Calcium carbonate / carbon composite carrier supported ruthenium catalyst, preparation method and application

Abstract

The invention relates to the technical field of noble metal catalysts, in particular to a calcium carbonate / carbon composite carrier supported ruthenium catalyst, a preparation method and application. According to the invention, calcium carbonate is used as a carrier, protein is used as an auxiliary agent, and the calcium carbonate / carbon composite carrier-loaded ruthenium nanoparticle material is successfully prepared through processes of adsorption, impregnation, drying, annealing and the like. By controlling the content of the protein additive, the loading capacity and size distribution of the nanoparticles can be optimized. The material can be applied to selective hydrogenation of catalytic nitro compounds, and shows high activity, selectivity and stability. Results show that the protein can improve the loading capacity and dispersity of ruthenium. Meanwhile, after high-temperature pyrolysis, the protein forms a small amount of nitrogen-doped carbon on the surface of calcium carbonate, and the carbon materials can stabilize the loaded metal ruthenium, so that the activity and stability of the catalyst are improved. The catalyst is simple in preparation process, stable in performance, low in cost and good in industrial production prospect.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal catalysts, and in particular to a calcium carbonate / carbon composite carrier-loaded ruthenium catalyst, a preparation method and application thereof. Background Art

[0002] Nitroaromatics and their derivatives are important bulk chemicals and fine chemicals, occupying a huge market share in the organic chemical industry. Reduction of nitro compounds is an important method for preparing aromatic amines and their derivatives. Catalytic hydrogenation technology using precious metals as catalysts and hydrogen as a hydrogen source is currently the most widely used technology for hydrogenation reduction of aromatic nitro compounds due to its advantages such as high catalyst activity, warm reaction conditions, and a wide range of hydrogen sources. However, precious metal catalysts have shortcomings such as high price, poor selectivity, and easy poisoning during use, which limits their large-scale promotion.

[0003] Among these precious metals, ruthenium has attracted widespread attention due to its relatively low price (about one tenth to one thirtieth of the price of other precious metals) and high activity. In order to further improve the utilization rate and recyclability of ruthenium, ruthenium is usually loaded on a carrier to construct a supported catalyst. Among many carriers, calcium carbonate has attracted widespread attention due to its low cost, easy availability, and good hydrogenation performance of the formed catalyst, but there are few reports on the research of calcium carbonate-loaded ruthenium materials.

[0004] It should be pointed out that the nitro hydrogenation reaction needs to be carried out at a relatively high temperature and pressure. The calcium carbonate-loaded ruthenium prepared in the previous reports cannot meet the application requirements, which is manifested in the low metal ruthenium loading and easy agglomeration, resulting in low metal utilization and activity that needs to be further improved; the formed ruthenium metal center has a weak interaction with calcium carbonate and is easily lost during the reaction, resulting in poor stability. Therefore, compared with other precious metal catalysts, there is still a certain gap in the catalytic performance of preparing aromatic amines in the hydrogenation reduction reaction of aromatic nitro compounds; therefore, a calcium carbonate / carbon-loaded ruthenium precious metal catalyst and its preparation method are particularly necessary to optimize the structure and performance of the material to improve its utilization efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a calcium carbonate / carbon composite carrier-supported ruthenium catalyst, a preparation method and an application thereof, so as to achieve the purpose of catalyzing the hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines with high activity, high selectivity and high stability under relatively mild conditions.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a calcium carbonate / carbon composite carrier-loaded ruthenium catalyst, comprising a carrier, wherein the carrier is eggshell powder, nitrogen-doped carbon is covered on the carrier to form a composite carrier, and metallic ruthenium is loaded on the composite carrier.

[0007] The preparation method of a calcium carbonate / carbon composite carrier-supported ruthenium catalyst comprises the following steps:

[0008] S1. Preparation of protein-coated calcium carbonate materials

[0009] The eggshell powder is evenly dispersed in water, the protein powder is added and fully stirred, and then filtered and dried at low temperature to obtain the protein-coated calcium carbonate material;

[0010] S2. Preparation of Ruthenium Precursor Supported by Calcium Carbonate / Carbon Composite Support

[0011] The S1 protein-coated calcium carbonate material is uniformly dispersed in water, and a ruthenium chloride solution and an aqueous solution of sodium borohydride are sequentially added dropwise under stirring, and then filtered and dried at low temperature to obtain a calcium carbonate / carbon composite carrier-loaded ruthenium precursor;

[0012] S3. Preparation of Ruthenium Catalyst Supported on Calcium Carbonate / Carbon Composite Support

[0013] Under a protective atmosphere, the precursor S2 is subjected to high-temperature pyrolysis to obtain the calcium carbonate / carbon composite carrier-supported ruthenium catalyst of the present invention.

[0014] Furthermore, in the S1, the eggshell powder is a powder obtained by grinding and sieving eggshells, and the particle size of the powder is 100-200 meshes; the egg white powder includes egg white protein powder.

[0015] Furthermore, the mass ratio of the eggshell powder to water is 1:10-100, and the mass ratio of the eggshell powder to protein powder is 1:0.1-2.

[0016] Furthermore, the mass ratio of the protein-coated calcium carbonate material to water is 1:10-100; the mass ratio of ruthenium element to protein-coated calcium carbonate material in the ruthenium chloride solution is 0.5-5:100; and the mass ratio of sodium borohydride to ruthenium element used in preparing the sodium borohydride aqueous solution is 1-10:1.

[0017] Furthermore, in the S3, the protective atmosphere includes one or more of nitrogen and argon; the pyrolysis temperature is 400-600° C., and the pyrolysis time is 1-3 hours.

[0018] The invention discloses an application of a calcium carbonate / carbon composite carrier-supported ruthenium catalyst, wherein the catalyst is applied to the hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines.

[0019] Furthermore, the aromatic nitro compounds include nitrobenzene, p-nitrofluorobenzene, p-nitrochlorobenzene, p-nitroiodobenzene, p-nitroanisole, p-nitrophenylacetonitrile, 2-chloro-1-fluoro-4-nitrobenzene, m-dinitrobenzene and m-nitrotrifluorotoluene.

[0020] Furthermore, the reaction temperature of the hydrogenation reduction is 40-60° C., the hydrogen pressure is 0.1-3 MPa, and the reaction time is 0.5-3 h.

[0021] Furthermore, when the catalyst is used, the conversion rate of the aromatic nitro compound can reach more than 96%, and the selectivity to the product can reach more than 98%.

[0022] Beneficial effects of the present invention:

[0023] 1. The process flow of the method of the present invention is simple. By introducing a protein additive, not only the content and dispersibility of metallic ruthenium are increased, but also during the carbonization process, the protein is pyrolyzed to form nitrogen-doped carbon coated on the surface of calcium carbonate, which can interact with ruthenium particles, thereby effectively promoting the hydrogenation reaction, and can meet the needs of large-scale industrial production;

[0024] 2. The calcium carbonate / carbon composite carrier of the present invention supports the ruthenium catalyst, and the surface of the calcium carbonate carrier is partially coated with nitrogen-doped carbon; this structure can not only help anchor the metal ruthenium particles and improve the stability of ruthenium during the hydrogenation reaction, but also adjust the electronic state of the active metal of ruthenium, thereby improving the selectivity and activity of the catalyst;

[0025] 3. The calcium carbonate / carbon composite carrier-loaded ruthenium catalyst of the present invention can achieve efficient hydrogenation of aromatic nitro compounds at near room temperature and normal pressure (40°C, 1 bar H2), with a conversion rate of more than 96%, a selectivity of more than 98%, and high catalytic activity. After the catalyst is recycled for 10 times, there is no performance degradation; its good performance comes from the introduction of protein additives, which increases the loading amount and dispersibility of ruthenium; the carbon coating layer formed during the pyrolysis of the protein additive can interact with metallic ruthenium, while optimizing its electronic structure, improving its activity and selectivity, and improving the stability of the metallic ruthenium particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is calcium carbonate / carbon supported ruthenium nanoparticles ( Figure 1 a), Calcium carbonate loaded ruthenium nanoparticles ( Figure 1 b) Transmission electron microscopy (TEM);

[0027] Figure 2 1 is a graph showing the cyclic stability results of Example 1 and Comparative Example 1 of the present invention;

[0028] Figure 3 It is a performance diagram of the catalyst of the present invention when used for hydrogenation of different aromatic nitro compound substrates. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0030] Principle of the technical solution of the present invention:

[0031] The present invention successfully prepares the ruthenium material loaded on the calcium carbonate / carbon composite carrier through a series of simple process steps.

[0032] Calcium carbonate is dispersed in an aqueous solution by grinding, and a protein solution is added under stirring to form a mixed solution. The mixed solution is filtered, and the obtained filter residue is dried to obtain a protein-coated calcium carbonate material.

[0033] The protein-coated calcium carbonate material powder is dispersed in water, and an aqueous solution of ruthenium trichloride is added dropwise during stirring. After 30 minutes, an aqueous solution of sodium borohydride is added dropwise thereto. After the addition is completed, the obtained solution is filtered and separated, and the obtained filter residue is dried to obtain a calcium carbonate-loaded ruthenium precursor; under a protective atmosphere, the obtained precursor is subjected to high-temperature pyrolysis to obtain a calcium carbonate / carbon-loaded ruthenium material.

[0034] Figure 1 (a) is a transmission electron micrograph of the catalyst formed by introducing the protein additive, from which it can be seen that the formed ruthenium nanoparticles have the characteristics of small particle size and uniform dispersion; Figure 1 (b) shows the catalyst formed without the introduction of protein additives. It can be seen from the figure that the ruthenium nanoparticles formed have a large particle size and are unevenly distributed.

[0035] The catalyst of the present invention has ruthenium nanoparticles with small particle size and uniform dispersion, and can form strong interaction with the carrier, thereby showing excellent performance in the hydrogenation reduction reaction of nitro compounds.

[0036] Example 1

[0037] (1) At room temperature, 1 g of ground and sieved egg shells were taken, and the particle size of the egg shells was 100-200 meshes; the egg shells were added to 50 mL of water, and ultrasonically dispersed for 20 min (25 kHz, 300 W) at a stirring intensity of 100 rpm, and the stirring intensity was maintained unchanged, and 0.3 g of egg white albumin (CAS: 9006-59-1) was added and stirred for 30 min, and then the mixed system was filtered, and the obtained filter residue was low-temperature dried at 60° C. for 8 h to obtain a protein-coated calcium carbonate material;

[0038] (2) At room temperature, 1 g of protein-coated calcium carbonate material was added to 50 mL of water, and stirred at 100 rpm for 10 min. The stirring intensity was maintained unchanged, and 4.0 mL of RuCl3 solution (5 mg / mL) was added dropwise during the stirring process. The stirring was continued for 30 min, and an aqueous solution of sodium borohydride (0.02 g of sodium borohydride was dissolved in 1 mL of water) was added dropwise to the reaction system, and then the stirring was continued for 3 h. The obtained mixed system was separated by suction filtration, and the obtained filter residue was dried at 60 ° C for 8 h to obtain a calcium carbonate-loaded ruthenium precursor;

[0039] (3) Under a nitrogen protective atmosphere, the obtained precursor is subjected to high temperature pyrolysis (500°C, 2h) to obtain a calcium carbonate / carbon composite carrier-loaded ruthenium material;

[0040] (4) The above catalyst (0.01 g) was loaded into a high temperature reactor, and 20 mL of a mixed solution of methanol and water (volume ratio, 4:1) was added to the reactor. Nitrobenzene (0.1 g) and hydrogen (1 MPa) were added to the reactor. The reaction was carried out at 60° C. for 3 h. The conversion rate of nitrobenzene was greater than 96%, and the selectivity of aniline was greater than 98%.

[0041] Comparative Example 1

[0042] (1) Take 1 g of egg shells from the same batch as in Example 1 and disperse them in 50 mL of water. The dispersion conditions are the same as in Example 1. Add 4.0 mL of RuCl3 solution (5 mg / mL) dropwise during stirring. After 30 minutes, add an aqueous solution of sodium borohydride (0.02 g of sodium borohydride dissolved in 1 mL of water) dropwise thereto. Continue stirring for 3 hours. Filter and separate the obtained mixed system. After drying the obtained filter residue, obtain a calcium carbonate-loaded ruthenium precursor. The drying conditions are the same as in Example 1.

[0043] (2) Under a nitrogen protective atmosphere, the obtained precursor is subjected to high temperature pyrolysis (500°C, 2h) to obtain a calcium carbonate-loaded ruthenium material;

[0044] (3) The above catalyst (0.01 g) was loaded into a high-temperature reactor, and 20 mL of a mixed solution of methanol and water (volume ratio, 4:1) was added to the reactor. Nitrobenzene (0.1 g) and hydrogen (1 MPa) were added to the reactor. The reaction was carried out at 60° C. for 3 h. The conversion rate of nitrobenzene was 47.9%, and the selectivity of aniline was greater than 99%.

[0045] Comparative Example 2

[0046] The same batch of egg shells (0.1 g) as in Example 1 were placed in a high-temperature reactor, 20 mL of a mixed solution of methanol and water (volume ratio, 4:1) was added to the reactor, nitrobenzene (0.1 g) and hydrogen (1 MPa) were added, and the reaction was carried out at 60° C. for 3 h. The conversion rate of nitrobenzene obtained was 0%.

[0047] Table 1 is a table showing the conversion rates of nitrobenzene catalytically hydrogenated to corresponding hydrogenated products by the catalysts prepared in Example 1 and Comparative Examples 1-2.

[0048]

[0049] As shown in Table 1, under the reaction conditions of 10:1 mass ratio of nitrobenzene to catalyst, 1Mpa H2, 60°C, and 3h reaction, the conversion rate of the catalyst (Ru / CaCO3-C) obtained by introducing the protein additive in Example 1 is >96%; the conversion rate of the catalyst (Ru / CaCO3) obtained by Example 2 without the introduction of the protein additive is only 47.9%; the conversion rate of the catalyst formed by Example 3 with only calcium carbonate, without the introduction of the protein additive and the metal ruthenium is 0%. It can be concluded that the metal ruthenium is the main active site of the hydrogenation reaction, and the introduction of the protein additive can improve the interaction between the carrier and the ruthenium nanoparticles, thereby enhancing the hydrogenation activity of the catalyst.

[0050] Figure 2 1 is a graph showing the cyclic stability results of Example 1 and Comparative Example 1; Figure 2 As shown, nitrobenzene (0.1 g), 20 mL of a mixed solution of methanol and water (volume ratio, 4:1) were added, and under the reaction conditions of a nitrobenzene to catalyst mass ratio of 10:1, 1 MPa H2, 60°C, and reaction time of 3 h, the calcium carbonate / carbon-supported ruthenium (Ru / CaCO3-C) catalyst formed after the introduction of the protein auxiliary had high cyclic stability, and after 10 cycles, the reaction activity did not show obvious attenuation; while the catalyst formed without the introduction of the protein auxiliary had an activity drop of nearly 72% after 10 cycles.

[0051] Example 2

[0052] Calcium carbonate / carbon-supported ruthenium catalyst (0.01 g) was placed in a high-temperature reactor, 20 mL of a mixed solution of methanol and water (volume ratio, 4:1) was added, different aromatic nitro compounds (0.8 mmol) and hydrogen (1 MPa) were added, and the reaction was carried out at 60° C. for 3 h. The conversion rate of the obtained nitro compound was at least greater than 96%, and the selectivity was at least greater than 98%.

[0053] Table 2 Performance of the catalyst of the present invention when used for hydrogenation of different aromatic nitro compound substrates

[0054]

[0055] From Table 2, Figure 3 It can be seen that Ru / CaCO3-C has strong substrate applicability and can achieve highly selective and highly active catalytic conversion of different aromatic nitro compound substrates.

[0056] The above examples demonstrate that the calcium carbonate / carbon-supported ruthenium catalyst obtained by the preparation method of the present invention can be applied to the selective hydrogenation of aromatic nitro compounds and exhibits extremely high activity, stability and selectivity.

[0057] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A calcium carbonate / carbon composite carrier-supported ruthenium catalyst, characterized in that: The invention comprises a carrier, wherein the carrier is eggshell powder, nitrogen-doped carbon is covered on the carrier to form a composite carrier, and metal ruthenium is loaded on the composite carrier.

2. The method for preparing a catalyst according to claim 1, characterized in that: The following steps are involved: S1. Preparation of protein-coated calcium carbonate materials The eggshell powder is evenly dispersed in water, the protein powder is added and fully stirred, and then filtered and dried at low temperature to obtain the protein-coated calcium carbonate material; S2. Preparation of Ruthenium Precursor Supported by Calcium Carbonate / Carbon Composite Support The S1 protein-coated calcium carbonate material is uniformly dispersed in water, and a ruthenium chloride solution and an aqueous solution of sodium borohydride are sequentially added dropwise under stirring, and then filtered and dried at low temperature to obtain a calcium carbonate / carbon composite carrier-loaded ruthenium precursor; S3. Preparation of Ruthenium Catalyst Supported on Calcium Carbonate / Carbon Composite Support Under a protective atmosphere, the precursor S2 is subjected to high-temperature pyrolysis to obtain the calcium carbonate / carbon composite carrier-supported ruthenium catalyst of the present invention.

3. The method for preparing the catalyst according to claim 2, characterized in that: In the S1, the eggshell powder is the powder obtained by grinding and sieving the eggshell, and the particle size of the powder is 100-200 meshes; the egg white powder includes egg white protein powder.

4. The method for preparing the catalyst according to claim 3, characterized in that: The mass ratio of the egg shell powder to water is 1:10-100, and the mass ratio of the egg shell powder to egg white powder is 1:0.1-2.

5. The method for preparing the catalyst according to claim 2, characterized in that: The mass ratio of the protein-coated calcium carbonate material to water is 1:10-100; the mass ratio of the ruthenium element to the protein-coated calcium carbonate material in the ruthenium chloride solution is 0.5-5:100; and the mass ratio of the sodium borohydride used in preparing the sodium borohydride aqueous solution to the ruthenium element is 1-10:

1.

6. The method for preparing the catalyst according to claim 2, characterized in that: In the S3, the protective atmosphere includes one or more of nitrogen and argon; the pyrolysis temperature is 400-600° C., and the pyrolysis time is 1-3 hours.

7. Use of the catalyst according to any one of claims 1 to 6, characterized in that: The catalyst is used for preparing aromatic amines by hydrogenation reduction of aromatic nitro compounds.

8. The use of the catalyst according to claim 7, characterized in that: The aromatic nitro compounds include nitrobenzene, p-nitrofluorobenzene, p-nitrochlorobenzene, p-nitroiodobenzene, p-nitroanisole, p-nitrophenylacetonitrile, 2-chloro-1-fluoro-4-nitrobenzene, m-dinitrobenzene and m-nitrotrifluorotoluene.

9. The use of the catalyst according to claim 8, characterized in that: The reaction temperature of the hydrogenation reduction is 40-60°C, the hydrogen pressure is 0.1-3MPa, and the reaction time is 0.5-3h.

10. The use of the catalyst according to claim 8, characterized in that: When the catalyst is used, the conversion rate of the aromatic nitro compound can reach more than 96%, and the selectivity to the product can reach more than 98%.

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