Rare earth modified cuprous oxide as well as preparation method and application thereof

Abstract

The invention discloses rare earth modified cuprous oxide and a preparation method and application thereof.According to the rare earth modified cuprous oxide, a conductive material serves as a carrier, cuprous oxide doped with rare earth metal is generated on the carrier in situ, and the rare earth metal is introduced into crystal lattices of the cuprous oxide; the preparation method comprises the following steps: mixing copper salt, rare earth salt and urea, dissolving in a solvent, uniformly mixing, putting the carrier into the solution, and performing solvothermal reaction to obtain the rare earth modified cuprous oxide. According to the invention, rare earth metal is introduced into Cu2O crystal lattices, so that the catalytic efficiency of the catalyst for generating ethylamine through electro-catalysis acetonitrile hydrogenation is improved, high Faraday efficiency can be maintained in acetonitrile electro-catalysis hydrogenation under industrial current, and the catalyst has considerable application value.

Description

Technical Field

[0001] The present invention relates to cuprous oxide and a preparation method and application thereof, and in particular to rare earth modified cuprous oxide and a preparation method and application thereof. Background Art

[0002] Ethylamine (EA) is a basic chemical widely used in industry and organic synthesis. It is a key component and intermediate in many pharmaceuticals, agrochemicals, dyes, emulsifiers, and fine chemicals. The global ethylamine market is expected to exceed US$2 billion by 2024. This substantial market size demonstrates the enormous commercial value of EA. Currently, thermal catalytic acetonitrile (AN) hydrogenation using hydrogen (H2) as a hydrogen source is the most important industrial method for producing EA. However, this method generally requires high temperature and high pressure, produces coupling byproducts such as diethylamine (DA) and triethylamine (TA), and the use of H2 increases transportation and storage costs. Therefore, there is an urgent need to find a safe, sustainable, and industrially viable alternative to thermal acetonitrile hydrogenation. In the current global pursuit of carbon neutrality, electrochemical hydrogenation of acetonitrile (AN-ECH) offers a green and sustainable method for synthesizing EA. Currently, copper-based catalysts have been found to exhibit good activity in the electrochemical hydrogenation of AN to EA, but cuprous oxide (CuO) has not been reported to be used. Furthermore, the catalytic activity of CuO (e.g., Faradaic efficiency) needs to be improved. Summary of the Invention

[0003] Objectives of the invention: The first objective of the present invention is to provide a rare earth-modified cuprous oxide having improved activity in the electrocatalytic hydrogenation of acetonitrile; the second objective of the present invention is to provide a method for preparing the rare earth-modified cuprous oxide; and the third objective of the present invention is to provide use of the rare earth-modified cuprous oxide in catalyzing the production of ethylamine from acetonitrile.

[0004] Technical solution: The rare earth modified cuprous oxide of the present invention uses a conductive material as a carrier, in situ generates cuprous oxide doped with rare earth metals on the carrier, and introduces rare earth metals into the crystal lattice of cuprous oxide.

[0005] Preferably, the rare earth metal is europium, cerium or gadolinium.

[0006] Preferably, the rare earth metal is europium, and the atomic ratio of europium to metal atoms in the raw material is 2-12%.

[0007] Preferably, the rare earth metal is cerium or gadolinium, and the atomic ratio of the rare earth metal to the metal atoms in the raw material is 12-22%.

[0008] Preferably, the carrier is nickel foam or copper foam. Further preferably, the thickness of the carrier is 0.1 to 1 mm.

[0009] The preparation method of the rare earth modified cuprous oxide of the present invention comprises the following steps: taking copper salt and rare earth salt and mixing them with urea and dissolving them in a solvent; after mixing them evenly, putting a carrier into the solution and performing solvent thermal reaction to obtain the rare earth modified cuprous oxide.

[0010] During the solvothermal reaction, copper salts undergo an oxidation-reduction reaction with urea to generate cuprous oxide. During the formation of the cuprous oxide lattice, rare earth atoms are introduced to replace the Cu atomic sites, and finally rare earth-modified cuprous oxide is generated in one step.

[0011] Preferably, the temperature of the solvent thermal reaction is 100-150° C.; further preferably, the reaction time is 10-15 h.

[0012] Preferably, the molar ratio of the copper and rare earth metal salts to urea is 9:4 to 9:8. The role of urea is to provide an alkaline environment and an oxygen source.

[0013] Preferably, the molar concentration of urea is 25 to 50 mmol L -1 The concentration of urea will change the alkalinity of the reaction solution and thus affect the formation of cuprous oxide.

[0014] Preferably, the copper salt is copper nitrate, copper chloride, copper acetate or copper sulfate.

[0015] Preferably, the rare earth salt is a rare earth nitrate, a rare earth chloride, a rare earth acetylacetonate, or a rare earth acetate. The rare earth modified cuprous oxide of the present invention is used in the electrocatalytic hydrogenation of acetonitrile to produce ethylamine.

[0016] Preferably, the support further includes pretreatment, specifically: alcohol washing, water washing and acid washing. Alcohol washing can wash away organic impurities on the surface of the nickel foam; acid washing can wash away the oxide layer on the surface of the nickel foam.

[0017] Invention Mechanism: The present inventors unexpectedly discovered that incorporating rare earth metals into the CuO lattice improves the catalytic efficiency of the electrocatalytic hydrogenation of acetonitrile to ethylamine, and maintains a high Faradaic efficiency in the electrocatalytic hydrogenation of acetonitrile at industrial-grade currents. This is likely because the incorporation of rare earth metals enables electron transfer from the rare earth metals to copper sites, enhancing acetonitrile adsorption and thus enhancing acetonitrile hydrogenation activity.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) the rare earth metal-modified cuprous oxide of the present invention has improved activity in the electrocatalytic hydrogenation of acetonitrile; (2) the rare earth metal is europium, which has the highest catalytic activity; (3) the present invention uses rare earth salt, copper salt and urea as raw materials and adopts a one-step aqueous phase to synthesize rare earth metal-modified cuprous oxide. The raw materials used in this method are all non-(low) toxic reagents and are easy to purchase. The process is simple and easy to prepare on a large scale; (4) the catalyst of the present invention has excellent electrocatalytic performance and stability for the acetonitrile hydrogenation reaction in an alkaline environment and has very broad commercial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The X-ray diffraction (XRD) pattern of the catalyst RE-Cu2O@NF prepared in Example 1 of the present invention;

[0020] Figure 2 High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the catalyst RE-Cu2O@NF prepared in Example 1 of the present invention, (a) is a 500 nm scale, and (b) is a 100 nm scale;

[0021] Figure 3 These are spherical aberration-corrected high-resolution scanning electron microscopy (AC-HRTEM) images of the catalyst RE-Cu2O@NF prepared in Example 1 of the present invention, with a 2 nm scale and a 1 nm scale, respectively;

[0022] Figure 4 This is a high-resolution Eu 3d X-ray photoelectron spectroscopy (XPS) of the catalyst RE-Cu2O@NF prepared in Example 1 of the present invention;

[0023] Figure 5 Polarization curves (LSV) of the catalyst RE-Cu2O@NF prepared in Example 1 of the present invention and the Cu2O prepared in Comparative Example 1 in 1 M acetonitrile and 1 M KOH;

[0024] Figure 6 Graph showing the Faraday efficiency and yield of acetonitrile hydrogenation in 8 wt % acetonitrile and 1 M KOH for the catalysts RE-Cu2O@NF prepared in Inventive Examples 1 to 8 and Comparative Examples 1 to 2 and Cu2O prepared in Comparative Example 1;

[0025] Figure 7 This is a graph showing the stability of the industrial-grade acetonitrile hydrogenation of the catalyst Eu-Cu2O@NF prepared in Example 1 of the present invention in 1 M KOH containing 8 wt% acetonitrile. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0027] Example 1

[0028] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is europium, and the atomic molar ratio of europium to metal atoms is 2%, comprises the following steps:

[0029] (1) Pretreatment of nickel foam

[0030] Take the thickness of 0.5mm, 2*4cm -2 The nickel foam of different sizes was first pretreated by ultrasonic washing with ethanol for 5 minutes, then ultrasonic washing with water for 5 minutes, and finally ultrasonic washing with 3M hydrochloric acid for 5 minutes.

[0031] (2) Preparation of Eu-Cu2O@NF electrocatalyst

[0032] 2.2 mmol of copper nitrate and 0.05 mmol of europium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110°C for 12 h to obtain rare earth Eu-modified cuprous oxide Eu-Cu2O@NF.

[0033] Example 2

[0034] On the basis of Example 1, the amount of copper nitrate was changed to 2.15 mol, the amount of europium nitrate was changed to 0.1 mol, and the atomic molar ratio of europium to metal atoms in the rare earth modified cuprous oxide was 5%.

[0035] Example 3

[0036] On the basis of Example 1, the amount of copper nitrate was changed to 2.1 mol, the amount of europium nitrate was changed to 0.15 mol, and the atomic molar ratio of europium to metal atoms in the rare earth modified cuprous oxide was 7%.

[0037] Example 4

[0038] On the basis of Example 1, the amount of copper nitrate was changed to 2.05 mol, the amount of europium nitrate was changed to 0.2 mol, and the atomic molar ratio of europium to metal atoms in the rare earth modified cuprous oxide was 9%.

[0039] Example 5

[0040] On the basis of Example 1, the amount of copper nitrate was changed to 2 mol, the amount of europium nitrate was changed to 0.25 mol, and the atomic molar ratio of europium to metal atoms in the rare earth modified cuprous oxide was 12%.

[0041] Example 6

[0042] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is cerium, and the atomic molar ratio of cerium to metal atoms is 12%, comprises the following steps:

[0043] (1) The pretreatment of nickel foam is the same as in Example 1;

[0044] (2) Preparation of Ce-Cu2O@NF electrocatalyst

[0045] 2 mmol of copper nitrate and 0.25 mmol of cerium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110 ° C for 12 h to obtain rare earth Ce-modified cuprous oxide Ce-Cu2O@NF.

[0046] Example 7

[0047] On the basis of Example 6, the amount of copper nitrate was changed to 1.75 mol, and the amount of cerium nitrate was changed to 0.5 mol. In the rare earth modified cuprous oxide, the atomic molar ratio of cerium to metal atoms was 22%.

[0048] Example 8

[0049] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is gadolinium, and the atomic molar ratio of gadolinium to metal atoms is 12%, comprises the following steps:

[0050] (1) The pretreatment of nickel foam is the same as in Example 1;

[0051] (2) Preparation of Gd-Cu2O@NF electrocatalyst

[0052] 2 mmol of copper nitrate, 0.25 mmol of gadolinium nitrate and 0.09 g of urea were mixed and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110°C for 12 h to obtain rare earth Gd-modified cuprous oxide Gd-Cu2O@NF.

[0053] Example 9

[0054] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is samarium, and the atomic ratio of samarium to metal atoms is 12%, comprises the following steps:

[0055] (1) The pretreatment of nickel foam is the same as in Example 1;

[0056] (2) Preparation of Sm-Cu2O@NF electrocatalyst

[0057] 2 mmol of copper nitrate and 0.25 mmol of samarium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110 ° C for 12 h to obtain rare earth Sm-modified cuprous oxide Sm-Cu2O@NF.

[0058] Example 10

[0059] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is neodymium, and the atomic ratio of neodymium to metal atoms is 12%, comprises the following steps:

[0060] (1) The pretreatment of nickel foam is the same as in Example 1;

[0061] (2) Preparation of Nd-Cu2O@NF electrocatalyst

[0062] 2 mmol of copper nitrate and 0.25 mmol of neodymium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110°C for 12 h to obtain rare earth Nd-modified cuprous oxide Nd-Cu2O@NF.

[0063] Example 11

[0064] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is terbium, and the atomic ratio of terbium to metal atoms is 12%, comprises the following steps:

[0065] (1) The pretreatment of nickel foam is the same as in Example 1;

[0066] (2) Preparation of Tb-Cu2O@NF electrocatalyst

[0067] 2 mmol of copper nitrate and 0.25 mmol of terbium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110°C for 12 h to obtain rare earth Tb-modified cuprous oxide Tb-Cu2O@NF.

[0068] Example 12

[0069] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is holmium, and the atomic ratio of holmium to metal atoms is 12%, comprises the following steps:

[0070] (1) The pretreatment of nickel foam is the same as in Example 1;

[0071] (2) Preparation of Ho-Cu2O@NF electrocatalyst

[0072] 2 mmol of copper nitrate and 0.25 mmol of holmium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110 ° C for 12 h to obtain rare earth Ho-modified cuprous oxide Ho-Cu2O@NF.

[0073] Example 13

[0074] The rare earth modified cuprous oxide of the present invention, wherein the rare earth metal is erbium, and the atomic ratio of erbium to metal atoms is 12%, comprises the following steps:

[0075] (1) The pretreatment of nickel foam is the same as in Example 1;

[0076] (2) Preparation of Er-Cu2O@NF electrocatalyst

[0077] 2 mmol of copper nitrate and 0.25 mmol of erbium nitrate were mixed with 0.09 g of urea and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110 ° C for 12 h to obtain rare earth Er-modified cuprous oxide Er-Cu2O@NF.

[0078] Comparative Example 1

[0079] A method for preparing Cu2O comprises the following steps:

[0080] (1) The pretreatment of nickel foam is the same as in Example 1;

[0081] (2) Preparation of Cu2O@NF electrocatalyst

[0082] 2.25 mmol of copper nitrate and 0.09 g of urea were mixed and dissolved in deionized water. After thorough mixing, the treated nickel foam was placed into the solution and subjected to a solvothermal reaction at 110 °C for 12 h to obtain Cu2O@NF.

[0083] Comparative Example 2

[0084] On the basis of Example 6, the amount of copper nitrate was changed to 2.1 mol, and the amount of cerium nitrate was changed to 0.15 mol. In the rare earth modified cuprous oxide, the atomic molar ratio of cerium to metal atoms was 7%.

[0085] Structural characterization

[0086] The Eu-Cu2O@NF electrocatalyst prepared in Example 1 was physically characterized by TEM, HRTEM and XRD.

[0087] From XRD ( Figure 1 ) It can be seen that the diffraction peak of the sample in Example 1 is consistent with the standard card of Cu2O and there is a slight offset, which proves the formation of Eu-modified Cu2O phase. At the same time, the diffraction peak of the sample in Comparative Example 1 synthesized under the same conditions is completely consistent with the standard card of Cu2O.

[0088] From SEM and TEM ( Figure 2 ) It can be seen that the size of Eu-Cu2O@NF prepared in Example 1 is 0.5-1 μm, and the morphology is mainly nano-needle-shaped.

[0089] From the spherical aberration electron microscope ( Figure 3 ) It can be seen that the atomic signal marked by the dotted line is significantly stronger than the surrounding signals, proving that the rare earth Eu atoms are successfully doped into the cuprous oxide lattice.

[0090] From XPS( Figure 4 ) It can be seen that the 3d signal of europium appears around 1150 eV, which also proves the successful introduction of europium.

[0091] Performance Testing

[0092] 1. The electrocatalytic hydrogenation performance of acetonitrile was tested in 1M acetonitrile and 1M KOH alkaline electrolyte using the Eu-Cu2O@NF electrocatalyst prepared in Example 1 and the Cu2O@NF catalyst prepared in Comparative Example 1. The LSV curves obtained were as follows: Figure 5 shown.

[0093] Depend on Figure 5 It can be seen that the Eu-Cu2O@NF electrocatalyst exhibits better performance than Cu2O@NF, with the response current at -1.3 V increasing from 170 mA cm -2 Increased to 270 mA cm -2 Therefore, the introduction of rare earth Eu effectively improved the acetonitrile hydrogenation performance of Cu2O.

[0094] 2. The electrocatalysts prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were used to test the electrocatalytic hydrogenation of acetonitrile in an alkaline electrolyte containing 8 wt% acetonitrile and 1 M KOH. The Faradaic efficiency obtained was as follows: Figure 6 shown.

[0095] Depend on Figure 6 It can be seen that the Faraday efficiency of Examples 1 to 8 and Comparative Examples 1 to 2 is the left bar graph, and the yield is the right bar graph. When the introduced rare earth metal is europium, in Examples 1 to 5, as the amount of europium introduced increases, the Faraday efficiency (FE) first decreases (98% → 90%), then increases (90% → 95%), and then decreases again (95% → 96%). When the introduced rare earth metal is cerium, when the atomic molar ratio is 7% (Comparative Example 2), the FE of Cu2O does not increase but decreases (78% → 74%). When the atomic molar ratio increases to 12% (Examples 6 and 7), the FE is improved (78% → 85%), and there is no significant change in FE as the amount of cerium introduced increases. When the introduced rare earth metal is gadolinium, when the atomic molar ratio is 12% (Example 8), the FE (79%) is basically equivalent to the effect of the same amount of cerium introduced (78%).

[0096] The rare earth-modified Cu2O electrocatalysts of Examples 1 to 8 exhibited better performance than Cu2O@NF. Therefore, rare earth has good universality in improving the acetonitrile hydrogenation performance of Cu2O.

[0097] 3. The Eu-Cu2O@NF electrocatalyst prepared in Example 1 was used to conduct an industrial-grade current test for ethylamine production in an alkaline electrolyte of 1 M KOH containing 8 wt% acetonitrile at a current of 2 A. The results are as follows: Figure 7 shown.

[0098] from Figure 7 It can be seen that the Eu-Cu2O@NF electrocatalyst can maintain a current of 2A for 26 hours and maintain a Faradaic efficiency of about 80%, proving its prospect for industrial application.

Claims

1. A rare earth modified cuprous oxide, characterized in that: With a conductive material as a carrier, cuprous oxide doped with a rare earth metal is in-situ generated on the carrier, and the rare earth metal is introduced into the crystal lattice of the cuprous oxide.

2. The rare earth modified cuprous oxide according to claim 1, characterized in that The rare earth metal is europium, cerium or gadolinium.

3. The rare earth modified cuprous oxide according to claim 1, characterized in that The rare earth metal is europium, and the atomic molar ratio of europium to metal atoms in the raw material is 2-12%.

4. The rare earth modified cuprous oxide according to claim 1, characterized in that The rare earth metal is cerium or gadolinium, and the atomic molar ratio of the rare earth metal to the metal atoms in the raw material is 12-22%.

5. The rare earth modified cuprous oxide according to claim 1, characterized in that The carrier is foamed nickel or foamed copper.

6. A method for preparing rare earth modified cuprous oxide according to any one of claims 1 to 5, characterized in that: The following steps are involved: Copper salt and rare earth salt are mixed with urea and dissolved in a solvent. After mixing evenly, a carrier is put into the solution and a solvent thermal reaction is performed to obtain rare earth modified cuprous oxide.

7. The method for preparing rare earth modified cuprous oxide according to claim 6, wherein: The temperature of the solvent thermal reaction is 100-150°C.

8. The method for preparing rare earth modified cuprous oxide according to claim 6, wherein: The molar ratio of the copper to the total rare earth metal salt to the urea is 9:4 to 9:

8.

9. The method for preparing rare earth modified cuprous oxide according to claim 6, wherein: The molar concentration of urea is 25-50 mmol L -1 .

10. Use of the rare earth modified cuprous oxide according to any one of claims 1 to 5 in the electrocatalytic hydrogenation of acetonitrile to produce ethylamine.

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