Direct Amination of Benzene with Ammonia by Flow Plasma Chemistry

Abstract

Amine derivatives, including aniline and allylic amines, can be formed in a single‐step process from benzene and an ammonia plasma in a micro‐reactor. 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,

Microreactor designed for efficient plasma–liquid segmented flows

“…Scaling laws taking into account the impact of liquid vapour pressure could therefore effectively predict bubble and slug lengths for a wide variety of liquids. Increasing the gas-to-liquid flow rate ratio also allowed the interfacial area to be increased up to 8 × 10 3 m 2 m −3 , which is in the range of data previously described in the literature for segmented flows 67,103–106 but is at least one order of magnitude higher than usually reported for gas–liquid plasma reactors 30,44,97,98 (see ESI† section SI.7).…”

“…Moreover, the microfluidic scale allows working with small distances between the electrodes. Microreactors have already demonstrated promising applications in gas–liquid plasma chemical processes for pollutant degradation, 39,40 nanoparticle synthesis 41–43 and development of new organic synthesis pathways for amination, 44,45 acylation 46 and oxidation reactions. 47–52…”

High-efficiency non-thermal plasma synthesis of imine macrocycles

“…39 A study using NTP in contact with MeOH and water was used to form carbon-carbon bonds via pinacol coupling. 40 The NTP-liquid interaction has also been exploited under continuous conditions: a microfluidic NTP setup was used to aminate benzene with ammonia without the need for catalyst, 41 and for direct N-acylation of amines by esters. 42 Within the last 5 years, NTP assisted synthesis has been extended to the formation of metal-organic [43][44][45] and covalent organic frameworks (COFs).…”