Electrocatalyst material of organic molecule modified metal hydroxide as well as preparation method and application of electrocatalyst material

Abstract

The invention relates to an electrocatalyst material of an organic molecule modified metal hydroxide as well as a preparation method and application of the electrocatalyst material. Organic molecules and metal salt are mixed and then dissolved in a solvent, the hydroxide integrated electrode material which is directly loaded on a substrate and modified by the organic molecules can be obtained under a specific deposition potential, and the hydroxide integrated electrode material shows excellent activity and selectivity in a reaction for preparing adipic acid through electro-catalysis of cyclohexanone and cyclohexanol oxidation. Compared with a traditionally prepared adipic acid electrosynthesis catalyst, the organic molecule modified metal hydroxide catalyst has the advantages of excellent performance, simplicity in operation and large-scale preparation, and can be applied to various reactions for electrocatalytic synthesis of dicarboxylic acid; the problems of low catalytic efficiency and complex catalyst preparation in the electro-catalytic synthesis reaction are solved.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalytic organic synthesis, and specifically relates to an electrocatalyst material modified by an organic molecule with a metal hydroxide, a preparation method thereof, and an application, specifically an application in the reaction of electrocatalytic oxidation of cyclohexanone and cyclohexanol to prepare adipic acid. Background Art

[0002] Adipic acid, also known as fatty acid, is a white monoclinic crystal at room temperature. It is the most valuable dibasic acid in aliphatic dibasic acids and is widely used in fields such as food, medicine, and chemical industry. In 2020, the global demand for adipic acid was 3.17 million tons, with a market value of over $7 billion. Among them, adipic acid is a key intermediate for synthesizing nylon and polyurethane, and can be further processed for the production of plasticizers, cosmetic additives, gelatin, lubricants, fertilizers, adhesives, pesticides, paper, and waxes. Currently, industrial production of adipic acid still uses traditional catalytic oxidation methods, using Cu as a catalyst and HNO 3 and NH 4 VO 3 as oxidants to oxidize cyclohexanone and cyclohexanol (collectively referred to as KAoil) to prepare adipic acid under the conditions of 0.1 - 0.4 Mpa and 60 - 80 °C. The strong acid heating conditions of this method pose high requirements for the anti-corrosion performance of production equipment. At the same time, the generation of nitrogen oxide pollutants such as N 2 O brings great harm to the environment, and the use of non-renewable fossil energy as fuel also does not meet the requirements of green and sustainable development.

[0003] Electrocatalytic oxidation of cyclohexanone and cyclohexanol to prepare adipic acid provides a sustainable approach to solve the above problems. The use of renewable electric energy and water as an oxygen source avoids the use of strong acids and strong oxidants, and the electrocatalytic process at room temperature and normal pressure avoids the harsh reaction conditions of traditional catalytic oxidation. At the same time, the anodic oxidation reaction for electrocatalytic preparation of adipic acid can be coupled with cathodic hydrogen production to further improve the added value of reaction products. Although there are many advantages, the process of electrocatalytic oxidation of KAoil to prepare adipic acid faces problems such as low catalytic efficiency due to slow reaction kinetics, poor solubility of organic reactants in water, and poor catalytic selectivity. The large-scale preparation of catalysts also faces difficulties such as cumbersome synthesis steps.

[0004] Therefore, the efficient preparation of an electrocatalyst for adipic acid electrosynthesis with high activity and high selectivity is the key to realizing the large-scale synthesis of adipic acid. Summary of the Invention

[0005] In view of the problems and challenges in the above technologies, the present invention provides an electrocatalyst material of an organic molecule-modified metal hydroxide, its preparation method and application, which is a non-precious metal adipic acid electro-synthesis catalyst. The metal hydroxide catalyst provided by the present invention has a unique organic molecule-modified structure, and the modified organic molecules form a hydrophobic region, effectively enhancing the enrichment of cyclohexanone and cyclohexanol molecules around the catalyst and improving the compatibility of organic substrate molecules in an aqueous solution. At the same time, the Π-Π interaction between organic molecules effectively improves the stability of the catalyst. The heteroatoms at the ends of the organic ligands coordinate with the metal sites, optimizing the electronic structure of the metal sites and promoting the electron transfer and molecular mass transfer processes during catalysis. These factors enable the present invention to have excellent catalytic performance for electrocatalytically preparing adipic acid from KA oil.

[0006] The object of the present invention can be achieved through the following solutions:

[0007] In the first aspect, the present invention provides an electrocatalyst material of an organic molecule-modified metal hydroxide, and the electrocatalyst material includes a substrate, a metal hydroxide loaded on the substrate, and an organic molecule modified on the metal hydroxide;

[0008] The N atom in the organic molecule coordinates with the metal in the metal hydroxide, thereby being modified on the metal hydroxide.

[0009] According to some embodiments of the present invention, the organic molecule (A) includes one or more of phthalazine, 2,2-bipyridine, 4,4-bipyridine, 1,2-bis(4-pyridyl)ethane, 5-NO 2 -1,10-phenanthroline.

[0010] According to some embodiments of the present invention, the metal hydroxide includes one or more of cobalt hydroxide, nickel hydroxide, iron hydroxide, cerium hydroxide, chromium hydroxide, and aluminum hydroxide.

[0011] According to some embodiments of the present invention, the substrate can be selected from carbon cloth, graphite sheet, nickel foam, and copper foam. A variety of carriers can be used as deposition electrodes.

[0012] In the second aspect, the present invention discloses a preparation method of an electrocatalyst material of an organic molecule-modified metal hydroxide, including the following steps:

[0013] Adding the organic molecule (A) into an electrolyte containing a metal salt (B), and performing electro-deposition using a three-electrode system, with the substrate material as the working electrode, to obtain the electrocatalyst material.

[0014] According to some embodiments of the present invention, the organic molecule (A) includes one or more of phthalazine, 2,2-bipyridine, 4,4-bipyridine, 1,2-bis(4-pyridyl)ethane, 5-NO2 One or more of 1,10-phenanthroline.

[0015] According to some embodiments of the present invention, the metal salt (B) is a metal nitrate; the metal includes one or more of cobalt, nickel, iron, cerium, chromium, and aluminum.

[0016] According to some embodiments of the present invention, the molar ratio of the organic molecule (A) to the metal salt (B) is 1:1 to 1:3.

[0017] According to some embodiments of the present invention, in the electrolyte, the solubility of the metal salt (B) is 0.1 to 0.3 M, preferably 0.15 to 0.22 M.

[0018] According to some embodiments of the present invention, the solvent in the electrolyte includes one or more of water and N,N-dimethylformamide, preferably water and N,N-dimethylformamide.

[0019] According to some embodiments of the present invention, during electrodeposition, the electrode clamp clamps the substrate material as the working electrode, and the obtained electrocatalyst material is loaded on the substrate material. The deposition potential for electrodeposition is -1 to -3 V, and the time is 180 to 220 s, preferably a deposition potential of -2 V and a time of 200 s. The Ag / AgCl electrode is used as the reference electrode, and a Chenhua 760e workstation is adopted. The potentiostatic deposition mode is selected, and the deposition potential is set to -2 V.

[0020] According to some embodiments of the present invention, the temperature (synthesis temperature) of the electrodeposition is 20 to 30 °C, preferably room temperature of 25 °C.

[0021] According to some embodiments of the present invention, the obtained electrocatalyst material is also subjected to washing and drying treatments. The solvents used during washing include one or more of water and ethanol. The drying method is drying at 50 to 70 °C, preferably 60 °C.

[0022] According to some embodiments of the present invention, the obtained electrocatalyst material does not require subsequent heat treatment.

[0023] In a third aspect, the present invention also provides an application of the electrocatalyst material in the reaction of electrocatalytic oxidation for preparing adipic acid.

[0024] The raw material compounds of the reaction include cyclohexanol, cyclohexanone, and their mixtures. The present invention uses the yield of adipic acid per unit time and per unit area to evaluate the catalyst. The electrocatalyst material of the present invention can be used to highly selectively catalyze the oxidation of cyclohexanone and cyclohexanol to prepare adipic acid.

[0025] The reaction is a catalytic KAoil conversion reaction, and the electrocatalyst material serves as the working electrode. The adipic acid electro-synthesis catalyst of the present invention has a unique integrated property and can be directly used as the working electrode for catalyzing the KAoil conversion.

[0026] The present invention directly prepares a metal hydroxide catalyst modified with organic molecules supported on a carrier by a one-step electrodeposition method, and uses this catalyst for electrocatalytically preparing adipic acid from cyclohexanone and cyclohexanol to obtain high-value-added chemicals.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The preparation process of the integrated electrode material of the metal hydroxide modified with organic molecules directly supported on the substrate proposed by the present invention is simple, easy to operate, and can be prepared on a large scale.

[0029] (2) The obtained catalyst can catalytically electro-synthesize adipic acid from cyclohexanone and cyclohexanol, which are industrially important reactions, with high activity and high selectivity at a wide potential, and pure hydrogen can be obtained at the cathode to achieve the green preparation of high-value-added chemical products. Description of the Drawings

[0030] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0031] Figure 1 is a synthesis schematic diagram;

[0032] Figure 2 is the X-ray diffraction pattern (XRD) of the nickel hydroxide catalyst modified with 4,4'-bipyridine molecules deposited in Example 1 and the standard diffraction card (PDF card) of nickel hydroxide;

[0033] Figure 3 is the comparison of the yields per unit time and per unit area of electrocatalytically preparing adipic acid from cyclohexanone by the nickel hydroxide catalyst modified with 4,4'-bipyridine molecules and the nickel hydroxide catalyst at 1.43 V to 1.73 V (vs. RHE);

[0034] Figure 4 is the comparison of the yields per unit time and per unit area of electrocatalytically preparing adipic acid from cyclohexanone by the nickel hydroxide catalysts modified with phthalazine, 2,2'-bipyridine, 1,2-bis(4-pyridyl)ethane, 5-NO 2 -1,10-phenanthroline molecules and the unmodified nickel hydroxide catalyst at 1.53 V (vs. RHE);

[0035] Figure 5Yield comparison of bimetallic hydroxide catalysts modified with 4,4'-bipyridine molecules and unmodified bimetallic hydroxide catalysts for the electrocatalytic preparation of adipic acid from cyclohexanone after two hours of electrolysis at 1.53 V (vs. RHE);

[0036] Figure 6 Yield comparison per unit time and per unit area of nickel hydroxide modified with sodium dodecyl sulfate and benzoate radicals and nickel hydroxide modified with 4,4'-bipyridine molecules prepared by the same method for the electrocatalytic preparation of adipic acid from cyclohexanone at 1.53 V (vs. RHE). Detailed implementation mode

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following examples are implemented on the premise of the technical solution of the present invention, providing detailed implementation methods and specific operation processes, which will help those skilled in the art to further understand the present invention. It should be noted that the protection scope of the present invention is not limited to the following embodiments. Several adjustments and improvements made on the premise of the concept of the present invention all belong to the protection scope of the present invention.

[0038] Example 1

[0039] In this example, a one-step electrodeposition method was used to prepare a metal hydroxide catalyst modified with an organic molecule. As Figure 1 shown, the electrodeposition preparation method of the metal nickel hydroxide catalyst modified with 4,4'-bipyridine molecules is as follows:

[0040] (1) Treatment of the supported substrate nickel foam: At room temperature, the nickel foam was ultrasonically treated in a 3M hydrochloric acid solution to remove the oxide layer on the surface of the nickel foam, and then ultrasonically cleaned in ultrapure water to obtain a clean nickel foam substrate for standby.

[0041] (2) Preparation of the deposition solution (electrolyte): The 4,4'-bipyridine molecules were dispersed in a 0.2M nickel nitrate solution, and the solvent was a mixed solution of water and N,N-dimethylformamide (volume ratio 3:2). Ultrasonic treatment was used to promote dissolution to obtain a homogeneous and transparent solution as the deposition solution. The molar ratio of 4,4'-bipyridine molecules to nickel nitrate was 1:2.

[0042] (3) Deposition process: The treated clean nickel foam was clamped by an electrode clip as the working electrode, and the Ag / AgCl electrode was used as the reference electrode. Using a Chenhua 760e workstation, the potentiostatic deposition mode was selected, and the deposition potential was set to -2V and the time was 200s.

[0043] The X-ray diffraction pattern (XRD) of the obtained catalyst material (Bipy-Ni(OH) 2 ) and the standard diffraction card (PDF card) of nickel hydroxide are as Figure 2 shown.

[0044] Performance test:

[0045] Taking nickel hydroxide modified with 4,4'-bipyridine prepared in Example 1 as an example, cyclohexanone was used as the reaction raw material. A one-square centimeter nickel hydroxide catalyst supported on a nickel foam substrate (without adding 4,4'-bipyridine molecules in the electrolyte) and a nickel hydroxide catalyst modified with 4,4'-bipyridine molecules were cut. A Pt sheet was selected as the counter electrode, Hg / HgO as the reference electrode, and a platinum electrode clip was used to clamp the electrode material loaded with nickel hydroxide cut into a certain size. 1.5 M aqueous sodium hydroxide solution was added to one side of the H-type electrolytic cell, and 0.1 M aqueous sodium hydroxide solution of cyclohexanone was added to the other side. The corresponding electrodes were inserted into the corresponding positions of the H-type electrolytic cell. Certain electrolysis potentials (1.43 V, 1.53 V, 1.63 V, 1.73 V vs. RHE) were applied respectively, and the electrolysis duration was set to 1 hour. After the electrolysis was completed, 100 μL of the electrolytic solution after the reaction was aspirated and added to a nuclear magnetic tube. After adding a quantitative internal standard of dimethyl sulfoxide and D 2 O, nuclear magnetic resonance was used for quantification. The results are as Figure 3 shown. Compared with the nickel hydroxide catalyst, the nickel hydroxide catalyst modified with 4,4'-bipyridine molecules showed higher catalytic activity.

[0046] Example 2

[0047] In this example, a one-step electrodeposition method was used to prepare an organically modified metal hydroxide catalyst. The electrodeposition preparation method of metal nickel hydroxide catalysts modified with phthalazine, 2,2'-bipyridine, 1,2-bis(4-pyridyl)ethane, 5-NO 2 -1,10-phenanthroline molecules is as follows:

[0048] (1) Treatment of the supported substrate nickel foam: At room temperature, nickel foam was ultrasonically treated in a 3 M hydrochloric acid solution to remove the oxide layer on the surface of nickel foam, and then ultrasonically cleaned in ultrapure water to obtain a clean nickel foam substrate for standby.

[0049] (2) Preparation of the deposition solution (electrolyte): As shown in Table 1, phthalazine (Ph), 2,2'-bipyridine (2,2'-Bipy), 1,2-bis(4-pyridyl)ethane (Bpa), 5-NO 2 -1,10-phenanthroline (Phen-NO 2 ) molecules were respectively dispersed in 0.2 M nickel nitrate solution, and ultrasonic treatment was used to promote dissolution to obtain a homogeneous and transparent solution as the deposition solution. The molar ratio of the molecules to nickel nitrate was 1:2.

[0050] Table 1 Different organic molecules

[0051] Catalyst Organic molecule Metal salt (0.2M) Ph-modified catalyst Phthalazine (Ph) Nickel nitrate 2,2’-Bipy-modified catalyst 2,2’-Bipyridine (2,2’-Bipy) Nickel nitrate Bpa-modified catalyst 1,2-Bis(4-pyridyl)ethane (Bpa) Nickel nitrate <![CDATA[Phen-NO 2 Modified catalyst]]> <![CDATA[5-NO 2 -1,10-phenanthroline (Phen-NO 2 )]]> Nickel nitrate

[0052] (3) Deposition process: The cleaned nickel foam is clamped by the electrode clamp as the working electrode, and the Ag / AgCl electrode is used as the reference electrode. Using the Chenhua 760e workstation, the potentiostatic deposition mode is selected, the deposition potential is set to -2V, and the time is 200s.

[0053] Performance test

[0054] Taking the nickel hydroxide modified by various molecules prepared in Example 2 as an example, cyclohexanone is used as the reaction raw material. Cut a one-square centimeter nickel hydroxide catalyst loaded on the nickel foam substrate and the above four kinds of nickel hydroxide catalysts modified by molecules. Select the Pt sheet as the counter electrode and Hg / HgO as the reference electrode. The platinum electrode clamp is used to clamp the electrode material loaded with nickel hydroxide cut into a certain size. Add 1.5M sodium hydroxide aqueous solution to one side of the H-type electrolytic cell, and add 0.1M cyclohexanone sodium hydroxide aqueous solution to the other side. Insert the corresponding electrodes into the corresponding positions of the H-type electrolytic cell. Apply a certain electrolysis potential (1.53V vs. RHE), and set the electrolysis duration to 1 hour. After the electrolysis is completed, aspirate 100 μL of the electrolytic solution after the reaction and add it to the NMR tube. After adding a quantitative internal standard dimethyl sulfoxide and D 2 O, quantitative analysis is carried out by NMR. The results are as Figure 4 shown. Compared with the nickel hydroxide catalyst, the nickel hydroxide catalyst modified with molecules shows higher catalytic activity. (The nickel hydroxide modified with the molecule is represented by the abbreviation of the molecule)

[0055] Example 3

[0056] In this example, a one-step electrodeposition method is used to prepare a 4,4'-bipyridine molecule-modified bimetallic hydroxide catalyst. The electrodeposition preparation method of the 4,4'-bipyridine molecule-modified bimetallic nickel hydroxide catalyst is as follows:

[0057] (1) Treatment of the loaded substrate nickel foam: At room temperature, the nickel foam is ultrasonically treated in a 3M hydrochloric acid solution to remove the oxide layer on the surface of the nickel foam, and then ultrasonically cleaned in ultrapure water to obtain a clean nickel foam substrate for standby.

[0058] (2) Preparation of the deposition solution (electrolyte): As shown in Table 2, the 4,4'-bipyridine molecules are respectively dispersed in solutions containing different nitrates, and ultrasonic treatment is used to promote dissolution to obtain a homogeneous and transparent solution as the deposition solution. The molar ratio of the bipyridine molecule to nickel nitrate is 1:2.

[0059] Table 2 Different metal salts

[0060]

[0061] (3) Deposition process: The cleaned nickel foam was clamped by the electrode clamp as the working electrode, and the Ag / AgCl electrode was used as the reference electrode. Using the Chenhua 760e workstation, the potentiostatic deposition mode was selected, and the deposition potential was set to -2V.

[0062] Performance test

[0063] Taking the bimetallic hydroxide modified by 4,4'-bipyridine prepared in Example 3 as an example, cyclohexanone was used as the reaction raw material. A one-square centimeter bimetallic hydroxide catalyst supported on a nickel foam substrate was cut. A Pt sheet was selected as the counter electrode, and Hg / HgO was used as the reference electrode. The platinum electrode clamp was used to clamp the electrode material loaded with nickel hydroxide cut into a certain size. 1.5M sodium hydroxide aqueous solution was added to one side of the H-type electrolytic cell, and 0.1M sodium hydroxide aqueous solution of cyclohexanone was added to the other side. The corresponding electrodes were inserted into the corresponding positions of the H-type electrolytic cell. A certain electrolysis potential (1.53V vs. RHE) was applied, and the electrolysis duration was set to 2 hours. After the electrolysis was completed, 100 μL of the electrolyzed solution after the reaction was aspirated and added to a nuclear magnetic tube. After adding a quantitative internal standard of dimethyl sulfoxide and D 2 O, nuclear magnetic resonance was used for quantification. The results are as Figure 5 shown. Compared with the unmodified bimetallic hydroxide catalyst, the bimetallic hydroxide catalyst with molecular modification showed higher catalytic activity.

[0064] Comparative Example 1

[0065] This comparative example provides a molecularly modified metal hydroxide. The preparation method is basically the same as that of Example 1, except that 4,4'-bipyridine was replaced with an equimolar amount of sodium dodecyl sulfate to obtain a dodecyl sulfate-modified nickel hydroxide material (SDS-Ni(OH) 2 ).

[0066] Comparative Example 2

[0067] This comparative example provides a molecularly modified metal hydroxide. The preparation method is basically the same as that of Example 1, except that 4,4'-bipyridine was replaced with sodium benzoate to obtain a benzoate-modified nickel hydroxide (Ben-Ni(OH) 2 ).

[0068] Performance test

[0069] The performance of the two samples with different molecular modifications obtained in the comparative examples was compared with the sample modified by 4,4'-bipyridine. The results are as Figure 6 shown. The catalytic performance of the nickel hydroxide sample modified by 4,4'-bipyridine is better than that of the samples in the comparative examples.

[0070] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An organic molecule modified metal hydroxide electrocatalyst material, characterized in that: The electrocatalyst material includes a substrate, a metal hydroxide supported on the substrate, and an organic molecule modified on the metal hydroxide; The nitrogen atom in the organic molecule coordinates with the metal in the metal hydroxide, thereby modifying the metal hydroxide; The organic molecules include one or more of phthalazine, 2,2-bipyridine, 4,4-bipyridine, 1,2-di(4-pyridyl)ethane, and 5-NO2-1,10-phenanthroline.

2. The electrocatalyst material of the organic molecule-modified metal hydroxide according to claim 1, characterized in that: The metal hydroxide includes one or more of cobalt hydroxide, nickel hydroxide, iron hydroxide, cerium hydroxide, chromium hydroxide and aluminum hydroxide.

3. The electrocatalyst material of the organic molecule-modified metal hydroxide according to claim 1, characterized in that: The substrate comprises one of carbon cloth, graphite sheet, foamed nickel and foamed copper.

4. A method for preparing an electrocatalyst material as claimed in claim 1, characterized in that: The steps include: Organic molecules are added to an electrolyte containing metal salts, the substrate material is used as a working electrode, and electrodeposition is performed using a three-electrode system to obtain an electrocatalyst material.

5. The method for preparing an electrocatalyst material according to claim 4, characterized in that: The metal salt is a metal nitrate; the metal includes one or more of cobalt, nickel, iron, cerium, chromium and aluminum.

6. The method for preparing an electrocatalyst material according to claim 4, characterized in that: The molar ratio of the organic molecule to the metal salt is 1:1 to 1:

3.

7. The method for preparing an electrocatalyst material according to claim 4, characterized in that: The solubility of the metal salt in the electrolyte is 0.1 to 0.3 M.

8. The method for preparing an electrocatalyst material according to claim 1, characterized in that: The solvent in the electrolyte includes one or more of water and N,N-dimethylformamide.

9. The method for preparing an electrocatalyst material according to claim 1, characterized in that: The deposition potential of the electrodeposition is -1 to -3 V, and the time is 180 to 220 s.

10. Use of the electrocatalyst material as claimed in claim 1 in a reaction of preparing adipic acid by electrocatalytic oxidation.

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