The European Commission’s Joint Research Centre (JRC) has issued a technical report entitled “Flow chemistry and the synthesis of energetic materials” . In this report, the JRC focuses on the synthesis of explosive materials using hazardous reagents.
One of the JRC’s lines of research is the safe development of high-purity explosives which are used for a variety of fields, including law enforcement, mining or security applications. Since 2014, they have actively worked in flow using Vapourtec flow chemistry platforms for their research.
This report summarises the current state of the art on flow chemistry and the associated benefits related to the synthesis of energetic materials. Nitrating organic compounds is the most common way of synthesising explosives.
Nitrations are highly exothermic reactions that need to be handled with care, especially in batch. To minimise the risk of a runaway reaction, batch nitrations are done at a small scale, with diluted reagents and with active cooling; all to prevent any hotspot and minimise by-products. This, of course, results in difficulties scaling up the process.
With a greater temperature control and smaller reactor volume, continuous flow offers a safer and more reproducible alternative compared to batch processes. Nitrations can be done with fuming nitric acid without risking generating hotspots that can lead to added impurities or runaway reactions.
Dr Manuel Nuño commented “this report is a great summary of the benefits of flow chemistry. One of the reactions we use to train new users is a nitration using fuming nitric acid. In batch, this would be unconceivable. Poor mixing and poor temperature control would lead to the generation of bi-products (double nitration) and the risk of runaway reactions. In flow, nitration chemistry is relatively trivial, and we can fine tune reaction conditions to selectively obtain the mononitro product.”
 Kyprianou, D., Rarata, G., Emma, G., Diaconu, G., Vahcic, M. and Anderson, D., Flow chemistry and the synthesis of energetic materials, EUR 31010 EN, Publications Office of the European Union, Luxembourg, 2022,