JPS5829762A - Preparation of indole - Google Patents

Abstract

PURPOSE:On the production of an indole by reaction of an aniline with an ethylene glycol, the oxygen dissolving in the starting materials are removed and they are fed to the reaction system to prevent the reduction in catalyst activity to prolong the interval between the catalyst reactivation. CONSTITUTION:The reaction between an aniline and an ethylene glycol is effected in the pressure of a catalyst such as CdS or SiO2-ZnO-AgO to produce an indole wherein the oxygen dissolving in the starting materials are removed and they are fed into the reaction system. The oxygen dissolving in the materials are removed by blowing an oxygen-free, inert gas such as hydrogen or nitrogen into them or bringing them into contact with a substance susceptible to oxidation such as copper or iron. Oxygen is removed to an extent of less than 1/50 concentration of the saturated solution, when they contact with the air under normal pressure and temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing indoles from anilines and ethylene glycols.

More specifically, the present invention relates to a method for extending the life of a catalyst when producing indoles from anilines and ethylene glycols in the presence of a catalyst.

Indoles are known as raw materials for the chemical industry, especially in recent years.
It has become an important substance as a raw material for flavoring and amino acid synthesis.

There have been several attempts to synthesize indoles in the past, but they all produced many by-products and were expensive raw materials, and the process to reach indoles was long and the operations were complicated. There were many. However, recently, a method using anilines and ethylene glycols as raw materials has been discovered as a method for synthesizing indoles in one step using inexpensive raw materials. Various solid acid catalysts and metal catalysts have been proposed as catalysts for the reaction of synthesizing indole from anilines and ethylene glycols.

For example, when a reaction for synthesizing indole from aniline and ethylene glycol is carried out over a long period of time using the various catalysts that have been proposed, the activity of the catalyst decreases, although the degree varies depending on the type of catalyst. . This decrease in the activity of the catalyst can be significantly reduced by performing the reaction in a hydrogen-containing gas atmosphere or by adding water to the reaction system, but it is still not enough to restore the activity of the catalyst. Therefore, there is a problem in that complicated catalyst regeneration treatment operations must be performed frequently.

As a result of intensive research into methods for suppressing the decline in catalytic activity and extending the regeneration interval of the eyebrow medium, the present inventors discovered that the raw materials anilines and ethylene glycol/L's could be replaced with non-oxidized sources such as hydrogen gas. The inventors have discovered that supplying the raw material to the reaction system after contacting it with a reactive gas to remove dissolved oxygen contained in the raw material is effective in suppressing a decrease in the activity of the catalyst, leading to the method of the present invention.

That is, the present invention is characterized in that when producing indoles by reacting anilines and ethylene glycols in the presence of a catalyst, dissolved oxygen contained in the raw materials is removed and then supplied to the reaction system. This is a method for producing indoles.

A method for producing indoles, which is an example of the method of the present invention, is a method for producing indoles in which anilines and ethylene glycols are reacted in the presence of a solid acid catalyst or a metal catalyst.

The anilines used in this method have the general formula (
1) A compound represented by (wherein R represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, or an alkoxy group) such as aniline, ortho-toluidine, meta-
Toluidine, para-toluidine, ortho-haloaniline, para-haloaniline, meta-haloaniline, ortho-
Examples of aminophenol, meta-aminophenol, and para-a include nophenol, ortho-anisidine, meta-anisidine, and para-anisidine. In addition, ethylene glycols C, ethylene glycol, propylene glycol, 1,2-butanediol, 1,2,4-butanetriol, glycerol, 2,3-butanediol,
Diethylene glycol, etc.

In addition, among the catalysts used, the solid acid catalyst is (1
) SL, Ai B, 34 B=, Sn, p6
, Ga, TA, B4°M9 to Z. Y, Op, AP,
Z7+, a catalyst containing an oxide or hydroxide of at least one element selected from Cd and lanthanide elements (hereinafter referred to as catalytic material (hereinafter referred to as RI), for example, OdO
,Z? LO-8'20JP402, A11203 B
2O3, S 02 0dQ, 5LO2Al2O3, S
rO2-MfO1T=o2-87LO2,'r=o2-
ZrO2, OjOBizO3, SA□+ -Y2O3,
5i02 B#203 BtO1SLO2-Ga2
o3.5Lo2La203.5LO204203, Bb
o2 Z? LOA,? Q, 5AO2MyO-OuO, etc. can be mentioned. Also (2) Pd, P4 c
r, p, zNL, 0+y, 7. n, Mer, c
A catalyst containing at least one element sulfide or selenide (hereinafter referred to as catalyst material (2)) selected from d and W, for example, pdS%PiS%0r81F4S
, N=s, aσS, Z? z8. Mv82, Od
a.

Examples include WB2, Z""S', and Cd84. Ma? ,=(3)p<,'rl,aa,M
71. BiJ, sr, y, Ai Z71
% Cd, N=, M9, I71. B400J G4
and inorganic salts of at least one element selected from lanthanide elements, i.e. halides, carbonates, nitrates,
sulfate, phosphoric acid, pyrophosphate, phosphomolybdate,
Kanai tungstate (hereinafter referred to as catalyst material (3))
Catalysts containing, 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 sulfate, indium sulfate, beryllium sulfate, cadmium nitrate, cobalt sulfate, zinc aluminum sulfate, Examples include magnesium chloride, cadmium sulfate, and cadmium phosphate.

Furthermore, as metal catalysts, C-hFP, Pi-, pd
, N=, Of, FClIr, Oζf%w, and RJ (hereinafter referred to as catalyst substance (4)).

Among these groups of catalysts, 5Lo2-Z710-A7 is most preferably used.
0. These include cadmium sulfide, cadmium sulfate, and Ai supported on a carrier with a large specific surface area.

These solid acid catalysts or metal catalysts can be produced by any known method. In other words, the catalyst substance (1) of the solid acid catalyst can be prepared by hydrolyzing the water-soluble salt of the catalyst constituent elements to form a hydroxide, and drying and calcining the resulting gel, or by exposing the easily decomposable salt to air. It can be manufactured by a method such as thermal decomposition in a medium.

Catalyst substance (2) among solid acid catalysts can be obtained by adding sodium sulfide 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. It can be manufactured by a method etc.

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

These solid acid catalysts or metal catalysts are each of the above-mentioned catalyst substances (1), (2), (3), and (4) singly or in a mixture of two or more thereof, or they are supported on a carrier. It's okay. As the carrier, any commonly used carrier can be used, and diatomaceous earth, pumice, titania, silica-alumina, alumina, magnesia, silica gel, activated carbon, activated clay, asbestos, etc. are usually used. A supported catalyst is prepared by supporting the catalyst substance on these carriers by a conventional method.

There is no particular restriction on the amount of the catalyst substance supported on the carrier (usually, an appropriate amount, for example 1 to 50%, of the catalyst substance may be supported depending on the carrier).

The reaction between anilines and ethylene glycols may be carried out in the presence of the above catalyst in any of the gas phase, liquid phase or gas-liquid mixed phase, but is usually carried out in the gas phase. Reactions in the gas phase can be carried out in fixed bed, fluidized bed or moving bed reactors.

When the vapors of anilines and ethylene glycols are brought into contact with a catalyst under heating to convert them into indo-μ compounds, various inert gaseous substances can be present as diluents for these vapors. Examples of such inert gaseous substances include hydrogen, nitrogen, carbon dioxide, and water vapor.

In particular, the use of hydrogen is preferred in order to maintain the activity of the catalyst. Furthermore, the use of steam suppresses the decomposition of ethylene glycols on the catalyst, so it is preferable to maintain the activity of the catalyst and increase the yield of indoles.

The anilines and ethylene glycols charged to the reactor are 0 ethylene glycols per mole of aniline.
．． The range is from 0.01 to 0.05 mol, preferably from 0.005 to 0.02 mol.

Anilines and ethylene glycols are either vaporized in advance or directly charged into the reactor in liquid form so that the liquid hourly space velocity relative to the catalyst is 001 to 51/l-catalyst/hr.

The reaction temperature is in the range of 200-600°C, preferably 25°C.
It is in the range of 0 to 500°C. The reaction pressure can be increased pressure, normal pressure, or reduced pressure.

In the method of the present invention for producing indoles as described above, the raw materials charged to the reaction system are aniline,
After removing the oxygen contained in the recycled liquid, which mainly contains ethylene glycols, aniline recovered from the reaction liquid by means such as distillation, and water used as necessary, the liquid is charged to the reaction system. .

As a method for removing oxygen contained in the raw material, either a commonly used physical removal method or a chemical removal method can be employed, but a physical removal method is usually used.

Physical removal methods include (1) a method of aerating and expelling a gas that does not contain oxygen and is inert to the synthesis reaction of indoles, such as nitrogen, hydrogen, carbon dioxide, -carbon oxide, or a mixture thereof; Examples include: (1) degassing under reduced pressure; and (2) heating to drive out dissolved gas.

Chemical removal methods include ■Easily oxidizable substances, such as ■Easily oxidizable metals such as copper, iron, nickel, and cobalt; ■Calcium hydride, nickel hydride, hydrides of alloys of magnesium and nickel, titanium and Examples include a method of contacting with a metal hydride such as a hydride of an alloy with iron, an easily oxidizable compound such as θ hydrazine, hydrogen, formic acid, and sodium borohydride in the presence or absence of a catalyst.

Oxygen contained in the raw material can be removed as long as it is sufficiently removed.
The purpose of the method of the present invention can be fully achieved as long as it is as follows.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 In a stainless steel reaction tube with an inner diameter of 25 mm, 5 to 4
The reactor was filled with 500 ml of a catalyst having a particle size of mm and subjected to a reaction.

The catalyst is compression molded powdered cadmium sulfide.

Hydrogen gas 'il/mL? + to the reaction tube, and the temperature of the catalyst layer was gradually raised from room temperature to 550°C and maintained at 350°C.

Aniline and a 33 wt % ethylene glycol aqueous solution, which had been sufficiently deoxidized and diluted by bubbling hydrogen gas in advance, were supplied to a vaporizer at 234 ji/hr and 48 g/hr, respectively, and introduced into a reaction tube for reaction. The temperature of the catalyst layer is
350 so that the conversion rate of ethylene glycol is 98
It was kept in the range ~380°C.

After the start of the reaction, the reaction solution obtained during 24 to 27 hours when the catalyst activity was stable (referred to as reaction solution A), and the reaction solution obtained between 240 to 245 hours to observe the change in catalyst activity. When the reaction solution (referred to as reaction solution B) was analyzed, the indole yields based on ethylene glycol were 67% and 67%, respectively.
It was 59chi.

The amount of dissolved oxygen in the aniline and 53 wt% ethylene glycol supplied as raw materials was measured and determined by the wave height of the oxygen reduction wave of a polarograph, and was found to be 1150 or less of the amount of dissolved oxygen at air saturation.

Examples 2 to 4 Same as Example 1, except that the catalyst was cadmium sulfate instead of cadmium sulfide, and 5Lo2-Z prepared by coprecipitation method.
? LO (weight composition ratio 1:1, B B T surface $260
(g/g) 7wt of A9 supported on a carrier, 5Lo2-Z? prepared by Mataha coprecipitation method. Experiments were conducted using LO-hlo (weight composition ratio 1:1=1).

The results are shown in Table-1.

Comparative Example 1.2.3.4 Except that no operation was performed to remove dissolved oxygen in the raw material aniline and 33 wt% ethylene glycol aqueous solution.
An experiment similar to Example 1.2.3.4 was conducted. The results are shown in Table-2.

Table 2 Example 5 A liquid phase synthesis reaction of indole was carried out using the reaction apparatus shown in Figure 1.

A reaction tube made of stainless steel IL having an inner diameter of 25 mm was filled with 5 ooml of a catalyst in which 10 wt % of A was supported on 5 to 4 layers of granular activated carbon, and the reaction tube was subjected to a reaction.

Hydrogen gas is supplied through the inlet pipe and released through the discharge pipe (■) to replace the air in the reactor. The temperature of the catalyst layer is gradually raised from room temperature to 500°C. The discharge pipe (■) is closed and the hydrogen pressure is 40.
The inlet tube was closed at 9/cd.

Aniline and ethylene glycol were supplied to the preheater at a rate of 465 g/hr and 31 g/hr, respectively, by bubbling hydrogen gas so that the amount of dissolved oxygen was 1150 or less when saturated with air, and introduced into the reaction tube through the introduction tubes ① and ②. and reacted. The temperature of the catalyst layer was gradually increased to '520°0, and thereafter maintained in the range of 620 to 550°0 so that the conversion rate of ethylene glycol was 98% or more. The reaction solution is in a conduit■
After being cooled to 40-45°C in condenser 1, it was stored in a gas-liquid separator. The pressure inside the gas-liquid separator is 40~4
Gas was appropriately released from the gas release tube (2) so that the ratio was 5 to 9/d. The reaction solution was intermittently discharged from the reaction solution discharge tube (■) and subjected to analysis.

After the start of the reaction, the reaction solution obtained during 24 to 27 hours when the catalyst activity was stable (referred to as reaction solution A), and the reaction solution obtained between 240 to 246 hours to observe the change in catalyst activity. When the reaction solution (referred to as reaction solution B) was analyzed, the indole yield based on ethylene glycol was 68.
Chi, it was 63 chi.

Comparative Example 5 An experiment similar to Example 5 was conducted except that the operation to remove dissolved oxygen contained in the raw materials aniline and ethylene glycol was not carried out, and the indole yield was the same as that of reaction solution A.
and 63% in reaction solution B, and 28φ in reaction solution B.

[Brief explanation of drawings]

Figure 1 shows the reaction apparatus for liquid phase synthesis used in Example 5. In Figure-1, each symbol is as follows. ■Gas inlet tube ■Cooler ■Aniline inlet tube Gas-liquid separator ■Ethylene glycol inlet tube ■Gas discharge tube ■Reaction gain
■Reaction liquid discharge pipe■Reaction liquid conduit diagram-1

Claims (1)

[Claims] 1) Production of indoles characterized in that when producing indoles by reacting anilines and ethylene glycols in the presence of a catalyst, dissolved oxygen contained in the raw materials is removed and then supplied to the reaction system. Law.