Microwave preparation method of carbon-based carrier catalyst

Abstract

The invention discloses a microwave preparation method of a carbon-based carrier catalyst, which comprises the following steps: roasting an activated carbon carrier in an inert atmosphere at 400-600 DEG C for 2-4 hours, and after roasting, cooling, washing and drying to obtain pretreated activated carbon; completely immersing the pretreated activated carbon in the active component precursor solution, and simultaneously applying microwaves and ultrasonic waves for impregnation; taking out the impregnated activated carbon, drying at 60-80 DEG C by adopting microwaves, and applying ultrasonic waves at the same time; the dried activated carbon is subjected to microwave and ultrasonic wave combined roasting activation in an inert atmosphere, the roasting temperature is 400-800 DEG C, the roasting time is 0.2-1 h, and the catalyst is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a microwave preparation method for a carbon-based carrier catalyst. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the rapid development of chemical industry, environmental protection, energy and other fields, the demand for high-performance catalysts is becoming increasingly urgent. Activated carbon has become an ideal catalyst carrier due to its high specific surface area, rich pore structure and good chemical stability.

[0004] However, traditional catalyst preparation processes using activated carbon as a carrier, such as impregnation and precipitation methods, have many drawbacks that are difficult to avoid. As far as the impregnation method is concerned, the active components are often limited by the diffusion rate during the impregnation process, and are prone to local enrichment on the surface of the activated carbon, resulting in poor dispersion uniformity. In the precipitation method, nucleation and growth during the precipitation process are difficult to control accurately, which often causes the active components to agglomerate, and the prepared catalyst particles are of different sizes and the active sites are unevenly distributed. Moreover, both of these traditional methods have the problem of lengthy preparation cycles, which greatly limits production efficiency. In addition, long-term high-temperature treatment and complex operating procedures result in high energy consumption and high production costs, and are not in line with the current environmental protection concept of energy conservation and emission reduction. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a microwave preparation method for a carbon-based supported catalyst to prepare a catalyst with high catalytic activity, high selectivity and good stability to meet various catalytic needs in industrial production and scientific research.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A microwave preparation method for a carbon-based supported catalyst comprises the following steps:

[0008] The activated carbon carrier is calcined at 400-600°C for 2-4 hours in an inert atmosphere. After calcination, the carrier is cooled, washed with water, and dried to obtain the pretreated activated carbon.

[0009] The pretreated activated carbon is completely immersed in the active component precursor solution, and microwave and ultrasonic waves are applied for impregnation;

[0010] The activated carbon after impregnation is taken out and dried by microwave at 60-80°C while applying ultrasonic wave;

[0011] The dried activated carbon is subjected to microwave-assisted ultrasonic calcination activation in an inert atmosphere at a calcination temperature of 400-800° C. for a calcination time of 0.2-1 h to obtain a catalyst.

[0012] Pre-treating activated carbon by high-temperature roasting can more effectively remove impurities that are difficult to remove by water washing, thereby improving the purity and specific surface area of ​​activated carbon. Compared with acid washing, it avoids environmental pollution and equipment corrosion problems that may be caused by acid treatment, and there is no chemical residue. Washing the roasted activated carbon with water can better remove impurities in the activated carbon to ensure the loading amount and catalytic activity of the active components.

[0013] As a new heating method, microwave technology has unique advantages such as fast, uniform and selective heating. When microwaves are radiated into a system containing activated carbon and active components, the molecules will vibrate and rotate rapidly under the drive of the microwave electromagnetic field, generating internal friction heat, achieving fast, uniform and selective heating effects. This characteristic enables the loading process of active components on activated carbon carriers to break free from the constraints of traditional heat conduction, accelerate diffusion and adsorption, and greatly improve the uniformity of dispersion; at the same time, due to the high efficiency of microwave heating, the preparation cycle is greatly shortened; furthermore, the precise energy utilization method effectively reduces energy consumption, which is in line with the requirements of the era of green development, and is expected to overcome many defects of traditional preparation processes and prepare catalysts with excellent performance.

[0014] During the calcination activation process, microwave heating and ultrasonic assistance are used. The mechanical vibration and cavitation effect of ultrasound can further promote the dispersion of metal nanoparticles, prevent agglomeration, and enhance the interaction between the carrier and the active components.

[0015] In some embodiments, the specific surface area of ​​the activated carbon is not less than 800 m 2 / g, pore size is 1-100nm.

[0016] In some embodiments, during the calcination pretreatment of activated carbon, the heating rate is 5-10°C / min; the inert atmosphere is nitrogen or argon. The gas flow rate is 5-10m 3 / h.

[0017] In some embodiments, the drying temperature is 80-100° C., and the drying time is 8-12 h.

[0018] In some embodiments, in the active component precursor solution, the active component is palladium chloride or copper nitrate.

[0019] Preferably, the concentration of the active component precursor solution is 0.1-1.0 mol / L, and the solvent is water, ethanol or a mixture of water and ethanol.

[0020] Preferably, the active component precursor solution also includes a dispersant, and the dispersant is polyvinyl pyrrolidone (PVP) or sodium dodecyl sulfate (SDS).

[0021] These polymer dispersants have high dispersing efficiency and good dispersing stability. Their molecular chains are long, and they can form thicker adsorption layers on the surface of dispersed particles, producing a larger steric hindrance effect. Even when the particles are close to each other, the steric hindrance of the long-chain molecules can prevent the particles from agglomerating, thereby playing a good dispersing role on the activated carbon particles, which is beneficial to improving the loading effect of the active components.

[0022] Further preferably, the mass percentage of the dispersant in the active component precursor solution is 5%-20%. The active component precursor solution is formed by fully dissolving and uniformly dispersing the active component precursor solution through stirring or ultrasonic oscillation.

[0023] In some embodiments, microwave and ultrasound are applied simultaneously during the impregnation process, the microwave condition is 100-300 W, the ultrasound condition is a frequency of 20-40 kHz and a power of 50-150 W, and the impregnation time is 10-30 min.

[0024] In some embodiments, during the drying process, the microwave condition is 300-600 W, the ultrasonic condition is a frequency of 20-40 kHz and a power of 50-100 W, and the drying time is 30-60 min.

[0025] In some embodiments, the heating rate during the calcination activation process is 8-15° C. / min.

[0026] Preferably, during the calcination activation process, the microwave conditions are 500-1000W, and the ultrasonic conditions are frequency 20-40kHz and power 100-200W.

[0027] Preferably, a catalyst is added during the calcination activation process, and the catalyst is a transition metal oxide.

[0028] Further preferably, the catalyst is selected from copper oxide, nickel oxide or cobalt oxide.

[0029] In some embodiments, the step of post-treating the prepared catalyst is further included, wherein the post-treatment is tableting, granulation or micronization.

[0030] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0031] (1) Activated carbon carrier calcination pretreatment helps to improve the mechanical strength of activated carbon, change the surface structure and chemical properties of activated carbon, increase the surface active sites, and improve the adsorption capacity and selectivity of target substances. In addition, compared with water bath treatment, it can more effectively remove some impurities that are difficult to remove by water washing; compared with acid washing treatment, it does not require the use of a large amount of acid, will not introduce new chemical impurities, will not have chemical residue problems, and avoids the environmental pollution and equipment corrosion problems that may be caused by acid treatment. The operation process is relatively simple and the cost may be relatively low.

[0032] (2) High uniformity of active component dispersion: Through the impregnation process under the synergy of microwave radiation and ultrasound and the synergistic effect of the dispersant, the active components can be highly evenly dispersed on the pore surface of the activated carbon carrier. Compared with the traditional impregnation method, the agglomeration of active components is greatly reduced, thereby improving the catalytic activity and selectivity of the catalyst. The addition of a small amount of catalyst during the calcination process also promotes the uniform distribution and grain growth of active components, and optimizes the microstructure of the catalyst.

[0033] (3) Short preparation cycle: The rapid heating characteristics of microwave technology are used throughout the various preparation steps such as impregnation, drying, and calcination activation. Compared with traditional preparation processes, microwaves can directly act on the inside of the material, causing the entire material to be heated at the same time. The heating speed is fast, which greatly shortens the drying and calcination time and improves production efficiency. At the same time, it can reduce the side reactions of the material at high temperatures (such as oxidation, decomposition, etc.), improve the purity and quality of the product, and meet the needs of rapid industrial production.

[0034] (4) Low energy consumption: Microwave heating is an internal heating method with high energy utilization rate. The equipment starts and stops quickly without preheating or cooling time. Compared with traditional external heating methods, the energy consumption required to achieve the same preparation effect is significantly reduced, which is in line with the current development trend of energy conservation and environmental protection. In addition, microwave equipment is equipped with a precise temperature control system that can monitor and adjust the heating process in real time to avoid damage to the material due to overheating.

[0035] (5) Microwave and ultrasonic synergy: Microwaves act directly on the material through electromagnetic waves, which can promote the molecular movement inside the material, achieve rapid and uniform heating, promote the loading and grain growth of active components, and increase its specific surface area, porosity and active site distribution. Ultrasonic waves promote the diffusion of active components in the pores of activated carbon and improve the loading uniformity through cavitation effect, mechanical vibration and micro-jet action. The combination of microwaves and ultrasonic waves can achieve rapid heating and efficient dispersion at the same time, significantly improving the performance of the catalyst.

[0036] (6) Excellent catalyst performance: The carbon-based supported catalyst obtained by microwave preparation process has higher catalytic activity, better selectivity and stronger stability when catalyzing various chemical reactions due to the uniform dispersion of active components and the optimization of the support pore structure. It can effectively reduce the reaction temperature and increase the reaction yield, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 The present invention is a process flow chart of a microwave preparation process for a carbon-based carrier catalyst. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] Example 1

[0042] Preparation of palladium / activated carbon catalyst

[0043] Activated carbon carrier pretreatment: Select a specific surface area of ​​1000m 2 / g, activated carbon with a pore size distribution between 2-50nm. Place it in a muffle furnace, heat it to 500℃ at a heating rate of 8℃ / min under nitrogen protection, and calcine it at this temperature for 2h. The calcined activated carbon is washed with deionized water, then placed in a drying device, dried at 90℃ for 10h, and set aside.

[0044] Preparation of active component precursor solution: palladium chloride was selected as the active component precursor, 0.5g palladium chloride was dissolved in 50mL of a mixed solution containing 10% ethanol and distilled water to prepare a solution with a concentration of 0.05mol / L. 0.1g PVP was added as a dispersant, and ultrasonic oscillation was performed for 30 minutes to fully dissolve and evenly disperse it to form an active component precursor solution.

[0045] Microwave impregnation: Add the pretreated activated carbon carrier to the prepared active component precursor solution, and transfer the mixed system to a microwave reaction device. Turn on the microwave and ultrasonic equipment, with the microwave condition at 200W and the ultrasonic condition at (20kHz, 100W), and impregnate for 20 minutes under microwave radiation.

[0046] During the microwave impregnation process, the activated carbon did not agglomerate.

[0047] Microwave drying: After microwave impregnation, the activated carbon carrier loaded with the active component precursor is taken out of the microwave reaction device, and the solid is separated from the impregnation liquid by centrifugal separation. The separated solid is placed in a microwave drying device, the microwave drying temperature and time are set, and the ultrasonic equipment is turned on, the ultrasonic frequency and power are set, the microwave condition is 450W, and the ultrasonic condition is (20kHz, 80W), and dried at 70°C for 45 minutes.

[0048] Microwave calcination activation: After microwave drying, the activated carbon carrier loaded with active component precursors was added with a small amount of copper oxide and transferred to a microwave calcination device. Under nitrogen protection, the gas flow rate was 8m 3 / h. Turn on the microwave equipment and the ultrasonic equipment, set the ultrasonic frequency and power, the microwave condition is 500W, the ultrasonic condition is 20kHz, 150W, increase the temperature to 600℃ at a heating rate of 10℃ / min, and maintain this temperature for 40min.

[0049] Post-treatment: The prepared palladium / activated carbon catalyst was pressed into tablets to make a sheet catalyst with a diameter of 3 mm and a thickness of 2 mm for use in the hydrogenation reaction of styrene.

[0050] According to tests, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate reached 97%, the product selectivity reached 98.5%, and after the catalyst was recycled 10 times, the catalytic activity could still be maintained at 93% of the initial activity.

[0051] Example 2

[0052] Preparation of copper / activated carbon catalyst

[0053] Activated carbon carrier pretreatment: Select a specific surface area of ​​900m 2 / g, activated carbon with a pore size distribution between 5-80nm. Place it in a muffle furnace, heat it to 450℃ at a heating rate of 6℃ / min under nitrogen protection, and calcine it at this temperature for 1.5h. The calcined activated carbon is washed with deionized water, then placed in a drying device, dried at 85℃ for 8h, and set aside.

[0054] Preparation of active component precursor solution: copper nitrate was selected as the active component precursor, 1.0 g of copper nitrate was dissolved in 80 mL of distilled water to prepare a solution with a concentration of 0.1 mol / L. 0.2 g of SDS was added as a dispersant, and it was fully dissolved and evenly dispersed by stirring for 40 minutes to form an active component precursor solution.

[0055] Microwave impregnation: Add the pretreated activated carbon carrier to the prepared active component precursor solution, and transfer the mixed system to a microwave reaction device. Turn on the microwave and ultrasonic equipment, with the microwave condition at 200W and the ultrasonic condition at 20kHz, 100W, and impregnate for 15 minutes under microwave radiation.

[0056] During the impregnation process, the activated carbon did not agglomerate.

[0057] Microwave drying: After microwave impregnation, the activated carbon carrier loaded with the active component precursor is taken out from the microwave reaction device, and the solid is separated from the impregnation liquid by filtration. The separated solid is placed in a microwave drying device, the microwave drying temperature and time are set, and the ultrasonic equipment is turned on, the ultrasonic frequency and power are set, the microwave condition is 450W, and the ultrasonic condition is 20kHz, 80W, and the drying is completed at 65°C for 50 minutes.

[0058] Microwave calcination activation: After adding a small amount of copper oxide to the dried activated carbon carrier loaded with the active component precursor, transfer it to a microwave calcination device under the protection of argon gas with a gas flow rate of 6m 3 / h. Turn on the microwave equipment and the ultrasonic equipment, set the ultrasonic frequency and power, the microwave condition is 500W, the ultrasonic condition is 20kHz, 150W, and the temperature is increased to 700℃ at a heating rate of 12℃ / min, and maintained at this temperature for 30min.

[0059] Post-treatment: The prepared copper / activated carbon catalyst is granulated to form a granular catalyst with a particle size of 0.5-1 mm for carbon monoxide oxidation reaction.

[0060] According to tests, under the conditions of reaction temperature of 150°C and oxygen content of 20%, the carbon monoxide conversion rate reached more than 90%, and after the catalyst was recycled for 8 times, the catalytic activity could still be maintained at more than 85% of the initial activity.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that the dispersant PVP is replaced by sodium pyrophosphate, and the rest is the same as Example 1.

[0063] During the impregnation process, the activated carbon agglomerates to a certain extent.

[0064] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 90%, the product selectivity was 96%, and after the catalyst was recycled 10 times, the catalytic activity remained at 90% of the initial activity.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that the dispersant PVP is omitted, and the rest is the same as Example 1.

[0067] During the impregnation process, the activated carbon agglomerates severely, the active components are poorly dispersed on the surface of the activated carbon, and the activity, selectivity and stability of the catalyst are reduced.

[0068] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 75%, the product selectivity was 90%, and after the catalyst was recycled 10 times, the catalytic activity remained at 80% of the initial activity.

[0069] Comparative Example 3

[0070] The difference from Example 1 is that ultrasonic assistance is omitted during the impregnation process, and the rest is the same as Example 1.

[0071] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 85%, the product selectivity was 95%, and after the catalyst was recycled 10 times, the catalytic activity remained at 85% of the initial activity.

[0072] Comparative Example 4

[0073] The difference from Example 1 is that microwave assistance is omitted during the impregnation process, and the rest is the same as Example 1.

[0074] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 80%, the product selectivity was 92%, and after the catalyst was recycled 10 times, the catalytic activity remained at 82% of the initial activity.

[0075] Comparative Example 5

[0076] The difference from Example 1 is that microwave assistance is omitted during the calcination activation process, and the rest is the same as Example 1.

[0077] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 82%, the product selectivity was 93%, and after the catalyst was recycled 10 times, the catalytic activity remained at 84% of the initial activity.

[0078] Comparative Example 6

[0079] The difference from Example 1 is that the ultrasonic assistance is omitted during the calcination activation process, and the rest is the same as Example 1.

[0080] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 86%, the product selectivity was 94%, and after the catalyst was recycled 10 times, the catalytic activity remained at 86% of the initial activity.

[0081] Comparative Example 7

[0082] The difference from Example 1 is that ultrasonic assistance is omitted in the drying process, and the rest is the same as Example 1.

[0083] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 88%, the product selectivity was 95%, and after the catalyst was recycled 10 times, the catalytic activity remained at 88% of the initial activity.

[0084] Comparative Example 8

[0085] The difference from Example 1 is that microwave assistance is omitted in the drying process, and the rest is the same as Example 1.

[0086] According to the test, under the conditions of reaction temperature of 80°C and hydrogen pressure of 1MPa, the styrene conversion rate was 87%, the product selectivity was 94%, and after the catalyst was recycled 10 times, the catalytic activity remained at 87% of the initial activity.

[0087] In the catalyst preparation process of the present invention, after adding a polymer dispersant (such as PVP, SDS, etc.), the activated carbon has almost no agglomeration phenomenon, and the dispersion uniformity reaches an excellent level. The catalyst activity is greatly improved, the catalytic reaction conversion rate is significantly improved, the selectivity is excellent, the selectivity for the target product is extremely high, and the side reaction is effectively suppressed. And after repeated recycling, the catalyst can still maintain high activity and good stability. These performances far exceed the situation where no dispersant is added and an inorganic dispersant is added, the index effect is outstanding, and the quality of the catalyst obtained meets the use standards of many industries with strict requirements on catalytic performance, such as chemical industry, environmental protection, and energy.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A microwave preparation method for a carbon-based carrier catalyst, characterized in that: The steps include: The activated carbon carrier is calcined at 400-600°C for 2-4 hours in an inert atmosphere. After calcination, the carrier is cooled, washed with water, and dried to obtain the pretreated activated carbon. The pretreated activated carbon is completely immersed in the active component precursor solution, and microwave and ultrasonic waves are applied for impregnation; The activated carbon after impregnation is taken out and dried by microwave at 60-80°C while applying ultrasonic wave; The dried activated carbon is subjected to microwave-assisted ultrasonic calcination activation in an inert atmosphere at a calcination temperature of 400-800° C. for a calcination time of 0.2-1 h to obtain a catalyst.

2. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: The specific surface area of ​​the activated carbon is not less than 800m 2 / g, pore size is 1-100nm.

3. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: During the calcination pretreatment of activated carbon, the heating rate is 5-10℃ / min; The inert atmosphere is nitrogen or argon.

4. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: In the active component precursor solution, the active component is palladium chloride or copper nitrate; Preferably, the concentration of the active component precursor solution is 0.1-1.0 mol / L, and the solvent is water, ethanol or a mixture of water and ethanol.

5. The microwave preparation method of carbon-based supported catalyst according to claim 4, characterized in that: The active component precursor solution also includes a dispersant, which is polyvinyl pyrrolidone or sodium dodecyl sulfate; Preferably, the mass percentage of the dispersant in the active component precursor solution is 5%-20%.

6. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: During the impregnation process, microwave and ultrasonic waves are applied simultaneously, the microwave condition is 100-300W, the ultrasonic condition is a frequency of 20-40kHz and a power of 50-150W, and the impregnation time is 10-30min.

7. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: During the drying process, the microwave conditions are 300-600 W, the ultrasonic conditions are frequency 20-40 kHz, power 50-100 W, and the drying time is 30-60 min.

8. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: The heating rate during the calcination activation process is 8-15℃ / min; Preferably, during the calcination activation process, the microwave conditions are 500-1000W, and the ultrasonic conditions are frequency 20-40kHz and power 100-200W.

9. The microwave preparation method of carbon-based supported catalyst according to claim 8, characterized in that: A catalyst is added during the calcination and activation process, wherein the catalyst is a transition metal oxide; Preferably, the catalyst is selected from copper oxide, nickel oxide or cobalt oxide.

10. The microwave preparation method of carbon-based supported catalyst according to claim 1, characterized in that: The method further comprises the step of post-treating the prepared catalyst, wherein the post-treatment is tableting, granulation or micronization.

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