Synthesis of glycerol carbonate catalyst, its preparation method and application

Abstract

The application discloses a kind of synthetic glycerol carbonate catalyst and its preparation method and application, belong to oil and fat chemical industry field.The method for preparing synthetic glycerol carbonate catalyst in the application includes the following steps: (1) copper salt, zinc salt, ligand are dissolved in alcohol solution, after 100-200 DEG C reaction 10-30h, temperature is reduced, centrifugal, washing, drying, to obtain carrier Cu-ZIF;(2) carrier Cu-ZIF is calcined at 600-1000 DEG C for 2-6h, to obtain copper-doped nitrogen carbon material;(3) by impregnation method, divalent palladium is loaded on copper-doped nitrogen carbon material, then using reducing agent, divalent palladium is reduced into palladium nanoparticle, to obtain palladium loaded Cu-ZIF catalyst, i.e.the synthetic glycerol carbonate catalyst is obtained.The catalyst of the application is simple in preparation, low in cost, and high in catalytic efficiency.

Description

Technical Field

[0001] This invention relates to a catalyst for the synthesis of glycerol carbonate, its preparation method and application, belonging to the field of oleochemical technology. Background Technology

[0002] Glyceryl carbonate, as a green chemical intermediate, has a cyclic structure with both hydroxyl and carbonyl groups. It can be used as a surfactant, electrolyte, synthetic intermediate, in the synthesis of polyurethane compounds, and in coatings, and has a wide range of applications in organic synthesis, oleochemicals, pharmaceuticals, plastics, and cosmetics production.

[0003] Currently, there are several processes for synthesizing glycerol carbonate from glycerol, including the phosgene method, transesterification method, urea alcoholysis method, and carbonylation method. Among these, the phosgene used in the phosgene method is not only highly corrosive but also extremely toxic. The transesterification method is still not widely used due to its high production cost and difficulty in separating the products. The urea alcoholysis method produces ammonia during the reaction, which places stringent requirements on the process equipment. In contrast, the carbonylation method is not only environmentally friendly and in line with the concept of sustainable development, but also produces only water as a final byproduct, making it a promising research hotspot.

[0004] Conventional catalysts used for the synthesis of glycerol carbonate include metal oxide catalysts, supported metal oxide catalysts, metal salt catalysts, ionic liquid catalysts, and enzyme catalysts. However, the use of metal salt catalysts and ionic liquid catalysts is limited because they are difficult to recover, and ionic liquid catalysts and enzyme catalysts have relatively high costs. Metal oxide catalysts and supported metal oxide catalysts are more commonly used, but they have low yields and conversion rates in the synthesis of glycerol carbonate, are difficult to separate in homogeneous catalysis, use some expensive precious metals, and have poor stability. Summary of the Invention

[0005] [Technical Issues]

[0006] The catalysts used in the synthesis of glycerol carbonate have low catalytic activity and poor stability, resulting in problems such as low yield, low conversion rate, and difficulty in separation during homogeneous catalysis.

[0007] [Technical Solution]

[0008] To address the aforementioned problems, this invention first synthesizes a copper-doped ZIF-8 support, then removes Zn through calcination to obtain a copper-doped nitrogen-carbon material (Cu-NC), and finally loads palladium onto it to obtain a catalyst for the synthesis of glycerol carbonate. The catalyst of this invention is simple to prepare, low in cost, and exhibits high catalytic efficiency.

[0009] The first objective of this invention is to provide a method for preparing a catalyst for the synthesis of glycerol carbonate, comprising the following steps:

[0010] (1) Dissolve copper salt, zinc salt and ligand in alcohol solution, react at 100-200℃ for 10-30h, cool, centrifuge, wash and dry to obtain the support Cu-ZIF;

[0011] (2) The Cu-ZIF support was calcined at 600-1000℃ for 2-6h to obtain copper-doped nitrogen-carbon material (Cu-NC);

[0012] (3) Divalent palladium is loaded onto copper-doped nitrogen-carbon material (Cu-NC) by impregnation, and then the divalent palladium is reduced to palladium nanoparticles by a reducing agent to obtain palladium-loaded Cu-ZIF catalyst, which is the catalyst for synthesizing glycerol carbonate.

[0013] In one embodiment of the present invention, the copper salt and zinc salt in step (1) are specifically zinc nitrate and copper nitrate.

[0014] In one embodiment of the present invention, the ligand in step (1) is one or more of 2-methylimidazole, imidazole, and benzimidazole to form a carrier backbone.

[0015] In one embodiment of the present invention, the alcohol solution in step (1) is methanol.

[0016] In one embodiment of the present invention, the ratio of copper salt, zinc salt, ligand and alcohol solution in step (1) is 0.08-0.8 mol: 1 mol: 8-10 g: 80-100 mL.

[0017] In one embodiment of the present invention, in step (1), copper salt and zinc salt can be dissolved in alcohol solution to obtain alcohol solution containing copper salt and zinc salt; then the ligand can be dissolved in alcohol solution to obtain alcohol solution containing ligand; finally, the alcohol solution containing ligand can be quickly poured into alcohol solution containing copper salt and zinc salt for reaction.

[0018] In one embodiment of the present invention, the cooling rate in step (1) is 1-5℃ / min, cooling down to room temperature; the cooling rate needs to be strictly controlled to ensure the crystallization yield and particle size of the carrier.

[0019] In one embodiment of the present invention, in step (1), centrifugation is performed at 5000-10000 rpm for 1-5 min, washing is performed with methanol, and drying is performed at 60-90℃ for 1-36 h.

[0020] In one embodiment of the present invention, step (3) is to first disperse copper-doped nitrogen-carbon material (Cu-NC) in methanol to obtain a carrier alcohol solution; then add divalent palladium salt solution dropwise to the carrier alcohol solution and react for 1-3 hours; after the addition is completed, add reducing agent solution dropwise and continue the reaction for 20-30 hours; after the reaction is completed, centrifuge, wash and dry to obtain a catalyst for synthesizing glycerol carbonate.

[0021] The concentration of copper-doped nitrogen-carbon material (Cu-NC) in the carrier alcohol solution is 1-10 mg / mL.

[0022] The divalent palladium salt solution is an aqueous solution of palladium chloride in ammonia, specifically, palladium chloride is dissolved in an aqueous solution with a mass fraction of 10%.

[0023] The concentration of palladium chloride in an aqueous solution of palladium chloride (ammonia chloride) is 0.9-1.5 mg / mL.

[0024] The mass of divalent palladium is 5-20% of the mass of copper-doped carbon-nitrogen materials (Cu-NC);

[0025] The reducing agent is sodium borohydride, and the reducing agent solution is an aqueous solution of the reducing agent with a concentration of 0.1-2 mg / mL;

[0026] The mass ratio of divalent palladium to reducing agent is 1:1-3;

[0027] The reaction conditions are: 20-30℃ (room temperature) and 100-1000rpm.

[0028] The second objective of this invention is to prepare a synthetic glycerol carbonate catalyst using the method described herein.

[0029] A third objective of this invention is to provide a method for synthesizing glycerol carbonate, wherein the method employs the glycerol carbonate synthesis catalyst described in this invention.

[0030] In one embodiment of the present invention, the method for synthesizing glycerol carbonate includes the following steps:

[0031] Glycerol, a catalyst for synthesizing glycerol carbonate, and potassium iodide (KI) are mixed evenly and reacted in the presence of oxygen and carbon monoxide to obtain glycerol carbonate.

[0032] The mass ratio of glycerol, the catalyst for synthesizing glycerol carbonate, and potassium iodide (KI) is 1-2:0.005-0.1:0.01-0.03.

[0033] The pressure ratio of oxygen to carbon monoxide is 1:2-3;

[0034] The reaction is carried out at 135-145℃ for 1-5 hours.

[0035] The fourth objective of this invention is the application of the glycerol carbonate synthesis catalyst described herein in the fields of oleochemicals, plastics, or cosmetics production.

[0036] [Beneficial Effects]

[0037] (1) The catalyst for synthesizing glycerol carbonate described in this invention is supported by NC material. The nitrogen species on the surface of NC material can not only regulate the chemical state and dispersion of Pd nanoparticles, but also promote the adsorption and activation of glycerol molecules. Furthermore, the palladium nanoparticles of the catalyst can still be well dispersed after use.

[0038] (2) The catalyst for synthesizing glycerol carbonate described in this invention loads palladium nanoparticles into Cu-doped NC materials, which is beneficial to improve the bimetallic synergistic effect of palladium and copper, and greatly improves the yield and selectivity of the reaction.

[0039] (3) The preparation conditions of the carrier Cu-NC described in this invention are atmospheric pressure conditions and the operation is simple. Its precursor is ZIF-8 material. Therefore, Cu-NC inherits the high specific surface area of ​​ZIF and its own uniform porous structure. It does not require the use of template agents. Under these conditions, the only byproduct of the reaction is water, which basically conforms to the concept of green chemistry and sustainable development. Attached Figure Description

[0040] Figure 1 This is the standard curve for the internal standard method.

[0041] Figure 2 This is the synthesis route diagram for Example 1.

[0042] Figure 3 The images shown are TEM and EDS images of the support and catalyst in Example 1; where a is a transmission electron microscope image of Cu-ZIF-8; b is a transmission electron microscope image of copper-doped ZIF-8 (Cu-ZIF-8); c is a scanning electron microscope image of palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); d is a transmission electron microscope image of palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); e is a mapping image of the full elemental composition of palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); fi are elemental diagrams of C, N, Cu, and Pd in ​​palladium-supported Cu-ZIF catalyst (Pd / Cu-NC).

[0043] Figure 4 The XRD patterns are for NC, Cu-NC, and Pd / Cu-NC in Example 1.

[0044] Figure 5 The image shows a scanning electron microscope (SEM) image of Pd / Cu0-NC in Comparative Example 2. Detailed Implementation

[0045] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0046] Test method:

[0047] The performance of gas chromatography is tested using a silanization method, specifically:

[0048] Weigh a certain amount of the reaction solution and add an excess of silanizing reagent; place the reaction solution, hexamethyldisilazane, and trimethylchlorosilane in a weight ratio of 1:9:3 into a 10 mL centrifuge tube; seal the tube, stir for 5 minutes, and let it stand at room temperature for 30 minutes to allow NH4Cl to precipitate as a white solid; then, add 0.5 mL (251.08 g / L) tetraethylene tritide internal standard solution to the mixture, centrifuge at 2500 rpm for 5 min, and take the supernatant for gas chromatography analysis.

[0049] The reaction products were analyzed by gas chromatography using a Nexis GC-2030. The chromatographic conditions were as follows: KB-Wax capillary column (30m*0.32mm*0.50μm), N2 as carrier gas, and a resolution of 1 / 20; the column temperature was programmed to 80℃ and held for 2 min, then increased to 260℃ at a rate of 30℃ / min; the vaporization chamber temperature was 280℃, and the detector temperature was 300℃.

[0050] Tetraethylene glycol tris(3-acetonitrile) was selected as the internal standard. Quantitative analysis was performed using the internal standard method with tetraethylene glycol as the internal standard.

[0051] Yield and selectivity were evaluated based on the peak areas of the unreacted glycerol silylated derivative and the resulting carbonate. The standard curve using the internal standard method is shown below. Figure 1 As shown.

[0052] Example 1

[0053] A method for preparing a catalyst for the synthesis of glycerol carbonate includes the following steps:

[0054] (1) In a 100 mL hydrothermal autoclave lined with polytetrafluoroethylene, 3.972 g Zn(NO3)2·6H2O and 0.27 g Cu(NO3)2·3H2O were dissolved in 45 mL methanol to obtain an alcoholic solution containing copper nitrate and zinc nitrate; wherein the molar ratio of Zn(NO3)2·6H2O and Cu(NO3)2·3H2O was 0.089:1;

[0055] Weigh 9.72 g of 2-methylimidazole and dissolve it in 45 mL of methanol to obtain an alcoholic solution containing 2-methylimidazole;

[0056] An alcohol solution containing 2-methylimidazole was rapidly poured into an alcohol solution containing copper nitrate and zinc nitrate, and the temperature was increased to 140°C at 5°C / min and reacted for 24 h. Then the temperature was decreased to room temperature at 2°C / min. After the reaction was completed, the mixture was centrifuged at 9000 rpm for 3 min, washed three times with methanol, and dried at 80°C for 12 h to obtain copper-doped ZIF-8 (Cu-ZIF-8).

[0057] (2) The copper-doped ZIF-8 (Cu-ZIF-8) carrier was placed in a high-temperature ceramic boat and calcined in a tube furnace at 5℃ / min to 950℃ for 4h under nitrogen protection to obtain copper-doped nitrogen-carbon material (Cu-NC).

[0058] (3) Add 0.0346 g of copper-doped nitrogen-carbon material (Cu-NC) to 30 mL of methanol and disperse it fully by magnetic stirring at 500 rpm for 10 min at room temperature to obtain a carrier alcohol solution;

[0059] 0.0099 g of palladium dichloride was dissolved in 9 mL of a 10% (w / w) ammonia solution to obtain an ammonia solution of palladium chloride.

[0060] Dissolve 0.0054 g of sodium borohydride in 6 mL of deionized water to obtain a sodium borohydride solution;

[0061] Palladium chloride aqueous solution was added dropwise to the carrier alcohol solution, and the reaction was continued at room temperature and 500 rpm for 2 h. Then sodium borohydride solution was added dropwise, and the reaction was continued at room temperature and 500 rpm for 24 h. After the reaction was completed, the mixture was centrifuged at 9000 rpm for 3 min, washed three times with methanol, and dried at 80 °C for 12 h to obtain the palladium-supported Cu-ZIF catalyst (Pd / Cu-NC).

[0062] Figure 3 The images show the TEM and EDS images of the support and catalyst in Example 1; where a is a transmission electron microscope (TEM) image of Cu-ZIF-8; b is a TEM image of the copper-doped ZIF-8 support (Cu-ZIF-8); c is a scanning electron microscope (SEM) image of the palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); d is a TEM image of the palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); e is a mapping of the elemental composition of the palladium-supported Cu-ZIF catalyst (Pd / Cu-NC); and fi are elemental diagrams of C, N, Cu, and Pd in ​​the palladium-supported Cu-ZIF catalyst (Pd / Cu-NC). Figure 3 It can be seen that Cu-ZIF-8, Cu-NC, and Pd / Cu-NC exhibit a consistent rhombic dodecahedral structure; the surface of Cu-NC is relatively uneven and covered with micropores (possibly due to zinc volatilization during pyrolysis), which contrasts sharply with Cu-NC and Cu-ZIF-8. Furthermore, the elemental diagram shows uniform co-doping of copper and nitrogen within the carbon framework.

[0063] Figure 4 The images show the XRD patterns of NC, Cu-NC, and Pd / Cu-NC in Example 1. Figure 4 It can be seen that new peaks appear in NC, Cu-NC, and Pd / Cu-NC.

[0064] Combination Figure 3 and Figure 4 It can be proven that the catalyst of Example 1 was successfully synthesized.

[0065] Example 2

[0066] The amount of Cu(NO3)2·3H2O in step (1) of Example 1 was adjusted to 0.27 (Example 1), 0.54g, 1.08g, 1.62g, and 2.16g, while other parameters remained the same as in Example 1, to obtain the catalyst; that is, (Pd / Cux-NC, where x represents the molar ratio of copper nitrate and zinc nitrate, and the molar ratios of 0.27g, 0.54g, 1.08g, 1.62g, and 2.16g are 0.089, 0.178, 0.356, 0.534, and 0.712, respectively).

[0067] Comparative Example 1

[0068] The Zn(NO3)2·6H2O step (1) in Example 1 was omitted, and methanol was replaced with an ammonia solution with a mass fraction of 10%; everything else remained the same as in Example 1, and the catalyst Pd / Cu(Im)2 was obtained.

[0069] Comparative Example 2

[0070] Omit Cu(NO3)2·3H2O in step (1) of Example 1, and keep everything else the same as in Example 1 to obtain the catalyst Pd / Cu0-NC.

[0071] Example 3

[0072] A method for synthesizing glycerol carbonate includes the following steps:

[0073] Add 1.446g glycerol, 0.007g catalyst and 0.018g KI to a 50mL polytetrafluoroethylene liner and stir well. Purge with O2 three times, then introduce oxygen and carbon monoxide (O2:CO = 1.3:2.7, where “:” represents the pressure ratio) and react at 140℃ for two hours.

[0074] The catalysts used were those prepared in Examples 1, 2 and Comparative Example 1.

[0075] The obtained reaction products were subjected to performance tests, and the test results are as follows:

[0076] Table 1 shows that the yield and selectivity of the prepared catalysts initially increased and then decreased with increasing copper content. Although the Pd / Cu0-NC prepared in Comparative Example 2 had a high yield, the loss of zinc resulted in the absence of a metallic support framework, leading to a fragmented overall framework (e.g., ...). Figure 5In contrast, the catalysts prepared in Examples 1 and 2 have intact metal frameworks and exhibit excellent yields and selectivity.

[0077] Table 1

[0078]

[0079] Example 4

[0080] The catalyst Pd / Cu obtained in Example 2 0.356 -NC repeated the experiment three times in parallel according to Example 3, and the specific results are as follows:

[0081] Table 2 shows that the catalyst Pd / Cu obtained in Example 2... 0.356 -NC activity can achieve a yield of 98% and a selectivity of 99%.

[0082] Table 2

[0083]

[0084] Comparative Example 3

[0085] Cu(NO3)2·3H2O in step (1) of Example 1 was omitted, and methanol was replaced with DMF; everything else remained the same as in Example 1, and the catalyst Pd / ZIF-4 was obtained.

[0086] Comparative Example 4

[0087] Cu(NO3)2·3H2O in step (1) of Example 1 was omitted, methanol was replaced with DMF, and 2-methylimidazolium was replaced with imidazolium; everything else remained the same as in Example 1, and the catalyst Pd / ZIF-7 was obtained.

[0088] Comparative Example 5

[0089] Step (2) of Example 1 is omitted, and everything else remains the same as in Example 1 to obtain the catalyst Pd / Cu-ZIF-8.

[0090] Comparative Example 6

[0091] The sodium borohydride (reducing agent) in step (3) of Example 1 is omitted, and everything else remains the same as in Example 1, to obtain the catalyst PdCl2 / Cu-NC.

[0092] The catalysts obtained in Comparative Examples 3-6 were reacted according to Example 3, and the reaction products were subjected to performance testing. The test results are as follows:

[0093] As can be seen from Table 3, Pd nanoparticles have higher activity than divalent palladium, and CuZIF-8 materials and their derivatives perform better than other metal-organic framework materials.

[0094] Table 3

[0095]

[0096] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for synthesizing glycerol carbonate, characterized in that, The method includes: mixing glycerol, a catalyst for synthesizing glycerol carbonate, and potassium iodide evenly, and reacting them in the presence of oxygen and carbon monoxide to obtain glycerol carbonate; The preparation method of the catalyst for synthesizing glycerol carbonate includes the following steps: (1) Dissolve copper salt, zinc salt and ligand in alcohol solvent, react at 100-200℃ for 10-30 h, cool, centrifuge, wash and dry to obtain the support Cu-ZIF; (2) The Cu-ZIF support was calcined at 600-1000℃ for 2-6h to obtain the copper-doped nitrogen-carbon material Cu-NC; (3) Divalent palladium is loaded onto copper-doped nitrogen-carbon material Cu-NC by impregnation method, and then the divalent palladium is reduced to palladium nanoparticles by reducing agent to obtain palladium-loaded copper-doped nitrogen-carbon material Cu-NC, which is the catalyst for the synthesis of glycerol carbonate.

2. The method according to claim 1, characterized in that, In step (1), the ratio of copper salt, zinc salt, ligand and alcohol solvent is 0.08-0.8 mol: 1 mol: 8-10 g: 80-100 mL.

3. The method according to claim 1, characterized in that, Step (1) involves first dissolving the copper and zinc salts in an alcohol solvent to obtain an alcohol solution containing the copper and zinc salts; then dissolving the ligands in an alcohol solvent to obtain an alcohol solution containing the ligands; and finally quickly pouring the alcohol solution containing the ligands into the alcohol solution containing the copper and zinc salts to react.

4. The method according to claim 1, characterized in that, Step (3) involves first dispersing the copper-doped nitrogen-carbon material Cu-NC in methanol to obtain a carrier alcohol solution; then adding the divalent palladium salt solution dropwise to the carrier alcohol solution and reacting for 1-3 hours; after the addition is complete, adding the reducing agent solution dropwise and continuing the reaction for 20-30 hours; after the reaction is complete, centrifuging, washing, and drying are performed to obtain the catalyst for synthesizing glycerol carbonate.

5. The method according to claim 1, characterized in that, The cooling rate in step (1) is 1-5℃ / min.

6. The method according to claim 1, characterized in that, In step (1), the ligand is one or more of 2-methylimidazole, imidazole, and benzimidazole.

7. The application of the method according to any one of claims 1-6 in the production of glyceryl carbonate in the fields of oleochemicals, plastics or cosmetics.

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