A carbon-coated catalyst, its preparation method and application

Abstract

This invention relates to a carbon-coated catalyst, its preparation method, and its application, belonging to the field of catalyst preparation. The catalyst includes a support and an active component, wherein the active component is carbon-coated copper nanoparticles. The loading of the active component in the catalyst is 5–50 wt%. The carbon-coated copper nanoparticles are composed of layered carbon material coating nano-copper, and the copper content in the carbon-coated copper nanoparticles is 10–68 wt%. Because the active component is encapsulated within the carbon material, the carbon-coated catalyst provided by this invention significantly reduces the loss and deactivation of the active component during the reaction process, improving the catalyst's stability and thus extending its lifespan. After 240 hours of reaction, the hydrogen chloride conversion rate remains above 85%, and the catalytic activity shows almost no decrease, indicating an extremely low copper loss rate.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically relating to a carbon-coated catalyst, its preparation method, and its application. Background Technology

[0002] Chlorine is an important basic raw material in the chemical industry, primarily used in the synthesis of chemical materials and organochlorine intermediates. However, most chlorine-related reactions often have low chlorine resource utilization rates, generating large amounts of hydrogen chloride as a byproduct. Currently, the main industrial method for treating hydrogen chloride byproducts is to absorb it with water and then produce inexpensive hydrochloric acid for sale. However, the hydrochloric acid produced from hydrogen chloride by water absorption is generally of low quality and has high transportation costs. Furthermore, the current market demand for hydrochloric acid is very limited, further restricting the treatment of hydrogen chloride byproducts. Converting hydrogen chloride byproducts into chlorine gas would not only solve the waste of hydrogen chloride resources but also achieve closed-loop recycling of chlorine resources, making it the most effective method for treating and recovering hydrogen chloride byproducts.

[0003] Currently, the main methods for preparing chlorine from hydrogen chloride include direct oxidation, electrolysis, and catalytic oxidation. Among these, catalytic oxidation, which uses oxygen to oxidize hydrogen chloride into chlorine and water under catalytic conditions, offers advantages such as strong adaptability to hydrogen chloride feedstocks, stable operation, low energy consumption, no side reactions, and low equipment costs. It is the optimal approach for treating byproduct hydrogen chloride and realizing the resource utilization of chlorine. The process is as follows:

[0004] 2HCl+1 / 2O2→Cl2+H2O-57.7kJ / mol.

[0005] The catalytic oxidation of hydrogen chloride to chlorine is a reversible exothermic reaction. While increasing the reaction temperature can increase the reaction rate, it also reduces the catalyst's lifespan. Furthermore, the high corrosiveness of hydrogen chloride further shortens the catalyst's lifespan. Therefore, developing low-temperature, highly active, and stable catalysts is crucial for achieving efficient industrial conversion of hydrogen chloride to chlorine. Since the application of copper-based catalysts in the catalytic oxidation of hydrogen chloride to chlorine, iron-based and chromium-based transition metal catalysts have been introduced. In recent years, highly active ruthenium-based, cerium-based, and suitable metal oxide catalysts have also been developed. Although these catalysts exhibit excellent conversion rates in the catalytic oxidation of hydrogen chloride to chlorine, they have not yet achieved industrial-scale production due to factors such as the high cost of ruthenium-based catalysts, the poor corrosion resistance of cerium-based catalysts, and the reduced catalyst lifespan caused by the high reaction temperature.

[0006] To address this, Chinese patent CN101125297A discloses a catalyst using copper salts, potassium salts, and rare earth metal salts as active components. Although the chlorine yield can reach 80.1%, the copper salt active component is easily lost at higher temperatures, resulting in a short catalyst lifespan. Chinese patent CN1915800A discloses a catalyst for the catalytic conversion of hydrogen chloride to chlorine using the precious metal ruthenium as the active component. While the lifespan is basically guaranteed, the catalyst's preparation cost is very high, which is not conducive to industrialization. Therefore, there is still a significant gap in the domestic application of catalysts that are resistant to hydrogen chloride corrosion, have high activity and stability, and are low in preparation cost for the catalytic oxidation of hydrogen chloride to chlorine. Summary of the Invention

[0007] This invention addresses the problems of easy loss of active components and high cost in existing catalysts used for the catalytic oxidation of hydrogen chloride to chlorine. It provides a carbon-coated catalyst, its preparation method, and its application. This catalyst possesses advantages such as high activity, low cost, long lifespan, and resistance to hydrogen chloride corrosion. The preparation method is simple, and when applied to the catalytic oxidation of hydrogen chloride to chlorine, it achieves a high conversion rate of chlorine, demonstrating great application potential.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A carbon-coated catalyst, comprising a support and an active component, wherein the active component is carbon-coated copper nanoparticles, the loading of the active component in the catalyst is 5-50 wt%, and the carbon-coated copper nanoparticles are composed of layered carbon materials coating nano-copper elements, wherein the copper content in the carbon-coated copper nanoparticles is 10-68 wt%.

[0010] Preferably, the loading of the active component in the catalyst is 15-50 wt%; preferably, the copper content in the carbon-coated copper nanoparticles is 40-66%. Preferably, the support is active alumina microspheres with an average particle size of 0.5-4.5 mm.

[0011] Preferably, the carbon-coated copper nanoparticles have a particle size of 5–60 nm, and more preferably 30–40 nm.

[0012] Preferably, the preparation method of the carbon-coated copper nanoparticles is selected from vapor deposition, solvothermal or hydrothermal methods, electrochemical methods, redox methods, etc., with vapor deposition being the preferred method.

[0013] A further preferred method for preparing carbon-coated copper nanoparticles is as follows:

[0014] Under an inert atmosphere, coal and copper naphthenate are heated in stages. In the first stage, the temperature is raised to 120-200℃ and held for 0.5-2 hours. In the second stage, the temperature is raised to 900-1000℃ and held for 1-4 hours. After cooling, carbon-coated copper nanoparticles are obtained.

[0015] More preferably, the first stage heating temperature is 150°C; the second stage heating temperature is 950°C.

[0016] Preferably, the coal is a coal with a high carbon content and is easy to graphitize, with a carbon content greater than 75 wt%.

[0017] Preferably, the mass ratio of coal to copper naphthenate is 0.5 to 4:1. More preferably, the mass ratio of coal to copper naphthenate is 1 to 4:1.

[0018] Preferably, the coal is pre-treated by grinding it through a 200-mesh sieve and drying it at 105°C for 12 hours.

[0019] Preferably, the temperature is raised using a programmed temperature rise method with a heating rate of 5–15 °C / min, and more preferably, the heating rate is 10 °C / min.

[0020] Preferably, the cooling is achieved by introducing nitrogen gas.

[0021] At a furnace temperature of approximately 150°C, copper naphthenate sublimates and becomes fully dispersed in the reactor. As the temperature rises to 900–1000°C, most of the coal-based carbon molecules obtained from coal pyrolysis are adsorbed, activated, and dissolved on the surface of the Cu nanoparticles produced by the pyrolysis of copper naphthenate. When the carbon dissolution in the Cu nanoparticles reaches supersaturation, carbon atoms precipitate in an ordered crystalline state and are neatly arranged on the surface of the Cu nanoparticles to form a graphene-like carbon layer, ultimately forming carbon-coated copper nanoparticles. A small amount of difficult-to-activate carbonaceous material is deposited at the tail end of the reactor during the cooling process after the reaction, carried by the N2 gas flow, thus separating from the carbon-coated copper deposited in the middle of the reactor.

[0022] The carbon layer coating on the surface of copper nanoparticles effectively prevents the loss of copper components. This is because HCl and O2 can penetrate the carbon layer into the catalyst and, under the catalytic action of the nano-copper, produce Cl2 and water vapor. Cl2 and water vapor can also be released into the reaction environment through the carbon layer. In this process, the copper nanoparticles inside the catalyst are protected by the carbon layer and are not easily lost.

[0023] This invention also provides a method for preparing a carbon-coated catalyst.

[0024] The carbon-coated copper nanoparticles prepared above were dispersed in water and impregnated onto activated alumina microspheres by equal volume. After drying and calcination, a carbon-coated catalyst was obtained.

[0025] The present invention also provides the application of the above-mentioned carbon-coated catalyst in the catalytic oxidation of hydrogen chloride to produce chlorine.

[0026] The above-mentioned carbon-coated catalyst was applied to the catalytic oxidation of hydrogen chloride to produce chlorine. Hydrogen chloride gas and oxygen were passed into a fixed tubular reactor loaded with the catalyst. The reaction temperature was 320–400 °C, and the hydrogen chloride mass hourly space velocity was 0.1–1.8 h⁻¹. -1 The molar ratio of hydrogen chloride gas to oxygen is (1-4):(1-2), and the pressure of the catalytic oxidation reaction is 1-4 atm.

[0027] Preferably, the pressure of the catalytic oxidation reaction is 1 to 2 atm.

[0028] Preferably, the temperature of the catalytic oxidation reaction is 320–380°C.

[0029] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0030] (1) The carbon-coated catalyst provided by this invention, because the active components are encapsulated inside the carbon material, can greatly reduce the loss and deactivation of the active components in the catalyst during the reaction process, improve the stability of the catalyst, and thus improve the service life of the catalyst. After 240 hours of reaction, the hydrogen chloride conversion rate is still above 85%, and the catalytic activity has hardly decreased, indicating that the copper loss rate is extremely low.

[0031] (2) The carbon in the carbon-coated catalyst provided by the present invention is prepared from coal, and the active component coated by carbon is elemental copper, both of which are inexpensive materials and have low preparation costs.

[0032] (3) The present invention uses a gas phase precipitation method to convert copper naphthenate into copper nanoparticles. Carbon material is vaporized and deposited onto the surface of copper nanoparticles to form a graphene-like carbon layer, which ultimately forms carbon-coated copper nanoparticles. Then, these nanoparticles are impregnated onto the surface of activated alumina. The preparation method is simple. Attached Figure Description

[0033] Figure 1 This is a TEM image of the carbon-coated copper prepared in Example 1.

[0034] Figure 2 This is a TEM image of the carbon-coated copper prepared in Comparative Example 2.

[0035] Figure 3 The image shows the EDS spectrum of the carbon-coated copper prepared in Example 1.

[0036] Figure 4 The image shows the XRD pattern of the carbon-coated copper prepared in Example 1.

[0037] Figure 5 The image shows the XPS spectrum of the carbon-coated copper prepared in Example 1.

[0038] Figure 6 This is the TG curve of the coal used in Example 1.

[0039] Figure 7 The image shows the TG curve of the carbon-coated copper prepared in Example 1. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto. The processes, conditions, and experimental methods for implementing the present invention, except as specifically mentioned below, are all common knowledge and general knowledge in the art.

[0041] The coal used in this embodiment of the invention was purchased from the Wucaiwan Coal Mine in the Zhundong Coalfield of Xinjiang. Its moisture content was 4.36%, ash content was 8.66%, volatile matter content was 10.98%, and fixed carbon content was 76%.

[0042] Test method for hydrogen chloride conversion rate:

[0043] (1) Detection principle

[0044] Cl₂ + 2KI = 2KCl + I₂

[0045] I₂ + 2Na₂S₂O₃ = 2NaI + Na₂S₄O₆

[0046] HCl + NaOH = NaCl + H₂O

[0047] (2) Preparation of 1.0 mol / L sodium thiosulfate (Na2S2O3) standard solution

[0048] Accurately weigh 158.12 g of anhydrous Na2S2O3, dissolve it in an appropriate amount of freshly boiled and cooled distilled water, add an appropriate amount of Na2CO3, and dilute to volume in a 1 L brown volumetric flask to obtain a 1.0 mol / L Na2S2O3 solution. Seal and store in the dark.

[0049] (3) Preparation of 1.0 mol / L NaOH standard solution

[0050] Accurately weigh 40.00 g of NaOH, dissolve it in distilled water, and dilute to volume in a 1 L volumetric flask to obtain a 1.0 mol / L NaOH solution. Seal and store.

[0051] (4) Preparation of 1.708 mol / L KI solution

[0052] Weigh 283.46 g of KI, dissolve it in distilled water, and dilute to volume in a 1 L brown volumetric flask to obtain a 1.0 mol / L KI solution. Seal and store in the dark.

[0053] (5) The specific operating steps are as follows: After the reaction system stabilizes, prepare a batch of KI solution at regular intervals, take out 100 mL for later use, switch the three-way valve at the outlet of the catalytic oxidation reactor, and pass the mixed gas after the reaction into the 100 mL KI solution taken out for later use, and absorb for 2 min. Titrate the sample bottle after absorbing the mixed gas with 1 mol / L Na2S2O3 standard solution, using starch as an indicator; then continue to titrate with 1 mol / L NaOH standard solution, using phenolphthalein as an indicator.

[0054] HCl conversion rate = V b / (V b +V d )×100%

[0055] V b This indicates the amount of Na₂S₂O₃ standard solution consumed in the titration, in mL.

[0056] V d This indicates the amount of NaOH standard solution consumed in the titration, in mL.

[0057] Example 1

[0058] The preparation of carbon-coated catalysts includes the following steps:

[0059] (1) Preparation of carbon-coated copper nanoparticles: Coal was used as raw material. First, it was ground and sieved (200 mesh), then dried in an oven at 105℃ for 12 hours. 5g of the ground coal sample and 2g of copper naphthenate were placed in a quartz tube of a tubular furnace. Nitrogen gas was introduced (150mL / min, 30min) to remove air from the tube. The temperature was increased at a rate of 10℃ / min from room temperature to 150℃, and held for 1 hour. Then, the temperature was increased again at a rate of 10℃ / min from 150℃ to 950℃, and held for another 2 hours. Nitrogen gas was then slowly introduced (30mL / min), allowing the tubular furnace to cool naturally to room temperature. The flocculent deposit in the middle of the quartz tube was removed, washed, and dried to obtain carbon-coated copper nanoparticles. The product was analyzed by EDS. The results (…) Figure 3 As can be seen, the copper content is 59.26%.

[0060] Figure 1 The image shows a TEM image of the prepared carbon-coated copper nanoparticles. As can be seen from the image, the particle size is about 35 nm and the dispersion is good. The black part is copper nanoparticles surrounded by a carbonaceous layer.

[0061] Figure 4The XRD pattern of the prepared carbon-coated copper nanoparticles shows that the three characteristic diffraction peaks of elemental copper correspond to the crystal planes (111), (200) and (220), respectively.

[0062] Figure 5 The image shows the XPS energy spectrum of carbon-coated copper nanoparticles, revealing the presence of C, N, O, and Cu elements.

[0063] Figure 6 The TG curve of the coal shows that the coal sample experienced the greatest weight loss (approximately 14%) between 400 and 600℃, with the main pyrolysis products being aliphatic hydrocarbons and benzene molecules. When the temperature is between 600 and 1000℃, the raw coal continues to lose weight, with the main byproduct being hydrogen gas generated due to the condensation of the coal structure. Between 900 and 1000℃, most of the coal pyrolyzes to yield coal-based carbon molecules.

[0064] Figure 7 This is the TG spectrum of carbon-coated copper nanoparticles. Compared to coal, carbon-coated copper nanoparticles exhibit increased thermal stability, which is more beneficial to the stability of the catalyst.

[0065] (2) The prepared carbon-coated copper nanoparticles were dispersed in water and impregnated on activated alumina microspheres by equal volume. After drying and calcination, a carbon-coated catalyst was obtained. The loading of the active component carbon-coated copper nanoparticles in the catalyst was 20 wt%.

[0066] The prepared carbon-coated catalyst was loaded into a fixed-bed reactor, and the reactor was heated using a three-stage furnace for temperature control. After preheating and stabilization, oxygen and hydrogen chloride were introduced, with a molar ratio of hydrogen chloride to oxygen of 2:1. The mass hourly space velocity (HHSV) of hydrogen chloride was 1.2 h⁻¹. -1 The reaction temperature was 350℃, and the reaction pressure was 1.5 atm. After 100 hours of reaction, the hydrogen chloride conversion rate was 87.43%; after 240 hours of reaction, the hydrogen chloride conversion rate was 87.69%. The catalytic activity did not decrease, indicating that the copper loss rate was extremely low.

[0067] Example 2

[0068] Preparation of carbon-coated catalysts:

[0069] (1) Using coal as raw material, first grind and sieve (200 mesh), and dry in an oven at 105℃ for 12 hours for later use; weigh 5g of the ground coal sample and 2g of copper naphthenate and place them in the quartz tube of the tubular furnace, purge the air in the tube with nitrogen (150mL / min, 30min), and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at the temperature for 1 hour, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 900℃. After holding at the temperature for 2 hours, slowly purge with nitrogen (30mL / min) and allow the tubular furnace to cool naturally to room temperature; take out the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 47.22wt%.

[0070] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 20 wt%.

[0071] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 81.39% after 100 hours of reaction and 80.88% after 240 hours of reaction.

[0072] Example 3

[0073] Preparation of carbon-coated catalysts:

[0074] (1) Using coal as raw material, first grind and sieve (200 mesh), and dry in an oven at 105℃ for 12 hours for later use; weigh 5g of the ground coal sample and 2g of copper naphthenate and place them in the quartz tube of the tubular furnace, purge the air in the tube with nitrogen (150mL / min, 30min), and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at the temperature for 2 hours, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 950℃. After holding at the temperature for 3 hours, slowly purge with nitrogen (30mL / min) and allow the tubular furnace to cool naturally to room temperature; take out the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 56.39wt%.

[0075] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 20 wt%.

[0076] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 86.99% after 100 hours of reaction and 84.51% after 240 hours of reaction.

[0077] Example 4

[0078] Preparation of carbon-coated catalysts:

[0079] (1) Using coal as raw material, it was first ground and sieved (200 mesh), and then dried in an oven at 105℃ for 12 hours for later use. 2.5g of the ground coal sample and 2.5g of copper naphthenate were weighed and placed in the quartz tube of a tubular furnace. Nitrogen gas was introduced (150mL / min, 30min) to remove the air in the tube, and the temperature was increased at a rate of 10℃ / min to raise the furnace temperature from room temperature to 200℃. After holding at this temperature for 0.5 hours, the temperature was increased again at a rate of 10℃ / min to raise the furnace temperature from 200℃ to 1000℃. After holding at this temperature for 1 hour, nitrogen gas was slowly introduced (30mL / min) to allow the tubular furnace to cool naturally to room temperature. The flocculent deposit in the middle of the quartz tube was removed, washed, and dried to obtain carbon-coated copper nanoparticles with a copper content of 65.73wt%.

[0080] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 50 wt%.

[0081] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 82.77% after 100 hours of reaction and 81.96% after 240 hours of reaction.

[0082] Example 5

[0083] Preparation of carbon-coated catalysts:

[0084] (1) Using coal as raw material, it was first ground and sieved (200 mesh), and then dried in an oven at 105℃ for 12 hours for later use. 5g of the ground coal sample and 1.25g of copper naphthenate were weighed and placed in a quartz tube of a tubular furnace. Nitrogen gas was introduced (150mL / min, 30min) to remove air from the tube, and the temperature was increased at a rate of 10℃ / min to raise the furnace temperature from room temperature to 120℃. After holding at this temperature for 0.5 hours, the temperature was increased again at a rate of 10℃ / min to raise the furnace temperature from 120℃ to 900℃. After holding at this temperature for 4 hours, nitrogen gas was slowly introduced (30mL / min) to allow the tubular furnace to cool naturally to room temperature. The flocculent deposit in the middle of the quartz tube was removed, washed, and dried to obtain carbon-coated copper nanoparticles with a copper content of 58.84wt%.

[0085] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 15 wt%.

[0086] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 79.74% after 100 hours of reaction and 79.55% after 240 hours of reaction.

[0087] Example 6

[0088] The carbon-coated copper nanoparticles obtained in Example 1 were loaded onto activated alumina microspheres at a loading amount of 30 wt%.

[0089] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 86.35% after 100 hours of reaction and 86.01% after 240 hours of reaction.

[0090] Example 7

[0091] The carbon-coated copper nanoparticles obtained in Example 1 were loaded onto activated alumina microspheres at a loading amount of 40 wt%.

[0092] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 86.55% after 100 hours of reaction and 85.68% after 240 hours of reaction.

[0093] Comparative Example 1

[0094] Preparation of carbon-coated catalysts:

[0095] (1) Using glucose as raw material, dry it in an oven at 105℃ for 12 hours for later use; weigh 5g of dried glucose and 2g of copper naphthenate and place them in a quartz tube of a tubular furnace. Purge nitrogen gas (150mL / min, 30min) to remove air from the tube and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at this temperature for 1 hour, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 950℃. After holding at this temperature for 2 hours, slowly purge nitrogen gas (30mL / min) and allow the tubular furnace to cool naturally to room temperature; remove the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 41.63wt%.

[0096] (2) The prepared carbon-coated copper was then dispersed in water and impregnated onto activated alumina microspheres by an equal volume. After drying and calcination, a carbon-coated catalyst was obtained. The loading was 20 wt%.

[0097] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 71.91% after 100 hours of reaction and 62.60% after 240 hours of reaction.

[0098] It can be seen that using coal as the carbon source for preparing carbon-coated copper exhibits superior activity and stability in the HCl-catalyzed oxidation to Cl2 compared to using glucose as the carbon source, and also has a significant cost advantage.

[0099] Comparative Example 2

[0100] Preparation of carbon-coated catalysts:

[0101] (1) Using coal as raw material, first grind and sieve (200 mesh), and dry in an oven at 105℃ for 12 hours for later use; weigh 5g of the ground coal sample and 10.5g of copper naphthenate and place them in the quartz tube of the tubular furnace, purge with nitrogen (150mL / min, 30min) to remove air from the tube, and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at the temperature for 1 hour, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 950℃. After holding at the temperature for 2 hours, slowly purge with nitrogen (30mL / min) and allow the tubular furnace to cool naturally to room temperature; take out the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 60.65wt%.

[0102] (2) The prepared carbon-coated copper was then dispersed in water and impregnated onto activated alumina microspheres by an equal volume. After drying and calcination, a carbon-coated catalyst was obtained. The loading was 20 wt%.

[0103] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 60.15% after 100 hours of reaction and 59.27% ​​after 240 hours of reaction.

[0104] Figure 2 This is a TEM image of carbon-coated copper obtained in this comparative example. The image shows that compared to... Figure 1 , Figure 2 The carbon-coated copper nanoparticles shown have a relatively small amount of elemental copper coating, leading to a decrease in catalytic efficiency. The carbon-coated catalyst prepared in Comparative Example 2 showed lower activity in the catalytic oxidation of HCl to Cl2 compared to Example 1. This may be because the amount of copper raw material used is too large, which is not conducive to the formation of carbon-coated copper. This may be because, during the formation of carbon-coated copper, the coal-based carbon molecules that should have been obtained from coal pyrolysis were adsorbed, activated, and dissolved on the surface of Cu nanoparticles produced by the pyrolysis of copper naphthenate. However, due to the excessive amount of copper source, a large number of Cu nanoparticles were produced by pyrolysis in the tube furnace. This prevented the coal-based carbon molecules from "coating" the surface of the Cu nanoparticles. Only a small portion could be coated, resulting in incomplete coating and a small amount of carbon-coated copper, which significantly reduced the catalytic performance.

[0105] Comparative Example 3

[0106] Preparation of carbon-coated catalysts:

[0107] (1) Using coal as raw material, first grind and sieve (200 mesh), and dry in an oven at 105℃ for 12 hours for later use; weigh 5g of the ground coal sample and 1g of copper naphthenate and place them in the quartz tube of the tubular furnace, purge the air in the tube with nitrogen (150mL / min, 30min), and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at the temperature for 1 hour, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 950℃. After holding at the temperature for 2 hours, slowly purge with nitrogen (30mL / min) and allow the tubular furnace to cool naturally to room temperature; take out the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 57.38wt%.

[0108] (2) The prepared carbon-coated copper was then dispersed in water and impregnated onto activated alumina microspheres in equal volume. After drying and calcination, a carbon-coated catalyst with a loading of 20 wt% was obtained.

[0109] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 73.99% after 100 hours of reaction and 73.36% after 240 hours of reaction.

[0110] Comparative Example 4

[0111] Preparation of carbon-coated catalysts:

[0112] (1) Using coal as raw material, first grind and sieve (200 mesh), and dry in an oven at 105℃ for 12 hours for later use; weigh 5g of the ground coal sample and 2g of copper naphthenate and place them in the quartz tube of the tubular furnace, purge the air in the tube with nitrogen (150mL / min, 30min), and raise the temperature at a rate of 10℃ / min to raise the furnace temperature from room temperature to 150℃. After holding at the temperature for 1 hour, raise the temperature at a rate of 10℃ / min to raise the furnace temperature from 150℃ to 850℃. After holding at the temperature for 2 hours, slowly purge with nitrogen (30mL / min) and allow the tubular furnace to cool naturally to room temperature; take out the flocculent deposit in the middle of the quartz tube, wash and dry it to obtain carbon-coated copper nanoparticles with a copper content of 45.62wt%.

[0113] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 20 wt%.

[0114] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 71.39% after 100 hours of reaction and 70.88% after 240 hours of reaction.

[0115] Comparative Example 5

[0116] Preparation of carbon-coated catalysts:

[0117] (1) Using coal as raw material, it was first ground and sieved (200 mesh), and then dried in an oven at 105℃ for 12 hours for later use. 5g of the ground coal sample and 2g of copper naphthenate were weighed and placed in a quartz tube of a tubular furnace. Nitrogen gas was introduced (150mL / min, 30min) to purge air from the tube, and the temperature was increased at a rate of 10℃ / min, raising the furnace temperature directly from room temperature to 950℃. After holding at this temperature for 2 hours, nitrogen gas was slowly introduced (30mL / min), allowing the tubular furnace to cool naturally to room temperature. The flocculent deposit in the middle of the quartz tube was removed, washed, and dried to obtain carbon-coated copper nanoparticles. The copper content of these carbon-coated copper nanoparticles was 28.14wt%.

[0118] (2) Carbon-coated copper was loaded onto activated alumina microspheres with a loading amount of 20 wt%.

[0119] Under the catalytic conditions of Example 1, the hydrogen chloride conversion rate was 56.64% after 100 hours of reaction and 55.93% after 240 hours of reaction.

Claims

1. The application of carbon-coated catalysts in the catalytic oxidation of hydrogen chloride to produce chlorine, characterized in that, The catalyst comprises a support and an active component, wherein the active component is carbon-coated copper nanoparticles and the support is activated alumina microspheres; the loading of the active component in the catalyst is 5-50 wt%, and the carbon-coated copper nanoparticles are composed of layered carbon material coating nano-copper, with a copper content of 59.26 wt%. The catalyst is prepared by dispersing carbon-coated copper nanoparticles in water, impregnating them in equal volumes onto activated alumina microspheres, and then drying and calcining them to obtain a carbon-coated catalyst. The preparation method of carbon-coated copper nanoparticles is as follows: Under an inert atmosphere, coal and copper naphthenate are heated in stages. In the first stage, the temperature is raised to 120~200℃ and held for 0.5~2 hours. In the second stage, the temperature is raised to 900~1000℃ and held for 1~4 hours. After cooling, carbon-coated copper nanoparticles are obtained.

2. The application of the carbon-coated catalyst according to claim 1 in the catalytic oxidation of hydrogen chloride to produce chlorine, characterized in that, The loading of the active component in the catalyst is 15~50wt%.

3. The application of the carbon-coated catalyst according to claim 1 in the catalytic oxidation of hydrogen chloride to produce chlorine, characterized in that, The heating is achieved using a programmed heating method; the cooling is achieved by introducing nitrogen gas.

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