JPS6222758A - Production of indole - Google Patents

Abstract

PURPOSE:To prevent the lowering of catalytic activity caused by the recycled use of recovered aniline in the vapor-phase reaction of ethylene glycol with aniline in the presence of a catalyst, by contacting the reaction liquid or recovered aniline with carbon dioxide gas. CONSTITUTION:Ethylene glycol is made to react with stoichiometrically excess aniline in the presence of a catalyst in vapor phase, and aniline is separated and recovered from the reaction liquid containing indole, side-reaction products and unreacted aniline by distillation and at the same time, recycled to the reaction system to obtain indole useful as a raw material in chemical industry, e.g. raw material of perfume, dye, etc. In the above process, the reaction liquid of the recovered aniline to be recycled is made to contact with carbon dioxide gas. The side reaction product poisoning the catalyst and difficult to be separated from aniline by distillation can be made harmless by this process. Accordingly, the objective compound can be produced in high yield keeping a sufficiently high catalytic activity for a long period even by the recycled use of aniline.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing indole from aniline and ethylene glycol. More specifically, the present invention relates to a method for preventing a decrease in catalyst activity due to recycled use of recovered aniline when producing indole by reacting aniline and ethylene glycol in the gas phase in the presence of a catalyst.

[Problems to be solved by conventional technology and invention]

Indole is widely used as a raw material for chemical industries such as perfumes and dyes, and has particularly attracted attention in recent years as a raw material for the synthesis of amino-chu. Traditionally, indole has been manufactured using expensive raw materials or through long and complicated processes. However, recently, a gas phase catalytic reaction of aniline and ethylene glycol has been discovered as a method for producing indole using inexpensive raw materials and in a simple process.

Various solid acid catalysts and metal catalysts have been proposed as catalysts for the reaction. When these catalysts are reacted over a long period of time, their activity decreases, although the degree varies depending on the type of catalyst and reaction conditions, and they require periodic regeneration by heating and calcination in an oxygen atmosphere. do. Regeneration operations are complicated, and if performed too frequently, they may impair the economics of the process. The details of the cause of this decrease in activity are not clear, but since reactivation is possible using conventional methods, the main cause is that organic matter becomes carbonaceous and deposits on the catalyst surface under the reaction conditions. This is thought to be because it covers the active sites of . The reduction in activity can be reduced by carrying out the reaction in a hydrogen atmosphere or by adding water to the reaction system, but this is not always sufficient.

On the other hand, it is known that in order to obtain indole in good yield, it is necessary to have a large excess of aniline present in the reaction system. Therefore, when producing indole industrially by this method, it is essential to separate and recover a large amount of aniline contained in the resulting reaction mixture and use it again as a raw material in the reaction. However, in this case, a problem arises in that the activity of the catalyst is significantly reduced compared to the case where recovered aniline is not used. In other words, if the reaction is carried out without recycling the recovered aniline, the catalyst can maintain sufficient reaction activity for several hundred hours, but if the recovered aniline is supplied under the same conditions, the catalyst The decrease in activity becomes significant, and the frequency of regeneration operations increases significantly. Therefore, it is presumed that the recovered aniline contains impurities that are harmful to the catalyst.

The reaction liquid obtained by condensing the gaseous reaction mixture exiting the reactor contains not only the produced indole and water, unreacted ethylene glycol, and excess aniline, but also a small number of various side reaction products. things exist. Although some of them have been isolated and fixed, the chemical structures and physicochemical properties of many side reaction products have not been clarified. If some of these side reaction products are recycled to the reactor without being separated from the recovered aniline or rendered harmless, they become carbonaceous and deposit on the catalyst surface, causing a decrease in its activity. is considered to be included.

Moreover, the aniline recovered by distillation according to conventional methods has a negative effect on the catalyst activity, and the side reaction products that cause the decrease in activity are difficult to separate from the aniline by distillation due to the vapor-liquid equilibrium relationship with the aniline. It is considered that

Therefore, the purpose of the present invention is to effectively render harmless such side reaction products that are harmful to the catalyst and difficult to separate by distillation, so that even when recovered aniline is used as a reaction raw material, there is no adverse effect on the activity of the catalyst. An object of the present invention is to provide a method for producing indole that can avoid the above problems.

[Means for solving problems]

As a result of various studies to achieve the object of the present invention, the inventors of the present invention discovered that when separating and recovering aniline by distillation and supplying it to the reactor again, the reaction solution containing this side reaction product and aniline is Contacting the recovered aniline with carbon dioxide and subsequent distillation, or contacting the recovered aniline with carbon dioxide before feeding it to the reactor, is extremely effective in rendering the side reaction products harmless to the catalyst. I discovered something. The indole production method of the present invention involves a gas phase reaction of ethylene glycol and a stoichiometrically excess amount of aniline in the presence of a catalyst, and the resulting indole, side reaction products, and unreacted aniline. A method for producing indole by separating and recovering aniline from a reaction solution containing it and recycling the recovered aniline to the gas phase reaction, characterized in that the reaction solution or the recovered aniline is brought into contact with carbon dioxide. That is.

In the method of the present invention, a solid acid catalyst or a metal catalyst ffl
(7) Aniline and ethylene glycol are reacted in the gas phase in the presence of the reaction.

Among the catalysts used in this method, the following can be mentioned as solid acid catalysts.

(1) Si, AI, B, Sb, Bi, Sn
, Pb, Ga, Ti, In.

Sr, Ca, , Zr, Be, Mg, Y, Cu
, Ag, Zn, Cd, and a lanthanide element (hereinafter referred to as catalyst material (1)).

PbO2, Al2O3-8203, 5i02-ZnO,
5i02-CaO.

5i02- In2O3, 5i02-8rO, 5i02
-CdO, 5i02-Al2O3, 5102-Mg0.
TiO2-9n02. Ti02-Zr02Cd02
-Bi203, 5i02- Y2O3, 5i02.
Bi2O3-BeO,5i02- Ga2O3,5i0
2-La2O3, 5i02-Ce203, 5i02
-ZnO-Age, 5i02-MgO-CuO, etc.

(2) Pd, Pt, Cr, Fe, Ni, C
The sulfide of at least one element selected from O, Zn, No, Cd and W is a catalyst containing selenide (hereinafter referred to as catalyst material (2)), for example, PdS.
, PtS, CrS, FeS.

NiS, Gas, ZnS, MoS2. CdS,
WS2. Zn5e, CdSe, etc.

(3) Fe, TI, Ca, Kn, Bi, S
t, Y, AI, Zn, Cd.

An inorganic salt of at least one element selected from Ni, Mg, In, Be, Co, Ga, and lanthanide elements, i.e., halides, carbonates, nitrates, sulfates, phosphoric acids 11? , pyrophosphorus butyrate, phosphomolybdate, silicotungsten salt resistant (hereinafter referred to as catalyst material (3)), for example, ferric sulfate, thallium sulfate.

Calcium sulfate, manganese sulfate, bismuth sulfate, strontium sulfate, yttrium sulfate, cadmium bromide, aluminum sulfate, zinc sulfate, nickel sulfate, cadmium chloride, magnesium 1dE acid, indium sulfate, beryllium sulfate, cadmium nitrate, cobalt sulfate, zinc aluminum sulfate , magnesium chloride, cadmium sulfate, cadmium phosphate, etc.

In addition, as a metal catalyst, Cu + A g * P t
+ P d * N r +Go, Fe, Ir,
Examples include catalysts containing at least one element selected from Os, Ru, and Rh (hereinafter referred to as catalyst material (4)).

Among the above-mentioned groups of catalytic substances, 5i02-Z is most preferably used in the group of catalytic substances (1).
nQ-Ago, in the group of catalyst substances (2), cadmium sulfide, in the group of catalyst substances (3), cadmium sulfide,
Further, the group of catalyst substances (4) includes Ag supported on a carrier having a large specific surface area.

These catalysts can be manufactured by any known method. That is, the catalyst substance (1) can be prepared by hydrolyzing a water-soluble salt of a catalyst constituent element to form a hydroxide, drying and calcining the resulting gel, or by thermally decomposing an easily decomposable salt in the air. It can be manufactured by a method etc.

The catalyst substance (2) is produced by adding sodium sulfate or potassium selenide to a water-soluble salt of a catalyst constituent element, or by contacting a catalyst constituent element or its salt with hydrogen sulfide gas or hydrogen selenide gas, etc. can do.

Furthermore, the catalyst substance (4), which is a metal catalyst, is a salt, hydroxide or oxide of a catalyst constituent element, which is mixed with hydrogen, formalin, formic acid,
It can be produced by a method of reducing with a reducing agent such as phosphorous acid or hydrazine.

These solid acid catalysts or metal catalysts contain the above-mentioned catalyst materials (1
), (2), (3), and (4) may be used alone, or a mixture of two or more thereof, or they may be supported on a carrier. As the carrier, any commonly used carrier can be used, and diatomaceous earth, pumice, titania, silica-alumina, alumina, magnesia, silica gel, activated clay, asbestos, etc. are usually used. A supported catalyst is prepared by supporting the catalyst substance on these phases by a conventional method.

There is no particular restriction on the supporting rod for the phase of the catalyst material,
Usually, the catalyst material is supported in an appropriate amount depending on the phase, for example 1 to 50%.

In the method for producing indole of the present invention, the reaction between aniline and ethylene glycol is carried out in the gas phase in the presence of the above-mentioned catalyst, and any of a fixed bed, fluidized bed, or moving reactor may be used as the reaction apparatus. obtain.

Aniline and ethylene glycol introduced into the reactor are
0.01- ethylene glycol per mole of aniline
A range of 1 mol is preferred, especially a range of 0.05 to 0.5 mol.

Aniline and ethylene glycol, which are raw materials, are introduced in an amount in a liquid hourly space velocity (LH3V) of O, Gl to 10 hr', and are vaporized in an evaporator before being introduced into the reactor. In addition, in that case, water vapor, hydrogen, -carbon oxide,
Carbon dioxide, methane, nitrogen, neon, argon, etc. may be included as a carrier gas. In particular, water vapor, hydrogen, and carbon oxide are preferred because they increase the catalyst life.

The reaction temperature is in the range of 200 to 600°C, especially 250 to 50°C.
A range of 0°C is preferred.

The reaction pressure can be selected to be any pressure below the pressure at which the raw materials or the components contained in the reaction mixture form a condensed phase at the reaction temperature, but in practical terms: 1. IX is preferably in the range of 105 to 1.0 x 10' Pa, 2. OX 1.05~5.0X106
The range of Pa is more preferable.

In the method of the present invention, the reaction liquid obtained by condensing the gaseous reaction mixture exiting the reactor for indole production may be used as it is, or the organic phase after two-phase separation into an aqueous phase and an organic phase may be used as carbon dioxide. After contacting with carbon dioxide, aniline is recovered, this recovered aniline is recovered from 1 or this reaction solution, and after this recovered aniline is brought into contact with carbon dioxide, it is recycled and reused in the reaction apparatus.

Carbon dioxide in the present invention is not particularly limited as long as it is pure CO2 gas or a gas containing CO2 gas. The mixed gas is H2+ rJ21 o21GO,
He, Ne, Ar, CH4, C2H6, C3HB
, C4H1(,.

Examples include C02-containing gases containing one or more substances that are gases at normal temperature and pressure, such as C2H4, C3H6, and C4H8. However, the substances that can be mixed with 002 in the method of the present invention are not limited to these, and are not particularly limited as long as they are gaseous within the range of processing conditions such as temperature and pressure for contacting the reaction liquid with CO2.

In the method of the present invention, the method of bringing the 002 gas into contact with the reaction solution containing side reaction products and aniline includes, for example, a method of placing the reaction solution and the 002 gas in a closed container and stirring;
A method of bubbling 002 gas into the reaction solution or C0
There is a method of spraying the reaction solution into a gas stream. However, the method is not limited to these methods, and the reaction solution and 002
Various methods that can bring the gas into contact are applicable. Furthermore, these methods may be of a batch type, semi-batch type, or continuous type.

In the present invention, there is no particular restriction on the partial pressure of the C02 gas brought into contact with the reaction solution, but the gauge pressure is usually 0.01 g/ct.
'n' - is fine. Further, the contact time between the reaction solution and the C02 gas is about 10 minutes to 50 hours. however,
The C02 gas partial pressure and contact time are not limited to this range, and the C02 partial pressure and time necessary to achieve the purpose of the present invention are determined depending on the side reaction products contained in the reaction solution. You just have to choose.

Generally, the lower the C02 gas partial pressure, the longer the contact time is desirable. Regarding the treatment temperature, it is preferably 150° C. or lower since there are problems such as evaporation of the reaction solution.

The recovered aniline obtained by the above-mentioned treatment is reused in the reaction as it is or mixed with fresh aniline.

[Action and effect of the invention]

According to the method of the present invention, ethylene glycol and aniline in a stoichiometric excess relative to the ethylene glycol are reacted in a gas phase, and the excess aniline is separated and recovered from the reaction liquid obtained by condensing the reaction mixture. When used as a raw material, by contacting the reaction solution with carbon dioxide and then separating and recovering aniline, or by contacting aniline separated and recovered from the reaction solution with carbon dioxide, side reaction products harmful to the catalyst can be produced. can be rendered harmless. Therefore, even if recovered aniline is used, the activity of the catalyst can be maintained for a long time and indole can be produced in good yield.

〔Example〕

The method and effects of the present invention will be specifically explained below with reference examples, comparative examples, and examples.

Reference Example 1 Powdered cadmium sulfide catalyst 50 was compression-molded to a particle size of 3 to 41 in a stainless steel reaction tube with an inner diameter of 25 g++a.
01 was charged and subjected to reaction. Hydrogen gas was supplied to the reaction tube at 2 It/win under a pressure of 7 kg/crn', and the temperature of the catalyst layer was gradually raised from room temperature to 350°C and maintained at 350°C. Next, Aniline and 33
% ethylene glycol aqueous solution, respectively 234 g/
After mixing and vaporizing at a rate of 48 g/hr and 48 g/hr, the mixture was supplied to a reaction tube to start the reaction. Immediately after the start of the reaction, the indole yield based on ethylene glycol was 74.8%. The yield decreased gradually over time and reached 62.0% 200 hours after the start of the reaction.

The aniline used in the reaction was commercially available industrial aniline.

Comparative Example 1 In Reference Example 1, the reaction mixture exiting the reaction tube was cooled to room temperature, the resulting condensate was separated into an aqueous phase and an organic phase, and aniline was distilled from the latter as follows. Separated and collected. In other words, the content score is 30j! distillation pot, inner diameter 8
0+sm, height 2000 m nominal size 7Jl/4inc
h 25 kg of the organic phase was charged into a glass distillation apparatus consisting of a Raschig ring packed bed and a condenser, and the pressure was 10 To
Batch distillation was performed at a reflux ratio of 0.2. First distillate 0.4
kg, followed by 20.3 kg of aniline fraction. Similar batch distillation was repeated to obtain about 80 kg of recovered aniline. As a result of analysis, the purity of recovered aniline was 99%.
It was before.

Using this recovered aniline, Example 1 was prepared in exactly the same manner as in Reference Example 1.
The indole synthesis reaction was carried out. The indole yield based on ethylene glycol immediately after the start of the reaction is shown in Reference Example 1.
It was 75.2%, which was almost the same as that, but it decreased to 43.6% 200 hours after the start of the reaction.

Reference Example 2 A stainless steel reaction tube with an inner diameter of 20cm was molded into a commercially available 5102 tablet with a diameter of 31111 and a height of 2.5III, and was filled with pellet-like fibers 4 (jOts I) carrying 13% silver. The indole synthesis reaction was carried out at normal pressure by maintaining the temperature at 350°C and supplying a mixed gas of aniline, ethylene glycol, and water, which had been pre-vaporized in a molar ratio of 12:1:30, to the reaction tube at a rate of 80 tSTP/hr. .

The indole yield based on ethylene glycol one hour after the start of the reaction was 70.5%. This yield gradually decreased with the passage of 1 hour, and 50 hours after the start of the reaction, 51
．． It was 0%. The aniline used in the reaction was the same commercially available industrial aniline as in Reference Example 1.

Comparative Example 2 The reaction mixture exiting the reaction tube in Reference Example 2 was cooled to room temperature, the resulting condensate was separated into an aqueous phase and an organic phase, and aniline was separated and recovered from the latter in the same manner as in Comparative Example 1. . Approximately 20 kg was collected. Aniline of minutes. The effective purity of the analysis was 89% or more.

Using this recovered aniline, an indole synthesis reaction was carried out under the same conditions as in Reference Example 2. Is the indole yield based on ethylene glycol one hour after the start of the reaction almost the same as that in Reference Example 2? It was 0.1%R, but it decreased to 43.4% within 50 poems after the start of the reaction.

Reference Example 3 Indole synthesis reaction was carried out in the same manner as Reference Example 2 except that the catalyst was changed. The catalyst was a 5i02 catalyst similar to that used in Reference Example 2, with 2.5% copper supported. The indole yield based on ethylene glycol one hour after the start of the reaction was 87.0%, and the indole yield after 50 hours was 41.8%.

Comparative Example 3 The reaction mixture exiting the reaction tube in Reference Example 3 was cooled to room temperature, the resulting condensate was separated into an aqueous phase and an organic phase, and aniline was extracted from the latter by distillation in the same manner as in Comparative Example 1. Separated and collected. As a result of analysis of the approximately 20 kg of aniline recovered,
The purity was over 98%.

Using this recovered aniline, an indole synthesis reaction was carried out under the same conditions as in the reference example. The indole yield based on ethylene glycol one hour after the start of the reaction was 66.7%, which is almost the same as in Reference Example 3.

However, it decreased to 33.3% 50 hours after the start of the reaction.

Example 1 140 kg of condensate obtained by cooling the reaction mixture from the indole synthesis reaction to room temperature under the same conditions as Reference Example 1
was placed in a closed stirring tank with a volume of 300), and the
After purging with 2 gases, the tank pressure becomes 1 kg/am gauge pressure.
002 gas was introduced until '2. After stirring at 500 rpm for 3 hours at 60°C No. 4, the organic phase was collected, and about 80 units of aniline was recovered by batch distillation using the same distillation apparatus and operating conditions as in Comparative Example 1. It was subjected to a similar indole synthesis reaction. Immediately after the start of the reaction. The indole yield based on ethylene glycol was 74.8%, which was almost the same as in Reference Example 1, and the yield after 200 hours was 8.
The yield was 1.2%, and the decrease in yield was smaller than that in Comparative Example 1.

Example 2 After introducing 002 gas into a stirring tank containing 140 kg of the reaction mixture in the same manner as in Example 1, the mixture was heated at 50 Or
Stirred at pm. After the treatment, the organic phase was collected and aniline was collected by distillation in exactly the same manner as in Comparative Example 1, and was subjected to an indole synthesis reaction. The indole yield based on ethylene glycol immediately after the start of the reaction was 74.6%, and the indole yield after 200 hours was 61.3%.

Example 3 After putting 140 kg of the reaction mixture into a stirring tank in the same manner as in Example 1, a mixed gas of 1% C0220 and 1% N280 was introduced into the tank until the internal pressure reached a gauge pressure of 1 kg/crn. The mixture was stirred at 500 rpm for 30 cycles at 60°C while being circulated.After the treatment, the organic phase was collected and aniline was collected in exactly the same manner as in Comparative Example 1, and subjected to the indole synthesis reaction. Immediately after the start of the reaction. and 200F
The indole yields based on ethylene glycol after ikf were 74.3% and 61.7%, respectively.

Example 4 Indole synthesis reaction under the same conditions as in Reference Example 1. The condensate obtained by cooling the reaction mixture from Q to room temperature was separated into two phases, an aqueous phase and an organic phase. Aniline was separated and recovered by batch distillation. Approximately 8 by distillation
0 kg of recovered aniline was obtained. Its purity was over 98%.

This recovered aniline was brought into contact with 002 gas in the same manner as in Example 1. The treated aniline was recovered and subjected to an indole synthesis reaction in the same manner as in Reference Example 1. Immediately after the start of the reaction, the indole yield based on ethylene glycol was 74.5%,
The indole yield 200 hours after the start of the reaction was 80.
It was 8%.

Example 5 35 kg of the reaction product liquid containing water obtained in the indole synthesis reaction under the same conditions as Reference Example 2 was placed in a closed type container with a volume of 7
01 stirring tank, purge with 002 gas as in Example 1, and reduce the system internal pressure to 7 kg/ctn' gauge pressure.
After introducing 02 gas, 500°C for 3 hours at 60°C.
Stirred with RP garden. After the treatment, aniline was recovered in the same manner as in Comparative Example 2, and a reaction was performed in the same manner as in Reference Example 2 using this aniline. The indole yield based on ethylene glycol after the start of the reaction was 70.0%,
After 50 hours, it was 51.2%, compared to Comparative Example 2.
There was less decrease in yield compared to

Example 6 35 kg of the reaction product liquid containing water from the indole synthesis reaction under the same conditions as in Reference Example 3 was placed in the same stirring tank as in Example 4 and purged with 002 gas in the same manner as in Example 1, until the system internal pressure was reduced. After introducing C02 gas to a gauge pressure of 1 kg/cm'', it was stirred at 60° C. for 3 hours at a 500 rpm bed. After the treatment, aniline was recovered in the same manner as in Comparative Example 3, and this aniline was used to prepare a reference sample. The reaction was carried out in the same manner as in Example 3. The indole yield based on ethylene glycol at 1 hour after the start of the reaction was 67.0%, and the indole yield at 50 hours after the start of the reaction was 42.6%. There was less decrease in yield compared to the previous method.

Claims (1)

[Claims] 1) Ethylene glycol and a stoichiometric excess of aniline are reacted in the gas phase in the presence of a catalyst, and aniline is extracted from the reaction solution containing the obtained indole, side reaction products, and unreacted aniline. A method for producing indole by separating and recovering the aniline and recycling the recovered aniline to the gas phase reaction, the method comprising bringing the reaction solution or the recovered aniline into contact with carbon dioxide. .