A catalyst for producing p-cyanobenzoic acid and a method for preparing the same
By using a copper-cobalt bimetallic doped MOF composite aerogel catalyst, the stability and selectivity problems of existing catalysts were solved, and the efficient and green synthesis of p-cyanobenzoic acid was achieved, improving the product yield and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG WEUNITE BIOTECH CO LTD
- Filing Date
- 2026-05-13
- Publication Date
- 2026-07-03
AI Technical Summary
Existing catalysts for the synthesis of p-cyanobenzoic acid suffer from problems such as harsh reaction conditions, poor selectivity, severe equipment corrosion, numerous byproducts, high separation and purification costs, poor catalyst stability, and rapid loss of active sites, making it difficult to achieve green industrial production.
A copper-cobalt bimetallic doped MOF composite aerogel catalyst was developed. By constructing a three-dimensional porous aerogel framework, the electron distribution of the active centers was optimized, the activation energy of the reaction was reduced, the aggregation of active particles was avoided, and a dense carbon protective layer was formed, thereby improving the stability of the catalyst.
It improves the yield and purity of p-cyanobenzoic acid, enhances the cyclic stability and reaction selectivity of the catalyst, reduces separation and purification costs, and is suitable for green industrial production.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the production of p-cyanobenzoic acid and its preparation method. Background Technology
[0002] p-Cyanobenzic acid is an important aromatic functional intermediate. Its molecular structure contains both carboxyl and cyano groups, allowing it to be derived into various high-value-added chemicals through esterification, amidation, and reduction reactions. It is widely used in pharmaceuticals, dyes, liquid crystal materials, and polymer synthesis. In the pharmaceutical industry, p-cyanobenzic acid is a key building block in the synthesis of antidiabetic, antithrombotic, and antitumor drugs. In the field of functional materials, as a comonomer, it can be used to prepare polymers such as polyimides and polyesters with special optoelectronic properties, and market demand continues to grow.
[0003] Currently, the mainstream industrial processes for preparing p-cyanobenzoic acid are mainly divided into three categories: chemical hydrolysis, bio-enzymatic catalysis, and transition metal catalytic cyanation. The chemical hydrolysis method uses terephthalonitrile as raw material and achieves monocyano conversion through controlled hydrolysis with strong base / strong acid. This process has problems such as harsh reaction conditions (requiring high temperature and pressure, and high concentration of acid and base system), poor selectivity (easily over-hydrolyzes to generate terephthalic acid, resulting in many by-products and high separation and purification costs), severe equipment corrosion, and large emissions of waste gas, wastewater, and solid waste. It does not conform to the trend of green chemical development.
[0004] Biocatalytic methods, using nitrile hydrolases as catalysts, utilize the regioselectivity of enzymes to achieve the single hydrolysis of terephthalonitrile, offering advantages such as mild reaction conditions, high selectivity, and environmental friendliness. However, existing enzyme catalysis technologies still have significant limitations: First, enzymes have poor stability, are sensitive to temperature, pH, and organic solvents, and high substrate concentrations or co-solvents easily lead to enzyme protein denaturation and inactivation, resulting in a low upper limit for substrate concentration in the reaction system and limited production efficiency. Second, enzyme preparations are costly, free enzymes are difficult to recover and reuse, and the preparation process of immobilized enzymes is complex and still suffers from activity loss. Third, enzyme catalytic reaction systems require strict control of buffer conditions, and protein and salt impurities must be removed during product separation, leading to complex post-processing procedures and difficulty in scaling up production, thus hindering their large-scale industrial application.
[0005] Transition metal-catalyzed cyanohydrin synthesis, using aryl halides (such as p-bromobenzoic acid) as raw materials, involves a one-step synthesis of p-cyanobenzoic acid via palladium-catalyzed cyanohydrin reaction. This is a green synthetic route that has emerged in recent years. However, existing palladium-based catalysts still have the following drawbacks: homogeneous palladium catalysts or supported palladium catalysts are prone to palladium nanoparticle migration and aggregation during the reaction, leading to the loss of active sites, resulting in fewer catalyst recycling cycles and rapid deactivation; some highly active palladium-based catalysts are prone to initiating side reactions such as dehalogenation and decarboxylation, leading to decreased selectivity of the target product and increased separation and purification costs.
[0006] Therefore, developing a catalyst that can improve the yield and purity of p-cyanobenzoic acid and has excellent cycle stability is of great significance for promoting the green industrial production of p-cyanobenzoic acid. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of existing catalysts for the synthesis of p-cyanobenzoic acid and to provide a catalyst for the production of p-cyanobenzoic acid and its preparation method.
[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing a catalyst for the production of p-cyanobenzoic acid, characterized by comprising the following steps: S1. The organic ligand solution was added dropwise to the cobalt source, stirred, aged, centrifuged, and the solid phase was collected and washed to obtain the cobalt-based MOF framework. S2. Disperse the cobalt-based MOF framework in a copper source, stir, filter, and take the solid phase to obtain copper-cobalt doped particles; S3. Disperse the reduced graphene oxide in deionized water, add sodium alginate, stir evenly, add the copper-cobalt doped particles and ammonium dihydrogen phosphate, continue stirring, let stand, centrifuge, take off the lower gel precipitate, wash, and freeze dry under vacuum to obtain the aerogel precursor. S4. The aerogel precursor is heated and carbonized in a hydrogen-argon mixed atmosphere, cooled, and ground to obtain the catalyst.
[0009] By constructing a copper-cobalt bimetallic doped MOF composite aerogel structure, the electron distribution of the active center was optimized, and the activation energy of the cyanation substitution reaction of bromobenzoic acid was reduced.
[0010] Reduced graphene oxide and sodium alginate rely on metal ions provided by copper-cobalt doped particles as crosslinking sites to form a three-dimensional porous aerogel framework, which uniformly encapsulates and anchors the copper-cobalt doped particles, preventing the active particles from agglomerating and stacking, while improving the overall structural stability.
[0011] By constructing defective active sites through carbonization, the system can resist long-term immersion and scouring by high-temperature organic solvents, reduce the dissolution and loss of Cu and Co metal ions, and prevent the active sites from detaching and becoming inactive.
[0012] As a preferred embodiment of the present invention, in step S1, the concentration of cobalt ions in the cobalt source is 0.15-0.17 mol / L; the concentration of organic ligand in the organic ligand solution is 0.65-0.75 mol / L, and the organic ligand is benzimidazole.
[0013] As a preferred embodiment of the present invention, in step S2, the concentration of copper ions in the copper source is 0.05-0.08 mol / L; the ratio of the cobalt-based MOF framework to the copper source is 0.8-1.2 g: 50-55 mL.
[0014] In a preferred embodiment of the present invention, in step S3, the copper-cobalt doped particles are modified copper-cobalt doped particles, and the preparation method of the modified copper-cobalt doped particles includes the following steps: The copper-cobalt doped particles were ultrasonically dispersed in a modified solution, refluxed at 60°C for 3-4 hours, filtered, and the solid phase was washed to obtain the modified copper-cobalt doped particles.
[0015] As a preferred embodiment of the present invention, the modified solution is obtained by mixing ethanol and deionized water evenly, then sequentially adding phytic acid, ammonium fluoride and sodium cocoyl glycinate, and stirring evenly; the mass ratio of ethanol, deionized water, phytic acid, ammonium fluoride and sodium cocoyl glycinate is 20-25:70-75:1.08-1.16:0.24-0.32:0.021-0.033.
[0016] As a preferred embodiment of the present invention, in step S3, the mass ratio of sodium alginate, reduced graphene oxide, deionized water, copper-cobalt doped particles and ammonium dihydrogen phosphate is 1.8-2.5g: 0.15-0.25g: 120-150mL: 0.5-0.8g: 0.3-0.4g.
[0017] As a preferred technical solution of the present invention, in step S4, the heating carbonization refers to raising the temperature from room temperature to 130-150℃ at a rate of 3-5℃ / min and holding it for 30-40min, then raising the temperature to 300-350℃ at a rate of 1-2℃ / min and holding it for 60-80min for pre-carbonization, and then raising the temperature to 400-550℃ at a rate of 1-2℃ / min and holding it for 3-4h for carbonization.
[0018] As a preferred technical solution of the present invention, in step S3, the vacuum freeze-drying refers to freeze-drying at -25°C and a vacuum degree of 10Pa for 10-20 hours.
[0019] As a preferred embodiment of the present invention, in step S4, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 5%, and the flow rate of the mixed atmosphere is 50-100 mL / min.
[0020] Another object of the present invention is to provide a catalyst for the production of p-cyanobenzoic acid.
[0021] The beneficial effects of this invention are: (1) The catalyst prepared by the present invention optimizes the electron distribution of the active center through the synergistic effect of copper-cobalt bimetallic doping, thereby improving catalytic activity and reaction selectivity; and constructs a porous crystal structure with a cobalt-based MOF framework, which is conducive to rapid diffusion and mass transfer.
[0022] (2) The catalyst prepared by the present invention forms a three-dimensional porous aerogel framework by reducing graphene oxide and crosslinking with sodium alginate, which uniformly wraps and anchors the copper-cobalt doped particles to avoid the aggregation and stacking of active particles; at the same time, the three-dimensional crosslinked network has both flexibility and structural strength, buffering high-temperature solvent corrosion and thermal stress impact, preventing the catalyst framework from pulverizing and collapsing, and improving the overall structural stability.
[0023] (3) The catalyst prepared by the present invention is carbonized in a weak reducing mixed atmosphere of hydrogen / argon to construct defective active sites, while forming a dense carbon protective layer to resist long-term immersion and scouring by high-temperature organic solvents, reduce the dissolution and loss of active metal ions, avoid the deactivation of active sites, and improve the cycle stability of the catalyst.
[0024] (4) The catalyst prepared by the present invention forms a triple synergistic effect of phytic acid coordination, fluoride ion etching and surfactant dispersion by surface modification of copper-cobalt doped particles. Phytic acid coordination anchors the active site, fluoride ions precisely regulate the electronic structure of the active center, and surfactants prevent particle aggregation. The three synergistically optimize the catalytic performance, improve the catalyst's targeted catalysis of the cyanation reaction of p-bromobenzoic acid, and increase the product yield. Detailed Implementation
[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific implementation methods, structures, features, and effects of the present invention are described in detail below with reference to embodiments. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are all conventional reagents, methods, and equipment in the art; and unless otherwise specified, the reagents, methods, and equipment used in each embodiment and comparative example are consistent.
[0026] Example 1 A method for preparing a catalyst for the production of p-cyanobenzoic acid includes the following steps: S1. Dissolve 2.794 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.608 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 35 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.157g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 1.0g of cobalt-based MOF framework in 53mL of copper source, stir for 4h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Mix 0.20g of reduced graphene oxide with 135mL of deionized water, sonicate for 35min, add 2.1g of sodium alginate, stir at room temperature for 1.5h, add 0.65g of copper-cobalt doped particles and 0.35g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1.2h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, freeze dry at -25℃ and 10Pa vacuum for 15h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 75 mL / min. The temperature was increased from room temperature to 140℃ at a rate of 4℃ / min and held for 35 min. Then, the temperature was increased to 325℃ at a rate of 1.5℃ / min and held for 70 min for pre-carbonization. Then, the temperature was increased to 475℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0027] Example 2 A method for preparing a catalyst for the production of p-cyanobenzoic acid includes the following steps: S1. Dissolve 2.619 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.136 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 30 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.121g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 0.8g of cobalt-based MOF framework in 50mL of copper source, stir for 3h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Take 0.15g of reduced graphene oxide and 120mL of deionized water, mix them, and sonicate for 30min. Add 1.8g of sodium alginate, stir at room temperature for 1h, add 0.5g of copper-cobalt doped particles and 0.3g of ammonium dihydrogen phosphate, continue stirring for 3h, let stand for 1h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, and freeze-dry at -25℃ and 10Pa vacuum for 10h to obtain the aerogel precursor. S4. Place the aerogel precursor in a tube furnace and introduce an argon atmosphere containing 5% hydrogen by volume at a flow rate of 50 mL / min. Increase the temperature from room temperature to 130℃ at a rate of 3℃ / min and hold for 30 min. Then, increase the temperature to 300℃ at a rate of 1℃ / min and hold for 60 min for pre-carbonization. Then, increase the temperature to 400℃ at a rate of 1℃ / min and hold for 3 h for carbonization. Allow it to cool naturally to room temperature and grind it to obtain the catalyst.
[0028] Example 3 A method for preparing a catalyst for the production of p-cyanobenzoic acid includes the following steps: S1. Dissolve 2.706 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.419 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 32 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.145g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 0.9g of cobalt-based MOF framework in 52mL of copper source, stir for 4h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Mix 0.18g of reduced graphene oxide with 125mL of deionized water, sonicate for 35min, add 1.95g of sodium alginate, stir at room temperature for 1.5h, add 0.6g of copper-cobalt doped particles and 0.32g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, freeze dry at -25℃ and 10Pa vacuum for 12h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 70 mL / min. The temperature was increased from room temperature to 135℃ at a rate of 3.5℃ / min and held for 35 min. Then, the temperature was increased to 310℃ at a rate of 1.5℃ / min and held for 65 min for pre-carbonization. Then, the temperature was increased to 450℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0029] Example 4 A method for preparing a catalyst for the production of p-cyanobenzoic acid includes the following steps: S1. Dissolve 2.881 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.797 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 40 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.169g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 1.1g of cobalt-based MOF framework in 54mL of copper source, stir for 5h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Mix 0.22g of reduced graphene oxide with 140mL of deionized water, sonicate for 40min, add 2.4g of sodium alginate, stir at room temperature for 2h, add 0.75g of copper-cobalt doped particles and 0.38g of ammonium dihydrogen phosphate, continue stirring for 4h, let stand for 1.5h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, freeze dry at -25℃ and vacuum degree 10Pa for 20h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 85 mL / min. The temperature was increased from room temperature to 145℃ at a rate of 4.5℃ / min and held for 40 min. Then, the temperature was increased to 345℃ at a rate of 2℃ / min and held for 80 min for pre-carbonization. Then, the temperature was increased to 520℃ at a rate of 2℃ / min and held for 4 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0030] Example 5 A method for preparing a catalyst for the production of p-cyanobenzoic acid includes the following steps: S1. Dissolve 2.969 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 7.080 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 40 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.193g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 1.2g of cobalt-based MOF framework in 55mL of copper source, stir for 5h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Take 0.25g of reduced graphene oxide and 150mL of deionized water, mix them, and sonicate for 40min. Add 2.5g of sodium alginate, stir at room temperature for 2h, add 0.8g of copper-cobalt doped particles and 0.4g of ammonium dihydrogen phosphate, continue stirring for 4h, let stand for 1.5h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, and freeze-dry at -25℃ and 10Pa vacuum for 20h to obtain the aerogel precursor. S4. Place the aerogel precursor in a tube furnace and introduce an argon atmosphere containing 5% hydrogen by volume at a flow rate of 100 mL / min. Increase the temperature from room temperature to 150℃ at a rate of 5℃ / min and hold for 40 min. Then, increase the temperature to 350℃ at a rate of 2℃ / min and hold for 80 min for pre-carbonization. Then, increase the temperature to 550℃ at a rate of 2℃ / min and hold for 4 h for carbonization. Allow it to cool naturally to room temperature and grind it to obtain the catalyst.
[0031] Example 6 The difference from Example 1 is that the copper-cobalt doped particles are replaced with modified copper-cobalt doped particles, while the rest of the operation and dosage remain unchanged.
[0032] The method for preparing the modified copper-cobalt doped particles includes the following steps: The copper-cobalt doped particles obtained in step S2 were ultrasonically dispersed in a modified solution composed of ethanol, deionized water, phytic acid, ammonium fluoride, and sodium cocoyl glycinate in a mass ratio of 20:70:1.08:0.24:0.021 at a material-to-liquid ratio of 1:80 g / mL. The solution was refluxed at 60°C for 3 hours, filtered, and the solid phase was washed to obtain the modified copper-cobalt doped particles.
[0033] Example 7 The difference from Example 1 is that the copper-cobalt doped particles are replaced with modified copper-cobalt doped particles, while the rest of the operation and dosage remain unchanged.
[0034] The method for preparing the modified copper-cobalt doped particles includes the following steps: The copper-cobalt doped particles obtained in step S2 were ultrasonically dispersed in a modified solution composed of ethanol, deionized water, phytic acid, ammonium fluoride, and sodium cocoyl glycinate in a mass ratio of 22:73:1.12:0.28:0.027 at a material-to-liquid ratio of 1.3:90 g / mL. The mixture was refluxed at 60°C for 3.5 h, filtered, and the solid phase was washed to obtain the modified copper-cobalt doped particles.
[0035] Example 8 The difference from Example 1 is that the copper-cobalt doped particles are replaced with modified copper-cobalt doped particles, while the rest of the operation and dosage remain unchanged.
[0036] The method for preparing the modified copper-cobalt doped particles includes the following steps: The copper-cobalt doped particles obtained in step S2 were ultrasonically dispersed in a modified solution composed of ethanol, deionized water, phytic acid, ammonium fluoride, and sodium cocoyl glycinate in a mass ratio of 25:75:1.16:0.32:0.033 at a material-to-liquid ratio of 1.6:100 g / mL. The solution was refluxed at 60°C and stirred for 3-4 hours. After filtration, the solid phase was washed to obtain the modified copper-cobalt doped particles.
[0037] Comparative Example 1 The difference from Example 1 is that the preparation method of this catalyst includes the following steps: S1. Dissolve 2.794 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.608 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 35 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Mix 0.20g of reduced graphene oxide with 135mL of deionized water, sonicate for 35min, add 2.1g of sodium alginate, stir at room temperature for 1.5h, add 0.65g of cobalt-based MOF framework and 0.35g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1.2h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, and freeze-dry at -25℃ and 10Pa vacuum for 15h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 75 mL / min. The temperature was increased from room temperature to 140℃ at a rate of 4℃ / min and held for 35 min. Then, the temperature was increased to 325℃ at a rate of 1.5℃ / min and held for 70 min for pre-carbonization. Then, the temperature was increased to 475℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0038] Comparative Example 2 The difference from Example 1 is that the preparation method of this catalyst includes the following steps: S1. Dissolve 2.794 g of cobalt nitrate hexahydrate in 60 mL of methanol and stir evenly at room temperature to obtain a cobalt source; dissolve 6.608 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the cobalt source, stir for 35 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a cobalt-based MOF framework; S2. Dissolve 0.157g of copper nitrate trihydrate in 10mL of ethanol and stir evenly at room temperature to obtain a copper source; disperse 1.0g of cobalt-based MOF framework in 53mL of copper source, stir for 4h, filter, and take the solid phase to obtain copper-cobalt doped particles. S3. Mix 2.1g sodium alginate and 135mL deionized water, stir at room temperature for 1.5h, add 0.65g of the copper-cobalt doped particles and 0.35g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1.2h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, and freeze-dry at -25℃ and 10Pa vacuum for 15h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 75 mL / min. The temperature was increased from room temperature to 140℃ at a rate of 4℃ / min and held for 35 min. Then, the temperature was increased to 325℃ at a rate of 1.5℃ / min and held for 70 min for pre-carbonization. Then, the temperature was increased to 475℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0039] Comparative Example 3 The difference from Example 1 is that the preparation method of this catalyst includes the following steps: S1. Dissolve 2.416 g of copper nitrate trihydrate in 60 mL of methanol and stir evenly at room temperature to obtain a copper source; dissolve 6.414 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the copper source, stir for 35 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a copper-based MOF framework; S2. Mix 0.20g of reduced graphene oxide with 135mL of deionized water, sonicate for 35min, add 2.1g of sodium alginate, stir at room temperature for 1.5h, add 0.65g of copper-based MOF framework and 0.35g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1.2h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, freeze dry at -25℃ and 10Pa vacuum for 15h to obtain the aerogel precursor; S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 75 mL / min. The temperature was increased from room temperature to 140℃ at a rate of 4℃ / min and held for 35 min. Then, the temperature was increased to 325℃ at a rate of 1.5℃ / min and held for 70 min for pre-carbonization. Then, the temperature was increased to 475℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0040] Comparative Example 4 The difference from Example 1 is that the preparation method of this catalyst includes the following steps: S1. Dissolve 1.933 g of copper nitrate trihydrate in 60 mL of methanol and stir evenly at room temperature to obtain a copper source; dissolve 3.776 g of benzimidazole in 80 mL of methanol and stir evenly at room temperature to obtain an organic ligand solution; add the organic ligand solution dropwise to the copper source, stir for 35 min, age at room temperature for 24 h, centrifuge, collect the solid phase and wash to obtain a copper-based MOF framework; S2. Dissolve 0.189 g of cobalt nitrate hexahydrate in 10 mL of ethanol and stir evenly at room temperature to obtain a cobalt source; disperse 1.0 g of copper-based MOF framework in 53 mL of cobalt source, stir for 4 h, filter, and take the solid phase to obtain cobalt-copper doped particles. S3. Take 0.20g of reduced graphene oxide and 135mL of deionized water, mix them, and sonicate for 35min. Add 2.1g of sodium alginate, stir at room temperature for 1.5h, add 0.65g of cobalt-copper doped particles and 0.35g of ammonium dihydrogen phosphate, continue stirring for 3.5h, let stand for 1.2h, centrifuge, discard the upper liquid phase, retain the lower gel precipitate, wash, and freeze-dry at -25℃ and 10Pa vacuum for 15h to obtain the aerogel precursor. S4. The aerogel precursor was placed in a tube furnace and a mixed atmosphere of argon gas containing 5% hydrogen by volume was introduced at a flow rate of 75 mL / min. The temperature was increased from room temperature to 140℃ at a rate of 4℃ / min and held for 35 min. Then, the temperature was increased to 325℃ at a rate of 1.5℃ / min and held for 70 min for pre-carbonization. Then, the temperature was increased to 475℃ at a rate of 1.5℃ / min and held for 3.5 h for carbonization. The mixture was then allowed to cool naturally to room temperature and ground to obtain the catalyst.
[0041] Application Example 1 Add 2 mL of N,N-dimethylformamide to a reaction vessel, then add 0.2 g of p-bromobenzoic acid, 0.13 g of potassium ferrocyanide, 0.54 g of tripotassium trihydrate phosphate, and 2 mg of the catalyst prepared in Example 1. Stir the reaction at 130 °C for 8 h, then add saturated sodium chloride solution to terminate the reaction. Filter while hot, then cool the filtrate to room temperature. Add 0.1 mol / L hydrochloric acid solution to adjust the pH to 5, add anhydrous ethanol, stir thoroughly, and let stand for 30 min. Filter and collect the filter cake. Concentrate the collected filtrate under reduced pressure at 0.08 MPa and 70 °C, then evaporate to dryness. Combine the resulting solid with the aforementioned filter cake. Wash the combined crude product three times with deionized water, filter, and add the filter cake to deionized water at 100 °C. Stir for 10 minutes. After 5 minutes, filter while hot. Let the filtrate stand at room temperature for 5 hours to precipitate a white solid. Filter again, collect the filter cake, dry it, and obtain 0.1429 g of p-cyanobenzoic acid. The purity was determined by HPLC to be 96.78%, and the yield was calculated to be 97.63%.
[0042] Application Example 2 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 2, while the other operations and amounts remained unchanged. 0.1405 g of p-cyanobenzoic acid was obtained, with a purity of 96.32% as determined by HPLC, and a yield of 96.72% was calculated.
[0043] Application Example 3 The difference from Application Example 1 is that the catalyst used was the catalyst prepared in Example 3, while the other operations and amounts remained unchanged. 0.1421 g of p-cyanobenzoic acid was obtained, with a purity of 96.57% as determined by HPLC, and a yield of 97.08% was calculated.
[0044] Application Example 4 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 4, while the other operations and amounts remained unchanged. 0.1424 g of p-cyanobenzoic acid was obtained, with a purity of 96.73% as determined by HPLC, and a yield of 97.28% was calculated.
[0045] Application Example 5 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 5, while the other operations and amounts remained unchanged. 0.1415 g of p-cyanobenzoic acid was obtained, with a purity of 96.49% as determined by HPLC, and a yield of 96.67% was calculated.
[0046] Application Example 6 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 6, while the other operations and amounts remained unchanged. 0.1431 g of p-cyanobenzoic acid was obtained, with a purity of 96.79% as determined by HPLC, and a yield of 97.76% was calculated.
[0047] Application Example 7 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 7, while the other operations and amounts remained unchanged. 0.1435 g of p-cyanobenzoic acid was obtained, with a purity of 96.82% as determined by HPLC, and a yield of 98.04% was calculated.
[0048] Application Example 8 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Example 8, while the other operations and amounts remained unchanged. 0.1433 g of p-cyanobenzoic acid was obtained, with a purity of 96.81% as determined by HPLC, and a yield of 97.90% was calculated.
[0049] Application Example 9 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Comparative Example 1, while the other operations and amounts remained unchanged. 0.0986 g of p-cyanobenzoic acid was obtained, with a purity of 84.74% as determined by HPLC, and a yield of 67.36% was calculated.
[0050] Application Example 10 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Comparative Example 2, while the other operations and amounts remained unchanged. 0.1255 g of p-cyanobenzoic acid was obtained, with a purity of 90.51% as determined by HPLC, and a yield of 85.73% was calculated.
[0051] Application Example 11 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Comparative Example 3, while the other operations and amounts remained unchanged. 0.0884 g of p-cyanobenzoic acid was obtained, with a purity of 81.39% as determined by HPLC, and a yield of 60.39% was calculated.
[0052] Application Example 12 The difference from Application Example 1 is that the catalyst used was the same as that prepared in Comparative Example 4, while the other operations and amounts remained unchanged. 0.1087 g of p-cyanobenzoic acid was obtained, with a purity of 87.78% as determined by HPLC, and a yield of 74.26% was calculated.
[0053] Application Example 13 2000L of N,N-dimethylformamide was added to a 5000L high-pressure reactor. The stirring device was turned on and the stirring speed was maintained at 250rpm. Then, 200kg of p-bromobenzoic acid, 127kg of potassium ferrocyanide, and 717kg of tripotassium phosphate trihydrate were added sequentially, and the mixture was stirred for 15min to ensure uniform mixing. Then, 4kg of the catalyst prepared in Example 7 was added. The reactor was closed, and nitrogen gas was introduced to replace the air in the reactor three times (each time at a nitrogen pressure of 0.3MPa, held for 5min). The temperature was raised to 130℃, and the pressure in the reactor was maintained at 0.3MPa. The reaction was stirred for 10h. After the reaction was completed, the heating was stopped. When the temperature in the reactor dropped to 90℃, 800L of saturated sodium chloride solution was slowly added and stirred for 10min. The bottom valve of the reactor was opened, and the mixture was filtered hot through a plate and frame filter press to separate and recover the catalyst. The filtered liquid was transferred to a 2000L cooling vessel and cooled to room temperature. Stirring was started, and 1mol / L hydrochloric acid solution was slowly added dropwise to adjust the pH of the system to 4. After the addition was completed, stirring was continued for 30 min. 1000L of anhydrous ethanol was added to the cooling vessel and stirred thoroughly for 1 h. The mixture was then allowed to stand for 1.5 h to allow p-cyanobenzoic acid to precipitate initially. The precipitate was then filtered through a centrifugal filter (3000 rpm) and the filter cake was collected. The filtrate was transferred to a vacuum distillation vessel and concentrated under vacuum conditions of 0.08 MPa and 70°C. After the solvent was evaporated, the resulting solid was combined with the aforementioned filter cake. The combined crude product was added to 1500L of deionized water and washed three times with stirring (centrifugation and filtration were performed after each wash, and the washing liquid was discarded). The filter cake was collected. 2000L of deionized water at 100℃ was added to the filter cake, and stirring was started for 10min. The mixture was filtered while hot, and the filtrate was collected and transferred to a 3000L crystallization vessel. The mixture was allowed to stand at room temperature for 5h, and white p-cyanobenzoic acid crystals precipitated. The crystals were filtered through a centrifuge and the filter cake was collected. The filter cake was dried at 70℃ and a vacuum of 10Pa for 12h to obtain 143.24kg of p-cyanobenzoic acid. The purity was determined by HPLC to be 96.53%, and the yield was calculated to be 97.86%.
[0054] The catalysts prepared in Examples 1-8 and Comparative Examples 1-4 were used as test samples. A laboratory batch reaction apparatus was used to simulate conventional laboratory operating conditions and 50 continuous cyclic catalytic tests were conducted. The single reaction system, material ratio and process conditions were consistent. The test results are shown in Tables 1-2 below.
[0055] Table 1
[0056] Table 2
[0057] Cyclic tests showed that the catalysts prepared in Examples 1-8 maintained a yield of over 94% after 50 cycles, with no obvious catalytic deactivation. After 50 cycles, the metal ion dissolution rate was low, and active sites were not easily detached. After 50 cycles, the porous structure of the catalyst remained well maintained, with no obvious breakage or loss, and the filtration and separation effect was good, allowing for stable recovery and reuse. In Comparative Example 1, without Cu doping, more Co sites were exposed, and the binding force was weak, making it easier to dissolve and lose during the reaction. The pore structure and carbon framework of the single-metal MOF were less stable, and the pores collapsed after multiple cycles, resulting in a significant decrease in specific surface area. In Comparative Example 2, without the addition of reduced graphene oxide, the anchoring effect of reduced graphene oxide was lost, and the metal dissolution increased significantly. In Comparative Example 3, without cobalt doping, the Cu metal dissolution was much higher than that of the bimetallic system. In Comparative Example 4, the metal loading concentration was reversed, and the electron distribution and coordination environment did not match, making it impossible to form an optimal structure. After multiple cycles, the regularity of the pore structure decreased, and the specific surface area decreased.
[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing a catalyst for the production of p-cyanobenzoic acid, characterized in that, Includes the following steps: S1. The organic ligand solution was added dropwise to the cobalt source, stirred, aged, centrifuged, and the solid phase was collected and washed to obtain the cobalt-based MOF framework. S2. Disperse the cobalt-based MOF framework in a copper source, stir, filter, and take the solid phase to obtain copper-cobalt doped particles; S3. Disperse the reduced graphene oxide in deionized water, add sodium alginate, stir evenly, add the copper-cobalt doped particles and ammonium dihydrogen phosphate, continue stirring, let stand, centrifuge, take off the lower gel precipitate, wash, and freeze dry under vacuum to obtain the aerogel precursor. S4. The aerogel precursor is heated and carbonized in a hydrogen-argon mixed atmosphere, cooled, and ground to obtain the catalyst.
2. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S1, the concentration of cobalt ions in the cobalt source is 0.15-0.17 mol / L; the concentration of organic ligand in the organic ligand solution is 0.65-0.75 mol / L, and the organic ligand is benzimidazole.
3. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S2, the concentration of copper ions in the copper source is 0.05-0.08 mol / L; the ratio of the cobalt-based MOF framework to the copper source is 0.8-1.2 g: 50-55 mL.
4. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S3, the copper-cobalt doped particles are modified copper-cobalt doped particles, and the preparation method of the modified copper-cobalt doped particles includes the following steps: The copper-cobalt doped particles were ultrasonically dispersed in a modified solution, refluxed at 60°C for 3-4 hours, filtered, and the solid phase was washed to obtain the modified copper-cobalt doped particles.
5. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 4, characterized in that, The modified solution is obtained by mixing ethanol and deionized water thoroughly, then sequentially adding phytic acid, ammonium fluoride, and sodium cocoyl glycinate, and stirring until homogeneous; the mass ratio of ethanol, deionized water, phytic acid, ammonium fluoride, and sodium cocoyl glycinate is 20-25:70-75: 1.08-1.16：0.24-0.32：0.021-0.033。 6. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S3, the mass ratio of sodium alginate, reduced graphene oxide, deionized water, copper-cobalt doped particles and ammonium dihydrogen phosphate is 1.8-2.5g: 0.15-0.25g: 120-150mL: 0.5-0.8g: 0.3-0.4g.
7. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S4, the heating carbonization refers to raising the temperature from room temperature to 130-150℃ at a rate of 3-5℃ / min and holding it for 30-40min, then raising the temperature to 300-350℃ at a rate of 1-2℃ / min and holding it for 60-80min for pre-carbonization, and then raising the temperature to 400-550℃ at a rate of 1-2℃ / min and holding it for 3-4h for carbonization.
8. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S3, the vacuum freeze-drying refers to freeze-drying at -25°C and a vacuum of 10 Pa for 10-20 hours.
9. The method for preparing a catalyst for the production of p-cyanobenzoic acid according to claim 1, characterized in that, In step S4, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 5%, and the flow rate of the mixed atmosphere is 50-100 mL / min.
10. A catalyst for the production of p-cyanobenzoic acid prepared by the method for preparing a catalyst for the production of p-cyanobenzoic acid as described in any one of claims 1-9.