CN116273123A - A large-scale preparation method of a supported single-atom catalyst - Google Patents

Abstract

A large-scale preparation method of a supported single-atom catalyst relates to the field of preparation of supported single-atom catalysts, and comprises the following steps: s1: dissolving a soluble metal complex with a ligand of a nitrogen-containing macrocyclic organic compound in an organic solvent to prepare a mixed solution; s2: adding a catalyst carrier into the mixed solution for isovolumetric impregnation to obtain a mixed material; s3: drying and grinding the mixed material to obtain catalyst precursor powder; s4: and roasting or cold plasma treating the catalyst precursor powder to obtain the supported monoatomic catalyst. The invention is improved on the basis of the traditional dipping method, the dipping method has mature technology, simple operation and easy control of parameters, thus being beneficial to realizing large-scale production and having low production cost.

Description

A large-scale preparation method of a supported single-atom catalyst

technical field

The invention relates to the field of preparation of supported single-atom catalysts, in particular to a large-scale preparation method of supported single-atom catalysts.

Background technique

Single-atom catalysts refer to a class of catalysts in which the metal components are dispersed in the form of single atoms. Theoretically, each metal atom of a single-atom catalyst is isolated and dispersed, and each atom is an active center, which makes this catalyst have the greatest atom utilization and the best reaction selectivity. Due to the very large surface energy of metal single atoms, it is difficult for them to exist stably without a load, and they will continue to aggregate into large nanoparticles, which limits the performance and application of single-atom catalysts. The support can effectively fix metal single atoms and prevent atoms from aggregating with each other. Therefore, the single-atom catalysts with real application value are basically supported single-atom catalysts.

The preparation methods of single-atom catalysts mainly include: co-precipitation method, mass separation soft landing method, impregnation method, atomic layer deposition method, sol immobilization method, precipitation deposition method, etc. Among them, the impregnation method is the most commonly used method for preparing traditional industrial catalysts because of its simple operation, mature technology, and easy control of parameters. Although there are various preparation methods for single-atom catalysts, there are still some technical problems to be solved: 1. The preparation methods of single-atom catalysts are generally complicated, costly or require high-pollution treatment methods such as pickling, making it difficult to apply to catalysts. Large-scale production; 2. During the preparation process of single-atom catalysts, metal atoms tend to aggregate, which affects the catalytic performance.

The invention patent application with publication number CN109806903A provides a single-atom palladium catalyst and its preparation method and application. In the method, a Pd precursor, a carbon source, and a nitrogen source are first dissolved in a solvent, and heated to obtain a transparent solution. The solvent was then lyophilized to obtain a dry solid mixture. Finally, the obtained solid mixture was placed in an inert gas atmosphere, and treated at a temperature of 600-1000° C. for 14 hours to obtain a monoatomic palladium catalyst. The carrier of the catalyst is carbon, which is completely derived from high-temperature carbonization of organic nitrogen sources and carbon sources, and the cost is high, so the industrialized large-scale production has little meaning.

The invention patent with the publication number CN109939676A relates to a single-atom palladium catalyst and its preparation and application in the selective hydrogenation of acetylene. The monoatomic palladium catalyst is prepared by the following method: first, the molecular sieve carrier is dried in an oven at 80° C. for 12 hours for later use. Prepare 60mL of 0.01mol/L palladium chloride solution, add polyvinyl alcohol according to 1% of the mass of palladium chloride, and put it in a high-low temperature reaction box at –120°C for stirring. The solvent of the palladium chloride solution is based on the ethanol:water volume ratio of 8: 2 configuration. According to the molar ratio of ascorbic acid and palladium in palladium chloride being 5:1, add the palladium chloride solution into the palladium chloride solution and stir at -120°C for 1 hour to prepare the palladium metal sol. Weigh 10g of the dried molecular sieve carrier, add it to the metal sol, stir for 2 hours, the stirring speed is 200r/min, after the reaction is completed, suction filter at –120°C and wash the product with deionized water, and finally dry it in an oven at 70°C 12h, a monoatomic palladium catalyst was obtained. The preparation process of this method is relatively complicated, and the patent does not provide any ethylene selectivity data to prove the performance of single atoms.

The invention patent with publication number CN112871154A provides a platinum single-atom catalyst, its preparation method and its application in the reaction of styrene selective catalytic hydrogenation of phenylacetylene. This method uses metal-organic frameworks (MOFs) as precursors to prepare support-supported platinum single-atom catalysts. First, disperse the carrier precursor metal salt into water, disperse the organic ligand into N,N-dimethylformamide, and mix the above two solutions ultrasonically to obtain the raw material solution, and then add the active component metal salt, at 50– The reaction was carried out under stirring in an oil bath at 150°C for 5-50 minutes to obtain a mixture; the mixture was suction-filtered, washed and dried. The sample obtained after drying is calcined at 400-800° C. for 1-24 h in air atmosphere, and the calcined solid is reduced at 100-500° C. for 1-12 h under hydrogen/inert atmosphere to obtain the catalyst. The catalyst is applied to the reaction of preparing styrene by selective hydrogenation of phenylacetylene, and the selectivity and conversion rate of styrene can be as high as 90%. Production.

The invention patent with the publication number CN109939718A provides a single-atom catalyst with high catalytic activity and its preparation method and application. In this invention, metal salt, zinc nitrate and ligand are subjected to solvothermal reaction, dissolved in a solvent to obtain a dispersion liquid, and then coated with a polymer and subjected to high temperature treatment in an inert atmosphere to obtain the single-atom catalyst with an empty shell structure. The single-atom catalyst prepared by the above method was applied to the hydrogenation reaction of nitrobenzene, and reacted for 1 hour at 110°C in a hydrogen atmosphere of 5 MPa. The calculated TOF value of the single-atom catalyst for the hydrogenation reaction of nitrobenzene was higher than that of the existing literature several times that of , showing excellent activity and selectivity. However, the carbon support of this method is also derived from the carbonization of MOFs and polymers, which is expensive and cannot be industrialized and mass-produced.

The invention patent with the publication number CN114950474A provides a method for regulating the dispersion of metal active centers of metal-supported catalysts using complex precursors. Soluble salt to obtain a metal salt solution; the auxiliary metal is one or more of chromium, palladium, copper; 2. Add ammonia water and ultrasonic treatment to obtain a metal complex solution; 3. Put the carrier at 280-350 ° C Pass water vapor under it for 8-24 hours to modify, add to the dispersant after drying, then add deionized water to it, reflux, filter, wash, and dry to obtain the modified carrier; 4. Add the carrier to the metal complex solution , adjust the pH of the system to 9-11 with ammonia water, impregnate with ultrasonic, wash with absolute ethanol, filter, filter, dry and roast. The metal catalyst prepared by the method can also improve the dispersion degree of its metal active center under the premise of high load. However, single-atom catalysts cannot be obtained by using this method. Theoretically speaking, after the method is pre-dispersed, the metal simple substance obtained during the roasting reduction process will reunite to form nanoparticles due to its large surface energy.

Based on the above research status, it can be seen that it is of great economic value to seek a simple, convenient and economical new process for large-scale preparation of supported single-atom catalysts.

Contents of the invention

The invention aims to provide a large-scale preparation method of a supported single-atom catalyst to solve the problem that the supported single-atom catalyst is difficult to realize large-scale production.

In order to solve the above technical problems, the specific scheme adopted in the present invention is: a large-scale preparation method of a supported single-atom catalyst, comprising the following steps: S1: dissolving a soluble metal complex whose ligand is a nitrogen-containing macrocyclic organic compound in an organic A mixed solution is prepared in a solvent; S2: add a catalyst carrier to the mixed solution for equal volume impregnation to obtain a mixed material; S3: dry and grind the mixed material to obtain a catalyst precursor powder; S4: process the catalyst precursor powder Calcination or cold plasma treatment, that is, the preparation of supported single-atom catalysts.

As a further optimization of the above technical solution, the roasting treatment in step S4 is a high-temperature ammoniation treatment under a mixed atmosphere of ammonia gas and inert gas.

As a further optimization of the above technical solution, the calcination in step S4 is high-temperature carbonization under an inert atmosphere.

As a further optimization of the above technical solution, the cold plasma treatment specifically includes the following steps:

S401: placing the catalyst precursor powder in a cold plasma device;

S402: passing a mixed atmosphere of inert gas and ammonia gas into the reaction chamber of the cold plasma device;

S403: Maintain the same mixed atmosphere as step S402, and process the catalyst precursor powder;

S404: close the ammonia gas, and continue to pass inert gas for purging;

S405: stirring and mixing the catalyst precursor powder in the reaction chamber;

S406: Steps S402-S405 are repeated for a total of N times of treatment to obtain a supported single-atom catalyst.

As a further optimization of the above technical solution, the nitrogen-containing macrocyclic organic compound is a porphyrin, a porphyrin salt or a soluble phthalocyanine structure.

As a further optimization of the above-mentioned technical scheme, the porphyrin is tetraphenylporphyrin, tetracarboxyphenylporphyrin, aminophenylporphyrin, hydroxyphenylporphyrin or nitrophenylporphyrin; the porphyrin salt is tetraphenylporphyrin Sodium porphyrin sulfonate.

As a further optimization of the above technical solution, the metal in the soluble metal complex is palladium, nickel or copper.

As a further optimization of the above-mentioned technical solution, the catalyst carrier is an oxide carrier, a carbide carrier or a temperature-labile polymer carrier.

As a further optimization of the above technical solution, the catalyst carrier is SiO ₂ , polystyrene, starch derivatives or cellulose derivatives.

As a further optimization of the above technical solution, SiO ₂ is a mesoporous structure with a specific surface area of 300 m ² /g.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. The present invention is improved on the basis of the traditional dipping method. The dipping method has mature technology, simple operation, and easy control of parameters, so it is beneficial to realize large-scale production, and the production cost is low.

2. The present invention cleverly uses the method of metal pre-dispersion, that is, the metal is separated from the nitrogen-containing macrocyclic organic ligand, and then impregnated on the catalyst carrier, effectively preventing the aggregation of metal atoms in the subsequent treatment process.

3. The invention introduces cold plasma technology, green, low temperature and high efficiency, which greatly shortens the preparation cycle of the catalyst, improves the performance of the catalyst, provides a feasible strategy for the industrial production of single-atom catalysts, and has great commercial value .

4. The present invention introduces cold plasma technology. Since the temperature of cold plasma treatment is relatively low, some high-molecular non-temperature-resistant carriers can be selected to ensure that the carrier does not change during the treatment process, and the source of the carrier is more abundant.

5. The production cost of the catalyst of the present invention is low, and the oxide support or carbide support commonly used in industry can be selected to prepare different supported metal single-atom catalysts, which greatly reduces the production cost.

Description of drawings

Fig. 1 is the preparation flowchart of supported single-atom catalyst;

Fig. 2 is the schematic diagram of cold plasma treatment device;

Fig. 3 is the long-time stability test test data curve chart at 70 ℃ for the catalyst made in embodiment 1 and the catalyst made in comparative example 3;

Fig. 4 is the in-situ infrared spectrum of the supported single-atom catalyst carbon monoxide.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but it is not intended to limit the protection scope of the present invention.

First of all, it needs to be explained that since the single-atom catalyst refers to a type of catalyst in which the metal component is dispersed in the form of a single atom, the supported single-atom catalyst in the present invention is a supported metal single-atom catalyst, as shown in Figure 1 The flow chart of the preparation of the supported single-atom catalyst, and the soluble metal complexes used in the preparation process are all commercially available products.

In the embodiment of the present invention, the metal of the soluble metal complex is palladium, nickel or copper, but actually in the preparation process of the supported single-atom catalyst, the metal of the soluble metal complex is not limited to the listed ones. Other transition metal single atoms can be used.

The ligands of the soluble metal complexes in the embodiments of the present invention are tetracarboxyphenylporphyrin and tetracarboxyphthalocyanine. However, in the actual preparation process of the supported single-atom catalyst, the ligand of the soluble metal complex can also be a porphyrin, a porphyrin containing different substituents, a porphyrin salt or a soluble phthalocyanine structure. Specifically, the porphyrin is Tetraphenylporphyrin, aminophenylporphyrin, hydroxyphenylporphyrin, nitrophenylporphyrin, etc., and the porphyrin salt is sodium tetraphenylporphyrin sulfonate, etc.

Among them, the supported single-atom catalyst whose metal is palladium is a supported palladium-based single-atom catalyst, the supported single-atom catalyst whose metal is nickel is a supported nickel-based single-atom catalyst, and the supported single-atom catalyst whose metal is copper is a supported Copper-based single-atom catalysts. The preparation method of the present invention will be described in detail below by taking the preparation methods of supported palladium-based single-atom catalysts, supported nickel-based single-atom catalysts, and supported copper-based single-atom catalysts as examples.

Example 1

The preparation method of supported palladium-based single-atom catalyst is as follows:

S1: Dissolve 8.34 mg of soluble palladium complex (ligand tetracarboxyphenylporphyrin) in 1200 ul of tetrahydrofuran solution, shake the bottle slightly to fully dissolve, and prepare a mixed solution;

S2: Add 1g of SiO ₂ as the catalyst carrier for equal volume impregnation, stir to mix the mixed solution fully until a mixed material with uniform color is formed; the specific surface area of the SiO ₂ used is 300m ² /g, which is a mesoporous structure.

S3: put the mixed material into a drying box, adjust the temperature to 85° C. and dry for 12 hours to obtain a catalyst precursor, and grind the catalyst precursor into powder;

S4: Take 100 mg of catalyst precursor powder as a sample and place it in a cold plasma device, and perform cold plasma treatment under a mixed atmosphere of ammonia gas and inert gas;

specific:

S401: Take 100 mg of catalyst precursor powder as a sample and place it in a cold plasma device;

S402: Pass a mixed atmosphere of argon and ammonia to the reaction chamber of the cold plasma device (as shown in Figure 2 is a schematic diagram of the cold plasma device) for 4 minutes, to remove the air in the reaction chamber, the volume of argon and ammonia The flow ratio is 4:1, and the total flow of the mixed atmosphere is 30ml/min;

S403: Maintain the same mixed atmosphere as in step S402, with a voltage of 100V and a current of 0.6A, and treat the catalyst precursor powder for 1 min;

S404: Then turn off the ammonia gas, and only purge with argon gas for 2 minutes to remove the residual gaseous ammonia gas, so as to prevent the residual ammonia gas from absorbing water when the reaction chamber is opened to process the sample, which will cause the sample to become damp.

S405: Stir and mix the samples in the reaction chamber evenly;

S406: Steps S402-S405 are repeated for a total of 10 times of treatment to obtain a gray-white supported single-atom catalyst.

In this example, 46.9 mg of the supported single-atom catalyst was obtained. After testing, the content of palladium in the prepared supported single-atom catalyst was 0.1%.

Since the temperature of the cold plasma treatment in this embodiment is relatively low, the catalyst carrier can also be a heat-resistant polymer carrier, such as nanoporous structure materials such as polystyrene, starch derivatives, and cellulose derivatives. Catalyst supports can be selected from a wide range of options.

In step S1 of this embodiment, the organic solvent used is tetrahydrofuran solution, and N,N-dimethylformamide, pyridine, aniline or pyrrole may also be used as the organic solvent. The selection of the organic solvent depends on the solubility of the macrocyclic organic compound in the organic solvent. The solubility is good, the priority is low boiling point, and it is easy to dry.

It should be noted that the equal-volume impregnation in this example is an equal-volume impregnation process of incipient wetness impregnation. For example, 1g of silica has a pore volume of 1.2ml, so when taking 1g of silica to prepare a sample, the volume of the mixed solution added is exactly 1.2ml; then vigorously stir and mix, and then dry. The metal complex in the 1.2ml mixed solution should be determined according to the palladium loading. For example, the loading of palladium is 0.1%, that is, 0.001g of palladium is loaded on 1g of silica, and the corresponding palladium complex can be calculated.

The raw material used in this example is a complex formed by a metal and a nitrogen-containing macrocyclic organic compound. For this complex, the metal is firmly fixed by coordinating with the nitrogen of the macrocyclic organic compound. The structure is shown in (1) below :

Moreover, this rigid structure makes the impregnated complex molecules have a strong self-dispersion ability. In this embodiment, the metal macrocyclic organic complex is simply impregnated, and the complex is attached to the channel wall of the carrier to realize the pre-dispersion and fixation of the metal, and then the cold plasma technology is introduced for treatment. The process system has low temperature, close to room temperature, low energy consumption and high efficiency, which greatly shortens the catalyst preparation cycle and improves the performance of the catalyst. It provides a feasible strategy for the industrial production of single-atom catalysts and has great commercial potential. value.

In the present invention, metals are mainly limited by macrocycles for pre-dispersion, and the nitrogen-containing macrocycle organics used can also be porphyrins and porphyrin salts of other various groups, such as porphyrin, aminophenylporphyrin, hydroxyl Phenylporphyrin, nitrophenylporphyrin, sodium tetraphenylporphyrin sulfonate, etc., as long as they have good solubility in certain solvents. In addition, the nitrogen-containing macrocyclic organic compound can also be a soluble phthalocyanine structure, such as the structure shown in (2) below:

The cold plasma technology in this embodiment is a dielectric discharge cold plasma technology, and this dielectric discharge cold plasma technology treats a catalyst precursor impregnated with a metal macrocyclic complex. According to the traditional industrial catalyst preparation method, after impregnating the metal precursor, it needs to be roasted and reduced. The dielectric discharge cold plasma technology of this embodiment replaces the traditional roasting and reduction process, and realizes the carbonization of metal macrocyclic organic matter and the reduction of metals at low temperature through dielectric discharge cold plasma. Cold plasma belongs to non-thermal equilibrium plasma, which has higher electron energy and lower gas temperature, which can improve atomic dispersion, enhance the interaction between metal and carrier, and have better resistance to carbon deposition. The supported single-atom catalysts prepared by cold plasma technology have the advantages of large specific surface area, fast reduction rate, and lattice defects of catalytic components, which lead to enhanced catalytic performance.

The carbon monoxide in-situ infrared CO-DRIFT test results of the obtained samples are shown in Fig. 4 . The infrared spectrogram results show that there is only one characteristic absorption peak at 2080cm ^-1 , which is attributed to the linear adsorption of CO. There is no absorption peak below 2000cm ^-1 , and there is no bridge adsorption and three-site adsorption of CO on the surface. It shows that the prepared catalyst is a single-atom catalyst.

Example 2

Preparation method of supported palladium-based single-atom catalyst:

The preparation method of this example is the same as that of Example 1, except that the catalyst precursor powder obtained in step S4 is subjected to high-temperature carbonization treatment under an inert gas to obtain a supported palladium-based single-atom catalyst;

specific:

Take 102.2 mg of catalyst precursor powder as a sample and place it in a closed container, and pass argon gas into the container. The flow rate of argon gas is 30ml/min, and the temperature in the container is raised to 600 ° C at a heating rate of 1 ° C / min. Treat at a temperature of 600° C. for 1 hour, and then lower the temperature naturally to prepare a supported palladium-based single-atom catalyst.

After inspection, the content of palladium in the prepared supported palladium-based single-atom catalyst is 0.1%.

Example 3

Preparation method of supported palladium-based single-atom catalyst:

The preparation method of this example is the same as that of Example 1, except that in step S4, the obtained catalyst precursor powder is subjected to high-temperature ammoniation treatment in a mixed atmosphere of ammonia gas and inert gas to obtain a supported palladium-based single-atom catalyst.

specific:

Take 102.2 mg of catalyst precursor powder as a sample and place it in a closed container, and introduce a mixed atmosphere of argon and ammonia into the container, the volume flow ratio of argon and ammonia in the mixed atmosphere is 4:1, mix The total flow rate of the atmosphere is 30ml/min, and the temperature in the container is raised to 600°C at a heating rate of 1°C/min, treated at 600°C for 1 hour, and then cooled naturally to prepare a supported palladium-based single-atom catalyst.

After inspection, the content of palladium in the prepared supported palladium-based single-atom catalyst is 0.1%.

Same as Example 1, the raw materials used in this example are still complexes formed by metals and nitrogen-containing macrocyclic organic compounds. More importantly, the catalyst precursor prepared after equal-volume impregnation of this soluble metal complex catalyst carrier is roasted under an inert gas environment (including the high-temperature carbonization of Example 2 and the high-temperature ammoniation of Example 3), The organic macrocyclic complex will form nitrogen-doped carbon in situ, which will effectively prevent the aggregation of the metal in the middle of the macrocycle during the formation of a single substance, thereby forming a single-atom dispersed structure anchored by nitrogen in the nitrogen-doped carbon, which is loaded on the carrier.

The present invention simply impregnates metal-macrocyclic organic complexes instead of forming MOFs or covalent organic framework materials (COFs) through polymerization, but pre-disperses and fixes them through the adsorption force of the carrier and the complexes, and then roasts them. This preparation process is very similar to the traditional catalyst preparation method, the process is simple, economical and conducive to large-scale preparation.

Example 4

Preparation method of supported nickel-based single-atom catalyst:

The preparation method of this embodiment is the same as that of Example 1, except that metal palladium is replaced by metal nickel.

Example 5

Preparation method of supported copper-based single-atom catalyst:

The preparation method of this embodiment is the same as that of Example 1, except that metal palladium is replaced by metal copper.

Example 6

Preparation method of supported palladium-based single-atom catalyst:

The preparation method of this example is the same as that of Example 1, except that the ligand used is tetracarboxyphthalocyanine.

Example 7

The preparation method of supported palladium-based single-atom catalyst is as follows:

S1: Dissolve 10.56 mg of soluble palladium complex (ligand tetracarboxyphenylporphyrin) in 1200 ul of tetrahydrofuran solution, shake the bottle slightly to fully dissolve, and prepare a mixed solution;

S2: Add 1.6 g of polystyrene as the catalyst carrier for equal-volume impregnation, and stir to fully mix the mixed solution until a mixed material with uniform color is formed.

S3: Put the mixed material into a drying box, adjust the temperature to 80° C. and dry for 12 hours to obtain a catalyst precursor, and grind the catalyst precursor into powder;

S4: Take 100 mg of catalyst precursor powder as a sample and place it in a cold plasma device, and perform cold plasma treatment under a mixed atmosphere of ammonia gas and inert gas;

specific:

S401: Take 100 mg of catalyst precursor powder as a sample and place it in a cold plasma device;

S402: Pass a mixed atmosphere of argon and ammonia to the reaction chamber of the cold plasma device (as shown in Figure 2 is a schematic diagram of the cold plasma device) for 4 minutes, to remove the air in the reaction chamber, the volume of argon and ammonia The flow ratio is 4:1, and the total flow of the mixed atmosphere is 30ml/min;

S403: Maintain the same mixed atmosphere as in step S402, with a voltage of 100V and a current of 0.6A, and treat the catalyst precursor powder for 1 min;

S404: Then turn off the ammonia gas, and only purge with argon gas for 2 minutes to remove the residual gaseous ammonia gas, so as to prevent the residual ammonia gas from absorbing water when the reaction chamber is opened to process the sample, which will cause the sample to become damp.

S405: Stir and mix the samples in the reaction chamber evenly;

S406: Steps S402-S405 are repeated for a total of 10 times of treatment to obtain a supported single-atom catalyst.

Comparative Example 1

The preparation method of Ni ₃ Zn/oCNT catalyst is as follows:

(1) First, carbon nanotubes are added to concentrated hydrochloric acid with a feed ratio of 1g:100ml, and stirred at room temperature for 24 hours to remove residual metal; then carbon nanotubes are added to concentrated nitric acid with a feed ratio of 1g:100ml, 140 Reflux at °C for 2 hours, filter and wash until neutral to obtain oxidized carbon nanotubes (oCNT).

(2) Immersion method: Dissolve 101mg of nickel nitrate hexahydrate and 33.7mg of zinc nitrate hexahydrate in 40ml of ethanol, then add 374mg of carbon dioxide nanotubes, stir ultrasonically for about 1 hour to ensure uniform dispersion, and then pass through a rotary evaporator The solvent ethanol was removed, and the temperature was kept in an oven at 100°C for 2 hours.

(3) The sample processed in step 2 is subjected to reduction treatment in a mixed atmosphere of hydrogen and argon, the flow rate of the mixed gas is 100ml/min, and the volume ratio of hydrogen in the mixed gas is 50%; The heating rate was raised to 500° C. and treated at a constant temperature for 2 hours, and then lowered to room temperature to obtain a Ni ₃ Zn/oCNT catalyst.

Wherein the loading amount of Ni is about 5wt.%.

For details, refer to Comparative Example 1 in patent CN109622000A.

Comparative Example 2

The 9.3nm Cu/Al ₂ O ₃ nanoparticle catalyst was prepared by ALD method. Spherical alumina powder (Nanodur, 99.5% Alfa Aesar) was used as a carrier, copper (II) hexafluoroacetylacetonate hydrate (Cu(hfac), Aladdin Industrial corporation 98%), and formalin (Aldrich, 37% HCHO and 15% CH ₃ OH in water) as precursors. The Cu(hfac) precursor was packed in a sealed stainless steel bottle and heated to 75 °C to obtain sufficient vapor pressure. Spherical alumina powder (Nanodur, 99.5% Alfa Aesa) was used as support. The sample was subjected to 5 Cu ALD cycles at 300°C to obtain a 9.3 nm Cu/Al ₂ O ₃ nanoparticle catalyst.

For details, refer to Copper Catalysts in Semi-Hydrogenation of Acetylene: From Single Atoms to Nanoparticles.

Comparative Example 3

Preparation of PdAg/MgAl-MMO catalyst.

Add the mixed solution of 1mol/L Na ₂ CO ₃ and NaOH dropwise to the mixed suspension containing 560 μL 36.3 mmol/L Na ₂ PdCl ₄ , 400 μL 50 mmol/L AgNO ₃ and MgAl-MMO until the pH value is 9, 60°C Under vigorous stirring for 9 hours. Centrifugal washing with deionized water, drying in an oven at 120°C for 12 hours, and then reducing at 550°C for 4 hours to obtain a PdAg/MgAl-MMO catalyst (theoretical loading is 1.0wt.%).

For the preparation of the reagents required for the experiment and the MgAl-MMO carrier, please refer to the article "Preparation of Composite Metal Oxide Supported Bimetallic PdAg Catalyst and Its Selective Hydrogenation Performance of Acetylene" published by Liu Yanan, He Yufei and others.

<Catalyst activity and selectivity test>

Catalysts prepared in Examples 1-6 and Comparative Examples 1-3 are carried out in accordance with the following method for catalyst activity and selectivity evaluation:

1) Take an appropriate amount of catalyst and place it in a small quartz tube reactor, and place the quartz tube reactor in a temperature-controllable tubular heating furnace;

2) Pass pure H ₂ into the quartz tube reactor, and reduce the sample at 120°C for 1 hour, and the reducing gas flow rate is 10mL/min;

3) After the reduction, the reaction gas is introduced into the quartz tube reactor, and the reaction is carried out at a certain temperature. Wherein, the reaction gas composition is (volume fraction): 0.33% acetylene, 0.66% hydrogen, 33% ethylene, the balance is nitrogen, the hydrogen-alkyne ratio is 20:1, the flow rate of the reaction gas is 50mL/min, and the reaction pressure is normal pressure.

4) The reaction gas outlet is connected to gas chromatography for online detection.

<Catalyst activity and selectivity analysis>

The results of the selective hydrogenation of acetylene over supported metal catalysts are as follows:

Table 1

The catalysts involved in the table are all palladium-based catalysts. It can be seen from Table 1 that when the reaction temperature is 70°C, the selectivities of the three unit catalysts (Examples 1-3, 6) are significantly better than those of Comparative Example 3. Although on the surface, the amount of catalyst used in Comparative Example 3 is 10 mg, and the amount of catalyst used in Examples 1-3, 6 is 30 mg, but the palladium loading of the former is 1%, and the palladium loading of the latter four is only 0.1%. It can be seen that the activity of the single-atom catalysts of Examples 1-3, 6 is also significantly better than that of Comparative Example 3.

Table 2

The amount of catalyst Reaction temperature/℃ Metal loading/% selectivity/% Conversion rate/% Example 4 300mg 200 0.1 90 95 Comparative Example 1 20mg 200 5 45 99

The catalysts involved in Table 2 are all Ni-based catalysts. It can be seen from Table 2 that the selectivity and activity of the single-atom catalyst in Example 4 are significantly better than those in Comparative Example 1.

table 3

The catalysts involved in Table 3 are all Cu-based catalysts. It can be seen from Table 3 that the selectivity and activity of the single-atom catalyst in Example 5 are significantly better than those in Comparative Example 2.

<Stability test analysis>

As shown in Fig. 3, it is the long-term stability test test data curve chart at 70 ℃ for the catalyst prepared in Example 1 and the catalyst prepared in Comparative Example 3,

As can be seen from Figure 3, the conversion rate of the supported palladium-based single-atom catalyst prepared in Example 1 is always close to or equal to 100%, the selectivity is about 90%, and it does not decay with the increase of the test time, and the stability is good .

The PdAg/MgAl-MMO catalyst prepared in Comparative Example 3 has a conversion rate of about 70% at 12-19h, and as the test time increases, it will show a decaying trend from 19h, and when the experiment is carried out to 24h, The conversion rate is only 60%. The selectivity of the catalyst prepared in Comparative Example 3 also showed a decreasing trend with the increase of the experiment time, and the conversion rate was about 70% at 12-18 hours, and the conversion rate was only 60% when the test was carried out to 24 hours.

It can be seen that the catalyst prepared by the preparation method of the present invention can maintain stability for a long time, which is better than the stability performance of the catalyst prepared by the prior art.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. The large-scale preparation method of the supported monoatomic catalyst is characterized by comprising the following steps of:

s1: dissolving a soluble metal complex with a ligand of a nitrogen-containing macrocyclic organic compound in an organic solvent to prepare a mixed solution;

s2: adding a catalyst carrier into the mixed solution for isovolumetric impregnation to obtain a mixed material;

s3: drying and grinding the mixed material to obtain catalyst precursor powder;

s4: and roasting or cold plasma treating the catalyst precursor powder to obtain the supported monoatomic catalyst.

2. The method for preparing a supported monoatomic catalyst according to claim 1, wherein the calcination treatment in step S4 is a high-temperature ammoniation treatment under a mixed atmosphere of ammonia gas and inert gas.

3. The method for large-scale preparation of a supported monoatomic catalyst according to claim 1, wherein the calcination treatment in step S4 is a high-temperature carbonization treatment under an inert atmosphere.

4. The method for preparing the supported monoatomic catalyst on a large scale according to claim 1, wherein the cold plasma treatment specifically comprises the following steps:

s401: placing a catalyst precursor powder in a cold plasma device;

s402: introducing a mixed atmosphere of inert gas and ammonia gas into a reaction cavity of the cold plasma device to remove air in the reaction cavity;

s403: continuously introducing the same mixed atmosphere as the step S402, adjusting voltage and current, and treating the catalyst precursor powder;

s404: closing ammonia gas, and continuing to blow inert gas;

s405: stirring and mixing catalyst precursor powder in a reaction cavity;

s406: repeating the steps S402 to S405, and carrying out accumulation treatment for N times to obtain the supported monoatomic catalyst.

5. The method for preparing the supported single-atom catalyst in large scale according to claim 1, wherein the nitrogen-containing macrocyclic organic is porphyrin, porphyrin containing different substituents, porphyrin salt or soluble phthalocyanine structure.

6. The method for preparing a supported single-atom catalyst according to claim 5, wherein the porphyrin is tetraphenylporphyrin, aminophenylporphyrin, hydroxyphenylporphyrin or nitrophenylporphyrin; the porphyrin salt is tetraphenylporphyrin sodium sulfonate.

7. The method for large-scale preparation of a supported monoatomic catalyst according to claim 1, wherein the metal in the soluble metal complex is palladium, nickel or copper.

8. The method for preparing the supported monoatomic catalyst on a large scale according to claim 1, wherein the catalyst carrier is an oxide carrier, a carbide carrier or a high molecular type carrier which is not resistant to temperature.

9. According to claim8, characterized in that the catalyst carrier is SiO ₂ Polystyrene, starch derivatives or cellulose derivatives.

10. The method for preparing the supported monoatomic catalyst in large scale according to claim 9, wherein the SiO ₂ Is of a specific surface area of 300m ² Mesoporous structure of/g.

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