Confinement type iodine-based homogeneous immobilized catalyst, preparation method and application thereof
By enhancing the electrostatic interaction between iodide ions and quaternary ammonium ions through the confinement effect of molecular sieves, a confined iodine-based homogeneous supported catalyst was constructed. This solved the problems of stability and complex preparation process of homogeneous supported catalysts, and achieved highly efficient catalysis of CO2 and epoxide reaction, reducing industrial costs and environmental impact.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-27
- Publication Date
- 2026-05-29
AI Technical Summary
Existing homogeneous supported catalysts have poor stability, the preparation process of confined catalysts is complicated and demanding, the time and economic costs of industrial synthesis are high, and there are also environmental pollution problems.
By enhancing the electrostatic interaction between iodide ions and quaternary ammonium ions through the confinement effect of molecular sieves, a confined structure was constructed to prepare a confined iodine-based homogeneous supported catalyst, which includes a support, iodide ions, magnesium ions, and quaternary ammonium ions. The molar ratio and pore size were optimized to simplify the preparation process and improve catalytic activity.
The catalyst significantly enhances CO2 adsorption and activation capabilities under mild conditions, improves the activation capacity of epoxides, achieves a propylene oxide conversion rate of over 73%, and a propylene carbonate selectivity of over 85%. It is also easy to recover, reducing synthesis costs and environmental pollution.
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Figure CN122098684A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to a confined iodine-based homogeneous supported catalyst, its preparation method, and its application. Background Technology
[0002] Carbon dioxide is a non-toxic, inexpensive, and highly promising C1 resource. Currently, the high-end and green development of chemical products is becoming a new trend. Catalytically converting CO2 into high-value-added chemicals is of great significance for energy conservation, emission reduction, and the recycling of carbon resources, and is also a major strategic issue for the scientific community. Among these, the cycloaddition reaction of CO2 to form cyclic carbonates is a reaction pathway that conforms to the principle of atom economy. It can replace toxic and polluting traditional reaction substrates such as phosgene, and the process is green, possessing extremely high economic value and market potential.
[0003] The synthesis of carbonates via cycloaddition reactions typically requires harsh conditions. Therefore, from an energy-saving and environmental protection perspective, developing catalysts that enable efficient CO2 conversion under mild conditions is crucial. Currently reported catalysts for synthesizing cyclic carbonates can be categorized into homogeneous and heterogeneous catalysts. Homogeneous catalysts mainly refer to homogeneous catalytic systems composed of halide anions and Lewis acids. Common homogeneous catalysts include ionic liquids, quaternary ammonium salts, Lewis acid metal complexes, and small organic molecules. These homogeneous catalysts have attracted widespread attention due to their high catalytic activity and good thermal stability. However, most homogeneous catalysts suffer from difficulties in separation after the reaction, high costs, and the need for environmentally harmful organic solvents during separation, making large-scale industrial application difficult. For example, patent application CN111393402A discloses a... A method for preparing propylene carbonate by the cycloaddition of CO2 with epoxides via acid / quaternary ammonium salt composite catalysis. The addition of acid significantly improves catalytic performance, but product separation is relatively difficult. Patent application CN112250656A discloses a method for synthesizing cyclic carbonates based on multi-active-center ionic liquid catalysis. The ionic liquid anion can promote the ring-opening of epoxides, but it is not easy to reuse.
[0004] Heterogeneous catalysts, due to their poor solubility in the reaction system, facilitate product separation and have thus gradually become a research focus in the field of green and efficient synthesis of cyclic carbonates. Currently developed heterogeneous catalysts include ion exchange resins, metal oxides, metal Schiff base complexes, and metal-organic frameworks (MOFs). However, current heterogeneous catalysts suffer from problems such as low catalyst activity due to insufficient active sites or decreased catalyst stability due to the loss of active sites during long-term use. Furthermore, the preparation processes of metal Schiff base complexes and MOFs are complex and expensive, making them unsuitable for large-scale production. For example, patent application CN116020568A discloses a heterogeneous catalyst for the synthesis of propylene carbonate, which is composed of a metal Schiff base complex, halide anions, and nanocage materials; the synthesis process of this catalyst is cumbersome and its structure is complex.
[0005] Compared to homogeneous and heterogeneous catalytic systems, homogeneous supported catalytic systems maintain high catalytic activity while facilitating product separation and purification, thus saving energy. However, publicly available homogeneous supported catalysts often require grafting with quaternary ammonium salts or ionic liquids, leading to poor catalyst stability and a rapid decline in catalytic activity. Traditional confined catalyst preparation requires the addition of solvents, encapsulating agents, and the construction of core-shell structures, making the synthesis process cumbersome and demanding. This significantly increases the time and economic costs of industrial synthesis and also causes environmental pollution. Therefore, finding a heterogeneous catalyst with a simple preparation process, high activity, high stability, and easily separable products is an urgent technical problem to be solved. Summary of the Invention
[0006] The purpose of this invention is to overcome the problems of poor stability and easy deactivation of existing homogeneous supported catalysts; the cumbersome and demanding preparation process of confined catalysts, the high time and economic costs in industrial synthesis, and the environmental pollution caused by confined catalysts. This invention provides a confined iodine-based homogeneous supported catalyst, its preparation method, and its application. This method enhances the I-type catalyst through the molecular sieve confinement effect. - The electrostatic interaction with quaternary ammonium ions constructs a confined structure, which significantly enhances the catalyst's ability to adsorb and activate CO2, while also activating epoxides, thereby improving its catalytic activity.
[0007] To achieve the above objectives, the first aspect of the present invention provides a confined iodine-based homogeneous immobilized catalyst, the catalyst comprising a support and iodine ions, magnesium ions and quaternary ammonium ions supported on the support, wherein the molar ratio of the magnesium ions, the quaternary ammonium ions, the iodine ions and the support is 0.01-1:4-15:1-30:1.
[0008] Preferably, the support is selected from at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3.
[0009] Preferably, the pore size of the carrier is 0.1-10 nm, more preferably 0.1-5 nm.
[0010] A second aspect of this invention provides a method for preparing a confined iodine-based homogeneous supported catalyst, the method comprising the following steps:
[0011] (1) React the carrier, alkali source, magnesium source, iodine source and water;
[0012] (2) The reaction product obtained in step (1) is mixed with an ammonium source to obtain a mixed solution, and then the mixed solution is crystallized.
[0013] Preferably, the molar ratio of the magnesium source, the alkali source, the iodine source, the water, the ammonium source, and the carrier is 0.01-1:0.1-2:0.1-2:4-15:0.1-2:1, more preferably 0.01-0.1:0.4-1.5:0.1-1:6-15:0.2-1:1.
[0014] Preferably, the support is selected from at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3.
[0015] Preferably, the pore size of the carrier is 0.1-10 nm, more preferably 0.1-5 nm.
[0016] Preferably, the magnesium source is selected from at least one of magnesium nitrate, magnesium acetate, and magnesium chloride.
[0017] Preferably, the alkali source is selected from at least one of sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia, n-butylamine, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.
[0018] Preferably, the iodine source is selected from at least one of potassium iodide, tetrabutylammonium iodide, potassium iodate, and tetrapropylammonium iodide.
[0019] Preferably, the ammonium source is selected from at least one of ammonium chloride, ammonium nitrate, ammonium fluoride, and ammonium bromide.
[0020] Preferably, in step (1), the reaction conditions include: a temperature of 100-200℃, more preferably 120-160℃; and a time of 0.5-4h, more preferably 0.5-3h.
[0021] Preferably, in step (2), the pH value of the mixed solution is 7-11, more preferably 7-10.
[0022] Preferably, in step (2), the crystallization conditions include: a temperature of 80-200℃, more preferably 100-170℃; and a time of 10-72h, more preferably 20-30h.
[0023] A third aspect of the present invention provides the application of the confined iodine-based homogeneous supported catalyst described above in the catalytic synthesis of cyclic carbonates from CO2 and epoxides.
[0024] The confined iodine-based homogeneous supported catalyst of this invention enhances the electrostatic interaction between iodide ions and quaternary ammonium ions through the molecular sieve confinement effect, constructing a confined structure, increasing the loading of active centers on the support framework, and strengthening the effective collision between reactant molecules and active centers. When the catalyst is used in the catalytic synthesis of cyclic carbonates from CO2 and epoxides, the increase in magnesium ion active sites improves the catalyst's ability to adsorb and activate CO2, and the increase in iodide ion active sites improves the catalyst's ability to activate epoxides. During the catalytic process, the conversion rate of propylene oxide can reach over 73%, and the selectivity of propylene carbonate can reach over 85%.
[0025] The method for preparing confined iodine-based homogeneous supported catalysts described in this invention constructs a confined structure by adjusting the ratio of alkali source, magnesium source, and iodine source. This structure can precisely control the content of magnesium ions in the framework, thereby adjusting the acidity of the support framework, increasing the adsorption of quaternary ammonium ions in the framework, and further controlling the content of iodine ions, thus enabling the targeted design of confined catalysts with different iodine contents.
[0026] The confined iodine-based homogeneous immobilized catalyst of the present invention is economical and environmentally friendly. The raw materials are inexpensive and readily available. It does not require reflux treatment with toxic organic solvents under harsh conditions, does not require the addition of encapsulating agents, and does not require the introduction of polymers to construct a core-shell structure. This greatly reduces the synthesis time and steps, produces no waste gas emissions, and the prepared catalyst is easy to recover. Attached Figure Description
[0027] Figure 1 The attached figure shows the physical adsorption and desorption of the confined iodine-based homogeneous supported catalyst Cat-2 prepared in Example 2;
[0028] Figure 2 This is a pore size distribution diagram of the confined iodine-based homogeneous supported catalyst Cat-2 prepared in Example 2. Detailed Implementation
[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.
[0030] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0031] The confined iodine-based homogeneous immobilized catalyst of the present invention comprises a support and iodine ions, magnesium ions and quaternary ammonium ions supported on the support, wherein the molar ratio of the magnesium ions, the quaternary ammonium ions, the iodine ions and the support is 0.01-1:0.2-4:0.1-2:1.
[0032] In a preferred embodiment, the molar ratio of magnesium ions, quaternary ammonium ions, iodide ions, and the support can be 0.01-0.1:0.2-2.5:0.1-1:1. In these preferred embodiments, the confined iodine-based homogeneous supported catalyst of the present invention has a support framework loaded with more active centers, and the catalyst exhibits better catalytic activity.
[0033] In this invention, the carrier can be at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3, preferably Beta molecular sieve.
[0034] like Figure 1 As shown, in the catalyst of the present invention, the support has a uniformly distributed microporous structure.
[0035] like Figure 2 As shown, in the catalyst of the present invention, the pore size of the support can be 0.1-10 nm, preferably 0.1-5 nm, and more preferably 0.4-2 nm. In the present invention, when the pore size of the support is within the above range (especially the preferred range), the catalyst can utilize the confinement effect to load more active centers on the support, thereby further improving the catalytic activity of the catalyst.
[0036] The confined iodine-based homogeneous immobilized catalyst of the present invention can be prepared by conventional methods in the art. In a preferred embodiment, the confined iodine-based homogeneous immobilized catalyst can be prepared by a method for preparing a confined iodine-based homogeneous immobilized catalyst, the method comprising:
[0037] (1) React the carrier, alkali source, magnesium source, iodine source and water;
[0038] (2) The reaction product obtained in step (1) is mixed with an ammonium source to obtain a mixed solution, and then the mixed solution is crystallized.
[0039] In the method described in this invention, the molar ratio of the magnesium source, the alkali source, the iodine source, the water, the ammonium source, and the support can be 0.01-1:0.1-2:0.1-2:4-15:0.1-2:1, preferably 0.01-0.1:0.4-1.5:0.1-1:6-15:0.2-1:1, and more preferably 0.01-0.06:0.5-1:0.1-0.6:8-12:0.4-0.8:1. In these embodiments, when the molar ratio of the magnesium source, the alkali source, the iodine source, the water, the ammonium source, and the support is within the above-mentioned range (especially the preferred range), the method can directionally regulate the iodine ion content, further improving the catalytic activity of the prepared catalyst.
[0040] In this invention, the carrier can be at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3, preferably Beta molecular sieve.
[0041] In the method described in this invention, the pore size of the support can be 0.1-10 nm, preferably 0.1-5 nm, and more preferably 0.4-2 nm. In the method described in this invention, when the pore size of the support is within the above range (especially the preferred range), the catalyst can utilize the confinement effect to load more active centers on the support, further improving the catalytic activity of the catalyst.
[0042] In this invention, the magnesium source can be at least one of magnesium nitrate, magnesium acetate, and magnesium chloride, preferably magnesium nitrate; the alkali source is selected from at least one of sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia, n-butylamine, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide, preferably tetrabutylammonium hydroxide; the iodine source can be at least one of potassium iodide, tetrabutylammonium iodide, potassium iodate, and tetrapropylammonium iodide, preferably tetrabutylammonium iodide. In this invention, when the added magnesium source, alkali source, and iodine source are of the above-mentioned types (especially the preferred types), the prepared catalyst exhibits excellent catalytic activity.
[0043] In this invention, the ammonium source can be at least one of ammonium chloride, ammonium nitrate, ammonium fluoride, and ammonium bromide, preferably ammonium fluoride. In the method described in this invention, when the added ammonium source is one of the above-mentioned ammonium salts (especially preferably ammonium salts), the ammonium source can slowly release alkalinity, control the pH value of the reaction environment, and further improve the catalytic activity of the prepared catalyst.
[0044] In a preferred embodiment, the ammonium source can be used as an aqueous solution, and the concentration of the aqueous solution can be 1-10 mol / L, more preferably 4-8 mol / L.
[0045] In the method described in this invention, the reaction conditions in step (1) may include: a temperature of 100-200°C, preferably 120-160°C, more preferably 130-150°C; and a time of 0.5-4 h, preferably 0.5-3 h, more preferably 1-2 h. In these embodiments, when the reaction conditions are within the above ranges (especially the preferred ranges), the catalyst prepared by the reaction exhibits excellent catalytic activity.
[0046] In the method described in this invention, in step (2), the pH value of the mixed solution can be 7-11, preferably 7-10, and more preferably 7-9. In these embodiments, when the pH value of the mixed solution is within the above range (especially the preferred range), the magnesium ions can be better immobilized on the support surface, thereby improving the catalytic activity of the catalyst.
[0047] In the method described in this invention, in step (2), the crystallization temperature is higher than the complete crystallization temperature and lower than the decomposition temperature, and the crystallization time is not less than the complete crystallization time. In a more preferred embodiment, the crystallization conditions include: a temperature of 80-200°C, preferably 100-170°C; and a time of 10-72 h, preferably 20-30 h. In these embodiments, when the crystallization conditions are within the above ranges (especially the preferred ranges), the prepared catalyst exhibits excellent catalytic activity.
[0048] In some embodiments, the method may further include cooling, separating, washing, and drying the crystallized product.
[0049] In a preferred embodiment, the cooling can be water cooling or natural cooling, more preferably natural cooling.
[0050] In a preferred embodiment, the solid-liquid separation can be centrifugal separation and / or vacuum filtration separation, more preferably vacuum filtration separation.
[0051] In some embodiments, the drying temperature is lower than the decomposition temperature of the catalyst, preferably 40-120°C, more preferably 70-90°C.
[0052] In some embodiments, the process of preparing the confined iodine-based homogeneous supported catalyst may include: mixing a support, a magnesium source, an iodine source, an alkali source, and water, stirring at room temperature for 10-30 min, and then incubating in an oil bath at 100-200°C for 0.5-4 h to obtain a first reaction product; then dissolving an ammonium source in water and adding it to the first reaction product to form a mixed solution with a pH of 7-11, and then crystallizing the mixed solution at 80-200°C for 10-72 h to obtain a second reaction product, wherein the molar ratio of the magnesium source, the alkali source, the iodine source, the water, the ammonium source, and the support may be 0.01-1:0.1-2:0.1-2:4-15:0.1-2:1; cooling the second reaction product to room temperature, filtering, washing alternately with ethanol and water, and drying in an oven at 40-120°C for 10-20 h. When the preparation method is carried out according to this embodiment, the prepared confined iodine-based homogeneous supported catalyst has superior catalytic activity.
[0053] The confined iodine-based homogeneous immobilized catalyst of the present invention can be used in the catalytic synthesis of cyclic carbonates from CO2 and epoxides. The magnesium ion active sites can adsorb and activate CO2, and the iodine ion active sites can activate epoxides. In the catalytic reaction involving the catalyst of the present invention, the conversion rate of propylene oxide can reach more than 73%, and the selectivity of propylene carbonate can reach more than 85%.
[0054] The following examples further illustrate the confined iodine-based homogeneous immobilized catalyst of the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.
[0055] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods in the art.
[0056] Unless otherwise specified, all experimental materials used in the following examples are commercially available.
[0057] Example 1
[0058] (1) Take 0.6g Beta molecular sieve, 0.051g magnesium nitrate hexahydrate, 1.1090g tetrabutylammonium iodide, 2.092g tetrabutylammonium hydroxide and 1g water, mix them and stir at room temperature for 20min, then in an oil bath at 140℃ for 1h.
[0059] (2) Take 0.188g of ammonium fluoride and 1.018g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 8. Then, crystallize the mixed solution at 140°C for 24 hours. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.02:0.3:0.8:0.5:11.
[0060] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous supported catalyst described in this invention, designated as Cat-1, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.02:1.1:0.3.
[0061] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-1 is 0.5 nm.
[0062] Example 2
[0063] (1) Take 0.6g TS-Beta molecular sieve, 0.051g magnesium nitrate hexahydrate, 1.1090g tetrabutylammonium iodide, 2.092g tetrabutylammonium hydroxide and 1g water, mix them and stir at room temperature for 20min, and then put the resulting solution in an oil bath at 140℃ for 1h.
[0064] (2) Take 0.188g of ammonium fluoride and 1.018g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 8. Then, crystallize the mixed solution at 140°C for 24 hours. The molar ratio of the TS-Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.019:0.29:0.79:0.49:10.94.
[0065] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous immobilized catalyst described in this invention, designated as Cat-2, is obtained, wherein the molar ratio of TS-Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodide ions supported on the surface of TS-Beta molecular sieve is 1:0.019:0.309:0.29.
[0066] like Figure 2 As shown in the figure, the N2 adsorption-desorption characterization results indicate that the pore size of the catalyst Cat-2 is 0.52 nm.
[0067] Example 3
[0068] (1) Take 0.6g Beta molecular sieve, 0.051g magnesium nitrate hexahydrate, 0.369g tetrabutylammonium iodide, 2.092g tetrabutylammonium hydroxide and 1g water, mix them and stir at room temperature for 20min, and then put the resulting solution in an oil bath at 100℃ for 4h.
[0069] (2) Take 0.188g of ammonium fluoride and 1.018g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 8. Then, crystallize the mixed solution at 140°C for 24 hours. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.02:0.1:0.8:0.5:11.
[0070] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous immobilized catalyst described in this invention, designated as Cat-3, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.02:0.9:0.1.
[0071] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-3 is 0.5 nm.
[0072] Example 4
[0073] (1) Take 0.6g Beta molecular sieve, 0.1g magnesium nitrate hexahydrate, 1.1090g tetrabutylammonium iodide, 3g tetrabutylammonium hydroxide and 1g water, mix them and stir at room temperature for 20min, and then put the resulting solution in an oil bath at 200℃ for 0.5h.
[0074] (2) Take 0.188g of ammonium fluoride and 1.018g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 9. Then, crystallize the mixed solution at 200℃ for 10h. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.04:0.3:0.12:0.5:11.
[0075] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous supported catalyst described in this invention, designated as Cat-4, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.04:0.42:0.3.
[0076] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-4 is 0.6 nm.
[0077] Example 5
[0078] (1) Take 0.6g Ti-Beta molecular sieve, 0.051g magnesium nitrate hexahydrate, 1.475g tetrabutylammonium iodide, 2.092g tetrabutylammonium hydroxide and 0.8g water, mix them and stir at room temperature for 20min, then put the resulting solution into an oil bath at 130℃ for 1h.
[0079] (2) Take 0.188g of ammonium fluoride and 1.018g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of . Then, crystallize the mixed solution at 80°C for 72h. The molar ratio of the Ti-Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.02:0.4:0.8:0.5:10.1.
[0080] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous immobilized catalyst described in this invention, designated as Cat-5, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.02:1.2:0.4.
[0081] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-5 is 0.53 nm.
[0082] Example 6
[0083] (1) Take 0.6g Beta molecular sieve, 0.025g magnesium nitrate hexahydrate, 0.37g tetrabutylammonium iodide, 0.2615g tetrabutylammonium hydroxide and 0.37g water, mix them and stir at room temperature for 20min, then put the resulting solution in an oil bath at 130℃ for 1h.
[0084] (2) Take 0.0376g of ammonium fluoride and 0.37g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 10. Then, crystallize the mixed solution at 140°C for 24 hours. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.01:0.1:0.1:0.1:4.
[0085] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous supported catalyst described in this invention, designated Cat-6, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.01:0.2:0.1.
[0086] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-6 is 0.65 nm.
[0087] Example 7
[0088] (1) Take 0.6g Beta molecular sieve, 2.55g magnesium nitrate hexahydrate, 7.76g tetrabutylammonium iodide, 5.23g tetrabutylammonium hydroxide and 1.36g water, mix them and stir at room temperature for 20min, then put the resulting solution in an oil bath at 140℃ for 1h.
[0089] (2) Take 0.752g of ammonium fluoride and 1.47g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 9. Then, crystallize the mixed solution at 140℃ for 20h. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.02:0.3:0.8:0.5:10.1.
[0090] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous immobilized catalyst described in this invention, designated as Cat-7, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.02:1.1:0.3.
[0091] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-7 is 0.53 nm.
[0092] Example 8
[0093] (1) Take 0.6g Beta molecular sieve, 1.417g magnesium chloride, 9.2417g tetrapropylammonium iodide, 4.754g tetrabutylammonium hydroxide and 2.72g water, mix them and stir at room temperature for 20min, then put the resulting solution into an oil bath at 220℃ for 5h.
[0094] (2) Take 0.94g of ammonium fluoride and 2.78g of water, mix and dissolve them, and pour them into the product obtained in step (1) to form a mixed solution with a pH value of 12. Then, crystallize the mixed solution at 220°C for 8 hours. The molar ratio of the Beta molecular sieve, the magnesium chloride, the tetrapropylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.05:0.35:0.8:0.5:11.
[0095] (3) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous supported catalyst described in this invention, designated Cat-8, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.05:1.15:0.35.
[0096] The N2 adsorption-desorption characterization results show that the pore size of the catalyst Cat-8 is 0.51 nm.
[0097] Comparative Example 1
[0098] (1) Take 0.6g Beta molecular sieve, 0.051g magnesium nitrate hexahydrate, 1.109g tetrabutylammonium iodide, 6g tetrabutylammonium hydroxide, 0.188g ammonium fluoride and 2.018g water, mix them and stir at room temperature for 20min to form a mixed solution with a pH of 12. Then, put the solution in an oil bath at 140℃ for 24h. The molar ratio of the Beta molecular sieve, the magnesium nitrate hexahydrate, the tetrabutylammonium iodide, the tetrabutylammonium hydroxide, the ammonium fluoride and the water is 1:0.02:0.3:2.3:0.5:11.
[0099] (2) After cooling the obtained product to room temperature, filter it and wash it alternately with ethanol and water. Then, dry the obtained product in an oven at 80°C for 12 hours. The confined iodine-based homogeneous supported catalyst described in this invention, designated as D-Cat-1, is obtained, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodide ions supported on the surface of Beta molecular sieve is 1:0.02:2.6:0.3.
[0100] The N2 adsorption-desorption characterization results show that the pore size of the catalyst D-Cat-1 is 0.8 nm.
[0101] Comparative Example 2
[0102] This comparative example was carried out according to the method of Example 1, except that magnesium nitrate hexahydrate was not added in step (1). The confined iodine-based homogeneous immobilized catalyst prepared in this comparative example is designated as D-Cat-2, wherein the molar ratio of Beta molecular sieve and quaternary ammonium ions and iodide ions supported on the surface of Beta molecular sieve is 1:1.1:0.05;
[0103] The N2 adsorption-desorption characterization results show that the pore size of the catalyst D-Cat-2 is 0.5 nm.
[0104] Comparative Example 3
[0105] This comparative example was carried out according to the method of Example 1, except that tetrabutylammonium hydroxide was not added in step (1). The confined iodine-based homogeneous supported catalyst prepared in this comparative example is designated as D-Cat-3, wherein the molar ratio of Beta molecular sieve and magnesium ions, quaternary ammonium ions, and iodine ions supported on the surface of Beta molecular sieve is 1:0.02:0.8:0.1.
[0106] The N2 adsorption-desorption characterization results show that the pore size of the catalyst D-Cat-3 is 0.4 nm.
[0107] Comparative Example 4
[0108] This comparative example was carried out according to the method of Example 1, except that tetrabutylammonium iodide was not added in step (1). The confined iodine-based homogeneous supported catalyst prepared in this comparative example is designated as D-Cat-4, wherein the molar ratio of Beta molecular sieve and magnesium ions and quaternary ammonium ions supported on the surface of Beta molecular sieve is 1:0.02:0.3.
[0109] The N2 adsorption-desorption characterization results show that the pore size of the catalyst D-Cat-4 is 0.5 nm.
[0110] Test case
[0111] The catalytic activity of the confined iodine-based homogeneous supported catalysts prepared in Examples 1-8 and Comparative Examples 1-4 in the cycloaddition reaction of propylene oxide was characterized by the following experimental steps:
[0112] 0.2 g of catalyst and 1 g of propylene oxide were placed in a 25 mL batch reactor, and 1.5 MPa of CO2 was introduced into the reactor. The mixture was magnetically stirred and reacted at 110 °C for 10 h. The resulting product was then separated into solid and liquid phases by centrifugation, and the resulting liquid was analyzed by liquid chromatography. The results are shown in Table 1.
[0113] Table 1
[0114] Example number propylene oxide conversion rate / % propylene carbonate selectivity / % Example 1 99.8 96.3 Example 2 99.8 89.7 Example 3 93.9 93.5 Example 4 89.2 90.2 Example 5 86.5 95.2 Example 6 87.2 92.5 Example 7 82.1 91.5 Example 8 73.6 85.8 Comparative Example 1 30.5 24.1 Comparative Example 2 20.1 21.5 Comparative Example 3 10.2 20.5 Comparative Example 4 40.2 10.2
[0115] As can be seen from the results in Table 1, by adopting the technical solution described in this invention, the confined iodine-based homogeneous supported catalyst of this invention enhances the electrostatic interaction between iodide ions and quaternary ammonium ions through the molecular sieve confinement effect, thereby constructing a confined structure and effectively controlling the loading of iodide ions and quaternary ammonium ions on the active sites of the catalyst. When the confined iodine-based homogeneous supported catalyst of this invention is applied to the catalytic synthesis of cyclic carbonates from CO2 and epoxides, it exhibits strong adsorption and activation capabilities for CO2, and can also activate epoxides, accelerating the ring-opening of epoxides. In the catalytic process, the catalysts Cat-1 to Cat-8 prepared in Examples 1-8 achieve a propylene oxide conversion rate of over 73% and a propylene carbonate selectivity of over 85%. In the preferred Examples 1-7, the propylene oxide conversion rate reaches over 80% and the propylene carbonate selectivity reaches over 89%. The D-Cat-1 prepared in Comparative Example 1 had an increased pore size, making it difficult to anchor TBAI within the pores, thus reducing the catalyst's performance. The D-Cat-2 to D-Cat-4 prepared in Comparative Examples 2-4 had further reduced catalytic activity and selectivity due to the lack of necessary components.
[0116] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A confined iodine-based homogeneous immobilized catalyst, characterized in that, The catalyst comprises a support and iodide ions, magnesium ions and quaternary ammonium ions supported on the support, wherein the molar ratio of the magnesium ions, the quaternary ammonium ions, the iodide ions and the support is 0.01-1:4-15:1-30:
1.
2. The confined iodine-based homogeneous supported catalyst according to claim 1, characterized in that, The support is selected from at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3; Preferably, the pore size of the carrier is 0.1-10 nm, more preferably 0.1-5 nm.
3. A method for preparing a confined iodine-based homogeneous supported catalyst, characterized in that, The method includes the following steps: (1) React the carrier, alkali source, magnesium source, iodine source and water; (2) The reaction product obtained in step (1) is mixed with an ammonium source to obtain a mixed solution, and then the mixed solution is crystallized.
4. The method according to claim 3, characterized in that, The molar ratio of the magnesium source, the alkali source, the iodine source, the water, the ammonium source, and the carrier is 0.01-1:0.1-2:0.1-2:4-15:0.1-2:1, preferably 0.01-0.1:0.4-1.5:0.1-1:6-15:0.2-1:
1.
5. The method according to claim 3 or 4, characterized in that, The support is selected from at least one of Beta molecular sieve, Ti-Beta molecular sieve, TS-Beta molecular sieve and Al2O3; Preferably, the pore size of the carrier is 0.1-10 nm, more preferably 0.1-5 nm.
6. The method according to claim 3 or 4, characterized in that, The magnesium source is selected from at least one of magnesium nitrate, magnesium acetate, and magnesium chloride; Preferably, the alkali source is selected from at least one of sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, ammonium bicarbonate, urea, ammonia, n-butylamine, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; Preferably, the iodine source is selected from at least one of potassium iodide, tetrabutylammonium iodide, potassium iodate, and tetrapropylammonium iodide; Preferably, the ammonium source is selected from at least one of ammonium chloride, ammonium nitrate, ammonium fluoride, and ammonium bromide.
7. The method according to claim 3, characterized in that, In step (1), the reaction conditions include: a temperature of 100-200℃, preferably 120-160℃; and a time of 0.5-4h, preferably 0.5-3h.
8. The method according to claim 3, characterized in that, In step (2), the pH value of the mixed solution is 7-11, preferably 7-10.
9. The method according to claim 3, characterized in that, In step (2), the crystallization conditions include: a temperature of 80-200℃, preferably 100-170℃; and a time of 10-72h, preferably 20-30h.
10. The application of the confined iodine-based homogeneous supported catalyst according to claim 1 or 2 in the catalytic synthesis of cyclic carbonates from CO2 and epoxides.