Sodium monatomic modified carbon surface loaded ruthenium cluster catalyst as well as preparation method and application thereof

Abstract

The invention 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, 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; wherein the weight ratio of the three-dimensional porous carbon skeleton in the catalyst is 65-86%, the weight ratio of the nitrogen atoms in the catalyst is 5-20%, the weight ratio of the sodium monatomic in the catalyst is 1-6%, and the weight ratio of the active component in the catalyst is 1-6%. The efficient ruthenium-based catalyst is developed, compared with a traditional nitrogen-doped carbon carrier, functionalization of the surface of the carrier is achieved by introducing sodium monatomic atoms, the acetylene hydrochlorination catalytic activity of the ruthenium-based catalyst can be greatly improved, and the potential of replacing a mercury-based catalyst in the industry is shown.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and relates to a sodium single atom modified carbon surface loaded ruthenium cluster catalyst and a preparation method and application thereof. Background Art

[0002] Polyvinyl chloride (PVC), one of the world's three major synthetic materials, is widely used in numerous fields, including industry, construction, agriculture, and daily life. In industry, vinyl chloride monomer (VCM) is the primary raw material for PVC synthesis. VCM production processes primarily include the ethylene process, the ethane process, and the carbide-acetylene process. Of these, the coal-based carbide-acetylene process dominates VCM production.

[0003] In the calcium carbide acetylene process, acetylene hydrochlorination is a key step in the production of vinyl chloride monomer. For a long time, the industry has widely used a carbon-supported mercuric chloride catalyst (HgCl2 / AC) to catalyze this reaction. However, mercury is a highly toxic metal, and its active component, mercuric chloride, easily sublimates and loses at temperatures above 200°C. This not only reduces catalyst activity but, more seriously, poses significant risks to human health. Therefore, the development of efficient, environmentally friendly, non-mercury catalysts has become a key challenge in the field of acetylene hydrochlorination.

[0004] Among the numerous research directions for non-mercury catalysts, precious metal catalysts such as Au, Pt, Pd, and Ru have garnered significant attention. Numerous studies have demonstrated that gold-based catalysts exhibit remarkable catalytic performance in the hydrochlorination of acetylene, making them a promising candidate to replace mercury catalysts. However, as a precious metal, gold is expensive and its reserves are limited, significantly limiting its application in large-scale industrial production. In contrast, ruthenium (Ru)-based catalysts have become a hot topic of research due to their relatively low price and similar performance to gold. Density functional theory (DFT) calculations reveal 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. RuCl3 exhibits the lowest energy barrier, suggesting that Ru-based catalysts have great potential for catalyzing the hydrochlorination of acetylene. However, the catalytic activity of Ru-based catalysts remains to be further improved. Summary of the Invention

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

[0006] Another object of the present invention is to provide a preparation method and application of a sodium single atom modified carbon surface loaded ruthenium cluster catalyst.

[0007] Technical solution: The present invention provides a sodium single-atom modified carbon surface-loaded ruthenium cluster catalyst, comprising a carbon support and an active component loaded 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 skeleton doped with nitrogen atoms, and the surface of the carbon support is modified by sodium single 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 single atoms in the catalyst is 1-6%, and the weight proportion of the active component in the catalyst is 1-6%.

[0008] Furthermore, the average pore size of the three-dimensional porous carbon skeleton is 0.1-10 nm, and the specific surface area is 10-2000 m 2 / g.

[0009] In a second aspect, 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: (1) A nitrogen-doped carbon support precursor was prepared from an organic ligand and zinc nitrate hexahydrate using a solvothermal method; (2) calcining the precursor prepared in step (1) in an inert atmosphere to obtain a nitrogen-doped carbon support; (3) impregnating the nitrogen-doped carbon support obtained in step (2) with a sodium salt solution, drying, and performing a secondary calcination treatment to obtain a nitrogen-doped carbon support modified with a sodium single atom; (4) An equal volume of the sodium single atom-modified nitrogen-doped carbon support prepared in step (3) is impregnated with a ruthenium source solution, and then dried to obtain a sodium single atom-modified carbon surface-loaded ruthenium cluster catalyst.

[0010] Furthermore, the organic ligand is one of methylimidazole, dimethylimidazole and trimethylimidazole.

[0011] Furthermore, in step (2), the calcination temperature is 500-2000°C.

[0012] Furthermore, in step (2), the inert atmosphere is one of nitrogen, argon, and helium, or a mixture thereof, and the flow rate of the inert gas is 20-200 mL / min.

[0013] Furthermore, in step (3), the sodium salt is one or a combination of trisodium tricyanate, sodium chloride, sodium sulfate, sodium carbonate, sodium chlorate, sodium thiocyanate, and sodium hydroxide.

[0014] Furthermore, in step (4), the ruthenium source is one or a combination of ruthenium chloride, ruthenium sulfate, nitric acid, carbonyl ruthenium, and ruthenium chlorate.

[0015] In a third aspect, the present invention provides the use of the above-mentioned sodium single atom-modified carbon surface-supported ruthenium cluster catalyst in the preparation of vinyl chloride by the reaction of acetylene and hydrogen chloride.

[0016] Furthermore, the reaction temperature is 50-350°C, and the acetylene space velocity is 10-1000 h -1 The gas flow ratio of the mixed gas of hydrogen chloride and acetylene is HCl:C2H2=1.1-1.3.

[0017] Beneficial Effects: Compared with existing technologies, this invention offers the following significant advantages: It addresses the environmental concerns of existing mercury-based acetylene hydrochlorination catalysts by developing a highly efficient ruthenium (Ru)-based catalyst. Compared to traditional nitrogen-doped carbon supports (NC supports), this invention functionalizes the NC support surface by introducing single alkali metal sodium (Na) atoms. This not only improves the dispersion of the Ru catalyst, allowing it to be dispersed as clusters on the support, increasing the exposure of the active surface. Furthermore, the strong Na-support interaction modulates the high valence state of Ru, enhancing its intrinsic catalytic activity. This significantly boosts the catalytic activity of Ru-based catalysts in acetylene hydrochlorination, demonstrating their potential as an industrial alternative to mercury-based catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 3 are XRD spectra of the catalyst (Ru / Na@NC) prepared in Example 1 and the catalyst (Ru / NC) prepared in Comparative Example 1.

[0019] Figure 2 This is the scanning electron microscope and EDS element distribution map of the sodium single atom modified nitrogen-doped carbon support (Na@NC) prepared in Example 1.

[0020] 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.

[0021] Figure 4 This is a spherical aberration electron microscope image of the catalyst (Ru / Na@NC) prepared in Example 1.

[0022] Figure 5 2 are N2 isothermal adsorption-desorption curves of the catalyst (Ru / Na@NC) prepared in Example 1 and the catalyst (Ru / NC) prepared in Comparative Example 1.

[0023] Figure 6 These are Raman images of the sodium single atom-modified nitrogen-doped carbon support (Na@NC) prepared in Example 1 and the nitrogen-doped carbon support (NC) prepared in Comparative Example 1.

[0024] Figure 7 This is a comparison chart of the catalytic activity of acetylene hydrochlorination at different acetylene to hydrogen chloride flow ratios of the catalyst in Example 1.

[0025] Figure 8 This is a comparison chart of the catalytic activity of acetylene hydrochlorination of catalysts with different sodium contents in Examples 1, 2, and 3.

[0026] Figure 9 1 is a comparison chart of the catalytic activity of acetylene hydrochlorination of different catalysts in Example 1 and Comparative Example 1.

[0027] Figure 10 This is a graph showing the catalytic activity of acetylene hydrochlorination of the catalyst (Ru / Co@NC) prepared in Comparative Example 2.

[0028] Figure 11 This is a graph showing the catalytic activity of acetylene hydrochlorination of the catalyst (Ru / K@NC) prepared in Comparative Example 3. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the solution was centrifugally dried with methanol and calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0032] (2) 0.1 g of trisodium tricyanocyanate was dissolved in 10 mL of distilled water, and 0.3 g of NC was immersed in the trisodium tricyanocyanate solution. The mixture was then calcined twice at 900 °C in an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content was 2 wt%).

[0033] (3) Na@NC was impregnated with ruthenium chloride in equal volumes and dried to obtain a sodium single atom-modified carbon surface-loaded ruthenium cluster catalyst, named Ru / Na@NC.

[0034] like Figure 1 As shown in FIG, the XRD pattern of the Ru / Na@NC catalyst prepared in this example shows two diffraction peaks at about 24° and 43°, corresponding to typical amorphous carbon (002) and graphite (101) phases, respectively, indicating that no obvious sodium metal clusters or other sodium-containing compounds are formed after calcination of the sodium precursor, and RuCl3 is also highly dispersed after impregnation of the support.

[0035] like Figure 2 As shown in the SEM image of the Na@NC catalyst prepared in this example, the element scanning distribution diagram can clearly show the uniform distribution of Na, C, N, and O elements, eliminating the formation of Na agglomerated particles.

[0036] like Figure 3 As shown in FIG, the HADDF-STEM image of the Na@NC catalyst prepared in this example can successfully prove that Na exists on the NC surface in the form of single atoms.

[0037] like Figure 4 As shown in FIG, the HADDF-STEM image of the Ru / Na@NC catalyst prepared in this example can successfully prove the high dispersion of Ru in the form of clusters.

[0038] like Figure 5 As shown in the figure, the N2 isothermal adsorption-desorption curve shows a significant rise in the micropores, indicating the presence of a large number of micropores. The curve also has obvious loops, indicating the presence of mesopores in Na@NC. This demonstrates the hierarchical pore structure of Na@NC and its large specific surface area.

[0039] Example 2

[0040] (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the solution was centrifugally dried with methanol and calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0041] (2) 0.8 g of trisodium tricyanocyanate was dissolved in 10 mL of distilled water, and 0.3 g of NC was immersed in the trisodium tricyanocyanate solution. The mixture was then calcined twice at 900 °C in an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content was 1 wt%).

[0042] (3) Na@NC was impregnated with ruthenium chloride in equal volumes and dried to obtain a sodium single atom-modified carbon surface-loaded ruthenium cluster catalyst, named Ru / Na@NC.

[0043] Example 3

[0044] (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the solution was centrifugally dried with methanol and calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0045] (2) 1.2 g of trisodium hexamethylenetetramine was dissolved in 10 mL of distilled water, and 0.3 g of NC was immersed in the trisodium hexamethylenetetramine solution. The mixture was then calcined twice at 900 °C in an Ar atmosphere to prepare a nitrogen-doped carbon support modified with a single Na atom, named Na@NC. (The Na content was 3 wt%).

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

[0047] Comparative Example 1 (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the solution was centrifugally dried with methanol and calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0048] (2) NC was impregnated with ruthenium chloride in equal volume and dried to obtain a ruthenium-based catalyst, named Ru / NC.

[0049] Depend on Figure 6 It can be seen that Raman spectroscopy further analyzed the surface structure of these porous carbon scaffolds. D / I G The ratio of Na@NC I indicates the degree of graphitization of these supports. D / I G The higher value may be caused by secondary calcination.

[0050] Comparative Example 2 (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the solution was centrifugally dried with methanol and calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0051] (2) 0.1 g of cobalt acetate was dissolved in 10 mL of distilled water, and 0.3 g of NC was impregnated in cobalt acetate. Then, the NC was calcined twice in an Ar atmosphere at 900 °C to prepare a Co atom-modified nitrogen-doped carbon support, which was named Co@NC.

[0052] (3) Co@NC was impregnated with ruthenium chloride in equal volumes and dried to obtain a sodium atom-modified carbon surface-loaded ruthenium cluster catalyst, named Ru / Co@NC.

[0053] Comparative Example 3 (1) A methanol solution of 0.5 g of dimethylimidazole and 0.3 g of zinc nitrate was stirred in 50 ml of methanol solution for 24 h; the mixture was centrifuged and dried with methanol, and then calcined at 900 °C in a hydrogen-argon mixture with a flow rate of 60 ml / min to prepare a nitrogen-doped carbon support, named NC.

[0054] (2) 0.1 g of potassium hexamethylenetetramine was dissolved in 10 mL of distilled water, and 0.3 g of NC was immersed in the potassium hexamethylenetetramine solution. The NC was then calcined twice in an Ar atmosphere at 900 °C to prepare a K-atom-modified nitrogen-doped carbon support, named K@NC.

[0055] (3) K@NC was impregnated with ruthenium chloride in equal volumes and dried to obtain a K atom-modified carbon surface-loaded ruthenium cluster catalyst, named Ru / K@NC.

[0056] Catalytic activity test of catalyst in acetylene hydrochlorination reaction: Test Example 1 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. A mixture of acetylene and hydrogen chloride (gas flow ratio of HCl:C₂H₂ = 1.1, 1.2, and 1.3) was introduced. The temperature was programmed to 180°C. Acetylene conversion was calculated by gas chromatography sampling every 6 minutes.

[0057] Depend on Figure 7 It can be seen that the acetylene conversion rate is above 60%. When the gas flow ratio HCl:C2H2=1.2, the acetylene conversion rate reaches above 75%, which has good acetylene hydrochlorination catalytic activity.

[0058] Test Example 2 The reactions were carried out in a micro-fixed-bed reactor. 50 mg of each of the catalysts prepared in Examples 1-4 and Comparative Examples 1 and 2 were placed in a quartz reaction tube. 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. Acetylene conversion was calculated by gas chromatography sampling every 6 minutes.

[0059] Depend on Figure 8-11 It can be seen from the comparison that the introduction of sodium single atoms can indeed improve the catalytic performance of the catalyst. At 180 °C, the volume space velocity is 1000 h -1 When the flow ratio of hydrogen chloride to acetylene is 1.2, Figure 8 It can be seen that the catalysts prepared in Examples 1-3 all achieved acetylene conversion rates of over 60% in the test, and the Ru / 2%Na@NC catalyst prepared in Example 1 achieved an acetylene conversion rate of nearly 80%. Figure 9It can be seen that the acetylene conversion rate of the catalyst (Ru / NC) prepared in Comparative Example 1 is only 50%. Figure 10 It can be seen that the acetylene conversion rate of the catalyst (Ru / Co@NC) prepared in Comparative Example 2 is only 59%. 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 proves that the sodium single atom-modified carbon surface-supported ruthenium cluster catalyst synthesized in the present invention has ultra-high catalytic activity, especially when the catalyst prepared using the 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, wherein the active component is ruthenium or a ruthenium compound, the carbon support is a three-dimensional porous carbon skeleton doped with nitrogen atoms, and the surface of the carbon support is modified by sodium single 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 single atoms in the catalyst is 1-6%, and the weight proportion of the active component in the catalyst is 1-6%.

2. The sodium single atom modified carbon surface supported ruthenium cluster catalyst according to claim 1, characterized in that: The average pore size of the three-dimensional porous carbon skeleton is 0.1-10 nm, and the specific surface area is 10-2000 m 2 / g.

3. The method for preparing a sodium single atom-modified carbon surface-supported ruthenium cluster catalyst according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) A nitrogen-doped carbon support precursor was prepared from an organic ligand and zinc nitrate hexahydrate using a solvothermal method; (2) calcining the precursor prepared in step (1) in an inert atmosphere to obtain a nitrogen-doped carbon support; (3) impregnating the nitrogen-doped carbon support obtained in step (2) with a sodium salt solution, drying, and performing a secondary calcination treatment to obtain a nitrogen-doped carbon support modified with a sodium single atom; (4) An equal volume of the sodium single atom-modified nitrogen-doped carbon support prepared in step (3) is impregnated with a ruthenium source solution, and then dried to obtain a sodium single atom-modified carbon surface-loaded 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, wherein In step (2), the calcination temperature is 500-2000°C.

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

7. The preparation method according to claim 3, wherein In step (3), the sodium salt is one or a combination of trisodium tricyanate, sodium chloride, sodium sulfate, sodium carbonate, sodium chlorate, sodium thiocyanate, and sodium hydroxide.

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

9. Use of the sodium single atom-modified carbon surface-supported ruthenium cluster catalyst according to any one of claims 1 to 2 in the preparation of vinyl chloride by the reaction of acetylene and hydrogen chloride.

10. Use of the sodium single atom modified carbon surface supported ruthenium cluster catalyst according to claim 9 for the reaction of acetylene and 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 The gas flow ratio of the mixed gas of hydrogen chloride and acetylene is HCl:C2H2=1.1-1.3.

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