In a first instance the TAILORCAT project focused on the use of copper as a hydrogenation catalyst, while copper is one of the cheapest base metals and readily available in large quantities. After a first general screening process, copper supported on layered double hydroxide (a type of clay also known as hydrotalcite) was found to hold the best cards in terms of catalytic activity. Gratifyingly, this catalyst was found free of copper leaching and this without the application of protective oxide layers onto the supported copper nanoparticles. Equally surprising this catalyst displayed markedly different activity levels in flow and batch reactors. This was found to relate to an inherent and unexpected acidity of the starting reaction mixture. As a result, a continuous loss of very small amounts of magnesium from the supporting clay material was observed. This work was published in the journal of Green Chemistry and bestowed hot article status: Green Chem., 2019, 21, 5000-5007 (DOI: 10.1039/C9GC00564A). Finally, using a combination of XRD and in situ UV-VIS, it could be shown that Cu(I) species play an important role.