A catalyst system and a continuous process for the production of trimellitic anhydride

Abstract

The application belongs to the field of fine chemical industry and provides a catalyst system and a continuous process for producing trimellitic anhydride, which comprises: a first-stage oxidation catalyst composed of 0.02-1% of cerium acetate and 0.5-5% of hydrogen peroxide; and a second-stage oxidation catalyst composed of 0.01-0.05% of copper acetate and 0.01-1% of manganese acetate. The application reduces the types and addition amount of catalysts, reduces the metal content in the product, and improves the yield of the product. Meanwhile, the application designs a continuous process flow, realizes continuous and efficient oxidation of trimethylbenzene, and realizes continuous production of rapid anhydride formation. Through continuous removal of acetic acid and water in the oxidation and anhydride formation processes, the reaction heat and product water are removed, the process is intensified, the forward reaction is promoted, and then the solvent acetic acid is reused through rectification separation. In addition, the continuous production process also solves the technical defect problems existing in the batch method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical industry, and particularly relates to a catalyst system for producing trimellitic anhydride and a continuous process. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing an understanding of the general context of the present application and is not necessarily recognized as prior art.

[0003] Trimellitic anhydride (TMA for short) is an important fine chemical raw material, which is widely used in the production of plasticizers for PVC resins, polyimide resin paints, water-soluble alkyd resins, epoxy resin curing agents, impregnating agents for low-voltage and pulse power containers, film, water treatment agents, surfactants, etc.

[0004] At present, the production methods of trimellitic anhydride mainly include liquid-phase air oxidation of trimethylbenzene, gas-phase air oxidation of trimethylbenzene, liquid-phase nitric acid oxidation of trimethylbenzene, etc.

[0005] The liquid-phase nitric acid oxidation of trimethylbenzene was developed successfully by Saarbergwerk Company in Germany in the 1970s and realized industrial production. The production process of the liquid-phase nitric acid oxidation of trimethylbenzene is simple, easy to operate, and has a high yield, with a yield of 90% and a product purity of 98.5%. The disadvantages are serious corrosion, high requirements for equipment materials, high production cost, high raw material cost, difficulty in removing residual nitrogen oxide byproducts, more byproducts, serious three-waste pollution, and operation danger, etc. The process is difficult to develop due to the above-mentioned shortcomings, and at present, this method has been basically eliminated.

[0006] The gas-phase air oxidation of trimethylbenzene was developed successfully by Nippon Shokubai Kagaku Kogyo K.K. in Japan in the 1970s. Vanadium, titanium, and phosphorus-containing compounds are used as catalysts, trimethylbenzene is oxidized to generate trimellitic acid, and trimellitic acid is dehydrated to generate trimellitic anhydride. The reaction principle is as follows:

[0007]

[0008] The gas-phase process has a simple process and far less equipment investment than the liquid-phase oxidation process, and the production cost is comparable to that of the liquid-phase oxidation process, which is suitable for small and medium-sized enterprises to invest in factory construction. The disadvantages are poor selectivity of the used catalyst and low yield, and at present, this method has not realized industrial production.

[0009] The liquid phase air oxidation method of meta-cumene is a widely used production process of trimellitic anhydride. The process uses meta-cumene (1,2,4-trimethylbenzene) as raw material, acetic acid as solvent, air as oxidant, and soluble salts of cobalt acetate and manganese acetate as main catalysts, and tetra-bromoethane as co-catalyst. The meta-cumene is oxidized to trimellitic acid in acetic acid solution at 200-220℃ and 2.0-2.3 MPa pressure, and the trimellitic acid is then dehydrated to trimellitic anhydride, with a product purity of up to 99%. The main problems currently existing are: a large number of catalysts are added, the use amount is large, the catalyst efficiency is low, the amount of hazardous waste is large, and in addition, it may lead to excessive metal ions in the trimellitic anhydride separation end; the currently developed segmented oxidation process in China is in a segmented intermittent mode, and after the first stage of oxidation reaction is completed, the second stage of oxidation is carried out. There are process adding catalyst, heating, pressurizing and other processes, the reaction kettle for oxidation reaction needs to be repeatedly heated and cooled, pressurized and depressurized, the equipment is easy to fatigue, the service life is shortened, the oxidation steps may enter the explosion danger zone due to each heating and pressurizing, and a little carelessness may cause explosion danger, the safety of production is very low, in addition, the intermittent process has long reaction time, incomplete reaction, many by-products, unstable quality, low product yield. SUMMARY

[0010] In order to solve the above problems, the application provides a catalyst system and a continuous process for producing trimellitic anhydride.

[0011] In order to achieve the above purpose, the application adopts the following technical scheme:

[0012] The first aspect of the application provides a catalyst system for producing trimellitic anhydride, comprising: a first stage oxidation catalyst and a second stage oxidation catalyst.

[0013] The first stage oxidation catalyst is composed of 0.02-1% cerium acetate and 0.5-5% hydrogen peroxide;

[0014] The second stage oxidation catalyst is composed of 0.01-0.05% copper acetate and 0.01-1% manganese acetate.

[0015] The designed oxidation catalyst system reduces the types and addition amount of catalysts, reduces the content of metal in the product, and improves the yield of the product.

[0016] The second aspect of the application provides a continuous production process of trimellitic anhydride, comprising:

[0017] Dilute cerium acetate with acetic acid to obtain a cerium acetate solution;

[0018] Mix copper acetate and manganese acetate uniformly, and dilute with acetic acid to obtain a mixed catalyst solution of copper acetate and manganese acetate;

[0019] Mixing uniformity of mesitylene, acetic acid, cerium acetate solution, hydrogen peroxide in a first stage oxidation kettle, air is introduced, and first stage oxidation reaction is carried out to obtain first stage oxidation material;

[0020] The first stage oxidation material is continuously introduced into a second stage oxidation kettle, air is introduced, and a second stage oxidation catalyst solution of copper acetate and manganese acetate is added, and second stage oxidation is carried out to obtain second stage oxidation material;

[0021] The second stage oxidation material is continuously introduced into an anhydride forming kettle to carry out dehydration and anhydride formation reaction to obtain crude trimellitic anhydride;

[0022] The acetic acid and water volatilized from the first stage oxidation kettle, the second stage oxidation kettle and the anhydride forming kettle are recovered, and the acetic acid is collected.

[0023] The present application designs a continuous process flow, realizes continuous and efficient oxidation of mesitylene and rapid anhydride formation. By continuously removing acetic acid and water during oxidation and anhydride formation, the reaction heat and product water are removed, the process is intensified, and the reaction is promoted in the forward direction. Then, through rectification separation, the solvent acetic acid is recycled. In addition, the continuous production process also solves the technical defects of the batch method.

[0024] In a third aspect, the present application provides a continuous production device for trimellitic anhydride, comprising: a first stage oxidation kettle T6, a second stage oxidation kettle T7, an anhydride forming kettle T9, and an acetic acid recovery rectification tower T11; the first stage oxidation kettle T6, the second stage oxidation kettle T7 and the anhydride forming kettle T9 are connected in sequence, the anhydride forming kettle T9 is connected in sequence with an acetic acid and water tube heat exchanger E1, an acetic acid receiving tank T10 and the acetic acid recovery rectification tower T11, and the outlet of the top of the anhydride forming kettle T9 is directly connected with the inlet of the middle of the acetic acid recovery rectification tower T11.

[0025] Advantages of the present application

[0026] (1) The present application designs a continuous process flow, realizes continuous and efficient oxidation of mesitylene and rapid anhydride formation. In the oxidation stage, two reaction kettles are connected in series to realize continuous and segmented oxidation. By designing an efficient catalyst system in the two oxidation kettles, the conversion rate of the raw material and the selectivity of the target product are improved. By controlling the pressure, the water produced in the reaction is removed, which promotes the deepening of the oxidation degree. In the oxidation process, repeated heating and cooling, and pressure increase and decrease are avoided, which improves safety. After the second stage oxidation, the material is directly introduced into the anhydride forming kettle. By designing an efficient catalyst system and controlling the pressure, the solvent and water are flashed out, the oxidation product of mesitylene is efficiently dehydrated to form anhydride, and the solvent and water are removed. Through rectification separation, the solvent acetic acid is recycled, and the continuous production of the whole process is realized.

[0027] (2) The invention designs an oxidation catalyst system: reduces the type and amount of catalyst, reduces the content of metal in the product, and improves the yield of the product. In the first stage of oxidation, cerium acetate is used as the main catalyst (the addition amount is 0.02-1% of the mass of trimethylbenzene), and 15% concentration of hydrogen peroxide is used as an auxiliary oxidation agent (the addition amount is 0.5-5% of the mass of trimethylbenzene); in the second stage of oxidation, a mixed catalyst system of copper acetate and manganese acetate is used, and the addition amount ratio is trimethylbenzene: copper acetate: manganese acetate = 1: 0.01-0.05%: 0.01-1%.

[0028] (3) The preparation method of the invention is simple, practical and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings accompanying the specification of the invention form a part of the specification and serve to further illustrate the invention, the exemplary embodiments of the invention and the description thereof, and do not limit the invention.

[0030] Figure 1 It is a schematic diagram of a continuous production device for trimellitic anhydride of the invention, wherein C1: air compressor, T1: air buffer tank, T2: hydrogen peroxide solution storage tank, T3: No. 1 catalyst tank, T4: trimethylbenzene raw material tank, T5: acetic acid raw material tank, T6: first stage oxidation kettle, T7: second stage oxidation kettle, T8: catalyst intermediate tank, T9: anhydride kettle, T10: acetic acid receiving tank, T11: acetic acid recovery rectification tower, T12: gas-liquid separation tank, T13: crude trimellitic anhydride buffer tank, P1: hydrogen peroxide solution storage tank discharge pump, P2: No. 2 catalyst tank discharge pump, P3: acetic acid raw material pump, P4: trimethylbenzene raw material pump, P5: catalyst intermediate tank discharge pump, P6: first stage oxidation kettle discharge booster pump, P7: acetic acid recovery tower feed pump, P8: acetic acid recycling pump, E1: acetic acid and water tube heat exchanger, E2: acetic acid recovery tower overhead heat exchanger. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in the invention have the same meaning as generally understood by those skilled in the art to which the invention belongs.

[0032] A catalyst system for producing trimellitic anhydride, comprising: a first stage oxidation catalyst, a second stage oxidation catalyst;

[0033] The first stage oxidation catalyst is composed of 0.02-1% of cerium acetate and 0.5-5% of hydrogen peroxide; the addition amount is 0.02-1% of the mass of trimethylbenzene,

[0034] The two-stage oxidation catalyst is mixed by 0.01-0.05% copper acetate and 0.01-1% manganese acetate, and the addition amount is 0.01-1% manganese acetate.

[0035] In some embodiments, the concentration of the hydrogen peroxide is 12-18%, or 15%.

[0036] A continuous production process of trimellitic anhydride, comprising:

[0037] Dilute cerium acetate with acetic acid to obtain a cerium acetate solution;

[0038] Mix copper acetate and manganese acetate uniformly, and dilute with acetic acid to obtain a mixed catalyst solution of copper acetate and manganese acetate;

[0039] Mix the trimethylbenzene, acetic acid, cerium acetate solution, and hydrogen peroxide in a first-stage oxidation kettle, pass in air, and perform first-stage oxidation reaction to obtain a first-stage oxidation material;

[0040] Continuously introduce the first-stage oxidation material into a second-stage oxidation kettle, pass in air, add the mixed catalyst solution of copper acetate and manganese acetate, and perform second-stage oxidation to obtain a second-stage oxidation material;

[0041] Continuously introduce the second-stage oxidation material into an anhydride forming kettle, and perform dehydration and anhydride formation reaction to obtain a crude trimellitic anhydride;

[0042] Recycle the acetic acid and water volatilized from the first-stage oxidation kettle, the second-stage oxidation kettle, and the anhydride forming kettle, and collect the acetic acid.

[0043] The present application realizes continuous and efficient oxidation of trimethylbenzene and rapid anhydride formation through the design of the oxidation catalyst system and the continuous process flow. In the oxidation stage, two reaction kettles are connected in series to realize continuous and segmented oxidation. By designing an efficient catalyst system and controlling the addition of different components of the catalyst into the two reaction kettles, the two oxidation kettles can bring out the water produced during the reaction by pressure control, thereby promoting the deepening of the oxidation degree. After the second-stage oxidation, the product is directly introduced into the anhydride forming kettle, and the solvent and water are flashed out by pressure control, realizing efficient dehydration and anhydride formation of the oxidation product of trimethylbenzene. The solvent and water discharged during the two-stage oxidation and anhydride formation processes are separated by rectification to realize the reuse of the solvent acetic acid.

[0044] In some embodiments, the conditions for the first-stage oxidation are: pressure 0.8-1.2 MPa, temperature 120-140℃, and rotation speed 40-60 revolutions per minute.

[0045] In some embodiments, the conditions for the second-stage oxidation are: pressure 2-2.2 MPa, temperature 200-220℃, and rotation speed 40-60 revolutions per minute.

[0046] In some embodiments, the dehydration to anhydride reaction is carried out at a temperature of 230-250°C, a pressure of 40-80 KPa, and a rotation speed of 40-60 rpm.

[0047] In some embodiments, the acetic acid and water volatilized from the first-stage oxidation kettle, the second-stage oxidation kettle, and the anhydride kettle are condensed by a shell-and-tube heat exchanger and then enter an acetic acid receiving tank, non-condensed gas is discharged through a pipeline on the upper part of the acetic acid receiving tank, and the acetic acid and water in the acetic acid receiving tank enter an acetic acid recovery rectification tower.

[0048] In some embodiments, a portion of the acetic acid and water volatilized from the anhydride kettle is directly introduced into the middle section of the acetic acid recovery rectification tower without cooling.

[0049] In some embodiments, the material volatilized from the acetic acid recovery rectification tower is condensed by a gas-liquid separator after being volatilized to obtain acetic acid.

[0050] Specifically, the process includes the following flow:

[0051] Before feeding, the catalyst is diluted and mixed: the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which are diluted with acetic acid from the acetic acid raw material tank T5; the trimethylbenzene raw material pump P4 and the acetic acid raw material pump P3 are opened to feed the first-stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:5-8, the hydrogen peroxide solution storage tank T2 is opened to inject 0.5-5% of the mass of trimethylbenzene, the No. 1 catalyst tank discharge pump P2 is opened to inject the catalyst into the first-stage oxidation kettle T6, and the mass of cerium acetate is 0.02-1% of the mass of trimethylbenzene.

[0052] Segmented oxidation: open air compressor C1, open the first stage oxidation reactor air inlet valve, into the air, through the pressure control valve control the pressure in the kettle 0.8-1.2 MPa, temperature 120-140 ℃, speed per minute 40-60 revolutions, the first stage oxidation, after the first stage oxidation kettle T6 liquid level reaches 65% ~ 70%, through the liquid level controller to the flow through the first stage oxidation reactor discharge booster pump P6, the reaction flow after the boost into the second stage oxidation reactor T7, open the second stage oxidation reactor air inlet valve, into the air, through the pressure control valve control the pressure in the kettle to 2-2.2 MPa, temperature 200-220 ℃, speed per minute 40-60 revolutions, open the catalyst intermediate tank discharge pump P5 to the second stage oxidation reactor T7 injection catalyst, according to the first stage oxidation kettle feed in the trimethylbenzene and copper acetate and manganese acetate mass ratio is 1:0.01-0.05%:0.01-1% supplement catalyst, to further strengthen the degree of oxidation reaction. Two stage oxidation process, the top of the reaction kettle part of the acetic acid and water through the pressure control valve into the acetic acid recovery distillation column T11, remove the heat and water generated by the reaction, due to the volatilization of acetic acid in the first stage oxidation kettle, resulting in an increase in the concentration of the reaction, through the acetic acid pipeline to supplement the acetic acid to the second stage reactor, the mass flow of acetic acid supplement is 0.1-0.5 times the initial acetic acid feed line into the first stage oxidation kettle.

[0053] Anhydride reaction: after the second stage oxidation kettle liquid level reaches 65% ~ 70%, through the liquid level controller to the reaction flow continuously into the anhydride kettle T9, through the pressure control valve control the pressure in the kettle 40-80 KPa, control temperature 230-250 ℃, speed per minute 40-60 revolutions, dehydration anhydride reaction, anhydride process will exist a large number of acetic acid and water volatilization, into the acetic acid recovery distillation column T11, thereby strengthening the anhydride process, crude anhydride through the liquid level controller control through the crude anhydride discharge valve discharge into T13 crude anhydride buffer tank subsequent refining treatment.

[0054] Acetic acid recovery: acetic acid and water volatilized from the first and second stage oxidation kettle and acetic acid and water gas volatilized from the anhydride kettle through the shell and tube heat exchanger E1, after condensation into the acetic acid receiver tank T10, the non-condensable gas is discharged through the upper pipeline of T10, the acetic acid and water in T10 tank is fed into the acetic acid recovery distillation column T11 through the distillation column feed pump P7, in addition, in order to reduce the distillation column kettle heating intensity and energy consumption, a part of the T9 anhydride kettle volatilized acetic acid and water is directly fed into the middle section of the acetic acid recovery distillation column T11 without cooling, the T11 column kettle temperature is controlled at 120 ℃, atmospheric pressure, the overhead gas phase is condensed through the overhead condenser E2, the condensate is fed into the T12 gas-liquid separation tank, the non-condensable gas is discharged from the tank top, the tank bottom liquid is partially refluxed through the reflux controller and partially used as waste water, the acetic acid purified through the distillation column is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0055] The application will be further described in detail in connection with specific examples, it should be pointed out that the specific examples are the explanation of the application but not the limitation.

[0056] Example 1

[0057] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0058] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 rpm per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged through the first stage oxidation kettle discharge booster pump P6 controlled by the liquid level controller, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 rpm per minute, the catalyst intermediate tank discharge pump P5 is opened to inject catalyst into the second stage oxidation kettle T7, the mass ratio of the trimethylbenzene, copper acetate and manganese acetate in the first stage oxidation kettle feeding is 1:0.04%:0.5% to supplement the catalyst, so as to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 through the pressure control valve to remove the heat and water generated in the reaction. Due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, and the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 through the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, and the rotation speed is 40 rpm per minute, so as to carry out the dehydration and anhydride formation reaction. A large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is used to recover the acetic acid and water, so as to strengthen the anhydride formation process. The crude anhydride is discharged through the crude anhydride discharge valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water from the anhydride kettle are condensed by the shell and tube heat exchanger E1, and then enter the acetic acid receiving tank T10. The non-condensable gas is discharged through the pipeline at the upper part of T10. The acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7. In order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling. The kettle temperature of T11 is controlled to 120°C, and the pressure is atmospheric pressure. The gas phase at the top of the tower is condensed through the tower top condenser E2. The condensed liquid enters the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, and the liquid at the bottom of the tank is refluxed through the reflux controller, and part of the liquid is treated as waste water. The purified acetic acid is pumped into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0059] Example 2:

[0060] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 1% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0061] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas from the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0062] Example 3:

[0063] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 4% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0064] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas from the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0065] Example 4:

[0066] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.8% of the mass of trimethylbenzene.

[0067] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the liquid level controller and the crude anhydride discharge valve to enter the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water in the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas in the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water in T9 is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0068] Example 5:

[0069] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.2% of the mass of trimethylbenzene.

[0070] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve V11 and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas from the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0071] Example 6:

[0072] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0073] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.05%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas from the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0074] Example 7:

[0075] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0076] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged from the first stage oxidation kettle by the liquid level controller and the feed booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank discharge pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.8% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 by the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 by the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water from the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas from the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water from the T9 anhydride kettle is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed by the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0077] Example 8:

[0078] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0079] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 120°C, the rotation speed is 40 rpm per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid is discharged through the first stage oxidation kettle discharge booster pump P6 controlled by the liquid level controller, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 rpm per minute, the catalyst intermediate tank discharge pump P5 is opened to inject catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the trimethylbenzene and the copper acetate and the manganese acetate in the first stage oxidation kettle is 1:0.04%:0.5% to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectification tower T11 through the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow rate of the supplemented acetic acid is 0.2 times of the initial acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the reaction liquid is fed into the anhydride kettle T9 through the liquid level controller, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 230°C, the rotation speed is 40 rpm per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectification tower T11 is carried out to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride discharge valve controlled by the liquid level controller, enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water in the first stage and second stage oxidation kettles and the volatilized acetic acid and water gas in the anhydride kettle are fed into the acetic acid receiving tank T10 through the shell and tube heat exchanger E1 after being condensed, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectification tower T11 through the rectification tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectification tower, part of the volatilized acetic acid and water in T9 is directly fed into the middle section of the acetic acid recovery rectification tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid is fed into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed through the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectification tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0080] Example 9:

[0081] Before feeding, the catalyst dilution mixing work is carried out first, the No. 1 catalyst tank T3 is filled with cerium acetate, which is diluted with acetic acid from the acetic acid raw material tank T5, the catalyst intermediate tank T8 is filled with copper acetate and manganese acetate, which is diluted with acetic acid from the acetic acid raw material tank T5; open the trimethylbenzene raw material pump P4, the acetic acid raw material pump P3 to feed the first stage oxidation kettle T6, the molar ratio of trimethylbenzene to acetic acid in the feed is 1:8, open the hydrogen peroxide solution storage tank T2 discharge pump P1, the injection amount is 2.5% of the mass of trimethylbenzene, open the No. 1 catalyst tank discharge pump P2 to inject catalyst into the first stage oxidation kettle T6, the mass of cerium acetate added is 0.5% of the mass of trimethylbenzene.

[0082] The air compressor C1 is opened, the air feeding valve of the first stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 1 MPa by the pressure control valve, the temperature is 140°C, the rotation speed is 40 revolutions per minute, the first stage oxidation is carried out, after the liquid level of the first stage oxidation kettle T6 reaches 70%, the liquid level controller is used to make the reaction liquid flow through the first stage oxidation kettle outlet booster pump P6, the reaction liquid is fed into the second stage oxidation kettle T7 after being boosted, the air feeding valve of the second stage oxidation kettle is opened, air is fed, the pressure in the kettle is controlled to 2 MPa by the pressure control valve, the temperature is 200°C, the rotation speed is 40 revolutions per minute, the catalyst intermediate tank outlet pump P5 is opened to inject the catalyst into the second stage oxidation kettle T7, the mass ratio of the catalyst to the veratrole and the copper acetate and the manganese acetate in the first stage oxidation kettle feeding is 1:0.04%:0.5% to supplement the catalyst, so as to further strengthen the oxidation reaction degree. During the two stage oxidation process, part of the acetic acid and water at the top of the reaction kettle is fed into the acetic acid recovery rectifying tower T11 through the pressure control valve to remove the heat and water generated in the reaction, due to the volatilization of part of the acetic acid in the first stage oxidation kettle, the concentration of the reaction liquid is increased, the acetic acid is supplemented into the second stage reaction kettle through the acetic acid supplement pipeline, the mass flow of the supplemented acetic acid is 0.2 times of the acetic acid feeding pipeline in the first stage oxidation kettle. After the liquid level of the second stage oxidation kettle reaches 70%, the liquid level controller is used to make the reaction liquid flow into the anhydride kettle T9, the pressure in the kettle is controlled to 40 KPa by the pressure control valve, the temperature is controlled to 250°C, the rotation speed is 40 revolutions per minute, the dehydration and anhydride formation reaction is carried out, a large amount of acetic acid and water volatilize during the anhydride formation process, the acetic acid recovery rectifying tower T11 is used to recover the acetic acid and water, so as to strengthen the anhydride formation process, the crude anhydride is discharged through the crude anhydride outlet valve and then enters the T13 crude anhydride buffer tank for subsequent refining treatment. The volatilized acetic acid and water in the first stage and second stage oxidation kettles and the volatilized acetic acid and water in the anhydride kettle are condensed after passing through the shell and tube heat exchanger E1 and then enter the acetic acid receiving tank T10, the non-condensable gas is discharged through the pipeline at the upper part of T10, the acetic acid and water in T10 are fed into the acetic acid recovery rectifying tower T11 through the rectifying tower feeding pump P7, in addition, in order to reduce the kettle heating intensity and energy consumption of the rectifying tower, part of the volatilized acetic acid and water in T9 is directly fed into the middle stage of the acetic acid recovery rectifying tower T11 without cooling, the kettle temperature of T11 is controlled to 120°C, the pressure is normal pressure, the gas phase at the top of the tower is condensed through the tower top condenser E2, the condensed liquid flows into the T12 gas-liquid separation tank, the non-condensable gas at the top of the tank is discharged, the liquid at the bottom of the tank is refluxed through the reflux controller, part of the liquid is treated as waste water, the acetic acid purified through the rectifying tower is fed into the acetic acid raw material tank T5 through the acetic acid recovery pump P8.

[0083] Table 1 reaction effect of trimellitic anhydride in different examples

[0084]

[0085] The examples 1-3 study the influence of the hydrogen peroxide amount on the yield and purity of trimellitic anhydride, and it can be seen that when the hydrogen peroxide amount is 2.5%, the yield and purity of trimellitic anhydride are the highest.

[0086] The examples 4-6 study the influence of the cerium acetate amount on the yield and purity of trimellitic anhydride, and it can be seen that when the cerium acetate amount is 0.2%, the yield and purity of trimellitic anhydride are the highest.

[0087] The examples 7-9 study the influence of the temperature of each oxidation stage on the yield and purity of trimellitic anhydride, and it can be seen that when the temperature of the first-stage oxidation is 140 DEG C and the temperature of the second-stage oxidation is 200 DEG C, the yield and purity of trimellitic anhydride are the highest.

[0088] Therefore, by designing the oxidation catalyst system, optimizing the catalyst addition amount and optimizing the reaction process conditions, the optimal reaction condition is determined, the yield and purity of trimellitic anhydride are improved, the continuous production process further improves the production efficiency, safety stability and reduces the reaction energy consumption.

[0089] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and for those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A continuous production process for trimellitic anhydride, characterized in that, include: Cerium acetate was diluted with acetic acid to obtain a cerium acetate solution; Copper acetate and manganese acetate were mixed evenly and diluted with acetic acid to obtain a mixed catalyst solution of copper acetate and manganese acetate. Pseudotrimethylbenzene, acetic acid, cerium acetate solution, and hydrogen peroxide are mixed evenly in a first-stage oxidation reactor, and air is introduced to carry out a first-stage oxidation reaction to obtain a first-stage oxide material. The first-stage oxide material is continuously introduced into the second-stage oxidation reactor, air is introduced, and then a mixed catalyst solution of copper acetate and manganese acetate is added to carry out the second-stage oxidation to obtain the second-stage oxide material. The two-stage oxide material is continuously introduced into the anhydride forming reactor for dehydration and anhydride formation reaction to obtain crude trimellitic anhydride. Acetic acid and water volatilized from the first-stage oxidation reactor, the second-stage oxidation reactor, and the anhydride formation reactor are recovered, and the acetic acid is collected to obtain the product.

2. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The oxidation catalyst consists of 0.02-1% cerium acetate and 0.5-5% hydrogen peroxide, with the addition amount based on the mass of pseudotrimethylbenzene; The two-stage oxidation catalyst is composed of 0.01-0.05% copper acetate and 0.01-1% manganese acetate, with the addition amount based on the mass of pseudotrimethylbenzene.

3. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The concentration of hydrogen peroxide is 12-18%.

4. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The concentration of hydrogen peroxide is 15%.

5. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The conditions for the first stage of oxidation are: pressure 0.8-1.2 MPa, temperature 120-140℃, and rotation speed 40-60 revolutions per minute.

6. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The conditions for the second-stage oxidation are: pressure of 2-2.2 MPa, temperature of 200-220℃, and rotation speed of 40-60 revolutions per minute.

7. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The conditions for the dehydration reaction to form anhydrides are: temperature 230-250℃, pressure 40-80KPa, and rotation speed 40-60 revolutions per minute.

8. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The acetic acid and water volatilized from the first-stage oxidation reactor, the second-stage oxidation reactor, and the anhydride-forming reactor are condensed through a shell-and-tube heat exchanger and then enter the acetic acid receiving tank. The non-condensable gas is discharged through the upper pipeline of the acetic acid receiving tank, and the acetic acid and water in the acetic acid receiving tank enter the acetic acid recovery distillation tower.

9. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, A portion of the acetic acid and water volatilized from the anhydride-forming reactor enters the middle section of the acetic acid recovery distillation column without cooling.

10. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The material distilled from the acetic acid recovery distillation column is condensed in the gas phase at the top of the column and then enters the gas-liquid separation to obtain acetic acid.

11. The continuous production process of trimellitic anhydride as described in claim 1, characterized in that, The continuous production unit includes: a primary oxidation reactor T6, a secondary oxidation reactor T7, an anhydride formation reactor T9, and an acetic acid recovery distillation column T11; the primary oxidation reactor T6, the secondary oxidation reactor T7, and the anhydride formation reactor T9 are connected in sequence; the anhydride formation reactor T9 is connected in sequence to the acetic acid and water tube heat exchanger E1, the acetic acid receiving tank T10, and the acetic acid recovery distillation column T11; the discharge port at the top of the anhydride formation reactor T9 is also directly connected to the feed port of the middle section of the acetic acid recovery distillation column T11.

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