Vaporization method and application of cyclohexanone-oxime, and cyclohexanone-oxime gas-phase Beckmann rearrangement reaction method

Abstract

The present invention relates to the technical field of caprolactam preparation, and discloses a cyclohexanone-oxime vaporization method and application thereof, and a cyclohexanone-oxime gas phase Beckmann rearrangement reaction method, the method comprises: atomizing an alcoholic solution of cyclohexanone-oxime to form atomized liquid drops, and then contacting with a high temperature carrier gas to vaporize; wherein the average particle size of the atomized liquid drops is less than 80 microns, and the average retention time of the cyclohexanone-oxime does not exceed 2 seconds. According to the vaporization method provided by the invention, the vaporization speed can be increased, the contact time of a liquid-phase cyclohexanone-oxime thermal medium can be reduced, the oxime vaporization effect can be greatly improved, the carbon deposition and coking rate of sprayed oxime can be reduced, byproducts can be reduced, and the product quality of caprolactam can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of caprolactam preparation, and in particular to a cyclohexanone oxime vaporization method and application thereof, and a cyclohexanone oxime gas-phase Beckmann rearrangement reaction method. Background Art

[0002] Cyclohexanone oxime Beckmann rearrangement reaction is one of the core technologies for industrial production of caprolactam. Cyclohexanone oxime vapor-phase Beckmann rearrangement process has the advantages of no by-product ammonium sulfate, low cost and environmental friendliness, so it has received more and more attention as a green production process for caprolactam.

[0003] Due to the high thermal sensitivity of cyclohexanone oxime, its vaporization process has become one of the difficulties in the gas phase rearrangement reaction and a key technology that needs to be solved urgently. Good cyclohexanone oxime vaporization can not only ensure the stable operation of the device, but also reduce the side reactions in the vaporization process, improve the selectivity of the reaction to caprolactam, and reduce the separation load of the subsequent refining unit of caprolactam.

[0004] Cyclohexanone oxime has poor thermal stability and is prone to thermal condensation, carbon deposition, and coking, which poses many problems. The thermal stability of gaseous cyclohexanone oxime after gasification is relatively stable. When using traditional shell and tube heat exchangers to vaporize cyclohexanone oxime, there will be serious carbon deposition and blockage, obvious thermal decomposition of cyclohexanone oxime, and high cyclohexanone content, making it difficult for the device to operate stably for a long period of time.

[0005] CN1379021A discloses a method for evaporating cyclohexanone oxime using a falling film evaporator, which is characterized in that the liquid film thickness in the tube is adjusted by controlling the overflow strength of cyclohexanone oxime, and the vaporization effect and vaporization speed of cyclohexanone oxime are guaranteed under the condition of appropriate liquid film thickness. This method has low vaporization efficiency, large cyclohexanone oxime circulation volume, high energy consumption and great operation difficulty.

[0006] CN202290053U discloses a heat-sensitive liquid vaporization device, including a vaporizer housing and an atomizing spray gun, which can realize rapid vaporization of heat-sensitive liquids. CN102755860A discloses a cyclohexanone oxime vaporization method, which is to introduce liquid cyclohexanone oxime into a vaporization device, contact with an atomizing medium in a two-fluid atomizing spray gun, and atomize into small droplets, and the cyclohexanone oxime small droplets contact with high-temperature gas to fully vaporize. Although the above method can reduce the coking of cyclohexanone oxime during the vaporization process to a certain extent, the problems of decomposition and carbon deposition of cyclohexanone oxime during the vaporization process are still not solved. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of poor cyclohexanone oxime vaporization effect, high decomposition rate and easy carbon deposition and coking in the prior art, and to provide a cyclohexanone oxime vaporization method and application thereof, and a method for gas-phase Beckmann rearrangement reaction of cyclohexanone oxime. The method can effectively improve the oxime vaporization effect, and the cyclohexanone oxime has a low carbon deposition and coking rate and a low by-product content.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for vaporizing cyclohexanone oxime, the method comprising: atomizing an alcohol solution of cyclohexanone oxime to form atomized droplets, and then contacting the atomized droplets with a high-temperature carrier gas for vaporization;

[0009] The average particle size of the atomized droplets is less than 80 μm, and the average residence time of cyclohexanone oxime is no more than 2 seconds.

[0010] The second aspect of the present invention provides application of the above-mentioned cyclohexanone oxime vaporization method in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime.

[0011] A third aspect of the present invention provides a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the method comprising:

[0012] (1) vaporizing cyclohexanone oxime by the above-mentioned vaporization method of cyclohexanone oxime to obtain a vaporized raw material;

[0013] (2) preheating the vaporized raw material and then contacting it with a catalyst to perform a gas-phase Beckmann rearrangement reaction;

[0014] (3) removing heavy components from the gas-phase Beckmann rearrangement reaction product, and then recovering the solvent and carrier gas;

[0015] (4) The recovered solvent and carrier gas are recycled to the vaporization process of cyclohexanone oxime in step (1).

[0016] The inventor of the present invention has found in research that the vaporization mode of cyclohexanone oxime is an important factor affecting the length of the start-up cycle and the quality of the caprolactam product. It is difficult to ensure the full vaporization of cyclohexanone oxime using the traditional heat exchanger mode. Even after sufficient heat exchange, the vaporization effect of cyclohexanone oxime is still not ideal enough. In the scheme of using a two-fluid atomizing nozzle as the dispersion means of cyclohexanone oxime, since the gas atomizing nozzle has a long spray distance under the action of gas, the cyclohexanone oxime droplets that are not vaporized in time are brought into the reactor by the high-speed airflow to coke, and the increase of the pressure drop of the catalyst bed may also be accelerated.

[0017] The cyclohexanone oxime vaporization method provided by the present invention matches the characteristics of the oxime supply system (alcohol, cyclohexanone oxime) through an atomization method, controls the average particle size of atomized droplets and the average residence time of cyclohexanone oxime, increases the vaporization speed, reduces the contact time of the liquid phase cyclohexanone oxime with the heat medium, can greatly improve the oxime vaporization effect, reduce the carbon deposition and coking rate of the ejected oxime, can effectively control the cyclohexanone content in the vaporization product to be maintained below 0.5 mol% and the octahydrophenazine content to be below 0.05 mol%, which is beneficial to improving the product quality of caprolactam. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of an integrated vaporization reaction device in a specific embodiment of the present invention;

[0019] Figure 2 The figure is a schematic diagram of the process flow adopted by the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime in one embodiment of the present invention.

[0020] Description of Reference Numerals

[0021] 1 Vaporized raw material inlet 2 High temperature carrier gas inlet 3 Nozzle

[0022] 4 Gas dispersion layer 5 Vaporizer cylinder 6 Reactant outlet

[0023] 7 Catalyst bed 8 Packing layer DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] A first aspect of the present invention provides a method for vaporizing cyclohexanone oxime, the method comprising: atomizing an alcohol solution of cyclohexanone oxime to form atomized droplets, and then contacting the atomized droplets with a high-temperature carrier gas for vaporization;

[0026] The average particle size of the atomized droplets is less than 80 μm, and the average residence time of cyclohexanone oxime is no more than 2 seconds.

[0027] Cyclohexanone oxime is a highly heat-sensitive substance. After being in contact with a high-temperature medium for a long time during the vaporization process, it is very easy to have many problems such as thermal condensation, carbon deposition, and coking. Therefore, the vaporization mode of the raw material is an important factor affecting the start-up cycle length of the cyclohexanone oxime gas-phase Beckmann rearrangement reaction and the quality of the caprolactam product. In the prior art, usually only the coking problem of the vaporization process is concerned, while the influence of the by-products in the vaporization process on the subsequent gas-phase rearrangement reaction effect is ignored. The inventors of the present invention have found in the study that during the vaporization process, the hydrolysis reaction of cyclohexanone oxime generates cyclohexanone and hydroxylamine, and the thermal condensation of two molecules of cyclohexanone oxime generates decahydrophenazine, and the decahydrophenazine dehydrogenates to obtain octahydrophenazine. The side reactions in the vaporization process seriously affect the utilization rate of cyclohexanone oxime on the one hand, affect the selectivity of caprolactam, and the presence of by-products also greatly increases the separation load of the subsequent refining unit.

[0028] The key to solving the above-mentioned vaporization problem is to increase the vaporization rate and reduce the contact time of the liquid cyclohexanone oxime with the heat medium. The most direct solution is to control the phase change time from liquid to gas phase and reduce the thickness of the liquid film.

[0029] The cyclohexanone oxime vaporization method provided by the present invention adopts an alcohol solution of cyclohexanone oxime for direct atomization, and by matching the atomization method with the characteristics of an oxime supply system (alcohol, cyclohexanone oxime), the average particle size of atomized droplets and the average residence time of cyclohexanone oxime are controlled, thereby greatly improving the oxime vaporization effect, reducing the carbon deposition rate of the sprayed oxime, reducing the thermal decomposition of cyclohexanone oxime, and reducing the generation of by-products.

[0030] According to some preferred embodiments of the present invention, the alcohol solution of cyclohexanone oxime is atomized in a top-down direction. The above preferred embodiments are beneficial to the vaporization of oxime and slow down the coking.

[0031] In the present invention, the average particle size of the atomized droplets is small, reflecting that the thickness of the liquid film is thin, which helps to increase the thermal contact area of ​​cyclohexanone oxime, improve the vaporization effect of cyclohexanone oxime and increase the vaporization speed. According to some preferred embodiments of the present invention, the average particle size of the atomized droplets is 30-70 μm.

[0032] In the present invention, the average particle size of the atomized droplets refers to the Sotel mean diameter, which refers to the ratio of the volume of all droplets in the liquid mist to the total surface area, and is represented by D32. Generally speaking, the smaller the average particle size of the atomized droplets, the larger the surface area of ​​the same volume of liquid, indicating that the finer the droplets, the easier they are to heat, evaporate and burn, and thus the better the atomization quality. However, too fine atomization is not good either. If the average particle size of the atomized droplets is too small, they will be immediately carried away by the airflow after being sprayed out through the nozzle, forming an overly concentrated mixture in a certain area.

[0033] In the present invention, the vaporization of cyclohexanone oxime is carried out in a vaporizer, and the average residence time of cyclohexanone oxime refers to the average residence time from the vaporization of cyclohexanone oxime in the cyclohexanone oxime alcohol solution to the vaporization of gaseous cyclohexanone oxime to the leaving of the vaporizer.

[0034] The average residence time (τ) of cyclohexanone oxime is defined as the effective volume V of the vaporizer. R The ratio of the characteristic volume flow rate V0 of cyclohexanone oxime. The effective volume of the vaporizer refers to the actual volume available for the vaporized raw material to pass through, in liters; the characteristic volume flow rate V0 of cyclohexanone oxime refers to the volume flow rate at a certain feed temperature and pressure, in liters / second.

[0035] According to the present invention, the average residence time of cyclohexanone oxime can be controlled by adjusting the effective volume of the vaporizer and / or the characteristic volume flow rate of cyclohexanone oxime, and those skilled in the art can make a selection according to actual conditions, as long as the average residence time of cyclohexanone oxime is within the above range. The control method of the effective volume of the vaporizer and / or the characteristic volume flow rate of cyclohexanone oxime is well known to those skilled in the art.

[0036] According to some preferred embodiments of the present invention, the average residence time of cyclohexanone oxime is 0.1-1 s. Controlling the average residence time of cyclohexanone oxime within the above preferred range is beneficial to the stability of cyclohexanone oxime and further reduces the coking of oxime.

[0037] In the present invention, preferably, the atomization is pressure atomization, and a certain pressure is utilized to atomize the alcohol solution of cyclohexanone oxime. The spray vaporization of cyclohexanone oxime of the prior art, such as the method disclosed in CN102755860A generally adopts the mode of medium atomization to atomize, it is necessary to rely on the atomizing medium of a certain pressure to form a high-speed airflow, so that a very high relative speed is formed between the two phases to achieve the purpose of atomization, but because the gas atomizing nozzle has a longer spray distance under the action of gas, the cyclohexanone oxime droplets that are not vaporized in time are brought into the reactor by the high-speed airflow so as to easily coke. In the present invention, it is not necessary to introduce the gas phase atomization medium.

[0038] According to some preferred embodiments of the present invention, the atomization pressure is less than 3 MPa, preferably not higher than 2 MPa, and more preferably 0.1-2 MPa.

[0039] According to the present invention, preferably, the vaporization temperature is 150-250° C., preferably 160-200° C. Controlling the vaporization temperature within the above range is beneficial to further avoid dimerization, polymerization, ring opening and carbon deposition and coking of cyclohexanone oxime.

[0040] In the present invention, an alcohol solution of cyclohexanone oxime is used as the oxime supply system. The inventors of the present invention have found in their research that if there is no alcohol solvent, the oxime is prone to undergo polymerization and decomposition in the spray gun, which increases the consumption of oxime and reduces the vaporization efficiency.

[0041] In a further preferred embodiment, in the alcohol solution of cyclohexanone oxime, the mass ratio of cyclohexanone oxime to alcohol is (15-60): (40-85), for example, it can be 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40 and other typical but non-limiting ratios or ranges therebetween. Preferably, the mass ratio of cyclohexanone oxime to alcohol is (35-50): (50-65). Within the above preferred composition range, it is beneficial to further improve the vaporization rate of cyclohexanone oxime, reduce the residence time, and avoid the dimerization, polymerization, ring opening and carbon deposition and coking of cyclohexanone oxime.

[0042] Preferably, the alcohol is a C1-C5 low-carbon alcohol, preferably methanol and / or ethanol, more preferably ethanol.

[0043] According to the present invention, the alcohol solution of cyclohexanone oxime is first atomized and then rapidly contacted with a high temperature carrier gas to achieve rapid vaporization of cyclohexanone oxime. Preferably, the temperature of the high temperature carrier gas is 200-500°C, preferably 300-500°C.

[0044] The present invention has a wide range of selection for the amount of the high-temperature carrier gas, which can be selected according to actual needs. Preferably, the molar ratio of the high-temperature carrier gas to the alcohol solution of cyclohexanone oxime is not less than 0.2:1, for example, it can be 0.2-70:1, wherein the molar amount of the alcohol solution of cyclohexanone oxime is calculated based on cyclohexanone oxime.

[0045] In the present invention, on the one hand, the high-temperature carrier gas is used to reduce the partial pressure of oxime vaporization to meet the vaporization requirements. On the other hand, the carrier gas required for heat transfer of the subsequent cyclohexanone oxime gas-phase Beckmann rearrangement reaction can also be introduced from the vaporizer (or can be introduced separately in the subsequent reactor). In some embodiments of the present invention, when used in conjunction with a fixed bed reactor or a moving bed reactor, in order to meet the vaporization requirements and the heat transfer requirements of the fixed bed or moving bed reaction, the amount of the high-temperature carrier gas is relatively high. Preferably, the molar ratio of the high-temperature carrier gas to the alcohol solution of cyclohexanone oxime is 20-70:1, wherein the molar amount of the alcohol solution of cyclohexanone oxime is calculated based on cyclohexanone oxime.

[0046] In other embodiments of the present invention, when used in conjunction with a fluidized bed reactor, the molar ratio of the high-temperature carrier gas to the alcohol solution of cyclohexanone oxime is 0.2-2:1, wherein the molar amount of the alcohol solution of cyclohexanone oxime is calculated based on cyclohexanone oxime.

[0047] In the above preferred embodiment, the vaporization method provided by the present invention adopts different nitrogen / cyclohexanone oxime molar ratios based on different reactors and process forms, which not only ensures the vaporization effect but also helps to improve the subsequent reaction effects of different reaction processes.

[0048] According to some preferred embodiments of the present invention, the molar ratio of the high temperature carrier gas to the alcohol solution of cyclohexanone oxime is 0.2-2:1, wherein the molar amount of the alcohol solution of cyclohexanone oxime is calculated based on cyclohexanone oxime. In the above case, the need for cyclohexanone oxime vaporization can be met, and compared with the prior art, the nitrogen / oxime molar ratio actually required for cyclohexanone oxime vaporization is greatly reduced, which is conducive to reducing energy consumption.

[0049] Preferably, the high temperature carrier gas is provided by an inert gas, preferably nitrogen.

[0050] According to some preferred embodiments of the present invention, the vaporization method is carried out in a vaporization device, and the vaporization device comprises a vaporization raw material inlet 1 for feeding the alcohol solution of cyclohexanone oxime into the vaporization device; and

[0051] A nozzle system for atomizing the alcohol solution of cyclohexanone oxime, wherein the nozzle system comprises a spray gun and a nozzle 3, wherein the nozzle 3 is provided with at least one nozzle, preferably 1 to 4 nozzles, and the outlet atomized droplets of any two nozzles do not cross; and

[0052] A high temperature carrier gas inlet 2, used to deliver the high temperature carrier gas into the vaporization device to contact with the atomized droplets sprayed from the nozzle of the nozzle system; and

[0053] A gas dispersion layer 4, used to disperse the vaporized product;

[0054] Preferably, the vaporized raw material inlet 1 is provided with a filter.

[0055] The alcohol solution of cyclohexanone oxime is fed into the nozzle system through the vaporization raw material inlet 1 for atomization, and the high-temperature carrier gas is fed into the vaporization device through the high-temperature carrier gas inlet 2, and then contacts with the atomized droplets, and the vaporized raw material is dispersed through the gas dispersion layer.

[0056] In the present invention, it can be understood that the atomized droplets sprayed from the nozzle are cone-shaped as a whole, and are composed of many small droplets suspended in the surrounding air or moving in it. The "atomized droplets at the outlets of any two nozzles do not intersect" means that the distribution space of the atomized droplets sprayed from any two nozzles does not intersect, so as to avoid collision of the atomized droplets before vaporization and cause coking.

[0057] Preferably, the vaporization raw material inlet 1 is provided with a filter, and the alcohol solution of cyclohexanone oxime passes through the vaporization raw material inlet 1 and enters the nozzle system after being filtered by the filter, which is beneficial to avoid clogging the nozzle. Preferably, the pore size of the filter is 200-500 mesh.

[0058] According to the present invention, preferably, the nozzle hole diameter is 0.02-0.7 mm, preferably 0.1-0.3 mm.

[0059] According to the present invention, preferably, the atomization cone angle of the nozzle is greater than 45°, preferably 50-65°. In the present invention, "atomization cone angle" refers to the angle between two tangent lines from the nozzle outlet to the outer envelope of the spray torch. Controlling the atomization cone angle within the above preferred range is beneficial to maximizing the spray area and spray volume.

[0060] In order to increase the vaporization rate, the spray distance of the nozzle should not be too long. Preferably, the spray distance of the nozzle is 200-600 mm, preferably 300-500 mm. The spray distance refers to the virtual spray distance of the nozzle.

[0061] In the present invention, the gas dispersion layer is used to disperse the vaporized cyclohexanone oxime raw material and dissipate heat. Conventional inert fillers such as glass balls can be used to form the gas dispersion layer. In a preferred case, the gas dispersion layer is a metal mesh or a metal filler layer. The metal filler layer can be composed of conventional metal fillers in the art, such as metal θ rings. The material of the metal mesh or metal filler can be a stainless steel alloy, such as 316L.

[0062] According to some preferred embodiments of the present invention, the gas dispersion layer is a metal mesh. The above preferred embodiments are advantageous for further improving the oxime vaporization effect and reducing the carbon deposition rate of the ejected oxime.

[0063] According to some preferred embodiments of the present invention, the pore size of the metal mesh is 2-8 mm.

[0064] The present invention has no specific limitation on the thickness of the gas dispersion layer, etc., and can be adjusted according to the effective volume of the corresponding vaporizer, as long as the required range of the average residence time of cyclohexanone oxime is met.

[0065] According to some particularly preferred embodiments of the present invention, the vaporization method of cyclohexanone oxime is carried out in a vaporization device, which includes a nozzle system, a gas dispersion layer, a vaporization raw material inlet and a high-temperature carrier gas inlet; the nozzle system includes a spray gun and a nozzle; preferably, the nozzle hole diameter is 0.02-0.5mm; the atomization cone angle of the nozzle is greater than 45°; the method comprises: introducing an alcohol solution of cyclohexanone oxime into the nozzle system through the vaporization raw material inlet, atomizing through the nozzle to form atomized droplets; introducing the high-temperature carrier gas into the vaporization device through the high-temperature carrier gas inlet, causing the atomized droplets to contact with the high-temperature carrier gas for vaporization, and then dispersing through the gas dispersion layer; wherein the average particle size of the atomized droplets is 40-70μm, and the average residence time of cyclohexanone oxime is 0.1-1s.

[0066] The second aspect of the present invention provides application of the above-mentioned cyclohexanone oxime vaporization method in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime.

[0067] The above-mentioned vaporization method is applied in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime in the following manner: it is used to provide the cyclohexanone oxime raw material required for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime.

[0068] The contents of cyclohexanone and octahydrophenazine in the cyclohexanone oxime vaporized by the above-mentioned vaporization method are extremely low. When the above-mentioned raw materials are used in the gas-phase Beckmann rearrangement reaction, it is directly reflected in the extremely low contents of cyclohexanone and octahydrophenazine in the gas-phase rearrangement product, thereby indicating that the loss of the cyclohexanone oxime raw material during the vaporization process is small and the utilization rate is high.

[0069] In some specific embodiments of the present invention, the vaporization device can be integrated with a cyclohexanone oxime gas-phase Beckmann rearrangement reactor for cyclohexanone oxime gas-phase Beckmann rearrangement reaction, for example Figure 1 The integrated vaporization reaction device shown. The integrated vaporization reaction device includes a vaporization raw material inlet 1, a high-temperature carrier gas inlet 2, a nozzle 3, a gas dispersion layer 4, a vaporizer barrel 5; a reactant outlet 6, a catalyst bed 7 and a porcelain ball layer 8. After the high-temperature carrier gas enters the vaporization device through the high-temperature carrier gas inlet 2, it contacts with the atomized droplets at the nozzle 3 and vaporizes; after the vaporized raw material is distributed through the gas dispersion layer 4, it passes through the upper porcelain ball layer of the catalyst and enters the catalyst bed 7 for reaction, and the gaseous product after the reaction leaves the first reactor through the bottom outlet. For the integrated vaporization reaction device, the effective volume of the vaporizer refers to the actual volume between the nozzle and the catalyst bed that can be used for the vaporized raw material to pass through.

[0070] In other specific embodiments of the present invention, the vaporization device can be applied to a fluidized bed reaction system for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, which is conducive to achieving the goal of large-scale industrialization. The fluidized bed reaction system includes a raw material tank, a vaporization device, a preheater, a fluidized bed reactor and a condensing device arranged in sequence along the logistics direction. The fluidized bed reaction system can also include a raw material pump, a high-temperature carrier gas storage tank and a flow meter. The alcohol solution of cyclohexanone oxime is extracted from the raw material tank by the raw material pump, sent to the vaporization device, atomized by the nozzle, and atomized droplets are obtained; at the same time, the high-temperature carrier gas enters the vaporization device through the flow meter and contacts the atomized droplets; the vaporized raw material is sent to the preheater for preheating, and then sent to the fluidized bed reaction system for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime; the reaction product is sent to the condensing device.

[0071] A third aspect of the present invention provides a method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the method comprising:

[0072] (1) vaporizing cyclohexanone oxime using the vaporization method of cyclohexanone oxime described in the first aspect to obtain a vaporized raw material;

[0073] (2) preheating the vaporized raw material and then contacting it with a catalyst to perform a gas-phase Beckmann rearrangement reaction;

[0074] (3) removing heavy components from the gas-phase Beckmann rearrangement reaction product, and then recovering the solvent and carrier gas;

[0075] (4) The recovered solvent and carrier gas are used to provide alcohol and high-temperature carrier gas in the vaporization of cyclohexanone oxime in step (1).

[0076] According to some preferred embodiments of the present invention, the preheating temperature is 200-300°C, preferably 220-260°C.

[0077] According to the present invention, the alcohol solvent and carrier gas in the gas-phase Beckmann rearrangement reaction product are recovered to provide alcohol and high-temperature carrier gas in the vaporization of cyclohexanone oxime in step (1). By adopting the above embodiment, about 90% of the alcohol solvent and carrier gas can be directly recycled, which can greatly improve the economic efficiency of the cyclohexanone oxime gas-phase Beckmann rearrangement process and reduce the raw material cost.

[0078] The present invention has no particular restrictions on the reaction conditions in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, and the conventional operating conditions and methods in the art can be used. The present invention also has no particular restrictions on the catalyst used in the cyclohexanone oxime gas-phase Beckmann rearrangement reaction, and any catalyst known in the art that can be used for the gas-phase Beckmann rearrangement reaction can be applied to the present invention.

[0079] Preferably, the gas-phase Beckmann rearrangement reaction in step (2) is carried out in a fluidized bed reaction system. The fluidized bed reaction system comprises at least one fluidized bed reactor. Preferably, in order to improve the conversion rate of cyclohexanone oxime, the fluidized bed reaction system comprises a fluidized bed reactor and a fixed bed reactor.

[0080] Preferably, the conditions of the gas-phase Beckmann rearrangement reaction include: a reaction temperature of 350-400°C, preferably 370-390°C; a pressure of 0.1-0.5 MPa, preferably 0.2-0.3 MPa; a mass space velocity of cyclohexanone oxime of 2-8 h -1 , preferably 4-6h -1 .

[0081] The present invention has no restrictions on the method and equipment for removing heavy components, and can be existing methods and equipment in the art, as long as the corresponding purpose can be achieved; for example, the equipment can use a deweighting tower. The present invention has no restrictions on the conditions of the deweighting tower, as long as it is conducive to removing heavy components; preferably, the conditions of the deweighting tower include: the tower top temperature is 208-209°C, the tower bottom temperature is 210-212°C, and the tower top pressure is 75-78kPa.

[0082] The present invention has no specific restrictions on the method and equipment for recovering the solvent and carrier gas, as long as the corresponding purpose can be achieved. For example, a gas recovery tower can be used to recover the alcohol solvent and carrier gas, and the stream containing the solvent and carrier gas flowing out of the top of the gas recovery tower is recovered by a circulation compressor to provide at least part of the alcohol and high-temperature carrier gas in the vaporization of cyclohexanone oxime in step (1).

[0083] Preferably, the conditions of the gas recovery tower include: a tower top temperature of 50-55°C, a tower bottom temperature of 130-140°C, and a vacuum degree of 64-65 kPa.

[0084] In this process, up to 90% of the solvent can be recovered, and the remaining 10% of the alcohol solvent can be separated into gas and liquid by rapid cooling and other methods to recover the liquid phase solvent, while impurities such as ammonia and trimethylamine can be removed. The final exhaust gas is treated by a biological sewage pool device and an incineration device.

[0085] By adopting the above-mentioned preferred embodiment, on the one hand, the direct discharge of alcohol solvent can be avoided and the emission of wastewater and waste gas can be greatly reduced. On the other hand, the solvent and carrier gas can be efficiently recovered and utilized. At the same time, the logistics flowing out from the top of the recovery tower has a certain temperature, which is beneficial to reduce the vaporization energy consumption and improve the economy of the cyclohexanone oxime gas-phase Beckmann rearrangement process.

[0086] According to some preferred embodiments of the present invention, the method further comprises: regenerating the catalyst after the reaction in step (2). The present invention has no particular limitation on the specific manner and conditions of the regeneration, and conventional regeneration methods in the art can be applied to the present invention.

[0087] The present invention will be described in detail below through examples.

[0088] The catalyst for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime used in the following examples is the microsphere molecular sieve catalyst prepared in Example 1 of CN109718826A.

[0089] Example 1 (fixed bed process)

[0090] The vaporization method is as follows Figure 1 The integrated vaporization reaction device shown is carried out, and the integrated vaporization reaction device includes a vaporization raw material inlet 1, a high-temperature carrier gas inlet 2, a nozzle 3, a gas dispersion layer 4, a vaporizer barrel 5; a reactant outlet 6, a catalyst bed 7, and a packing layer 8, wherein the packing is a ceramic ball.

[0091] After the high-temperature carrier gas enters the vaporization device through the high-temperature carrier gas inlet 2, it contacts and vaporizes the atomized droplets at the nozzle 3; the vaporized raw material is distributed through the gas dispersion layer 4, wherein the gas dispersion layer is a metal mesh (316L material) with a pore size of 4.75 mm.

[0092] The nozzle 3 is provided with a nozzle, the nozzle orifice diameter is 0.3 mm, the atomization cone angle is 52°, and the spray distance is 380 mm.

[0093] The vaporized raw material used is an ethanol solution of cyclohexanone oxime, wherein the mass ratio of cyclohexanone oxime to ethanol is 45:55; the high-temperature carrier gas used is nitrogen at 440-480°C (an independent electric heater is used to heat the circulating nitrogen), the nitrogen / oxime molar ratio is 60, and the oxime feed rate is 50kg / h. The raw material is vaporized according to the conditions in Table 1. After the vaporized raw material is distributed through the gas dispersion layer 4, it passes through the upper ceramic ball layer of the catalyst and enters the catalyst bed layer 7 for reaction. The mass space velocity of cyclohexanone oxime is 0.5-0.7h -1 , the reaction pressure is 0.15MPa, and the catalyst bed reaction temperature is 390-410℃.

[0094] The gaseous products after the reaction were collected through the bottom outlet. After 500 hours of reaction, the product composition was analyzed and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097] Example 2 (Fluidized Bed Process)

[0098] The reaction is carried out in a fluidized bed reaction system, which includes a raw material tank, a vaporizer, a preheater, a fluidized bed reactor, and a condensing device arranged in sequence along the direction of the flow. The fluidized bed reaction system may also include a raw material pump, a high-temperature carrier gas storage tank, and a flow meter. The fluidized bed reactor is manufactured by Beijing Weikendu Technology Co., Ltd. The vertical 316L stainless steel reactor has an inner diameter of 80 mm and a length of 630 mm, and a settling section with an inner diameter of 150 mm and a length of 300 mm.

[0099] The vaporization device includes a nozzle system, a gas dispersion layer, a vaporization raw material inlet and a high-temperature carrier gas inlet; the nozzle system is arranged at the top of the vaporization device, and the nozzle system includes a spray gun and a nozzle, an axial nozzle is arranged in the axial direction of the nozzle, the nozzle direction is downward, the nozzle hole diameter is 0.45mm, the injection cone angle of the axial nozzle is 58°, and the injection distance is 340mm. The vaporized raw material is distributed through the gas dispersion layer, wherein the gas dispersion layer is a metal mesh (316L material) with a pore size of 4.75mm.

[0100] The vaporization raw material used is an ethanol solution of cyclohexanone oxime, wherein the mass ratio of cyclohexanone oxime to ethanol is 35:65; the high-temperature carrier gas used is nitrogen at ~300°C, the nitrogen / oxime molar ratio is ~2, and the feed amount of oxime is ~1kg / h. The raw material is vaporized according to the conditions in Table 1, the alcohol solution of cyclohexanone oxime is pumped out from the raw material tank by a raw material pump, sent to the vaporization device, atomized by a nozzle, and atomized droplets are obtained; at the same time, the high-temperature carrier gas enters the vaporization device through the flowmeter and contacts the atomized droplets; the vaporized raw material passes through the gas dispersion layer and is sent out of the vaporization device, sent to the preheater to be preheated to 270°C, and then sent to the fluidized bed reactor for cyclohexanone oxime gas-phase Beckmann rearrangement reaction; the pipeline is kept at 200°C, and the MHSV of cyclohexanone oxime is 4.2h -1 The reaction temperature of the fluidized bed reactor is 396°C and the reaction pressure is 0.15MPa.

[0101] The reaction product was collected after being cooled by a condensation device. After reacting for 48 hours, the composition was analyzed as shown in Table 1.

[0102] Table 2

[0103]

[0104] Example 3 (fixed bed process)

[0105] The method of Example 1 was followed, except that the mass ratio of cyclohexanone oxime to ethanol was 15:85, and the nitrogen / oxime molar ratio was 0.5. The vaporization conditions were as shown in Table 3. After 200 hours of reaction, the product composition was analyzed, and the results were as shown in Table 3.

[0106] Table 3

[0107]

[0108] Example 4 (fixed bed process)

[0109] The method of Example 1 was followed, except that the volume of the vaporizer was increased by 50%, glass balls with a diameter of 3-5 mm were used to replace the metal mesh, and the filling volume of the glass balls accounted for half of the volume of the vaporizer. The vaporization conditions are shown in Table 4. After the reaction was continued for 100 hours, the composition of the product was analyzed, and the results are shown in Table 4.

[0110] Table 4

[0111]

[0112] Comparative Example 1 (fixed bed process)

[0113] The method of Example 2 is followed, except that a fixed bed is used instead of a fluidized bed, and a shell and tube heat exchanger is used as a cyclohexanone oxime vaporizer, and cyclohexanone oxime is vaporized by heat exchange between the reactor products of the tube side and the shell side.

[0114] The mass space velocity of cyclohexanone oxime is 1h -1 , the cyclohexanone oxime feed rate is 75kg / h, the alcohol oxime mass ratio is 1.8, the nitrogen oxime molar ratio is 46, and the catalyst bed reaction temperature is 350-390℃.

[0115] The reaction system was operated for a total of 58 hours after the oxime was introduced. Since the raw material preheater could not fully vaporize the cyclohexanone oxime-methanol solution, cyclohexanone oxime was seriously coked and deposited under high temperature conditions, which increased the system resistance and forced the test to be interrupted. After the test was stopped, the reactor was inspected and it was found that coke was generated at the inlet of the fixed bed reactor and the catalyst was deactivated in large quantities. Based on the above results, it is believed that the insufficient heat supply required for vaporization and the slow vaporization rate are the main reasons for the poor vaporization effect of cyclohexanone oxime.

[0116] Analysis of the product composition showed that the cyclohexanone oxime conversion rate was 99.8 mol %, the caprolactam selectivity was 92.5 mol %, the cyclohexanone content was about 1.9 mol %, and the octahydrophenazine content was 0.3 mol %.

[0117] Comparative Example 2 (fixed bed process)

[0118] The method of Comparative Example 1 is followed, except that a steam heating sleeve is installed in front of the fixed bed reactor as a vaporizer, and the steam heating sleeve is 26 m long and 25 mm in diameter.

[0119] The operation cycle of the industrial side-line device was increased to 13 days, and the vaporization temperature of methanol oxime was finally reduced from 163°C in the early stage of operation to 155°C. Through the analysis of the reaction products, the cyclohexanone oxime conversion rate can be maintained at about 99.5 mol%, the caprolactam selectivity reaches 95.5 mol%, the cyclohexanone content is 0.25-0.5 mol%, and the octahydrophenazine is 0.18-0.28 mol%. As the reaction time increases, the cyclohexanone and octahydrophenazine increase rapidly. After the device was shut down, it was found that although the installation of the sleeve preheater improved the phenomenon of insufficient vaporization capacity of the preheater, there was still a slight coking phenomenon on the vaporizer tube wall, and with the appearance of coking on the tube wall, the vaporization effect of the vaporizer continued to decline.

[0120] Comparative Example 3 (Fixed Bed Process)

[0121] The method of Example 2 is different in that a fixed bed is used instead of a fluidized bed, and the vaporization device of Example 1 in CN102755860A is used for vaporization. Cyclohexanone oxime is introduced into the vaporization device through the liquid feed port, the feed rate is 100 Kg / h, the feed temperature is 120°C, and the feed pressure is 0.4 MPa. The liquid phase feed is first mixed with the mixed gas nitrogen and then introduced into the atomizing spray gun through the liquid feed port. The mixed nitrogen feed rate is 5 Nm 3 / h, the feed pressure is 0.4MPa. The atomizing medium nitrogen is introduced from the gas feed port of the atomizing spray gun, with a flow rate of 37Nm 3 / h, the pressure is 0.25MPa (absolute pressure), and the mixed fluid enters the atomizing gun cavity. Under the action of nitrogen atomizing medium, cyclohexanone oxime is quickly atomized into small droplets. High-temperature nitrogen is introduced through the high-temperature gas inlet and introduced into the vaporization device through the high-temperature gas distributor. The nitrogen flow rate is 2092kg / h. The cyclohexanone oxime droplets contact with 430℃ high-temperature nitrogen and vaporize instantly. The high-temperature nitrogen flow rate is 1046kg / h, and the temperature after vaporization is 350℃. The vaporized cyclohexanone oxime gas is led out of the vaporization device through the gas phase material outlet and enters the fixed bed reactor.

[0122] The reaction conditions of the fixed bed reactor were the same as those in Example 2. After 144 hours of reaction, the product composition was analyzed, with a cyclohexanone oxime conversion of 99.90 mol%, a caprolactam selectivity of 94.62 mol%, a cyclohexanone content of 0.64%, and an octahydrophenazine content of 0.42%.

[0123] Comparative Example 4 (Fluidized Bed Process)

[0124] The cyclohexanone oxime was evaporated according to the falling film evaporation method of Example 1 in CN1379021A (space velocity 4h -1, operation time 60 days), the decomposition rate of cyclohexanone oxime was 0.12%. Then the evaporated cyclohexanone oxime raw material was sent to a fluidized bed reactor, and a gas phase Beckmann rearrangement reaction was carried out according to the method of Example 2. After 60 days of reaction, the product composition was analyzed, and the cyclohexanone oxime conversion rate was 99.5mol%, the caprolactam selectivity was 95mol%, and the cyclohexanone content was 1mol%.

[0125] The following test example is used to illustrate the method of the gas phase Beckmann rearrangement reaction of cyclohexanone oxime:

[0126] The schematic diagram of the process flow of the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime is as follows: Figure 2 shown.

[0127] Cyclohexanone oxime was vaporized in an oxime vaporizer according to the method in Example 2, and the obtained vaporized raw material was sent to a preheater, and after being preheated at 250°C, it was sent to a fluidized bed system to contact with a catalyst for a gas-phase Beckmann rearrangement reaction; the conditions of the gas-phase Beckmann rearrangement reaction were the same as those in Example 2. The gas-phase Beckmann rearrangement reaction product was subjected to a heavy component removal treatment, and then the light component material flow from the top of the heavy component removal tower was sent to a gas recovery tower. The tower top temperature was 52°C, the tower bottom temperature was 134°C, and the vacuum degree was 64.66 kPa.

[0128] The ethanol gas flow flowing out of the gas recovery tower top is recycled by a circulating compressor (150°C, 166.65kPa) to recover 90% of the ethanol gas and nitrogen for recycling, and the remaining 10% is diverted for further separation and quenching for gas-liquid separation, and the ethanol liquid is recovered, and ammonia and trimethylamine are removed (the conditions for removing ammonia are 15°C, 160kPa, the tower top temperature for removing trimethylamine is 83.3°C, the tower bottom temperature is 88.6°C, and the vacuum degree is 101.32kPa). The final exhaust gas is treated in a biological sewage pool device and an incineration device. The recovered liquid ethanol returns to the vaporization step, is mixed with cyclohexanone oxime, and vaporized.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for vaporizing cyclohexanone oxime, characterized in that: The method comprises: atomizing an alcohol solution of cyclohexanone oxime to form atomized liquid droplets, and then contacting with a high-temperature carrier gas to vaporize; The average particle size of the atomized droplets is less than 80 μm, and the average residence time of cyclohexanone oxime is no more than 2 seconds.

2. The method according to claim 1, wherein: The average particle size of the atomized droplets is 30-70 μm; Preferably, the average residence time of cyclohexanone oxime is 0.1-1 s.

3. The method according to claim 1 or 2, wherein: The alcohol solution of cyclohexanone oxime is atomized in a top-down direction; Preferably, the atomization is pressure atomization, and the atomization pressure is less than 3MPa, preferably 0.1-2MPa; Preferably, the vaporization temperature is 150-250°C, preferably 160-200°C.

4. The method according to any one of claims 1 to 3, wherein: In the alcohol solution of cyclohexanone oxime, the mass ratio of cyclohexanone oxime to alcohol is (15-60):(40-85), preferably (35-55):(45-65); Preferably, the alcohol is a C1-C5 low-carbon alcohol, preferably methanol and / or ethanol, more preferably ethanol.

5. The method according to any one of claims 1 to 4, wherein: The temperature of the high temperature carrier gas is 200-500°C, preferably 300-500°C; Preferably, the molar ratio of the high temperature carrier gas to the alcohol solution of cyclohexanone oxime is not less than 0.5:1, preferably (0.5-2):1, wherein the molar amount of the alcohol solution of cyclohexanone oxime is calculated based on cyclohexanone oxime; Preferably, the high temperature carrier gas is provided by an inert gas, preferably nitrogen.

6. The method according to any one of claims 1 to 5, wherein: The vaporization method is carried out in a vaporization device, which comprises a vaporization raw material inlet (1) for feeding the alcohol solution of cyclohexanone oxime into the vaporization device; and A nozzle system for atomizing the alcohol solution of cyclohexanone oxime, the nozzle system comprising a spray gun and a nozzle (3), the nozzle (3) being provided with at least one nozzle, preferably 1 to 4 nozzles, and the outlet atomized droplets of any two nozzles do not cross; as well as A high temperature carrier gas inlet (2) is used to deliver the high temperature carrier gas into the vaporization device to contact with the atomized liquid droplets sprayed by the nozzle of the nozzle system; as well as A gas dispersion layer (4), used to disperse the vaporized product; Preferably, the vaporized raw material inlet (1) is provided with a filter.

7. The method according to claim 6, wherein: The nozzle orifice diameter is 0.02-0.5 mm; the atomization cone angle of the nozzle is greater than 45°, preferably 50-65°; Preferably, the spraying distance of the nozzle is 300-600 mm.

8. The method according to claim 6 or 7, wherein: The gas dispersion layer is a metal mesh or a metal filler layer, preferably a metal mesh; Preferably, the pore size of the metal mesh is 2-8 mm.

9. Use of the cyclohexanone oxime vaporization method according to any one of claims 1 to 8 in the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime.

10. A method for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, the method comprising: (1) vaporizing cyclohexanone oxime using the method for vaporizing cyclohexanone oxime according to any one of claims 1 to 8 to obtain a vaporized raw material; (2) preheating the vaporized raw material and then contacting it with a catalyst to perform a gas-phase Beckmann rearrangement reaction; (3) removing heavy components from the gas-phase Beckmann rearrangement reaction product, and then recovering the solvent and carrier gas; (4) The recovered solvent and carrier gas are recycled to the vaporization process of cyclohexanone oxime in step (1).

11. The method according to claim 10, wherein: The preheating temperature is 200-300°C, preferably 220-260°C; Preferably, the gas-phase Beckmann rearrangement reaction in step (2) is carried out in a fluidized bed reaction system; Preferably, the conditions of the gas phase Beckmann rearrangement reaction include: reaction temperature of 350-400°C, pressure of 0.1-0.5 MPa, mass space velocity of cyclohexanone oxime of 2-8 h -1 .

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