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ACHEMA 2012: Microreactors Trendtopic: How to Use Microreactors to Produce Explosives

| Editor: Dominik Stephan

The larger the reaction vessel, the quicker products can be made – or so you might think. Microreactors show just how wrong that assumption is: in fact, they can be used to produce explosive materials – nitroglycerine, for instance – around ten times faster than in conventional vessels, and much more safely as well. At the ACHEMA trade fair, held June 18-22 in Frankfurt, researchers demonstrate microreactors they use for a very broad range of chemical processes...

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Microreactors are a trend topic for the chemical industry - now scientist from German Fraunhofer institute demonstrates how these vessels can be used for a very broad range of chemical processes, including explosives...
Microreactors are a trend topic for the chemical industry - now scientist from German Fraunhofer institute demonstrates how these vessels can be used for a very broad range of chemical processes, including explosives...
(Picture: Fraunhofer)

If the task is to tunnel through a mountain, workers turn to explosives: the 15-kilometer-long Gotthard Tunnel, for instance, was created by blasting through the rock with explosive gelatin made largely out of the nitroglycerine – better-known as dynamite. Producing these explosives calls for extreme caution. After all, no one wants a demonstration of explosive force in the lab.

Because the production process generates heat, it must proceed slowly: drop for drop, the reagents are added to the agitating vessel that holds the initial substance. A mixture that heats up too suddenly can cause an explosion. The heat generated cannot be permitted to exceed the heat dissipated.

Dynamite Tonite – Nitroglycerine Production With Microreactors

Researchers at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal have developed a method for safer production of nitroglycerine: a microreactor process, tailored to this specific reaction. What makes the process safer are the tiny quantities involved. If the quantities are smaller, less heat is generated. And because the surface is very expansive compared to the volume involved, the system is very easy to cool.

Another benefit: the tiny reactor produces the explosive material considerably faster than in agitating vessels. Unlike a large agitating vessel filled before the slow reaction proceeds, the microreactor works continuously: the base materials flow through tiny channels into the reaction chamber in “assembly-line fashion“. There, they react with one another for several seconds before flowing through other channels into a second microreactor for processing – meaning purification.

How Purifications in Microreactors Work

This is because the interim product still contains impurities that need to be removed for safety reasons. Purification in the microreactor functions perfectly: the product produced meets pharmaceutical specifications and in a modified form can even be used in nitro capsules for patients with heart disease. “This marks the first use of microreactors in a process not only for synthesis of a material but also for its subsequent processing,“ observes Dr. Stefan Löbbecke, deputy division director at ICT. The microreactor process is already successfully in use in industry.

When developing a microreactor, researchers match the reactors to the reaction desired – learn how on page 2!

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