A gas-solid phase catalytic reaction distillation separation integrated method

Abstract

The invention discloses an integrated method for rectification and separation of gas-solid catalytic reaction, wherein the high-temperature mixed gas of phthalonitrile discharged from the gas-solid continuous amination reaction of phthalic acid directly enters a separation system without cooling, and the separation system comprises three packing towers: the first packing tower is used to separate most of the organic components in the reaction mixed gas, the crude product separated from the bottom of the first packing tower is transferred to the third packing tower for rectification and separation, and the gas discharged from the top of the first packing tower enters the second packing tower; the second packing tower is used to separate the moisture and organic components in the gas, and the gas after separation treatment is returned to the gas-solid continuous amination reaction system of phthalic acid; the third packing tower is used to rectify and separate the crude product separated from the first packing tower, and obtain low-boiling substances, phthalonitrile products and high-boiling substances respectively. The equipment structure of the invention is relatively simple, the process is simple, the industry is easy to realize, the temperature is effectively utilized, the capture rate is high, the yield is high, and the product purity is high.

Description

Technical Field

[0001] The invention relates to the technical field of separation and purification, and in particular to an integrated method for gas-solid phase catalytic reaction, rectification and separation. Background Art

[0002] In industrial production, phthalic acid is subjected to an amination reaction to obtain phthalonitrile. The resulting reaction mixture system needs to be purified to remove a large amount of water vapor, ammonia, nitrogen, organic components, etc. mixed therein to obtain a high-purity phthalonitrile product.

[0003] Since the reaction mixture system has a high temperature and complex components, the purification process and equipment used are relatively complex and difficult to control, and the purity of the product needs to be improved.

[0004] For example, Chinese patent application 2021115198212 discloses a reactor and a continuous distillation reaction method and system, which includes the following steps: an ammonia synthesis reaction step; a transportation step; an ammonia treatment step; and a distillation step. In the transportation step, the method requires heat exchange treatment of the high-temperature mixed product, and the temperature of the high-temperature mixed product is adjusted to 200-240°C before passing into a stripping tower.

[0005] Chinese patent application 2023117244587 discloses a method for rapid cooling and absorption of aromatic hydrocarbon ammoxidation reaction gas, wherein the aromatic hydrocarbon ammoxidation reaction gas enters a capture system for gas-liquid contact, the obtained capture product enters a tower internals system and is countercurrently contacted with a fresh solvent, the obtained tail gas is subjected to gas treatment, and the obtained absorption liquid is divided into three parts, the first part is returned to the tower internals system, the second part is returned to the capture system as the capture liquid phase of the gas-liquid contact, and the third part is recovered and refined by solvent to obtain the target product, wherein the capture system includes a sandy A leaky collecting tube; a gas phase inlet is arranged on the end face of the inlet end of the collecting tube, and the aromatic ammoxidation reaction gas enters the collecting system from the gas phase inlet; a first liquid phase feed inlet and a second liquid phase feed inlet are arranged on the side of the inlet end of the collecting tube, and the collected liquid phase is divided into a first collected liquid phase and a second collected liquid phase, the first collected liquid phase enters the collecting system from the first liquid phase feed inlet in a spray state, and the second collected liquid phase enters the collecting system from the second liquid phase feed inlet in a tangential feeding state; the tower internals system is divided into a quenching section, an absorption section, and a purification section from bottom to top. In the report, the collecting system and the tower internals system are complex in structure and must be precisely controlled, otherwise blockage is likely to occur.

[0006] As mentioned above, for the gas-solid phase catalytic reaction distillation separation integrated technology for phthalic acid amination, the following requirements still exist: relatively simple equipment structure, simple process, easy industrial implementation, effective temperature utilization, high capture rate, high yield, high product purity, etc. Summary of the invention

[0007] The inventors of the present invention have conducted intensive research and have achieved the goal of allowing the high-temperature mixed gas of phthalonitrile discharged from the solid-phase continuous amination reaction of phthalic acid gas to directly enter a separation system without cooling. The separation system includes three packed towers. In the separation system, phthalonitrile, benzonitrile, methylbenzonitrile, cyanobenzamide, water and other substances are effectively separated from the gas. The separated mixed material is distilled to obtain a high-quality phthalonitrile product. The effectively separated gas is returned to the solid-phase continuous amination reaction system of phthalic acid gas for application, thereby completing the present invention.

[0008] The object of the present invention is to provide an integrated method for gas-solid phase catalytic reaction distillation separation, in which the high-temperature mixed gas of phthalonitrile discharged from the gas-solid phase continuous amination reaction of phthalic acid is directly fed into a separation system without cooling.

[0009] The separation system consists of three packed columns:

[0010] The first packed tower is used to separate most of the organic components in the reaction mixed gas. The crude product separated at the bottom of the first packed tower is transferred to the third packed tower for distillation separation. The exhaust gas from the top of the first packed tower enters the second packed tower.

[0011] The second packed tower is used to separate the moisture and organic components in the gas. The separated gas is returned to the solid phase continuous amination reaction system of phthalic acid gas.

[0012] The third packed tower is used to distill and separate the crude product separated by the first packed tower to obtain low-boiling products, phthalonitrile products and high-boiling products respectively.

[0013] In a preferred embodiment, the low boiling products obtained in the third packed tower can be directly used as by-products, or part of the low boiling products can be recycled to the first packed tower as eluent to enhance product separation.

[0014] In the present invention, the gas-solid phase continuous amination reaction of phthalic acid refers to the continuous amination reaction of isophthalic acid, terephthalic acid, phthalic acid or phthalic anhydride with an ammonia stream in the presence of a solid catalyst to obtain isophthalonitrile, terephthalonitrile or phthalonitrile.

[0015] In industrial production, the high-temperature mixed gas discharged from the reaction bed of the solid-phase continuous amination reaction of phthalic acid gas has a relatively high temperature, usually 230-350°C, more typically 280-310°C. In addition to the target product phthalonitrile, it also contains a large amount of organic components, such as: unreacted phthalic acid or phthalic anhydride, such as phthalic acid, phthalic anhydride, isophthalic acid, or terephthalic acid; low-boiling substances, such as m-methylbenzonitrile, p-methylbenzonitrile and benzonitrile; and inorganic components, such as ammonia, water vapor, and nitrogen.

[0016] Preferably, in the high-temperature mixed gas, the weight of the organic phase accounts for 10-30% of the total weight of the mixed gas.

[0017] The pressure of the high-temperature mixed gas discharged from the reaction bed is usually 0.12-0.18 MPa, especially about 0.14 MPa.

[0018] In a preferred embodiment, the intake rate of the high-temperature mixed gas is 400-900 Nm³ / h, more preferably 500-800 Nm³ / h.

[0019] In the present invention, the high-temperature mixed gas discharged from the reaction bed of the solid-phase continuous amination reaction of phthalic acid gas is directly fed to the first packed tower of the separation system without any cooling or heat exchange treatment, and the gas is introduced from the upper part of the bottom of the first packed tower. The eluent is sprayed on the upper part of the first packed tower, and the mixed gas is fully separated in the first packed tower. Most of the organic components and the eluent are enriched at the bottom of the tower to form a crude product, which then enters the third packed tower for distillation, and the inorganic components and a small part of the organic components enter the second packed tower at the top of the tower.

[0020] In the first packed tower, at least one of structured packing, wire mesh corrugated packing and plate wave packing is used as packing, preferably wire mesh corrugated packing. Studies have found that when such packing is used, the organic component and the inorganic component in the mixed gas can be effectively separated.

[0021] In a preferred embodiment, the packing height in the first packed tower is 6 m to 10 m, more preferably 8 m.

[0022] In the first packed tower, benzonitrile, m-methylbenzonitrile or p-methylbenzonitrile is used as the eluent to avoid increasing the impurities in the system.

[0023] In a preferred embodiment, the flow rate of the eluent added to the first packed tower is 50-450 kg / h, preferably 180-420 kg / h; the temperature of the eluent is 30-60°C, preferably 40-50°C.

[0024] In a more preferred embodiment, the mass ratio of the eluent in the first packed tower to the mass ratio of the organic components in the high-temperature mixed gas is (0.5-3):1, more preferably about 1:1.

[0025] As the spray liquid of the first packed tower, part of it comes from the low boiling point organic matter recycled from the second packed tower, part of it comes from the low boiling point organic matter recycled from the third packed tower, and the rest comes from the fresh spray liquid.

[0026] In a preferred embodiment, the bottom liquid phase temperature of the first packed tower is 130-220°C, preferably 130-210°C, the top gas phase temperature is 60-110°C, preferably 85-100°C, and the top pressure is 0.12-0.16 MPa, more preferably 0.13-0.14 MPa.

[0027] After the mixed gas is fully separated by the first packed tower, the top gas mainly containing inorganic components and a small part of organic components (mainly benzonitrile, m-methylbenzonitrile or p-methylbenzonitrile used as the spray liquid of the first packed tower) enters the middle section of the middle packing of the second packed tower, and the low-boiling point organic component enters the bottom of the tower as a distillation liquid to form a bottom liquid. After the bottom liquid is separated by heat exchange, part of it is cooled and recycled to the first packed tower as a spray liquid, and part of it is heated and circulated to the lower part of the second packed tower as a heat source. Water vapor, ammonia and nitrogen are discharged from the top of the tower, and condensed water and ammonia and nitrogen mixed gas are obtained by cooling and separation. The water content in the gas is very low and can be circulated to the solid-phase continuous amination reaction system of phthalic acid gas for reuse.

[0028] In the second packed tower, at least one of structured packing, wire mesh corrugated packing and plate wave packing is used as the packing, and wire mesh corrugated packing is preferred.

[0029] In a preferred embodiment, the packing height in the second packed tower is 5 m to 7 m, more preferably 6 m.

[0030] In the second packed tower, water produced in the phthalic acid gas-solid phase continuous amination reaction system is preferably used as the eluent.

[0031] In a preferred embodiment, the bottom liquid phase temperature of the second packed tower is 180-215° C., the top gas phase temperature is 10-40° C., preferably 30-40° C., and the top pressure is 0.12-0.16 MPa, preferably 0.13 MPa.

[0032] In the third packed tower, at least one of structured packing, wire mesh corrugated packing and plate wave packing is used as the packing, and wire mesh corrugated packing is preferred.

[0033] In a preferred embodiment, the packing height in the third packed tower is 10 m-14 m, more preferably 12 m.

[0034] In a preferred embodiment, the inner diameter of the third packed tower is smaller than that of the first packed tower and the second packed tower, and the inner diameter of the first packed tower is equal to that of the second packed tower.

[0035] In the present invention, the third packed tower is a negative pressure distillation tower, and the crude organic component separated from the bottom of the first packed tower is transferred to the third packed tower by a decompression system, and distilled and separated in the third packed tower to obtain low-boiling products, phthalonitrile products and high-boiling products.

[0036] The low boiling point substances such as benzonitrile, m-methylbenzonitrile or p-methylbenzonitrile can be directly collected as by-products, or part of the low boiling point substances can be cooled and then recycled to the first packed tower as spray liquid to enhance product separation.

[0037] The temperature of the recycled low boiling point is 30-60°C, preferably 40-50°C, more preferably about 45°C.

[0038] The high boiling substances such as amides such as cyanobenzamide are enriched at the bottom of the third packed tower to form a distillate, which is discharged and heat exchanged, part of which is cooled and recovered, and part of which is heated and circulated to the lower part of the third packed tower as a heat source.

[0039] In a preferred embodiment, the bottom liquid phase temperature of the third packed tower is 255-285°C, preferably 260-265°C, the top gas phase temperature is 80-130°C, preferably 115-125°C, and the top pressure is 0.005-0.030MPa, preferably 0.015-0.025MPa.

[0040] The present invention has the following beneficial effects:

[0041] (1) The high-temperature mixed gas of phthalonitrile discharged from the solid-phase continuous amination reaction of phthalic acid gas enters the separation system directly without cooling, thus avoiding side reactions such as hydrolysis caused by the cooling process, avoiding heat loss, and maximizing heat utilization;

[0042] (2) The solid-phase continuous amination reaction of phthalic acid gas and the product separation are completed continuously and in an integrated manner, and the process is simple;

[0043] (3) The three packed towers of the separation system have simple structure and high separation efficiency;

[0044] (4) The water content of the gas separated from the top of the second packed tower is very low, less than 4%, and is suitable for recycling to the solid-phase continuous amination reaction system of phthalic acid gas to reduce emissions;

[0045] (5) The low-boiling substances separated from the third packed tower can be recycled as the eluent of the first packed tower, which not only enhances product separation but also reduces the amount of fresh spray liquid used;

[0046] (6) The method of the present invention has a high capture rate and a high product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of a separation system showing a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0049] Example 1

[0050] Phthalic anhydride undergoes a gas-solid phase continuous amination reaction, the mixed gas temperature at the reactor bed outlet is 280±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 500±10Nm³ / h, and the weight of the organic phase in the mixed gas is 100kg / h.

[0051] Mixed gas enters Figure 1 In the separation system shown in the figure, the diameter of the first packed tower of the separation system is 0.6m, the packing in the tower is mesh corrugated regular packing, the packing height is 8m, the spray liquid benzonitrile is added at a flow rate of 300kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature of the bottom of the first packed tower is controlled at 130±5°C, the gas phase temperature at the top of the first packed tower is controlled at 89±2°C, the top pressure is 0.13MPa, the top component enters the second packed tower, and 279kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third packed tower for vacuum distillation.

[0052] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated structured packing, the packing height is 6m, the liquid phase temperature of the tower bottom is 180±5℃, the gas phase temperature of the tower top is 30±2℃, and the pressure of the tower top is 0.12MPa. The water content of the gas separated and treated by the second packed tower is less than 3.5%, which is directly recycled to the phthalic anhydride gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 121kg / h of benzonitrile, which is recycled to the first packed tower as a spray liquid.

[0053] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated structured packing, the packing height is 12m, the bottom liquid temperature is 263±5℃, the top gas temperature is 117±2℃, and the top pressure is 0.025MPa. After vacuum distillation in the third packed tower, 30kg / h of low-boiling benzonitrile is obtained, which is recycled to the first packed tower as a spray liquid, and the phthalonitrile product is 90kg / h, the phthalonitrile content is 99.5%, and the capture rate is 98%.

[0054] Production proceeded smoothly for 30 days without any blockage in the system.

[0055] Example 2

[0056] Phthalic anhydride undergoes a gas-solid phase continuous amination reaction, the mixed gas temperature at the reactor bed outlet is 280±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 500±10Nm³ / h, and the weight of the organic phase in the mixed gas is 100kg / h.

[0057] Mixed gas enters Figure 1In the separation system shown in FIG. 1 , the diameter of the first packed tower of the separation system is 0.6 m, the packing in the tower is a mesh corrugated regular packing, the packing height is 8 m, the spray liquid benzonitrile is added at a flow rate of 50 kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature at the bottom of the first packed tower is 150±5°C, the gas phase temperature at the top of the first packed tower is 99±2°C, the pressure at the top of the tower is 0.14 MPa, the top component enters the second packed tower, and 116 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0058] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated structured packing, the packing height is 6m, the liquid phase temperature of the tower bottom is 182±5℃, the gas phase temperature of the tower top is 30±2℃, and the pressure of the tower top is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 3.5%, which is directly recycled to the phthalic anhydride gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 31kg / h of benzonitrile and is recycled to the first packed tower as a spray liquid.

[0059] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated structured packing, the packing height is 12m, the bottom liquid temperature is 268±5℃, the top gas temperature is 121±2℃, and the top pressure is 0.025MPa. After vacuum distillation in the third packed tower, 5kg / h of low-boiling benzonitrile is obtained, which is recycled to the first packed tower as a spray liquid, and 85kg / h of phthalonitrile product, 99.6% phthalonitrile content, and 92% capture rate.

[0060] Production proceeded smoothly for 5 days without any blockage in the system.

[0061] Example 3

[0062] Isophthalic acid undergoes a gas-solid phase continuous amination reaction, the mixed gas temperature at the reactor bed outlet is 310±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 800±10Nm³ / h, and the weight of the organic phase in the mixed gas is 190kg / h.

[0063] Mixed gas enters Figure 1 In the separation system shown in FIG. 1 , the diameter of the first packed tower of the separation system is 0.6 m, the packing in the tower is a mesh corrugated regular packing, the packing height is 8 m, the spray liquid benzonitrile is added at a flow rate of 190 kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature at the bottom of the first packed tower is 160±5°C, the gas phase temperature at the top of the first packed tower is 96±2°C, the pressure at the top of the tower is 0.14 MPa, the top component enters the second packed tower, and 262 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0064] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated regular packing, the packing height is 6m, the liquid phase temperature of the tower bottom is 185±5℃, the gas phase temperature of the tower top is 35±2℃, and the pressure of the tower top is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 4.0%, which is directly recycled to the isophthalic acid gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 45kg / h of benzonitrile and is recycled to the first packed tower as a spray liquid.

[0065] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated regular packing, the packing height is 12m, the bottom liquid temperature is 265±5℃, the top gas temperature is 120±2℃, and the top pressure is 0.020MPa. After vacuum distillation in the third packed tower, 20kg / h of low-boiling benzonitrile is obtained, which is recycled to the first packed tower as a spray liquid to obtain 173kg / h of isophthalonitrile product, with an isophthalonitrile content of 99.6% and a capture rate of 95%.

[0066] Production proceeded smoothly for 30 days without any blockage in the system.

[0067] Example 4

[0068] Isophthalic acid undergoes a gas-solid phase continuous amination reaction, the mixed gas temperature at the reactor bed outlet is 310±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 800±10Nm³ / h, and the weight of the organic phase in the mixed gas is 190kg / h.

[0069] Mixed gas enters Figure 1 The separation system shown in the figure has a tower diameter of 0.6 m, a tower filler of mesh corrugated regular packing, a packing height of 8 m, a spray liquid m-methyl benzonitrile added at a flow rate of 95 kg / h in the first packed tower, and a temperature of 45±5°C. After the system runs stably, the bottom liquid temperature of the first packed tower is 201±5°C, the top gas temperature of the first packed tower is 98±2°C, the top pressure is 0.14 MPa, the top component enters the second packed tower, and 257 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0070] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated regular packing, the packing height is 6m, the liquid phase temperature of the tower bottom is 213±5℃, the gas phase temperature of the tower top is 35±2℃, and the pressure of the tower top is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 4.0%, which is directly recycled to the isophthalic acid gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 25kg / h of m-methyl benzonitrile and is recycled to the first packed tower as a spray liquid.

[0071] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated regular packing, the packing height is 12m, the bottom liquid temperature is 265±5℃, the top gas temperature is 120±2℃, and the top pressure is 0.018MPa. After vacuum distillation in the third packed tower, 19kg / h of low-boiling meta-methyl benzonitrile is obtained, which is recycled to the first packed tower as a spray liquid to obtain 170kg / h of isophthalonitrile product, with an isophthalonitrile content of 99.5% and a capture rate of 93%.

[0072] Production proceeded smoothly for 10 days without any blockage in the system.

[0073] Example 5

[0074] Isophthalic acid undergoes a gas-solid phase continuous amination reaction, the mixed gas temperature at the reactor bed outlet is 310±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 800±10Nm³ / h, and the weight of the organic phase in the mixed gas is 190kg / h.

[0075] Mixed gas enters Figure 1 In the separation system shown in FIG. 1 , the diameter of the first packed tower of the separation system is 0.6 m, the packing in the tower is mesh corrugated regular packing, the packing height is 8 m, the spray liquid benzonitrile is added at a flow rate of 420 kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature at the bottom of the first packed tower is 160±5°C, the gas phase temperature at the top of the first packed tower is 96±2°C, the pressure at the top of the tower is 0.14 MPa, the top component enters the second packed tower, and 390 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0076] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated regular packing, the packing height is 6m, the liquid phase temperature of the tower bottom is 185±5℃, the gas phase temperature of the tower top is 35±2℃, and the pressure of the tower top is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 4.0%, which is directly recycled to the isophthalic acid gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 220kg / h of benzonitrile, which is recycled to the first packed tower as a spray liquid.

[0077] The diameter of the third packed tower is 0.4m, the packing in the tower is plate wave packing, the packing height is 12m, the bottom liquid temperature is 262±5℃, the top gas temperature is 123±2℃, and the top pressure is 0.019MPa. After vacuum distillation in the third packed tower, 40kg / h of low-boiling benzonitrile and 168kg / h of isophthalonitrile product are obtained, the isophthalonitrile content is 99.7%, and the capture rate is 92%.

[0078] Production proceeded smoothly for 10 days without any blockage in the system.

[0079] Example 6

[0080] Terephthalic acid undergoes gas-solid phase continuous ammoniation reaction, the mixed gas temperature at the reactor bed outlet is 290±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 800±10Nm³ / h, and the weight of the organic phase in the mixed gas is 210kg / h.

[0081] Mixed gas enters Figure 1 In the separation system shown in FIG. 1 , the diameter of the first packed tower of the separation system is 0.6 m, the packing in the tower is a mesh corrugated regular packing, the packing height is 8 m, the spray liquid benzonitrile is added at a flow rate of 420 kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature at the bottom of the first packed tower is 183±5°C, the gas phase temperature at the top of the first packed tower is 95±2°C, the pressure at the top of the tower is 0.14 MPa, the top component enters the second packed tower, and 423 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0082] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated structured packing, the packing height is 6m, the bottom liquid temperature is 184±5℃, the top gas temperature is 35±2℃, and the top pressure is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 4.0%, which is directly recycled to the terephthalic acid gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 207kg / h of benzonitrile, which is recycled to the first packed tower as spray liquid.

[0083] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated structured packing, the packing height is 12m, the bottom liquid temperature is 260±5℃, the top gas temperature is 120±2℃, and the top pressure is 0.016MPa. After vacuum distillation in the third packed tower, 41kg / h of low-boiling benzonitrile and 198.5kg / h of terephthalonitrile product are obtained, with a terephthalonitrile content of 99.7% and a capture rate of 97%.

[0084] Production proceeded smoothly for 30 days without any blockage in the system.

[0085] Example 7

[0086] Terephthalic acid undergoes gas-solid phase continuous ammoniation reaction, the mixed gas temperature at the reactor bed outlet is 290±5℃, the pressure is 0.14MPa, the mixed gas flow rate is 800±10Nm³ / h, and the weight of the organic phase in the gas is 210kg / h.

[0087] Mixed gas enters Figure 1In the separation system shown in FIG. 1 , the diameter of the first packed tower of the separation system is 0.6 m, the packing in the tower is a mesh corrugated regular packing, the packing height is 8 m, the spray liquid p-methylbenzonitrile is added at a flow rate of 210 kg / h in the first packed tower, and the temperature is 45±5°C. After the system runs stably, the liquid phase temperature at the bottom of the first packed tower is 218±5°C, the gas phase temperature at the top of the first packed tower is 95±2°C, the pressure at the top of the tower is 0.14 MPa, the top component enters the second packed tower, and 282 kg / h of crude product is obtained at the bottom of the tower. The crude product enters the third tower for vacuum distillation.

[0088] The diameter of the second packed tower is 0.6m, the packing in the tower is a corrugated regular packing, the packing height is 6m, the bottom liquid temperature is 215±5℃, the top gas temperature is 33±2℃, and the top pressure is 0.13MPa. The water content of the gas separated and treated by the second packed tower is less than 4.0%, and the gas is directly recycled to the terephthalic acid gas-solid phase continuous amination reaction system for recycling. The second packed tower recovers 138kg / h of p-methylbenzonitrile and is recycled to the first packed tower as a spray liquid.

[0089] The diameter of the third packed tower is 0.4m, the packing in the tower is a corrugated regular packing, the packing height is 12m, the bottom liquid temperature is 261±5℃, the top gas temperature is 122±2℃, and the top pressure is 0.016MPa. After vacuum distillation in the third packed tower, 20kg / h of low-boiling methyl benzonitrile is obtained, which is recycled to the first packed tower as a spray liquid to obtain 196.5kg / h of terephthalonitrile product, with a terephthalonitrile content of 99.6% and a capture rate of 96%.

[0090] Production proceeded smoothly for 30 days without any blockage in the system.

[0091] The present invention is described in detail above in conjunction with specific embodiments and / or exemplary examples and drawings, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A gas-solid phase catalytic reaction and distillation separation integrated method, characterized in that: The high-temperature mixed gas of phthalonitrile discharged from the solid-phase continuous amination reaction of phthalic acid gas is directly fed into the separation system without cooling. The separation system consists of three packed columns: The first packed tower is used to separate most of the organic components in the reaction mixed gas. The crude product separated at the bottom of the first packed tower is transferred to the third packed tower for distillation separation. The exhaust gas from the top of the first packed tower enters the second packed tower. The second packed tower is used to separate the water and organic components in the gas. The separated gas is returned to the solid phase continuous amination reaction system of phthalic acid gas. The low boiling point organic components enter the tower kettle to form distilled liquid. The distilled liquid is continuously discharged, cooled by the heat exchange part and reused in the first packed tower as spray liquid. The third packed tower is used to distill and separate the crude product separated from the first packed tower to obtain low-boiling products, phthalonitrile products and high-boiling products. The low-boiling products are partially recycled to the first packed tower as eluent. The temperature of the high-temperature mixed gas is 230-350°C. The inner diameter of the third packed tower is smaller than that of the first packed tower and the second packed tower, and the inner diameter of the first packed tower is equal to the inner diameter of the second packed tower. The high-temperature mixed gas discharged from the reaction bed in the solid-phase continuous amination reaction of phthalic acid gas is directly fed into the first packed tower of the separation system, and the gas is introduced from the upper part of the tower kettle of the first packed tower. The eluent is sprayed on the upper part of the first packed tower. The mixed gas is separated in the first packed tower, and most of the organic components and the eluent are enriched at the bottom of the tower to form a crude product, which then enters the third packed tower for rectification, and the inorganic components and a small part of the organic components enter the second packed tower at the top of the tower; The addition flow rate of the eluent in the first packed tower is 50-450 kg / h; the temperature of the eluent is 30-60°C; the bottom liquid temperature of the first packed tower is 130-220°C, the top gas temperature is 60-110°C, and the top pressure is 0.12-0.16MPa. The gas at the top of the first packed tower enters the middle section of the packing in the middle of the second packed tower, and the distilled liquid in the second packed tower is partially heated and circulated to the lower part of the tower to provide a heat source, and water vapor, ammonia and nitrogen are discharged from the top of the tower. After cooling, water is separated from ammonia and nitrogen, and the separated gas can be circulated to the solid-phase continuous amination reaction system of phthalic acid gas for reuse; The second packed tower has a bottom liquid temperature of 180-215°C, a top gas temperature of 10-40°C, and a top pressure of 0.12-0.16MPa. The third packed tower is a negative pressure distillation tower, and the crude organic component separated from the bottom of the first packed tower is transferred to the third packed tower by a decompression system, and distilled and separated in the third packed tower to obtain low-boiling substances, phthalonitrile products and high-boiling substances; The bottom liquid phase temperature of the third packed tower is 255-285°C, the top gas phase temperature is 80-130°C, and the top pressure is 0.005-0.030MPa.

2. The method according to claim 1, characterized in that The mass ratio of the eluent in the first packing tower to the mass ratio of the organic components in the high-temperature mixed gas is (0.5-3):

1.

3. The method according to claim 1, characterized in that The pressure of the high-temperature mixed gas is 0.12-0.18MPa, and the intake volume of the high-temperature mixed gas is 400-900 Nm³ / h.

4. The method according to claim 1, characterized in that In the first packed tower, the second packed tower and the third packed tower, at least one of structured packing, wire mesh corrugated packing and plate wave packing is used as the packing respectively and independently.

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