Preparation method and application of zirconium pillared montmorillonite loaded Ru-based catalyst

Abstract

The invention provides a preparation method of a zirconium pillared montmorillonite loaded Ru-based catalyst, which is applied to a reaction for preparing cyclohexene by partial hydrogenation of benzene. The montmorillonite has a large specific surface area, the zirconium oxide has good hydrophilicity, the excellent performance of the montmorillonite and the excellent performance of the zirconium oxide pillared montmorillonite are combined, and the catalyst carrier which is low in cost, high in specific surface area and high in hydrophilicity is prepared. Due to the special layered structure of the montmorillonite, exchangeable cations are contained between the layers and can be exchanged by Ru < 3 + > in the hydrothermal reaction process, Ru is anchored between the montmorillonite layers, and compared with an impregnation method for loading, the stability is higher. The loading capacity of the catalyst Ru used in the invention is far lower than that of a non-loaded Ru-based catalyst commonly used in industry, the raw material montmorillonite is cheap and easy to obtain, a large amount of alkaline wastewater is not generated in the preparation process, and the catalyst has the advantages of low cost, environmental friendliness and high stability.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical engineering, and in particular relates to a preparation method of a zirconium pillared montmorillonite-supported Ru-based catalyst and application thereof. Background Art

[0002] Cyclohexene is an important chemical raw material. Many important fine chemicals such as nylon, polyester, feed, medicine and pesticide can be produced with cyclohexene as raw material. In particular, nylon-66, which is widely used in automobile tires, electrical appliances, electronics and other industries, has broad application prospects in China. There are two process routes for nylon-6 and nylon-66, as follows. The traditional production route is: benzene is completely hydrogenated into cyclohexane, then oxidized into a mixture of cyclohexanol and cyclohexanone, and cyclohexanol is separated and dehydrogenated into cyclohexanone to prepare nylon. In this traditional route, cyclohexane oxidation belongs to a free radical reaction. Due to safety reasons, the conversion rate can only be controlled below 5%, and there are disadvantages such as many by-products, high energy consumption, low yield and low raw material utilization. The route of partially hydrogenating benzene to produce cyclohexene, and then hydrating and deoxygenating cyclohexene to cyclohexanone avoids the cyclohexane oxidation process. The by-product cyclohexane can be reused, and 1 / 3 less hydrogen can be consumed. It is an environmentally friendly, atomic economic, energy-saving and efficient chemical production process route. The two process routes of complete hydrogenation and partial hydrogenation are as follows: .

[0003] The catalyst commonly used in the partial hydrogenation of benzene to produce cyclohexene is a ruthenium-based catalyst. Most of the catalysts currently used in industry are non-loaded or highly loaded catalysts, and the production cost is relatively high. In order to reduce production costs, low-loaded ruthenium-based catalysts have become a research hotspot. CN103191732B discloses a preparation method of a catalyst for the partial hydrogenation of benzene to produce cyclohexene. The method prepares ruthenium, palladium, and zinc alloys by metallurgical molding, uses a large amount of precious metal materials, and the cost is relatively high and the conversion rate of benzene is not high. CN116764629A discloses a preparation method of a graphene-supported ruthenium-based catalyst. The catalyst is a supported catalyst, but with graphene as a carrier, the cost is relatively high, and the preparation method is also relatively complicated, which is not conducive to industrial production. The hydrotalcite carrier, which is studied more, will produce a large amount of alkaline wastewater during the preparation process, which is unfriendly to the environment, and the selectivity of cyclohexene is not high.

[0004] Montmorillonite has the characteristics of large specific surface area, strong adsorption, low price, easy raw material availability, easy modification, etc. It is an excellent catalyst carrier, but the precious metals loaded in the commonly used loading method are easy to fall off and the stability is not strong. 3+ Replacing the exchangeable cations between montmorillonite layers and then reducing them with hydrogen has stronger stability. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst and its application in the reaction of partial hydrogenation of benzene to produce cyclohexene.

[0006] The present invention adopts the following technical solution: A method for preparing a zirconium pillared montmorillonite-supported Ru-based catalyst, characterized in that the catalyst carrier is zirconium pillared montmorillonite, comprising the following steps: (1) Add montmorillonite to pure water and stir evenly to obtain a montmorillonite suspension with a mass fraction of 1-5%; (2) adding ZrOCl2·8H2O into pure water, stirring in a water bath at 70-100°C for 2-6 h, and cooling to room temperature to obtain a zirconium crosslinking agent; (3) Add the zirconium crosslinking agent dropwise to the montmorillonite suspension under vigorous stirring, stir for 4-6 hours, let stand for 8-12 hours, filter, dry in an oven at 60-100°C for 8-16 hours, grind evenly, and then calcine at high temperature for 2-3 hours. The calcination temperature is 400-600°C and the heating rate is 2-5°C / min to obtain zirconium pillared montmorillonite Zr-MMT; (4) Dispersing the zirconium pillared montmorillonite Zr-MMT into pure water, adding RuCl3 and CTAB, stirring thoroughly, and then conducting a hydrothermal reaction. Finally, filtering, washing, drying, and reducing, the zirconium pillared montmorillonite supported Ru-based catalyst Ru / Zr-MMT is obtained.

[0007] The mass fraction of montmorillonite in the suspension in step (1) is 1-5%.

[0008] In the step (2), the water bath temperature is 70-100°C.

[0009] In the step (3), the drying temperature is 60-100°C, the drying time is 8-16 h, the roasting temperature is 400-600°C, and the heating rate is 2-5°C / min.

[0010] In the step (4), the hydrothermal reaction temperature is 150-170°C and the reaction time is 2-4 h.

[0011] In the step (4), the amount of RuCl3 added is 1-20% of the mass of Zr-MMT, and the amount of CTAB added is 30-50% of the mass of Zr-MMT.

[0012] In the step (4), the reduction method is to use hydrogen reduction, the reduction temperature is 250-350°C, and the reduction time is 2-3 hours.

[0013] The loading amount of Ru in the zirconium pillared montmorillonite-supported Ru-based catalyst is 1-10%, and more preferably 5%.

[0014] The present invention provides a method for preparing the above-mentioned zirconium pillared montmorillonite supported Ru-based catalyst and application thereof in the reaction of preparing cyclohexene by partial hydrogenation of benzene.

[0015] The beneficial effects of the present invention are: The present invention uses zirconium oxide pillared montmorillonite, combines the excellent hydrophilicity of zirconium oxide with the high specific surface area of ​​montmorillonite, and applies it to the carrier of the catalyst for partial hydrogenation of benzene to cyclohexene, thereby preparing a low-load catalyst with strong stability. Due to the special layered structure of montmorillonite, there are exchangeable cations between the layers, which can be replaced by Ru in the hydrothermal process. 3+ Exchange, Ru is anchored to the interlayer of montmorillonite, and has strong stability; compared with traditional catalysts, the catalyst carrier raw materials are easily available and low in price, the catalyst preparation process is simpler, environmentally friendly, economical and effective, and has high industrial application value. DETAILED DESCRIPTION

[0016] The embodiments of the present invention are described in detail below. The embodiments are intended to explain the present invention but are not to be construed as limiting the present invention.

[0017] Example 1 Weigh 2.08 g ZrOCl2·8H2O, add 80 mL pure water, stir in a water bath at 85℃ for 3 h, and cool to obtain a zirconium crosslinker. Weigh 4 g sodium montmorillonite and disperse it in 200 mL pure water. Slowly drop the zirconium crosslinker into the dispersion under vigorous stirring, stir for 4 h and then stand for 8 h. Filter the obtained mixture, dry it, grind it, and calcine it in a muffle furnace at a heating rate of 5℃ / min to 500℃ for 2 h to obtain zirconium pillared montmorillonite with a zirconium oxide content of 20%, which is recorded as 20%Zr-MMT.

[0018] Weigh 2 g of 20% Zr-MMT and disperse it in 70 mL of pure water. Add 0.2161 g RuCl3 and 0.8 g hexadecyltrimethylammonium bromide (CTAB) and stir for 2 h. Then transfer the mixture to a 100 mL hydrothermal reactor and perform hydrothermal reaction at 160 °C for 3 h. After the reaction, filter and wash the precipitate until no chloride ions are detected, dry it at 80 °C, and finally reduce it with hydrogen at 300 °C for 2 h in a reduction furnace to obtain the target catalyst, which is recorded as 5% Ru / 20% Zr-MMT.

[0019] Embodiment 2: The other conditions were the same as those in Example 1, except that the mass of ZrOCl2·8H2O was changed to 0 g, and the target catalyst was recorded as 5%Ru / 0%Zr-MMT.

[0020] Embodiment 3: Other conditions were the same as in Example 1, except that the mass of ZrOCl2·8H2O was changed to 1.04 g, and the target catalyst was recorded as 5%Ru / 10%Zr-MMT.

[0021] Embodiment 4: Other conditions were the same as in Example 1, except that the mass of ZrOCl2·8H2O was changed to 3.12 g, and the target catalyst was recorded as 5%Ru / 30%Zr-MMT.

[0022] Embodiment 5: Other conditions were the same as in Example 1, except that the mass of ZrOCl2·8H2O was changed to 4.16 g, and the target catalyst was recorded as 5%Ru / 40%Zr-MMT.

[0023] Example 6 The other conditions were the same as in Example 1, except that CTAB was replaced by ethylenediaminetetraacetic acid (EDTA).

[0024] Example 7 The other conditions were the same as in Example 1, except that CTAB was replaced by polyvinylpyrrolidone (PVP).

[0025] Performance Test: The reactor used in the present invention is a high-pressure reactor with an inner lining volume of 500 mL and equipped with automatic temperature control and mechanical stirring functions. 0.5 g of catalyst, 100 mL of pure water and 2 g of ZnSO4·7H2O are added to the inner lining, and 50 mL of benzene is added to the feed tank. Subsequently, hydrogen is repeatedly purged 5 times to exhaust the air in the reactor. The reaction conditions are 150°C, 5 MPaH2 pressure, and 1000 rpm. When the temperature rises to the set temperature, the benzene in the feed tank is added to the inner lining, the reaction is started, and a sample is taken every 10 min. All products are analyzed by gas chromatography, the chromatographic column is a PEG capillary column, and the detector is FID.

[0026] Table 1, benzene conversion, cyclohexene selectivity and yield when the catalysts prepared in Examples 1-5 were used for partial hydrogenation of benzene for 30 min.

[0027]

[0028] Stability test: After the performance test of the 5%Ru / 20%Zr-MMT catalyst, the catalyst in the autoclave was collected by centrifugation and used for the second cycle. The collected catalyst was added to the autoclave. Other conditions were the same as the performance test method. One repetition was one cycle.

[0029] Table 2, Stability test of the catalyst prepared in Example 1 for partial hydrogenation of benzene

[0030] The above description is only a typical implementation of the present invention, and all improvements and modifications made according to the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst, characterized in that: The following steps are involved: (1) Add montmorillonite into pure water and stir evenly to obtain a montmorillonite suspension; (2) Add ZrOCl2·8H2O to pure water, stir in a water bath for 2-6 h, and cool to room temperature to obtain a zirconium crosslinking agent; (3) Add the zirconium crosslinking agent dropwise into the montmorillonite suspension under vigorous stirring, stir for 4-6 hours, let stand for 8-12 hours, filter, dry, grind evenly, and then calcine at high temperature for 2-3 hours to obtain zirconium pillared montmorillonite Zr-MMT; (4) Dispersing the zirconium pillared montmorillonite Zr-MMT into pure water, adding RuCl3 and CTAB, stirring thoroughly, and then conducting a hydrothermal reaction. Finally, filtering, washing, drying, and reducing, the zirconium pillared montmorillonite supported Ru-based catalyst Ru / Zr-MMT is obtained.

2. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to claim 1, characterized in that: The mass fraction of montmorillonite in the suspension in step (1) is 1-5%.

3. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to claim 1, characterized in that: The water bath temperature in step (2) is 70-100°C.

4. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to the claims, characterized in that: In step (3), the drying temperature is 60-100°C, the drying time is 8-16 h, the roasting temperature is 400-600°C, and the heating rate is 2-5°C / min.

5. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to the claims, characterized in that: In step (4), the hydrothermal reaction temperature is 150-170°C and the reaction time is 2-4 h.

6. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to claim 1, characterized in that: The amount of RuCl3 added in step (4) is 1-20% of the mass of Zr-MMT.

7. A method for preparing a zirconium pillared montmorillonite supported Ru-based catalyst according to claim 1, characterized in that: In step (4), the reduction method is to use hydrogen reduction, the reduction temperature is 250-350°C, and the reduction time is 2-3 h.

8. The zirconium pillared montmorillonite supported Ru-based catalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The loading amount of Ru in the zirconium pillared montmorillonite-supported Ru-based catalyst is 1-10%.

9. Use of the zirconium pillared montmorillonite supported Ru-based catalyst according to claim 8 in the reaction of partial hydrogenation of benzene to cyclohexene.

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