A kind of method that o-ethylaniline dehydrocyclization prepares indole

Abstract

The invention relates to a method for preparing indole through dehydrocyclizing o-ethylaniline. The method is characterized in that an RU-Al2O3 used as a catalyst boric acid adopted as a cocatalyst are added to a slurry bed reactor, nitrogen is introduced before a reaction to displace air, and o-ethylaniline is dehydrocyclized under a oxygen-free condition in order to synthesize indole. The method has the characteristics of low reaction temperature, easiness in operation and high indole selectivity.

Description

technical field [0001] The invention relates to an indole production technology, which belongs to the field of fine chemical industry. Background technique [0002] Indole is an intermediate for the production of tryptophan, and it is also a raw material for a series of pharmaceuticals, spices, dyes and other organic intermediates. There are not many preparation methods for indole at home and abroad, and the methods for large-scale production of indole mainly include ethylene glycol Alcohol-aniline method and o-nitroethylbenzene method. [0003] The ethylene glycol-aniline method requires a large amount of aniline as a diluent, which has the disadvantages of high energy consumption for aniline recovery, low product purity, multiple purifications, and high production costs. [0004] The o-nitroethylbenzene method first obtains o-ethylaniline by reducing o-nitroethylbenzene, and then adds o-ethylaniline to a fixed-bed reactor for dehydrocyclization to prepare indole. Most of ...

AI Technical Summary

Problems solved by technology

[0003] The ethylene glycol-aniline method requires a large amount of aniline as a diluent, and the recovery of aniline requires high energy consumption, low product purity, multiple purifications, and high production costs.

[0004] The o-nitroethylbenzene method first obtains o-ethylaniline by reducing o-nitroethylbenzene, and then adds o-ethylaniline to a fixed-bed reactor for dehydrocyclization to prepare indole. Most of the dehydrocyclization of o-ethylaniline uses Al 2 o 3 , SiO 2 -Al 2 o 3 , but the reaction temperature is high, generally above 600°C, and the indole yield is low (below 30%). In the later stage, CuO-Al is prepared by improving the catalyst and adding copper and boron 2 o 3 -B 2 o 3 The three-way catalyst is used for the dehydrocyclization of o-ethylaniline, which greatly improves the yield and conversion rate, but there are still high reaction temperatures (about 700 ° C), and B in the catalyst 2 o 3 Due to the high temperature, it is easy to lose during the reaction, and the performance of the catalyst will gradually decrease, and the lost B 2 o 3 It will condense on the inner wall of the reactor outlet, causing the reactor to be blocked, and there are also disadvantages such as high energy consumption and large equipment investment