Lignin C-N coupling electro-catalysis reaction system, product and application

Abstract

The invention relates to the technical field of electrochemical catalysis, in particular to a lignin C-N coupling electro-catalysis reaction system, a product and application. The system comprises an electrolytic tank, and an anode, a cathode, an electrolyte and a reaction substrate which are arranged in the electrolytic tank, the surface layer of the anode is a PbO2 catalyst layer; the surface layer of the cathode is a TivO2 catalyst layer loaded with Pd; the cathode potential is-0.4 + / -0.05 V relative to the reversible hydrogen electrode potential; the total reaction electric quantity in the electrolytic tank is 250 + / -20 coulomb; the reaction substrate comprises lignin and industrially discharged oxynitride; and a stirring part is arranged in the electrolytic tank. The product is prepared from the system. The application refers to application of the system in preparation of aromatic imine compounds. The aromatic imine compound can be prepared through mild catalysis, and the effects of energy conservation and emission reduction are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical catalysis, in particular to a lignin C-N coupling electrocatalytic reaction system, product and application. BACKGROUND

[0002] Lignocellulosic biomass is the most abundant renewable resource on earth, which is composed of cellulose, hemicellulose and lignin. Among them, lignin, as the main renewable aromatic polymer in nature, accounts for 15%-35% of the total amount of lignocellulosic biomass. Its efficient utilization is considered as an important sustainable path to replace the petroleum chemical route to prepare aromatic chemicals. However, due to the complex molecular structure of lignin, it is difficult to be effectively converted, and most of the lignin is directly discarded or burned as low-value fuel.

[0003] In recent years, the high-value utilization of lignin has become the focus of the field of lignocellulosic biomass refining, and developing new depolymerization methods to realize directional conversion is the key research direction to break through the bottleneck of lignin utilization. Electro-catalytic depolymerization technology, as a renewable energy driven conversion method, has significant advantages compared with traditional thermal catalysis, such as green and sustainable, normal temperature and pressure, and atom economy. At present, researchers have focused on the selective depolymerization of C-C and C-O bonds of the most important β-O-4 linkage (which accounts for about 50% of lignin) in electro-catalytic lignin, and there are few reports on the controllable depolymerization and re-coupling of lignin, which is worthy of further in-depth study.

[0004] Introducing nitrogen sources into the lignin depolymerization and value-added system to form C-N coupling products not only avoids the recondensation of lignin depolymerization active intermediates aldehyde / ketone, increases the yield of monomer products, but also opens up a new direction for the diversified application of renewable lignin resources, and significantly improves the economic value of the products. However, the commonly used C-N coupling method for lignin is a thermal catalytic C-N coupling method, which often needs to rely on high-temperature and high-pressure (100-500 °C, 1-200 bar) hydrogenation amination process, and needs to be coupled with high-value amine or ammonia in multiple reaction steps, which not only has high energy consumption, low yield, but also is not environmentally friendly. Although the existing electro-catalytic method can catalyze lignin depolymerization to obtain monomers at normal temperature and pressure, however, this process is difficult to effectively couple with the C-N coupling reaction of nitrogen sources, so as to directly synthesize high-value nitrogen-containing chemicals.

[0005] Therefore, it is necessary to provide a lignin C-N coupling electrocatalytic reaction system, product and application to solve the problems of high energy consumption, low yield and environmental unfriendliness of the existing thermal catalytic C-N coupling method, and the problem that the existing electro-catalytic method cannot catalyze the lignin depolymerization system to form C-N coupling products with nitrogen sources. SUMMARY

[0006] The application aims to provide a lignin C-N coupling electrocatalytic reaction system, a product and an application, and specific technical solutions are as follows. In the first aspect, the application provides a lignin C-N coupling electrocatalytic reaction system, comprising an electrolytic cell and an anode, a cathode, an electrolyte and a reaction substrate arranged in the electrolytic cell. The surface layer of the anode is a PbO2 catalytic layer. The surface layer of the cathode is a Ti v O2 catalytic layer loaded with Pd; wherein the Pd monatomic atom is limited and loaded in a Ti v O2 vacancy; v represents the Ti vacancy. The cathode potential is -0.4±0.05 V relative to the reversible hydrogen electrode potential. The total electric quantity in the electrolytic cell is 250±20 coulombs. The electrolyte comprises a phosphoric acid aqueous solution and acetonitrile in a volume ratio of 7±0.5:3±0.5; the molar concentration of the phosphoric acid aqueous solution is 1±0.2 mol / L. The reaction substrate comprises lignin and industrially discharged nitrogen oxide; the mass concentration of the lignin in the electrolyte is 2±0.2 mg / mL; and the molar concentration of the nitrogen oxide in the electrolyte is 10±1 mmol / L. A stirring component is arranged in the electrolytic cell.

[0007] Optionally, the anode is a lead plate; and the step of preparing the PbO2 catalytic layer on the surface layer of the lead plate comprises: Step A1, polishing to remove the oxide layer on the surface of the lead plate, and then sequentially performing alcohol washing and acid washing on the surface of the lead plate; Step A2, placing the lead plate after acid washing in an acid solution for electro-oxidation treatment to obtain the PbO2 catalytic layer.

[0008] Optionally, the acid solution is a 0.5±0.05 mol / L sulfuric acid aqueous solution; The electro-oxidation treatment adopts a current density of 100±10 mA / cm 2 , and an electro-oxidation time of 1±0.2 h.

[0009] Optionally, the cathode is carbon paper; and the step of preparing the Ti v O2 catalytic layer loaded with Pd on the surface layer of the carbon paper comprises: Step B1, preparing Ti v O2 nanosheets; Specifically, a protonated titanate crystal is mixed with a tetrabutylammonium hydroxide solution to form a Ti vacancy, and the Ti vO2nanosheets; wherein the molar ratio of tetrabutylammonium hydroxide in the tetrabutylammonium hydroxide solution to H + in the protonated titanate crystal is 1:1; Step B2, preparing Pd / Ti v O2powder; Specifically, 25±2mg / mL of Pd hydrochloric acid solution is mixed with alcohol and water mixture according to the volume ratio of 25±5µL:40±5mL to form a mixture; the Ti v O2nanosheets are added to the mixture to form a suspension; the suspension is subjected to ultraviolet irradiation treatment, so that Pd monatomic atoms are confined and loaded in the Ti v O2vacancies in Ti v O2powder; the mass concentration of the Ti v O2nanosheets in the suspension is 3.7±0.3mg / mL; Step B3, preparing Pd / Ti v O2slurry; 10±0.5mg of the Pd / Ti v O2powder is added to the first mixed solution, and after ultrasonic treatment, Pd / Ti v O2slurry is obtained; The first mixed solution includes 2±0.2mL of isopropyl alcohol, 1±0.1mL of ultrapure water and 100±10uL of Nafion solution; Step B4, the Pd / Ti v O2slurry is sprayed on the surface of the carbon paper after the first calcination treatment, and after drying, the Pd-loaded Ti v O2catalytic layer is obtained; During spraying, the carbon paper is fixed on a hot stage at 100±5℃, and is uniformly sprayed at a moving speed of 2±0.2cm / s, and is dried for 3±0.5min after each layer of spraying, until the total spraying load reaches 2mg / cm 2 The above completes the spraying.

[0010] Optionally, the protonated titanate crystal is H 1.07 Ti 1.73 O4, the obtaining steps of which include: First, TiO2, K2CO3 and Li2CO3 are mixed according to the molar ratio of 1.73:0.4:0.14, and then, a layered titanate crystal K 0.8 Ti 1.73 Li 0.27 O4 is obtained through a second calcination treatment; Secondly, the layered titanate crystal is added into 1±0.2 mol / L hydrochloric acid aqueous solution at 15-25 °C, and a first stirring treatment is performed to obtain a solution containing protonated titanate crystal precursor; Finally, the protonated titanate crystal precursor is collected by filtration, washed with water to neutral, and then dried by air to obtain the protonated titanate crystal; The protonated titanate crystal precursor is K 0.8 Ti 1.73 Li 0.27 O4·H2O; The second calcination treatment adopts a calcination temperature of 1000±10 °C and a calcination time of 20±0.5 h; The first stirring treatment adopts a stirring rate of 600±50 rpm and a stirring time of 72±0.5 h, and the hydrochloric acid aqueous solution is replaced every day; The back-and-forth oscillation treatment adopts a back-and-forth oscillation frequency of 180±10 times / min and an oscillation time of 168±0.5 h.

[0011] Optionally, the Pd hydrochloric acid solution includes a PdCl2 acid solution with a pH value of 0.3±0.04; The alcohol-water mixed solution includes ethanol and water in a volume ratio of 0.5±0.1:9.5±0.1; The ultraviolet irradiation treatment adopts an ultraviolet light intensity of 2.0±0.5 mW / cm 2 and an irradiation time of 10±2 min; The ultrasonic treatment adopts an ultrasonic frequency of 80±20 Hz and an ultrasonic time of 30±5 min; The first calcination treatment adopts a calcination temperature of 400±20 °C and a calcination time of 10±0.5 h.

[0012] Optionally, the lignin includes white poplar lignin extract; The extraction step of the white poplar lignin extract includes: Degradation reaction: 20±1 g of white poplar powder is mixed with 240±5 ml of a second mixed solution, and a reflux treatment is performed under an inert atmosphere to obtain a reflux liquid; The reflux treatment adopts a reflux temperature of 85±5 °C and a reflux time of 3±0.3 h; the second mixed solution includes dioxane and hydrochloric acid solution in a volume ratio of 9±0.2:1±0.2; the molar concentration of the hydrochloric acid solution is 0.2±0.05 mol / L; Filtering and washing: the reflux liquid is filtered after being cooled to 15-25°C to obtain a first filtrate and a filter residue; the filter residue is washed with a third mixed solution until the washing liquid is transparent; the first filtrate and all the washing liquid are mixed to obtain a second filtrate; the third mixed solution comprises dioxane and water in a volume ratio of 9±0.2:1±0.2; Neutralization and concentration: the second filtrate is neutralized to pH 3.5±0.5 with a saturated NaHCO3 solution, and then subjected to a reduced-pressure concentration treatment to obtain a concentrated liquid; the concentration temperature used in the reduced-pressure concentration treatment is 45±3°C, the concentration time is 1±0.1 h, and the pressure is 0.87-0.97 atm; Precipitation and purification: the concentrated liquid is added dropwise into 500±10 ml of ice water, and is left to stand at 4°C overnight; the precipitated dark brown oil-like lignin is collected, washed with water, and freeze-dried for 48±0.5 h to obtain white poplar lignin extract.

[0013] Optionally, the nitrogen-oxygen compound comprises at least one of inorganic nitrogen-oxygen compounds and organic nitro compounds.

[0014] In a second aspect, the present application provides an aromatic imine compound product prepared by using the lignin C-N coupling electrocatalytic reaction system.

[0015] In a third aspect, the present application provides an application of the lignin C-N coupling electrocatalytic reaction system in the preparation of aromatic imine compounds.

[0016] The technical solution of the present application has at least the following beneficial effects: (1) The lignin C-N coupling electrocatalytic reaction system provided by the present application uses a Pd-loaded Ti v O2 catalytic layer at the cathode to mildly catalyze the reaction substrate; specifically, a Pd monatomic atom can catalyze the cleavage of the C aryl –O bond in the β-O-4 linkage of lignin to form syringyl glycerol and guaiacyl glycerol; under the stirring action of the stirring part, the syringyl glycerol and guaiacyl glycerol are migrated to the anode and are electro-oxidized by the PbO2 catalytic layer on the surface of the anode to form active syringaldehyde intermediates and guaiacol intermediates; and the nitrogen-oxygen compound discharged by industry is used as an oxidant. vO2 electroreduction forms active nitrogen species (such as amines); these active nitrogen species undergo CN coupling with active syringaldehyde intermediates and guaiacol intermediates at the electrode interface to form aromatic imine compounds. Aromatic imine compounds are intermediates for the synthesis of β-lactam antibiotics and can also serve as pesticide intermediates, dyes, anti-pigmentation drugs, luminescent materials, and ligand materials, possessing significant economic value. Furthermore, this invention uses a specific volume ratio of phosphoric acid aqueous solution and acetonitrile in the electrolyte. Acetonitrile helps promote the dissolution of the reaction substrate, preparing it for participation in the catalytic reaction. The phosphate anions in the phosphoric acid aqueous solution can strongly localize water molecules and hydrated hydrogen ions in the electrolyte around them, thereby reducing the enrichment of water molecules and hydrated hydrogen ions around the aromatic imine compounds, significantly reducing the hydrolysis probability of the aromatic imine compounds and improving their stability. Therefore, this invention can mildly electrocatalyze the formation of CN-coupled aromatic imine compounds from lignin and nitrogen oxides emitted from industrial sources, with a yield >74% (calculated based on β-O-4 bond content), achieving energy saving and emission reduction effects, and solving the problems existing in existing thermocatalytic CN coupling methods and existing electrocatalytic methods.

[0017] (2) The PbO2 catalyst layer prepared on the surface of the lead plate in this invention has high conductivity and stable catalytic activity. In the preparation process, the oxide layer on the surface of the lead plate is first polished to remove the oxide layer, and then the surface of the lead plate is washed with alcohol to remove the surface grease and avoid the grease from hindering the subsequent acid washing solution from contacting the lead matrix. Subsequently, the surface of the lead plate is acid washed to remove the subsurface oxide. Finally, the PbO2 catalyst layer is prepared by electro-oxidation treatment.

[0018] (3) The Pd-loaded Ti prepared by the present invention v The O2 catalyst layer can confine and load Pd single atoms onto Ti. v The Ti vacancies in O2 effectively stabilize Pd single atoms, preventing their migration and aggregation. During preparation, layered titanate crystals are added to a 1±0.2 mol / L hydrochloric acid aqueous solution at 15-25°C, followed by a first stirring treatment, allowing the H+ in the hydrochloric acid to dissolve. + Diffusion into layered titanate crystals replaced K in the layered titanate crystals. + and Li + A protonated titanate crystal precursor was obtained; after washing with water until neutral, it was then air-dried to obtain protonated titanate crystals; the protonated titanate crystals were mixed with tetrabutylammonium hydroxide solution at a specific molar ratio and reacted. During the reaction, the H in the protonated titanate crystals... + With OH in tetrabutylammonium hydroxide solution - The reaction generates water molecules, which leave the titanate crystal and subsequently form Ti vacancies within the titanate crystal. Further, step B2 is used to confine Pd single atoms onto Ti. vTi vacancies in O2; subsequently, Pd supported Ti was prepared by combining steps B3 and B4 v O2 catalytic layer; wherein, the first calcination treatment of carbon paper in step B4 is to calcine and oxidize the surface of carbon paper to generate hydrophilic carboxyl groups, which facilitates uniform and stable loading of Pd / Ti in step B3 v O2 slurry, and then Pd supported Ti was prepared v O2 catalytic layer.

[0019] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the drawings shown.

[0021] Figure 1 Ti prepared in the embodiments v Atomic force microscope image of O2 nanosheet Figure 2 Pd supported Ti prepared in the embodiments v Transmission electron microscope image of O2 catalytic layer Figure 3 Pd supported Ti prepared in the embodiments v X-ray energy spectrum (Pd) image of O2 catalytic layer Figure 4 Pd supported Ti prepared in the embodiments v X-ray energy spectrum (Ti) image of O2 catalytic layer Figure 5 Pd supported Ti prepared in the embodiments v X-ray energy spectrum (O) image of O2 catalytic layer Figure 6 Pd supported Ti prepared in the embodiments v High-angle annular dark-field scanning transmission image of O2 catalytic layer Figure 7 Scanning electron microscope image of PbO2 catalytic layer prepared in the embodiments Figure 8 Gas chromatogram of electrocatalytic product of lignin C-N coupling electrocatalytic reaction system Figure 9 Mass spectrum of vanillin aniline product Figure 10is the mass spectrum of the product of the anisaldehyde aniline; The accompanying drawings are incorporated into and constitute a part of this specification. Figure 8 The “1” in the above formula represents vanillin aniline, and its chemical structural formula is: ; The “2” in the above formula represents anisaldehyde aniline, and its chemical structural formula is: Figure 8 . DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Embodiment: A lignin C-N coupling electrocatalytic reaction system, comprising an electrolytic cell and an anode, a cathode, an electrolyte and a reaction substrate arranged in the electrolytic cell; The surface layer of the anode is a PbO2 catalytic layer; The surface layer of the cathode is a Ti v O2 catalytic layer loaded with Pd; wherein the Pd monatomic atom is confined and loaded in the Ti v O2 vacancy in the Ti The cathode potential is -0.4 V relative to the reversible hydrogen electrode potential; The total electric quantity in the electrolytic cell is 250 coulombs; The electrolyte comprises a phosphoric acid aqueous solution and acetonitrile in a volume ratio of 7:3; the molar concentration of the phosphoric acid aqueous solution is 1 mol / L; The reaction substrate comprises lignin and industrially discharged nitrogen oxide; the mass concentration of the lignin in the electrolyte is 2 mg / mL; the molar concentration of the nitrogen oxide in the electrolyte is 10 mmol / L; A stirring component (such as a stirring blade; specifically, the stirring blade is arranged on a stirring shaft, the end of the stirring shaft away from the stirring blade is arranged outside the electrolytic cell, and the stirring shaft is driven by a motor).

[0024] The anode is a lead plate; the step of preparing the PbO2 catalytic layer on the surface layer of the lead plate comprises: Step A1, first polish to remove the oxide layer on the surface of the lead plate, and then sequentially perform alcohol washing and acid washing on the surface of the lead plate; ​Step A2, placing the acid-washed lead plate in an acid solution for electro-oxidation treatment to obtain the PbO2catalytic layer.

[0025] The acid solution is a 0.5 mol / L aqueous sulfuric acid solution; The electro-oxidation treatment adopts a current density of 100 mA / cm 2 , and the electro-oxidation time is 1 h.

[0026] The cathode is carbon paper; the step of preparing the Pd-loaded Ti v O2catalytic layer on the surface layer of the carbon paper includes: Step B1, preparing Ti v O2nanosheets; Specifically, the protonated titanate crystal is mixed with a tetrabutylammonium hydroxide solution to form Ti vacancies, and the Ti v O2nanosheets are obtained through back-and-forth oscillation treatment; wherein the molar ratio of tetrabutylammonium hydroxide in the tetrabutylammonium hydroxide solution to H + in the protonated titanate crystal is 1:1; Step B2, preparing Pd / Ti v O2powder; Specifically, 25 mg / mL of Pd hydrochloric acid solution is mixed with an alcohol-water mixture in a volume ratio of 25 µL:40 mL to form a mixed solution; the Ti v O2nanosheets are added to the mixed solution to form a suspension; the suspension is subjected to ultraviolet irradiation treatment, so that Pd monatomic atoms are confined in the Ti vacancies in the Ti v O2, and after drying, Pd / Ti v O2powder is obtained; the mass concentration of the Ti v O2nanosheets in the suspension is 3.7 mg / mL; Step B3, preparing Pd / Ti v O2slurry; 10 mg of the Pd / Ti v O2powder is added to a first mixed solution, and after ultrasonic treatment, Pd / Ti v O2slurry is obtained; The first mixed solution includes 2 mL of isopropyl alcohol, 1 mL of ultrapure water, and 100 uL of Nafion solution (i.e., perfluorosulfonic acid resin solution); Step B4, spraying the Pd / Ti v O2slurry on the surface of the carbon paper after the first calcination treatment, and drying to obtain the Pd-loaded Ti v O2catalytic layer; During spraying, the carbon paper is fixed on a 100°C hot plate and sprayed evenly at a moving speed of 2 cm / s. Each layer is dried for 3 minutes after spraying until the total spray load reaches 2 mg / cm. 2 The painting process is now complete.

[0027] The protonated titanate crystal is H 1.07 Ti 1.73 O4, the steps to obtain it include: First, TiO2, K2CO3, and Li2CO3 were mixed in a molar ratio of 1.73:0.4:0.14. Then, a second calcination treatment was performed to obtain layered titanate crystals. 0.8 Ti 1.73 Li 0.27 O4; Next, at 15 ~ 25°C (specifically 20°C), the layered titanate crystals are added to a 1 mol / L hydrochloric acid aqueous solution and subjected to a first stirring treatment to obtain a solution containing a protonated titanate crystal precursor. Finally, the protonated titanate crystal precursor was collected by filtration, washed with water until neutral, and then air-dried to obtain the protonated titanate crystal. The protonated titanate crystal precursor is K 0.8 Ti 1.73 Li 0.27 O4·H2O; The second calcination treatment uses a calcination temperature of 1000°C and a calcination time of 20 hours; The first stirring process uses a stirring rate of 600 rpm and a stirring time of 72 h, and the hydrochloric acid aqueous solution is replaced daily. The reciprocating oscillation process uses a reciprocating oscillation frequency of 180 times / min and an oscillation time of 168 hours.

[0028] The Pd hydrochloric acid solution includes a PdCl2 acid solution with a pH of 0.3; The alcohol-water mixture comprises ethanol and water in a volume ratio of 0.5:9.5; The ultraviolet light intensity used in the ultraviolet irradiation treatment was 2.0 mW / cm². 2 The irradiation time used was 10 minutes; The ultrasonic treatment used an ultrasonic frequency of 80 Hz and an ultrasonic time of 30 min. The first calcination treatment uses a calcination temperature of 400°C and a calcination time of 10 hours.

[0029] The lignin includes poplar lignin extract; The extraction steps of the poplar lignin extract include: Degradation reaction: 20g of poplar wood powder was mixed with 240ml of the second mixed solution and refluxed under an inert atmosphere to obtain reflux liquid; The reflux treatment uses a reflux temperature of 85°C and a reflux time of 3 hours; the second mixed solution comprises dioxane and hydrochloric acid solution in a volume ratio of 9:1; the molar concentration of the hydrochloric acid solution is 0.2 mol / L; Filtration and washing: The reflux liquid is cooled to 15-25°C (specifically 20°C) and then filtered to obtain a first filtrate and a filter residue; the filter residue is washed with a third mixed solution until the washing liquid is a transparent liquid; the first filtrate and all the washing liquids are mixed to form a second filtrate; the third mixed solution includes dioxane and water in a volume ratio of 9:1. Neutralization and concentration: The second filtrate was neutralized to pH 3.5 using a saturated NaHCO3 solution, and then concentrated under reduced pressure to obtain a concentrated solution; the concentration treatment under reduced pressure was carried out at a concentration temperature of 45°C, a concentration time of 1 hour, and a pressure of 0.92 atmospheres. Precipitation and purification: The concentrated solution was added dropwise to 500 ml of ice water and allowed to stand overnight at 4°C; the precipitated dark brown oily lignin was collected, centrifuged, washed with water, and freeze-dried for 48 h to obtain poplar lignin extract.

[0030] See Figure 1 The Ti prepared in this embodiment v The thickness of the O2 nanosheets is basically maintained in the range of 1.0~1.2nm.

[0031] See Figures 2-5 In this embodiment, the Pd-loaded Ti is prepared on the surface of the carbon paper. v The O2 catalyst layer has a sheet-like structure, and Pd and Ti v O2 is evenly distributed in this layered structure.

[0032] See Figure 6 In this embodiment, the Ti vacancies are evenly distributed in Ti. v In O2, and can confine Pd single atoms to Ti v In the Ti vacancy in O2.

[0033] See Figure 7 The PbO2 catalyst layer prepared in this embodiment is a uniform and dense structural layer.

[0034] Figure 8 The image shows the gas chromatogram of the electrocatalytic products of the lignin-CN coupling electrocatalytic reaction system. The method for obtaining the gas chromatographic data is as follows: The electrocatalysis product sample is neutralized to pH 7 by 1 mol / L potassium hydroxide solution, dissolved in an extractant, mixed and separated, and then the lower layer solution is taken for gas chromatography analysis. The gas chromatograph used is GC-2014 (Shimadzu Corporation); the extractant used is dichloromethane, and the volume is 3 times the volume of the electrolyte.

[0035] Referring to Figure 8 The electrocatalysis product prepared in the embodiment is mainly vanillin anil and syringaldehyde anil, and the sum of the yields of the two is greater than 74% (calculated based on the content of β-O-4 bond).

[0036] Figure 9 The mass spectrum of the vanillin anil product is shown in FIG. 4. Figure 10 The mass spectrum of the syringaldehyde anil product is shown in FIG. 5. Mass spectrometry is a method that uses electromagnetic principles to dissociate the molecules of the sample to be tested into ions with different masses, and then arranges and collects them into a mass spectrum according to the mass-to-charge ratio (m / z). Among them, Figure 9 and Figure 10 The mass spectrum data acquisition method is as follows: The electrocatalysis product sample is neutralized to pH 7 by 1 mol / L potassium hydroxide solution, dissolved in an extractant, mixed and separated, and then the lower layer solution is taken for mass spectrometry analysis. The gas chromatograph-mass spectrometer used is GCMS-QP2010 (Shimadzu Corporation); the extractant used is dichloromethane, and the volume is 3 times the volume of the electrolyte.

[0037] Referring to Figure 9 The mass-to-charge ratio 227 represents the molecular weight of vanillin anil, the mass-to-charge ratio 212 represents a fragment obtained by losing a methoxy group (-OCH3) of vanillin anil, the mass-to-charge ratio 104 represents an aniline methylene cation radical obtained by further cracking of vanillin anil, and the mass-to-charge ratio 77 represents a phenyl cation. Therefore, it can be determined that the product is vanillin anil.

[0038] Referring to Figure 10 The mass-to-charge ratio 257 represents the molecular weight of syringaldehyde anil, the mass-to-charge ratio 242 represents a fragment obtained by losing a methoxy group (-OCH3) of syringaldehyde anil, the mass-to-charge ratio 104 represents an aniline methylene cation radical obtained by further cracking of syringaldehyde anil, and the mass-to-charge ratio 77 represents a phenyl cation. Therefore, it can be determined that the product is syringaldehyde anil.

[0039] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation made under the inventive concept of the present application, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A lignin-CN coupled electrocatalytic reaction system, characterized in that, It includes an electrolytic cell and the anode, cathode, electrolyte, and reaction substrate disposed within the electrolytic cell; The surface layer of the anode is a PbO2 catalyst layer; The surface layer of the cathode is Ti loaded with Pd. v O2 catalyst layer; wherein, Pd single-atom confinement is supported on Ti v In the Ti vacancy in O2; v represents the Ti vacancy; The cathode potential is -0.4 ± 0.05 V relative to the reversible hydrogen electrode potential; The total amount of electricity reacted in the electrolytic cell was 250 ± 20 coulombs; The electrolyte comprises an aqueous solution of phosphoric acid and acetonitrile in a volume ratio of 7±0.5:3±0.5; the molar concentration of the aqueous solution of phosphoric acid is 1±0.2 mol / L. The reaction substrates include lignin and nitrogen oxides emitted from industrial sources; the mass concentration of lignin in the electrolyte is 2 ± 0.2 mg / mL; the molar concentration of nitrogen oxides in the electrolyte is 10 ± 1 mmol / L. A stirring component is provided in the electrolytic cell.

2. The lignin-CN coupling electrocatalytic reaction system as described in claim 1, characterized in that, The anode is a lead plate; the step of preparing the PbO2 catalyst layer on the surface of the lead plate includes: Step A1: First, polish to remove the oxide layer on the surface of the lead plate, and then perform alcohol washing and acid washing on the surface of the lead plate in sequence; Step A2: Place the acid-washed lead plate in an acid solution for electro-oxidation treatment to obtain the PbO2 catalyst layer.

3. The lignin-CN coupling electrocatalytic reaction system as described in claim 2, characterized in that, The acid solution is a 0.5±0.05mol / L sulfuric acid aqueous solution; The current density used in the electro-oxidation treatment is 100±10 mA / cm². 2 The electro-oxidation time was 1 ± 0.2 h.

4. The lignin-CN coupling electrocatalytic reaction system as described in claim 1, characterized in that, The cathode is carbon paper; the Pd-loaded Ti is prepared on the surface of the carbon paper. v The steps involved in creating the O2 catalyst layer include: Step B1, Preparation of Ti v O2 nanosheets; Specifically, protonated titanate crystals are mixed and reacted with tetrabutylammonium hydroxide solution to form Ti vacancies, and then subjected to reciprocating oscillation to obtain Ti. v O2 nanosheets; wherein the tetrabutylammonium hydroxide in the tetrabutylammonium hydroxide solution reacts with the H in the protonated titanate crystals. + The molar ratio is 1:1; Step B2, Preparation of Pd / Ti v O2 powder; Specifically, a 25±2 mg / mL Pd hydrochloric acid solution and an alcohol-water mixture were mixed at a volume ratio of 25±5 µL: 40±5 mL to form a mixture; the Ti... v O2 nanosheets are added to the mixture to form a suspension; the suspension is then subjected to ultraviolet light irradiation to confine Pd single atoms within Ti. v Pd / Ti is obtained by filling the Ti vacancies in O2 and then drying it. v O2 powder; Ti in the suspension v The mass concentration of O2 nanosheets was 3.7 ± 0.3 mg / mL; Step B3: Preparation of Pd / Ti v O2 slurry; 10±0.5 mg of the Pd / Ti v O2 powder was added to the first mixed solution, and after ultrasonic treatment, Pd / Ti was obtained. v O2 slurry; The first mixed solution comprises 2±0.2 mL isopropanol, 1±0.1 mL ultrapure water, and 100±10 μL Nafion solution; Step B4, the Pd / Ti v O2 slurry is sprayed onto the surface of carbon paper after the first calcination treatment, and after drying, the Pd-loaded Ti is obtained. v O2 catalyst layer; During spraying, the carbon paper is fixed on a hot table at 100±5℃ and sprayed evenly at a moving speed of 2±0.2cm / s. Each layer is dried for 3±0.5min after spraying until the total spray load reaches 2mg / cm. 2 The painting process is now complete.

5. The lignin-CN coupling electrocatalytic reaction system as described in claim 4, characterized in that, The protonated titanate crystal is H 1.07 Ti 1.73 O4, the steps to obtain it include: First, TiO2, K2CO3, and Li2CO3 were mixed in a molar ratio of 1.73:0.4:0.

14. Then, a second calcination treatment was performed to obtain layered titanate crystals. 0.8 Ti 1.73 Li 0.27 O4; Next, at 15 ~ 25°C, the layered titanate crystals are added to a hydrochloric acid aqueous solution of 1 ± 0.2 mol / L and subjected to a first stirring treatment to obtain a solution containing a protonated titanate crystal precursor. Finally, the protonated titanate crystal precursor was collected by filtration, washed with water until neutral, and then air-dried to obtain the protonated titanate crystal. The protonated titanate crystal precursor is K 0.8 Ti 1.73 Li 0.27 O4·H2O; The second calcination treatment uses a calcination temperature of 1000±10°C and a calcination time of 20±0.5h; The first stirring process uses a stirring rate of 600±50 rpm and a stirring time of 72±0.5 h, and the hydrochloric acid aqueous solution is replaced daily. The reciprocating oscillation process uses a reciprocating oscillation frequency of 180±10 times / min and an oscillation time of 168±0.5h.

6. The lignin-CN coupling electrocatalytic reaction system as described in claim 4, characterized in that, The Pd hydrochloric acid solution includes a PdCl2 acid solution with a pH value of 0.3 ± 0.04; The alcohol-water mixture comprises ethanol and water in a volume ratio of 0.5±0.1:9.5±0.1; The ultraviolet light intensity used in the ultraviolet irradiation treatment was 2.0 ± 0.5 mW / cm². 2 The irradiation time used was 10±2 min; The ultrasonic treatment used an ultrasonic frequency of 80±20Hz and an ultrasonic time of 30±5min. The first calcination treatment uses a calcination temperature of 400±20°C and a calcination time of 10±0.5h.

7. The lignin-CN coupling electrocatalytic reaction system as described in claim 1, characterized in that, The lignin includes poplar lignin extract; The extraction steps of the poplar lignin extract include: Degradation reaction: 20±1g of poplar wood powder was mixed with 240±5ml of the second mixed solution and refluxed under an inert atmosphere to obtain reflux liquid; The reflux treatment uses a reflux temperature of 85±5℃ and a reflux time of 3±0.3h; the second mixed solution includes dioxane and hydrochloric acid solution in a volume ratio of 9±0.2:1±0.2; the molar concentration of the hydrochloric acid solution is 0.2±0.05mol / L; Filtration and washing: The reflux liquid is cooled to 15-25°C and then filtered to obtain a first filtrate and a filter residue; the filter residue is washed with a third mixed solution until the washing liquid is a transparent liquid; the first filtrate and all the washing liquids are mixed to form a second filtrate; the third mixed solution includes dioxane and water in a volume ratio of 9±0.2:1±0.

2. Neutralization and concentration: The second filtrate was neutralized to pH 3.5±0.5 using a saturated NaHCO3 solution, and then concentrated under reduced pressure to obtain a concentrated solution; the concentration treatment was carried out at a concentration temperature of 45±3℃, a concentration time of 1±0.1h, and a pressure of 0.87~0.97 atmospheres. Precipitation and purification: The concentrated solution was added dropwise to 500±10ml of ice water and allowed to stand overnight at 4℃; the precipitated dark brown oily lignin was collected, centrifuged, washed with water, and freeze-dried for 48±0.5h to obtain poplar lignin extract.

8. The lignin-CN coupling electrocatalytic reaction system as described in claim 1, characterized in that, The nitrogen oxides include at least one of inorganic nitrogen oxides and organic nitro compounds.

9. An aromatic imine compound product, characterized in that, It is prepared using the lignin CN-coupled electrocatalytic reaction system as described in any one of claims 1 to 8.

10. The application of the lignin CN-coupled electrocatalytic reaction system as described in any one of claims 1 to 8 in the preparation of aromatic imine compounds.

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