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

Abstract

The present invention provides a method for preparing a Ru-based catalyst supported by zirconium pillared montmorillonite, which is used in the partial hydrogenation of benzene to cyclohexene. Montmorillonite has a large specific surface area, and zirconium oxide has good hydrophilicity. By combining the excellent properties of the two, zirconium oxide pillared montmorillonite is used to prepare a low-cost, high specific surface area, and highly hydrophilic catalyst carrier. Due to the special layered structure of montmorillonite, the interlayers contain exchangeable cations, which can be absorbed by Ru during the hydrothermal reaction. 3+ The Ru is anchored to the interlayers of montmorillonite during the exchange process, resulting in greater stability compared to impregnation loading. The Ru loading of the catalyst used in this patent is far lower than that of the unsupported Ru-based catalysts commonly used in industry. Furthermore, the raw material montmorillonite is inexpensive and readily available, and the preparation process does not produce a large amount of alkaline wastewater. This method has the advantages of low cost, environmental friendliness, and strong stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical industry, 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 used to produce a variety of important fine chemicals, including nylon, polyester, feed, pharmaceuticals, and pesticides. Nylon-6,6, in particular, is widely used in the automotive, tire, electrical, and electronics industries and holds broad application prospects in China. There are two production routes for nylon-6 and nylon-6, as follows. The traditional production route involves complete hydrogenation of benzene to cyclohexane, followed by oxidation to a mixture of cyclohexanol and cyclohexanone. The cyclohexanol is separated and then dehydrogenated to cyclohexanone, which is then used to produce nylon. In this traditional route, cyclohexane oxidation is a free radical reaction, and due to safety concerns, the conversion rate can only be controlled below 5%. This route also suffers from numerous byproducts, high energy consumption, low yield, and low raw material utilization. The partial hydrogenation of benzene to cyclohexene, followed by hydration and deoxygenation of the cyclohexene to cyclohexanone, avoids the cyclohexane oxidation process, allows for reuse of the byproduct cyclohexane, and reduces hydrogen consumption by one-third, offering an environmentally friendly, atom-efficient, energy-efficient, and highly efficient chemical production process. The two process routes of complete hydrogenation and partial hydrogenation are as follows:

[0003] .

[0004] 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-supported or highly supported 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. This method prepares ruthenium, palladium, and zinc alloys by metallurgical molding, uses a large amount of precious metal materials, is costly, and the conversion rate of benzene is not high. CN116764629A discloses a preparation method of a graphene-supported ruthenium-based catalyst. This catalyst is a supported catalyst, but uses graphene as a carrier, is costly, and the preparation method is also complex, which is not conducive to industrial production. The hydrotalcite carrier, which has been studied more, produces a large amount of alkaline wastewater during the preparation process, is environmentally unfriendly, and the selectivity of cyclohexene is also not high.

[0005] Montmorillonite has the characteristics of large specific surface area, strong adsorption, low price, easy to obtain raw materials, easy to modify, etc. It is an excellent catalyst carrier, but the commonly used loading method easily causes the precious metal to fall off and has low stability. 3+ Replacing the exchangeable cations between montmorillonite layers and then reducing them with hydrogen has stronger stability. Summary of the Invention

[0006] 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 partial hydrogenation of benzene to cyclohexene.

[0007] The present invention adopts the following technical solutions:

[0008] 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:

[0009] (1) Add montmorillonite to pure water and stir evenly to obtain a montmorillonite suspension with a mass fraction of 1-5%;

[0010] (2) Add ZrOCl2·8H2O to pure water, stir in a water bath at 70-100°C for 2-6 hours, and cool to room temperature to obtain a zirconium crosslinking agent;

[0011] (3) Add the zirconium crosslinking agent dropwise to the montmorillonite suspension under vigorous stirring, stir for 4-6 hours, let it stand for 8-12 hours, filter, dry in an oven at 60-100℃ for 8-16 hours, grind it evenly, and then calcine it at high temperature for 2-3 hours. The calcination temperature is 400-600℃ and the heating rate is 2-5℃ / min to obtain zirconium pillared montmorillonite Zr-MMT.

[0012] (4) Dispersing the zirconium pillared montmorillonite Zr-MMT into pure water, adding RuCl3 and CTAB and 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.

[0013] The mass fraction of montmorillonite in the suspension in step (1) is 1-5%.

[0014] The water bath temperature in step (2) is 70-100°C.

[0015] 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.

[0016] In step (4), the hydrothermal reaction temperature is 150-170°C, and the reaction time is 2-4 h.

[0017] In 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.

[0018] 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.

[0019] The Ru loading amount in the zirconium pillared montmorillonite-supported Ru-based catalyst is 1-10%, more preferably 5%.

[0020] The present invention provides a preparation method of the above-mentioned zirconium pillared montmorillonite-supported Ru-based catalyst and its application in the reaction of partially hydrogenating benzene to produce cyclohexene.

[0021] The beneficial effects of the present invention are:

[0022] The present invention uses zirconium oxide pillared montmorillonite, combined with the excellent hydrophilicity of zirconium oxide and the high specific surface area of ​​montmorillonite, to form a catalyst carrier for the 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 during the hydrothermal process. 3+ Exchange, Ru is anchored to the interlayer of montmorillonite, with strong stability; compared with traditional catalysts, the catalyst carrier raw materials are easily available and low-priced, the catalyst preparation process is simple, environmentally friendly, economical and effective, and has high industrial application value. DETAILED DESCRIPTION

[0023] The following describes in detail embodiments of the present invention. The embodiments are intended to explain the present invention but are not to be construed as limiting the present invention.

[0024] Example 1

[0025] 2.08 g of ZrOCl2·8H2O was weighed and added to 80 mL of pure water. The mixture was stirred in an 85°C water bath for 3 h and cooled to obtain a zirconium crosslinker. 4 g of sodium montmorillonite was dispersed in 200 mL of pure water. The zirconium crosslinker was slowly added dropwise to the dispersion under vigorous stirring. The mixture was stirred for 4 h and then allowed to stand for 8 h. The resulting mixture was filtered, dried, ground, and calcined in a muffle furnace at a heating rate of 5°C / min to 500°C for 2 h to obtain zirconium pillared montmorillonite with a 20% zirconium oxide content, designated as 20%Zr-MMT.

[0026] 2 g of 20% Zr-MMT was weighed and dispersed in 70 mL of pure water. 0.2161 g of RuCl3 and 0.8 g of cetyltrimethylammonium bromide (CTAB) were added and stirred for 2 h. The mixture was then transferred to a 100 mL hydrothermal reactor and hydrothermally reacted at 160°C for 3 h. After the reaction, the precipitate was filtered and washed until no chloride ions were detected, dried at 80°C, and finally reduced with hydrogen in a reduction furnace at 300°C for 2 h to obtain the target catalyst, which was recorded as 5% Ru / 20% Zr-MMT.

[0027] Example 2:

[0028] 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.

[0029] Example 3:

[0030] 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.

[0031] Example 4:

[0032] 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.

[0033] Example 5:

[0034] 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.

[0035] Example 6

[0036] Other conditions were the same as in Example 1, except that CTAB was replaced with ethylenediaminetetraacetic acid (EDTA).

[0037] Example 7

[0038] Other conditions were the same as in Example 1, except that CTAB was replaced with polyvinylpyrrolidone (PVP).

[0039] Performance testing:

[0040] The reactor used in this invention is a high-pressure reactor with a 500 mL liner volume and equipped with automatic temperature control and mechanical stirring. 0.5 g of catalyst, 100 mL of pure water, and 2 g of ZnSO₄·7H₂O were added to the liner, and 50 mL of benzene was added to the feed tank. The reactor was then purged with hydrogen five times to expel air from the interior. The reaction conditions were 150°C, 5 MPaH₂ pressure, and 1000 rpm. When the temperature reached the set point, the benzene from the feed tank was added to the liner, and the reaction was initiated. Samples were taken every 10 minutes. All products were analyzed by gas chromatography using a PEG capillary column and an FID detector.

[0041] Table 1 shows the benzene conversion, cyclohexene selectivity and yield of the catalysts prepared in Examples 1-5 when used in the partial hydrogenation of benzene for 30 min.

[0042]

[0043] Stability test:

[0044] After the performance test of the 5%Ru / 20%Zr-MMT catalyst, the catalyst in the autoclave was centrifuged and collected for a second cycle. The collected catalyst was added to the autoclave. Other conditions were the same as the performance test method. This was repeated once, which constituted one cycle.

[0045] Table 2, Stability test of the catalyst prepared in Example 1 for partial hydrogenation of benzene

[0046]

[0047] The above description is only a typical embodiment of the present invention, and any improvements and modifications made based on the present invention should also be considered to be within the scope of protection 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 to 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 to the montmorillonite suspension under vigorous stirring, stir for 4-6 hours, let it 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 and stirring thoroughly, and then conducting a hydrothermal reaction. The hydrothermal reaction temperature is 150-170 ° C, and the reaction time is 2-4 h. Finally, the zirconium pillared montmorillonite supported Ru-based catalyst Ru / Zr-MMT is obtained after filtration, washing, drying, and reduction. The reduction method is to use hydrogen reduction, the reduction temperature is 250-350 ° C, and the reduction time is 2-3 h.

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

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

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

6. The zirconium pillared montmorillonite-supported Ru-based catalyst prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The loading amount of Ru in the zirconium pillared montmorillonite-supported Ru-based catalyst is 1-10%.

7. Use of the zirconium pillared montmorillonite-supported Ru-based catalyst according to claim 6 in the partial hydrogenation of benzene to cyclohexene.

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