CN101007779A - Method and device for making indole - Google Patents

Abstract

The invention relates to a one-step catalyzed synthesis of indole from aniline and ethylene glycol as raw materials. The invention uses Ag-based heterogeneous catalysts to carry out flow-type gas-solid-phase catalytic reaction technology in a fixed-bed reactor. Aniline and ethylene glycol are mixed in proportion and continuously fed into a fixed-bed reactor. Under the atmosphere of water vapor and hydrogen, a heterogeneous catalytic reaction is carried out on a solid catalyst bed to synthesize indole in one step. The catalytic process not only has the advantages of high activity, high selectivity and high stability, but also has the characteristics of simple process, continuous operation, low cost and environmental friendliness.

Description

A kind of method and device for preparing indole

technical field

The invention relates to a method for preparing indole, in particular to a method for synthesizing indole by one-step catalysis of aniline and ethylene glycol.

The invention also relates to a device for carrying out the method described above.

Background technique

Indole is an important heterocyclic compound and an important intermediate of medicine, pesticide, spice, dye and feed additive. Synthetic indole has important industrial application value, its market demand is growing very fast, and its development prospect is broad. Due to the needs of industrial production in my country, there is an urgent need for a production process for the synthesis of indole with simple process, low cost and environmental friendliness.

The current industrial production of indole is basically some traditional methods. One is extracted from coal tar. Coal tar contains 0.2% indole. Remove strong base and phenol from the 220-270°C fraction of coal tar, and then heat it with potassium at 100-125°C to form indole potassium. After hydrolysis, rectification and recrystallization, it can be obtained indole. Due to limited resources of coal tar, complicated separation devices and high energy consumption, it has great limitations. Another method is the o-chlorotoluene method. O-chlorotoluene is chlorinated, cyanided, ammoniated, and dehydrated to obtain indoline, and then dehydrogenated to obtain indole. Due to the numerous synthesis steps and complicated separation process, the energy consumption is high, the cost is high, and a large amount of waste is generated in the preparation process, which causes environmental pollution.

Another method is the o-aminoethylbenzene method. o-Aminoethylbenzene is dehydrocyclized at 550°C under the protection of nitrogen and in the presence of aluminum nitrate or aluminum oxide, then undergoes vacuum distillation to obtain indoline, and then dehydrogenates at 640°C , the product is obtained. This method also has many synthetic steps, harsh reaction conditions, low indole yield, high cost, waste inorganic salts in the reaction and pollutes the environment, and is rarely used in industry.

Recently, the one-step synthesis of indole from aniline and ethylene glycol has attracted much attention. Under the catalysis of Ag-based heterogeneous catalysts, in the temperature range of 320-400°C and under the pressure of 1-50 atm, aniline and ethylene glycol can react in one step to form indole. The reaction process is shown in formula 1. The method not only has low raw material price, low production cost, simple operation process and high indole yield, but also has obvious advantages of less waste causing environmental pollution in the reaction process, and is the most promising method for synthesizing indole.

Formula 1

In the 1980s, Japan conducted a large number of related researches on the catalytic process. Matsuda et al. found that catalysts such as Cd, Cu, Ag and Zn all have certain activities for the one-step synthesis of indole from aniline and ethylene glycol (US Patent 4436917). At 350°C and normal pressure, the yield of indole in the fixed-bed reaction is above 20% (excess aniline, calculated as ethylene glycol), and the indole yield of the Ag/SiO ₂ -ZnO catalyst reaches above 40%. . But the experiment also found a major problem: the catalyst deactivated within a few hours, and the yield plummeted. This is mainly due to the fact that both aniline and indole contain N atoms with lone pairs of electrons. The chemical adsorption of these substances on the catalyst is particularly strong, it is difficult to desorb, and it is easy to deactivate due to carbon deposition. Matsuda has improved the catalytic process by introducing anti-deactivation water vapor and H ₂ into the reaction system, and the deactivation situation has been improved, but it is still not optimistic.

T.Honda et al developed the Ag-Co/SiO ₂ -ZnO catalyst in 1989 (European Patent 0427287). He first prepared the SiO ₂ -ZnO carrier with a specific surface of 240m ² /g by co-precipitation method of water glass and zinc nitrate, and then loaded 0.6% Co and 11% Ag successively by separate leaching method to obtain Ag-Co/SiO ₂ -ZnO catalyst. The results show that under the conditions of 1.0MPa and 375℃, the yield of indole synthesized by one-step method of aniline and ethylene glycol on Ag-Co/SiO ₂ -ZnO catalyst in a fixed bed reaches 78%, and the stability of the catalyst is relatively good. . Moreover, the catalyst can be regenerated by burning carbon, and the performance of the catalyst remains basically unchanged after regeneration.

Recently, domestic studies on the synthesis of such indole have also begun. The literature (Acta Catalytica Sinica 2003 Vol.24No.6 471~474) reported that Ag/SiO ₂ and Cu/SiO ₂ catalysts were developed by impregnation method, and the catalytic performance of the one-step synthesis of indole from aniline and ethylene glycol was investigated. The indole yield of the two catalysts can reach about 80%, but the catalyst deactivates quickly, and the yield of the catalyst decreases rapidly after 3 hours of reaction.

In summary, the catalysts for one-step synthesis of indole from aniline and ethylene glycol have established a good foundation after 20 to 30 years of research, and the Ag-Co/SiO ₂ -ZnO catalyst has good activity, selectivity and stability. However, the preparation process of Ag-Co/SiO ₂ -ZnO catalyst is relatively complicated. First, the SiO ₂ -ZnO carrier should be prepared by water glass and zinc nitrate co-precipitation method, and then the Ag-Co/SiO ₂ -ZnO catalyst should be prepared by impregnation. , and the cost of the catalyst is relatively expensive. Domestically, Ag/SiO ₂ and Cu/SiO ₂ catalysts have been developed by the impregnation method with a simple preparation process, but the stability of the catalysts is relatively poor, and the industrial applicability is not strong.

Contents of the invention

The object of the present invention is to provide a kind of method for preparing indole.

Another object of the present invention is to provide a reaction device for realizing the above method.

In order to achieve the above object, the method for preparing indole provided by the present invention adopts Ag-based heterogeneous catalyst and fixed bed flow type gas-solid reaction process, and the mixture of raw material aniline and ethylene glycol is transported to the preheater with a pump, and after preheating After the heater is vaporized, enter the catalyst bed in the reactor for catalytic reaction to generate a liquid product containing indole; the reaction conditions are as follows:

The molar ratio of aniline and ethylene glycol is 5:1 to 15:1, the reaction temperature is 300-450°C, the reaction pressure is 0.1-5.0MPa; the temperature of the preheater is 200-400°C, the mixture of aniline and ethylene glycol The feed space velocity of the feed is 0.1-2.0h ^-1 , the water feed space velocity is 0.05-1.0h ^-1 , and the hydrogen space velocity is 50-1000h ^-1 .

The method for preparing indole, wherein the reaction temperature is 375°C, the reaction pressure is 1.0MPa; the temperature of the preheater is 280°C, the feed space velocity of the mixture of aniline and ethylene glycol is 0.42h ^-1 , water The feed space velocity is 0.21h ^-1 .

In the method for preparing indole, the liquid product containing indole is subjected to rectification to obtain indole.

The method for preparing indole, wherein the aniline and ethylene glycol are continuously fed, and after reacting on the catalyst bed, the liquid product is continuously discharged.

In the method for preparing indole, the mixture of aniline and ethylene glycol is vaporized together with adding water in a preheater, which can suppress the carbon deposition of the catalyst and improve the service life of the catalyst.

The method for preparing indole, wherein the reaction is carried out under H ₂ atmosphere, and the reduced H ₂ can inhibit the carbon deposition of the catalyst and improve the life of the catalyst.

The device provided by the present invention for realizing the above-mentioned preparation method mainly includes:

A preheater for vaporizing raw materials and water;

A hydrogen gas inlet, used to bring the vaporized raw materials and water in the preheater into the reactor;

A reactor, which is filled with a catalyst for catalytic reaction of vaporized raw materials and water;

The product collection tank is used to receive the product and carry out phase separation, and the product is discharged through the discharge port at the bottom of the product collection tank;

Raw materials, water and hydrogen enter the preheater through the circulation pump respectively.

Said device, wherein the outlet of the product collection tank is connected with a rectification tower, the temperature of the product collection tank is 100-200°C; the rectification tower rectifies the product, and the product after rectification enters the product storage tank, unreacted raw materials enter the reactant storage tank to participate in the reaction again; water vapor and hydrogen enter the preheater from the product collection tank for circulation.

Said device, wherein the product in the product collection tank enters the rectification tower through a circulating pump.

Said device, wherein water vapor and hydrogen enter the preheater through a circulating compressor.

The Ag-based heterogeneous catalyst adopted in the present invention is based on Ag as the main active component, and one or more of the following elements are auxiliary agents, which are carried on the carrier by impregnation method: Li, Na, K, Rb of group IA and Cs, Be, Mg, Ca, Sr and Ba of Group IIA, Zn and Cd of Group IIB, Mn, Tc, Re and Tl of Group VIIB, Sc, Y and La of Group IIIB, Fe and Co of Group VIII , Ni, Ru, Rh, Pd, Os, Ir and Pt. The carrier is made of silica, MCM-41, SBA-15, activated carbon or aluminum oxide. The specific surface area of the carrier is 100-500m ² /g, the pore volume is 0.5-2.0cm ³ /g, the pore size distribution is 5-1000 Ȧ, Ag accounts for 1-30.0% of the total weight of the catalyst, and each additive contributes to the total weight of the catalyst. The weight accounts for 0.01-10.0%, and the sum of all auxiliary agents accounts for 0.05-15.0% in the total weight of the catalyst.

The impregnation method is as follows: firstly, commercially available SiO ₂ with high specific surface area and large pores is used as the carrier of the catalyst. Then the active components of the catalyst and auxiliary agents are impregnated onto the carrier by means of co-impregnation or sub-impregnation. The key of this method is to select suitable additives to adjust the activity and selectivity of the catalyst, especially to adjust and improve the stability of the catalyst. In this way, the catalytic activity, selectivity and stability of the catalyst we developed are relatively high, and have strong industrial application value, and the complicated step of preparing the carrier by coprecipitation method is omitted, the preparation process of the catalyst is simple and reliable, and the cost of the catalyst is low. relatively low. By using such a catalyst, the present invention can be accomplished further.

The Ag-based heterogeneous catalyst is reduced and activated before use. The specific method of restoration is as follows. Reduction is carried out under H ₂ gas containing N ₂ , the volume content of H ₂ in the mixed gas is 10-100%, the space velocity of the mixed gas is 200-8000h ^-1 , the reduction temperature is 100-500°C, and the reduction time is 1 ~20 hours.

After the catalytic reaction is carried out for a long time, such as 500-5000 hours, the conversion rate, selectivity and indole yield of the reaction decrease obviously, and more macromolecular carbon-containing compounds are accumulated in the catalyst, which needs to be regenerated. In the catalyst regeneration method of the present invention, the regenerated gas is nitrogen containing a small amount of oxygen. After the gas is purified, it enters the catalyst bed of the reactor for carbon burning reaction, and then the catalyst is reduced with hydrogen to carry out the catalytic reaction again.

Description of drawings

Figure 1 is a schematic diagram of the basic device of the present invention.

Detailed ways

Example 1

Using the reaction apparatus shown in Fig. 1, the reaction was carried out under the following reaction conditions.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. Catalyst loading is 6ml, the ratio of aniline and ethylene glycol is 10: 1 (molar ratio), reaction temperature 325 ℃, reaction pressure 0.1MPa; The temperature of preheater 280 ℃, the feeding of aniline and ethylene glycol mixture material The space velocity is 0.21h ^-1 , the water feed space velocity is 0.11h ^-1 , and the hydrogen space velocity is 860h ^-1 . 12 hours sampling analysis. This example is a one-way reaction.

The specific reaction process is as follows: 10:1 aniline and ethylene glycol are placed in the reactant storage tank 1, pumped into the preheater 3 with a precision double plunger pump 2 at a flow rate of 0.21h ^-1 , and put into the water tank 4. Water is pumped into the preheater at a flow rate of 0.11h ^-1 by a precision double plunger pump 5, and vaporized together with the reaction materials. The hydrogen gas entering the preheater entrains vaporized aniline, ethylene glycol and water at a flow rate of 860 h ^-1 into the reactor 6 for catalytic reaction. The hydrogen must be purified in advance through purification tanks 7 and 8 with built-in silica gel, 5A molecular sieve activated carbon and deoxidizer. The reaction products are collected via product collection tanks 12 and 13, respectively. A stop valve 14 is provided at the bottom of the product collection tanks 12 and 13 . The hydrogen is vented after the pressure relief of the back pressure valve 15. The temperature of the product collection tank is maintained at room temperature (if the product needs to be rectified by a rectification tower, the temperature of the product collection tank is 100-200°C), and the collected liquid includes two phases of water/oil, which are separated into water by a separatory funnel Phase and oil phase, respectively analyze the aniline, ethylene glycol and indole in it, and add the data obtained respectively, and finally calculate the conversion rate of ethylene glycol in the catalytic reaction, the selectivity of indole and the formation of indole Indole yield. Reaction data are listed in Table 1.

Example 2

Utilize the reaction apparatus that Fig. 1 increases, carry out reaction under following reaction condition.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. Catalyst loading is 6ml, the ratio of aniline and ethylene glycol is 10: 1 (molar ratio), reaction temperature 375 ℃, reaction pressure 0.1MPa; The temperature of preheater 280 ℃, the feeding of aniline and ethylene glycol mixture material The space velocity is 0.21h ^-1 , the water feed space velocity is 0.11h ^-1 , and the hydrogen space velocity is 860h ^-1 . 12 hours sampling analysis. Reaction data are listed in Table 1.

This example is a one-way reaction. The specific reaction process is as described in Example 1.

Example 3

Using the reaction apparatus shown in Fig. 1, the reaction was carried out under the following reaction conditions.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. Catalyst loading is 6ml, the ratio of aniline and ethylene glycol is 10: 1 (molar ratio), reaction temperature 375 ℃, reaction pressure 1.0MPa; The temperature of preheater 280 ℃, the feeding of aniline and ethylene glycol mixture material The space velocity is 0.21h ^-1 , the water feed space velocity is 0.11h ^-1 , and the hydrogen space velocity is 860h ^-1 . 12 hours sampling analysis. Reaction data are listed in Table 1.

This example is a one-way reaction. The specific reaction process is as described in Example 1.

Example 4

Using the reaction apparatus shown in Fig. 1, the reaction was carried out under the following reaction conditions.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. Catalyst loading is 6ml, the ratio of aniline and ethylene glycol is 10: 1 (molar ratio), reaction temperature 375 ℃, reaction pressure 1.0MPa; The temperature of preheater 280 ℃, the feeding of aniline and ethylene glycol mixture material The space velocity is 0.42h ^-1 , the space velocity of water feed is 0.21h ^-1 , and the space velocity of hydrogen is 430h ^-1 . 12 hours sampling analysis.

This embodiment is a one-way reaction, and the specific reaction process is as described in Example 1. Reaction data are listed in Table 1.

Example 5

Using the reaction apparatus shown in Fig. 1, the reaction was carried out under the following reaction conditions.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. The catalyst loading amount is 6ml, the ratio of aniline and ethylene glycol is 10:1 (molar ratio), reaction temperature: 375°C, reaction pressure: 1.0MPa; preheater temperature: 280°C, mixed material of aniline and ethylene glycol The feed space velocity is 0.42h ^-1 , the water feed space velocity is 0.21h ^-1 , and the hydrogen space velocity is 300h ^-1 . 24-hour sample analysis.

This embodiment is a one-way reaction, and the specific reaction process is as described in Example 1. Reaction data are listed in Table 1.

Example 6

Using the reaction apparatus shown in Fig. 1, the reaction was carried out under the following reaction conditions.

The production method adopts an Ag-based heterogeneous catalyst prepared by a simple impregnation method, and prepares indole from aniline and ethylene glycol in one step. Catalyst loading is 6ml, the ratio of aniline and ethylene glycol is 10: 1 (molar ratio), reaction temperature 375 ℃, reaction pressure 1.0MPa; The temperature of preheater 280 ℃, the feeding of aniline and ethylene glycol mixture material The space velocity is 0.42h ^-1 , the water feed space velocity is 0.21h ^-1 , and the hydrogen space velocity is 300h ^-1 . Sampling and analysis every 50 hours. A life test of 500 hours was continuously performed. Reaction data are listed in Table 2.

This embodiment only carries out one-way reaction. The specific reaction process is as described in Example 1.

As can be seen from the results in Table 1, using the Ag-based heterogeneous catalyst of the present invention, in a fixed-bed reactor, aniline and ethylene glycol are used to synthesize indole in one step. Different reaction conditions have a greater impact on the catalytic performance of Ag-based catalysts for the synthesis of indole. The optimal reaction conditions are as follows: reaction temperature: 375°C, reaction pressure: 1.0MPa; preheater temperature: 280°C, feed space velocity of aniline and ethylene glycol mixture: 0.42h ^-1 , water feed The space velocity is 0.21h ^-1 , and the space velocity of hydrogen is 300h ^-1 . Under these conditions, the conversion rate of the ethylene glycol of Ag-based heterogeneous catalyst reaches 96.2%, and the selectivity of forming indole reaches 84.3%, and the yield of forming indole reaches 81.1%, which is better than the best result reported in the literature (selection property reaches 78%, and the yield of generating indole reaches 78%), and there is a certain improvement.

Table 2 lists the lifetime experimental results of Ag-based heterogeneous catalysts. It can be seen that under the optimal reaction conditions, the conversion rate of ethylene glycol and the yield of indole in the continuous feed reaction of aniline and ethylene glycol for 500 hours have declined to a certain extent, but they can still maintain a high level . The important thing is that the selectivity of forming indole increases with the prolongation of the reaction time, and remains basically unchanged after reaching 88%. This result is very meaningful, because high selectivity is particularly important for industrial applications. It is reported in the literature that the selectivity of the Ag-based heterogeneous catalyst is 78%, and with the prolongation of the reaction time (such as hundreds of hours), various indicators such as the selectivity of the catalyst have a certain decline. Indoles are macromolecules containing nitrogen and benzene rings, which tend to generate carbon deposits on the catalyst, thereby causing temporary deactivation of the catalyst. Compared with the literature results, our results obviously have certain characteristics and have obvious industrial application value.

The process adopts a single-pass reaction in the laboratory test, and a circular reaction in large-scale industrial production, that is, the excess aniline, water and hydrogen added in the reaction are circulated in the reaction device, which can save resources and achieve environmental friendliness. Purpose.

On the basis of the above-mentioned embodiments, the outlets of the product collection tanks 12 and 13 can also send the product to the rectification column 17 through the circulation pump 16, and further rectify the product. At this time, the temperature of the product collection tanks 12 and 13 is 100-200°C. The rectifying column 17 rectifies the product and the product enters the product storage tank 18, and the unreacted raw material enters the reactant storage tank 1 to participate in the reaction again; water vapor and hydrogen enter the pre-processing tank 12, 13 by the product collection tank 19 through the circulation compressor 19. Heater 3 circulates.

In summary, the one-step catalytic synthesis of indole from aniline and ethylene glycol has the advantages of simple process flow, high production efficiency and continuous and convenient operation, and can realize industrial production.

Table 1 Performance of heterogeneous silver-based catalysts under different process conditions

Temperature °C Pressure MPa Liquid space velocity h ^-1 water space velocity h ^-1 gas space velocity h ^-1 time h Conversion rate(%) Selectivity (%) Yield (%) 325 0.1 0.21 0.11 860 12 74.7 44.6 33.4 375 0.1 0.21 0.11 860 12 93.1 49.7 46.3 375 1 0.21 0.11 860 12 87.5 48.4 42.3 375 1 0.42 0.21 430 12 91.2 51.8 47.3 375 1 0.42 0.21 300 twenty four 96.2 84.3 81.1

The stability performance of table 2 heterogeneous silver-based catalyst

Response time h Temperature °C Pressure MPa Liquid space velocity h ^-1 water space velocity h ^-1 gas space velocity h ^-1 Conversion rate(%) Selectivity (%) Yield (%) 50 375 1 0.42 0.21 300 96.2 84.3 81.1 100 375 1 0.42 0.21 300 94.7 86.3 81.7 150 375 1 0.42 0.21 300 94.2 85.8 80.8 200 375 1 0.42 0.21 300 90.5 86.7 78.5 250 375 1 0.42 0.21 300 88.4 87.3 77.2 300 375 1 0.42 0.21 300 85.2 88.1 75.1 350 375 1 0.42 0.21 300 84.4 88.3 74.5 400 375 1 0.42 0.21 300 82.6 87.8 72.5 450 375 1 0.42 0.21 300 82.0 88.0 72.2 500 375 1 0.42 0.21 300 80.7 87.2 70.4

Claims (10)

1. A method for preparing indole, using Ag-based heterogeneous catalyst and fixed-bed flow-type gas-solid reaction process, the mixture of raw material aniline and ethylene glycol is transported to the preheater by pump, and then vaporized by the preheater Enter the catalyst bed layer in the reactor to carry out catalytic reaction, generate the liquid product containing indole; Reaction condition is as follows: The molar ratio of aniline and ethylene glycol is 5:1 to 15:1, the reaction temperature is 300-450°C, the reaction pressure is 0.1-5.0MPa; the temperature of the preheater is 200-400°C, the mixture of aniline and ethylene glycol The feed space velocity of the feed is 0.1-2.0h ^-1 , the water feed space velocity is 0.05-1.0h ^-1 , and the hydrogen space velocity is 50-1000h ^-1 . 2. The method for preparing indole as claimed in claim 1, characterized in that, the reaction temperature is 375°C, the reaction pressure is 1.0MPa; the temperature of the preheater is 280°C, and the feed of the aniline and ethylene glycol mixture The space velocity is 0.42h ^-1 , and the water feed space velocity is 0.21h ^-1 . 3. The method for preparing indole according to claim 1, characterized in that the liquid product containing indole is subjected to rectification to obtain indole. 4. The method for preparing indole as claimed in claim 1, characterized in that the aniline and ethylene glycol are continuously fed, and after the reaction on the catalyst bed, the liquid product is continuously discharged. 5. The method for preparing indole as claimed in claim 1, characterized in that the mixture of aniline and ethylene glycol is vaporized together with water in a preheater. 6. The method for preparing indole according to claim 1 or 5, characterized in that the reaction is carried out under _H2 atmosphere. 7. A device for realizing the preparation method of claim 1, mainly comprising: A preheater for vaporizing raw materials and water; A hydrogen gas inlet, used to bring the vaporized raw materials and water in the preheater into the reactor; A reactor, which is filled with a catalyst for catalytic reaction of vaporized raw materials and water; The product collection tank is used to receive the product and carry out phase separation, and the product is discharged through the discharge port at the bottom of the product collection tank; Raw materials, water and hydrogen enter the preheater through the circulation pump respectively. 8. The device according to claim 7, characterized in that a rectification tower is connected to the outlet of the product collection tank, and the temperature of the product collection tank is 100-200°C; the rectification tower rectifies the product , the rectified product enters the product storage tank, and the unreacted raw materials enter the reactant storage tank to participate in the reaction again; water vapor and hydrogen enter the preheater from the product collection tank for circulation. 9. The device according to claim 8, characterized in that the product from the product collection tank enters the rectification tower through a circulation pump. 10. The apparatus of claim 7, wherein water vapor and hydrogen enter the preheater through a recycle compressor.

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