JPH052377B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for regenerating a catalyst for producing indoles. Indoles are fragrances, dyes, alkaloids,
It also has various industrial uses as a raw material for the essential amino acid tryptophan. A method for producing indoles in which anilines and ethylene glycol are reacted in the presence of a catalyst is known, and various proposals have been made regarding the catalysts used at that time. For example, JP-A-56-36451 discloses a dehydrogenation catalyst, JP-A-56-55366 discloses a copper-containing catalyst, and JP-A-56-53652 discloses a cadmium sulfate and/or zinc sulfate catalyst. but,
JP-A-56-86154 discloses cadmium phosphate,
Catalysts selected from zinc phosphate, aluminum phosphate, boron phosphate and silver are furthermore
JP-A-110672 proposes magnesium oxide-containing catalysts. However, when producing indoles by reacting anilines and ethylene glycol in the presence of a catalyst, the catalyst deteriorates over time, resulting in a decrease in catalytic activity and selectivity to indoles, resulting in a reduction in the yield of indoles. becomes significantly worse. For example, in the case of a cadmium sulfate catalyst, experiments conducted by the present inventors showed that the yield of indoles decreased by more than 10% about 100 hours after the reaction started. Furthermore, since the method for producing indoles from anilines and ethylene glycol is a recently developed technology, no proposal has yet been made for a method for regenerating a deteriorated catalyst. The inventors conducted extensive research on a method for regenerating catalysts used in the production of indoles from anilines and ethylene glycol because they deteriorate in a relatively short period of time. As a result, if the catalyst is a metal sulfate catalyst among the deteriorated catalysts, it is found that if the catalyst is a metal sulfate catalyst, water is added to it for 5 to 20 minutes at a temperature below 200℃.
It was discovered that indoles can be produced again in a high yield if the indoles are used after containing % of the indoles, leading to this invention. This invention is used in a method for producing indoles by reacting anilines and ethylene glycol in the presence of a catalyst, and the deteriorated metal sulfate catalyst is made to contain 5 to 20% water by weight at a temperature of 200°C or less. The present invention relates to a method for regenerating a catalyst for producing indoles, which is characterized by the following. This invention can be commonly applied to metal sulfate catalysts that have deteriorated when used in a method for producing indoles by reacting anilines and ethylene glycol in the presence of a catalyst. Typical applicable metal sulfate catalysts include, for example, cadmium sulfate, zinc sulfate, calcium sulfate, vanadyl sulfate,
Examples of catalysts include metal sulfates such as metal sulfates and mixtures thereof, and catalysts include metal sulfates other than these metal sulfates, such as lithium, rubidium, potassium, cesium, sodium, aluminum, copper, zinc, magnesium, silver, nickel, iron, May contain halides, nitrates, sulfates, phosphates, carbonates, oxides, hydroxides, etc. of cobalt, manganese, tin, vanadium, lead, molybdenum, strontium, cadmium, palladium, thallium, etc. . In the present invention, when moisture is added to the deteriorated metal sulfate catalyst, it is necessary to do so at a temperature of 200° C. or lower for the following reasons. Metal sulfates used as catalysts usually have water of crystallization and are heated at temperatures of 250 to 450℃.
When this water of crystallization evaporates at a reaction temperature of , active sites are formed. However, as the reaction time increases, these active sites become poisoned by deposits and become deactivated. In this invention, when the catalyst, which has already deteriorated due to water of crystallization being removed at the reaction temperature, is re-introduced with water at a temperature below 200°C, preferably between room temperature and below the temperature at which water of crystallization jumps, new active sites can be formed. It is based on the discovery that it is possible. Although there are no particular restrictions on the method of making the deteriorated catalyst contain water, a method of flowing water vapor alone or together with an inert gas such as nitrogen, argon, or helium through the catalyst layer is suitable. If the water content is less than 5% by weight, crystallization water will not be sufficiently imparted to the metal sulfate;
If the amount is too high, the catalyst shape may collapse, so 5~
It should be 20% by weight, preferably 5-15% by weight. Further, when a catalyst containing water is aged at 250 to 400°C, the catalytic activity is further improved. Although the aging atmosphere is not particularly limited, a suitable aging time is 1 to 20 hours. According to this invention, a deteriorated metal sulfate catalyst can be easily regenerated by a simple operation. When producing indoles by reacting anilines and ethylene glycol in the presence of a regenerated metal sulfate catalyst, the anilines and ethylene glycol, which are the raw materials for the reaction, do not need to be of particularly high purity. As the raw material anilines, compounds represented by the following general formula are useful. (However, in the formula, R ¹ represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a nitro group, or a hydroxyl group, and R ² represents a hydrogen atom or an alkyl group.) Representative examples of anilines include aniline, m −
Methylaniline, m-ethylaniline, o-toluidine, m-toluidine, o-anisidine, m-
Examples include anisidine, p-anisidine, m-aminophenol, and o-aminophenol. The ratio of aniline and ethylene glycol introduced into the reactor is 0.01 to 10 mol, preferably 0.02 to 10 mol, of ethylene glycol per 1 mol of aniline.
It is 5 moles. Further, the raw material is introduced into the reactor in advance in a vapor state or in a liquid state so that the liquid hourly space velocity (LHSV) relative to the catalyst is 0.05 to 10/-catalyst/hr. The reaction is carried out at a temperature of 250 to 450°C, preferably 300 to 400°C, and the pressure may be increased, normal pressure, or reduced pressure. Further, the reaction can be carried out in any of the gas phase, liquid phase, or gas-liquid mixed phase, but is usually carried out in the gas phase. Indoles produced by the reaction can be easily separated and recovered from the reaction product by conventional methods such as distillation and extraction. Next, examples and comparative examples will be shown. In each example, analysis of the reaction products was performed by gas chromatography. In addition, the reaction rate (%) of ethylene glycol, the selectivity (%) of indole, and the yield (%) of indole comply with the following definitions. Ethylene glycol reaction rate (%) = Number of moles of consumed ethylene glycol/Number of moles of supplied ethylene glycol x 10
0 Selectivity of indole (%) = Number of moles of indole produced/
Number of moles of consumed ethylene glycol × 100 Indole yield (%) = Number of moles of produced indole / Number of moles of supplied ethylene glycol × 100 Example 1 The molar ratio of CdSO ₄ :ZnSO ₄ :CsSO ₄ is 10:1:
Composite catalyst pellets (4 mmφ x 5 mmL) consisting of 0.1 cadmium sulfate, zinc sulfate, and cesium sulfate
25 ml was filled into a stainless steel U-shaped reactor with an inner diameter of 18 mmφ and a height of 500 mmH. The water content (including crystal water) in the catalyst was 8.8% by weight. The temperature inside the reactor was maintained at 375°C, and a mixture of aniline and ethylene glycol with a molar ratio of 25:1 was introduced at a flow rate of 45 ml/hr (LHSV = 1.8/-catalyst/hr), and at the same time The reaction was carried out by flowing hydrogen gas (carrier gas) at a flow rate of 40 ml/〓. Table 1 shows the ethylene glycol reaction rate, indole selectivity, and indole yield at 2 hours and 100 hours after starting the reaction. After 100 hours of continuous reaction, the catalyst layer
100% H ₂ O:N ₂ = 1:4 (volume ratio) mixed gas
After treating at 120℃ for 4 hours while flowing at a flow rate of ml/〓, the temperature was raised to 300℃ and N ₂ gas was passed through.
The catalyst was regenerated by aging. Next, using the regenerated catalyst (water content 9.0% by weight), aniline and ethylene glycol were reacted under the same reaction conditions as above. Table 1 shows the reaction rate of ethylene glycol, selectivity of indole, and yield of indole two hours after the start of the reaction.

[Table] Examples 2 to 7 Aniline and ethylene glycol were reacted in the same manner as in Example 1, except that the metal sulfate catalysts listed in Table 2 were used as catalysts. Reaction rate of ethylene glycol, selectivity of indole, and indole at 2 hours after starting the reaction, 100 hours after starting the reaction, and 2 hours after using a regenerated catalyst regenerated in the same manner as in Example 1. The yield was as shown in Table 2.

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Claims (1)

[Claims] 1. Moisture is added to the deteriorated metal sulfate catalyst used in the method of producing indoles by reacting anilines and ethylene glycol in the presence of a catalyst at 200°C.
A method for regenerating a catalyst for producing indoles, the method comprising making the catalyst contain 5 to 20% by weight at the following temperature.