Modified molecular sieve and its application in industrial-grade dimethyl carbonate dehydration

Abstract

The application provides a method for removing water from industrial-grade dimethyl carbonate by using a hydrophilic molecular sieve; aims to provide a molecular sieve with good water absorption performance and stability, a preparation method with high efficiency, safety, green environmental protection, and a method for preparing the hydrophilic molecular sieve on a large scale; the method comprises the following steps: dispersing potassium hydroxide and aluminum hydroxide into a solvent, adding strontium nitrate and silica sol to obtain a reaction liquid A, moving the reaction liquid A into a polytetrafluoroethylene-lined stainless steel reaction kettle, and reacting at 80-140 DEG C for 20-24 h to obtain a product hydrophilic molecular sieve; then the molecular sieve is soaked in a silver nitrate solution to obtain a silver-modified molecular sieve; and belongs to the technical field of fine chemical industry.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a hydrophilic molecular sieve for dehydrating industrial-grade dimethyl carbonate, its modified preparation method, and its application. Background Technology

[0002] Dimethyl carbonate (DMC) is an important organic compound with wide applications in industry and laboratories. Due to the presence of functional groups such as methyl, methoxy, carbonyl, and carbonylmethyl in its molecule, it can react with various alcohols, phenols, amines, hydrazines, and esters, exhibiting diverse reactivity and wide range of uses. In 1992, it was registered as a non-toxic solvent in Europe, making it an environmentally friendly organic chemical raw material that meets the requirements of modern "clean processes." DMC possesses excellent physical properties such as good compatibility, high dielectric constant, and low viscosity, and is widely used as a solvent in lithium-ion battery electrolytes, enabling batteries to have high current density, good antioxidant properties, good conductivity, and long battery life.

[0003] Domestic and international DMC production processes are mainly divided into three categories: phosgene method, methanol liquid / gas phase oxidation carbonylation method, and transesterification method. However, industrially produced DMC may contain impurities such as water, acids, alkalis, or other organic substances, which may affect its performance and effectiveness in various applications. Therefore, purifying DMC to 99.99% electronic grade is of great significance for the green transformation of new energy.

[0004] Traditional separation technologies mainly include distillation, extraction, absorption, and crystallization. With the development of the chemical industry, their separation efficiency and processing capacity are constantly improving. Meanwhile, modern separation technologies such as supercritical extraction, novel adsorption technologies, and membrane separation technologies are also constantly developing. Compared with other methods, adsorption separation does not require high temperature or high pressure conditions. It achieves precise control of the separation process by adjusting parameters such as temperature and flow rate, resulting in low cost, low energy consumption, and convenient operation.

[0005] Molecular sieves are porous materials with a regular pore structure, suitable for adsorption and separation. Their molecular size and shape determine their selectivity in adsorption and separation. By selecting molecular sieves with different pore sizes, efficient separation of molecules of different sizes, shapes, and polarities can be achieved. They have wide applications in petrochemicals, gas separation, environmental protection, and biopharmaceuticals, and their high selectivity, controllability, and renewability make them an important tool in adsorption and separation processes.

[0006] Chinese patent CN118026198A reports a method for synthesizing hydrophilic molecular sieves. This invention introduces silanol groups to adjust the framework of the molecular sieve, thereby improving its hydrophilicity. Ion exchange is also performed, further enhancing the hydrophilic properties. However, this method has a long reaction time, low efficiency, uses a large amount of organic reagents, and is difficult to scale up for industrial production. Summary of the Invention

[0007] To address the aforementioned shortcomings, the purpose of this invention is to provide a method for dewatering industrial-grade dimethyl carbonate using hydrophilic molecular sieves.

[0008] Therefore, the technical solution provided by this invention is as follows:

[0009] A method for dehydrating industrial-grade dimethyl carbonate using a hydrophilic molecular sieve comprises the following steps:

[0010] 1) The hydrophilic molecular sieve is packed into the adsorption column and the two sides are filled with quartz wool;

[0011] 2) Fill the bubbler with deionized water, open the air valve, close the adsorption column valve, control the helium flow rate at 3-5 sccm with the mass flow controller, and turn on the helium for purging.

[0012] 3) After the helium gas in step 2) has stabilized, close the air valve and open the adsorption column valve to allow the helium gas to carry the deionized water through the adsorption column in step 1).

[0013] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection.

[0014] The structure of the hydrophilic molecular sieve is as follows:

[0015]

[0016] Furthermore, in the above-mentioned method for removing water from industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the ratio of the hydrophilic molecular sieve to deionized water is 0.4–1 g: 30–100 mL.

[0017] Furthermore, in the above-mentioned method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the hydrophilic molecular sieve is synthesized by the following method:

[0018] 3) Disperse potassium hydroxide and aluminum hydroxide in a solvent, then add strontium nitrate and silica sol to mix and obtain a reaction solution. Transfer the reaction solution into a reaction vessel and react at 80-140℃ for 20-24 hours to obtain the product, hydrophilic molecular sieve.

[0019] 4) The hydrophilic molecular sieve prepared in step 1) is immersed in silver nitrate solution for ion exchange to obtain silver-modified hydrophilic molecular sieve.

[0020] The molar ratio of aluminum hydroxide, silica sol, potassium hydroxide, and strontium nitrate in step 1) is 0.25–0.6:1–3:0.66:0.01.

[0021] Furthermore, in the above-mentioned method for removing water from industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the solvent in step 1) is deionized water.

[0022] Furthermore, in the above-mentioned method for removing water from industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the concentration of silver nitrate in step 2) is 0.01–0.05 mol / L.

[0023] Furthermore, in the above-mentioned method for removing water from industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the mass ratio of the hydrophilic molecular sieve to the silver nitrate solution in step 2) is 1:20 to 50.

[0024] Furthermore, in the above-mentioned method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the ion exchange time in step 2) is 40–80 min.

[0025] Furthermore, in the above-mentioned method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves, the reactor is a stainless steel reactor lined with polytetrafluoroethylene.

[0026] Furthermore, in the above-mentioned method for preparing hydrophilic molecular sieves for dehydrating industrial-grade dimethyl carbonate, the reaction system pressure is atmospheric pressure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The molecular sieve provided in this application has no organic template, which effectively avoids environmental pollution. Moreover, the synthesis process is simple, convenient, easy to operate, and has a short reaction time.

[0029] 2. The technical solution provided in this application alters the potassium ions in the molecular sieve framework through ion exchange, thereby enhancing the polarity of the molecular sieve and further improving its hydrophilicity.

[0030] 3. The technical solution provided by this invention uses hydrophilic molecular sieves for water removal, which can efficiently remove trace amounts of water from industrial-grade dimethyl carbonate, thereby improving the purity of dimethyl carbonate and meeting the demand for high-quality dimethyl carbonate. Attached Figure Description

[0031] Figure 1 The XRD pattern of the molecular sieve obtained in Case 1;

[0032] Figure 2 SEM image of the molecular sieve obtained in Case 1;

[0033] Figure 3 This is the design drawing of the molecular sieve used as an adsorbent in the dynamic water adsorption device obtained from Implementation Case 1;

[0034] Figure 4 The molecular sieve obtained from Implementation Case 1 is used as an adsorbent in dynamic water adsorption breakthrough diagram. Detailed Implementation

[0035] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves. The method includes the following steps in sequence:

[0038] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0039] 2) Add 30 mL of deionized water to the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3 sccm using the mass flow controller, and turn on the helium gas for purging.

[0040] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0041] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection;

[0042] Real-time gas chromatography analysis showed that water began to elute through the adsorption bed at 250 min / g for molecular sieve K-4, and water began to elute through the adsorption bed at 400 min / g for silver-modified molecular sieve AgK-0.025.

[0043] The preparation method of the hydrophilic molecular sieve used in this embodiment includes the following steps:

[0044] (1) Add 0.7g potassium hydroxide and 0.4g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0045] (2) After cooling the solution obtained in step (1) to room temperature, add 0.05g of strontium nitrate, then add 4.6g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0046] (3) The molecular sieve gel obtained in step (2) is transferred into a reactor for crystallization reaction at 140°C for 24 hours.

[0047] (4) The liquid obtained after the reaction in step (3) is filtered, washed and dried to obtain hydrophilic molecular sieve K-4.

[0048] (5) The hydrophilic molecular sieve K-4 obtained in step (4) was ion exchanged in a 0.025 mol / L silver nitrate solution for 1 h in the dark. The solution after the reaction was filtered, washed and dried overnight to obtain silver modified molecular sieve AgK-0.025.

[0049] Example 2

[0050] This embodiment provides a method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves. The method includes the following steps in sequence:

[0051] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0052] 2) Put 30 mL of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3 sccm with the mass flow controller, and turn on the helium gas for purging.

[0053] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0054] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection; through real-time detection and analysis by gas chromatography, water begins to elute through the adsorption bed of the silver-modified molecular sieve AgK-0.05 at 250 min / g. Although the elution point is the same as that in Example 1 as in the unmodified case, the slope of the mass transfer region of the silver-modified molecular sieve AgK-0.05 is higher, and the diffusion coefficient of water molecules inside the pores is stronger.

[0055] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0056] 1) Add 0.7g potassium hydroxide and 0.4g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0057] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 4.6g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0058] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0059] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-4.

[0060] 5) The hydrophilic molecular sieve K-4 obtained in step 4) was ion exchanged in a 0.05 mol / L silver nitrate solution for 1 h in the dark. The solution after the reaction was filtered, washed, and dried overnight to obtain silver-modified molecular sieve AgK-0.05.

[0061] Example 3

[0062] This embodiment provides a method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves. The method includes the following steps in sequence:

[0063] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0064] 2) Put 30 mL of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3 sccm with the mass flow controller, and turn on the helium gas for purging.

[0065] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0066] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection; through real-time detection and analysis by gas chromatography, water begins to elute through the adsorption bed at 270 min / g of the silver-modified molecular sieve.

[0067] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0068] 1) Add 0.7g potassium hydroxide and 0.4g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0069] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 4.6g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0070] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0071] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-4.

[0072] 5) The hydrophilic molecular sieve K-4 obtained in step 4) was subjected to ion exchange in a 0.01 mol / L silver nitrate solution for 1 h in the dark. The solution after reaction was filtered, washed, and dried overnight to obtain silver-modified molecular sieve AgK-0.01.

[0073] Example 4

[0074] This embodiment provides a method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves. The method includes the following steps in sequence:

[0075] 1) Pack 1g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0076] 2) Put 100mL of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3sccm with the mass flow controller, and turn on the helium gas for purging.

[0077] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0078] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection;

[0079] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0080] 1) Add 0.7g potassium hydroxide and 0.4g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0081] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 4.6g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0082] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0083] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-4;

[0084] 5) The hydrophilic molecular sieve K-4 obtained in step 4) was subjected to ion exchange in a 0.01 mol / L silver nitrate solution for 1 h in the dark. The solution after reaction was filtered, washed, and dried overnight to obtain silver-modified molecular sieve AgK-0.01.

[0085] Real-time gas chromatography analysis showed that water began to elute through the adsorption bed at a molecular sieve concentration of 330 min / g.

[0086] Comparative Example 1

[0087] This embodiment provides a method for dehydrating industrial-grade dimethyl carbonate using hydrophilic molecular sieves. The method includes the following steps in sequence:

[0088] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0089] 2) Put 30ml of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3sccm with the mass flow controller, and turn on the helium gas for purging.

[0090] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0091] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection; through real-time detection and analysis by gas chromatography, water begins to elute through the adsorption bed at 280 min / g of molecular sieve.

[0092] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0093] 1) Add 0.7g potassium hydroxide and 0.2g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0094] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 2.3g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0095] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0096] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-2.

[0097] Comparative Example 2

[0098] This comparative example provides a method for dehydrating industrial-grade dimethyl carbonate using a hydrophilic molecular sieve. The method comprises the following steps:

[0099] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0100] 2) Put 30 mL of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3 sccm with the mass flow controller, and turn on the helium gas for purging.

[0101] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0102] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection; through real-time detection and analysis by gas chromatography, water begins to elute through the adsorption bed at 250 min / g of molecular sieve.

[0103] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0104] 1) Add 0.7g potassium hydroxide and 0.2g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0105] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 4.6g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0106] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0107] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-1.

[0108] Comparative Example 3

[0109] This comparative example provides a method for dehydrating industrial-grade dimethyl carbonate using a hydrophilic molecular sieve. The method comprises the following steps:

[0110] 1) Pack 0.4g of molecular sieve into the adsorption column and fill both sides with quartz wool;

[0111] 2) Put 30 mL of deionized water into the bubbler, open the air valve, close the adsorption column valve, control the helium flow rate to 3 sccm with the mass flow controller, and turn on the helium gas for purging.

[0112] 3) After the helium gas in step 2) stabilizes, close the air valve and open the adsorption column valve to allow the helium gas to carry dimethyl carbonate and methanol through the adsorption column in step 1).

[0113] 4) Turn on the gas chromatograph and pass the tail gas described in step 3) into the gas chromatograph for real-time detection; 5) Through real-time detection and analysis by gas chromatography, water begins to elute through the adsorption bed when the molecular sieve reaches 170 min / g.

[0114] A method for preparing a hydrophilic molecular sieve for dehydration of industrial-grade dimethyl carbonate includes the following steps:

[0115] 1) Add 0.7g potassium hydroxide and 0.2g aluminum hydroxide to 2mL of deionized water and heat at 100℃ for 10min to obtain a clear solution.

[0116] 2) After cooling the solution obtained in step 1) to room temperature, add 0.05g of strontium nitrate, then add 6.9g of silica sol and 5mL of deionized water, and stir at room temperature for 60min to obtain molecular sieve gel.

[0117] 3) Transfer the molecular sieve gel obtained in step 2) into a reaction vessel for crystallization reaction, and crystallize at 140℃ for 24h.

[0118] 4) The liquid obtained after the reaction in step 3) is filtered, washed, and dried to obtain hydrophilic molecular sieve K-8.

[0119] By X-ray diffraction pattern ( Figure 1 It can be seen that the synthesized molecular sieve belongs to the KFI type; through Figure 3 The apparatus shown was used for dynamic water permeation experiments. Comparing Examples 1-3, it can be seen that the hydrophilicity of the silver-modified molecular sieve is affected compared to the unmodified molecular sieve. Although the elution point of water through the adsorption column increased in Comparative Examples 1 and 2 compared to Example 1, Example 1 has a larger diffusion coefficient than Comparative Examples 1 and 2. The morphology and size of the modified molecular sieve are also different. Figure 2 There was no significant change. Water was eluted through the adsorption column at 400 min / g, which was a very significant enhancement compared to elution at 250 min / g before modification.

Claims

1. A modified molecular sieve characterized by, The modified molecular sieve is synthesized by the following method: 1) dispersing potassium hydroxide and aluminum hydroxide into a solvent, then adding strontium nitrate and silica sol to obtain a reaction solution, moving the reaction solution into a reaction kettle, and reacting at 80-140 DEG C for 20-24 h to obtain a product modified molecular sieve; 2) soaking the modified molecular sieve prepared in step 1) of step 1) in a silver nitrate solution to perform ion exchange, and obtaining a silver modified modified molecular sieve; The molar ratio of the aluminum hydroxide, silica sol, potassium hydroxide and strontium nitrate in step 1) is 0.25-0.6:1-3:0.66:0.

01.

2. The modified molecular sieve of claim 1, wherein, The solvent in step 1) is deionized water.

3. The modified molecular sieve of claim 1, wherein, The concentration of the silver nitrate in step 2) is 0.02-0.4 mol / L.

4. The modified molecular sieve of claim 1, wherein, The mass ratio of the modified molecular sieve to the silver nitrate solution in step 2) is 1:20-50.

5. The modified molecular sieve of claim 1, wherein The ion exchange time in step 2) is 40-80 min.

6. The modified molecular sieve of claim 1, wherein, The reaction kettle is a polytetrafluoroethylene-lined stainless steel reaction kettle.

7. The modified molecular sieve of claim 1 for the preparation of technical grade dimethyl carbonate characterized by, The modified molecular sieve in claim 1 is used for water removal to remove trace water in industrial-grade dimethyl carbonate.

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