JPH0432065B2 - - Google Patents

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, and have become particularly important in recent years as raw materials for perfumery and amino acid synthesis. There have been several attempts to synthesize indoles in the past, but all of them involved many by-products, expensive raw materials, long steps to produce indoles, and complicated operations. 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. Using various proposed catalysts, e.g.
When the reaction for synthesizing indole from aniline and ethylene glycol is carried out over a long period of time, 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 recover the activity of the catalyst. In order to achieve this, there was a problem in that complicated catalyst regeneration treatment operations had to be carried out frequently. As a result of intensive research into methods for suppressing the decline in catalyst activity and lengthening the catalyst regeneration interval, the present inventors discovered that the raw materials anilines and ethylene glycols were brought into contact with a non-oxidizing gas such as hydrogen gas. ,
The inventors have discovered that supplying the raw material to the reaction system after removing dissolved oxygen contained in the raw material is effective in suppressing a decrease in catalyst activity, 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. The method for producing indoles, which is the object 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 are:
General formula () (In the formula, R is a hydrogen atom, a halogen atom, a hydroxyl group,
This is a compound represented by an alkyl group or an alkoxy group). For example, aniline, ortho-
Toluidine, meta-toluidine, para-toluidine, ortho-haloaniline, para-haloaniline, meta-haloaniline, ortho-aminophenol, meta-aminophenol, para-aminophenol, ortho-anisidine, meta-anidine, para-anisidine, etc. can give. In addition, ethylene glycols include ethylene glycol, propylene glycol, 1,2-butanediol,
1,2,4-butanetriol, glycerol,
These include 2,3-butanediol and diethylene glycol. Among the catalysts used, solid acid catalysts include (1) Si, Al, B, Sb, Bi, Sn, Pb, Ga, Ti,
Oxide or hydroxide of at least one element selected from Zr, Be, Mg, Y, Cu, Ag, Cd, and lanthanide elements (hereinafter referred to as catalyst material (1))
Catalysts containing, for example, CdO, ZnO−Sb ₂ O−
PbO ₂ , Al ₂ O ₃ −B ₂ O ₃ , SiO ₂ −CdO, SiO ₂ −
Al ₂ O ₃ , SiO ₂ −MgO, TiO ₂ −SnO ₂ , TiO ₂ −
_{ZrO2 ,} CdO- _{Bi2O3 , SiO2} - _Y2O3 , _{SiO2 - Bi2O3}
−BeO, SiO ₂ −Ga ₂ O ₃ , SiO ₂ −La ₂ O ₃ , SiO ₂ −
_Ce2O3 , BiO2 _- ZnO-AgO, _{SiO2 -} MgO-CuO
etc. can be given. Also (2) Pd, Pt, Cr,
A catalyst containing a sulfide or selenide of at least one element selected from Fe, Ni, Co, Zn, Mo, Cd and W (hereinafter referred to as catalyst material (2));
For example, PdS, PtS, Crs, FeS, NiS, CoS,
Examples include ZnS, MoS ₂ , CdS, WS ₂ , ZnSe, and CdSe. Also (3) Fe, Tl, Ca, Mn, Bi,
Sr, Y, Al, Zn, Cd, Ni, Mg, In, Be, CO,
Inorganic salts of at least one element selected from Ga and lanthanide elements, i.e. halides;
Catalysts containing carbonates, nitrates, sulfates, phosphoric acid, pyrophosphates, phosphomolybdates, silicotungstates (hereinafter referred to as catalyst substances (3)), such as ferric sulfate, thallium sulfate, sulfuric acid Calcium, 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, aluminum zinc sulfate, chloride Magnesium, cadmium sulfate, cadmium phosphate, etc. can be mentioned. Furthermore, as metal catalysts, Cu, Ag, Pt,
Examples include catalysts containing at least one element selected from Pd, Ni, Co, Fe, Ir, Os, Ru, and Rh (hereinafter referred to as catalyst substance (4)). Among these groups of catalysts, the most preferably used are SiO ₂ −
ZnO−AgO, cadmium sulfide, cadmium sulfate,
and Ag 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, 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. Furthermore, the catalyst substance (4), which is a metal catalyst, can be produced by reducing the salt, hydroxide, or oxide of the catalyst constituent elements with a reducing agent such as hydrogen, formalin, 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 if it's hot. 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, and 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. Steam of anilines and ethylene glycols,
When converting into indoles by contacting with a catalyst under heating, 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 is preferable in order to suppress the decomposition of ethylene glycols on the catalyst, maintain the activity of the catalyst, and increase the yield of indoles. The anilines and ethylene glycols to be charged to the reactor are in the range of 0.01 to 0.5 mol of ethylene glycol per 1 mol of aniline, preferably
It ranges from 0.05 to 0.2 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 0.01 to 5/-catalyst/hr. The reaction temperature ranges from 200 to 600℃, preferably 250℃
~500℃ range. The reaction pressure may be increased pressure, normal pressure or reduced pressure. The method of the present invention is a method for producing indoles as described above, in which anilines and ethylene glycols, which are the raw materials charged into the reaction system, and recycled materials mainly containing aniline recovered from the reaction solution by means such as distillation, are used. After removing oxygen contained in the liquid and water used as necessary, the reactor is charged into the reaction system. For example, the amount of dissolved oxygen at room temperature and pressure is about 50 ppm for aniline, about 10 ppm for ethylene glycol, and about 10 ppm for water. 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 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 monoxide, or a mixture thereof;
Examples include a method of degassing under reduced pressure and a method of expelling dissolved gas by heating. Chemical removal methods include easily oxidizable substances, such as easily oxidized metals such as copper, iron, nickel, and cobalt, calcium hydride, nickel hydride,
In the presence of easily oxidizable compounds and catalysts, such as metal hydrides such as hydrides of alloys of magnesium and nickel, hydrides of alloys of titanium and iron, ○ hahydrazine, hydrogen, formic acid, sodium borohydride, etc.
Alternatively, a method can be mentioned in which the catalyst is catalyzed in its absence. The more oxygen contained in the raw material is removed, the better from the point of view of maintaining the activity of the catalyst. The purpose of the method of the present invention can be fully achieved if the saturated solubility is 1/50 or less of the saturated solubility. 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, 3
500 ml of a catalyst having a particle size of ~4 mm was charged and subjected to the reaction.
The catalyst is compression molded powdered cadmium sulfide. Hydrogen gas was supplied to the reaction tube at a rate of 2/min, and the temperature of the catalyst layer was gradually raised from room temperature to 350℃.
I kept it there. Aniline and a 33 wt % ethylene glycol aqueous solution, which had been sufficiently deoxygenated by bubbling hydrogen gas in advance, were supplied to the vaporizer at 234 g/hr and 48 g/hr, respectively, and introduced into the reaction tube for reaction. The temperature of the catalyst layer was maintained in the range of 350 to 380°C so that the conversion rate of ethylene glycol was 98%. A reaction solution (referred to as reaction solution A) obtained during 24 to 27 hours after the start of the reaction, when the activity of the catalyst was stable;
In order to observe changes in the activity of the catalyst, we analyzed the reaction solution obtained between 240 and 243 hours (referred to as reaction solution B), and found that the indole yields based on ethylene glycol were 67% and 59%, respectively. It was hot. When the amount of dissolved oxygen in aniline and 33wt% ethylene glycol, which were supplied as raw materials, was measured using the wave height of the oxygen reduction wave using a polarograph, they were each less than 1/50 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, SiO ₂ -ZnO prepared by coprecipitation method (weight composition ratio 1:1, BET surface area
Experiments were conducted using a carrier in which 7wt% of Ag was supported (260 m ² /g) or a SiO ₂ -ZnO-AgO (weight composition ratio 1:1:1) prepared by a coprecipitation method. The results are shown in Table-1.

[Table] Comparative Examples 1, 2, 3, 4 The same experiments as in Examples 1, 2, 3, and 4 were carried out except that the operation to remove dissolved oxygen in the raw material aniline and 33 wt% ethylene glycol aqueous solution was not performed. I did it. The results are shown in Table-2.

[Table] Example 5 A liquid phase synthesis reaction of indole was carried out using the reaction apparatus shown in Figure 1. 3 in a stainless steel reaction tube with an inner diameter of 25 mm.
~4 mm granular activated carbon was filled with 500 ml of catalyst supporting 10 wt% of Ag and subjected to reaction. Hydrogen gas was sent through the inlet pipe and discharged through the discharge pipe to replace the air in the reactor. The temperature of the catalyst bed was gradually raised from room temperature to 300℃, and the discharge pipe was closed to set the hydrogen pressure to 40Kg/ ^cm3 . The inlet tube was closed. Aniline and ethylene glycol were supplied to the heater at 465 g/hr and 31 g/hr, respectively, by bubbling hydrogen gas so that the amount of dissolved oxygen was less than 1/50 of the amount of saturated air. Ethylene glycol is introduced from E, then hydrogen gas is introduced from conduits 11 and 14, and discharge pipe 1 is introduced.
Dissolved oxygen and other gases are released from 2,15. After reducing the dissolved oxygen to less than 1/50th of the saturated solubility, add 465g/each of aniline and ethylene glycol.
The mixture was introduced into the reaction tube through a heat heater and reacted at 31 g/Hr. The temperature of the catalyst layer was gradually raised to 320°C, and thereafter maintained in the range of 320 to 350°C so that the conversion rate of ethylene glycol was 98% or higher. The reaction liquid passed through a conduit and was cooled to 40-45°C in a condenser, and then stored in a gas-liquid separator. Gas was appropriately discharged from the gas discharge pipe 8 so that the pressure within the gas-liquid separator was 40 to 45 kg/cm ³ . The reaction solution was intermittently discharged from the reaction solution discharge pipe 9 and subjected to analysis. A reaction solution (referred to as reaction solution A) obtained during 24 to 27 hours after the start of the reaction, when the activity of the catalyst was stable;
In order to observe changes in the activity of the catalyst, we analyzed the reaction solution obtained between 240 and 243 hours (referred to as reaction solution B), and found that the indole yields based on ethylene glycol were 68% and 63%, respectively. It was hot. Comparative Example 5 The same experiment as in Example 5 was conducted except that the operation to remove dissolved oxygen contained in the raw materials aniline and ethylene glycol was not performed. The indole yield was 63% in reaction solution A, and the indole yield was 63% in reaction solution A. In B, it was 28%.

[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 introduction pipe, ...Aniline introduction pipe,
...Ethylene glycol introduction tube, ...Reactor,
...reaction liquid conduit, ...cooler, ...gas-liquid separator, ...gas discharge pipe, ...reaction liquid discharge pipe,
... storage tank, ... conduit, ... discharge pipe, ...
Storage tank, ...conduit, ...discharge pipe, ...heater, ...heater, A...aniline inlet, E...
...Ethylene glycol inlet.

Claims (1)

[Claims] 1. When producing indole by reacting anilines and ethylene glycols in the presence of a catalyst, after removing dissolved oxygen contained in the raw materials,
A method for producing indoles, characterized by supplying them to a reaction system.