Process for the preparation of an alumina-supported catalyst and use thereof

Abstract

The application provides a preparation method of an alumina supported catalyst and application of the alumina supported catalyst in a reaction of partial hydrogenation of benzene to cyclohexene. Benefited from alkali treatment, the surface of the carrier is rich in various charged ions, so that the metal can be uniformly distributed on the surface of the carrier in the loading process, thereby obtaining a highly dispersed Ru-based catalyst. The catalyst involved in the application has a much lower content of metal Ru than a traditional industrial RuZn catalyst, has a more excellent cost advantage, and provides a great economic value for subsequent industrial application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of an alumina supported catalyst and application of the alumina supported catalyst in a reaction of partial hydrogenation of benzene to cyclohexene. BACKGROUND

[0002] Cyclohexene is an important fine chemical, which can be used as an intermediate for the production of chemicals such as medicines, pesticides, dyes and detergents. In the production of caprolactam, cyclohexanol can be generated by hydration of cyclohexene, cyclohexanone can be generated by dehydration of cyclohexanol, cyclohexanone oxime can be generated by aminooxidation of cyclohexanone, and caprolactam can be generated by molecular rearrangement of cyclohexanone oxime. At present, the production methods of cyclohexene include partial hydrogenation of benzene to cyclohexene, dehydration of cyclohexanol, dehydrogenation of cyclohexane and Birch reduction. Since the process of partial hydrogenation of benzene to cyclohexene is simple and the production cost is low, it is often used for industrial production of cyclohexene.

[0003] Cyclohexene has a C=C double bond and is relatively active in chemical properties, and is easy to be deeply hydrogenated to cyclohexane in the hydrogenation process, so the reaction of partial hydrogenation of benzene to cyclohexene is more likely to generate cyclohexane in thermodynamics. In order to improve the yield of cyclohexene, a suitable catalytic system needs to be selected to avoid excessive hydrogenation of the product to generate cyclohexane. For example, Liu et al. [Liu jie, et al. Chemcatchem 2015; 7: 846-855] deposited Cu on Ru / MgAl-LDH, deposited Cu on low-coordinated Ru to reduce the hydrogenation ability of the catalyst, thereby improving the yield of cyclohexene. Compared with the blank sample, the Cu-promoted Ru catalyst can increase the yield of cyclohexene from 27.5% to a maximum of 44.0%. Song et al. [Song yihui, et al. Chemcatchem 2022; 14: 1-11] introduced Zn into LiAl-LDH, constructed a Ru 0 / Ru δ+ -O-Zn structure, and utilized the abundant hydroxyl groups on the surface of LDH to improve the yield of cyclohexene, and the maximum yield of cyclohexene can reach 43.2%. Zhou et al. [Zhou gongbing, et al. Chemcatchem 2018; 10: 1184-1191] prepared a RuZn catalyst by reducing Ru 3+ ions with Zn powder and dissolving excess Zn by hydrochloric acid treatment. Patent CN106140154B proposes a completely opposite conclusion, that is, the proportion of catalyst pore diameter in the range of 2-15 nm should be less than 50% to facilitate the generation of cyclohexene and improve the stability of the catalyst. In the case that the content of Ru is 5 wt%, a catalytic activity of 50-80 (i.e., conversion rate 50% and selectivity of cyclohexene 80%) can be obtained. SUMMARY

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

[0005] In order to achieve the above-mentioned application purposes, the application provides the following technical solutions.

[0006] A preparation method of an alumina-supported catalyst, comprising the following steps:

[0007] (1) alkali treatment of an alumina carrier;

[0008] (2) measurement of the isoelectric point of the alumina carrier after alkali treatment;

[0009] (3) mixing and stirring of the alumina carrier after alkali treatment with water;

[0010] (4) addition of Ru salt, adjustment of pH, and continuous stirring;

[0011] (5) after complete adsorption of the Ru salt, addition of a reducing agent to obtain an alumina-supported ruthenium-based catalyst Ru-Al2O3.

[0012] The alkali treatment in step (1) is specifically as follows: the alumina carrier is dispersed in 0.8-1.2 mol / L alkali liquor, heated to reflux at 75-90℃ for 10-15 h, and dried to obtain the alumina carrier after alkali treatment; preferably, the alumina carrier is dispersed in 1 mol / L alkali liquor, heated to reflux at 80℃ for 12 h, and dried to obtain the alumina carrier after alkali treatment.

[0013] The alkali is one or more of Na2CO3, NaOH, ammonia water, or hexamethylenetetramine.

[0014] 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 and added to the solution with adjusted pH, after stirring for 1 h, the terminal 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.

[0015] The Ru salt is one or more of RuCl3, Ru(NH3)6Cl3, Ru(acac)3, or Ru(NO)(NO3)3.

[0016] The pH adjustment in step (4) is adjusted by using ammonia water or dilute sulfuric acid, and the adjusted pH is equal to the isoelectric point ± (0.5-4.0); the isoelectric point is the isoelectric point measured in step (2).

[0017] In the Ru-Al2O3, the loading amount of the metal Ru is 0.5 wt%-5.0 wt%.

[0018] The stirring time in step (3) is 1-3 h, preferably 2 h; and the stirring time in step (4) is 2-3.5 h, preferably 3 h.

[0019] An alumina supported catalyst for partial hydrogenation of benzene to cyclohexene.

[0020] The present application has the following advantages:

[0021] The present application provides a preparation method of an alumina supported catalyst and its application in the reaction of partial hydrogenation of benzene to cyclohexene. Benefiting from the alkali treatment of the alumina carrier, the carrier surface is rich in various charged ions. These charged ions can make the metal ions uniformly distributed on the carrier surface in the process of adsorbing the metal ions, thereby avoiding the agglomeration of the metal, and finally preparing a highly dispersed Ru-based catalyst. Benefiting from the high dispersion of the metal, the Ru-based catalyst involved in the present application can obtain a higher cyclohexene yield under the condition of a lower metal loading amount. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in detail below with reference to the examples, which are only used to illustrate the present application and should not be regarded as limiting the scope of the present application.

[0023] The present application provides a preparation method of an alumina supported catalyst and its application in the reaction of partial hydrogenation of benzene to cyclohexene. In the present application, the catalytic performance evaluation device used is a tank reactor, which is similar to the production device for the production of cyclohexene by partial hydrogenation of benzene in industrial production.

[0024] In the present application, unless otherwise specified, the evaluation method for the partial hydrogenation of benzene to cyclohexene is as follows: a certain amount of catalyst and water are loaded into a tank reactor, hydrogen is filled and then evacuated, and this is repeated three times to remove the air in the tank. After pressure buildup and leak detection, the reaction is heated, and after the target temperature is reached, benzene is added, and the timing reaction is started.

[0025] In the present application, unless otherwise specified, the reaction conditions for the partial hydrogenation of benzene to cyclohexene are as follows: 5.0 MPa, 140℃, rotation speed 1000 r / min, catalyst 1.5 g, benzene 50 mL, water 100 mL, and 3 g of zinc sulfate.

[0026] In the present application, the conversion of benzene and the selectivity of cyclohexene listed in Table 1 are obtained under the condition that the conversion is about 50 mol% unless otherwise specified.

[0027] In the present application, the determination operation of the isoelectric point is specifically as follows: a certain amount of water is measured, the pH of the solution is adjusted by HCl or NaOH, the initial pH of the solution is adjusted to different gradients of 1-13, a certain amount of dry Al2O3 is weighed each time and added to the adjusted pH solution, after stirring for 1 h, the final pH of the solution after stirring is recorded, and the pH at the platform is the isoelectric point. The mass ratio of water to Al2O3 is 10:1.

[0028] In order to further illustrate the present application, the following examples are used for detailed description, but the protection scope of the present application is not limited to the following examples.

[0029] Example 1

[0030] Preparation of alumina: 60 g of Al(NO3)3·9H2O is weighed and dissolved in deionized water, 10 g of urea is added, after complete dissolution, it is loaded into an autoclave, hydrothermal treatment is carried out at 120℃ for 24 h, filtration, drying, and finally calcination at 600℃ for 5 h, and the obtained is alumina.

[0031] Alkaline treatment: the above alumina carrier is dispersed in a 1 mol / L Na2CO3 solution, heated and refluxed at 80℃ for 12 h, and dried to obtain the alkaline-treated alumina carrier.

[0032] 1 g of the alkaline-treated alumina carrier is weighed, and the isoelectric point of the alumina carrier is measured according to the above method. The isoelectric point of the carrier is measured to be 6.5.

[0033] 10 g of the above alkaline-treated alumina carrier is weighed and added to 100 mL of deionized water, stirred for 2 h, 0.63 g of RuCl3 is added, the pH is adjusted to 7.5 with ammonia water, stirred for 3 h, after the metal is completely adsorbed, KBH4 is added, and the obtained after reduction is an alumina-supported ruthenium-based catalyst, denoted as Ru-Al2O3. The loading amount of metal Ru is 3.0 wt%, and the amount of substance of KBH4 is four times that of RuCl3.

[0034] Example 2

[0035] 20 g of commercial Al2O3 carrier (Yichang Supeng Technology Co., Ltd., model A06) is weighed, first calcined at 600℃ for 5 h, and then used as a catalyst carrier.

[0036] The above alumina carrier is dispersed in a 1 mol / L Na2CO3 solution, heated and refluxed at 80℃ for 12 h, and dried to obtain the alkaline-treated alumina carrier.

[0037] Take 1 g of the above alumina, and measure the isoelectric point of the alumina carrier according to the method described in the summary. The carrier isoelectric point is measured to be 7.3.

[0038] Take 10 g of the above alumina carrier, add 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 then add KBH4 after the metal is completely adsorbed. The obtained after reduction is an alumina supported ruthenium-based catalyst. The loading of metal Ru is 3.0 wt%, and the amount of substance of KBH4 is four times that of RuCl3.

[0039] Example 3

[0040] The alumina supported ruthenium-based catalyst is prepared according to Example 1, except that the pH in this embodiment is 9.5.

[0041] Example 4

[0042] The alumina supported ruthenium-based catalyst is prepared according to Example 1, except that the pH in this embodiment is 10.5.

[0043] Example 5

[0044] The alumina supported ruthenium-based catalyst is prepared according to Example 1, except that the Ru salt in this embodiment is Ru(NH3)6Cl3.

[0045] Example 6

[0046] The alumina supported ruthenium-based catalyst is prepared according to Example 2, except that the pH in this embodiment is 9.5.

[0047] Example 7

[0048] The alumina supported ruthenium-based catalyst is prepared according to Example 2, except that the pH in this embodiment is 11.

[0049] Example 8

[0050] The alumina supported ruthenium-based catalyst is prepared according to Example 2, except that the Ru salt in this embodiment is Ru(NH3)6Cl3.

[0051] Example 9

[0052] The alumina supported ruthenium-based catalyst is prepared according to Example 1, except that the base solution in this embodiment is hexamethylenetetramine.

[0053] Example 10

[0054] An alumina-supported ruthenium-based catalyst was prepared according to the preparation method of Example 2, except that the loading of metal ruthenium was 5.0 wt% in this example.

[0055] Example 11

[0056] An alumina-supported ruthenium-based catalyst was prepared according to the preparation method of Example 1, except that the pH was controlled to 5.0 by dilute sulfuric acid in this example.

[0057] Example 12

[0058] An alumina-supported ruthenium-based catalyst was prepared according to the preparation method of Example 2, except that the pH was controlled to 5.0 by dilute sulfuric acid in this example.

[0059] Comparative Example 1

[0060] Alumina was prepared according to the preparation method of Example 1. After the preparation of alumina was completed, 10 g was weighed and added to 100 mL of deionized water, stirred for 2 h, then RuCl3was added, completely dissolved, then KBH4was added, reacted for 1 h, then filtered, and the obtained was an alumina-supported ruthenium-based catalyst. Among them, the loading of metal Ru was 3.0 wt%, and the amount of substance of KBH4was four times that of RuCl3.

[0061] Comparative Example 2

[0062] 10 g of commercial Al2O3carrier (Yichang Supeng Technology Co., Ltd., model A06) was weighed and added to 100 mL of deionized water, stirred for 2 h, then RuCl3was added, completely dissolved, then KBH4was added, reacted for 1 h, then filtered, and the obtained was an alumina-supported ruthenium-based catalyst. Among them, the loading of metal Ru was 3.0 wt%, and the amount of substance of KBH4was four times that of RuCl3.

[0063] The above sample was subjected to benzene partial hydrogenation activity evaluation, and the evaluation conditions were as described above. The catalytic activity test results are shown in Table 1.

[0064] Table 1 Performance results of benzene partial hydrogenation of examples

[0065]

[0066] From the implementation results, the Ru-based catalyst prepared by the method of the patent has higher cyclohexene yield compared with the comparative examples. This is mainly due to the fact that after alkaline treatment, a large number of charged ions will be formed on the surface of the carrier. These charged ions can uniformly adsorb metal ions on the surface of the carrier during the loading of the metal, thereby preparing a highly dispersed Ru-based catalyst. The high dispersion of the metal Ru enables the Ru-based catalyst of the patent to obtain a higher cyclohexene yield at a lower Ru loading. Compared with the traditional RuZn catalyst (Ru content of 90 wt% to 95 wt%) in the industry, the catalyst invented by the patent has a lower cost advantage.

Claims

1. A method for producing an alumina-supported catalyst for partial hydrogenation of benzene to cyclohexene, characterized by, The method comprises the following steps: (1) alkali treatment of the alumina carrier; (2) measurement of the isoelectric point of the alumina carrier after alkali treatment; (3) mixing and stirring the alumina carrier after alkali treatment with water; (4) adding a Ru salt, adjusting the pH, and continuing to stir; (5) after the Ru salt is completely adsorbed, adding a reducing agent to obtain an alumina-supported ruthenium-based catalyst Ru-Al2O3; The alkali treatment in step (1) is specifically as follows: dispersing the alumina carrier in 0.8-1.2 mol / L alkali liquor, heating under reflux at 75-90°C for 10-15 h, and drying to obtain the alumina carrier after alkali treatment. In step (4), the pH is adjusted using ammonia water or dilute sulfuric acid, and the adjusted pH is the isoelectric point ± (0.5-4.0); the isoelectric point is the isoelectric point measured in step (2).

2. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, The alkali treatment in step (1) is specifically as follows: dispersing the alumina carrier in 1 mol / L alkali liquor, heating under reflux at 80°C for 12 h, and drying to obtain the alumina carrier after alkali treatment.

3. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, The alkali is one or more of Na2CO3, NaOH, ammonia water, or hexamethylenetetramine.

4. The process for preparing an alumina supported catalyst for the partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, In step (2), the isoelectric point is measured as follows: measuring a certain amount of water, adjusting the pH of the solution using HCl or NaOH, adjusting the initial pH of the solution to 1-13, weighing a certain amount of dry Al2O3 and adding it to the solution with the adjusted pH, stirring for 1 h, and recording the final pH of the solution after stirring; the isoelectric point is the pH at the plateau; the mass ratio of water to Al2O3 is 10:

1.

5. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene 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.

6. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, In the Ru-Al2O3, the loading of metallic Ru is 0.5 wt%-5.0 wt%.

7. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, The stirring time in step (3) is 1-3 h, and the stirring time in step (4) is 2-3.5 h.

8. The method for preparing an alumina supported catalyst for partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, The stirring time in step (3) is 2 h.

9. The process for preparing an alumina supported catalyst for the partial hydrogenation of benzene to cyclohexene according to claim 1, characterized in that, The stirring time in step (4) is 3 h.

10. The alumina-supported catalyst prepared by the method of any one of claims 1-9 for use in the partial hydrogenation of benzene to cyclohexene.

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