JPS6287566A - Production of indole - Google Patents

Abstract

PURPOSE:To produce indole preventing the lowering of catalytic activity, by reacting ethylene glycol with excess aniline in vapor phase in the presence of a catalyst, recovering aniline from the obtained reaction liquid and recycling the recovered aniline to the reaction system, wherein the recovered aniline is heat-treated in the presence of iron ion before recycling. CONSTITUTION:Ethylene glycol is made to react with stoichiometrically excess aniline in vapor phase in the presence of a catalyst (e.g. solid acid catalyst, metallic catalyst, etc.) and the reaction liquid containing indole, side reaction products and unreacted aniline is distilled to separate aniline. The recovered aniline is added with 0.001-5wt% iron compound and heated at 25-180 deg.C, preferably 50-130 deg.C and the treated aniline is recycled to the reaction system. The side reaction product poisonous to the catalyst is made harmless by the heat-treatment. The heat-treatment in the presence of iron ion may be carried out on the reaction liquid prior to the separation 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 when recovering and using aniline in a method for 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 acids. 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 in one simple step using inexpensive raw materials.

Various solid acid catalysts and metal catalysts have been proposed as catalysts for the reaction. When these catalysts are reacted with each other for a long period of time, their activity decreases, although the degree varies depending on the type of catalyst and reaction conditions, and periodic regeneration operations by heating and calcination in an oxygen atmosphere are required. do. Regeneration operations are complicated, and if performed too frequently, they may impair the economics of the process.

Although the details of the cause of this decrease in activity are not clear, it is possible to reactivate it using conventional methods.
The main reason is thought to be that the organic matter becomes carbonaceous under the reaction conditions and deposits on the catalyst surface, covering the active sites of the catalyst. 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, when the reaction is carried out without recycling the recovered aniline, if the recovered aniline is supplied to a catalyst that can maintain sufficient reaction activity for several hundred hours, with other conditions being exactly the same. The activity of the catalyst decreases significantly, and the frequency of regeneration operations increases significantly. Therefore, it is presumed that the recovered aniline contains impurities that are harmful to the catalyst.'t1. Ru.

The reaction liquid obtained by condensing the gaseous reaction mixture exiting the reactor contains not only the produced indole and water, unreacted ethylene glyfur, and excess aniline, but also small amounts of various side reaction products. things exist. Although some of them have been isolated and recovered, 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

Previously, the present inventors have effectively rendered harmless side reaction products that are harmful to such catalysts and difficult to separate by distillation from aniline, and even if recovered aniline is used as a reaction raw material,
As a method that can avoid adverse effects on the activity of the catalyst, by separating and recovering aniline by distillation and before supplying it to the reactor again, the side reaction products and the solution containing aniline are heat-treated to reduce the side reaction products. It has been found that it is extremely effective to convert a substance into a non-volatile substance to facilitate distillation separation from aniline.

However, this method requires treatment under harsh conditions such as temperatures in the range of 100 to 350°C and pressures higher than the saturated vapor pressure of the treatment solution, and has drawbacks such as loss of indole and equipment costs. there were.

The problem of the present invention is to effectively remove such side reaction products that are harmful to the catalyst and difficult to separate by distillation, and to avoid adverse effects on the activity of the catalyst even if the recovered aniline is used as a reaction raw material. The object of the present invention is to provide an improved method.

(Means for solving the problem) As a result of intensive studies to solve the above problem, the present inventors found that
Before separating and recovering aniline by distillation and supplying it to the reactor again, the side reaction product and the reaction solution containing aniline, or the recovered aniline, is heat-treated in the presence of iron ions to prevent the side reaction. It has been found that the method is extremely effective in making the product harmless to catalysts, and the method of the present invention has been developed.

That is, the present invention performs a gas phase reaction of ethylene glycol and aniline in a stoichiometric excess relative to ethylene glycol in the presence of a catalyst, and contains the obtained indole, side reaction products, and unreacted aniline. In a method for producing indole by separating and recovering aniline from a reaction solution and recycling the recovered aniline to the gas phase reaction, the reaction solution or the recovered aniline is heat-treated in the presence of iron ions. This is a method for producing indole, which is characterized by:

The method for producing indole, which is the object of the present invention, is a method in which aniline and ethylene glycol are reacted in a gas phase in the presence of a solid acid catalyst or a metal catalyst.

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

(11Si, AI, 13.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, -B20. , Sin□−Z
nO, Sin, -Cab.

5in2-4n20. , 5in2-8rO, 5in2
-CdO,Sin, -A1203. Sin2-Mg
O, Tie, -8nO,, Tie, -ZrO□Cd
O2-Bi2O3,Sin, -Y2O,,5in2.
Bi, 0. -BaO.

5in2-Ga,O,,Sin,-La203. Si
n, -Co,○.

5in2-ZnO-Ago, Sin2-MgO-C
uO et al.

(2) Pd, Pt, Cr, Fe, Ni, Co
A catalyst containing a sulfide or selenide of at least one element selected from , Zn, Mo, Cd and W (hereinafter referred to as catalyst material (2)), such as PdS,
PtS, CrS, FeS, Nip.

CoS, ZnS, MQsl, 'ccis, ws
,, Zn5e, CdSe, etc.

(31Fe, TI, Ca, Mn, Bi, St
, Y, AI, Zn, Cd.

Ni + Mg + In + Be + Co +
Inorganic salts of at least one element selected from Ga and lanthanide elements, i.e. halides, carbonates, nitrates,
Catalysts containing sulfates, phosphates, pyrophosphates, phosphomolybdates, silicotungstates (hereinafter referred to as catalyst substances (3)), such as ferric sulfate, thallium sulfate, calcium sulfate, manganese sulfate , bismuth sulfate, strontium sulfate, yttrium sulfate, cadmium bromide, aluminum sulfate, zinc sulfate, di-nochel sulfate, cadmium chloride, magnesium sulfate, indium sulfate, beryllium sulfate, cadmium nitrate, cobalt sulfate, zinc aluminum sulfate, magnesium chloride , cadmium sulfate, cadmium phosphate, etc.

In addition, as metal catalysts, Cu, Ag, Pt, Pd
, Ni.

Examples include catalysts containing at least one element selected from Co, Fe, Ir, Os, Ru, and Rh (hereinafter referred to as catalyst material (4)).

Among the above groups of catalyst materials, the group of catalyst materials (1) is the most preferably used one, Sin! -Zn
O-Ago, in the group of catalyst materials (2), cadmium sulfide, in the group of catalyst materials (3), cadmium sulfate, and in the group of catalyst materials (4), Ag supported on a carrier with a large specific surface area. Can be mentioned.

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) can be prepared by adding sodium sulfate or potassium selenide to the water-soluble salt of the catalyst constituent element, or by contacting the catalyst constituent element or its salt with hydrogen sulfide gas or hydrogen selenide gas, etc. can be manufactured.

Furthermore, the catalyst substance (material), which is a metal catalyst, is a salt, hydroxide, or oxide of the 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 are the aforementioned catalyst materials tl.
), +21. +31. +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, Seeker alumina, alumina, magnesia, silica gel, activated clay, asbestos, etc. are usually used. A supported catalyst is prepared by supporting the catalyst substance on these carriers by a conventional method.

The amount of the catalyst substance supported on the carrier is not particularly limited,
Generally, a suitable amount, for example 1 to 50%, of the catalyst material may be supported depending on the carrier.

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
Ethylene glycol 0.01 to 1 mole of aniline
A range of 1 mol is preferred, especially a range of 0.05 to 0.5 mol.

The amount of introduced aniline and ethylene glycol, which are the raw materials 44, is in the range of 0.01 to 10 hr, and is introduced into the reaction apparatus after being vaporized in an evaporator in advance. Further, at that time, water vapor, hydrogen, carbon oxide, carbon dioxide, methane, nitrogen, neon, argon, etc. may be entrained as a carrier gas. In particular, water vapor,
Hydrogen, carbon oxides are preferred as they increase catalyst life.

The reaction temperature is in the range of 200 to 600 °C, especially 250 to 5
A range of 00'C is preferred.

The reaction pressure can be selected from any pressure above the atmospheric pressure and below the pressure at which the raw materials or components contained in the reaction mixture form a condensed phase at the reaction temperature; however, in practical terms, 1. The range of 1.times.10' to 1.0.times.10'Pa is preferable; 2. OX 1. O'~5. OX10
'Pa range is more preferable.

In the method of the present invention, a reaction liquid obtained by condensing a gaseous reaction mixture exiting a reaction apparatus for producing indole under the above conditions, or an aniline distillate after indole has been separated from this reaction liquid is used, The reaction solution containing the reaction product and aniline or the recovered aniline is heat-treated in the presence of iron ions.

The iron ions added to the reaction solution or the recovered aniline may be either divalent or trivalent iron ions, and various iron compounds that provide these iron ions in an aqueous solution can be used.

For example, iron halides such as ferrous chloride, ferric chloride, ferrous bromide, ferric bromide, ferrous fluoride, or ferric iodide, ferrous sulfate, sulfuric acid, etc. Examples include mineral acid iron such as ferric iron, ferrous nitrate, and ferric nitrate; organic acid iron such as iron acetate and iron oxalate (■ and ■ valence); and compounds such as ammonium iron sulfate and potassium iron sulfate. .

Hydrates of these can also be used. Preferably,
Iron compounds that are easily soluble in water are often used.

However, even poorly soluble compounds may be used in suspension form.

These compounds are generally added to the reaction solution or recovered aniline in the form of an aqueous solution. When these reaction solutions or recovered aniline contain a dissolved amount of water, the above-mentioned iron compound may be added directly.

The amount of iron compound added is usually 0.001% to 5% by weight, preferably 0.000% by weight based on the reaction solution or recovered aniline.
1 weight% to 0.5% by weight.

The heat treatment temperature is 25-180°C, preferably 50-1
It is 300C. The heat treatment may be carried out under normal pressure, or may be carried out under increased pressure if necessary.

If the heat treatment temperature is too high, indole will be lost, which is not preferable.

As mentioned above, heat treatment in the presence of iron ions can cause harmful effects that reduce the activity of the catalyst contained in the reaction solution or recovered anidine under mild conditions such as lower heating temperature and time than simple heat treatment. AE by-products.

You can do it for free.

This heat treatment may be carried out batchwise or continuously. In the case of a continuous type, complete mixing, extrusion flow, or intermediate fluid mixing may be used; however, the closer to extrusion flow, the better the volumetric efficiency will be.

In the reaction product liquid or recovered aniline that has been heat-treated as described above, side reaction products that are harmful to the catalyst have been rendered harmless by the heat treatment as described above, so these are removed by distillation separation using a conventional method. . The aniline thus obtained is reused in the reaction as is or mixed with fresh aniline.

(Operation and Effects of the Invention) According to the method of the present invention, an excess of anionic acid than the stoichiometric amount relative to ethylene glycol is introduced into the reaction apparatus, and this excess phosphoric acid is separated and recovered from the reaction product. When used as a raw material, side reaction products harmful to the catalyst can be rendered harmless by subjecting it to heat treatment in the presence of iron ions.

Therefore, the activity of the catalyst can be maintained for a long time and indole can be produced in good yield.

That is, the present invention provides an industrial method for producing indole using aniline and ethylene glycol as raw materials.

(Example) Hereinafter, the method and effects of the present invention will be explained in more detail using reference examples, comparative examples, and examples.

Reference example 1 Inner diameter 25. Catalyst 500- is made by compression molding powdered cadmium sulfide to a particle size of 3 to 4 in a stainless steel reaction tube.
was charged and subjected to reaction. Hydrogen gas was supplied to the reaction tube at a rate of 2/min under a pressure of 7b/cy<, and the temperature of the catalyst layer was gradually raised from room temperature to 350°C.
was held at Next, aniline and 33% ethylene glycol aqueous solution were added at 234 g/hr and 48 g, respectively.
/hr, and after being vaporized, the mixture was supplied to a reaction tube to perform a reaction. The indole yield based on ethylene glycol immediately after the start of the reaction was 74.896. This yield gradually decreased over time and reached 52.0% 310 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. It was separated and collected. That is, a distillation pot with an internal volume of 30 mm, an internal diameter of 8
0 Kei, height 2000, m nominal size 1/41 nc
h 25g of the above organic phase was charged into a glass distillation apparatus consisting of a packed bed of rash rings and a condenser, and the pressure was 10T.
Batch distillation was performed at a reflux ratio of 0.2. First distillate 0.
Aniline fractions of 4 ky and then 20.3 kti were distilled. Repeat the same batch distillation to obtain approximately 80 ky
of recovered aniline was obtained. As a result of the analysis, the purity of the recovered aniline was 99% or more.

Using this recovered aniline, an indole synthesis reaction was carried out under exactly the same conditions as in Reference Example 1. The indole yield based on ethylene glycol immediately after the start of the reaction was 75.296, which was approximately the same as in Reference Example 1, but it decreased to 43.6% 195 hours after the start of the reaction.

Reference Example 2 A stainless steel reaction tube with an inner diameter of 20 mm was filled with 400 d of a commercially available tablet-formed SiO pellet having a diameter of 3 m and a height of 2.5 mm and carrying 1396 silver. 3 reaction tubes
A raw material mixture of 12:1:30 molar ratio of A, Nilin and ethylene glycol oyohi water, which was maintained at 50'C and previously vaporized, was heated at 300 g/hr for 1. At the same time, hydrogen gas was supplied to the reaction tube at a rate of 60/STP/hr, and an indole synthesis reaction was carried out at normal pressure.

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 time, and 50 hours after the start of the reaction, 51
．． It was 096. The aniline used in the reaction was the same commercially available industrial aniline as in Reference Example 1.

Comparative example 2 Reference example 2. The reaction mixture exiting the reaction tube is cooled to room temperature, and the resulting condensate is separated into two phases: an aqueous phase and an organic phase.
The latter was separated and recovered in the same manner as in Comparative Example 1. The approximately 20ky aniline recovered was analyzed and found to have a purity of 9996.
That was it.

Using this recovered aniline, an indole synthesis reaction was carried out under the same conditions as in Reference Example 2. The indole yield based on ethylene glycol 1 hour after the start of the reaction was 70.196, which was almost the same as that in Reference Example 2, but
It decreased to 43.496 at 0 hours.

Comparative Example 3 The indole synthesis reaction was carried out under the same conditions as in Reference Example 1, with heating using a heating medium while stirring. After the internal temperature reached 2000C, it was maintained at this temperature for 2 hours. At this time,
It showed a vapor pressure of approximately 6 ky/cd.

Approximately 80 ky of aniline was recovered from this heat-treated liquid by batch distillation using the same distillation apparatus and operating conditions as in Comparative Example 1, and subjected to the same indole synthesis reaction as in Reference Example 1. Immediately after the start of the reaction, the indole yield based on ethylene glycol was 75.0%, which was approximately the same as in Reference Example 1. Thereafter, the reaction was continued for 320 hours, and the yield at this time was 45.096, which was a reaction result comparable to that of Reference Example 1.

Example 1 100 kg of an organic phase obtained in the indole synthesis reaction under the same conditions as Reference Example 1 and 100 g of an aqueous solution containing 3.09 g of ferric chloride were placed in a stainless steel stirring tank with a steam jacket. and heated with steam while stirring gently. After the internal temperature reached 100°C, it was maintained at this temperature for 1 hour.

One aniline of about 80 ky was recovered from this heat-treated liquid by batch distillation using the same distillation apparatus and operating conditions as in Comparative Example 1, and subjected to the same indole synthesis reaction as in Reference Example 1. Immediately after the start of the reaction, the indole yield based on ethylene glycol was 74.6%, which was approximately the same as in Reference Example 1. After that, the reaction continued for 310 hours, but
The yield at this time was 51.8%, and a reaction result comparable to that of Reference Example 1 was obtained.

Example 2 The recovered aniline 80b obtained in Comparative Example 1 was charged with 1/2 aqueous solution containing iron sulfate 409 in the same manner as in Example 1 into a stainless steel stirring tank equipped with a steam jacket, and slowly stirred. Heat with steam while stirring. The internal temperature is 4
After reaching 0°C, it was held at this temperature for 1 hour.

Aniline 64&9 was recovered from this heat-treated liquid by batch distillation using the same distillation apparatus and operating conditions as in Comparative Example 1. Reference Example 1 and total (subjected to the same indole synthesis reaction. Immediately after the start of the reaction, the indole yield based on ethylene glycol was 74.8%, and the reaction was continued for 310 hours, but the indole yield at that time was 74.8%. is 48
It was 1%.

Example 3 In the indole synthesis reaction under the same conditions as Reference Example 2,
25 kg of the obtained organic phase and 100 kg of a suspension containing 2.51 kg of ferric sulfate were placed in a stainless steel stirred tank equipped with a steam jacket and heated with steam while being gently stirred. After the internal temperature reached 100°C, it was maintained at this temperature for 1 hour.

Approximately 20 kQ of aniline was recovered from this heat-treated liquid by batch distillation using the same distillation apparatus and operating conditions as in Comparative Example 1, and an indole synthesis reaction was carried out under exactly the same conditions as in Reference Example 2. The indole yield based on ethylene glycol 1 hour after the start of the reaction was almost the same as in Reference Example 2.
It was 0.0%. When the reaction was further continued, the indole yield at 310 hours after the start of the reaction was 51.6%.
Therefore, compared to Comparative Example 2, a reaction result with less decrease in yield was obtained.

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. The method for producing indole by separating and recovering the aniline and recycling the recovered aniline in the gas phase reaction is characterized in that the reaction solution or the recovered aniline is heat-treated in the presence of iron ions. Method for producing indole.