Radial moving bed reactor and process for the production of caprolactam

Abstract

The present application relates to a moving bed reactor, in particular to a radial moving bed reactor and a preparation method of caprolactam. The reactor comprises a reactor shell, and a center pipe with through holes, a catalyst bed and a material distributor arranged from inside to outside in the reactor shell; wherein a plurality of heat-removing partitions vertically connected with the pipe wall of the center pipe are arranged along the circumferential direction of the center pipe; an upper ineffective reaction zone, an effective reaction zone and a lower ineffective reaction zone are arranged from top to bottom in the catalyst bed; wherein the part of the center pipe in the upper ineffective reaction zone and the lower ineffective reaction zone is without through holes, and the upper part of the heat-removing partition is arranged as an ineffective part in the upper ineffective reaction zone. The space utilization of the moving bed reactor of the present application is improved, the problem of uneven axial distribution of gas flow is effectively avoided, and the reaction temperature is controlled, which is used in the process of producing caprolactam by gas phase Beckmann rearrangement of cyclohexanone oxime, can reduce the amount of carrier gas, improve the reaction efficiency, conversion rate and selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radial moving bed reactor, in particular to a radial moving bed reactor and a preparation method of caprolactam. BACKGROUND

[0002] The moving bed reactor is a reactor form for realizing fluid-solid phase contact, and the solid material is gradually moved downward to the bottom for discharge in the reactor by gravity, and the fluid is in contact with the solid material to react. The moving bed reactor has the characteristics of both fixed bed reactor and fluidized bed reactor, and is particularly suitable for reactions with medium catalyst deactivation rate and the need for cyclic regeneration. The operating performance and catalyst requirements of the moving bed reactor are between those of the fixed bed and the fluidized bed. Compared with the fixed bed, the moving bed reactor has the characteristics of small pressure drop and low investment; compared with the fluidized bed, the moving bed reactor has the advantages of small back mixing ratio, low degree of catalyst pulverization, uniform reaction product distribution, and flexible solid residence time. Therefore, the moving bed reactor has been widely used in the fields of catalytic reforming, gasoline desulfurization, heavy oil lightening, methanol conversion, waste treatment and recovery, etc.

[0003] The existing moving bed reactor can be divided into concurrent moving bed, countercurrent moving bed and cross-flow moving bed according to the relative flow mode of solid material and gas phase material. Studies have shown that the cross-flow moving bed can obtain a larger aeration cross section, and the channels of the two phases can be separated, so it has been more widely used in industrial practice. In the gas-solid cross-flow moving bed, in order to make the raw gas phase uniformly distributed in the catalyst bed, a large flow rate is usually used, but a large flow rate will lead to uneven axial distribution of gas flow in the reactor, and even cause short circuiting.

[0004] Moreover, the cross-flow moving bed has been criticized for its limited internal heat removal. To solve this problem, most moving bed reactors use a multi-stage series method with inter-stage heat exchange (for example, CN102875469A) or an external reactor heat exchange method (for example, CN105218304A) to remove heat, but the above two methods will result in low space utilization of the reactor, large equipment investment and complex operation.

[0005] In addition, in the moving bed reactor, due to the different deactivation times of different catalysts, the service life of the catalyst is long, up to several tens or hundreds of hours, and short, only a few hours, so the replacement frequency of the catalyst is quite different; the former can use an intermittent moving bed reactor, and the latter can use a continuous moving bed reactor. SUMMARY

[0006] The present application aims to overcome the uneven axial distribution of catalyst in the moving bed reactor in the prior art, which affects the reaction effect, and solve the problem of rapid temperature rise caused by a large amount of reaction heat release in the reaction process, which affects the reaction effect, and provide a radial moving bed reactor and a preparation method of caprolactam.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a radial moving bed reactor, wherein the reactor comprises a reactor shell, and a central pipe with a through hole, a catalyst bed and a material distributor arranged from inside to outside in the reactor shell; wherein a plurality of heat-removing partitions vertically connected with the pipe wall of the central pipe are arranged at intervals along the circumferential direction of the central pipe; an upper ineffective reaction zone, an effective reaction zone and a lower ineffective reaction zone are arranged from top to bottom in the catalyst bed; wherein the central pipe has no through hole in the part of the upper ineffective reaction zone and the lower ineffective reaction zone, and the upper part of the heat-removing partition is arranged as an ineffective part in the upper ineffective reaction zone.

[0008] The second aspect of the present application provides a preparation method of caprolactam, which comprises: introducing raw materials and catalyst into a reactor for reaction respectively; the raw materials comprise cyclohexanone oxime, carrier gas and solvent; wherein the reactor is the moving bed reactor of the first aspect.

[0009] Through the above technical solution, the radial moving bed reactor provided by the present application can achieve the following effects: on the one hand, a plurality of heat-removing partitions are arranged in the catalyst bed, which can obtain a larger aeration cross section when adopting cross flow form, and facilitate the full contact between the catalyst and the reaction raw materials; and the reactor can be operated in a lower pressure drop mode by adopting cross flow mode; at the same time, the moving mode matches the service life of the catalyst, which can ensure the long-period operation of the reaction system; on the other hand, the heat-removing partition can also complete the heat exchange process during the reaction process, realize the stability of the temperature gradient in the bed, realize the heat exchange in the reactor, effectively stabilize the reaction temperature, solve the heat transfer problem commonly existing in the moving bed reactor, and improve the reaction effect; thirdly, the catalyst discharge port is arranged to include an inner ring group and an outer ring group, and is arranged in a limited relationship, which can improve the flow effect of the catalyst in the catalyst bed; the upper ineffective reaction zone is arranged to make the influence of the bed movement process on the reaction process small.

[0010] Moreover, the space utilization rate of the whole reactor is improved, the problem of uneven axial distribution of gas flow is effectively avoided, and the production load requirement can be met; and the present application is especially suitable for the process of producing caprolactam from cyclohexanone oxime by gas phase Beckmann rearrangement.

[0011] The preparation method of caprolactam provided by the present application can reduce the amount of carrier gas, improve the reaction efficiency, and at the same time improve the reaction conversion rate and the reaction selectivity.

[0012] Other advantages of the present invention will be described in detail in the following specific embodiments. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of one embodiment of the radial moving bed reactor of the present invention;

[0014] Figure 2 This is a schematic diagram of the structure of the radial moving bed reactor of the present invention, showing the cooperation between the central tube and the heat extraction partition.

[0015] Figure 3 This is a diagram showing the relationship between the axial length h1 of the central tube and the total length H, and the height h2 of the ineffective part of the heat extraction separator and the total height L in the radial moving bed reactor of the present invention.

[0016] Figure 4 This is a top cross-sectional view of the inner and outer ring groups at the catalyst outlet in the radial moving bed reactor of the present invention.

[0017] Explanation of reference numerals in the attached figures

[0018] 1-Reactor shell; 2-Catalyst bed; 3-First material inlet / outlet

[0019] 4-Second material inlet / outlet; 5-Central pipe; 6-Heat extraction separator.

[0020] 7-Catalyst delivery pipe; 8-Material distributor; 9-Through hole

[0021] 101 - Catalyst inlet; 102 - Catalyst outlet Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] In this invention, unless otherwise stated, the radially moving bed reactor is vertically arranged perpendicular to the horizontal plane. The directional terms used, such as "above," "below," "upper end," "lower end," "top," and "bottom," generally refer to the upper or lower based on the corresponding component in the illustration, and also correspond to the upper or lower in natural space. "Inner" and "outer" refer to the inner and outer contours of the corresponding component (e.g., the inner and outer of the reactor shell or the inner and outer of the catalyst bed). "From the inside to the outside" refers to the direction of extension from the central tube to the reactor shell. These terms are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0024] As previously stated, the first aspect of the present invention provides a radially moving bed reactor, a preferred embodiment of which is as follows: Figure 1 , 3 As shown, the reactor includes: a reactor shell 1, and a central tube 5 with through holes 9, a catalyst bed 2, and a material distributor 8 arranged from the inside to the outside of the reactor shell 1; wherein, a plurality of heat-extracting partitions 6 are arranged at intervals along the circumference of the central tube 5 and perpendicularly connected to the tube wall of the central tube 5; an upper ineffective reaction zone, an effective reaction zone, and a lower ineffective reaction zone are arranged from top to bottom in the catalyst bed 2; wherein, the portions of the central tube 5 located in the upper and lower ineffective reaction zones do not have through holes, and the upper part of the heat-extracting partition 6 is configured as an ineffective portion located in the upper ineffective reaction zone.

[0025] The inventors discovered that moving bed reactors have a compact space, making it difficult to add new components. Therefore, it is generally challenging to effectively control the temperature rise in strongly exothermic or endothermic reactions by incorporating heat-extracting or heat-absorbing internal components within the reactor. Furthermore, achieving accurate control of the heat extraction process in commonly used radial reactors requires careful consideration of the heat transfer properties of the heat transfer internal components and the influence of reaction kinetics on the heat transfer process, which increases design complexity. In addition, for radial moving beds, uniform fluid distribution within the bed is a key focus in reactor design, and the uniformity of the reactor bed is also a design challenge. This invention addresses this issue by placing a heat-extracting separator 6 within the upper ineffective and effective reaction zones of the catalyst bed 2. Combined with the dimensional constraints and interrelationships of the central tube 5 and the heat-extracting separator 6 within the upper ineffective reaction zone, this facilitates fluid flow and uniform distribution, while simultaneously enabling effective heat exchange, temperature control, and improved reaction efficiency.

[0026] In this invention, the upper ineffective reaction zone and the lower ineffective reaction zone refer to the areas within the catalyst bed 2 where no reaction occurs. The upper ineffective reaction zone allows the catalyst entering from the top of the reactor shell 1 to be remixed and distributed before entering the effective reaction zone of the catalyst bed 2 to react with the catalyst; the lower ineffective reaction zone serves to buffer deactivated catalyst and discharge it in a measured manner.

[0027] It should be understood that the catalyst bed 2 is disposed in the interlayer between the central tube 5 and the material distributor 8; the central tube 5 passes through the upper ineffective reaction zone, the effective reaction zone, and the lower ineffective reaction zone of the catalyst bed 2. Through holes on the central tube 5 are used for material passage, with the portion having through holes located within the effective reaction zone, allowing material to flow between the central tube 5 and the catalyst bed 2; the material distributor 8 is used to disperse the gas (carrying the reactants) feed and to evenly distribute the gas radially into the catalyst bed 2. The reacted gas passes through the catalyst bed 2 and is collected back into the central tube 5, and is then discharged from the moving bed reactor through the outlet 4; alternatively, the material is fed through the central tube 5, and the gas is evenly distributed into the catalyst bed 2 by the material distributor 8, with the material passing through 8 being discharged from the moving bed reactor through the outlet 3; the catalyst in the catalyst bed 2 moves from top to bottom under gravity.

[0028] According to a preferred embodiment of the present invention, such as Figure 2 As shown, the heat extraction separator 6 is disposed on the outer peripheral surface of the central tube 5 and is formed as a plate extending along the axial direction of the central tube 5.

[0029] According to the present invention, preferably, such as Figure 2 As shown, the heat-extracting separator 6 is located within the catalyst bed 2; in the direction perpendicular to the axial direction of the central tube 5, the distance between two adjacent heat-extracting separators 6 gradually increases from the inside to the outside; that is, multiple heat-extracting separators 6 are radially distributed around the outer periphery of the central tube 5. This makes the catalyst bed 2 more uniformly distributed, improves the space utilization of the reactor, and further facilitates effective heat exchange within the moving bed reactor, thereby facilitating precise control of the reaction temperature.

[0030] In a preferred embodiment, the shortest distance between two adjacent heat-extracting separators 6 is at least 6 times, more preferably at least 10 times, the average particle size of the catalyst particles packed in the catalyst bed 2. This preferred embodiment is more conducive to heat extraction and also to catalyst flow.

[0031] In this invention, there is no limitation on the particle size of the catalyst. Conventional catalysts in the art can be used in this invention. For example, the particle size of the catalyst particles can preferably be above 0.5 mm, and more preferably 0.8-5 mm.

[0032] In this invention, preferably, a plurality of heat-extracting partitions 6 are arranged along the diametrical extension direction of the central tube 5, in which case the cross-section formed by two adjacent heat-extracting partitions 6 is fan-shaped. More preferably, a plurality of heat-extracting partitions 6 are evenly spaced around the circumference of the central tube 5.

[0033] In this invention, the heat-extracting separator 6 achieves heat extraction through heat exchange to control the temperature during the catalytic reaction process. This heat exchange can be achieved using any existing method. Preferably, the heat-extracting separator 6 has a channel for the flow of the heat exchange medium. Adopting this preferred embodiment of the invention facilitates more effective control of the reaction temperature and solves the heat transfer problem, thereby making the reaction within the catalyst bed 2 more stable and uniform. It is understood that the channel can be sealed, with a heat exchange medium pre-installed inside; or it can be an unsealed channel. In this case, those skilled in the art can further provide a heat exchange medium inlet and outlet on the heat-extracting separator 6 according to actual needs, and the heat exchange medium inlet and outlet are connected to the channel.

[0034] Preferably, the heat exchanger 6 is provided with a heat exchange medium inlet (not shown in the figure) and a heat exchange medium outlet (not shown in the figure), and the heat exchange medium inlet and the heat exchange medium outlet are respectively connected to the channel for the flow of the heat exchange medium.

[0035] More preferably, the heat exchange medium inlet and heat exchange medium outlet are located at the top and bottom of the heat extraction partition 6, respectively. It should be understood that, in this scheme, the heat extraction medium can be in the form of top inlet and top outlet, or bottom inlet and top outlet.

[0036] Preferably, the reactor further includes a heat exchange pipeline connected to the heat extraction partition 6, the heat exchange pipeline being positioned above (preferably directly above) the heat extraction partition 6 and within the upper ineffective reaction zone. In this preferred embodiment, the heat exchange pipeline does not affect the fluid flow within the catalyst bed 2.

[0037] It should be understood that the heat exchange pipeline can realize the heat exchange function of the heat extraction partition 6, and any existing device and its matching pipeline can be used. The present invention does not limit this.

[0038] This invention places no limitation on the heat exchange medium. Preferably, the heat exchange medium is molten salt, heat transfer oil, or water. The molten salt is a heat-conducting molten salt, which may be at least one of the following: halides of alkali metals and alkaline earth metals, nitrates, and sulfates, specifically, for example, molten sodium nitrate and / or potassium nitrate.

[0039] In one specific embodiment, the heat exchange separator 6 is a pair of plates. The pair of plates are a pair of plates on which a heat exchange medium can flow inside, and the plates are preferably pillow-type heat exchange plates or plate-type heat exchange plates.

[0040] In this invention, there are no restrictions on the fixing method of the heat-extracting separator 6, as long as it facilitates fluid flow and uniform distribution within the catalyst bed 2; for example, the heat-extracting separator 6 can be suspended from the top within the catalyst bed 2. It is understood that a gap can be left between the heat-extracting separator 6 and the catalyst bed 2, and the central tube 5, which can be selected by those skilled in the art according to actual needs; for example, the gap can be smaller than the particle size of the catalyst, so that the catalyst will not get stuck in the gap or pass through it.

[0041] In one specific embodiment of the present invention, the arrangement of the central tube 5 and the heat extraction separator 6 in the upper ineffective reaction zone can help improve the stability of the reaction system and maximize the technical effect of the catalyst. Preferably, as Figure 3 As shown, the axial length h1 of the portion of the central tube 5 located in the upper ineffective reaction zone satisfies the following condition with respect to the total length H of the central tube 5: h1 / H ≤ 0.4, preferably h1 / H ≤ 0.3. In this invention, both h1 and H refer to the vertical direction.

[0042] In one specific embodiment of the present invention, preferably, in the vertical direction, the height h2 of the ineffective portion of the heat-extracting separator 6 and the total height L of the heat-extracting separator 6 satisfy the following condition: h2 / L≤0.2, preferably h2 / L≤0.1. Here, h2 and L both refer to the vertical direction.

[0043] In one specific embodiment of the present invention, preferably, in the vertical direction, the upper edge of the heat-extracting separator 6 is higher than the lower edge of the portion of the central tube 5 located within the upper ineffective reaction zone (e.g., Figure 3 (As shown by the dashed line).

[0044] In one specific embodiment of the present invention, preferably, as shown in the example... Figure 3 As shown, the through hole 9 is disposed on the wall of the central tube 5 between two adjacent heat-extracting separators 6. Preferably, the central tube 5 is located in the portion within the effective reaction zone (e.g., Figure 3 The area below the dashed line (the region responsible for logistics distribution) has a variable opening ratio. For example, the opening ratio decreases from top to bottom. Preferably, the opening ratio varies from 1% to 15% along the central tube 5 from top to bottom.

[0045] In one specific embodiment of the present invention, preferably, the ratio of the pore diameter to the catalyst particle diameter is not greater than 1, and more preferably, this ratio is not greater than 0.8. That is, the pore diameter of the through hole is smaller than the catalyst particle diameter.

[0046] In a preferred embodiment, the radially moving bed reactor further includes a plurality of catalyst feed pipes 7 disposed within the reactor shell 1. The catalyst feed pipes 7 are located above the catalyst bed 2 and are spaced apart along the circumferential direction of the central pipe 5; they are used to allow the catalyst to flow into the catalyst bed 2. Those skilled in the art can freely select the number of catalyst feed pipes 7 according to actual needs.

[0047] The present invention restricts the material inlet and outlet (material, such as raw material) positions of the radial moving bed reactor, enabling the raw material and catalyst to contact and react within the catalyst bed 2. Preferably, as Figure 1 As shown, the moving bed reactor further includes: a catalyst inlet 101, a catalyst outlet 102, a first material inlet / outlet 3, and a second material inlet / outlet 4; the catalyst inlet 101 and the catalyst outlet 102 are connected to the catalyst bed 2; the catalyst inlet 101 and the catalyst outlet 102 are respectively located at the upper and lower ends of the reactor shell 1, for introducing the catalyst into the catalyst bed 2 to react with the raw materials, and then drawing out the deactivated catalyst after the reaction; the second material inlet / outlet 4 is connected to the central tube 5, and the first material inlet / outlet 3 is connected to the catalyst bed 2. Preferably, the first material inlet / outlet 3 and the second material inlet / outlet 4 are respectively located on opposite sides of the reactor shell 1.

[0048] In this invention, the first material inlet / outlet 3 and the second material inlet / outlet 4 refer to each inlet / outlet being either an inlet or an outlet. For example, in one mode, the first material inlet / outlet 3 is an outlet and the second material inlet / outlet 4 is an inlet; in another mode, the first material inlet / outlet 3 is an inlet and the second material inlet / outlet 4 is an outlet.

[0049] In this invention, the catalyst falls freely from the catalyst bed to the catalyst outlet 102 under its own gravity. Those skilled in the art can further add a collector to facilitate better discharge. The collector can be any existing material collection device; this invention has no limitations in this regard. A valve is provided at the catalyst outlet 102, allowing for either continuous or intermittent discharge. Generally, considering catalyst deactivation, those skilled in the art typically use continuous discharge to remove the deactivated catalyst. The discharge amount can be selected according to actual needs.

[0050] In one specific embodiment of the present invention, such as Figure 4As shown, preferably, the catalyst outlet 102 includes a plurality of openings arranged in a ring along the circumference of the reactor shell 1. That is, the plurality of openings are arranged around the central axis of the reactor shell 1 and are distributed in a ring shape.

[0051] In one specific embodiment of the present invention, preferably, the plurality of openings are divided into an inner ring group and an outer ring group, wherein the inner ring group is disposed below the central tube 5 and the outer ring group is disposed below the material distributor 8.

[0052] In this invention, the multiple openings included in each of the inner and outer ring groups can be arranged in a ring at equal intervals along the circumference of the reactor shell 1. The diameters of the multiple openings can be the same, and can be set to 15-50 times the diameter of the catalyst particles. The number of openings included in each of the inner and outer ring groups can be adjusted according to the diameter of the reactor shell 1 to ensure catalyst removal as required by this invention. For example... Figure 4 As shown.

[0053] In one specific embodiment of the present invention, such as Figure 4 As shown, (a) shows the inner ring assembly and the central tube, and (b) shows the outer ring assembly and the reactor shell. Preferably, the diameter d1 of the circle formed by the centers of the openings in the inner ring assembly, the diameter d2 of the circle formed by the centers of the openings in the outer ring assembly, the diameter D1 of the central tube 5, and the diameter D2 of the reactor shell 1 satisfy the following: D1-d1≤0.3D2, D2-d2≤0.3D2; preferably, D1-d1≤0.15D2, D2-d2≤0.15D2.

[0054] In the radial moving bed reactor of the present invention, the raw material can pass through the catalyst bed 2 in a centrifugal or centripetal manner. The centrifugal manner refers to the raw material entering the central tube 5, catalyst bed 2, and material distributor 8 sequentially through the second material inlet / outlet 4, and exiting from the first material inlet / outlet 3. The centripetal manner refers to the raw material entering the material distributor 8, catalyst bed 2, and central tube 5 sequentially through the first material inlet / outlet 3, and exiting the reactor from the second material inlet / outlet 4.

[0055] In a specific embodiment of the present invention, preferably, when the first material inlet / outlet 3 introduces reaction raw materials and the second material inlet / outlet 4 discharges products, the openings of the inner ring group are closed and the openings of the outer ring group are open, for discharging the catalyst that has been deactivated on the outside of the catalyst bed 2; or

[0056] When the second material inlet / outlet 4 is fed with the reaction raw material and the first material inlet / outlet 3 discharges the product, the openings of the outer ring group are closed and the openings of the inner ring group are open, for discharging the catalyst that has been deactivated on the inner side of the catalyst bed 2.

[0057] In this invention, the catalyst generally needs to be purged before it is discharged from the moving bed reactor, preferably using an inert gas as the purging medium.

[0058] In this invention, preferably, there are no restrictions on the reactor shell 1; preferably, the reactor shell 1 is cylindrical. In this invention, the radially moving bed reactor is typically also equipped with a temperature control component for controlling the reaction temperature within the catalyst bed 2 and a pressure regulating component for controlling the reaction pressure, etc., which will not be elaborated upon here.

[0059] This invention has no limitations on the application of the radial moving bed reactor; it can be applied to any strongly endothermic or strongly exothermic reaction process, and the reaction process is relatively unaffected by changes in the reaction temperature gradient. Furthermore, reactions requiring continuous catalyst unloading due to the limited single-pass catalyst lifetime can also utilize the moving bed reactor described in this invention. The moving bed reactor of this invention is particularly suitable for the gas-phase Beckmann rearrangement process of cyclohexanone oxime to caprolactam production, in which the reactants (including a mixture of cyclohexanone oxime, carrier gas, and solvent) enter the moving bed reactor in gaseous form. In application, those skilled in the art can connect multiple moving bed reactors in parallel or in series according to actual needs to achieve multiple catalyst beds working together and increase throughput; preferably, the total number of moving bed reactors connected in parallel or in series is no more than four.

[0060] In one specific embodiment of the radial moving bed reactor of the present invention, as follows: Figure 1 As shown, the raw material enters through the first material inlet / outlet 3, passes through the material distributor 8, and then enters the catalyst bed 2. Simultaneously, the catalyst is fed from the catalyst inlet 101 through the catalyst discharge pipe 7 to the upper ineffective zone of the catalyst bed 2. After heat exchange, the catalyst enters the effective reaction zone of the catalyst bed 2, flowing downwards by gravity. Meanwhile, a heat exchange medium flows within the heat extraction separator 6. The raw material and catalyst undergo a catalytic reaction within the effective reaction zone of the catalyst bed 2. During the reaction, the reaction temperature is controlled by adjusting the heat exchange medium in the heat extraction separator 6, thus stabilizing the temperature gradient within the bed. After the reaction is complete, the reactants are drawn out through the central pipe 5 from the second material inlet / outlet 4, and the deactivated catalyst is continuously or intermittently discharged from the catalyst outlet 102.

[0061] In this invention, if the catalyst activity cannot meet the reaction requirements, regenerated or fresh catalyst can be optionally introduced through the catalyst inlet 101 and removed through the catalyst outlet 102. Further, corresponding to the aforementioned different operations, the catalyst can be removed from the opening of the inner ring group or the opening of the outer ring group. When the moving bed reactor of this invention is used for the preparation of caprolactam, the rearrangement reaction catalyst has a long activity lifetime, allowing for intermittent loading and unloading.

[0062] In this invention, the flow direction of the heat exchange medium can be controlled to form a cross-flow mixing with the catalyst, and heat exchange can be achieved in the moving bed reactor under the cross-flow state.

[0063] The present invention provides the above-mentioned radial moving bed reactor, in which the above-mentioned structural features work together to solve the problems of uneven distribution of catalyst along the gas flow axis in the moving bed reactor, and the drastic temperature rise caused by a large amount of exothermic reaction during the reaction process, thereby effectively improving the reaction efficiency in the reactor.

[0064] A second aspect of the present invention provides a method for preparing caprolactam, the method comprising: introducing raw materials and a catalyst into a reactor for reaction; the raw materials comprising cyclohexanone oxime, a carrier gas and a solvent; wherein the reactor is the moving bed reactor described in the first aspect above.

[0065] In this invention, preferably, a heat exchange medium flows through the heat extraction partition 6 in the moving bed reactor. The range of selectable heat exchange media is the same as that in the first aspect described above, and will not be repeated here.

[0066] Preferably, the vaporization rate of the heat exchange medium is no more than 30%. This preferred embodiment is more conducive to making the bed temperature of the catalyst bed 2 more uniform.

[0067] Preferably, the raw material passes through the catalyst bed 2 of the moving bed reactor in a centrifugal or centripetal manner. The centrifugal or centripetal manner is as described above.

[0068] According to the present invention, preferably, the molar ratio of the carrier gas to the cyclohexanone oxime is 5-100:1, more preferably 5-50:1. The method of the present invention can reduce the amount of carrier gas used.

[0069] Preferably, the weight ratio of the solvent to the cyclohexanone oxime is 1-100:1, more preferably 1-20:1.

[0070] The present invention does not limit the carrier. Preferably, the carrier gas is a protective gas, more preferably at least one of nitrogen, argon, a saturated hydrocarbon with a boiling point not exceeding 180°C, and a halogenated hydrocarbon with a boiling point not exceeding 180°C. The saturated hydrocarbon with a boiling point not exceeding 180°C can be, for example, at least one of methanol, ethanol, and propanol, and the halogenated hydrocarbon with a boiling point not exceeding 180°C can be, for example, at least one of 1-chloroethane, 1-chloropropane, and 1-chlorobutane.

[0071] The present invention does not limit the solvent. Preferably, the solvent is an organic solvent, more preferably a C1-C6 fatty alcohol, and even more preferably at least one of methanol, ethanol and propanol.

[0072] According to the present invention, preferably, the reaction conditions include: a reaction temperature of 200-500°C, a reaction pressure of 0.1-1 MPa, and a weight hourly space velocity of cyclohexanone oxime of 0.3-20 h⁻¹. -1 More preferably 0.3-5h -1 .

[0073] According to a preferred embodiment of the present invention, the method further includes: controlling the temperature rise of the reaction to be no higher than 100°C, preferably no higher than 80°C, and more preferably no higher than 60°C by using the heat extraction separator 6. More preferably, the reaction temperature is above 300°C. Specifically, the temperature rise of the reaction can be controlled by controlling the inlet and outlet temperatures of the reactor reactants to keep the reaction temperature within the above-mentioned range.

[0074] According to the present invention, preferably, the catalyst is a molecular sieve catalyst. The molecular sieve catalyst may be, for example, at least one of all-silica molecular sieves and titanium-silica molecular sieves. It is granulated into particles for use and packed to form a catalyst bed. The particle size of the catalyst particles is preferably 0.5 mm or more, and more preferably 0.8-5 mm.

[0075] The method provided by this invention further controls the temperature conditions in the moving bed reactor, which can effectively improve catalyst activity, reduce catalyst removal, and enhance reaction efficiency. In a preferred embodiment of this invention, preferably, the average temperature T1 (the average of the highest and lowest temperatures in the upper ineffective reaction zone) in the moving bed reactor is equal to the lowest temperature T in the effective reaction zone. min Satisfy: T min Satisfy: T min -T1≤50℃, T is preferred min -T1≤30℃.

[0076] In a preferred embodiment of the present invention, preferably, the average temperature T2 (which is the average of the highest and lowest temperatures in the lower ineffective reaction zone) in the moving bed reactor is related to T... minSatisfy: T min -T2≤80℃.

[0077] The caprolactam preparation method provided in this invention, using the radial moving bed reactor of this invention and combined with the above-mentioned conditional features, can synergistically reduce the amount of carrier gas used, improve reaction efficiency, and simultaneously improve reaction conversion rate and reaction selectivity.

[0078] The present invention will be described in detail below through embodiments. Wherein,

[0079] Caprolactam selectivity % = Amount of caprolactam generated / Amount of cyclohexanone oxime converted × 100%.

[0080] Example 1

[0081] This embodiment illustrates the radial moving bed reactor and the method for preparing caprolactam according to the present invention.

[0082] like Figures 1-4 As shown, in the radial moving bed reactor, the reactor shell 1 is cylindrical, and the heat-extracting partition 6 is disposed in the effective reaction zone within the catalyst bed 2 and is disposed on the outer circumferential surface of the central tube 5, and is formed as a plate extending axially along the central tube 5. There are 110 heat-extracting partitions 6, which are evenly arranged along the circumferential direction of the central tube 5 and are respectively located in the diameter extension direction of the central tube 5. The shortest distance between two adjacent heat-extracting partitions 6 is 15 mm.

[0083] The reactor shell has a diameter D2 of 3m, the central tube 5 has a diameter D1 of 2m, a height H of 6m, an axial length h1 of 0.8m, a heat-extracting separator 6 with a height L of 4m, and an ineffective section h2 of 0.4m. The inner ring assembly has a diameter d1 and a distance of 0.4m from the central tube D1. The inner ring assembly consists of 5 equally spaced openings with a diameter of 50mm. The effective reaction zone of the central tube has a height of 4m, with an upper opening ratio of 10% and a lower opening ratio of 8%, each occupying 50% of the effective reaction zone height.

[0084] A mixture of cyclohexanone oxime, methanol, and nitrogen (i.e., the raw material) enters the central tube 5 through the second material inlet / outlet 4, and then distributes the raw material within the catalyst bed 2 through the central tube 5; the inlet temperature of the raw material in the catalyst bed 2 is 350℃. Simultaneously, a silica molecular sieve (specifically S-1, with an average particle size of 1.5 mm) enters the catalyst bed 2 through the catalyst feed inlet 101, flowing downwards within the catalyst bed 2 under its own gravity. The raw material reacts with the catalyst in the effective reaction zone, and the heat of reaction is removed by the heat extraction separator 6. The reactants passing through the catalyst bed 2 are collected by the material distributor 8 and leave the reactor through the first material inlet / outlet 3. The discharged reactants enter downstream for separation and purification, where the reactants and solvent are separated by distillation to obtain crude caprolactam. The rearrangement reaction catalyst has a long active lifetime and is handled intermittently, with the catalyst discharged from the inner ring opening of the catalyst outlet 102.

[0085] Since the reaction is exothermic, the heat generated during the reaction process is continuously removed by the heat extraction separator 6, and the bed temperature rise is stably controlled to not exceed 60℃. The vaporization rate of the heat exchange medium is 15%. The heat exchange medium is high-pressure (pressure 3.5MPa) saturated water.

[0086] The catalyst removal rate is 50 kg / h, the molar ratio of nitrogen to cyclohexanone oxime is 35:1, and the mass ratio of methanol to cyclohexanone oxime is 2.0:1. The inlet temperature of the second material inlet / outlet 4 of the reactor is 340℃, the outlet temperature of the first material inlet / outlet 3 is 395℃, the reaction pressure is 0.46 MPa, and the weight hourly space velocity of cyclohexanone oxime is 1 h⁻¹. -1 At this point, the average temperature T1 of the upper ineffective reaction zone is 315℃, the lowest temperature of the effective reaction zone is 340℃, and the average temperature T2 of the lower ineffective reaction zone is 300℃.

[0087] After 1000 hours of operation, the fluid flow uniformity in the bed was 97%. A sample of the catalyst was taken from catalyst outlet 102. Thermogravimetric analysis showed that the amount of carbon deposited on the catalyst was 3.2 wt% of the catalyst weight.

[0088] Gas chromatography analysis of the product showed that the cyclohexanone oxime conversion rate was 99.99% and the caprolactam selectivity was 96.5%, and that the cyclohexanone oxime conversion rate and caprolactam selectivity did not change over time.

[0089] Comparative Example 1

[0090] The method is the same as in Example 1, except that no heat extraction separator is set up. In order to maintain the same process parameters, the circulating gas volume is increased by 30%.

[0091] In this comparative example, the catalyst bed temperature rise was around 100℃. Testing showed that the cyclohexanone oxime conversion rate was 99.99%, and the caprolactam selectivity was 94%, with neither the cyclohexanone oxime conversion rate nor the caprolactam selectivity changing over time.

[0092] Example 2

[0093] The method is the same as in Example 1, except that the molar ratio of nitrogen to cyclohexanone oxime is 20:1, and the mass ratio of methanol to cyclohexanone oxime is 5:1; the outlet temperature of the first material inlet / outlet 3 is 390°C, the reaction pressure is 0.46 MPa, and the weight hourly space velocity of cyclohexanone oxime is 1 h⁻¹. -1 .

[0094] Gas chromatography analysis of the product showed that the cyclohexanone oxime conversion rate was 99.99% and the caprolactam selectivity was 96.5%, and that the cyclohexanone oxime conversion rate and caprolactam selectivity did not change over time.

[0095] Example 3

[0096] The method is the same as in Example 1, except that the number of heat-extracting separators 6 is 80, the shortest distance between two adjacent heat-extracting separators 6 is 22 mm, and the cyclohexanone oxime conversion rate and caprolactam selectivity do not change over time.

[0097] In this embodiment, the reaction temperature was kept stable below 80°C, the cyclohexanone oxime conversion rate was 99.99%, and the caprolactam selectivity was 95%.

[0098] Example 4

[0099] The method is the same as in Example 1, except that the height h2 of the ineffective part of the heat separator 6 is 0m; the average temperature T1 of the upper ineffective reaction zone is 280°C; and the cyclohexanone oxime conversion and caprolactam selectivity do not change with time.

[0100] In this embodiment, the catalyst removal rate needs to be increased to 60 kg / h to maintain the same effect as in Example 1.

[0101] Example 5

[0102] The method is the same as in Example 1, except that...

[0103] The axial length h1 of the central tube is 0.4m, and the height h2 of the ineffective part of the heat-absorbing separator 6 is 0m.

[0104] The average temperature T1 of the upper ineffective reaction zone was 240℃. Furthermore, the cyclohexanone oxime conversion and caprolactam selectivity did not change over time.

[0105] In this embodiment, the catalyst removal rate needs to be increased to 70 kg / h, the cyclohexanone oxime conversion rate is 99.9%, and the caprolactam selectivity is 94%.

[0106] Example 6

[0107] The method is the same as in Example 1, except that...

[0108] The distance between the inner ring diameter d1 and the central tube D1 is 0.8m.

[0109] In this embodiment, the difference from the implementation effect in Example 1 is that the catalyst sample taken from catalyst outlet 102 and the carbon deposition of the catalyst obtained by thermogravimetric analysis is 2.5 wt% of the catalyst weight.

[0110] Example 7

[0111] The method is the same as in Example 1, except that the central tube is uniformly perforated along the axial direction, with a perforation rate of 10%.

[0112] In this embodiment, after 1000 hours of reaction operation, the fluid flow uniformity in the bed was 95%, the cyclohexanone oxime conversion rate was 99.95%, and the caprolactam selectivity was 96%.

[0113] The results above show that, compared to Comparative Example 1, the embodiment using the radial moving bed reactor provided by the present invention exhibits better cyclohexanone oxime conversion and caprolactam selectivity when used for caprolactam preparation. Specifically, comparing Examples 1 and Examples 2 and 3 reveals that the scheme employing the preferred heat extraction separator of the present invention demonstrates higher caprolactam selectivity while maintaining a high conversion rate.

[0114] A comparison of Examples 1 with Examples 4 and 5 shows that by controlling the axial length h1 of the central tube and the height h2 of the ineffective part of the heat extraction separator 6 within the limits of the present invention, the catalyst reaction activity can be effectively improved and the amount of catalyst removed can be reduced, which is beneficial to improving the reaction effect.

[0115] A comparison of Examples 1 and 6 shows that the method of limiting the catalyst outlet setting provided by the present invention results in a more reasonable catalyst discharge and effectively improves the catalyst utilization rate.

[0116] A comparison of Examples 1 and 7 shows that the porosity method provided by the present invention results in a more stable reaction and better overall stability of the reaction bed under long-term operation conditions.

[0117] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A radially moving bed reactor, characterized in that, The reactor includes: a reactor shell (1), and a central tube (5) with through holes, a catalyst bed (2), and a material distributor (8) arranged from the inside to the outside of the reactor shell (1); wherein, a plurality of heat-extracting partitions (6) are arranged at intervals along the circumferential direction of the central tube (5) and perpendicularly connected to the tube wall of the central tube (5); an upper ineffective reaction zone, an effective reaction zone, and a lower ineffective reaction zone are arranged from top to bottom in the catalyst bed (2); wherein, the portions of the central tube (5) located in the upper and lower ineffective reaction zones do not have through holes, and the upper part of the heat-extracting partition (6) is set as an ineffective portion located in the upper ineffective reaction zone; The heat extraction separator (6) is disposed on the outer peripheral surface of the central tube (5) and is formed as a plate extending axially along the central tube (5).

2. The reactor according to claim 1, characterized in that, Multiple heat extraction separators (6) are provided along the diametrical extension direction of the central tube (5).

3. The reactor according to claim 1, characterized in that, The shortest distance between two adjacent heat extraction separators (6) is more than 6 times the average particle size of the catalyst particles packed in the catalyst bed (2).

4. The reactor according to claim 3, characterized in that, The shortest distance between two adjacent heat extraction separators (6) is more than 10 times the average particle size of the catalyst particles packed in the catalyst bed (2).

5. The reactor according to claim 1, characterized in that, The heat extraction partition (6) is provided with a channel for the heat exchange medium to circulate; And / or, the moving bed reactor further includes a heat exchange pipeline connected to the heat extraction partition (6), the heat exchange pipeline being disposed above the heat extraction partition (6) and located within the upper ineffective reaction zone.

6. The reactor according to claim 5, characterized in that, The heat exchanger (6) is provided with a heat exchange medium inlet and a heat exchange medium outlet, which are respectively connected to the channel.

7. The reactor according to claim 6, characterized in that, The heat exchange medium inlet and heat exchange medium outlet are located at the top and bottom of the heat extraction partition (6), respectively.

8. The reactor according to claim 1, characterized in that, The axial length h1 of the portion of the central tube (5) located in the upper ineffective reaction zone satisfies the following relationship with the total length H of the central tube (5): h1 / H≤0.4; And / or, in the vertical direction, the height h2 of the ineffective part of the heat-collecting separator (6) and the total height L of the heat-collecting separator (6) satisfy: h2 / L≤0.2; And / or, in the vertical direction, the upper edge of the ineffective portion of the heat extraction separator (6) is higher than the lower edge of the portion of the central tube (5) located within the upper ineffective reaction zone.

9. The reactor according to claim 8, characterized in that, The axial length h1 of the portion of the central tube (5) located in the upper ineffective reaction zone satisfies the following relationship with the total length H of the central tube (5): h1 / H≤0.3; And / or, in the vertical direction, the height h2 of the ineffective part of the heat-extracting separator (6) and the total height L of the heat-extracting separator (6) satisfy: h2 / L≤0.

1.

10. The moving bed reactor according to claim 1, characterized in that, The through hole is provided on the pipe wall of the central tube (5) between two adjacent heat extraction separators (6); And / or, the portion of the central tube (5) located within the effective reaction zone has a variable porosity.

11. The moving bed reactor according to claim 10, characterized in that, Along the central tube (5) from top to bottom, the range of the opening ratio is 1%-15%.

12. The reactor according to claim 1, characterized in that, The moving bed reactor also includes a plurality of catalyst feed pipes (7) disposed in the reactor shell (1). The plurality of catalyst feed pipes (7) are located above the catalyst bed (2) and are distributed at intervals along the circumferential direction of the central pipe (5).

13. The reactor according to claim 1, characterized in that, The moving bed reactor also includes: a catalyst inlet (101), a catalyst outlet (102), a first material inlet / outlet (3), and a second material inlet / outlet (4); The catalyst inlet (101) and catalyst outlet (102) are connected to the catalyst bed (2); the catalyst inlet (101) and catalyst outlet (102) are respectively located at the upper end and lower end of the reactor shell (1); The second material inlet / outlet (4) is connected to the central tube (5), and the first material inlet / outlet (3) is connected to the catalyst bed (2).

14. The reactor according to claim 13, characterized in that, The catalyst outlet (102) includes a plurality of openings arranged in a ring along the circumferential direction of the reactor shell (1).

15. The reactor according to claim 14, characterized in that, The multiple openings are divided into an inner ring group and an outer ring group, wherein the inner ring group is located below the central tube (5) and the outer ring group is located below the material distributor (8).

16. The reactor according to claim 15, characterized in that, The diameter d1 of the circle formed by the center of each opening in the inner ring group, the diameter d2 of the circle formed by the center of each opening in the outer ring group, the diameter D1 of the central tube (5), and the diameter D2 of the reactor shell (1) satisfy the following: D1 - d1 ≤ 0.3D2, D2 - d2 ≤ 0.3D2.

17. The reactor according to claim 16, characterized in that, The diameter d1 of the circle formed by the center of each opening in the inner ring group, the diameter d2 of the circle formed by the center of each opening in the outer ring group, the diameter D1 of the central tube (5), and the diameter D2 of the reactor shell (1) satisfy the following: D1 - d1 ≤ 0.2D2, D2 - d2 ≤ 0.2D2.

18. The reactor according to any one of claims 15-17, characterized in that, When the first material inlet / outlet (3) is used to introduce reaction raw materials and the second material inlet / outlet (4) is used to discharge products, the openings of the inner ring group are closed and the openings of the outer ring group are open, for discharging the catalyst that has been deactivated on the outside of the catalyst bed (2); or When the second material inlet / outlet (4) is used to introduce reaction raw materials and the first material inlet / outlet (3) is used to discharge products, the openings of the outer ring group are closed and the openings of the inner ring group are open, which is used to discharge the catalyst that has been deactivated inside the catalyst bed (2).

19. A method for preparing caprolactam, the method comprising: The raw materials and catalyst are introduced into the reactor for reaction, respectively; the raw materials include cyclohexanone oxime, carrier gas and solvent; characterized in that the reactor is a moving bed reactor as described in any one of claims 1-18.

20. The method according to claim 19, characterized in that, The heat exchange medium flows through the heat extraction partition (6) in the moving bed reactor; And / or, the raw material is passed through the catalyst bed (2) of the moving bed reactor in a centrifugal or centripetal manner.

21. The method according to claim 20, characterized in that, The vaporization rate of the heat exchange medium is no more than 30%; And / or, the heat exchange medium is molten salt, heat transfer oil, or water.

22. The method according to any one of claims 19-21, characterized in that, The molar ratio of the carrier gas to the cyclohexanone oxime is 5-100:1, and the weight ratio of the solvent to the cyclohexanone oxime is 1-100:

1. And / or, the carrier gas is at least one of nitrogen, argon, a saturated hydrocarbon with a boiling point not exceeding 180°C, and a halogenated hydrocarbon with a boiling point not exceeding 180°C; and / or The solvent is a C1-C6 fatty alcohol; And / or, the reaction conditions include: a reaction temperature of 200-500℃, a reaction pressure of 0.1-1 MPa, and a weight hourly space velocity of cyclohexanone oxime of 0.3-20 h⁻¹. -1 ; And / or, the method further includes: controlling the temperature rise of the reaction to not exceed 100°C by means of a heat-extracting separator (6).

23. The method according to claim 22, characterized in that, The method further includes controlling the temperature rise of the reaction to not exceed 80°C by means of a heat extraction separator (6).

24. The method according to claim 23, characterized in that, The method further includes controlling the temperature rise of the reaction to not exceed 60°C by means of a heat extraction separator (6).

25. The method according to any one of claims 19-21 and 23-24, characterized in that, The average temperature T1 of the upper ineffective reaction zone and the lowest temperature T of the effective reaction zone in the moving bed reactor min Satisfy: T min - T1≤50℃; And / or, the average temperature T2 of the lower ineffective reaction zone in the moving bed reactor and T min Satisfy: T min - T2≤80℃.

26. The method according to claim 25, characterized in that, The average temperature T1 of the upper ineffective reaction zone and the lowest temperature T of the effective reaction zone in the moving bed reactor min Satisfy: T min - T1≤30℃.

27. The method according to claim 22, characterized in that, The average temperature T1 of the upper ineffective reaction zone and the lowest temperature T of the effective reaction zone in the moving bed reactor min Satisfy: T min - T1≤50℃; And / or, the average temperature T2 of the lower ineffective reaction zone in the moving bed reactor and T min Satisfy: T min - T2≤80℃.

28. The method according to claim 27, characterized in that, The average temperature T1 of the upper ineffective reaction zone and the lowest temperature T of the effective reaction zone in the moving bed reactor min Satisfy: T min - T1≤30℃.

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