A metal carbide catalyst, its preparation and application

Abstract

This invention discloses a method for preparing a metal carbide catalyst for dichloroethane cracking. Specifically, an anion exchange resin is first subjected to simultaneous ion exchange with silicate and metal-containing anions, followed by pyrolysis at high temperature to obtain a composite material of metal carbide and silica. Subsequently, the silica portion of the composite material is removed, resulting in a metal carbide catalyst with a high specific surface area. This preparation method is simple, and the obtained catalyst has a large specific surface area and high strength, showing broad application prospects in the dichloroethane cracking reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, specifically relating to a method for preparing a metal carbide catalyst for dichloroethane cracking. Background Technology

[0002] Transition metal carbides are "intercalary alloys." The presence of carbon increases the distance between metal atoms, leading to an increase in valence electrons and a higher Fermi level density. Therefore, transition metal carbides exhibit catalytic performance similar to noble metal catalysts in certain reactions. Typically, the preparation of metal carbides involves methods such as chemical vapor deposition and temperature-programmed reduction carbonization. These processes are complex, and the use of hydrogen gas poses certain risks, resulting in low yields and high costs.

[0003] Ion exchange resins are a class of materials with smooth surfaces, controllable particle size, high strength, and no powdering or flaking during use, making them widely used in industry. Currently, the preparation of porous carbon materials using ion exchange resins as a carbon source generally involves three stages: pre-crosslinking, pyrolysis, and activation. Pre-crosslinking is necessary because the crosslinking degree of ion exchange resins is relatively poor, and a pre-crosslinking process is usually required to prevent thermal deformation during pyrolysis. The activation process typically involves etching the carbon skeleton with alkaline activators to create pores, aiming to obtain materials with high specific surface area. However, the carbon yield is low due to carbon loss caused by etching. In Chinese patent applications CN201711295470.5 and CN201711294620.0, we provided a method for preparing porous carbon materials based on ion exchange resins. This involves first ion-exchanging anion exchange resin with an alkaline silicate, then pyrolyzing it at high temperature to obtain a composite material of carbon and silica, and finally removing the silica component from the composite material to obtain a carbon material with high specific surface area. In Chinese patent application CN201911284862.0, we provided a method for preparing an ion exchange resin-based carbon-supported metal catalyst, which involves first ion-exchanging an anion exchange resin with an alkaline silicate solution and an anionic metal complex, then pyrolyzing it at high temperature to obtain a composite material of carbon, silicon oxide and metal, and then removing the silicon oxide component from the composite material to obtain the carbon-supported metal catalyst.

[0004] We further expand upon existing methods by simultaneously adding silicate and metal-containing anion solutions to an ion-exchange solution. This involves simultaneously exchanging silicate and metal-containing anions in an anion exchange resin or zwitterion resin, followed by high-temperature pyrolysis to obtain a composite material of metal carbide and silicon oxide. The silicon oxide component in the composite material is then removed to obtain a metal carbide catalyst. During high-temperature pyrolysis, metal ions interact with carbon to form metal carbides, while silicate ions are converted to silicon oxide. After pyrolysis, the silicon oxide is removed, yielding a carbide material with a high specific surface area. This preparation method is simple, yields metal carbides with large specific surface area and high strength, and shows broad application prospects in the cracking reaction of dichloroethane. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a metal carbide catalyst for the cracking of dichloroethane, which is simple and can directly obtain the metal carbide catalyst.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] 1. A method for preparing a metal carbide catalyst for the cracking of dichloroethane, comprising the following specific steps:

[0008] (a) Ion exchange resin is subjected to simultaneous ion exchange with silicate and solution containing metal anions;

[0009] (b) Ion exchange resin containing silicate and metal anions is pyrolyzed at high temperature to obtain a composite material of metal carbide and silicon oxide.

[0010] (c) Remove the silicon oxide material component from the composite material to obtain a metal carbide.

[0011] The ion exchange resin mentioned in step (a) above is one or more of anion exchange resin or zwitterionic ion exchange resin. Zwitterionic ion exchange resin refers to an ion exchange resin that contains both anion and cation exchange groups.

[0012] In step (a) above, the anion exchange resin and the zwitterion exchange resin contain one or more of the following functional groups: quaternary ammonium group, primary amine, secondary amine, tertiary amine, or quaternary phosphonium group.

[0013] The silicate mentioned in step (a) above is a soluble alkali metal silicate, and the mass concentration of the silicate and anionic metal complex solution is 0.5% to 30%.

[0014] The silicate mentioned in step (a) above is one or more of Na2O·nSiO2 (sodium silicate) with a modulus between 1 and 3.

[0015] The metal-containing anion mentioned in step (a) above is MoO4. 2- (Molybdate), WO4 2- W 12 O 41 10- One or more of (tungstate) are present.

[0016] In step (a) above, after ion exchange, the mass ratio of silica to ion exchange resin is 0.1 to 3.5; the mass ratio of metal-containing anions to ion exchange resin is 0.001 to 0.5.

[0017] The pyrolysis temperature described in step (b) above is 500 to 1000°C, and the time is 0.2 to 12 hours.

[0018] In step (c) above, silicon oxide is removed by one or more of alkali metal hydroxides, alkali metal salts, hydrofluoric acid, alkali metal fluorides, or ammonium fluoride.

[0019] In step (c) above, the mass concentration of the silica removal reagent solution is 1% to 70%; the mass ratio of the silica removal reagent to silica is 1.2 to 100.

[0020] In step (c) above, the temperature of the reaction to remove the silica reagent is 0 to 200°C, and the soaking time is 0.2 to 48 hours.

[0021] The specific surface area of ​​the metal carbides prepared by this method ranges from 100 to 3000 m². 2 / g.

[0022] The preparation method is simple, and the resulting catalyst has a large specific surface area and high strength, showing broad application prospects in the cracking reaction of dichloroethane. Attached Figure Description

[0023] Figure 1 This is the X-ray diffraction (XRD) pattern of the metal carbide catalyst obtained in Example 1 of this invention.

[0024] Figure 2 This is the thermogravimetric (TG) diagram of the metal carbide catalyst obtained in Example 1 according to the present invention.

[0025] Figure 3 This is a diagram showing the results of the dichloroethane cracking reaction using the metal carbide catalyst obtained in Example 1 according to the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0027] Example 1

[0028] 150 mL of Amberlite IRA-900 macroporous strong base ion exchange resin was packed into an ion exchange column. Ion exchange was performed by passing 2 L of a mixed solution of 1.0 M Na2SiO3 and 0.01 M (NH4)2MoO4 through the ion exchange column from bottom to top at a rate of 1.5-2 mL / min. The sample was then filtered, dried, and obtained.

[0029] The above sample was placed in a tube furnace and heated to 700℃ at a rate of 2℃ / min under an Ar atmosphere, and held at that temperature for 3 hours to carbonize the sample, obtaining a composite material of molybdenum carbide and silicon dioxide. After ion exchange, the mass ratio of silicon dioxide to the initial ion exchange resin raw material was 1.0; the mass ratio of the metal in the metal-containing anion to the initial ion exchange resin raw material was 0.02.

[0030] Spherical molybdenum carbide catalysts were obtained by immersion in 5% HF for 12 hours to remove silica from molybdenum carbide and silica. The catalysts had a BET specific surface area of ​​796 m². 2 / g, pore size distribution of 0.5-50nm, Mo content in metal carbide catalyst is 8% by mass. XRD of the sample is as follows: Figure 1 As shown, typical molybdenum carbide signal peaks appeared, indicating that this route for the synthesis of molybdenum carbide is feasible. The TG values ​​of the sample are as follows: Figure 2 As shown, the mass of the material first increases and then decreases with the increase in temperature in the air atmosphere. The increase corresponds to the process of molybdenum carbide being oxidized to molybdenum oxide, which also confirms the synthesis of molybdenum carbide.

[0031] Example 2

[0032] 50 mL of Amberlite IRA-717 gel-type strong base ion exchange resin was packed into an ion exchange column. Ion exchange was performed by passing 1 L of a mixed solution of 0.5 M Na2SiO3 and 0.01 M Na2MoO4 through the ion exchange column from bottom to top at a rate of 1.5-2 mL / min. The sample was then filtered, dried, and obtained.

[0033] The above sample was placed in a tube furnace under a N2 atmosphere, heated to 600℃ at a rate of 5℃ / min, and held for 2 hours to carbonize the sample, obtaining a composite material of molybdenum carbide and silicon dioxide. After ion exchange, the mass ratio of silicon dioxide to the initial ion exchange resin raw material was 0.5; the mass ratio of the metal in the metal-containing anion to the initial ion exchange resin raw material was 0.02.

[0034] The silica in the molybdenum carbide and silica composite material was removed by soaking in 2M NaOH solution at 50°C for 48 hours to obtain a spherical molybdenum carbide catalyst with a pore size distribution of 0.5-3 nm and a Mo mass content of 3% in the metal carbide catalyst.

[0035] Example 3

[0036] 100 mL of D301 macroporous strong base ion exchange resin was packed into an ion exchange column, and 2 L of 0.3 M Na2SiO3 and 0.05 M (NH4) were added. 10 W 12 O 41 The mixed solution was passed through an ion exchange column from bottom to top at a rate of 2-3 mL / min for ion exchange, then filtered, dried, and the sample was obtained.

[0037] The above sample was placed in a tube furnace and heated to 600℃ at a rate of 3℃ / min under a He atmosphere, and held for 3 hours to carbonize the sample, obtaining a composite material of tungsten carbide and silicon dioxide. After ion exchange, the mass ratio of silicon dioxide to the initial ion exchange resin raw material was 0.3; the mass ratio of the metal in the metal-containing anion to the initial ion exchange resin raw material was 0.1.

[0038] Spherical tungsten carbide catalysts were obtained by soaking in 2M NaF solution for 12 hours to remove silica from the tungsten carbide and silica composite material. The pore size distribution was 0.5-50 nm, and the mass content of W in the metal carbide catalyst was 0.1%.

[0039] Example 4

[0040] 150 mL of Amberlite IRA-717 gel-type strong base ion exchange resin was packed into an ion exchange column, and ion exchange was performed with 2 L of a mixed solution of 1.0 M Na2SiO3 and 0.05 M Na2WO4 at a rate of 1.0-1.5 mL / min. The sample was then filtered, dried, and obtained.

[0041] The above sample was placed in a tube furnace under a N2 atmosphere, heated to 800℃ at a rate of 2℃ / min, and held for 3 hours to carbonize the sample, obtaining a tungsten carbide and silicon oxide composite material. After ion exchange, the mass ratio of silicon dioxide to the initial ion exchange resin raw material was 1.0; the mass ratio of metal to the initial ion exchange resin raw material in the metal-containing anions used was 0.1.

[0042] Spherical tungsten carbide catalysts were obtained by immersion in 10% HF solution for 24 hours to remove silica from the tungsten carbide and silica composite material. The catalysts had a BET specific surface area of ​​681 m². 2 / g, with a pore size distribution of 0.5-3nm, and the mass content of W in the metal carbide catalyst is 0.3%.

[0043] Example 5

[0044] The reaction for preparing vinyl chloride by cracking dichloroethane was carried out using the spherical molybdenum carbide catalyst prepared in Example 1 in a fixed-bed reactor. The catalyst dosage was 0.1 g, and the reaction temperature was set at 300 °C. Dichloroethane was introduced into the reactor via nitrogen bubbling at a flow rate of 5 mL / min. The space velocity of dichloroethane was 24 h⁻¹. -1 The reaction was considered to have started when the temperature reached 300℃. The feed gas and gaseous products were analyzed online using an Agilent 8890B gas chromatograph equipped with a TCD and FID detector. The reaction results are attached. Figure 3 .

Claims

1. A method for preparing a metal carbide catalyst, characterized in that, Includes the following steps: (a) Ion exchange resin is subjected to ion exchange with a mixed solution of silicate and metal anions; (b) An ion exchange resin containing silicate and metal anions is pyrolyzed at high temperature to obtain a composite material of metal carbide and silicon oxide; the pyrolysis temperature is 500 to 1000 °C and the time is 0.2 to 12 hours. (c) Remove the silicon oxide component from the composite material to obtain a metal carbide catalyst; The ion exchange resin is one or more of anion exchange resin or zwitterionic ion exchange resin. Zwitterionic ion exchange resin refers to an ion exchange resin that contains both anion and cation exchange groups. The anion exchange resin and zwitterion exchange resin are one or more of Amberlite IRA-900, Amberlite IRA-717, and D301. The metal anion mentioned in step (a) above is MoO4. 2- WO4 2- W 12 O 41 10- One or more of the silicates are selected, wherein the silicate is one or more of Na2O·nSiO2 with a modulus between 1 and 3, i.e., n = 1-3.

2. The preparation method according to claim 1, characterized in that: The pyrolysis temperature in step (b) is 700-1000 ℃, and the time is 2-6 hours.

3. The preparation method according to claim 1, characterized in that: The pyrolysis temperature in step (b) is 800-900 ℃, and the time is 3-4 hours.

4. The preparation method according to claim 1, characterized in that: The silicate mentioned is a soluble alkali metal silicate; The mass concentrations of silicate and metal anions in the mixed solution range from 0.5% to 50%.

5. The preparation method according to claim 1, characterized in that: The mass concentration of silicate in silicate and metal anion-containing solutions is 10-30%, and the mass concentration of metal anion-containing solutions is 10-30%.

6. The preparation method according to claim 1, characterized in that: The mass concentration of silicate in silicate and metal-containing anionic solutions is 15-25%, and the mass concentration of metal-containing anionic solutions is 15-20%.

7. The preparation method according to claim 1 or 4, characterized in that: The salt containing metal anions used in the preparation of the mixed solution in step (a) above is one or more of the ammonium or sodium salts of metal anions.

8. The preparation method according to claim 1, characterized in that: After ion exchange, the mass ratio of silica to the initial ion exchange resin raw material is 0.1 to 3.5; the mass ratio of metal to the initial ion exchange resin raw material in the metal-containing anions used is 0.001 to 0.

5.

9. The preparation method according to claim 1, characterized in that: After ion exchange, the mass ratio of silica to the initial ion exchange resin raw material is 1-3.0, and the mass ratio of metal to the initial ion exchange resin raw material in the metal-containing anions used is 0.05-0.

3.

10. The preparation method according to claim 1, characterized in that: After ion exchange, the mass ratio of silica to the initial ion exchange resin raw material is 1.5-2.0; the mass ratio of metal to the initial ion exchange resin raw material in the metal-containing anions used is 0.1-0.

2.

11. The preparation method according to claim 1, characterized in that: Remove the silica component from the composite material using one or more of the following silica removal reagents: hydrofluoric acid, alkali metal hydroxide, alkali metal salt, alkali metal fluoride, or ammonium fluoride. The composite material of metal carbide and silicon oxide was immersed in a solution of silicon oxide removal reagent; The mass concentration of the solution is from 1% to 70%; The mass ratio of the silica removal reagent to silica in the composite material is between 1.2 and 100. The reaction temperature for removing the silica component is 0 to 200 °C, and the soaking time in the reagent is 0.2 to 48 hours.

12. The preparation method according to claim 11, characterized in that: The composite material of metal carbide and silicon oxide was immersed in a solution of silicon oxide removal reagent; The mass concentration of the solution is 5-30%; the mass ratio of the silica removal reagent to the silica in the composite material is 2-30. The reaction temperature for removing the silica component is 10-80 °C, and the soaking time in the reagent is 12-48 hours.

13. The preparation method according to claim 11, characterized in that: The composite material of metal carbide and silicon oxide was immersed in a solution of silicon oxide removal reagent; The mass concentration of the solution is 15-25%; the mass ratio of the silica removal reagent to the silica in the composite material is 10-20. The reaction temperature for removing the silica component is 20-50 °C, and the soaking time in the reagent is 24-36 hours.

14. The preparation method according to claim 1, characterized in that: The specific surface area of ​​the metal carbide catalyst is between 50 and 3000 m². 2 / g, the mass content of one or two of Mo and W in the metal carbide catalyst is 0.01% to 20%.

15. The preparation method according to claim 14, characterized in that: The specific surface area of ​​the metal carbide catalyst is 796 m². 2 / g; the mass content of one or two of Mo and W in the metal carbide catalyst is 1-10%.

16. The preparation method according to claim 15, characterized in that: The mass content of one or two of Mo and W in the metal carbide catalyst is 5-10%.

17. The application of a metal carbide catalyst prepared by any one of the preparation methods according to claims 1-16 in the catalytic cracking of dichloroethane.

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