A catalyst for preparing benzene from cyclohexane by dehydrogenation and a preparation method and application thereof

Abstract

The application discloses a catalyst for preparing benzene by dehydrogenation of cyclohexane and a preparation method and application thereof. The catalyst comprises an oxide and a carbide. The oxide is gamma-Al2O3, and the carbide is Ta3C2. The application further discloses a preparation method of the catalyst. The method comprises the following steps: preparing Ta3AlC2 by using a high-temperature calcination method, immersing the Ta3AlC2 in a hydrofluoric acid solution, mixing and carrying out a hydrothermal reaction, washing for several times and drying to obtain Ta3C2. Then, the carbide and the oxide are mixed, and the catalyst is obtained after calcination. The application further discloses a method for preparing benzene by using the catalyst to carry out a dehydrogenation reaction of cyclohexane.

Description

Technical Field

[0001] This application relates to a catalyst for the dehydrogenation of cyclohexane to benzene, its preparation method and application, and belongs to the field of chemical engineering. Background Technology

[0002] With the widespread adoption of the cyclohexene hydration process for producing cyclohexanol, cyclohexane production capacity has increased year by year, leading to greater pressure on cyclohexane consumption. This has made the dehydrogenation of cyclohexane to produce benzene a viable technological route. In this scenario, a factory producing adipic acid or caprolactam, possessing both cyclohexene hydration and cyclohexane oxidation facilities, could technically utilize the cyclohexane byproduct from the cyclohexene hydration process directly in the cyclohexane oxidation process – a near-perfect solution. However, the cyclohexane oxidation method is gradually being phased out due to its high safety risks and significant environmental issues related to the treatment of the waste alkaline solution. As cyclohexane production capacity continues to increase, while the capacity for producing adipic acid and caprolactam from cyclohexane remains limited, the pressure on the cyclohexane market is growing annually, even leading to price inversions between benzene and cyclohexane. Therefore, using the benzene and hydrogen produced from cyclohexane dehydrogenation as feedstock for the cyclohexene hydration process has become an option for relevant factories.

[0003] In the cyclohexane dehydrogenation reaction, the active component of the catalyst is a noble metal such as platinum, the acidic component is mainly a halogen (chlorine or fluorine), and the support is alumina. The noble metal constitutes the active dehydrogenation center. Raney nickel or other non-noble metal catalysts are also used. In operating units, bimetallic or multimetallic catalysts are often used, with the multimetallic component acting as a co-catalyst to improve catalyst performance. Among existing catalysts, Ni, Ir, Pd, and Pt are commonly used as the active components of dehydrogenation catalysts. Pt exhibits high activity in cycloalkanes dehydrogenation due to its high activation ability for CH bonds. Under the same active component content, the higher the metal dispersion, the higher the catalyst activity. However, the recovery of noble metals used in catalysts is difficult and expensive. Summary of the Invention

[0004] This patent describes the preparation of metal carbides, which are then mixed with alumina. This process is inexpensive, simple, and results in a strong bond and interaction between the carbides and alumina. When applied to the dehydrogenation of cyclohexane to benzene, it exhibits good catalyst activity, high cyclohexane conversion and benzene selectivity, and good stability.

[0005] According to one aspect of this application, a catalyst for the dehydrogenation of cyclohexane to benzene is provided, which can improve the conversion rate of cyclohexane and the selectivity of benzene;

[0006] The catalyst includes Ta3C2 and γ-Al2O3;

[0007] In the catalyst, the mass ratio of Ta3C2 to γ-Al2O3 is 1:(10-30).

[0008] According to another aspect of this application, a method for preparing the above-mentioned catalyst is provided, comprising the following steps:

[0009] 1) Preparation of Ta3AlC2 by high-temperature calcination;

[0010] 2) The Ta3AlC2 obtained in 1) is immersed in a solution containing hydrofluoric acid to obtain Ta3C2;

[0011] 3) Mix the Ta3C2 obtained in 2) with γ-Al2O3 and calcine to obtain the catalyst.

[0012] The high-temperature calcination method for preparing Ta3AlC2 includes the following steps:

[0013] Raw materials containing tantalum source, aluminum source and carbon powder are mixed and calcined to obtain Ta3AlC2.

[0014] The tantalum source is selected from tantalum powder;

[0015] The aluminum source is selected from aluminum powder;

[0016] Optionally, the molar ratio of the tantalum source, aluminum source and carbon powder is 3:(0.9~1):2;

[0017] Optionally, the molar ratio of the tantalum source, aluminum source and carbon powder is any value among 3:0.9:2, 3:0.95:2, 3:1:2 or any range between the two.

[0018] Optionally, the calcination temperature is 1000–1400°C;

[0019] Optionally, the calcination temperature is any value among 1000℃, 1100℃, 1200℃, 1300℃, and 1400℃, or a range between any two.

[0020] Optionally, the calcination time is 1 to 6 hours.

[0021] Optionally, the calcination time is any value among 1h, 2h, 3h, 4h, 5h, and 6h, or a range between any two.

[0022] The concentration of hydrofluoric acid in the solution containing hydrofluoric acid is 30-50 wt%.

[0023] Optionally, the concentration of hydrofluoric acid in the solution containing hydrofluoric acid is any value among 30wt%, 35wt%, 40wt%, 45wt%, and 50wt%, or a range between any two.

[0024] Optionally, the solid-liquid ratio of the Ta3AlC2 obtained in step 1) to the hydrofluoric acid-containing solution is 1:(10-30)g / ml;

[0025] Optionally, the solid-liquid ratio of the Ta3AlC2 obtained in step 1) to the hydrofluoric acid-containing solution is any value among 1:10 g / ml, 1:15 g / ml, 1:20 g / ml, 1:25 g / ml, and 1:30 g / ml, or any range between two of them.

[0026] The impregnation temperature is 40–80°C;

[0027] Optionally, the impregnation temperature is any value among 40°C, 50°C, 60°C, 70°C, and 80°C, or a range between any two.

[0028] The soaking time is 28–112 hours;

[0029] Optionally, the impregnation time is any value or a range between 28h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h, 110h, and 112h. Preferably, the Ta3C2 is dried.

[0030] Optionally, the drying temperature is 60–100°C;

[0031] Optionally, the drying temperature is any value among 60°C, 70°C, 80°C, 90°C, and 100°C, or a range between any two.

[0032] Optionally, the drying time is 12 to 36 hours.

[0033] Optionally, the drying time is any value among 12h, 18h, 24h, 30h, and 36h, or a range between any two.

[0034] The mass ratio of Ta3C2 obtained in step 2) to γ-Al2O3 is 1:(10-30);

[0035] Optionally, the mass ratio of Ta3C2 to γ-Al2O3 obtained in step 2) is any value among 1:10, 1:20, and 1:30, or any range between the two.

[0036] The mixing includes mechanical mixing or wet mixing;

[0037] The roasting temperature is 500–600°C;

[0038] Optionally, the calcination temperature is any value among 500°C, 550°C, and 600°C, or a range between any two.

[0039] The roasting time is 4 to 8 hours.

[0040] Optionally, the roasting time is any value among 4h, 5h, 6h, 7h, and 8h, or a range between any two.

[0041] The Ta3C2 and the catalyst were washed before drying;

[0042] Optionally, the solvent used for washing is selected from water and / or ethanol.

[0043] According to another aspect of this application, a method for preparing benzene by dehydrogenation of cyclohexane is provided, comprising the following steps:

[0044] In a reactor, a material containing hydrogen and cyclohexane is introduced and reacted with a catalyst to obtain a product containing benzene.

[0045] The catalyst is selected from the catalysts described above or the catalysts prepared by the preparation method described above.

[0046] The flow rate of the hydrogen gas is 5–10 ml / min;

[0047] The hydrogen flow rate is any value among 5 ml / min, 6 ml / min, 7 ml / min, 8 ml / min, 9 ml / min, and 10 ml / min, or a range between any two.

[0048] The mass hourly space velocity of the material is 2-4 h. -1 .

[0049] Optionally, the mass hourly space velocity of the material is 2h. -1 3h -1 4h -1 Any value in the range or any value between the two.

[0050] The reaction temperature is 280–340°C;

[0051] Optionally, the temperature of the reaction is any value or a range between 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, and 340°C.

[0052] The reaction time is 2-3 hours;

[0053] Optionally, the reaction time is any value among 2h, 2.5h, and 3h, or a range between any two.

[0054] The reaction pressure is 0.1–0.4 MPa.

[0055] Optionally, the pressure of the reaction is any value among 0.1 MPa, 0.2 MPa, 0.3 MPa, and 0.4 MPa, or a range between any two.

[0056] The reactor is a fixed-bed reactor.

[0057] The beneficial effects that this application can produce include:

[0058] 1) The catalyst provided in this application can be applied to the dehydrogenation reaction of cyclohexane to prepare benzene and improve the conversion rate of cyclohexane and the selectivity of the benzene produced.

[0059] 2) The preparation method of the catalyst provided in this application is stable, controllable, and reproducible.

[0060] 3) The method for preparing benzene by dehydrogenation of cyclohexane provided in this application uses the catalyst provided in this application, which has a fast reaction rate and high yield, and can be applied to large-scale production. Attached Figure Description

[0061] Figure 1 Catalyst 1 # X-ray powder diffraction pattern of Ta3C2.

[0062] Figure 2 Catalyst 1 # Scanning electron microscope image of Ta3C2 in [the image]. Detailed Implementation

[0063] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0064] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially. The gas chromatograph used was an Agilent 7890B gas chromatograph.

[0065] Examples 1-28

[0066] Preparation of catalysts

[0067] Taking item 1 in Tables 1-2 as an example, tantalum powder, aluminum powder, and carbon powder with a molar ratio of 3:(0.9-1):2 were ground to obtain a mixture; this mixture was calcined in an open tube furnace at 1400℃ for 2 hours to obtain Ta3AlC2. Ta3AlC2 was then soaked in a 40wt% hydrofluoric acid solution (the solid-liquid ratio of Ta3AlC2 to hydrofluoric acid solution was 1:20 g / ml) at 60℃ for 56 hours; after washing several times with ethanol, it was dried at 70℃ for 24 hours to obtain Ta3C2. Ta3C2 and γ-Al2O3 were mixed using a wet mixing method (the mass ratio of Ta3C2 to γ-Al2O3 was 1:20), and calcined at 550℃ in an argon atmosphere for 4 hours. The resulting catalyst Ta3C2 / γ-Al2O3 was designated as catalyst 1. # .

[0068] Following the steps below, adjust the type and amount of each raw material and the reaction parameters to obtain a series of catalysts numbered 2 to 28, denoted as catalyst 2. # ~Catalyst 28 # As shown in Table 1 below:

[0069] Table 1

[0070]

[0071]

[0072]

[0073] Table 2

[0074]

[0075]

[0076] The explanations for columns 1 and 2 above are as follows:

[0077] Mixing methods: mechanical mixing (method 1), wet mixing (method 2).

[0078] Washing solvents: deionized water (solution 1), ethanol (solution 2), and a mixed solution of deionized water and ethanol (solution 3).

[0079] XRD characterization

[0080] Catalyst 1 was analyzed using a Miniflex 600 X-ray diffractometer with a Cu target. # Powder diffraction yielded catalyst 1. # The Ta3C2 diffraction peaks in the image conform to the characteristic peaks of Ta3C2 (e.g., ...). Figure 1 (As shown).

[0081] SEM characterization

[0082] Scanning electron microscopy (SEM) (JSM-7800F) on catalyst 1 # Morphological analysis of Ta3C2 (e.g.) Figure 2 (As shown).

[0083] Gas chromatography characterization

[0084] The composition of the products of cyclohexane dehydrogenation reaction was analyzed using an Agilent 7890B gas chromatograph (FID detector, HP-5 capillary column).

[0085] Application Example 1

[0086] The catalyst is used in the dehydrogenation reaction of cyclohexane to prepare benzene.

[0087] Catalysts 1 to 28 prepared in Example 1 # ~Catalyst 28 # The catalyst was used to prepare benzene from cyclohexane via dehydrogenation. The reaction proceeded at 310°C and 0.2 MPa for 3 hours, with the feedstock contacting the catalyst in the reactor to produce a benzene-containing product. The mass hourly space velocity (WHSV) was 3 h⁻¹. -1 The H2 flow rate was 8 ml / min. The feedstock was fed into a fixed-bed reactor containing 3 g of the catalyst, and benzene was prepared by dehydrogenation.

[0088] After the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 3.

[0089] Table 3

[0090]

[0091]

[0092] As can be seen from the table, the prepared catalysts all exhibit high catalytic activity in the dehydrogenation reaction to produce benzene.

[0093] Application Example 2

[0094] Catalyst 1 prepared in Table 1 # The dehydrogenation of cyclohexane to prepare benzene was carried out. After the reaction parameters were varied and the reaction stabilized, both the reactants and products were analyzed using online gas chromatography. The results are shown in Table 4.

[0095] Table 4

[0096]

[0097]

[0098] The table shows that reaction temperature and H2 flow rate have a significant impact on the conversion rate of cyclohexane.

[0099] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A catalyst for the dehydrogenation of cyclohexane to benzene, characterized in that, The catalyst includes Ta3C2 and γ-Al2O3; In the catalyst, the mass ratio of Ta3C2 to γ-Al2O3 is 1:(10~30).

2. A method for preparing the catalyst according to claim 1, characterized in that, Includes the following steps: 1) Preparation of Ta3AlC2 by high-temperature calcination; 2) The Ta3AlC2 obtained in 1) is immersed in a solution containing hydrofluoric acid to obtain Ta3C2; 3) Mix the Ta3C2 obtained in 2) with γ-Al2O3 and calcine to obtain the catalyst.

3. The preparation method according to claim 2, characterized in that, The high-temperature calcination method for preparing Ta3AlC2 includes the following steps: Raw materials containing tantalum source, aluminum source and carbon powder are mixed and calcined to obtain Ta3AlC2.

4. The preparation method according to claim 3, characterized in that, The tantalum source is selected from tantalum powder; The aluminum source is selected from aluminum powder.

5. The preparation method according to claim 3, characterized in that, The molar ratio of the tantalum source, aluminum source and carbon powder is 3:(0.9~1):

2.

6. The preparation method according to claim 3, characterized in that, The calcination temperature is 1000~1400℃.

7. The preparation method according to claim 3, characterized in that, The calcination time is 1 to 6 hours.

8. The preparation method according to claim 2, characterized in that, The concentration of hydrofluoric acid in the solution containing hydrofluoric acid is 30~50wt%.

9. The preparation method according to claim 2, characterized in that, The solid-liquid ratio of the Ta3AlC2 obtained in step 1) to the hydrofluoric acid-containing solution is 1:(10~30)g / ml.

10. The preparation method according to claim 2, characterized in that, The immersion temperature is 40~80℃.

11. The preparation method according to claim 2, characterized in that, The soaking time is 28~112 hours.

12. The preparation method according to claim 2, characterized in that, The Ta3C2 was dried.

13. The preparation method according to claim 12, characterized in that, The drying temperature is 60~100℃.

14. The preparation method according to claim 12, characterized in that, The drying time is 12-36 hours.

15. The preparation method according to claim 2, characterized in that, The mass ratio of Ta3C2 obtained in step 2) to γ-Al2O3 is 1:(10~30); The mixing includes mechanical mixing methods; The roasting temperature is 500~600℃; The roasting time is 4 to 8 hours.

16. The preparation method according to claim 2, characterized in that, The mass ratio of Ta3C2 obtained in step 2) to γ-Al2O3 is 1:(10~30); The mixing includes wet mixing; The roasting temperature is 500~600℃; The roasting time is 4 to 8 hours.

17. The preparation method according to claim 12, characterized in that, The Ta3C2 and the catalyst were washed before drying.

18. The preparation method according to claim 17, characterized in that, The solvent used for washing is selected from water and / or ethanol.

19. A method for preparing benzene by dehydrogenation of cyclohexane, characterized in that, Includes the following steps: In a reactor, a material containing hydrogen and cyclohexane is introduced and reacted with a catalyst to obtain a product containing benzene. The catalyst is selected from the catalyst according to claim 1 or the catalyst prepared by the preparation method according to any one of claims 2 to 7; The flow rate of the hydrogen gas is 5~9 ml / min; The reaction temperature is 290~340℃.

20. The method according to claim 19, characterized in that, The mass hourly space velocity of the material is 2-4 h. -1 .

21. The method according to claim 19, characterized in that, The reaction time is 2-3 hours; The reaction pressure is 0.1~0.4 MPa.

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