A sodium monatomic modified carbon surface supported ruthenium cluster catalyst, a preparation method and application thereof

Abstract

The application discloses a sodium monatomic modified carbon surface loaded ruthenium cluster catalyst, which comprises a carbon carrier and an active component loaded on the surface of the carbon carrier, and the active component is ruthenium or a ruthenium compound; the carbon carrier is a three-dimensional porous carbon skeleton doped with nitrogen atoms, and the surface of the carbon carrier is modified by sodium monatomic atoms; wherein the weight proportion of the three-dimensional porous carbon skeleton in the catalyst is 65-86%, the weight proportion of the nitrogen atoms in the catalyst is 5-20%, the weight proportion of the sodium monatomic atoms in the catalyst is 1-6%, and the weight proportion of the active component in the catalyst is 1-6%. The application develops a high-efficiency ruthenium-based catalyst, compared with a traditional nitrogen-doped carbon carrier, the functionalization of the carrier surface is realized by introducing sodium monatomic atoms, the catalytic activity of the ruthenium-based catalyst in ethyne hydrochlorination is greatly improved, and the potential of replacing a mercury-based catalyst in industry is shown.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a sodium single-atom modified carbon surface supported ruthenium cluster catalyst, its preparation method and application. Background Technology

[0002] Polyvinyl chloride (PVC), one of the world's three major synthetic materials, is widely used in many fields, including industry, construction, agriculture, and people's daily lives. Industrially, vinyl chloride monomer (VCM) is the main raw material for synthesizing PVC, and the production processes for VCM mainly include the ethylene process, the ethane process, and the calcium carbide acetylene process. Among these, the calcium carbide acetylene process, which uses coal as its raw material, dominates the production of VCM.

[0003] In the calcium carbide acetylene process, the acetylene hydrochlorination reaction is a crucial step in the production of vinyl chloride monomer. For a long time, carbon-supported mercuric chloride catalysts (HgCl2 / AC) have been commonly used industrially to catalyze this reaction. However, mercury is a highly toxic metal, and its compound mercuric chloride readily sublimates and is lost at temperatures above 200°C. This not only reduces catalyst activity but, more seriously, causes significant harm to human health. Therefore, developing efficient and environmentally friendly non-mercury catalysts has become a critical issue urgently needing to be addressed in the field of acetylene hydrochlorination.

[0004] Among the many research directions on non-mercury catalysts, noble metal catalysts such as Au, Pt, Pd, and Ru have received widespread attention. Numerous studies have shown that gold-based catalysts exhibit significant catalytic performance in the hydrochlorination of acetylene and are considered strong candidates to replace mercury catalysts. However, gold, as a precious metal, is expensive and has limited reserves, which greatly restricts its application in large-scale industrial production. In contrast, ruthenium (Ru)-based catalysts have gradually become a research hotspot due to their relatively low price and similar performance to gold. Density functional theory (DFT) calculations show that the energy barriers for the hydrochlorination of acetylene catalyzed by HgCl2, AuCl3, and RuCl3 are 16.3, 11.9, and 9.1 kcal / mol, respectively, with RuCl3 having the lowest energy barrier. This indicates that Ru-based catalysts have great potential in catalyzing the hydrochlorination of acetylene. However, the catalytic activity of Ru-based catalysts still needs further improvement. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to address the hazards of mercury catalysts and the problems of high price and limited reserves of gold-based catalysts, and to propose a ruthenium-based catalyst, and further improve the activity of the catalyst by providing a sodium single-atom modified carbon surface supported ruthenium cluster catalyst.

[0006] Another objective of this invention is to provide a method for preparing a sodium single-atom modified carbon surface supported ruthenium cluster catalyst and its application.

[0007] Technical Solution: The present invention provides a sodium single-atom modified carbon surface supported ruthenium cluster catalyst, comprising a carbon support and an active component supported on the surface of the carbon support, wherein the active component is ruthenium or a ruthenium compound, the carbon support is a three-dimensional porous carbon framework doped with nitrogen atoms, and the surface of the carbon support is modified by sodium single atoms; wherein the three-dimensional porous carbon framework accounts for 65-86% by weight in the catalyst, the nitrogen atoms account for 5-20% by weight in the catalyst, the sodium single atoms account for 1-6% by weight in the catalyst, and the active component accounts for 1-6% by weight in the catalyst.

[0008] Furthermore, the three-dimensional porous carbon framework has an average pore size of 0.1-10 nm and a specific surface area of ​​10-2000 m². 2 / g.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned sodium single-atom modified carbon surface supported ruthenium cluster catalyst, comprising the following steps:

[0010] (1) A nitrogen-doped carbon support precursor was prepared by a solvothermal method from organic ligands and zinc nitrate hexahydrate;

[0011] (2) The precursor obtained in step (1) is subjected to calcination heat treatment in an inert atmosphere to obtain a nitrogen-doped carbon support.

[0012] (3) The nitrogen-doped carbon support obtained in step (2) is impregnated with sodium salt solution, dried, and then calcined twice to obtain a nitrogen-doped carbon support modified with sodium single atom.

[0013] (4) The sodium single-atom modified nitrogen-doped carbon support obtained in step (3) is impregnated with ruthenium source solution in equal volume, and then dried to prepare sodium single-atom modified carbon surface supported ruthenium cluster catalyst.

[0014] Furthermore, the organic ligand is one of methylimidazole, dimethylimidazole, and trimethylimidazole.

[0015] Furthermore, in step (2), the roasting temperature is 500-2000℃.

[0016] Further, in step (2), the inert atmosphere is one or a mixture of nitrogen, argon, and helium, and the flow rate of the inert gas is 20-200 mL / min.

[0017] Furthermore, in step (3), the sodium salt is one or a combination of several of the following: trisodium tricyanate, sodium chloride, sodium sulfate, sodium carbonate, sodium chlorate, and sodium thiocyanate.

[0018] Furthermore, in step (4), the ruthenium source is one or a combination of ruthenium chloride, ruthenium sulfate, ruthenium nitrate, ruthenium carbonyl, and ruthenium chlorate.

[0019] Thirdly, the present invention provides the application of the above-mentioned sodium single-atom modified carbon surface supported ruthenium cluster catalyst in the reaction of acetylene and hydrogen chloride to prepare vinyl chloride.

[0020] Furthermore, the reaction temperature is 50-350℃, and the acetylene space velocity is 10-1000 h⁻¹. -1 The gas flow rate ratio of the mixed gas of hydrogen chloride and acetylene is HCl:C2H2 = 1.1-1.3.

[0021] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention develops a highly efficient ruthenium (Ru)-based catalyst to address the environmentally unfriendly nature of existing mercuric hydrochlorination catalysts for acetylene. Compared with traditional nitrogen-doped carbon supports (NC supports), this invention functionalizes the NC support surface by introducing alkali metal sodium (Na) single atoms. On the one hand, this promotes the dispersion of the Ru catalyst, allowing Ru to be dispersed into clusters loaded on the support, increasing the exposure of the active surface. On the other hand, the strong interaction between the Na and the support regulates the high valence state of Ru, improving its intrinsic catalytic activity. This significantly enhances the catalytic activity of Ru-based catalysts for the hydrochlorination of acetylene, demonstrating its potential to replace mercury-based catalysts in industry. Attached Figure Description

[0022] Figure 1 The images show the XRD patterns of the catalyst (Ru / Na@NC) prepared in Example 1 and the catalyst (Ru / NC) prepared in Comparative Example 1.

[0023] Figure 2 The images show scanning electron microscope (SEM) and EDS elemental distribution maps of the sodium single-atom modified nitrogen-doped carbon support (Na@NC) prepared in Example 1.

[0024] Figure 3 This is a spherical aberration electron microscope image of the sodium single-atom modified nitrogen-doped carbon support (Na@NC) prepared in Example 1.

[0025] Figure 4 This is a spherical aberration electron microscope image of the catalyst (Ru / Na@NC) prepared in Example 1.

[0026] Figure 5 The N2 isothermal adsorption-desorption curves are those of the catalyst (Ru / Na@NC) prepared in Example 1 and the catalyst (Ru / NC) prepared in Comparative Example 1.

[0027] Figure 6These are Raman images of the sodium-doped carbon support (Na@NC) modified with a single atom as prepared in Example 1 and the nitrogen-doped carbon support (NC) prepared in Comparative Example 1.

[0028] Figure 7 This is a comparison chart of the catalytic activity of acetylene hydrochlorination with different acetylene to hydrogen chloride flow ratios in Example 1.

[0029] Figure 8 This is a comparison chart of the catalytic activity of acetylene hydrochlorination catalysts with different sodium contents in Examples 1, 2, and 3.

[0030] Figure 9 This is a comparison chart of the catalytic activities of different catalysts in the acetylene hydrochlorination of Example 1 and Comparative Example 1.

[0031] Figure 10 This is a graph showing the catalytic activity of the catalyst (Ru / Co@NC) prepared in Comparative Example 2 for the hydrochlorination of acetylene.

[0032] Figure 11 This is a graph showing the catalytic activity of the catalyst (Ru / K@NC) prepared in Comparative Example 3 for the hydrochlorination of acetylene. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] (1) 0.5 g dimethylimidazole and 0.3 g zinc nitrate were stirred in 50 ml methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 ℃, and named NC.

[0036] (2) Dissolve 0.1 g of trisodium trihexacyanate in 10 mL of distilled water, immerse 0.3 g of NC in the trisodium trihexacyanate solution, and then perform a second calcination at 900 °C under an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content is 2 wt%).

[0037] (3) Na@NC was impregnated with ruthenium chloride in equal volume and dried to obtain a sodium single-atom modified carbon surface supported ruthenium cluster catalyst, named Ru / Na@NC.

[0038] like Figure 1As shown, the XRD pattern of the Ru / Na@NC catalyst prepared in this embodiment shows two diffraction peaks at approximately 24° and 43°, corresponding to typical amorphous carbon (002) and graphite (101) phases, respectively. This indicates that no obvious sodium metal clusters or other sodium-containing compounds were formed after the sodium precursor was calcined, and the RuCl3 impregnation support was also highly dispersed.

[0039] like Figure 2 As shown in the SEM image and elemental distribution map of the Na@NC catalyst prepared in this embodiment, the uniform distribution of Na, C, N and O elements can be clearly seen, eliminating the formation of Na agglomerates.

[0040] like Figure 3 As shown, the HADDF-STEM image of the Na@NC catalyst prepared in this embodiment successfully proves that Na exists in the form of single atoms on the NC surface.

[0041] like Figure 4 As shown, the HADDF-STEM image of the Ru / Na@NC catalyst prepared in this embodiment successfully demonstrates the high dispersion of Ru in clusters.

[0042] like Figure 5 As shown, the N2 isothermal adsorption-desorption curve shows a significant increase in the micropores, proving the presence of a large number of micropores; the curve also exhibits a clear loop, indicating the presence of mesopores in Na@NC. This demonstrates the hierarchical porous structure of Na@NC, resulting in a large specific surface area.

[0043] Example 2

[0044] (1) 0.5 g dimethylimidazole and 0.3 g zinc nitrate were stirred in 50 ml methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 ℃, and named NC.

[0045] (2) Dissolve 0.8 g of trisodium trihexacyanate in 10 mL of distilled water, immerse 0.3 g of NC in the trisodium trihexacyanate solution, and then perform a second calcination at 900 °C under an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content is 1 wt%).

[0046] (3) Na@NC was impregnated with ruthenium chloride in equal volume and dried to obtain a sodium single-atom modified carbon surface supported ruthenium cluster catalyst, named Ru / Na@NC.

[0047] Example 3

[0048] (1) 0.5 g dimethylimidazole and 0.3 g zinc nitrate were stirred in 50 ml methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 ℃, and named NC.

[0049] (2) Dissolve 1.2 g of trisodium trihexacyanate in 10 mL of distilled water, immerse 0.3 g of NC in the trisodium trihexacyanate solution, and then perform a second calcination at 900 °C under an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content is 3 wt%).

[0050] (3) Na@NC was impregnated with ruthenium chloride in equal volume and dried to obtain a sodium single-atom modified carbon surface supported ruthenium cluster catalyst, named Ru / Na@NC.

[0051] Comparative Example 1

[0052] (1) 0.5 g dimethylimidazole and 0.3 g zinc nitrate were stirred in 50 ml methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 ℃, and named NC.

[0053] (2) NC was impregnated with ruthenium chloride in equal volume and dried to obtain a ruthenium-based catalyst, named Ru / NC.

[0054] Depend on Figure 6 As can be seen, Raman spectroscopy further analyzed the surface structure of these porous carbon scaffolds. Figure I D / I G The ratio represents the degree of graphitization of these carriers. Specifically, relative to NC, Na@NC I D / I G The value is relatively high, which may be due to secondary calcination.

[0055] Comparative Example 2

[0056] (1) 0.5 g dimethylimidazole and 0.3 g zinc nitrate were stirred in 50 ml methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 ℃, and named NC.

[0057] (2) Dissolve 0.1 g cobalt acetate in 10 mL of distilled water, impregnate 0.3 g NC in cobalt acetate, and then calcine it again at 900 °C under Ar atmosphere to prepare a nitrogen-doped carbon support modified with Co atoms, named Co@NC.

[0058] (3) Co@NC was impregnated with ruthenium chloride in equal volume and dried to obtain sodium single-atom modified carbon surface supported ruthenium cluster catalyst, named Ru / Co@NC.

[0059] Comparative Example 3

[0060] (1) 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate were stirred in 50 ml of methanol solution for 24 h; after centrifugation and drying, the nitrogen-doped carbon support was prepared by calcination in a nitrogen-argon mixture with a flow rate of 60 ml / min at 900 °C, and named NC.

[0061] (2) Dissolve 0.1 g potassium hexacyanate in 10 mL of distilled water, immerse 0.3 g NC in potassium hexacyanate solution, and then perform secondary calcination at 900 °C under Ar atmosphere to prepare nitrogen-doped carbon support modified with K atoms, named K@NC.

[0062] (3) K@NC was impregnated with ruthenium chloride in equal volume and dried to obtain a ruthenium cluster catalyst supported on a carbon surface modified with K atoms, named Ru / K@NC.

[0063] Catalytic activity test of catalyst in acetylene hydrochlorination reaction:

[0064] Test Example 1

[0065] The reaction was carried out in a micro fixed-bed reactor. 50 mg of the catalyst prepared in Example 1 was placed in a quartz reaction tube, and a mixture of acetylene and hydrogen chloride (gas flow rate ratio of HCl:C2H2 = 1.1, 1.2, 1.3) was introduced. The temperature was programmed to 180 °C, and the conversion rate of acetylene was calculated by gas chromatography sampling and analysis every 6 min.

[0066] Depend on Figure 7 It can be seen that the acetylene conversion rate is above 60%, and when the gas flow rate ratio of HCl:C2H2=1.2, the acetylene conversion rate reaches above 75%, demonstrating excellent catalytic activity for acetylene hydrochlorination.

[0067] Test Example 2

[0068] The reaction was carried out in a micro fixed-bed reactor. 50 mg of the catalysts prepared in Examples 1-4 and Comparative Examples 1 and 2 were placed in quartz reaction tubes, and a mixture of acetylene and hydrogen chloride (with a volume ratio of acetylene to hydrogen chloride of 1:1.2) was introduced. The temperature was programmed to 180 °C, and the conversion rate of acetylene was calculated by gas chromatography sampling and analysis every 6 min.

[0069] Depend on Figure 8-11As can be seen from the comparison, the introduction of sodium single atoms can indeed improve the catalytic performance of the catalyst, achieving a volume space velocity of 1000 h⁻¹ at 180 °C. -1 When the flow rate ratio of hydrogen chloride to acetylene is 1.2, from Figure 8 It can be seen that the catalysts prepared in Examples 1-3 all achieved acetylene conversion rates of over 60% in the tests, with the Ru / 2%Na@NC catalyst prepared in Example 1 achieving an acetylene conversion rate of nearly 80%. Figure 9 It can be seen that the catalyst (Ru / NC) prepared in Comparative Example 1 has an acetylene conversion rate of only 50%. Figure 10 It can be seen that the catalyst (Ru / Co@NC) prepared in Comparative Example 2 has an acetylene conversion rate of only 59%, which is... Figure 11 It can be seen that the acetylene conversion rate of the catalyst (Ru / K@NC) prepared in Comparative Example 3 is only 50%, which fully demonstrates that the sodium single-atom modified carbon surface supported ruthenium cluster catalyst synthesized in this invention has extremely high catalytic activity, especially the catalyst prepared using sodium-modified support has the highest catalytic activity in the reaction of acetylene and hydrogen chloride to prepare vinyl chloride.

Claims

1. A sodium single-atom modified carbon surface supported ruthenium cluster catalyst, characterized in that, The catalyst comprises a carbon support and an active component loaded on the surface of the carbon support. The active component is ruthenium or a ruthenium compound. The carbon support is a three-dimensional porous carbon framework doped with nitrogen atoms, and the surface of the carbon support is modified with sodium single atoms. The three-dimensional porous carbon framework accounts for 65-86% of the weight of the catalyst, the nitrogen atoms account for 5-20% of the weight of the catalyst, the sodium single atoms account for 1-6% of the weight of the catalyst, and the active component accounts for 1-6% of the weight of the catalyst.

2. The sodium single-atom modified carbon surface supported ruthenium cluster catalyst as described in claim 1, characterized in that, The three-dimensional porous carbon framework has an average pore size of 0.1-10 nm and a specific surface area of ​​10-2000 m². 2 / g.

3. The method for preparing the sodium single-atom modified carbon surface supported ruthenium cluster catalyst according to any one of claims 1-2, characterized in that, Includes the following steps: (1) A nitrogen-doped carbon support precursor was prepared by a solvothermal method from organic ligands and zinc nitrate hexahydrate; (2) The precursor obtained in step (1) is subjected to calcination heat treatment in an inert atmosphere to obtain a nitrogen-doped carbon support. (3) The nitrogen-doped carbon support obtained in step (2) is impregnated with sodium salt solution, dried, and then calcined twice to obtain a nitrogen-doped carbon support modified with sodium single atom. (4) The sodium single-atom modified nitrogen-doped carbon support obtained in step (3) is impregnated with ruthenium source solution in equal volume, and then dried to prepare sodium single-atom modified carbon surface supported ruthenium cluster catalyst.

4. The preparation method according to claim 3, characterized in that, in step (1), the organic ligand is one of methylimidazole, dimethylimidazole, and trimethylimidazole.

5. The preparation method according to claim 3, characterized in that, In step (2), the roasting temperature is 500-2000℃.

6. The preparation method according to claim 3, characterized in that, In step (2), the inert atmosphere is one or a mixture of nitrogen, argon, and helium, and the flow rate of the inert gas is 20-200 mL / min.

7. The preparation method according to claim 3, characterized in that, In step (3), the sodium salt is one or a combination of several of the following: trisodium trichlorocyanurate, sodium chloride, sodium sulfate, sodium carbonate, sodium chlorate, and sodium thiocyanate.

8. The preparation method according to claim 3, characterized in that, In step (4), the ruthenium source is one or a combination of ruthenium chloride, ruthenium sulfate, ruthenium nitrate, ruthenium carbonyl, and ruthenium chlorate.

9. The application of the sodium single-atom modified carbon surface supported ruthenium cluster catalyst as described in any one of claims 1-2 in the reaction of acetylene with hydrogen chloride to prepare vinyl chloride.

10. The application of the sodium single-atom modified carbon surface supported ruthenium cluster catalyst as described in claim 9 in the reaction of acetylene with hydrogen chloride to prepare vinyl chloride, characterized in that, The reaction temperature is 50-350℃, and the acetylene space velocity is 10-1000 h⁻¹. -1 The gas flow rate ratio of the mixed gas of hydrogen chloride and acetylene is HCl:C2H2 = 1.1-1.3.

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