Method for converting hanging type tetracyclododecene into bridge type tetracyclododecene

Abstract

The invention relates to a method for converting hanging type tetracyclododecene into bridge type tetracyclododecene. According to the method, p-tert-butylhydroquinone is taken as a polymerization inhibitor, inert gas is taken as diluent gas, a two-section tubular reactor is adopted, excessive hanging type tetracyclododecene fractions in the tetracyclododecene production process are converted into bridge type tetracyclododecene, the bridge type tetracyclododecene is rectified and refined, a high-bridge type tetracyclododecene product is obtained, and the hanging type proportion is 0.01%-2%; before being introduced into the tubular reactor, the hanging tetracyclododecene fraction needs to be treated with sodium sulfite and alkali liquor to remove trace peroxide, so that the peroxide is kept at 5-50 ppm (iodometric method), and the safety of the process is guaranteed. According to the process, excessive hanging type tetracyclododecene fractions which are originally required to be rectified and abandoned in a tetracyclododecene preparation process are recycled; meanwhile, oxidation yellowing caused by too high hanging tetracyclododecene content in the tetracyclododecene storage process is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of tetracyclododecene production, and specifically relates to a method for converting pentacyclic tetracyclododecene into bridged tetracyclododecene. Background Art

[0002] As a high-performance thermoplastic engineering plastic, COC is widely used in pharmaceutical packaging, optical lenses, display polarizers, optical films, medical optical components, and other fields. Lens-grade COC is in short supply in the market, and tetracyclododecene is the monomer for synthesizing lens-grade COC.

[0003] There are many reports on the synthesis of tetracyclododecene (TCD). Most of them use the reaction described in patent CN112592248A, in which dicyclopentadiene and norbornene are reacted at 230°C, and then the tetracyclododecene product is obtained through multi-step distillation. Experiments have found that tetracyclododecene exists in two isomers, a bridged (endo-type) and a penta-type (exo-type) in the reaction. The bridged configuration is more kinetically preferred, but the penta-type is more stable thermodynamically. Due to the vigorous development of the optical lens material market, the production capacity of tetracyclododecene has gradually increased. In industry, in order to improve production efficiency, higher reaction temperatures are mostly selected to carry out. Therefore, although the reaction product is mainly composed of the bridged tetracyclododecene, accounting for 85-93%, the penta-type tetracyclododecene also accounts for 7%-15%.

[0004] When used in the production of COC, the degree of polymerization of exo-tetracyclododecene is much lower than that of the bridge-tetracyclododecene, affecting production efficiency and, as the cycle accumulates, affecting the stability of COC performance. Because the double bond of exo-tetracyclododecene is less sterically hindered than the bridge-tetracyclododecene, it is easily oxidized during storage, causing the product to turn yellow and affecting the quality of the produced COC. Therefore, the industry generally disposes the majority of the exo-tetracyclododecene fraction as waste liquid during the distillation process for tetracyclododecene production, maintaining the proportion of exo-tetracyclododecene in the product below 4%.

[0005] Because exo-tetracyclododecene is thermodynamically more stable, converting bridging tetracyclododecene to exo-tetracyclododecene is relatively easy. Patent CN116947587A treats tetracyclododecene with a molecular sieve catalyst to obtain exo-tetracyclododecane, yielding tetracyclododecene with a high exo-tetracyclododecene content. Patent CN90107778 uses a silica-alumina catalyst to isomerize bridging tetracyclododecene to exo-tetracyclododecene to obtain COC with exceptional properties. The exo-tetracyclododecene yield reaches up to 40%. However, no process for converting bridging tetracyclododecene to exo-tetracyclododecene has been reported. Consequently, the exo-tetracyclododecene fraction in the tetracyclododecene production process has long been unutilized at high value. Summary of the Invention

[0006] In response to the above-mentioned problems existing in the prior art, the object of the present invention is to provide a method for converting hanging tetracyclododecene into bridged tetracyclododecene. The hanging tetracyclododecene fraction is treated with sodium sulfite and alkali solution to remove trace amounts of peroxides. Then, tert-butylhydroquinone is used as an inhibitor and an inert gas is used as a diluent. A two-stage tubular reactor is used to convert the hanging tetracyclododecene fraction into bridged tetracyclododecene. The process has high selectivity and a safe and reliable preparation process. The prepared high-bridged tetracyclododecene product has a hanging tetracyclododecene content of only 0.01%-2%, and the product does not turn yellow during long-term storage. This avoids the low-value utilization of the hanging tetracyclododecene fraction in the tetracyclododecene preparation process.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] A method for converting exo-tetracyclododecene into bridging-tetracyclododecene comprises the following steps:

[0009] 1) In a reaction vessel, treating the fraction containing exo-tetracyclododecene with unsaturated sulfate and alkali to remove trace amounts of peroxides;

[0010] 2) using a hydroquinone polyphenol as a polymerization inhibitor and an inert gas as a diluent in a two-stage tubular reactor to convert the exo-tetracyclododecene fraction in step 1) into the bridging tetracyclododecene;

[0011] 3) The bridged tetracyclododecene obtained in step 2) is distilled to remove light and heavy components to obtain a high-bridged tetracyclododecene product.

[0012] The above reaction equation is:

[0013]

[0014] In a specific embodiment, the fraction containing exo-tetracyclododecene described in step 1) is a heavy component of the distillation process of the product obtained by preparing tetracyclododecene by the traditional dicyclopentadiene and norbornene addition method, wherein the content of bridged tetracyclododecene is 20wt%-80wt%, including but not limited to 30wt%, 40wt%, 50wt%, 60wt%, and 70wt%, and the content of exo-tetracyclododecene is 80wt%-20wt%, including but not limited to 70wt%, 60wt%, 50wt%, 40wt%, and 30wt%.

[0015] In a specific embodiment, the alkali solution in step 1) is one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide aqueous solutions, preferably sodium hydroxide aqueous solution; the concentration of the alkali solution is 0.01-0.2 wt%, preferably 0.06-0.12 wt%; the mass ratio of the alkali solution to the exo-tetracyclododecene fraction is 1-10:1, preferably 2-6:1.

[0016] In a specific embodiment, the unsaturated sulfate in step 1) is sulfite, hyposulfite, thiosulfate, thiosulfite, pyrosulfite, or dithionite; the metal element of the unsaturated sulfate is an alkali metal, preferably sodium, that is, the unsaturated sulfate is a sodium salt of an unsaturated sulfate; and the unsaturated sulfate accounts for 0.1%-5wt%, preferably 0.5-2wt%, of the exo-tetracyclododecene fraction.

[0017] In a specific embodiment, the treatment temperature in step 1) is 40-80°C, preferably 55-65°C; and the treatment time is 0.5-8h, preferably 2-5h.

[0018] In a specific embodiment, the catechol polyphenol polymerization inhibitor described in step 2) is one or more of catechol, hydroquinone, p-tert-butylcatechol, di-tert-butylhydroquinone, and methylhydroquinone, preferably p-tert-butylcatechol; the amount of the polymerization inhibitor added is 100-1000 ppm, preferably 300-600 ppm, based on the total amount of tetracyclododecene.

[0019] In a specific embodiment, the inert gas in step 2) is one or more of nitrogen, hydrogen, argon, and helium, preferably nitrogen; the molar ratio of the inert gas to tetracyclododecene is 0.5-10:1, preferably 2-5:1.

[0020] In a specific embodiment, in the two-stage series tubular reactor described in step 2), the reaction temperature of the first reactor is 290-380°C, preferably 300-350°C; the residence time is 5-20s, preferably 8-12s; the reaction pressure is 0.1-3Mpa, preferably 0.35-0.9Mpa; the reaction temperature of the second reactor is 230-260°C, preferably 235-245°C; the residence time is 1-30min, preferably 8-15min; and the reaction pressure is 0.1-0.8Mpa, preferably 0.15-0.4Mpa.

[0021] In a specific embodiment, the distillation to remove light and heavy elements in step 3) is performed by batch distillation with 25-40 plates, a reflux ratio of 1-10:1, and a top vacuum of 0.8-1.2 KPa. The fraction with a production temperature of 89.3-90.2° C. is collected to obtain the high-bridged tetracyclododecene product.

[0022] The positive effects of the present invention are:

[0023] The present invention aims to provide a method for converting exo-tetracyclododecene into bridging-tetracyclododecene. The method utilizes the instability of tetracyclododecene at high temperatures, allowing rapid cracking into norbornene and cyclopentadiene, followed by rapid cooling. This method leverages the kinetically easier generation of bridging-tetracyclododecene. Exo-tetracyclododecene is cleverly converted into bridging-tetracyclododecene. Since cycloolefins such as tetracyclododecene readily polymerize at high temperatures, a two-stage tubular reactor is employed, in which a polymerization inhibitor and diluent gas are introduced, followed by heating and cracking, followed by cooling and subsequent polymerization. This reconfiguration of the product configuration allows the exo-tetracyclododecene fraction to be converted into bridging-tetracyclododecene.

[0024] To prevent side reactions such as polymerization and explosion caused by oxygen free radicals during the high-temperature process, the exo-tetracyclododecene fraction is pre-treated with unsaturated sulfate and alkali to remove trace peroxides to 5-50 ppm. This process offers advantages such as low polymer formation, good reaction selectivity, high yield, and enhanced safety, making it suitable for industrial production. The resulting high-bridged tetracyclododecene product contains only 0.01%-2% of the exo-tetracyclododecene, and the product remains stable during long-term storage. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below by way of examples, but is not limited thereto.

[0026] In the present invention, raw materials, unless otherwise specified, are commercially available; equipment, unless otherwise specified, is conventionally used in the art.

[0027] The gas chromatography analysis method used in this invention was a Shimadzu Angilent 7820A gas chromatograph, a DB-5 capillary column (5% Phenyl Methyl Siloxan, 30 m × 0.32 mm × 0.25 μm), and a flame detector (FID). The injector and detector temperatures were both 290°C; the column temperature was initially maintained at 100°C for 1 minute, then increased at 15°C / min to 250°C and held for 5 minutes. The column pressure was 8.59 psi, and the flow rate was 1.5 mL / min. The injection volume was 0.2 μL. Conversion and selectivity were calculated using the area normalization method.

[0028] The product color number testing method of the present invention is as follows: using the CS-810 desktop spectrophotometer from Hangzhou Caipu Technology Co., Ltd., the product is added to a 40-33 mm cuvette at room temperature, placed in the instrument, the measurement mode is set to Pt-Co color number mode, and the test result is directly read.

[0029] Example 1

[0030] In a 10L glass stirred kettle, add 2 kg of a fraction containing 50% exo-tetracyclododecene, followed by a 0.08% aqueous sodium hydroxide solution (3 times the mass of the exo-tetracyclododecene). Then, add sodium sulfite (1% of the mass of the exo-tetracyclododecene) and stir at 60°C for 3 hours. The upper organic phase is then purified and collected. Iodine titration tests reveal peroxides below 50 ppm.

[0031] 450ppm of p-tert-butylcatechol was added to the above organic phase and pumped into two series-connected tubular reactors. At the same time, nitrogen with a molar ratio of 3:1 to tetracyclododecene was added through a flowmeter. The reaction temperature of the first reactor was 330°C, the residence time was 10S, and the reaction pressure was 0.5Mpa; the reaction temperature of the second reactor was 240°C, the residence time was 10min, and the operating pressure was 0.2Mpa. After the reaction was completed, the reaction liquid was collected, sampled for chromatographic analysis, and the yield of the isomerization-type tetracyclododecene was calculated. At the same time, the collected reaction liquid was introduced into an intermittent distillation device with 30 plates, a reflux ratio of 1:1, and a top vacuum of 1Kpa. The fraction with a production temperature of 89.3-90.2°C was collected, which was the high-bridge tetracyclododecene product. The product purity was analyzed by chromatography, and the color number was tested after being placed at room temperature for one month. The chromatographic test results of the reaction liquid and the product, as well as the color number test results of the product after storage, are shown in Table 2

[0032] Examples 2 to 10

[0033] The operations of Examples 2 to 10 are similar to those of Example 1, except for the isomerization reaction. The specific conditions are shown in Table 1.

[0034] Comparative Example 1

[0035] The method is the same as that of Example 1, except that the tetracyclododecene in Comparative Example 1 is not subjected to deperoxide treatment and directly enters the isomerization reaction process. The experimental results are shown in Table 2

[0036] Table 1 Specific reaction conditions of Examples 1 to 10

[0037]

[0038] Table 2 Example and comparative example reaction result data

[0039]

Claims

1. A method for converting exo-tetracyclododecene into bridging-tetracyclododecene, comprising the following steps: 1) In a reaction vessel, treating the fraction containing exo-tetracyclododecene with unsaturated sulfate and alkali to remove trace amounts of peroxides; 2) using a hydroquinone polyphenol as a polymerization inhibitor and an inert gas as a diluent in a two-stage tubular reactor to convert the exo-tetracyclododecene fraction in step 1) into the bridging tetracyclododecene; 3) The bridged tetracyclododecene obtained in step 2) is distilled to remove light and heavy components to obtain a high-bridged tetracyclododecene product.

2. The preparation method according to claim 1, wherein The fraction containing exo-tetracyclododecene in step 1) is a heavy component of the distillation process of the product obtained by preparing tetracyclododecene by the traditional dicyclopentadiene and norbornene addition method, wherein the content of bridged tetracyclododecene is 20wt%-80wt%, and the content of exo-tetracyclododecene is 80wt%-20wt%.

3. The preparation method according to claim 1 or 2, wherein The alkali solution in step 1) is one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide aqueous solutions, preferably sodium hydroxide aqueous solution; the concentration of the alkali solution is 0.01-0.2wt%, preferably 0.06-0.12wt%; the mass ratio of the alkali solution to the exo-tetracyclododecene fraction is 1-10:1, preferably 2-6:

1.

4. The preparation method according to any one of claims 1 to 3, wherein The unsaturated sulfate in step 1) is sulfite, sulfoxylate, thiosulfate, thiosulfite, pyrosulfite, or dithionite; the metal element of the unsaturated sulfate is an alkali metal, preferably sodium. That is, the unsaturated sulfate is a sodium salt of an unsaturated sulfate; the unsaturated sulfate accounts for 0.1%-5wt% of the hanging tetracyclododecene fraction, preferably 0.5-2wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that The treatment temperature in step 1) is 40-80° C., preferably 55-65° C.; the treatment time is 0.5-8 h, preferably 2-5 h.

6. The preparation method according to any one of claims 1 to 5, characterized in that The catechol polyphenol polymerization inhibitor described in step 2) is one or more of catechol, hydroquinone, p-tert-butylcatechol, di-tert-butylhydroquinone, and methylhydroquinone, preferably p-tert-butylcatechol; the amount of the polymerization inhibitor added is 100-1000 ppm, preferably 300-600 ppm, based on the total amount of tetracyclododecene.

7. The preparation method according to any one of claims 1 to 6, wherein The inert gas in step 2) is one or more of nitrogen, hydrogen, argon, and helium, preferably nitrogen; the molar ratio of the inert gas to tetracyclododecene is 0.5-10:1, preferably 2-5:

1.

8. The preparation method according to any one of claims 1 to 7, wherein In step 2), the reaction temperature of the first reactor of the two-stage serial tubular reactor is 290-380° C., preferably 300-350° C.; Residence time 5-20s, preferably 8-12s; reaction pressure 0.1-3Mpa, preferably 0.35-0.9Mpa; reaction temperature of the second reactor 230-260°C, preferably 235-245°C; residence time 1-30min, preferably 8-15min; reaction pressure 0.1-0.8Mpa, preferably 0.15-0.4Mpa.

9. The preparation method according to any one of claims 1 to 8, wherein The distillation for removing light and heavy gases in step 3) is performed by batch distillation, with a plate number of 25-40, a reflux ratio of 1-10:1, a top vacuum of 0.8-1.2 KPa, and a fraction with a production temperature of 89.3-90.2°C is collected.

Images