Direct Amination of Benzene with Ammonia by Flow Plasma Chemistry

Amine derivatives, including aniline and allylic amines, can be formed in a single-step process from benzene and an ammonia plasma in a microreactor. Different process parameters such as temperature, residence time, and plasma power were evaluated to improve the reaction yield and its selectivity toward aminated products and avoid hydrogenated or oligomerized products. In parallel, simulation studies of the process have been carried out to propose a global mechanism and gain a better understanding of the influence of the different process parameters. The exploration of diverse related alkenes showed that the double bonds, conjugation, and aromatization influenced the amination mechanism. Benzene was the best reactant for amination based on the lifetime of radical intermediates. Under optimized conditions, benzene was aminated in the absence of catalyst with a yield of 3.8 % and a selectivity of 49 % in various amino compounds. Direct amination of benzene is demonstrated with a plasma microreactor. Using ammonia plasma, this process was optimized by studying the influence of temperature, residence time and power of the plasma. Various compounds were evaluated to study influence of double bond, conjugation, and aromaticity. Under optimized conditions, direct amination of benzene gave of total yield of 3.8 %.image

Automated summary

Amine derivatives, including aniline and allylic amines, can be synthesized in a single-step process using benzene and ammonia plasma in a microreactor. The influence of different process parameters such as temperature, residence time, and plasma power on the reaction yield and selectivity towards aminated products is evaluated. Simulation studies are conducted to propose a global mechanism and understand the role of various process parameters. The direct amination of benzene is demonstrated with a yield of 3.8% and selectivity of 49% under optimized conditions, and the influence of double bonds, conjugation, and aromatization on the amination mechanism is studied.