CN114957009B - A kind of method for synthesizing glyceryl carbonate - Google Patents

Abstract

The invention discloses a method for synthesizing glycerol carbonate, belonging to the technical field of synthesizing glycerol carbonate by urea alcoholysis. Urea and glycerin with the mol ratio of 1.5:1 are used as raw materials; the preparation method comprises the steps of adding raw materials and a catalyst into a container, placing the container in a constant-temperature oil bath, and reacting for 6-8 h at 105-125 ℃ to obtain the glycerol carbonate. The catalyst used in the invention is a metal-free catalytic system, is a high-efficiency catalyst without adding metal for the first time in the system, and has the advantages of high reaction efficiency, low reaction temperature, good circulation stability, easy separation from the reaction system and the like.

Description

A kind of method for synthesizing glyceryl carbonate

Technical field

The invention belongs to the technical field of synthesizing glyceryl carbonate through the alcoholysis of urea, and in particular relates to a method for synthesizing glyceryl carbonate through the alcoholysis of urea using urea and glycerol as raw materials.

Background technique

As a special biochemical substance, glycerol carbonate (GC) has the characteristics of high boiling point, low volatility, low freezing point, strong polarity, non-toxic, and biodegradable. Widely used in food, medicine, cosmetics, textiles, coatings, plastics, machinery, military, aviation, aerospace, integrated circuits and new energy. The synthesis methods of glycerol carbonate include phosgene method, CO oxidative carbonylation method, transesterification method, glycerol and urea carbonylation method and CO ₂ conversion method. Among them, glycerol alcoholysis using glycerol and urea as raw materials is considered to be a high molecular efficiency process. Because ammonia is a by-product produced during the alcoholysis of urea, it can also be used as a raw material for the synthesis of urea, and is considered a green process for the synthesis of glycerol carbonate.

During the synthesis process, it is important to select the catalyst.

The catalysts used to synthesize glycerol carbonate from glycerol and urea are mainly the following: zinc-based catalysts (Co ₃ O ₄ /ZnO and Co ₅₀ Zn ₅₀ -350 composite materials, porous ZnO, zinc-aluminum composite materials, etc.), magnesium-based catalysts ( MgO, Au-MgO, Au-Pd-MgO, HT (Mg/Zn/Al) and Mg-Al-Zr), tungsten-based catalyst (SW ₂₁ , WO ₃ /TiO ₂ , ionic liquid catalyst (MPR[pmim][ Cl]+ZnO, PS-(Im) ₂ ZnBr ₂ , Q-MMTs and [PS-(Im) ₂ MX ₂ ]) and other catalysts (γ-zirconium phosphate, La ₂ O ₃ , La ₂ Cu _0.5 Fe _0.5 O ₄ etc.).

These catalysts can be mainly classified into two types: homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts have relatively high catalytic efficiency and fast reaction rates. However, there is a problem of difficulty in separating the product and the catalyst, which greatly increases the production cost. Heterogeneous catalysts can be separated from product and catalyst by simple filtration. However, since the catalyst and reactants belong to a heterogeneous system, its catalytic efficiency is reduced, and the amount of reactants converted per unit time and unit mass of the catalyst is small. In addition, existing catalysts require higher temperatures to convert glycerol into glycerol carbonate.

In summary, the above-mentioned catalysts that catalyze the reaction of urea and glycerol to synthesize glycerol carbonate have certain defects. Mainly in terms of catalytic efficiency and catalyst separation, especially at lower temperatures, the catalytic performance is poor.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the background technology and provide a method for synthesizing glyceryl carbonate through urea alcoholysis. Using glycerin and urea as raw materials, in the presence of a catalyst, a kettle reaction is used to synthesize glycerol carbonate through urea alcoholysis. Glyceryl carbonate. Achieve the effects of high yield of glycerol carbonate, short reaction time, low energy consumption (lower reaction temperature), and no pollution.

The catalyst used in the present invention is a solid nitrogen-containing nanocarbon catalyst (carbon quantum dot). The catalyst itself is nanoscale tiny carbon particles, which can form colloids in the reaction system and are highly dispersed in the reaction liquid to achieve ultra-efficient catalytic conversion. The amount of catalyst used is only a few thousandths of the existing reports. In addition, after the reaction, the product and catalyst can be separated by simple centrifugal separation technology.

The specific technical solutions of the present invention are as follows:

A method for synthesizing glyceryl carbonate, using urea and glycerin with a molar ratio of 1.5:1 as raw materials; performing an alcoholysis reaction of urea in the presence of a catalyst to obtain glyceryl carbonate. The specific steps are: adding raw materials and catalyst to a container, Place in a constant temperature oil bath and react for 6 to 8 hours at 105 to 125°C to obtain glycerol carbonate; the catalyst is a solid nitrogen-containing nanocarbon material (carbon quantum dots), and the amount of catalyst is 0.002% to glycerin weight. 0.006%.

The catalyst is prepared according to the following steps: put chitosan, aluminum nitrate nonahydrate, citric acid and water with a molar ratio of 2.0 to 5.0:1.5:1.0:1000 in a round-bottomed flask, stir continuously until completely dissolved, and then add Phosphoric acid, the amount of phosphoric acid used is the same as that of aluminum nitrate nonahydrate, and then use 1:1 ammonia water to adjust the reaction solution to pH=4.5, continue stirring for 3 hours, evaporate on an 80°C water bath for 24 hours to remove the water, and evaporate to dryness The product is carbonized in a muffle furnace at 300°C. After carbonization, it is cooled to room temperature. The obtained carbon material is ground into a powder with a particle size of 40-60 mesh. The ground powder and nitric acid with a concentration of 4mol/L are mixed at the ratio of 1g:10mL. The mixture was stirred under heating conditions at 60°C for 5 hours, then rinsed with water, filtered with suction, and dried at 80°C for 24 hours to obtain the catalyst.

Preferably, the molar ratio of chitosan, aluminum nitrate nonahydrate, citric acid and water is: 3.0:1.5:1.0:1000.

Beneficial effects:

1. The catalyst used in the present invention is a metal-free catalytic system, which is the first high-efficiency catalyst in this system that does not add metal.

2. The reaction efficiency is high. Under the same conditions, the TOF is thousands of times that of the homogeneous catalysts reported in the literature.

3. The reaction temperature is low, and the reaction can efficiently synthesize glycerol carbonate at 110-125°C.

4. The catalyst has good cycle stability and is easy to separate from the reaction system.

Description of the drawings

Figure 1 is the XPS pattern of Cat2 prepared in Example 2.

Figure 2 is a cycle reaction diagram of Cat2 prepared in Example 2.

Figure 3 is a diagram of the interruption reaction of Cat2 prepared in Example 2.

Detailed ways

Example 1

(1) Preparation of nitrogen-containing nanocarbon catalysts by sol-gel method

Take 2.68g chitosan, 4.8g aluminum nitrate nonahydrate, 1.60g citric acid and 140ml water (molar ratio, chitosan/aluminum nitrate nonahydrate/citric acid/water = 2.0/1.5/1.0/1000) in a circle In the bottom flask, continue stirring until completely dissolved, add 0.9 ml of phosphoric acid, adjust the reaction solution to pH=4.5 with 1:1 ammonia water, continue stirring for 3 hours, pour the reaction solution into the crucible, and evaporate on an 80°C water bath for 24 hours Remove moisture. The evaporated product is carbonized in a muffle furnace at 300°C. After carbonization, it is cooled to room temperature, and the obtained carbon material is ground into powder with a particle size of 40-60 mesh. Add 1g of ground powder and 10ml of nitric acid with a concentration of 4mol/L into a single-mouth bottle with magnetic stirring, stir for 5h under heating conditions at 60°C, then rinse with water and filter, and dry at 80°C for 24h to obtain a solid Nanocarbon material Cat1 (nitrogen content is 6%).

(2) Test experiment on reaction of alcoholysis of urea to synthesize glyceryl carbonate

In a three-necked flask, add 45g of urea, 46g of glycerol, and 0.001g of catalyst (less than 1/2000 of the currently reported catalyst dosage). Place it in a constant temperature water bath, heat to 115°C, and perform a decompression reaction at a pressure of 7kPa. The reaction lasts for 6 hours. After sampling, chromatographic analysis was performed, and the yield of glyceryl carbonate was calculated using the internal standard method. The selectivity of glyceryl carbonate is 95%, and the yield of glyceryl carbonate is 62.9%.

Example 2

(1) Preparation of nitrogen-containing nanocarbon catalysts by sol-gel method

Take 4.05g chitosan, 4.80g aluminum nitrate nonahydrate, 1.60g citric acid and 140ml water (chitosan/aluminum nitrate nonahydrate/citric acid/water = 3.0/1.5/1.0/1000) in a round-bottomed flask, After continuing to stir until completely dissolved, add 0.9 ml of phosphoric acid, adjust the pH of the reaction solution to 4.5 with 1:1 ammonia water, continue stirring for 3 hours, pour the reaction solution into a crucible, and evaporate on an 80°C water bath for 24 hours to remove water. The evaporated product is carbonized in a muffle furnace at 300°C. After carbonization, it is cooled to room temperature, and the obtained carbon material is ground into powder with a particle size of 40-60 mesh. Add 1g of ground powder and 10ml of nitric acid with a concentration of 4mol/L into a single-mouth bottle with magnetic stirring, stir for 5h under heating conditions at 60°C, then rinse with water and filter, and dry at 80°C for 24h to obtain a solid Nanocarbon material Cat2 (nitrogen content is 12%). The XPS pattern of the prepared solid nanocarbon material Cat2 is shown in Figure 1.

(2) Test experiment on reaction of alcoholysis of urea to synthesize glyceryl carbonate

In a three-necked flask, add 45g of urea, 46g of glycerin, and 0.002g of Cat2, place it in a constant temperature water bath, heat to 125°C, and perform a pressure reduction reaction at a pressure of 7kPa. Samples were taken at 8 hours of reaction, analyzed by chromatography, and used the internal standard method. , the yield of glycerol carbonate is calculated. The selectivity to glyceryl carbonate was 99%, and the yield of glyceryl carbonate was 93.2%. In addition, the catalyst was recovered through filtration, dried in a vacuum oven at 80°C for 24 hours, and recycled five times. The specific results are shown in Table 1 and Figure 2. In addition, a heterogeneous test was conducted on the catalyst. The catalyst was filtered while hot after reacting for 4 hours, and the obtained filtrate continued to react under the same conditions. The reaction results are shown in Figure 3. It proves that there is no loss of active components during the reaction.

Table 1 Experimental results of cycle reactions for the synthesis of glycerol carbonate catalyzed by solid catalysts

Number of reactions Glyceryl carbonate selectivity Glyceryl carbonate yield 1 99% 93.2% 2 99% 91.8% 3 98% 91.6% 4 98% 90.9% 5 99% 90.1%

Example 3:

(1) Preparation of nitrogen-containing nanocarbon catalysts by sol-gel method

Take 6.69g chitosan, 4.80g aluminum nitrate nonahydrate, 1.60g citric acid and 140ml water (chitosan/aluminum nitrate nonahydrate/citric acid/water = 5.0/1.5/1.0/1000) in a round-bottomed flask, After continuing to stir until completely dissolved, add 0.9 ml of phosphoric acid, adjust the pH of the reaction solution to 4.5 with 1:1 ammonia water, continue stirring for 3 hours, pour the reaction solution into a crucible, and evaporate on an 80°C water bath for 24 hours to remove water. The evaporated product is carbonized in a muffle furnace at 300°C. After carbonization, it is cooled to room temperature, and the obtained carbon material is ground into powder with a particle size of 40-60 mesh. Add 1g of ground powder and 10ml of nitric acid with a concentration of 4mol/L into a single-mouth bottle with magnetic stirring, stir for 5h under heating conditions at 60°C, then rinse with water and filter, and dry at 80°C for 24h to obtain a solid Nanocarbon material Cat3 (nitrogen content is 15%).

(2) Test experiment on reaction of alcoholysis of urea to synthesize glyceryl carbonate

In a three-necked flask, add 45g of urea, 46g of glycerol, and 0.003g of catalyst, place it in a constant temperature water bath, heat to 105°C, and perform a pressure reduction reaction at a pressure of 7kPa. Samples were taken after 7 hours of reaction, and analyzed by chromatography using the internal standard. Method, the yield of glycerol carbonate is calculated. The selectivity to glyceryl carbonate was 98%, and the yield of glyceryl carbonate was 78.4%.

Claims (2)

1. A method for synthesizing glycerol carbonate uses urea and glycerol with a mol ratio of 1.5:1 as raw materials; in the presence of a catalyst, carrying out urea alcoholysis reaction to obtain glycerol carbonate, wherein the specific steps are that raw materials and the catalyst are added into a container, and the container is placed into a constant-temperature oil bath to react for 6 to 8 hours at the temperature of 105 to 125 ℃ to obtain the glycerol carbonate; the catalyst is solid nitrogen-containing nano carbon quantum dots, and the dosage of the catalyst is 0.002% -0.006% of the weight of the glycerol;

the catalyst is prepared by the following steps: chitosan, aluminum nitrate nonahydrate, citric acid and water with the molar ratio of 2.0-5.0:1.5:1.0:1000 are placed in a round-bottom flask, after continuous stirring until the mixture is completely dissolved, phosphoric acid is added, the dosage of the phosphoric acid is the same as the dosage of the aluminum nitrate nonahydrate, ammonia water with the ratio of 1:1 is used for regulating the pH value of the reaction solution to be 4.5, stirring is continued for 3 hours, water is removed by evaporation on a water bath with the temperature of 80 ℃ for 24 hours, the evaporated product is placed in a muffle furnace with the temperature of 300 ℃ for carbonization, the carbonized product is cooled to room temperature, and the obtained carbon material is ground into powder with the particle size of 40-60 meshes; stirring the ground powder and nitric acid with the concentration of 4mol/L for 5 hours at the temperature of 60 ℃ according to the proportion of 1g to 10mL, washing with water, filtering, and drying for 24 hours at the temperature of 80 ℃ to obtain the catalyst.

2. A method of synthesizing glycerol carbonate according to claim 1, wherein the molar ratio of chitosan, aluminum nitrate nonahydrate, citric acid and water is 3.0:1.5:1.0:1000.