A process for the preparation of methylhexahydrophthalic anhydride
By using a combination of Ni/Co modified catalyst and thin-film evaporator in a fluidized bed hydrogenation reactor, the problem of low purity of methylhexahydrophthalic anhydride was solved, and high-purity, high-yield production of methylhexahydrophthalic anhydride was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENGHE MATERIALS & SCI TECH CO LTD
- Filing Date
- 2023-12-21
- Publication Date
- 2026-06-23
AI Technical Summary
In the existing process for preparing methylhexahydrophthalic anhydride, the product purity is not high, catalyst residue affects the product appearance, and side reactions generate impurities that are difficult to separate, resulting in performance indicators not meeting the standards.
Hydrogenation was carried out in a fluidized bed hydrogenation reactor using a Ni/Co modified catalyst, combined with vacuum distillation using a thin-film evaporator. The hydrogenation conditions and separation process were optimized. The Ni/Co modified catalyst and methyltetrahydrophthalic anhydride were uniformly mixed in the fluidized bed. The spent catalyst was replaced periodically, and a thin-film evaporator was used for efficient separation.
This method improves the purity and yield of methylhexahydrophthalic anhydride, reduces catalyst residue, produces a transparent product with excellent performance indicators, and achieves stable and efficient production.
Smart Images
Figure CN117843598B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical raw material synthesis technology, and specifically relates to a method for preparing methylhexahydrophthalic anhydride. Background Technology
[0002] Methylhexahydrophthalic anhydride is produced from methyltetrahydrophthalic anhydride via catalytic hydrogenation. There are one-step and two-step methods; catalysts can be supported by noble metals such as platinum, palladium, and ruthenium, or Raney nickel; hydrogenation can be done in bulk or in the presence of a solvent; there are intermittent and continuous hydrogenation processes; and there are low-pressure and high-pressure processes. Due to differences in hydrogenation processes and catalysts, the corresponding pressures and temperatures also differ, and the hydrogenation side reactions also vary slightly, ultimately affecting product performance.
[0003] In current methyltetrahydrophthalic anhydride hydrogenation processes, a batch reactor is typically used with Raney nickel as the catalyst. The catalyst and methyltetrahydrophthalic anhydride are blended and hydrogenated under strong stirring. Due to the fine particle size of Raney nickel, the high viscosity of methyltetrahydrophthalic anhydride, and the significant density difference between Raney nickel and methyltetrahydrophthalic anhydride, some of the catalyst is broken into even finer powder under strong stirring. After the hydrogenation reaction, the material settles in a settling tank for more than 8 hours to allow the catalyst to settle and be recovered. Under this process, the catalyst settling rate is slow, which not only affects the process progress but also prevents the finer catalyst powder from completely settling to the bottom. The catalyst powder remains in the methylhexahydrophthalic anhydride product. In actual epoxy resin curing applications, when preparing transparent products, the catalyst residue will generate yellow spots during the curing stage, affecting the product's appearance.
[0004] When selecting methyltetrahydrophthalic anhydride as the raw material, a mixture containing at least two isomers should be chosen. The position of the double bonds, the methyl group, and the cis-trans configuration all affect the degree of hydrogenation. During hydrogenation, due to the influence of temperature, pressure, catalyst, and hydrogen atoms, the anhydride in the molecule is prone to condensation, hydrogenolysis, and cross-linking side reactions, generating high-boiling and low-boiling impurities that are difficult to separate. This not only affects the reaction conversion rate, selectivity, and product color, but also the impurities introduced by the raw material and the high-boiling byproducts generated during the reaction are easily coked and adsorbed on the catalyst surface, leading to catalyst poisoning. Methyltetrahydrophthalic anhydride and its isomers have similar boiling points to methylhexahydrophthalic anhydride, but both have high boiling points, making effective separation by traditional methods such as distillation difficult after the reaction, ultimately affecting product performance.
[0005] The properties of methylhexahydrophthalic anhydride are mainly tested by indicators such as appearance, color, iodine value, acid value, anhydride content, free acid, and crystallization point. The degree of hydrogenation of the double bond is judged by the iodine value, which is generally required to be less than 2.0, that is, a hydrogenation rate greater than 98%, and preferably less than 0.5. The lower the iodine value, the more transparent the appearance and color will be in theory. The normal acid value is 660-680 (mgKOH / g), the normal anhydride content is ≥40.5%, and the normal free acid content is ≤0.3%. During the hydrogenation process of methyltetrahydrophthalic anhydride, byproducts will affect the acid value and anhydride value of the product. Lower free acid content results in a lower crystallization point, and the compressive strength will be improved after epoxy resin curing. Patent CN1736996A uses a composite hydrogenation catalyst (a polymer of nickel skeleton and bis(bis-diphenylphosphine oxyethylene)tetrabromodicopper as a catalyst) to hydrogenate at 100-140°C and 1-4 MPa for 2-6 hours, achieving a yield of 90-95%. Although the performance indicators and process operation have been improved, the upper limit of the entire process is still limited, and the purity of the prepared methylhexahydrophthalic anhydride is insufficient.
[0006] Therefore, to prepare high-purity methylhexahydrophthalic anhydride, optimization is needed in the hydrogenation process route, hydrogenation equipment, selection of methyltetrahydrophthalic anhydride, selection of catalyst type and dosage, as well as process parameters such as hydrogenation temperature and pressure. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide a method for preparing methylhexahydrophthalic anhydride, which solves the problem of low purity of methylhexahydrophthalic anhydride products in the prior art.
[0008] This invention provides a method for preparing methylhexahydrophthalic anhydride, comprising the following steps:
[0009] Using unisomerized refined methyltetrahydrophthalic anhydride as raw material, the raw material and hydrogen are fed into a fluidized bed hydrogenation reactor, followed by the addition of a special catalyst. Hydrogenation is then carried out by thoroughly mixing the raw material and catalyst under the action of an in-reactor circulation pump. Waste hydrogen and light components of methyltetrahydrophthalic anhydride are collected from the top gas phase of the reactor, while waste catalyst is collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, is collected from the side of the reactor by a pump controlling the liquid level. The crude methylhexahydrophthalic anhydride is then sent to a separation device equipped with a thin-film evaporator for vacuum distillation to obtain the finished product, methylhexahydrophthalic anhydride. The special catalyst is a Ni / Co modified catalyst.
[0010] The unisolated purified methyltetrahydrophthalic anhydride is obtained by removing light components and polyanhydrides by vacuum distillation of crude methyltetrahydrophthalic anhydride.
[0011] The crude methyltetrahydrophthalic anhydride is a mixture of 3-methyltetrahydrophthalic anhydride and 4-methyltetrahydrophthalic anhydride in a mass ratio of 30–70:30–70. The preferred mass ratio is 25–75:75–25.
[0012] The preparation method of the Ni / Co modified catalyst includes the following steps:
[0013] Add 20-25 wt% activated carbon to 75-80 wt% nickel nitrate and soak at 60-80℃ for 2-3 hours. Then add 5-10 wt% cobalt nitrate dropwise into the mixture and stir magnetically for 5-15 minutes to ensure uniform mixing. Soak at 90-100℃ for 8-11 hours. After the reaction is complete, remove the activated carbon and dry it at 120-140℃ under a nitrogen atmosphere for 2-4 hours. Then calcine the activated carbon at 500-600℃ under a nitrogen atmosphere for 5-7 hours to obtain the Ni / Co modified catalyst.
[0014] The amount of Ni / Co modified catalyst used is 2-5% of the mass of the raw materials in the reactor, preferably 2-3%.
[0015] The hydrogenation conditions are: temperature 80–160℃, pressure 1.5–7.0 MPa, and hydrogenation time 8–15 hours. Preferably, the temperature is 90–140℃ and the pressure is 2.0–6.0 MPa.
[0016] The vacuum distillation conditions are: temperature 130–150°C, vacuum degree -0.08–-0.05 MPa. Light components and polyanhydrides are removed by vacuum distillation. In this invention, a thin-film evaporator is used for vacuum distillation to improve evaporation efficiency and reduce the high-temperature residence time.
[0017] The obtained methylhexahydrophthalic anhydride is colorless and transparent, with an iodine value ≤0.4, an acid value of 660~670mgKOH / g, anhydride content ≥40.5%, color ≤3, and purity ≥99.0%.
[0018] Compared to batch hydrogenation, this invention achieves more uniform mixing of methyltetrahydrophthalic anhydride and hydrogen, resulting in better heat transfer and increased catalyst contact area. The absence of hot spots within the reactor leads to less self-polymerization of methyltetrahydrophthalic anhydride, resulting in a higher yield of methylhexahydrophthalic anhydride. Furthermore, since Raney nickel catalyst is not used, there is no catalyst residue in the product, thus improving overall product quality. Simultaneously, the catalyst does not require sedimentation and recovery; it is recycled within the reactor, requiring only periodic removal of 0.2–0.5% of the spent catalyst and replenishment with fresh catalyst.
[0019] Beneficial effects
[0020] (1) The present invention uses a Ni / Co modified catalyst in the hydrogenation process. Compared with the traditional Raney nickel catalyst, it has moderate activity, high hydrogenation efficiency, fewer by-products, high yield, stable acid value and anhydride content, and the resulting methylhexahydrophthalic anhydride product has excellent performance.
[0021] (2) The present invention uses a fluidized bed hydrogenation reactor for hydrogenation. The particles in the bed are constantly stirred, so that the reactants and products are constantly mixed and contacted. The reaction rate is fast and the conversion rate is high. The biggest feature of this reactor is that the catalyst can be continuously added and the waste catalyst can be continuously discharged. The operating cycle is long and uninterrupted production can be carried out. The resulting methylhexahydrophthalic anhydride product has few by-products, high purity, and stable product quality.
[0022] (3) The present invention adopts a steam-heated thin film evaporation post-treatment process, which has a simple structure, high heat transfer efficiency, short product residence time, high yield and low color, thereby further improving the quality of the product. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation
[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims. Performance Testing:
[0025] ① The acid value of the product was measured according to the method of GB / T 24138-2022;
[0026] ② The iodine value of the product was measured according to the SH / T 0234-92 method;
[0027] ③ The color of the product is measured according to the GB / T 3143 method.
[0028] The preparation method of the Ni / Co modified catalyst used in the examples includes the following steps:
[0029] Add 20g of activated carbon to 75g of nickel nitrate and soak at 80℃ for 2 hours. Then add 5g of cobalt nitrate into the mixture and stir magnetically for 5-15 minutes to ensure uniform mixing. Soak at 100℃ for 8 hours. After the reaction is complete, remove the activated carbon and dry it at 130℃ under a nitrogen atmosphere for 3 hours. Then calcine the activated carbon at 500℃ under a nitrogen atmosphere for 6 hours to obtain the Ni / Co modified catalyst.
[0030] The purified methyltetrahydrophthalic anhydride used in the examples was obtained by vacuum distillation of crude methyltetrahydrophthalic anhydride to remove light components and polyacid anhydrides. The crude methyltetrahydrophthalic anhydride was a mixture of 3-methyltetrahydrophthalic anhydride and 4-methyltetrahydrophthalic anhydride in a mass ratio of 25:75. The vacuum distillation conditions were: temperature 140°C, vacuum degree -0.06 MPa.
[0031] Example 1
[0032] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 30g of Ni / Co modified catalyst was added at 3% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 3g / h.
[0033] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 125°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 9 hours. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The finished product yield was 98.1%, with an iodine value of 0.11, an acid value of 667, anhydride content of 41.7%, color of 2.06, and purity of 99.2%.
[0034] Example 2
[0035] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 32g of Ni / Co modified catalyst was added at 3.2% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 3g / h.
[0036] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 125°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 9 hours. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The finished product yield was 98.5%, with an iodine value of 0.09, an acid value of 666, anhydride content of 41.3%, color of 1.02, and purity of 99.55%.
[0037] Example 3
[0038] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 32g of Ni / Co modified catalyst was added at 3.2% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 3g / h.
[0039] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 135°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 9 hours. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The yield of the finished product was 96.60%, the iodine value was 0.73, the acid value was 663, the anhydride content was 41.45%, the color was 1.02, and the purity was 98.75%.
[0040] Example 4
[0041] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 32g of Ni / Co modified catalyst was added at 3.2% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 3g / h.
[0042] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 125°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 10h. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The finished product yield was 96.60%, with an iodine value of 0.88, an acid value of 668, anhydride content of 41.60%, color of 3.82, and purity of 99.05%.
[0043] Example 5
[0044] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 32g of Ni / Co modified catalyst was added at 3.2% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 2g / h.
[0045] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 125°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 9 hours. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The finished product yield was 98.5%, with an iodine value of 0.09, an acid value of 666, anhydride content of 41.3%, color of 1.02, and purity of 99.55%.
[0046] Comparative Example 1
[0047] 2000g of refined methyltetrahydrophthalic anhydride was added to a heated feed tank. The air in the reactor was replaced with nitrogen three times. Then, 1000g of refined methyltetrahydrophthalic anhydride was introduced into the fluidized bed hydrogenation reactor as a bed material. 32g of Raney nickel catalyst was added at 3.2% of the material. The catalyst was replenished starting after the material residence time was 9 hours. Waste catalyst was discharged at a rate of 3g / h.
[0048] The fluidized bed reactor was initially heated. When the reaction reached 80°C, hydrogen gas was introduced from the bottom. Once the pressure reached 3.0 MPa, the hydrogen supply was stopped. After the temperature stabilized at 125°C, the remaining 1000g of refined methyltetrahydrophthalic anhydride and hydrogen gas in the feed tank were fed back into the fluidized bed hydrogenation reactor at a flow rate of 100g / h. The pressure inside the reactor was stabilized at 5.0 MPa, and the material residence time was 9 hours. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride were collected from the top of the reactor in the gas phase, while the waste catalyst was collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, was collected from the side using a pump with controlled liquid level and transferred to a heated product tank. The obtained crude methylhexahydrophthalic anhydride was then subjected to vacuum distillation in a separation unit equipped with a thin-film evaporator at a vacuum of -0.06 MPa and a temperature of 140°C to obtain the finished product, methylhexahydrophthalic anhydride. The finished product yield was 94.36%, with an iodine value of 9.11, an acid value of 663, anhydride content of 41.10%, color of 21.4, and purity of 96.5%.
Claims
1. A method for preparing methylhexahydrophthalic anhydride, comprising the following steps: Using unisomerized refined methyltetrahydrophthalic anhydride as raw material, the raw material and hydrogen are fed into a fluidized bed hydrogenation reactor. A special catalyst is then added, and the raw material and catalyst are thoroughly mixed under the action of an in-reactor circulation pump for hydrogenation. Waste hydrogen and the light components of methyltetrahydrophthalic anhydride are collected from the top gas phase of the reactor, while the waste catalyst is collected from the bottom. The hydrogenation product, crude methylhexahydrophthalic anhydride, is collected from the side of the reactor, with the liquid level controlled by a pump. The crude methylhexahydrophthalic anhydride is then sent to a separation unit equipped with a thin-film evaporator for vacuum distillation to obtain the finished product, methylhexahydrophthalic anhydride. The special catalyst is a Ni / Co modified catalyst, and the preparation method of the Ni / Co modified catalyst includes the following steps: Add 20-25 wt% activated carbon to 75-80 wt% nickel nitrate and soak at 60-80℃ for 2-3 hours. Then add 5-10 wt% cobalt nitrate dropwise into the mixture and stir magnetically for 5-15 minutes to ensure uniform mixing. Soak at 90-100℃ for 8-11 hours. After the reaction is complete, remove the activated carbon and dry it at 120-140℃ under a nitrogen atmosphere for 2-4 hours. Then calcine the activated carbon at 500-600℃ under a nitrogen atmosphere for 5-7 hours to obtain the Ni / Co modified catalyst.
2. The preparation method according to claim 1, characterized in that: The unisomerized refined methyltetrahydrophthalic anhydride is obtained by removing light components and polyanhydrides by vacuum distillation of crude methyltetrahydrophthalic anhydride.
3. The preparation method according to claim 2, characterized in that: The crude methyltetrahydrophthalic anhydride is a mixture of 3-methyltetrahydrophthalic anhydride and 4-methyltetrahydrophthalic anhydride in a mass ratio of 30~70:30-70.
4. The preparation method according to claim 1, characterized in that: The amount of Ni / Co modified catalyst used is 2-5% of the mass of the raw materials in the reactor.
5. The preparation method according to claim 1, characterized in that: The hydrogenation conditions are: temperature 80–160℃, pressure 1.5–7.0 MPa, and hydrogenation time 8–15 hours.
6. The preparation method according to claim 1, characterized in that: The vacuum distillation conditions are: temperature 130~150℃, vacuum degree -0.08~-0.05Mpa.
7. The preparation method according to claim 1, characterized in that: The obtained methylhexahydrophthalic anhydride is colorless and transparent, with an iodine value ≤0.4, an acid value of 660~670mgKOH / g, anhydride content ≥40.5%, color ≤3, and purity ≥99.0%.