Supported catalyst for synthesizing dimethyl carbonate from carbon dioxide through electro-catalysis, preparation method and application

Abstract

The invention relates to the technical field of catalysts, in particular to a supported catalyst for synthesizing dimethyl carbonate through electro-catalysis of carbon dioxide, a preparation method and application. The preparation method of the supported catalyst for synthesizing the dimethyl carbonate by electro-catalyzing the carbon dioxide comprises the following steps: S1, adding a nitrogen source, a carbon source, a metal salt and nano silicon dioxide into a solvent, heating, drying and calcining to obtain a calcined precursor; s2, etching, washing, filtering, drying and ball-milling the calcined precursor to obtain porous powder; s3, dispersing the porous powder, adding palladium salt, reducing, washing, filtering and drying to obtain the dimethyl carbonate catalyst for carbon dioxide electrosynthesis. The catalyst provided by the invention can promote direct electrolysis of carbon dioxide and methanol at normal temperature to synthesize dimethyl carbonate.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a supported catalyst for electrocatalytically synthesizing dimethyl carbonate from carbon dioxide, a preparation method and an application thereof. Background Art

[0002] The conversion of carbon dioxide to prepare organic carbonates is considered one of the important measures to achieve high-value utilization of CO2. Energy level analysis shows that the energy required to synthesize carboxylic acids or carbonates using carbon dioxide as raw material is low, and the corresponding energy utilization efficiency and economy are high. Dimethyl carbonate (DMC) is an environmentally friendly green chemical product that has received widespread attention at home and abroad in recent years. It has a huge market size in the chemical, pharmaceutical, new energy and other industrial fields. In recent years, especially with the rapid development of the new energy industry and the industrial application of lithium-ion batteries, sodium-ion batteries, etc., the demand for electrolytes has also increased year by year, and the electrolyte solvent market will also expand further. Therefore, the chemical conversion of CO2 to prepare dimethyl carbonate products can not only realize large-scale recycling of CO2, but also bring huge economic value. It is an important path to achieve CO2 emission reduction and high-value utilization, and it is also an effective technical path to help achieve the goal of carbon neutrality.

[0003] The direct synthesis of dimethyl carbonate from CO2 and methanol is a new method for the green and sustainable production of dimethyl carbonate. The raw materials are cheap and easy to obtain, there are few by-products, it is environmentally friendly and low-cost, and it has great development potential. At present, the direct synthesis of dimethyl carbonate from carbon dioxide and methanol mainly includes thermal catalysis and electrocatalysis. In recent years, a series of studies have been conducted on the direct synthesis of dimethyl carbonate from carbon dioxide and methanol by thermal catalysis in terms of catalyst selection, the use of dehydrating agents, and the improvement of carbon dioxide solubility. However, from the current research results, there are still problems such as low reaction efficiency, catalyst deactivation during the reaction, and high reaction pressure. The direct synthesis of dimethyl carbonate from electrocatalysis of carbon dioxide and methanol is currently mainly focused on the research of catalysts.

[0004] In recent years, many people have done some research on the synthesis of catalysts, but the choice of catalysts mainly uses precious metal catalysts such as Pd / C and Pd-Au. Although these precious metal catalysts have good catalytic properties, their high prices limit their long-term development. Although other catalysts such as Ni single-atom catalysts can be applied to this field recently, Ni single-atom catalysts still need to add Pd / C catalysts to the solution in the step of synthesizing dimethyl carbonate to obtain dimethyl carbonate products. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, a preparation method and application thereof. The catalyst can promote direct electrolysis of carbon dioxide and methanol to synthesize dimethyl carbonate at room temperature.

[0006] To this end, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides, in an optional embodiment, a method for preparing a supported catalyst for electrocatalytically synthesizing dimethyl carbonate from carbon dioxide, comprising the following steps:

[0008] S1: After adding a nitrogen source, a carbon source, a metal salt and nano-silicon dioxide into a solvent, heating, drying and calcining are performed to obtain a calcined precursor.

[0009] S2: etching, filtering, washing, drying and ball milling the calcined precursor to obtain porous powder.

[0010] S3: After dispersing the porous powder, add palladium salt, and then reduce, wash, filter and dry to obtain a catalyst for electrosynthesis of dimethyl carbonate from carbon dioxide.

[0011] Preferably, the nitrogen source is selected from one or more of dicyandiamide, melamine, urea, polyaniline, polypyrrole, polyamide or amino acid; and / or, the carbon source is selected from one or more of glucose, starch, sucrose, fructose, galactose, cellulose, citric acid, lactic acid, acetic acid, methylcellulose, hydroxypropyl methylcellulose or carboxymethyl cellulose; and / or, the metal is selected from one or more of nickel, copper, cobalt, iron, chromium, manganese or molybdenum; and / or, the mass ratio of the nitrogen source to the carbon source is 1-20:1, the mass ratio of the carbon source to the metal salt is 0.001-0.01:1, and the mass ratio of the nano-silicon dioxide to the total mass of the nitrogen source and the carbon source is 0.1-10:1.

[0012] Preferably, when etching is performed, the etchant used is selected from one or more of hydrofluoric acid, sodium hydroxide or potassium hydroxide, preferably hydrofluoric acid, and the mass ratio of the etchant to the calcined precursor is 0.2-2:1; and / or, the palladium salt is selected from one or more of palladium chloride, ammonium chloropalladate, dichlorotetraamminepalladium, ammonium tetrachloropalladate, bis(ethylenediamine)palladium chloride, tetraaminopalladium tetrachloropalladium, sodium tetrachloropalladate, potassium tetrachloropalladate, dichlorodiamminepalladium, potassium chloropalladate, palladium nitrate, tetraaminopalladium nitrate, palladium nitrate dihydrate, palladiumous nitrate hydrate, palladium acetate, trimethylpalladium acetate, palladium propionate, palladium benzoate, triphenylphosphine palladium acetate, tetraaminopalladium sulfate, palladium acetylacetonate, palladium bromide or palladium iodide; and / or, when reducing is performed, the reducing agent used is selected from one or more of sodium borohydride, potassium borohydride, ascorbic acid, hydrazine hydrate or hydrogen.

[0013] In the present invention, the purpose of etching is to remove nano-silicon dioxide and unstable metal particles.

[0014] Preferably, in step S1, the calcination temperature is 700-1000°C and the time is 1-8 hours; and / or the calcination is carried out under a protective gas, and the protective gas is selected from one or more of argon, nitrogen or helium.

[0015] In a second aspect, the present invention provides, in an optional embodiment, a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, which is prepared by the above-mentioned preparation method.

[0016] In a third aspect, the present invention provides, in an optional embodiment, a supported catalyst prepared by the above preparation method or use of the above supported catalyst in electrocatalytic synthesis of dimethyl carbonate from carbon dioxide.

[0017] Preferably, the electrocatalytic process is specifically as follows:

[0018] (1) adding methanol raw material, electrolyte and the electrocatalytic carbon dioxide synthesis dimethyl carbonate catalyst into an electrolytic cell, or,

[0019] The electrocatalytic carbon dioxide to dimethyl carbonate catalyst is coated on a cathode electrode, and a methanol feedstock and an electrolyte are added to an electrolytic cell, or,

[0020] The electrocatalytic carbon dioxide to dimethyl carbonate catalyst is coated on a cathode electrode, and a methanol raw material, an electrolyte and the electrocatalytic carbon dioxide to dimethyl carbonate catalyst are added to an electrolytic cell;

[0021] (2) introducing CO2 raw material and electrolyzing it under constant current or constant voltage to generate dimethyl carbonate;

[0022] Wherein, the mass ratio of the electrocatalytic carbon dioxide synthesis dimethyl carbonate catalyst to methanol is 0.00003-0.005:1.

[0023] Preferably, the electrolyte is selected from one or more of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, magnesium chloride, magnesium bromide, magnesium iodide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium iodide; and / or, the concentration of the electrolyte is 0.01-5 mol / L, preferably 0.1-0.3 mol / L.

[0024] Preferably, during the electrocatalytic process, the flow rate of the carbon dioxide is 5-50 mL / min; and / or, the electrocatalytic process adopts constant current electrolysis or constant voltage electrolysis, and the current density of the constant current electrolysis is 5-30 mA / cm 2 The voltage of the constant voltage electrolysis is 4-11 V. The reaction pressure of the electrocatalysis is 0.1-0.5 MPa; and / or the temperature of the electrocatalysis is 15-35°C.

[0025] In the present invention, the cathode electrode material used in electrocatalysis is a conductive metal or carbon or an electrode coated with the electrocatalytic carbon dioxide synthesis of dimethyl carbonate catalyst, and the anode electrode material is one of graphite, platinum, glassy carbon, boron-doped diamond, and carbon fiber materials.

[0026] Compared with the prior art, the present invention has one of the following beneficial effects:

[0027] 1. The catalyst provided by the present invention can promote the direct electrolysis of carbon dioxide and methanol to synthesize dimethyl carbonate at room temperature.

[0028] 2. The present invention uses carbon dioxide and methanol as raw materials to directly synthesize dimethyl carbonate. The raw materials are cheap and easily available, there are few by-products, it is environmentally friendly and low in cost. It is a new green and sustainable method for producing dimethyl carbonate.

[0029] 3. The present invention uses an electrocatalyst with high conductivity and excellent catalytic performance to promote the electrolysis of carbon dioxide and methanol to synthesize dimethyl carbonate, and the reaction conditions are mild and safe.

[0030] 4. The present invention utilizes green wind power or photovoltaic resources to reduce and utilize carbon dioxide in carbon-rich areas on a large scale. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific 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.

[0032] In a specific embodiment of the present invention, the metal is selected from one or more of nickel, copper, cobalt, iron, chromium, manganese or molybdenum. The metal can be any combination of two or more of nickel, copper, cobalt, iron, chromium, manganese or molybdenum. The mass ratio of any two metal combinations in the present invention can be 1:0.5-2, but the present invention is not limited thereto.

[0033] In a specific embodiment of the present invention, the nitrogen source is selected from one or more of dicyandiamide, melamine, urea, polyaniline, polypyrrole, polyamide or amino acid. The nitrogen source can be a combination of any two or more of dicyandiamide, melamine, urea, polyaniline, polypyrrole, polyamide or amino acid. The mass ratio of any two nitrogen sources in the present invention can be 1:0.5-2, but the present invention is not limited thereto.

[0034] In a specific embodiment of the present invention, the carbon source is selected from one or more of glucose, starch, sucrose, fructose, galactose, cellulose, citric acid, lactic acid, acetic acid, methylcellulose, hydroxypropyl methylcellulose or carboxymethyl cellulose. The carbon source can be any combination of two or more of glucose, starch, sucrose, fructose, galactose, cellulose, citric acid, lactic acid, acetic acid, methylcellulose, hydroxypropyl methylcellulose or carboxymethyl cellulose. The mass ratio of any two carbon source combinations in the present invention can be 1:0.5-2, and the present invention is not limited thereto.

[0035] In a specific embodiment of the present invention, the palladium salt is selected from palladium chloride, ammonium chloropalladate, dichlorotetraamminepalladium, ammonium tetrachloropalladate, bis(ethylenediamine)palladium chloride, tetraaminopalladium tetrachloropalladium, sodium tetrachloropalladate, potassium tetrachloropalladate, dichlorodiamminepalladium, potassium chloropalladate, palladium nitrate, tetraaminopalladium nitrate, palladium nitrate dihydrate, palladium nitrate hydrate, palladium acetate, trimethylpalladium acetate, palladium propionate, palladium benzoate, triphenylphosphine palladium acetate, tetraaminopalladium sulfate, palladium acetylacetonate, palladium bromide or palladium iodide. The selection of palladium salt can be palladium chloride, ammonium chloropalladate, dichlorotetraamminepalladium, Ammonium tetrachloropalladate , bis(ethylenediamine)palladium chloride, tetraaminopalladium tetrachloride, sodium tetrachloropalladate, potassium tetrachloropalladate, dichlorodiamminepalladium, potassium chloropalladate, palladium nitrate, tetraaminopalladium nitrate, palladium nitrate dihydrate, palladium nitrate hydrate, palladium acetate, trimethylpalladium acetate, palladium propionate, palladium benzoate, triphenylphosphine palladium acetate, tetraaminopalladium sulfate, palladium acetylacetonate, palladium bromide or palladium iodide. The mass ratio of any two palladium salt combinations in the present invention can be 1:0.5-2, but the present invention is not limited thereto.

[0036] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0037] Example 1

[0038] This embodiment provides a method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, comprising the following steps:

[0039] S1: Dissolve 5g of dicyandiamide and 0.5g of glucose in deionized water to obtain a uniform solution A; then dissolve 61mg of NiCl2·6H2O in deionized water to obtain a uniform solution B; then drip the B solution into the A solution under stirring. Then add 5.5g of nano-SiO2 to the above mixed solution, and then heat and dry to obtain a powder sample. The dried powder sample is transferred to a tube furnace and heated to 900℃ at a rate of 3℃ / min in an Ar atmosphere for calcination for 2 hours to obtain a calcined precursor.

[0040] S2: The calcined precursor was etched with hydrofluoric acid, washed with deionized water for multiple times, filtered, dried, and ball-milled at 1000 rpm for 6 h to obtain porous Ni-NC powder;

[0041] S3: 90 mg of porous Ni-NC powder was ultrasonically dispersed in 5 mL of ethanol-water (volume ratio of 1:1) solution to obtain a mixed solution, and then 1.25 mL of potassium tetrachloropalladate with a concentration of 12.25 mmol / L was slowly added to the above solution. After stirring for 1 hour, 1 mL of freshly prepared sodium borohydride solution with a concentration of 10 mg / mL was slowly dripped into the mixture, and continued to stir until the palladium in the potassium tetrachloropalladate was completely reduced to Pd crystal particles. Finally, centrifugation, washing, and drying were performed to obtain the supported catalyst PdNi@porous NC.

[0042] This example also provides five applications of supported catalysts PdNi@porous NC in electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, specifically:

[0043] (1) Taking the area as 1cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 50 mL of methanol, 0.1 mol / L NaBr and 100 mg of supported catalyst PdNi@porous NC were added to a single-chamber electrolytic cell, and the titanium foil cathode electrode and the special graphite anode electrode were fixed to the electrolytic cell. The reflux condenser and the temperature control device were then connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 20 mL / min until saturated, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 12 mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 60 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 189.86 μmol h -1 , and its Faradaic efficiency is 84.81%.

[0044] (2) With an area of ​​4.5 cm 2The carbon paper was used as the cathode electrode. Then, 50 mL of methanol and 0.1 mol / L NaBr were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 200 mg of the supported catalyst PdNi@porous NC was added to the one-chamber electrolytic cell. Then, the carbon paper cathode electrode and the graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously passed into the electrolytic cell at a flow rate of 5 mL / min until saturated. Then, the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 12 mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 50 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 766.16 μmol h -1 , and its Faradaic efficiency is 76.05%.

[0045] (3) With an area of ​​6.75 cm 2 The carbon paper was used as the cathode electrode. Then, 50 mL of methanol and 0.2 mol / L NaCl were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 50 mg of the supported catalyst PdNi@porous NC was added to the one-chamber electrolytic cell, and the carbon paper cathode electrode and the graphite anode electrode were fixed to the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 15 mL / min until the reaction pressure reached 0.5 MPa. Then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 7.41 mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.5MPa for 60 minutes. After the reaction was completed, the product was separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 662.81 μmol / h -1 , and its Faradaic efficiency is 71.03%.

[0046] (4) 5 mg of supported catalyst PdNi@porous NC, 800 μl of ethanol, and 200 μl of 5 wt% Nafion were ultrasonically dispersed for more than 1 hour to obtain a uniformly dispersed catalyst ink. Then, 200 μl of the catalyst ink was taken out and evenly coated on an area of ​​1 cm by ultrasonic spraying or drop coating. 2On the carbon paper, after drying, the carbon paper electrode coated with the loaded catalyst PdNi@porous NC is used as the cathode electrode. Then, 50mL of methanol and 0.1mol / LNaBr are added to a single-chamber electrolytic cell, and the carbon paper cathode electrode coated with the loaded catalyst PdNi@porous NC and the special graphite anode electrode are fixed to the electrolytic cell. Then connect the reflux condenser and the temperature control device to the electrolytic cell. Continuously pass high-purity CO2 gas into the electrolytic cell at a flow rate of 10mL / min until saturated, then seal the electrolytic cell, turn on the external power supply, and control the current density at 12mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 30 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 178.92 μmol h -1 , and its Faradaic efficiency is 79.92%.

[0047] (5) 5 mg of supported catalyst PdNi@porous NC, 800 μl of ethanol, and 200 μl of Nafion were ultrasonically dispersed for more than 1 hour to obtain a uniformly dispersed catalyst ink. Then, 200 μl of the catalyst ink was taken out and evenly coated on an area of ​​1 cm by ultrasonic spraying or drop coating. 2 On the carbon paper, after drying, the carbon paper electrode coated with the loaded catalyst PdNi@porous NC is used as the cathode electrode. Then, 50mL methanol, 0.1mol / LNaBr and 10mg loaded catalyst PdNi@porous NC are added to a chamber electrolytic cell, and then the carbon paper cathode electrode coated with the loaded catalyst PdNi@porous NC and the special graphite anode electrode are fixed to the electrolytic cell. Then connect the reflux condenser and the temperature control device to the electrolytic cell. Continuously pass high-purity CO2 gas into the electrolytic cell at a flow rate of 10mL / min until saturated, then seal the electrolytic cell, turn on the external power supply, and control the current density at 12mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 45min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 199.75μmol h -1 , and its Faradaic efficiency is 89.23%.

[0048] Example 2

[0049] This embodiment provides a method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, comprising the following steps:

[0050] S1: Dissolve 5g of dicyandiamide and 0.5g of glucose in deionized water to obtain a uniform solution A; then dissolve 80mg of CuCl2·2H2O in deionized water to obtain a uniform solution B; then drip the B solution into the A solution under stirring. Then add 55.0g of nano-SiO2 to the above mixed solution, and then heat and dry to obtain a powder sample. The dried powder sample is transferred to a tube furnace and heated to 800℃ at a rate of 5℃ / min in an Ar atmosphere for calcination for 1 hour to obtain a calcined precursor.

[0051] S2: The calcined precursor was etched with hydrofluoric acid, washed with deionized water for multiple times, filtered, dried, and ball-milled at 1000 rpm for 6 h to obtain a porous powder Cu-NC;

[0052] S3: 90 mg of porous Cu-NC powder sample was ultrasonically dispersed in 5 mL of ethanol-water (volume ratio of 1:1) solution to obtain a mixed solution, and then 2.5 mL of potassium tetrachloropalladate with a concentration of 12.25 mmol / L was slowly added to the above solution. After stirring for 1 hour, 2 mL of freshly prepared sodium borohydride solution with a concentration of 10 mg / mL was slowly dripped into the mixture, and continued to stir until the palladium in the potassium tetrachloropalladate was completely reduced to Pd crystal particles. Finally, centrifugation, washing, and drying were performed to obtain the supported catalyst PdCu@porous NC.

[0053] This example also provides four applications of supported catalysts PdCu@porous NC in electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, specifically:

[0054] (1) With an area of ​​6.75 cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 30mL of methanol and 0.1mol / LNaBr were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 50mg of the loaded catalyst PdCu@porous NC was added to the one-chamber electrolytic cell, and the prepared cathode electrode and graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 30mL / min until the reaction pressure reached 0.3MPa, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 14.81mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.3MPa for 45min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 1324.39μmol h -1 , and its Faradaic efficiency is 71.01%.

[0055] (2) With an area of ​​6.75 cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 50 mL of methanol and 0.1 mol / L NaBr were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 100 mg of the loaded catalyst PdCu@porous NC was added to the one-chamber electrolytic cell, and the prepared cathode electrode and graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously passed into the electrolytic cell at a flow rate of 20 mL / min until saturated, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 12 mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 30 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 1169.21 μmol h -1 , and its Faradaic efficiency is 77.37%.

[0056] (3) With an area of ​​4.5 cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 50mL of methanol and 0.1mol / LNaBr were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 50mg of the loaded catalyst PdCu@porous NC was added to the one-chamber electrolytic cell, and the prepared cathode electrode and graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously passed into the electrolytic cell at a flow rate of 20mL / min until saturated, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 22.22mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.1MPa for 30 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 1367.78 μmol h -1 , and its Faradaic efficiency is 73.32%.

[0057] (4) With an area of ​​6.75 cm 2The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 40mL of methanol and 0.1mol / LNaCl were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 30mg of the loaded catalyst PdCu@porous NC was added to the one-chamber electrolytic cell, and the prepared cathode electrode and graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 50mL / min until the reaction pressure reached 0.3MPa, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 14.81mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.3MPa for 60min. After the reaction was completed, the product was separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 1413.22μmol h -1 , and its Faradaic efficiency is 75.78%.

[0058] Example 3

[0059] This embodiment provides a method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, comprising the following steps:

[0060] S1: Dissolve 5g of dicyandiamide and 0.5g of glucose in deionized water to obtain a uniform solution A; then dissolve 40mg of CuCl2·2H2O and 31mg of NiCl2·6H2O in deionized water to obtain a uniform solution B; then drip the B solution into the A solution under stirring. Then add 11.0g of nano-SiO2 to the above mixed solution, and then heat and dry to obtain a powder sample. The dried powder sample is transferred to a tube furnace and heated to 900℃ at a rate of 3℃ / min in an Ar atmosphere for calcination for 2 hours to obtain a calcined precursor.

[0061] S2: The calcined precursor was etched with hydrofluoric acid, washed with deionized water for multiple times, filtered, dried, and ball-milled at 1000 rpm for 6 h to obtain porous powder NiCu-NC;

[0062] S3: 90 mg of porous NiCu-NC powder sample was ultrasonically dispersed in 5 mL of ethanol-water (volume ratio of 1:1) solution to obtain a mixed solution, and then 1.25 mL of potassium tetrachloropalladate with a concentration of 12.25 mmol / L was slowly added to the above solution. After stirring for 1 hour, 1 mL of freshly prepared sodium borohydride solution with a concentration of 10 mg / mL was slowly dripped into the mixture, and continued to stir until the palladium in the potassium tetrachloropalladate was completely reduced to Pd crystal particles. Finally, centrifugation, washing, and drying were performed to obtain the supported catalyst PdNiCu@porous NC.

[0063] This embodiment provides an application of a supported catalyst PdNiCu@porous NC in a catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, specifically:

[0064] With an area of ​​6.75cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 50mL of methanol and 0.3mol / LNaBr were added to the one-chamber electrolytic cell and stirred thoroughly until the electrolyte was dissolved. Then, 30mg of the loaded catalyst PdNiCu@porous NC was added to the one-chamber electrolytic cell, and the prepared cathode electrode and graphite anode electrode were fixed on the electrolytic cell. The reflux condenser and the temperature control device were connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 30mL / min until the reaction pressure reached 0.5MPa, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 22.22mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out at 25°C and 0.5MPa for 60 min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 2351.76 μmol h -1 , and its Faradaic efficiency is 84.05%.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a supported catalyst for electrocatalytically synthesizing dimethyl carbonate from carbon dioxide, comprising the following steps:

[0067] S1: Dissolve 5g of dicyandiamide and 0.5g of glucose in deionized water to obtain a uniform solution A; then dissolve 61mg of NiCl2·6H2O in deionized water to obtain a uniform solution B; then drip solution B into solution A under stirring, and then heat and dry to obtain a powder sample. The dried powder sample was transferred to a tube furnace and heated to 900℃ at a rate of 3℃ / min in an Ar atmosphere and calcined for 2 hours to obtain Ni@NC.

[0068] S2: 90 mg Ni@NC was ultrasonically dispersed in 5 mL ethanol-water (volume ratio of 1:1) solution to obtain a mixed solution, and then 1.25 mL of 12.25 mmol / L potassium tetrachloropalladate was slowly added to the above solution. After stirring for 1 hour, 1 mL of 10 mg / mL sodium borohydride solution was slowly dripped into the mixture, and continued to stir until the palladium in the potassium tetrachloropalladate was completely reduced to Pd crystal particles. Finally, centrifugation, washing, and drying were performed to obtain the supported catalyst PdNi@NC.

[0069] This comparative example also provides an application of a supported catalyst PdNi@NC in electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, specifically:

[0070] With an area of ​​1cm 2 The titanium foil was used as the cathode electrode, and it was polished with sandpaper and acid-washed for later use. Then, 50mL of methanol, 0.1mol / LNaBr and 100mg of loaded catalyst PdNi@NC were added to a single-chamber electrolytic cell, and the titanium foil cathode electrode and the special graphite anode electrode were fixed to the electrolytic cell. The reflux condenser and the temperature control device were then connected to the electrolytic cell. High-purity CO2 gas was continuously introduced into the electrolytic cell at a flow rate of 20mL / min until saturated, and then the electrolytic cell was sealed, the external power supply was turned on, and the current density was controlled at 12mA / cm 2 (calculated based on the cathode electrode area), the electrochemical synthesis reaction was carried out under mild conditions of 25°C and 0.1MPa for 60min. After the reaction was completed, the products were separated and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography, and the yield of dimethyl carbonate was 151.89μmol h -1 , and its Faradaic efficiency is 67.85%.

[0071] Although the principles of the present invention are described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are merely explanations of the exemplary implementations of the present invention, and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute limitations on the scope of the present invention, and any obvious changes such as equivalent transformations, simple replacements, etc. based on the technical solution of the present invention, without departing from the spirit and scope of the present invention, fall within the protection scope of the present invention.

Claims

1. A method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, characterized in that: The following steps are involved: S1: adding a nitrogen source, a carbon source, a metal salt and nano-silicon dioxide into a solvent, heating, drying and calcining to obtain a calcined precursor; S2: etching, filtering, washing, drying and ball milling the calcined precursor to obtain a porous powder; S3: After dispersing the porous powder, add palladium salt, and then reduce, wash, filter and dry to obtain a catalyst for electrosynthesis of dimethyl carbonate from carbon dioxide.

2. The method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide according to claim 1, characterized in that: The nitrogen source is selected from one or more of dicyandiamide, melamine, urea, polyaniline, polypyrrole, polyamide or amino acid; and / or, The carbon source is selected from one or more of glucose, starch, sucrose, fructose, galactose, cellulose, citric acid, lactic acid, acetic acid, methylcellulose, hydroxypropyl methylcellulose or carboxymethylcellulose; and / or, The metal is selected from one or more of nickel, copper, cobalt, iron, chromium, manganese or molybdenum; and / or, The mass ratio of the nitrogen source to the carbon source is 1-20:1, the mass ratio of the carbon source to the metal salt is 0.001-0.01:1, and the mass ratio of the nano-silicon dioxide to the total mass of the nitrogen source and the carbon source is 0.1-10:

1.

3. The method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide according to claim 1, characterized in that: When etching, the etchant used is selected from one or more of hydrofluoric acid, sodium hydroxide or potassium hydroxide, and the mass ratio of the etchant to the calcined precursor is 0.2-2:1; and / or, The palladium salt is selected from one or more of palladium chloride, ammonium chloropalladate, dichlorotetraamminepalladium, ammonium tetrachloropalladate, bis(ethylenediamine)palladium chloride, tetraaminopalladium tetrachloropalladate, sodium tetrachloropalladate, potassium tetrachloropalladate, dichlorodiamminepalladium, potassium chloropalladate, palladium nitrate, tetraaminopalladium nitrate, palladium nitrate dihydrate, palladium nitrate hydrate, palladium acetate, trimethylpalladium acetate, palladium propionate, palladium benzoate, triphenylphosphine palladium acetate, tetraaminopalladium sulfate, palladium acetylacetonate, palladium bromide or palladium iodide; and / or, When performing the reduction, the reducing agent used is selected from one or more of sodium borohydride, potassium borohydride, ascorbic acid, hydrazine hydrate or hydrogen.

4. The method for preparing a supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide according to claim 1, characterized in that: In step S1, the calcination temperature is 700-1000°C and the time is 1-8 hours; and / or, The calcination is carried out under a protective gas, and the protective gas is selected from one or more of argon, nitrogen or helium.

5. A supported catalyst for electrocatalytic synthesis of dimethyl carbonate from carbon dioxide, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 4.

6. Use of a supported catalyst prepared by the preparation method according to any one of claims 1 to 4 or the supported catalyst according to claim 5 in electrocatalytic synthesis of dimethyl carbonate from carbon dioxide.

7. The use according to claim 6, characterized in that: The electrocatalytic process is specifically as follows: (1) adding methanol raw material, electrolyte and the electrocatalytic carbon dioxide synthesis dimethyl carbonate catalyst into an electrolytic cell, or, The electrocatalytic carbon dioxide to dimethyl carbonate catalyst is coated on a cathode electrode, and a methanol feedstock and an electrolyte are added to an electrolytic cell, or, The electrocatalytic carbon dioxide to dimethyl carbonate catalyst is coated on a cathode electrode, and a methanol raw material, an electrolyte and the electrocatalytic carbon dioxide to dimethyl carbonate catalyst are added to an electrolytic cell; (2) introducing CO2 raw material and electrolyzing it under constant current or constant voltage to generate dimethyl carbonate; Wherein, the mass ratio of the electrocatalytic carbon dioxide synthesis dimethyl carbonate catalyst to methanol is 0.00003-0.005:

1.

8. The use according to claim 7, characterized in that: The electrolyte is selected from one or more of sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, magnesium chloride, magnesium bromide, magnesium iodide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium iodide; and / or, The concentration of the electrolyte is 0.01-5 mol / L.

9. The use according to claim 6, characterized in that: During the electrocatalytic process, the flow rate of the carbon dioxide is 5-50 mL / min; and / or, The electrocatalysis adopts constant current electrolysis or constant voltage electrolysis, and the current density of the constant current electrolysis is 5-30mA / cm 2 , the voltage of the constant voltage electrolysis is 4-11V.

10. The use according to claim 6, characterized in that: The electrocatalytic reaction pressure is 0.1-0.5 MPa; and / or, The temperature of the electrocatalysis is 15-35°C.