JPH0314306B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing indoles from anilines and ethylene glycols, in which a degraded catalyst used in the reaction is regenerated and used repeatedly. (Prior art and its problems) Indoles are known as raw materials for the chemical industry, and indoles in particular have recently become important substances as raw materials for perfumes and amino acid synthesis. There have been many attempts to synthesize indoles in the past, but all of them had problems such as expensive raw materials with many by-products and complicated manufacturing processes. Recently, a catalyst system has been discovered that is effective in the reaction of synthesizing indoles using inexpensive raw materials anilines and ethylene glycols and in a short process. For example, Cu-Cr, Cu-Co, Pd/
Examples include SiO ₂ , Pt/SiO ₂ , Cds, etc., but all catalyst systems have drawbacks such as severe reduction in reaction activity and low reaction activity, and cannot be used as practical catalysts. The present inventors have conducted various studies on this reaction and have already clarified that the performance of the reaction can be improved by adding water to the reaction system, carrying out the reaction under pressure, etc. Furthermore, the present inventors have found that a catalyst system containing any of the elements of Group B of the Periodic Table of Elements, such as Cu, Ag, and Au, as an active ingredient is effective for the production of indoles, and the reaction takes a long time. We found that it is possible to implement However, even if these catalysts are used, it is inevitable that the catalyst deteriorates with the passage of reaction time, the catalyst activity and selectivity to indoles decrease, and the yield of indoles deteriorates. Therefore, for industrial implementation of this method, it is important to be able to regenerate and repeatedly use the catalyst that has deteriorated during the reaction. Catalyst regeneration methods vary depending on the physical properties of the catalyst, and a recently developed method, namely a method for producing indoles from anilines and ethylene glycols, requires an appropriate method for regenerating a deteriorated catalyst. The end is not proposed. An object of the present invention is to provide an industrial method for producing indoles in which a degraded catalyst used in a method for producing indoles from anilines and ethylene glycols is regenerated and used repeatedly. (Means for Solving the Problems) The present inventors have diligently studied the above-mentioned problems and have determined that the catalyst used to produce indoles from anilines and ethylene glycols, in particular We discovered that one of the reasons for the deterioration of group metal-containing catalysts is that when anilines and ethylene glycols are reacted, they are adsorbed onto the catalyst, and as the reaction time progresses, carbon precipitates. The method of the present invention has been achieved in which a deteriorated catalyst is regenerated by an appropriate method and used repeatedly for the production of indoles. That is, the present invention provides a method for producing indoles from anilines and ethylene glycols in the presence of a catalyst containing a metal from Group B of the Periodic Table of the Elements, in which the catalyst deteriorated during the reaction is heated at 200 to 450°C.
This is a method for producing indoles, which is characterized in that they are regenerated by contacting with an inert gas containing 5 vol% or less of oxygen in the temperature range of , and used repeatedly. The anilines used in the method of the present invention have the general formula () (wherein R represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, or an alkoxy group). For example, aniline, o
-・m-・or p-toluidine, o-・m・
Alternatively, examples thereof include p-haloaniline, o-, m-, or p-hydroxyaniline, o-, m-, or p-anisidine, and the like. Also, ethylene glycols, ethylene glycol, propylene glycol, 1,2-butanediol, 1,2,4-butanetriol, glycerol, 2,3-butanediol, diethylene glycol, and the like. The catalyst used in the method of the present invention is a catalyst system containing as an active ingredient one or more of Cu, Ag, and Au, which are group B elements of the periodic table of elements, and can be combined with these. As an element, B,
C, O, Mg, Al, Si, P, S, Ca, Ti, Cr,
Mn, Fe, Co, Ni, Zn, Ga, Ge, Se, Sr, Zr,
Mo, Ru, Rh, Pd, Cd, In, Sn, Sb, Te,
Ba, La, Ce, W, Ir, Pt, Tl, Pb, Bi, Th,
Se etc. can be given. The aforementioned catalysts may be used alone or in the presence of common carriers such as diatomaceous earth, activated clay, zeolite, silica, alumina, and silica.
It is used supported on alumina, titania, chromia, thoria, magnesia, calcia, zinc oxide, etc. Raw materials for Group B metals include nitrates, sulfates, phosphates, carbonates, halides, organic acid salts, etc. for Cu and Ag; gold chlorides,
Alkali metal chloroaurates, gold cyanide, alkali metal gold cyanide, etc. can generally be used. As a method for preparing the catalyst, the usual kneading method, coprecipitation method, impregnation method, and a combination of the above-mentioned methods can be applied. For example, a method of mixing various raw materials, adding a small amount of water, and kneading with a kneader, etc., a method of making various raw materials into an aqueous solution, adding a precipitant to this, and co-precipitating it as an insoluble precipitate; It can be prepared by impregnating raw materials. The obtained catalyst composition is usually dried at 180° C. or lower, and suitable granulation additives, molding aids, etc. are added and molded, or the catalyst composition is crushed and used as it is. In the method of the present invention, such a catalyst gradually deteriorates with the passage of reaction time, so this deteriorated catalyst is regenerated by the regeneration method described below and used repeatedly. In the method of the present invention, the reaction between anilines and ethylene glycols is carried out in the gas phase in the presence of a catalyst, but any reaction mode such as fixed bed, fluidized bed or moving bed is possible. The anilines and ethylene glycols introduced into the reactor are in the range of 0.01 to 5 mol of ethylene glycol per 1 mol of aniline, preferably
It ranges from 0.05 to 1 mole. The amount of introduced raw materials anilines and ethylene glycols is 0.01 to 0.01 in terms of liquid hourly space velocity (LHSV).
It is in the range of 10 hr ^-1 and is vaporized in an evaporator before being introduced into the reactor. Also, at that time, water vapor,
hydrogen, carbon monoxide, carbon dioxide, methane, nitrogen,
Neon, argon, or the like may be used as a carrier gas. Among them, water vapor, hydrogen, and carbon monoxide are preferable because they have the effect of increasing the service life of the catalyst. The reaction temperature ranges from 200 to 600℃, preferably 250℃
~500℃ range. The reaction can be carried out under reduced pressure, normal pressure, or increased pressure, but normal pressure or increased pressure is preferable. The regenerated catalyst used in the method of the present invention is obtained by heat-treating the degraded catalyst used for the production of indoles under the above reaction conditions at 20 to 450°C in an inert gas containing 5 vol% or less oxygen. That's how it was played. Although it is convenient to regenerate a deteriorated catalyst while the deteriorated catalyst remains in the reactor, it may also be performed by taking the catalyst out of the reactor. The purpose of this heat treatment is to remove carbon deposited during the reaction, which is a cause of catalyst deterioration, but this is usually a combustion reaction and generates heat. Therefore,
Supply gas temperature (inlet temperature) is 200℃~450℃,
The temperature should preferably be 250°C to 400°C. If the temperature is too high, the temperature of the catalyst during heat treatment will rise too much due to the combustion exothermic reaction, causing sintering of the active components in the catalyst and reducing the catalytic activity.
On the other hand, if the temperature is too low, the combustion reaction will not occur or will be difficult to occur, and sufficient regeneration will not occur. The gas used for regeneration is an inert gas containing less than 5% oxygen by volume, preferably less than 2% oxygen. If the oxygen concentration is too high, the combustion reaction will proceed too quickly, leading to a decrease in catalyst activity. Although there is no particular lower limit to the oxygen concentration, if the oxygen concentration is too low, the regeneration time becomes longer, which is economically disadvantageous. N ₂ , Ar, He, CO ₂ , H ₂ O, etc. can be used as the inert gas, but for economical reasons, a mixture of nitrogen and air containing a specified amount of oxygen is used for regeneration. It is preferable to use The gas supply flow rate is determined by considering the pressure loss in the catalyst layer and the time required for regeneration, but it is usually 5 m/sec or less, especially from 1 cm/sec to 1 m/sec.
A range of sec is used. The gas supply method may be to supply oxygen-containing inert gas in one pass, or
A method may also be used in which a predetermined amount of oxygen is supplied while circulating an inert gas within the system, and there is no particular restriction. By performing these regeneration operations, carbonaceous matter deposited on the catalyst can be removed, but in order to make the regeneration effect more pronounced, subsequent to the above regeneration operation, under an oxygen-containing gas, preferably air atmosphere,
It is preferable to carry out the heat treatment at a temperature of 450°C to 600°C, preferably 480°C to 550°C, for 5 hours or more, preferably about 10 to 20 hours. By carrying out this operation, the stability of the catalyst is increased and the reaction can be carried out for a long time without any change over time. (Action and Effect of the Invention) A catalyst containing a group B metal of the periodic table used for producing indoles through the reaction of anilines and ethylene glycols gradually deposits carbonaceous material over the course of the reaction time. Deposits and deteriorates. By heat-treating this deteriorated catalyst in an inert gas containing 5 vol% or less oxygen at a temperature of 200 to 470°C, carbonaceous matter is effectively removed and the catalyst activity is restored. The method of the present invention is effective for producing indoles using anilines and ethylene glycols.
The present invention provides an industrial method for producing indoles by regenerating a group metal-containing catalyst that has deteriorated after being used in a reaction under optimal conditions and repeatedly using the regenerated catalyst. (Examples) Hereinafter, the method of the present invention will be explained in detail with reference to Examples and Comparative Examples. Example 1 and Comparative Example 1 A stainless steel reaction tube with an inner diameter of 20 mm was filled with 400 c.c. of a commercially available tablet-formed SiO ₂ catalyst having a diameter of 3 mm and a height of 2.5 mm and carrying 13% silver thereon. Keep the reaction tube at 350℃ and pre-vaporize aniline,
The molar ratio of ethylene glycol and water is 12:
Indole synthesis reaction was carried out by supplying raw materials of 1:30 at 300 g/hr and hydrogen gas at 60 lSTP/hr to the reaction tube at the same time. Note that the reaction was carried out at normal pressure. After reacting for a certain period of time, the catalyst was regenerated. The regeneration conditions are shown in Table 1. Note that the cylinder linear velocity of the oxygen-containing gas was 15 Ncm/sec. After regeneration, the catalyst was heat-treated at 500° C. for 15 hours in an air atmosphere, and then the reaction was performed again under the same conditions as before regeneration. Table 1 shows the conversion rate of ethylene glycol and the yield of the produced indole in the reactions before and after regeneration. Note that the conversion rate of ethylene glycols and the yield of indole follow the definitions below. Conversion rate of ethylene glycol = Number of moles of ethylene glycol consumed/Number of moles of ethylene glycol supplied x 100 Yield of indole = Number of moles of indole produced/Number of moles of ethylene glycols supplied x 100 In addition, in the table The conversion rate and yield are those obtained at the 25th hour of the reaction (however, the values in parentheses indicate the 50th hour).

[Table] Example 2 and Comparative Example 2 A reaction was carried out according to the method shown in Example 1 and Comparative Example 1, including catalyst regeneration conditions, with only the catalyst being changed. The catalyst was the same as the catalyst carrier used in Example 1, with 2.5% copper supported thereon. Table 2 shows the conversion rate of ethylene glycol and the yield of indole produced in the reactions before and after regeneration.

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Claims (1)

[Claims] 1. In a method for producing indoles by reacting anilines and ethylene glycols in the presence of a catalyst containing at least one metal from Group B of the Periodic Table of the Elements, the catalyst degraded during the reaction is A method for producing indoles, which comprises regenerating and repeatedly using oxygen by contacting it with an inert gas containing 5 vol% or less of oxygen in the temperature range of ~450°C.