Bismuth-containing catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of organic synthesis catalysis. The invention provides a bismuth-containing catalyst as well as a preparation method and application thereof. The bismuth-containing catalyst comprises oxide components of magnesium, aluminum and bismuth. The bismuth-containing catalyst is used in a reaction for synthesizing cyclic carbonate by using a transesterification method with carbonic ester and diol as raw materials, has the advantages of high stability, high activity, strong reusability and the like, and can be used for preparing cyclic carbonate with high selectivity, high yield and easy product separation by using carbonic ester and diol raw materials under mild conditions.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis catalysis, and specifically relates to a bismuth-containing catalyst and a preparation method and application thereof. Background Art

[0002] Cyclic carbonates are a very important class of chemicals and organic intermediates, with high boiling point, low odor, low toxicity and biodegradability. Among cyclic carbonates, ethylene carbonate is often used as a reaction medium in the production of polymer compounds and various chemical processes; propylene carbonate can be used as a solvent and plasticizer for dielectric polymers in batteries and capacitors, and an intermediate for the production of polycarbonates and fine chemicals; 1,2-butene carbonate is mainly used to produce plasticizers, surfactants and reactive intermediate materials for polymers, and can also be used as a degreasing solvent, paint stripper, wood adhesive resin, foundry sand adhesive, etc.

[0003] At present, the synthesis methods of cyclic carbonates mainly include phosgene method, carbon dioxide and epoxide cycloaddition method, direct coupling of carbon dioxide and diol, urea alcoholysis method, transesterification method, etc. Among them, the transesterification method uses diol and carbonate as raw materials to synthesize cyclic carbonate. The reaction conditions are simple and mild, the raw materials are easy to obtain, the product is easy to separate, and the equipment requirements are low, so it is currently a commonly used synthesis method.

[0004] The diol raw materials that use diols and carbonates through ester exchange reactions mainly include ethylene glycol (EG), propylene glycol (PG), 1,2-butanediol (BG), etc. Diols have many important application values, such as making explosives, plastics, paints, etc., but their main application areas are in the polyester industry. With the rapid development of my country's polyester industry in recent years, the demand for diols has increased year by year. At present, the coal-to-ethylene glycol production process produces about 10% of by-products of fusel alcohols, accompanied by rich methanol, ethanol, ethylene glycol, 1,2-butanediol and other substances. Therefore, making full use of them as raw materials and synthesizing cyclic carbonates through ester exchange reactions with carbonates is a very green way.

[0005] At present, the catalysts used in the ester exchange method mainly include acid-base homogeneous catalysts (mainly acid-base metal salts, ionic liquids, etc.) and heterogeneous acid-base catalysts (solid catalysts prepared from modified alkali metal and alkaline earth metal oxides, hydrotalcite, etc.).

[0006] Serra et al. (Tetrahed.Lett.2013,54,5518–5522.) prepared a Merrifield resin-supported choline chloride catalyst. In isopropanol solvent, KI was added as a co-catalyst. The reaction was carried out at 85°C and 1.0MPa CO2 pressure for 12 hours, and the PC yield was 99%. After the catalyst was recycled 4 times, the yield dropped to below 80%; Cheng et al. reported a polystyrene resin-supported hydroxyl-functionalized quaternary ammonium salt. The reaction was carried out at 110°C and 2.0MPa CO2 pressure for 4 hours, and the PC yield was 98%. The catalyst could be recycled 6 times; Kleij et al. (Green Chem.2017,19,5488–5493.) reported a Merrifield resin-supported resorcinol-derived quaternary ammonium salt catalyst. The reaction was carried out at 80°C and 0.5MP pressure for 18 hours, and the PC yield was 99%. After the catalyst was recycled 9 times, the yield dropped significantly. CN105153104A discloses a method for synthesizing propylene carbonate. The method uses CO2 and propylene oxide as raw materials, loads ionic liquid on bentonite as a catalyst, and synthesizes propylene carbonate in a high-pressure reactor.

[0007] However, the above-mentioned resin-loaded ionic liquid catalytic system still has great limitations, mainly reflected in: 1) low catalytic activity and harsh reaction conditions: such as high reaction temperature (120-150°C), high CO2 pressure (up to 9.0MPa), long reaction time (up to 24h for ester exchange method), need to add co-catalyst or solvent, etc.; 2) short service life of the catalyst: the catalyst can usually only be recycled 4 to 6 times; 3) although the catalyst provided by the existing method is highly active and selective, it still needs to be loaded on a carrier, which is subject to certain limitations in practical applications.

[0008] Therefore, how to find a highly active and highly selective heterogeneous transesterification catalyst that does not require solvents and carriers is of great value and significance for the production of high-quality cyclic carbonates. Summary of the invention

[0009] In view of the problems existing in the prior art, the object of the present invention is to provide a bismuth-containing catalyst and a preparation method and use thereof, wherein the bismuth-containing catalyst comprises magnesium, aluminum and bismuth oxide components. The bismuth-containing catalyst is used in the reaction of synthesizing cyclic carbonates by an ester exchange method using carbonates and diols as raw materials. The catalyst has the advantages of high stability, high activity and strong reusability, and can prepare cyclic carbonates with high selectivity, high yield and easy product separation from carbonates and diols as raw materials under mild conditions.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a bismuth-containing catalyst comprising oxide components of magnesium, aluminum and bismuth.

[0012] The bismuth-containing catalyst provided by the present invention has a completely new component, and a heterogeneous transesterification catalyst with excellent catalytic performance can be obtained by matching magnesium, aluminum and bismuth oxides. The bismuth-containing catalyst is used in the reaction of synthesizing cyclic carbonates by the transesterification method using carbonates and diols as raw materials. The catalyst has the advantages of high stability, high activity and strong reusability, and can prepare cyclic carbonates with high selectivity, high yield and easy product separation from carbonates and diols as raw materials under mild conditions.

[0013] 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.

[0014] As a preferred technical solution of the present invention, the bismuth-containing catalyst includes Mg x Al y Bi z O, wherein x=2-4, for example, 2, 2.1, 2.3, 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9 or 4, y=0.5-0.9, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 or 0.9, z=0.1-0.5, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, and y+z=1, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0015] Preferably, the bismuth-containing catalyst is in the form of flakes with a particle size of 30 to 45 nm, for example, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm or 45 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] In the reaction of synthesizing cyclic carbonate, the single aluminum oxide component has almost no catalytic effect, and the single magnesium oxide component has a certain catalytic effect, but it is not very good. The present invention can improve the catalytic effect to a considerable extent by preparing magnesium aluminum hydrotalcite, and the addition of bismuth can further improve the catalytic effect.

[0017] The unique structure of magnesium aluminum hydrotalcite and the replaceability of anions and cations determine that it can replace a variety of elements and change its own acidity and alkalinity and activity. x Al y Bi zO), wherein the ratio of the divalent positive element (referring to magnesium) to the trivalent positive element (referring to aluminum and bismuth) is preferably (2-4):1, and more preferably 3:1; if the magnesium content is further increased, the valence ratio will change and the basic structure will be changed. Since magnesium oxide is alkaline, excessive addition may lead to alkaline transition, which is not suitable for catalytic reaction. If the aluminum content is increased, there will be too many acidic sites, which will lead to a decrease in catalytic activity.

[0018] In a second aspect, the present invention provides a method for preparing the bismuth-containing catalyst according to the first aspect, the preparation method comprising the following steps:

[0019] The soluble salts of magnesium, aluminum and bismuth, an alkali source and a solvent are mixed to obtain a mixed solution; the mixed solution is sequentially subjected to crystallization treatment and roasting treatment to obtain a bismuth-containing catalyst.

[0020] The preparation method of the present invention is simple and easy to operate, has low production cost and can be scalable for production. The prepared bismuth-containing catalyst has the advantages of strong alkalinity, high stability and high activity.

[0021] As a preferred technical solution of the present invention, calculated based on the molar amounts of magnesium, aluminum and bismuth, the ratio of the sum of the molar amounts of soluble salts of aluminum and bismuth to the molar amount of soluble salts of magnesium is 1:(2-4), for example, it can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0022] Preferably, calculated based on the elemental molar amounts of aluminum and bismuth, the molar amount of the soluble salt of aluminum to the molar amount of the soluble salt of bismuth is (1-9):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the soluble salt of magnesium includes any one or a combination of at least two of magnesium nitrate, magnesium chloride, magnesium carbonate or magnesium sulfate. Typical but non-limiting examples of the combination include: a combination of magnesium nitrate and magnesium chloride, a combination of magnesium chloride and magnesium carbonate, or a combination of magnesium carbonate and magnesium sulfate.

[0024] Preferably, the soluble salt of aluminum includes any one or a combination of at least two of aluminum nitrate, aluminum chloride, aluminum carbonate or aluminum sulfate. Typical but non-limiting examples of the combination include: a combination of aluminum nitrate and aluminum chloride, a combination of aluminum chloride and aluminum carbonate, or a combination of aluminum carbonate and aluminum sulfate, etc.

[0025] Preferably, the soluble salt of bismuth includes any one or a combination of at least two of bismuth nitrate, bismuth chloride, bismuth sulfate or bismuth acetate. Typical but non-limiting examples of the combination include: a combination of bismuth nitrate and bismuth chloride, a combination of bismuth chloride and bismuth sulfate, or a combination of bismuth sulfate and bismuth acetate, etc.

[0026] As a preferred technical solution of the present invention, the alkali source includes an alkaline solution, and the alkaline solute in the alkaline solution includes any one or a combination of at least two of NaOH, KOH, NaHCO3, Na2CO3 or ammonia water. Typical but non-limiting examples of the combination include: a combination of NaOH and KOH, a combination of KOH and NaHCO3, or a combination of NaHCO3 and ammonia water, etc.

[0027] Preferably, the hydroxide ion concentration of the alkaline solution is 1 to 10 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the solvent comprises deionized water.

[0029] Preferably, the pH value of the mixed solution is 9-11, for example, it can be 9, 9.2, 9.4, 9.6, 9.8, 10, 10.2, 10.4, 10.6, 10.8 or 11, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the mixing method comprises: mixing soluble salts of magnesium, aluminum and bismuth with a solvent, dispersing them under ultrasonic stirring for 0.5 to 2 hours, for example, 0.5 hours, 1 hour, 1.5 hours or 2 hours, etc., and then dropping an alkaline solution into the soluble salts and the solvent, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, after obtaining the mixed solution, before performing the crystallization treatment, the mixed solution is further stirred for 0.5 to 2 hours, for example, 0.5 hours, 1 hour, 1.5 hours or 2 hours, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the temperature of the crystallization treatment is 40-120°C, for example, it can be 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the crystallization treatment time is 4 to 24 hours, for example, it can be 6 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] If the crystallization temperature is too low, the catalyst crystal growth will be insufficient, a uniform hydrotalcite structure cannot be formed, and the bismuth element is unevenly distributed. If the temperature is too high, the crystallization speed may be too fast, affecting the uniformity of the catalyst structure.

[0035] As a preferred technical solution of the present invention, after the crystallization treatment and before the calcination treatment, the obtained mixed system is subjected to a solid-liquid separation treatment, and the obtained solid is washed to neutrality and dried before being subjected to the calcination treatment.

[0036] Preferably, the drying temperature is 70-120°C, for example, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the drying time is 12 to 24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the calcination temperature is 400-800°C, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 500°C or 800°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the calcination time is 2 to 8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] In a third aspect, the present invention provides a method for synthesizing a cyclic carbonate, using the bismuth-containing catalyst described in the first aspect or the bismuth-containing catalyst obtained by the preparation method described in the second aspect.

[0041] As a preferred technical solution of the present invention, the method comprises: mixing carbonate, diol and the bismuth-containing catalyst, and performing a catalytic synthesis reaction to obtain a cyclic carbonate.

[0042] It is understood that the raw material used to synthesize the cyclic carbonate is a linear carbonate, including but not limited to at least one of dimethyl carbonate, ethylene carbonate, and ethyl methyl carbonate.

[0043] As a preferred technical solution of the present invention, the molar ratio of the carbonate to the diol is (2-10):1, for example, it can be 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 numerical range are also applicable.

[0044] Preferably, the mass ratio of the bismuth-containing catalyst to the diol is (0.001-0.2):1, for example, it can be 0.001:1, 0.005:1, 0.01:1, 0.02:1, 0.04:1, 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1 or 0.2:1, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the temperature of the catalytic synthesis reaction is 80-200°C, for example, it can be 80°C, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the insulation time of the catalytic synthesis reaction is 20 to 200 min, for example, it can be 20 min, 60 min, 100 min, 140 min, 180 min, 220 min, 260 min or 300 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0048] The present invention provides a heterogeneous catalyst for synthesizing cyclic carbonates, which has a new composition and contains oxide components of magnesium, aluminum and bismuth. Therefore, the catalyst raw material is cheap and easy to obtain, and has high activity, high stability, can be reused many times and can be scaled up for production. Compared with homogeneous catalysts, it has the advantages of easy separation of catalyst and product and high product selectivity.

[0049] When the catalyst prepared by the present invention is used to synthesize cyclic carbonate, the process is simple and the experimental conditions are mild. Compared with other synthesis routes, it does not require other solvents, harsh conditions such as high temperature and high pressure, and the reaction time is shorter; the diol conversion rate is as high as more than 96%, and the cyclic carbonate selectivity is as high as more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a SEM characterization picture of the bismuth-containing catalyst obtained in Example 1. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0052] 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.

[0053] Example 1

[0054] This embodiment provides a preparation method and application of a bismuth-containing catalyst, and the preparation method and application include the following steps:

[0055] (1) 7.68 g of Mg(NO3)2·6H2O, 3.455 g of Al(NO3)3·9H2O, 0.496 g of Bi(NO3)3·5H2O and 100 ml of deionized water were mixed to prepare solution A, and the mixture was dispersed under ultrasonic stirring for 1 h. NaOH and Na2CO3 were dissolved in deionized water to prepare solution B with a hydroxide ion concentration of 4 mol / L. Solution B was then added dropwise to solution A through an alkaline burette until the pH of the mixed solution reached 10, thereby obtaining a mixed solution.

[0056] (2) After stirring the mixed solution in step (1) for 1 hour, the mixture was crystallized at 120° C. for 12 hours, and the obtained slurry was filtered. The filtered solid was washed with deionized water until neutral, and then dried at 100° C. for 10 hours. After drying, the solid was ground and calcined at 500° C. for 5 hours to obtain Mg3Al 0.9 Bi 0.1 O composite catalyst;

[0057] (3) 18.0 g of dimethyl carbonate, 4.5 g of 1,2-butanediol and 0.17 g of the Mg3Al obtained in step (2) were added. 0.9 Bi 0.1 O was added into the reactor, the reaction temperature was 150°C, and the reaction was carried out at 500 rpm for 100 min to obtain a cyclic carbonate.

[0058] Figure 1 The bismuth-containing catalyst (Mg3Al 0.9 Bi 0.1 The SEM characterization image of the O composite catalyst) shows that the obtained catalyst has a flaky morphology.

[0059] Example 2

[0060] This embodiment provides a preparation method and application of a bismuth-containing catalyst, and the preparation method and application include the following steps:

[0061] (1) 5.12 g of Mg(NO3)2·6H2O, 3.376 g of Al(NO3)3·9H2O, 0.485 g of Bi(NO3)3·5H2O and 100 ml of deionized water were mixed to prepare solution A, and the mixture was dispersed under ultrasonic stirring for 2 h. NaOH and NaHCO3 were dissolved in deionized water to prepare solution B with a hydroxide ion concentration of 2 mol / L. Solution B was then added dropwise to solution A through an alkaline burette until the pH of the mixed solution reached 10, thereby obtaining a mixed solution.

[0062] (2) After stirring the mixed solution in step (1) for 2 hours, the mixture was crystallized at 100°C for 8 hours to obtain a slurry, which was filtered. The filtered solid was washed with deionized water several times until it was neutral, and then dried at 120°C for 12 hours. After drying, the solid was ground and calcined at 500°C for 5 hours to obtain Mg2Al 0.9 Bi 0.1 O catalyst;

[0063] (3) 9.0 g of dimethyl carbonate, 4.5 g of 1,2-butanediol and 0.10 g of the Mg2Al obtained in step (2) were added. 0.9 Bi 0.1 O was added into the reactor, the reaction temperature was 160°C, and the reaction was carried out at 500 rpm for 20 min to obtain a cyclic carbonate.

[0064] Example 3

[0065] This embodiment provides a preparation method and application of a bismuth-containing catalyst, and the preparation method and application include the following steps:

[0066] (1) 10.24 g of Mg(NO3)2·6H2O, 3.376 g of Al(NO3)3·9H2O, 0.485 g of Bi(NO3)3·5H2O and 100 ml of deionized water were mixed to prepare solution A, and the mixture was dispersed under ultrasonic stirring for 1 h. NaOH was dissolved in deionized water to prepare solution B with a hydroxide ion concentration of 10 mol / L. Solution B was then added dropwise to solution A through an alkaline burette until the pH of the mixed solution reached 10, thereby obtaining a mixed solution.

[0067] (2) After stirring the mixed solution in step (1) for 0.5 h, the mixture was crystallized at 60° C. for 24 h to obtain a slurry, which was filtered. The filtered solid was washed with deionized water several times until it was neutral, and then dried at 70° C. for 24 h. After drying, the solid was ground and calcined at 400° C. for 8 h to obtain Mg4Al 0.9 Bi 0.1 O catalyst;

[0068] (3) 45.0 g of dimethyl carbonate, 4.5 g of 1,2-butanediol and 0.9 g of Mg4Al obtained in step (2) were added. 0.9 Bi 0.1 O was added into the reactor, the reaction temperature was 80°C, and the reaction was carried out at 500 rpm for 300 min to obtain a cyclic carbonate.

[0069] Example 4

[0070] This embodiment provides a preparation method and application of a bismuth-containing catalyst, and the preparation method and application include the following steps:

[0071] (1) 7.68 g of Mg(NO3)2·6H2O, 3.376 g of Al(NO3)3·9H2O, 0.432 g of Bi(NO3)3·5H2O and 100 ml of deionized water were mixed to prepare solution A, and the mixture was dispersed under ultrasonic stirring for 0.5 h. NaOH and Na2CO3 were dissolved in deionized water to prepare solution B with a hydroxide ion concentration of 4 mol / L. Solution B was then added dropwise to solution A through an alkaline burette until the pH of the mixed solution reached 10.5, thereby obtaining a mixed solution.

[0072] (2) After stirring the mixed solution in step (1) for 0.5 h, the mixture was crystallized at 60° C. for 12 h to obtain a slurry, which was filtered. The filtered solid was washed with deionized water several times until it was neutral, and then dried at 80° C. for 12 h. After drying, the solid was ground and calcined at 500° C. for 5 h to obtain Mg3Al 0.9 Bi 0.1 O catalyst;

[0073] (3) 18.0 g of dimethyl carbonate, 4.5 g of 1,2-butanediol and 0.24 g of Mg3Al2O3 prepared in step (2) were added to the mixture. 0.9 Bi 0.1 O was added into the reactor, the reaction temperature was 150°C, and the reaction was carried out at 500 rpm for 40 min to obtain a cyclic carbonate.

[0074] Example 5

[0075] The only difference between this embodiment and embodiment 4 is that the reaction time in step (3) is 30 min, and the other conditions are the same as those in embodiment 4.

[0076] Example 6

[0077] The only difference between this embodiment and embodiment 4 is that the reaction temperature in step (3) is 120° C., and the other conditions are the same as those in embodiment 4.

[0078] Example 7

[0079] The only difference between this embodiment and embodiment 6 is that the catalyst after the synthesis of cyclic carbonate in step (3) of embodiment 6 is separated, washed and dried, and then the catalyst is reused in step (3) to catalyze the synthesis of cyclic carbonate. The catalyst is reused 5 times. Other conditions are the same as those in embodiment 6.

[0080] Example 8

[0081] The only difference between this embodiment and embodiment 1 is that in step (3), "4.5 g 1,2-butanediol" is replaced by "3.1 g ethylene glycol", and the other conditions are the same as those in embodiment 1.

[0082] Example 9

[0083] The only difference between this embodiment and embodiment 1 is that in step (3), "4.5 g 1,2-butanediol" is replaced by "3.6 g 1,2-propylene glycol", and the other conditions are the same as those in embodiment 1.

[0084] Example 10

[0085] The only difference between this embodiment and embodiment 1 is that in step (3), "4.5 g 1,2-butanediol" is replaced by "4.6 g propylene glycol" and the reaction temperature in step (3) is 160° C. Other conditions are the same as those in embodiment 1.

[0086] Comparative Example 1

[0087] This comparative example provides a preparation method and application of a bismuth-containing catalyst, and the preparation method and application include the following steps:

[0088] (1) 2.425 g of Bi(NO3)3·5H2O and 100 ml of deionized water were mixed and dispersed under ultrasonic stirring for 0.5 h, NaOH was dissolved in deionized water to prepare a solution B with a hydroxide ion concentration of 4 mol / L, and then solution B was added dropwise to solution A through an alkaline burette until the pH of the mixed solution reached 10.5 to obtain a mixed solution;

[0089] (2) After stirring the mixed solution in step (1) for 0.5 h, the mixture was crystallized at 60° C. for 12 h to obtain a slurry, which was filtered. The filtered solid was washed with deionized water several times until it was neutral, and then dried at 80° C. for 12 h. After drying, the solid was ground and calcined at 500° C. for 5 h to obtain a Bi2O3 catalyst;

[0090] (3) 18.0 g of dimethyl carbonate, 4.5 g of 1,2-butanediol and 0.24 g of the Bi2O3 catalyst prepared in step (2) were added to a reactor, the reaction temperature was 120° C., and the reaction was carried out at 500 rpm for 40 min to obtain a cyclic carbonate.

[0091] Comparative Example 2

[0092] The difference between this comparative example and comparative example 1 is that the "2.425 g Bi(NO3)3·5H2O" in step (1) is replaced by "1.875 g Al(NO3)3·9H2O", and the other conditions are the same as those in comparative example 1.

[0093] Comparative Example 3

[0094] The only difference between this comparative example and comparative example 1 is that the "2.425 g Bi(NO3)3·5H2O" in step (1) is replaced by "7.68 g Mg(NO3)2·6H2O", and the other conditions are the same as those in comparative example 1.

[0095] Comparative Example 4

[0096] The only difference between this comparative example and comparative example 1 is that the "2.425g Bi(NO3)3·5H2O" in step (1) is replaced by "7.68g Mg(NO3)2·6H2O and 3.751g Al(NO3)3·9H2O", and the other conditions are the same as those in comparative example 1.

[0097] Comparative Example 5

[0098] The only difference between this comparative example and comparative example 1 is that the "2.425g Bi(NO3)3·5H2O" in step (1) is replaced by "7.68g Mg(NO3)2·6H2O and 4.851g Al(NO3)3·9H2O", and the other conditions are the same as those in comparative example 1.

[0099] The cyclic carbonate solution obtained in step (3) of Example 1-11 and Comparative Example 1-5 was centrifuged at 3000 rpm for 3 min, and an appropriate amount of the supernatant was added with an internal standard substance (biphenyl) and quantitatively analyzed by gas chromatography internal standard method. The test results are shown in Table 1.

[0100] Table 1

[0101] Group Diol conversion Cyclic carbonate selectivity Cyclic carbonate yield Example 1 96.1％ 99.8％ 95.9％ Example 2 97.1％ 98.7％ 95.8％ Example 3 95.9％ 99.6％ 95.5％ Example 4 95.1％ 99.8％ 94.9％ Example 5 96.4％ 99.5％ 95.9％ Example 6 92.8％ 98.2％ 91.1％ Example 7 95.8％ 98.1％ 93.9％ Example 8 96.90％ 99.90％ 96.8％ Example 9 99.1％ 99.9％ 99.0％ Example 10 98.1％ 99.6％ 97.7％ Comparative Example 1 12.3％ 13.7％ 1.6％ Comparative Example 2 24.5％ 33.7％ 8.2％ Comparative Example 3 33.7％ 90.8％ 30.5％ Comparative Example 4 48.9％ 91.6％ 44.7％ Comparative Example 5 21.64％ 87.3％ 18.8％

[0102] It can be seen from Table 1 that:

[0103] The bismuth-containing catalyst prepared by the present invention is applied to the synthesis of cyclic carbonate, and the glycol conversion rate is ≥92%, the product cyclic carbonate selectivity is ≥98%, and the cyclic carbonate yield is as high as 91% or more; when the bismuth-containing catalyst prepared in Example 7 is reused 5 times (the data of Example 7 in Table 1 is the fifth utilization), it still has a good catalytic effect, and the cyclic carbonate yield is still ≥93%; it can be seen from Examples 8, 9, and 10 that the prepared bismuth-containing catalyst can achieve a relatively high selectivity and yield for the corresponding cyclic carbonate products, whether it is for preparing ethylene carbonate from ethylene glycol, preparing propylene carbonate from 1,2-propylene glycol, or preparing glycerol carbonate from glycerol.

[0104] The catalysts prepared in Comparative Examples 1-3 contain only a single metal oxide, the catalyst prepared in Comparative Example 4 is Mg-Al oxide, and the catalyst prepared in Comparative Example 5 is Mg-Bi oxide. When applied to the synthesis of cyclic carbonates, the selectivity and yield of cyclic carbonates are low, indicating that only when the catalyst contains three metals of magnesium, aluminum and bismuth at the same time, the selectivity and yield of the catalytic synthesis of cyclic carbonates are good.

[0105] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0106] 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.

[0107] 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.

[0108] 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 bismuth-containing catalyst, characterized in that Includes oxide components of magnesium, aluminum and bismuth.

2. The bismuth-containing catalyst according to claim 1, characterized in that The bismuth-containing catalyst includes Mg x Al y Bi z O, wherein x=2-4, y=0.5-0.9, z=0.1-0.5, and y+z=1.

3. A method for preparing a bismuth-containing catalyst according to claim 1, characterized in that: The preparation method comprises the following steps: The soluble salts of magnesium, aluminum and bismuth, an alkali source and a solvent are mixed to obtain a mixed solution; the mixed solution is sequentially subjected to crystallization treatment and roasting treatment to obtain a bismuth-containing catalyst.

4. The preparation method according to claim 3, characterized in that: Calculated based on the molar amounts of magnesium, aluminum and bismuth, the ratio of the sum of the molar amounts of soluble salts of aluminum and bismuth to the molar amount of soluble salts of magnesium is 1:(2-4); Calculated based on the molar amounts of aluminum and bismuth, the molar amount of the soluble salt of aluminum to the molar amount of the soluble salt of bismuth is (1-9):1; Preferably, the soluble salt of magnesium includes any one or a combination of at least two of magnesium nitrate, magnesium chloride, magnesium carbonate or magnesium sulfate; Preferably, the soluble salt of aluminum includes any one or a combination of at least two of aluminum nitrate, aluminum chloride, aluminum carbonate or aluminum sulfate; Preferably, the soluble salt of bismuth includes any one or a combination of at least two of bismuth nitrate, bismuth chloride, bismuth sulfate or bismuth acetate.

5. The preparation method according to claim 3 or 4, characterized in that: The alkali source comprises an alkaline solution, and the alkaline solute in the alkaline solution comprises any one or a combination of at least two of NaOH, KOH, NaHCO3, Na2CO3 or ammonia water; Preferably, the hydroxide ion concentration of the alkaline solution is 1 to 10 mol / L; Preferably, the solvent comprises deionized water; Preferably, the pH value of the mixed solution is 9 to 11; Preferably, the mixing method comprises: mixing soluble salts of magnesium, aluminum and bismuth with a solvent, dispersing them under ultrasonic stirring for 0.5 to 2 hours, and then dropping an alkaline solution into the soluble salts and the solvent.

6. The preparation method according to any one of claims 3 to 5, characterized in that: After obtaining the mixed solution, before performing the crystallization treatment, stirring the mixed solution for another 0.5 to 2 hours; Preferably, the temperature of the crystallization treatment is 40 to 120°C; Preferably, the crystallization treatment time is 4 to 24 hours.

7. The preparation method according to any one of claims 3 to 6, characterized in that: After the crystallization treatment and before the calcination treatment, the obtained mixed system is subjected to a solid-liquid separation treatment, the obtained solid is washed to neutrality and dried, and then subjected to the calcination treatment; Preferably, the drying temperature is 70-120°C; Preferably, the drying time is 12 to 24 hours; Preferably, the calcination temperature is 400-800°C; Preferably, the calcination treatment time is 2 to 8 hours.

8. A method for synthesizing a cyclic carbonate, characterized in that: The bismuth-containing catalyst according to claim 1 or 2 or the bismuth-containing catalyst obtained by the preparation method according to any one of claims 3 to 7.

9. The method according to claim 8, characterized in that The method comprises: mixing carbonate, diol and the bismuth-containing catalyst, and performing a catalytic synthesis reaction to obtain a cyclic carbonate.

10. The method according to claim 9, characterized in that The molar ratio of the carbonate to the diol is (2-10):1; Preferably, the mass ratio of the bismuth-containing catalyst to the diol is (0.001-0.2):1; Preferably, the temperature of the catalytic synthesis reaction is 80 to 200°C; Preferably, the insulation time of the catalytic synthesis reaction is 20 to 200 minutes.

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