above ranges is beneficial to improving the yield of the target product. For example, the first microreactor can have a reaction channel having an inner diameter selected from 200 µm, 500 µm, 1,000 µm, 5,000 µm, or 10,000 µm, and the second microreactor can have a reaction channel having an inner diameter selected from 200 µm, 500 µm, 1,000 µm, 8,000 µm, or 10,000 µm. More preferably, the first microreactor has a reaction channel having an inner diameter selected from 200 to 2,000 µm, and the second microreactor has a reaction channel having an inner diameter selected from 500 to 10,000 µm.

[0041] In order to further improve the purity of the target product and reduce the energy loss of the synthesis method, preferably, the above synthesis method further includes subjecting the cracked reaction product system to heat exchange in a micro heat exchanger, removing carbon dioxide through a gas-liquid separation device, and then rectificating it, to obtain the desired product.

[0042] The subject application is further described in detail below with reference to specific examples, which cannot be understood as limiting the claimed scope in the subject application.

[0043] The microchannel device system used in Examples 1 to 5 was provided by Shanghai Timo Fluid Technology Co., Ltd. (model: Shanghai Timo TMP / S3047-32-3 / A2000), wherein the first microreactor had a reaction channel having an inner diameter of 1,000 µm, and the second microreactor had a reaction channel having an inner diameter of 8,000 µm.

[0044] In the examples, the device shown in FIG. 1 was used to prepare the oxetane compound, and the synthesis method included the following steps: Transesterification section: trimethylolpropane (TMP) and dimethyl carbonate (DMC) were mixed at a certain molar ratio, and a stoichiometric amount of a basic catalyst was added based on the weight of TMP, mixed well, and placed in the raw material storage tank 10 to be preheated; the mixture was fed through the first feeding pump 11 into the first microreactor 20 for transesterification reaction, and remained for certain time, to obtain a reaction product system containing an esterified intermediate; methanol and remaining DMC were removed from the above reaction product system containing an esterified intermediate in the thin-film evaporator 30, the recovered raw materials were placed in the light end collection tank 50, and the esterified intermediate was stored in the esterified intermediate storage tank 40.

[0045] Cracking section: a basic catalyst was added into the esterified intermediate, and an appropriate amount of water was selectively added and mixed well; then the mixture was fed through the second feeding pump 41 into the second microreactor 60 and remained for certain time to carry out the cracking reaction; after having been cooled through the micro heat exchanger 70, it was fed into the gas-liquid separation tank 80 to remove carbon dioxide, to obtain a crude product;

[0046] Product separation: the crude product was fed to the rectification device 90 for rectification separation, to obtain the corresponding product.

[0047] The process parameters in Examples 1 to 5 were shown in Table 1. Table 1SectionParameterExample 1Example 2Example 3Example 4Example 5TransesterificationWeight of TMP, g402.0402.0402.0402.0402.0n (TMP):n (DMC)1:1.51:31:31:2.251:2.25Content of catalyst (NaOH), ppm300300300300300Flow rate for the first feeding pump, mL / min10.315.515.512.412.4Reaction temperature, °C100120120120120Residence time, min1215151313Cracking ReactionWater content, ppm30,00080808080Content of catalyst (KOH), ppm3003,0003003003,000Flow rate for the second feeding pump, mL / min8.28.68.68.38.3Cracking temperature, °C300300260260300Pressure, MPa3.0 to 3.53.0 to 3.53.0 to 3.53.0 to 3.53.0 to 3.5Residence time, min68116Product SeparationTotal yield, %92.393.496.195.794.0Product proportion (%) A:B:C96.4:0.8:2.86.1:92.8:1.12.5:5.6:91.956.3:1.4:42.358.4:40.9:0.7

[0048] The products in Table 1 have the following structures: Product A: 3-ethyl-3-hydroxymethyloxetane Product B: bis[1-ethyl(3-oxetanyl)methyl]ether Product C: bis[1-ethyl(3-oxetanyl)methyl] carbonate Example 6

[0049] It differed from Example 1 in that: the reaction temperature of the transesterification reaction was 80°C, and the temperature of the cracking reaction was 300°C.

[0050] The total yield of products was 83.4%, wherein the proportions (%) of products A, B, and C were 95.7%, 1.2%, and 3.1%, respectively.Example 7

[0051] It differed from Example 1 in that: the reaction temperature of the transesterification reaction was 160°C, and the temperature of the cracking reaction was 260°C.

[0052] The total yield of products was 90.8%, wherein the proportions (%) of products A, B, and C were 92.0%, 4.6%, and 3.4%, respectively.Example 8

[0053] It differed from Example 1 in that: the molar ratio of trimethylolpropane to carbonate ester was 1:1, and the content of the basic catalyst in the transesterification reaction was 800 ppm.

[0054] The total yield of products was 80.7%, wherein the proportions (%) of products A, B, and C were 94.5%, 3.3%, and 2.2%, respectively.Example 9

[0055] It differed from Example 1 in that: the molar ratio of trimethylolpropane to carbonate ester was 5:1, and the content of the basic catalyst in the transesterification reaction was 100 ppm.

[0056] The total yield of products was 84.7%, wherein the proportions (%) of products A, B, and C were 95.1%, 2.9%, and 2.0%, respectively.Example 10

[0057] It differed from Example 1 in that: the reaction temperature of the transesterification reaction was 50°C, the residence time of the transesterification reaction was 60 min, and the temperature of the cracking reaction was 400°C.

[0058] The total yield of products was 85.7%, wherein the proportions (%) of products A, B, and C were 98.3%, 1.3%, and 0.4%, respectively.Example 11

[0059] It differed from Example 1 in that: the reaction temperature of the transesterification reaction was 300°C, the residence time of the transesterification reaction was 1 min, and the temperature of the cracking reaction was 200°C.

[0060] The total yield of products was 86.2%, wherein the proportions (%) of products A, B, and C were 39.5%, 46.9%, and 13.6%, respectively.Example 12

[0061] It differed from Example 1 in that: the reaction temperature of the transesterification reaction was 200°C, the residence time of the transesterification reaction was 30 min, and the temperature of the cracking reaction was 150°C.

[0062] The total yield of products was 96.8%, wherein the proportions (%) of products A, B, and C were 29.3%, 50.1%, and 20.6%, respectively.Example 13

[0063] It differed from Example 1 in that: the content of the basic catalyst in the transesterification reaction was 50,000 ppm.

[0064] The total yield of products was 91.3%, wherein the proportions (%) of products A, B, and C were 95.2%, 2.0%, and 2.8%, respectively.Example 14

[0065] It differed from Example 1 in that: the content of the basic catalyst in the transesterification reaction was 10,000 ppm.

[0066] The total yield of products was 93.4%, wherein the proportions (%) of products A, B, and C were 96.8%, 1.2%, and 2.0%, respectively.Example 15

[0067] It differed from Example 1 in that: the content of the basic catalyst in the transesterification reaction was 30,000 ppm.

[0068] The total yield of products was 91.8%, wherein the proportions (%) of products A, B, and C were 95.3%, 1.6%, and 3.1%, respectively.Example 16

[0069] It differed from Example 1 in that: the content of the basic catalyst in the transesterification reaction was 8,000 ppm.

[0070] The total yield of products was 93.1%, wherein the proportions (%) of products A, B, and C were 96.0%, 1.8%, and 2.2%, respectively.Example 17

[0071] It differed from Example 1 in that: the content of the basic catalyst in the transesterification reaction was 5,000 ppm.

[0072] The total yield of products was 92.8%, wherein the proportions (%) of products A, B, and C were 96.2%, 1.9%, and 2.3%, respectively.Example 18

[0073] It differed from Example 1 in that: the first microreactor had a reaction channel having an inner diameter of 100 µm, and the second microreactor had a reaction channel having an inner diameter of 100 µm.

[0074] The total yield of products was 81.3%, wherein the proportions (%) of products A, B, and C were 95.6%, 1.0%, and 3.4%, respectively.Example 19

[0075] It differed from Example 1 in that: the first microreactor had a reaction channel having an inner diameter of 10,000 µm, and the second microreactor had a reaction channel having an inner diameter of 10,000 µm.

[0076] The total yield of products was 91.8%, wherein the proportions (%) of products A, B, and C were 95.5%, 2.0%, and 2.5%, respectively.Example 20

[0077] It differed from Example 1 in that: the first microreactor had a reaction channel having an inner diameter of 200 µm, and the second microreactor had a reaction channel having an inner diameter of 200 µm.

[0078] The total yield of products was 90.7%, wherein the proportions (%) of products A, B, and C were 94.9%, 2.1%, and 3.0%, respectively.Example 21

[0079] It differed from Example 1 in that: the catalyst in the cracking reaction was sodium methoxide and the content thereof was 1,000 ppm, and the water content of the cracking reaction was 100,000 ppm.

[0080] The total yield of products was 93.5%, wherein the proportions (%) of products A, B, and C were 97.2%, 2.0%, and 0.8%, respectively.Example 22

[0081] It differed from Example 1 in that: the catalyst in the transesterification reaction was sodium methoxide and the content thereof was 10,000 ppm, the catalyst in the cracking reaction was sodium methoxide and the content thereof was 1,000 ppm, and the water content of the cracking reaction was 100,000 ppm.

[0082] The total yield of products was 95.8%, wherein the proportions (%) of products A, B, and C were 97.5%, 1.9%, and 0.6%, respectively.Example 23

[0083] It differed from Example 1 in that: the catalyst in the transesterification reaction was sodium methoxide and the content thereof was 10,000 ppm, the catalyst in the cracking reaction was sodium methoxide and the content thereof was 300 ppm, and the water content of the cracking reaction was 10 ppm.

[0084] The total yield of products was 96.5%, wherein the proportions (%) of products A, B, and C were 3.5%, 94.6%, and 1.9%, respectively.Example 24

[0085] It differed from Example 1 in that: the temperature of the cracking reaction was 100°C.

[0086] The total yield of products was 66.8%, wherein the proportions (%) of products A, B, and C were 3.9%, 1.7%, and 94.4%, respectively.Example 25

[0087] It differed from Example 1 in that: the temperature of the cracking reaction was 450°C.

[0088] The total yield of products was 82.9%, wherein the proportions (%) of products A, B, and C were 43.4%, 56.5%, and 0.1%, respectively.Example 26

[0089] It differed from Example 1 in that: the temperature for transesterification was 30°C.

[0090] The total yield of products was 78.6%, wherein the proportions (%) of products A, B, and C were 94.1%, 2.4%, and 3.5%, respectively.Example 27

[0091] It differed from Example 1 in that: the temperature for transesterification was 350°C.

[0092] The total yield of products was 79.0%, wherein the proportions (%) of products A, B, and C were 94.5%, 2.6%, and 2.9%, respectively.

[0093] In the Comparative Examples, a conventional reaction device was used to prepare the oxetane compound, and the synthesis method included the following steps: (1) Transesterification section: TMP, DMC, and toluene were charged into a stainless steel stirred tank with rectification tower and condenser, stirred and mixed well, then a catalyst was added; the mixture was heated for reaction; the generated methanol was collected at the top of the tower, until there was no methanol distilled out from the top of the tower; it was continued to be distilled by heating to remove the solvent toluene and remaining DMC, to obtain an esterified intermediate; (2) Cracking section: a basic catalyst was added and an appropriate amount of water was selectively added for cracking at a certain temperature and under negative pressure while distilling, to obtain a product.

[0094] The process parameters in Comparative Examples 1 to 5 were shown in Table 2. Table 2SectionParameterComparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5TransesterificationTMP, g402.0402.0402.0402.0402.0Toluene, g300.0300.0300.0300.0300.0n (TMP):n (DMC)1:1.51:31:31:2.251:2.25Content of catalyst (NaOH), ppm300300300300300Reaction temperature, °C80 to 12080 to 12080 to 12080 to 12080 to 120Reaction time, h68888CrackingWater content, ppm30,00080808080Content of catalyst (KOH), ppm3003,0003003003,000Cracking temperature, °C160 to 200160 to 260160 to 190160 to 200160 to 260Pressure, MPa-0.1-0.1-0.1-0.1-0.1Cracking time, h10128812Product SeparationTotal yield, %72.367.577.471.866.0Product proportion, % A:B:C89.9:0.7:9.74.1:21.7:74.25.3:0.2:94.552.7:0.3:47.052.0:10.6:37.4

[0095] From the results in the Comparative Examples, it can be seen that the production yield by the conventional tank reactor is lower than that of the microchannel device system, and the selectivity of bis[1-ethyl(3-oxetanyl)methyl]ether is significantly lower than expectation and cannot meet the design requirements for product distribution.

[0096] Based on the above descriptions, by comparing Examples 1 to 27 and Comparative Examples 1 to 5, it can be seen that the above embodiments of the invention achieve the following technical effects: the synthesis method provided by the subject application can greatly improve the yield of three oxetane compounds, shorten the reaction time, while realizing the co-production of three oxetane compounds.

[0097] By comparing Examples 1, 6, 7, 10 to 12, and 24 to 27, it can be seen that limiting the temperatures of the transesterification reaction and the cracking reaction to the preferred ranges of the subject application is beneficial to improving the total yield of three oxetane compounds, and can control the proportions of three products by controlling the cracking temperature.

[0098] By comparing Examples 1, 8, 9, 13 to 17, 21, and 23, it can be seen that limiting the molar ratio of trimethylolpropane to carbonate ester, the content of the basic catalyst used in the transesterification reaction, and the content of the basic catalyst used in the cracking reaction to the preferred ranges of the subject application is beneficial to improving the total yield of three oxetane compounds.

[0099] By comparing Examples 1, 18, 19, and 20, it can be seen that limiting the inner diameters of the channels of the first and second microreactors to the preferred ranges of the subject application is beneficial to improving the total yield of three oxetane compounds.

Claims

1. A method for synthesizing an oxetane compound by a microreactor, <b>characterized in that, the method for synthesizing an oxetane compound by a microreactor includes feeding trimethylolpropane and a carbonate ester into the microreactor in the presence of a basic catalyst, and synthesizing the oxetane compound under solvent or solvent-free condition through a microreaction continuous flow process, wherein the basic catalyst comprises a first basic catalyst and a second basic catalyst, and the method for synthesizing an oxetane compound by a microreactor include: continuously feeding the first basic catalyst, the trimethylolpropane, and the carbonate ester to a first microreactor for transesterification reaction, to obtain a reaction product system containing an esterified intermediate; extracting the esterified intermediate from the reaction product system containing the esterified intermediate; feeding the esterified intermediate and the second basic catalyst into a second microreactor for cracking reaction, to obtain a cracked reaction product system; and subjecting the cracked reaction product system to gas-liquid separation treatment, to obtain the oxetane compound, and wherein the first microreactor has a reaction channel having an inner diameter selected from 200 to 10,000 µm, and the second microreactor has a reaction channel having an inner diameter selected from 200 to 10,000 µm; preferably, the first microreactor has a reaction channel having an inner diameter selected from 200 to 2,000 µm, and the second microreactor has a reaction channel having an inner diameter selected from 500 to 10,000 µm.

2. The method for synthesizing an oxetane compound by a microreactor according to claim 1, characterized in that, the solvent is one or more of the group consisting of halogenated hydrocarbons, benzene, toluene, xylene, nitrobenzene, and acetonitrile.

3. The method for synthesizing an oxetane compound by a microreactor according to claim 1, characterized in that, the temperature of the first microreactor is 50 to 300°C, and the residence time of the first microreactor is 1 to 60 min; and the reaction temperature of the second microreactor is 150 to 400°C, and the residence time of the second microreactor is 1 to 8 min.

4. The method for synthesizing an oxetane compound by a microreactor according to claim 3, characterized in that, the temperature of the first microreactor is 100 to 200°C; and the reaction temperature of the second microreactor is 200 to 300°C.

5. The method for synthesizing an oxetane compound by a microreactor according to any of claims 1, 3, and 4, characterized in that, the molar ratio of the trimethylolpropane to the carbonate ester is 1:(1 to 5), and the content of the basic catalyst is 100 ppm to 50,000 ppm.

6. The method for synthesizing an oxetane compound by a microreactor according to claim 5, characterized in that, the molar ratio of the trimethylolpropane to the carbonate ester is 1:(1.5 to 3), and the content of the basic catalyst is 100 ppm to 10,000 ppm.

7. The method for synthesizing an oxetane compound by a microreactor according to claim 5 or 6, <b>characterized in that, the carbonate ester is selected from one or more of the group consisting of dimethyl carbonate, diethyl carbonate, and dipropyl carbonate; and the basic catalyst is selected from one or more of alkali metal hydroxides, sodium alkoxides, potassium alkoxides, and alkali metal carbonates.

8. The method for synthesizing an oxetane compound by a microreactor according to claim 7, <b>characterized in that, the first basic catalyst and the second basic catalyst are independently selected from one or more of alkali metal hydroxides, sodium alkoxides, potassium alkoxides, and alkali metal carbonates, respectively; preferably, the first basic catalyst and the second basic catalyst are independently selected from one or more of the group consisting of sodium methoxide, sodium ethoxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate, respectively; preferably, the amount of the first basic catalyst is 200 to 500 ppm, and the amount of the second basic catalyst is 300 to 3,000 ppm.

9. The method for synthesizing an oxetane compound by a microreactor according to claim 1, characterized in that, in the process of the cracking reaction, the synthesis method further includes: adding water to the esterified intermediate, and the water content of the system in the process of the cracking reaction is 10 to 100,000 ppm.

10. The method for synthesizing an oxetane compound by a microreactor according to claim 1, characterized in that, the device used in the extraction process is selected from a thin-film evaporator or a rectification tower.