Carbon-based bimetallic supported catalyst as well as preparation method and application thereof

Abstract

The invention discloses a carbon-based bimetallic supported catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: successively dispersing 1g / 100ml of chloroplatinic acid solution and copper chloride solution into 200ml of deionized water according to the mass ratio of Pt to Cu of 1: 1, and adjusting the pH value to 9; adding 1.5 ml of a polyethylene glycol solution with the mass concentration of 1% while stirring; after stirring for 15 minutes, dropwise adding a certain amount of newly prepared 0.1 mol / L sodium borohydride solution; adding activated carbon powder treated by nitric acid according to a mass ratio (Pt: Cu: C = 1: 1: (50-200)), and continuously stirring at 300 r / min for 2 hours to load the metal nanoparticles onto the activated carbon; carrying out suction filtration, and washing with deionized water at 70 DEG C for multiple times; and drying in a vacuum drying oven at 100 DEG C for 12 hours to obtain the Pt-Cu / C catalyst. The catalyst is simple in preparation method, can be used for one-step green synthesis of adipic acid by oxidizing cyclohexane with molecular oxygen, and is mild in reaction condition, convenient to separate, green, environment-friendly and pollution-free.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a method for preparing a carbon-based bimetallic supported catalyst Pt-Cu / C for preparing adipic acid from cyclohexane in one step. Background Art

[0002] Adipic acid, the oxidation product of cyclohexane, is an important chemical intermediate. Its main industrial application is the production of nylon 6,6 fibers and resins. A small amount is used in AA esters and polyester polyols (such as polyurethane), which work well in the field of plasticizers (such as PVC). Nylon 6,6 fibers can be used in different important products, such as carpet yarn, tire ropes, household items, clothes, etc. In recent years, the global production and consumption of adipic acid have shown a steady growth trend. Therefore, the process research of adipic acid preparation from cyclohexane is of great value and significance.

[0003] The traditional method for producing adipic acid is the two-step oxidation of cyclohexane, which first oxidizes cyclohexane into cyclohexanol and cyclohexanone, and then oxidizes it into adipic acid using nitric acid. This process is mature, has a high utilization rate of C atoms, and is widely used in industry, but the process is complex, the reaction conditions are harsh (high temperature and high pressure), and the use of nitric acid for oxidation not only causes serious corrosion to the equipment, but also causes serious environmental pollution.

[0004] In recent years, the research on carbon material catalysis has been growing internationally, and the research on carbon materials such as activated carbon, carbon nanotubes and graphene has been increasing. With the deepening of the research on carbon materials, it is found that carbon materials have good stability, suitable mechanical strength, strong acid and alkali resistance, rich pore structure and flexible and controllable surface chemical properties. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a carbon-based bimetallic supported catalyst and a preparation method and use thereof.

[0006] The technical solution of the present invention is as follows: A method for preparing a carbon-based bimetallic supported catalyst Pt-Cu / C, Chloroplatinic acid and copper chloride were prepared into 1 g / 100 ml aqueous solutions respectively, and the above aqueous solutions were taken in a ratio of Pt to Cu of 1:1 and dispersed into 200 ml deionized water successively; Adjust the pH to 9 and add 1.5 ml of 1% polyethylene glycol solution under stirring; After stirring for 15 min, freshly prepared 0.1 mol / L sodium borohydride solution was added dropwise; Add activated carbon powder treated with nitric acid and continue stirring for 2 h to load the metal nanoparticles onto the activated carbon; Filter and wash with 70 ℃ deionized water several times; The mixture was dried in a vacuum drying oven at 100° C. for 12 h to obtain the Pt-Cu / C catalyst.

[0007] In the preparation method, sodium carbonate or ammonia water is used to adjust the pH.

[0008] The mesh number of the activated carbon is 150-200 meshes, and the activated carbon is soaked in nitric acid with a nitric acid concentration of 1-4 mol / L.

[0009] The preparation method comprises adding activated carbon powder treated with nitric acid at a mass ratio of Pt:Cu:C=1:1:50-200.

[0010] The mass concentration of the polyethylene glycol solution is 0.5%-2%.

[0011] According to the Pt-Cu / C catalyst obtained by the preparation method, the number of surface carboxyl groups and the total acidity of the activated carbon after being treated with nitric acid are increased; Pt and Cu nanometal particles are evenly dispersed on the activated carbon, and the particle size of the metal particles is 1-3 nm.

[0012] The Pt-Cu / C catalyst is used for catalyzing the oxidation of cyclohexane by molecular oxygen to synthesize adipic acid in a one-step process.

[0013] The beneficial effects of the present invention are: 1) The carrier activated carbon is treated with nitric acid, which directionally changes the functional group ratio on the surface of the activated carbon, and accordingly modifies the surface properties of the activated carbon, thereby promoting the oxidation of cyclohexane; 2) The metal loading described above introduces the loading of non-precious metal Cu on the basis of single Pt loading, thereby reducing the use of precious metal Pt and effectively reducing the preparation cost of the catalyst. In addition, the addition of the second metal component has a certain promoting effect on the conversion rate of cyclohexane and the selectivity of adipic acid, which is due to the synergistic effect between the two metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a comparison chart of the catalytic effects of activated carbon, single metal supported catalysts Pt / C, Cu / C and the bimetal supported catalyst Pt-Cu / C in catalyzing the production of adipic acid from cyclohexane.

[0015] Figure 2 is a transmission electron microscope (TEM) image of the Pt-Cu / C catalyst. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example 1

[0017] Add 200 ml of deionized water to a 500 ml three-necked flask, transfer 1.1 ml of the prepared 1 g / 100 ml chloroplatinic acid aqueous solution into the three-necked flask, and stir to disperse evenly; add 1.5 ml of 1% polyethylene glycol solution and keep stirring; after 15 min, add a certain amount of freshly prepared 0.1 mol / L sodium borohydride solution; add 0.5 g of activated carbon powder treated with nitric acid and continue stirring for 2 h; filter and wash with 70 ℃ deionized water several times; dry in a 100 ℃ vacuum drying oven for 12 h to obtain Pt / C material. Example 2

[0018] Add 200 ml of deionized water to a 500 ml three-necked flask, transfer 1.1 ml of the prepared 1 g / 100 ml copper chloride solution into the three-necked flask, and stir to disperse evenly; add an appropriate amount of sodium carbonate to adjust the pH to 9; add 1.5 ml of a 1% polyethylene glycol solution and keep stirring; after 15 min, add a certain amount of freshly prepared 0.1 mol / L sodium borohydride solution; add 0.5 g of activated carbon powder treated with nitric acid and continue stirring for 2 h; filter and wash with 70 ℃ deionized water several times; dry in a 100 ℃ vacuum drying oven for 12 h to obtain the Cu / C material. Example 3

[0019] Add 200 ml of deionized water to a 500 ml three-necked flask, transfer 0.55 ml of the prepared 1 g / 100 ml chloroplatinic acid aqueous solution into the three-necked flask, transfer 0.55 ml of the prepared 1 g / 100 ml chloroplatinic acid aqueous solution into the three-necked flask, stir and disperse evenly; add an appropriate amount of sodium carbonate to adjust the pH to 9; add 1.5 ml of a 1% polyethylene glycol solution and keep stirring; after 15 min, add a certain amount of freshly prepared 0.1 mol / L sodium hydride solution of boron; add 0.5 g of activated carbon powder treated with nitric acid and continue stirring for 2 h; filter and wash with 70 ℃ deionized water several times; dry in a 100 ℃ vacuum drying oven for 12 h to obtain Pt-Cu / C material.

[0020] The Pt / C, Cu / C, and Pt-Cu / C catalysts prepared in the above examples are used to prepare adipic acid from cyclohexane in one step. Figure 1 It can be seen that Example 3 is the best. The cyclohexane conversion rate of the Pt-Cu / C catalyzed cyclohexane oxidation reaction described in Example 3 is increased from 25.24% to 34.97%, and the adipic acid yield is increased from 12.84% to 19.56% compared with the Pt / C catalyst described in Example 1.

[0021] The preparation method of the Pt / C, Cu / C and Pt-Cu / C catalysts prepared by the present invention is simple, feasible and environmentally friendly. Figure 2 , Pt and Cu nanometals are evenly dispersed on the carrier activated carbon, with a particle size of 1~3 nm.

[0022] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a carbon-based bimetallic supported catalyst Pt-Cu / C, characterized in that: Chloroplatinic acid and copper chloride were prepared into 1 g / 100 ml aqueous solutions respectively, and the above aqueous solutions were taken in a ratio of Pt to Cu of 1:1 and dispersed into 200 ml deionized water successively; Adjust the pH to 9 and add 1.5 ml of 1% polyethylene glycol solution under stirring; After stirring for 15 min, freshly prepared 0.1 mol / L sodium borohydride solution was added dropwise; Add activated carbon powder treated with nitric acid and continue stirring for 2 h to load the metal nanoparticles onto the activated carbon; Filter by suction and wash with 70℃ deionized water several times; The mixture was dried in a vacuum drying oven at 100° C. for 12 h to obtain the Pt-Cu / C catalyst.

2. The preparation method according to claim 1, characterized in that: Sodium carbonate or ammonia is used to adjust pH.

3. The preparation method according to claim 1, characterized in that The mesh number of the activated carbon is 150-200 meshes, and the activated carbon is soaked in nitric acid with a nitric acid concentration of 1-4 mol / L.

4. The preparation method according to claim 1, characterized in that: Add activated carbon powder treated with nitric acid at a mass ratio of Pt:Cu:C=1:1:50-200.

5. The preparation method according to claim 1, characterized in that: The mass concentration of the polyethylene glycol solution is 0.5%-2%.

6. A Pt-Cu / C catalyst obtained according to the preparation method according to any one of claims 1 to 5, characterized in that: The number of surface carboxyl groups and the total acidity of activated carbon increased after treatment with nitric acid; Pt and Cu nanometal particles were evenly dispersed on the activated carbon, and the particle size of the metal particles was 1~3 nm.

7. Use of the Pt-Cu / C catalyst according to claim 6, characterized in that: Used to catalyze the one-step oxidation of cyclohexane with molecular oxygen to synthesize adipic acid.

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