Indole synthesis catalyst, preparation method thereof, and synthesis method of indole compounds

Abstract

The present invention relates to the field of catalysts, and discloses an indole synthesis catalyst, a preparation method thereof, and a synthesis method of indole compounds, including: (1) impregnating a silica carrier with a solution containing a zinc precursor, followed by first drying and first calcination to obtain a modified carrier; (2) mixing a first slurry containing the modified carrier with a second solution containing a precursor of a first active component to obtain a mixture; (3) contacting the mixture with a precipitating agent, controlling the pH to be 8-10, carrying out a precipitation reaction, followed by aging, second drying and second calcination; (4) mixing the product obtained in step (3), a soluble compound of a second active component, and an optional binder and an optional peptizing agent, carrying out shaping, third drying and third calcination. The catalyst prepared by this method has high catalytic activity and good stability.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and specifically to an indole synthesis catalyst, a preparation method thereof, and a method for synthesizing indole compounds. Background Art

[0002] Indole is a compound formed by the parallel connection of pyrrole and benzene, also known as benzopyrrole. Indole and its derivatives widely exist in nature, mainly in natural flower oils, such as jasmine, neroli, narcissus, sweet violet, etc. As an important chemical raw material, it has a wide range of applications in many fields such as agriculture, medicine, and dyes. It can not only be used as a fragrance (e.g., for the blending of artificial flower essential oils), a raw material for synthetic dyes, but also as a highly efficient plant growth regulator, fungicide, etc., and can also be used to synthesize vasodilators, antipyretics, stimulants, antihypertensive drugs, antihistamines, etc.

[0003] Before the 1990s, indole was mainly synthesized industrially by extracting it from coal tar and wash oil fractions. The indole content in high-temperature coal tar is about 0.1 - 0.16%. Generally, the coal tar and wash oil fractions are subjected to alkali washing and acid washing to obtain methylnaphthalene fractions, and then through rectification cutting, the 225 - 256 °C distillation section is first collected, melted with potassium hydroxide, washed and extracted with benzene, and then hydrolyzed at 50 - 70 °C to obtain crude indole oil. The crude indole oil is further rectified, cooled, crystallized, and centrifugally filtered to obtain refined indole. However, the indole obtained by this method has a strong odor, which greatly limits its application fields in industry, especially in the fragrance industry. At the same time, the separation steps of this method are numerous and the cost is high, which also restricts its industrial development.

[0004] The one-step catalytic synthesis of indole from aniline and ethylene glycol was proposed in the 1990s. This method has cheap and easily available raw materials, fewer reaction steps, low production costs, and no by-products such as inorganic salts in the reactants, and is the most economical one among many indole synthesis methods. In the prior art, indole and its derivative synthesis catalysts are mainly divided into two categories: non-noble metal catalysts and noble metal catalysts. Non-noble metal catalysts mainly include cadmium compounds, lead compounds, silicon-copper oxides, and solid catalysts containing other elements. Among them, non-noble metal cadmium and lead compounds are highly toxic and cause serious pollution to the environment during use. Therefore, they have been phased out in industrialization. Although the silicon-copper oxide catalyst has high activity, low price, and no pollution to the environment, the catalyst stability is poor and the deactivation phenomenon is serious. The indole yield of other solid acid catalysts is relatively low. Noble metal catalysts are mainly loaded with silver, palladium, ruthenium, rhodium, etc. Among them, catalysts such as ruthenium-based and rhodium-based have very complex structures, sometimes ligands need to be added, and they are expensive. At the same time, there are problems such as high reaction temperature and easy deactivation of the catalyst.

[0005] Therefore, how to prepare an indole synthesis catalyst with high activity, high stability and low reaction temperature through a simple and low-cost method will be an important research direction in this field. Summary of the Invention

[0006] The object of the present invention is to overcome the problems of insufficient activity and stability of the existing indole synthesis catalyst, and to provide an indole synthesis catalyst, a preparation method thereof, and a synthesis method of indole compounds. The indole synthesis catalyst prepared by this preparation method has high catalytic activity and good stability.

[0007] In order to achieve the above object, on the one hand, the present invention provides a preparation method of an indole synthesis catalyst, and the preparation method includes:

[0008] (1) Impregnating a silica carrier with a solution containing a zinc precursor, and then performing first drying and first calcination to obtain a modified carrier;

[0009] (2) Mixing a first slurry containing the modified carrier with a second solution containing a precursor of a first active component to obtain a mixed solution;

[0010] Wherein, the first active component is selected from at least one of Ag, Pd, and Ru;

[0011] (3) Contacting the mixed solution with a precipitant, controlling the pH to be 8-10, performing a precipitation reaction, and then performing aging, second drying and second calcination;

[0012] (4) Mixing the product obtained in step (3), a soluble compound of a second active component, and an optional binder and an optional peptizing agent, performing shaping, third drying and third calcination;

[0013] Wherein, the second active component is selected from at least one of Cu, Co, Ni, and Fe.

[0014] On the second aspect, the present invention provides an indole synthesis catalyst prepared by the above preparation method;

[0015] The indole synthesis catalyst includes a modified carrier, a first active component and a second active component;

[0016] Wherein, the modified carrier includes silica and a modified component zinc; the first active component is selected from at least one of Ag, Pd, and Ru; the second active component is selected from at least one of Cu, Co, Ni, and Fe.

[0017] On the third aspect, the present invention provides a synthesis method of indole compounds, and the synthesis method includes: contacting ethylene glycol, aniline and a catalyst in the presence of hydrogen and water;

[0018] Among them, the catalyst is the indole synthesis catalyst described in the second aspect.

[0019] Through the above technical solutions, the present invention provides a preparation method of a new indole synthesis catalyst. By depositing and impregnating a noble metal first active component on a zinc oxide-modified support, the active components of the catalyst can be evenly distributed on the support. Then, by introducing a second active component, the amount of the first active component can be reduced, the cost of the catalyst can be lowered, and the utilization efficiency of the active components of the catalyst can be significantly improved, effectively inhibiting the sintering and agglomeration of the active components during the reaction process. Through the synergistic effect of the first active component, the second active component, and the modified support, the anti-sintering performance of the active components can be improved, and the catalyst has good stability during use, is not easily deactivated, and has a low reaction temperature, which can reduce the equipment investment cost and maintenance cost of the indole and its derivative synthesis system. It also has important application potential in the field of environmentally friendly chemical catalysis. The preparation method has a simple process flow, is conducive to large-scale production, and meets the requirements of the indole and its derivative synthesis field for efficient and stable catalysts. Specific Embodiments

[0020] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0021] The first aspect of the present invention provides a preparation method of an indole synthesis catalyst, and the preparation method includes:

[0022] (1) Impregnating a silica support with a solution containing a zinc precursor, and then performing first drying and first calcination to obtain a modified support;

[0023] (2) Mixing a first slurry containing the modified support with a second solution containing a precursor of a first active component to obtain a mixture;

[0024] Among them, the first active component is selected from at least one of Ag, Pd, and Ru;

[0025] (3) Contacting the mixture with a precipitating agent, controlling the pH to be 8 - 10, performing a precipitation reaction, and then performing aging, second drying, and second calcination;

[0026] (4) Mixing the product obtained in step (3), a soluble compound of a second active component, and an optional binder and an optional peptizing agent, performing shaping, third drying, and third calcination;

[0027] Among them, the second active component is selected from at least one of Cu, Co, Ni, and Fe.

[0028] The present invention has a relatively wide selection range for the silica carrier, which can be silica of any morphology and size. For example, it can be silica powder, which can be commercially obtained by those skilled in the art.

[0029] According to some preferred embodiments of the present invention, the specific surface area of the silica carrier is 400-700 m 2 / g.

[0030] The inventors of the present invention found in the research that pre-modifying the silica carrier with zinc oxide is beneficial for the subsequent more sufficient loading of the active component on the carrier, avoiding possible agglomeration or over-impregnation of the active component. The reason may be that the interaction between the active component and the silica carrier is weak, and it is easy to move, aggregate and sinter at a higher reaction temperature. Zinc oxide can be monolayer dispersed on the silica. The introduction of zinc oxide can highly disperse the first active component particles added subsequently on the carrier, avoiding agglomeration and sintering, thereby improving the utilization rate of the active component in the catalyst and the overall performance of the catalyst.

[0031] According to some preferred embodiments of the present invention, relative to 100 parts by weight of the silica carrier, the amount of the zinc precursor in terms of zinc element is 1-10 parts by weight, preferably 3-7 parts by weight. For example, the specific amounts can be 3, 4, 5, 6, 7 parts by weight, etc. or any range between any two of them. Adopting the above preferred embodiments is beneficial for the high dispersion of the active component on the surface of the carrier, thereby improving the stability of the catalyst. Excessive zinc oxide may exacerbate the side reactions and reduce the selectivity of indole.

[0032] The present invention has no special limitation on the conditions of the impregnation in step (1), and any conventional conditions in the art can be adopted as long as the zinc component can be loaded onto the silica carrier.

[0033] According to some preferred embodiments of the present invention, the temperature of the impregnation is 20-60 °C and the time is 1-6 h.

[0034] In the present invention, the solvent in the solution containing the zinc precursor is preferably water. The present invention has no special limitation on the concentration of the solution, and those skilled in the art can select according to the actual metal loading requirements.

[0035] According to the present invention, preferably, the zinc precursor is selected from at least one of zinc nitrate, chloride nitrate, acetate, sulfate, and chloride. The zinc precursor may also contain crystal water, and the present invention has no special requirements for this.

[0036] The present invention has no particular limitation on the manner and conditions of the first drying. Preferably, the first drying is evaporation drying.

[0037] Preferably, the conditions for the first drying include: the temperature is 70 - 150 °C, preferably 100 - 120 °C, and the time is 1 - 24 h, preferably 2 - 6 h.

[0038] According to some preferred embodiments of the present invention, the conditions for the first calcination include: the temperature is 250 - 750 °C, preferably 450 - 650 °C, and the time is 0.5 - 10 h, preferably 3 - 6 h.

[0039] In the present invention, first, the first slurry containing the modified support is mixed with the second solution containing the precursor of the first active component to obtain a mixed solution, and then a precipitant is introduced for precipitation impregnation, which can make the active component basically fully adsorbed on the surface of the support, improve the utilization rate of the active component, and the obtained catalyst has a relatively uniform particle size distribution, further improving the catalytic activity of the prepared indole synthesis catalyst.

[0040] According to some preferred embodiments of the present invention, in step (2), based on the mass of the silica support in the modified support, the dosage of the precursor of the first active component in terms of elements is 0.1 - 30 wt%, preferably 2 - 20 wt%, and more preferably 4 - 15 wt%.

[0041] According to some preferred embodiments of the present invention, the first active component is Ag.

[0042] According to the present invention, the first slurry also contains water to disperse the modified support. The present invention has no particular limitation on the dosage of water in the first slurry, as long as it can play a dispersing role.

[0043] The present invention has no particular limitation on the solvent in the second solution, and water is preferred. The present invention also has no particular limitation on the dosage of the solvent in the second solution, which is based on being able to fully dissolve the precursor of the first active component and being beneficial for the impregnation and loading of the first active component. Those skilled in the art can select according to actual needs.

[0044] According to some preferred embodiments of the present invention, in step (2), the conditions for the mixing include: the temperature is 40 - 90 °C, preferably 65 - 85 °C; the time is 0.1 - 2 h, preferably 0.5 - 1 h. Adopting the above preferred embodiments is beneficial for the active component to be preferentially adsorbed on the surface of the support, avoiding precipitation nucleation from occurring in the solution rather than on the support.

[0045] According to the present invention, preferably, the mixing is carried out under stirring conditions, and the stirring rate is 100 - 500 rpm.

[0046] According to the present invention, in step (3), the pH is controlled to be 8 - 10, preferably 8.5 - 9.5, to carry out the precipitation reaction.

[0047] The present invention has a relatively wide selection range for the precipitant, and any conventional precipitant in the art can be applied to the present invention. Preferably, the precipitant is selected from at least one of ammonium bicarbonate, sodium carbonate, sodium hydroxide, ammonia water, and urea, and preferably ammonium bicarbonate.

[0048] In the present invention, preferably, the precipitant is provided by an aqueous solution of the precipitant, and the concentration of the aqueous solution of the precipitant is 0.1 - 2 mol / L.

[0049] The precipitant can be contacted with the mixed solution through a conventional feeding device such as a peristaltic pump in the art, and the addition amount of the precipitant is subject to meeting the above pH requirement.

[0050] According to some preferred embodiments of the present invention, the aging temperature is 40 - 90 °C, preferably 65 - 85 °C, and the time is 4 - 24 h, preferably 6 - 16 h.

[0051] In the present invention, the preparation method also optionally includes: washing the aged product until the filtrate is neutral, for example, the filtrate pH = 7 and the filtrate conductivity is less than 50 s / m. The washing can be carried out in any conventional manner in the art, and the present invention has no special requirements for this.

[0052] According to the present invention, preferably, in step (3), the second drying is evaporation drying, and the conditions for the second drying include: the temperature is 70 - 150 °C, preferably 100 - 120 °C, and the time is 1 - 24 h, preferably 2 - 6 h.

[0053] According to the present invention, preferably, the conditions for the second calcination include: the temperature is 300 - 1000 °C, preferably 350 - 650 °C, and the time is 0.5 - 10 h, preferably 3 - 6 h.

[0054] The present invention has no particular limitation on the type of the soluble compound of the second active component, as long as it can provide the second active component. For example, it can be nitrates, acetates, sulfates, chlorides, etc. containing the second active component.

[0055] According to some preferred embodiments of the present invention, in step (4), based on the mass of the silica carrier in the product obtained in step (3), the dosage of the soluble compound of the second active component in terms of elements is 0.01 - 20 wt%, preferably 3 - 15 wt%, and preferably 5 - 10 wt%.

[0056] According to some preferred embodiments of the present invention, the second active component is Cu.

[0057] According to some particularly preferred embodiments of the present invention, the first active component is Ag and the second active component is Cu. By combining the above first active component and second active component, the reaction activity of the catalyst can be further improved and the indole yield can be increased.

[0058] In the present invention, those skilled in the art can optionally add a binder, peptizing agent, etc. according to the needs of shaping. The present invention has no particular limitation on the types of the binder and peptizing agent, and can be a conventional selection in the art.

[0059] According to the present invention, preferably, the binder is selected from at least one of sesbania powder, starch, methylcellulose, and cellulose powder, and preferably sesbania powder.

[0060] Preferably, the mass ratio of the binder to the product obtained in step (3) is (1 - 5):100.

[0061] Preferably, the peptizing agent is selected from at least one of nitric acid, hydrochloric acid, and ammonia water, and preferably nitric acid.

[0062] Preferably, the mass ratio of the peptizing agent to the product obtained in step (3) is (1 - 5):100.

[0063] In the present invention, there is no particular limitation on the shaping method in step (4), and those skilled in the art can select according to actual needs. For example, it can be extrusion molding.

[0064] According to the present invention, preferably, in step (4), the temperature of the third calcination is 300 - 1000 °C, preferably 350 - 650 °C, and the time is 0.5 - 10 h, preferably 3 - 6 h.

[0065] According to some preferred embodiments of the present invention, the preparation method further includes: under the presence of hydrogen, performing a reduction treatment on the product of the third calcination. The present invention has a relatively wide selection range for the conditions of the reduction treatment, and is based on being able to reduce at least part of the active component to the elemental state, and those skilled in the art can select according to actual needs.

[0066] According to the present invention, preferably, the conditions of the reduction treatment include: the temperature is 250 - 450 °C, preferably 280 - 320 °C, and the time is 1 - 6 h, preferably 2 - 4 h.

[0067] The second aspect of the present invention provides an indole synthesis catalyst prepared by the above preparation method.

[0068] According to the present invention, the indole synthesis catalyst comprises a modified support, a first active component and a second active component;

[0069] Wherein, the modified support comprises silica and a modified component zinc; the first active component is selected from at least one of Ag, Pd and Ru; the second active component is selected from at least one of Cu, Co, Ni, and Fe.

[0070] According to the present invention, preferably, based on the mass of the modified support, the content of the first active component in terms of element is 0.1-30 wt%, preferably 2-20 wt%, and more preferably 4-15 wt%; the content of the second active component in terms of element is 0.01-20 wt%, preferably 3-15 wt%, and more preferably 5-10 wt%, and the content of the modified component zinc is 1-10 wt%, preferably 3-7 wt%.

[0071] Preferably, the mass ratio of the first active component in terms of element to the second active component in terms of element is 1:(1-3), preferably 1:(1.2-2). In the above preferred case, it is beneficial to further improve the conversion rate and selectivity of the catalyst.

[0072] The third aspect of the present invention provides a method for synthesizing an indole compound, the synthesis method comprising: contacting ethylene glycol, aniline and a catalyst in the presence of hydrogen and water;

[0073] Wherein, the catalyst is the indole synthesis catalyst described in the second aspect.

[0074] According to some preferred embodiments of the present invention, the conditions of the contact include: the reaction temperature is 200-320 °C, preferably 270-290 °C; the reaction pressure is 0.01-1 MPa, preferably 0.05-0.2 MPa; the molar ratio of aniline to ethylene glycol is (1-15):1, preferably (5-10):1; the volume space velocity of the total material of aniline and ethylene glycol is 0.01-1 h -1 , preferably 0.1-0.6 h -1 ; the volume space velocity of the water feed is 0.01-1 h -1 , preferably 0.1-1 h -1 ; the volume space velocity of hydrogen is 0.1-20 h -1 , preferably 0.2-10 h -1 .

[0075] Adopting the above preferred reaction conditions is beneficial to inhibiting the carbon deposition formation rate, slowing down the catalyst deactivation rate, and increasing the indole yield.

[0076] The present invention will be described in detail below through examples.

[0077] Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially purchased.

[0078] The specific surface area of the silica powder used in the following examples is 660 m 2 / g.

[0079] Example 1

[0080] 1. Place 100 g of commercially available silica powder in a beaker. Dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silica powder. After impregnation for 2 h, dry at 120 °C for 2 h and then calcine at 500 °C for 4 h to obtain a modified support.

[0081] 2. Disperse the modified support in deionized water to form a first slurry under mechanical stirring. Add 9.449 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution. Pour the second mixed solution into the first slurry and stir and impregnate at 80 °C and 300 rpm for 0.5 h to obtain a second mixed slurry.

[0082] 3. Use a peristaltic pump to drip 1 mol / L ammonium bicarbonate solution into the second mixed slurry, controlling the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitate by suction and wash the filter cake with deionized water until the filtrate pH = 7 and the conductivity < 50. Then place the filter cake in an oven and dry at 120 °C to constant weight, and then calcine at 500 °C for 4 h to obtain a composite oxide.

[0083] 4. Mix the composite oxide, 3.5 g of sawdust powder, 2.5 g of nitric acid, and 30.419 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry at 120 °C to constant weight and calcine at 500 °C for 4 h to obtain the catalyst precursor.

[0084] 5. Place the catalyst precursor in a tubular furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain a catalyst. Based on the mass of silica, the composition of the catalyst analyzed by ICP is: the Ag content is 3.01 wt%, the Cu content is 7.98 wt%, and the Zn content is 5.01 wt%.

[0085] Example 2

[0086] 1. Place 100 g of commercially available silica powder in a beaker. Dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silica powder. After impregnation for 2 h, dry at 120 °C for 2 h and then calcine at 500 °C for 4 h to obtain a modified support.

[0087] 2. Disperse the modified carrier in deionized water to form a first slurry under mechanical stirring. Add 12.599 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution, pour the second mixed solution into the first slurry, and stir and impregnate at 80 °C and 300 rpm for 1 h to obtain a second mixed slurry.

[0088] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry, controlling the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitation liquid by suction, and wash the filter cake with deionized water until the pH of the filtrate = 7 and the conductivity < 50. Then place the filter cake in an oven and dry at 120 °C to constant weight, and then calcine at 500 °C for 4 h to obtain a composite oxide.

[0089] 4. Mix the composite oxide, 3.5 g of sawdust powder, 2.5 g of nitric acid, and 30.419 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into pellets. Let the extruded pellets stand at room temperature for 2 h, then dry at 120 °C to constant weight and calcine at 500 °C for 4 h to obtain the catalyst precursor.

[0090] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain a catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is: the content of Ag is 3.99 wt%, the content of Cu is 8.02 wt%, and the content of Zn is 4.99 wt%.

[0091] Example 3

[0092] 1. Place 100 g of commercial silica powder in a beaker, dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution, pour the first mixed solution into the silica powder, after impregnating for 2 h, dry at 120 °C for 2 h and then calcine at 500 °C for 4 h to obtain a modified carrier.

[0093] 2. Dissolve the modified carrier in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution, pour the second mixed solution into the first slurry, and stir and impregnate at 80 °C and 300 rpm for 2 h to obtain a second mixed slurry.

[0094] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry, controlling the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitation liquid by suction, and wash the filter cake with deionized water until the pH of the filtrate = 7 and the conductivity < 50. Then place the filter cake in an oven and dry at 120 °C to constant weight, and then calcine at 500 °C for 4 h to obtain a composite oxide.

[0095] 4. Mix the composite oxide, 3.5 g of sesbania powder, 2.5 g of nitric acid, and 30.419 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 500 °C for 4 h to obtain the catalyst precursor.

[0096] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is as follows: the content of Ag is 5.02 wt%, the content of Cu is 8.01 wt%, and the content of Zn is 4.97 wt%.

[0097] Example 4

[0098] 1. Place 100 g of commercial silica powder in a beaker. Dissolve 18.20 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silica powder, and after impregnation for 2 h, dry it at 150 °C for 1 h and then calcine it at 550 °C for 4 h to obtain the modified carrier.

[0099] 2. Dissolve the modified carrier in deionized water to form a first slurry under mechanical stirring. Add 18.899 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution. Pour the second mixed solution into the first slurry and stir and impregnate it at 60 °C and 300 rpm for 1 h to obtain a second mixed slurry.

[0100] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry, and control the end point pH = 8.5. Then age it at 85 °C for 8 h. After aging, filter the precipitate by suction, and wash the filter cake with deionized water until the pH of the filtrate is 7 and the conductivity < 50. Then place the filter cake in an oven and dry it at 110 °C to constant weight, and then calcine it at 600 °C for 4 h to obtain the composite oxide.

[0101] 4. Mix the composite oxide, 4 g of sesbania powder, 2 g of nitric acid, and 30.419 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 600 °C for 3 h to obtain the catalyst precursor.

[0102] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is as follows: the content of Ag is 6.01 wt%, the content of Cu is 7.97 wt%, and the content of Zn is 4 wt%.

[0103] Example 5

[0104] 1. Place 100 g of commercial silicon oxide powder in a beaker. Dissolve 31.85 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silicon oxide powder. After impregnation for 2 h, dry at 120 °C for 2 h and then calcine at 450 °C for 6 h to obtain a modified support.

[0105] 2. Dissolve the modified support in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution. Pour the second mixed solution into the first slurry and stir and impregnate at 70 °C and 300 rpm for 1 h to obtain a second mixed slurry.

[0106] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry and control the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitate by suction and wash the filter cake with deionized water until the filtrate pH = 7 and the conductivity < 50. Then place the filter cake in an oven and dry at 120 °C to constant weight, and then calcine at 400 °C for 5 h to obtain a composite oxide.

[0107] 4. Mix the composite oxide, 3.5 g of sesbania powder, 2.5 g of nitric acid, and 22.814 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry at 120 °C to constant weight and calcine at 650 °C for 4 h to obtain the catalyst precursor.

[0108] 5. Place the catalyst precursor in a tubular furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain a catalyst. Based on the mass of the support, the composition of the catalyst analyzed by ICP is: the content of Ag is 4.99 wt%, the content of Cu is 6.02 wt%, and the content of Zn is 7 wt%.

[0109] Example 6

[0110] 1. Place 100 g of commercial silicon oxide powder in a beaker. Dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silicon oxide powder. After impregnation for 2 h, dry at 120 °C for 2 h and then calcine at 500 °C for 4 h to obtain a modified support.

[0111] 2. Dissolve the modified support in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50%) to deionized water to obtain a second mixed solution. Pour the second mixed solution into the first slurry and stir and impregnate at 80 °C and 300 rpm for 0.5 h to obtain a second mixed slurry.

[0112] 3. Use a peristaltic pump to drop 1 mol / L ammonium bicarbonate solution into the second mixed slurry, and control the end point pH = 9. Then age at 80 °C for 8 h. After the aging is completed, filter the precipitate by suction, and wash the filter cake with deionized water until the pH of the filtrate = 7 and the conductivity < 50. Then place the filter cake in an oven and dry it at 120 °C to constant weight, and then calcine it at 500 °C for 4 h to obtain the composite oxide.

[0113] 4. Mix the composite oxide, 3.5 g of sesbania powder, 2.5 g of nitric acid, and 26.616 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 500 °C for 4 h to obtain the catalyst precursor.

[0114] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is: the content of Ag is 5.01 wt%, the content of Cu is 6.99 wt%, and the content of Zn is 5.00 wt%.

[0115] Example 7

[0116] 1. Place 100 g of commercial silica powder in a beaker, dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution, pour the first mixed solution into the silica powder, after impregnation for 2 h, dry it at 120 °C for 2 h, and then calcine it at 500 °C for 4 h to obtain the modified carrier.

[0117] 2. Dissolve the modified carrier in (1) in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50%) to deionized water to obtain a second mixed solution, pour the second mixed solution into the first slurry, and stir and impregnate at 80 °C and 300 rpm for 0.58 h to obtain a second mixed slurry.

[0118] 3. Use a peristaltic pump to drop 1 mpl / L ammonium bicarbonate solution into the second mixed slurry, and control the end point pH = 9. Then age at 80 °C for 8 h. After the aging is completed, filter the precipitate by suction, and wash the filter cake with deionized water until the pH of the filtrate = 7 and the conductivity < 50. Then place the filter cake in an oven and dry it at 120 °C to constant weight, and then calcine it at 500 °C for 4 h to obtain the composite oxide.

[0119] 4. Mix the composite oxide, 3.5 g of sesbania powder, 2.5 g of nitric acid, and 34.221 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 500 °C for 4 h to obtain the catalyst precursor.

[0120] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the support, the composition of the catalyst analyzed by ICP is as follows: the content of Ag is 5.02 wt%, the content of Cu is 8.97 wt%, and the content of Zn is 5.01 wt%.

[0121] Comparative Example 1

[0122] 1. Place 100 g of commercial silica powder in a beaker. Dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silica powder. After impregnation for 2 h, dry it at 120 °C for 2 h and then calcine it at 500 °C for 4 h to obtain a modified support.

[0123] 2. Mix the modified support, 3.5 g of carob powder, 2.5 g of nitric acid, and 30.419 g of copper nitrate trihydrate, and knead and extrude the obtained mixture into strips. Let the extruded strips stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 500 °C for 4 h to obtain the catalyst precursor.

[0124] 3. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the support, the composition of the catalyst analyzed by ICP is as follows: the content of Cu is 8.01 wt% and the content of Zn is 4.99 wt%.

[0125] Comparative Example 2

[0126] 1. Place 100 g of commercial silica powder in a beaker. Dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution. Pour the first mixed solution into the silica powder. After impregnation for 2 h, dry it at 120 °C for 2 h and then calcine it at 500 °C for 4 h to obtain a modified support.

[0127] 2. Dissolve the modified support in (1) in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50%) to deionized water to obtain a second mixed solution. Pour the second mixed solution into the first slurry and stir and impregnate it at 80 °C and 300 rpm for 0.5 h to obtain a second mixed slurry.

[0128] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry, controlling the end point pH = 9. Then age it at 80 °C for 8 h. After aging, filter the precipitate, wash the filter cake with deionized water until the filtrate pH = 7 and the conductivity < 50. Then place the filter cake in an oven and dry it at 120 °C to constant weight and calcine it at 500 °C for 4 h to obtain a composite oxide.

[0129] 4. Mix the composite oxide, 3.5 g of sesbania powder, and 2.5 g of nitric acid, knead and extrude the obtained mixture into strips, let the extruded strips stand at room temperature for 2 h, then dry to constant weight at 120 °C, and calcine at 500 °C for 4 h to obtain the catalyst precursor.

[0130] 5. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is: the Ag content is 5.01 wt%, and the Zn content is 4.99 wt%.

[0131] Comparative Example 3

[0132] 1. Dissolve 100 g of commercial silica powder in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50%) to deionized water to obtain a first mixed solution, pour the first mixed solution into the first slurry, and stir and impregnate at 80 °C and 300 rpm for 0.5 h to obtain a second mixed slurry.

[0133] 2. Dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry with a peristaltic pump, and control the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitation liquid by suction, wash the filter cake with deionized water until the pH of the filtrate is 7 and the conductivity < 50. Then place the filter cake in an oven and dry to constant weight at 120 °C, and calcine at 500 °C for 4 h to obtain the composite oxide.

[0134] 3. Mix the composite oxide, 3.5 g of sesbania powder, 2.5 g of nitric acid, and 34.221 g of copper nitrate trihydrate, knead and extrude the obtained mixture into strips, let the extruded strips stand at room temperature for 2 h, then dry to constant weight at 120 °C, and calcine at 500 °C for 4 h to obtain the catalyst precursor.

[0135] 4. Place the catalyst precursor in a tube furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain the catalyst. Based on the mass of the carrier, the composition of the catalyst analyzed by ICP is: the Ag content is 5.02 wt%, and the Cu content is 8.97 wt%.

[0136] Comparative Example 4

[0137] 1. Place 100 g of commercial silica powder in a beaker, dissolve 22.75 g of zinc nitrate hexahydrate in deionized water to obtain a first mixed solution, pour the first mixed solution into the silica powder, after impregnation for 2 h, dry at 120 °C for 2 h, and then calcine at 500 °C for 4 h to obtain the modified carrier.

[0138] 2. Dissolve the modified support in deionized water to form a first slurry under mechanical stirring. Add 15.749 g of silver nitrate solution (concentration 50 wt%) to deionized water to obtain a second mixed solution, and add 30.419 g of copper nitrate trihydrate to deionized water to obtain a third mixed solution. Pour the second and third mixed solutions into the first slurry, and stir and impregnate at 80 °C and 300 rpm for 2 h to obtain a second mixed slurry.

[0139] 3. Use a peristaltic pump to dropwise add 1 mol / L ammonium bicarbonate solution to the second mixed slurry, and control the end point pH = 9. Then age at 80 °C for 8 h. After aging, filter the precipitate by suction, and wash the filter cake with deionized water until the filtrate pH = 7 and the conductivity < 50. Then place the filter cake in an oven and dry it at 120 °C to constant weight, and then calcine it at 500 °C for 4 h to obtain a composite oxide.

[0140] 4. Mix the composite oxide, 3.5 g of carboxymethyl cellulose and 2.5 g of nitric acid, and knead and extrude the obtained mixture into pellets. Let the extruded pellets stand at room temperature for 2 h, then dry them at 120 °C to constant weight and calcine them at 500 °C for 4 h to obtain the catalyst precursor.

[0141] 5. Place the catalyst precursor in a tubular furnace at 450 °C and reduce it in a hydrogen atmosphere for 4 h to obtain a catalyst. Based on the mass of the support, according to ICP analysis, the composition of the catalyst is: the content of Ag is 4.89 wt%, the content of Cu is 8.01 wt%, and the content of Zn is 4.99 wt%.

[0142] Test Example

[0143] Test Example 1 Activity Test:

[0144] Crush and screen out 100 mL of 20-40 mesh catalyst prepared in the above examples and comparative examples and load them into a fixed-bed reactor. After the catalyst is kept at a constant temperature of 290 °C in a pure hydrogen atmosphere under normal pressure in the reactor for 4 h, the raw materials and water are transported to the preheater through a feed pump. The raw materials, water and hydrogen are mixed and preheated in the preheater and then enter the reactor for reaction. After the reaction, the product is separated into gas and liquid, and the liquid-phase product enters the product tank for enrichment. Under the reaction conditions of 290 °C, 0.2 MPa, and a molar ratio of aniline to ethylene glycol of 7:1, the liquid hourly space velocity of the reaction liquid of the aniline and ethylene glycol mixed solution is 0.2 h -1 , and the hydrogen volumetric space velocity is 0.2 h -1 , and the liquid hourly space velocity of the water reaction liquid is 0.2 h -1 . The results of the reaction for 4 h are shown in Table 1.

[0145] Table 1

[0146]

[0147] Test Example 2: Catalyst Life Test

[0148] 100 mL of the catalyst with a particle size of 20 - 40 mesh obtained by crushing and screening the catalysts prepared in Example 3 and Comparative Example 3 was charged into a fixed-bed reactor. After the catalyst was kept at a constant temperature of 290 °C for 4 h under normal pressure and in a pure hydrogen atmosphere in the reactor, the raw materials and water were transported to the preheater through a feed pump. The raw materials, water, and hydrogen were mixed and preheated in the preheater and then entered the reactor for reaction. After the reaction, the product was subjected to gas-liquid separation, and the liquid-phase product entered the product tank for enrichment. Under the reaction conditions of 290 °C, 0.2 MPa, a molar ratio of aniline to ethylene glycol of 7:1, the liquid hourly space velocity of the reaction liquid of the aniline and ethylene glycol mixed solution was 0.2 h -1 , and the volumetric hourly space velocity of hydrogen was 0.2 h -1 , and the liquid hourly space velocity of water was 0.2 h -1 . The analysis results are shown in Table 2

[0149] Table 2

[0150]

[0151] As can be seen from the above table, the conversion rate and selectivity of the examples are both above 80%, indicating that the preparation method provided by the present invention effectively reduces the noble metal loading and significantly improves the reaction activity and stability of the catalyst by introducing a certain amount of non-noble metals to replace noble metals. Compared with Comparative Example 3, the conversion rate of the catalyst in Example 3 remained at 100% after running for 72 h, and the selectivity was stable at about 83 - 85%, indicating that the modification of the support by introducing zinc oxide additives effectively inhibited the deactivation of the catalyst during the reaction and improved the stability of the catalyst

[0152] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention

Claims

1. A preparation method of an indole synthesis catalyst, characterized in that, The preparation method includes the following steps: (1) Impregnating a silica carrier with a solution containing a zinc precursor, followed by first drying and first calcination to obtain a modified carrier; (2) Mixing a first slurry containing the modified carrier with a second solution containing a precursor of a first active component to obtain a mixture; wherein the first active component is Ag; (3) Contacting the mixture with a precipitant, controlling the pH to be 8 - 10, carrying out a precipitation reaction, followed by aging, second drying and second calcination; (4) Mixing the product obtained in step (3), a soluble compound of a second active component, a binder and a peptizing agent, followed by shaping, third drying and third calcination; wherein the second active component is Cu; In the prepared catalyst, based on the mass of the modified carrier, the content of the first active component in terms of element is 0.1 - 6.01 wt%; the mass ratio of the first active component in terms of element to the second active component in terms of element is 1:(1 - 3).

2. The preparation method according to claim 1, wherein, The specific surface area of the silica support is 400 - 700 m 2 / g; The dosage of the zinc precursor in terms of zinc element is 1 - 10 parts by weight relative to 100 parts by weight of the silica carrier.

3. The preparation method according to claim 1 or 2, wherein The first drying is evaporation drying, and the conditions of the first drying include: temperature 70 - 150 °C, time 1 - 24 h; The conditions of the first calcination include: temperature 250 - 750 °C, time 0.5 - 10 h.

4. The preparation method according to claim 1 or 2, wherein In step (2), the conditions of the mixing include: temperature 40 - 90 °C, time 0.1 - 2 h; The mixing is carried out under stirring conditions, and the stirring rate is 100 - 500 rpm.

5. The preparation method according to claim 1 or 2, wherein In step (3), the precipitant is selected from at least one of ammonium bicarbonate, ammonium carbonate, sodium hydroxide, ammonia water, and urea; The precipitant is provided by an aqueous solution of the precipitant, and the concentration of the aqueous solution of the precipitant is 0.1 - 2 mol / L.

6. The preparation method according to claim 1 or 2, wherein The temperature of the aging is 40 - 90 °C, and the time is 4 - 24 h; The product after aging is washed until the filtrate is neutral and the conductivity of the filtrate is less than 50 s / m; In step (3), the second drying is evaporation drying, and the conditions of the second drying include: temperature 70 - 150 °C, time 1 - 24 h; The conditions of the second calcination include: temperature 300 - 1000 °C, time 0.5 - 10 h.

7. The preparation method according to claim 1 or 2, wherein The binder is selected from at least one of sesbania powder, starch, methyl cellulose and cellulose powder; The mass ratio of the binder to the product obtained in step (3) based on the silica carrier is (1 - 5):100; The peptizing agent is selected from at least one of nitric acid, hydrochloric acid and ammonia water; The mass ratio of the peptizing agent to the product obtained in step (3) based on the silica carrier is (1 - 5):100; In step (4), the temperature of the third calcination is 300 - 1000 °C, and the time is 0.5 - 10 h.

8. The preparation method according to claim 1 or 2, wherein The preparation method further includes: carrying out a reduction treatment on the product of the third calcination in the presence of hydrogen; The conditions of the reduction treatment include: temperature 250 - 450 °C, time 1 - 6 h.

9. An indole synthesis catalyst prepared by the preparation method according to any one of claims 1 - 8; The indole synthesis catalyst includes a modified support, a first active component, and a second active component; Among them, The modified support includes silica and a modified component zinc; the first active component is Ag; the second active component is Cu.

10. A method for synthesizing an indole compound, characterized in that, The synthesis method includes: contacting ethylene glycol, aniline, and the catalyst in the presence of hydrogen and water; wherein, the catalyst is the indole synthesis catalyst described in claim 9.

11. The synthesis method according to claim 10, wherein The conditions of the contact include: the reaction temperature is 200 - 320 °C, the reaction pressure is 0.01 - 1 MPa, the molar ratio of aniline to ethylene glycol is (1 - 15):1, the volume space velocity of the total material of aniline and ethylene glycol is 0.01 - 1 h -1 , the volume space velocity of the water feed is 0.01 - 1 h -1 , the volume space velocity of hydrogen is 0.1 - 20 h -1 .

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