Method for producing high-purity cyclohexanone oxime and built-in membrane two-stage ammoximation reaction system

Abstract

The present application relates to the technical field of caprolactam preparation, and particularly discloses a method for producing high-purity cyclohexanone oxime and an internal membrane two-stage ammonoxidation reaction system. The cyclohexanone, hydrogen peroxide and ammonia are introduced into a first reactor containing methylene-modified TS-1 molecular sieve, and a first-stage ammonoxidation reaction is carried out at 90-120 DEG C. After 1-5 min, the obtained first-stage reaction liquid is sent into a second reactor, and a second-stage ammonoxidation reaction is carried out at 70-88 DEG C. After solid-liquid separation, a mixed clear liquid containing cyclohexanone oxime and water is obtained. The mixed clear liquid is extracted with toluene, and the extract is subjected to rectification to obtain cyclohexanone oxime. The two-stage differential ammonoxidation reaction is adopted, the first-stage reaction is carried out at high temperature and fast, and the second-stage reaction is carried out at low temperature and mature, and the reaction efficiency is improved by using a specific ammonoxidation catalyst, so that the cyclohexanone oxime is efficiently prepared. The internal membrane separation catalyst is used, so that the catalyst can be completely recovered.

Description

Technical Field

[0001] This invention relates to the field of caprolactam preparation technology, and in particular to a method for producing high-purity cyclohexanone oxime and a two-stage ammonification reaction system with an internal membrane. Background Technology

[0002] Caprolactam is a basic chemical raw material widely used in military technology, textiles, and other fields, such as automotive parts, electronic and electrical housings, and mechanical gears. Currently, the main production process for caprolactam is the homogeneous ammonoxime process (its flow chart can be found in [reference needed]). Figure 1 This technology has matured over many years, resulting in stable and reliable product quality. However, the ammoniation reaction stage requires the addition of tert-butanol as a co-solvent to increase the solubility of the reactants and stabilize the intermediate hydroxylamine, while also protecting the catalyst (such as the titanium-silicon molecular sieve TS-1). After the ammoniation reaction, an external filtration system is needed to recover the catalyst, followed by distillation to recover the tert-butanol. This process involves a long external catalyst recovery system, and the filtration system is prone to clogging, affecting the system's stable operation. Furthermore, tert-butanol recovery consumes a large amount of steam, resulting in extremely high energy costs. After tert-butanol recovery, the remaining mixed solution containing cyclohexanone oxime and water needs to be extracted with toluene to form a toluene solution containing cyclohexanone oxime (i.e., toluene oxime). After washing with water and toluene recovery, relatively pure cyclohexanone oxime is obtained. Since toluene carries away most of the by-product impurities, after toluene is recycled to a certain stage, the by-product impurities can be removed through purification to ensure the purity of cyclohexanone oxime. The purity of cyclohexanone oxime directly affects the quality of the final product, caprolactam.

[0003] With the advancement of domestic catalyst research and production technology in recent years, a new aqueous ammonium oxime catalyst—Ti-MWW (titanium silicate molecular sieve)—has emerged, exhibiting superior hydrophilicity, alkali resistance, and reactivity. Based on this catalyst, a heterogeneous ammonium oxime production technology without tert-butanol has been developed. In this technology, tert-butanol is no longer added as a co-solvent during the reaction stage. The organic and aqueous phases are strongly mixed through stirring during the reaction. After the ammonium oxime reaction, an external filtration system is used to recover the catalyst. However, due to the poor miscibility of cyclohexanone oxime with water, and the small particle size and high hydrophilicity of the added Ti-MWW catalyst, filtration is challenging, leading to more frequent clogging and cleaning of the filtration system. The resulting mixed solution containing cyclohexanone oxime and water after filtration is extracted with cyclohexane. The remaining aqueous phase is partially returned to the reactor and partially stripped as wastewater. The resulting cyclohexane solution containing cyclohexanone oxime (i.e., cyclohexane oxime) is washed with water and coalesced before being directly fed into the rearrangement process. Under the action of fuming sulfuric acid catalyst, cyclohexanone oxime reacts to produce a crude caprolactam sulfate solution, which is then separated and purified to obtain caprolactam. Cyclohexane is recovered using the heat of the rearrangement reaction, but the recovered cyclohexane contains a small amount of sulfur trioxide, requiring neutralization with alkali before recycling. Currently, there is no effective treatment for the byproduct organic impurities generated during the ammonoximation reaction, and the resulting rearrangement reaction solution is dark in color, making it difficult to obtain high-quality caprolactam even after separation and purification.

[0004] Currently, both traditional homogeneous and heterogeneous ammonium oxime technologies conduct the entire reaction in a single reactor, and the reaction temperature has a significant impact on the ammonium oxime reaction. Above 90°C, the reaction is rapid, but byproducts also increase accordingly, resulting in poor selectivity; below 80°C, there are fewer byproducts, but the conversion rate is lower. Furthermore, both of these production technologies employ external filtration systems to filter the catalyst. These systems are complex and cumbersome, prone to clogging during operation, and require frequent backflushing or switching to a backup system. Therefore, there is an urgent need to develop a method for preparing high-purity cyclohexanone oxime to improve the quality of subsequent caprolactam while avoiding the use of tert-butanol and reducing production costs. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for producing high-purity cyclohexanone oxime and a two-stage ammoniation reaction system with an embedded membrane. The method employs a two-stage differentiated ammoniation reaction: a high-temperature, rapid reaction in the first stage and a low-temperature aging reaction in the second stage. By combining a specific ammoniation catalyst to improve reaction efficiency, high-purity and efficient preparation of cyclohexanone oxime is achieved.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for producing high-purity cyclohexanone oxime, comprising the following steps: S1. Cyclohexanone, hydrogen peroxide and ammonia are introduced into the first reactor containing methylene-modified TS-1 molecular sieve, and a primary ammonium oxime reaction is carried out at 90℃~120℃. After 1min~5min, the primary reaction solution is obtained. S2. The first-stage reaction solution is fed into the second reactor and subjected to a second-stage ammonium oxime reaction at 70℃~88℃. Solid-liquid separation is performed to obtain a mixed clear liquid containing cyclohexanone oxime and water. S3. Extract the mixed clear liquid with toluene, and distill the extract to obtain cyclohexanone oxime.

[0007] Compared to existing technologies, the method for producing high-purity cyclohexanone oxime provided by this invention employs a two-stage differentiated ammoniation reaction. A high-temperature, rapid first-stage ammoniation reaction achieves a conversion rate of 75%–95%; the remaining reaction process is completed through a low-temperature, aging second-stage ammoniation reaction, achieving a conversion rate of over 99.9%. This invention uses a methylene-modified TS-1 molecular sieve as a catalyst. Introducing the methylene organic structure into the molecular sieve enhances its organophilic ability, promotes the adsorption of cyclohexanone onto the molecular sieve catalyst during the ammoniation reaction, increases heterogeneous reaction activity, improves conversion rate and selectivity, reduces catalyst usage, and extends the catalyst's lifespan during the cyclohexanone ammoniation process.

[0008] Preferably, in S1, the preparation method of the methylene-modified TS-1 molecular sieve includes the following steps: Step a: Mix bis(triethoxysilyl)methane, template agent solution and water, and perform the first hydrolysis to obtain mixed system A; Step b: Mix tetrabutyl titanate, tetraethyl silicate, template agent solution and water, and perform a second hydrolysis to obtain mixed system B; Step c: Mix the mixture system A, the mixture system B and hydrogen peroxide, then precrystallize at 55℃~65℃, then crystallize at 170℃~190℃, and finally calcine at 430℃~470℃ to obtain the methylene-modified TS-1 molecular sieve.

[0009] The present invention provides a method for preparing methylene-modified TS-1 molecular sieves. Bis(triethoxysilyl)methane is used as a methylene introducing agent, tetrabutyl titanate as a titanium source, and tetraethyl silicate as a silicon source. Bis(triethoxysilyl)methane has a slow hydrolysis rate, while tetrabutyl titanate and tetraethyl silicate have faster hydrolysis rates. By hydrolyzing the raw materials with different hydrolysis rates separately, the problem of inconsistent hydrolysis rates can be solved, which is beneficial for subsequent pre-crystallization to form fragments with certain bridged methylene structures and tetracoordinated titanium structures. The present invention introduces methylene structures into the molecular sieve synthesis process, using hydrolysis and pre-crystallization to assist the synthesis. Hydrogen peroxide can form a complex with titanium, preventing the formation of TiO2. Finally, calcination is used to embed the titanium and methylene structures into the molecular sieve framework, thus obtaining methylene-modified TS-1 molecular sieves.

[0010] It should be noted that the order of steps a and b is not limited in this invention.

[0011] More preferably, the template agent solution comprises a tetrapropylammonium hydroxide solution.

[0012] More preferably, the concentration of the template agent solution is 0.8M to 1.2M.

[0013] More preferably, in step a, the mass ratio of bis(triethoxysilyl)methane, template agent solution and water is (1.3~2.1):(23~26):(8~10).

[0014] More preferably, in step a, the temperature of the first hydrolysis is 15℃~30℃, and the time of the first hydrolysis is 8h~12h.

[0015] More preferably, in step b, the mass ratio of tetrabutyl titanate, tetraethyl silicate, template agent solution and water is (1.5~2):(17~20):(23~26):(8~10).

[0016] More preferably, in step b, the temperature of the second hydrolysis is 15℃~30℃, and the time of the second hydrolysis is 30min~50min.

[0017] More preferably, in step c, the mass concentration of the hydrogen peroxide is 25% to 35%.

[0018] More preferably, in step c, the molar ratio of silicon, titanium and template agent in the mixing system is (8~12):(0.4~0.6):(4~6), and the mass ratio of hydrogen peroxide to bis(triethoxysilyl)methane in step a is (5~7):(1.3~2.1).

[0019] More preferably, in step c, the pre-crystallization time is 4h~5h.

[0020] More preferably, in step c, the crystallization time is 30h~50h.

[0021] More preferably, in step c, the calcination time is 5h~7h.

[0022] Preferably, the particle size of the methylene-modified TS-1 molecular sieve is 3 μm to 10 μm. More preferably, the particle size of the methylene-modified TS-1 molecular sieve is 5 μm to 10 μm.

[0023] Preferably, in S1 to S2, the ammonia includes ammonia gas or ammonia water.

[0024] Preferably, in S1, the mass concentration of the hydrogen peroxide is 25% to 35%.

[0025] Preferably, in S1, the molar ratio of cyclohexanone, hydrogen peroxide and ammonia is 1:(1.1~1.2):(1.05~1.1).

[0026] Preferably, in S1, the mass concentration of methylene-modified TS-1 molecular sieve in the raw material of the primary ammonium oxime reaction is 2.5% to 3.5%.

[0027] It should be noted that in S1~S2 of the present invention, the ratio of the reactants cyclohexanone, hydrogen peroxide, ammonia and methylene-modified TS-1 molecular sieve in the reaction solution during the primary and secondary ammonium oximation reactions are all within the above range.

[0028] Preferably, in S1, the temperature of the primary ammonium oxime reaction is 90°C to 110°C.

[0029] Preferably, in S2, the temperature of the secondary ammonium oxime reaction is 75°C to 88°C.

[0030] Preferably, in S2, the time for the secondary ammonium oxime reaction is 10 min to 60 min.

[0031] Preferably, in step S2, the pore size of the filter membrane used for solid-liquid separation is 1 μm to 5 μm. More preferably, in step S2, the pore size of the filter membrane used for solid-liquid separation is 1 μm to 4 μm.

[0032] In this invention, the pore size of the filter membrane should be smaller than the particle size of the methylene-modified TS-1 molecular sieve to ensure complete recovery of the methylene-modified TS-1 molecular sieve.

[0033] In S2 of this invention, in addition to cyclohexanone oxime and water, the mixed clear liquid also contains a small amount of unreacted ammonia (less than 3%), a trace amount of unreacted cyclohexanone (less than 100 ppm), and some byproducts (such as nitrocyclohexane, cyclohexylamine, etc.).

[0034] Preferably, in step S3, the extraction is performed using a two-stage extraction process.

[0035] Preferably, in step S3, the extraction temperature is 48℃~52℃ and the extraction time is 20min~40min.

[0036] Preferably, in step S3, the mass ratio of toluene to cyclohexanone oxime during extraction is 1:(0.6~1).

[0037] For example, in S3, the process of distilling toluene oxime also includes: washing with water.

[0038] Preferably, in S3, the distillation is carried out using two-stage distillation.

[0039] More preferably, in S3, the temperature of the first-stage distillation is 78℃~82℃ and the pressure is -82kPa~-78kPa; the temperature of the second-stage distillation is 130℃~140℃ and the pressure is -92kPa~-88kPa.

[0040] In this invention, after secondary extraction with toluene, the mixed clear liquid is extracted from the oxime-water mixed phase to the toluene phase, producing toluene oxime (i.e., the extract) and an aqueous phase. The toluene oxime is then washed with toluene water and distilled to produce high-purity cyclohexanone oxime, which can be directly fed into the subsequent rearrangement system. The aqueous phase, after recovering organic matter through wastewater stripping, is partially sent to the sewage pipeline (the cyclohexanone oxime content in this wastewater is ≤100ppm), and partially used as a tail gas absorbent in the two-stage reactors (i.e., the first and second reactors) to absorb the ammonia escaping from the reaction, forming ammonia water, which is then returned to the first reactor for reuse. This also serves as a means of maintaining the water balance within the first reactor.

[0041] Secondly, the present invention provides a two-stage ammonium oxime reaction system with an internal membrane for producing the mixed clear liquid containing cyclohexanone oxime and water, wherein the two-stage ammonium oxime reaction system with an internal membrane includes a first reactor and a second reactor. The first reactor is used to carry out a primary ammonium oxime reaction; The second reactor is used for a secondary ammonium oxime reaction, and the top of the second reactor is connected to the first reactor via a pipeline; the second reactor has a built-in filter for solid-liquid separation. The second reactor is connected to a discharge pipe for discharging the mixed clear liquid.

[0042] Preferably, the first reactor is equipped with a first stirring device.

[0043] Preferably, the second reactor is provided with a second stirring device and an inner guide tube, the inner guide tube being located outside the second stirring device.

[0044] In this invention, the two-stage reactor is equipped with stirring and an internal guide tube to enhance mixing, so as to ensure the selectivity of the ammonium oxime reaction.

[0045] More preferably, the membrane tubes of the filter are vertically distributed on the outside of the inner guide tube, and multiple membrane tubes are connected in parallel.

[0046] During normal operation of the two-stage ammonium oxime reaction system with built-in membrane of the present invention, the built-in membrane of the second reactor undergoes pre-membrane treatment, that is, a catalyst coating (pre-membrane layer) is formed on the surface of the filter membrane tube using a catalyst, which enhances the filtration effect of the catalyst. As the reaction gradually stabilizes, the pre-membrane layer also gradually stabilizes. The presence of the pre-membrane layer increases the filtration effect and ensures that the built-in membrane can operate stably for a long time. Due to the protection of the catalyst coating, the filter membrane can be used for a relatively long period of time (not less than six months). When the filter membrane flux is insufficient, the transmembrane pressure difference will gradually increase, the reactor output will gradually decrease, and the output will decrease, requiring online regeneration or replacement of the filter membrane.

[0047] Preferably, the bottom of the second reactor is connected to the feed system of the first reactor via a pipe.

[0048] The recycled reactants (including the recycled catalyst) are drawn from the bottom of the second reactor, transported by a centrifugal pump, and after heat exchange with a cooling medium, sent to the first reactor. The main purpose of this operation is to ensure an overall balance between the amount of feed added to the first reactor and the amount of material discharged after solid-liquid separation in the second reactor, while also enhancing the mixing of the reactants. Ammonia and hydrogen peroxide can be mixed with the recycled reactants from the second reactor before being added from the bottom of the first reactor.

[0049] Preferably, the tops of the first reactor and the second reactor are respectively connected to the ammonia absorption tower via pipelines.

[0050] The present invention has the following beneficial effects: The oximation reaction of this invention is carried out in a specific two-stage series reactor. By limiting the temperature and time of the first-stage ammonium oximation reaction (high temperature, short contact), cyclohexanone, hydrogen peroxide, and ammonia in the first reactor can react rapidly at high temperature under the action of a catalyst. After reaching a certain conversion rate and selectivity, the reaction mixture is sent to the second reactor (the catalyst also enters the second reactor with the reaction liquid). The second reactor is the main reactor. Cyclohexanone, hydrogen peroxide, ammonia, and catalyst are added appropriately according to the conversion rate and selectivity. The temperature of the second-stage ammonium oximation reaction is lower than that of the first-stage reaction, and the reaction residence time is longer, which is conducive to the low-temperature maturation of the ammonium oximation reaction, thereby ensuring complete reaction while controlling the occurrence of reaction byproducts. After the second-stage ammonium oximation reaction is completed, the reaction liquid is precisely filtered through a small-pore filter and a clear mixed liquid containing cyclohexanone oxime and water is sent out.

[0051] The catalyst separation system of this invention adopts the "built-in membrane separation" method, which realizes the complete recovery of the catalyst, ensures that the reaction product (i.e., the mixed clear liquid containing cyclohexanone oxime and water) does not carry the catalyst, and improves the catalyst utilization efficiency. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the apparatus used in the prior art for producing cyclohexanone oxime (a mixed solution containing cyclohexanone oxime and water) based on the homogeneous ammonoxime process; Figure 1 In the diagram, A represents cyclohexanone, B represents ammonia, C represents hydrogen peroxide, D represents tert-butanol, and E represents a mixed solution containing cyclohexanone oxime and water; 1 represents a reactor, 101 represents a stirring device, 2 represents a filtration device, 3 represents a tert-butanol recovery tower, and 4 represents an ammonia absorption tower. Figure 2 This is a schematic diagram of the structure of the built-in membrane two-stage ammonium oxime reaction system in an embodiment of the present invention; Figure 2 In the diagram, A represents cyclohexanone, B represents ammonia, C represents hydrogen peroxide, and F represents a mixed clear liquid containing cyclohexanone oxime and water; 5 represents the first reactor, 501 represents the first stirring device; 6 represents the second reactor, 601 represents the second stirring device, and 602 represents the filter; 4 represents the ammonia absorption tower; 7 represents the heat exchanger; 8 represents the first mixer, and 9 represents the second mixer. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0054] This invention provides a two-stage ammonium oxime reaction system with an internal membrane (see...) Figure 2 The system is used to produce the mixed clear solution containing cyclohexanone oxime and water. The built-in membrane two-stage ammonium oxime reaction system includes a first reactor 5 and a second reactor 6. The first reactor 5 is used to carry out a primary ammonium oxime reaction; The second reactor 6 is used for a secondary ammonium oxime reaction, and the top of the second reactor 6 is connected to the first reactor 5 via a pipe; the second reactor 6 has a built-in filter 602 for solid-liquid separation. The second reactor 6 is connected to a discharge pipe for discharging the mixed clear liquid.

[0055] In some embodiments, the first reactor 5 is provided with a first stirring device 501.

[0056] In some embodiments, the second reactor 6 is provided with a second stirring device 601 and an inner guide tube, the inner guide tube being located outside the second stirring device 601.

[0057] More preferably, the membrane tubes of the filter 602 are vertically distributed on the outside of the inner guide tube, and multiple membrane tubes are connected in parallel.

[0058] In some embodiments, the bottom of the second reactor 6 is connected to the feeding system of the first reactor 5 via a pipe.

[0059] In some embodiments, the circulating reaction material is drawn from the bottom of the second reactor 6, transported by a centrifugal pump, and after being heated by a heat exchanger 7, sent to the first reactor 5; ammonia and hydrogen peroxide are added from the bottom of the first reactor 5 after being mixed with the circulating reaction material from the second reactor 6 through a mixer 8 and a mixer 9, respectively.

[0060] In some embodiments, the tops of the first reactor 5 and the second reactor 6 are respectively connected to the ammonia absorption tower 4 via pipelines.

[0061] Unless otherwise specified in the preparation method, all raw materials used in this invention are commercially available products.

[0062] In this embodiment of the invention, the conversion rate testing method includes: The samples were analyzed by gas chromatography (injection vaporization temperature: 300℃; temperature program: starting at 30℃ and increasing to 200℃ at 5℃ / min, holding for 10min; carrier gas flow rate: 2mL / min; column membrane: Carbowax; column length: 60m; inner diameter: 0.52mm; membrane thickness: 0.5μm) to obtain the contents of cyclohexanone and cyclohexanone oxime. Then, the conversion rate is calculated using the following formula: Ketone conversion rate % = 1 - Cyclohexanone content / (Cyclohexanone content + Cyclohexanone oxime content × 0.867 + Reaction impurity content) × 100%.

[0063] In this embodiment of the invention, the formula for calculating selectivity is: Oxime selectivity % = Cyclohexanone oxime content × 0.867 / (Cyclohexanone content + Cyclohexanone oxime content × 0.867 + Reaction impurity content) / Conversion rate × 100%.

[0064] In the above formulas for calculating ketone conversion and oxime selectivity, the content refers to the mass percentage of each component in the reaction solution; 0.867 represents the molecular weight ratio of cyclohexanone and cyclohexanone oxime, i.e., 98 / 113=0.867.

[0065] To better illustrate the present invention, further examples are provided below.

[0066] Example 1 This embodiment provides a method for producing high-purity cyclohexanone oxime, including the following steps: S1. Cyclohexanone, 35% hydrogen peroxide, ammonia, and methylene-modified TS-1 molecular sieve are introduced into the first reactor. The feeding rate is adjusted so that the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia is 1:1.15:1.07 and the mass concentration of methylene-modified TS-1 molecular sieve is 3%. The first-stage ammonium oxime reaction is carried out at 100℃. After 3 minutes, the first-stage reaction solution is obtained.

[0067] S2. The primary reaction solution is fed into the second reactor, and the content of each material in the reaction solution is detected. The secondary ammonium oxime reaction is carried out at 80°C. After 35 minutes, the reaction solution is filtered through a filter (the pore size of the filter membrane is 3μm) to obtain a mixed clear solution containing cyclohexanone oxime and water.

[0068] The conversion rate of the primary ammonium oximation reaction was 90.02% and the conversion rate of the secondary ammonium oximation reaction was 99.98%, with a selectivity of 99.90%.

[0069] S3. The mixed clear liquid was subjected to two-stage extraction with toluene (extraction temperature 50℃, extraction time 30 min, mass ratio of toluene to cyclohexanone oxime 1:0.8), separated, and the toluene oxime was washed with water and subjected to two-stage distillation (first-stage distillation temperature 80℃, pressure -80 kPa; second-stage distillation temperature 135℃, pressure -90 kPa, to obtain cyclohexanone oxime. The purity was tested to be 99.98%.

[0070] Compared to the traditional homogeneous ammonium oxime process, the steam consumption for cyclohexanone oxime is significantly reduced. Based on a 150,000-ton / year production unit, the homogeneous ammonium oxime production process requires 33 tons of steam per hour for the ammonium oxime step, while the tert-butanol recovery process requires 21 tons of steam per hour. Using the method for producing high-purity cyclohexanone oxime provided by this invention, the ammonium oxime process alone requires only 12 tons of steam per hour, greatly reducing energy consumption.

[0071] Although the steam consumption of the existing heterogeneous production process for cyclohexane extraction can be reduced to 12 tons / hour, its conversion rate of ammoniation reaction is only 99.70%, the selectivity is only 99.75%, and there are many impurities in the by-products.

[0072] The preparation method of the above-mentioned methylene-modified TS-1 molecular sieve includes the following steps: Step a: Mix 1.7g of bis(triethoxysilyl)methane, 25.4g of 1M tetrapropylammonium hydroxide solution and 9.4g of water, and stir and hydrolyze at room temperature for 10h to obtain mixed system A.

[0073] Step b: Mix 1.7g tetrabutyl titanate, 18.8g tetraethyl silicate, 25.4g 1M tetrapropylammonium hydroxide solution and 9.3g water, and stir and hydrolyze at room temperature for 40min to obtain mixed system B.

[0074] This embodiment does not limit the order of steps a and b.

[0075] Step c: Mix the above mixed system A, the above mixed system B and 5.2g of 30% hydrogen peroxide, stir until clear, and obtain a yellow mother liquor; pre-crystallize the obtained mother liquor at 60℃ for 4.5h, place it in a reaction vessel, crystallize at 180℃ for 40h, filter, wash, dry, calcine at 450℃ for 6h, grind, and obtain methylene-modified TS-1 molecular sieve with a particle size of 4μm~8μm.

[0076] Example 2 This embodiment provides a method for producing high-purity cyclohexanone oxime, including the following steps: S1. Cyclohexanone, 35% hydrogen peroxide, ammonia, and methylene-modified TS-1 molecular sieve were introduced into the first reactor. The feeding rate was adjusted so that the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia was 1:1.1:1.05 and the mass concentration of methylene-modified TS-1 molecular sieve was 2.6%. The first-stage ammonium oxime reaction was carried out at 115℃. After 5 minutes, the first-stage reaction solution was obtained.

[0077] S2. The primary reaction solution is fed into the second reactor and subjected to a secondary ammonium oxime reaction at 88°C. After 40 minutes, the reaction solution is filtered through a filter (the pore size of the filter membrane is 2 μm) to obtain a mixed clear solution containing cyclohexanone oxime and water.

[0078] The conversion rate of the primary ammonium oximation reaction was 93.03% and the conversion rate of the secondary ammonium oximation reaction was 99.95%, with a selectivity of 99.88%.

[0079] S3. The mixed clear liquid was subjected to two-stage extraction with toluene (extraction temperature 48℃, extraction time 30min, mass ratio of toluene to cyclohexanone oxime 1:0.6), separated, and the toluene oxime was washed with water and subjected to two-stage distillation (first-stage distillation temperature 78℃, pressure -78kPa; second-stage distillation temperature 130℃, pressure -88kPa, to obtain cyclohexanone oxime).

[0080] The preparation method of the above-mentioned methylene-modified TS-1 molecular sieve includes the following steps: Step a: Mix 1.36g of bis(triethoxysilyl)methane, 23g of 1.2M tetrapropylammonium hydroxide solution and 10g of water, and stir and hydrolyze at room temperature for 12h to obtain mixed system A.

[0081] Step b: Mix 1.53g tetrabutyl titanate, 17g tetraethyl silicate, 23g tetrapropylammonium hydroxide solution (1.2M) and 10g water, and stir and hydrolyze at room temperature for 50 minutes to obtain mixed system B.

[0082] This embodiment does not limit the order of steps a and b.

[0083] Step c: Mix the above mixed system A, the above mixed system B and 5g of 35% hydrogen peroxide, stir until clear, and obtain a yellow mother liquor; pre-crystallize the obtained mother liquor at 65℃ for 4h, place it in a reaction vessel, crystallize at 190℃ for 30h, filter, wash, dry, calcine at 430℃ for 7h, grind, and obtain methylene-modified TS-1 molecular sieve with a particle size of 3μm~6μm.

[0084] Example 3 This embodiment provides a method for producing high-purity cyclohexanone oxime, including the following steps: S1. Cyclohexanone, 35% hydrogen peroxide, ammonia, and methylene-modified TS-1 molecular sieve are introduced into the first reactor. The feeding rate is adjusted so that the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia is 1:1.2:1.1 and the mass concentration of methylene-modified TS-1 molecular sieve is 3.3%. The first-stage ammonium oxime reaction is carried out at 90℃. After 2 minutes, the first-stage reaction solution is obtained.

[0085] S2. The primary reaction solution is fed into the second reactor and subjected to a secondary ammonium oxime reaction at 75°C. After 25 minutes, the reaction solution is filtered through a filter (the pore size of the filter membrane is 4 μm) to obtain a mixed clear solution containing cyclohexanone oxime and water.

[0086] The conversion rate of the primary ammonium oximation reaction was 87.89% and the conversion rate of the secondary ammonium oximation reaction was 99.80%, with a selectivity of 99.90%.

[0087] S3. The mixed clear liquid was subjected to two-stage extraction with toluene (extraction temperature 52℃, extraction time 30min, mass ratio of toluene to cyclohexanone oxime 1:1), separated, and the toluene oxime was washed with water and subjected to two-stage distillation (first-stage distillation temperature 82℃, pressure -82kPa; second-stage distillation temperature 140℃, pressure -92kPa, to obtain cyclohexanone oxime).

[0088] The preparation method of the above-mentioned methylene-modified TS-1 molecular sieve includes the following steps: Step a: Mix 2.04 g of bis(triethoxysilyl)methane, 26 g of 0.8 M tetrapropylammonium hydroxide solution and 8 g of water, and stir and hydrolyze at room temperature for 9 h to obtain mixed system A.

[0089] Step b: Mix 1.87g tetrabutyl titanate, 20g tetraethyl silicate, 26g tetrapropylammonium hydroxide solution (0.8M) and 8g water, and stir and hydrolyze at room temperature for 30 minutes to obtain mixed system B.

[0090] This embodiment does not limit the order of steps a and b.

[0091] Step c: Mix the above mixed system A, the above mixed system B and 7g of hydrogen peroxide with a mass concentration of 25%, stir until clear, and obtain a yellow mother liquor; pre-crystallize the obtained mother liquor at 55℃ for 5h, place it in a reaction vessel, crystallize at 170℃ for 50h, filter, wash, dry, calcine at 465℃ for 5h, grind, and obtain methylene-modified TS-1 molecular sieve with a particle size of 5μm~10μm.

[0092] Comparative Example 1 This comparative example provides a method for producing cyclohexanone oxime, the operation steps and conditions of which are similar to those in Example 1, except that in S1, the methylene-modified TS-1 molecular sieve is replaced with a conventional TS-1 molecular sieve (purchased from Zibo Hengyi Chemical Technology Co., Ltd.). The remaining operations and parameter settings are the same as in Example 1 and will not be repeated here.

[0093] Tests showed that the conversion rate of the primary ammonium oximation reaction in S1-S2 was 81.05%, and the conversion rate of the secondary ammonium oximation reaction was 90.20%, with a selectivity of 89.52%.

[0094] Comparative Example 2 This comparative example provides a method for producing cyclohexanone oxime, the operation and condition parameters of which are similar to those in Example 1, except that in S1, the temperature of the primary ammonoximation reaction is replaced with 125°C and the reaction time is replaced with 30s. The remaining operation and parameter settings are the same as in Example 1 and will not be described again.

[0095] Tests showed that the conversion rate of the primary ammonium oximation reaction in S1-S2 was 87.51%, and the conversion rate of the secondary ammonium oximation reaction was 95.33%, with a selectivity of 97.88%.

[0096] Comparative Example 3 This comparative example provides a method for producing cyclohexanone oxime, the operation and condition parameters of which are similar to those in Example 1, except that in S1, the temperature of the primary ammoniation reaction is replaced with 85°C and the reaction time is replaced with 10 min. The remaining operation and parameter settings are the same as in Example 1 and will not be described again.

[0097] Tests showed that the conversion rate of the primary ammonium oximation reaction in S1-S2 was 81.36%, and the conversion rate of the secondary ammonium oximation reaction was 93.65%, with a selectivity of 98.75%.

[0098] Comparative Example 4 This comparative example provides a method for producing cyclohexanone oxime, the operation and condition parameters of which are similar to those in Example 1, except that in S2, the temperature of the secondary ammoniation reaction is replaced with 95°C and the reaction time is replaced with 5 min. The remaining operation and parameter settings are the same as in Example 1 and will not be described again.

[0099] Tests showed that the conversion rate of the primary ammonium oximation reaction in S1-S2 was 90.07%, and the conversion rate of the secondary ammonium oximation reaction was 98.91%, with a selectivity of 97.16%.

[0100] Comparative Example 5 This comparative example provides a method for producing cyclohexanone oxime, the operation and condition parameters of which are similar to those in Example 1, except that in S2, the temperature of the secondary ammonoximation reaction is replaced with 65°C and the reaction time is replaced with 80 min. The remaining operation and parameter settings are the same as in Example 1 and will not be repeated.

[0101] Tests showed that the conversion rate of the primary ammonium oximation reaction in S1-S2 was 89.95%, and the conversion rate of the secondary ammonium oximation reaction was 94.89%, with a selectivity of 95.15%.

[0102] Comparative Example 6 This comparative example provides a method for producing cyclohexanone oxime, the operation steps and conditions of which are similar to those in Example 1, except that in S1, the time for the primary ammoniation reaction is replaced with 10 min, and the secondary ammoniation reaction is not performed. Specifically, it includes the following steps: S1. Cyclohexanone, 35% hydrogen peroxide, ammonia, and methylene-modified TS-1 molecular sieve are introduced into the first reactor. The feeding rate is adjusted so that the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia is 1:1.15:1.07 and the mass concentration of methylene-modified TS-1 molecular sieve is 3%. The first-stage ammonium oxime reaction is carried out at 100℃. After 10 min, the reaction solution is filtered through an external filter device (the pore size of the filter membrane is 3 μm) to obtain a mixed clear liquid containing cyclohexanone oxime and water.

[0103] S2 is the same as S3 in Example 1, and will not be described again.

[0104] Tests showed that the conversion rate of the primary ammonium oxime reaction in S1 was 94.56%, and the selectivity was 93.64%.

[0105] Comparative Example 7 This comparative example provides a method for producing cyclohexanone oxime, the operation steps and conditions of which are similar to those in Example 1, except that in S1, the time for the secondary ammoniation reaction is replaced with 90 min, and the primary ammoniation reaction is not performed. Specifically, it includes the following steps: S1. Cyclohexanone, 35% hydrogen peroxide, ammonia, and methylene-modified TS-1 molecular sieve were introduced into the second reactor. The feeding rate was adjusted so that the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia was 1:1.15:1.08 and the mass concentration of methylene-modified TS-1 molecular sieve was 3%. A secondary ammonium oxime reaction was carried out at 80°C. After 90 min, the reaction solution was filtered through a filter (the pore size of the filter membrane was 3 μm) to obtain a mixed clear liquid containing cyclohexanone oxime and water.

[0106] S2 is the same as S3 in Example 1, and will not be described again.

[0107] Tests showed that the conversion rate of the secondary ammonium oxime reaction in S1 was 77.87%, and the selectivity was 86.25%.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing high-purity cyclohexanone oxime, characterized in that, Includes the following steps: S1. Cyclohexanone, hydrogen peroxide and ammonia are introduced into the first reactor containing methylene-modified TS-1 molecular sieve, and a primary ammonium oxime reaction is carried out at 90℃~120℃. After 1min~5min, the primary reaction solution is obtained. S2. The first-stage reaction solution is fed into the second reactor and subjected to a second-stage ammonium oxime reaction at 70℃~88℃. Solid-liquid separation is performed to obtain a mixed clear liquid containing cyclohexanone oxime and water. S3. Extract the mixed clear liquid with toluene, and distill the extract to obtain cyclohexanone oxime.

2. The method for producing high-purity cyclohexanone oxime as described in claim 1, characterized in that, In S1, the mass concentration of methylene-modified TS-1 molecular sieve in the raw material of the primary ammonium oxime reaction is 2.5% to 3.5%.

3. The method for producing high-purity cyclohexanone oxime as described in claim 1 or 2, characterized in that, In S1, the particle size of the methylene-modified TS-1 molecular sieve is 3μm~10μm; in S2, the pore size of the filter membrane used for solid-liquid separation is 1μm~5μm.

4. The method for producing high-purity cyclohexanone oxime as described in claim 1, characterized in that, The preparation method of the methylene-modified TS-1 molecular sieve includes the following steps: Step a: Mix bis(triethoxysilyl)methane, template agent solution and water, and perform the first hydrolysis to obtain mixed system A; Step b: Mix tetrabutyl titanate, tetraethyl silicate, template agent solution and water, and perform a second hydrolysis to obtain mixed system B; Step c: Mix the mixture system A, the mixture system B and hydrogen peroxide, then precrystallize at 55℃~65℃, then crystallize at 170℃~190℃, and finally calcine at 430℃~470℃ to obtain the methylene-modified TS-1 molecular sieve.

5. The method for producing high-purity cyclohexanone oxime as described in claim 4, characterized in that, The template agent solution comprises a tetrapropylammonium hydroxide solution with a concentration of 0.8M to 1.2M; the hydrogen peroxide has a mass concentration of 25% to 35%.

6. The method for producing high-purity cyclohexanone oxime as described in claim 4 or 5, characterized in that, In step a, the mass ratio of bis(triethoxysilyl)methane, template agent solution and water is (1.3~2.1):(23~26):(8~10); In step b, the mass ratio of tetrabutyl titanate, tetraethyl silicate, template agent solution and water is (1.5~2):(17~20):(23~26):(8~10); In step c, the molar ratio of silicon, titanium and template agent in the mixing system is (8~12):(0.4~0.6):(4~6), and the mass ratio of hydrogen peroxide to bis(triethoxysilyl)methane in step a is (5~7):(1.3~2.1).

7. The method for producing high-purity cyclohexanone oxime as described in claim 4, characterized in that, In step a, the temperature of the first hydrolysis is 15℃~30℃, and the time of the first hydrolysis is 8h~12h; In step b, the temperature of the second hydrolysis is 15℃~30℃, and the time of the second hydrolysis is 30min~50min; In step c, the pre-crystallization time is 4h~5h; the crystallization time is 30h~50h; and the calcination time is 5h~7h.

8. The method for producing high-purity cyclohexanone oxime as described in claim 1, characterized in that, In S1, the molar ratio of cyclohexanone, hydrogen peroxide, and ammonia is 1:(1.1~1.2):(1.05~1.1); In S2, the time for the secondary ammonoximation reaction is 10 min to 60 min.

9. A two-stage ammonium oxime reaction system with an internal membrane, used to produce the mixed clear solution containing cyclohexanone oxime and water as described in any one of claims 1 to 8, characterized in that, The built-in membrane two-stage ammonium oxime reaction system includes a first reactor and a second reactor; The first reactor is used to carry out a primary ammonium oxime reaction; The second reactor is used for a secondary ammonium oxime reaction, and the top of the second reactor is connected to the first reactor via a pipeline; the second reactor has a built-in filter for solid-liquid separation. The second reactor is connected to a discharge pipe for discharging the mixed clear liquid.

10. The two-stage ammonium oxime reaction system with built-in membrane as described in claim 9, characterized in that, The first reactor is equipped with a first stirring device; The second reactor is equipped with a second stirring device and an inner guide tube, the inner guide tube being located outside the second stirring device; the membrane tubes of the filter are vertically distributed outside the inner guide tube, and multiple membrane tubes are connected in parallel.

Images