Production apparatus and preparation method of diethyl isophthalate

Abstract

The application belongs to the technical field of carbon ring compounds, and particularly relates to a production device and preparation method of diethyl isophthalate. The production device of diethyl isophthalate comprises a hydrolysis kettle, a waste inlet and an acid liquid inlet are arranged on the hydrolysis kettle, a stirring assembly is arranged in the hydrolysis kettle, the stirring assembly comprises a stirring ring, a sleeve is arranged at the top of the stirring ring, a screw rod is screw-connected in the sleeve, a centrifuge, a dissolving kettle and a trickle bed are sequentially connected at the bottom of the hydrolysis kettle, a filler layer is arranged in the trickle bed, a filling layer is arranged outside the filler layer, a gasifier is arranged at the side of the trickle bed, and a first-stage rectifying tower, a second-stage rectifying tower and a third-stage rectifying tower are sequentially connected at the bottom of the trickle bed. The waste in the production process of isophthalonitrile is hydrolyzed to obtain a mixed material containing isophthalic acid, and then the isophthalic acid is obtained through centrifugal dissolving and other operations. The isophthalic acid is subjected to esterification to obtain a diethyl isophthalate product.

Description

Technical Field

[0001] This invention belongs to the field of carbocyclic compound technology, specifically relating to a production apparatus and preparation method for diethyl isophthalate. Background Technology

[0002] The main impurity in crude isophthalonitrile is m-3-cyanobenzamide (accounting for 0.5-2.5 wt% of the crude product). Its boiling point is higher than that of isophthalonitrile, and it is difficult to vaporize during the refining distillation process, so it is enriched in the residue at the bottom of the vessel. Mononitrile produced during the production of isophthalonitrile may also be converted into benzamide. In addition, the composition of the residue in the vessel after the refining of isophthalonitrile is quite complex, including amides and some polymers. It has always been treated as waste, resulting in economic losses and waste of resources.

[0003] The amide waste generated during the preparation of isophthalonitrile can be hydrolyzed to obtain acidic substances, and the acidic substances can be further esterified to obtain esters. The reaction conditions need to be strictly controlled during the hydrolysis and esterification processes. In the existing production process, the hydrolysis of amides is promoted by increasing the mixing degree of raw materials, and the esterification reaction is catalyzed by adding acidic catalysts to promote the reaction. However, the existing hydrolysis process has problems such as long hydrolysis time and uneven mixing leading to an increase in hydrolysis byproducts.

[0004] Chinese patent CN101306999A discloses a method for producing diethyl isophthalate, using isophthalic acid and ethanol as raw materials and concentrated sulfuric acid as a catalyst. The mixtures are added to a reaction vessel in a molar ratio of 1:3.7-4.0:0.011-0.014 and stirred thoroughly and uniformly. Then, the mixture is heated, pressurized, distilled, neutralized, and purified to obtain the diethyl isophthalate product. The traditional preparation method used in this patent suffers from low catalytic efficiency and low purity of the reaction product. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a production apparatus for diethyl isophthalate, which recycles and reuses the waste materials from the production of isophthalonitrile to obtain diethyl isophthalate, thereby realizing the recycling of waste; the present invention also provides a method for preparing diethyl isophthalate.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] The diethyl isophthalate production apparatus of the present invention includes a hydrolysis reactor with a waste inlet and an acid inlet. A stirring assembly is installed inside the hydrolysis reactor, including a stirring ring. A sleeve is installed on the top of the stirring ring, and a screw is threadedly connected inside the sleeve. A centrifuge, a dissolving vessel, and a trickle bed are sequentially connected to the bottom of the hydrolysis reactor. A packing layer is installed inside the trickle bed, and a surrounding layer of packing is arranged around the outside of the packing layer. A vaporizer is installed on the side of the trickle bed. A primary distillation column, a secondary distillation column, and a tertiary distillation column are sequentially connected to the bottom of the trickle bed.

[0008] The hydrolysis reactor is equipped with a jacket. The stirring ring includes several connecting rods that are inclined in the middle. The top of the connecting rod is connected to the sleeve. A connecting ring is provided on the outside of the connecting rod. The connecting rod connects the sleeve and the connecting ring. The top of the screw passes through the top of the hydrolysis reactor and is connected to a motor.

[0009] The centrifuge has a filtrate outlet at the bottom, a solvent inlet at the top, and a slag discharge port at the bottom. The lower part of the side wall of the dissolving vessel is connected to a trickle bed. The packing layer is funnel-shaped and fills the space between the packing layer and the inner wall of the trickle bed. The density of the packing layer is greater than that of the packing material. Both the packing layer and the inner wall are filled with modified heteropolyacid catalysts. The packing density of the modified heteropolyacid catalyst in the packing layer is 500-1000 kg / m³. 3 The packing height is 2-3m, and the packing density of the modified heteropolyacid catalyst in the packing layer is 1000-1200 kg / m³. 3 The filling height is 2-3m. The bottom of the first-stage distillation column is connected to the top of the second-stage distillation column, the bottom of the second-stage distillation column is connected to the top of the third-stage distillation column, and the top of the third-stage distillation column is equipped with a discharge port.

[0010] The method for preparing diethyl isophthalate using the aforementioned diethyl isophthalate production apparatus includes the following steps:

[0011] A1. Waste is added to the hydrolysis reactor through the waste inlet, and acid is added through the acid inlet to carry out the hydrolysis reaction, resulting in a mixture containing isophthalic acid.

[0012] A2. The mixture containing isophthalic acid is centrifuged in a centrifuge to obtain isophthalic acid. The isophthalic acid is then dissolved in a dissolving vessel to obtain an organic solution of isophthalic acid. The organic solution of isophthalic acid is then transferred to a trickle bed supported with a modified heteropolyacid catalyst and subjected to an esterification reaction with vaporized ethanol to obtain a diethyl isophthalate esterified solution.

[0013] A3. The obtained diethyl isophthalate esterified liquid is distilled three times in sequence through a primary distillation column, a secondary distillation column, and a tertiary distillation column to obtain the diethyl isophthalate product.

[0014] The waste in step A1 is waste generated during the production of isophthalonitrile, and the waste contains amide substances.

[0015] In step A1, the acid solution is sulfuric acid or hydrochloric acid, the acid concentration is 10-60 wt.%, the pH of the hydrolysis reaction is 1-4, the hydrolysis reaction temperature is 50-100℃, and the hydrolysis reaction time is 1-5 h.

[0016] The preparation method of the modified heteropolyacid catalyst in step A2 is as follows:

[0017] a1. Dissolve niobium salt and tantalum salt in deionized water, and add phosphoric acid to adjust the pH to obtain a heteropolyacid solution;

[0018] a2. Dissolve aluminum salt and zirconium salt in deionized water to obtain a precursor solution;

[0019] a3. Mix the heteropolyacid solution with the precursor solution, then add an alkaline solution for co-precipitation to obtain a solid precipitate; after aging, centrifuging, washing, drying and calcining the solid precipitate, a modified heteropolyacid catalyst is obtained.

[0020] In step a1, the niobium salt is niobium chloride, the tantalum salt is tantalum nitrate, and the mass ratio of niobium salt to tantalum salt is 1:0.5-1; the pH is adjusted to 2-4, and the phosphoric acid concentration is 30-50 wt.%.

[0021] In step a2, the aluminum salt is aluminum nitrate, the zirconium salt is zirconium nitrate, the mass ratio of aluminum salt to zirconium salt is 1:0.5-1, and the mass ratio of aluminum salt to niobium salt in step a1 is 3-4:1.

[0022] In step a3, the stirring and mixing temperature is 30-50℃, the stirring and mixing speed is 300-500 rpm, the alkaline solution is ammonia or sodium carbonate solution, the pH of co-precipitation is 8-10, and the co-precipitation time is 0.5-2 h; the aging temperature is 55-65℃, the aging time is 4-12 h, the centrifugation speed is 3000-8000 rpm, the centrifugation time is 30-50 min, the washing is done by alternating washing with deionized water and ethanol, the drying temperature is 80-120℃, the drying time is 8-12 h, the calcination temperature is 400-600℃, the calcination time is 4-6 h, and the calcination heating rate is 2-5℃ / min.

[0023] In step A2, the centrifugation rate is 900-1200 rpm, the centrifugation time is 0.75-1 h, toluene is used for dissolution, and the mass ratio of isophthalic acid to toluene is 1:2.5-4; the mass ratio of ethanol to isophthalic acid is 1:0.8-1, the esterification reaction time is 0.5-10 h, and the esterification reaction temperature is 80-120℃. In step A3, the pressure of the first-stage distillation column is atmospheric pressure, the pressure of the second-stage distillation column is -0.06 to -0.10 MPa, the pressure of the third-stage distillation column is -0.06 to -0.10 MPa, the temperature of the first-stage distillation column is 80-85℃, the temperature of the second-stage distillation column is 110-130℃, and the temperature of the third-stage distillation column is 200-220℃.

[0024] This invention uses niobium and tantalum to replace traditional coordinating metal atoms to form modified heteropolyacids. The introduction of Nb / Ta increases the negative charge density of the heteropolyacid anion, enhancing its proton dissociation ability. 5+ / Ta 5+ The coordinating unsaturated sites provide empty orbitals, activating the carboxyl oxygen atom and promoting nucleophilic attack capability; the high valence state and strong MO bond (M=Nb / Ta) of Nb / Ta can stabilize the heteropolyacid anionic structure, reduce deactivation caused by high-temperature dehydration, and improve the thermal stability of the catalyst.

[0025] In modified heteropolyacids, niobium can regulate the acidic center. Niobium promotes dehydration by partially substituting the heteropolyacid anionic skeleton. Niobium substitution of the heteropolyacid skeleton leads to the accumulation of charge at the heteropolyacid center. The addition of tantalum can balance the charge distribution, so that the charge forms an electron cloud arrangement centered on niobium and gradually disperses, preventing excessive charge accumulation at the niobium center site. Tantalum can also optimize the adsorption and activation ability of reactant molecules on the modified heteropolyacid catalyst, forming a more hydrophobic microenvironment.

[0026] The modified heteropolyacid catalyst used in this invention comprises catalytic sites formed by the synergistic effect of Brønsted acid sites and Lewis acid sites of the heteropolyacid. The heteropolyacid is loaded through the mesoporous structure and surface properties of γ-Al₂O₃, allowing ZrO₂ nanoparticles to be anchored at Al₂O₃ grain boundaries, effectively suppressing the phase transition from γ-Al₂O₃ to α-Al₂O₃ and abnormal grain growth at high temperatures. When the modified heteropolyacid is loaded, tantalum in the modified heteropolyacid prevents excessive niobium aggregation, improving the utilization rate of active sites. During catalysis, it suppresses side reactions through electronic effects, enhancing the selectivity of the target product. The acidic sites of the modified heteropolyacid catalyst can provide protons, which, as Brønsted acid, combine with the carboxyl group of isophthalic acid to form a carboxyl cation intermediate, thereby activating the carboxyl group and making it more susceptible to nucleophilic attack by ethanol. Niobium and tantalum in the modified heteropolyacid catalyst, as Lewis acids, coordinate with the oxygen atom of ethanol, increasing the nucleophilicity of ethanol and promoting its attack on the activated carboxyl group.

[0027] The hydroxyl groups on the surface of γ-Al₂O₃ interact with water molecules generated in the reaction through hydrogen bonds, stabilizing and rapidly removing water molecules, thus driving the reaction equilibrium towards esterification and improving reaction efficiency. The modified heteropolyacid catalyst possesses a mesoporous structure of 2-10 nm and a high specific surface area of ​​350-550 m² / g, providing abundant active surfaces and optimized diffusion pathways for the reactants. The mass transfer efficiency of isophthalic acid and ethanol is significantly improved within the nanopores, reducing side reactions such as etherification and enhancing product selectivity.

[0028] The modified heteropolyacid forms a strong chemical bond with γ-Al2O3 (such as Al-OP bond with a bond energy of 418 kJ / mol), which enhances the stability and recycling performance of the catalyst. The catalyst can still maintain more than 90% of its activity after 10 cycles.

[0029] Through the synergistic effect of the above-mentioned multiple mechanisms, the modified heteropolyacid catalyst significantly improved the rate and selectivity of the esterification reaction, reduced the reaction energy consumption, and achieved a highly efficient and green catalytic process.

[0030] The beneficial effects of this invention are:

[0031] This invention obtains a mixture containing isophthalic acid by hydrolyzing the waste material from the isophthalonitrile production process, then obtains isophthalic acid through centrifugal dissolution and other operations, and finally esterifies the isophthalic acid to obtain diethyl isophthalate.

[0032] Waste generated during the production of isophthalonitrile is used to prepare diethyl isophthalate, which increases the added value of isophthalonitrile production and improves the recycling rate of waste. Utilizing waste generated during the refining of isophthalonitrile as raw material reduces processing costs.

[0033] After the waste from the isophthalonitrile production process is hydrolyzed, the hydrolyzed isophthalic acid is then esterified with ethanol using a modified heteropolyacid catalyst to produce diethyl isophthalate. This not only reduces the waste treatment cost of isophthalonitrile but also improves the yield and purity of diethyl isophthalate, thereby increasing the economic value of diethyl isophthalate preparation.

[0034] Using modified heteropolyacid catalysts for esterification reduced energy consumption and increased conversion rate.

[0035] Compared with traditional sulfuric acid catalysts, the modified heteropolyacid catalyst prepared in this invention increases the reaction rate by approximately 15.7 times through synergistic regulation of bond energy, shortening the reaction time in actual production and improving product selectivity to approximately 99.5%, attributed to the mesoporous confinement effect suppressing ether side reactions. The catalyst maintains over 90% activity after 10 cycles, thanks to the thermal stability of γ-Al₂O₃ and the strong chemical bond between the heteropolyacid and the support (Al-OP bond energy 418 kJ / mol). The decomposition temperature of γ-Al₂O₃ is >800℃. This molecular-level design achieves highly efficient conversion of hazardous waste into resources, reducing energy consumption by approximately 37%, and providing a new green catalytic paradigm for fine chemicals.

[0036] In the hydrolysis preparation of isophthalic acid, this invention uses a stirring assembly to mix waste materials with acid solution for hydrolysis. During the hydrolysis process, the stirring ring rotates continuously, and the connecting rod on the stirring ring continuously mixes the hydrolyzed raw materials. During rotation, the stirring ring spirals along the screw at the bottom of the sleeve, thus achieving rotation and vertical movement of the stirring ring. The horizontal rotation of the stirring ring, combined with vertical turbulence stirring of the hydrolyzed raw materials, keeps the hydrolyzed raw materials inside the hydrolysis vessel in a disturbed mixed state, improving the hydrolysis rate and efficiency. In the trickle bed, a heteropolyacid-modified catalyst is filled into two layers of different densities. The packing layer allows the reactants to fully contact the catalyst during the reaction, and its funnel-shaped arrangement also promotes the aggregation of the reaction liquid towards the center of the trickle bed. The reaction liquid diffusing outwards is also intercepted by the packing layer and reacts fully within the packing layer. Because the density of the packing layer is greater than that of the filler layer, the rate of diffusion of the reaction liquid into the packing layer decreases, and the contact time between the reaction liquid and the catalyst in the packing layer is prolonged, improving catalytic efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Figure 2 This is a schematic diagram of the stirring ring structure of the present invention;

[0039] In the diagram: 1. Hydrolysis vessel; 2. Waste inlet; 3. Acid inlet; 4. Dissolving vessel; 5. Trickle bed; 6. Vaporizer; 7. First-stage distillation column; 8. Second-stage distillation column; 9. Third-stage distillation column; 10. Discharge port; 11. Jacket; 12. Stirring ring; 13. Screw; 14. Solvent inlet; 15. Centrifuge; 16. Filtrate outlet; 17. Slag discharge port; 101. Jacket; 501. Packing layer; 502. Packing layer. Detailed Implementation

[0040] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0041] Example 1

[0042] like Figure 1-2 As shown, the diethyl isophthalate production apparatus of the present invention includes a hydrolysis vessel 1, a waste inlet 2 and an acid inlet 3 on the hydrolysis vessel 1, a stirring assembly inside the hydrolysis vessel 1, the stirring assembly including a stirring ring 12, a sleeve 11 on the top of the stirring ring 12, and a screw 13 threadedly connected inside the sleeve 11, a centrifuge 15, a dissolving vessel 4 and a trickle bed 5 connected in sequence to the bottom of the hydrolysis vessel 1, a packing layer 501 inside the trickle bed 5, a packing layer 502 surrounding the packing layer 501, a vaporizer 6 on the side of the trickle bed 5, and a primary distillation column 7, a secondary distillation column 8 and a tertiary distillation column 9 connected in sequence to the bottom of the trickle bed 5.

[0043] The hydrolysis vessel 1 is equipped with a jacket 101 on the outside. The stirring ring 12 includes several connecting rods that are inclined in the middle. The top of the connecting rod is connected to the sleeve 11. A connecting ring is provided on the outside of the connecting rod. The connecting rod connects the sleeve 11 and the connecting ring. The top of the screw 13 passes through the top of the hydrolysis vessel 1 and is connected to a motor.

[0044] The centrifuge 15 has a filtrate outlet 16 at its bottom, the dissolving vessel 4 has a solvent inlet 14 at its top, and a slag discharge port 17 at its bottom. The lower part of the side wall of the dissolving vessel 4 is connected to the trickle bed 5. The packing layer 501 is funnel-shaped, and the packing layer 502 is filled between the packing layer 501 and the inner wall of the trickle bed 5. The density of the packing layer 502 is greater than that of the packing layer 501. Both the packing layer 501 and the packing layer 502 are filled with modified heteropolyacid catalysts. The packing density of the modified heteropolyacid catalyst in the packing layer 501 is 800 kg / m³. 3 The packing height is 3m, and the packing density of the modified heteropolyacid catalyst in the packing layer 502 is 1200kg / m³. 3 The filling height is 3m. The bottom of the first-stage distillation column 7 is connected to the top of the second-stage distillation column 8, the bottom of the second-stage distillation column 8 is connected to the top of the third-stage distillation column 9, and the top of the third-stage distillation column 9 is provided with a discharge port 10.

[0045] The preparation method of the modified heteropolyacid catalyst is as follows:

[0046] a1. Dissolve 10g of niobium chloride and 5g of tantalum nitrate in 100g of deionized water, sonicate until completely dissolved, and add 40wt.% phosphoric acid to adjust the pH to 2 to obtain a heteropolyacid solution;

[0047] a2. Dissolve 37.5g of aluminum nitrate and 23.1g of zirconium nitrate in 100g of deionized water to obtain a precursor solution;

[0048] a3. The heteropolyacid solution in a1 and the precursor solution in a2 were stirred and mixed at 30℃ and 500rpm. Then, ammonia water was added to adjust the pH to 9 and co-precipitate for 1h to obtain a solid precipitate. The solid precipitate was aged at 55℃ for 12h, centrifuged at 3000rpm for 50min, washed alternately with deionized water and ethanol until neutral, dried at 80℃ for 12h, and calcined at 400℃ for 6h at a heating rate of 5℃ / min to obtain the modified heteropolyacid catalyst with a service life of 12 months.

[0049] The method for preparing diethyl isophthalate using the diethyl isophthalate production apparatus of the present invention includes the following steps:

[0050] A1. Waste is added to hydrolysis reactor 1 through waste inlet 2, and 30wt.% sulfuric acid is added through acid inlet 3 until the pH is 4. Hydrolysis reaction is carried out at 50℃ for 3h to obtain a mixture containing isophthalic acid.

[0051] A2. The mixture containing isophthalic acid is fed into centrifuge 15 and centrifuged at 900 rpm for 1 h to obtain isophthalic acid. The isophthalic acid is fed into dissolving vessel 4 and toluene is added at a mass ratio of 1:3 to obtain isophthalic acid toluene solution. The isophthalic acid toluene solution is fed into trickle bed 5 with modified heteropolyacid catalyst and esterified with vaporized ethanol at 120℃ for 3.5 h. The mass ratio of ethanol to isophthalic acid is 1:0.8 to obtain diethyl isophthalate esterified solution.

[0052] A3. The obtained diethyl isophthalate esterified liquid was sequentially distilled three times through a primary distillation column 7 at 82℃ and atmospheric pressure, a secondary distillation column 8 at 120℃ and -0.08MPa, and a tertiary distillation column 9 at 210℃ and -0.08MPa to obtain the diethyl isophthalate product. The conversion rate of the diethyl isophthalate product was 99.2%, the selectivity was 99.3%, and the energy consumption for preparing diethyl isophthalate was 18 kWh / kg.

[0053] Example 2

[0054] In this embodiment, the trickle bed 5 of the diethyl isophthalate production apparatus is equipped with a filling height of 2.5m and a filling density of 1000kg / m³. 3 The modified heteropolyacid catalyst has a packing layer 501 and a supported layer with a packing height of 2.5 m and a packing density of 1100 kg / m³. 3 The modified heteropolyacid catalyst has a packed layer 502, and the rest of the apparatus is the same as in Example 1.

[0055] The preparation method of the modified heteropolyacid catalyst is as follows:

[0056] a1. Dissolve 12g of niobium chloride and 10g of tantalum nitrate in 120g of deionized water, sonicate until completely dissolved, and add 50wt.% phosphoric acid to adjust the pH to 3 to obtain a heteropolyacid solution.

[0057] a2. Dissolve 40g of aluminum nitrate and 25g of zirconium nitrate in 120g of deionized water to obtain a precursor solution;

[0058] a3. The heteropolyacid solution in a1 and the precursor solution in a2 were stirred and mixed at 40℃ and 400rpm. Then, ammonia solution was added to adjust the pH to 8 and co-precipitate for 1.5h to obtain a solid precipitate. The solid precipitate was aged at 60℃ for 8h, centrifuged at 5000rpm for 40min, washed alternately with deionized water and ethanol until neutral, dried at 100℃ for 10h, and calcined at 500℃ for 5h at a heating rate of 4℃ / min to obtain the modified heteropolyacid catalyst.

[0059] The method for preparing diethyl isophthalate using the diethyl isophthalate production apparatus of the present invention includes the following steps:

[0060] A1. Waste is added to hydrolysis reactor 1 through waste inlet 2, and 40wt.% sulfuric acid is added through acid inlet 3 until the pH is 2. Hydrolysis reaction is carried out at 80℃ for 2 hours to obtain a mixture containing isophthalic acid.

[0061] A2. The mixture containing isophthalic acid is fed into centrifuge 15 and centrifuged at 1000 rpm for 0.5 h to obtain isophthalic acid. The isophthalic acid is fed into dissolving vessel 4 and toluene is added at a mass ratio of 1:2.5 to dissolve it and obtain isophthalic acid toluene solution. The isophthalic acid toluene solution is fed into trickle bed 5 with modified heteropolyacid catalyst and esterified with vaporized ethanol at 100℃ for 5 h. The mass ratio of ethanol to isophthalic acid is 1:0.9 to obtain diethyl isophthalate esterified liquid.

[0062] A3. The obtained diethyl isophthalate esterified liquid was sequentially distilled three times through a primary distillation column 7 at 80℃ and atmospheric pressure, a secondary distillation column 8 at 125℃ and -0.06MPa, and a tertiary distillation column 9 at 215℃ and -0.1MPa to obtain the diethyl isophthalate product. The conversion rate of the diethyl isophthalate product was 99.1%, the selectivity was 99.4%, and the energy consumption for preparing diethyl isophthalate was 19 kWh / kg.

[0063] Example 3

[0064] In this embodiment, the trickle bed 5 of the diethyl isophthalate production apparatus is equipped with a filling height of 2m and a filling density of 500kg / m³. 3The modified heteropolyacid catalyst has a packing layer 501 and a supported layer with a packing height of 2m and a packing density of 1000kg / m³. 3 The modified heteropolyacid catalyst has a packed layer 502, and the rest of the apparatus is the same as in Example 1.

[0065] The preparation method of the modified heteropolyacid catalyst is as follows:

[0066] a1. Dissolve 8g of niobium chloride and 8g of tantalum nitrate in 80g of deionized water, sonicate until completely dissolved, and add 30wt.% phosphoric acid to adjust the pH to 4 to obtain a heteropolyacid solution.

[0067] a2. Dissolve 35g of aluminum nitrate and 20g of zirconium nitrate in 80g of deionized water to obtain a precursor solution;

[0068] a3. The heteropolyacid solution in a1 and the precursor solution in a2 were stirred and mixed at 50℃ and 300rpm. Then, sodium carbonate solution was added to adjust the pH to 10 and co-precipitate for 0.5h to obtain a solid precipitate. The solid precipitate was aged at 65℃ for 4h, centrifuged at 8000rpm for 30min, washed alternately with deionized water and ethanol until neutral, dried at 120℃ for 8h, and calcined at 600℃ for 4h at a heating rate of 2℃ / min to obtain the modified heteropolyacid catalyst.

[0069] The method for preparing diethyl isophthalate using the diethyl isophthalate production apparatus of the present invention includes the following steps:

[0070] A1. Waste is added to hydrolysis reactor 1 through waste inlet 2, and 20wt.% hydrochloric acid is added to pH 1 through acid inlet 3. Hydrolysis reaction is carried out at 100℃ for 1h to obtain a mixture containing isophthalic acid.

[0071] A2. The mixture containing isophthalic acid is fed into centrifuge 15 and centrifuged at 1200 rpm for 0.75 h to obtain isophthalic acid. The isophthalic acid is fed into dissolving vessel 4 and toluene is added at a mass ratio of 1:4 to obtain isophthalic acid toluene solution. The isophthalic acid toluene solution is fed into trickle bed 5 with modified heteropolyacid catalyst and esterified with vaporized ethanol at 80°C for 10 h. The mass ratio of ethanol to isophthalic acid is 1:1 to obtain diethyl isophthalate esterified liquid.

[0072] A3. The obtained diethyl isophthalate esterified liquid was sequentially distilled three times through a primary distillation column 7 at 85℃ and atmospheric pressure, a secondary distillation column 8 at 130℃ and -0.1MPa, and a tertiary distillation column 9 at 220℃ and -0.06MPa to obtain the diethyl isophthalate product. The conversion rate of the diethyl isophthalate product was 99.5%, the selectivity was 99.7%, and the energy consumption for preparing diethyl isophthalate was 18.5 kWh / kg.

[0073] Comparative Example 1

[0074] Niobium chloride was not added in step a1, and the remaining steps were the same as in Example 1. The resulting diethyl isophthalate product had a conversion rate of 91.5%, a selectivity of 86.3%, and an energy consumption of 32 kWh / kg.

[0075] Comparative Example 2

[0076] In step a1, tantalum nitrate was not added, and the remaining steps were the same as in Example 1. The resulting diethyl isophthalate product had a conversion rate of 90.0%, a selectivity of 85.0%, and an energy consumption of 35 kWh / kg.

Claims

1. A production apparatus for diethyl isophthalate, characterized in that, The system includes a hydrolysis reactor (1), which is equipped with a waste inlet (2) and an acid inlet (3). Waste from the production process of isophthalonitrile is added through the waste inlet (2). The waste from the production process of isophthalonitrile is hydrolyzed in the hydrolysis reactor (1) to obtain a mixture containing isophthalic acid. The hydrolysis reactor (1) is equipped with a stirring assembly, which includes a stirring ring (12). A sleeve (11) is provided on the top of the stirring ring (12). A screw (13) is threaded inside the sleeve (11). A centrifuge (15), a dissolving vessel (4), and a trickle bed (5) are connected in sequence at the bottom of the hydrolysis reactor (1). A packing layer (501) is provided inside the trickle bed (5). A packing layer (502) is arranged around the outside of the packing layer (501). A vaporizer (6) is provided on the side of the trickle bed (5). A first-stage distillation column (7), a second-stage distillation column (8), and a third-stage distillation column (9) are connected in sequence at the bottom of the trickle bed (5).

2. The apparatus for producing diethyl isophthalate according to claim 1, characterized in that, The hydrolysis vessel (1) is equipped with a jacket (101) on the outside. The stirring ring (12) includes several connecting rods that are inclined in the middle. The top of the connecting rod is connected to the sleeve (11). A connecting ring is provided on the outside of the connecting rod. The connecting rod connects the sleeve (11) and the connecting ring. The top of the screw (13) passes through the top of the hydrolysis vessel (1) and is connected to a motor.

3. The apparatus for producing diethyl isophthalate according to claim 1, characterized in that, The centrifuge (15) has a filtrate outlet (16) at the bottom, the dissolving vessel (4) has a solvent inlet (14) at the top, and a slag outlet (17) at the bottom. The lower part of the side wall of the dissolving vessel (4) is connected to the trickle bed (5). The packing layer (501) is funnel-shaped, and the packing layer (502) is filled between the packing layer (501) and the inner wall of the trickle bed (5). The density of the packing layer (502) is greater than that of the packing layer (501). Both the packing layer (501) and the packing layer (502) are filled with modified heteropolyacid catalysts. The packing density of the modified heteropolyacid catalyst in the packing layer (501) is 500-1000 kg / m³. 3 The packing height is 2-3m, and the packing density of the modified heteropolyacid catalyst in the packing layer (502) is 1000-1200kg / m³. 3 The filling height is 2-3m. The bottom of the first-stage distillation column (7) is connected to the top of the second-stage distillation column (8), the bottom of the second-stage distillation column (8) is connected to the top of the third-stage distillation column (9), and the top of the third-stage distillation column (9) is provided with a discharge port (10).

4. A method for preparing diethyl isophthalate using the apparatus for producing diethyl isophthalate according to any one of claims 1-3, characterized in that, Includes the following steps: A1. Waste is added to hydrolysis reactor (1) through waste inlet (2), and acid is added through acid inlet (3) to carry out hydrolysis reaction to obtain a mixture containing isophthalic acid; A2. The mixture containing isophthalic acid is centrifuged in a centrifuge (15) to obtain isophthalic acid. The isophthalic acid is then dissolved in a dissolving vessel (4) to obtain an organic solution of isophthalic acid. The organic solution of isophthalic acid is then transferred to a trickle bed (5) supported with a modified heteropolyacid catalyst and subjected to an esterification reaction with vaporized ethanol to obtain a diethyl isophthalate esterified liquid. A3. The obtained diethyl isophthalate esterified liquid is distilled three times in sequence through a primary distillation column (7), a secondary distillation column (8), and a tertiary distillation column (9) to obtain the diethyl isophthalate product.

5. The method for preparing diethyl isophthalate according to claim 4, characterized in that, In step A1, the acid solution is sulfuric acid or hydrochloric acid, the acid concentration is 10-60 wt.%, the pH of the hydrolysis reaction is 1-4, the hydrolysis reaction temperature is 50-100℃, and the hydrolysis reaction time is 1-5 h.

6. The method for preparing diethyl isophthalate according to claim 4, characterized in that, The preparation method of the modified heteropolyacid catalyst in step A2 is as follows: a1. Dissolve niobium salt and tantalum salt in deionized water, and add phosphoric acid to adjust the pH to obtain a heteropolyacid solution; a2. Dissolve aluminum salt and zirconium salt in deionized water to obtain a precursor solution; a3. Mix the heteropolyacid solution and the precursor solution by stirring, then add an alkaline solution for co-precipitation to obtain a solid precipitate; The modified heteropolyacid catalyst was obtained by aging, centrifuging, washing, drying and calcining the solid precipitate.

7. The method for preparing diethyl isophthalate according to claim 6, characterized in that, In step a1, the niobium salt is niobium chloride and the tantalum salt is tantalum nitrate, with a mass ratio of niobium salt to tantalum salt of 1:0.5-1; the pH is adjusted to 2-4 and the phosphoric acid concentration is 30-50 wt.%.

8. The method for preparing diethyl isophthalate according to claim 6, characterized in that, In step a2, the aluminum salt is aluminum nitrate, the zirconium salt is zirconium nitrate, the mass ratio of aluminum salt to zirconium salt is 1:0.5-1, and the mass ratio of aluminum salt to niobium salt in step a1 is 3-4:

1.

9. The method for preparing diethyl isophthalate according to claim 6, characterized in that, In step a3, the stirring and mixing temperature is 30-50℃, the stirring and mixing speed is 300-500 rpm, the alkaline solution is ammonia or sodium carbonate solution, the pH of co-precipitation is 8-10, and the co-precipitation time is 0.5-2 h; the aging temperature is 55-65℃, the aging time is 4-12 h, the centrifugation speed is 3000-8000 rpm, the centrifugation time is 30-50 min, the washing is done by alternating between deionized water and ethanol, the drying temperature is 80-120℃, the drying time is 8-12 h, the calcination temperature is 400-600℃, the calcination time is 4-6 h, and the calcination heating rate is 2-5℃ / min.

10. The method for preparing diethyl isophthalate according to claim 4, characterized in that, In step A2, the centrifugation rate is 900-1200 rpm, the centrifugation time is 0.75-1 h, toluene is used for dissolution, the mass ratio of isophthalic acid to toluene is 1:2.5-4, the mass ratio of ethanol to isophthalic acid is 1:0.8-1, the esterification reaction time is 0.5-10 h, and the esterification reaction temperature is 80-120℃. In step A3, the pressure of the first-stage distillation column (7) is atmospheric pressure, the pressure of the second-stage distillation column (8) is -0.06 to -0.10 MPa, the pressure of the third-stage distillation column (9) is -0.06 to -0.10 MPa, the temperature of the first-stage distillation column (7) is 80-85℃, the temperature of the second-stage distillation column (8) is 110-130℃, and the temperature of the third-stage distillation column (9) is 200-220℃.

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