Process for preparing glutaraldehyde through cyclopentene oxidation

Abstract

A technology for preparing glutaraldehyde through cyclopentene oxidation belongs to the technical field of organic synthesis, glutaraldehyde is prepared through cyclopentene oxidation by adopting a photocatalysis-electrocatalysis synergistic catalyst g-C3N4 / TiO2 (at) Au-Co / N-G. The catalyst is of a unique core-shell structure, is stable in property, promotes an oxygen reduction reaction in a catalysis technology, and has good catalytic activity. The conversion rate of cyclopentene and the selectivity of glutaraldehyde are remarkably improved, and the effect is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method and system for preparing glutaraldehyde by oxidizing cyclopentene under photo-electric synergistic catalysis. Background Art

[0002] Glutaraldehyde is an important fine chemical product and intermediate, capable of cross-linking and solidifying proteins. It is widely used in fields such as biopharmaceutical engineering, cellular immunology, biochemical engineering, leather chemistry, histochemistry, microbiology, and environmental protection. Currently, the main industrial methods for preparing glutaraldehyde include the acrolein-ethyl vinyl ether method and the cyclopentene oxidation method. The cyclopentene oxidation method is the most commonly used, but the traditional cyclopentene oxidation method suffers from low catalyst activity, poor selectivity, harsh reaction conditions, and severe environmental pollution.

[0003] Existing processes for oxidizing cyclopentene to produce glutaraldehyde often use heteropolyacids and tungsten-based molecular sieves as catalysts. These processes typically have low yields, generally around 70%, and require large amounts of oxidants such as hydrogen peroxide and ozone. This not only increases production costs but also generates large amounts of wastewater and waste residue, polluting the environment. Furthermore, traditional reaction processes often rely on batch operations, resulting in low space-time yields and difficulty meeting the requirements of large-scale industrial production.

[0004] Therefore, developing an efficient, green and environmentally friendly process for preparing glutaraldehyde by oxidizing cyclopentene has important practical significance and application promotion value. Summary of the Invention

[0005] In order to solve the deficiencies of the prior art, the present invention proposes a process for preparing glutaraldehyde by oxidizing cyclopentene, which adopts a photo-electrocatalytic method to effectively solve various problems in the prior art.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0007] A process for preparing glutaraldehyde by oxidizing cyclopentene comprises the following steps:

[0008] (1) Catalyst preparation: Supported carbon nitride (g-C3N4) / titanium dioxide (TiO2) composite nanomaterials were synthesized as photocatalysts, and nitrogen-doped graphene-supported gold-cobalt alloy nanoparticles (Au-Co / NG) were prepared as electrocatalysts. The photocatalyst and electrocatalyst were assembled into a core-shell structure (g-C3N4 / TiO2@Au-Co / NG) synergistic catalyst by electrostatic adsorption;

[0009] (2) Photocatalytic oxidation reaction: cyclopentene and the synergistic catalyst are dispersed in a mixed solvent of acetonitrile and water, oxygen is introduced, and a photocatalytic oxidation reaction is carried out under visible light irradiation to generate an epoxycyclopentane intermediate;

[0010] (3) Electrocatalytic oxidation reaction: The photocatalytic oxidation reaction solution is transferred to a dual-chamber electrochemical reactor. A carbon cloth electrode modified with a synergistic catalyst is used as the anode, oxygen is introduced into the cathode, and a DC voltage is applied to perform an electrocatalytic oxidation reaction to promote the further oxidation of cyclopentene oxide to glutaraldehyde.

[0011] (4) Product separation: The electrocatalytic oxidation reaction liquid is subjected to reduced pressure distillation to separate the solvent, and then decolorized by adsorption on an activated carbon column, and finally purified by membrane filtration to obtain glutaraldehyde.

[0012] In the present invention, the preparation method of the photocatalyst is: melamine and titanium dioxide nanoparticles are mixed in a certain proportion, calcined at high temperature under a nitrogen atmosphere to obtain a supported g-C3N4 / TiO2 nanomaterial, and then doped with metal atoms to enhance the light response range, wherein the doping amount of metal atoms is 0.5-5% by mass.

[0013] Specifically: ①Mix melamine and titanium dioxide nanoparticles in a mass ratio of 5:1, add them into deionized water and ultrasonically disperse them for 30 minutes to form a uniform suspension; ②Evaporate the suspension to dryness at 80°C with magnetic stirring to obtain a precursor powder; ③Place the precursor powder in a tube furnace, heat it to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine it at a constant temperature for 4 hours; ④After cooling naturally to room temperature, grind the product into fine powder to obtain a loaded g-C3N4 / TiO2 composite nanomaterial; ⑤Dope metal atoms by impregnation: disperse the g-C3N4 / TiO2 composite nanomaterial in ferric nitrate solution, where Fe 3+ The concentration was 0.05 mol / L, and after ultrasonic treatment for 1 h, it was stirred and evaporated to dryness at 60 ° C, and then calcined at 300 ° C for 2 h to obtain doped Fe 3+ g-C3N4 / TiO2 photocatalyst, in which Fe 3+ The doping amount is 1% by mass.

[0014] In the present invention, the preparation method of the electrocatalyst is: using a chemical reduction method, mixing a mixed solution of chloroauric acid and cobalt nitrate with a nitrogen-doped graphene dispersion, and reducing it under the action of a reducing agent to obtain an Au-Co / NG electrocatalyst, wherein the molar ratio of gold to cobalt is (1-3):1.

[0015] Specifically: ① Graphene oxide was prepared by the improved Hummers method: graphite powder was reacted with concentrated sulfuric acid, sodium nitrate and potassium permanganate in an ice bath, then the temperature was gradually raised to 35°C and 98°C for reaction, and finally hydrogen peroxide was added to terminate the reaction. Graphene oxide was obtained after washing, centrifugation and drying; ② Graphene oxide was dispersed in deionized water and ultrasonically stripped for 2 hours to obtain a graphene oxide dispersion; ③ urea was added to the graphene oxide dispersion, wherein the mass ratio of graphene oxide to urea was 1:10, and a hydrothermal reaction was carried out at 180°C for 12 hours to obtain nitrogen-doped graphene (NG); ④ chloroauric acid (HAuCl4) and cobalt nitrate were added to the graphene oxide dispersion. (Co(NO3)2) is configured into a mixed solution in a molar ratio of 1:1, wherein the concentration of Au is 0.01 mol / L; ⑤ NG is dispersed in the above mixed solution to obtain an NG concentration of 1 mg / mL, and ultrasonic dispersion is performed for 30 minutes; ⑥ Under rapid stirring, a sodium borohydride (NaBH4) solution with a concentration of 0.1 mol / L is added dropwise as a reducing agent, and the molar ratio of NaBH4 to metal ions is 5:1; ⑦ After continuing to stir the reaction for 2 hours, centrifugation is performed, and the mixture is washed with deionized water and ethanol several times, and vacuum dried at 60°C for 12 hours to obtain an Au-Co / NG electrocatalyst, wherein the molar ratio of gold to cobalt is 1:1.

[0016] In the present invention, the preparation method of the synergistic catalyst is as follows: dispersing the photocatalyst and the electrocatalyst in an ethanol solution, adjusting the pH value to 3-5, mixing under ultrasonic action, and then centrifuging, washing, and drying to obtain a core-shell structured synergistic catalyst.

[0017] Specifically: ① The photocatalyst was dispersed in an ethanol solution to a concentration of 10 mg / mL, and the pH value was adjusted to 3 with hydrochloric acid; ② The electrocatalyst was dispersed in an ethanol solution to a concentration of 10 mg / mL, and the pH value was adjusted to 10 with aqueous ammonia; ③ Under ultrasonic action, the electrocatalyst solution was slowly added dropwise to the photocatalyst solution, and the mass ratio of photocatalyst to electrocatalyst was 2:1; ④ After continuing ultrasonic mixing for 30 minutes, stirring at room temperature for 12 hours allowed the photocatalyst and electrocatalyst to assemble into a core-shell structure through electrostatic adsorption; ⑤ Centrifugal separation, washing with ethanol several times, and vacuum drying at 60°C for 12 hours to obtain the core-shell structure synergistic catalyst g-C3N4 / TiO2@Au-Co / NG.

[0018] In the present invention, in the photocatalytic oxidation reaction, the concentration of cyclopentene is 0.1-1 mol / L, the amount of the co-catalyst is 5-20% of the mass of cyclopentene, the volume ratio of acetonitrile / water is (1-5):1, the oxygen flow rate is 10-100 mL / min, the reaction temperature is 30-40°C, and the reaction time is 1-5 hours; the anode oxygen flow rate of the electrocatalytic reaction is 50-200 mL / min, the reaction temperature is 30-40°C, the reaction time is 1-3 hours, and the DC voltage is 0.8-1.2V.

[0019] In the present invention, during product separation, the pressure of the reduced pressure distillation is 0.01-0.1 MPa, the temperature is 40-60°C, the filling amount of the activated carbon column is 5-10% of the volume of the reaction liquid, the adsorption temperature is 20-40°C, the adsorption time is 0.5-2h, the molecular weight cutoff of the membrane filtration is 1000Da, the operating pressure is 0.1-0.5 MPa, and the temperature is 20-40°C.

[0020] Specifically, the process flow of the photocatalytic oxidation reaction is as follows: ① In a quartz reactor with a condensation reflux device, 150 mL of acetonitrile and 50 mL of deionized water were added to form an acetonitrile-water mixed solution with a volume ratio of 3:1; ② 50 mmol of cyclopentene and 0.5 g of a synergistic catalyst were added to the mixed solvent; ③ The reactor was sealed, oxygen was introduced at an oxygen flow rate of 50 mL / min, and the air in the reactor was exhausted; ④ A magnetic stirrer was turned on at a stirring speed of 500 rpm to ensure uniform mixing of the reaction system; ⑤ An LED visible light source was turned on to irradiate the reaction system with a wavelength range of 450-550 nm and a light intensity of 200 mW / cm 3 ⑥ Place the reactor in a constant temperature water bath, control the reaction temperature to 30°C, and the reaction time to 3h.

[0021] The process of electrocatalytic oxidation reaction is as follows: ① 0.1g of the synergistic catalyst is dispersed in 10mL of 5% by mass Nafion solution and ultrasonicated for 30min to form a uniform catalyst ink; ② an area of ​​not less than 10cm 2 The carbon cloth was washed with ethanol and deionized water in turn, and then dried at 60 ° C; ③ The catalyst ink was evenly coated on the surface of the carbon cloth with a pipette, and the coating amount was 0.5 mg / cm 2, and then dried at room temperature to obtain a carbon cloth electrode modified with a system catalyst; ④ Select a dual-chamber electrochemical reactor, install the prepared carbon cloth electrode in the anode chamber, install a gas diffusion electrode in the cathode chamber, and install a proton exchange membrane between the anode chamber and the cathode chamber; ⑤ Transfer the photocatalytic oxidation reaction liquid to the anode chamber, and introduce oxygen into the cathode chamber at an oxygen flow rate of 100 mL / min; ⑥ Connect a DC power supply, apply a constant voltage of 1.0 V, control the reaction temperature to 30°C, and the reaction time to 2 h; ⑦ During the reaction, monitor the current changes by a constant potentiostat, take samples and analyze them regularly, and monitor the generation amount and selectivity of glutaraldehyde.

[0022] The process flow of product separation is as follows: ① solvent separation by reduced pressure distillation: the electrocatalytic oxidation reaction liquid is transferred to a rotary evaporator, distilled at 50°C under a reduced pressure of 0.05MPa, the acetonitrile solvent is recovered, and the temperature is continued to rise to 60°C to evaporate most of the water to obtain a concentrated solution; ② activated carbon column adsorption decolorization: after the concentrated solution is cooled to room temperature, it is slowly passed through an activated carbon column with a flow rate controlled at 1mL / min, and adsorption decolorization is performed at room temperature, and the effluent is collected, wherein the activated carbon column has an inner diameter of 2cm, a column height of 20cm, and is filled with 20g of activated carbon; ③ membrane filtration purification: the decolorized effluent is passed through a membrane filtration device with an operating pressure controlled at 0.3MPa and a temperature of 30°C for cyclic filtration, wherein the filter membrane is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 1000Da, and then the permeate is collected and concentrated under reduced pressure at low temperature to obtain a high-purity glutaraldehyde product, and the product purity and yield are analyzed.

[0023] In the present invention, the preparation system used in the above process includes a photocatalytic reaction device, an electrocatalytic reaction device and a product separation device, wherein the photocatalytic reaction device includes a reaction vessel, a visible light source, an oxygen introduction device and a stirring device, wherein the reaction vessel is made of quartz material, the visible light source is an LED, etc., with a wavelength of 450-550nm, the oxygen passing device includes an oxygen cylinder and a gas flow meter, and the stirring device is a magnetic stirrer; the electrocatalytic reaction device includes a dual-chamber electrochemical reactor, a DC power supply, an anode electrode and a cathode electrode, wherein the dual-chamber electrochemical reactor is divided into an anode chamber and a cathode chamber by a proton exchange membrane, the anode electrode is a carbon cloth electrode modified with a synergistic catalyst, the cathode electrode is a gas diffusion electrode, and the output voltage of the DC power supply is 0.8-1.2V; the product separation device includes a vacuum distillation device, an activated carbon column and a membrane filtration device, wherein the vacuum distillation device includes a distillation flask, a condenser and a vacuum pump, the activated carbon column is a glass column, the membrane filtration device includes a membrane assembly and a high-pressure pump, and the filter membrane is a polyethersulfone ultrafiltration membrane.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The catalyst of the present application adopts a unique core-shell structure, with g-C3N4 / TiO2 as the photocatalytic core, generating photogenerated electron-hole pairs under visible light irradiation, and Au-Co / NG as the electrocatalytic shell, generating active oxygen through oxygen reduction reaction. The photogenerated electrons are transferred to the electrocatalytic shell through the interface, promoting the oxygen reduction reaction, while the photogenerated holes remain in the photocatalytic core, oxidizing cyclopentene to generate epoxycyclopentane intermediates. This synergistic effect not only improves the separation efficiency of photogenerated carriers, but also enhances the generation capacity of active oxygen, thereby significantly improving the conversion rate of cyclopentene and the selectivity of glutaraldehyde;

[0026] (2) The process route of the present application adopts a two-stage oxidation process. In the first stage, photocatalytic oxidation generates an epoxycyclopentane intermediate, and in the second stage, electrocatalytic oxidation converts the intermediate into glutaraldehyde. This step-by-step oxidation process avoids the problem of over-oxidation in the traditional one-step oxidation process and improves the selectivity of glutaraldehyde.

[0027] (3) The present application adopts membrane filtration to replace the distillation scheme in the traditional process for product purification, thereby avoiding the decomposition of glutaraldehyde by high temperature and effectively improving the yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The XRD patterns of the catalyst of this application at various stages (photocatalyst, electrocatalyst, synergistic catalyst) and the comparison diagram with traditional catalysts are shown. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0030] Example 1

[0031] A process for preparing glutaraldehyde by oxidizing cyclopentene, wherein the preparation method comprises the following steps:

[0032] S1: Catalyst preparation

[0033] S1-1: Preparation of photocatalyst: 1. Melamine and titanium dioxide nanoparticles were mixed in a mass ratio of 5:1, added to deionized water and ultrasonically dispersed for 30 minutes to form a uniform suspension; 2. The suspension was evaporated to dryness under magnetic stirring at 80 ° C to obtain a precursor powder; 3. The precursor powder was placed in a tube furnace, heated to 550 ° C at a heating rate of 5 ° C / min under a nitrogen atmosphere, and calcined at a constant temperature for 4 hours; 4. After cooling naturally to room temperature, the product was ground into fine powder to obtain a loaded g-C3N4 / TiO2 composite nanomaterial; 5. Metal atom doping was performed by impregnation method: the g-C3N4 / TiO2 composite nanomaterial was dispersed in ferric nitrate solution, wherein Fe 3+The concentration was 0.05 mol / L, and after ultrasonic treatment for 1 h, it was stirred and evaporated to dryness at 60 ° C, and then calcined at 300 ° C for 2 h to obtain doped Fe 3+ g-C3N4 / TiO2 photocatalyst, in which Fe 3+ The doping amount is 0.5-5% by mass;

[0034] S1-2: Preparation of electrocatalysts: ① Graphene oxide was prepared by the improved Hummers method: graphite powder was reacted with concentrated sulfuric acid, sodium nitrate and potassium permanganate in an ice bath, and then the temperature was gradually raised to 35°C and 98°C for reaction. Finally, hydrogen peroxide was added to terminate the reaction. After washing, centrifugation and drying, graphene oxide was obtained; ② Graphene oxide was dispersed in deionized water and ultrasonically stripped for 2 hours to obtain a graphene oxide dispersion; ③ Urea was added to the graphene oxide dispersion, wherein the mass ratio of graphene oxide to urea was 1:10, and a hydrothermal reaction was carried out at 180°C for 12 hours to obtain nitrogen-doped graphene (NG); ④ Chloroauric acid (HAuCl4) and nitrate were added to the dispersion. ⑤ NG was dispersed in the above mixed solution to obtain an NG concentration of 1 mg / mL, and ultrasonic dispersion was performed for 30 minutes; ⑥ Under rapid stirring, a 0.1 mol / L sodium borohydride (NaBH4) solution was added dropwise as a reducing agent, and the molar ratio of NaBH4 to metal ions was 5:1; ⑦ After continuing to stir the reaction for 2 hours, centrifugation was performed, and the mixture was washed with deionized water and ethanol several times, and vacuum dried at 60°C for 12 hours to obtain an Au-Co / NG electrocatalyst, wherein the molar ratio of gold to cobalt was (1-3):1;

[0035] S1-3: Preparation of synergistic catalyst: ① Disperse the photocatalyst in an ethanol solution to a concentration of 10 mg / mL, and adjust the pH value to 3 with hydrochloric acid; ② Disperse the electrocatalyst in an ethanol solution to a concentration of 10 mg / mL, and adjust the pH value to 10 with ammonia water; ③ Under ultrasonic action, slowly add the electrocatalyst solution dropwise to the photocatalyst solution, with a mass ratio of photocatalyst to electrocatalyst of 2:1; ④ Continue ultrasonic mixing for 30 minutes, and stir at room temperature for 12 hours to allow the photocatalyst and electrocatalyst to assemble into a core-shell structure through electrostatic adsorption; ⑤ Centrifuge, wash with ethanol several times, and vacuum dry at 60°C for 12 hours to obtain the core-shell structure synergistic catalyst g-C3N4 / TiO2@Au-Co / NG;

[0036] S2: Photocatalytic oxidation reaction: ① In a quartz reactor with a condenser reflux device, acetonitrile and deionized water were added to prepare 200-300 mL of an acetonitrile-water mixed solution in a volume ratio of (1-5):1; ② Cyclopentene and a synergistic catalyst were added to the mixed solvent so that the concentration of cyclopentene in the solution was 0.1-1 mol / L, and the amount of the synergistic catalyst was 5-20% of the mass of cyclopentene; ③ The reactor was sealed, oxygen was introduced at an oxygen flow rate of 10-100 mL / min, and the air in the reactor was exhausted; ④ A magnetic stirrer was turned on at a stirring speed of 500 rpm to uniformly mix the reaction system; ⑤ An LED visible light source was turned on to irradiate the reaction system with a wavelength range of 450-550 nm and a light intensity of 200 mW / cm 3 ;⑥ Place the reactor in a constant temperature water bath, control the reaction temperature to 30-40°C, and the reaction time to 1-5h;

[0037] S3: Electrocatalytic oxidation reaction: ① Disperse 0.1 g of the synergistic catalyst in 10 mL of a 5% mass percent Nafion solution and ultrasonicate for 30 min to form a uniform catalyst ink; ② Place the catalyst in an area of ​​not less than 10 cm 2 The carbon cloth was washed with ethanol and deionized water in turn, and then dried at 60 ° C; ③ The catalyst ink was evenly coated on the surface of the carbon cloth with a pipette, and the coating amount was 0.5-1 mg / cm 2 , and then dried at room temperature to obtain a carbon cloth electrode modified with a system catalyst; ④ Select a dual-chamber electrochemical reactor, install the prepared carbon cloth electrode in the anode chamber, install a gas diffusion electrode in the cathode chamber, and install a proton exchange membrane between the anode chamber and the cathode chamber; ⑤ Transfer the photocatalytic oxidation reaction liquid to the anode chamber, and introduce oxygen into the cathode chamber at an oxygen flow rate of 50-200mL / min; ⑥ Connect a DC power supply, apply a constant voltage of 0.8-1.2V, control the reaction temperature to 30-40℃, and the reaction time to 1-3h;

[0038] S4: Product separation

[0039] S4-1: Separation of solvent by vacuum distillation: Transfer the electrocatalytic oxidation reaction solution to a rotary evaporator and distill at 40-60°C under a reduced pressure of 0.01-0.1 MPa to recover acetonitrile and water to obtain a concentrated solution;

[0040] S4-2: Decolorization by adsorption on an activated carbon column: After the concentrate is cooled to room temperature, it is slowly passed through an activated carbon column at a flow rate of 1 mL / min at 20-40°C for adsorption decolorization for 0.5-2 h. The effluent is collected. The activated carbon column is filled with 5-10% of the reaction solution volume.

[0041] S4-3: Membrane filtration purification: The decolorized effluent is passed through a membrane filtration device with an operating pressure of 0.1-0.5 MPa and a temperature of 30°C for circulation filtration. The filtration membrane is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 1000 Da. The permeate is then collected and concentrated under reduced pressure at low temperature to obtain a high-purity glutaraldehyde product.

[0042] Example 2

[0043] This embodiment uses the preparation process of Example 1, selects different process parameters, and conducts comparative tests as test examples.

[0044] Test Example 1

[0045] S1 is doped with 1% Fe 3+ The photocatalyst and the electrocatalyst with a gold-cobalt Au-Co molar ratio of 1:1 were used to prepare a synergistic catalyst;

[0046] In S2, the acetonitrile-water solvent includes 150 mL of acetonitrile and 50 mL of deionized water, the amount of cyclopentene added is 50 mmol, the amount of the co-catalyst added is 0.5 g, the flow rate of oxygen is 50 mL / min, the photocatalytic oxidation reaction temperature is 30°C, and the reaction time is 3 h;

[0047] In S3, the coating amount of the carbon cloth electrode is 0.5 mg / cm 2 In the dual-chamber electrochemical reactor, the flow rate of oxygen into the cathode chamber was 100 mL / min, the voltage of the applied current was 1.0 V, the electrocatalytic oxidation reaction temperature was 30 ° C, and the reaction time was 2 h;

[0048] In S4, the reduced pressure conditions for vacuum distillation are 0.05 MPa and a temperature of 50°C. The filling amount of the activated carbon column used for adsorption decolorization is 5%, the adsorption temperature is 30°C, the adsorption time is 1 hour, and the pressure of membrane filtration purification is 0.3 MPa and the temperature is 30°C.

[0049] Test Example 2

[0050] S1 is doped with 3% Fe 3+ The photocatalyst and the electrocatalyst with a gold-cobalt Au-Co molar ratio of 3:1 were used to prepare the synergistic catalyst;

[0051] In S2, the acetonitrile-water solvent includes 200 mL of acetonitrile and 40 mL of deionized water, the amount of cyclopentene added is 80 mmol, the amount of the co-catalyst added is 0.8 g, the flow rate of oxygen is 80 mL / min, the photocatalytic oxidation reaction temperature is 35°C, and the reaction time is 4 h;

[0052] In S3, the coating amount of the carbon cloth electrode is 0.75 mg / cm 2In the dual-chamber electrochemical reactor, the flow rate of oxygen into the cathode chamber was 150 mL / min, the voltage of the applied current was 1.2 V, the electrocatalytic oxidation reaction temperature was 35 ° C, and the reaction time was 1.5 h;

[0053] In S4, the reduced pressure conditions for vacuum distillation are 0.03 MPa and a temperature of 45°C. The filling amount of the activated carbon column used for adsorption decolorization is 8%, the adsorption temperature is 25°C, the adsorption time is 1.5 h, and the pressure of membrane filtration purification is 0.2 MPa and the temperature is 25°C.

[0054] Test Example 3

[0055] S1 is doped with 5% Fe 3+ The photocatalyst and the electrocatalyst with a gold-cobalt Au-Co molar ratio of 3:2 were used to prepare the synergistic catalyst;

[0056] In S2, the acetonitrile-water solvent includes 250 mL of acetonitrile and 50 mL of deionized water, the amount of cyclopentene added is 100 mmol, the amount of the synergistic catalyst added is 1.0 g, the flow rate of the oxygen is 100 mL / min, the photocatalytic oxidation reaction temperature is 40°C, and the reaction time is 5 h;

[0057] In S3, the coating amount of the carbon cloth electrode is 1.0 mg / cm 2 In the dual-chamber electrochemical reactor, the flow rate of oxygen into the cathode chamber was 200 mL / min, the voltage of the applied current was 0.8 V, the electrocatalytic oxidation reaction temperature was 40 ° C, and the reaction time was 3 h;

[0058] In S4, the reduced pressure conditions for vacuum distillation are 0.01 MPa and a temperature of 60°C. The filling amount of the activated carbon column used for adsorption decolorization is 10%, the adsorption temperature is 40°C, the adsorption time is 2 hours, and the pressure of membrane filtration purification is 0.5 MPa and the temperature is 40°C.

[0059] The results of the above three groups of test cases were sorted out and the following data were obtained.

[0060] Table 1 Experimental results of test examples 1-3

[0061]

[0062] The following are comparative test examples, which are compared from different directions.

[0063] Comparative Example 1

[0064] In this example, a conventional catalyst (WO3 / SiO2) was used to oxidize cyclopentene to prepare glutaraldehyde, and the process method adopted a common process.

[0065] Experimental conditions

[0066] Catalyst: WO3 / SiO2 with a WO3 loading of 15%, purchased from Sigma-Aldrich;

[0067] Reaction parameters: 50 mmol of cyclopentene, 0.5 g of catalyst, 150 mL of acetonitrile and 50 g of deionized water as solvent, 50 mL / min of oxygen flow rate, 60°C temperature, 5 h reaction time. Product isolation was performed by distillation at 80°C under atmospheric pressure. The results are shown in Table 2.

[0068] Table 2 Test results of traditional catalysts

[0069]

[0070] The cyclopentanone by-product was detected by GC-MC, which proved that the traditional catalyst had the problem of over-oxidation.

[0071] WO3 is severely agglomerated on the SiO2 surface, and the utilization rate of active sites is low.

[0072] Comparative Example 2

[0073] In this example, a simple photocatalytic system (g-C3N4) was used to oxidize cyclopentene to produce glutaraldehyde.

[0074] Experimental conditions

[0075] Catalyst: g-C3N4, obtained by calcining melamine at 550℃;

[0076] Reaction parameters: 50 mmol of cyclopentene, 0.5 g of catalyst, 150 mL of acetonitrile and 50 g of deionized water as solvent, 50 mL / min of oxygen flow rate, visible light (450-550 nm), reaction temperature of 30° C., reaction time of 5 h, and product separation as in Experimental Example 1. The obtained results are shown in Table 3.

[0077] Table 3 Results of simple photocatalytic test

[0078]

[0079] UV-Vis: The photocatalyst g-C3N4 only responds to ultraviolet light and has low visible light utilization efficiency.

[0080] Comparative Example 3

[0081] In this example, a simple electrocatalytic system (Au-Co / NG) was used to oxidize cyclopentene to produce glutaraldehyde.

[0082] Experimental conditions

[0083] Catalyst: Au-Co / NG with a gold-cobalt molar ratio of 1:1, same as in Experiment 1;

[0084] Reaction parameters: cyclopentene 50 mmol, catalyst modified carbon cloth electrode, coating amount 0.5 mg / cm 2 The solvent was prepared from 150 mL of acetonitrile and 50 mL of deionized water, the cathode oxygen flow rate was 100 mL / min, a DC voltage of 1.0 V was applied, the reaction temperature was 30° C., the reaction time was 5 h, and the product was separated as in Experimental Example 1. The obtained result data are shown in Table 4.

[0085] Table 4 Results of simple electrocatalytic test

[0086]

[0087]

[0088] The electrocatalytic oxygen reduction overpotential is high and the efficiency of active oxygen generation is low; after the reaction, Co 2+ Oxidation to Co 3+ , the catalytic activity decays.

[0089] The three groups of comparative examples were compared with Experimental Example 1, and the test results are shown in Table 5.

[0090] Table 5 Comparison of the results of Test Example 1 and Comparative Examples 1-3

[0091] Group Conversion rate Selectivity Yield Energy consumption Reaction temperature By-product content Test Example 1 98.3％ 85.6％ 84.1％ 0.9kWh / mol 30℃ ＜2％ Comparative Example 1 75.2％ 70.5％ 53.0％ 1.8kWh / mol 60℃ 29.5％ Comparative Example 2 78.5％ 70.1％ 55.0％ - 30℃ 29.9％ Comparative Example 3 68.3％ 60.8％ 41.5％ 2.3kWh / mol 30℃ 38.7％

[0092] Experimental results analysis

[0093] (1) Improved conversion rate and selectivity

[0094] The yields of Experimental Example 1 were increased by 58.7%, 52.9%, and 102.7% compared with Comparative Examples 1-3, respectively, demonstrating that the photo-electrosynergistic effect significantly inhibited side reactions and could reduce the production of by-products such as cyclopentanone; the core-shell structure of the synergistic catalyst promoted the directional transfer of photogenerated electrons and reduced excessive oxidation.

[0095] (2) Reduced energy consumption

[0096] The reaction temperature of Experimental Example 1 is 30°C lower than that of Comparative Example 1, the energy consumption is reduced by 50%, and no high-temperature and high-pressure equipment is required. The high energy consumption of Comparative Example 3 is due to the need to overcome the high overpotential of simple electrocatalysis. The synergistic system achieves pre-activation through photocatalysis to reduce the electrocatalytic barrier, reduce electrocatalytic energy consumption, and thus reduce overall energy consumption.

[0097] (3) Catalyst stability

[0098] The yield of g-C3N4 in comparative example 2 decreased significantly after 5 cycles, while the activity retention rate of the catalyst in the experimental example was still above 90% after 10 cycles. The core-shell structure can effectively protect the active sites and greatly improve the stability of the catalyst.

[0099] (4) Product purity and separation

[0100] The conventional distillation in Comparative Example 1 resulted in the decomposition of glutaraldehyde and a decrease in purity, whereas the membrane filtration technology in Experimental Example 1 enabled the purity to reach 99.2%, thereby improving the yield.

[0101] (5) Synergistic catalysis

[0102] The single catalytic systems of Comparative Examples 2 and 3 demonstrate that photocatalysis and electrocatalysis alone cannot achieve the efficiency of a synergistic system, demonstrating the technical superiority of synergistic catalysis.

[0103] Example 3

[0104] In this example, XRD analysis was performed on the photocatalyst, electrocatalyst, synergistic catalyst, and traditional catalyst (WO3 / SiO2). Figure 1 shown.

[0105] (1) Figure 1 -a, pure g-C3N4 (red) shows a typical interlayer stacking diffraction peak (002 crystal plane) at 2θ=27.4°, corresponding to the layered structure of graphite carbon nitride; pure TiO2 (blue) shows characteristic peaks at 2θ=25.3° (anatase phase 101 crystal plane), 37.8° (anatase phase 004 crystal plane), and 48.0° (anatase phase 200 crystal plane); Fe-doped g-C3N4 / TiO2 (green) shows that the anatase phase 101 crystal plane peak of TiO2 shifts to a low angle, indicating that Fe 3+ The successful incorporation of Fe into the TiO2 lattice resulted in lattice distortion, and the 27.4° peak intensity of g-C3N4 decreased slightly, but the peak shape remained intact, indicating that Fe doping did not destroy the layered structure of g-C3N4.

[0106] Fe 3+ Doping extends the visible light response range of the photocatalyst without changing the crystal structure of g-C3N4 and TiO2, ensuring efficient separation of photogenerated carriers.

[0107] (2) Figure 1 -b, the Au-Co alloy (blue) shows alloy diffraction peaks at 2θ=38.2° (111 crystal plane of gold) and 44.2° (111 crystal plane of cobalt), and the peak positions are between pure Au (38.2°) and pure Co (44.3°), indicating the formation of Au-Co solid solution; nitrogen-doped graphene (NG) (red) shows the 002 crystal plane peak of graphene at 2θ=26.5°, and the peak broadening indicates that the graphene is a nanosheet structure. At the same time, a weak 100 crystal plane peak appears at 43.3°, proving that nitrogen doping introduces lattice defects.

[0108] It shows that the formation of Au-Co alloy optimizes the electronic structure of oxygen reduction active sites, while nitrogen-doped graphene provides a highly conductive base, and the two synergistically improve the electrocatalytic efficiency.

[0109] (3) Figure 1 -c, the synergistic catalyst g-C3N4 / TiO2@Au-Co / NG (red) simultaneously shows the 25.1° peak of iron-doped g-C3N4 and the 38.2° and 44.2° peaks of Au-Co alloy, indicating that the core-shell structure is successfully assembled; no new impurity peaks appear, and the intensity of each peak does not significantly attenuate compared with that of a single catalyst, proving that the photocatalyst and the electrocatalyst have formed a close interface through the core-shell structure of electrostatic adsorption, with stable structure and chemical properties.

[0110] It is explained that the formation of the synergistic catalyst core-shell structure promotes the directional migration of photogenerated electrons from the g-C3N4 / TiO2 core to the Au-Co / NG shell, inhibits carrier recombination, and enhances the photocatalytic-electrocatalytic synergistic effect.

[0111] (4) Figure 1 -c, the characteristic peaks of the fresh synergistic catalyst (red) are sharp and intense, while the peak position and peak shape of the catalyst (blue) after 10 cycles remain basically unchanged. Only the peak intensity of 38.2° of Au-Co alloy decreases slightly, indicating that the metal nanoparticles do not undergo obvious agglomeration. No oxidation peaks, such as 36.9° of Co3O4, are observed, proving that the catalyst maintains high stability during the reaction.

[0112] It shows that the core-shell structure effectively protects the Au-Co alloy nanoparticles through physical coating, preventing them from oxidation or agglomeration during recycling, thereby maintaining high catalytic activity.

[0113] (5) Figure 1 -d, compared with the synergistic catalyst of the present application (blue), the traditional WO3 / SiO2 catalyst (red) shows characteristic peaks at 2θ=23.1° (002 crystal plane of WO3) and 24.3° (amorphous peak of SiO2), but the peak intensity is low and broadened, indicating that WO3 has poor dispersion on the SiO2 surface and low utilization of active sites. Compared with the synergistic catalyst of the present application, the high crystallinity and sharp characteristic peaks indicate its structural advantage.

[0114] In summary, the unique core-shell structure of the photo-electrocatalyst g-C3N4 / TiO2@Au-Co / NG of the present application is stable, and it promotes the oxygen reduction reaction in the process of catalyzing the oxidation of cyclopentene to prepare glutaraldehyde, significantly improving the conversion rate of cyclopentene and the selectivity of glutaraldehyde, with remarkable effects.

Claims

1. A process for preparing glutaraldehyde by oxidation of cyclopentene, characterized in that: The following steps are involved: (1) Catalyst preparation: Synthesize supported carbon nitride / titanium dioxide composite nanomaterials as photocatalysts, prepare nitrogen-doped graphene-supported gold-cobalt alloy nanoparticles as electrocatalysts, and assemble the photocatalyst and electrocatalyst into a core-shell structured synergistic catalyst through electrostatic adsorption; (2) Photocatalytic oxidation reaction: cyclopentene and the synergistic catalyst are dispersed in a mixed solvent of acetonitrile and water, oxygen is introduced, and a photocatalytic oxidation reaction is carried out under visible light irradiation to generate an epoxycyclopentane intermediate; (3) Electrocatalytic oxidation reaction: The photocatalytic oxidation reaction liquid is transferred to a dual-chamber electrochemical reactor. A carbon cloth electrode modified with a synergistic catalyst is used as the anode, oxygen is introduced into the cathode, and a DC voltage is applied to carry out an electrocatalytic oxidation reaction to promote the further oxidation of cyclopentene oxide to glutaraldehyde. (4) Product separation: The electrocatalytic oxidation reaction liquid is subjected to reduced pressure distillation to separate the solvent, and then decolorized by adsorption on an activated carbon column, and finally purified by membrane filtration to obtain glutaraldehyde.

2. The process according to claim 1, characterized in that: The preparation method of the photocatalyst is: mixing melamine and titanium dioxide nanoparticles in a certain proportion, calcining at high temperature under a nitrogen atmosphere to obtain a supported g-C3N4 / TiO2 nanomaterial, and then doping with metal atoms to enhance the light response range, wherein the doping amount of the metal atoms is 0.5-5% by mass.

3. The process according to claim 2, wherein: The specific steps are as follows: ①Mix melamine and titanium dioxide nanoparticles in a mass ratio of 5:1, add them into deionized water and ultrasonically disperse them for 30 minutes to form a uniform suspension; ②Evaporate the suspension to dryness at 80°C with magnetic stirring to obtain a precursor powder; ③Place the precursor powder in a tube furnace, heat it to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcine it at a constant temperature for 4 hours; ④After cooling naturally to room temperature, grind the product into fine powder to obtain a supported g-C3N4 / TiO2 composite nanomaterial; ⑤Dope the metal atoms by impregnation: disperse the g-C3N4 / TiO2 composite nanomaterial in ferric nitrate solution, where Fe 3+ The concentration was 0.05 mol / L, and after ultrasonic treatment for 1 h, it was stirred and evaporated to dryness at 60 ° C, and then calcined at 300 ° C for 2 h to obtain doped Fe 3+ g-C3N4 / TiO2 photocatalyst, in which Fe 3+ The doping amount is 1% by mass.

4. The process according to claim 1, wherein: The electrocatalyst is prepared by chemical reduction, mixing a mixed solution of chloroauric acid and cobalt nitrate with a nitrogen-doped graphene dispersion, and reducing the mixture under the action of a reducing agent to obtain an Au-Co / NG electrocatalyst, wherein the molar ratio of gold to cobalt is (1-3):

1.

5. The process according to claim 3, wherein: The specific steps are as follows: ① Graphene oxide is prepared by the improved Hummers method: graphite powder is reacted with concentrated sulfuric acid, sodium nitrate and potassium permanganate under ice bath conditions, and then the temperature is gradually raised to 35°C and 98°C for reaction, and finally hydrogen peroxide is added to terminate the reaction. Graphene oxide is obtained after washing, centrifugation and drying; ② Graphene oxide is dispersed in deionized water and ultrasonically exfoliated for 2 hours to obtain a graphene oxide dispersion; ③ Urea is added to the graphene oxide dispersion, wherein the mass ratio of graphene oxide to urea is 1:10, and a hydrothermal reaction is carried out at 180°C for 12 hours to obtain nitrogen-doped graphene; ④ Chloroauric acid and cobalt nitrate are prepared into a mixed solution in a molar ratio of 1:1, wherein the concentration of Au is 0.01 mol / L; ⑤ NG is dispersed in the above mixed solution to obtain an NG concentration of 1 mg / mL, and ultrasonic dispersion is carried out for 30 minutes; ⑥ Under rapid stirring, a concentration of 0.1 mol / L sodium borohydride solution as a reducing agent, with a molar ratio of NaBH4 to metal ions of 5:1; ⑦ After continuing to stir the reaction for 2 hours, centrifuge, wash with deionized water and ethanol multiple times, and vacuum dry at 60°C for 12 hours to obtain an Au-Co / NG electrocatalyst, in which the molar ratio of gold to cobalt is 1:

1.

6. The process according to claim 1, characterized in that: The preparation method of the synergistic catalyst comprises the following steps: dispersing the photocatalyst and the electrocatalyst in an ethanol solution, adjusting the pH value to 3-5, mixing under ultrasonic action, and then centrifuging, washing and drying to obtain a core-shell structured synergistic catalyst.

7. The process according to claim 6, wherein: The specific steps are as follows: ① The photocatalyst is dispersed in an ethanol solution to a concentration of 10 mg / mL, and the pH value is adjusted to 3 with hydrochloric acid; ② The electrocatalyst is dispersed in an ethanol solution to a concentration of 10 mg / mL, and the pH value is adjusted to 10 with aqueous ammonia; ③ Under the action of ultrasound, the electrocatalyst solution is slowly added dropwise to the photocatalyst solution, and the mass ratio of photocatalyst to electrocatalyst is 2:1; ④ After continuing ultrasonic mixing for 30 minutes, stirring at room temperature for 12 hours allows the photocatalyst and electrocatalyst to assemble into a core-shell structure through electrostatic adsorption; ⑤ Centrifugal separation, washing with ethanol several times, and vacuum drying at 60°C for 12 hours to obtain the core-shell structure synergistic catalyst g-C3N4 / TiO2@Au-Co / NG.

8. The process according to claim 1, wherein: In the photocatalytic oxidation reaction, the concentration of cyclopentene is 0.1-1 mol / L, the amount of the co-catalyst is 5-20% of the mass of cyclopentene, the volume ratio of acetonitrile / water is (1-5):1, the oxygen flow rate is 10-100 mL / min, the reaction temperature is 30-40°C, and the reaction time is 1-5 h; the anode oxygen flow rate of the electrocatalytic reaction is 50-200 mL / min, the reaction temperature is 30-40°C, the reaction time is 1-3 h, and the DC voltage is 0.8-1.2 V.

9. The process according to claim 8, wherein: In the product separation, the pressure of the reduced pressure distillation is 0.01-0.1 MPa, the temperature is 40-60°C, the filling amount of the activated carbon column is 5-10% of the volume of the reaction liquid, the adsorption temperature is 20-40°C, the adsorption time is 0.5-2 h, the molecular weight cutoff of the membrane filtration is 1000 Da, the operating pressure is 0.1-0.5 MPa, and the temperature is 20-40°C.

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