Petal-shaped manganese dioxide as well as preparation method and application thereof

Abstract

The invention provides petal-shaped manganese dioxide as well as a preparation method and application thereof. According to the preparation method, petal-shaped manganese dioxide with a definite shape can be obtained by adopting a specific structure-directing agent and controlling preparation parameters. The preparation method is simple and easy to operate and low in production cost, and the prepared petal-shaped manganese dioxide can be used as a single manganese dioxide heterogeneous catalyst, has abundant surface active sites and acid-base centers, has excellent catalytic performance in the field of synthesis of cyclic carbonate through transesterification, and has the advantages of high stability and high activity. The invention relates to manganese dioxide with other morphologies. The synthesis conditions of the transesterification can be milder, the use amount of the catalyst is less, other organic solvents or harsh reaction conditions such as high temperature and high pressure are not needed, and large-scale application and production are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of heterogeneous catalysis and relates to petal-shaped manganese dioxide and a preparation method and application thereof. Background Art

[0002] Cyclic carbonates have unique chemical properties such as high dielectric constant, high boiling point, low toxicity and biodegradability, and are often used as lithium-ion battery electrolytes, non-polar protic solvents, and monomers of polyurethanes and polycarbonates. For example, 1,2-butylene carbonate is not only an excellent benign polar organic solvent that can replace traditional harmful polar aprotic solvents such as dimethylformamide, N-methyl-2-pyrrolidone and acetonitrile, but can also be used as an organic intermediate and is widely used in the production of plasticizers, gas separation, electrochemistry and other fields.

[0003] At present, the known cyclic carbonate synthesis methods mainly include CO2 and epoxide cycloaddition method, urea alcoholysis method and transesterification method. Among them, CO2 and epoxide cycloaddition method produces side reactions and water while obtaining the target product, which increases the cost of post-processing processing technology; the use of organic solvents in urea alcoholysis method will lead to the decomposition of catalysts, resulting in a decrease in product selectivity and a decrease in reaction yield. Therefore, the transesterification method with simple and mild reaction conditions, high selectivity and easy separation has become a more advantageous development direction.

[0004] One of the key points of the process route for synthesizing cyclic carbonates through transesterification is the selection and use of catalysts. Currently, the commonly used catalysts mainly include a series of rich Homogeneous and heterogeneous catalysts with Lewis acid-base active centers. For example, CN103721697A discloses a catalyst for synthesizing propylene carbonate, which is a composite oxide composed of an active component zinc oxide and an auxiliary oxide, wherein the auxiliary element is a complex of Fe and Zr, but the synthesis method requires the addition of a co-catalyst, and the catalytic system is complex. CN115155656A discloses a method for synthesizing cyclic carbonates using vicinal diols and urea as raw materials, using a catalyst with a hydroxy quaternary phosphonium salt structure, which has a high activity, but requires the presence of a halide, and the preparation process produces ammonia, which is easily limited to a certain extent.

[0005] Although heterogeneous catalysts have the advantages of high selectivity, simple separation and strong recyclability, they still have defects such as poor catalytic stability and easy deactivation after use. In addition, the reaction of butylene carbonate using heterogeneous catalysts still requires high temperature and catalyst dosage. Therefore, it is of great significance to develop an efficient and stable heterogeneous catalyst to achieve efficient preparation of cyclic carbonates under mild conditions. Summary of the invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a petal-shaped manganese dioxide and a preparation method and use thereof. The preparation method can synthesize a stable petal-shaped manganese dioxide material, and the material also has the advantages of high stability, high activity and strong reusability. When used as a catalyst, linear carbonates can be catalyzed to generate cyclic carbonates with high selectivity and high yield under mild conditions.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing petal-shaped manganese dioxide, the preparation method comprising the following steps:

[0009] Manganese salt, ammonium salt, solvent and structure directing agent are mixed and subjected to hydrothermal treatment to obtain petal-shaped manganese dioxide.

[0010] The preparation method of the present invention can obtain petal-shaped manganese dioxide with a clear shape by adopting a specific structure-directing agent and controlling the preparation parameters. The particles of the petal-shaped manganese dioxide are composed of flake manganese dioxide, which are stacked and combined to form a petal-shaped surface morphology, and the overall particle contour is preferably spherical. The preparation method of the present invention is simple and easy to operate, and has low production cost. The prepared petal-shaped manganese dioxide can be used as a single manganese dioxide heterogeneous catalyst, has abundant surface active sites and acid-base centers, has excellent catalytic performance in the field of synthesizing cyclic carbonates by transesterification reaction, and has the advantages of high stability and high activity.

[0011] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] As a preferred technical solution of the present invention, the preparation method comprises first mixing a manganese salt, an ammonium salt and a solvent to obtain a mixed solution, and then adding the structure directing agent to mix.

[0013] The present invention finds that separately mixing the manganese ammonium raw material and the structure directing agent in the preparation method can make the morphology of the product more uniform and the petal-like morphology grown is more complete.

[0014] Preferably, the mixing method includes stirring, and the stirring time is 0.5 to 5 hours, for example 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0015] As a preferred technical solution of the present invention, the molar ratio of the manganese salt to the ammonium salt is (2-10):1, for example 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0016] Preferably, the manganese salt used in the preparation method of the present invention is a soluble manganese salt, for example, the manganese salt includes any one or a combination of at least two of manganese nitrate, manganese chloride, manganese carbonate, manganese oxalate, manganese phosphate, potassium permanganate, manganese acetate or manganese sulfate, typical but non-limiting examples of the combination include a combination of manganese nitrate and manganese chloride, a combination of manganese carbonate or potassium permanganate, a combination of manganese oxalate and manganese phosphate, or a combination of manganese chloride and manganese sulfate, etc.

[0017] Preferably, the ammonium salt comprises one or a combination of at least two of ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium chloride or ammonium nitrate, typical but non-limiting examples of the combination include a combination of ammonium sulfate and ammonium carbonate, a combination of ammonium chloride and ammonium bisulfate, a combination of ammonium nitrate and ammonium carbonate, a combination of ammonium carbonate and ammonium bicarbonate, or a combination of ammonium sulfate and ammonium bisulfate, etc.

[0018] Preferably, the solvent comprises water.

[0019] As a preferred technical solution of the present invention, the structure directing agent includes one or a combination of at least two of organosiloxane, sodium sulfate, anhydrous sodium phosphate, polyvinyl pyrrolidone, sodium lignin sulfonate, sodium tripolyphosphate, sodium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium thiosulfate and potassium phosphate. Typical but non-limiting examples of the combination include a combination of organosiloxane and sodium sulfate, a combination of anhydrous sodium phosphate and polyvinyl pyrrolidone, a combination of sodium lignin sulfonate and sodium tripolyphosphate, a combination of sodium dihydrogen phosphate and trisodium phosphate, a combination of disodium hydrogen phosphate and sodium dihydrogen phosphate, or a combination of sodium thiosulfate and potassium phosphate, etc.

[0020] Preferably, the molar ratio of the structure directing agent to the manganese salt is 1:(5-40), for example 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35 or 1:40, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0021] In the present invention, if the molar ratio of the structure directing agent to the manganese salt is too low, it is not conducive to the full growth of the product, while if the molar ratio of the structure directing agent to the manganese salt is too high, it will lead to excessively fast crystal growth and uneven crystal growth.

[0022] In the preparation method of the present invention, the petal-shaped structure is mainly obtained by the joint action of the structure directing agent at a specific temperature, and the proportion of the amount of manganese salt and ammonium salt is to reduce the manganese ion, which has no obvious effect on the product morphology. When adding the directing agent, a suitable hydrothermal temperature should be matched. The integrity of the product morphology approaches completeness as the hydrothermal time increases. If the hydrothermal time is too short, the molding is incomplete, and the degree of reduction of manganese salt, especially potassium permanganate, to manganese dioxide is also incomplete. Therefore, if the hydrothermal time is too short, a large amount of potassium permanganate will remain.

[0023] As a preferred technical solution of the present invention, the temperature of the hydrothermal treatment is 80-180°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, and the time is 6-100h, for example, 6h, 16h, 26h, 36h, 46h, 56h, 66h, 76h, 86h, 96h or 100h, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0024] In the present invention, if the hydrothermal temperature is too low, it is not conducive to the formation of petal-like morphology, and if the hydrothermal temperature is too high, it will lead to too fast crystallization and the formation of manganese dioxide with other morphologies such as rods.

[0025] In the present invention, if the hydrothermal treatment time is too short, it is not conducive to the full growth of petal-shaped manganese dioxide, and some parts of the growth are incomplete. If the hydrothermal treatment time is too long, it will lead to multiple growth on the crystal surface, resulting in too few defects and affecting the catalytic effect.

[0026] As a preferred technical solution of the present invention, after the hydrothermal treatment, solid-liquid separation, washing and drying are carried out in sequence to obtain petal-shaped manganese dioxide.

[0027] Preferably, the drying temperature is 50-160°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130, 140°C, 150°C or 160°C, and the time is 8-36h, for example 8h, 12h, 16h, 20h, 24h, 28h, 32h and 36h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] As a preferred technical solution of the present invention, the method for preparing petal-shaped manganese dioxide comprises the following steps:

[0029] (1) according to the molar ratio of soluble manganese salt to ammonium salt being (2-10):1, weighing soluble manganese salt and ammonium salt, dissolving them in ultrapure water, stirring for 0.5-5h to mix evenly, adding a structure directing agent, controlling the molar ratio of the structure directing agent to the soluble manganese salt to be 1:(5-40), stirring and mixing again to obtain a mixed solution;

[0030] (2) The mixed solution is transferred to a hydrothermal autoclave with a polytetrafluoroethylene liner, and the volume of the mixed solution is controlled to account for 40% to 70% of the solvent in the hydrothermal autoclave. After constant temperature hydrothermal treatment at 80 to 180° C. for 6 to 100 hours, it is cooled to room temperature in air, washed with ethanol and water for multiple times, and dried at 50 to 160° C. overnight to obtain petal-shaped manganese dioxide.

[0031] In a second aspect, the present invention provides a petal-shaped manganese dioxide obtained according to the preparation method provided in the first aspect.

[0032] In a third aspect, the present invention provides a method for catalytically synthesizing cyclic carbonates, wherein the method uses the petal-shaped manganese dioxide provided in the second aspect as a catalyst to catalyze the generation of cyclic carbonates from linear carbonates.

[0033] As a preferred technical solution of the present invention, the method for catalytic synthesis of cyclic carbonate comprises the following steps:

[0034] The linear carbonate, the diol substance and the petal-shaped manganese dioxide described in the second aspect are mixed and heated to obtain the cyclic carbonate.

[0035] The present invention uses the obtained petal-shaped manganese dioxide as a heterogeneous catalyst to carry out an ester exchange reaction, catalyzing the linear carbonate to generate a cyclic carbonate. The synthesis conditions are mild, the amount of catalyst used is small, and other organic solvents or harsh reaction conditions such as high temperature and high pressure are not required. In addition, the petal-shaped manganese dioxide can show high activity, high stability, high selectivity for cyclic carbonate and high yield advantages in this reaction.

[0036] As a preferred technical solution of the present invention, the molar ratio of the linear carbonate to the diol substance is (1-10):1, for example 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0037] Preferably, the mass ratio of the glycol substance to the petal-shaped manganese dioxide is 1:(0.001-0.03), for example, it can be 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025 or 1:0.03, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0038] Preferably, the insulation temperature of the heat treatment is 80-160°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C, and the insulation time is 20-200min, for example, 20min, 40min, 60min, 80min, 100min, 120min, 140min, 160min, 180min or 200min, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0039] Preferably, the linear carbonate comprises any one of dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate or a combination of at least two thereof, typical but non-limiting examples of the combination comprising a combination of dimethyl carbonate and diethyl carbonate, a combination of dimethyl carbonate and ethyl methyl carbonate or a combination of ethyl methyl carbonate and dimethyl carbonate.

[0040] Preferably, the diol substance includes any one of 1,2-butanediol, ethylene glycol, 1,3-butanediol, 1,2-propylene glycol, glycerol, 1,2-pentanediol, 1,2-hexanediol or 2,3-butanediol, or a combination of at least two thereof. Typical but non-limiting examples of the combination include a combination of 1,2-butanediol and ethylene glycol, a combination of 1,3-butanediol and 1,2-propylene glycol, a combination of glycerol and 1,2-pentanediol, and a combination of 1,2-hexanediol or 2,3-butanediol.

[0041] The method for catalytically synthesizing cyclic carbonates carried out in the present invention can also use glycerol as a raw material, and the reaction carried out utilizes two ortho-hydroxyl groups in glycerol, so it can also be used as the diol substance in the present invention.

[0042] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0043] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0044] (1) The preparation method of the present invention can obtain petal-shaped manganese dioxide with a clear shape by using a specific structure-directing agent and controlling the preparation parameters; the preparation method has a simple production process, is easy to operate and has a low production cost.

[0045] (2) The petal-shaped manganese dioxide obtained by the preparation method can be used as a single manganese dioxide heterogeneous catalyst, has abundant surface active sites and acid-base centers, and is rich in oxygen vacancies; it has excellent catalytic performance in the field of ester exchange reaction to synthesize cyclic carbonates, has the advantages of high stability and high activity, and has the advantages of easy separation of catalyst and product and recyclability compared to homogeneous catalysts.

[0046] (3) The method for catalytic synthesis of cyclic carbonates of the present invention has a simple process and mild experimental conditions. Compared with other synthesis routes, it does not require solvents, harsh conditions such as high temperature and high pressure, and has a shorter reaction time and a smaller amount of catalyst. When linear carbonates and diols are used as raw materials, the conversion rate of diols can be as high as 98% or more, and the selectivity of cyclic carbonates can be as high as 99% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a scanning electron microscope image of the petal-shaped manganese dioxide obtained in Example 1;

[0048] Figure 2 This is a scanning electron microscope image of the petal-shaped manganese dioxide obtained in Example 14;

[0049] Figure 3 This is a scanning electron microscope image of the irregular rod-shaped manganese dioxide obtained in Comparative Example 2;

[0050] Figure 4 This is a scanning electron microscope image of the needle-shaped manganese dioxide obtained in Comparative Example 3;

[0051] Figure 5 This is a scanning electron microscope image of the petal-shaped manganese dioxide obtained in Example 27. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0053] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0054] Example 1

[0055] This embodiment provides a method for preparing petal-shaped manganese dioxide, the preparation method comprising:

[0056] (1) manganese nitrate is used as manganese salt and ammonium nitrate is used as ammonium salt. The molar ratio of manganese salt to ammonium salt is 4:1. The manganese salt and ammonium salt are weighed and dissolved in ultrapure water. The mixture is stirred for 3 hours to be uniformly mixed. A structure directing agent, organosiloxane, is added to control the molar ratio of the structure directing agent to the manganese salt to be 1:20. The mixture is stirred again to be uniformly mixed to obtain a mixed solution.

[0057] (2) The mixed solution is transferred to a hydrothermal autoclave with a polytetrafluoroethylene liner, and the volume of the mixed solution is controlled to account for 50% of the solvent in the hydrothermal autoclave. After constant temperature hydrothermal treatment at 100° C. for 52 hours, it is cooled to room temperature in air, washed with ethanol and water for multiple times, and dried at 90° C. overnight to obtain petal-shaped manganese dioxide.

[0058] Example 2

[0059] This embodiment provides a method for preparing petal-shaped manganese dioxide, the preparation method comprising:

[0060] (1) manganese chloride is taken as manganese salt, ammonium bicarbonate is taken as ammonium salt, and the molar ratio of manganese salt to ammonium salt is 10:1. The manganese salt and ammonium salt are weighed and dissolved in ultrapure water, and stirred for 1 hour to mix evenly. The structure-directing agent sodium lignin sulfonate is added, and the molar ratio of the structure-directing agent to the manganese salt is controlled to be 1:40. The mixture is stirred again to mix evenly to obtain a mixed solution;

[0061] (2) The mixed solution is transferred to a hydrothermal autoclave with a polytetrafluoroethylene liner, and the volume of the mixed solution is controlled to account for 50% of the solvent in the hydrothermal autoclave. After constant temperature hydrothermal treatment at 80° C. for 100 h, it is cooled to room temperature in air, washed with ethanol and water for multiple times, and dried at 80° C. overnight to obtain petal-shaped manganese dioxide.

[0062] Example 3

[0063] This embodiment provides a method for preparing petal-shaped manganese dioxide, the preparation method comprising:

[0064] (1) manganese oxalate is taken as manganese salt and ammonium sulfate is taken as ammonium salt. The molar ratio of manganese salt to ammonium salt is 2:1. The manganese salt and ammonium salt are weighed and dissolved in ultrapure water. The mixture is stirred for 1 hour to be uniformly mixed. A structure-directing agent, polyvinyl pyrrolidone, is added to control the molar ratio of the structure-directing agent to the manganese salt to be 1:5. The mixture is stirred again to be uniformly mixed to obtain a mixed solution.

[0065] (2) The mixed solution is transferred to a hydrothermal autoclave with a polytetrafluoroethylene liner, and the volume of the mixed solution is controlled to account for 50% of the solvent in the hydrothermal autoclave. After constant temperature hydrothermal treatment at 180° C. for 6 h, it is cooled to room temperature in air, washed with ethanol and water for multiple times, and dried at 160° C. overnight to obtain petal-shaped manganese dioxide.

[0066] Example 4

[0067] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:3. Except for the above, other conditions are exactly the same as those in Example 1.

[0068] Example 5

[0069] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:5. Except for the above, other conditions are exactly the same as those in Example 1.

[0070] Example 6

[0071] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:10. Except for the above, other conditions are exactly the same as those in Example 1.

[0072] Example 7

[0073] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:30. Except for the above, other conditions are exactly the same as those in Example 1.

[0074] Example 8

[0075] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:40. Except for the above, other conditions are exactly the same as those in Example 1.

[0076] Example 9

[0077] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the molar ratio of the structure directing agent to the manganese salt is adjusted from 1:20 to 1:43. Except for the above, other conditions are exactly the same as those in Example 1.

[0078] Example 10

[0079] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal temperature is adjusted from 140° C. to 60° C. Except for the above, other conditions are exactly the same as those in Example 1.

[0080] Embodiment 11

[0081] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal temperature is adjusted from 140° C. to 80° C. Except for the above, other conditions are exactly the same as those in Example 1.

[0082] Example 12

[0083] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal temperature is adjusted from 140° C. to 180° C. Except for the above, other conditions are exactly the same as those in Example 1.

[0084] Embodiment 13

[0085] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal temperature is adjusted from 140° C. to 200° C. Except for the above, other conditions are exactly the same as those in Example 1.

[0086] Embodiment 14

[0087] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 hours to 4 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0088] Embodiment 15

[0089] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 hours to 6 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0090] Example 16

[0091] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 hours to 25 hours. Except for the above, other conditions are exactly the same as those in Example 1.

[0092] Embodiment 17

[0093] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 h to 75 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0094] Embodiment 18

[0095] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 h to 100 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0096] Embodiment 19

[0097] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the hydrothermal time is adjusted from 52 h to 102 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0098] Embodiment 20

[0099] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organic siloxane to sodium sulfate. Except for the above, other conditions are exactly the same as those in Example 1.

[0100] Embodiment 21

[0101] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organic siloxane to anhydrous sodium phosphate. Except for the above, other conditions are exactly the same as those in Example 1.

[0102] Embodiment 22

[0103] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organic siloxane to polyvinyl pyrrolidone. Except for the above, other conditions are exactly the same as those in Example 1.

[0104] Embodiment 23

[0105] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organosiloxane to sodium lignin sulfonate. Except for the above, other conditions are exactly the same as those in Example 1.

[0106] Embodiment 24

[0107] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organic siloxane to disodium hydrogen phosphate. Except for the above, other conditions are exactly the same as those in Example 1.

[0108] Embodiment 25

[0109] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organic siloxane to sodium thiosulfate. Except for the above, other conditions are exactly the same as those in Example 1.

[0110] Embodiment 26

[0111] This embodiment provides a method for preparing petal-shaped manganese dioxide. In the preparation method, the structure directing agent is adjusted from organosiloxane to potassium phosphate. Except for the above, other conditions are exactly the same as those in Example 1.

[0112] Embodiment 27

[0113] This embodiment provides a method for preparing petal-shaped manganese dioxide, which comprises adding manganese salt, ammonium salt and structure directing agent to a solvent and mixing them simultaneously in step (1). Except for the above, other conditions are exactly the same as those in Example 1.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing manganese dioxide, wherein the method does not use a structure directing agent. Except for the above, other conditions are exactly the same as those in Example 1.

[0116] Comparative Example 2

[0117] This comparative example provides a method for preparing manganese dioxide, and the preparation method refers to the preparation method in the prior art document (ACS Catal. 2018, 8, 4, 3435-3446), specifically:

[0118] (1) Weigh 3.6 g potassium permanganate and 1.42 g ammonium oxalate monohydrate and add them to 70 mL of deionized water;

[0119] (2) After stirring for 0.5 h, the mixed solution was transferred to a 100 mL hydrothermal autoclave with a polytetrafluoroethylene liner, and subjected to constant temperature hydrothermal treatment at 180 ° C for 24 h, and then cooled to room temperature in air. After being washed with ethanol and water for multiple times, it was dried at 105 ° C overnight to obtain irregular rod-shaped manganese dioxide.

[0120] Comparative Example 3

[0121] This comparative example provides a method for preparing manganese dioxide, and the preparation method refers to the preparation method in the prior art document (ACS Catal. 2018, 8, 4, 3435-3446), specifically:

[0122] (1) Weigh 1.352 g of manganese sulfate monohydrate, 1.18 g of ammonium thiosulfate, 1.98 g of ammonium sulfate, and 0.10 g of potassium nitrate, and add them to 40 mL of deionized water;

[0123] (2) After stirring for 0.5 h, the mixed solution was transferred to a 100 mL hydrothermal autoclave with a polytetrafluoroethylene liner, and subjected to constant temperature hydrothermal treatment at 120° C. for 20 h, and then cooled to room temperature in air. After multiple washings with ethanol and water, the mixture was dried at 105° C. overnight to obtain needle-shaped manganese dioxide.

[0124] Comparative Example 4

[0125] This comparative example provides a method for preparing manganese dioxide, which refers to the preparation method in the prior art document (Journal of Environmental Management. 2019, 251: 109563), specifically:

[0126] First, 0.51g KMnO4 was dissolved in 35mL deionized water, and then 0.7mL HCl (37wt.%) was slowly dripped in. After stirring for 15 minutes, the mixture was transferred to a 50mL hydrothermal reactor with a polytetrafluoroethylene liner and reacted at 110°C for 6 hours. The obtained product was washed three times with deionized water and anhydrous ethanol. The final product was dried at 60°C for 24 hours and sealed for use.

[0127] The manganese dioxide obtained in the embodiment and the comparative example was tested by scanning electron microscope to observe the morphology and structure of the product:

[0128] Figure 1-5 The scanning electron microscope images of the manganese dioxide obtained in Example 1, Example 14, Comparative Example 2, Comparative Example 3 and Example 27 are respectively shown. It can be seen from the figure that the manganese dioxide obtained by the preparation method has a perfect petal-like morphology. If the hydrothermal time is too short, the crystal growth will be incomplete, and an incomplete petal-like morphology will be obtained. Comparative Example 2 and Comparative Example 3 are based on the schemes recorded in the prior art documents. Due to the lack of a structure-directing agent and the difference in hydrothermal temperature, the product morphology obtained is irregular rod-shaped and needle-shaped manganese dioxide. For the manganese dioxide obtained in other embodiments, the molar ratio of the structure-directing agent to the manganese salt is too low, which is not conducive to the full growth of the product. If the molar ratio of the structure-directing agent to the manganese salt is too high, it will cause the crystal to grow too fast and the crystal to grow unevenly. If the hydrothermal temperature is too low, it is not conducive to the formation of a petal-like morphology. If the hydrothermal temperature is too high, it will cause the crystal to grow too fast, which will cause the formation of manganese dioxide with other morphologies such as rods. If the hydrothermal treatment time is too short, it is not conducive to the full growth of petal-shaped manganese dioxide, and some parts of the growth are incomplete. If the hydrothermal treatment time is too long, it will lead to multiple growth on the crystal surface, resulting in too few defects. Separately mixing the manganese ammonium raw material and the structure directing agent will make the product morphology more uniform and the petal-shaped morphology will be more complete.

[0129] Application Example 1

[0130] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the method uses the manganese dioxide obtained in Examples 1-26 and Comparative Examples 1-4 as a catalyst, and the method comprises the following steps:

[0131] 10.8 g of dimethyl carbonate was taken as a linear carbonate, 1,2-butanediol was taken as a diol substance, the linear carbonate, the diol substance and manganese dioxide were mixed, the molar ratio of the linear carbonate to the diol substance was controlled to be 3:1, the mass ratio of the diol substance to the manganese dioxide was controlled to be 1:0.01, and the mixture was heated at 120° C. for 20 min to perform an ester exchange reaction to generate a reactant solution. After the reactant solution was centrifuged, an appropriate amount of the supernatant was added to an internal standard substance (biphenyl), and the target product 1,2-butylene carbonate was quantitatively analyzed by gas chromatography internal standard method. The results are recorded in Table 1.

[0132] Table 1

[0133]

[0134]

[0135] It can be seen from Table 1 that:

[0136] From the comparison of the results of the manganese dioxide in Example 1 and Examples 1-4, it is found that the petal-shaped manganese dioxide catalyst has extremely excellent catalytic activity, while the catalytic effect of the needle-shaped and irregular rod-shaped products obtained in Comparative Examples 2 and 3 is less than 20%, indicating that the petal-shaped morphology is a necessary condition. However, not all flower-shaped products have suitable catalytic effects. The catalytic effect of the petal-shaped product obtained in Comparative Example 4 is only 18%;

[0137] It can be concluded from Examples 4-9 that a too low molar ratio of the structure directing agent to the manganese salt is not conducive to sufficient growth of the product, while a too high molar ratio of the structure directing agent to the manganese salt will result in excessively rapid crystallization and uneven crystal growth, which is not conducive to petal-shaped formation and affects the catalytic effect.

[0138] It can be concluded from Examples 10-13 that if the hydrothermal temperature is too low, it will be not conducive to the formation of a petal-like morphology, and a poor and incomplete petal-like morphology and a lower yield of cyclic carbonate will be obtained. If the hydrothermal temperature is too high, it will lead to too fast crystallization, resulting in the formation of manganese dioxide in other morphologies such as rods, which is not conducive to the formation of cyclic carbonates. This shows that only when the catalyst has a relatively complete morphology and exposes more active sites, the selectivity and yield of the catalytic synthesis of cyclic carbonates are good.

[0139] It can be concluded from Examples 14-19 that if the hydrothermal treatment time is too short, it will not be conducive to the full growth of petal-shaped manganese dioxide, and some parts will have incomplete growth. If the hydrothermal treatment time is too long, it will lead to multiple growth on the crystal surface, resulting in too few defects and affecting the catalytic effect.

[0140] It can be concluded from Examples 20-26 and Comparative Example 1 that the addition of a structure directing agent is necessary for the synthesis of petal-shaped manganese dioxide.

[0141] Application Example 2

[0142] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, wherein the diol substance is replaced by 1,2-butanediol with 2,3-butanediol, and the target product obtained is 2,3-butenyl carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0143] Application Example 3

[0144] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, wherein the diol substance is replaced by 1,2-butanediol with 1,3-butanediol, and the target product obtained is 1,3-butenyl carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0145] Application Example 4

[0146] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, wherein the diol substance is replaced by 1,2-butanediol with ethylene glycol, and the target product obtained is vinyl carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0147] Application Example 5

[0148] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method replaces the diol substance from 1,2-butanediol with 1,2-propylene glycol, and the target product obtained is 1,2-propylene carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0149] Application Example 6

[0150] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method replaces the diol substance from 1,2-butanediol with 1,3-propylene glycol, and the target product obtained is 1,3-propylene carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0151] Application Example 7

[0152] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the diol substance is replaced by 1,2-butanediol with propylene glycol, and the target product obtained is glycerol carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0153] Application Example 8

[0154] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, wherein the diol substance is replaced by 1,2-butanediol with 1,2-pentanediol, and the target product obtained is 1,2-pentenyl carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0155] Application Example 9

[0156] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, wherein the diol substance is replaced by 1,2-butanediol with 1,2-hexanediol, and the target product obtained is 1,2-hexenyl carbonate. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0157] Application Example 10

[0158] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method adjusts the amount of manganese dioxide so that the mass ratio of the glycol substance to the manganese dioxide is adjusted from 1:0.01 to 1:0.001. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0159] Application Example 11

[0160] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method adjusts the amount of manganese dioxide so that the mass ratio of the glycol substance to the manganese dioxide is adjusted from 1:0.01 to 1:0.005. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0161] Application Example 12

[0162] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method adjusts the amount of manganese dioxide so that the mass ratio of the glycol substance to the manganese dioxide is adjusted from 1:0.01 to 1:0.02. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0163] Application Example 13

[0164] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method adjusts the amount of manganese dioxide so that the mass ratio of the glycol substance to the manganese dioxide is adjusted from 1:0.01 to 1:0.03. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0165] Application Example 14

[0166] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the method uses the manganese dioxide obtained in Example 1 as a catalyst, and the method adjusts the amount of manganese dioxide so that the mass ratio of the glycol substance to the manganese dioxide is adjusted from 1:0.01 to 1:0.035. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0167] Application Example 15

[0168] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the heating temperature is adjusted from 120°C to 60°C. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0169] Application Example 16

[0170] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the heating temperature is adjusted from 120°C to 80°C. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0171] Application Example 17

[0172] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the heating temperature is adjusted from 120°C to 100°C. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0173] Application Example 18

[0174] This application example provides a method for catalytic synthesis of cyclic carbonates, wherein the heating temperature is adjusted from 120°C to 160°C. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0175] Application Example 19

[0176] This application example provides a method for catalytically synthesizing cyclic carbonates, wherein the heating temperature is adjusted from 120°C to 180°C. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0177] The results obtained from Application Example 2-19 are recorded in Table 2.

[0178] Table 2

[0179] Manganese dioxide Diol conversion Cyclic carbonate selectivity Cyclic carbonate yield Application Example 2 98.3％ 99.8％ 98.10％ Application Example 3 97.3％ 99.6％ 96.91％ Application Example 4 98.7％ 99.8％ 98.50％ Application Example 5 99.4％ 98.5％ 97.91％ Application Example 6 98.8％ 99.2％ 98.01％ Application Example 7 97.8％ 99.1％ 96.92％ Application Example 8 97.9％ 99.3％ 97.21％ Application Example 9 98.1％ 99.9％ 98.00％ Application Example 10 96.9％ 99.3％ 96.2％ Application Example 11 97.4％ 98.9％ 96.3％ Application Example 12 98.9％ 99.3％ 98.2％ Application Example 13 98.7％ 98.9％ 97.6％ Application Example 14 99.4％ 98.5％ 97.91％ Application Example 15 4.89％ 99.3％ 4.86％ Application Example 16 95.4％ 98.7％ 94.1％ Application Example 17 96.2％ 99.1％ 95.3％ Application Example 18 97.4％ 98.3％ 95.7％ Application Example 19 98.2％ 65.2％ 64.03％

[0180] It can be seen from Table 2 that:

[0181] The petal-shaped manganese dioxide catalyst prepared by the present invention is applied to the synthesis of cyclic carbonates, with a glycol conversion rate of ≥97%, a product cyclic carbonate selectivity of ≥99%, and a cyclic carbonate yield of more than 96%. From the results of Example 1 in Application Example 1 and the results of Application Examples 2-9, it can be seen that the prepared petal-shaped manganese dioxide catalyst can obtain quite high cyclic carbonate selectivity and yield for preparing corresponding cyclic carbonates from a variety of linear carbonates.

[0182] From the results of application examples 15-19, it was found that too low a heating reaction temperature would result in too few activated active sites and extremely low conversion rate; a higher heating reaction temperature would result in an increase in by-products, thereby reducing the selectivity of cyclic carbonate and the yield of cyclic carbonate. This indicates that only when the heating reaction reaches a certain temperature and the catalyst activates more exposed active sites, the selectivity and yield of catalytic synthesis of cyclic carbonate are good.

[0183] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0184] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0185] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing petal-shaped manganese dioxide, characterized in that: The preparation method comprises the following steps: Manganese salt, ammonium salt, solvent and structure directing agent are mixed and subjected to hydrothermal treatment to obtain petal-shaped manganese dioxide.

2. The preparation method according to claim 1, characterized in that: The preparation method comprises: firstly mixing a manganese salt, an ammonium salt and a solvent to obtain a mixed solution, and then adding the structure directing agent to mix; Preferably, the mixing method includes stirring, and the stirring time is 0.5 to 5 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the manganese salt to the ammonium salt is (2-10):1; Preferably, the manganese salt includes any one or a combination of at least two of manganese nitrate, manganese chloride, manganese carbonate, manganese oxalate, manganese phosphate, potassium permanganate or manganese sulfate; Preferably, the ammonium salt comprises one or a combination of at least two of ammonium sulfate, ammonium bisulfate, ammonium carbonate, ammonium bicarbonate, ammonium chloride or ammonium nitrate; Preferably, the solvent comprises water.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The structure directing agent includes one or a combination of at least two of organic siloxane, sodium sulfate, anhydrous sodium phosphate, polyvinyl pyrrolidone, sodium lignin sulfonate, sodium tripolyphosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium thiosulfate and potassium phosphate; Preferably, the molar ratio of the structure directing agent to the manganese salt is 1:(5-40).

5. The preparation method according to any one of claims 1 to 4, characterized in that: The temperature of the hydrothermal treatment is 80-180° C., and the time is 6-100 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that: After the hydrothermal treatment, solid-liquid separation, washing and drying are sequentially performed to obtain petal-shaped manganese dioxide; Preferably, the drying temperature is 50-160° C. and the drying time is 8-36 hours.

7. A petal-shaped manganese dioxide, characterized in that: Obtained according to the preparation method according to any one of claims 1 to 6.

8. A method for catalytic synthesis of cyclic carbonates, characterized in that: The method uses the petal-shaped manganese dioxide described in claim 7 as a catalyst to catalyze linear carbonate to generate cyclic carbonate.

9. The method according to claim 8, characterized in that The method comprises the following steps: Linear carbonate, diol and the petal-shaped manganese dioxide according to claim 7 are mixed and heated to obtain cyclic carbonate.

10. The method according to claim 9, characterized in that The molar ratio of the linear carbonate to the diol substance is (1-10):1; Preferably, the mass ratio of the glycol substance to the petal-shaped manganese dioxide is 1:(0.001-0.03); Preferably, the heat treatment is carried out at a holding temperature of 80 to 160° C. and a holding time of 20 to 200 min.

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