A continuous oxidation process of chloro-o-xylene

Abstract

A continuous oxidation reaction process of o-xylene chloride includes batching, continuous oxidation, tail gas condensation, flash distillation, acetic acid recovery, tail gas treatment and crude anhydride treatment steps. A bubbling reaction tower with a dehydration section and other matching equipment are used as a continuous o-xylene chloride liquid-phase air reaction device. The device, combined with the oxidation process of the invention, can continuously discharge the water generated during the reaction from the reaction system, greatly reduce the inhibitory effect of water on the reaction, and improve the product yield; at the same time, the device adopts a continuous feeding and discharging production mode to greatly improve the utilization efficiency of the reaction device, and avoid the frequent pressure increase and reduction, temperature increase and decrease of the reaction equipment caused by the intermittent process, which causes equipment fatigue damage.

Description

Technical Field

[0001] The invention relates to the field of chemical production technology, and in particular to a chloro-o-xylene continuous oxidation device and an oxidation process. Background Art

[0002] Monochlorophthalic anhydride is a key raw material for synthesizing some high-value polyimide monomers, such as biphenyl dianhydride (BPDA), triphenyl dianhydride, bisphenol A dianhydride (BPADA), triphenyl dianhydride (HQDPA), and diphenyl ether dianhydride (OPDA). It is also an ideal raw material for synthesizing low-cost thermoplastic polyimide polyetherimide (PEI) and polythioetherimide (PTEI). At present, the preparation methods of monochlorophthalic anhydride include: phthalic anhydride melt or gas phase chlorination method, mononitrophthalic anhydride chlorination method, monochloro-o-xylene gas phase air catalytic oxidation method, and monochloro-o-xylene liquid phase air catalytic oxidation method.

[0003] CN1526710A discloses a method of using monosodium phthalate as raw material, water as medium, weak alkaline solution as pH value regulator of reaction system, and directly carrying out chlorination reaction with chlorine. This method has large chlorine consumption, produces more waste water, and has a large amount of impurities difficult to separate in the product, so the separation cost is high. In addition, the 3-chloro product produced by this process is small, and the product has a narrow scope of application.

[0004] The gas-phase catalytic oxidation method of monochloro-o-xylene (DE2336875) proposed by BASF of Germany in 1974 is to use a fixed bed catalyst of vanadium titanium oxide and introduce the steam of monochloro-o-xylene for gas-phase air oxidation. As a result, the yield is low, the separation of product impurities is difficult, and the equipment is seriously corroded. The results of the operation of a 1,000-ton annual chlorophthalic anhydride unit built by a domestic enterprise using a similar process are consistent with those of BASF.

[0005] CN1560045A discloses a method for continuous oxidation of o-xylene in liquid phase by air in three stirred reactors in series. Although such stirring reaction can improve the mass transfer effect, it is relatively risky to implement. The main reason is that the o-xylene in liquid phase by air oxidation system is highly corrosive. Once the mechanical seal of the stirring is corroded, the lubricating oil may enter the reactor and cause an explosion. There have been cases in this regard.

[0006] In summary, the current synthesis methods of chlorophthalic anhydride all have disadvantages such as low product yield, high cost, or low equipment utilization, causing equipment fatigue damage, and shortening service life. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a continuous oxidation device and oxidation process of chloro-o-xylene, specifically, a bubbling reaction tower with a dehydration section and other supporting equipment are used as a continuous chloro-o-xylene liquid-phase air reaction device. The device, combined with the oxidation process of the present invention, can continuously discharge the water generated in the reaction process from the reaction system, greatly reduce the inhibitory effect of water on the reaction, and improve the product yield; at the same time, the device adopts a production method of continuous feeding and continuous discharging, which greatly improves the utilization efficiency of the reaction device and avoids the frequent pressure increase and reduction, temperature increase and reduction caused by the intermittent process, which causes equipment fatigue damage.

[0008] The continuous oxidation device and oxidation process of o-xylene chloride of the present invention solve the problems of large equipment investment, high failure rate and poor safety caused by the continuous oxidation of o-xylene chloride in liquid phase and air by connecting multiple stirring kettles in series, and also solve the problems of large equipment investment and low production efficiency caused by the continuous oxidation of o-xylene chloride in liquid phase and air by microchannel reactor in the prior art. The present invention is a safe, reliable and efficient production method for producing monochlorophthalic anhydride.

[0009] Specifically, the present invention provides a reaction device for continuous oxidation of chloro-o-xylene and an oxidation process thereof, so that chloro-o-phthalic acid can be prepared safely, stably and efficiently.

[0010] The invention provides a chloro-o-xylene continuous oxidation reaction device, comprising a batching kettle (R2), a feeding pump (P1), a bubbling reaction tower (R1) with a dehydration section (T1), an oxidation condenser (E1), a flash tank (V1), a flash material condenser (E2), an acetic acid storage tank (V2), a tail gas alkali absorption tower (T2), and a circulation pump (P2).

[0011] The bubbling reaction tower (R1) with a dehydration section has an aspect ratio of 2 to 20, preferably 2 to 12, and a condenser is arranged on the top of the tower.

[0012] The bubbling reaction tower (R1) is divided into three sections from top to bottom, the first section is a dehydration section, the second section is a free space section, and the third section is a reaction section. The height of the dehydration section accounts for 20-60% of the total height of the bubbling reaction tower (R1), preferably 20-50%; the height of the free space section accounts for 20-50% of the total height of the bubbling reaction tower (R1), and the height of the reaction section accounts for 20-80% of the total height of the bubbling reaction tower (R1).

[0013] A liquid distributor, a filler, and a filler support grid are installed in the dehydration section; a gas distributor and a bubbling tower plate are installed horizontally at the lower part of the reaction section, the gas distributor is arranged below the bubbling tower plate, and the gas distributor is connected to the air inlet of the bubbling reaction tower (R1); a raw material feed pipe is provided above the reaction section and is connected to a feeding pump; a discharge pipe is provided at the bottom of the tower and is connected to a flash tank; a tail gas pipe and a reflux pipe are provided at the top of the tower, the tail gas pipe is connected to the gas phase inlet of the condenser, and the reflux pipe is connected to the liquid outlet of the condenser; the air inlet of the bubbling reaction tower (R1) is connected to an air compressor (M1).

[0014] The material of the bubbling reaction tower is corrosion-resistant material: the shell of the tower is one of titanium / steel composite plate, titanium-palladium / steel composite plate, zirconium / titanium / steel composite plate, and tantalum / steel composite plate; the material of the gas distributor of the dehydration section and the reaction section is one of three materials: titanium, titanium-palladium alloy, and zirconium; the filler of the dehydration section is titanium or zirconium wire mesh structured filler, or ceramic orifice plate corrugated structured filler or other suitable structured filler, and can also be a random filler made of corrosion-resistant material, such as ball rings, rectangular saddle rings, Raschig rings, step rings, flat rings, etc.

[0015] The oxidation condenser (E1) is a finned condenser, tube-in-tube condenser, floating head condenser or U-tube condenser with a liquid storage tank at the bottom, and the volume of the liquid storage section is greater than 0.2m 3 , the material is one of the three materials: titanium, titanium-palladium alloy, and zirconium.

[0016] The flash tank (V1) is equipped with internal coil heating and external jacket heating; the shell material of the flash tank is one of several materials such as titanium / steel composite plate, titanium palladium / steel composite plate, zirconium / titanium / steel composite plate, tantalum / steel composite plate, etc., and the internal coil material is one of three materials: titanium, zirconium, and tantalum.

[0017] A continuous oxidation reaction process of chloro-o-xylene, comprising the steps of batching, continuous oxidation, tail gas condensation, flash evaporation, acetic acid recovery, tail gas treatment and crude anhydride treatment;

[0018] The ingredients include raw material o-xylene chloride, acetic acid, catalyst and accelerator prepared in proportion;

[0019] The continuous oxidation is carried out in a liquid phase under the conditions of a pressure of 1.3 to 3 MPa, a temperature of 160 to 260° C., and a water content of 0 to 8% in the reaction system.

[0020] The present invention gathers water vapor by arranging a dehydration section, and arranges a condenser at the top of the tower to discharge condensed water, thereby controlling the water content of the entire system to be 0-8%, thereby ensuring the reaction rate and yield.

[0021] Specifically, it is achieved by controlling the water content of the continuous oxidation step, which can be achieved by setting a dehydration section on the upper part of the reactor in combination with a condenser on the top, enriching water vapor through the dehydration section, and then condensing it in the condenser, continuously discharging part of the condensate, thereby controlling the water content of the reaction system.

[0022] The batching steps are:

[0023] The materials are prepared according to the ratio of o-xylene chloride mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100: 300-500: 0.5-3: 0.5-4; preferably o-xylene chloride mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100: 400-500: 0.5-2: 0.5-2, stirred, heated to 50-180° C., preferably 80-120° C., maintained for 0.5-5 hours, preferably 1-2 hours, to complete the preparation.

[0024] The catalyst is an acetate selected from one or a combination of cobalt acetate, manganese acetate, zirconium acetate, nickel acetate, hafnium acetate, and sodium acetate; the promoter is a bromide selected from one or a combination of tetrabromoethane, hydrogen bromide, and sodium bromide.

[0025] The continuous oxidation step is: continuously adding the prepared materials into a continuous bubbling reactor, and simultaneously introducing compressed oxygen-rich gas or air into the lower part of the reactor, and performing a liquid phase continuous oxidation reaction under the conditions of a pressure of 1.3 to 3 MPa, a temperature of 160 to 260° C., and a water content of 0 to 8% in the reaction system.

[0026] Preferably, the liquid phase continuous oxidation reaction is carried out under the conditions of a pressure of 1.8 to 2.5 MPa, a reaction temperature of 180 to 250° C., and a water content of 3 to 6%.

[0027] Among them, the material flow rate (kg / min): the air flow rate under standard conditions (m 3 / min) ratio = 1:1.1-1.8, preferably 1:1.2-1.7; the oxygen content of the tail gas is controlled within 7% (volume ratio).

[0028] The tail gas condensation step comprises: condensing the water vapor at the top of the bubbling reactor, and treating the uncondensed tail gas by passing it through a tail gas alkali absorption tower, wherein a part of the condensate flows back to the dehydration section at the top of the reactor, and a part is taken out for acetic acid recovery.

[0029] The flash distillation step comprises: dissolving the chlorophthalic acid generated by the oxidation reaction in acetic acid, and continuously flash distilling the bubbling reactor R1, and performing crude anhydride treatment after the flash distillation is completed.

[0030] The acetic acid recovery step comprises: condensing and collecting the flashed acetic acid and other vapors to achieve acetic acid recovery.

[0031] The crude anhydride treatment step is as follows: chlorophthalic acid generated by oxidation reaction is dissolved in acetic acid, and a crude anhydride product is obtained by continuous flash evaporation and distillation.

[0032] The distillation process is to first distill acetic acid by normal pressure distillation, then distill under reduced pressure at 170-230°C and 1-5kpa absolute pressure, convert chlorophthalic acid into chlorophthalic anhydride and distill it out from the distillation kettle to obtain crude chlorophthalic anhydride, and further purify it to obtain chlorophthalic anhydride product. The distilled acetic acid is recovered.

[0033] At least one embodiment of the present invention provides a continuous oxidation reaction process and device for chloro-o-xylene, comprising a batching kettle (R2), a feeding pump (P1), a bubbling reaction tower (R1) with a dehydration section (T1), an oxidation condenser (E1), a flash tank (V1), a flash material condenser (E2), an acetic acid storage tank (V2), a tail gas alkali absorption tower (T2), and a circulation pump (P2).

[0034] The bubbling reaction tower (R1) is divided into three sections from top to bottom, the first section is a dehydration section, the second section is a free space section, and the third section is a reaction section; the length-to-diameter ratio of the bubbling reaction tower is 2 to 20. The dehydration section accounts for 20 to 60% of the total height of the bubbling reaction tower (R1), the free space section accounts for 20 to 50% of the total height of the bubbling reaction tower (R1), and the reaction section accounts for 20 to 80% of the total height of the bubbling reaction tower (R1).

[0035] The specific steps include:

[0036] 1. Ingredients

[0037] The materials are prepared according to the ratio of o-xylene chloride mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100: 300-500: 0.5-3: 0.5-4; preferably, the ratio of o-xylene chloride mass: acetic acid mass: catalyst mass: promoter mass = 100: 400-500: 0.5-2: 0.5-2, stirred, heated to 80-120° C., maintained for 1-2 hours, and the preparation is completed.

[0038] 2. Continuous oxidation

[0039] The prepared materials (raw materials, catalyst and promoter) are continuously added into a continuous bubbling reactor (R1), and compressed oxygen-rich gas or air (oxygen content is greater than 20% v / v) is introduced into the lower part of the reactor to carry out a liquid phase continuous oxidation reaction at a pressure of 1.3 to 3 MPa and a temperature of 160 to 260° C., preferably, at a pressure of 1.8 to 2.5 MPa and a reaction temperature of 180 to 250° C.

[0040] Among them, the material flow rate (kg / min): the air flow rate under standard conditions (m 3 / min) ratio = 1:1.1-1.8, preferably 1:1.2-1.7; the oxygen content of the tail gas is controlled within 7% (volume ratio).

[0041] The catalyst is an acetate, selected from one or a combination of acetates such as cobalt acetate, manganese acetate, zirconium acetate, nickel acetate, hafnium acetate, sodium acetate, etc.

[0042] The promoter is a bromide, selected from tetrabromoethane, hydrogen bromide, sodium bromide or a combination thereof.

[0043] After the reaction is completed, the acetic acid, water vapor and reaction tail gas vaporized in the upper part of the bubbling tower are distilled in the dehydration section (T1) to concentrate the water vapor and then come out from the top of the tower.

[0044] The present invention arranges a reflux valve and a production valve below the condenser (E1), and adjusts the reflux ratio through DCS to make the water content of the reaction system a constant value between 0 and 8% and to achieve dynamic balance, thereby realizing continuous oxidation.

[0045] 3. Exhaust gas condensation

[0046] The water vapor at the top of the tower (R1) is condensed by heat exchange in the reaction tail gas condenser (E1), and the uncondensed tail gas is treated in the tail gas alkali absorption tower (T2). Part of the condensate flows back to the dehydration section (T1) at the top of the bubbling reactor, and part is taken out and sent to acetic acid recovery.

[0047] 4. Flash Steaming

[0048] The chlorophthalic acid generated by the reaction is dissolved in acetic acid and continuously enters the flash tank (V1) from the bubbling reactor (R1). The acetic acid is evaporated to recover the acetic acid, and part of the oxidation products such as acetic acid and chlorophthalic acid are treated with crude anhydride.

[0049] 5. Acetic acid recovery

[0050] The flashed acetic acid and other vapors are condensed in the condenser (E2) and then enter the dilute acetic acid storage tank (V2) to achieve acetic acid recovery.

[0051] 6. Exhaust gas treatment

[0052] The non-condensable gas passing through the condensers (E1, E2) is absorbed by the tail gas alkali absorption tower (T2) for tail gas treatment.

[0053] 7. Crude anhydride treatment

[0054] Part of the acetic acid and chlorophthalic acid and other oxidation products from the flash tank are first distilled out of acetic acid by normal pressure distillation, and then distilled under reduced pressure at 170-230°C and 1-5kPa absolute pressure. Chlorophthalic acid is converted into chlorophthalic anhydride and distilled out from the distillation kettle to obtain crude chlorophthalic anhydride, which is further refined to obtain chlorophthalic anhydride products. The distilled acetic acid is recovered for acetic acid.

[0055] The beneficial effects of the present invention include the following aspects:

[0056] 1. The chloro-o-xylene continuous oxidation device and oxidation process disclosed in the present invention adopt a continuous oxidation process, that is, the production method is continuous feeding and continuous discharging. This production method greatly improves the utilization efficiency of the reaction device and avoids fatigue damage to the reaction equipment caused by frequent pressure increase and decrease, temperature increase and decrease caused by the intermittent process.

[0057] 2. The chloro-o-xylene continuous oxidation device and oxidation process disclosed in the present invention adopt a bubbling reaction tower with a dehydration section and other supporting equipment as the chloro-o-xylene liquid-phase air continuous reaction device. The device, combined with the continuous oxidation process of the present invention, can continuously discharge the water generated by the reaction during the reaction from the reaction system, keep the water content of the reaction system below 8%, greatly reduce the inhibitory effect of water on the reaction, ensure the reaction rate and conversion rate, and improve the product yield.

[0058] 3. The continuous oxidation process disclosed in the present invention enables the oxidation system to control the flow rate of materials so that the reaction is always at a constant temperature that is suitable for the oxidation reaction. This greatly improves the situation in which large temperature fluctuations in intermittent reactions lead to excessive combustion of materials and solvents at the peak of the reaction, and inadequate reaction in the later stage of the reaction due to low temperature. This can reduce losses and improve yields.

[0059] 4. The chloro-o-xylene continuous oxidation device and oxidation process disclosed in the present invention adopts a bubbling reaction tower, and there is no rotating part in the reactor, so the equipment investment is small, the failure rate is low, and the reliability is high, which is very suitable for large-scale industrial production. The problem of large equipment investment, high failure rate and poor safety caused by the continuous oxidation of chloro-o-xylene liquid phase air by multi-stage stirred kettles in series is solved, and the problem of large equipment investment and low production efficiency caused by the continuous oxidation of chloro-o-xylene liquid phase air by microchannel reactor is also solved.

[0060] 5. The present invention realizes full-automatic control of the reaction system, reduces the number of operators on site, and the continuous oxidation process of the present invention reduces the amount of material held in the reactor compared with the batch process of the same production capacity, greatly improving the safety of the system. It is a highly efficient production method for monochlorophthalic anhydride. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings illustrate exemplary embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure. These drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification.

[0062] Figure 1 This is a continuous oxidation reaction process flow chart of Example 1 of the present invention

[0063] Wherein R1-bubble reactor, T1-dehydration packing layer, R2-batch kettle, E1-tail gas condenser, E2-flash condenser, T2-tail gas alkali absorption tower, V1-flash tank, V2-acetic acid storage tank, M-air compressor, P1-feeding pump, P2-alkali liquid pump;

[0064] 1-mixed material, 2-compressed air, 3-reacted material, 4-reaction tail gas, 5-tail gas after condensation, 6, 7-cooling water, 8-reflux condensate, 9-produced condensate, 10-acetic acid steam, anhydride steam, 11-acetic acid, 12-flash tail gas, 13-crude anhydride, 14-acetic acid, 15-alkaline water. DETAILED DESCRIPTION

[0065] The present application is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is to be understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present application. It should also be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings.

[0066] Example 1 (Low Temperature Oxidation)

[0067] 1) Ingredients

[0068] Add 7000 kg of chloro-o-xylene, acetic acid, acetate catalyst and bromide promoter in the ratio of chloro-o-xylene mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100:450:1.5:2, wherein the ratio of acetate catalyst is: cobalt acetate: manganese acetate: zirconium acetate = 1:1.2:0.005; the bromide is tetrabromoethane: sodium bromide = 3:1, and add the prepared materials into the batching kettle R2, heat and stir to 80°C, maintain for 1 hour, and complete the material preparation.

[0069] 2) Continuous oxidation

[0070] The feed pump P1 under the kettle is fed at 1.2m 3 / h flow rate into the continuous bubbling reactor R1, when the material level in the bubbling reactor reaches a height of 1.5m, stop adding; then introduce compressed air to 1.3MPa. Turn on the thermal oil heating, and turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the tail gas alkali absorption tower T2 circulation pump. When the temperature in the bubbling reactor R1 reaches 160℃, observe the magnetic oxygen meter of the reactor tail and show that the oxygen content in the vented tail gas starts to change from the oxidation reaction, and turn on the feed pump P1 again at 1.2m 3 / h flow rate to add materials to the bubbling reactor R1, adjust the amount of compressed air introduced, so that the oxygen content in the reaction exhaust gas is controlled at about 7% (volume ratio), when the liquid level of the condenser reflux tank reaches 0.3m, open the reflux valve and the extraction valve below the condenser E1, adjust the reflux ratio through DCS to make the water content of the reaction system constant at 3% and achieve dynamic equilibrium. Keep the pressure in the reactor R1 at 1.9MPa and the temperature at 200℃.

[0071] 3) Exhaust gas condensation

[0072] The water vapor at the top of the R1 tower is condensed through heat exchange in the reaction tail gas condenser E1, and the uncondensed tail gas is treated in the tail gas absorption unit. Most of the condensate is refluxed to the dehydration section at the top of the bubbling reactor, and the produced acetic acid aqueous solution is sent to the acetic acid recovery unit.

[0073] 4) Flash evaporation

[0074] The oxidation reaction product enters the continuous flash tank V1 from the bubbling reactor R1 for flash evaporation to separate acetic acid, water and other vapors, and then enters the crude anhydride treatment unit.

[0075] 5) Acetic acid recovery unit

[0076] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2 to achieve acetic acid recovery.

[0077] 6) Exhaust gas treatment unit

[0078] The non-condensable gas from condensers E1 and E2 is absorbed by tail gas alkali absorption tower T2, and the tail gas is treated by alkali washing.

[0079] 7) Crude anhydride processing unit

[0080] The crude anhydride from the flash tank V1 can be sent to a distillation tower for refining. First, acetic acid is distilled out by normal pressure distillation, and then reduced pressure distillation is performed at 200°C and an absolute pressure of 3kPa to obtain the chlorophthalic anhydride product.

[0081] The crude anhydride from the flash tank V1 was sampled and tested for purity and yield. The acetic acid consumption was calculated based on the acetic acid yield after distillation.

[0082] Example 2 (Medium Temperature Oxidation)

[0083] 1) The ingredients are the same as in Example 1

[0084] 2) Continuous oxidation

[0085] The feed pump P1 under the kettle is fed at 1.2m 3 / h flow rate into the continuous bubbling reactor R1, when the material level in the bubbling reactor reaches a height of 1.5m, stop adding; then introduce compressed air to 1.3MPa. Turn on the thermal oil heating, and turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the tail gas absorption tower T2 circulation pump. When the temperature in the bubbling reactor R1 reaches 160℃, observe the reaction tail magnetic oxygen meter to show that the oxygen content in the vented tail gas starts to change from the beginning when the oxidation reaction begins, turn on the feed pump P1 again, at 1.2m 3 / h flow rate to add materials to the bubbling reactor R1, adjust the amount of compressed air introduced, so that the oxygen content in the reaction exhaust gas is controlled at about 7% (volume ratio), when the liquid level of the condenser reflux tank reaches 0.3m, open the reflux valve and the extraction valve below the condenser E1, and adjust the reflux ratio through DCS to make the water content of the reaction system a constant value of 4% and achieve dynamic equilibrium. Keep the pressure in the reactor R1 at 2.1MPa and the temperature at 215℃.

[0086] 3) Exhaust gas condensation

[0087] The water vapor at the top of the R1 tower is condensed through heat exchange in the reaction tail gas condenser E1, and the uncondensed tail gas is treated in the tail gas absorption unit. Most of the condensate is refluxed to the dehydration section at the top of the bubbling reactor, and the produced acetic acid aqueous solution is sent to the acetic acid recovery unit.

[0088] 4) Flash unit

[0089] The chlorophthalic acid material generated by the oxidation reaction enters the continuous flash tank V1 from the bubbling reactor R1 for flash evaporation, and then enters the crude anhydride treatment unit.

[0090] 5) Acetic acid recovery unit

[0091] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2 to achieve acetic acid recovery.

[0092] 6) Exhaust gas treatment unit

[0093] The non-condensable gas from condensers E1 and E2 is absorbed by tail gas alkali absorption tower T2, and the tail gas is treated by alkali washing.

[0094] 7) Crude anhydride processing unit

[0095] The crude anhydride from the flash tank V1 can be sent to a distillation tower for refining. First, acetic acid is distilled out by normal pressure distillation, and then reduced pressure distillation is performed at 200°C and an absolute pressure of 3kPa to obtain the chlorophthalic anhydride product.

[0096] The crude anhydride from the flash tank V1 was sampled and tested for purity and yield. The acetic acid consumption was calculated based on the acetic acid yield after distillation.

[0097] Example 3 (High Temperature Oxidation)

[0098] 1) Ingredients: Same as Example 1

[0099] 2) Continuous oxidation

[0100] The feed pump P1 under the kettle is fed at 1.2m 3 / h flow rate into the continuous bubbling reactor R1, when the material level in the bubbling reactor reaches a height of 1.5m, stop adding; then introduce compressed air to 1.3 ~ 1.7MPa. Turn on the thermal oil heating, and turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the tail gas absorption tower T2 circulation pump. When the temperature in the bubbling reactor R1 reaches 170℃, observe the magnetic oxygen meter of the reaction tail to show that the oxygen content in the vented tail gas starts to change. The oxidation reaction begins, and the feed pump P1 is turned on again at 1.2m 3 / h flow rate to add materials to the bubbling reactor R1, adjust the amount of compressed air introduced, so that the oxygen content in the reaction exhaust gas is controlled at about 7% (volume ratio), when the liquid level of the condenser reflux tank reaches 0.3m, open the reflux valve and the extraction valve below the condenser E1, adjust the reflux ratio through DCS to make the water content of the reaction system a constant value of 6% and achieve dynamic equilibrium. Keep the pressure in the reactor R1 at 2.3MPa and the temperature at 238℃.

[0101] 3) Exhaust gas condensation

[0102] The water vapor at the top of the R1 tower is condensed through heat exchange in the reaction tail gas condenser E1, and the uncondensed tail gas is treated in the tail gas absorption unit. Most of the condensate is refluxed to the dehydration section at the top of the bubbling reactor, and the produced acetic acid aqueous solution is sent to the acetic acid recovery unit.

[0103] 4) Flash unit

[0104] The chlorophthalic acid material generated by the oxidation reaction enters the continuous flash tank V1 from the bubbling reactor R1 for flash evaporation, and then enters the crude anhydride detection unit.

[0105] 5) Acetic acid recovery unit

[0106] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2 to achieve acetic acid recovery.

[0107] 6) Exhaust gas treatment unit

[0108] The non-condensable gas from condensers E1 and E2 is absorbed by tail gas alkali absorption tower T2, and the tail gas is treated by alkali washing.

[0109] 7) Crude anhydride detection unit

[0110] The crude anhydride from the flash tank V1 can be sent to a distillation tower for refining. First, acetic acid is distilled out by normal pressure distillation, and then reduced pressure distillation is performed at 200°C and an absolute pressure of 3kPa to obtain the chlorophthalic anhydride product.

[0111] The crude anhydride from the flash tank V1 was sampled and tested for purity and yield. The acetic acid consumption was calculated based on the acetic acid yield after distillation.

[0112] Example 4

[0113] 1) Ingredients

[0114] Add 7000 kg of chloro-o-xylene, acetic acid, acetate catalyst and bromide promoter in the ratio of chloro-o-xylene mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100:500:2:2, wherein the ratio of acetate catalyst is: cobalt acetate: manganese acetate: nickel acetate = 1:1:0.02; the promoter bromide is hydrogen bromide: sodium bromide = 3:1, add the material into the batching kettle R2, heat and stir to 80°C, maintain for 1 hour, and complete the material preparation.

[0115] 2) Continuous oxidation implementation

[0116] The feed pump P1 under the kettle is fed at 1.2m 3 / h flow rate into the continuous bubbling reactor R1, and stop adding when the material level in the bubbling reactor reaches a height of 1.5m; then introduce compressed air to 1.5MPa. Turn on the thermal oil heating, turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the circulating pump of the tail gas absorption tower T2.

[0117] When the temperature in the bubbling reactor R1 reaches 170°C, the oxidation reaction begins when the oxygen content in the exhaust gas changes from the beginning to the beginning, and the feed pump P1 is turned on again at 1.2 m 3 / h flow rate to add materials to the bubbling reactor R1, adjust the amount of compressed air introduced, so that the oxygen content in the reaction exhaust gas is controlled at about 7% (volume ratio), when the liquid level of the condenser reflux tank reaches 0.3m, open the reflux valve and the extraction valve below the condenser E1, adjust the reflux ratio through DCS to make the water content of the reaction system a constant value of 6% and achieve dynamic equilibrium. Keep the pressure in the reactor R1 at 2.0MPa and the temperature at 215℃.

[0118] 3) Exhaust gas condensation

[0119] The water vapor at the top of the R1 tower is condensed through heat exchange in the reaction tail gas condenser E1, and the uncondensed tail gas is treated in the tail gas absorption unit. Most of the condensate is refluxed to the dehydration section at the top of the bubbling reactor, and the produced acetic acid aqueous solution is sent to the acetic acid recovery unit.

[0120] 4) Flash unit

[0121] The chlorophthalic acid material generated by the oxidation reaction enters the continuous flash tank V1 from the bubbling reactor R1 for flash evaporation, and then enters the crude anhydride treatment unit.

[0122] 5) Acetic acid recovery unit

[0123] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2 to achieve acetic acid recovery.

[0124] 6) Exhaust gas treatment unit

[0125] The non-condensable gas from condensers E1 and E2 is absorbed by tail gas alkali absorption tower T2, and the tail gas is treated by alkali washing.

[0126] 7) Crude anhydride processing unit

[0127] The crude anhydride from the flash tank V1 can be sent to a distillation tower for refining. First, acetic acid is distilled out by normal pressure distillation, and then reduced pressure distillation is performed at 230°C and an absolute pressure of 5kPa to obtain the chlorophthalic anhydride product.

[0128] The crude anhydride from the flash tank V1 was sampled and tested for purity and yield. The acetic acid consumption was calculated based on the acetic acid yield after distillation.

[0129] Example 5

[0130] 1) Ingredients

[0131] Add 7000 kg of chloro-o-xylene, acetic acid, acetate catalyst and bromide promoter in the ratio of chloro-o-xylene mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100:500:3:3, wherein the ratio of acetate catalyst is: cobalt acetate: manganese acetate: nickel acetate = 1:1:0.02; the bromide is hydrogen bromide: sodium bromide = 3:1, and add the material into the batching kettle R2, heat and stir to 80°C, maintain for 1 hour, and complete the material preparation.

[0132] Steps 2)-7) are the same as in Example 4.

[0133] Comparative Example 1 (intermittent oxidation)

[0134] According to the raw material ratios of Example 1, the material preparation is completed.

[0135] The feed pump P1 under the kettle is fed at 1.2m 3 / h flow rate to add all 200kg of materials in the batching kettle into the bubbling reactor R1, and then introduce compressed air to 1.3MPa. Turn on the heat transfer oil heating, and turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the tail gas absorption tower T2 circulating pump. When the temperature in the bubbling reactor R1 reaches 160°C, observe the reaction tail magnetic oxygen meter to show that the oxygen content in the vented tail gas begins to change when the oxidation reaction begins to initiate, adjust the amount of compressed air introduced, so that the oxygen content in the reaction vented tail gas is controlled at about 7% (volume ratio), when the liquid level of the condenser reflux tank reaches 0.2m, open the reflux valve under the condenser E1 for reflux. Keep the pressure in the reactor at 2.1MPa and the temperature at 215°C. When the oxygen content of the tail gas reaches more than 18%, or the reaction temperature drops below 170°C. Stop passing compressed air to end the reaction.

[0136] The reacted materials enter the continuous flash tank V1 from the bubbling reactor R1, and then enter the crude anhydride treatment unit.

[0137] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2, and then go to the acetic acid recovery unit. The non-condensable gas is absorbed by the absorption tower and then goes to the tail gas treatment unit.

[0138] The crude anhydride after flash evaporation is sampled to test the purity and yield, and the acetic acid consumption is calculated based on the acetic acid yield after distillation.

[0139] Comparative Example 2 (intermittent oxidation + no dehydration)

[0140] The material preparation was completed according to the raw material ratios of Example 1, and a common bubbling reactor was used to replace the bubbling reactor with a dehydration section of the present invention.

[0141] The feed pump P1 under the kettle is used to feed the material at a rate of 1.1 m 3 / h flow rate to add all 200kg of materials in the batching kettle into an ordinary bubbling reactor (without dehydration section), and then introduce compressed air to 1.2MPa. Turn on the heat transfer oil heating, and turn on the cooling water of the tail gas condenser E1 and the flash condenser E2, and turn on the tail gas absorption tower T2 circulating pump. When the temperature in the bubbling reactor reaches 180°C, observe the oxidation reaction initiated by the oxygen content in the exhaust gas from the beginning of the change of the magnetic oxygen instrument of the reaction tail, and adjust the amount of compressed air introduced to control the oxygen content in the reaction exhaust gas to about 7% (volume ratio). Keep the pressure in the reactor at 2.0MPa and the temperature at 210°C. When the oxygen content of the tail gas reaches more than 18%, or the reaction temperature drops below 170°C, stop passing compressed air to end the reaction.

[0142] The reacted materials enter the continuous flash tank V1 from the bubbling reactor for flash evaporation, and then the crude anhydride coming out from the bottom enters the crude anhydride treatment unit.

[0143] The flashed acetic acid and other vapors are condensed by condenser E2 and enter the dilute acetic acid storage tank V2, and then go to the acetic acid recovery unit. The non-condensable gas is absorbed by the absorption tower and then goes to the tail gas treatment unit.

[0144] The crude anhydride obtained after flash evaporation was sampled and tested for purity and yield, and the acetic acid consumption was calculated based on the acetic acid yield after distillation.

[0145] The equipment specifications of the embodiment of the present invention are shown in Table 1.

[0146] Table 1

[0147]

[0148] The test experimental data of the embodiments of the present invention and the comparative examples are shown in Table 2.

[0149] Table 2

[0150]

[0151] Table 1 shows the composition of reactants and chlorine utilization in Examples 1-6 and Comparative Examples 1-2. The samples tested were the crude anhydride analysis results obtained after vacuum distillation of the oxidation products in each embodiment. Some impurities have been pumped into the vacuum system, so the purity is not much different, which also shows that the liquid phase air oxidation product of chloro-o-xylene has much fewer impurities than other processes.

[0152] The material ratios of Examples 1-3 and Comparative Example are the same, and the test and calculation data show that:

[0153] (1) For the liquid-phase air oxidation reaction of chloro-o-xylene, as the reaction temperature increases, the consumption of acetic acid increases, and the content of phthalic anhydride in the product increases due to dechlorination. Among them, the medium-temperature oxidation product has the highest yield.

[0154] (2) The yield of monochlorophthalic anhydride by the continuous oxidation process is significantly higher than that by the intermittent oxidation process, and in particular, the medium-temperature oxidation process of Example 2 has the best result.

[0155] In Examples 4 and 5, different catalyst ratios are used, and the test data show that increasing the amount of catalyst and co-catalyst can make the oxidation reaction more thorough and reduce other impurities in the product. However, it also brings more serious side effects of deep oxidation of chloro-o-xylene and acetic acid, and also causes more serious dechlorination of chlorophthalic anhydride, reducing the product yield.

[0156] Therefore, the addition ratio of catalyst and co-catalyst in the raw materials needs to be properly balanced, the mass of o-xylene chloride: the mass of acetic acid: the mass of acetate catalyst: the mass of bromide promoter = 100: 300-500: 0.5-3: 0.5-4; preferably, the mass of o-xylene chloride: the mass of acetic acid: the mass of acetate catalyst: the mass of bromide promoter = 100: 400-500: 0.5-2: 0.5-2.

[0157] Those skilled in the art should understand that the above embodiments are only for the purpose of clearly illustrating the present disclosure, and are not intended to limit the scope of the present application. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present application.

Claims

1. A continuous oxidation reaction process of chloro-o-xylene, characterized in that: It includes batching, continuous oxidation, tail gas condensation, flash evaporation, acetic acid recovery, tail gas treatment and crude anhydride treatment steps; The ingredients include raw material o-xylene chloride, acetic acid, catalyst and accelerator prepared in proportion; The continuous oxidation is to continuously add the prepared materials into the bubbling reactor, and at the same time introduce compressed oxygen-rich gas or air into the lower part of the reactor, and carry out liquid phase continuous oxidation reaction under the conditions of 1.3-3Mpa pressure, 160-260°C, and 0-8% water content of the reaction system; the flow rate of the materials is measured in kg / min; the flow rate of the air under standard conditions is measured in m 3 / min meter ratio = 1:1.1~1.8, exhaust gas oxygen content is controlled within 7% volume ratio; The bubbling reaction tower (R1) is divided into three sections from top to bottom, the first section is a dehydration section, the second section is a free space section, and the third section is a reaction section; the height of the dehydration section accounts for 20 to 50% of the total height of the bubbling reaction tower (R1), the height of the free space section accounts for 20 to 50% of the total height of the bubbling reaction tower (R1), the height of the reaction section accounts for 20 to 80% of the total height of the bubbling reaction tower (R1), and the total height of the three sections is 100%.

2. The reaction process according to claim 1, characterized in that: The batching step comprises: preparing materials according to the ratio of chloro-o-xylene mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100: 300-500: 0.5-3: 0.5-4, stirring, heating to 50-180° C., maintaining for 0.5-5 hours, and completing the batching.

3. The reaction process according to claim 2, characterized in that: The batching step comprises: preparing materials according to the ratio of chloro-o-xylene mass: acetic acid mass: acetate catalyst mass: bromide promoter mass = 100: 400-500: 0.5-3: 0.5-3, stirring, heating to 80-120° C., maintaining for 1-2 hours, and completing the batching.

4. The reaction process according to any one of claims 1 to 3, characterized in that: The reaction conditions of the continuous oxidation step are: liquid phase continuous oxidation reaction is carried out under a pressure of 1.8 to 2.5 MPa, a reaction temperature of 180 to 250° C., and a water content of 3 to 6%.

5. The reaction process according to claim 4, characterized in that: The flow rate of materials is measured in kg / min; the flow rate of air under standard conditions is measured in m 3 / min meter ratio = 1:1.2~1.

7.

6. The reaction process according to claim 1 or 2, characterized in that: The catalyst is an acetate selected from one or a combination of cobalt acetate, manganese acetate, zirconium acetate, nickel acetate, hafnium acetate, and sodium acetate; the promoter is a bromide selected from one or a combination of tetrabromoethane, hydrogen bromide, and sodium bromide.

7. The reaction process according to claim 1 or 2, characterized in that: The water vapor at the top of the bubbling reactor is condensed, and the uncondensed tail gas is treated by the tail gas alkali absorption tower. Part of the condensate is refluxed to the dehydration section at the top of the reactor, and part is taken out for acetic acid recovery; the acetic acid recovery refers to the condensation and collection of the flashed acetic acid and other vapors to achieve acetic acid recovery.

8. The reaction process according to claim 1 or 2, characterized in that: The chlorophthalic acid generated by the oxidation reaction is dissolved in acetic acid, and the crude anhydride product is obtained by continuous flash evaporation and distillation.

9. The reaction process according to claim 8, characterized in that: The specific conditions of the distillation are: distilling the acetic acid by atmospheric distillation, and then distilling under reduced pressure at 170-230° C. and an absolute pressure of 1-5 kPa.

10. A reaction device used in the continuous oxidation reaction process of o-xylene chloride according to any one of claims 1 to 9, characterized in that: It includes a batching kettle (R2), a feeding pump (P1), a bubbling reaction tower (R1) with a dehydration section (T1), an oxidation condenser (E1), a flash tank (V1), a flash material condenser (E2), an acetic acid storage tank (V2), a tail gas alkali absorption tower (T2), and a circulation pump (P2); The bubbling reaction tower (R1) with a dehydration section has an aspect ratio of 2 to 20, and a condenser is arranged on the top of the tower; the bubbling reaction tower (R1) is divided into three sections from top to bottom, the first section is a dehydration section, the second section is a free space section, and the third section is a reaction section; the height of the dehydration section accounts for 20 to 50% of the total height of the bubbling reaction tower (R1), the height of the free space section accounts for 20 to 50% of the total height of the bubbling reaction tower (R1), the height of the reaction section accounts for 20 to 80% of the total height of the bubbling reaction tower (R1), and the total height of the three sections is 100%.

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