A synthesis method and application of a catalytic material for the efficient catalytic reduction of nitroaromatics

Abstract

The present invention discloses a method for synthesizing a catalytic material for highly efficient catalytic reduction of nitroarenes and its application. By synthesizing two-dimensional metal-organic framework Co MOF, controlling the concentration of Na2PdCl4, and in-situ synthesizing ultra-small Pd nanoparticles at the edges of its two-dimensional structure, a highly efficient catalytic material Co MOF@Pd for catalytic reduction of nitroarenes is finally obtained. Under the condition of the same Pd content, using NaBH4 as the hydrogen source, the conversion rate of Co MOF@Pd for highly efficient catalytic reduction of nitroarenes exceeds 99%, and the TOF value reaches 9800 h ‑1 , which is 206 times that of commercial PdC with a Pd content of 10 wt%. In addition, this catalyst has good cycle stability. After 5 cycles, the catalytic activity remains 86%, while the catalytic activity of PdC is only 45%. The synthesis method of the present invention is simple, low-cost, has high catalytic activity, and the catalyst is easy to separate, recover and recycle.

Description

Technical Field

[0001] The invention belongs to the field of fine chemical technology, and specifically relates to a synthesis method and application of a high-efficiency catalyst for high-efficiency catalytic reduction of nitroaromatics. Background Art

[0002] Aromatic nitro compounds and nitrophenols are among the major harmful pollutants commonly found in wastewater. 4-nitrophenol (4-NP) is a representative example, which is highly toxic and may cause irritation, inflammation, skin allergies, and respiratory problems. Therefore, it is necessary to find effective technologies to remove 4-NP from industrial wastewater before it is discharged into the environment. 4-Aminophenol (4-AP) is less toxic and more biodegradable. It is also an important intermediate material for the production of analgesic and antipyretic drugs. Therefore, by using NaBH 4 Reducing 4-NP to 4-AP as a reducing agent is a feasible and universal method to eliminate harmful 4-NP and realize the resource recovery of pollutants. However, the reduction reaction of 4-NP to 4-AP is thermodynamically feasible, but kinetically hindered due to the large activation barrier. Therefore, it is necessary to use an active catalyst to accelerate the reduction reaction.

[0003] Noble metals (such as Au, Pd, Pt and Ag) or noble metal-based materials (such as PdC with 10% Pd) are excellent catalysts for the reduction of 4-NP. However, they are expensive and have poor reusability, which has become an obstacle to large-scale application. Seeking effective methods to improve catalytic ability and increase catalyst stability is an effective way to solve the above problems. The high cost, limited supply and high loading activity of common noble metal-based catalysts limit their large-scale application. Therefore, it is of great significance to use the high specific surface area and high exposure sites of metal organic frameworks as carriers to in situ synthesize and load ultra-small palladium nanoparticles to reduce costs and achieve stable and efficient catalytic hydrogenation reduction of nitroaromatics.

[0004] This patent utilizes the high specific surface area and high exposure sites of metal-organic frameworks as carriers to in situ synthesize and load ultra-small palladium nanoparticles, achieving stable and efficient catalytic hydrogenation reduction of nitroaromatics. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses a synthesis method and application of a high-efficiency catalyst for high-efficiency catalytic reduction of nitroaromatics.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention provides a method for synthesizing a high-efficiency catalyst for high-efficiency catalytic reduction of nitroaromatics, comprising the following steps:

[0008] Step (1): 208 mg of cobalt acetate tetrahydrate is dissolved in ultrapure water, and the solution is slowly added dropwise into a mixed organic phase solution containing 25 mg of terephthalic acid, chloroform, and N,N-dimethylacetamide (DMAC). After the aqueous phase and the organic phase are separated immediately, a pink solid is precipitated at the interface after standing for 4-5 hours.

[0009] Step (2): Collect the pink solid obtained in step (1), wash each 5 mg of the solid with 4 mL of N,N-dimethylacetamide (DMAC), and dry at 60 °C for 24 h to obtain a two-dimensional metal organic framework Co MOF (2D Co MOF);

[0010] Step (3): Take 3.5 mg of two-dimensional metal organic framework Co MOF (2D Co MOF) and disperse it in 5 mL of ethylene glycol, add 1 μL of sodium chloropalladate solution, heat to 60 °C, keep it for 5 h, then centrifuge it, wash it three times with 4 mL of the mixed solution, and dry it at 60 °C for 24 h to obtain the Co MOF-loaded palladium nanocomposite catalyst Co MOF@Pd; wherein the Pd content is 0.08%.

[0011] Furthermore, in step (1), the volumes of the ultrapure water, the chloroform, and the N,N-dimethylacetamide (DMAC) are all 6 mL.

[0012] Furthermore, the sodium chloropalladate (Na 2 PdCl 4 ) solution is 0.04 mol L -1 .

[0013] Furthermore, the mixed solution in step (3) is anhydrous ethanol (EtOH) and acetone (CH 3 COCH 3 ), the anhydrous ethanol (EtOH) and the acetone (CH 3 COCH 3 )’s volume ratio is 1:8.

[0014] Furthermore, the centrifugation condition in step (3) is 10,000 rpm, 2 min each time.

[0015] The present invention also provides the use of the highly efficient catalytic reduction nitroaromatic catalytic material Co MOF@Pd as a catalyst in catalyzing the reduction reaction of nitroaromatic compounds.

[0016] Further, the nitroaromatic hydrocarbon includes any one or more of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2-fluoro-4-nitrophenol, 2-chloro-4-nitrophenol, 2-bromo-4-nitrophenol and 2-methyl-4-nitrophenol; in the catalytic reaction system, the reaction is carried out in 3 mL of water, NaBH 4 As a hydrogen source, the concentration was 30 mmol L -1 , the concentration of nitroaromatic hydrocarbons was 0.1 mmol L -1 The dosage of Co MOF@Pd and commercial PdC (10 wt%) is based on the Pd content in the material. The Pd concentration is 0.25 μg mL -1 .

[0017] The beneficial effects of the present invention are:

[0018] (1) The nanomaterial prepared by the present invention has high catalytic activity for the reduction of nitroaromatic hydrocarbons (TOF value up to 9800 h -1 , reaching 206 times that of PdC), the conversion rate exceeded 99%. After the reaction was completed, it was filtered and recovered. After being reused five times, the catalytic activity of Co MOF@Pd was retained by 86%, while PdC only retained 45%;

[0019] (2) The preparation method of the present invention is simple, inexpensive, has mild reaction conditions, is applicable to a wide range of substrates, and is conducive to large-scale production and utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the transmission electron microscope of the Co MOF@Pd nanomaterial of the present invention;

[0021] Figure 2 It is the UV-visible spectra of Co MOF@Pd and Co MOF catalytic reduction of 4-NP in the present invention;

[0022] Figure 3 This is a high performance liquid chromatogram of the catalytic reduction of 4-NP by Co MOF@Pd of the present invention;

[0023] Figure 4 The UV-visible spectrum is a comparison of the catalytic reduction activity of 4-NP by commercial PdC (10 wt%) of the present invention;

[0024] Figure 5 This is a comparison chart of the TOF values ​​of the commercial PdC and Co MOF@Pd reducing 4-NP of the present invention;

[0025] Figure 6 The cyclic stability diagram of the catalytic reduction of 4-NP by Co MOF@Pd of the present invention and commercial PdC (10 wt%);

[0026] Figure 7 This is a comparison chart of the activity of the Co MOF@Pd catalytic reduction of substrates such as 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol;

[0027] FIG8 is a catalytic reduction diagram of Co MOF@Pd reducing 4-NP to 4-AP, and is also an abstract drawing of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0029] Example 1 Synthesis of Co MOF@Pd Nanomaterials

[0030] Dissolve 208 mg of cobalt acetate tetrahydrate in ultrapure water and slowly drop it into a mixed organic phase solution containing 25 mg of terephthalic acid, 6 mL of chloroform and 6 mL of DMAC. After the aqueous phase-organic phase demixing phenomenon occurs, a pink solid precipitates at the demixing interface. Collect the solid, wash it with DMAC, and dry it to obtain 2D Co MOF. Weigh 3.5 mg of Co MOF and disperse it in 5 mL of ethylene glycol. Add Na 2 PdCl 4 Solution 1 μL (Na 2 PdCl 4 Mother liquor concentration = 0.04 mol L -1 ), heat the reaction to 60 °C for 5 h, collect by centrifugation, and wash with EtOH:CH 3 COCH 3 = 1:8 mixed solution 4 mL was washed three times and dried to obtain Co MOF@Pd. It was dropped on a copper grid and the morphology was examined using a transmission electron microscope. Figure 1 As shown, Co MOF is a two-dimensional sheet structure, and 2.3 nm Pd nanoparticles are loaded on the edge of Co MOF.

[0031] Example 2 Co MOF@Pd nanomaterial catalytic reduction of 4-NP

[0032] The reaction was carried out in 3 mL of water, NaBH 4 As a hydrogen source, the concentration was 30 mmol L -1 , the concentration of nitroaromatic hydrocarbons was 0.1 mmol L -1 The dosage of Co MOF@Pd is based on the Pd content in the material, and the Pd concentration is 0.25 μg mL -1 , using Co MOF as a control. The reaction progress was monitored by UV-visible spectrophotometer, and the product was verified by high performance liquid chromatography. Figure 2 As shown in the figure, in the above solution, when Co MOF@Pd is used as the catalyst, 4-NP has a maximum absorption peak at 400 nm. As time goes by, the absorption peak at 400 nm gradually decreases. High performance liquid chromatography proves that after the catalytic reaction, the raw material disappears and the product is 4-AP ( Figure 3 ). In contrast, Co MOF does not have any catalytic activity, proving that Pd is the active metal in Co MOF@Pd.

[0033] Example 3 Comparison of the catalytic reduction activity of Co MOF@Pd and commercial PdC for 4-NP

[0034] The reaction was carried out in 3 mL of water, NaBH 4 As a hydrogen source, the concentration was 30 mmol L -1 , the concentration of nitroaromatic hydrocarbons was 0.1 mmol L -1 The amount of commercial PdC (10 wt%) is based on the Pd content in the material, and the Pd concentration is 0.25 μg mL -1 The reaction progress was tracked by monitoring the absorption peak at 400 nm using a UV-visible spectrophotometer. Figure 4 As shown. As time goes by, the absorption peak at 400 nm gradually decreases, but the degree of decrease is far less than that of the reaction with Co MOF@Pd as a catalyst. The amount of reduced 4-NP and active metal (Pd) in the catalyst is significantly correlated with the catalytic activity, so the turnover frequency (TOF: the molar amount of product converted per mole of active metal catalyst used per hour) is used to objectively evaluate the intrinsic activity of the catalyst. The TOF of Co-MOF@Pd catalyst (9800 h -1 ) is much better than commercial PdC, such as Figure 5 shown.

[0035] Example 4 Comparison of the reproducibility of Co MOF@Pd and commercial PdC catalyzed 4-NP reduction

[0036] The experimental scheme was the same as that of Example 2 and Example 3. In the circulation experiment, the catalyst was separated by centrifugation (10,000 rpm, 5 minutes), and the catalyst was washed with ultrapure water before being used again for 4-NP catalytic reduction. Figure 6 As shown, after five reuses, the catalytic activity of CoMOF@Pd was retained by 86%, while that of PdC was only 45%.

[0037] Example 5 Comparison of the catalytic reduction activities of various nitroaromatic hydrocarbons by Co MOF@Pd

[0038] Nitroaromatic hydrocarbons include 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2-fluoro-4-nitrophenol, 2-chloro-4-nitrophenol, 2-bromo-4-nitrophenol and 2-methyl-4-nitrophenol. In the catalytic reaction system, the reaction was carried out in 3 mL of water and NaBH 4 As a hydrogen source, the concentration was 30 mmol L -1 , the concentration of nitroaromatic hydrocarbons was 0.1 mmol L -1 The dosage of Co MOF@Pd and commercial PdC (10 wt%) is based on the Pd content in the material. The Pd concentration is 0.25 μg mL -1 The reaction progress was monitored by UV-Vis spectrophotometer and the product was confirmed by HPLC. Figure 7 As shown, Co MOF@Pd has a wide range of applications and can efficiently catalyze the reduction of various nitroaromatic hydrocarbons.

[0039] Example 6 Co MOF@Pd catalytic reduction of 4-NP

[0040] The slow reduction growth of palladium nanoparticles was achieved at the edge of 2D Co-MOF, such as Figure 8 As shown in Figure 2, the obtained nanocatalyst Co-MOF@Pd has a good catalytic activity for the rapid reduction of 4-NP to 4-AP (TOF = 9800 h -1 ), at the same Pd content, the TOF of Co-MOF@Pd is 206 times that of commercial PdC (10 wt%).

[0041] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A method for synthesizing Co MOF@Pd, a highly efficient catalytic reduction material for nitroaromatics. It is characterized in that The steps include: Step (1): 208 mg of cobalt acetate tetrahydrate was dissolved in ultrapure water, and the solution was added dropwise into a mixed organic phase solution containing 25 mg of terephthalic acid, chloroform and N,N-dimethylacetamide. Water-organic phase separation occurred immediately. After standing for 4-5 hours, a pink solid precipitated at the interface of the separation. Step (2): Collect the pink solid obtained in step (1), wash each 5 mg of the solid with 4 mL of N,N-dimethylacetamide, and dry at 60°C for 24 h to obtain a two-dimensional metal organic framework Co MOF; Step (3): Take 3.5 mg of the two-dimensional metal organic framework Co MOF and disperse it in 5 mL of ethylene glycol. Add 1 μL of sodium chloropalladate solution, heat it to 60 °C, keep it for 5 h, then centrifuge it, wash it three times with 4 mL of the mixed solution, and dry it at 60 °C for 24 h to obtain the highly efficient catalytic reduction of nitroaromatics catalytic material Co MOF@Pd.

2. A method for synthesizing Co MOF@Pd, a highly efficient catalytic reduction nitroaromatic material, according to claim 1, It is characterized in that The volumes of the ultrapure water, the chloroform, and the N,N-dimethylacetamide in step (1) are all 6 mL.

3. A method for synthesizing Co MOF@Pd, a highly efficient catalytic reduction nitroaromatic catalytic material according to claim 1, It is characterized in that The concentration of the sodium chloropalladate solution is 0.04 mol L -1 .

4. The method for synthesizing Co MOF@Pd, a highly efficient catalytic reduction nitroaromatic material according to claim 1, It is characterized in that The mixed solution in step (3) is anhydrous ethanol and acetone, and the volume ratio of the anhydrous ethanol to the acetone is 1:

8.

5. The method for synthesizing Co MOF@Pd, a highly efficient catalytic reduction nitroaromatic material according to claim 1, It is characterized in that The centrifugation condition in step (3) is 10,000 rpm, 2 min.

6. A method for synthesizing a highly efficient catalytic reduction nitroaromatic catalytic material Co MOF@Pd according to any one of claims 1 to 5, It is characterized in that The highly efficient catalytic reduction nitroaromatic catalytic material Co MOF@Pd is used as a catalyst in the catalytic reduction reaction of nitroaromatic compounds.

7. A method for synthesizing a highly efficient catalytic reduction nitroaromatic material Co MOF@Pd according to claim 6, It is characterized in that The nitroaromatic hydrocarbons include any one or more of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2-fluoro-4-nitrophenol, 2-chloro-4-nitrophenol, 2-bromo-4-nitrophenol and 2-methyl-4-nitrophenol.

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