Preparation method and application of superfine copper oxide nanomaterials for promoting electrocatalytic construction of c-n bond to synthesize urea
By preparing ultrafine copper oxide nanopowder catalysts, the problems of low selectivity and high energy consumption in the electrocatalytic synthesis of urea were solved, realizing efficient and low-cost urea synthesis, which is suitable for industrial applications.
Patent Information
- Application Number
- CN202311653648.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-05
- Publication Date
- 2026-03-20
- Estimated Expiration
- 2043-12-05
AI Technical Summary
Existing electrocatalytic synthesis of urea suffers from numerous competing reactions and a wide variety of products, limiting urea selectivity. Furthermore, traditional synthesis processes are characterized by high energy consumption and severe environmental pollution.
Ultrafine copper oxide nanoparticles were used as catalysts and prepared by low-temperature oil-phase reaction and ultrasonic precipitation method. This increased the contact area of reactants, exposed a large number of active sites, and promoted CN bond formation.
It improves the selectivity of urea to 82.7%, has mild synthesis conditions, low cost, is suitable for large-scale production, and has good prospects for industrial application.
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Figure CN117509707B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of nanomaterials and energy and environmental science and engineering, and particularly relates to a preparation method of superfine copper oxide nanomaterials for promoting electrocatalysis to construct C-N bonds to synthesize urea.
[0002] The application relates to a preparation method of the catalyst.
[0003] The application also relates to the use of the catalyst in the coupling synthesis of urea with nitrite and carbon dioxide as nitrogen source and carbon source, respectively. BACKGROUND
[0004] Urea is one of the simplest organic compounds and is also one of the most widely used chemical fertilizer varieties at present, and has a wide range of uses in the fields of agriculture, industry, feed additives, cosmetics, medicine and the like. In the industrial synthesis process of urea, not only a large amount of energy is consumed for synthesizing urea from ammonia and carbon dioxide under high temperature and high pressure (NH3+CO2→CO(NH2)2, 150-250℃, 150-350bar), but also a large amount of fossil fuel is consumed for synthesizing raw material ammonia by the Haber-Bosch method (N2+H2→NH3, 350-550℃, 150-350bar), greenhouse gases are released, and problems such as energy crisis and environmental pollution are caused, so a new strategy for producing urea is needed. Compared with the harsh industrial synthesis process, the electrocatalysis technology under room temperature conditions can couple carbon dioxide and potassium nitrite to synthesize urea, and is a renewable synthesis method with application prospects.
[0005] In the process of electrocatalytic synthesis of urea, carbon dioxide reduction, nitrite reduction and even hydrogen evolution reaction are all competitive reactions in the synthesis process of urea, and a large number of product species limit the selectivity of urea synthesis. In the design concept of electrocatalysts, the strategy of adjusting the interface structure and regulating the material surface electron structure is mostly adopted to realize the maximum adsorption and activation of reactant species, so the design and synthesis of high-efficiency catalysts for promoting the formation of C-N bonds and improving the Faraday efficiency of urea synthesis have become a research hotspot in the field of electrocatalytic synthesis of urea. SUMMARY
[0006] The purpose of the application is to cope with the challenge of a large number of competitive reactions, a large number of product species and limited urea selectivity in the process of electrocatalytic synthesis of urea, and a superfine copper oxide powder is synthesized. The superfine powder has a large specific surface area, increases the contact of reactant species, and the characteristics of interface complexation and grain boundary concentration expose a large number of active sites to promote the formation of C-N bonds to synthesize urea. The electrocatalytic test results show that the selectivity of urea is as high as 82.7%. The electrocatalyst has low synthesis cost, mild synthesis conditions, is easy to mass-produce, and has good industrial application prospects.
[0007] In the present application, the ultrafine copper oxide powder refers to the average particle size of copper oxide powder being 10 nm or less; for example, the ultrafine copper oxide powder refers to the average particle size of copper oxide powder being 10 nm, 9 nm, 8 nm, 7 nm, 6 nm or 5 nm or less. The average particle size of the ultrafine copper oxide powder is greater than 0.
[0008] The ultrafine copper oxide nanopowder catalyst for promoting the construction of C-N bond for the efficient synthesis of urea is proposed in the present application, which can be seen from the transmission electron micrograph (as shown in the accompanying Figure 1 ), the synthesized copper oxide catalyst is irregular nanoparticle morphology with a size of about 5 nm, and can exist independently, which is beneficial to the contact and reaction of materials and reaction raw materials in the catalytic process. X-ray diffraction shows CuO phase (as shown in the accompanying Figure 2 ), due to the nanometer size effect, each diffraction peak is broadened, and the position of the signal peak corresponds to the standard crystal card PDF # 48-1548. In further high-resolution transmission micrograph, it can be seen that the lattice of irregular particles is distorted, and even there is amorphous phase of atomic disorder distribution (as shown in the accompanying Figure 3 ). The existence of these distorted lattices and amorphous phases makes the surface atoms of the particles in an activated state, with high surface energy, which is beneficial to the efficient adsorption and conversion of reactants.
[0009] The preparation method of the ultrafine copper oxide nanomaterial for promoting the construction of C-N bond for the synthesis of urea by electrocatalysis in the present application includes low-temperature oil phase reaction and ultrasonic precipitation processes, so that the copper source is dissolved in the oil phase solution, the nanometer powder is precipitated by ultrasonic precipitation at room temperature, and finally washed with anhydrous ethanol and vacuum dried to obtain the target electrocatalyst.
[0010] The present application adopts the following scheme:
[0011] A preparation method of ultrafine copper oxide nanomaterial for promoting the construction of C-N bond for the synthesis of urea by electrocatalysis, comprising the following steps:
[0012] ①Mixing oleylamine and n-octylamine to obtain a mixed solvent, purging Ar into the mixed solvent to remove the dissolved oxygen in the solution, adding cuprous chloride into the mixed solvent, increasing the temperature to 120-150°C (for example, to 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C), maintaining for 1-5h (for example, 1h, 2h, 3h, 4h or 5h) to completely dissolve the cuprous chloride to obtain a cuprous chloride solution; in the cuprous chloride solution, the concentration of cuprous chloride is 1mg / mL-100mg / mL. For example, in the cuprous chloride solution, the concentration of cuprous chloride is 5mg / mL, 10mg / mL, 15mg / mL, 16.7mg / mL, 18mg / mL, 20mg / mL, 25mg / mL, 30mg / mL, 33mg / mL, 34mg / mL, 35mg / mL, 40mg / mL, 45mg / mL, 50mg / mL, 55mg / mL, 60mg / mL, 65mg / mL, 70mg / mL, 75mg / mL, 80mg / mL, 85mg / mL, 90mg / mL, 95mg / mL or 100mg / mL.
[0013] ②After the cuprous chloride is completely dissolved in the solution, the reactor is lowered to 50-90°C, Ar is removed, and the solution is allowed to contact with air to gradually form copper oxide, and the process is maintained for 1-5h;
[0014] ③After the reaction is completed, anhydrous ethanol is added into the reaction solution, ultrasonic treatment is performed, centrifugation is performed to obtain ultrafine copper oxide powder, and finally the obtained grayish brown powder is washed with anhydrous ethanol and vacuum dried to obtain ultrafine copper oxide nanomaterials for promoting electrocatalytic construction of C-N bond to synthesize urea.
[0015] Further, in step ①, the mixed solvent does not contain oxygen during the preparation of the cuprous chloride solution.
[0016] Further, in the synthesis method, the volume ratio (mL) of oleylamine to n-octylamine is 1, and the volume ratio (mL) of the oil phase solution (the oil phase solution is oleylamine and n-octylamine) in the reaction system to the volume (mL) of anhydrous ethanol added in the ultrasonic precipitation process is 1:1-1.5 (for example, the volume ratio is 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1).
[0017] Further, the specific synthesis method is as follows:
[0018] ①In a 50mL three-necked flask, 15mL oleylamine and 15mL n-octylamine are added, Ar is purged to remove the dissolved oxygen in the solution, 500mg of cuprous chloride is accurately weighed and added into the mixed solvent, the temperature is increased to 135°C, and the cuprous chloride is completely dissolved by maintaining for 2h;
[0019] After the cuprous chloride is completely dissolved in the solution, the reactor is lowered to 60 degrees Celsius, Ar is removed, and the solution is gradually allowed to contact air to form copper oxide, and the process is maintained for 5 hours;
[0020] After the reaction is completed, a proper amount of anhydrous ethanol is added to the reaction solution, ultrasonic treatment is performed for 30 minutes, centrifugation is performed to obtain superfine copper oxide powder, the powder is washed with anhydrous ethanol for three times, and vacuum drying is performed to obtain a grayish brown powder, which is the superfine copper oxide nanomaterial for promoting electrocatalytic construction of a C-N bond to synthesize urea.
[0021] The activity of the electrocatalyst prepared in the application can be tested by the following method:
[0022] 5 mg of the catalyst is weighed and dispersed in 1 mL of isopropanol, 20 μL of a nafion binder is added, ultrasonic treatment is performed for 20 minutes, and then 100 μL of the dispersion is accurately taken and drop-casted on a 1 cm 2 square carbon paper surface, and after drying, the carbon paper is used as a working electrode for electrocatalytic testing; a three-electrode test system is used in an H-type electrolytic cell to test the electrocatalytic reaction. The carbon paper drop-casted with the catalyst prepared above is used as a working electrode, a saturated Ag / AgCl electrode is used as a reference electrode, and a 1 cm 2 square Pt sheet is used as a counter electrode, and the H-type electrolytic cell is separated by a nafion 117 proton membrane. 0.01M KNO2 solution is used as an electrolyte solution, CO2 is saturated in advance during the electrocatalytic test, and CO2 reaction gas is continuously introduced during the test. A constant potential test method is used, a certain potential (-0.3 to -0.7V vs RHE) is applied, and the urea content in the solution is detected after a certain period of time;
[0023] The urea content is detected by first detecting the ammonia content in the solution by using an indigo blue method, then adding urease to the solution to hydrolyze urea in the solution into ammonia and CO2, and then detecting the total ammonia content in the solution by using the indigo blue method again. The difference between the two ammonia contents is the amount of ammonia produced by the hydrolysis of urea, and the urea yield is calculated in this way. Through analysis of experimental data, it can be proved that the prepared catalyst can effectively promote electrochemical construction of a C-N bond to synthesize urea, and the selectivity of urea is as high as 82.7%, (as shown in the attached Figure 4 ) which is the best catalytic material for promoting C-N bond formation reported at present.
[0024] The electrocatalyst provided by the application has the following advantages:
[0025] 1. The ultra-small size has a large specific surface area, which increases the contact area with reaction raw materials, and is beneficial to the adsorption and conversion of reaction species.
[0026] 2. The catalyst has more phase composite structure and grain boundary, which exposes more active sites to promote the formation of C-N bond, and improves the selectivity and yield of urea synthesis.
[0027] 3. The catalyst has high reactivity, and the selectivity of electrocatalytic CO2 and KNO2 coupling synthesis of urea is as high as 82.7%, and the electrocatalytic reaction conditions are mild, and the reaction process is easy to control.
[0028] 4. The catalyst synthesis process is simple, the raw materials and cost are low, and has application potential for large-scale production. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 : Transmission electron micrograph of the ultra-fine copper oxide powder prepared in Example 1 of the present application;
[0030] Figure 2 : X-ray diffraction spectrum of the ultra-fine copper oxide powder prepared in Example 1 of the present application;
[0031] Figure 3 : High-resolution transmission electron micrograph of the ultra-fine copper oxide powder prepared in Example 1 of the present application;
[0032] Figure 4 : Selectivity performance of the ultra-fine copper oxide powder prepared in Example 1 of the present application for electrocatalytic synthesis of urea. DETAILED DESCRIPTION
[0033] The present application will be described in detail below in conjunction with the drawings and specific examples. However, the following examples are only for the purpose of explaining the present application, and the protection scope of the present application should include the entire content of the claims, and through the description of the following examples, those skilled in the art can fully realize the entire content of the claims of the present application.
[0034] Example 1:
[0035] In a 50 mL three-necked flask, 15 mL of oleylamine and 15 mL of n-octylamine were added to obtain a mixed solvent, Ar was introduced into the mixed solvent to exclude the dissolved oxygen in the mixed solvent, 500 mg of cuprous chloride was accurately weighed and added into the mixed solvent, the temperature was raised to 135℃, and maintained for 2 h to make the cuprous chloride completely dissolved; after the cuprous chloride was completely dissolved in the solution, the reactor was lowered to 60℃, and the Ar was removed to allow the solution to contact with air to gradually form copper oxide, and this process was maintained for 5 hours; after the reaction was completed, 30 mL of anhydrous ethanol was added to the reaction solution, ultrasonic treatment was performed for 30 minutes, centrifugation was performed at a speed of 10000 rpm to obtain ultra-fine copper oxide powder, and finally the powder was washed with anhydrous ethanol for three times, and the obtained grayish brown powder was vacuum dried to obtain ultra-fine copper oxide nanomaterial with an average particle size of about 5 nm for promoting electrocatalytic construction of C-N bond for synthesis of urea, as shown in Figure 1The average particle size of the dispersed small particle material is about 5 nm, Figure 2 The XRD result shows the phase of CuO, Figure 3 The high-resolution transmission electron micrograph of CuO particles shows that the particle size of CuO nanoparticles is about 5 nm.
[0036] 5 mg of CuO nanoparticle catalyst was weighed and dispersed in 1 mL of isopropanol, and after adding 20 μL of nafion binder, it was ultrasonicated for 20 minutes, and then 100 μL of the dispersion was accurately pipetted and evenly drop-coated on the surface of a 1 cm 2 carbon paper, which was dried and used as a working electrode for electrocatalytic testing; the electrocatalytic reaction test was carried out in a three-electrode test system in an H-type electrolytic cell. The above-mentioned carbon paper drop-coated with the catalyst was used as the working electrode, a saturated Ag / AgCl electrode was used as the reference electrode, and a 1 cm 2 Pt sheet with a size of 1 cm was used as the counter electrode, and the nafion 117 proton membrane was used to separate the middle of the H-type electrolytic cell. 0.01 M KNO2 solution was used as the electrolyte solution, and CO2 was introduced in advance to saturation during the electrocatalytic test, and CO2 reaction gas was continuously introduced during the test. A constant potential test method was used, a certain potential (-0.3 to -0.7 V vs RHE) was applied and the reaction was continued for a period of time, and then the urea content in the solution was detected;
[0037] Among them, for the detection of urea content, first, the indigo blue method was used to detect the ammonia content in the solution, then urease was added to the solution to hydrolyze the urea in the solution into ammonia and CO2, and the indigo blue method was used again to detect the total ammonia content in the solution. The difference between the two ammonia contents is the amount of ammonia produced by the hydrolysis of urea, and the urea yield is calculated in this way. Through the analysis of experimental data, it can be proved that the prepared catalyst can effectively promote the electrochemical construction of C-N bond to synthesize urea, (such as Figure 4 ) The selectivity of urea is as high as 82.7%, which is the best catalyst material for promoting C-N bond formation reported so far.
[0038] Example Two:
[0039] In a 50 mL three-necked flask, 15 mL of oleylamine and 15 mL of n-octylamine were added to obtain a mixed solvent, Ar was introduced into the mixed solvent to exclude the dissolved oxygen in the mixed solvent, 1000 mg of cuprous chloride was accurately weighed and added into the mixed solution, the temperature was raised to 135°C, and maintained for 2 h to make the cuprous chloride completely dissolved; after the cuprous chloride was completely dissolved in the solution, the reactor was lowered to 60°C, and then Ar was removed to allow the solution to gradually generate copper oxide by contacting with air, and this process was maintained for 5 hours; after the reaction was completed, 30 mL of anhydrous ethanol was added into the reaction solution, ultrasonic treatment was performed for 30 minutes, centrifugation was performed at a speed of 10000 rpm to obtain superfine copper oxide powder, and finally the superfine copper oxide powder was washed with anhydrous ethanol for three times, and the obtained gray-brown powder was vacuum dried to obtain superfine copper oxide nanomaterials with an average particle size of about 5 nm for promoting the electrocatalytic construction of C-N bond to synthesize urea.
[0040] Example Three
[0041] In a 50 mL three-necked flask, 15 mL of oleylamine and 15 mL of n-octylamine were added to obtain a mixed solvent, Ar was introduced into the mixed solvent to exclude the dissolved oxygen in the mixed solvent, 1000 mg of cuprous chloride was accurately weighed and added into the mixed solution, the temperature was raised to 135°C, and maintained for 2 h to make the cuprous chloride completely dissolved; after the cuprous chloride was completely dissolved in the solution, the reactor was lowered to 60°C, and then Ar was removed to allow the solution to gradually generate copper oxide by contacting with air, and this process was maintained for 5 hours; after the reaction was completed, 30 mL of anhydrous ethanol was added into the reaction solution, ultrasonic treatment was performed for 30 minutes, centrifugation was performed at a speed of 10000 rpm to obtain superfine copper oxide powder, and finally the superfine copper oxide powder was washed with anhydrous ethanol for three times, and the obtained gray-brown powder was vacuum dried to obtain superfine copper oxide nanomaterials with an average particle size of about 5 nm for promoting the electrocatalytic construction of C-N bond to synthesize urea.
[0042] Example Four
[0043] In a 50 mL three-necked flask, 15 mL of oleylamine and 15 mL of n-octylamine were added to obtain a mixed solvent, Ar was introduced into the mixed solvent to exclude the dissolved oxygen in the mixed solvent, 1000 mg of cuprous chloride was accurately weighed and added into the mixed solution, the temperature was raised to 135°C, and maintained for 2 h to make the cuprous chloride completely dissolved; after the cuprous chloride was completely dissolved in the solution, the reactor was lowered to 60°C, and then Ar was removed to allow the solution to gradually generate copper oxide by contacting with air, and this process was maintained for 5 hours; after the reaction was completed, 30 mL of anhydrous ethanol was added into the reaction solution, ultrasonic treatment was performed for 30 minutes, centrifugation was performed at a speed of 10000 rpm to obtain superfine copper oxide powder, and finally the superfine copper oxide powder was washed with anhydrous ethanol for three times, and the obtained gray-brown powder was vacuum dried to obtain superfine copper oxide nanomaterials with an average particle size of about 5 nm for promoting the electrocatalytic construction of C-N bond to synthesize urea.
[0044] Example Five
[0045] In a 50mL three-necked flask, 15mL oleylamine and 15mL n-octylamine were added to obtain a mixed solvent, Ar was introduced into the mixed solvent to exclude the dissolved oxygen in the mixed solvent, 1000mg cuprous chloride was accurately weighed and added into the mixed solution, the temperature was raised to 135℃ and maintained for 1h to make the cuprous chloride completely dissolved; after the cuprous chloride was completely dissolved in the solution, the reactor was lowered to 60℃, Ar was removed, and the solution was allowed to contact with air to gradually generate copper oxide, and the process was maintained for 5h; after the reaction was completed, 30mL of anhydrous ethanol was added into the reaction solution, ultrasonic treatment was performed for 60min, centrifugation was performed at a speed of 10000rpm to obtain superfine copper oxide powder, and finally the obtained powder was washed with anhydrous ethanol for three times and vacuum dried to obtain a grayish brown powder, which was the superfine copper oxide nanomaterial with an average particle size of about 5nm for promoting electrocatalytic construction of C-N bond to synthesize urea.
[0046] The part of the present application which is not described in detail belongs to the known technology of those skilled in the art. The above-described embodiments are only used to describe the preferred embodiments of the present application, and the preferred embodiments do not describe all the details and limit the present application to the specific embodiments. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope of the present application defined in the claims.
Claims
1. An application of an ultrafine copper oxide nanomaterial for directly promoting the electrocatalytic construction of CN bonds in the synthesis of urea, characterized in that, The ultrafine copper oxide nanomaterial is prepared by the following method, which includes the following steps: ① Mix oleylamine and n-octylamine to obtain a mixed solvent. Pass Ar into the mixed solvent to remove dissolved oxygen. Add cuprous chloride to the mixed solvent. Raise the temperature to 120~150℃ and maintain it for 1~5 h to completely dissolve the cuprous chloride and obtain a cuprous chloride solution. ② After the temperature of the cuprous chloride solution drops to 50~90℃, Ar is removed, allowing the solution to come into contact with air and gradually generate copper oxide. This process is maintained for 1~5 hours. ③ After the reaction is complete, anhydrous ethanol is added to the reaction solution, followed by sonication and centrifugation to obtain ultrafine copper oxide powder. Finally, the powder is washed with anhydrous ethanol and vacuum dried to obtain a grayish-brown powder, which is the ultrafine copper oxide nanomaterial that promotes the electrocatalytic construction of CN bonds to synthesize urea. The ultrafine copper oxide nanomaterial refers to copper oxide nanomaterials with an average particle size of less than 10 nm, and the ultrafine copper oxide powder has an average particle size greater than 0. The synthesized copper oxide catalyst has an irregular nanoparticle morphology and can exist separately. The lattice of the irregular particles is distorted, and there is also an amorphous phase with disordered atomic distribution. The presence of these distorted lattices and amorphous phases keeps the surface atoms of the particles in an activated state with high surface energy, which is beneficial to the efficient adsorption and conversion of reactants. In step ①, the ratio of cuprous chloride mass to the mixed solvent of oleylamine and n-octylamine ranges from 500 mg / 30 mL to 1000 mg / 30 mL.
2. The application as described in claim 1, characterized in that, In step ①, the temperature is raised to 135℃ and maintained for 1-5 hours.
3. The application as described in claim 1, characterized in that, In step ③, the ultrasonic time after adding anhydrous ethanol is 0.5 h to 2 h.