Green electricity, green hydrogen and green ammonia coupling device and coupling method for caprolactam production

Abstract

The invention discloses a green electricity, green hydrogen and green ammonia coupling device and method for caprolactam production, and belongs to the technical field of caprolactam production. Solar energy is converted into green electricity through the photovoltaic power generation device, energy is provided for hydrogen production through water electrolysis, after hydrogen is purified through pressure swing adsorption, ammonia gas is synthesized through nitrogen and hydrogen catalysis, ammonia water is prepared, and green energy conversion and utilization are achieved. The prepared modified titanium silicalite molecular sieve is efficient in catalytic performance in a ketone ammoximation reaction and can be recycled, and waste and environmental pressure are reduced. The prepared modified ionic liquid has surface activity, a P = O bond is introduced into an alkenyl mercaptan click reaction to coordinate with a zinc element, the hydrolysis rate of a titanium source is slowed down, titanium atoms are uniformly doped into a molecular sieve framework, the multilayer porous titanium silicalite molecular sieve with the high specific surface area is obtained, and the ionic liquid surface activity enables titanium active sites to be distributed more reasonably; the catalyst improves catalytic activity and circulation capability, solves the problem of poor performance of a traditional catalyst, prolongs the service life and reduces the cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of caprolactam production, and particularly relates to a green electricity, green hydrogen, and green ammonia coupling device and coupling method for caprolactam production. Background Art

[0002] Caprolactam is an important organic chemical raw material and has wide applications in industrial production. It is the monomer for preparing nylon 6. Nylon 6 is widely used in many fields such as textiles, engineering plastics, automotive parts, electronic appliances, etc. due to its good wear resistance, corrosion resistance, flexibility, and high strength. For example, in the textile industry, nylon 6 fibers can be used to make clothing, carpets, etc.; in the field of engineering plastics, it can be used to manufacture mechanical parts, automotive interiors, etc., and its excellent performance meets the diverse material requirements of different industries.

[0003] Cyclohexanone oxime is an important intermediate for preparing caprolactam, the monomer of nylon - 6, and is mainly obtained by ammoximation of cyclohexanone, hydrogen peroxide, and ammonia using titanium silicalite molecular sieve as a catalyst. In industrial production, titanium silicalite molecular sieve (TS - 1) is used as a catalyst. During the synthesis process of titanium silicalite molecular sieve, due to the mismatch between the hydrolysis rates of the silicon source and the titanium source, and the relatively fast hydrolysis rate of the titanium source, a large amount of non - framework titanium without catalytic activity is generated during the synthesis process. The low content of framework titanium and high content of anatase result in a low conversion rate and poor lifespan of the catalytic ammoximation reaction, seriously affecting the production efficiency. Secondly, after the titanium silicalite molecular sieve operates for a period of time, the catalytic performance of the catalyst will deteriorate and deactivation occurs. Deactivation is divided into temporary deactivation and permanent deactivation. The temporarily deactivated catalyst can be regenerated to restore part or all of its activity, but when permanent deactivation occurs, it cannot be recycled, causing waste of resources and environmental pollution.

[0004] In the existing caprolactam production, there are still many problems with traditional production methods: on the one hand, the utilization of energy is not efficient and environmentally friendly. In some production processes, the energy consumption is large and relies on traditional non - renewable energy sources, which not only have a high cost but also produce a large amount of pollutants such as carbon emissions, causing great pressure on the environment. On the other hand, during the caprolactam production process, the coordination between various links is poor, and the efficient integration of green electricity, green hydrogen, and green ammonia cannot be achieved, resulting in low energy utilization efficiency and poor environmental performance in the overall production process, affecting the production efficiency and quality of caprolactam and restricting the sustainable development of the industry. Summary of the Invention

[0005] In view of the above situation, to overcome the defects of the prior art, the present invention constructs a green electricity, green hydrogen, and green ammonia coupling device and the corresponding coupling method, optimizes the caprolactam production process by modifying the titanium silicalite molecular sieve, improves the energy utilization efficiency, improves the catalyst performance, and realizes the green, efficient, and sustainable production of caprolactam.

[0006] To achieve the above object, the following technical solutions are adopted: On the one hand, the present invention provides a method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production, including the following steps:

[0007] (1) Obtain green electricity by solar photovoltaic power generation. Adopt the electrolytic water hydrogen production technology to decompose water into hydrogen and oxygen using green electricity. Use the pressure swing adsorption technology for hydrogen purification. Then, using nitrogen and hydrogen as raw materials, catalytically synthesize ammonia under high temperature and high pressure, and the ammonia is further synthesized into ammonia water;

[0008] (2) Add cyclohexanone, ammonia water, and hydrogen peroxide into the oximation reaction kettle in proportion. Use cyclohexanone as the starting material, ammonia water to provide the amine source, hydrogen peroxide as the oxidant, and then add a modified titanium silicalite molecular sieve as the catalyst to carry out the ketone-ammonia oximation reaction to obtain cyclohexanone oxime;

[0009] (3) Filter the cyclohexanone oxime to separate the modified titanium silicalite molecular sieve catalyst. After the catalyst is washed, dried and other treatments, it is recycled. Distill the filtered cyclohexanone oxime reaction solution to further purify the reaction product;

[0010] (4) Add the product purified in step (3) into the rearrangement reaction kettle, add concentrated sulfuric acid as the rearrangement reagent, carry out the Beckmann rearrangement reaction to convert the oxime into caprolactam, filter to separate the caprolactam solid, wash the separated caprolactam solid to remove the impurities and acidic catalyst attached to the surface, and then refine the caprolactam to meet the index requirements.

[0011] Furthermore, the modified titanium silicalite molecular sieve is prepared by the following steps:

[0012] S1. Add imidazole monomer and dimethyl carbonate into tetrahydrofuran, then add a phase transfer agent, heat up to 100 °C and react for 10 h, then distill off the tetrahydrofuran solvent, control the temperature below 15 °C, add 12-mercaptododecanoic acid, age for 3 h, filter, and dry to obtain a yellow intermediate ionic liquid. Mix the yellow intermediate ionic liquid with diphenylvinylphosphine oxide and a photoinitiator, and under ultraviolet light irradiation, through the alkenyl thiol click reaction, obtain a modified ionic liquid;

[0013] S2. Hydrothermally treat the molecular sieve at 140 °C for 2 h, then restore to room temperature, mix it evenly with a titanium source and the modified ionic liquid, and then transfer it to a reaction kettle, crystallize at 250 °C for 12 h, then cool the reaction product to room temperature, filter, wash, and dry to obtain the modified titanium silicalite molecular sieve.

[0014] Further, in the step S1, the weight ratio of the imidazole monomer, dimethyl carbonate, tetrahydrofuran, phase transfer agent, and 12-mercaptododecanoic acid is 3.5:5 - 10:10 - 15:0.01 - 0.05:4 - 6.

[0015] Further, in the step S1, the weight ratio of the yellow intermediate ionic liquid, diphenylvinylphosphine oxide, and photoinitiator is 1:1.5 - 3:0.015 - 0.03.

[0016] Further, the weight ratio of the molecular sieve, titanium source, and modified ionic liquid is 3:0.5 - 1:50 - 80.

[0017] Further, the molecular sieve is ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 28.

[0018] Further, the imidazole monomer is one of 1-ethylimidazole, 1-ethyl-3-methylimidazole, and 1-butylimidazole.

[0019] Further, the phase transfer agent is one of tetrabutylammonium bromide, cetyltrimethylammonium chloride, and cetyltrimethylammonium chloride.

[0020] Further, the photoinitiator is one of BASF 369, BASF 754, BASF 907, and BASF 1173.

[0021] Further, the titanium source is one of titanium chloride, titanium oxide, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.

[0022] On the other hand, the present invention provides a green electricity, green hydrogen, and green ammonia coupling device for caprolactam production, including: a green energy preparation unit, an oximation reaction unit, a product purification unit, and a rearrangement and refining unit.

[0023] Further, the green energy preparation unit includes:

[0024] A photovoltaic power generation device that converts solar energy into green electricity,

[0025] An electrolytic water hydrogen production device that uses green electricity to decompose water into hydrogen and oxygen,

[0026] A hydrogen purification device that purifies hydrogen through adsorption and desorption processes,

[0027] A synthetic ammonia device that synthesizes green ammonia from nitrogen and hydrogen;

[0028] An ammonia water production device that synthesizes the produced green ammonia into ammonia water.

[0029] Further, the photovoltaic power generation device is connected to the power input end of the electrolytic water hydrogen production device through a cable. The high-purity hydrogen outlet of the hydrogen purification device is connected to the hydrogen inlet of the ammonia synthesis device through a pipeline. At the same time, the nitrogen inlet of the ammonia synthesis device is connected to a nitrogen source, and the ammonia outlet of the ammonia synthesis device is introduced into the ammonia water production device. The ammonia water production device connects the ammonia water to the oximation reaction unit through a pipeline;

[0030] Further, the oximation reaction unit includes:

[0031] An oximation reaction kettle for carrying out the ketone oximation reaction;

[0032] A cyclohexanone storage device for storing and feeding cyclohexanone;

[0033] A hydrogen peroxide storage device for storing and feeding hydrogen peroxide;

[0034] A catalyst addition device for accurately adding a modified titanium silicalite molecular sieve catalyst.

[0035] Further, the ammonia water production device, the cyclohexanone storage device, and the hydrogen peroxide storage device are respectively connected to different feed inlets of the oximation reaction kettle through pipelines, and the discharge outlet of the oximation reaction kettle is connected to the product purification unit through a pipeline;

[0036] Further, the product purification unit includes:

[0037] A cyclohexanone oxime filtration device for separating the modified titanium silicalite molecular sieve catalyst;

[0038] A distillation device for distilling and purifying the cyclohexanone oxime reaction solution.

[0039] Further, the discharge outlet of the oximation reaction kettle is connected to the feed inlet of the cyclohexanone oxime filtration device, the filtrate outlet of the cyclohexanone oxime filtration device is connected to the feed inlet of the distillation device through a pipeline, and the purified product outlet of the distillation device is connected to the rearrangement and refining unit through a pipeline.

[0040] Further, the rearrangement and refining unit includes:

[0041] A rearrangement reaction kettle for carrying out the Beckmann rearrangement reaction;

[0042] A caprolactam filtration device for separating caprolactam solids,

[0043] A washing device for washing the caprolactam solids.

[0044] Further, the purification product outlet of the distillation device of the product purification unit is connected to the feed inlet of the rearrangement reactor, the discharge outlet of the rearrangement reactor is connected to the feed inlet of the caprolactam filtration device, and the solid discharge outlet of the caprolactam filtration device is connected to the feed inlet of the washing device.

[0045] The beneficial effects of the present invention are as follows:

[0046] (1) The coupling method and coupling device of the present invention make full use of green energy. The photovoltaic power generation device converts solar energy into green electricity to provide energy for subsequent electrolysis of water to produce hydrogen. The green electricity is used to decompose water into hydrogen and oxygen, and then the hydrogen is purified by pressure swing adsorption technology. Then, nitrogen and hydrogen are used as raw materials to catalytically synthesize ammonia and further produce ammonia water under high temperature and high pressure, realizing the green conversion and utilization of energy, which conforms to the concept of sustainable development. Moreover, the modified titanium silicalite molecular sieve prepared by the present invention shows high catalytic performance in the ketone ammoximation reaction, can effectively promote the reaction, improve the reaction conversion rate and production efficiency, and can be recycled, reducing the waste of the catalyst and the pressure on the environment;

[0047] (2) The modified ionic liquid prepared by the present invention has surface activity by introducing 12-mercaptododecanoic acid. This surface activity helps the dispersion of the ionic liquid in the reaction system and its interaction with other substances. At the same time, the imidazole monomer and diphenylethylene phosphine oxide are coupled by the thiol-ene click reaction, and the diphenylethylene phosphine oxide introduces a P=O bond into the ionic liquid. This bond can stably coordinate with zinc elements. During the synthesis process of titanium silicalite molecular sieve, the coordination of the P=O bond with zinc elements can slow down the hydrolysis rate of the titanium source. This regulatory effect avoids the formation of non-framework titanium and promotes the formation of MFI-structured titanium silicalite molecular sieve crystals, ensuring that titanium atoms can be evenly incorporated into the framework structure of the molecular sieve, thereby obtaining a titanium silicalite molecular sieve with a high specific surface area and multi-layer pore channels. The surface activity of the ionic liquid makes the distribution of titanium active sites in the molecular sieve more reasonable, further improving the catalytic activity and cyclic catalytic ability of the molecular sieve, better meeting the requirements of green production, effectively solving the problem of poor performance of titanium silicalite molecular sieve catalysts in traditional methods, extending the service life of the catalyst, and reducing production costs. Description of the Drawings

[0048] Figure 1 is a schematic structural diagram of a green electricity, green hydrogen, and green ammonia coupling device for caprolactam production according to the present invention;

[0049] Figure 2 is an SEM image of the titanium silicalite molecular sieve of Example 5 of the present invention;

[0050] Figure 3 is the detection result of the catalytic ability of the titanium silicalite molecular sieve of Examples 3-5 and Comparative Examples 1-2 of the present invention;

[0051] Figure 4 This is the detection result of the cyclic catalytic ability of the titanium-silicon molecular sieve in Examples 3-5 and Comparative Examples 1-2 of the present invention.

[0052] Legend: 1. Green energy preparation unit; 11. Photovoltaic power generation device; 12. Electrolytic water hydrogen production device; 13. Hydrogen purification device; 14. Ammonia synthesis device; 15. Ammonia water production device; 2. Oximation reaction unit; 21. Oximation reaction kettle; 22. Cyclohexanone storage; 23. Hydrogen peroxide storage; 24. Catalyst addition device; 3. Product purification unit; 31. Cyclohexanone oxime filtration device; 32. Distillation device; 4. Rearrangement and refining unit; 41. Rearrangement reaction kettle; 42. Caprolactam filtration device; 43. Washing device.

[0053] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. Detailed implementation manners

[0054] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0055] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for demonstration purposes, but cannot limit the content of this application.

[0056] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The test materials used in the following embodiments are all obtained from commercial channels unless otherwise specified.

[0057] Example 1

[0058] A green electricity, green hydrogen, and green ammonia coupling device for caprolactam production

[0059] According to the appendix Figure 1 , the coupling device includes: a green energy preparation unit 1, an oximation reaction unit 2, a product purification unit 3, and a rearrangement and refining unit 4;

[0060] The green energy preparation unit 1 includes:

[0061] A photovoltaic power generation device 11 that converts solar energy into green electric energy,

[0062] The electrolytic water hydrogen production device 12 decomposes water into hydrogen and oxygen using green electricity.

[0063] The hydrogen purification device 13 purifies hydrogen through adsorption and desorption processes.

[0064] The ammonia synthesis device 14 synthesizes green ammonia using nitrogen and hydrogen as raw materials.

[0065] The ammonia water production device 15 synthesizes the produced green ammonia into ammonia water.

[0066] The photovoltaic power generation device 11 is connected to the power input end of the electrolytic water hydrogen production device 12 through a cable. The high-purity hydrogen outlet of the hydrogen purification device 13 is connected to the hydrogen feed port of the ammonia synthesis device through a pipeline. At the same time, the nitrogen feed port of the ammonia synthesis device is connected to a nitrogen source. The ammonia outlet of the ammonia synthesis device is introduced into the ammonia water production device 15, and the ammonia water production device 15 connects the ammonia water to the oximation reaction unit 2 through a pipeline.

[0067] The oximation reaction unit 2 includes:

[0068] An oximation reaction kettle 21 for carrying out the ketone oximation reaction.

[0069] A cyclohexanone storage tank 22 for storing and feeding cyclohexanone.

[0070] A hydrogen peroxide storage tank 23 for storing and feeding hydrogen peroxide.

[0071] A catalyst addition device 24 for accurately adding a modified titanium silicalite molecular sieve catalyst.

[0072] The ammonia water production device 15, the cyclohexanone storage tank 22, and the hydrogen peroxide storage tank 23 are respectively connected to different feed ports of the oximation reaction kettle 21 through pipelines. The discharge port of the oximation reaction kettle 21 is connected to the product purification unit 3 through a pipeline.

[0073] The product purification unit 3 includes:

[0074] A cyclohexanone oxime filtration device 31 for separating out the modified titanium silicalite molecular sieve catalyst.

[0075] A distillation device 32 for distilling and purifying the cyclohexanone oxime reaction solution.

[0076] The discharge port of the oximation reaction kettle 21 is connected to the feed port of the cyclohexanone oxime filtration device 31. The filtrate outlet of the cyclohexanone oxime filtration device 31 is connected to the feed port of the distillation device 32 through a pipeline. The purified product outlet of the distillation device 32 is connected to the rearrangement and refining unit 4 through a pipeline.

[0077] The rearrangement and refining unit 4 includes:

[0078] Rearrangement reactor 41, used for carrying out Beckmann rearrangement reaction;

[0079] Caprolactam filtration device 42, used for separating out caprolactam solid,

[0080] Washing device 43, used for washing the caprolactam solid;

[0081] The purification product outlet of the distillation device 32 of the product purification unit 3 is connected to the feed inlet of the rearrangement reactor 41, the discharge outlet of the rearrangement reactor 41 is connected to the feed inlet of the caprolactam filtration device 42, and the solid discharge outlet of the caprolactam filtration device 42 is connected to the feed inlet of the washing device 43.

[0082] Example 2

[0083] A method for coupling green electricity, green hydrogen, and green ammonia in caprolactam production

[0084] The coupling method includes the following steps:

[0085] (1) Obtain green electricity by solar photovoltaic power generation. Adopt the electrolytic water hydrogen production technology to decompose water into hydrogen and oxygen by using green electricity. Adopt the pressure swing adsorption technology for hydrogen purification. Then, use nitrogen and hydrogen as raw materials to catalytically synthesize ammonia under high temperature and high pressure, and ammonia is further synthesized into ammonia water;

[0086] (2) Add cyclohexanone, ammonia water, and hydrogen peroxide into the oximation reactor in proportion. Use cyclohexanone as the starting material, ammonia water as the amine source, hydrogen peroxide as the oxidant, and add modified titanium silicalite molecular sieve as the catalyst to carry out the ketone-ammonia oximation reaction to obtain cyclohexanone oxime;

[0087] (3) Filter the cyclohexanone oxime to separate out the modified titanium silicalite molecular sieve catalyst. The catalyst is recovered and reused after being washed, dried, etc. Distill the filtered cyclohexanone oxime reaction solution to further purify the reaction product;

[0088] (4) Add the product purified in step (3) into the rearrangement reactor, add concentrated sulfuric acid as the rearrangement reagent to carry out the Beckmann rearrangement reaction to convert the oxime into caprolactam. Separate out the caprolactam solid by filtration, wash the separated caprolactam solid to remove the impurities and acidic catalyst attached to the surface, and then refine the caprolactam to meet the index requirements

[0089] Example 3

[0090] Modified titanium silicalite molecular sieve

[0091] The modified titanium silicalite molecular sieve is prepared by the following steps:

[0092] S1. Add imidazole monomer and dimethyl carbonate into tetrahydrofuran, then add a phase transfer agent. After heating to 100 °C, react for 10 h. Then evaporate the tetrahydrofuran solvent. Control the temperature below 15 °C, add 12-mercaptododecanoic acid, age for 3 h, filter, and dry to obtain a yellow intermediate ionic liquid. Mix the yellow intermediate ionic liquid with diphenylvinylphosphine oxide and a photoinitiator, and under ultraviolet light irradiation, obtain a modified ionic liquid through an alkenyl thiol click reaction;

[0093] S2. Hydrothermally treat the molecular sieve at 140 °C for 2 h, then restore to room temperature, mix it evenly with a titanium source and the modified ionic liquid, and then transfer it to a reaction kettle. Crystallize at 250 °C for 12 h. Then cool the reaction product to room temperature, filter, wash, and dry to obtain the modified titanium silicalite molecular sieve.

[0094] In the step S1, the weight ratio of the imidazole monomer, dimethyl carbonate, tetrahydrofuran, phase transfer agent, and 12-mercaptododecanoic acid is 3.5:5:10:0.01:4; in the step S1, the weight ratio of the yellow intermediate ionic liquid, diphenylvinylphosphine oxide, and photoinitiator is 1:1.5:0.015; the weight ratio of the molecular sieve, titanium source, and modified ionic liquid is 3:0.5:50; the molecular sieve is a ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 28; the imidazole monomer is 1-ethylimidazole; the phase transfer agent is tetrabutylammonium bromide; the photoinitiator is BASF 369; the titanium source is titanium chloride.

[0095] Example 4

[0096] Modified titanium silicalite molecular sieve

[0097] The preparation steps of the modified titanium silicalite molecular sieve are the same as those in Example 1.

[0098] In the step S1, the weight ratio of the imidazole monomer, dimethyl carbonate, tetrahydrofuran, phase transfer agent, and 12-mercaptododecanoic acid is 3.5:10:15:0.05:6; in the step S1, the weight ratio of the yellow intermediate ionic liquid, diphenylvinylphosphine oxide, and photoinitiator is 1:3:0.03; the weight ratio of the molecular sieve, titanium source, and modified ionic liquid is 3:1:80; the molecular sieve is a ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 28; the imidazole monomer is 1-ethyl-3-methylimidazole; the phase transfer agent is cetyltrimethylammonium chloride; the photoinitiator is BASF 754; the titanium source is tetraethyl titanate.

[0099] Example 5

[0100] Modified titanium silicalite molecular sieve

[0101] The preparation steps of the modified titanium silicalite molecular sieve are the same as those in Example 1.

[0102] In the step S1, the weight ratio of imidazole monomer, dimethyl carbonate, tetrahydrofuran, phase transfer agent and 12-mercaptododecanoic acid is 3.5:7.5:12:0.03:5; in the step S1, the weight ratio of yellow intermediate ionic liquid, diphenylvinylphosphine oxide and photoinitiator is 1:2:0.02; the weight ratio of molecular sieve, titanium source and modified ionic liquid is 3:0.7:70; the molecular sieve is ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 28; the imidazole monomer is 1-butylimidazole; the phase transfer agent is cetyltrimethylammonium chloride; the photoinitiator is BASF 1173; the titanium source is tetrabutyl titanate.

[0103] Comparative Example 1

[0104] In this comparative example, the modified ionic liquid in Example 5 was replaced with a conventional ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, and the remaining raw materials, raw material dosages and preparation steps remained unchanged.

[0105] Comparative Example 2

[0106] In this comparative example, the modified ionic liquid in Example 5 was replaced with a yellow intermediate ionic liquid, and the remaining raw materials, raw material dosages and preparation steps remained unchanged.

[0107] Test Example 1

[0108] Evaluation of Structural Characteristic Parameters of Titanium Silicalite Molecular Sieve

[0109] The crystal content of MFI-structured titanium silicalite molecular sieve in the titanium silicalite molecular sieves in Examples 3-5 and Comparative Examples 1-2 was detected by X-ray diffraction, the titanium content of the titanium silicalite molecular sieves in Examples 3-5 and Comparative Examples 1-2 was measured by inductively coupled plasma emission spectrometry, and the pore volume and BET specific surface area of the titanium silicalite molecular sieves in Examples 3-5 and Comparative Examples 1-2 were measured by ASAP 2020PLUS rapid specific surface and pore size analyzer. The above test results are shown in Table 1.

[0110] Table 1 Evaluation Results of Structural Characteristic Parameters of Titanium Silicalite Molecular Sieve

[0111]

[0112] As can be seen from Table 1, Examples 3-5 are superior to Comparative Examples 1-2 in terms of the structural characteristic parameters of the titanium silicalite molecular sieve. In Examples 3-5, the content of the MFI-structured titanium silicalite crystals is relatively high, all being 95% or above, while that in Comparative Example 1 is 90%, and in Comparative Example 2 it is only 85%. This indicates that the titanium silicalite prepared by the method of the present invention has a more regular crystal structure, which is beneficial to the exertion of its catalytic performance. In terms of the titanium content of the titanium silicalite, Examples 3-5 also have an advantage, while the comparative examples are relatively low. A higher titanium content helps to provide more active sites and enhance the catalytic activity. Examples 3-5 also perform excellently in terms of pore volume and BET specific surface area. The BET specific surface area of Example 5 reaches 502.5 m 2 / g, and the pore volume is 0.415 cm 3 / g, while the BET specific surface area of Comparative Example 1 is 460.5 m 2 / g, and the pore volume is 0.245 cm 3 / g. The BET specific surface area of Comparative Example 2 is only 428.7 m 2 / g, and the pore volume is 0.224 cm 3 / g. A larger pore volume and specific surface area are beneficial to the diffusion of reactants and products, improving the reaction rate and selectivity, further proving the effectiveness of the modified ionic liquid prepared by the present invention in optimizing the structure of the titanium silicalite molecular sieve, and enabling the titanium silicalite prepared in Examples 3-5 to have more excellent structural characteristics.

[0113] Test Example 2

[0114] Microscopic Morphology Characterization of Titanium Silicalite Molecular Sieve

[0115] The microscopic morphology of the titanium silicalite molecular sieve in Example 5 was observed by a Hitachi SU8010 field emission scanning electron microscope, and its SEM image is shown in Figure 2 .

[0116] As can be seen from the appendix Figure 2 It can be seen that the titanium silicalite molecular sieve has a relatively rough surface and relatively obvious edges and corners, with a larger specific surface area. Therefore, more active sites can be exposed, and the rough surface and edges and corners can provide more support and stability, reducing the wear and deactivation of the catalyst and extending the service life of the catalyst.

[0117] Test Example 3

[0118] Detection of the Catalytic Ability of Titanium Silicalite Molecular Sieve

[0119] Use a pipette to accurately measure 8mmol of cyclohexanone and add it to a three-necked flask, then add 48mmol of H2O2 with a mass fraction of 30%, then add 32mmol of ammonia water (calculated as NH3), and finally add 0.24g of titanium silicalite catalyst, turn on the magnetic stirrer, stir to make the reactants and the catalyst fully mixed, slowly heat up, raise the temperature of the reaction system to 115°C, and keep the temperature stable. After the reaction is completed, cool the reaction solution to room temperature, transfer the reaction solution to a centrifuge tube, use a centrifuge to centrifuge to separate the titanium silicalite catalyst, take an appropriate amount of supernatant after centrifugation, add a certain amount of acetophenone as an internal standard, mix well, use a microsyringe to draw the mixed sample solution, and inject it into a gas chromatograph for detection and analysis.

[0120] The gas chromatography analysis method is as follows:

[0121] A GC9560 gas chromatograph was used with an injection volume of 0.5 μL, a split ratio of 10:1, an injection port temperature of 270°C, a detector temperature of 250°C, an initial column box temperature of 60°C for 3 min, and then the temperature was increased to 180°C at a rate of 15°C / min and kept for 2 min.

[0122] Then the conversion rate of the reactant cyclohexanone and the selectivity of the product cyclohexanone oxime were calculated. The results are shown in Figure 3 .

[0123] Cyclohexanone conversion rate (%) = (cyclohexanone mole number in raw material - cyclohexanone mole number in product) / cyclohexanone mole number in raw material × 100%

[0124] Cyclohexanone oxime selectivity (%) = the number of moles of cyclohexanone oxime generated in the product / the number of moles of cyclohexanone consumed to generate all products × 100%.

[0125] By the attached Figure 3 It is known that Examples 3-5 are significantly better than Comparative Examples 1-2 in terms of cyclohexanone conversion rate and cyclohexanone oxime selectivity. The cyclohexanone conversion rate in the examples is high, which means that more cyclohexanone participates in the reaction and is converted into products, and the selectivity of the product cyclohexanone oxime is also high, indicating that the proportion of the target product cyclohexanone oxime generated during the reaction is larger and the side reactions are less, which fully demonstrates that the modified titanium silicon molecular sieve prepared by the present invention has excellent catalytic activity and selectivity, can effectively promote the cyclohexanone ammoximation reaction, improve the efficiency of the reaction and the purity of the product, in contrast, the catalytic effect when used in the comparative examples is poor, which further proves the key role of the modified ionic liquid in the present invention in improving the catalytic ability of the catalyst.

[0126] Test Example 4

[0127] Detection of cyclic catalytic ability of titanium silicalite molecular sieve

[0128] The titanium silicalite molecular sieves prepared in each example and comparative example were respectively subjected to 10 repeated cyclohexanone ammoximation reaction tests. After each test was completed, the reaction solution containing the catalyst was first centrifuged at a rate of 1200 r / min for 3 min, and then filtered to separate the catalyst. Subsequently, the catalyst was placed in deionized water with 8 times its mass and oscillated and washed for 15 min to remove the chemical substances adsorbed on the surface of the catalyst. After that, it was filtered and separated again to obtain the washed catalyst. The washed catalyst was placed in a drying oven at 60 °C and dried to a constant weight. After being taken out and naturally cooled to room temperature, it was used as the catalytic component for the next oxime reaction test. This was carried out successively 10 times. After the 10th cyclohexanone ammoximation reaction, the conversion rate of cyclohexanone as the reactant and the selectivity of cyclohexanone oxime as the product were calculated, and based on this, the reduction rate of cyclohexanone conversion and the reduction rate of cyclohexanone oxime selectivity were calculated. The results are shown in Figure 4 .

[0129] Reduction rate of cyclohexanone conversion (%) = (cyclohexanone conversion rate in the 10th time - cyclohexanone conversion rate in the 1st time) / cyclohexanone conversion rate in the 1st time × 100%.

[0130] Reduction rate of cyclohexanone oxime selectivity (%) = (cyclohexanone oxime selectivity in the 10th time - cyclohexanone oxime selectivity in the 1st time) / cyclohexanone oxime selectivity in the 1st time × 100%.

[0131] As can be seen from the attached Figure 4 In the detection of the cyclic catalytic ability of the titanium silicalite molecular sieve, Examples 3 - 5 showed more excellent cyclic stability. As the number of cycles increased, the reduction rates of cyclohexanone conversion and cyclohexanone oxime selectivity in Examples 3 - 5 were relatively low, indicating that after multiple cycles of use, the decline in their catalytic activity and selectivity was relatively small. This shows that the modified titanium silicalite molecular sieve of the present invention has good cyclic use performance, can still maintain a high catalytic efficiency after multiple repeated uses, reduces the loss and replacement frequency of the catalyst, and reduces the production cost. While the reduction rates of cyclohexanone conversion and cyclohexanone oxime selectivity in Comparative Examples 1 - 2 were relatively high, indicating that their cyclic stability was poor and the catalytic performance decreased significantly after multiple uses. This once again verified the advantages of the titanium silicalite molecular sieve prepared by using the modified ionic liquid in the present invention in terms of structure and performance, making it not only perform excellently in the initial catalytic performance, but also maintain good catalytic effects during the cyclic use process, providing strong support for the sustainable production of caprolactam.

[0132] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0133] The above describes the present invention and its implementation manners. Such description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design, without creative efforts, ways and embodiments similar to the technical solution without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production, characterized in that: It includes the following steps: (1) Obtain green electricity through solar photovoltaic power generation, adopt the technology of electrolyzing water to produce hydrogen, use green electricity to decompose water into hydrogen and oxygen, adopt pressure swing adsorption technology for hydrogen purification, then use nitrogen and hydrogen as raw materials to catalytically synthesize ammonia under high temperature and high pressure, and further synthesize ammonia water into ammonia; (2) Add cyclohexanone, ammonia water and hydrogen peroxide into the oximation reaction kettle in proportion. Use cyclohexanone as the starting material, ammonia water provides the amine source, hydrogen peroxide as the oxidant, and then add modified titanium silicalite molecular sieve as the catalyst to carry out the ketone-ammonia oximation reaction to obtain cyclohexanone oxime; (3) Filter the cyclohexanone oxime, separate the modified titanium silicalite molecular sieve catalyst, and the catalyst is recycled after washing, drying and other treatments. Distill the filtered cyclohexanone oxime reaction solution to further purify the reaction product; (4) Add the product purified in step (3) into the rearrangement reaction kettle, add concentrated sulfuric acid as the rearrangement reagent, carry out the Beckmann rearrangement reaction to convert the oxime into caprolactam, filter to separate the caprolactam solid, wash the separated caprolactam solid to remove the impurities and acidic catalyst attached to the surface, and then refine the caprolactam to meet the index requirements; The modified titanium silicalite molecular sieve is prepared by the following steps: S1. Add imidazole monomer and dimethyl carbonate into tetrahydrofuran, then add a phase transfer agent, heat up to 100 °C and react for 10 h, then evaporate the tetrahydrofuran solvent, control the temperature below 15 °C, add 12-mercaptododecanoic acid, age for 3 h, filter, and dry to obtain a yellow intermediate ionic liquid. Mix the yellow intermediate ionic liquid with diphenylethenylphosphine oxide and a photoinitiator, and under ultraviolet light irradiation, through the alkenyl thiol click reaction, obtain a modified ionic liquid; S2. Hydrothermally treat the molecular sieve at 140 °C for 2 h, then restore to room temperature, mix it evenly with a titanium source and a modified ionic liquid, then transfer it to a reaction kettle, crystallize at 250 °C for 12 h, then cool the reaction product to room temperature, filter, wash, and dry to obtain the modified titanium silicalite molecular sieve.

2. The method for coupling green electricity, green hydrogen and green ammonia for caprolactam production according to claim 1, characterized in that: In step S1, the weight ratio of the imidazole monomer, dimethyl carbonate, tetrahydrofuran, phase transfer agent and 12-mercaptododecanoic acid is 3.5:5-10:10-15:0.01-0.05:4-6.

3. The green electricity, green hydrogen, and green ammonia coupling method for caprolactam production according to claim 2, wherein: In step S1, the weight ratio of the yellow intermediate ionic liquid, diphenylethenylphosphine oxide and photoinitiator is 1:1.5-3:0.015-0.

03.

4. The method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production according to claim 3, characterized in that: The weight ratio of the molecular sieve, titanium source and modified ionic liquid is 3:0.5-1:50-80.

5. The method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production according to claim 4, characterized in that: The molecular sieve is ZSM-5 molecular sieve, and the silica-alumina ratio of the ZSM-5 molecular sieve is 28.

6. The green electricity, green hydrogen, and green ammonia coupling method for caprolactam production according to claim 5, characterized in that: The imidazole monomer is one of 1-ethylimidazole, 1-ethyl-3-methylimidazole and 1-butylimidazole.

7. The method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production according to claim 6, characterized in that: The phase transfer agent is one of tetrabutylammonium bromide, cetyltrimethylammonium chloride and cetyltrimethylammonium chloride.

8. The method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production according to claim 7, characterized in that: The photoinitiator is one of BASF 369, BASF 754, BASF 907 and BASF 1173.

9. The method for coupling green electricity, green hydrogen, and green ammonia for caprolactam production according to claim 8, wherein: The titanium source is one of titanium chloride, titanium oxide, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.

10. A green electricity, green hydrogen, and green ammonia coupling device for caprolactam production according to claim 9, characterized in that: It includes: a green energy preparation unit (1), an oximation reaction unit (2), a product purification unit (3), and a rearrangement and refining unit (4); The green energy preparation unit (1) includes: a photovoltaic power generation device (11) that converts solar energy into green electric energy, a water electrolysis hydrogen production device (12) that decomposes water into hydrogen and oxygen using green electricity, a hydrogen purification device (13) that purifies hydrogen through adsorption and desorption processes, a synthetic ammonia device (14) that synthesizes green ammonia using nitrogen and hydrogen as raw materials; an ammonia water production device (15) that synthesizes ammonia water from the produced green ammonia; The photovoltaic power generation device (11) is connected to the power input end of the water electrolysis hydrogen production device (12) through a cable. The high-purity hydrogen outlet of the hydrogen purification device (13) is connected to the hydrogen feed port of the synthetic ammonia device through a pipeline. At the same time, the nitrogen feed port of the synthetic ammonia device is connected to a nitrogen source. The ammonia outlet of the synthetic ammonia device is introduced into the ammonia water production device (15), and the ammonia water production device (15) connects the ammonia water to the oximation reaction unit (2) through a pipeline; The oximation reaction unit (2) includes: an oximation reaction kettle (21) for carrying out the ketone oximation reaction; a cyclohexanone storage device (22) for storing and adding cyclohexanone; a hydrogen peroxide storage device (23) for storing and adding hydrogen peroxide; a catalyst addition device (24) for accurately adding a modified titanium silicalite catalyst; The ammonia water production device (15), the cyclohexanone storage device (22), and the hydrogen peroxide storage device (23) are respectively connected to different feed ports of the oximation reaction kettle (21) through pipelines. The discharge port of the oximation reaction kettle (21) is connected to the product purification unit (3) through a pipeline; The product purification unit (3) includes: a cyclohexanone oxime filtration device (31) for separating the modified titanium silicalite catalyst; a distillation device (32) for distilling and purifying the cyclohexanone oxime reaction solution; The discharge port of the oximation reaction kettle (21) is connected to the feed port of the cyclohexanone oxime filtration device (31). The filtrate outlet of the cyclohexanone oxime filtration device (31) is connected to the feed port of the distillation device (32) through a pipeline. The purified product outlet of the distillation device (32) is connected to the rearrangement and refining unit (4) through a pipeline; The rearrangement and refining unit (4) includes: a rearrangement reaction kettle (41) for carrying out the Beckmann rearrangement reaction; a caprolactam filtration device (42) for separating caprolactam solids, a washing device (43) for washing the caprolactam solids; The purified product outlet of the distillation device (32) of the product purification unit (3) is connected to the feed port of the rearrangement reaction kettle (41). The discharge port of the rearrangement reaction kettle (41) is connected to the feed port of the caprolactam filtration device (42). The solid discharge port of the caprolactam filtration device (42) is connected to the feed port of the washing device (43).

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