Preparation method of supported catalyst and preparation method of glycerol carbonate

Abstract

The invention provides a preparation method of a supported catalyst and a preparation method of glycerol carbonate. The preparation method of the supported catalyst comprises the following steps: obtaining a carbon precursor, reacting the carbon precursor with alkali liquor to obtain a first mixed solution, carbonizing the second mixed solution to obtain a first solid product, and post-treating the first solid product to obtain a modified activated carbon carrier; the alkali liquor comprises an inorganic alkali compound and an organic alkali compound; uniformly mixing the modified activated carbon carrier with impregnation liquid to obtain a second mixed solution, drying the second mixed solution to obtain a mixture, and roasting the mixture in a protective atmosphere to obtain the supported catalyst, the impregnation liquid comprises nitrate and an alkaline compound. The supported catalyst provided by the invention has very high catalytic activity and is easy to separate and recover, the preparation method is simple, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of glycerol carbonate, and particularly relates to a preparation method of a supported catalyst and a preparation method of glycerol carbonate. Background Art

[0002] Glycerol carbonate is an important glycerol derivative, which has the characteristics of good biodegradability, low toxicity and high boiling point, and is widely used in many fields such as food, medicine, cosmetics, coatings, new materials, new energy, etc.

[0003] Common methods for preparing glycerol carbonate include transesterification method, CO oxidative carbonylation method, zinc acetate catalysis method, urea alcoholysis method, CO 2 direct synthesis method, etc.; among them, the method of preparing glycerol carbonate by transesterification with glycerol and dimethyl carbonate as raw materials under the action of a catalyst is favored because of its advantages such as high product purity, good product chromaticity and mild reaction conditions. In the method of preparing glycerol carbonate by transesterification, the following main catalytic systems have been reported for this reaction: (1) metal oxide catalyst; (2) supported metal oxide catalyst; (3) metal salt catalyst; (4) ionic liquid catalyst; (5) enzyme catalyst. However, due to the low activity of metal oxide catalysts, it is difficult to recover supported metal oxide catalysts, metal salt catalysts and ionic liquid catalysts, the preparation method of metal salt catalysts is complex, and ionic liquid catalysts and enzyme catalysts also have relatively high costs, which are restricted in practical applications. Summary of the Invention

[0004] Aiming at the problems of low activity, difficult recovery, complex preparation method and high cost of the catalyst in the existing glycerol carbonate preparation system, the present application provides a preparation method of a supported catalyst and a preparation method of glycerol carbonate.

[0005] On the one hand, the present invention provides a preparation method of a supported catalyst, including the following steps: Obtain a carbon precursor, react the carbon precursor with an alkali solution to obtain a first mixed solution, subject the first mixed solution to carbonization treatment to obtain a first solid product, and subject the first solid product to post-treatment to obtain a modified activated carbon carrier; the alkali solution includes inorganic base compounds and organic base compounds; Mix the modified activated carbon carrier with an impregnation solution evenly to obtain a second mixed solution, dry the second mixed solution to obtain a mixture, and calcine the mixture under a protective atmosphere to obtain the supported catalyst; The impregnation solution includes nitrate and an alkaline compound.

[0006] Preferably, the obtaining of the carbon precursor includes the following steps: Obtain carbon-based powder materials, heat and pre-treat the carbon-based powder materials under a protective atmosphere to obtain carbon powder, and wash the carbon powder to obtain a carbon precursor.

[0007] Preferably, obtaining the carbon-based powder materials includes the following steps: crushing the carbon-based raw materials and sieving them through a 40-60 mesh sieve to obtain the carbon-based powder materials; The carbon-based raw materials include biomass carbon sources; The heating temperature for the heating pre-treatment is 140-160 °C, and the heating time is 1-2 h; Washing the carbon powder to obtain the carbon precursor includes the following steps: washing the carbon powder with an acidic solution and deionized water in sequence to obtain the carbon precursor, and the carbon precursor is neutral.

[0008] Preferably, the inorganic base compounds include alkali metal hydroxides, and the organic base compounds include alkali metal salt compounds of alcohols; The mass ratio of the carbon precursor, inorganic base compounds, and organic base compounds is 1:(1-1.5):(3-5); In the step of reacting the carbon precursor with the alkali solution, the reaction time is 3-4 h.

[0009] Preferably, carbonizing the first mixed solution to obtain a first solid product includes the following steps: carbonizing the first mixed solution under a protective atmosphere to obtain the first solid product; The carbonization temperature for carbonizing the first mixed solution is 800-900 °C, and the carbonization time is 3-4 h.

[0010] Preferably, post-treating the first solid product to obtain a modified activated carbon carrier includes the following steps: washing the first solid product with deionized water and an alcohol solvent until it is neutral to obtain a second solid product, and drying the second solid product at a temperature of 100-110 °C for 10-12 h to obtain the modified activated carbon carrier.

[0011] Preferably, the impregnating solution further contains deionized water; in the impregnating solution, the molar ratio of nitrate, basic compound, and deionized water is 1:(2-3):(5-8); The mass ratio of the impregnating solution to the modified activated carbon carrier is 1:(5-8); Mixing the modified activated carbon carrier with the impregnating solution evenly to obtain a second mixed solution includes the following steps: dispersing the modified activated carbon carrier into the impregnating solution and impregnating for 6-8 h to obtain the second mixed solution; In the step of drying the second mixed solution to obtain a mixture, the drying temperature is 100-110 °C.

[0012] Preferably, in the roasting step of roasting the mixture under a protective atmosphere, the roasting temperature is 550-700 °C and the roasting time is 3-5 h.

[0013] On the other hand, the present invention also provides a method for preparing glycerol carbonate, comprising the following steps: Preparing the glycerol carbonate by reacting a carbonate ester and glycerol under the catalysis of a supported catalyst; The supported catalyst is prepared by the method for preparing the supported catalyst described above.

[0014] Preferably, preparing the glycerol carbonate by reacting a carbonate ester and glycerol under the catalysis of a supported catalyst comprises the following steps: Reacting the carbonate ester, glycerol and the supported catalyst at a temperature of 85-90 °C for 1-2 h to obtain the glycerol carbonate; The molar ratio of the carbonate ester to glycerol is (2.5-3.5):1; The mass of the supported catalyst is 0.05%-0.1% of the mass of the glycerol.

[0015] The method for preparing a supported catalyst provided by the present application has the following effects: The supported catalyst provided by the present invention has high catalytic activity for the reaction of preparing glycerol carbonate by transesterification, and the yield of glycerol carbonate can reach more than 80%.

[0016] Compared with existing metal-supported catalysts, homogeneous catalysts, etc., there are generally problems such as insufficient mechanical strength, difficulty in separation and recycling, and impact on product quality. The supported catalyst provided by the present invention has good mechanical stability and is easy to separate and recycle; the supported catalyst provided by the present invention is solid carbon powder and can be separated from the product only by filtration and can be reused repeatedly.

[0017] The supported catalyst provided by the present invention has stable chemical properties, is not easily deactivated during the reaction catalysis process, and does not corrode the equipment. The method for preparing the supported catalyst provided by the present application is simple and has low cost. Detailed embodiments

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In order to illustrate the technical solutions of the present invention, the following will be illustrated by specific examples.

[0020] In the first aspect, the present application provides a method for preparing a supported catalyst, comprising the following steps: A carbon precursor is obtained. The carbon precursor and an alkali solution are reacted to obtain a first mixed solution. The first mixed solution is carbonized to obtain a first solid product. The first solid product is post-treated to obtain a modified activated carbon support. The alkali solution includes inorganic base compounds and organic base compounds. The modified activated carbon support is mixed uniformly with an impregnating solution to obtain a second mixed solution. The second mixed solution is dried to obtain a mixture. The mixture is calcined under a protective atmosphere to obtain the supported catalyst. The impregnating solution includes nitrates and basic compounds.

[0021] Specifically, in the step of reacting the carbon precursor with the alkali solution to obtain the first mixed solution, the alkali solution includes inorganic base compounds and organic base compounds. The inorganic base compounds and organic base compounds have strong alkalinity, causing the carbon element on the surface of the carbon precursor to react with the alkali to form soluble organic acid salts and other substances, such as sodium carbonate, thereby generating a large number of tiny pores and channels on the surface and inside of the carbon precursor, and forming an unpenetrated pore structure on the surface of the carbon precursor, making the pore structure of the modified activated carbon support richer and more conducive to providing sites for subsequent alkali metal loading.

[0022] Carbonizing the first mixed solution is beneficial to cause the organic components in the carbon precursor to undergo a deep carbonization reaction. At the same time, the organic acid salts generated by the reaction are gradually converted into gas and escape, thereby increasing the etching and pore expansion effect on the carbon precursor, forming a rich pore structure, providing sites for alkali metal loading, and improving the adsorption performance and catalytic performance.

[0023] The preparation method of a supported catalyst provided by this application has the following effects: 1) The supported catalyst provided by the present invention has high catalytic activity for the reaction of preparing glycerol carbonate by transesterification, and the yield of glycerol carbonate can reach more than 80%. 2) Compared with existing metal-supported catalysts, homogeneous catalysts, etc., there are generally problems such as insufficient mechanical strength, difficulty in separation and recycling, and impact on product quality. The supported catalyst provided by the present invention has good mechanical stability and is easy to separate and recycle. The supported catalyst provided by the present invention is solid carbon powder and can be separated from the product only by filtration and can be reused repeatedly. 3) The supported catalyst provided by the present invention has stable chemical properties, is not easily deactivated during the reaction catalysis process, and does not corrode the equipment. The preparation method of the supported catalyst provided by this application is simple and has low cost.

[0024] In some embodiments, the obtaining of the carbon precursor includes the following steps: Carbon-based powder is obtained. The carbon-based powder is heated and pretreated under a protective atmosphere to obtain carbon powder. The carbon powder is washed to obtain the carbon precursor.

[0025] Specifically, being under a protective atmosphere means that there is no air in the container and the container is filled with a protective gas. The protective gas includes one of nitrogen gas and noble gases; preferably, the protective gas is nitrogen gas.

[0026] The carbon-based powder is subjected to heat pretreatment to initiate the thermal decomposition reaction of the organic components in the carbon-based powder, preliminarily carbonize the carbon-based powder, and stabilize the prototype of the carbon structure; meanwhile, free water and bound water will be evaporated, reducing the water content in the subsequent obtained carbon precursor.

[0027] The carbon powder is washed to obtain a carbon precursor, and the washing is to remove the contained ash and impurities.

[0028] In some embodiments, obtaining the carbon-based powder includes the following steps: crushing and sieving a carbon-based raw material through a 40-60 mesh sieve to obtain the carbon-based powder; The carbon-based raw material includes a biomass carbon source; The heating temperature of the heat pretreatment is 140-160 °C, and the heating time is 1-2 h.

[0029] Specifically, the biomass carbon source includes wood raw materials, and the wood raw materials include moso bamboo, poplar, etc.

[0030] Crushing and sieving a carbon-based raw material through a 40-60 mesh sieve to obtain a carbon-based powder specifically means grinding the carbon-based raw material for crushing and then passing it through a 40-60 mesh sieve to obtain the carbon-based powder. A 40-mesh sieve is preferred.

[0031] Under a protective atmosphere, the carbon-based powder is subjected to heat pretreatment at a heating temperature of 140-160 °C for 1-2 h, and after heating, carbon powder is obtained. Within the range of a heating temperature of 140-160 °C and a heating time of 1-2 h, the organic components in the carbon-based powder can be decomposed, and at the same time, free water and bound water can be evaporated, which is beneficial to subsequent carbonization treatment. Specifically, the heating temperature can be 140 °C, 142 °C, 145 °C, 148 °C, 150 °C, 153 °C, 155 °C, 158 °C, 160 °C, etc.

[0032] In some embodiments, washing the carbon powder to obtain a carbon precursor includes the following steps: sequentially washing the carbon powder with an acidic solution and deionized water to obtain the carbon precursor, and the carbon precursor is neutral.

[0033] Specifically, the acidic solution includes an inorganic acid solution, and the inorganic acid solution includes a hydrochloric acid solution, a sulfuric acid solution, etc. Further preferably, the acidic solution is a hydrochloric acid solution.

[0034] First, wash the carbon powder with an acidic solution at least once, and then wash it with deionized water at least once after the acidic solution washing to remove the ash and impurities contained. After the deionized water washing, the obtained carbon precursor is neutral.

[0035] In some embodiments, the inorganic base compounds include alkali metal hydroxides, and the organic base compounds include alkali metal salts of alcohols.

[0036] Inorganic base compounds and organic base compounds belong to strong base compounds, which are beneficial to the separation of hydroxide ions, etching the surface of the carbon precursor, promoting the reaction of carbon elements on the surface of the carbon precursor with the base, and facilitating the generation of a large number of tiny pores and channels on the surface and inside of the carbon precursor.

[0037] In some preferred embodiments, the alkali metal hydroxide includes one or both of sodium hydroxide and potassium hydroxide.

[0038] The alkali metal salts of alcohols include one or more of sodium ethoxide, sodium methoxide, and sodium propoxide.

[0039] In some embodiments, the alkali solution further includes deionized water, which is used to dissolve alkali metal hydroxides and alkali metal salts of alcohols.

[0040] In some embodiments, the mass ratio of the carbon precursor, inorganic base compounds, and organic base compounds is 1:(1 - 1.5):(3 - 5); In the step of reacting the carbon precursor and the alkali solution, the reaction time is 3 - 4 h.

[0041] Specifically, limiting the mass ratio of the carbon precursor, inorganic base compounds, and organic base compounds ensures that there are enough strong base compounds, so that the base reacts with the carbon elements in the carbon precursor, etching the carbon precursor and generating a large number of tiny pores and channels on the surface and inside of the carbon precursor.

[0042] The reaction time is in the range of 3 - 4 h. Controlling the reaction time is beneficial to generating a large number of tiny pores and channels inside the carbon precursor, facilitating the better formation of a rich pore structure during the subsequent carbonization process, and providing sites for subsequent alkali metal loading.

[0043] In some embodiments, the steps of carbonizing the first mixed solution to obtain a first solid product include: carbonizing the first mixed solution under a protective atmosphere to obtain a first solid product; The carbonization temperature for carbonizing the first mixed solution is 800 - 900 °C, and the carbonization time is 3 - 4 h.

[0044] Specifically, the protective gas used in the protective atmosphere includes at least one of nitrogen and noble gases. At a carbonization temperature of 800-900 °C and a carbonization time of 3-4 h, under high-temperature conditions, it can cause salts such as Na 2 CO 3 etc. gradually transform into gaseous state and escape, thereby increasing the etching and pore expansion effect on the material, further expanding and connecting tiny pores, forming a more abundant pore network, greatly increasing the specific surface area and porosity of the modified activated carbon carrier, providing sites for subsequent alkali metal loading, and thus significantly improving the adsorption performance and catalytic performance of the supported catalyst. At the same time, the carbonization temperature of the carbonization treatment is in the range of 800-900 °C and the carbonization time is 3-4 h, which can also cause the organic components in the carbon precursor to undergo a deep carbonization reaction to form a more stable graphitized structure.

[0045] Specifically, the carbonization temperature can be 800 °C, 820 °C, 840 °C, 860 °C, 880 °C, 890 °C, 900 °C, etc.

[0046] In some embodiments, post-treating the first solid product to obtain the modified activated carbon carrier includes the following steps: washing the first solid product with deionized water and an alcohol solvent until neutral to obtain a second solid product, and drying the second solid product at a temperature of 100-110 °C for 10-12 h to obtain the modified activated carbon carrier.

[0047] Specifically, washing with deionized water removes water-soluble inorganic salts and inorganic basic compounds such as sodium hydroxide on the surface of the first solid product, and washing with an alcohol solvent removes organic salts and organic basic compounds such as sodium ethoxide that are soluble in the alcohol solvent.

[0048] Drying the second solid product at a temperature of 100-110 °C for 10-12 h is used to remove the water and alcohol solvent on the surface.

[0049] The alcohol solvent includes ethanol.

[0050] In some embodiments, the impregnation solution further contains deionized water; in the impregnation solution, the molar ratio of nitrate, basic compound and deionized water is 1: (2-3): (5-8); The mass ratio of the impregnation solution to the modified activated carbon carrier is 1: (5-8).

[0051] Specifically, when preparing the impregnation solution, nitrate, alkaline compound and deionized water are uniformly mixed. The molar ratio of nitrate, alkaline compound and deionized water in the impregnation solution is in the range of 1: (2-3): (5-8). The alkaline compound contained in the impregnation solution provides a strong alkaline environment, has an impregnation corrosion effect, changes the internal skeleton structure of the modified activated carbon carrier, opens up the pores inside the modified activated carbon carrier to form micropores, reduces its specific surface area, increases the micropore volume and the micropore volume ratio, and forms a loading site.

[0052] During the calcination process, nitrates can undergo redox reactions with the surface functional groups of the modified activated carbon carrier to generate a large number of strong alkaline sites.

[0053] In some embodiments, the modified activated carbon support and the impregnation liquid are mixed uniformly to obtain a second mixed solution, comprising the following steps: dispersing the impregnation liquid into the modified activated carbon support, impregnating for 6 to 8 hours, to obtain the second mixed solution; In the step of drying the second mixed solution to obtain a mixture, the drying temperature is 100° C. to 110° C.

[0054] Specifically, the impregnation liquid is dispersed into the modified activated carbon carrier, and ultrasound can be used to disperse the impregnation liquid into the modified activated carbon carrier, which helps the nitrate and the alkaline compound to be uniformly adsorbed on the surface of the modified activated carbon carrier. Specifically, the impregnation time refers to the time after the impregnation liquid is dispersed into the modified activated carbon carrier, and then left to stand for 6 to 8 hours to facilitate the impregnation of the impregnation liquid into the modified activated carbon carrier, wherein the impregnation time can be 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, etc.

[0055] The second mixed solution is dried to a constant weight, and the water in the second mixed solution is removed to obtain a mixture having nitrate and alkaline compound structures adsorbed on the surface of the modified activated carbon carrier. Specifically, the drying temperature can be 100°C, 102°C, 105°C, 108°C, 110°C, etc.

[0056] In some embodiments, the nitrate comprises one or more of sodium nitrate, potassium nitrate, and calcium nitrate.

[0057] In some embodiments, the alkaline compound includes one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0058] The above-mentioned types of nitrates and alkaline compounds are used as the impregnation solution, which has high selectivity and less intermediate by-products.

[0059] Further preferably, the nitrate comprises NaNO 3 , alkaline compounds include NaOH.

[0060] In some embodiments, during the roasting step of the mixture under a protective atmosphere, the roasting temperature is 550-700 °C and the roasting time is 3-5 h.

[0061] Specifically, the protective gas used in the protective atmosphere includes at least one of nitrogen and noble gases.

[0062] Within the range of a roasting temperature of 550-700 °C and a roasting time of 3-5 h, a redox reaction can occur between the nitrate and the surface functional groups of the modified activated carbon support, generating a large number of strong basic sites. If the roasting temperature is too high, it may cause sintering or overreaction of the modified activated carbon support, damaging the internal active structure; if the roasting temperature is too low, the redox reaction between the nitrate and the surface functional groups of the modified activated carbon support cannot occur.

[0063] Specifically, the roasting temperature can be 550 °C, 580 °C, 600 °C, 630 °C, 650 °C, 680 °C, 700 °C, etc., as long as the roasting temperature is within the range of 550-700 °C. The roasting time can be 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc., as long as the roasting time is within the range of 3-5 h.

[0064] In a second aspect, the present application provides a method for preparing glycerol carbonate, comprising the following steps: Preparing the glycerol carbonate by catalytic reaction of a carbonate and glycerol with a supported catalyst; The supported catalyst is prepared by the preparation method of the supported catalyst described above.

[0065] The method for preparing glycerol carbonate provided by the present application uses the supported catalyst prepared by the present application as the catalyst for the esterification reaction, which has stable chemical properties, is not easily deactivated during the catalytic process, has no corrosion to equipment. At the same time, the catalyst has high mechanical strength, is easy to separate and recycle from the reaction system, and can be reused multiple times.

[0066] In some embodiments, preparing the glycerol carbonate by catalytic reaction of a carbonate and glycerol with a supported catalyst includes the following steps: Reacting the carbonate, glycerol and the supported catalyst at a temperature of 85-90 °C for 1-2 h to obtain the glycerol carbonate; The molar ratio of the carbonate to glycerol is (2.5-3.5):1; The mass of the supported catalyst is 0.05%-0.1% of the mass of the glycerol.

[0067] Specifically, a reaction temperature of 85-90 °C and a reaction time of 1-2 h contribute to the formation of glycerol carbonate by the catalytic action of the supported catalyst with a large number of basic sites on the carbonate and glycerol.

[0068] When the mass of the supported catalyst is in the range of 0.05% - 0.1% of the mass of glycerol, it can increase the reaction rate and accelerate the progress of the reaction.

[0069] A method for preparing glycerol carbonate provided by this application has the following reaction mechanism.

[0070] In the first step, a large number of basic sites provided by the supported catalyst, denoted as B in the following formula, cause glycerol to deprotonate to form glycerol oxide anions, and the reaction is as follows. - to form glycerol oxide anions by deprotonating glycerol, and the reaction is as follows.

[0071] .

[0072] In the second step, the carbonyl radical of dimethyl carbonate reacts with the glycerol oxide anion to form hydroxyalkyl carbonate and methanol anion; .

[0073] In the third step, further intermolecular reactions occur in the presence of the catalyst to generate glycerol carbonate and methanol molecules as by-products.

[0074] .

[0075] The present invention will be further described below through examples.

[0076] Example 1 S1: Preparation of modified activated carbon support S11: Take pre-treated moso bamboo as the carbon-based raw material. After grinding the moso bamboo into powder and passing it through a 40-mesh sieve, carbon-based powder is obtained. Place the carbon-based powder in a carbonization furnace and heat it under the protection of a nitrogen atmosphere for pre-treatment to obtain carbon powder. The heating pre-treatment temperature is 150 °C, and the heating pre-treatment time is 1 h. First, wash the carbon powder with dilute hydrochloric acid with a mass concentration of 3% at least once, and then wash it with deionized water at least once after the acid washing to remove the ash and impurities present to obtain a carbon precursor. The carbon precursor obtained after the washing is neutral.

[0077] S12: React the carbon precursor obtained in step S11 with the alkali solution under ultrasonic action for 3 h to obtain a first mixed solution. Transfer the first mixed solution to a carbonization furnace and carry out carbonization treatment under the protection of a nitrogen atmosphere to obtain a first solid product. The heating temperature for the carbonization treatment is 850 °C, the heating time for the carbonization treatment is 3.5 h, and the heating rate is 2 °C / min. Among them, the alkali solution contains deionized water, sodium hydroxide, and sodium ethoxide, and the mass ratio of the carbon precursor, sodium hydroxide, and sodium ethoxide is 1:1:3.

[0078] The first solid product obtained above was washed with deionized water and ethanol until neutral to obtain a second solid product, and the second solid product was placed in a blast drying oven and dried at 105 °C for 11 h to obtain a modified activated carbon support.

[0079] S2: Preparation of supported catalyst Sodium nitrate, sodium hydroxide and deionized water were weighed according to a molar ratio of 1:2:5 to prepare an impregnation solution. The impregnation solution and the modified activated carbon support prepared in step S12 were weighed according to a mass ratio of 1:5. The impregnation solution was dispersed into the modified activated carbon support under ultrasonic action and impregnated for 7 h to obtain a second mixed solution. The second mixed solution was dried to constant weight at a temperature of 100 °C to obtain a mixture. Subsequently, the mixture was placed in a muffle furnace and calcined at 600 °C for 5 h in an atmosphere of N 2 to obtain a supported catalyst.

[0080] S3: Preparation of glycerol carbonate In a reaction vessel, carbonate and glycerol with a molar ratio of 3:1 were added, and the supported catalyst prepared in step S2 was added. The reaction vessel was placed in a constant temperature oil bath and transesterification reaction was carried out at 90 °C for 2 h to obtain the product glycerol carbonate. The amount of the supported catalyst used was 0.1% of the mass of glycerol.

[0081] Example 2 Most steps of this example are the same as those of Example 1. The difference is that in step S12 of this example, the mass ratio of carbon precursor, sodium hydroxide and sodium ethoxide is 1:1.5:3.5. The rest is the same as Example 1.

[0082] Example 3 Most steps of this example are the same as those of Example 1. The difference is that in step S12 of this example, the mass ratio of carbon precursor, sodium hydroxide and sodium ethoxide is 1:2:3. The rest is the same as Example 1.

[0083] Example 4 Most steps of this example are the same as those of Example 1. The difference is that in step S11 of this example, the heating pretreatment temperature is 160 °C and the heating pretreatment time is 2 h; in step S12, the heating temperature of the carbonization treatment is 900 °C and the heating time of the carbonization treatment is 4 h. The rest is the same as Example 1.

[0084] Example 5 Most steps of this example are the same as those of Example 1. The difference is that in step S12 of this example, the heating temperature of the carbonization treatment is 960 °C and the heating time of the carbonization treatment is 3 h. The rest is the same as Example 1.

[0085] Example 6 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S11 of this embodiment, there is no heating pretreatment step. The rest is the same as in Embodiment 1.

[0086] Embodiment 7 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the mass ratio of the impregnating solution to the modified activated carbon carrier is 1:6. The rest is the same as in Embodiment 1.

[0087] Embodiment 8 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the mass ratio of the impregnating solution to the modified activated carbon carrier is 1:10. The rest is the same as in Embodiment 1.

[0088] Embodiment 9 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the mass ratio of the impregnating solution to the modified activated carbon carrier is 1:2.5. The rest is the same as in Embodiment 1.

[0089] Embodiment 10 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the molar ratio of sodium nitrate, sodium hydroxide to deionized water for preparing the impregnating solution is 1:3:8. The rest is the same as in Embodiment 1.

[0090] Embodiment 11 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the molar ratio of sodium nitrate, sodium hydroxide to deionized water for preparing the impregnating solution is 1:2.5:6. The rest is the same as in Embodiment 1.

[0091] Embodiment 12 Most steps in this embodiment are the same as those in Embodiment 1. The differences are as follows: In step S2 of this embodiment, the molar ratio of sodium nitrate, sodium hydroxide to deionized water for preparing the impregnating solution is 1:3:10. The rest is the same as in Embodiment 1.

[0092] Comparative Example 1 Mix glycerol and dimethyl carbonate with a molar ratio of 1:3 evenly, add an appropriate amount of solid catalyst potassium carbonate, and place an appropriate-sized magnetic stir bar. Connect a spherical condenser to the neck of the round-bottom flask and pass cooling water. Start stirring, adjust the speed of the magnetic stirrer to an appropriate value, and heat in an oil bath to 90 °C for reaction for 2 h. Remove the catalyst from the obtained liquid material to obtain glycerol carbonate, and the catalyst potassium carbonate is 0.1% of the mass of glycerol.

[0093] Comparative Example 2 Weigh a certain amount of copper nitrate pentahydrate, zinc nitrate hexahydrate, and manganese nitrate (the molar ratio of copper nitrate pentahydrate, zinc nitrate hexahydrate, and manganese nitrate is 7.5:1:2.1) into a round-bottom flask, pour deionized water into it, mix well, and stir at room temperature for 4 h to obtain a mixed solution.

[0094] Drop the above-obtained mixed solution into sodium carbonate solution and sodium citrate oxalate solution until the pH = 6, stir magnetically at 60 °C for 2 h, age at room temperature for 12 h, filter, wash with distilled water multiple times until the pH = 6, and then dry at 120 °C for 24 h. After drying, calcine at 550 °C for 4 h and cool to obtain the catalyst.

[0095] Put the catalyst prepared by the above method into a 250 mL round-bottom flask, add glycerol and dimethyl carbonate with a molar ratio of 1:3, mix well, and put in a magnetic stirrer bar of appropriate size. Connect a spherical condenser to the neck of the round-bottom flask and pass cooling water. Start stirring, adjust the speed of the magnetic stirrer to an appropriate size, and heat in an oil bath to 90 °C for 2 h. Remove the catalyst from the obtained liquid material to obtain glycerol carbonate, and the catalyst is 0.1% of the mass of glycerol.

[0096] Comparative Example 3 Most of the steps in this example are the same as those in Example 1. The difference is that in step S12 of this example, there is no sodium hydroxide, and the carbon precursor is directly transferred to the carbonization furnace, and the rest is the same as in Example 1.

[0097] Comparative Example 4 Most of the steps in this example are the same as those in Example 1. The difference is that in step S12 of this example, there is no sodium ethoxide, and the carbon precursor is directly transferred to the carbonization furnace, and the rest is the same as in Example 1.

[0098] Performance test The products prepared in the above examples and comparative examples are rectified and filtered to obtain glycerol carbonate, and the yield and purity of glycerol carbonate are calculated, and the conversion rate of glycerol is calculated. The calculation results are shown in Table 1.

[0099] The test results are shown in Table 1.

[0100] It should be noted that the yield of glycerol carbonate in each example and comparative example in Table 1 refers to that after obtaining the crude glycerol carbonate and then rectifying and filtering to obtain pure glycerol carbonate, the yield of glycerol carbonate = pure glycerol carbonate / crude glycerol carbonate × 100%.

[0101] Table 1 As can be seen from Table 1, when comparing Example 1 with Comparative Examples 1 and 2 in the preparation of glycerol carbonate, the catalyst used in Comparative Example 1 is potassium carbonate, and the catalyst used in Comparative Example 2 is a catalyst prepared from copper nitrate pentahydrate, zinc nitrate hexahydrate, and manganese nitrate. The yield of glycerol carbonate obtained is low, the glycerol conversion rate is low, and the purity is low. This shows that the supported catalyst prepared by the preparation method of the supported catalyst of the present application has a high yield of glycerol carbonate, a high purity, and a high glycerol conversion rate, indicating that the supported catalyst provided by the present application has high catalytic activity and can improve the yield of glycerol carbonate.

[0102] When comparing Examples 1-2 with Comparative Examples 3 and 4, the lye in Comparative Example 3 does not contain inorganic base compounds, and Comparative Example 4 does not contain organic base compounds. The yield of glycerol carbonate obtained is low, the glycerol conversion rate is low, and the purity is low. This shows that in the preparation of the modified activated carbon support, the added lye should contain both inorganic base compounds and organic base compounds. When comparing Examples 1-2 with Example 3, it shows that within the range of the mass ratio of the carbon precursor, inorganic base compounds, and organic base compounds of 1:(1~1.5):(3~5), the glycerol conversion rate, the purity, and the yield of glycerol carbonate are high. When comparing Example 1 with Example 6, in Example 6, there is no heating pretreatment step in the step of preparing the carbon precursor, and the yield of glycerol carbonate obtained is low, the glycerol conversion rate is low, and the purity is low. This shows that without the heating pretreatment step, it affects the subsequent carbonization treatment and the reaction activity of the supported catalyst. The comparison between Examples 1, 4, and Example 5 shows that when the carbonization treatment temperature is higher than 800~900 °C, it affects the etching and pore expansion effect and reduces the reaction activity of the supported catalyst.

[0103] When comparing Examples 1, 7 with Examples 8, 9, when the mass ratio of the impregnating solution to the modified activated carbon support is lower than 1:(5~8), the amount of the impregnating solution contained is small, the impregnation and corrosion effect is weak, the number of loading sites is small, and the reaction activity of the supported catalyst is reduced, and the purity and yield of glycerol carbonate obtained are low; when the mass ratio of the impregnating solution to the modified activated carbon support is higher than 1:(5~8), the amount of the impregnating solution contained is large and the amount of the modified activated carbon support is small, which affects the reaction rate and the yield of glycerol carbonate is low.

[0104] Comparing Examples 1, 10-11 with Example 12, the molar ratio of nitrate, alkaline compound and deionized water is not in the range of 1: (2-3): (5-8), which affects the formation of loading sites, reduces the reaction activity of the loaded catalyst, and the purity and yield of the obtained glycerol carbonate are low; this indicates that the molar ratio of nitrate, alkaline compound and deionized water is in the range of 1: (2-3): (5-8), the alkaline compound contained provides a strong alkaline environment, has an impregnation corrosion effect, changes the internal skeleton structure of the modified activated carbon carrier, opens up the pores inside the modified activated carbon carrier to form micropores, reduces its specific surface area, increases the micropore volume and the micropore volume ratio, forms loading sites, the reaction activity of the loaded catalyst is high, and the purity and yield of the obtained glycerol carbonate are high.

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for preparing a supported catalyst, characterized in that: The following steps are involved: Obtaining a carbon precursor, reacting the carbon precursor with an alkaline solution to obtain a first mixed solution, carbonizing the first mixed solution to obtain a first solid product, and post-treating the first solid product to obtain a modified activated carbon carrier; The alkali solution includes inorganic alkali compounds and organic alkali compounds; The modified activated carbon carrier and the impregnation solution are uniformly mixed to obtain a second mixed solution, the second mixed solution is dried to obtain a mixture, and the mixture is calcined under a protective atmosphere to obtain the supported catalyst; The impregnation solution includes nitrates and alkaline compounds.

2. The method for preparing a supported catalyst according to claim 1, wherein The method of obtaining the carbon precursor comprises the following steps: A carbon-based powder is obtained, the carbon-based powder is heated and pre-treated under a protective atmosphere to obtain carbon powder, and the carbon powder is washed to obtain a carbon precursor.

3. The method for preparing a supported catalyst according to claim 2, characterized in that: The method for obtaining the carbon-based powder comprises the following steps: crushing the carbon-based raw material and passing it through a 40-60 mesh sieve to obtain the carbon-based powder; The carbon-based raw material includes a biomass carbon source; The heating temperature of the heating pretreatment is 140-160°C, and the heating time is 1-2h; Washing carbon powder to obtain a carbon precursor comprises the following steps: washing the carbon powder with an acidic solution and deionized water in sequence to obtain a carbon precursor, wherein the carbon precursor is neutral.

4. The method for preparing a supported catalyst according to claim 1, characterized in that: The inorganic base compound includes an alkali metal hydroxide, and the organic base compound includes an alkali metal salt compound of an alcohol; The mass ratio of the carbon precursor, the inorganic base compound and the organic base compound is 1: (1-1.5): (3-5); In the step of reacting the carbon precursor with the alkali solution, the reaction time is 3 to 4 hours.

5. The method for preparing a supported catalyst according to claim 1, characterized in that: Carbonizing the first mixed solution to obtain a first solid product comprises the following steps: carbonizing the first mixed solution under a protective atmosphere to obtain a first solid product; The first mixed solution is carbonized at a temperature of 800-900° C. and a carbonization time of 3-4 hours.

6. The method for preparing a supported catalyst according to claim 1, characterized in that: Post-processing the first solid product to obtain a modified activated carbon carrier includes the following steps: washing the first solid product with deionized water and an alcohol solvent until it is neutral to obtain a second solid product, and drying the second solid product at a temperature of 100-110°C for 10-12 hours to obtain the modified activated carbon carrier.

7. The method for preparing a supported catalyst according to claim 1, characterized in that: The impregnation solution further comprises deionized water; in the impregnation solution, the molar ratio of nitrate, alkaline compound and deionized water is 1:(2-3):(5-8); The mass ratio of the impregnation liquid to the modified activated carbon carrier is 1:(5-8); The modified activated carbon carrier is mixed with the impregnation liquid to obtain a second mixed solution, which comprises the following steps: dispersing the modified activated carbon carrier into the impregnation liquid, and impregnating for 6 to 8 hours to obtain the second mixed solution; In the step of drying the second mixed solution to obtain a mixture, the drying temperature is 100-110°C.

8. The method for preparing a supported catalyst according to claim 1, characterized in that: In the step of calcining the mixture under a protective atmosphere, the calcination temperature is 550-700° C. and the calcination time is 3-5 hours.

9. A method for preparing glycerol carbonate, characterized in that: The following steps are involved: The glycerol carbonate is prepared by treating carbonate and glycerol under the catalysis of a supported catalyst; The supported catalyst is prepared by the method for preparing a supported catalyst according to any one of claims 1 to 8.

10. The method for preparing glycerol carbonate according to claim 9, characterized in that: The process of preparing the glycerol carbonate by using carbonate and glycerol under the catalysis of a supported catalyst comprises the following steps: reacting the carbonate, glycerol and the supported catalyst at 85-90° C. for 1-2 hours to obtain the glycerol carbonate; The molar ratio of carbonate to glycerol is (2.5-3.5):1; The mass of the supported catalyst is 0.05% to 0.1% of the mass of the glycerol.

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