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Catalysts are important additives that are used to increase the material and energy efficiency of chemical reactions and processes. Although catalysts operate in cycles that should restore their initial activity over and over again, they do deactivate over time. Researchers from Utrecht University and University of Twente have now developed a powerful analytical tool that marks dead catalyst particles for deletion, providing a technique to physically remove them from a stream of particles. They published their results on 9 December in Nature Catalysis.

More efficient

The researchers explain: "Because the deactivation of catalyst particles is a heterogeneous process, picking out the dead catalyst particles from a large catalyst volume is like trying to find a bunch of needles in a haystack." Weeding out deactivated particles means that only active catalyst material remains, thus ensuring cleaner and more efficient chemical reactions and processes.

The study was a joint research project of Ph.D. candidates Anne-Eva Nieuwelink (Utrecht University) and Jeroen Vollenbroek (University of Twente), under supervision of Prof. Bert Weckhuysen (Utrecht University) and researchers from the MESA+ Institute at the University of Twente, including Prof. Mathieu Odijk and Prof. Albert van den Berg. The project is part of the NWO Gravitation Program MCEC.

Fluorescent

The researchers came up with a novel method to mark the catalyst particles that are still active. That method relies on the staining reaction of catalyst particles with styrene-derivatives. The molecules become fluorescent when they react with an active site in the catalyst particle, which means that active particles light up, and dead particles do not. The mix of stained particles is then fed through a droplet microreactor, where the particles are sorted using an electrostatic field in as little as 200 milliseconds.

To check the accuracy of the sorting technique, the researchers analyzed the sorted particles using micro-X-Ray fluorescence and fluorescence microscopy, which confirmed the success of the technique. Depending on the specific probe molecule used, the researchers report that the technique is 92–100% effective in picking out the most active particles.