Preparation method and application of alumina supported catalyst

Abstract

The invention provides a preparation method of an alumina supported catalyst and application of the alumina supported catalyst in a reaction for preparing cyclohexene through partial hydrogenation of benzene. Due to the fact that the surface of the carrier is rich in various charged ions after alkali treatment, metal can be evenly distributed on the surface of the carrier in the loading process, and therefore the high-dispersion Ru-based catalyst is obtained. According to the catalyst, the content of metal Ru is far lower than that of a traditional industrial RuZn catalyst, the cost advantage is more excellent, and large economic value is provided for subsequent industrial application of the catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for preparing an alumina-supported catalyst and application of the catalyst in a reaction of partially hydrogenating benzene to produce cyclohexene. Background Art

[0002] Cyclohexene is an important fine chemical that can be used as an intermediate in the production of chemicals such as medicines, pesticides, dyes, and detergents. In the production of caprolactam, cyclohexene can be hydrated to produce cyclohexanol, cyclohexanol can be oxidized and dehydrated to produce cyclohexanone, cyclohexanone can be ammoximated to produce cyclohexanone oxime, and then the molecules are rearranged to produce caprolactam. At present, the production methods of cyclohexene include partial hydrogenation of benzene to produce cyclohexene, dehydration of cyclohexanol, dehydrogenation of cyclohexane, and Birch reduction. Since the partial hydrogenation of benzene to produce cyclohexene is simple and has low production costs, it is often used in industrial production of cyclohexene.

[0003] Cyclohexene has a C=C double bond and is chemically active. It is easy to deeply hydrogenate to produce cyclohexane during the hydrogenation process. Therefore, the partial hydrogenation of benzene to produce cyclohexene is thermodynamically easier to produce cyclohexane. In order to increase the yield of cyclohexene, it is necessary to select a suitable catalytic system to avoid excessive hydrogenation of the product to produce cyclohexane. For example, Liu et al. [Liu jie, et al. Chemcatchem 2015; 7: 846-855] deposited Cu on Ru / MgAl-LDH and deposited Cu on low-coordinated Ru to reduce the catalyst hydrogenation ability, thereby increasing the cyclohexene yield. Compared with the blank sample, the cyclohexene yield of the Cu-promoted Ru catalyst increased from 27.5% to 44.0% at most. Song et al. [Song yihui, et al. Chemcatchem 2022; 14:1-11] introduced Zn into LiAl-LDH and constructed Ru 0 / Ru δ+ -O-Zn structure, and the use of abundant hydroxyl groups on the surface of LDH to improve the cyclohexene yield of the catalyst, the maximum cyclohexene yield can reach 43.2%. Zhou et al. [Zhou gongbing, et al. Chemcatchem 2018; 10: 1184-1191] reduced Ru by Zn powder 3+ ions, and hydrochloric acid treatment to dissolve excess metal Zn, thereby preparing a RuZn catalyst. Patent CN106140154B puts forward a completely opposite conclusion, believing that the proportion of catalyst pores in the range of 2~15 nm should be less than 50%, which is conducive to the formation of cyclohexene and can improve the stability of the catalyst. When the Ru content is 5 wt%, a catalytic activity of 50-80 (i.e., a conversion rate of 50% and a cyclohexene selectivity of 80%) can be obtained. Summary of the invention

[0004] The present invention aims to provide a method for preparing an alumina-supported catalyst, which is mainly used for partial hydrogenation of benzene to produce cyclohexene. Compared with the traditional RuZn catalyst (with a metal Ru content of more than 90 wt%), the catalyst provided by the present invention has the advantages of low metal Ru content and low catalyst cost burden, and has a price advantage in large-scale industrial applications.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A method for preparing an alumina-supported catalyst comprises the following steps: (1) treating the alumina support with alkali; (2) measuring the isoelectric point of the alumina support after alkali treatment; (3) mixing and stirring the alkali-treated alumina carrier with water; (4) Add Ru salt, adjust pH, and continue stirring; (5) After all the Ru salt is adsorbed, a reducing agent is added to obtain an alumina-supported ruthenium-based catalyst Ru-Al2O3.

[0006] The alkali treatment in step (1) is specifically as follows: dispersing the alumina carrier in a 0.8-1.2 mol / L alkali solution, heating and refluxing at 75-90°C for 10-15 h, and drying to obtain the alkali-treated alumina carrier; preferably, dispersing the alumina carrier in a 1 mol / L alkali solution, heating and refluxing at 80°C for 12 h, and drying to obtain the alkali-treated alumina carrier.

[0007] The base is one or more of Na2CO3, NaOH, ammonia water or hexamethylenetetramine.

[0008] The determination of the isoelectric point in step (2) is specifically as follows: a certain amount of water is measured, the pH of the solution is adjusted with HCl or NaOH, the initial pH of the solution is adjusted to 1-13, a certain amount of dry Al2O3 is weighed each time and added to the adjusted pH solution, after stirring for 1 hour, the final pH of the solution after stirring is recorded, and the pH at the platform is the isoelectric point; wherein the mass ratio of water to Al2O3 is 10:1.

[0009] The Ru salt is one or more of RuCl3, Ru(NH3)6Cl3, Ru(acac)3 or Ru(NO)(NO3)3.

[0010] In step (4), the pH is adjusted using ammonia water or dilute sulfuric acid, and the adjusted pH = isoelectric point ± (0.5 ~ 4.0); the isoelectric point is the isoelectric point measured in step (2).

[0011] In the Ru-Al2O3, the loading amount of metal Ru is 0.5 wt%~5.0 wt%.

[0012] The stirring time in step (3) is 1 to 3 h, preferably 2 h; the stirring time in step (4) is 2 to 3.5 h, preferably 3 h.

[0013] An alumina-supported catalyst for partial hydrogenation of benzene to cyclohexene.

[0014] The beneficial effects of the present invention are as follows: The present invention provides a method for preparing an alumina-supported catalyst and its application in the reaction of preparing cyclohexene by partial hydrogenation of benzene. Thanks to the alkali treatment of the alumina carrier, the carrier surface is rich in various charged ions. These charged ions can be evenly distributed on the carrier surface during the adsorption of metal ions, thereby avoiding the agglomeration of metals and finally preparing a highly dispersed Ru-based catalyst. Benefiting from the high dispersion of metals, the Ru-based catalyst involved in the present invention can obtain a higher cyclohexene yield under the condition of a lower metal loading. DETAILED DESCRIPTION

[0015] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0016] The present invention provides a method for preparing an alumina supported catalyst, which is applied to the reaction of preparing cyclohexene by partial hydrogenation of benzene. In the present invention, the catalytic performance evaluation device used is a kettle reactor, which is similar to the production device of preparing cyclohexene by partial hydrogenation of benzene in industrial production.

[0017] In the present invention, unless otherwise specified, the evaluation method for preparing cyclohexene by partial hydrogenation of benzene is as follows: a certain amount of catalyst and water are taken, loaded into a kettle reactor, filled with hydrogen and then emptied, and this process is repeated three times to exhaust the air in the kettle. After the pressure is held down and leaks are detected, the reaction temperature is raised, and after reaching the target temperature, benzene is added to start the timing reaction.

[0018] In the present invention, unless otherwise specified, the reaction conditions for partial hydrogenation of benzene to produce cyclohexene are: 5.0 MPa, 140°C, rotation speed 1000 r / min, catalyst 1.5 g, benzene 50 mL, water 100 mL, and zinc sulfate 3 g.

[0019] In the present invention, unless otherwise specified, the benzene conversion rate and cyclohexene selectivity listed in Table 1 are obtained under the condition that the conversion rate is about 50 mol %.

[0020] In the present invention, the isoelectric point determination operation is specifically as follows: a certain amount of water is measured, the pH of the solution is adjusted with HCl or NaOH, the initial pH of the solution is adjusted to different gradients of 1 to 13, a certain amount of dry Al2O3 is weighed each time and added to the adjusted pH solution, after stirring for 1 hour, the final pH of the solution after stirring is recorded, and the pH at the platform is the isoelectric point. Among them, the mass ratio of water to Al2O3 is 10:1.

[0021] To further illustrate the present invention, the following embodiments are described in detail, but the protection scope of the present invention is not limited to the following embodiments.

[0022] Example 1 Preparation of alumina: Weigh 60 g Al(NO3)3·9H2O and dissolve it in deionized water. Add 10 g urea. After it is completely dissolved, put it into a hydrothermal kettle, hydroheat it at 120℃ for 24 h, filter and dry it, and finally roast it at 600℃ for 5 h. The result is alumina.

[0023] Alkali treatment: The above-mentioned alumina carrier was dispersed in 1 mol / L Na2CO3 solution, heated under reflux at 80°C for 12 h, and the obtained alumina carrier was dried to obtain an alkali-treated alumina carrier.

[0024] Weigh 1 g of the alkali-treated alumina support and measure the isoelectric point of the alumina support according to the above method. The isoelectric point of the support was 6.5.

[0025] Weigh 10 g of the above-mentioned alkali-treated alumina support, add it to 100 mL of deionized water, stir for 2 h, then add 0.63 g of RuCl3, adjust the pH to 7.5 with ammonia water, stir for 3 h, and after all the metals are adsorbed, add KBH4. After reduction, the result is a ruthenium-based catalyst supported on alumina, which is recorded as Ru-Al2O3. The loading amount of metal Ru is 3.0 wt%, and the amount of KBH4 is four times that of RuCl3.

[0026] Example 2 Weigh 20 g of commercial Al2O3 carrier (Yichang Supeng Technology Co., Ltd., model A06), calcine it at 600 °C for 5 h, and then use it as a catalyst carrier.

[0027] The above-mentioned alumina support was dispersed in 1 mol / L Na2CO3 solution, heated under reflux at 80°C for 12 h, and dried to obtain an alkali-treated alumina support.

[0028] Weigh 1 g of the above aluminum oxide, and measure the isoelectric point of the aluminum oxide carrier according to the method described in the Summary of the Invention. The isoelectric point of the carrier is 7.3.

[0029] Weigh 10 g of the above alumina support, add it to 100 mL of deionized water, stir for 2 h, add RuCl3, adjust the pH to 8.0 with ammonia water, stir for 3 h, and after all the metals are adsorbed, add KBH4, and after reduction, the result is the alumina-supported ruthenium-based catalyst. The loading amount of metal Ru is 3.0 wt%, and the amount of KBH4 is four times that of RuCl3.

[0030] Example 3 An alumina-supported ruthenium-based catalyst was prepared with reference to Example 1. The difference from Example 1 was that the pH in this example was 9.5.

[0031] Example 4 The alumina-supported ruthenium-based catalyst was prepared with reference to Example 1. The difference from Example 1 was that the pH in this example was 10.5.

[0032] Example 5 An alumina-supported ruthenium-based catalyst was prepared with reference to Example 1. The difference from Example 1 is that the Ru salt in this example is Ru(NH3)6Cl3.

[0033] Example 6 The alumina-supported ruthenium-based catalyst was prepared with reference to Example 2. The difference from Example 2 was that the pH in this example was 9.5.

[0034] Example 7 An alumina-supported ruthenium-based catalyst was prepared with reference to Example 2. The difference from Example 2 was that the pH in this example was 11.

[0035] Example 8 An alumina-supported ruthenium-based catalyst was prepared with reference to Example 2. The difference from Example 2 is that the Ru salt in this example is Ru(NH3)6Cl3.

[0036] Example 9 The alumina-supported ruthenium-based catalyst was prepared with reference to Example 1. The difference from Example 1 is that the alkali solution in this example is hexamethylenetetramine.

[0037] Example 10 An alumina-supported ruthenium-based catalyst was prepared with reference to Example 2. The difference from Example 2 was that the loading amount of metallic ruthenium in this example was 5.0 wt%.

[0038] Embodiment 11 The alumina-supported ruthenium-based catalyst was prepared with reference to Example 1. The difference from Example 1 is that in this example, dilute sulfuric acid was used to control the pH to 5.0.

[0039] Example 12 The alumina-supported ruthenium-based catalyst was prepared with reference to Example 2. The difference from Example 2 was that in this example, dilute sulfuric acid was used to control the pH to 5.0.

[0040] Comparative Example 1 Alumina was prepared according to the preparation method of alumina in Example 1. After the preparation of alumina was completed, 10 g was weighed and added to 100 mL of deionized water. After stirring for 2 h, RuCl3 was added. After it was completely dissolved, KBH4 was added. After reacting for 1 h, it was filtered to obtain a ruthenium-based catalyst supported on alumina. Among them, the loading amount of metal Ru was 3.0 wt%, and the amount of KBH4 was four times that of RuCl3.

[0041] Comparative Example 2 Weigh 10 g of commercial Al2O3 carrier (Yichang Supeng Technology Co., Ltd., model A06), add it to 100 mL of deionized water, stir for 2 h, add RuCl3, after it is completely dissolved, add KBH4, react for 1 h, and filter to obtain alumina-supported ruthenium-based catalyst. The loading amount of metal Ru is 3.0 wt%, and the amount of KBH4 is four times that of RuCl3.

[0042] The above samples were subjected to partial hydrogenation activity evaluation of benzene. The evaluation conditions were as described above. The catalytic activity test results are listed in Table 1.

[0043] Table 1 Performance results of partial hydrogenation of benzene in Example

[0044] From the implementation results, the Ru-based catalyst prepared by the method involved in this patent has a higher cyclohexene yield than the comparative example. This is mainly due to the formation of abundant charged ions on the carrier surface after alkali treatment. These charged ions can evenly adsorb metal ions on the carrier surface during the metal loading process, thereby preparing a highly dispersed Ru-based catalyst. This high dispersion of metal Ru enables the Ru-based catalyst involved in this patent to obtain a higher cyclohexene yield at a lower metal Ru loading. Compared with the traditional industrial RuZn catalyst (Ru content of 90 wt%~95 wt%), the catalyst invented by this patent has a lower cost advantage.

Claims

1. A method for preparing an alumina supported catalyst, characterized in that: The following steps are involved: (1) treating the alumina support with alkali; (2) measuring the isoelectric point of the alumina support after alkali treatment; (3) mixing and stirring the alkali-treated alumina carrier with water; (4) Add Ru salt, adjust pH, and continue stirring; (5) After all the Ru salt is adsorbed, a reducing agent is added to obtain an alumina-supported ruthenium-based catalyst Ru-Al2O3.

2. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The alkali treatment in step (1) is specifically as follows: dispersing the alumina carrier in a 0.8-1.2 mol / L alkali solution, heating and refluxing at 75-90° C. for 10-15 h, and drying to obtain an alkali-treated alumina carrier.

3. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The alkali treatment in step (1) is specifically as follows: dispersing the alumina carrier in a 1 mol / L alkali solution, heating under reflux at 80° C. for 12 h, and drying to obtain an alkali-treated alumina carrier.

4. The method for preparing an alumina-supported catalyst according to claim 2 or 3, characterized in that: The base is one or more of Na2CO3, NaOH, ammonia water or hexamethylenetetramine.

5. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The determination of the isoelectric point in step (2) is specifically as follows: a certain amount of water is measured, the pH of the solution is adjusted with HCl or NaOH, the initial pH of the solution is adjusted to 1-13, a certain amount of dry Al2O3 is weighed each time and added to the adjusted pH solution, after stirring for 1 hour, the final pH of the solution after stirring is recorded, and the pH at the platform is the isoelectric point; wherein the mass ratio of water to Al2O3 is 10:

1.

6. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The Ru salt is one or more of RuCl3, Ru(NH3)6Cl3, Ru(acac)3 or Ru(NO)(NO3)3.

7. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The pH of step (4) is adjusted using ammonia water or dilute sulfuric acid, and the adjusted pH = isoelectric point ± (0.5 ~ 4.0); the isoelectric point is the isoelectric point measured in step (2).

8. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: In the Ru-Al2O3, the loading amount of metal Ru is 0.5 wt%~5.0 wt%.

9. The method for preparing an alumina-supported catalyst according to claim 1, characterized in that: The stirring time in step (3) is 1 to 3 h, preferably 2 h; the stirring time in step (4) is 2 to 3.5 h, preferably 3 h.

10. An application of an alumina supported catalyst, characterized in that: To produce cyclohexene by partial hydrogenation of benzene.

Images