Copper-palladium MOF catalyst for synthesis of glycerol carbonate as well as preparation method and application of copper-palladium MOF catalyst

Abstract

The invention discloses a copper-palladium MOF catalyst for synthesis of glycerol carbonate as well as a preparation method and application of the copper-palladium MOF catalyst, and belongs to the technical field of oleochemical industry. The preparation method of the catalyst comprises the following steps: dissolving terephthalic acid and Cu (NO3) 2.3 H2O in a mixed solution of N, N-dimethylacetamide and absolute methanol, and reacting for 10-30 hours at the temperature of 100-200 DEG C to obtain a Cu-MOF-2 carrier; then dispersing the obtained Cu-MOF-2 in absolute methanol, loading bivalent palladium on a carrier by adopting an impregnation method, and adding sodium borohydride to obtain the synthesized glycerol carbonate catalyst Pd / Cu-MOF-2. According to the present invention, the copper-palladium catalyst is synthesized during the simple stirring process, the high dispersion of the palladium is achieved, the high yield and the extremely high selectivity are obtained during the reaction process, and the reaction activity is not significantly reduced after the catalyst is repeatedly used for five times.

Description

Technical Field

[0001] The invention relates to the technical field of oil and fat chemical industry, and in particular to a copper-palladium MOF catalyst for synthesizing glycerol carbonate, and a preparation method and application thereof. Background Art

[0002] Glycerol is one of the main by-products in the biodiesel industry, and its efficient recycling has always been an important topic in the field of scientific research. Glycerol carbonate, as a green chemical intermediate with hydroxyl and carbonyl groups, has a ring structure and is widely used in many fields such as surfactants, electrolytes, synthetic intermediates, synthesis of polyurethane compounds and coatings. In addition, it also has broad application prospects in organic synthesis, oil and fat chemicals, medicine, plastics and cosmetics production.

[0003] Methods for synthesizing glycerol carbonate include phosgene method, transesterification method and enzyme-catalyzed oil hydrolysis method. Although the phosgene method is effective, it has great safety risks due to the strong corrosiveness and toxicity of phosgene. Although the transesterification method can produce glycerol carbonate, its high production cost and difficulty in product separation limit its large-scale application. Although urea alcoholysis is a feasible process, ammonia will be produced during the reaction, and the requirements for process equipment are very high. In contrast, the carbonylation method is an environmentally friendly process that conforms to the concept of sustainable development because its only by-product is water. This makes the carbonylation method a hot topic in current research and has significant advantages.

[0004] At present, the catalysts used in the carbonylation synthesis of glycerol carbonate include PdCl2(phen)@Y, commercial Pd / C, Pd / CeO2, etc., and alloy catalysts are used in the carbonylation synthesis of glycerol carbonate because of their high activity, selectivity, high stability and other characteristics. For example, patent CN117861703A discloses a copper-palladium alloy prepared by an impregnation calcination method. In the catalyst preparation process, calcination is usually used to improve the stability of the catalyst, which can remove organic residues in the precursor, improve the crystallinity of the catalyst, promote the uniform distribution of active components, and enhance the binding force between the active center and the carrier. These effects can significantly reduce the loss of active species during the reaction process, thereby improving the stability and service life of the catalyst. Therefore, in the preparation of traditional supported catalysts, calcination is usually an indispensable step, but there is a problem of high energy consumption. Summary of the invention

[0005] [Technical issues]

[0006] The technical problem to be solved by the present invention is that the supported catalyst used for the synthesis of glycerol carbonate has the problems of high energy consumption, low conversion rate and poor stability.

[0007] [Technical solution]

[0008] In order to solve the above technical problems, the present invention provides a copper-palladium MOF catalyst for the synthesis of glycerol carbonate, a preparation method and an application thereof. Divalent palladium is loaded onto a carrier by an impregnation method, and sodium borohydride is added to obtain a catalyst for synthesizing glycerol carbonate. The catalyst for synthesizing glycerol carbonate of the present invention synthesizes a copper-palladium catalyst in a simple stirring process, and has the characteristics of simple preparation, low cost, high catalytic efficiency and good stability.

[0009] The first object of the present invention is to provide a method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate, comprising the following steps:

[0010] (1) dissolving terephthalic acid and Cu(NO3)2·3H2O in a mixed solution of N,N-dimethylacetamide and anhydrous methanol, mixing them evenly, and reacting them at 100-200°C for 10-30h to obtain a carrier Cu-MOF-2;

[0011] (2) the carrier Cu-MOF-2 obtained in step (1) is dissolved in anhydrous methanol to obtain a carrier solution;

[0012] (3) mixing the palladium chloride solution with the carrier solution obtained in step (2), then adding sodium borohydride, stirring, filtering, and drying to obtain the catalyst Pd / Cu-MOF-2.

[0013] In one embodiment of the present invention, in step (1), the mass ratio of Cu(NO3)2·3H2O to terephthalic acid is 3 to 5:1.

[0014] In one embodiment of the present invention, in step (1), the mass volume ratio of Cu(NO3)2·3H2O to the mixed solution is 2.5g:50-70mL.

[0015] In one embodiment of the present invention, in step (1), the mass volume ratio of terephthalic acid to the mixed solution is 0.60 g:50-70 mL.

[0016] In one embodiment of the present invention, in step (1), the volume ratio of N,N-dimethylacetamide to anhydrous methanol is 7 to 11:1.

[0017] In one embodiment of the present invention, in step (2), the mass volume ratio of Cu-MOF-2 and anhydrous methanol is 0.35 g:20-40 mL.

[0018] In one embodiment of the present invention, in step (3), the palladium chloride solution is obtained by dissolving palladium chloride in an aqueous ammonia solution with a mass concentration of 10 to 20%.

[0019] In one embodiment of the present invention, in step (3), the mass ratio of sodium borohydride to palladium chloride is 15 to 20:1.

[0020] In one embodiment of the present invention, in step (3), the mass ratio of Cu-MOF-2 to palladium chloride is 60 to 80:1.

[0021] In one embodiment of the present invention, in step (3), the stirring time is 20 to 24 hours.

[0022] The second object of the present invention is to provide a copper-palladium MOF catalyst for the synthesis of glycerol carbonate prepared by the above-mentioned preparation method.

[0023] The third object of the present invention is to provide an application of the copper-palladium MOF catalyst for synthesizing glycerol carbonate in catalyzing the carbonylation of glycerol.

[0024] [Beneficial Effects]

[0025] (1) The catalyst for synthesizing glycerol carbonate described in the present invention uses a metal organic framework material (MOF) as a carrier, and palladium (Pd) is loaded on the MOF material by stirring, and then it is reduced using sodium borohydride; during this process, palladium and copper form a copper-palladium alloy, thereby significantly improving the performance of the catalyst; in addition, the catalyst also enhances the adsorption and activation ability of glycerol molecules, effectively improving the synthesis efficiency of glycerol carbonate.

[0026] (2) The catalyst for synthesizing glycerol carbonate described in the present invention is an alloy catalyst, which is synthesized by a method of loading with stirring at room temperature. In this process, Cu-MOF-2 is used as a carrier, and divalent palladium is chemically adsorbed thereon by stirring at room temperature to form a stable Pd / Cu-MOF-2 catalyst. The present invention synthesizes the loaded catalyst by a simple impregnation method, has high stability and yield, so no calcination is required, the operation is simple, and the stability of the catalyst is extremely high.

[0027] (3) The catalyst of the present invention is prepared under normal pressure and is easy to operate. The catalyst uses Cu-MOF-2 as a carrier and is loaded with palladium (Pd) to form Pd / Cu-MOF-2, which retains the advantages of high specific surface area and uniform porous structure of the carrier. More importantly, the only by-product of the catalytic reaction is water, which basically conforms to the concept of green chemistry and sustainable development. This design not only improves the catalytic efficiency, but also ensures environmental protection and sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The Fourier infrared spectra of the catalysts of Example 1 and Comparative Examples 1-2 are shown;

[0029] Figure 2XRD diagram of the catalyst Pd / Cu-MOF-2 and the carrier Cu-MOF-2 in Example 1. DETAILED DESCRIPTION

[0030] Example 1

[0031] A method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate specifically comprises the following steps:

[0032] (1) In a 100 mL hydrothermal autoclave lined with polytetrafluoroethylene, 0.59 g of terephthalic acid was added and dissolved in 54 mL of N,N-dimethylacetamide (DMA) and 6 mL of anhydrous methanol, and then 2.49 g of Cu(NO3)2·3H2O was added and mixed evenly. The temperature was raised to 120°C in the hydrothermal autoclave at a rate of 5°C / min, and the reaction was carried out at this temperature for 24 h. Then, the temperature was lowered to room temperature at a rate of 2°C / min. After the reaction was completed, the reaction was filtered, and the retained solid was washed three times with DMA and methanol, respectively, and then dried at 100°C for 12 h to obtain Cu-MOF-2.

[0033] (2) 0.35 g of the Cu-MOF-2 obtained above was placed in a 250 mL beaker and dispersed with 30 mL of anhydrous methanol to obtain a carrier solution; then 0.0047 g of PdCl2 was weighed and dissolved in an ammonia solution with a mass concentration of 17% to obtain a PdCl2 solution; then, the PdCl2 solution was poured into the carrier solution, and after stirring for 2 h, 0.078 g of sodium borohydride was added to the solution, stirred for 24 h, filtered, and dried at 80 ° C for 24 h to obtain Pd / Cu-MOF-2.

[0034] Example 2

[0035] (1) In a 100 mL hydrothermal autoclave lined with polytetrafluoroethylene, 0.70 g of terephthalic acid was added and dissolved in 52 mL of N,N-dimethylacetamide (DMA) and 7 mL of anhydrous methanol, and then 2.15 g of Cu(NO3)2·3H2O was added and mixed evenly. The temperature was raised to 120°C in the hydrothermal autoclave at a rate of 5°C / min, and the reaction was carried out at this temperature for 24 h. Then, the temperature was lowered to room temperature at a rate of 2°C / min. After the reaction was completed, the solid was filtered and washed three times with DMA and methanol, respectively, and then dried at 100°C for 12 h to obtain Cu-MOF-2.

[0036] (2) 0.26 g of the Cu-MOF-2 obtained above was placed in a 250 mL beaker and dispersed with 25 mL of anhydrous methanol to obtain a carrier solution; then 0.0033 g of PdCl2 was weighed and dissolved in an ammonia solution with a mass concentration of 15% to obtain a PdCl2 solution; then, the PdCl2 solution was poured into the carrier solution, and after stirring for 2 h, 0.059 g of sodium borohydride was added to the solution, stirred for 24 h, filtered, and dried at 80 ° C for 24 h to obtain Pd / Cu-MOF-2.

[0037] Example 3

[0038] (1) In a 100 mL hydrothermal autoclave lined with polytetrafluoroethylene, 0.59 g of terephthalic acid was added and dissolved in 55 mL of N,N-dimethylacetamide (DMA) and 5 mL of anhydrous methanol, and then 2.49 g of Cu(NO3)2·3H2O was added and mixed evenly. The temperature was raised to 120°C in the hydrothermal autoclave at a rate of 5°C / min, and the reaction was carried out at this temperature for 24 h. Then, the temperature was lowered to room temperature at a rate of 2°C / min. After the reaction was completed, the solid was filtered and washed three times with DMA and methanol, respectively, and then dried at 100°C for 12 h to obtain Cu-MOF-2.

[0039] (2) 0.44 g of the Cu-MOF-2 obtained above was placed in a 250 mL beaker and dispersed with 40 mL of anhydrous methanol to obtain a carrier solution; then 0.0059 g of PdCl2 was weighed and dissolved in an ammonia solution with a mass concentration of 17% to obtain a PdCl2 solution; then, the PdCl2 solution was poured into the carrier solution, and after stirring for 2 h, 0.11 g of sodium borohydride was added to the solution, stirred for 24 h, filtered, and dried at 80 ° C for 24 h to obtain Pd / Cu-MOF-2.

[0040] Comparative Example 1

[0041] A method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate specifically comprises the following steps:

[0042] Basically the same as Example 1, except that the sodium borohydride in step (2) is discarded, and the rest of the process is basically the same as described in Example 1 to obtain PdCl2 / Cu-MOF-2.

[0043] Comparative Example 2

[0044] A method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate specifically comprises the following steps:

[0045] PdCl2 and Cu-MOF-2 in step (2) were put into a mortar and ground together, and then 30 mL of methanol was added and stirred. The rest of the contents were basically the same as described in Example 1 to obtain Pd / Cu-MOF-2 (milled).

[0046] Figure 1 The Fourier transform infrared spectra of Example 1 and Comparative Examples 1-2 show that both the Pd / Cu-MOF-2 catalyst and other comparative metal organic framework catalysts perfectly inherit the basic functional groups that the metal organic framework should have.

[0047] Figure 2 The XRD patterns of the catalyst Pd / Cu-MOF-2 and the carrier in Example 1 show that palladium has been successfully loaded on the surface of the carrier.

[0048] Test Example 1

[0049] The catalyst in Example 1 was used and the reaction was carried out in a 50 mL autoclave. 1.44 g of glycerol was added to a 50 mL polytetrafluoroethylene liner, and 0.01 g, 0.015 g, 0.02 g, 0.025 g, 0.03 g of catalyst and 0.018 g of KI were tested and stirred evenly, purged with O2 three times, and then oxygen and carbon monoxide (O2:CO=1.3:2.7) were charged and reacted at 140°C for two hours. The results showed that the yield increased when the amount of catalyst increased, and a higher yield was obtained at 0.025 g.

[0050] Table 1 Catalyst activity of Example 1

[0051]

[0052] Test Example 2

[0053] The catalyst in Example 1 was used to react in a 50 mL autoclave. 1.44 g of glycerol, 0.025 g of catalyst (Pd / Cu-MOF-2) and 0.018 g of KI were added to a 50 mL polytetrafluoroethylene liner and stirred evenly. The mixture was purged with O2 three times, and then oxygen and carbon monoxide (O2:CO=1.3:2.7) were introduced. The reaction was carried out at 140°C for 1, 2, 3, 4 and 5 hours respectively. The results showed that as time increased, a higher yield could be obtained in 4 hours.

[0054] Table 2 Catalyst activity of Example 1

[0055]

[0056] Test Example 3

[0057] The catalyst in Example 1 was used to react in a 50 mL autoclave. 1.44 g of glycerol, 0.025 g of catalyst (Pd / Cu-MOF-2) and 0.018 g of KI were added to a 50 mL polytetrafluoroethylene liner and stirred evenly. The mixture was purged with O2 three times, and then oxygen and carbon monoxide (O2:CO=1.3:2.7) were introduced. The reaction was carried out at 140°C for four hours. The experiment was repeated three times and the average value was taken. The results showed that the catalyst activity could achieve a yield of 89.52% and a selectivity of 99.07%.

[0058] Table 3 Catalyst activity of Example 1

[0059]

[0060] Test Example 4

[0061] According to the three catalysts obtained in Example 1 and Comparative Examples 1 to 2, the activity was tested. 1.44 g of glycerol, 0.025 g of catalyst and 0.018 g of KI were added to a 50 mL polytetrafluoroethylene liner and stirred evenly. The mixture was purged with O2 three times, and then oxygen and carbon monoxide (O2:CO=1.3:2.7) were added. The mixture was reacted at 140°C for four hours. The results showed that the catalytic activity of Pd / Cu-MOF-2 was better, probably because the interaction between copper and palladium in Pd / Cu-MOF-2 improved the catalytic activity through electron transfer and interfacial effects. The presence of copper enhances the catalytic performance of palladium and promotes the adsorption and activation of reactants. PdCl2 as a precursor may be more easily reduced to active palladium particles during the reaction, but the synergistic effect of the palladium loading form and copper is not as direct as that of Pd / Cu-MOF-2. Therefore, although there is a synergistic effect of copper, the activity of palladium is suppressed to a certain extent. The milled Pd / Cu-MOF-2 (milled) may result in smaller palladium particles, affecting its catalytic activity. Smaller particle size may lead to an increase in surface atomic density, but it may also reduce the synergistic effect of copper and palladium, thereby reducing the catalytic activity.

[0062] Table 4 Catalyst activities of Example 1 and Comparative Examples 1 to 2

[0063]

[0064] Test Example 5

[0065] The catalyst obtained in Example 1 was tested for stability, and the reaction was carried out in a 50 mL autoclave. 1.44 g glycerol, 0.025 g catalyst (Pd / Cu-MOF-2) and 0.018 g KI were added to a 50 mL polytetrafluoroethylene liner and stirred evenly, purged with O2 three times, and then filled with oxygen and carbon monoxide (O2:CO=1.3:2.7), reacted at 140°C for four hours, centrifuged after the reaction, separated the reaction liquid from the catalyst, and then reused, put in the same equivalent reactants, and repeated five times. The results show that the alloy Pd / Cu-MOF-2 catalyst has high stability, and the yield decreases little after five cycles of catalysis.

[0066] Table 5 Stability of the catalyst of Example 1

[0067]

[0068] Table 6 Stability of the catalyst of Comparative Example 1

[0069]

[0070] Table 7 Stability of the catalyst of Comparative Example 2

[0071]

[0072] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate, characterized in that: The steps include: (1) dissolving terephthalic acid and Cu(NO3)2·3H2O in a mixed solution of N,N-dimethylacetamide and anhydrous methanol, mixing them evenly, and reacting them at 100-200°C for 10-30h to obtain a carrier Cu-MOF-2; (2) the carrier Cu-MOF-2 obtained in step (1) is dissolved in anhydrous methanol to obtain a carrier solution; (3) mixing the palladium chloride solution with the carrier solution obtained in step (2), then adding sodium borohydride, stirring, filtering, and drying to obtain the catalyst Pd / Cu-MOF-2.

2. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (1), the mass ratio of Cu(NO3)2·3H2O to terephthalic acid is 3-5:1; the mass volume ratio of Cu(NO3)2·3H2O to the mixed solution is 2.5:50-70 g / mL.

3. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (1), the mass volume ratio of terephthalic acid to the mixed solution is 0.60:50-70 g / mL.

4. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (1), the volume ratio of N,N-dimethylacetamide to anhydrous methanol is 7 to 11:

1.

5. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (2), the mass volume ratio of Cu-MOF-2 and anhydrous methanol is 0.35:20-40 g / mL.

6. The method for preparing a copper-palladium MOF catalyst for glycerol carbonate synthesis according to claim 1, characterized in that: In step (3), the palladium chloride solution is obtained by dissolving palladium chloride in an ammonia solution with a mass concentration of 10 to 20%.

7. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (3), the mass ratio of sodium borohydride to palladium chloride is 15 to 20:

1.

8. The method for preparing a copper-palladium MOF catalyst for the synthesis of glycerol carbonate according to claim 1, characterized in that: In step (3), the mass ratio of Cu-MOF-2 to palladium chloride is 60 to 80:

1.

9. A copper-palladium MOF catalyst for the synthesis of glycerol carbonate prepared by the method of any one of claims 1 to 8.

10. Use of the copper-palladium MOF catalyst for glycerol carbonate synthesis according to claim 9 in catalyzing glycerol carbonylation.

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