A bimetallic catalyst, its preparation method and use

Abstract

The application discloses a bimetallic catalyst and a preparation method and application thereof. The bimetallic catalyst comprises a hierarchical pore molecular sieve, a metal oxide additive and an active component Pt, and the metal oxide additive and the active component Pt are loaded on the hierarchical pore molecular sieve. The application greatly improves the production efficiency of cyclohexane dehydrogenation by being matched with a continuous reactor-fixed bed. The cyclohexane conversion rate is as high as 98.9%, the selectivity can reach 99.5%, and the catalyst can be stably operated for a long time.

Description

Technical Field

[0001] This application relates to a bimetallic catalyst, its preparation method, and its application, belonging to the field of catalyst technology. Background Technology

[0002] Hydrogen energy, as a high-energy-density and clean green energy source, is of great significance for improving the human living environment. Hydrogen is gaseous at room temperature and pressure, and liquid at ultra-low temperature and high pressure. It is also the most abundant element in nature and has the best thermal conductivity of any gas, approximately 10 times higher than most gases. However, from the current development perspective in China, the storage and transportation of hydrogen energy are the main bottlenecks restricting its widespread application. Compared with traditional hydrogen storage technologies, organic liquid hydrogen storage has advantages such as high hydrogen storage density and reversible reaction process; safe and convenient hydrogen carrier storage and transportation, suitable for long-distance transportation; and no CO or CO2 emissions during hydrogen storage and supply.

[0003] Cyclohexane possesses a hydrogen storage capacity as high as 7.1 wt%, primarily derived from the extensive synthesis of benzene through hydrogenation. Its production process and storage and transportation technologies are quite mature, providing a prior guarantee for large-scale hydrogen storage and transportation. However, the technical challenge of cyclohexane hydrogen storage lies in hydrogen supply, specifically the dehydrogenation process of cyclohexane. This reaction requires the catalyst to have suitable dehydrogenation activity to avoid excessive dehydrogenation as much as possible, and its hydrogenation activity should not be too high to suppress the occurrence of the reverse reaction. Chinese invention patent (CN108906031A) reports a method for dehydrogenation using a molybdenum-silica dehydrogenation catalyst. The results show that the conversion rate of methylcyclohexane dehydrogenation using the molybdenum-silica catalyst is 95.6%, and the selectivity for toluene is 86.5%. Furthermore, Chinese invention patent (CN104190456A) reports a method for dehydrogenation using a Ni2P catalyst. The results show that the conversion rate of cyclohexane dehydrogenation using the Ni2P catalyst is 98.5%, and the selectivity for toluene is 97.0%. Under the same reaction temperature, active metal content, and support environment, the reactivity of Mo-based and Ni₂P catalysts is significantly lower than that of Pt-based catalysts. This demonstrates that Pt exhibits higher low-temperature dehydrogenation activity compared to other noble metal catalysts and Ni and Mo oxide catalysts. However, while Pt-based catalysts have high activity, they suffer from rapid deactivation rates and are highly susceptible to deactivation due to carbon deposition or sintering, resulting in low stability. Developing novel catalysts and modifying existing dehydrogenation catalysts to explore efficient and energy-saving new dehydrogenation processes is of great significance for the application of organic liquid cyanide hydrogen storage materials. Summary of the Invention

[0004] To improve the selectivity and stability of cycloalkane dehydrogenation and to prepare a catalyst with excellent activity for cycloalkane dehydrogenation, this application first treats the original molecular sieve sample with alkali, and uses the resulting hierarchical porous molecular sieve as a catalyst support; one or more of the oxide promoter active components CaO, ZrO2, TiO2, BaO, La2O3, CeO2, and MgO are added to the support; the Pt metal active component and the oxide promoter active component on the support are loaded onto the support by impregnation.

[0005] According to one aspect of this application, a bimetallic catalyst is provided, comprising a hierarchical porous molecular sieve, a metal oxide promoter, and an active component Pt, wherein the metal oxide promoter and the active component Pt are supported on the hierarchical porous molecular sieve.

[0006] The active component Pt in the bimetallic catalyst accounts for 0.01 to 10 wt% of the hierarchical porous molecular sieve;

[0007] Optionally, the active component Pt in the bimetallic catalyst accounts for any value or a range between two values ​​from 0.01 wt%, 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt%, and 10 wt% of the hierarchical porous molecular sieve.

[0008] Optionally, the ratio of metal atoms in the metal oxide additive to the atomic ratio of the active component Pt is 1:0.01 to 100.

[0009] Optionally, the ratio of metal atoms in the metal oxide additive to the atomic ratio of the active component Pt is any ratio or a range between two ratios, which is 1:0.01, 1:01, 1:1, 1:10, 1:50, or 1:100.

[0010] Optionally, the metal oxide additive is selected from at least one of CaO, ZrO2, TiO2, BaO, La2O3, CeO2, and MgO.

[0011] According to another aspect of this application, a method for preparing a bimetallic catalyst is provided, comprising the following steps:

[0012] A) The parent molecular sieve is placed in a solution containing alkali for treatment, stirred, centrifuged and washed, dried (a), and calcined (a) to obtain a multi-level porous molecular sieve.

[0013] B) The multi-level porous molecular sieve is mixed with a salt solution containing auxiliary elements, impregnated in equal volume I, dried b, and calcined b to obtain an intermediate product;

[0014] C) The intermediate product is mixed with an aqueous platinum source, impregnated in equal volume II, dried c, and calcined c to obtain the bimetallic catalyst.

[0015] Optionally, in step A), the parent molecule is screened from at least one of ZSM-5 molecular sieve, Beta molecular sieve, ZSM-11 molecular sieve, and MOR molecular sieve.

[0016] Optionally, the alkali is selected from at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0017] Optionally, the concentration of the alkali-containing solution is 0.1 to 1.0 mol / L.

[0018] Optionally, the concentration of the alkali-containing solution is any value or a range between two of the following: 0.1 mol / L, 0.25 mol / L, 0.5 mol / L, 0.75 mol / L, and 1.0 mol / L.

[0019] Optionally, the solid-liquid ratio of the parent molecular sieve to the alkali-containing solution is 1g:10-50mL.

[0020] Optionally, the solid-liquid ratio of the parent molecular sieve to the alkali-containing solution is any value or a range between two values ​​from 1g:10mL, 1g:20mL, 1g:30mL, 1g:40mL, 1g:50mL.

[0021] Optionally, in step A), the salt solution containing the auxiliary element is a nitrate containing at least one of Ca, Zr, Ti, Ba, La, Ce, and Mg.

[0022] Optionally, the concentration of the salt solution containing the auxiliary element is 0.001 to 0.1 g / mL.

[0023] Optionally, the concentration of the salt solution containing the auxiliary element is any value among 0.001 g / mL, 0.01 g / mL, and 0.1 g / mL, or a range between two values.

[0024] Optionally, in step C), the platinum source is selected from at least one of H2PtCl6, Pt(NO3)2, and KPtCl.

[0025] Optionally, the concentration of the platinum source aqueous solution is 0.001–0.1 g / mL.

[0026] Optionally, in step C), the concentration of the platinum source aqueous solution is any value among 0.001 g / mL, 0.01 g / mL, and 0.1 g / mL, or a range between two values.

[0027] Optionally, in step A), the stirring temperature is 30–90°C, and the stirring time is 10–60 min.

[0028] Optionally, in step A), the stirring temperature is any value among 30°C, 45°C, 55°C, 70°C, and 90°C, or a range between two values.

[0029] Optionally, in step A), the stirring time is any value among 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min, or a range between two of these values.

[0030] Optionally, the temperature of the drying process a is 60–120°C.

[0031] Optionally, the temperature of the drying process a is any value among 60°C, 80°C, 100°C, and 120°C, or a range between two values.

[0032] Optionally, the temperature of calcination a is 500-700℃, and the calcination time is 2-8 hours.

[0033] Optionally, the temperature of the calcination a is any value among 500℃, 550℃, 600℃, 650℃, and 700℃, or a range between two values.

[0034] Optionally, the roasting time a is any value among 2h, 4h, 6h, and 8h, or a range between two values.

[0035] Optionally, in step B), the time for the equal-volume impregnation I is 12 to 24 hours.

[0036] Optionally, in step B), the time for the equal volume impregnation I is any value among 12h, 16h, 20h, and 24h, or a range between two values.

[0037] Optionally, the drying temperature b is 60–120°C.

[0038] Optionally, the temperature of the drying process b is any value among 60°C, 80°C, 100°C, and 120°C, or a range between two values.

[0039] Optionally, the temperature of calcination b is 500–1000°C, and the calcination time is 2–8 hours.

[0040] Optionally, the temperature of the calcination b is any value or a range between two of 500℃, 700℃, 800℃, 900℃, and 1000℃.

[0041] Optionally, the roasting time b is any value among 2h, 4h, 6h, and 8h, or a range between two values.

[0042] Optionally, the time for the equal-volume impregnation II is 12 to 24 hours.

[0043] Optionally, the time for the equal volume impregnation II is any value among 12h, 16h, 20h, and 24h, or a range between two values.

[0044] Optionally, the drying temperature is 60–120°C.

[0045] Optionally, the drying temperature c is any value among 60°C, 80°C, 100°C, and 120°C, or a range between two values.

[0046] Optionally, the calcination temperature is 500–700°C, and the calcination time is 2–8 hours.

[0047] Optionally, the temperature of the calcination c is any value among 500℃, 600℃, and 700℃, or a range between two values.

[0048] Optionally, the roasting time c is any value among 2h, 4h, 6h, and 8h, or a range between two values.

[0049] According to another aspect of this application, the application of the above-mentioned bimetallic catalyst in the dehydrogenation of cycloalkanes is provided, wherein a mixed gas containing nitrogen and cycloalkanes is contacted with the bimetallic catalyst to react and obtain the target product.

[0050] The cycloalkanes are selected from C6 to C6. 10 Cycloalkanes;

[0051] The target product includes benzene.

[0052] Optionally, the bimetallic catalyst is pre-reduced before use, with the pre-reduction temperature being 300–600°C and the pre-reduction time being 1–3 hours.

[0053] Optionally, the pre-reduction temperature is any value among 300℃, 400℃, 500℃, and 600℃, or a range between two values.

[0054] Optionally, the pre-restore time is any value among 1h, 2h, and 3h, or a range between two values.

[0055] Optionally, the molar ratio of nitrogen to cycloalkanes is 1 to 20:1.

[0056] Optionally, the molar ratio of nitrogen to cycloalkanes is any value among 1:1, 5:1, 10:1, 15:1, and 20:1, or a range between two values.

[0057] Optionally, the space velocity of the mixed gas is 5000–10000 h⁻¹. -1 .

[0058] Optionally, the space velocity of the mixed gas is 5000 h⁻¹. -1 7500h -1 10000h -1 Any value in the range or between two values.

[0059] Optionally, the reaction pressure is 0.1 to 0.5 MPa, and the reaction temperature is 250 to 350 °C.

[0060] Optionally, the reaction is carried out under hydrogen-containing conditions, with H2 and cycloalkanes (C6-C6) reacting. 10 The molar ratio of ) is 0 to 1:1.

[0061] The beneficial effects that this application can produce include:

[0062] 1) The bimetallic catalyst provided in this application has excellent reaction performance and good stability for the dehydrogenation reaction of cycloalkanes, with fast reaction rate, high yield and good catalyst regeneration performance.

[0063] 2) The preparation method of the bimetallic catalyst provided in this application is simple, highly operable, and can be used for large-scale industrial production. Detailed Implementation

[0064] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0065] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0066] Product analysis was performed using an Agilent 7890B gas chromatograph online. Organic compounds were analyzed using an FID detector (column: PEG-20M), and N2 and H2 were analyzed using a TCD detector (column: TDX-01).

[0067] In the embodiments of this application, the conversion rate and selectivity are calculated as follows:

[0068] In the embodiments of this application, the prepared catalyst was subjected to cyclohexane dehydrogenation testing. The conversion rate of cyclohexane and the selectivity of benzene were defined as follows:

[0069]

[0070]

[0071] As one embodiment, the preparation method of the catalyst for cyclohexane dehydrogenation is carried out according to the following steps:

[0072] (1) Add ZSM-5 molecular sieve to alkaline solution, stir at 50-85℃ for 20-40 min, centrifuge, wash, dry, and calcinate;

[0073] (2) Impregnate the aqueous solution of the auxiliary metal oxide with the hierarchical porous ZSM-5 obtained in step (1) in equal volume for 12-24 hours, and then dry and calcine to obtain the precursor modified with metal oxide.

[0074] (3) Impregnate H2PtCl6·6H2O with the precursor obtained in step (2) in equal volume, and after drying and calcination, obtain a bimetallic catalyst modified with metal oxide additives.

[0075] The parent molecular sieves in the following examples are all ZSM-5 molecular sieves.

[0076] Example 1: Preparation of Catalyst

[0077] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0073 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0159 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 1. # The loading of the active metal component Pt is 0.1 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 1:1.

[0078] Example 2 Preparation of Catalyst

[0079] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0365 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0159 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 2. #The loading of the active metal component Pt is 0.1 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0080] Example 3: Preparation of Catalyst

[0081] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0726 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0159 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 3. # The loading of the active metal component Pt is 0.1 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 10:1.

[0082] Example 4: Preparation of Catalyst

[0083] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0218 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0478 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 4. # The loading of the active metal component Pt is 0.3 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 1:1.

[0084] Example 5: Preparation of Catalyst

[0085] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.1089 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0478 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 5. # The loading of the active metal component Pt is 0.3 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0086] Example 6 Preparation of Catalyst

[0087] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.2179 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0478 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 6. # The loading of the active metal component Pt is 0.3 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 10:1.

[0088] Example 7 Preparation of Catalyst

[0089] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0363 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 7. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 1:1.

[0090] Example 8: Preparation of Catalyst

[0091] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.1816 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 8. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0092] Example 9 Preparation of Catalyst

[0093] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.3631 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 800°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 9. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 10:1.

[0094] Example 10 Preparation of Catalyst

[0095] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.1816 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 700°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 10. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0096] Example 11 Preparation of Catalyst

[0097] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it to 65°C in a water bath, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.1816 g of Ca(NO3)2·4H2O and add it dropwise to 6.00 g of the hierarchical porous molecular sieve and stir evenly. Impregnate for 12 h, place it in an oven at 120°C for 12 h, and calcine at 900°C for 4 h to obtain precursor 1. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined precursor 1 and impregnate for 12 h. Place the solution in an oven at 120°C for 12 h, and calcine at 550°C for 3 h. This is recorded as sample 11. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0098] Preparation of catalyst in Comparative Example 1

[0099] Take 300 ml of an aqueous solution containing 0.2 mol / L NaOH, heat it in a water bath to 65°C, add 10.00 g of the parent molecular sieve, stir at 65°C for 30 min, then centrifuge and wash until the washing solution is neutral. Dry the obtained molecular sieve solid at 120°C for 12 h, and calcine at 550°C for 3 h to obtain a hierarchical porous molecular sieve. Take 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O and add it dropwise to the calcined hierarchical porous molecular sieve for 12 h. Place the solution in an oven at 120°C for 12 h and calcine at 550°C for 3 h, and record this as sample 12. # The loading of the active metal component Pt is 0.5 wt%.

[0100] Preparation of catalyst in Comparative Example 2

[0101] Add 4.2 ml of a solution containing 0.1816 g of Ca(NO3)2·4H2O dropwise to 6.00 g of hierarchical porous molecular sieve and stir until homogeneous. Let it soak for 12 h, then place it in an oven at 120℃ for 12 h and calcine at 900℃ for 4 h to obtain precursor 1. Add 4.2 ml of a solution containing 0.0796 g of H2PtCl6·6H2O dropwise to the calcined precursor 1 and let it soak for 12 h. Place the solution in an oven at 120℃ for 12 h and calcine at 550℃ for 3 h, and record this as sample 13. # The loading of the active metal component Pt is 0.5 wt%, and the atomic ratio of the loaded CaO to the active component Pt is 5:1.

[0102] Examples 12-20: Application of the catalyst

[0103] Take 0.30g of the sample after tableting and sieving through a 40-60 mesh, and put it into a fixed-bed reactor. First, pretreat it at 550℃ for 60min in N2 atmosphere (30ml / min), then reduce it with H2 (100ml / min) for 60min, and then reintroduce N2 (30ml / min). After turning off H2, cool it to 300℃, feed cyclohexane (0.04ml / min) and react for 1h before analysis.

[0104] Application of catalysts in Comparative Examples 3-4

[0105] Take 0.30g of the sample after tableting and sieving through a 40-60 mesh, and put it into a fixed-bed reactor. First, pretreat it at 550℃ for 60min in a N2 atmosphere (30ml / min). Then, reduce it with H2 (100ml / min) for 60min, and then reintroduce N2 (30ml / min). After turning off H2, cool it down to 300℃, feed it with cyclohexane (0.04ml / min), and react for 1h before analysis.

[0106] Table 1 shows the activity evaluation results in the examples.

[0107] Example Sample number Ca / Pt Pt / ZSM-5 Ca / calcination temperature Conversion rate % Selectivity % Example 12 <![CDATA[Sample 1 # > 1 0.1wt% 800℃ 75.5 83.5 Example 13 <![CDATA[Sample 2 # > 5 0.1wt% 800℃ 77.2 80.9 Example 14 <![CDATA[Sample 4 # > 1 0.3wt% 800℃ 85.9 90.1 Example 15 <![CDATA[Sample 5 # > 5 0.3wt% 800℃ 86.7 92.8 Example 16 <![CDATA[Sample 7 # > 1 0.5wt% 800℃ 93.5 95.5 Example 17 <![CDATA[Sample 8 # > 5 0.5wt% 800℃ 98.9 99.5 Example 18 <![CDATA[Sample 9 # > 10 0.5wt% 800℃ 92.9 93.6 Example 19 <![CDATA[Sample 10 # > 5 0.5wt% 700℃ 89.3 93.5 Example 20 <![CDATA[Sample 11 # > 5 0.5wt% 900℃ 80.8 89.4 Comparative Example 3 <![CDATA[Sample 12 # > 0 0.5wt% 800℃ 85.9 89.3 Comparative Example 4 <![CDATA[Sample 13 # > 5 0.5wt% 800℃ 73.4 71.1

[0108] As can be seen from Table 1, Example 19 exhibits good activity and selectivity for the target product in the specific preparation method described above.

[0109] 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 method for preparing a bimetallic catalyst for the dehydrogenation of cyclohexane to benzene, characterized in that, Includes the following steps: A) The parent molecular sieve is placed in a solution containing alkali for treatment, stirred, centrifuged and washed, dried (a), and calcined (a) to obtain a hierarchical porous molecular sieve. The stirring temperature is 30~90℃, and the stirring time is 10~60min; The temperature of calcination a is 500~700℃, and the calcination time of a is 2~8h; The solid-liquid ratio of the parent molecular sieve to the alkali-containing solution is 1g:10~50mL; The concentration of the alkali-containing solution is 0.1~1.0 mol / L; B) The multi-level porous molecular sieve is mixed with a salt solution containing auxiliary elements, impregnated in equal volume I, dried b, and calcined b to obtain an intermediate product; The temperature of calcination b is 500~900℃, and the calcination time of b is 2~8h; C) The intermediate product is mixed with an aqueous platinum source, impregnated with an equal volume of II, dried c, and calcined c to obtain the bimetallic catalyst; in, In step A), the parent molecule is screened from at least one of ZSM-5 molecular sieve, Beta molecular sieve, ZSM-11 molecular sieve, and MOR molecular sieve; The alkali is selected from at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate; The bimetallic catalyst comprises a hierarchical porous molecular sieve, a metal oxide promoter, and an active component Pt, wherein the metal oxide promoter and the active component Pt are supported on the hierarchical porous molecular sieve. The active component Pt in the bimetallic catalyst accounts for 0.3~0.5 wt% of the hierarchical porous molecular sieve; The ratio of metal atoms to active component Pt in the metal oxide additive is 1:1~10; The metal oxide additive is selected from at least one of CaO, ZrO2, TiO2, BaO, La2O3, CeO2, and MgO.

2. The preparation method according to claim 1, characterized in that, In step B), the salt solution containing the auxiliary element is a nitrate containing at least one of Ca, Zr, Ti, Ba, La, Ce, and Mg.

3. The preparation method according to claim 1, characterized in that, In step B), the concentration of the salt solution containing the auxiliary element is 0.001~0.1 g / mL.

4. The preparation method according to claim 1, characterized in that, In step C), the platinum source is selected from at least one of H2PtCl6, Pt(NO3)2, and K2PtCl6.

5. The preparation method according to claim 1, characterized in that, In step C), the concentration of the platinum source aqueous solution is 0.001~0.1 g / mL.

6. The preparation method according to claim 1, characterized in that, In step A), the temperature of drying a is 60~120℃.

7. The preparation method according to claim 1, characterized in that, In step B), the time for the equal volume impregnation I is 12-24 hours.

8. The preparation method according to claim 1, characterized in that, In step B), the drying temperature is 60~120℃.

9. The preparation method according to claim 1, characterized in that, In step C), the time for the equal volume impregnation II is 12-24 hours.

10. The preparation method according to claim 1, characterized in that, In step C), the drying temperature is 60~120℃.

11. The preparation method according to claim 1, characterized in that, In step C), the temperature of calcination c is 500~700℃, and the calcination time is 2~8h.

12. The application of a bimetallic catalyst obtained by the preparation method according to any one of claims 1 to 11 in the dehydrogenation of cyclohexane to benzene, characterized in that, A mixture of nitrogen and cyclohexane is contacted with the bimetallic catalyst to react and obtain the target product, benzene.

13. The application according to claim 12, characterized in that, The bimetallic catalyst is pre-reduced before use. The pre-reduction temperature is 300~600℃ and the pre-reduction time is 1~3h.

14. The application according to claim 12, characterized in that, The molar ratio of nitrogen to cyclohexane is 1~20:

1.

15. The application according to claim 12, characterized in that, The space velocity of the mixed gas is 5000~10000 h⁻¹ -1 .

16. The application according to claim 12, characterized in that, The reaction pressure is 0.1~0.5MPa, and the reaction temperature is 250~350℃.

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