A production method of 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization

Abstract

The application discloses a preparation method of 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization, and nitrogen-doped porous carbon is prepared by carbonizing melamine sponge, the nickel is loaded by cooperating with wetting of a surfactant and ultrasonic cavitation, and the loaded nickel catalyst is obtained by roasting and reduction. 1,2,3,6-tetrahydrophthalic anhydride is heated and refluxed in an organic solvent and catalyst to isomerize, the catalyst is recovered by filtration, and the product is obtained by cooling and crystallizing the filtrate. The method utilizes the through macroporous structure to eliminate the mass transfer resistance, and the nitrogen-anchored nickel prevents agglomeration, so that the catalyst is low in cost, recyclable and free of waste water.

Description

Technical Field

[0001] This invention relates to the field of compound isomerization technology, and more particularly to a method for preparing 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization. Background Technology

[0002] 3,4,5,6-Tetrahydrophthalic anhydride is an important intermediate in the synthesis of fine chemicals such as pesticides, pharmaceuticals, plasticizers, and epoxy resin curing agents. Industrially, the mainstream synthetic route involves a Diels-Alder addition reaction between maleic anhydride and 1,3-butadiene to generate 1,2,3,6-tetrahydrophthalic anhydride. Subsequently, under the action of a catalyst, a double bond isomerization reaction yields the thermodynamically more stable target product, 3,4,5,6-tetrahydrophthalic anhydride.

[0003] In the isomerization reaction step, traditional catalysts are mainly divided into two categories: one is homogeneous strong acid catalysts, such as p-toluenesulfonic acid and phosphorus pentoxide; the other is noble metal catalysts, such as palladium on carbon (Pd / C).

[0004] However, the aforementioned prior art has the following drawbacks:

[0005] Homogeneous strong acid catalytic systems: After the reaction, catalysts such as p-toluenesulfonic acid and phosphorus pentoxide require extensive neutralization treatment steps, including water washing and alkali washing. This not only results in a cumbersome process but also generates large amounts of high-concentration organic saline wastewater, placing significant environmental pressure on the system. Furthermore, these strong acids severely corrode reaction equipment, increasing maintenance costs. In addition, the use of phosphorus pentoxide can easily lead to side reactions such as material agglomeration and product color darkening.

[0006] Noble metal catalytic systems: Noble metal catalysts, represented by Pd / C, are expensive, and precious metal resources are scarce, which is not conducive to cost control in large-scale industrial production. At the same time, traditional carbon supports are mostly microporous structures, which have greater resistance to mass transfer of organic macromolecules, and ordinary activated carbon is highly hydrophobic, resulting in uneven loading of metal active components and easy agglomeration, which affects catalytic efficiency and catalyst stability.

[0007] Therefore, developing a low-cost, highly active, easily separable, environmentally friendly heterogeneous catalyst with excellent mass transfer performance and its application process is of great practical significance for the green industrial production of 3,4,5,6-tetrahydrophthalic anhydride.

[0008] Therefore, this invention is proposed to solve the above-mentioned technical problems. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization, comprising the following steps:

[0010] S1. Melamine sponge is carbonized at 700~900℃ for 2~4 hours under an inert atmosphere, cooled, ground and sieved to obtain nitrogen-doped porous carbon;

[0011] S2. Dissolve nickel salt and surfactant in deionized water to prepare an impregnation solution, add nitrogen-doped porous carbon obtained in step S1, perform ultrasonic treatment for 30-60 minutes, and then dry.

[0012] S3. The dried solid is calcined and reduced at 400~600℃ under a reducing atmosphere to obtain a nickel-supported catalyst;

[0013] S4. Dissolve 1,2,3,6-tetrahydrophthalic anhydride in an organic solvent, add the nickel-supported catalyst obtained in step S3, and carry out an isomerization reaction under reflux heating conditions.

[0014] S5. After the reaction is complete, filter to recover the catalyst, cool the filtrate to crystallize, and dry to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0015] Preferably, the inert atmosphere in step S1 is argon, and the heating rate for carbonization is 2~10℃ / min.

[0016] Preferably, the grinding and sieving in step S1 involves grinding the carbonized product and then passing it through a 100-200 mesh sieve.

[0017] Preferably, the nickel salt in step S2 is selected from one or more of nickel nitrate and nickel acetate, and the surfactant is selected from one or more of polyethylene glycol and hexadecyltrimethylammonium bromide.

[0018] Preferably, the power of the ultrasonic treatment in step S2 is 200~400W.

[0019] Preferably, the reducing atmosphere in step S3 is a mixture of hydrogen and argon, wherein the hydrogen component is 5% to 20%.

[0020] Preferably, the organic solvent in step S4 is selected from one or more of toluene and xylene.

[0021] Preferably, the reaction temperature under the heating and reflux conditions in step S4 is 120~160℃, and the reaction time is 2~6 hours.

[0022] Preferably, the filtration in step S5 is vacuum filtration.

[0023] Preferably, the temperature of the filtration is not lower than 120°C.

[0024] The beneficial effects of this invention are:

[0025] This invention uses melamine sponge as a carbon source to prepare a nitrogen-doped porous carbon support through high-temperature carbonization under an inert atmosphere. Melamine sponge itself has a three-dimensional network structure, and after carbonization, it retains its abundant pore structure. This porous structure facilitates mass transfer and diffusion between reactants and products, effectively reducing the mass transfer resistance of organic macromolecules during the catalytic process. Simultaneously, melamine, as a nitrogen source, successfully incorporates nitrogen into the carbon framework during carbonization, forming abundant nitrogen-containing functional groups. These nitrogen-containing functional groups not only stabilize the active metallic component nickel through coordination, preventing its aggregation during the reaction, but also regulate the electronic properties of the carbon support, improving the surface activity of the catalyst and thus enhancing the efficiency of the catalytic isomerization reaction. Furthermore, this invention employs a synergistic impregnation method using surfactant wetting and ultrasonic cavitation, solving the problem of uneven loading caused by the hydrophobicity of the carbon support, allowing the active component to penetrate deep into the pores. Moreover, the heterogeneous catalyst of this invention can be recovered simply by filtration, with no wastewater discharge and no equipment corrosion. Attached Figure Description

[0026] Figure 1 SEM image of the nickel-supported catalyst prepared in Example 1;

[0027] Figure 2 The image shows a SEM image of the Ni / ordinary activated carbon catalyst prepared in Comparative Example 2. Detailed Implementation

[0028] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a method for preparing 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization, comprising the following steps:

[0030] 1. Preparation of 1,2,3,6-tetrahydrophthalic anhydride by the Diels-Alder reaction:

[0031] In a high-pressure reactor, maleic anhydride:xylene:1,3-butadiene = 100g:200mL:60g was added. The reactor was closed, and nitrogen was introduced three times to purge the mixture. Then, 1,3-butadiene gas was introduced until the pressure reached 0.6~0.8MPa. Stirring was started, and the temperature was raised to 80℃ and maintained for 4 hours. After the reaction, the mixture was cooled to room temperature, and the reaction solution was transferred to a crystallizer and allowed to crystallize at 0-5℃ for 2 hours. The mixture was then filtered, and the filter cake was dried in a vacuum drying oven at 50℃ for 4 hours to obtain 1,2,3,6-tetrahydrophthalic anhydride.

[0032] 2. Catalytic isomerization to prepare 3,4,5,6-tetrahydrophthalic anhydride:

[0033] S1. Melamine sponge is carbonized at 700~900℃ for 2~4 hours under an inert atmosphere, cooled, ground and sieved to obtain nitrogen-doped porous carbon;

[0034] S2. Dissolve nickel salt and surfactant in deionized water to prepare an impregnation solution, add nitrogen-doped porous carbon obtained in step S1, perform ultrasonic treatment for 30-60 minutes, and then dry.

[0035] S3. The dried solid is calcined and reduced at 400~600℃ under a reducing atmosphere to obtain a nickel-supported catalyst;

[0036] S4. Dissolve 1,2,3,6-tetrahydrophthalic anhydride in an organic solvent, add the nickel-supported catalyst obtained in step S3, and carry out an isomerization reaction under reflux heating conditions.

[0037] S5. After the reaction is complete, filter to recover the catalyst, cool the filtrate to crystallize, and dry to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0038] In this invention, the inert atmosphere in step S1 is argon, and the heating rate for carbonization is 2~10℃ / min.

[0039] In this invention, the grinding and sieving in step S1 refers to grinding the carbonized product and then passing it through a 100-200 mesh sieve.

[0040] In this invention, the nickel salt in step S2 is selected from one or more of nickel nitrate and nickel acetate, with nickel nitrate being preferred. The nickel nitrate in this invention is preferably the common nickel nitrate hexahydrate. The surfactant is selected from one or more of polyethylene glycol and hexadecyltrimethylammonium bromide, with polyethylene glycol being preferred.

[0041] In this invention, the power of the ultrasonic treatment in step S2 is 200~400W.

[0042] In this invention, the reducing atmosphere in step S3 is a mixture of hydrogen and argon, wherein the hydrogen component is 5% to 20%.

[0043] In this invention, the organic solvent in step S4 is selected from one or more of toluene and xylene, with xylene being preferred.

[0044] In this invention, the reaction temperature under the heating and reflux conditions in step S4 is 120~160℃, and the reaction time is 2~6 hours.

[0045] In this invention, the filtration in step S5 is vacuum filtration.

[0046] In this invention, the temperature of the filtration is not lower than 120°C.

[0047] The present invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] This embodiment describes a method for preparing 3,4,5,6-tetrahydrophthalic anhydride using catalytic isomerization, comprising the following steps:

[0050] S1. Cut the melamine sponge into small pieces, wash it three times with deionized water and twice with anhydrous ethanol, and dry it in an 80℃ oven for 12 hours. Place the dried sponge in a tube furnace and heat it to 800℃ at 5℃ / min under an argon atmosphere for 3 hours. After naturally cooling to room temperature, take it out and grind it in a mortar through a 100~200 mesh sieve to obtain nitrogen-doped porous carbon.

[0051] S2. Weigh out nickel nitrate hexahydrate and polyethylene glycol in deionized water according to the ratio of nitrogen-doped porous carbon: nickel nitrate hexahydrate: polyethylene glycol: deionized water = 2g: 5g: 0.5g: 50mL to prepare an impregnation solution. Add the nitrogen-doped porous carbon obtained in step S1, place it in an ultrasonic cleaner, and ultrasonically treat it for 45 minutes at a power of 300W. Then, evaporate the suspension at 80℃.

[0052] S3. The dried solid was calcined and reduced at 500℃ for 3 hours under a 10% H2 / Ar mixed atmosphere at a rate of 5℃ / min. After natural cooling, a nickel-supported catalyst was obtained, such as... Figure 1 As shown;

[0053] S4. Add the following ingredients to a three-necked flask according to the ratio of 1,2,3,6-tetrahydrophthalic anhydride:xylene:catalyst = 50g:200mL:2.5g, start stirring, heat to 140℃ and reflux, and react for 4 hours.

[0054] S5. After the reaction is complete, filter while hot (not lower than 120℃), transfer the filtrate to a crystallizer, cool naturally to room temperature, place it in an ice-water bath (0~5℃), let it stand for 2 hours to crystallize, then filter by suction, and dry the filter cake in a vacuum drying oven at 50℃ for 4 hours to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0055] Example 2

[0056] This embodiment describes a method for preparing 3,4,5,6-tetrahydrophthalic anhydride using catalytic isomerization, comprising the following steps:

[0057] S1. Cut the melamine sponge into small pieces, wash it three times with deionized water and twice with anhydrous ethanol, and dry it in an 80℃ oven for 12 hours. Place the dried sponge in a tube furnace and heat it to 700℃ at 2℃ / min under an argon atmosphere. Carbonize it for 2 hours, cool it naturally to room temperature, and then grind it in a mortar through a 100~200 mesh sieve to obtain nitrogen-doped porous carbon.

[0058] S2. Weigh out nickel nitrate hexahydrate and polyethylene glycol in deionized water according to the ratio of nitrogen-doped porous carbon: nickel nitrate hexahydrate: polyethylene glycol: deionized water = 2g: 5g: 0.5g: 50mL to prepare an impregnation solution. Add the nitrogen-doped porous carbon obtained in step S1, place it in an ultrasonic cleaner, and ultrasonically treat it for 60 minutes at a power of 200W. Then, evaporate the suspension at 80℃.

[0059] S3. The dried solid was calcined and reduced at 400°C for 3 hours under a 5% H2 / Ar mixed atmosphere at a rate of 5°C / min. After natural cooling, a nickel-supported catalyst was obtained.

[0060] S4. Add the 1,2,3,6-tetrahydrophthalic anhydride:xylene:catalyst in a ratio of 50g:200mL:2.5g to a three-necked flask, start stirring, heat to 120℃ and reflux, and react for 6 hours.

[0061] S5. After the reaction is complete, filter while hot (not lower than 120℃), transfer the filtrate to a crystallizer, cool naturally to room temperature, place it in an ice-water bath (0~5℃), let it stand for 2 hours to crystallize, then filter by suction, and dry the filter cake in a vacuum drying oven at 50℃ for 4 hours to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0062] Example 3

[0063] This embodiment describes a method for preparing 3,4,5,6-tetrahydrophthalic anhydride using catalytic isomerization, comprising the following steps:

[0064] S1. Cut the melamine sponge into small pieces, wash it three times with deionized water and twice with anhydrous ethanol, and dry it in an oven at 80℃ for 12 hours. Place the dried sponge in a tube furnace and heat it to 900℃ at 10℃ / min under an argon atmosphere. Carbonize it for 4 hours, cool it naturally to room temperature, and then grind it in a mortar through a 100~200 mesh sieve to obtain nitrogen-doped porous carbon.

[0065] S2. Weigh out nickel nitrate hexahydrate and polyethylene glycol in deionized water according to the ratio of nitrogen-doped porous carbon: nickel nitrate hexahydrate: polyethylene glycol: deionized water = 2g: 5g: 0.5g: 50mL to prepare an impregnation solution. Add the nitrogen-doped porous carbon obtained in step S1, place it in an ultrasonic cleaner, and ultrasonically treat it for 30 minutes at a power of 400w. Then, evaporate the suspension at 80℃.

[0066] S3. The dried solid was calcined and reduced at 600°C for 3 hours under a 20% H2 / Ar mixed atmosphere at a rate of 5°C / min. After natural cooling, a nickel-supported catalyst was obtained.

[0067] S4. Add the following ingredients to a three-necked flask in a ratio of 1,2,3,6-tetrahydrophthalic anhydride:xylene:catalyst = 50g : 200mL : 2.5g, start stirring, heat to 160℃ and reflux, and react for 2 hours.

[0068] S5. After the reaction is complete, filter while hot (not lower than 120℃), transfer the filtrate to a crystallizer, cool naturally to room temperature, place it in an ice-water bath (0~5℃), let it stand for 2 hours to crystallize, then filter by suction, and dry the filter cake in a vacuum drying oven at 50℃ for 4 hours to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0069] Comparative Example 1

[0070] In a dry three-necked flask, add 50g of 1,2,3,6-tetrahydrophthalic anhydride and 200 mL of xylene dried by molecular sieve. Under stirring and nitrogen protection, slowly add 2.5g of phosphorus pentoxide powder in batches, controlling the addition rate. After the addition is complete, install a condenser with a drying tube and heat the reaction system to 140℃ and reflux for 4 hours. After the reaction is complete, stop heating and cool the reaction solution to below room temperature. Under ice-water bath cooling and strong stirring, very slowly add the reaction solution dropwise into a beaker containing crushed ice and water to quench any remaining phosphorus pentoxide. Transfer the mixture to a separatory funnel to separate the organic phase (xylene layer). The aqueous phase was extracted twice with xylene, and the organic phases were combined. The combined organic phase was then neutralized with 5% sodium carbonate aqueous solution to neutralize the residual acid, followed by washing with saturated brine. The organic phase was dried with anhydrous magnesium sulfate, filtered to remove the desiccant, and the filtrate was concentrated by rotary evaporation (60°C) to obtain 3,4,5,6-tetrahydrophthalic anhydride.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 1 is that the catalyst support used is commercially available ordinary activated carbon. 5g of nickel nitrate hexahydrate and 0.5g of polyethylene glycol were dissolved in 50mL of deionized water, and the activated carbon was added. The mixture was ultrasonically treated (300W) for 45 minutes, dried by rotary evaporation at 80℃, and then calcined and reduced at 500℃ for 3 hours under a 10% H2 / Ar atmosphere with a heating rate of 5℃ / min to obtain the Ni / ordinary activated carbon catalyst. Figure 2 As shown.

[0073] Comparative Example 3

[0074] The difference between Comparative Example 3 and Example 1 is that the catalyst used in Comparative Example 3 is a noble metal Pd / C catalyst, while the other steps are the same as in Example 1.

[0075] Experimental Test

[0076] The yield and purity of 3,4,5,6-tetrahydrophthalic anhydride prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the activity retention rate of the catalyst after continuous operation for 500 h was recorded. The results are shown in Table 1.

[0077] Yields were determined by gas chromatography with external standard method. A standard curve was plotted using 3,4,5,6-tetrahydrophthalic anhydride standard with a purity ≥99.5%, and the product yield was calculated by comparing the peak area of ​​the sample with the standard curve. Purity was determined by high performance liquid chromatography (HPLC) using a C18 reversed-phase column, a mobile phase of methanol-water (60:40 v / v), a flow rate of 1.0 mL / min, and a detection wavelength of 254 nm. The product purity was calculated by peak area normalization method. The catalyst activity retention rate was based on the product yield of the first reaction. The ratio of the product yield after 500 h of continuous operation to the first yield was the activity retention rate.

[0078] Table 1

[0079]

[0080] As shown in the table, the product yield, purity, and catalyst activity retention of Examples 1-3 are all superior to those of the comparative example. This is due to the synergistic effect of the catalyst support and the preparation process. First, the carbonization of the melamine sponge forms a through-structure, eliminating the mass transfer resistance of the 1,2,3,6-tetrahydrophthalic anhydride macromolecules, allowing the reactants to quickly contact the active sites. At the same time, the nitrogen atoms remaining in the carbon skeleton anchor nickel through coordination, effectively inhibiting metal agglomeration during high-temperature reactions. In contrast, Comparative Example 2 uses ordinary activated carbon (mainly microporous, without nitrogen doping), which easily agglomerates nickel and has slow mass transfer, resulting in a yield of only 74.0% and an activity retention rate of only 66.7%. Second, this invention uses surfactant wetting and ultrasonic cavitation for synergistic impregnation, improves the hydrophobic surface of the carbon support with polyethylene glycol, and forces the nickel precursor into deep channels through ultrasonic cavitation, achieving highly uniform dispersion of nickel. Comparative Example 1 (homogeneous phosphorus pentoxide) requires water and alkali washing, resulting in low product purity (89.2%), a yield of only 64.3%, and the inability to recover the catalyst. Comparative Example 3 (precious metal Pd / C) exhibits strong performance (yield 85.0%, activity retention 86.2%), but is costly.

[0081] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing 3,4,5,6-tetrahydrophthalic anhydride by catalytic isomerization, characterized in that, Includes the following steps: S1. Melamine sponge is carbonized at 700~900℃ for 2~4 hours under an inert atmosphere, cooled, ground and sieved to obtain nitrogen-doped porous carbon; S2. Dissolve nickel salt and surfactant in deionized water to prepare an impregnation solution, add nitrogen-doped porous carbon obtained in step S1, perform ultrasonic treatment for 30-60 minutes, and then dry. S3. The dried solid is calcined and reduced at 400~600℃ under a reducing atmosphere to obtain a nickel-supported catalyst; S4. Dissolve 1,2,3,6-tetrahydrophthalic anhydride in an organic solvent, add the nickel-supported catalyst obtained in step S3, and carry out an isomerization reaction under reflux heating conditions. S5. After the reaction is complete, filter to recover the catalyst, cool the filtrate to crystallize, and dry to obtain 3,4,5,6-tetrahydrophthalic anhydride.

2. The method according to claim 1, characterized in that, The inert atmosphere described in step S1 is argon, and the heating rate for carbonization is 2~10℃ / min.

3. The method according to claim 1, characterized in that, The grinding and sieving mentioned in step S1 refers to grinding the carbonized product and then passing it through a 100-200 mesh sieve.

4. The method according to claim 1, characterized in that, The nickel salt in step S2 is selected from one or more of nickel nitrate and nickel acetate, and the surfactant is selected from one or more of polyethylene glycol and hexadecyltrimethylammonium bromide.

5. The method according to claim 1, characterized in that, The power of the ultrasonic treatment in step S2 is 200~400W.

6. The method according to claim 1, characterized in that, The reducing atmosphere in step S3 is a mixture of hydrogen and argon, wherein the hydrogen component is 5% to 20%.

7. The method according to claim 1, characterized in that, The organic solvent mentioned in step S4 is selected from one or more of toluene and xylene.

8. The method according to claim 1, characterized in that, The reaction temperature under the heating and reflux conditions described in step S4 is 120~160℃, and the reaction time is 2~6 hours.

9. The method according to claim 1, characterized in that, The filtration described in step S5 is vacuum filtration.

10. The method according to claim 9, characterized in that, The temperature of the filtration is not lower than 120°C.

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