A continuous process for the preparation of benzocyclobutene precursors

Abstract

The application relates to the field of monomer synthetic chemistry and discloses a continuous preparation process of benzocyclobutene primary product, which comprises a continuous vacuum cracking section and a refrigeration impurity removal section, a temperature rising HCl removal and extraction section, a washing, drying and extractant recovery section. The process solves the defects of low yield of the benzocyclobutene primary product synthesized by the vacuum cracking method, intermittent reaction, the fact that HCl components in the cracking product cannot be effectively recovered, the fact that the product is easy to emulsify in the washing process of the cracking product, and the fact that the alkali solution is large in quantity. The benzocyclobutene primary product prepared by the application can be used as a raw material for preparing electronic-grade benzocyclobutene, and is favorable for solving the current problems in chips, semiconductors and advanced composite materials.

Description

Technical Field

[0001] This invention relates to the field of monomer synthesis chemistry, and specifically to a continuous preparation process for benzocyclobutene primary products. Background Technology

[0002] Benzocyclobutene (BCB) possesses a rigid benzene ring and a four-membered ring structure that readily opens. Ring opening typically occurs around 200°C, forming an o-dimethylquinone intermediate. Upon heating, ring opening forms a polymer with a linear or network structure. BCB polymers exhibit excellent mechanical properties, superior electrical properties, low moisture absorption, high flatness, high thermal and chemical stability, and are easily and uniformly formed into films with high flatness. Their excellent overall performance makes them widely applicable and suitable as advanced chip packaging materials.

[0003] There is currently no publicly available continuous preparation process for benzocyclobutene primary products, and it remains a closely guarded technology. Traditional processes for preparing benzocyclobutene primary products suffer from drawbacks such as low product yield, intermittent reaction and cooling processes, ineffective recovery of HCl components from pyrolysis products, easy emulsification of products during washing, and large amounts of alkali used.

[0004] To address the shortcomings of intermittent flash vacuum pyrolysis technology for large-scale industrial production applications, the main considerations were made regarding four key process flows: the reaction section, the cooling and separation section, the HCl removal section, and the washing section.

[0005] I. Reaction Section The publicly disclosed process for preparing benzocyclobutene primary product by vacuum pyrolysis of o-methylbenzyl chloride is an intermittent flash vacuum pyrolysis method: Benzocyclobutene was prepared by evaporating liquid o-methylbenzyl chloride in the preheating zone of a tubular reactor and then flashing it under vacuum in the pyrolysis zone. The production process is simple; however, the vacuum level is low, at 25-50 mbar, resulting in many side reactions and oligomers. The BCB yield is only about 35%, and the continuous reaction time is only 1-4 hours, making it impossible to synthesize benzocyclobutene primary products continuously for a long time.

[0006] II. Cooling and Separation Section The existing publicly disclosed cooling and separation processes for pyrolysis products are mainly single-stage liquid nitrogen quenching and multi-stage liquid nitrogen quenching: 1. One-stage liquid nitrogen quenching process: A mixture of vacuum pyrolysis products and nitrogen enters a cooler using liquid nitrogen as the cooling medium. Most of the pyrolysis products cool and solidify, settling at the bottom of the cooler, while nitrogen and some pyrolysis products are discharged from the system. The equipment is simple and easy to operate; however, it consumes a large amount of liquid nitrogen, has poor cooling and separation efficiency, and the reaction products have insufficient residence time, resulting in nitrogen carrying pyrolysis products out of the system and significant product loss.

[0007] 2. Multi-stage liquid nitrogen quenching process: The mixture of vacuum pyrolysis products and nitrogen enters two or more coolers that use liquid nitrogen as the cooling medium. The pyrolysis products are cooled and solidified, deposited at the bottom of the coolers, while the nitrogen is discharged from the system.

[0008] It has a long residence time and good separation effect; however, the equipment is complex and difficult to operate; and the consumption of liquid nitrogen is large.

[0009] III. HCl Removal Section The currently disclosed HCl removal process is the alkaline washing method: Alkaline solutions such as NaOH and Na2CO3 are added to the pyrolysis product cooler, and most of the HCl is removed by washing.

[0010] It has high removal efficiency and is easy to operate; however, the pyrolysis products are prone to emulsification, resulting in significant loss of pyrolysis products.

[0011] IV. Washing Section The publicly disclosed process for removing residual HCl from pyrolysis products is a "strong alkali washing + water washing" process: The pyrolysis products were washed with strong alkalis such as NaOH and KOH, and the raffinate phase was separated. Then, the excess alkali solution was removed by washing with pure water.

[0012] It is simple to operate with few steps; however, it requires a large amount of strong alkali, the pyrolysis products are prone to emulsification, and the product loss is significant. Summary of the Invention

[0013] In view of this, the present invention discloses a continuous preparation process for benzocyclobutene primary products to overcome the shortcomings of the prior art.

[0014] It should be noted that the continuous preparation process of benzocyclobutene primary product is a new low-consumption and high-yield process independently developed based on the mature process of generating benzocyclobutene primary product by cracking o-methylbenzyl chloride. This solves the problems of low product yield, intermittent reaction and cooling processes, ineffective recovery of HCl component in cracking products, easy emulsification of cracking products during washing, and large amount of alkali solution used in the existing process, thus meeting the growing domestic demand for this important organic intermediate.

[0015] To achieve the above objectives, the present invention adopts the following technical solution: A process for preparing benzocyclobutene includes the following steps: (1) Vacuum feeding and mixing section: Liquid o-methylbenzyl chloride is mixed with high-purity nitrogen at a certain volume ratio under a certain vacuum at a certain feed rate and then heated to a certain temperature to completely vaporize the liquid o-methylbenzyl chloride, which is then used as the feed for the vacuum high-temperature section. (2) Vacuum pyrolysis section: A mixture of nitrogen and gaseous o-methylbenzyl chloride is continuously fed into a high-temperature tubular reactor under a certain vacuum, and reacted at a certain temperature to obtain a mixture of gaseous reaction products and nitrogen. (3) Vacuum cryogenic cooling section: The gaseous reaction products and nitrogen mixture are continuously fed into a vacuum cryogenic cooling device under a certain vacuum degree. All the gaseous reaction products are cooled into liquid and solid states and deposited in the cooling device. Nitrogen is discharged from the system, thus achieving the separation of reaction products and nitrogen. A vacuum pump is installed at the end of the vacuum cryogenic cooling device to provide a vacuum atmosphere for the vacuum feeding and mixing section, the vacuum pyrolysis section, and the vacuum cryogenic cooling section. (4) HCl removal section: The reaction products, after being cooled under vacuum at low temperature, are heated to room temperature. The HCl in the solid pyrolysis products evaporates into a gaseous state, which is then absorbed by ultrapure water to obtain a hydrochloric acid solution. After the HCl is removed, the solid pyrolysis products are heated and transformed into liquid pyrolysis products, which are deposited at the bottom of the cooler.

[0016] (5) Extraction section: The pyrolysis reaction products after HCl removal are extracted and separated to obtain an extract phase containing liquid reaction products and a raffinate phase containing polymer reaction products. (6) Washing section: The extract phase containing the liquid reaction product was subjected to a first-stage water washing, a second-stage alkaline washing, and a third-stage water washing to remove residual HCl from the extract phase, yielding an organic phase and an aqueous phase containing the reaction product, respectively. (7) Drying and filtration section: The organic phase containing the reaction product is first dried to remove residual water, and then filtered to remove the water-containing desiccant, to obtain the dehydrated reaction product. (8) Extractant recovery section: The dehydration reaction product is subjected to vacuum distillation at a certain temperature and pressure. The extraction solvent is obtained at the top of the column and can be recycled, while the primary product of benzocyclobutene is obtained at the bottom of the column.

[0017] Furthermore, in step (1) above, the heating temperature of liquid o-methylbenzyl chloride is 90-110℃; the purity of high-purity nitrogen is 99.0-99.9%; the volume ratio of high-purity nitrogen to liquid o-methylbenzyl chloride is 20000:1-40000:1; the feeding rate of liquid o-methylbenzyl chloride is 0.050-0.200ml / min; and the vacuum degree is 5-10mbar.

[0018] The further beneficial effect of the above-mentioned method lies in the addition of a vacuum feeding and mixing section compared to the disclosed process. This invention employs continuous feeding and continuous heating evaporation under a vacuum atmosphere. Compared to processes without a vacuum mixing section, it provides a highly dilute environment for the vacuum high-temperature pyrolysis of the raw material o-methylbenzyl chloride. After a large amount of nitrogen is mixed with a small amount of raw material, the intermolecular distance of the o-methylbenzyl chloride molecules is relatively large, avoiding the probability of mutual polymerization to form polymers under high-temperature conditions. This creates conditions for the intramolecular ring-closing reaction of the raw material molecules to generate benzocyclobutene. With the new process, due to the reduced polymer yield from the pyrolysis reaction, the polymer aggregation rate clogging the reaction channels in the tubular reactor is greatly reduced, allowing the reaction time to be sustained for more than 300 hours, achieving continuous reaction. Simultaneously, due to the reduced polymer yield, the benzocyclobutene yield can reach over 60%. This not only improves the benzocyclobutene yield but also achieves a continuous pyrolysis reaction.

[0019] Furthermore, in step (2) above, the high-temperature tubular reactor has a length of 900-1600 mm, an inner diameter of 6-12 mm, and a wall thickness of 2-4 mm; the heating temperature of the high-temperature tubular reactor is 600-800℃; and the vacuum degree is 4-8 mbar.

[0020] The further beneficial effects of the above-mentioned method are that, in the reaction section, the present invention adopts a continuous flash vacuum pyrolysis process. Compared with the intermittent flash vacuum pyrolysis process, the present invention has fewer side reactions, higher benzocyclobutene content in the product, less polymer, and higher overall yield of benzocyclobutene monomer.

[0021] Furthermore, in step (3) above, the vacuum cryogenic cooling device is a two-stage cooling device, wherein the first stage cooler is a cryogenic constant temperature cooling device, and the coolant is at least one of ethylene glycol, propylene glycol, and methanol, preferably ethylene glycol; the first stage cooling temperature is -10 to -40°C; the second stage cooler consists of two cold traps connected in series, and the coolant is liquid nitrogen, with a dosage of 0.3-0.7 times the volume of the cooler; the vacuum degree is 3-7 mbar.

[0022] The further beneficial effects of the above-mentioned method are that, in the cooling and separation section, the present invention employs a continuous three-stage vacuum cooling process. Based on the principle of entropy increase, the present invention rationally designs the cooler sequence, which not only reduces the amount of liquid nitrogen used but also enhances the cooling effect by increasing the cooling area. Compared with a single-stage liquid nitrogen quenching process, the separation effect between nitrogen and pyrolysis products is better; compared with a multi-stage liquid nitrogen quenching process, the present invention uses less liquid nitrogen.

[0023] Furthermore, in step (4) above, the heating rate is 10-20℃ / min, the final temperature is 20-25℃, the mass ratio of pure water to theoretical HCl is 1:2 to 1:3, and the concentration of the resulting hydrochloric acid solution is 28-31%.

[0024] The further beneficial effect of adopting the above-mentioned methods is that, in the disclosed methods, HCl is not effectively recovered and reused, but only neutralized with alkaline solution. In the HCl removal section of this invention, a uniformly heated HCl removal process is adopted, and pure water absorption is used to produce hydrochloric acid solution; this can solve the problem of generating a large amount of acidic wastewater from the direct washing method for HCl removal, and can also eliminate the emulsification problem caused by direct water washing.

[0025] Furthermore, in step (5) above, the extraction temperature is 25-85℃, the extractant is a pentane / hexane mixture, and the amount used is 0.5-5 times the amount of the cracking product after deHCl removal; in the pentane / hexane mixture, the mass ratio of pentane to hexane is (1-4):1.

[0026] The further beneficial effect of the above method is that, after extraction, the mass percentage of oligomers in the extract phase containing the reaction products is 1-5%.

[0027] Furthermore, in step (6) above, the temperature of the first-stage water washing is 25-85℃, and the amount of pure water used for washing is 0.5-3 times the volume of the raffinate obtained from extraction; the temperature of the second-stage alkaline washing is 25-85℃, and the alkaline washing agent is a solution of sodium bicarbonate, sodium carbonate, and sodium hydroxide, preferably a sodium bicarbonate solution, and the amount of alkaline washing agent used is 0.5-5 times the volume of the organic phase after the first-stage water washing; the concentration of the sodium bicarbonate solution is 5-20%; the temperature of the third-stage water washing is 25-85℃, and the amount of pure water used for washing is 0.5-5 times the volume of the organic phase after the alkaline washing.

[0028] The further beneficial effect of the above-mentioned method is that, compared with the disclosed method, the three-stage washing process not only reduces the amount of alkali solution used, but also avoids emulsification after a large amount of alkali solution is mixed with the organic phase, thus reducing product loss. In the washing section, this invention employs a three-stage washing process: the first stage uses water to remove most of the residual HCl from the reaction product; the second stage uses sodium bicarbonate solution to remove the remaining HCl; and the third stage uses water to remove excess sodium bicarbonate solution. After the three-stage washing, the HCl content in the reaction product is below 1 ppm.

[0029] Furthermore, in step (7) above, the desiccant is anhydrous magnesium sulfate, anhydrous calcium hydroxide, or anhydrous calcium oxide, and the amount of desiccant used is 0.5-2 times that of the organic phase after washing; the desiccant is removed by vacuum filtration, and the filtration pressure is 20-50 mbar.

[0030] The further beneficial effect of the above method is that, after drying, the water content in the reaction product is 0.0001-0.001%.

[0031] Furthermore, in step (8) above, the temperature at the top of the reduced pressure distillation column is 60-80℃ and the pressure is 10-60mbar. The extractant recovered at the top of the column is used in the extraction section of step (2), and the benzocyclobutene primary product is obtained at the bottom of the column.

[0032] The further beneficial effect of the above method is that, after recycling, the recovery rate of the extractant is 90-95%.

[0033] Ultimately, the total yield of benzocyclobutene was 70%–75%, the HCl recovery rate was 85–90%, and the extractant recovery rate was 90–95%.

[0034] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are: (1) Regarding the reaction, this invention achieves continuous and stable feeding of liquid o-methylbenzyl chloride under high vacuum conditions; the preheater temperature is reasonably set to ensure that the liquid o-methylbenzyl chloride is completely evaporated in the preheater and mixed evenly with nitrogen in a gaseous state before entering the quartz tube reactor for cracking reaction. This ensures that the pressure does not fluctuate and the material does not accumulate during the reaction process; the high vacuum degree of the reaction system allows the gaseous o-methylbenzyl chloride molecules to enter the reaction zone with a larger intermolecular distance, reducing the probability of intermolecular polymerization and which is beneficial to improving the yield of benzocyclobutene.

[0035] (2) In terms of cooling separation, a three-stage cooling device is set up. The first-stage cooler adopts a low-temperature circulating refrigeration method, which reduces the amount of liquid nitrogen refrigerant used in the second and third-stage coolers. The cooling method is reasonably configured, which is more energy-efficient compared with the one-stage and multi-stage liquid nitrogen rapid cooling process.

[0036] (3) Regarding HCl removal, a uniform heating method is used to slowly remove HCl, and pure water is used to absorb the removed HCl gas to produce hydrochloric acid solution. This not only eliminates the problem of organic phase emulsification caused by direct washing, but also achieves efficient utilization of by-products.

[0037] (4) In terms of extraction and washing, the polymer in the pyrolysis products is first extracted and separated. The extract phase is then treated with a water-alkali-water washing process to remove residual HCl impurities in the organic phase. Compared with the direct strong alkali washing process, the amount of alkali solution used is reduced. At the same time, a low-concentration weak base salt is used as the washing reagent, which eliminates emulsification during the extraction process. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a simplified flowchart of the continuous preparation of benzocyclobutene (BCB) primary product according to one embodiment of the present invention.

[0040] Figure 2 This is a liquid chromatogram of crude benzocyclobutene (BCB) after pyrolysis. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0043] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0044] In the description of this invention, it should be understood that the terms "middle", "upper", "lower", "rise", "fall", "vertical", "surface", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0045] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0046] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0047] This invention discloses a continuous vacuum pyrolysis synthesis process for benzocyclobutene.

[0048] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0049] Example 1 A continuous preparation process for benzocyclobutene primary product includes the following steps: (1) Vacuum feeding and mixing section: First, nitrogen gas is introduced into the system at a flow rate of 3 L / min to replace the air in the feeding mixing section, reaction section, and cooling separation section. The vacuum pump is then turned on to adjust the vacuum level in the feeding mixing section to 10 mbar. The metering pump is then turned on, and liquid o-methylbenzyl chloride is added to the preheater and heated until completely vaporized. The nitrogen and o-methylbenzyl chloride mixture is then used as a raw material in the reaction section. The preheater temperature is 90°C.

[0050] (2) Vacuum pyrolysis section: A tubular reactor was heated to 720°C, and a mixture of nitrogen and o-methylbenzyl chloride was introduced into the quartz tube reactor. The heating rate of the tubular reactor was 5°C / h. The vacuum level of the continuous flash vacuum pyrolysis section was 8 mbar. A mixture of gas-phase pyrolysis products and nitrogen was obtained.

[0051] (3) Vacuum cryogenic cooling section: Turn on the primary cooler's circulating refrigeration device and adjust the cooling temperature to -20℃. Add liquid nitrogen to the secondary cooler to 20% of its maximum liquid level and to the tertiary cooler to 10% of its maximum liquid level. Pass the gas-phase pyrolysis products sequentially into the primary, secondary, and tertiary coolers to obtain solid-phase pyrolysis products and carrier gas, respectively. The gas-phase pyrolysis products cool into solids and deposit at the bottom of the coolers. Nitrogen gas is discharged from the system through a vacuum pump, thus achieving the separation of pyrolysis products and nitrogen gas.

[0052] The vacuum degree of the vacuum cryogenic cooling section is 6 mbar.

[0053] (4) HCl removal section: The solid pyrolysis products were heated to room temperature and decomposed to obtain HCl gas and liquid reaction products. Solid HCl volatilized into a gaseous state, and the HCl gas was absorbed by ultrapure water to obtain a hydrochloric acid solution. The liquid reaction products settled at the bottom, achieving separation of HCl from the liquid pyrolysis products. The heating rate was 15℃ / min, the final heating temperature was 23℃, and the mass ratio of pure water to theoretical HCl was 1:2.57. (5) Extraction section: The liquid pyrolysis products were extracted with a pentane / hexane mixture at 28°C. The amount of pentane / hexane mixture was three times the volume of the liquid pyrolysis products. The extract phase containing benzocyclobutene and the raffinate phase containing oligomers were obtained, respectively. The mass ratio of pentane to hexane was 3.5:1, and the volume ratio of pentane / hexane mixture to liquid pyrolysis products was 2.0:1.

[0054] (6) Washing section: The extract phase containing the benzocyclobutene reaction product was subjected to a three-stage washing process. The first stage involved washing with water to remove most of the HCl remaining in the extract phase at a temperature of 26°C. The second stage involved washing with alkali to remove the remaining HCl remaining in the extract phase at a temperature of 28°C. The third stage involved washing with water to remove the weak alkali remaining in the extract phase at a temperature of 25°C.

[0055] (7) Drying and filtration section: The washing product was dehydrated and dried at 25°C. The resulting solid-liquid mixture was then filtered at 50 mbar and 26°C to obtain the filtered product and the water-absorbing solid desiccant. The desiccant used was anhydrous calcium hydroxide, and the amount of desiccant was 0.8 times the mass of the washing product.

[0056] (8) Extractant recovery section: The filtered product obtained in step (7) is subjected to vacuum distillation. The solvent recovered at the top of the column is used as the extractant in the extraction section of step (5). The product obtained at the top of the column is benzocyclobutene.

[0057] Example 2 The only difference from Example 1 is that in step (1) of the vacuum feeding and mixing section, the preheater heating temperature is 60°C.

[0058] Example 3 The only difference from Example 1 is that in step (1) of the vacuum feeding and mixing section, the preheater heating temperature is 70°C.

[0059] Example 4 The only difference from Example 1 is that in step (1) of the vacuum feeding and mixing section, the preheater heating temperature is 80°C.

[0060] Example 5 The only difference from Example 1 is that in step (1) of the vacuum feeding and mixing section, the preheater heating temperature is 100°C.

[0061] Example 6 The only difference from Example 1 is that in step (2), the pyrolysis temperature is 730°C in the continuous flash vacuum pyrolysis section.

[0062] Example 7 The only difference from Example 1 is that in step (2), the pyrolysis temperature is 740°C in the continuous flash vacuum pyrolysis section.

[0063] Example 8 The only difference from Example 1 is that in step (2), the pyrolysis temperature is 750°C in the continuous flash vacuum pyrolysis section.

[0064] Example 9 The only difference from Example 1 is that in step (2), the pyrolysis temperature is 760°C in the continuous flash vacuum pyrolysis section.

[0065] Example 10 The only difference from Example 1 is that in step (2), the pyrolysis temperature is 770°C in the continuous flash vacuum pyrolysis section.

[0066] Example 11 The only difference from Example 1 is that in step (2), the vacuum degree in the continuous flash vacuum pyrolysis section is 12 mbar.

[0067] Example 12 The only difference from Example 1 is that in step (2), the vacuum degree in the continuous flash vacuum pyrolysis section is 14 mbar.

[0068] Example 13 The only difference from Example 1 is that in step (2), the vacuum degree in the continuous flash vacuum pyrolysis section is 16 mbar.

[0069] Example 14 The only difference from Example 1 is that in step (2), the vacuum degree in the continuous flash vacuum pyrolysis section is 18 mbar.

[0070] Example 15 The only difference from Example 1 is that in step (3) the vacuum cryogenic cooling section, a one-stage liquid nitrogen cooling process is used, and the cooling temperature is -10℃.

[0071] Example 16 The only difference from Example 1 is that in step (3) the vacuum cryogenic cooling section, a one-stage liquid nitrogen cooling process is used, and the cooling temperature is -20℃.

[0072] Example 17 The only difference from Example 1 is that in step (3) the vacuum cryogenic cooling section, a one-stage liquid nitrogen cooling process is used, and the cooling temperature is -30℃.

[0073] Example 18 The only difference from Example 1 is that in step (3) the vacuum cryogenic cooling section, a one-stage liquid nitrogen cooling process is used, and the cooling temperature is -40℃.

[0074] Example 19 The only difference from Example 1 is that in step (5) of the extraction process, the volume ratio of the pentane / hexane mixture to the liquid cracking product is 0.5:1.

[0075] Example 20 The only difference from Example 1 is that in step (5) of the extraction process, the volume ratio of the pentane / hexane mixture to the liquid cracking product is 1.0:1.

[0076] Example 21 The only difference from Example 1 is that in step (5) of the extraction process, the volume ratio of the pentane / hexane mixture to the liquid cracking product is 1.5:1.

[0077] Example 22 The only difference from Example 1 is that in step (5) of the extraction process, the volume ratio of the pentane / hexane mixture to the liquid cracking product is 2.5:1.

[0078] Example 23 The only difference from Example 1 is that in step (5) of the extraction process, the volume ratio of the pentane / hexane mixture to the liquid pyrolysis product is 3.0:1.

[0079] Performance testing Benzocyclobutene products obtained in Examples 1-23 were used to determine the yield and content of benzocyclobutene in each product. The yield of benzocyclobutene was calculated as: actual yield of benzocyclobutene / theoretical yield of benzocyclobutene × 100%. The content of benzocyclobutene was determined by high-performance liquid chromatography (HPLC). The results are shown in Tables 1, 2, and 3.

[0080] Table 1 Performance test results of Examples 1 to 14

[0081] Table 2 Performance test results of Examples 15 to 18

[0082] Table 3 Performance test results of Examples 19 to 23

[0083] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A continuous preparation process for benzocyclobutene primary product, characterized in that, Specifically, the following steps are included: (1) Continuous vacuum pyrolysis and cryogenic purification section: Liquid o-methylbenzyl chloride and high-purity nitrogen are mixed under vacuum and heated until the liquid o-methylbenzyl chloride is completely vaporized. The mixture of nitrogen and gaseous o-methylbenzyl chloride is then fed into a high-temperature tubular reactor and reacted continuously under vacuum to obtain a mixture of gaseous reaction products and nitrogen. Subsequently, the mixture of gaseous reaction products and nitrogen is continuously fed into a vacuum cryogenic cooling device under vacuum. All gaseous reaction products are cooled into liquid and solid states that are deposited in the cooling device, while nitrogen is discharged from the system, thus achieving the separation of reaction products and nitrogen. (2) Heating and HCl removal and extraction section: The reaction product, after being cooled under vacuum at low temperature, was heated to room temperature. The HCl in the product evaporated into a gaseous state, which was absorbed by ultrapure water to obtain a hydrochloric acid solution. The pyrolysis reaction product after HCl removal was extracted and separated to obtain an extract phase containing liquid reaction products and a raffinate phase containing polymer reaction products. (3) Washing, drying and extractant recovery section: The extract phase containing the liquid reaction product was subjected to a first-stage water washing, a second-stage alkaline washing, and a third-stage water washing to remove residual HCl from the extract phase, yielding an organic phase and an aqueous phase containing the reaction product, respectively. The organic phase containing the reaction product was first dried to remove residual water, and then filtered to remove the water-containing desiccant, yielding the dehydrated reaction product. The dehydration reaction product was subjected to vacuum distillation, and the extraction solvent was obtained at the top of the column, while the benzocyclobutene primary product was obtained at the bottom of the column.

2. The continuous preparation process of the benzocyclobutene primary product as described in claim 1, characterized in that, In step (1), the heating temperature of liquid o-methylbenzyl chloride is 90-110℃; the purity of high-purity nitrogen is 99.0-99.9%; the volume ratio of high-purity nitrogen to liquid o-methylbenzyl chloride is 20000:1-40000:1; the feeding rate of liquid o-methylbenzyl chloride is 0.050-0.200ml / min; and the vacuum degree is 5-10mbar.

3. The continuous preparation process of the benzocyclobutene primary product as described in claim 1, characterized in that, In step (1), the heating temperature of the high-temperature tubular reactor is 600-800℃; the vacuum degree is 4-8mbar.

4. The continuous preparation process of the benzocyclobutene primary product as described in claim 1, characterized in that, In step (1), the vacuum cryogenic cooling device is a two-stage cooling device, wherein the first stage cooler is a cryogenic constant temperature cooling device, the coolant is one of ethylene glycol, propylene glycol, or methanol, and the first stage cooling temperature is -10 to -40℃; the second stage cooler consists of two cold traps connected in series, the coolant is liquid nitrogen, and the amount used is 0.3-0.7 times the volume of the cooler; the vacuum degree is 3-7 mbar.

5. The continuous preparation process of benzocyclobutene primary product according to claim 1, characterized in that, In step (2), the heating rate is 10-20℃ / min, and the final temperature is 20-25℃; the mass ratio of pure water to theoretical HCl is 1:(2-3).

6. The continuous preparation process of benzocyclobutene primary product according to claim 1, characterized in that, In step (2), the extraction temperature is 25-85℃, the extractant is a pentane / hexane mixture, and the amount used is 0.5-5 times the amount of the cracking product after deHCl removal; in the pentane / hexane mixture, the mass ratio of pentane to hexane is (1-4):

1.

7. The continuous preparation process of benzocyclobutene primary product according to claim 1, characterized in that, In step (3), the temperature of the first-stage water washing is 25-85℃, and the amount of pure water used for washing is 0.5-3 times the volume of the raffinate obtained from extraction; the temperature of the second-stage alkaline washing is 25-85℃, and the alkaline washing agent is sodium bicarbonate, sodium carbonate, or sodium hydroxide, and the amount of alkaline washing agent used is 0.5-5 times the volume of the organic phase after the first-stage water washing; the concentration of the sodium bicarbonate solution is 5-20%; the temperature of the third-stage water washing is 25-85℃, and the amount of pure water used for washing is 0.5-5 times the volume of the organic phase after the alkaline washing.

8. The continuous preparation process of benzocyclobutene primary product according to claim 1, characterized in that, In step (3), the desiccant is anhydrous magnesium sulfate, anhydrous calcium hydroxide, or anhydrous calcium oxide. The amount of desiccant used is 0.5-2 times that of the organic phase after washing. The desiccant is removed by vacuum filtration at a pressure of 20-50 mbar.

9. The continuous preparation process of benzocyclobutene primary product according to claim 1, characterized in that, In step (3), the temperature at the top of the vacuum distillation column is 60-80℃ and the pressure is 10-60mbar. The extractant recovered at the top of the column is used in the extraction section of step (2), and the benzocyclobutene primary product is obtained at the bottom of the column.

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