Catalyst for preparing trimellitic anhydride and application thereof in preparing trimellitic anhydride

Abstract

The present application relates to trimellitic anhydride production technical field, especially trimellitic anhydride preparation catalyst and its application in trimellitic anhydride preparation.The present application provides a kind of trimellitic anhydride preparation catalyst, including the following weight parts of raw materials: main catalyst 5-10 parts, side chain oxidation promoter 1 part;The main catalyst is made of cobalt, manganese bimetallic organic framework and SBA-15 molecular sieve composite.The process of the present application has very high yield and purity when preparing trimellitic anhydride, and the best effect is example 1, the yield reaches 150%, and the purity reaches 99.9%.

Description

TECHNICAL FIELD

[0001] The present application relates to trimellitic anhydride production technology field, especially to the preparation of trimellitic anhydride catalyst and its application in the preparation of trimellitic anhydride. BACKGROUND

[0002] At present, for the production process of trimellitic anhydride, mainly including intermittent oxidation method and continuous oxidation method, wherein intermittent oxidation method is mainly with trimethyl benzene as raw material, acetic acid as solvent, through catalyst in high temperature and high pressure liquid phase air oxidation, trimellitic acid is generated, and then through cooling and decompression crystallization, deacidification and intramolecular dehydration to obtain trimellitic anhydride; Continuous oxidation process is a process of continuously inputting materials and inputting compressed air while continuously discharging materials under the condition of maintaining reaction.

[0003] For the existing catalyst for preparing trimellitic anhydride, mainly through metal ions as catalyst, such as the catalyst for producing trimellitic anhydride disclosed in the patent with publication number CN110560109B, which adopts vanadium and titanium elements as main catalytic elements of supported catalyst, but the molar yield of trimellitic anhydride is only about 65%. Therefore, it is urgent to develop a new catalyst to improve the yield of trimellitic anhydride. SUMMARY

[0004] Based on the technical problems existing in the background technology, the present application provides a catalyst for preparing trimellitic anhydride and its application in the preparation of trimellitic anhydride, which improves the yield of trimellitic anhydride in preparation.

[0005] The catalyst for preparing trimellitic anhydride comprises the following raw materials by weight: 5-10 parts of main catalyst, 1 part of side chain oxidation promoter;

[0006] The main catalyst is composed of cobalt, manganese bimetallic organic framework and SBA-15 molecular sieve.

[0007] Preferably, the preparation method of the main catalyst comprises the following steps:

[0008] Step one. Dissolve cobalt salt, manganese salt and organic ligand in DMF-acetonitrile mixed solvent for reaction, and then wash and dry the product after reaction to obtain cobalt, manganese bimetallic organic framework;

[0009] Step two. Disperse cobalt, manganese bimetallic organic framework and SBA-15 molecular sieve in methanol, stir, suction filter and dry to obtain the main catalyst.

[0010] Preferably, in step one, the cobalt salt is cobalt acetate;

[0011] The manganese salt is manganese acetate;

[0012] The organic ligand is 2-amino terephthalic acid and 2-methyl imidazole mixed at a mass ratio of 1:0.5-1.5;

[0013] The DMF and acetonitrile are mixed at a volume ratio of 3-5:1.

[0014] Preferably, in the step one, the mass-volume ratio of the cobalt salt, the manganese salt, the organic ligand and the DMF-acetonitrile mixed solvent is 1g:0.1-0.5g:0.5-1.5g:50-100mL.

[0015] The reaction condition is: temperature 60-120℃, time 18-36h.

[0016] In the step two, the mass-volume ratio of the cobalt, the manganese bimetallic organic framework, the SBA-15 molecular sieve and the methanol is 1g:1-2g:50-100mL.

[0017] Preferably, the side chain oxidation promoter is tetrabromoethane.

[0018] The application also provides an application of the above catalyst in preparing trimellitic anhydride.

[0019] S1: trimethylbenzene and acetic acid are added into a batching tank, the catalyst is added into an oxidation tower, the material in the batching tank is transported to the oxidation tower after being heated by a feeding heater, and air / oxygen is introduced into the oxidation tower to perform an oxidation reaction, so that trimellitic acid is generated;

[0020] S2: the trimellitic acid reaction solution in S1 is transported to a crystallization kettle, and is crystallized by temperature reduction and pressure reduction, and the crystallized material is pressed into an anhydride kettle by residual pressure, and the material is dehydrated in the anhydride kettle to obtain a crude trimellitic anhydride;

[0021] S3: the crude trimellitic anhydride in S2 is treated by a light-removing tower and a rectifying tower, and a finished trimellitic anhydride is obtained.

[0022] Preferably, the temperature of the oxidation reaction in S1 is 220-245℃, and the pressure is 2.0-2.5MPa.

[0023] Preferably, the mass ratio of trimethylbenzene, acetic acid and the catalyst in S1 is 1:1-10:0.01-0.1.

[0024] Preferably, the temperature of the material in S1 after being heated by the feeding heater is 140-160℃, and the temperature of the air / oxygen introduced into the oxidation tower is 160-180℃.

[0025] The beneficial technical effects of the application are:

[0026] The process of the present application has high yield and purity in preparing trimellitic anhydride, wherein the best effect is achieved in Example 1, the yield reaches 150%, and the purity reaches 99.9%, because the present application adopts a new catalyst and optimizes the related process parameters, the pore size distribution of SBA-15 molecular sieve is narrow, the pore volume is large, and the specific surface area is large, the addition of ligands 2-amino terephthalic acid and 2-methyl imidazole improves the active sites of cobalt and manganese, the cobalt and manganese bimetallic organic framework is uniformly dispersed in the channels and surface of SBA-15 molecular sieve, thereby improving the contact area of the catalyst and the catalytic efficiency; in addition, the side chain oxidation promoter can promote the contact efficiency of the benzene ring side chain with oxygen and the oxidation of the benzene ring side chain, thereby further improving the yield of trimellitic anhydride. DETAILED DESCRIPTION

[0027] The raw materials of the present application are purchased from the market unless otherwise specified.

[0028] The SBA-15 is purchased from Aladdin, the pore size is 6-11 nm, the specific surface area (m 2 / g) is 600-800.

[0029] Preparation Example 1

[0030] The catalyst of the present embodiment includes 5 parts of the main catalyst and 1 part of the side chain oxidation promoter.

[0031] The preparation method of the main catalyst is as follows:

[0032] Step one. Dissolve the cobalt salt, manganese salt and organic ligand in the DMF-acetonitrile mixed solvent, stir at 90℃ for 24h, after the reaction, the product is washed and dried at 70℃ to obtain the cobalt and manganese bimetallic organic framework;

[0033] Step two. Disperse the cobalt and manganese bimetallic organic framework and SBA-15 molecular sieve in methanol, stir at room temperature for 24h, suction filter, and dry at 70℃ to obtain the main catalyst.

[0034] In the step one, the cobalt salt is cobalt acetate, the manganese salt is manganese acetate, the organic ligand is a mixture of 2-amino terephthalic acid and 2-methyl imidazole in a mass ratio of 1:1, the DMF and acetonitrile are mixed in a volume ratio of 4:1, and the mass-volume ratio of the cobalt salt, manganese salt, organic ligand and DMF-acetonitrile mixed solvent is 1g:0.3g:1g:50mL;

[0035] In the step two, the mass-volume ratio of the cobalt and manganese bimetallic organic framework, SBA-15 molecular sieve and methanol is 1g:1.5g:50mL.

[0036] The side chain oxidation promoter is tetraethylammonium bromide.

[0037] Preparation Example 2

[0038] The difference between the present preparation example and Preparation Example 1 is that the catalyst comprises 7.5 parts of the main catalyst and 1 part of the side chain oxidation promoter.

[0039] Preparation Example 3

[0040] The difference between the present preparation example and Preparation Example 1 is that the catalyst comprises 10 parts of the main catalyst and 1 part of the side chain oxidation promoter.

[0041] Preparation Example 4

[0042] The difference between the present preparation example and Preparation Example 1 is that in the second step, the mass-volume ratio of the cobalt-manganese bimetallic organic framework, the SBA-15 molecular sieve and the methanol is 1 g:1 g:50 mL.

[0043] Preparation Example 5

[0044] The difference between the present preparation example and Preparation Example 1 is that in the second step, the mass-volume ratio of the cobalt-manganese bimetallic organic framework, the SBA-15 molecular sieve and the methanol is 1 g:2 g:50 mL.

[0045] Example 1

[0046] (1) Oxidation process

[0047] 400 kg of acetic acid and 200 kg of mesitylene are put into a batching tank, 0.5 kg of catalyst (obtained from Preparation Example 1) is added into an oxidation tower, and the material in the batching tank is heated to 150°C and then sent to the oxidation tower. An air compressor is used as an air and pressure source, and the compressed air is preheated to 170°C and then bubbled into the oxidation tower through a gas distributor in the oxidation tower. Under the conditions of a temperature of 230°C and a pressure of 2.2 MPa, the mesitylene and the oxygen in the air are subjected to an oxidation reaction to generate trimellitic acid. The acetic acid is used as both a solvent and a heat carrier in the oxidation reaction process.

[0048] During the oxidation process, the oxygen content in the tail gas is detected and analyzed to control the oxygen content. In addition, the tail gas contains part of acetic acid and mesitylene. The tail gas is subjected to three-stage condensation (hot water cooling + air + circulating water cooling) and cooling separation in an oxidation separation tower. The cooled acetic acid is returned to the oxidation tower for repeated use. The separated tail gas enters a tail gas absorption tower and is sprayed and absorbed with 1% acetic acid solution. The obtained dilute acetic acid is recovered to a dilute acetic acid tank. After two-stage tail gas absorption, the tail gas enters a tail gas alkali absorption tower for alkali spraying treatment. After the tail gas absorption meets the standards, the tail gas is discharged into the atmosphere, and the waste liquid is sent to a sewage treatment field for treatment.

[0049] (2) Crystallization and dehydration process

[0050] The oxidized trimellitic acid reaction solution flows from the oxidation tower into the crystallization kettle, and crystallization is carried out by reducing temperature and pressure. After the tail gas is released to release pressure, the material is rapidly cooled to form crystals. The crystallized material is pressurized into the anhydride kettle by the remaining pressure. The tail gas in the crystallization process is condensed by the crystallization condenser (circulating water cooling) and then sent to the normal pressure acid absorption tower. After being sprayed and absorbed by 1% acetic acid solution, the tail gas is treated by alkali spraying in the normal pressure alkali absorption tower. After the tail gas is absorbed to the standard, it is discharged into the atmosphere. The waste liquid is sent to the sewage treatment field for treatment.

[0051] The anhydride kettle is heated by heat conduction oil. The material is dehydrated to trimellitic anhydride at a temperature of 230°C. Due to the increase of the temperature in the kettle, part of the acetic acid and water in the material will evaporate. The tail gas is condensed by the anhydride condenser (circulating water cooling) and then sent to the normal pressure acid absorption tower system for spray absorption by 1% dilute acetic acid to recover acetic acid. Then, the recovered acetic acid is sprayed and absorbed by alkali in the normal pressure alkali absorption tower. The absorbed dilute acetic acid is sent to the dilute acetic acid tank. The tail gas after absorption to the standard is discharged into the atmosphere.

[0052] (3) Acetic acid recovery process

[0053] The dilute acetic acid is pumped from the dilute acetic acid storage tank into the feed preheater, preheated, and then enters the azeotropic distillation column. The acetic acid collected at the bottom of the column enters the evaporation tower. The gas phase at the top is condensed and then enters the oil-water phase separation tank for phase separation. The oil phase returns to the azeotropic distillation column, and the water phase enters the solvent recovery column to recover the azeotropic agent. The waste water at the bottom of the solvent recovery column enters the waste water collection tank in the device. The gas phase at the top of the evaporation tower provides heat source for a reboiler of the azeotropic distillation column. The gas phase after condensation is sent to the concentrated acid tank.

[0054] (4) Distillation process

[0055] The crude trimellitic anhydride produced in the anhydride process enters the gas phase feed kettle of the distillation column after removing light components by the light component removal column. Part of the material is heated into gas phase and enters the distillation column. The distillation is carried out under the conditions of vacuum 0.37 kPa and temperature 250°C to obtain qualified trimellitic anhydride product. The trimellitic anhydride product is cut and packaged by a slicing machine in the slicing and packaging room. The distillation process has two-stage condensation recovery system. The condensation medium temperature cannot be too low to prevent the system from being blocked due to the direct condensation of trimellitic anhydride. Therefore, the distillation column condenser is cooled by hot water at a temperature of about 160°C (byproduct 0.6 MPa steam). The first and second switching condensers of the distillation column are further cooled by heat conduction oil at a temperature of 50°C. The material that does not form gas phase in the gas phase feed kettle of the distillation column enters the batch distillation kettle, is condensed by removing heavy components, and then reenters the light component removal column and is heated into gas phase to reenter the distillation system.

[0056] (5) Tail gas treatment process

[0057] The material evaporated from the rectification kettle is condensed in two stages, and the tail gas is connected to the vacuum system. The ejector pump absorbs or traps the pollutants in the tail gas while vacuumizing, so the wastewater contains a certain amount of pollutants. After collection, it is sent to the wastewater treatment station for treatment. The exhaust gas of the vacuum pump is sent to the atmospheric alkali absorption tower for absorption treatment.

[0058] (6) Waste residue incineration process

[0059] The light components obtained by rectification are mixed with the rectification residues and sent to the incinerator for incineration treatment. The waste liquid is incinerated at a temperature of 950°C. After incineration, the catalyst is recovered through horizontal furnace, vertical furnace, waste heat boiler, air heat exchanger, multi-tube dust collector, spray tower and other equipment. The incineration tail gas is sent to 45 meters high for emission by a fan.

[0060] Example 2

[0061] The difference between this example and Example 1 is that the catalyst obtained in Preparation Example 2 is used in this example, and the rest is exactly the same as Example 1.

[0062] Example 3

[0063] The difference between this example and Example 1 is that the catalyst obtained in Preparation Example 3 is used in this example, and the rest is exactly the same as Example 1.

[0064] Example 4

[0065] The difference between this example and Example 1 is that the catalyst obtained in Preparation Example 4 is used in this example, and the rest is exactly the same as Example 1.

[0066] Example 5

[0067] The difference between this example and Example 1 is that the catalyst obtained in Preparation Example 5 is used in this example, and the rest is exactly the same as Example 1.

[0068] Comparative Example 1

[0069] The difference between this example and Example 1 is that the catalyst of this example includes cobalt acetate, manganese acetate and tetraethylammonium bromide, and the mass ratio of the cobalt acetate, manganese acetate and tetraethylammonium bromide is 1:1:1, and the rest is exactly the same as Example 1.

[0070] The yield and purity of trimellitic anhydride in Examples 1-5 and Comparative Example 1 were determined. The yield of trimellitic anhydride was calculated based on trimethylbenzene, and the results are shown in Table 1.

[0071] Table 1: Determination results of trimellitic anhydride yield and purity

[0072] Group Yield (%) Purity (%) Example 1 150 99.9 Example 2 136 99.1 Example 3 130 99.6 Example 4 125 97.6 Example 5 138 97.8 Comparative Example 1 123 97.3

[0073] As known from Table 1, the process of the present application has high yield and purity when preparing trimellitic anhydride, wherein the best effect is Example 1, the yield reaches 150%, and the purity reaches 99.9%, because the present application adopts a new catalyst and cooperates with the optimization of related process parameters, the pore size distribution of SBA-15 molecular sieve is relatively narrow, the pore volume is relatively large, and the specific surface area is relatively large, the addition of ligand 2-aminoterephthalic acid and 2-methyl imidazole improves the active sites of cobalt and manganese, the cobalt and manganese bimetallic organic framework is uniformly dispersed in the channel and surface of SBA-15 molecular sieve, thereby improving the contact area of the catalyst and the catalytic efficiency; in addition, the side chain oxidation promoter can promote the contact efficiency of the benzene ring side chain with oxygen and promote the oxidation of the benzene ring side chain, thereby further improving the yield of trimellitic anhydride.

[0074] The above only describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A catalyst for the preparation of trimellitic anhydride, characterized in that, The raw materials include the following ingredients by weight: 5-10 parts of a main catalyst, 1 part of a side chain oxidation promoter; The main catalyst is composed of a cobalt-manganese bimetallic organic framework and SBA-15 molecular sieve; The method steps for preparing the main catalyst are as follows: Step one. Dissolve cobalt salt, manganese salt and organic ligand in DMF-acetonitrile mixed solvent for reaction, and then wash and dry the product after reaction to obtain cobalt-manganese bimetallic organic framework; Step two. Disperse the cobalt-manganese bimetallic organic framework and SBA-15 molecular sieve in methanol, stir, suction filter and dry to obtain the main catalyst; In step one, the cobalt salt is cobalt acetate; The manganese salt is manganese acetate; The organic ligand is a mixture of 2-amino terephthalic acid and 2-methyl imidazole in a mass ratio of 1:0.5-1.5; The DMF and acetonitrile are mixed in a volume ratio of 3-5:1; In step one, the mass-volume ratio of cobalt salt, manganese salt, organic ligand and DMF-acetonitrile mixed solvent is 1g:0.1-0.5g:0.5-1.5g:50-100mL; The reaction conditions are as follows: temperature 60-120℃, time 18-36h; In step two, the mass-volume ratio of cobalt-manganese bimetallic organic framework, SBA-15 molecular sieve and methanol is 1g:1-2g:50-100mL; The side chain oxidation promoter is tetraethylammonium bromide.

2. Use of the catalyst of claim 1 in the preparation of trimellitic anhydride.

3. Use of the catalyst according to claim 2 for the preparation of trimellitic anhydride, characterized in that, The method steps are as follows: S1: Put trimethylbenzene and acetic acid into a batching tank, and put the catalyst into an oxidation tower; the material in the batching tank is sent to the oxidation tower after being heated by a feeding heater, and air / oxygen is introduced into the oxidation tower for oxidation reaction to generate trimellitic acid; S2: The trimellitic acid reaction solution in S1 is sent to a crystallization kettle for crystallization by reducing temperature and pressure, and the crystallized material is pressed into an anhydride kettle by residual pressure for dehydration to obtain crude trimellitic anhydride; S3: The crude trimellitic anhydride in S2 is treated by a light removal tower and a rectification tower to obtain finished trimellitic anhydride.

4. Use of the catalyst according to claim 3 for the preparation of trimellitic anhydride, characterized in that, The temperature of the oxidation reaction in S1 is 220-245℃, and the pressure is 2.0-2.5MPa.

5. Use of the catalyst according to claim 3 for the preparation of trimellitic anhydride, characterized in that, The mass ratio of trimethylbenzene, acetic acid and catalyst in S1 is 1:1-10:0.01-0.

1.

6. Use of the catalyst according to claim 3 for the preparation of trimellitic anhydride, characterized in that, The temperature of the material after being heated by the feeding heater in S1 is 140-160℃, and the temperature of the air / oxygen introduced into the oxidation tower is 160-180℃.