A silver single-atom catalyst, its preparation method and application

Abstract

The present invention relates to the technical field of catalysts, and particularly to a silver single-atom catalyst, a preparation method thereof, and an application. The present invention provides a silver single-atom nano-catalyst, comprising a metal-organic framework substrate and silver single atoms monodispersed and grown on the metal-organic framework substrate. The silver single atoms provided by the present invention can be applied to the electrocatalytic oxidation of propylene to produce propylene glycol, and have high selectivity and activity, good stability, and low cost in the reaction of electrochemically catalytically oxidizing propylene to produce propylene glycol. Compared with the metal-organic framework substrates of the prior art, the silver single-atom catalyst can efficiently electrocatalytically oxidize propylene to propylene glycol in an aqueous solution, and the Faraday efficiency of producing propylene glycol reaches 36% at a potential of 2.4 V relative to the standard hydrogen electrode, and the propylene glycol yield reaches 57.5 g / cm<supgt;2< / supgt;<subgt;catalyst< / subgt> / h at a potential of 3.0 V relative to the standard hydrogen electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a silver single-atom catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] 1,2-propanediol is a basic chemical and has various uses in the pharmaceutical, cosmetic, food manufacturing industries, etc. By 2026, the global demand for 1,2-propanediol is expected to reach 716.67 million US dollars, and the compound annual growth rate of 1,2-propanediol during the five years from 2021 to 2026 is 7.8%. Generally, the production of 1,2-propanediol from propylene mainly relies on direct and indirect routes. The direct route is limited due to the high cost of hydrogen peroxide and the low conversion rate of propylene. The indirect route includes the oxidation of propylene to propylene oxide and the hydration of propylene oxide. However, the indirect route for the production of 1,2-propanediol has two main drawbacks: on the one hand, the preparation and purification of propylene oxide require an external oxidant and complex steps respectively, resulting in uncontrollable environmental pollution and high-intensity energy consumption; on the other hand, the hydration of propylene oxide needs to be carried out under harsh conditions because the reaction is endothermic. Therefore, it is necessary to explore a cost-effective and sustainable strategy for oxidizing propylene to 1,2-propanediol. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a silver single-atom catalyst, a preparation method thereof, and an application thereof. The silver single atoms provided by the present invention have high selectivity and activity and low cost in the reaction of electrochemically catalyzing the oxidation of propylene to produce propanediol.

[0004] Another object of the present invention is to provide a new method for electrochemically catalyzing the oxidation of propylene to produce propanediol with mild reaction conditions, simple process, and environmental friendliness.

[0005] The present invention provides a silver single-atom nanocatalyst, including a metal-organic framework substrate and silver single atoms uniformly dispersed on the metal-organic framework substrate.

[0006] Preferably, in the silver single-atom nanocatalyst, the mass fraction of silver single atoms is 1% - 5%.

[0007] Preferably, the size of the metal-organic framework substrate is 0.8 - 1.2 μm.

[0008] The present invention also provides a preparation method of a silver single-atom nanocatalyst, including the following steps:

[0009] A) Mix zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid, and N,N-dimethylformamide, and carry out a solvothermal reaction to obtain a metal-organic framework;

[0010] B) Mix the metal-organic framework with a dispersing reagent to obtain a dispersion of the metal-organic framework.

[0011] C) Mix the dispersion of the metal-organic framework and a silver salt solution, and after stirring and reacting, obtain a silver single-atom catalyst.

[0012] Preferably, in step A), the dosage ratio of zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide is 0.1 - 0.3 mol : 0.1 - 0.3 mol : 0.5 - 2 mL : 5 - 15 mL;

[0013] The temperature of the solvothermal reaction is 100 - 150 °C, and the time is 20 - 30 h.

[0014] Preferably, in step B), the dispersing reagent includes tetrahydrofuran and / or DMF;

[0015] The dosage ratio of UiO-bpy to the dispersing reagent is 20 - 200 mg : 10 - 100 mL.

[0016] Preferably, in step C), the mass ratio of the metal-organic framework to the silver salt is 2 - 6 : 1.

[0017] Preferably, in step C), the temperature of the stirring reaction is 10 - 40 °C, and the time is 10 - 30 h.

[0018] The present invention also provides an application of the silver single-atom nanocatalyst described above or the silver single-atom nanocatalyst prepared by the preparation method described above in the electrocatalytic oxidation of propylene to produce propylene glycol.

[0019] The present invention also provides a production method of propylene glycol, including the following steps:

[0020] a) Ultrasonically mix a silver single-atom catalyst, a Nafion solution and ethanol to obtain a uniform solution; the silver single-atom catalyst is the silver single-atom nanocatalyst described above or the silver single-atom nanocatalyst prepared by the preparation method described above;

[0021] b) Mix the solution with carbon paper to prepare a working electrode;

[0022] Using a silver / silver chloride electrode as a reference electrode, a graphite rod as a counter electrode, and a perchlorate solution as an electrolyte, electrochemically catalytically oxidize propylene in the voltage range of 1.3 - 5.0 V at normal temperature and pressure to obtain propylene glycol.

[0023] The silver single-atom nanocatalyst provided by the present invention can be applied to the electrocatalytic oxidation of propylene to produce propylene glycol. In the reaction of electrochemically catalytically oxidizing propylene to produce propylene glycol, it has high selectivity and activity and low cost. Compared with the metal-organic framework (UiO-bpy) substrate of the prior art, the silver single-atom catalyst can efficiently electrocatalytically oxidize propylene to propylene glycol in an aqueous solution. The Faraday efficiency of producing propylene glycol reaches 36% at a potential of 2.4 V versus the standard hydrogen electrode, and the yield of propylene glycol reaches 57.5 g / cm 2 催化剂 / h.

[0024] Compared with other catalytic materials, the silver single-atom catalyst provided by the present invention is easy to synthesize in large quantities and has low cost. In the catalytic reaction, the catalyst used in the present invention has high selectivity and good stability. Brief Description of the Drawings

[0025] Figure 1 It is the SEM image of the silver single-atom catalyst in Example 1 of the present invention;

[0026] Figure 2 It is the TEM image of the silver single-atom catalyst in Example 1 of the present invention;

[0027] Figure 3 It is the high-resolution transmission electron microscope image of the silver single-atom catalyst in Example 1 of the present invention;

[0028] Figure 4 It is the X-ray diffraction pattern of the silver single-atom catalyst and UiO-bpy in Example 1 of the present invention;

[0029] Figure 5 It is the linear sweep voltammetry curve of the silver single-atom catalyst and UiO-bpy in different atmospheres in Example 3 of the present invention;

[0030] Figure 6 It is the Faraday efficiency diagram of the silver single-atom catalyst and UiO-bpy producing propylene glycol at different potentials in Example 3 of the present invention;

[0031] Figure 7 It is the rate diagram of the silver single-atom catalyst and UiO-bpy producing propylene glycol at different potentials in Example 3 of the present invention;

[0032] Figure 8 It is the Faraday efficiency diagram of the silver single-atom catalyst in Example 3 of the present invention catalytically producing propylene glycol by cycling 10 times at a potential of 2.4 V versus the standard hydrogen electrode. Detailed Description of the Invention

[0033] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] The present invention provides a silver single-atom nanocatalyst, which includes a metal-organic framework (UiO-bpy) substrate and silver single atoms uniformly dispersed on the metal-organic framework (UiO-bpy) substrate.

[0035] Specifically, the silver single-atom nanocatalyst includes a metal-organic framework substrate and silver single atoms monodispersed and grown on the metal-organic framework substrate.

[0036] In certain embodiments of the present invention, in the silver single-atom nanocatalyst, the mass fraction of silver single atoms is 1% to 5%; specifically, it is 2.6%.

[0037] In certain embodiments of the present invention, the silver single-atom nanocatalyst presents a uniform octahedral morphology.

[0038] In certain embodiments of the present invention, the size of the metal-organic framework (UiO-bpy) substrate is 0.8 to 1.2 μm; specifically, it is 1.1 μm.

[0039] The present invention also provides a preparation method of the above-mentioned silver single-atom nanocatalyst, which includes the following steps:

[0040] A) Mix zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide, and carry out a solvothermal reaction to obtain a metal-organic framework (UiO-bpy);

[0041] B) After mixing the metal-organic framework (UiO-bpy) with a dispersing agent, a dispersion of the metal-organic framework (UiO-bpy) is obtained;

[0042] C) Mix the dispersion of the metal-organic framework and a silver salt solution, and after stirring and reacting, a silver single-atom catalyst is obtained.

[0043] In step A):

[0044] Mix zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide, and carry out a solvothermal reaction to obtain a metal-organic framework (UiO-bpy).

[0045] In certain embodiments of the present invention, the dosage ratio of zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide is 0.1 - 0.3 mol: 0.1 - 0.3 mol: 0.5 - 2 mL: 5 - 15 mL.

[0046] In certain embodiments of the present invention, the temperature of the solvothermal reaction is 100 - 150 °C, and the time is 20 - 30 h.

[0047] In certain embodiments of the present invention, after the solvothermal reaction, it further includes: centrifugation and drying.

[0048] The rotation speed of the centrifugation is 8000 - 12000 r / min, and the drying temperature is 50 - 80 °C.

[0049] In step B):

[0050] After mixing the metal-organic framework (UiO-bpy) with the dispersing reagent, a dispersion of the metal-organic framework (UiO-bpy) is obtained.

[0051] In certain embodiments of the present invention, the dispersing reagent includes tetrahydrofuran and / or DMF.

[0052] In certain embodiments of the present invention, the dosage ratio of UiO-bpy to the dispersing reagent is 20 - 200 mg: 10 - 100 mL; specifically 100 mg: 20 mL.

[0053] In step C):

[0054] After mixing the dispersion of the metal-organic framework and the silver salt solution and stirring and reacting, a silver single-atom catalyst is obtained.

[0055] In certain embodiments of the present invention, the mass ratio of UiO-bpy to the silver salt is 2 - 6: 1; specifically 4: 1.

[0056] In certain embodiments of the present invention, the silver salt is silver nitrate; the mass concentration of the silver salt solution is 0.1% - 1%; specifically 0.13%.

[0057] In certain embodiments of the present invention, the temperature of the stirring reaction is 10 - 40 °C, specifically 25 °C; the time is 10 - 30 h, specifically 12 h. The reaction is a chelation reaction.

[0058] In certain embodiments of the present invention, after the stirring reaction, it further includes: centrifugation and drying.

[0059] In certain embodiments of the present invention, the rotation speed of the centrifugation is 8000 - 12000 r / min, and the drying temperature is 20 - 60 °C.

[0060] The present invention also provides an application of the silver single-atom nanocatalyst described above or the silver single-atom nanocatalyst prepared by the preparation method described above in the electrocatalytic oxidation of propylene to produce propylene glycol.

[0061] Specifically, the present invention provides a method for producing propylene glycol, comprising the following steps:

[0062] a) Ultrasonically mixing a silver single-atom catalyst, a Nafion solution and ethanol to obtain a uniform solution; the silver single-atom catalyst is the silver single-atom nanocatalyst described above or the silver single-atom nanocatalyst prepared by the preparation method described above;

[0063] b) Mixing the solution with carbon paper to prepare a working electrode;

[0064] Using a silver / silver chloride electrode as a reference electrode, a graphite rod as a counter electrode, and a perchlorate solution as an electrolyte, electrochemically catalytically oxidizing propylene in the voltage range of 1.3 - 5.0 V at normal temperature and pressure to obtain propylene glycol.

[0065] In step a):

[0066] In certain embodiments of the present invention, the dosage ratio of the silver single-atom catalyst, the Nafion solution and ethanol is 8 - 12 mg: 40 - 60 μL: 0.5 - 1.5 mL; specifically 10 mg: 50 μL: 1 mL.

[0067] The mass concentration of the Nafion solution is 5%.

[0068] The time for ultrasonic mixing is 0.5 - 1.5 h; specifically 1 h.

[0069] In step b):

[0070] In certain embodiments of the present invention, mixing the solution with carbon paper specifically includes:

[0071] Dropping the solution evenly on the carbon paper.

[0072] The size of the carbon paper is 2 cm × 2 cm.

[0073] In certain embodiments of the present invention, the perchlorate is potassium perchlorate; the concentration of the perchlorate solution is 0.1 mol / L, and the solvent is water.

[0074] In certain embodiments of the present invention, the voltage is 2.2 V, 2.4 V, 2.6 V, 2.8 V or 3.0 V.

[0075] In certain embodiments of the present invention, the electrochemical catalytic oxidation reaction of propylene is carried out in a flow-through electrolytic cell, and propylene enters the flow-through electrolytic cell through a gas flowmeter.

[0076] The present invention places no special restrictions on the sources of raw materials used above, and they can be commercially available generally.

[0077] To further illustrate the present invention, the following provides a detailed description of a silver single-atom catalyst, its preparation method, and its application provided by the present invention in conjunction with embodiments, but it should not be construed as a limitation of the protection scope of the present invention.

[0078] The raw materials used in the following examples are all commercially available generally.

[0079] Example 1

[0080] A silver single-atom catalyst includes a metal-organic framework (UiO-bpy) substrate and silver single atoms monodispersed and grown on the metal-organic framework (UiO-bpy) substrate (with a size of 1.1 μm). Its synthesis method includes:

[0081] 1) Mix 0.105 mol of zirconium chloride, 0.105 mol of 2,2'-bipyridine-5,5'-dicarboxylic acid, 1 mL of formic acid, and 10 mL of N,N-dimethylformamide, and then carry out a solvothermal reaction at 120 °C for 24 h, centrifuge (at a rotation speed of 10000 r / min), and dry at 60 °C to obtain the metal-organic framework (UiO-bpy);

[0082] 2) Take 100 mg of UiO-bpy and disperse it in 20 mL of tetrahydrofuran to obtain a dispersion of UiO-bpy;

[0083] 3) Mix the dispersion of UiO-bpy and a silver nitrate solution with a mass concentration of 0.13%. The mass ratio of UiO-bpy to silver nitrate is 4:1. After stirring and reacting at 25 °C for 12 h, centrifuge (at a rotation speed of 10000 r / min), and dry at 40 °C to obtain the silver single-atom catalyst.

[0084] In the silver single-atom nanocatalyst, the mass fraction of silver single atoms is 2.6%.

[0085] The silver single-atom catalyst prepared in Example 1 was analyzed by scanning electron microscopy, and the results are as Figure 1 shown. Figure 1 This is the SEM image of the silver single-atom catalyst in Example 1 of the present invention. From Figure 1 it can be seen that the silver single-atom catalyst presents a uniform octahedral morphology, and the average side length is 1.1 μm.

[0086] The silver single-atom catalyst prepared in Example 1 was analyzed by transmission electron microscopy, and the results are asFigure 2 As shown Figure 2 This is the TEM image of the silver single-atom catalyst in Example 1 of the present invention. From Figure 2 it can be seen that the silver single-atom catalyst presents a uniform octahedral morphology, and the average side length is 1.1 μm.

[0087] Figure 3 This is the high-resolution transmission electron microscope image of the silver single-atom catalyst in Example 1 of the present invention. From Figure 3 it can be seen that the silver atoms in the silver single-atom catalyst are uniformly distributed, and no aggregation state is found.

[0088] Figure 4 This is the X-ray diffraction pattern of the silver single-atom catalyst and UiO-bpy in Example 1 of the present invention. From Figure 4 it can be seen that the silver atoms in the silver single-atom catalyst are uniformly distributed, and no aggregation state is found.

[0089] Example 2

[0090] A production method of propylene glycol, comprising the following steps:

[0091] 1) Disperse 10 mg of the silver single-atom catalyst prepared in Example 1 and 50 μL of a Nafion solution with a mass concentration of 5% in 1 mL of ethanol, and ultrasonically mix for 1 h to obtain a uniform solution;

[0092] 2) Drop the solution obtained in step 1) evenly on a 2 cm × 2 cm carbon paper; use this carbon paper as the working electrode, a silver / silver chloride electrode as the reference electrode, a graphite rod as the counter electrode, use a 0.1 mol / L aqueous potassium perchlorate solution as the electrolyte, and propylene enters the flow-through electrolytic cell through a gas flowmeter, and perform an electrochemical catalytic oxidation reaction of propylene in the flow-through electrolytic cell to obtain propylene glycol. Apply an overpotential and detect the current density through an electrochemical workstation.

[0093] Example 3

[0094] Test of current density and product selectivity of the silver single-atom catalyst in the electrochemical catalytic oxidation of propylene to produce propylene glycol:

[0095] Under the reaction conditions of Example 2, a constant potential test is carried out. Set the potential relative to the standard hydrogen electrode to 2.2 V and perform a constant potential test for 1 h. The hydrogen gas generated at the cathode during the reaction is discharged into the air. After the reaction, the concentration of the produced propylene glycol is detected by nuclear magnetic resonance hydrogen spectrum. After the test is completed, change the potential to 2.4 V, 2.6 V, 2.8 V, and 3.0 V respectively, and perform the test using the same process.

[0096] The linear sweep voltammetry curve of the silver single-atom catalyst in the range of 1-3 V is as Figure 5 shown. Figure 5This is the linear sweep voltammetry curve of the silver single-atom catalyst and UiO-bpy in Example 3 of the present invention under different atmospheres. From Figure 5 It can be seen that the current of the silver single-atom catalyst in the propylene atmosphere is higher than that in the argon atmosphere, while the difference in the current of UiO-bpy between the propylene atmosphere and the argon atmosphere is not significant, indicating that the silver single-atom catalyst has more excellent electrocatalytic oxidation activity for propylene.

[0097] Figure 6 This is the Faraday efficiency diagram of the silver single-atom catalyst and UiO-bpy in Example 3 of the present invention for producing propylene glycol at different potentials. From Figure 6 It can be seen that at all applied potentials, the Faraday efficiency of the silver single-atom catalyst always exceeds that of UiO-bpy. In particular, at a potential of 2.4 V versus the standard hydrogen electrode, the maximum Faraday efficiency of the silver single-atom catalyst reaches 36.0%, which is 3.3 times that of UiO-bpy.

[0098] Figure 7 This is the rate diagram of the silver single-atom catalyst and UiO-bpy in Example 3 of the present invention for producing propylene glycol at different potentials. From Figure 7 It can be seen that at a potential of 3.0 V versus the standard hydrogen electrode, the silver single-atom catalyst achieved a high yield of 57.5 g / cm 2 催化剂 / h, while almost no product was detected for UiO-bpy at all applied potentials, proving that the substrate UiO-bpy has almost no electrocatalytic oxidation activity for propylene.

[0099] Example 4

[0100] Stability test of the silver single-atom catalyst in the electrocatalytic oxidation of propylene to produce propylene glycol at an overpotential of 2.4 V versus the standard hydrogen electrode:

[0101] Under the reaction conditions of Example 2, a constant potential test was carried out. The potential versus the standard hydrogen electrode was set to 2.4 V, and the constant potential test was carried out for 1 h. The hydrogen generated at the cathode during the reaction was discharged into the air. The concentration of propylene glycol produced after the reaction was detected by nuclear magnetic resonance hydrogen spectrum. After the reaction, the electrolyte was replaced and the same test conditions were used again, and the cyclic test was carried out 10 times.

[0102] Figure 8 This is the Faraday efficiency diagram of the silver single-atom catalyst in Example 3 of the present invention for catalytically producing propylene glycol at a potential of 2.4 V versus the standard hydrogen electrode for 10 cycles. From Figure 8 It can be seen that during the 10 tests, the Faraday efficiency of propylene glycol hardly decayed, proving that the silver single-atom catalyst has good stability in the cyclic test.

[0103] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of silver single-atom nanocatalyst in electrocatalytic oxidation of propylene to produce propylene glycol; The silver single-atom nanocatalyst includes a metal-organic framework substrate and silver single atoms uniformly dispersed on the metal-organic framework substrate.

2. The application according to claim 1, characterized in that, In the silver single-atom nanocatalyst, the mass fraction of silver single atoms is 1% - 5%.

3. The application according to claim 1, characterized in that The size of the metal-organic framework substrate is 0.8 - 1.2 μm.

4. The application according to claim 1, characterized in that, The preparation method of the silver single-atom nanocatalyst includes the following steps: A) Mix zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide, and carry out a solvothermal reaction to obtain a metal-organic framework; B) After mixing the metal-organic framework with a dispersing reagent, a dispersion of the metal-organic framework is obtained; C) Mix the dispersion of the metal-organic framework and a silver salt solution, and after stirring and reacting, a silver single-atom catalyst is obtained.

5. The application according to claim 4, wherein In step A), the dosage ratio of zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, formic acid and N,N-dimethylformamide is 0.1 - 0.3 mol: 0.1 - 0.3 mol: 0.5 - 2 mL: 5 - 15 mL; The temperature of the solvothermal reaction is 100 - 150 °C, and the time is 20 - 30 h.

6. The application according to claim 4, wherein In step B), the dispersing reagent includes tetrahydrofuran and / or DMF; The dosage ratio of the metal-organic framework to the dispersing reagent is 20 - 200 mg: 10 - 100 mL.

7. The application according to claim 4, characterized in that, In step C), the mass ratio of the metal-organic framework to the silver salt is 2 - 6:

1.

8. The application according to claim 4, wherein In step C), the temperature of the stirring reaction is 10 - 40 °C, and the time is 10 - 30 h.

9. A production method of propylene glycol, including the following steps: a) Ultrasonically mix a silver single-atom nanocatalyst, a Nafion solution and ethanol to obtain a uniform solution; the silver single-atom nanocatalyst includes a metal-organic framework substrate and silver single atoms uniformly dispersed on the metal-organic framework substrate; b) Mix the solution with carbon paper to prepare a working electrode; Using a silver / silver chloride electrode as a reference electrode and a graphite rod as a counter electrode, and using a perchlorate solution as an electrolyte, electrochemically catalytically oxidize propylene in the voltage range of 1.3 - 5.0 V under normal temperature and pressure to obtain propylene glycol.

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