Catalyst for synthesizing indole as well as preparation method and application of catalyst

Abstract

The invention provides a preparation method of a catalyst for synthesizing indole, which comprises the following steps: sequentially impregnating silicon dioxide in a manganese salt solution, a first alkali solution, a silver nitrate solution containing an auxiliary agent M and a second alkali solution by adopting an impregnation method, standing for 0-72 hours at the temperature of 0-50 DEG C during each impregnation, and drying for 0-72 hours at the drying temperature of 20-290 DEG C after each standing, the auxiliary agent M is any one or more of aluminum nitrate, zirconium nitrate, lanthanum nitrate and cerium nitrate. Manganese dioxide is used as an anchor point, so that silver oxide is effectively dispersed and anchored on the surface of a silicon dioxide carrier modified with manganese dioxide; and finally, a nitrate auxiliary agent with the atomic radius larger than that of silver atoms is added and used for inhibiting the rate of increasing the particle size of the silver particles due to agglomeration of the silver particles caused by high-temperature sintering. The preparation process does not involve treatment at 300 DEG C or above and roasting treatment, and the preparation method is simple in step.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a catalyst for synthesizing indole and a preparation method and application thereof. Background Art

[0002] Indole is an important fine chemical product known as the "king of heterocycles". It is one of the most widely distributed heterocyclic compounds in nature and has a wide range of uses in the fields of food, fuel, fragrance, pesticide and fluorescent probe. The method of synthesizing indole from aniline and ethylene glycol is a new method developed by Japan in the mid-1990s to synthesize indole from the reaction raw materials in one step. This method has the advantages of low price, simple operation process, few by-products and non-toxicity, and is the most economical of many indole synthesis methods.

[0003] The key to the one-step synthesis of indole from aniline and ethylene glycol is the catalyst. Most of the catalysts used in industry are silver-based catalysts supported by silica as reported in patents. However, there is often a lack of strong interaction between silica and active metallic silver in existing silver-based catalysts, and there are relatively few methods for selectively adjusting active metallic silver. Other methods that load main catalysts such as copper or zinc on carriers such as silica and then add other co-catalysts to achieve the synthesis of indole often require higher reaction temperatures (around 350°C) and have problems such as easy deactivation of the catalyst.

[0004] A Chinese patent (CN111054326B) discloses a supported catalyst and its preparation method and its application in catalyzing ethylene glycol and aniline. 2 O 3 As a carrier, metal Pt was loaded on Al by impregnation method. 2 O 3 On the carrier, the loading mass fraction of metal Pt is 3%, and then the prepared supported catalyst is calcined at 500°C for 4 hours. The supported catalyst needs to be calcined at 500°C for 4 hours during its preparation process, and the preparation temperature condition is high and time-consuming. Summary of the invention

[0005] The invention aims to provide a catalyst for synthesizing indole, a preparation method and an application thereof. The invention utilizes the characteristics of manganese hydroxide generated in situ on a silica carrier being easy to decompose (decomposition temperature 140° C.) to effectively disperse the decomposed manganese dioxide on the surface of the silica carrier; utilizes the characteristics of silver hydroxide being easy to decompose at room temperature to disperse and anchor the decomposed silver oxide on the surface of the silica carrier modified with manganese dioxide; finally, a nitrate auxiliary agent having an atomic radius larger than that of silver atoms is added to inhibit the agglomeration of silver particles due to high-temperature sintering so as to increase the particle size of the silver particles; the preparation process of the preparation method does not involve treatment at a temperature higher than 300° C., and does not require roasting treatment, and the preparation method has simple steps.

[0006] To achieve the above object, the present invention proposes the following technical solutions:

[0007] A preparation method of a catalyst for synthesizing indole, comprising: using an impregnation method to sequentially immerse silicon dioxide in a manganese salt solution, a first alkaline solution, a silver nitrate solution containing an auxiliary agent M, and a second alkaline solution, and each time the impregnation is performed, the solution is allowed to stand at a temperature of 0 to 50° C. for 0 to 72 hours, and after each time the solution is allowed to stand, the solution is dried at a drying temperature of 20 to 290° C. for 0 to 72 hours;

[0008] The auxiliary agent M is any one or more of aluminum nitrate, zirconium nitrate, lanthanum nitrate and cerium nitrate.

[0009] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0010] Step 1: immersing the pre-dried silicon dioxide in a manganese salt solution, allowing it to stand, and drying it to obtain a first product;

[0011] The manganese salt in the manganese salt solution is any one of manganese sulfate, manganese chloride, and manganese nitrate, or a mixture of more than one of them. The molar ratio of the manganese salt to silicon dioxide is Mn:SiO 2 =0.002~0.1, the liquid-to-solid ratio of manganese salt solution to silicon dioxide is 1~3mL / g;

[0012] Step 2: immersing the first product in a first alkaline solution, allowing it to stand, drying it, then washing it with deionized water, and drying it to obtain a second product;

[0013] The first alkaline solution is any one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, the molar ratio of the first alkaline solution to the manganese salt solution is alkali / Mn=0.5-2.5, and the liquid-solid ratio of the first alkaline solution to silicon dioxide is 1-3 mL / g;

[0014] Step 3: immersing the second product in a silver nitrate solution containing an auxiliary agent M, allowing it to stand, and drying to obtain a third product;

[0015] The molar ratio of the silver nitrate solution to the auxiliary agent M is Ag / M=10-30, the mass ratio of the silver nitrate solution to silicon dioxide is 0.016-0.175, and the liquid-solid ratio of the silver nitrate solution to silicon dioxide is 1-3 mL / g;

[0016] The auxiliary agent M is any one of lanthanum nitrate and cerium nitrate or a mixture of the two;

[0017] Step 4: immersing the third product in a second alkaline solution, allowing it to stand, drying it, then washing it with deionized water, and drying it to obtain a catalyst;

[0018] The second alkaline solution is any one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, the molar ratio of the second alkaline solution to the manganese salt solution is alkali / Mn=0.5-2.5, and the liquid-solid ratio of the second alkaline solution to silicon dioxide is 1-3 mL / g;

[0019] Step 5: placing the catalyst in a hydrogen atmosphere for reduction treatment, the temperature of the reduction treatment being 180-230° C.;

[0020] The standing temperature in step 1, step 2, step 3 and step 4 is 25-30° C., the standing time is 12-24 hours, the drying temperature is 100-200° C., and the drying time is 24 hours.

[0021] As a preferred technical solution of the present invention, the silicon dioxide is a large silicon ball with a diameter of 2 to 5 mm;

[0022] Alternatively, the silicon dioxide is a silica gel ball with a diameter of 0.25 to 0.38 mm.

[0023] As a preferred technical solution of the present invention, the manganese salt in the manganese salt solution is manganese nitrate;

[0024] The molar ratio of the manganese salt to silicon dioxide is Mn:SiO 2 =0.013~0.03, the liquid-to-solid ratio of manganese salt solution to silicon dioxide is 1.5~2mL / g.

[0025] As a preferred technical solution of the present invention, the molar ratio of the silver nitrate solution to the auxiliary agent M is Ag / M=20-25, the mass ratio of the silver nitrate solution to silicon dioxide is 0.05-0.1, and the liquid-solid ratio of the silver nitrate solution to silicon dioxide is 1.5-2 mL / g. For example: Ag / La=20, Ag / La=25, Ag / Ce=20, Ag / Ce=25.

[0026] As a preferred technical solution of the present invention, the molar ratio of the first alkaline solution to the manganese salt solution is alkali / Mn=1.1-1.2, and the liquid-solid ratio of the first alkaline solution to silicon dioxide is 1.5-2 mL / g;

[0027] The molar ratio of the second alkaline solution to the manganese salt solution is alkali / Mn=1.1-1.2, and the liquid-to-solid ratio of the second alkaline solution to silicon dioxide is 1.5-2 mL / g.

[0028] The invention provides a catalyst for synthesizing indole, which is prepared by the method for preparing the catalyst for synthesizing indole as described above.

[0029] As a preferred technical solution of the present invention, the catalyst includes 88-99% by mass of silicon dioxide, 1-12% of silver oxide, 1.5-5.0% of manganese dioxide, 0.1-0.5% of the oxide of the auxiliary agent M and 0.1-0.5% of oxide E, wherein the oxide E is any one or more of sodium oxide and potassium oxide.

[0030] As a preferred technical solution of the present invention, the catalyst comprises 88-94% by mass of silicon dioxide, 6-12% by mass of silver oxide, 1.5-3.0% by mass of manganese dioxide, 0.1-0.3% by mass of the oxide of the auxiliary agent M and 0.1-0.3% by mass of the oxide E.

[0031] The invention discloses an application of a catalyst for synthesizing indole in catalyzing a one-step reaction of preparing indole from aniline and ethylene glycol.

[0032] The present invention provides a catalyst for synthesizing indole, a preparation method thereof and an application thereof, which have the following beneficial effects compared with the prior art:

[0033] (1) First, silicon dioxide is impregnated with a manganese salt solution to generate manganese hydroxide on the surface of silicon dioxide in situ, and manganese hydroxide is easily decomposed by heat (Mn(OH) 2 →MnO+H 2 O, 140 ° C) characteristics, effectively decomposed manganese dioxide dispersed on the surface of silica; then the silica carrier anchored with manganese dioxide was impregnated with silver nitrate solution, and the characteristics of silver hydroxide that can be easily decomposed at room temperature (2AgOH→Ag 2 O+H 2 O, room temperature), so that the decomposed silver oxide is anchored on the surface of silicon dioxide modified with manganese dioxide, so that the silver oxide is effectively combined with the surface of silicon dioxide modified with manganese dioxide, the number of surface active sites per unit mass of silver particles is increased, and efficient utilization of both silver particles and silicon dioxide surface is achieved.

[0034] (2) Adding auxiliary agents such as lanthanum nitrate and / or cerium nitrate to the silver nitrate solution, taking advantage of the fact that the radius of lanthanum atoms or cerium atoms is larger than that of silver atoms, inhibits the rate at which the silver particles increase in size due to high-temperature sintering during the use of the catalyst, slows down the rate of catalyst deactivation, and thus makes the catalyst have a higher catalytic activity.

[0035] (3) In the preparation process of the catalyst of the technical solution of the present application, the standing temperature is 0-50°C and the drying temperature is 20-290°C, and no treatment above 300°C is involved. No calcination treatment is required, that is, no toxic or harmful gases are released. The preparation method is simple and can realize large-scale production of the silica-supported catalyst.

[0036] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0037] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are not drawn to scale according to actual reference objects. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the present invention will be described by way of example and with reference to the accompanying drawings, in which:

[0039] Figure 1 TEM photo of the catalyst prepared in Example 1;

[0040] Figure 2 This is the TEM photo of the catalyst prepared in Comparative Example 3. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0042] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular form of "a", "an" or "the" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. "Include" or "comprise" and other similar words mean that the elements or objects appearing before "include" or "comprise" include the features, wholes, steps, operations, elements and / or components listed after "include" or "comprise", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0043] In the embodiment of the present invention:

[0044] Silicon spheres were purchased from Qingdao Chenrong New Materials Co., Ltd., FNG-C type, with a silicon dioxide content of ≥98wt.%, and a diameter of 2-5mm;

[0045] Macroporous silica gel balls were purchased from Qingdao Bangkai High-tech Materials Co., Ltd., with a pore size of 9 nm, a pore volume of 0.8-1.0 mL / g, a specific surface area of ​​300-400 m2 / g, a heating loss (150°C) of <3 wt.%, and a diameter of 0.25-0.38 mm (40-60 mesh);

[0046] Anhydrous manganese sulfate was purchased from MacLean Reagent Co., Ltd., with a content of ≥99wt.%;

[0047] Anhydrous manganese chloride was purchased from MacLean Reagent Co., Ltd., with a content of ≥99wt.%;

[0048] Silver nitrate was purchased from Xilong Science Co., Ltd., with a content of ≥99.8wt.%;

[0049] Lanthanum nitrate was purchased from Shandong Desheng New Materials Co., Ltd., with a content of ≥99.99wt.%;

[0050] Cerium nitrate was purchased from Jiaxing Zhejia Biotechnology Co., Ltd., with a content of ≥95wt.%;

[0051] Aluminum nitrate was purchased from Nanjing Kangmanlin Chemical Industry Co., Ltd., with a content of ≥98wt.%;

[0052] Zirconium nitrate trihydrate was purchased from Shandong Desheng New Materials Co., Ltd., with a content of ≥99.5wt.%;

[0053] Manganese nitrate aqueous solution was purchased from Aladdin Reagent Co., Ltd., with a content of 50wt.%;

[0054] Sodium hydroxide was purchased from Jinan Qinghai Chemical Co., Ltd., with a content of 98.5wt.%;

[0055] Potassium hydroxide was purchased from Jinan Kunfeng Chemical Co., Ltd., with a content of ≥90wt.%.

[0056] Example 1

[0057] The present application provides a method for preparing a catalyst for synthesizing indole, and the specific preparation process is as follows:

[0058] The preparation of the silver-based catalyst of the present invention is carried out in an open container.

[0059] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 4.76g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0060] Step 2: Weigh 1.79g of sodium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in the sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it to room temperature, and obtain the second product.

[0061] Step 3: Weigh 6 g of silver nitrate and 0.612 g of lanthanum nitrate (the molar ratio of silver nitrate to lanthanum nitrate is Ag / La=25), prepare 60 mL of nitrate solution, immerse the second product in the above nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain a third product.

[0062] Step 4: Weigh 1.695 g of sodium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the above sodium hydroxide solution, let it stand at 25° C. for 24 hours, then dry it at 200° C. for 6 hours, wash it with deionized water, and then dry it at 200° C. to finally obtain the catalyst.

[0063] In the catalyst of Example 1 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide, lanthanum trioxide and sodium oxide are 91.73 wt.%, 6.26 wt.%, 1.77 wt.%, 0.12 wt.% and 0.12 wt.%, respectively.

[0064] The TEM image of the catalyst prepared in the present embodiment is as follows: Figure 1 shown.

[0065] The catalyst prepared in Example 1 of the present application is used to catalyze the one-step preparation of indole from aniline and ethylene glycol.

[0066] Example 2

[0067] The preparation of the silver-based catalyst of the present invention is carried out in an open container.

[0068] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 4.76g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0069] Step 2: Weigh 1.2768g of potassium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it down at room temperature to obtain the second product.

[0070] Step 3: Weigh 6 g of silver nitrate and 0.612 g of lanthanum nitrate (the molar ratio of silver nitrate to lanthanum nitrate is Ag / La=25), prepare 60 mL of nitrate solution, immerse the second product in the above nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain a third product.

[0071] Step 4: Weigh 2.3778 g of potassium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the above sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, wash it with deionized water, and then dry it at 200°C to finally obtain the catalyst.

[0072] In the catalyst of Example 2 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide, lanthanum trioxide and potassium oxide are 91.73wt.%, 6.25wt.%, 1.76wt.%, 0.13wt.% and 0.13wt.%, respectively.

[0073] Example 3

[0074] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 9.52g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0075] Step 2: Weigh 1.79g of sodium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in the sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it to room temperature, and obtain the second product.

[0076] Step 3: Weigh 6 g of silver nitrate and 0.612 g of lanthanum nitrate (the molar ratio of silver nitrate to lanthanum nitrate is Ag / La=25), prepare 60 mL of nitrate solution, immerse the second product in the above nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain a third product.

[0077] Step 4: Weigh 1.695 g of sodium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the above sodium hydroxide solution, let it stand at 25° C. for 24 hours, then dry it at 200° C. for 6 hours, wash it with deionized water, and then dry it at 200° C. to finally obtain the catalyst.

[0078] In the catalyst of Example 3 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide, lanthanum trioxide and sodium oxide are 90.13 wt.%, 6.14 wt.%, 3.47 wt.%, 0.13 wt.% and 0.13 wt.%, respectively.

[0079] Example 4

[0080] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 4.76g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0081] Step 2: Weigh 1.79g of sodium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in the sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it to room temperature, and obtain the second product.

[0082] Step 3: Weigh 6 g of silver nitrate and prepare 60 mL of nitrate solution. Immerse the second product in the nitrate solution, let it stand at 25° C. for 24 hours, then dry it at 100° C. for 6 hours, and cool it down at room temperature to obtain the third product.

[0083] Step 4: Weigh 1.695 g of sodium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the above sodium hydroxide solution, let it stand at 25° C. for 24 hours, then dry it at 200° C. for 6 hours, wash it with deionized water, and then dry it at 200° C. to finally obtain the catalyst.

[0084] In the catalyst of Example 4 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide and sodium oxide are 91.84 wt.%, 6.26 wt.%, 1.77 wt.% and 0.13 wt.%, respectively.

[0085] Example 5

[0086] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 4.76g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0087] Step 2: Weigh 1.79g of sodium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in the sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it to room temperature, and obtain the second product.

[0088] Step 3: Weigh 6 g of silver nitrate and 1.224 g of lanthanum nitrate (the molar ratio of silver nitrate to lanthanum nitrate is Ag / La=12.5), prepare 60 mL of nitrate solution, immerse the second product in the above nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain a third product.

[0089] Step 4: Weigh 1.695 g of sodium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the above sodium hydroxide solution, let it stand at 25° C. for 24 hours, then dry it at 200° C. for 6 hours, wash it with deionized water, and then dry it at 200° C. to finally obtain the catalyst.

[0090] In the catalyst of Example 5 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide, lanthanum trioxide and sodium oxide are 91.62 wt.%, 6.24 wt.%, 1.76 wt.%, 0.26 wt.% and 0.12 wt.%, respectively.

[0091] Comparative Example 1

[0092] Step 1: Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 4.76g of manganese nitrate solution (50%) and dilute it to 60mL with deionized water, immerse the silicon spheres in the manganese nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain the first product.

[0093] Step 2: Weigh 1.79g of sodium hydroxide and prepare it into 60mL of aqueous solution, immerse the first product in the sodium hydroxide solution, let it stand at 25°C for 24 hours, then dry it at 200°C for 6 hours, cool it to room temperature, wash it with deionized water, and then dry it at 100°C for 6 hours, cool it to room temperature, and obtain the second product.

[0094] Step 3: Weigh 6 g of silver nitrate and 0.612 g of lanthanum nitrate (the molar ratio of silver nitrate to lanthanum nitrate is Ag / La=25), prepare 60 mL of nitrate solution, immerse the second product in the above nitrate solution, let it stand at 25°C for 24 hours, then dry it at 100°C for 6 hours, and cool it down at room temperature to obtain a third product.

[0095] Step 4: Weigh 1.695 g of sodium hydroxide to prepare 60 mL of sodium hydroxide solution, immerse the third product in the sodium hydroxide solution, let it stand at 25° C. for 24 hours, then dry it at 200° C. for 6 hours, wash it with deionized water, and then calcine it at 500° C. to finally obtain the catalyst.

[0096] In the catalyst of Comparative Example 1 of the present application, the contents of silicon dioxide, silver oxide, manganese dioxide, lanthanum trioxide and sodium oxide are 91.73 wt.%, 6.27 wt.%, 1.76 wt.%, 0.11 wt.% and 0.13 wt.%, respectively.

[0097] Comparative Example 2

[0098] This comparative example 2 provides a catalyst for catalyzing the one-step preparation of indole from aniline and ethylene glycol, which is prepared by the following preparation method.

[0099] The catalyst preparation is carried out in an open vessel.

[0100] Dry the silicon spheres at 200°C for 12 hours, then weigh 60g of the silicon spheres and cool them to room temperature. Weigh 6g of silver nitrate and 0.612g of lanthanum nitrate (Ag / La=25 at this time), prepare a 60mL solution, immerse the silicon spheres in the above nitrate solution, dry at 100°C for 6 hours, and obtain the first product after cooling. Weigh 1.695g of sodium hydroxide and prepare a 60mL sodium hydroxide solution, immerse the first product in the above sodium hydroxide solution, and let it stand at 25°C for 24 hours. Wash with deionized water, then dry at 200°C to obtain the catalyst.

[0101] In the catalyst, the contents of silicon dioxide, silver oxide, lanthanum trioxide and sodium oxide are 92.6wt.%, 6.75wt.%, 0.35wt.% and 0.30wt.% respectively.

[0102] Comparative Example 3

[0103] This comparative example 3 provides a catalyst for catalyzing the one-step preparation of indole from aniline and ethylene glycol, which is prepared by the following preparation method.

[0104] The catalyst preparation is carried out in an open vessel.

[0105] The silicon spheres were dried at 200°C for 12 hours, and then 60 g of the silicon spheres were weighed and cooled to room temperature. 5.86 g of silver nitrate was weighed and prepared into 60 mL of solution, and the silicon spheres were immersed in the above silver nitrate solution and dried at 100°C for 6 hours to obtain the first product. The first product was then calcined at 500°C for 6 hours, and the catalyst was obtained after cooling.

[0106] In the catalyst, the contents of silicon dioxide and silver oxide are 93.35 wt. % and 6.65 wt. %, respectively.

[0107] The TEM photo of the catalyst prepared in Comparative Example 3 is as follows: Figure 2 shown.

[0108] Experimental example

[0109] In order to further illustrate the progress of the present invention, the catalyst samples prepared in Examples 1 to 6 of the present invention and the catalyst samples prepared in Comparative Examples 1-2 were subjected to reduction treatment using a mixture of hydrogen and nitrogen before the reaction, wherein the reduction treatment temperature was 180 to 230°C, the time was 180 hours, and the volume concentration of hydrogen in the mixture was 80%. The activity was evaluated in a Φ20 mm fixed bed reactor, specifically when the raw material cyclohexanol space velocity was 0.40 h -1 The activity evaluation was carried out under the conditions of controlling the reaction temperature to 325°C, aniline / ethylene glycol = 7:1, and the catalyst loading to 100 mL, and the indole yield = indole content in the reaction organic phase / theoretical indole content in the organic phase * 100%. The results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] It can be seen from the experimental results in Table 1 above that the silver-based catalysts prepared by the preparation methods of Examples 1 to 5 of the present invention all showed higher indole product yields than the comparative examples under similar silver loading conditions during activity evaluation.

[0114] (1) By comparing Example 1 with Example 3, it can be seen that adding an appropriate amount of manganese nitrate during preparation can increase the indole yield;

[0115] (2) By comparing Example 4 with Example 1, Example 2, Example 3 and Example 5, it can be seen that without the addition of the auxiliary agent lanthanum nitrate, the indole yield (81.5%) of Example 4 is the lowest, indicating that adding an appropriate amount of auxiliary agents such as lanthanum nitrate can improve the indole yield of the catalyst;

[0116] (3) By comparing Comparative Example 1 with Example 1, Example 2, Example 3 and Example 5, it can be seen that the indole yield (79.5%) of the catalyst prepared by calcination is the lowest, indicating that avoiding high-temperature calcination during the catalyst preparation process can increase the indole yield of the catalyst.

[0117] Therefore, it can be seen from Examples 1-5 that catalysts with higher indole yields need to add appropriate amounts of manganese nitrate and lanthanum nitrate during preparation and avoid high temperature calcination. Finally, the selected processing conditions are within the optimal range proposed by the present invention, and the effect is better.

[0118] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A method for preparing a catalyst for synthesizing indole, characterized in that: The method comprises: using an impregnation method to sequentially immerse silicon dioxide in a manganese salt solution, a first alkaline solution, a silver nitrate solution containing an auxiliary agent M, and a second alkaline solution, and each time the impregnation is performed, the silicon dioxide is allowed to stand at a temperature of 0 to 50° C. for 0 to 72 hours, and after each standing, the silicon dioxide is dried at a drying temperature of 20 to 290° C. for 0 to 72 hours; The auxiliary agent M is any one or more of aluminum nitrate, zirconium nitrate, lanthanum nitrate and cerium nitrate.

2. The method for preparing a catalyst for synthesizing indole according to claim 1, wherein The preparation method comprises the following steps: Step 1: immersing the pre-dried silicon dioxide in a manganese salt solution, allowing it to stand, and drying it to obtain a first product; The manganese salt in the manganese salt solution is any one of manganese sulfate, manganese chloride, and manganese nitrate, or a mixture of more than one of them; the molar ratio of the manganese salt to silicon dioxide is Mn:SiO2=0.002-0.1; and the liquid-to-solid ratio of the manganese salt solution to silicon dioxide is 1-3 mL / g; Step 2: immersing the first product in a first alkaline solution, allowing it to stand, drying it, then washing it with deionized water, and drying it to obtain a second product; The first alkaline solution is any one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, the molar ratio of the first alkaline solution to the manganese salt solution is alkali / Mn=0.5-2.5, and the liquid-solid ratio of the first alkaline solution to silicon dioxide is 1-3 mL / g; Step 3: immersing the second product in a silver nitrate solution containing an auxiliary agent M, allowing it to stand, and drying to obtain a third product; The molar ratio of the silver nitrate solution to the auxiliary agent M is Ag / M=10-30, the mass ratio of the silver nitrate solution to silicon dioxide is 0.016-0.175, and the liquid-solid ratio of the silver nitrate solution to silicon dioxide is 1-3 mL / g; The auxiliary agent M is any one of lanthanum nitrate and cerium nitrate or a mixture of the two; Step 4: immersing the third product in a second alkaline solution, allowing it to stand, drying it, then washing it with deionized water, and drying it to obtain a catalyst; The second alkaline solution is any one of a sodium hydroxide solution and a potassium hydroxide solution or a mixed solution of the two, the molar ratio of the second alkaline solution to the manganese salt solution is alkali / Mn=0.5-2.5, and the liquid-solid ratio of the second alkaline solution to silicon dioxide is 1-3 mL / g; Step 5: placing the catalyst in a hydrogen atmosphere for reduction treatment, the temperature of the reduction treatment being 180-230° C.; The standing temperature in step 1, step 2, step 3 and step 4 is 25-30° C., the standing time is 12-24 hours, the drying temperature is 100-200° C., and the drying time is 24 hours.

3. The method for preparing a catalyst for synthesizing indole according to claim 1 or 2, characterized in that: The silicon dioxide is a large silicon ball with a diameter of 2 to 5 mm; Alternatively, the silicon dioxide is a silica gel ball with a diameter of 0.25 to 0.38 mm.

4. The method for preparing a catalyst for synthesizing indole according to claim 2, wherein: The manganese salt in the manganese salt solution is preferably manganese nitrate; The molar ratio of the manganese salt to silicon dioxide is Mn:SiO2=0.013-0.03, and the liquid-to-solid ratio of the manganese salt solution to silicon dioxide is 1.5-2 mL / g.

5. The method for preparing a catalyst for synthesizing indole according to any one of claim 2, characterized in that: The molar ratio of the silver nitrate solution to the auxiliary agent M is preferably Ag / M=20-25, the mass ratio of the silver nitrate solution to silicon dioxide is 0.05-0.1, and the liquid-to-solid ratio of the silver nitrate solution to silicon dioxide is 1.5-2 mL / g.

6. The method for preparing a catalyst for synthesizing indole according to any one of claim 2, characterized in that: The molar ratio of the first alkaline solution to the manganese salt solution is alkali / Mn=1.1-1.2, and the liquid-to-solid ratio of the first alkaline solution to silicon dioxide is 1.5-2 mL / g; The molar ratio of the second alkaline solution to the manganese salt solution is alkali / Mn=1.1-1.2, and the liquid-to-solid ratio of the second alkaline solution to silicon dioxide is 1.5-2 mL / g.

7. A catalyst for synthesizing indole, characterized in that A catalyst prepared by the method for preparing a catalyst for synthesizing indole as described in any one of claims 1 to 7.

8. The catalyst for synthesizing indole according to claim 7, characterized in that The catalyst comprises 88-99% by mass of silicon dioxide, 1-12% of silver oxide, 1.5-5.0% of manganese dioxide, 0.1-0.5% of oxide of auxiliary agent M and 0.1-0.5% of oxide E, wherein the oxide E is any one or more of sodium oxide and potassium oxide.

9. The catalyst for synthesizing indole according to claim 8, characterized in that The catalyst comprises 88-94% by mass of silicon dioxide, 6-12% by mass of silver oxide, 1.5-3.0% by mass of manganese dioxide, 0.1-0.3% by mass of oxide of auxiliary agent M and 0.1-0.3% by mass of oxide E.

10. Use of the catalyst for synthesizing indole according to any one of claims 7 to 9 in catalyzing the one-step preparation of indole from aniline and ethylene glycol.

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