Secondary gas-phase quenching reactor for producing N-methylaniline

Abstract

The utility model discloses a two-stage gas-phase quenching reactor for producing N-methylaniline, which comprises a first-stage reactor, a second-stage reactor and internal parts which are arranged as a whole and are inseparable. Therefore, the alcohol-amine ratio (the molar ratio of methanol to aniline) of the second-stage gas-phase quenching reactor is adjustable, the mixed material is uniformly distributed, and the methanol and the aniline are subjected to high-selectivity reaction. The second-stage reactors are tubular reactors, a three-stage mixing distributor for methanol and materials is arranged at a first-stage inlet, initial distribution of the materials is provided, and uniform mixing of methanol and main materials is adjusted. An annular calandria type quenching methanol distributor is arranged between the secondary reactors, and distribution nozzles are uniformly arranged on the whole circumferential surface. The shell side of the reactor adopts heat transfer oil for heat transfer, and an annular baffle plate is arranged in the reactor. The two-stage reactor is provided with a double-tube-plate structure, so that the influence on the product purity caused by entering a reaction product after a small amount of heat-conducting oil leaks is prevented.

Description

Technical Field

[0001] The utility model relates to the field of a two-stage gas phase rapid cooling reactor, in particular to a two-stage gas phase rapid cooling reactor for producing N-methylaniline. Background Art

[0002] Methylaniline is an important chemical raw material, mainly used for the following purposes: the main intermediate of the new generation of low-toxic herbicides mefenacet, the raw material for the synthesis of low-toxic insecticide buprofezin, the production of pharmaceutical intermediates and cationic dye intermediates, and the high-clean non-metallic gasoline antiknock agent to increase the octane number. The early strong acid liquid phase catalytic reaction process was gradually eliminated due to strong acid corrosion and environmental problems. At present, the production of N-methylaniline mainly adopts the production method of aniline and methanol gas phase reaction process. Aniline and methanol are synthesized by nucleophilic substitution reaction under the action of acidic catalyst. The reaction formula is as follows:

[0003] C6H5-NH2+CH3OH→C6H5-NHCH3+H2O

[0004] The generated N-methylaniline will further react with methanol to replace the H in the NH group to generate N,N-dimethylaniline.

[0005] C6H5-NHCH3+CH3OH→C6H5-N(CH3)2+H2O

[0006] Although the gas phase reaction process solves the problems of corrosion and environmental protection of the liquid phase method, the core catalytic reaction process and reactor design have not been studied in depth, resulting in excessively high reaction temperatures and poor reaction efficiency. Common problems are that in the initial and final stages of the catalyst, the alcohol-amine ratio cannot be adjusted, the reaction temperature is difficult to control, and the reaction effect is poor. This is mainly reflected in the high hot spot temperature of the reactor, which exceeds 250°C and is unevenly distributed, which is prone to temperature runaway and poses a safety hazard. The temperature difference between different reaction tubes is more than 15°C. The high temperature brings about a large increase in reactions that are more sensitive to temperature, such as the secondary substitution side reaction of N-methylaniline and methanol, the alkylation side reaction of the benzene ring, and the methanol dehydration side reaction. On the one hand, it leads to a decrease in product yield and an increase in material consumption; on the other hand, it increases the difficulty of distillation separation and the content of impurity components in the product, resulting in the product being unable to reach the premium product indicators when operated according to the designed process.

[0007] In addition, the heat transfer oil used for heat transfer is a mixture, some of which have a boiling point close to that of the product N-methylaniline and the by-product N,N-dimethylaniline of this process. Once it enters the material system, the distillation system cannot separate it and it will affect the product purity as it enters the product, resulting in the product N-methylaniline failing to reach the technical indicator of 99.5% for premium products.

[0008] In order to solve the above problems, the utility model provides a two-stage gas phase rapid cooling reactor for producing N-methylaniline. Utility Model Content

[0009] In view of the deficiencies of the prior art, the utility model provides a two-stage gas phase quenching reactor for producing N-methylaniline, through which the reaction alcohol amine ratio can be adjusted, the mixed material distribution can be uniform, the reaction temperature can be accurately controlled, the generation of reaction product impurities N,N-dimethylaniline and benzene ring alkylation products can be reduced, the high selectivity of N-methylaniline can be improved, and the material consumption can be reduced. In addition, a double tube sheet structure is provided to prevent heat transfer oil from entering the material system, so as to solve the technical problem that the heat transfer oil has materials with similar boiling points to the product N-methylaniline of this process, which affects the product purity and causes the product N-methylaniline to fail to reach the "99.5% technical index of the superior grade".

[0010] To achieve the above purpose, the utility model is implemented by the following technical scheme: comprising a first-stage reactor and a second-stage reactor, characterized in that welded tube sheets are installed at both symmetrical ends of the first-stage reactor, a plurality of reaction tubes are welded in the welded tube sheets, two expansion tube sheets are fixedly connected in the first-stage reactor, the surfaces of the plurality of reaction tubes are expanded in the expansion tube sheets, the upper and lower ends of the reaction tubes respectively penetrate the sides of the two welded tube sheets, an upper tube box is installed on the upper end face of the first-stage reactor, a material inlet is arranged on the upper end face of the upper tube box, an inlet primary distributor is fixedly connected in the upper tube box, an adjustable methanol distribution plate is fixedly connected in the upper tube box, a material distribution inner plate is fixedly connected in the adjustable methanol distribution plate, a material distribution outer plate is fixedly connected in the adjustable methanol distribution plate, a methanol distributor is installed between the first-stage reactor and the second-stage reactor, a reactor inner wall is arranged in the methanol distributor, and a material distribution inner wall is arranged on the reactor inner wall A reactor outer edge is arranged, an annular main pipe is fixedly connected between the inner wall of the reactor and the outer edge of the reactor, a plurality of distribution branches are fixedly connected to the annular main pipe, a plurality of short pipes are fixedly connected to each of the distribution branches, a plurality of nozzles are provided on each of the short pipes, a quenching methanol inlet is fixedly connected to the side of the methanol distributor, one end of the quenching methanol inlet penetrates the inner wall of the reactor and is connected to the annular main pipe, a heat transfer oil inlet is provided on the surface of the first-stage reactor and the second-stage reactor, a heat transfer oil outlet is provided on the surface of the first-stage reactor and the second-stage reactor, the heat transfer oil inlet and the heat transfer oil outlet are symmetrically arranged in the circumferential direction, a baffle type 1 is fixedly connected in the first-stage reactor, a baffle type 2 is fixedly connected in the first-stage reactor, the baffle type 1 and the baffle type 2 are staggered, and the heat exchange capacity between the heat transfer oil and the reaction tube is enhanced, a lower pipe box is installed on the lower end surface of the second-stage reactor, and a material outlet is provided on the lower end surface of the lower pipe box.

[0011] As the preferred technical solution of the utility model, the number of reactor stages is 2-8, preferably 2-3, and the amount of quenched methanol matches the number of material stages after the reaction temperature is raised, which can be set to 1-7, preferably 1-2.

[0012] As a preferred technical solution of the utility model, the molar ratio of methanol to raw material aniline added to the inlet of the first-stage reactor is 0.001-3, preferably 0.01-0.1.

[0013] As a preferred technical solution of the utility model, the material distribution inner plate has uniformly distributed distribution holes with a diameter of 10-50mm, and the distribution holes are preferably 16-20mm. The material distribution outer plate has uniformly distributed distribution holes with a diameter of 2-20mm, and the distribution holes are preferably 8-12mm.

[0014] As a preferred technical solution of the utility model, the nozzle is located at the bottom of the short tube, and the nozzle spray angle is 60-160 degrees, preferably 90-120 degrees.

[0015] The utility model provides a two-stage gas phase rapid cooling reactor for producing N-methylaniline, which has the following beneficial effects:

[0016] The two-stage reaction of the reactor has a double-tube sheet structure. A heat transfer oil detection and discharge port is set between the double-tube sheets to reduce the possibility of heat transfer oil entering the reaction material system. When a small amount of heat transfer oil leaks, it enters the interlayer of the double-tube sheet and is discharged in time through the discharge port without entering the material system. This can improve the reaction effect of the reactor and increase the purity of the product.

[0017] Heat transfer oil is used on the shell side of the reactor to transfer heat. The heat transfer oil inlet and outlet are symmetrically arranged in the circumferential direction. An annular baffle is arranged in the reactor to enhance the heat exchange capacity between the heat transfer oil and the reaction tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of a two-stage gas phase quenching reactor for producing N-methylaniline proposed by the utility model;

[0019] Figure 2 This is a schematic diagram of the top view of the structure of a methanol distributor of a two-stage gas phase quenching reactor for producing N-methylaniline proposed by the utility model;

[0020] Figure 3 This is a schematic diagram of the top view of the structure of a two-stage gas phase quenching reactor for producing N-methylaniline proposed by the utility model;

[0021] Figure 4 The utility model discloses a structural schematic diagram of a methanol distributor of a two-stage gas phase quenching reactor for producing N-methylaniline.

[0022] In the figure: 1 inlet primary distributor, 2 first stage reactor, 3 methanol distributor, 4 second stage reactor, 5 annular main pipe, 6 distribution branch pipe, 7 short pipe, 8 nozzle, 9 reactor outer edge, 10 reactor inner wall, 11 quenching methanol inlet, 12 welded tube sheet, 13 expansion tube sheet, 14 reaction tube, 15 baffle type 1, 16 baffle type 2, 17 heat transfer oil outlet, 18 heat transfer oil inlet, 19 upper tube box, 20 material inlet, 21 material outlet, 22 lower tube box, 23 adjusting methanol distribution plate, 24 material distribution inner plate, 25 material distribution outer plate. DETAILED DESCRIPTION

[0023] The following is a further detailed description of the implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0024] refer to Figure 1-4 The utility model provides a technical solution: comprising a first-stage reactor 2 and a second-stage reactor 4, characterized in that welded tube sheets 12 are installed at both symmetrical ends of the first-stage reactor 2, multiple reaction tubes 14 are welded in the welded tube sheets 12, two expansion tube sheets 13 are fixedly connected in the first-stage reactor 2, the surfaces of multiple reaction tubes 14 are expanded in the expansion tube sheets 13, and the upper and lower ends of the reaction tubes 14 respectively penetrate the sides of the two welded tube sheets 12, an upper tube box 19 is installed on the upper end surface of the first-stage reactor 2, a material inlet 20 is arranged on the upper end surface of the upper tube box 19, an inlet initial distributor 1 is fixedly connected in the upper tube box 19, an adjustable methanol distribution plate 23 is fixedly connected in the upper tube box 19, a material distribution inner plate 24 is fixedly connected in the adjustable methanol distribution plate 23, a material distribution outer plate 25 is fixedly connected in the adjustable methanol distribution plate 23, and a mixing distributor of methanol and materials is provided to provide initial distribution of materials and adjust the mixing uniformity of methanol and main materials;

[0025] The mixing distributor includes a material distribution inner plate 24, a material distribution outer plate 25, a methanol adjustment distribution plate 23, a circumferential distribution plate, a dead zone baffle and other parts. The main material first enters the elliptical distribution inner plate, and the inner plate is evenly distributed with distribution holes with a diameter of 10-50mm, and the distribution holes are preferably 16-20mm. After the material is initially distributed by the elliptical distribution inner plate, it enters the elliptical distribution outer plate, and the outer plate is evenly distributed with distribution holes with a diameter of 2-20mm, and the distribution holes are preferably 8-12mm. Between the inner and outer plates is the methanol adjustment distribution plate 23, which is a ring tube structure, divided into an outer ring tube and a multi-layer inner ring tube. The outer ring tube is arranged on the periphery of the inner distribution plate, and other multi-layer inner ring tubes are distributed in the area of ​​the inner distribution plate to ensure that the main material and methanol are evenly mixed. After the mixed and evenly distributed materials pass through the outer distribution plate, they enter the circumferential distribution plate. A dead zone baffle and a support plate are arranged at the center of the circumferential distribution plate. The circular diameter of the support plate is 1.0-1.2 times, preferably 1.05-1.08 times, of the diameter of the lower non-pipeline area. The structure of the circumferential distribution plate, the dead zone baffle and the support plate can ensure that the materials evenly enter the reaction tube 14 for reaction;

[0026] A methanol distributor 3 is installed between the first-stage reactor 2 and the second-stage reactor 4. A reactor inner wall 10 is provided in the methanol distributor 3. A reactor outer edge 9 is provided on the reactor inner wall 10. An annular main pipe 5 is fixedly connected between the reactor inner wall 10 and the reactor outer edge 9. The annular main pipe 5 is arranged at a dead zone position close to the reactor cylinder wall and does not occupy an effective flow area. The annular width at the dead zone position is set to 1.1-3 times of the distributor main pipe, preferably 1.3-1.5 times;

[0027] A plurality of distribution branch pipes 6 are fixedly connected to the annular main pipe 5, and a plurality of short pipes 7 are fixedly connected to each distribution branch pipe 6. A plurality of nozzles 8 are provided on each short pipe 7. The nozzles 8 are arranged at the bottom of the short pipes 7, and the spray angle of the nozzles 8 is 60-160 degrees, preferably 90-120 degrees, so as to ensure that the quenched methanol is uniformly sprayed into the main reaction material. In addition to uniform cooling, the properties of the materials entering the second-stage reactor 4 are basically the same, and the temperature difference in the same plane is less than 2°C. A quenched methanol inlet 11 is fixedly connected to the side of the methanol distributor 3, and one end of the quenched methanol inlet 11 passes through the inner wall 10 of the reactor and is connected to the annular main pipe 5;

[0028] A quenching methanol inlet 11 is fixedly connected to the side of the methanol distributor 3, and one end of the quenching methanol inlet 11 penetrates the inner wall 10 of the reactor and is connected to the annular main pipe 5. A heat transfer oil inlet 18 is provided on the surface of the first-stage reactor 2 and the second-stage reactor 4, and a heat transfer oil outlet 17 is provided on the surface of the first-stage reactor 2 and the second-stage reactor 4. 2-12 corresponding inlets and outlets are provided for the heat transfer oil, preferably 2-4, which are symmetrically arranged in the circumferential direction. An annular baffle is provided in the reactor to enhance the heat exchange capacity between the heat transfer oil and the reaction tube 14. A baffle 1 type 15 is fixedly connected in the first-stage reactor 2, and a baffle 2 type 16 is fixedly connected in the first-stage reactor 2. The baffle 1 type 15 and the baffle 2 type 16 are staggered to enhance the heat exchange capacity between the heat transfer oil and the reaction tube 14. A lower pipe box 22 is installed on the lower end surface of the second-stage reactor 4, and a material outlet 21 is provided on the lower end surface of the lower pipe box 22.

[0029] Among them, the reactor level is 2-8, preferably 2-3, the amount of quenched methanol matches the level of the material after the reaction temperature rises, which can be set to 1-7, preferably 1-2, and the process sets a separate vaporized methanol raw material, and methanol is used as a regulating methanol or quenched material to adjust the alcohol amine ratio. First, the separately vaporized methanol is added at the entrance of the first-stage reactor 2, and a mixing distributor for methanol and materials is provided, which can adjust the alcohol amine ratio of the first-stage reaction and improve the reaction performance. . In addition, the separately vaporized methanol can be added at the entrance of the second-stage reactor 4, which has two effects. On the one hand, it can reduce the material temperature of the first-stage reaction and reduce the amount of reaction byproducts with higher temperature sensitivity such as the secondary substitution side reaction of N-methylaniline and methanol, the alkylation side reaction of the benzene ring, and the methanol dehydration side reaction caused by the temperature rise; on the other hand, the alcohol amine ratio of the second-stage reaction can be adjusted at the same time, the conversion rate of aniline and the selectivity of N-methylaniline can be increased, and the problem that the alcohol amine ratio cannot be adjusted in time due to the fixed concentration of methanol and aniline in the batching tank in the existing industrial device is changed. In the present invention, the molar ratio of the vaporized methanol to the raw material aniline is 0.01-5, preferably 0.1-0.5;

[0030] The molar ratio of methanol to raw material aniline added to the inlet of the first-stage reactor 2 is 0.001-3, preferably 0.01-0.1;

[0031] The material distribution inner plate 24 has uniformly distributed distribution holes with a diameter of 10-50 mm, preferably 16-20 mm, and the material distribution outer plate 25 has uniformly distributed distribution holes with a diameter of 2-20 mm, preferably 8-12 mm.

[0032] The nozzle 8 is located at the bottom of the short tube 7, and the nozzle 8 has a spraying angle of 60-160 degrees, preferably 90-120 degrees.

[0033] The working principle of the utility model is that methanol is used as regulating methanol or quenching material to adjust the alcohol-amine ratio. First, methanol that is vaporized and preheated to 190° C. is added to the inlet of the first-stage reactor 2, and a mixing distributor for methanol and materials is provided, which can adjust the alcohol amine ratio of the first-stage reaction and improve the reaction performance. The mixed raw materials enter the upper pipe box 19 through the material inlet 20, and the materials are evenly distributed to the reaction tube 14 through the inlet primary distributor 1. At this time, the materials enter the first-stage reactor 2 of the secondary gas-phase quenching reactor. After the catalyst bed completes the reaction, the shell-side heat transfer oil can control the reaction discharge temperature to about 200° C. Then, gaseous methanol is introduced into the annular main pipe 5 through the quenching methanol inlet 11, and the gaseous methanol is sprayed into the materials through the nozzle 8, which can achieve the cooling of the material mixture to 195° C. and increase the alcohol amine ratio. The materials after quenching and cooling enter the reaction tube 14 in the second-stage reactor 4. After the catalyst bed completes the reaction, the shell-side heat transfer oil controls the reaction discharge temperature to about 200° C., and then enters the next step through the material outlet 21.

[0034] The center of the reactor is a dead zone, such as Figure 3 In the L length region shown, the heat transfer oil here basically does not flow, and it is also impossible to transfer heat to the material in the reaction tube 14 here, and reduce the reaction temperature, resulting in a temperature runaway of the reaction tube 14 in an industrial device, and a significant reduction in the reaction selectivity. The patent sets the central L length region as a blank region, and the ratio of the blank region length L to the reactor diameter d is controlled to be 0.01-0.3, preferably 0.05-0.15.

[0035] The above is only a preferred specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and utility model concept of the utility model within the technical scope disclosed by the utility model, which should be included in the protection scope of the utility model. For those skilled in the art, it is obvious that the utility model is not limited to the details of the above exemplary embodiments, and the utility model can be implemented in other specific forms without departing from the spirit or basic features of the utility model.

Claims

1. A two-stage gas phase quenching reactor for producing N-methylaniline, comprising a first-stage reactor (2) and a second-stage reactor (4), characterized in that: The first-stage reactor (2) is symmetrically provided with welded tube sheets (12) at both ends, a plurality of reaction tubes (14) are welded in the welded tube sheets (12), two expansion tube sheets (13) are fixedly connected in the first-stage reactor (2), the surfaces of the plurality of reaction tubes (14) are expanded in the expansion tube sheets (13), the upper and lower ends of the reaction tubes (14) respectively penetrate the side surfaces of the two welded tube sheets (12), an upper tube box (19) is provided on the upper end surface of the first-stage reactor (2), a material inlet (20) is provided on the upper end surface of the upper tube box (19), and a material inlet (20) is fixed in the upper tube box (19). The first stage reactor (2) and the second stage reactor (4) are connected to an inlet primary distributor (1), the upper pipe box (19) is fixedly connected with an adjustable methanol distribution plate (23), the adjustable methanol distribution plate (23) is fixedly connected with a material distribution inner plate (24), the adjustable methanol distribution plate (23) is fixedly connected with a material distribution outer plate (25), a methanol distributor (3) is installed between the first stage reactor (2) and the second stage reactor (4), a reactor inner wall (10) is arranged in the methanol distributor (3), a reactor outer edge (9) is arranged on the reactor inner wall (10), and the reactor inner wall (10) and the reactor outer edge (9) are connected to each other. A ring main pipe (5) is fixedly connected between the first stage reactor (2) and the second stage reactor (4), a plurality of distribution branch pipes (6) are fixedly connected to the ring main pipe (5), a plurality of short pipes (7) are fixedly connected to each of the distribution branch pipes (6), a plurality of nozzles (8) are provided on each of the short pipes (7), a quenching methanol inlet (11) is fixedly connected to the side of the methanol distributor (3), one end of the quenching methanol inlet (11) passes through the inner wall (10) of the reactor and is connected to the ring main pipe (5), a heat transfer oil inlet (18) is provided on the surface of the first stage reactor (2) and the second stage reactor (4), and the first stage reactor (2) and the second stage reactor (4) are connected to the first stage reactor (2) and the second stage reactor (4) respectively. The surface of the secondary reactor (4) is provided with a heat transfer oil outlet (17), and the heat transfer oil inlet (18) and the heat transfer oil outlet (17) are symmetrically arranged in the circumferential direction. A baffle plate 1 (15) is fixedly connected inside the first-stage reactor (2), and a baffle plate 2 (16) is fixedly connected inside the first-stage reactor (2). The baffle plates 1 (15) and the baffle plates 2 (16) are arranged alternately to enhance the heat exchange capacity between the heat transfer oil and the reaction tube (14). A lower tube box (22) is installed on the lower end surface of the second-stage reactor (4), and a material outlet (21) is arranged on the lower end surface of the lower tube box (22).

2. A two-stage gas phase quenching reactor for producing N-methylaniline according to claim 1, characterized in that: The number of reactor stages is 2-8, and the amount of quenched methanol matches the number of material stages after the reaction temperature is raised, which can be set to 1-7.

3. A two-stage gas phase quenching reactor for producing N-methylaniline according to claim 1, characterized in that: The molar ratio of methanol to raw material aniline introduced into the inlet of the first-stage reactor (2) is 0.001-3.

4. A two-stage gas phase quenching reactor for producing N-methylaniline according to claim 1, characterized in that: The material distribution inner plate (24) is evenly distributed with distribution holes having a diameter of 10-50 mm, and the material distribution outer plate (25) is evenly distributed with distribution holes having a diameter of 2-20 mm.

5. A two-stage gas phase quenching reactor for producing N-methylaniline according to claim 1, characterized in that: The nozzle (8) is located at the bottom of the short tube (7), and the nozzle (8) has a spraying angle of 60-160 degrees.

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