Spinel oxide catalysts are active in the liquid-phase oxidation of 2-butanol to MEK -the batch tests at different loadings highlight an impact of the amount of catalyst on the rates. It is reasonable to assume that, in aqueous conditions, the reaction occurs according to the commonly accepted mechanism involving the dissociative adsorption of the alcohol on the catalyst surface, followed by its deprotonation. Both in continuous flow and batch catalytic tests, the catalyst activity was enhanced by pressure, i.e. by the concentration of the oxygen dissolved in the aqueous medium. Therefore, the reaction mechanism shall be one in which O 2 could be involved in the rate-limiting step. One option is the Langmuir-Hinshelwood model, in which two surface species are bonded on neighbouring sites (Figure ). In our case, this entails the dissociative adsorption of O2 on the catalyst surface, followed by the extraction of hydrogen from the surface Our results show that cobaltite-based catalysts are relatively stable in the liquid phase and their activity is preserved over weeks of continuous operation, while previously it was only demonstrated by reusability in discontinuous settings. Nevertheless, during the initial exploratory flow test, the activity of Co3O4 under the same conditions decreased over time (days 7-8 vs 15-16, Figure ). The catalyst does not seem to have undergone any considerable physical changes. The surface area did not decrease during the process (if anything, it increased, Table ), even though some crystallite growth was experienced (but stayed nanocrystalline, Table ). No deposited species was detected by FT-IR, nor any chemical modification was seen by XPS. The spinels are completely black, and colour changes cannot easily be perceived. We deem it unlikely anyway that adsorbed organic species would be stable enough to deactivate the solid (it has been proposed that the presence of the aqueous phase is beneficial because it could dissolve inhibiting species into water, even more so in a flow system). A possible, alternative explanation is that the system took time to reach the steady state, and that the catalyst bed underwent alteration during the process. As a matter of fact, the recovered solid turned from a powder, occupying the entire bed of the CatCart, to a pellet (Figure ). The pressure and flow must have compressed the solid, which did not resist the push due to its sponginess. The macroporosity of the cobaltites causes it to have a very low apparent density and to be fragile. The structural collapse did not reduce the surface area, but decreased the volume of the empty space within the material, reducing the length of the bed (hence the contact time between the reaction species and the solid), and altering the mass transfer phenomena. The catalytic results of the test at constant conditions seem to corroborate this hypothesis, with the activity decreasing and then stabilising (Figure ). While other works focus on the use in alcohol oxidation of nanoparticle catalysts, with highly controlled shapes, precise compositions and well-defined surfaces to make them more active and selective, the core of our work is the development of a more industrially relevant flow process. Such catalysts might not be suitable for prolonged flow operation because their structure might be altered and, on top of that, the flowing fluid phase would wash the particles away, as a specialised filter would be required to keep the particles in the bed, and the resulting bed would be thick, causing a high-pressure load up which would compress the bed, causing clogging. While we developed a working continuous flow system with our nanocrystalline combustion cobaltites in the form of micro/macroscopic porous powders, our study shows that particles with a relatively fragile and expanded framework, even though this could be beneficial for the catalysis, might not be ideal candidates for such a process. More sturdy and compact materials such as the ones prepared by coprecipitation or thermal decomposition of salts may be more suitable for industrial processes.