CN115710721A

CN115710721A - Electrochemical synthesis nitrogen-containing aromatic compound electrode material and preparation method and application thereof

Info

Publication number: CN115710721A
Application number: CN202211293465.1A
Authority: CN
Inventors: 宋俊玲; 李金昆; 冯嘉桐; 王傲; 徐向亚
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2022-10-21
Filing date: 2022-10-21
Publication date: 2023-02-24

Abstract

The invention discloses an electrochemical synthesis nitrogen-containing aromatic compound electrode material, and a preparation method and application thereof. The novel electro-catalysis electrode material is prepared by taking copper salt with rich content as a raw material and introducing syringic acid from biomass as a ligand, so that a novel syringic acid copper-based MOFs nano material is obtained and is applied to electro-catalysis reaction of aromatics and nitrogen-containing inorganic salt. Under mild conditions, electrochemical C-H activation and C-N coupling reaction are realized in aqueous solution. And the catalyst shows high catalytic activity, selectivity and stability in the electrochemical synthesis of the nitrogen-containing aromatic compound. Therefore, the nanomaterial disclosed by the invention has wide application prospects in the aspects of electrocatalysis synthesis of high-added-value products such as nitrogen-containing aromatic ring compounds and energy conversion devices such as sewage treatment, conversion of lignin solid wastes and fuel cells.

Description

Electrochemical synthesis nitrogen-containing aromatic compound electrode material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of energy and environment treatment, and particularly relates to an electrochemical synthesis nitroaromatic compound electrode material, and a preparation method and application thereof.

Background

Lignin is a natural polyhydroxy aromatic compound, is a renewable resource next to cellulose, and accounts for about one fourth of the total amount of terrestrial biomass, but due to the very complex structure and low availability, the lignin has limited application in industry and agriculture, and about 98% of the lignin is treated in a combustion mode, so that a large amount of greenhouse gas is generated, and the greenhouse effect is increased. At present, lignin is treated as a waste product of the pulp and paper industry, and the waste lignin imposes a great load on the environment.

The rapid development of industry and agriculture is accompanied by the consumption of non-renewable fossil energy, the overuse of nitrogenous fertilizers and the discharge of industrial waste water in large quantities, so that nitrate is one of the most common pollutants in surface water and underground water. The large amount of nitrate in the water body not only seriously damages the nitrogen circulation process in the nature, but also is reduced into nitrite by microorganisms which are easy to be in the environment, and after being absorbed by human bodies, the nitrite can cause risks such as liver injury, hyper-erythrohemoglobinemia, even carcinogenesis, teratogenesis, mutation and the like, so that along with the increasingly serious nitrate pollution of underground water and surface water, the nitrate-containing water threatens the human health and the ecological system, and becomes one of the environmental problems to be solved urgently.

The aromatic nitro compound is an important chemical raw material and a synthetic intermediate, is widely applied in production and life, can be used as an intermediate of explosives, perfumes and dyes, and is an important functional group of a plurality of medicines and pesticides. At present, electrophilic substitution on an aromatic hydrocarbon ring is generally adopted for directly nitrifying, oxidizing aromatic amine and nitro substitution of aromatic halide for preparing the aromatic nitro compound, particularly, the most classical nitration reaction uses mixed acid (concentrated nitric acid/concentrated sulfuric acid) as a reagent, so that the serious environmental unfriendly problems exist, including the disadvantages of large amount of waste acid, high equipment corrosivity, harsh reaction conditions, poor atom economy and the like, and the development of the aromatic nitro compound is limited. With increasing requirements on environment and energy, the development of green electrochemical synthesis of chemical aromatic nitro compounds inevitably provides a simple, efficient and renewable new path for preparing nitrogen-containing chemicals from biomass, and has important significance for expanding the application of biomass resources. In electrocatalytic synthesis, electrode materials are key to electrochemical reactions, and although noble metal catalysts generally exhibit good electrocatalytic activity, their high cost and stability limit their application in practical production.

Disclosure of Invention

This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.

The present invention has been made keeping in mind the above and/or other problems occurring in the prior art.

Therefore, the present invention is to overcome the disadvantages of the prior art and provide a simple preparation method and application of an electrocatalyst capable of electrocatalytically synthesizing nitroaromatics and aminoaromatics. In order to solve the technical problems, the invention provides the following technical scheme: placing the cleaned conductive substrate electrode in a mixed solution of copper salt, syringic acid and DMF, and uniformly stirring the mixed solution; and transferring the mixed solution into a 50mL reaction kettle, reacting for a period of time under the solvothermal condition, naturally cooling to room temperature, washing the obtained sample for more than 3 times by using absolute ethyl alcohol and deionized water, and then carrying out vacuum drying overnight at 60 ℃ to obtain the prepared Cu-based MOFs nano material loaded on the conductive substrate.

As a preferable aspect of the present invention, wherein: the conductive base electrode material includes: one or more of carbon paper, carbon cloth, foamed nickel, foamed copper and stainless steel net.

As a preferable aspect of the present invention, wherein: the copper salt refers to at least one of nitrate, chlorate, sulfate, phosphate, acetate and carbonate, and can also be widely used for preparing nano materials of salts corresponding to Mn, fe, co, ni, cu and Zn.

As a preferable aspect of the present invention, wherein: the temperature of the solvothermal reaction is 80-160 ℃, and the reaction time is more than 10 minutes.

As a preferable aspect of the present invention, wherein: the solvent can be one or more of N, N-dimethylformamide, methanol, ethanol, ethylene glycol and isobutanol.

It is still another object of the present invention to overcome the deficiencies of the prior art and to provide an application of phenol and its derivatives in electrocatalytic synthesis of nitroaromatic compounds and aminoaromatic compounds with high efficiency with aqueous solutions of nitrogen-containing inorganic salts.

In order to solve the technical problems, the invention provides the following technical scheme: the Cu-based MOFs nano material is used as an electrocatalytic catalyst, and phenol, derivatives of the phenol and the phenol, and nitrogen-containing inorganic salt are efficiently converted into nitro aromatic ring compounds and amino aromatic compounds through electrocatalytic oxidation and electrocatalytic reduction reactions, so that phenol substances obtained from lignin are converted into high-value-added chemicals, and a green and environment-friendly electrochemical synthesis method is provided for treating lignin and nitrogen-containing inorganic salt wastewater.

As a preferable aspect of the present invention, wherein: the phenol and derivatives thereof include: at least one of phenol, 4-methoxyphenol, guaiacol, syringol and p-hydroxyphenyl propane, and the concentration of the compound is 0.05M or more.

As a preferable aspect of the present invention, wherein: the nitrogen-containing inorganic salt includes: one or more of nitrate aqueous solution, nitrite aqueous solution and NOx-containing salt aqueous solution.

As a preferable aspect of the present invention, wherein: the high value-added chemicals include: one or more of p-aminophenol, p-nitrophenol, o-nitrophenol and corresponding derivatives.

As a preferable aspect of the present invention, wherein: the system is a three-electrode system, an H-shaped electrolytic cell is adopted, a stone grinding rod sheet is used as a counter electrode, a reference electrode is HgO/Hg, an electrolyte solution is KOH or NaOH aqueous solution, the pH value is in a range of 1-14, the electrolytic voltage is-3.0V, and the reaction is carried out for more than 10 minutes under constant voltage.

As a preferable aspect of the present invention, wherein: the electrode material is applied to the fields of electro-catalysis organic synthesis, environmental management, new energy conversion, devices and the like.

The invention has the beneficial effects that:

(1) The application provides a flower-shaped nano Cu-based MOFs electrode material, wherein a copper salt and a bio-based syringic acid ligand are reacted by adopting a solvothermal method, so that the nano material can be rapidly prepared on a large scale. Simple process, high yield, little environmental pollution, low raw material price and low production cost. The prepared material has excellent performance in the field of electrocatalytic organic synthesis.

(2) The application provides a preparation method of the electrode material, which is characterized in that a conductive substrate is placed in a reaction mixed solution, and the electrode material can be obtained on a large scale by a solvothermal method and a rapid reaction under mild conditions. The synthesis method is simple, and the condition is mild, thereby being beneficial to realizing large-scale industrial production.

(3) The application provides a Cu-based MOFs electrode material, which has wide application prospect in the field of electrocatalysis organic synthesis of nitrogen-containing aromatic micromolecules, and particularly can be used for synthesizing aromatic nitro compounds, aromatic amino groups, amides, nitriles, nitrogen-containing heterocyclic compounds and the like in electrocatalysis C-N coupling and C-H active reaction; the method can also be applied to the electrocatalysis biomass conversion, and the biomass comprises the fields of lignin, cellulose, hemicellulose and the like, and the fields of electrocatalysis for preparing hydrogen, ammonia water, fuel cells and the like, and has excellent conversion rate, selectivity, high Faraday efficiency and good stability. In the whole reaction process, the device and equipment are simple, so that the method has wide market application prospect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor. Wherein:

FIG. 1 is a powder X-ray diffraction pattern of a typical Cu-based MOFs electrode material described in example 2.

FIG. 2 is a scanning electron micrograph of typical Cu-based MOFs electrode material described in example 3, with an inset showing an enlarged view.

FIG. 3 is a FT-IR spectrum of the Cu-based MOFs electrode material described in example 4.

FIG. 4 is a plot of polarization of the Cu-based MOFs electrode material described in example 5 at a scan rate of 5 mVs-1.

FIG. 5 is a mass spectrum of the product obtained by catalyzing phenol with Cu-based MOFs as described in example 6.

FIG. 6 is a nuclear magnetic spectrum of the product obtained by catalyzing phenol with Cu-based MOFs as described in example 7.

FIG. 7 is a mass spectrum of a product obtained by catalyzing 4-phenoxymethylphenol by the Cu-based MOFs described in example 8.

FIG. 8 is a nuclear magnetic spectrum of a product obtained by catalyzing 4-phenoxymethylphenol by the Cu-based MOFs described in example 8.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

Example 1

Preparation of Cu-based nanomaterials

Is measured by a distance of 24cm ² Ultrasonically treating foamed nickel in 3M HCl for 15 minutes to remove surface oxides, ultrasonically treating the foamed nickel in acetone for 5 minutes to remove surface organic matters, cleaning the foamed nickel by deionized water, placing the substrate electrode in a mixture of 2mmol of copper nitrate, 3mmol of syringic acid and 15ml of DMMF, and stirring for 30 minutes; and then transferring the mixed solution into a 50mL reaction kettle, reacting for 30 minutes under the condition of 130 ℃ solvothermal conditions, naturally cooling to room temperature, washing the obtained sample for more than 3 times by using absolute ethyl alcohol and deionized water, and then drying in vacuum for 10 hours at 60 ℃ to obtain the prepared Cu-based MOFs nano material loaded on the conductive substrate.

Example 2

Crystal structure analysis of samples

Powder X-ray diffraction was carried out on an X-ray powder diffractometer of model D8 from Bruker, germany, under the conditions of a fixed-target monochromatic light source Cu-Ka, wavelength

The scanning range is 5-50 degrees, and the scanning step is 0.02 degree. Sample # 1 is a typical electrode material prepared in example 1, as shown in fig. 1. The X-ray diffraction pattern obtained by fitting was investigated with sample No. 1 in FIG. 1And (3) comparing the spectra obtained by X-ray diffraction test after grinding into powder to obtain the diffraction peaks of the prepared nano material and the prepared crystal MOFs, thereby indicating the successful preparation of the nano material with the structure.

Example 3

Characterization of sample morphology

The prepared sample morphology was subjected to characterization test by SEM, as shown in fig. 2. The prepared electrode material is in a flower cluster structure consisting of spindle-shaped particles and is uniform in size. The nano material with the shape exposes more reaction active sites, and the one-dimensional direction can promote the electron transmission and mass transfer process in the catalysis process, thereby effectively improving the catalysis performance of the catalyst.

Example 4

The infrared absorption spectrum of the sample No. 1 is measured on a Nicolet 6700 total reflection Fourier infrared spectrometer, the result is shown in figure 3, and the figure shows that the broad absorption peak of the syringic acid ligand is 3227-3363cm ^-1 The correspondence is an O-H bond, and after the ligand and metal are combined into the MOF material, the peak disappears, indicating that the unsaturated coordination bond on the ligand is coordinated to the metal. 2837cm ^-1 And 617cm ^-1 The peak at (a) corresponds to the C-H oscillation. At the same time, 1110cm ^-1 The peak at (a) is due to the C-O-C bond, indicating that methoxy groups are still present on the ligand. In addition, at 1384cm ^-1 And 1665cm ^-1 The nearby peak corresponds to the coordinate binding group carboxylate (-COO-) between the organic ligand and the metal. This also demonstrates the successful fabrication of Cu-based MOFs nanomaterials.

Example 5

Polarization curve of electrode material

A Cu-based MOFs electrode material was used as a working electrode, then an Hg/HgO electrode and a graphite rod piece were used as a reference electrode and a counter electrode, respectively, and a solution containing 0.1g of phenoxyphenol or phenol (0.08 g), 0.2g of sodium nitrite, dissolved in 50mL of water, was adjusted to pH 13 with a concentrated potassium hydroxide solution as an electrolyte and an electrolytic solution. Shanghai Chenhua 760E electrochemical workstation at 5mV s ^-1 Is proceeding at a rate ofPolarization curve testing of LSV, linear Sweep Voltammetry (LSV) testing was preceded by a sweep of 20 cycles at 100mV/s to reach steady state and then testing was performed at a sweep rate of 5 mV/s. The potential values were calculated from the equation E vs RHE = E vs Hg/HgO +0.098+0.059pH, where E vs RHE is the relative reversible hydrogen electrode potential (V) and E vs Hg/HgO is the relative Hg/HgO electrode potential (V). As shown in FIG. 4, it can be seen that compared with the blank electrode, the Cu-based MOFs nano material as the catalyst has excellent performance for phenol nitration catalysis, and the current density is significantly increased under the same voltage, especially the current density can exceed 100mA/cm under the voltage of 2.0V (vs RHE) ² And the current density meets the requirement of industrial current density, and can be used in industrial production practical application.

Example 6

The Cu-based MOFs nano material is used as a catalyst, 1M potassium hydroxide solution containing 50mM of phenol and 50mM of sodium nitrite is subjected to electrocatalysis, the obtained product is characterized by mass spectrometry, as shown in figure 5, the mass spectrometry of the product solution obtained after electrocatalysis shown in figure 5, as can be seen in the figure, C-H of phenol is activated by the catalyst, C-N coupling reaction is carried out on the phenol and nitrite, and a series of coupling products are obtained through nitration reaction.

Example 7

Liquid chromatogram of reaction solution for catalyzing phenol by electrode material

The Cu-based MOFs nanomaterial was used as a catalyst to electrocatalysis 1M potassium hydroxide solution containing 50mM phenol and 50mM sodium nitrite, and the obtained product was characterized by liquid chromatography, as shown in FIG. 6, which is a nuclear magnetic spectrum obtained after 1 hour of electrocatalysis reaction, and it was determined that the product was a nitroaromatic compound.

Example 8

The Cu-based MOFs nano material is used as a catalyst, 1M potassium hydroxide solution containing 50mM of lignin model compound 4-phenoxymethylphenol and 50mM of sodium nitrite is subjected to electrocatalysis, the obtained product is characterized by mass spectrometry, as shown in figure 7, the mass spectrogram of the product solution obtained after electrocatalysis is, as can be seen in the figure, C-H of the 4-phenoxymethylphenol is activated by the catalyst, C-N coupling reaction is carried out on the catalyst and nitrite, and a single coupling product is obtained through nitration reaction. As shown in fig. 8, the nuclear magnetic spectrum of the obtained product shows that the catalyst shows high activity and high selectivity for different substrates. The catalyst is cheap and easy to obtain, has high activity and is beneficial to industrial application and popularization, so the technology has certain guiding significance for synthesizing electrocatalytic biomass micromolecule materials.

It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims

1. The preparation method of the electrode material for electrochemically synthesizing the nitrogen-containing aromatic compound is characterized by comprising the following steps:

mixing copper salt solution and syringic acid in certain proportion, mixing transition metal salt and syringic acid with water or organic solvent including N, N' -dimethyl formamide or methanol, ethanol, glycol and other alcohol solvent, and setting inside high pressure reaction kettle with PTFE lining at 80-160 deg.c for over 10 min to obtain final product with molecular formula of C ₉ H ₈ O ₅ Cu。

2. The preparation method according to claim 1, wherein the copper salt is any one of copper nitrate, copper carbonate, copper sulfate, copper acetate and copper chloride, and the mixing mass ratio of the copper salt, the syringic acid and the solvent is 0.1-2.0: 0.1 to 5.0:1 to 50; preferably 1:0.1 to 2.0:0.3 to 3.0:5 to 10.

3. The application of the nano electro-catalyst prepared by the method of any one of claim 1 is characterized by comprising the application of the nano electro-catalyst to the environmental engineering fields of electro-catalytic wastewater treatment, soil treatment, coating, anti-counterfeiting, printing, textiles, toxic gas adsorption and the like; the method is applied to the field of synthesis of drug intermediates; the method is applied to electrocatalysis C-N coupling and C-H active reaction to synthesize aromatic nitro compounds, aromatic amino, amides, nitriles, nitrogen-containing heterocyclic compounds and the like; the method can also be applied to the field of electrocatalysis biomass conversion, wherein the biomass comprises lignin, cellulose, hemicellulose and the like, and the field of electrocatalysis for preparing hydrogen, ammonia water, fuel cells and the like.

4. The application of the electrode material as claimed in claim 1, which comprises the steps of supporting the prepared electro-catalyst material on a conductive substrate, placing the substrate in an electrolytic bath containing nitrogen inorganic salt and phenol derivative aqueous solution, and applying different voltages to carry out electro-catalytic reaction for different times.

5. The method of claim 1, wherein the base electrode comprises at least one of a metallic titanium foil, a stainless steel metal, a copper foam, a nickel foam, a carbon felt cloth, a carbon paper, and a carbon fiber cloth.

6. The application of the nitrogen-containing inorganic salt and the phenol derivative in the electrocatalytic reaction as set forth in claim 4, wherein the in-situ electrochemical reduction is carried out in an electrolytic bath of the aqueous solution of the nitrogen-containing inorganic salt and the phenol derivative by applying different voltages in the range of-3.0 to 3.0V to a reversible hydrogen electrode.

7. The application of the nitrogen-containing inorganic salt and phenol derivative in electrocatalytic reaction as set forth in claim 4, wherein different voltages are applied in an electrolytic bath for electrocatalytic reaction for different periods of time within a range of 10 minutes or more.

8. Use in an electrocatalytic reaction as set forth in claim 4, wherein the inorganic salts containing nitrogen in the electrolyte solution are nitrate, nitrite, and NO _x One or more of aqueous solutionsThe pH range is 1-14.

9. Use in an electrocatalytic reaction as set forth in claim 4 wherein said source of phenolic derivatives in said electrolyte solution is at least one of phenol, 4-methoxyphenol, p-methylphenol, lignin and its degradation products, cellulose and its degradation products, hemicellulose and its degradation products.

10. The use according to claim 4 in electrocatalytic reactions, wherein the ratio of the amount of the phenol derivative to the amount of the nitrogen-containing inorganic salt in the electrolyte solution is 1:0.01 to 20.